nrgjeff Posted July 14, 2016 Share Posted July 14, 2016 Looks like a decent shot a local severe today. BNA sounding had reasonably good lapse rate for this time of year. A little more heating ahead of existing thunderstorms should yield close to the CAPE that SPC advertises. I still think a little less if heating gets cut off too early. Upper winds are pretty light but not zero like they could be mid-July. Kentucky upper wind is a little better but Tennessee south has greater instability. Some leading edge isolated straight line winds would not surprise me. Like to see a little better consolidation for shelfies. New stuff may go on the Plateau as well. Full MD http://www.spc.noaa.gov/products/md/md1273.html Link to comment Share on other sites More sharing options...
nrgjeff Posted August 18, 2016 Share Posted August 18, 2016 Sent a little thunderstorm treat to Knoxville. Any shelfies? Link to comment Share on other sites More sharing options...
rbowman Posted August 18, 2016 Share Posted August 18, 2016 A lot of clouds in mid Tenn this morning. May cut back on heating and uplift from below as Jeff stated above.Sent from my LG-H901 using Tapatalk Link to comment Share on other sites More sharing options...
jaxjagman Posted September 19, 2016 Author Share Posted September 19, 2016 Though it would be into next years severe thread from the IMME.It's the most interesting thing i've seen yet.We still have the 2nd half of severe season coming up thouugh.It'll be interesting when we get into FMA and watching the TNI Link to comment Share on other sites More sharing options...
nrgjeff Posted September 20, 2016 Share Posted September 20, 2016 La Nina would help in the severe department. Chart above matches Nina precip. Just shifted slightly west which follows the long trend of central US trough tendency. Link to comment Share on other sites More sharing options...
jaxjagman Posted October 18, 2016 Author Share Posted October 18, 2016 DAY 3 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0226 AM CDT TUE OCT 18 2016 VALID 201200Z - 211200Z ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE MID AND UPPER OH VALLEY ACROSS THE MID-SOUTH REGION... ...SUMMARY... A FEW STRONG/LOCALLY SEVERE STORMS WILL BE POSSIBLE THURSDAY AFTERNOON AND EVENING FROM THE MID AND UPPER OHIO VALLEY SOUTH-SOUTHWESTWARD ACROSS THE MID-SOUTH. ...SYNOPSIS... A MID-LEVEL TROUGH INITIALLY ALIGNED OVER THE CENTRAL U.S. IS PROGGED TO CONTINUE ADVANCING EWD WITH TIME...AMPLIFYING AND ACQUIRING NEGATIVE TILT BY THE END OF THE PERIOD. AS THIS OCCURS...A WEAK FRONTAL WAVE INITIALLY INVOF THE KY/TN AREA IS EXPECTED TO GRADUALLY STRENGTHEN AND SHIFT NEWD ACROSS ERN KY AND WV...WHILE A TRAILING COLD FRONT SWEEPS SEWD ACROSS THE SRN PLAINS AND SERN STATES. THIS LOW/FRONT WILL FOCUS A BAND OF SHOWERS AND EMBEDDED THUNDERSTORMS -- PARTICULARLY DURING THE AFTERNOON AND EVENING HOURS. ...MID AND UPPER OH VALLEY REGION SSWWD ACROSS THE MID-SOUTH... AS THE FRONTAL WAVE STRENGTHENS AND MOVES INTO THE CENTRAL APPALACHIANS REGION THROUGH LATE AFTERNOON...A TRAILING COLD FRONT IS FORECAST TO SHIFT ACROSS THE KY/TN AND AL/MS VICINITIES THROUGH THE AFTERNOON. MODEST DESTABILIZATION OF THE PRE-FRONTAL WARM SECTOR AND INCREASING LARGE-SCALE ASCENT SHOULD YIELD AN INCREASE IN CONVECTIVE COVERAGE AND INTENSITY THROUGH THE AFTERNOON AND INTO THE EVENING HOURS. WEAKLY VEERING/INCREASING FLOW WITH HEIGHT IN THE WARM SECTOR IMMEDIATELY AHEAD OF THE FRONT WILL PROVIDE SHEAR SUFFICIENT FOR ORGANIZED UPDRAFTS...WHICH MAY LOCALLY ENHANCE STORM INTENSITY/LONGEVITY...POSSIBLY RESULTING IN ISOLATED/LOW-END SEVERE RISK. AS SUCH...A 5%/MRGL RISK AREA IS BEING INTRODUCED ATTM...ALONG AND W OF THE APPALACHIAN CREST. Link to comment Share on other sites More sharing options...
jaxjagman Posted October 20, 2016 Author Share Posted October 20, 2016 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1230 AM CDT THU OCT 20 2016 VALID 201200Z - 211200Z ...THERE IS A MRGL RISK OF SVR TSTMS FROM SWRN NY SWWD ACROSS THE OH AND TN VALLEYS INTO THE LOWER MS VALLEY... ...SUMMARY... A FEW SEVERE STORMS WILL BE POSSIBLE THURSDAY AFTERNOON AND EVENING FROM SOUTHWEST NEW YORK ACROSS WESTERN PENNSYLVANIA AND EASTERN OHIO AND SOUTHWESTWARD ACROSS THE MID-SOUTH. ...SYNOPSIS... A STRONG UPPER TROUGH WILL SHIFT EWD ACROSS THE MS VALLEY DURING THE DAY AND TOWARD THE OH/TN VALLEYS INTO THE GREAT LAKES THU NIGHT. AT THE SFC...LOW PRESSURE WILL MOVE FROM KY INTO WRN PA BY 00Z WITH COLD FRONT TRAILING SWWD INTO THE LOWER MS VALLEY. E OF THE SFC LOW...A WARM FRONT WILL LIFT NWD ACROSS PA AND SWRN NY. SWLY WINDS WILL MAINTAIN LOWER TO MID 60S F DEWPOINTS ACROSS THE WARM SECTOR WHICH WILL RESULT IN INSTABILITY SUPPORTIVE OF SCATTERED THUNDERSTORMS. INCREASING SWLY FLOW ALOFT WILL ENHANCE SHEAR PROFILES AND WILL LIKELY SUPPORT ISOLATED SEVERE THUNDERSTORMS MAINLY DURING THE AFTERNOON. ELSEWHERE...A LARGE AREA OF HIGH PRESSURE WILL RESULT IN STABLE CONDITIONS W OF THE MS RIVER EXCEPT FOR THE PACIFIC NW WHERE LOW-TOPPED SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE IN ASSOCIATION WITH A LOW-AMPLITUDE SHORTWAVE TROUGH. ...SWRN NY SWWD ACROSS THE OH VALLEY AND MID-SOUTH... AN EXTENSIVE AREA OF RAIN AND THUNDERSTORMS IS EXPECTED TO BE ONGOING ALONG THE LENGTH OF THE COLD FRONT THU MORNING FROM THE ARKLATEX NEWD ACROSS THE OH VALLEY...AND IN ASSOCIATION WITH WARM ADVECTION OVER PA/NY WITH STRONG SWLY 850 MB FLOW. WINDS ALOFT WILL INCREASE WITH THE APPROACHING UPPER TROUGH THROUGHOUT THE DAY...WITH FLOW ROUGHLY PARALLEL TO THE COLD FRONT. THIS...ALONG WITH AREAS OF HEATING...SHOULD ALLOW FOR AN UPTICK IN CONVECTIVE INTENSITY AND COVERAGE BY AFTERNOON...MAINLY FROM ERN TN/KY NEWD INTO PA. HERE...THE COMBINATION OF DEEP-LAYER SHEAR AND INSTABILITY SHOULD SUPPORT AT LEAST ISOLATED FAST-MOVING CELLS OR LINE SEGMENTS CAPABLE OF MARGINALLY SEVERE WIND OR HAIL. FOR NRN AREAS INCLUDING ERN OH...WRN PA AND SWRN NY...LOW-LEVEL SHEAR WILL BE ENHANCED BY THE PRESENCE OF THE WARM FRONT. IF ENOUGH DESTABILIZATION OCCURS...A FEW SUPERCELLS COULD NOT BE RULED OUT WITH PERHAPS A WEAK/BRIEF TORNADO THREAT. ..JEWELL/GLEASON.. 10/20/2016 Link to comment Share on other sites More sharing options...
