Hoosier Posted February 26, 2012 Share Posted February 26, 2012 Not particularly excited about this threat but in order to keep it separated from the winter talk, here we go. Good model agreement on a rather deep low moving into the upper Midwest, which will occlude and bring at least a low end severe weather threat especially on Wednesday. Latest runs of the NAM and GFS bring some CAPE into the region although it is rather marginal with the NAM being the most aggressive. Forecast soundings across the Ohio Valley on Wednesday morning show strong deep layer flow with aforementioned modest CAPE, and somewhat of a stable layer near the surface. Wind looks like the highest threat but the magnitude will be dependent on how efficient that near surface stable layer is. A severe threat may continue into the afternoon. Could envision a slight risk as we get closer, especially for areas south of I-70. Link to comment Share on other sites More sharing options...
Hoosier Posted February 26, 2012 Author Share Posted February 26, 2012 IND ALTHOUGH MODELS DO NOT YET PRODUCE SIGNIFICANT INSTABILITY TUESDAY NIGHT...OTHER INDICES AND SREF POST PROCESSED GUIDANCE...ALONG WITH VERY STRONG LOW LEVEL WIND FIELDS...SUGGEST THUNDER IS A SIGNIFICANT THREAT TUESDAY NIGHT...WITH A MUCH LOWER BUT NONZERO THREAT TUESDAY AFTERNOON AS WELL. WE ARE NOT YET OUTLOOKED FOR SEVERE...BUT IF WAA/MOISTURE TRANSPORT IS ENOUGH TO ALLOW INSTABILITY TO DEVELOP...STRONGLY SHEARED ATMOSPHERE WOULD PROMOTE A SEVERE WEATHER THREAT. WILL HAVE TO MONITOR CLOSELY AS THE WEEK PROGRESSES. Link to comment Share on other sites More sharing options...
Hoosier Posted February 26, 2012 Author Share Posted February 26, 2012 LMK THE BIGGEST QUESTION IS WHETHER THERE WILL BE SURFACE-BASED CONVECTION, AND THE ASSOCIATED SEVERE THREAT. SPC DAY 3 SLIGHT RISK IS WEST OF THE MISSISSIPPI, BUT THE PROBABILITIES EXTEND WELL INTO WEST-CENTRAL KENTUCKY. MODEL SOUNDINGS ARE STABLE, BUT TEMPS ARE TOO COOL. OUR FORECAST IS A FEW DEGREES WARMER, BUT MAY STILL NOT BE WARM ENOUGH, IN WHICH CASE THE SEVERE THREAT WOULD BE MORE SUBSTANTIAL. WILL NOT PLAY IT UP JUST YET BUT THE DYNAMICS ARE ENOUGH TO WARRANT MENTION OF GUSTY WINDS IN THE HWO. Link to comment Share on other sites More sharing options...
Tim from Springfield (IL) Posted February 26, 2012 Share Posted February 26, 2012 ILX: AT THIS TIME...IT IS UNCLEAR WHETHER THE WARM SECTOR WILL MAKE IT ANY FURTHER NORTH THAN SOUTHEASTERN IL BEFORE THE OCCLUDED COLD FRONT PUSHES THROUGH AROUND 06Z WED. THIS WILL IMPACT THE POTENTIAL FOR SEVERE WEATHER...WITH THE GREATER INSTABILITY RESTRICTED TO THE SOUTH AND MORE FAVORABLE WIND FIELDS FURTHER NORTH NEAR THE LOW WHICH IS FORECAST TO MOVE ACROSS NORTHERN IA INTO WI TUESDAY NIGHT. SUFFICIENT BULK SHEAR AND HELICITY WILL EXIST FOR ROTATING UPDRAFTS IF STORMS CAN TAP INTO THE BOUNDARY LAYER...BUT THIS BECOMES LESS LIKELY FURTHER NORTH OF THE WARM FRONT. THERE SHOULD BE AT LEAST SOME ELEVATED INSTABILITY FOR STRONG CONVECTION WHICH WILL HAVE THE POTENTIAL FOR HAIL AND STRONG WINDS. Link to comment Share on other sites More sharing options...
