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Mar. 27-31 Severe Threats


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0z euro is in for thursday...pockets of 1000+ SB cape in the OV at 18z. pockets of 500+ cape at 4/1 0z. 

 

Surface Low of 990ish SW corner of lower Michigan at 18z. 

 

Surface Low of 990ish just ne of lower michigan at 4/1 0z. 

 

Winds are veered from 18-0z at the surface. 

 

Dews of 55+ throughout the OV north to michigan. 

 

 

Edit: Precip product shows streaks....indicative of bowing segments/supercells?  

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE WILMINGTON OH

 

 

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...

 

-- Changed Discussion --

COUPLE OF IMPORTANT THINGS HAPPEN TONIGHT. FIRST...WEAK SHORTWAVE ENERGY MIGRATING OUT OF TEX/ARK WILL INDUCE CONVECTIVE COMPLEXES WITH ENHANCEMENT OF FORCING FROM SHORTWAVE TROUGH OVER NEB MENTIONED ABOVE. BOTH OF THESE FORCING MECHANISMS WILL MOVE EAST THROUGH THE NIGHT AND IMPINGE ON WRN FLANK OF ATLANTIC LONGWAVE RIDGE AND STILL STRONG HIGH PRESSURE OFF THE ATLANTIC COAST. HEIGHTS/PRESSURES WILL BE DYNAMICALLY DROPPING OVER IA/WI AS PHASING OF THE IA SHORTWAVE TROUGH WITH FURTHER ENERGY DROPPING SOUTH OUT OF CANADA. THIS ALL WILL INDUCE A DRAMATIC INCREASE IN MAGNITUDE OF A MIGRATING LOW LEVEL JET MAXIMA OUT OF THE MS VALLEY AND INTO AND ACROSS THE OHIO VALLEY...BRINGING A RAPID CHANGE IN PWAT. DETERMINISTIC MODELS STILL SHOWING A 70-75KT H85 JET CROSSING THE AREA LATE TONIGHT AND THURSDAY MORNING WITH MOISTURE FLUX ANOMALIES IN EXCESS OF +5 SIGMA AND A VERY STRONG WAA/THETA-E ADV SIGNAL. THIS THERMODYNAMIC FORCING IN ACCORD WITH LIFT FROM THE WEAK SHORTWAVE FROM THE ARK-LA-TEX INTO THE OHIO VALLEY WILL PROMOTE A BAND OF RAIN/SHOWERS TO CROSS THE AREA LATER TONIGHT AND THRU THURS MORNING. CALIBRATED PROBS OF THUNDER AND PLANAR INSTBY INDICES ARE NOT IMPRESSIVE SO EXPECT MOST/ALL OF THIS TO BE THUNDER-FREE...AND BRINGING 0.50" TO 0.75" OF RAIN. THERE IS SOME CONCERN THAT ANOMALOUS LOW LEVEL JET MAY BEGIN TO MIX OUT SOME STRONGER GUSTS ON THE BACK EDGE OF RAIN ON THURSDAY MORNING...BEST CHANCES ACROSS WRN/CNTL OH AND ERN IND WHERE A 40-45 