jaxjagman Posted November 20, 2016 Author Share Posted November 20, 2016 ZCZC SPCSWOD48 ALL ACUS48 KWNS 200923 SPC AC 200923 DAY 4-8 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0323 AM CST SUN NOV 20 2016 VALID 231200Z - 281200Z ...DISCUSSION... MODEL CONSENSUS MAINTAINS A PROGRESSIVE UPPER PATTERN THROUGH DAYS 4-8...BUT SIGNIFICANT DIFFERENCES IN TIMING AND AMPLITUDE OF INDIVIDUAL SHORTWAVES BEGIN TO EMERGE AFTER DAY 6. DAY 4 (WEDNESDAY) UPPER TROUGH IS FORECAST TO DEAMPLIFY AS IT MOVES THROUGH THE EASTERN STATES...AND THE ASSOCIATED SURFACE LOW WILL OCCLUDE OVER THE GREAT LAKES. TRAILING COLD FRONT WILL MOVE THROUGH THE TENNESSEE VALLEY AND A PORTION OF THE SOUTHEASTERN STATES. INLAND MOISTURE ADVECTION SHOULD WEAKEN AS THE PRIMARY LOW-LEVEL JET SHIFTS FARTHER AWAY FROM THE COAST AND TOWARD THE TENNESSEE AND OHIO VALLEYS. THUS CONVECTION DEVELOPING ALONG AND AHEAD OF THE FRONT WILL ENCOUNTER DIMINISHING INSTABILITY...LIMITING THE SEVERE THREAT. DAY 5-6 (THURSDAY THROUGH FRIDAY) THE FRONT WILL STALL NEAR THE GULF COAST WITH STABLE CONDITIONS INLAND. ..DIAL.. 11/20/2016 Fixing to head off to Florida in a couple hours for T-Giving :).Better chance for severe looks possible the week after next. Link to comment Share on other sites More sharing options...
jaxjagman Posted November 28, 2016 Author Share Posted November 28, 2016 Euro shows some good gust tomorrow night into the early morning hours.Seems like there could be some good damage from the recent fires,the trees that have been burned should be rather weak,plus add the drought in as well Link to comment Share on other sites More sharing options...
jaxjagman Posted November 28, 2016 Author Share Posted November 28, 2016 DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1155 PM CST SUN NOV 27 2016 VALID 291200Z - 301200Z ...THERE IS A SLGT RISK OF SVR TSTMS TUESDAY NIGHT ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY...AND ADJACENT GULF COAST...INTO PORTIONS OF THE TENNESSEE VALLEY... ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS AREAS SURROUNDING THE SLIGHT RISK...AS FAR NORTHEAST AS THE SOUTHERN APPALACHIANS... ...SUMMARY... SEVERE STORMS ARE POSSIBLE ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY AND ADJACENT GULF COASTAL AREAS...NORTHEASTWARD TOWARD THE SOUTHERN APPALACHIANS...TUESDAY NIGHT. ACTIVITY MAY BE ACCOMPANIED BY POTENTIALLY DAMAGING WIND GUSTS...SEVERE HAIL...AND THE RISK FOR A FEW TORNADOES...ONE OR TWO OF WHICH COULD BE STRONG. ...SYNOPSIS... THE CENTER OF A BROAD DEEP LOWER/MID TROPOSPHERIC CYCLONE MAY LINGER OVER THE UPPER MIDWEST THROUGH THE BALANCE OF THIS PERIOD...BUT IT APPEARS LIKELY TO BEGIN TO GRADUALLY FILL/WIND DOWN. AS IT DOES... AND THE REMNANTS OF ONE SIGNIFICANT SHORT WAVE IMPULSE TURN EAST NORTHEAST OF THE LOWER GREAT LAKES REGION DURING THE DAY...SOUTHERLY LOW-LEVEL WIND FIELDS ACROSS AND EAST OF THE MISSISSIPPI VALLEY STILL APPEAR LIKELY TO BE IN THE PROCESS OF WEAKENING EARLY IN THE DAY. HOWEVER...MODELS CONTINUE TO INDICATE THAT THE LAST ONE OR TWO...IN A SERIES OF SHORT WAVE PERTURBATIONS DIGGING INTO LARGE-SCALE UPPER TROUGHING OVER THE INTERIOR U.S....WILL EMERGE FROM THE FOUR CORNERS REGION DURING THE DAY. AS DOWNSTREAM SUBTROPICAL RIDGING CENTERED OVER THE CARIBBEAN/BAHAMAS REMAINS STRONG...AS FAR NORTHWEST AND NORTH AS PORTIONS OF THE EASTERN GULF AND SOUTH ATLANTIC COAST STATES...IT APPEARS THAT THE AXIS OF THE REMNANT TROUGHING WILL PIVOT IN POSITIVELY TILTED FASHION ACROSS THE SOUTH CENTRAL PLAINS...MIDDLE MISSISSIPPI VALLEY AND OZARK PLATEAU BY 12Z WEDNESDAY. IN THIS MANNER...GUIDANCE INDICATES THAT IT WILL CONTRIBUTE TO INCREASING DIFLUENT AND DIVERGENT UPPER FLOW ALONG A STALLED FRONTAL ZONE...WHICH IS EXPECTED TO EXTEND FROM THE SOUTHERN APPALACHIANS THROUGH PORTIONS OF THE LOWER MISSISSIPPI VALLEY AND WESTERN GULF COAST REGION AT THE OUTSET OF THE PERIOD. THE FRONT MAY BE PRECEDED BY A CONVECTIVELY GENERATED OUTFLOW BOUNDARY NEAR COASTAL