Hoosier Posted February 26, 2012 Author Share Posted February 26, 2012 Interesting to see the NAM bringing MLCAPE in excess of 500 J/kg toward the IN/MI border on Wednesday with surface temps only near 50. Low/mid level lapse rates are pretty decent so that's probably why. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted February 27, 2012 Share Posted February 27, 2012 00z NAM really increases the potential for severe convection across Illinois/Indiana and into Ohio. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted February 27, 2012 Share Posted February 27, 2012 Looks mainly like a forced squall line/mcs type scenario but the 00z NAM brings in 500-1000 ml cape into a good chunk of Indiana and Ohio. As has been the case this year, the models tend to underestimate temperatures with these type of storms and in turn underestimate instability. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2012 Author Share Posted February 27, 2012 Looks mainly like a forced squall line/mcs type scenario but the 00z NAM brings in 500-1000 ml cape into a good chunk of Indiana and Ohio. As has been the case this year, the models tend to underestimate temperatures with these type of storms and in turn underestimate instability. 00z NAM brings mid 50's dewpoints up to LAF-CMH. Link to comment Share on other sites More sharing options...
andyhb Posted February 27, 2012 Share Posted February 27, 2012 00z GFS for the second system...my god... Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2012 Author Share Posted February 27, 2012 There might be some threat almost up to the MI border if the NAM is right. Link to comment Share on other sites More sharing options...
B-Rent Posted February 27, 2012 Share Posted February 27, 2012 You all have a great shot of seeing something Wednesday. I'll be having surgery that morning, by being incapacitated, that greatly increases the threat level. Sent from my ADR6400L Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2012 Author Share Posted February 27, 2012 Huge temperature gradient in northern IN/OH funny finger of higher dews extending back to the surface low Link to comment Share on other sites More sharing options...
andyhb Posted February 27, 2012 Share Posted February 27, 2012 ...and it looks like the first system has trended stronger for this region...this is gonna be a hell of a week for svr wx in all likelihood. Link to comment Share on other sites More sharing options...
andyhb Posted February 27, 2012 Share Posted February 27, 2012 DAY 3 CONVECTIVE OUTLOOKNWS STORM PREDICTION CENTER NORMAN OK 0228 AM CST MON FEB 27 2012 VALID 291200Z - 011200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OH VALLEY STATES TO NRN MS/NRN AL/NRN GA/CAROLINAS... ...SYNOPSIS... PROGRESSIVE UPPER-AIR PATTERN FCST TO CONTINUE ACROSS NRN/WRN CONUS THROUGH PERIOD. LEADING STG SHORTWAVE TROUGH...AND EMBEDDED 500-MB LOW...ARE FCST TO MOVE FROM MN/IA BORDER REGION EWD ACROSS LOWER MI AND LE TO SERN ONT...WRN NY...WRN PA AND WV BY END OF PERIOD. SFC AND MIDLEVEL LOWS WILL BE NEARLY COLLOCATED...THOUGH OCCLUSION/TRIPLE-POINT LOW SHOULD FORM OVER OR JUST OFFSHORE NJ DURING 1/06-1/12Z