MPH GUST IS POSSIBLE...BUT TEMPORAL NATURE OF THIS THREAT SHOULD BE SHORT/ISOLATED SO NO ADVISORY NOR MENTION IN HWO AT THIS TIME. BIGGER CONCERN FOR IMPACT WEATHER COMES THURS AFTN/EVE IN WAKE OF THIS MORNING RAIN EVENT. THERE/S NOW A BETTER SIGNAL IN HIGHER-RES GUIDANCE THAT A WINDOW OF DRYING /AND PERHAPS SOME INSOLATION/ MAY OCCUR IN THE SUBSIDENCE REGION BEHIND THIS WAVE OF RAIN. WITH STRONG WAA REGIME CONTINUING...TEMPS MAY QUICKLY REBOUND INTO THE LOWER 70S AS DWPTS CONTINUE TO RISE TOWARD 60F IN THE OPEN WARM SECTOR. WHILE PRIMARY SHORTWAVE TROUGH/HEIGHT FALLS WILL GLANCE THE OHIO VALLEY TO THE NORTHWEST...THERE/S ENOUGH HEIGHT FALL TO FORCE COLD FRONT EAST INTO INDIANA AT PEAK HEATING /21Z/ AND INDUCE DEEP MOIST CONVECTION IN A WEAK-MOD UNSTABLE AIRMASS AMIDST VERY STRONG LOW-MID TROPOSPHERIC FLOW. 30.00Z HIRES-W-ARW WRF IS A GOOD REPRESENTATION OF A SCENARIO THAT WOULD BE OF CONCERN...WITH BANDS OF STRONG CONVECTION DEVELOPING OVER IND/KY AND PUSHING EAST INTO THE AREA LATE AFTN/EARLY EVE. FCST SOUNDINGS AND BACKGROUND CALIBRATED PROBS /SREF/ AND OTHER DERIVED FIELDS SUGGEST AN ENVIRONMENT SUPPORTING SVR CONVECTION IN PLACE...WITH STRONG SHEAR AND WEAK-MOD INSTBY. ENOUGH LOW LEVEL DIRECTIONAL/SPEED SHEAR TO HAVE TORNADO CONCERN ESP FOR ANY MORE DISCRETE STORMS FORMING AWAY FROM FRONT. WHILE LATEST SWODY2 HAS FOCUS FURTHER WEST OF ILN CWA...THERE/S MENTION OF EXPANSION BOTH IN THREAT AND SPACE OF SEVERE THREAT IN THE OHIO VALLEY...AND THIS CERTAINLY HAS SUPPORT VIA SREF PROBS...ANALOGS...AND OTHER DERIVED SVR PROB PRODUCTS. THERE/S PLENTY OF UNCERTAINTY AS HIGHLIGHTED NICELY IN SWODY2...AND CONCERNS OF TIMING/FORCING/INSOLATION OF COLD FRONT AND DEGREE OF INSTBY...BUT A SCENARIO EXISTS WHERE WRN 1/2 OF ILN CWA COULD SEE A BIGGER THREAT OF SVR WEATHER THAN WHAT IS CURRENTLY INDICATED SHOULD SEVERAL KEY FEATURES BECOME MORE ALIGNED...AND THIS WOULD INCLUDE TORNADO/LARGE HAIL/DAMAGING WIND THREATS. EVEN MUCH MORE COARSE ECMWF SHOWS A NOTED UPTICK IN CONVECTIVE QPF OVER ILN CWA THURSDAY EVENING. SO FORECAST ALLOWS FOR WIDESPREAD MORNING RAINS...A BRIEF LULL...AND THEN INCREASE IN RAIN/STORM PROBS THURS AFTN INTO EVE AS COLD FRONT CROSSES AREA.