LOUISIANA... MISSISSIPPI AND ALABAMA. HOWEVER...MODELS APPEAR INCREASINGLY BULLISH WITH SOUTHERLY 850 MB JET STRENGTHENING (50-70 KT)...NEAR AND EAST OF THE LOWER MISSISSIPPI VALLEY TUESDAY EVENING. THIS IS EXPECTED TO ACCOMPANY A DEVELOPING FRONTAL WAVE...AND APPEARS LIKELY TO SUPPORT AN INFLUX OF BOUNDARY LAYER MOISTURE (CHARACTERIZED BY MID/UPPER 60S F SURFACE DEW POINTS) OFF THE WESTERN GULF OF MEXICO... AT LEAST AS FAR NORTHEAST AS PORTIONS OF THE TENNESSEE VALLEY. ...LOWER MISSISSIPPI VALLEY INTO SOUTHERN APPALACHIANS... IT APPEARS THAT THE ENVIRONMENT WILL BECOME INCREASINGLY CONDUCIVE TO ORGANIZED SEVERE STORM DEVELOPMENT ACROSS THE LOWER MISSISSIPPI VALLEY BY TUESDAY EVENING. BENEATH CONTINUING STRONG CYCLONIC MID-LEVEL FLOW...DEEP LAYER VERTICAL SHEAR WILL BE MORE THAN FAVORABLE...AND ENLARGING LOW-LEVEL HODOGRAPHS COULD PROMOTE A THREAT FOR TORNADOES...IN ADDITION TO A RISK FOR SEVERE HAIL AND POTENTIALLY DAMAGING WIND GUSTS. HOWEVER...TORNADIC POTENTIAL REMAINS A BIT UNCERTAIN...AND MAY LARGELY HINGE ON THE DEGREE TO WHICH A RESIDUAL NEAR-SURFACE STABLE LAYER LINGERS ACROSS SOUTHERN LOUISIANA... MISSISSIPPI AND ALABAMA. AT THE PRESENT TIME...IT IS APPEARING INCREASINGLY PROBABLE THAT LARGE-SCALE FORCING FOR ASCENT COULD SUPPORT AN ORGANIZING LINE OF THUNDERSTORMS ALONG OR AHEAD OF THE EASTWARD ADVANCING COLD FRONT. DAMAGING WIND GUSTS MAY BECOME THE PRIMARY THREAT WITH THIS ACTIVITY...WHICH COULD DEVELOP NORTHEASTWARD THROUGH PORTIONS OF THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS BY LATE TUESDAY NIGHT. OTHERWISE...SUSTAINED DISCRETE SUPERCELL DEVELOPMENT ALSO APPEARS POSSIBLE WITHIN A NARROW CORRIDOR OF RICHER BOUNDARY LAYER MOISTENING PRECEDING THE EVOLVING SQUALL LINE...PARTICULARLY ACROSS PARTS OF SOUTHEAST/EAST CENTRAL MISSISSIPPI INTO WEST CENTRAL ALABAMA BY THE 30/03-06Z TIME FRAME. ONE OR TWO STRONG TORNADOES MAY NOT BE OUT OF THE QUESTION. ..KERR.. 11/28/2016 Link to comment Share on other sites More sharing options...
jaxjagman Posted November 28, 2016 Author Share Posted November 28, 2016 DAY 4-8 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0349 AM CST MON NOV 28 2016 VALID 011200Z - 061200Z ...DISCUSSION... THE POTENTIAL MID/UPPER FLOW EVOLUTION ACROSS THE EASTERN PACIFIC INTO NORTH AMERICA LATE THIS WEEK THROUGH EARLY NEXT WEEK IS BECOMING MORE UNCLEAR. INCREASING SPREAD IS EVIDENT AMONG THE MEDIUM-RANGE MODELS...PERHAPS MOST NOTABLY IN ASSOCIATION WITH TROUGHING FORECAST TO DIG INLAND OF THE PACIFIC COAST BY EARLY THURSDAY. THE PAST FEW DAYS...GUIDANCE IN GENERAL HAS SUGGESTED THAT A SIGNIFICANT EMBEDDED IMPULSE WILL SPLIT OFF THE MAIN BELT OF WESTERLIES...AND DIG SOUTHWARD THROUGH SOUTHERN CALIFORNIA AND BAJA BY NEXT WEEKEND...BEFORE TURNING EAST NORTHEASTWARD ACROSS NORTHERN MEXICO LATE NEXT WEEKEND INTO EARLY NEXT WEEK. PRECEDING THE EASTWARD ACCELERATION OF THIS FEATURE...CONFLUENT DOWNSTREAM FLOW WOULD ALLOW SURFACE RIDGING WITH POTENTIALLY COOL/COLD AIR TO DEVELOP EAST SOUTHEASTWARD ACROSS MOST AREAS EAST OF THE ROCKIES...AS FAR SOUTH AS THE GULF COAST. THIS WOULD MAINTAIN GENERALLY STABLE CONDITIONS WITH NEGLIGIBLE CONVECTIVE POTENTIAL. RECENT RUNS OF THE GFS/NCEP MREF GENERALLY MAINTAIN THIS SCENARIO. HOWEVER...OTHER MEDIUM-RANGE GUIDANCE...INCLUDING THE ECMWF/ECENS... HAVE TRENDED MORE PROGRESSIVE WITH THE VIGOROUS SOUTHERN STREAM IMPULSE. AT THE OTHER EXTREME OF THE SPECTRUM...COMPARED TO THE GFS... THE 28/00Z DETERMINISTIC ECMWF INDICATES A SOLUTION THAT MAY SUPPORT STRONG CYCLOGENESIS INLAND OF THE LOUISIANA/MISSISSIPPI GULF COAST... THROUGH THE OHIO VALLEY AND GREAT LAKES...LATE THIS WEEKEND INTO EARLY NEXT WEEK. TRENDS WILL NEED TO BE MONITORED. IF THIS OUTPUT COMES CLOSE TO VERIFYING...IT WOULD PROBABLY BE ACCOMPANIED BY CONSIDERABLE SEVERE THUNDERSTORM POTENTIAL ACROSS AT LEAST THE CENTRAL GULF STATES THROUGH MUCH OF THE SOUTHEAST. ..KERR.. 11/28/2016 Link to comment Share on other sites More sharing options...