TIME FRAME. SFC COLD FRONT SHOULD MOVE UP OH VALLEY AND EWD INTO CENTRAL/SRN APPALACHIANS...WHILE TRAILING SEGMENT MORE SLOWLY CROSSES PORTIONS MS/AL/NRN LA AND SE TX. SVR POTENTIAL WILL BE FOCUSED ALONG/AHEAD OF THIS FRONT IN OUTLINED AREA. SWRN-MOST PORTION OF FRONT SHOULD BECOME DIFFUSE AND STALL OVER S TX LATE IN PERIOD...AS WAA REGIME INTENSIFIES ACROSS PLAINS STATES IN ADVANCE OF NEXT SUBSTANTIAL MID-UPPER PERTURBATION. SHORTWAVE TROUGH OVER BERING SEA ATTM SHOULD COMBINE WITH UPSTREAM SPEED MAX AND AMPLIFY...WHILE MOVING SEWD ACROSS NERN PAC AND INTO PAC NW DAYS 1-2. BY START OF DAY-3 PERIOD...EXPECT SYNOPTIC-SCALE TROUGHING TO DEVELOP OVER WRN CONUS...BRACKETED BY BROAD AREA OF CYCLONIC FLOW COVERING ALMOST ALL OF CONUS W OF 100W. LEE TROUGHING WILL OCCUR OVER SRN...CENTRAL AND NRN HIGH PLAINS...THOUGH MOISTURE RETURN INTO THIS REGIME SHOULD BE TOO SCANT TO SUPPORT SVR POTENTIAL UNTIL AFTER PERIOD. ...OH VALLEY TO LOWER MS VALLEY AND AL... BAND OF STG-SVR TSTMS MAY BE ONGOING EARLY IN PERIOD OVER WRN PORTIONS OUTLOOK AREA...AND SHOULD INTENSIFY/REORGANIZE DURING DAY AS FOREGOING AIR MASS DESTABILIZES. MAIN SVR MODE SHOULD BE DAMAGING WIND...THOUGH A FEW TORNADOES AND MRGL-SVR HAIL ARE POSSIBLE. BOUNDARY-LAYER AIR MASS IS FCST TO DESTABILIZE DIURNALLY AHEAD OF FRONT...FROM OH VALLEY SWWD ACROSS TN VALLEY REGION TO PORTIONS LA/MS. ALTHOUGH LAPSE RATES ALOFT WILL BE MRGL...PRIND LOW-LEVEL MOISTURE/HEATING WILL BE SUFFICIENT TO SUPPORT PREFRONTAL CORRIDOR OF 500-1000 J/KG MLCAPE FROM NRN PORTIONS MS/AL AT LEAST AS FAR NE AS CENTRAL/SRN OH. ALTHOUGH DIRECTIONAL SHEAR WILL BE LACKING...STG LOW-MIDDLE LEVEL SPEED SHEAR WILL LENGTHEN HODOGRAPHS AND CONTRIBUTE TO FAVORABLE SRH FOR QUASI-LINEAR CONVECTIVE CIRCULATIONS AND/OR EMBEDDED SUPERCELLS. ORGANIZED SVR POTENTIAL IS EXPECTED TO DECREASE WITH SWD EXTENT ALONG/AHEAD OF FRONT TOWARD GULF COAST...DESPITE GREATER SFC DEW POINTS. WITH UPPER PERTURBATION AND RELATED ISALLOBARIC FORCING MOVING AWAY WELL NE OF LOWER DELTA REGION...SFC FLOW WILL VEER/WEAKEN WITH TIME...REDUCING BOTH LOW-LEVEL CONVERGENCE AND VERTICAL SHEAR. ...CAROLINAS/OVERNIGHT... SECONDARY RELATIVE MAX IN SVR POTENTIAL MAY OCCUR AFTER DARK ACROSS SRN PIEDMONT/COASTAL PLAIN REGION...MAINLY OVER CAROLINAS. THIS MAY TAKE FORM OF NEW DEVELOPMENT OR CONTINUATION OF ACTIVITY FROM NRN PORTIONS GA/AL. MAIN UNCERTAINTY ATTM...ESPECIALLY WITH NEWD EXTENT OVER CAROLINAS...WILL BE HOW MUCH EROSION OF SHALLOW/STABLE LAYER NEAR SFC WILL TAKE PLACE AND PERMIT DAMAGING GUSTS TO REACH SFC. FCST SOUNDINGS SUGGEST EFFECTIVE SFC-BASED PARCELS ARE POSSIBLE....SO WILL INCLUDE CATEGORICAL-CRITERIA PROBABILITIES IN DEFERENCE TO INTENSITY OF WIND FIELDS AND LIKELIHOOD OF AT LEAST MRGLLY FAVORABLE MOISTURE AT AND JUST ABOVE SFC. SRN FRINGE OF MID-UPPER HEIGHT FALLS WITH GREAT-LAKES CYCLONE WILL BRUSH ACROSS THIS AREA DURING 1/03Z-1/09Z TIME FRAME. THIS WILL OVERLAP SOME PERIOD OF FAVORABLE LOW-LEVEL AND DEEP-LAYER SPEED SHEAR BEFORE PREFRONTAL SFC FLOW VEERS UNFAVORABLY IN RESPONSE TO TRIPLE-POINT/MID-ATLANTIC SFC CYCLOGENESIS. ..EDWARDS.. 02/27/2012 Link to comment Share on other sites More sharing options...