-- End Changed Discussion --

 

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Dr. Forbes seems to be buying into what NAM shows now.

 

12900970_10153513002618201_3768062154189

THURSDAY 3/31

It looks like a complicated day with thunderstorms from overnight already ongoing in the Gulf Coast states with severe continuing or redeveloping from them and another round developing along the cold front behind them. Another concentrated area of severe storms will likely be over the Midwest. Severe thunderstorms in south MI, northeast, central and south IL, IN, north-central and west OH, west and central KY, southeast MO, TN, east AR, AL, northwest GA, MS, LA, extreme east TX, west FL panhandle. TORCON - 5 IN, south IL, west KY, AL, MS; 4- southeast MO, central KY, TN, west OH, northeast LA; 3 other areas above. A lower chance of isolated severe thunderstorms in southwest NC, northeast GA, northwest SC. TORCON - 2.
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Dr. Forbes seems to be buying into what NAM shows now.

 

12900970_10153513002618201_3768062154189

 

 

 

It's looking like a pretty good performance from the NAM and to a lesser extent the ECMWF as far as the slower timing.  NAM was hinting at slower even in its normally bad timeframe.

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It's looking like a pretty good performance from the NAM and to a lesser extent the ECMWF as far as the slower timing.  NAM was hinting at slower even in its normally bad timeframe.

 

I'm somewhat skeptical of how it's handling the low, though. The RAP is starting to come into view and it doesn't seem to really back up the trailing low idea so the NAM is still on it's own with that. It'll be interesting to see what the SPC says for the update coming up.

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Long-range HRRR is about as reliable as hour 84 NAM... but this is looking good so far. Central Illinois is in the clear of rain by 07z. Even if the rain gets pushed back by 5 hours and the rain stops at 12z, there's still plenty of opportunity for clouds to clear up before the front approaches.

 

h3KQjfj.png

 

There's a "warm front" behind that squall in Mississippi... seen very well with the dew points.

 

ElmEjQI.png

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I'm somewhat skeptical of how it's handling the low, though. The RAP is starting to come into view and it doesn't seem to really back up the trailing low idea so the NAM is still on it's own with that. It'll be interesting to see what the SPC says for the update coming up.

SPC seemed to be buying it on the overnight outlook:

 

...

AT SFC...CYCLONE NOW STRENGTHENING OVER IML/OGA REGION IS EXPECTED  TO WEAKEN SOMEWHAT BY START OF DAY-2 PERIOD...BECOMING ELONGATED  AREA OF LOW PRESSURE WITH CENTERS POSSIBLE OVER IA/WI BORDER REGION  AND INVOF MKC...BUT STRETCHED OUT ALONG COLD FRONT.  
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DAY 2 CONVECTIVE OUTLOOK 

NWS STORM PREDICTION CENTER NORMAN OK 

1230 PM CDT WED MAR 30 2016 

VALID 311200Z - 011200Z 

...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PORTIONS MUCH OF 

MS...FAR NE LA/SE AR...W TN/KY...SE IL AND SW IND... 

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE DEEP SOUTH TO LAKE 

MICHIGAN... 

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE NORTHERN GULF COAST TO 

THE MIDWEST AND PORTIONS OF THE CAROLINAS... 

..SUMMARY 

MULTIPLE ROUNDS OF SEVERE THUNDERSTORMS ARE EXPECTED FROM THE LOWER 

MISSISSIPPI VALLEY NORTH AND EAST TO THE MIDDLE MISSISSIPPI AND OHIO 

VALLEYS INTO THE DEEP SOUTH ON THURSDAY. TORNADOES...VERY LARGE HAIL 

AND DAMAGING WINDS ALL WILL BE POSSIBLE. 

..SYNOPSIS 

MULTIFACETED THREAT WILL UNFOLD ON THURSDAY. STRONG VERTICAL SHEAR 

ASSOCIATED WITH LARGER-SCALE UPPER TROUGH WILL COINCIDE WITH 

EXPANDING WARM SECTOR FROM THE GULF COAST TO THE MID-MS/OH VALLEY 

REGION. SPORADIC SEVERE WILL LIKELY BE ONGOING DURING THE MORNING 

ACROSS PARTS OF THE LOWER MS VALLEY WITH BROADER AREA OF 

SHOWERS/THUNDERSTORMS FROM LOWER MI S/SW TO THE MID/LOWER MS VALLEY. 

THIS ACTIVITY SHOULD DIMINISH/SHIFT E/NE TO NEAR OH THROUGH THE 

WESTERN TN VALLEY BY 18Z. AS A RESULT...RECOVERY ACROSS THE WARM 

SECTOR APPEARS LIKELY. A SECOND ROUND OF SEVERE THUNDERSTORMS SHOULD 

THEN EVOLVE ALONG THE SOUTHEASTWARD ADVANCING COLD FRONT DURING THE 

LATE AFTERNOON INTO THE OVERNIGHT HOURS FROM NEAR LAKE MICHIGAN 

SOUTHWARD THROUGH THE DEEP SOUTH. 