jaxjagman Posted November 28, 2016 Author Share Posted November 28, 2016 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0659 AM CST MON NOV 28 2016 VALID 281300Z - 291200Z ...THERE IS AN ENH RISK OF SVR TSTMS FROM THE NORTHERN PARTS OF THE TEXAS/LOUISIANA BORDER AREA TO NORTHERN MISSISSIPPI... ...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM EAST TEXAS TO WESTERN PARTS OF TENNESSEE AND ALABAMA... ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK FROM EAST TEXAS TO ALABAMA AND WESTERN KENTUCKY... ...SUMMARY... THUNDERSTORMS WILL SHIFT FROM EAST TEXAS AND THE ARKLATEX REGION ACROSS THE LOWER MISSISSIPPI VALLEY AND MID SOUTH. THE SEVERE-STORM THREAT COULD REACH THE TENNESSEE VALLEY OVERNIGHT. DAMAGING WINDS WILL BE THE PRIMARY THREAT...WITH A FEW TORNADOES ALSO POSSIBLE. OTHER DAYTIME STORMS OVER PARTS OF MISSOURI MAY PRODUCE HAIL APPROACHING SEVERE LIMITS. ...SYNOPSIS... A PRONOUNCED...STACKED...DEEP-TROPOSPHERIC CYCLONE -- CURRENTLY CENTERED OVER NORTHEASTERN SOUTH DAKOTA -- WILL REMAIN THE DOMINANT SYNOPTIC FEATURE TODAY AND TONIGHT...WITH CYCLONIC FLOW FROM THE PACIFIC COAST TO THE SOUTHERN/CENTRAL APPALACHIANS. THE DEEP-LAYER LOW ITSELF IS FORECAST TO DRIFT ERRATICALLY NORTHWARD OVER THE EASTERN DAKOTAS AND WEST-CENTRAL/NORTHWESTERN MINNESOTA THROUGH THE PERIOD...BECOMING EVER MORE DEEPLY OCCLUDED IN LOW LEVELS. THE BASAL SHORTWAVE TROUGH FOR THIS SYSTEM -- NOW EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER FAR WEST TEXAS AND EASTERN NEW MEXICO -- IS EXPECTED TO EJECT RAPIDLY NORTHEASTWARD ACROSS NORTH TEXAS AND OKLAHOMA TODAY... REACHING NORTHERN ARKANSAS AND EASTERN MISSOURI BY 00Z. THIS PERTURBATION WILL CONTINUE NORTHEASTWARD TO SOUTHERN ONTARIO BY 12Z. MEANWHILE...AN INITIALLY WEAKER SHORTWAVE TROUGH -- CURRENTLY POSITIONED OVER THE INLAND PACIFIC NORTHWEST...WILL DIG SOUTHEASTWARD TO PARTS OF ARIZONA AND NEW MEXICO BY THE END OF THE PERIOD. AT THE SURFACE...THE SOUTHERN PLAINS COLD FRONT LARGELY HAS OVERTAKEN ITS PRECEDING DRYLINE...AND EXTENDS FROM A NEBULOUS WARM-FRONTAL INTERSECTION IN SOUTHEASTERN KANSAS SOUTHWESTWARD ACROSS CENTRAL OKLAHOMA AND SOUTHWEST TEXAS. THE OCCLUDED FRONT WAS DRAWN FROM THERE NORTHWARD TO THE EASTERN DAKOTAS LOW. A WARM FRONT WAS ANALYZED NEAR THE LOUISIANA COAST...ARCHING NORTHWARD OVER EAST TEXAS TOWARD THE TEXARKANA AREA...BECOMING ILL-DEFINED AMIDST STRONGER BAROCLINIC INFLUENCES OF CONVECTION FARTHER NORTH. THE COLD FRONT SHOULD PROCEED SOUTHEASTWARD TODAY...REACHING PARTS OF NORTHERN MISSISSIPPI...CENTRAL/SOUTHWESTERN LOUISIANA AND SOUTH TEXAS DURING LATE AFTERNOON. MEANWHILE THE WARM FRONT WILL MOVE ERRATICALLY NORTHEASTWARD ACROSS PORTIONS OF LOUISIANA...SOUTHERN ARKANSAS AND MISSISSIPPI. ...EAST TEXAS TO THE TENNESSEE VALLEY REGION... SCATTERED THUNDERSTORMS ARE ONGOING ACROSS PARTS OF NORTH-CENTRAL AND NORTHEAST TEXAS INTO WESTERN ARKANSAS...IN A REGIME WHERE SBCAPE DWINDLES AND SBCINH INCREASES WITH NORTHEASTWARD EXTENT. THE WARM-ADVECTION/CONFLUENT-FLOW REGIME IN LOW LEVELS OVER EAST TEXAS ALSO SHOULD SUPPORT SLOWLY INCREASING THUNDERSTORM COVERAGE AND INTENSITY FROM NOW THROUGH THE AFTERNOON...AS BOTH REGIMES SHIFT EASTWARD AND PERHAPS MERGE. THE TEXAS PART OF THESE PROCESSES MAY POSE AN INCREASING SEVERE THREAT THROUGH LATE MORNING AS THEY SHIFT OVER THE ARKLATEX REGION INTO MIDDAY; A RELATED MESOSCALE DISCUSSION (NUMBER 1826) WILL ADDRESS THE NEAR-TERM DETAILS. OTHERWISE...THE SEVERE-STORM THREAT IS EXPECTED TO SHIFT EASTWARD AND RAMP UP THROUGH THE DAYLIGHT HOURS -- PRIMARILY WIND DAMAGE...BUT ALSO WITH ISOLATED HAIL AND A FEW TORNADOES POSSIBLE. THE FOREGOING WARM SECTOR WILL DESTABILIZE GRADUALLY FROM A BLEND OF THETA-E ADVECTION AND DIABATIC SURFACE HEATING...THE LATTER RENDERED GRADUAL AND PATCHY BY CLOUD/PRECIP FIELDS. THE MAIN UNCERTAINTY IS THE EXTENT OF FAVORABLE SURFACE-BASED DESTABILIZATION NORTHEASTWARD TOWARD THE LOWER OHIO VALLEY IN A NARROW AND VERY MARGINAL WARM SECTOR...FOLLOWING ONGOING CLOUDS AND PRECIP...AND RESULTING IN LOWER UNCONDITIONAL SEVERE PROBABILITIES IN THAT AREA COMPARED TO FARTHER SOUTH. WITH SOUTHWARD EXTENT NEAR THE GULF COAST AND INTO THE MORE FAVORABLE MOISTURE...LIFT WILL BE MORE QUESTIONABLE BENEATH STRONGER CAPPING -- AS EVIDENT UPSTREAM IN THE 12Z CRP SOUNDING -- WHILE THE MAIN CYCLONE OCCLUDES AND OVERALL MASS RESPONSE PEAKS FARTHER NORTH. GIVEN THESE CONSTRAINTS...THE MOST FAVORABLE PARAMETRIC JUXTAPOSITION APPEARS TO BE IN AND NEAR THE ENHANCED RISK...WHERE MODIFIED RAOBS AND FORECAST SOUNDINGS SUGGEST THAT THE MLCAPE WILL RISE TO THE 500-1000 J/KG RANGE BETWEEN I-10 AND I-20 AND 300-800 J/KG NORTHWARD OVER SOUTHERN ARKANSAS AND NORTHERN MISSISSIPPI. DEEP SHEAR GENERALLY WILL BE STRONGEST OVER THE NORTHERN PART OF THE CATEGORICAL SLIGHT AND ENHANCED RISK