Stebo Posted February 27, 2012 Share Posted February 27, 2012 Just to put the graphical representation to the outlook. Link to comment Share on other sites More sharing options...
andyhb Posted February 27, 2012 Share Posted February 27, 2012 ninja'd i'll delete mine Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2012 Author Share Posted February 27, 2012 Have to admit that I wasn't expecting a 30% area yet. The 12z NAM brings instability a bit farther north. Definitely feeling a little better about a severe threat than yesterday. Link to comment Share on other sites More sharing options...
wxdudemike Posted February 27, 2012 Share Posted February 27, 2012 Have to admit that I wasn't expecting a 30% area yet. The 12z NAM brings instability a bit farther north. Definitely feeling a little better about a severe threat than yesterday. What I'm confused about is the CAPE placement seems to lag behind QPF output on where convection lies. Maybe it is better to run off of severe parameters instead of QPF details at this stage of the game though. NAM definitely wants to play ball. The GFS doesn't as much though....At least both models bring in mid 50s dew's. Maybe the GFS is too cool? Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2012 Author Share Posted February 27, 2012 What I'm confused about is the CAPE placement seems to lag behind QPF output on where convection lies. Maybe it is better to run off of severe parameters instead of QPF details at this stage of the game though. NAM definitely wants to play ball. The GFS doesn't as much though....At least both models bring in mid 50s dew's. Maybe the GFS is too cool? I noticed that too. A little unclear whether the best shot at severe will be with preexisting activity moving into the area or redevelopment along the cold front. The latter may be more problematic given that low level convergence will be weakening. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2012 Author Share Posted February 27, 2012 Will be curious to see what kind of low topped storm threat there may be closer to the surface low on Wednesday. 12z NAM has MLCAPE of 500+ J/kg around Chicago into far southern MI. Link to comment Share on other sites More sharing options...
Stebo Posted February 27, 2012 Share Posted February 27, 2012 I noticed that too. A little unclear whether the best shot at severe will be with preexisting activity moving into the area or redevelopment along the cold front. The latter may be more problematic given that low level convergence will be weakening. Redevelopment in the dryslot would be my going bet right now. Though your concern about convergence is a valid concern. Link to comment Share on other sites More sharing options...
AppsRunner Posted February 27, 2012 Share Posted February 27, 2012 ECM has 70f temps approaching the route 6 corridor Wednesday... can't wait Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted February 27, 2012 Share Posted February 27, 2012 NAM continues to clear things out behind the early morning storms, but pushes the best convergence and shear to the East while developing sb instability across Indiana and Ohio by Wednesday Afternoon and Evening. It'll be interesting to see if more storms or a second line of storms can fire by afternoon/evening. If nothing else, the clearing and afternoon sunshine should help increase mixing and increase wind gusts. Link to comment Share on other sites More sharing options...
wxdudemike Posted February 28, 2012 Share Posted February 28, 2012 NAM continues to clear things out behind the early morning storms, but pushes the best convergence and shear to the East while developing sb instability across Indiana and Ohio by Wednesday Afternoon and Evening. It'll be interesting to see if more storms or a second line of storms can fire by afternoon/evening. If nothing else, the clearing and afternoon sunshine should help increase mixing and increase wind gusts. Yeah I'm wondering if it may be a case where we have some decent SB instability and even pretty good shear aloft but lack the surface convergence to fire a good line. Link to comment Share on other sites More sharing options...