..LOWER MS AND TN VALLEYS REGION 

AREAS OF SCATTERED THUNDERSTORM CLUSTERS AND BOWING LINE SEGMENTS 

WILL LIKELY BE PRODUCING AT LEAST ISOLATED SEVERE AT THE BEGINNING 

OF THE PERIOD. ALL HAZARD TYPES WILL BE POSSIBLE WITH THIS INITIAL 

ACTIVITY...THOUGH LARGE HAIL IS THE MAIN CONCERN AS STORMS COULD BE 

SLIGHTLY ELEVATED. ANY STORMS THAT ARE SURFACE BASED HOWEVER WILL 

HAVE AN ACCOMPANYING STRONG WIND AND TORNADO THREAT. THIS ACTIVITY 

SHOULD MIGRATE NORTHEAST AND DIMINISH DURING THE MORNING...WHILE 

LEAVING AN OUTFLOW BOUNDARY AND COLD POOL ACROSS PARTS OF THE 

ARKLAMISS REGION. STRONG WARM ADVECTION REGIME AND AT LEAST MODEST 

SURFACE HEATING SHOULD ALLOW FOR AIRMASS RECOVERY BY THE 

AFTERNOON...THOUGH THERE COULD BE POCKETS WHERE RECOVERY IS POOR IN 

A RELATIVE SENSE...LEADING TO GAPS IN HIGHER PROBABILITY SEVERE. 

UNCERTAINTY IN WHERE THIS MAY OCCUR WILL NEGATE ANY SEPARATION IN 

ENHANCED PROBABILITY AREA. ADDITIONAL UNCERTAINTY EXISTS WITH 

REGARDS TO STORM COVERAGE GIVEN STRONGER FORCING FOR ASCENT WILL BE 

FOCUSED MORE OVER THE MID-MS/OH VALLEY REGION. 

MID TO UPPER 60S DEWPOINTS COUPLED WITH MODERATE INSTABILITY...STEEP 

LAPSE RATES AND STRONG LOW TO MID-LEVEL SHEAR WILL SUPPORT 

SUPERCELLS CAPABLE OF TORNADOES...LARGE HAIL AND DAMAGING WINDS. 

GIVEN THERMODYNAMIC AND KINEMATIC PARAMETER SPACE...SIG SEVERE 

POTENTIAL EXISTS WITH VERY LARGE HAIL AND PERHAPS A STRONG TORNADO 

OR TWO POSSIBLE. DURING THE NIGHT AS A SWLY LLJ INCREASES...STORMS 

MAY CONCEAL INTO AN EASTWARD PROPAGATING BOW/MCS...IMPACTING 

PORTIONS OF AL...MIDDLE/WRN TN AND INTO GA. 

..MID-MS AND LOWER OH VALLEY REGION 

ONGOING CONVECTION AT THE BEGINNING OF THE PERIOD WILL SHIFT 

NORTHEAST TOWARD THE MID/UPPER OH VALLEY AND APPALACHIANS BY MIDDAY. 