AREAS...BENEATH A 150-170-KT 250-MB JET AND A BROAD SWATH OF 80-100-KT 500-MB FLOW. LOW-LEVEL SHEAR WILL BE STRONG OVER THE ENTIRE OUTLOOK BUT GREATEST NEAR THE WARM FRONT...WHERE FLOW IS MORE SOUTHERLY TO SOUTHEASTERLY... SUPPORTING GREATER DIRECTIONAL SHEAR. EFFECTIVE SRH GENERALLY SHOULD REACH THE 300-500 J/KG RANGE AND LOCALLY HIGHER...BEFORE SURFACE WINDS VEER SOUTHWESTERLY. ANY SUPERCELLS IN THIS ENVIRONMENT WILL POSE A RISK FOR TORNADOES AS WELL. A MORE CONCENTRATED/SUBSTANTIAL TORNADO THREAT MAY BECOME APPARENT AS MESOSCALE DETAILS BECOME LESS NEBULOUS...GIVEN FAVORABLE STORM MODES. WITH TIME THE DOMINANT STORM MODE WILL BECOME QUASI-LINEAR...GIVEN THE PERSISTENT GEOMETRY OF DEEP-LAYER FLOW BEING LARGELY PARALLEL TO THE SOUTHWEST-NORTHEAST-ALIGNED ZONE OF STRONGEST LOW-LEVEL FORCING FOR CONVECTION. THE DOMINANT...QUASI-LINEAR BAND OF CONVECTION SHOULD WEAKEN FROM NORTH TO SOUTH THIS EVENING AND OVERNIGHT AS ITS NORTHERN EXTENT OUTRUNS THE SURFACE WARM SECTOR. SOME SEVERE THREAT MAY PERSIST LATE TONIGHT OVER MIDDLE TENNESSEE AND ALABAMA WHERE THETA-E WILL BE HIGHER. Link to comment Share on other sites More sharing options...
nrgjeff Posted November 28, 2016 Share Posted November 28, 2016 No concerns for Tennessee. However I think North Alabama and North Mississippi could get really active late Tuesday night. IFF they can reach high temps in the 70s Tuesday, the stage would be set for low-moderate instability overnight. Tuesday night into Wednesday morning could become a classic low CAPE high shear severe weather outbreak. Note I write could, not will and not even should. Conditional at the moment, but it is definitely something to watch. SPC hatched their slight valid for Tuesday night. Link to comment Share on other sites More sharing options...
jaxjagman Posted November 29, 2016 Author Share Posted November 29, 2016 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1154 PM CST MON NOV 28 2016 VALID 291200Z - 301200Z ...THERE IS AN ENH RISK OF SVR TSTMS ACROSS ERN LA...MUCH OF MS...PARTS OF SRN TN... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SABINE RIVER NEWD INTO SRN KY... ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE CENTRAL GULF COAST NEWD INTO KY... ...SUMMARY... SEVERE STORMS ARE EXPECTED ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY AND ADJACENT GULF COASTAL AREAS...AND EXTENDING NORTHEASTWARD INTO TENNESSEE AND KENTUCKY. THE THREAT SHOULD PEAK TUESDAY EVENING AND OVERNIGHT. STORMS MAY BE ACCOMPANIED BY TORNADOES...HAIL...AND DAMAGING WIND...WITH A FEW STRONG TORNADOES POSSIBLE. ...SYNOPSIS... THE UPPER AIR PATTERN WILL FEATURE A STATIONARY UPPER LOW CENTERED OVER THE NORTHERN PLAINS AND UPPER MS VALLEY...WITH BROAD AREA OF CYCLONIC FLOW FROM THE ROCKIES ACROSS THE SOUTHERN PLAINS AND LOWER MS VALLEY AND INTO THE LOWER GREAT LAKES. EARLY IN THE DAY...A LEADING SHORTWAVE TROUGH WILL DISSIPATE AS IT MOVES FROM THE OH VALLEY ACROSS THE NORTHEASTERN STATES WITH SLIGHT HEIGHT RISES TO THE SOUTHWEST. HOWEVER...BY LATE TUESDAY EVENING...A LARGER SHORTWAVE TROUGH WILL ROTATE EASTWARD ACROSS THE SOUTHERN PLAINS AND WILL APPROACH THE MS RIVER INTO WEDNESDAY MORNING. AT THE SURFACE...A LOW PRESSURE TROUGH WILL EXTEND FROM THE MIDDLE MS VALLEY SOUTHWARD TOWARD THE SABINE RIVER BY 00Z...WITH A SECONDARY SURFACE LOW MOVING FROM AR ACROSS TN...KY...AND INTO SOUTHERN OH BY WEDNESDAY MORNING. EXTENDING SOUTHWESTWARD FROM THE LOW WILL BE AN INTENSIFYING COLD FRONT WHICH WILL SWEEP EASTWARD TO AN EASTERN KY TO SOUTHEAST LA LINE BY WEDNESDAY MORNING. AHEAD OF THIS FRONT... RAPID WARM AIR ADVECTION WILL OCCUR IN THE LOW-LEVELS DURING THE DAY AS A WARM FRONT PUSHES NORTHWARD...WITH 850 MB FLOW INCREASING TO 50 KT BY 00Z. A MOISTENING AND DESTABILIZING AIR MASS WILL MATERIALIZE ACROSS THE WARM SECTOR WITH MID 60S F DEWPOINTS APPROACHING THE SOUTHERN BORDER OF TN BY EVENING AND NEAR 70 F DEWPOINTS ACROSS LA AND MS. LIFT ALONG THE COLD FRONT...WITH INCREASING SHEAR PROFILES AND FAVORABLE LARGE-SCALE SUPPORT SHOULD ALLOW FOR A CORRIDOR OF SIGNIFICANT SEVERE WEATHER POTENTIAL ACROSS THE ENHANCED RISK AREA. ...EASTERN AR AND NORTHERN LA...MS...NORTHERN AL...TN...KY... SUBSTANTIAL LOW-LEVEL MOISTURE IS ALREADY IN PLACE ACROSS THE CENTRAL GULF COAST WITH DEWPOINTS NEAR 70 F OVER LA AS OF MONDAY EVENING. AS THE WARM FRONT SHIFTS NORTHWARD DURING THE DAY... MOISTENING WILL OCCUR AND SOME MODELS SUCH AS THE WRF-ARW AND THE HRRR SHOW SCATTERED THUNDERSTORMS DEVELOPING IN THE WARM ADVECTION ZONE FROM NEAR THE SABINE RIVER EASTWARD ACROSS LA AND PERHAPS INTO CENTRAL MS. IF THIS OCCURS...THESE WOULD LIKELY TAKE THE FORM OF SUPERCELLS AS SHEAR PROFILES WILL BE QUITE STRONG ALOFT...WITH MODERATE SRH OF 200-300 M2/S2 PRESENT ALONG THE WARM FRONT. HAIL AND A TORNADO ARE CONDITIONALLY