andyhb Posted February 28, 2012 Share Posted February 28, 2012 DAY 2 CONVECTIVE OUTLOOKNWS STORM PREDICTION CENTER NORMAN OK 1254 AM CST TUE FEB 28 2012 VALID 291200Z - 011200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS MS/AL TO OH VALLEY AND CAROLINAS... ...SYNOPSIS... PROGRESSIVE AND RATHER HIGHLY AMPLIFIED UPPER-AIR PATTERN FCST THROUGH PERIOD. STG SHORTWAVE TROUGH CURRENTLY LOCATED OVER NV AND SRN CA IS EXPECTED TO DEVELOP EMBEDDED/CLOSED 500-MB LOW DAY-1. THIS LOW WILL REACH SRN MN BY START OF DAY-2 PERIOD...MOVING EWD ACROSS LOWER MI AND LH TO SRN ONT BY 1/12Z. FARTHER UPSTREAM...SERIES OF SHORTWAVE TROUGHS -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER AK AND GULF OF AK -- WILL PHASE WITH SPEED MAX ASSOCIATED WITH PERTURBATION NOW MOVING NEWD ACROSS CENTRAL ALEUTIANS. COMBINED SYSTEM SHOULD AMPLIFY AS IT MOVES SEWD DAY-1...RESULTING IN STG SHORTWAVE TROUGH OVER PAC NW COAST AROUND 29/12Z. NWRN TROUGHING WILL AMPLIFY FURTHER THROUGH DAY-2...YIELDING BOTH UPPER LOW OVER SERN AB/SWRN SK...AND BROADLY CYCLONIC FLOW ACROSS MOST OF CONUS W OF 100W. AT SFC...CYCLONE SHOULD REMAIN ESSENTIALLY STACKED WITH RESPECT TO MIDLEVEL LOW THROUGH PERIOD. SECONDARY LOW SHOULD DEVELOP AT FRONTAL/OCCLUSION TRIPLE POINT DURING 1/00Z-1/06Z TIME FRAME...OVER OR JUST OFFSHORE NJ COAST...AND MOVE EWD ALONG WARM FRONT. AT 29/12Z...COLD FRONT SHOULD EXTEND FROM NRN IL SSWWD ACROSS SERN MO AND NERN THROUGH CENTRAL TX...WITH WARM FRONT FROM NRN IL ESEWD ACROSS OH AND WV. WARM FRONT WILL MOVE SLOWLY NEWD ACROSS OH/WV AND PORTIONS PA BEFORE BEING OVERTAKEN BY COLD FRONT...WHICH SHOULD MOVE SEWD TO VA...NRN AL...CENTRAL MS AND SE TX BY END OF PERIOD. SWRN SEGMENT OF FRONT WILL DECELERATE/WEAKEN OVER MS/LA/TX LATE IN PERIOD. ...MS/AL TO OH VALLEY... SOME SVR POTENTIAL MAY CARRY OVER FROM LATE DAY-1 PERIOD IN FORM OF BAND OF STG-SVR TSTMS OVER AR...SERN MO AND LOWER OH VALLEY. SWWD EXTENT OF BACKBUILDING OF THIS ACTIVITY ACROSS LA AND PERHAPS SE TX REMAINS UNCERTAIN DURING DAY...GIVEN DEPARTURE OF MOST FAVORABLE DEEP-LAYER LIFT WELL NE OF AREA. SVR POTENTIAL...MAINLY DAMAGING WIND BUT WITH TORNADOES POSSIBLE...SHOULD RAMP UP DURING MIDDAY/AFTERNOON HOURS FROM OH TO MS/AL. THERE...STRONGEST LOW-LEVEL LIFT ALONG/AHEAD OF SFC COLD FRONT WILL IMPINGE ON AIR MASS DESTABILIZED BY COMBINATION OF DIABATIC SFC HEATING AND THETAE ADVECTION. SFC DEW POINTS MID-UPPER 50S F SHOULD REACH PORTIONS OH/PA/WRN WV...WITH 60S FROM CENTRAL/ERN KY SWWD ACROSS TN VALLEY REGION. THIS WILL OFFSET MODEST MIDLEVEL LAPSE RATES ENOUGH TO YIELD WEAK CINH...BENEATH ABOUT 500-1000 J/KG MLCAPE...IN