GIVEN STRONG SOUTH/SOUTHWESTERLY DEEP LAYER FLOW...MOISTURE WILL 

QUICKLY STREAM NORTHWARD AND HEATING IN THE WAKE OF MORNING 

CONVECTION WILL RESULT IN STRONG DESTABILIZATION WITH SBCAPE VALUES 

APPROACHING 1000 J/KG AS FAR NORTH AND NORTHERN IL/IND INTO FAR SW 

LOWER MI. FURTHER SOUTH ACROSS PARTS OF SOUTHERN IL...AND ADJACENT 

PORTIONS OF THE LOWER OH VALLEY...BETTER MOISTURE WILL RESULT IN 

HIGHER CAPE VALUES...APPROACHING 2500 J/KG. THUNDERSTORMS ARE 

EXPECTED TO DEVELOP ALONG THE SOUTHEASTWARD ADVANCING COLD FRONT 

NEAR THE SFC LOW OVER NRN INTO CNTRL IL BY MID-AFTERNOON AND 

INCREASE IN COVERAGE/INTENSITY WITH SOUTHERN AND EASTERN EXTENT INTO 

PARTS OF SE IL/SW IND/W KY/FAR SE MO. SUPERCELLS WITH ALL SEVERE 

HAZARDS WILL BE POSSIBLE ACROSS THE SLIGHT RISK AREA WITH LARGE HAIL 

BEING THE PRIMARY CONCERN. ACROSS THE ENHANCED RISK AREA...SIG HAIL 

AND A FEW TORNADOES /POTENTIALLY STRONG/ ARE POSSIBLE. THIS ACTIVITY 

SHOULD GROW UPSCALE INTO BOWING SEGMENTS WITH EASTWARD EXTENT 

OVERNIGHT FROM CENTRAL IND/KY INTO OH AND THE APPALACHIANS BY THE 

END OF THE PERIOD.

 

4J33VRq.png

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noice

 

THE MAIN CONCERN FOR SEVERE THUNDERSTORMS WILL BE ON THURSDAY. MODEL
GUIDANCE CONTINUES TO SLOW THE PROGRESSION OF THE SURFACE COLD FRONT
OVER THE AREA ON THURSDAY. AS A RESULT...IT APPEARS THE SEVERE
WEATHER THREAT WILL ALSO EXTEND INTO EASTERN ILLINOIS AND
NORTHWESTERN INDIANA DURING THE LATE MORNING THROUGH AT LEAST THE
MID AFTERNOON HOURS...WHICH LOOKS TO INCLUDE AT LEAST PORTIONS OF
THE CHICAGO AREA. THIS SLOWER FRONTAL TIMING LOOKS TO ALLOW
TEMPERATURES TO WARM WELL INTO THE 60S TO NEAR 70 WITHIN THE
PREFRONTAL AIRMASS...AND THIS IN COMBINATION WITH DEWPOINTS EXPECTED
TO BE NEAR 60 BENEATH A CORRIDOR OF STEEPENING MID-LEVEL LAPSE
RATES...MLCAPE VALUES IN EXCESS OF 1000 J/KG APPEAR TO BE VERY
POSSIBLE. THE KINEMATIC FIELD OVER THE AREA LOOKS
IMPRESSIVE...WITH A MID LEVEL JET (AROUND 500 MB) EXPECTED TO BE
NEAR 70 KT...WHICH SHOULD RESULT IN VERY STRONG DEEP LAYER SHEAR.
A MAINLY UNIDIRECTIONAL SHEAR PROFILE SUGGESTS STRONG AND DAMAGING
WINDS WILL BE GOOD THREAT WITH THESE STORMS. HOWEVER...THERE COULD
ALSO BE DECENT THREATS OF LARGE HAIL GIVEN THE GOOD POTENTIAL FOR
SUPER CELL STORM STRUCTURES.

KJB

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The latest Euro cut the cape amounts quite a bit again. The northern half of IN struggles to break 500.

 

 

Looks like it only gets temps into the low 60s or so.  With 850 mb temps pushing 10C, would take a lot of rain/heavy overcast to keep temps that low.

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FWIW here's the 12Z 4km WRF-NMM for tomorrow at 21Z spitting out an interesting helicity track.

Environment should have unidirectional wind profile/straight line hodograph during this time and place but still interesting it's spitting out an isolated storm like that.

57e8437c4a75ab7437f599e6ef6c3f1d.jpg

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LOT cwa should be in a good position to catch these storms as they develop/mature, with better chances south of I-80 and toward the Indiana border.  Would be much more concerned about a supercell tornado threat into/near the metro area if there was just a bit more directional shear, but can't dismiss it entirely.

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The Springfield to Decatur area has been getting smoked all day. Hearing reports of a house fire caused by lightning as well as a hole blown in the interstate due to lightning.

 

It was on I-72 (near Exit 96) on the south side of Springfield, near Knight's Action Park:

 

https://www.facebook.com/WICSABC20/photos/a.313389284282.183751.296561024282/10154082072639283/?type=3&theater

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