POSSIBLE WITH THE EARLY/MIDDAY ACTIVITY. IN THE WAKE OF ANY EARLY ACTIVITY...AND PRECEDING THE COLD FRONT... MOISTENING AND DESTABILIZATION WILL CONTINUE...WITH FORECAST SOUNDINGS SHOWING A SMALL CAPPING INVERSION AROUND 800 MB. THIS SHOULD ENSURE THAT WARM SECTOR DEVELOPMENT IS FOCUSED ALONG THE COLD FRONT...WHICH WILL ALSO LIMIT THE NUMBER OF STORMS INITIALLY AND BE FAVORABLE FOR SUPERCELLS. INSTABILITY WILL BE STRONGER THAN THE PREVIOUS DAY...AND SHEAR WILL REMAIN VERY STRONG WITH HODOGRAPHS FAVORING TORNADIC SUPERCELLS AS WELL AS HAIL AND WIND. THE LIKELIHOOD OF DISCRETE SUPERCELLS...AMPLE MOISTURE...AND VERY STRONG SHEAR ALL SUGGEST A COUPLE TORNADOES MAY BE STRONG. SOME DIFFERENCES EXIST IN TERMS OF HOW FAR EAST OR WEST THE COLD FRONT DEVELOPMENT WILL TAKE PLACE...BUT GENERAL MODEL CONSENSUS IS NEAR THE MS RIVER ALONG THE AR/MS BORDER...AND EXTENDING SOUTHWESTWARD THROUGH THE EVENING ACROSS EASTERN LA AND OVER MUCH OF MS. THE INITIAL DEVELOPMENT AROUND 00Z MAY MOVE FROM EASTERN AR/NORTHERN MS INTO MIDDLE TN AND EVENTUALLY SOUTHERN KY WITH A TORNADO AND WIND THREAT. FURTHER DEVELOPMENT IS ALSO EXPECTED AROUND 03Z FROM CENTRAL LA INTO CENTRAL MS...EITHER JUST AHEAD OF THE FRONT OR IN A PRE-FRONTAL CONFLUENCE LINE. HERE...DEWPOINTS WILL BE IN THE UPPER 60S F...AND INSTABILITY WILL BE ON THE ORDER OF 1000 J/KG WHICH WILL CLEARLY BE SUFFICIENT FOR SUPERCELLS AND A FEW TORNADOES GIVEN THE AMPLE MOISTURE. ..JEWELL/LEITMAN.. 11/29/2016 Link to comment Share on other sites More sharing options...
jaxjagman Posted November 29, 2016 Author Share Posted November 29, 2016 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0654 AM CST TUE NOV 29 2016 VALID 291300Z - 301200Z ...THERE IS AN ENH RISK OF SVR TSTMS FROM EASTERN LOUISIANA TO NORTHWESTERN ALABAMA AND SOUTHERN MIDDLE TENNESSEE... ...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM SOUTHEAST TEXAS TO SOUTH-CENTRAL KENTUCKY AND CENTRAL/NORTHERN ALABAMA... ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK.... ...SUMMARY... SEVERE STORMS ARE EXPECTED MAINLY THIS EVENING AND TONIGHT ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY AND ADJACENT GULF COASTAL AREAS...AND EXTENDING NORTHEASTWARD INTO TENNESSEE AND KENTUCKY. DAMAGING WIND...ISOLATED HAIL...AND A FEW STRONG TORNADOES ARE POSSIBLE. ...SYNOPSIS... THE DOMINANT UPPER-AIR FEATURE FOR THIS FORECAST PERIOD WILL REMAIN A LARGE...STACKED...OCCLUDED CYCLONE...NOW CENTERED OVER THE EASTERN PART OF THE SOUTH DAKOTA/NORTH DAKOTA LINE. THE DEEP-LAYER LOW IS EXPECTED TO MEANDER ERRATICALLY AND VERY SLOWLY EASTWARD ACROSS CENTRAL MINNESOTA THROUGH TOMORROW MORNING. MEANWHILE...A BASAL SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER PARTS OF NEW MEXICO AND ARIZONA -- WILL PIVOT EASTWARD OVER PARTS OF OKLAHOMA...NORTHWEST TEXAS AND SOUTHERN NEW MEXICO BY 00Z. BY 12Z... THIS PERTURBATION SHOULD REACH THE OZARKS...NORTH-CENTRAL AND WEST-CENTRAL TEXAS...MAINTAINING A PRONOUNCED POSITIVE TILT. AT THE SURFACE...A QUASISTATIONARY FRONTAL ZONE WAS DRAWN FROM A WEAK LOW OVER SOUTH-CENTRAL TEXAS EAST-NORTHEASTWARD ACROSS THE MIDDLE/UPPER TEXAS COASTAL PLAIN...SOUTHWESTERN/CENTRAL LOUISIANA... AND CENTRAL/NORTHERN MISSISSIPPI...ARCHING NORTHWARD AND NORTHWESTWARD TOWARD THE DEEP-LAYER CYCLONE. THE FRONT BECAME MORE ILL-DEFINED WITH NORTHWARD EXTENT FROM THE COASTAL OUTFLOW BOUNDARY. THE OUTFLOW BOUNDARY...PRODUCED AND REINFORCED BY PRIOR/OVERNIGHT CONVECTION...WAS ANALYZED ACROSS THE GULF COASTAL PLAIN...FROM NORTHEASTERN GEORGIA SOUTHWESTWARD ACROSS EXTREME SOUTHERN ALABAMA AND MISSISSIPPI...THEN SOUTH-CENTRAL/SOUTHWESTERN LOUISIANA...BEFORE INTERSECTING THE FRONT NORTH OF THE GOLDEN TRIANGLE AREA OF EXTREME SOUTHEAST TEXAS. THE OUTFLOW BOUNDARY IS EXPECTED TO RETREAT NORTHEASTWARD ACROSS THE MISSISSIPPI DELTA REGION AND MUCH OF MISSISSIPPI AND ALABAMA THROUGHOUT TODAY...THEN NORTHERN ALABAMA... MUCH OF WESTERN/MIDDLE TENNESSEE...AND PERHAPS INTO SOUTHERN KENTUCKY THIS EVENING AND OVERNIGHT. EXCEPT WHERE LOCAL...CONVECTIVE REINFORCEMENTS OCCUR...THE BAROCLINIC GRADIENT WITH THE OUTFLOW BOUNDARY ALSO WILL BECOME MORE DIFFUSE WITH TIME. ...SOUTHEAST TEXAS AND LOUISIANA TO WESTERN/MIDDLE TENNESSEE... SOME WESTWARD ADJUSTMENT HAS BEEN MADE TO THE MARGINAL-RISK PROBABILITIES IN DEFERENCE TO THE POTENTIAL FOR DIURNAL CONVECTION TO DEVELOP NEAR OR EVEN SOMEWHAT POLEWARD OF A WAVY SEGMENT OF THE FRONT OVER SOUTHEAST TEXAS...BEFORE THE BAROCLINIC ZONE ACCELERATES SOUTHEASTWARD. EITHER THIS CONVECTION...OR ADDITIONAL DEVELOPMENT LATER THIS AFTERNOON AND EVENING OVER LOUISIANA AND SOUTHEAST ARKANSAS NEAR THE FRONT...WILL MOVE NORTHEASTWARD AND BECOME SURFACE-BASED AS THE WARM SECTOR RETURNS INLAND. ADDITIONAL THUNDERSTORMS SHOULD FORM THROUGHOUT THIS EVENING ACROSS PARTS OF LOUISIANA AND