PREFRONTAL CORRIDOR THAT GRADUALLY BROADENS WITH SWD EXTENT. VERY STG DEEP-LAYER WINDS ARE FCST...YIELDING EFFECTIVE SHEAR MAGNITUDES 60-75 KT IN MANY FCST SOUNDINGS...DESPITE LACK OF LOW-LEVEL DIRECTIONAL SHEAR. PREDOMINANT QUASI-LINEAR MODE IS EXPECTED. OH VALLEY/APPALACHIANS SVR THREAT WILL DIMINISH WITH TIME DURING EVENING/OVERNIGHT HOURS...FROM N-S...AS CONVECTIVE SYSTEM ENCOUNTERS PROGRESSIVELY MORE STABLE AIR. EXCEPTION MAY BE AROUND SRN RIM OF APPALACHIANS/PIEDMONT...OVER AL/GA INTO CAROLINAS...WHERE BROADER AREA OF FAVORABLE MOISTURE WILL PERSIST...TRANSITIONING INTO OVERNIGHT THREAT. ...OVERNIGHT HOURS...CAROLINAS... CONVECTION MAY MOVE ENEWD INTO THIS REGION FROM SRN PART OF PREVIOUS REGIME...OR DEVELOP ANEW...AFTER 00Z. THIS WILL RESULT IN LOBE OF NOCTURNAL SVR POTENTIAL...WITH DAMAGING GUSTS AND A FEW TORNADOES POSSIBLE. SRN FRINGE OF HEIGHT FALLS ASSOCIATED WITH GREAT LAKES TROUGH WILL BRUSH ACROSS THIS AREA...AS WILL ENHANCED MIDLEVEL HEIGHT GRADIENT AND RESULTANT 55-65 KT 500-MB WINDS. VEERING RELATED TO MID-ATLC LOW GENESIS WILL RENDER DEEP-LAYER WIND PROFILES NEARLY UNIDIRECTIONAL DURING GREATEST CONVECTIVE THREAT...BUT ALSO CHARACTERIZED BY STG SPEED SHEAR THAT WILL ELONGATE LOW-LEVEL HODOGRAPHS. PRIMARY UNCERTAINTY REMAINS DEPTH/MAGNITUDE OF NEAR-SFC STABLE LAYER...WHOSE SLOPE AND DEPTH EACH SHOULD BECOME MORE SHALLOW WITH TIME AMIDST STG LOW-LEVEL THETAE ADVECTION. FCST SOUNDINGS SUGGEST SFC-BASED EFFECTIVE LIFTED PARCELS EVEN WITH SHALLOW SKIN LAYER OF COOLING...THROUGH WHICH DAMAGING GUSTS SHOULD BE ABLE TO PENETRATE. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted February 28, 2012 Share Posted February 28, 2012 12z HRW continues to look impressive early tomorrow across portions of the Ohio Valley. Link to comment Share on other sites More sharing options...
Stebo Posted February 28, 2012 Share Posted February 28, 2012 12z HRW continues to look impressive early tomorrow across portions of the Ohio Valley. What are the lines? 0-3km helicity? The fill I can tell is MLCAPE. Link to comment Share on other sites More sharing options...
Chinook Posted February 28, 2012 Share Posted February 28, 2012 ECM has 70f temps approaching the route 6 corridor Wednesday... can't wait This might be an interesting one. Severe storms on February 29th. How often does that happen? At most, once in four years. I think Toledo and Cleveland may get some gusty storms, with a bigger threat for Cincinnati. Supercell composite value of 12 at Cincinnati. 700mb wind of 60kt at Cincinnati. Link to comment Share on other sites More sharing options...