MISSISSIPPI...WHETHER ON THE FRONT OR IN WARM-SECTOR CONVERGENCE ZONES...MOVING NORTHEASTWARD TOWARD ALABAMA AND WESTERN/MIDDLE TENNESSEE. COLLECTIVELY...THIS ACTIVITY SHOULD EVOLVE INTO THE PRIMARY...SOUTHWEST/NORTHEAST-ORIENTED BELT OF CONVECTION OVERNIGHT. SUPERCELLS AND SMALL BOWS EACH ARE POSSIBLE. DAMAGING GUSTS MAY BE THE MOST NUMEROUS EVENT TYPE...BUT TORNADOES (SOME CAPABLE OF SIGNIFICANT DAMAGE) ALONG WITH ISOLATED SEVERE HAIL WILL BE POSSIBLE. THE ENVIRONMENT ALONG AND SOUTH OF THE RETREATING OUTFLOW BOUNDARY WILL BECOME MORE FAVORABLE FROM MID AFTERNOON INTO THE EARLY OVERNIGHT HOURS...AS THE LOW-LEVEL JET INTENSIFIES AND HODOGRAPHS ENLARGE...AMIDST FAVORABLY RICH BOUNDARY-LAYER MOISTURE AND MINIMAL CINH. INCREASING LOW-LEVEL MOISTURE WILL BE MANIFEST BY SURFACE DEW POINTS MID/UPPER 60S F ALONG THE RETREATING BOUNDARY AND 70S NEAR THE GULF...WITH WARM-SECTOR PW OF 1.25-1.5 INCHES BEING COMMON. OVER THE DELTA REGION AND EASTWARD TOWARD WESTERN ALABAMA...THIS WILL OFFSET NOCTURNAL/DIABATIC COOLING STABILIZATION ENOUGH TO MAINTAIN EFFECTIVELY SURFACE--BASED INFLOW WELL INTO THE OVERNIGHT HOURS... WITH MLCAPE AROUND 1500-2000 J/KG NEAR I-10 AND 500-1000 J/KG IN NORTHERN PORTIONS OF MISSISSIPPI/ALABAMA AND SOUTHERN TENNESSEE. THE SEVERE THREAT WILL SHIFT EASTWARD ACROSS THE OUTLOOK AREAS OVERNIGHT AND MAY PERSIST TO THE END OF THE PERIOD AS THE CONVECTIVE PLUME REACHES EASTERN TENNESSEE...NORTHWESTERN GEORGIA...AND EASTERN/SOUTHERN ALABAMA. ...NORTHERN TENNESSEE TO CENTRAL KENTUCKY... SCATTERED THUNDERSTORMS ARE EXPECTED TO PASS ACROSS THIS AREA ROUGHLY AFTER 03Z...IN TWO EPISODES THAT MAY MERGE ON THE NORTHERN END: 1. NORTHEASTWARD-MOVING...MAINLY ELEVATED ACTIVITY IN A STRONG WARM-ADVECTION PLUME ALONG AND NORTHEAST OF THE RETREATING OUTFLOW BOUNDARY...AND 2. THE NORTHEAST SEGMENT OF THE PRIMARY SW-NE CONVECTIVE BAND SHIFTING EAST-NORTHEASTWARD INTO WHATEVER REMAINS OF THE WARM SECTOR. FAVORABLE SURFACE-BASED DESTABILIZATION THIS EVENING...BEHIND THE RETREATING OUTFLOW AIR AND PRIOR TO PASSAGE OF THE MAIN NEAR-FRONTAL THUNDERSTORM BAND...BECOMES MORE UNCERTAIN WITH NORTHEASTWARD EXTENT FROM MIDDLE TENNESSEE ACROSS CENTRAL/SOUTHERN KENTUCKY. ASSORTED PLANAR PROGS AND MODEL FORECAST SOUNDINGS VARY CONSIDERABLY ON THE MAGNITUDE OF AVAILABLE BUOYANCY FOR CONVECTION -- MAINLY RELATED TO TIMING OF EROSION OF STATIC STABILITY FROM RAIN-COOLED ANTECEDENT AIR. HOWEVER THERE IS REASONABLE AGREEMENT IN PRINCIPLE ON A NORTHEASTWARD DIMINISHING OF BOTH AVAILABLE THETA-E AND DURATION OF WARM-SECTOR INFLOW FOR ANY CONVECTION THAT DOES MOVE ACROSS THIS AREA. TO REFLECT THESE UNCERTAINTIES...UNCONDITIONAL SEVERE PROBABILITIES DECREASE STEADILY NORTHEASTWARD ACROSS KENTUCKY... THOUGH THE ACTUAL SEVERE THREAT LIKELY WILL HAVE A SHARP NORTHERN BOUND SOMEWHERE IN THAT PROBABILITY GRADIENT. ..EDWARDS/MOSIER.. 11/29/2016 Link to comment Share on other sites More sharing options...
jaxjagman Posted November 29, 2016 Author Share Posted November 29, 2016 NAM4k..S/MID/TN Valley Link to comment Share on other sites More sharing options...
nrgjeff Posted November 29, 2016 Share Posted November 29, 2016 No heart for severe wx today, not even a desk chase overnight. Was looking for downed trees and power lines on the OBS thread. Figure we are all horrified by what we see in/around Gatlinburg. Anyway we have another safety issue tonight, with a late night nocturnal severe wx threat for MS/AL, perhaps southern middle Tenn. Nobody should chase that crap at night. The following is more for the information and safety. Warm front lifting north is dangerous. People will goto bed in what feels like stable conditions. In fact the soundings may be fairly stable early, before quickly destabilizing. Deep layer and low level shear will both be very high. CAPE is somewhat conditional, but surging dews will bring low LCLs either way. Low CAPE high shear tornado event is possible/probable. Tornado event would be localized, so I am not using outbreak language. Looking at models the EHI numbers are pretty impressive for a low CAPE deal. The shear numbers are quite high for any time of year. Throw a boundary in there and we have a volatile situation overnight. Some research shows the rate of destabilization is more important than the final number. Some high-res models going linear; however, beware in Dixie. Models are programmed for the Plains. Cells will start discrete, perhaps remaining so for a few hours. Also possible an initial line actually breaks up into cells. People need 2-3 ways to be notified, ways that can wake up someone sleeping. Bottom line: Hatched 10% tornado is clearly justified. A small 15% hatched area would not surprise me in later outlooks. Link to comment Share on other sites More sharing options...
jaxjagman Posted November 29, 2016 Author Share Posted November 29, 2016 3 hours ago, nrgjeff said: No heart for severe wx today, not even a desk chase overnight. Was looking for downed trees and power lines on the OBS thread. Figure we are all horrified by what we see in/around Gatlinburg. Anyway we have another safety issue tonight, with a late night nocturnal severe wx threat for MS/AL, perhaps southern middle Tenn. Nobody should chase that crap at night. The following is more for the information and safety. Warm front lifting north is dangerous. People will goto bed in what feels like stable conditions. In fact the soundings may be fairly stable early, before quickly destabilizing. Deep layer and low level shear will both be very high. CAPE is somewhat conditional, but surging dews will bring low LCLs either way. Low CAPE high shear tornado event is possible/probable. Tornado event would be localized, so I am not using outbreak language. Looking at models the EHI numbers are pretty impressive for a low CAPE deal. The shear numbers are quite high for any time of year. Throw a boundary in there and we have a volatile situation overnight. Some research shows the rate of destabilization is more important than the final number. Some high-res models going linear; however, beware in Dixie. Models are programmed for the Plains. Cells will start discrete, perhaps remaining so for a few hours. Also possible an initial line actually breaks up into cells. People need 2-3 ways to be notified, ways that can wake up someone sleeping. Bottom line: Hatched 10% tornado is clearly justified. A small 15% hatched area would not surprise me in later outlooks. Link to comment Share on other sites More sharing options...
jaxjagman Posted December 14, 2016 Author Share Posted December 14, 2016 15% added to the SW Valley http://www.spc.noaa.gov/products/exper/day4-8/# Link to comment Share on other sites More sharing options...
nrgjeff Posted December 14, 2016 Share Posted December 14, 2016 Stout southern stream upper level short-wave comes out Saturday, but most of the low level kinematics is well east due to the main northern stream system. Possibly some of the strong upper level winds mix down again. Regardless it is totally veered off everywhere, good news if you do not like tornadoes. Could be some straight line winds Saturday. SPC does mention the possibility of anafrontal which would shut down severe. Looks like storms will at least try to go in the warm sector. However shallow arctic air could undercut the storms. Despite being a weekend I am not at all excited about the set-up. At least we can catch up some more on much needed rainfall. In other news the KC Chiefs will host the Tennessee Titans in an ice bowl on Sunday. Cheers! Link to comment Share on other sites More sharing options...
jaxjagman Posted December 16, 2016 Author Share Posted December 16, 2016 NAM don't look bad.Might be doing what it does best at this range ,over doing it.GFS isn't horrid as it also shows a tornado threat.Believe though IF the GFS sticks to what it's showing recently that slight risk box will be expanded further N and E the next update.Either way,that's going to be a potent line coming through with some heavy rain. Link to comment Share on other sites More sharing options...
jaxjagman Posted December 16, 2016 Author Share Posted December 16, 2016 Went N and E,thought it'd make it to Nashville Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CST Fri Dec 16 2016 Valid 171200Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY AFTERNOON INTO SATURDAY NIGHT ACROSS THE LOWER MISSISSIPPI VALLEY... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS SURROUNDING AREAS FROM THE GULF COAST INTO THE LOWER OHIO VALLEY... ...SUMMARY... Severe storms are possible Saturday afternoon into Saturday night across the lower Mississippi Valley. Potentially damaging wind gusts may be the primary threat, but a couple of tornadoes are not out of the question. ...Synopsis... A pair of significant short wave impulses, emerging from split branches of westerlies across the eastern Pacific/western North American, appear likely to continue to come increasingly in phase as they turn east northeast of the Rockies through an increasingly confluent regime across the Mississippi Valley during this period. Consolidation of strongest mid-level height falls may not occur until late Saturday evening into early Sunday across the Great Lakes. With a significant reinforcing intrusion of arctic air already ongoing early Saturday across much of the northern and central Plains (in association with the northern branch impulse), surface frontal wave development to the lee of the Rockies may remain relatively subdued, at least until it reaches the lower Great Lakes/St. Lawrence Valley late in the period. Still, as the increasingly sheared southern branch impulse accelerates northeast of the Four Corners region, models generally suggest that pre-frontal south southwesterly 850 mb flow will restrengthen to 50-70 kt across southeastern portions of the Ozark Plateau/Mid South through the Ohio Valley late Saturday afternoon into Saturday Night. This is expected to occur on the southern periphery of strong mid/upper jet intensification, including 110-130+ kt at 500 mb, in a belt across the middle Mississippi Valley into the lower Great Lakes region. Coinciding with these developments, models also all generally indicate a substantive Gulf moisture return in a plume ahead of the arctic front, across the lower Mississippi Valley, through the Ohio Valley and western slopes of the Appalachians. ...lower Mississippi Valley into Ohio Valley... Boundary layer moistening, characterized by lower/mid 60s surface dew points, is expected to contribute to substantive destabilization in at least a pre-frontal corridor across the lower Mississippi Valley. CAPE on the order of 500-1000 J/kg appears likely, in the presence of strong deep layer vertical shear supportive of organized severe storm development. By late afternoon, the southern fringe of strongest mid-level forcing for ascent appears likely to overspread areas near/ahead of a developing wave along the surface frontal zone across parts of eastern Arkansas into western Tennessee. This is expected to provide the support for the initiation of the most significant thunderstorm development. This could include supercells initially, but frontal forcing and largely unidirectional low/mid-level wind profiles may allow for rapid upscale evolution of a squall line, with damaging wind gusts the primary severe weather threat. This activity is expected to tend to develop northeastward and eastward into portions of the Ohio and Tennessee Valleys through Saturday night, where/when the extent of the erosion of an initially cool/cold surface based layer remains the primary uncertainty concerning continuing severe weather potential. Otherwise, despite weaker mid/upper forcing for ascent farther to the south, mid-level inhibition may gradually weaken enough to allow for additional thunderstorm development Saturday night along a pre-frontal low-level confluence zone across parts of Louisiana into Mississippi. This may include discrete supercells, at least initially, with more clockwise curved low-level hodographs appearing to support somewhat greater potential for a couple of tornadoes. Link to comment Share on other sites More sharing options...
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