KokomoWX Posted February 28, 2012 Share Posted February 28, 2012 DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1129 AM CST TUE FEB 28 2012 VALID 291200Z - 011200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID/LOWER MS VALLEY EWD TO THE MID-ATLANTIC/CAROLINA COAST... ..SYNOPSIS A WEAKENING UPPER LOW INITIALLY CROSSING THE MID MO/UPPER MS VALLEYS IS EXPECTED TO CONTINUE MOVING EWD ACROSS THE UPPER GREAT LAKES REGION THROUGH THE PERIOD...AS A SECOND/LARGE TROUGH EXPANDS OVER THE WRN CONUS. ON THE SRN FRINGE OF THESE TWO FEATURES...VERY FAST WLY/WSWLY FLOW ALOFT IS PROGGED FROM THE SOUTHWEST/SRN ROCKIES ACROSS MUCH OF THE CENTRAL AND ERN CONUS. AT THE SURFACE...A DEEP/OCCLUDED LOW IS INITIALLY PROGGED OVER THE SRN MN VICINITY...WITH A COLD FRONT EXTENDING FROM A CENTRAL IL TRIPLE POINT SWWD INTO TX...AND A WARM FRONT DRAPED EWD ACROSS THE OH VALLEY. THE LOW IS FORECAST TO WEAKEN THROUGH THE PERIOD AS IT SHIFTS EWD ACROSS THE UPPER GREAT LAKES...WITH THE TRAILING COLD FRONT LIKEWISE PROGGED TO WEAKEN AS IT CROSSES THE OH/TN VALLEYS THROUGH THE DAY...AND THEN CROSSES THE APPALACHIANS THROUGH THE END OF THE PERIOD. WHILE WEAKENING OVERALL...THIS STORM SYSTEM SHOULD SUPPORT WIDESPREAD CONVECTION AND A FAIRLY LARGE SEVERE THREAT AREA. ..MID/LOWER MS VALLEY EWD TO THE MID-ATLANTIC COAST WIDESPREAD SHOWERS AND THUNDERSTORMS SHOULD BE ONGOING INVOF THE ADVANCING COLD FRONT AT THE START OF THE PERIOD...AND EWD ACROSS THE OH/TN VALLEYS IN THE ZONE OF WARM ADVECTION AHEAD OF THE SYSTEM. THE ONGOING PRECIPITATION/CLOUD COVER ACROSS THE BULK OF THE FORECAST SEVERE RISK AREA WILL ACT TO HINDER HEATING/DESTABILIZATION DURING THE DAY...BUT EXPECT AMPLE CAPE -- AIDED BY NWD ADVECTION OF HIGHER THETA-E AIR -- TO SUPPORT ONGOING STORMS. THOUGH INSTABILITY SHOULD REMAIN LIMITED IN MOST AREAS...VERY STRONG KINEMATIC ENVIRONMENT WILL EXIST...WITH VERY STRONG/QUASI-UNIDIRECTIONAL WSWLY FLOW EXPECTED THROUGHOUT THE CLOUD-BEARING LAYER. WHILE LIMITED POTENTIAL FOR HAIL AND A COUPLE OF ISOLATED TORNADOES APPEARS POSSIBLE...MAIN SEVERE THREAT THIS PERIOD WILL LIKELY BE DAMAGING WINDS -- WITH FAST-MOVING LINES/LINE SEGMENTS. THE GREATEST THREAT SHOULD OCCUR THROUGH THE AFTERNOON ALONG AND WEST OF THE APPALACHIANS -- INCLUDING THE MID AND UPPER OH AND TN VALLEYS. SOME THREAT MAY CROSS THE APPALACHIANS OVERNIGHT AS THE WEAKENING FRONT ADVANCES...WITH THREAT POSSIBLY REACHING THE MID-ATLANTIC/CAROLINA COAST THROUGH THE END OF THE PERIOD. ..GOSS.. 02/28/2012 Link to comment Share on other sites More sharing options...
wxdudemike Posted February 29, 2012 Share Posted February 29, 2012 0z NAM finally busts out a line of convection for us up in central Ohio. Would hate to waste up to 1,000 j/kg mixed layer CAPE Link to comment Share on other sites More sharing options...
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