February 20 Severe Weather Threat

[ukrocks]

I'm hearing January of 2008 being mentioned as an analog as well. Not sure if others have heard that too?

[Hoosier]

00z NAM has about 300-500 J/kg MUCAPE into the Lakes while the GFS is less bullish. 

[chase_stormz]

I saw 3/12/12 on the GFS list but didn't even want to mention it. 

 

1/21/1999 as well smh 

[Thunder Road]

With a low as strong as it depicts on the NAM, it will be easy to pump of good moisture and warm air, despite having lots of snow cover, maybe the snow cover could enhance instability 

 

Moisture isn't the problem.  The Gulf is open and we've got wind screaming out of the south transporting plenty (too much) moisture into the GLOV.

 

If anything, the snow keeps any potential instability for being surface-based, since there would be a sharp inversion in the boundary layer from warmer temps at, say, 850 mb, to a frozen surface on the ground.

[andyhb]

   DAY 3 CONVECTIVE OUTLOOK  

   NWS STORM PREDICTION CENTER NORMAN OK

   0229 AM CST TUE FEB 18 2014

 

   VALID 201200Z - 211200Z

 

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM ROUGHLY THE MS VALLEY

   REGION EWD TO THE APPALACHIANS...AND FROM SRN PORTIONS OF THE GREAT

   LAKES SWD TO THE GULF COAST...

 

   ...SYNOPSIS...

   LARGE-SCALE UPPER TROUGHING IS FORECAST TO CONTINUE EXPANDING ACROSS

   THE CENTRAL U.S. WITH TIME...WITH THE ENTIRE U.S. UNDER THE

   INFLUENCE OF CYCLONIC FLOW ALOFT BY THE END OF THE PERIOD.  THIS

   EXPANSION OF LONG-WAVE TROUGHING WILL OCCUR DUE TO THE INTERACTION

   OF TWO SMALLER-SCALE TROUGHS -- ONE ADVANCING EWD AND THEN NEWD

   ACROSS THE CENTRAL U.S. WHILE A SECOND DIGS SEWD OUT OF WRN CANADA

   INTO THE NRN ROCKIES THROUGH THE END OF THE PERIOD.  THE

   INITIAL/CENTRAL U.S. TROUGH -- A VERY INTENSE FEATURE PROGGED TO

   TAKE ON A NEGATIVE TILT AS IT CROSSES THE MID AND UPPER MS/OH

   VALLEYS THROUGH THE SECOND HALF OF THE PERIOD -- WILL BE THE PRIMARY

   FEATURE OF INTEREST WITH RESPECT TO SEVERE CONVECTION THIS PERIOD.

 

   AS THIS SYSTEM ADVANCES/STRENGTHENS...A SURFACE LOW -- PROGGED

   INITIALLY TO LIE INVOF THE KS/MO BORDER AREA -- IS FORECAST TO SHIFT

   RAPIDLY NNEWD AND DEEPEN SUBSTANTIALLY WITH TIME...REACHING THE

   UPPER GREAT LAKES REGION AS A SUB-980 MB CYCLONE BY MIDNIGHT. 

   MEANWHILE...A STRONG/TRAILING COLD FRONT SHOULD EXTEND FROM ROUGHLY

   LK MI SSWWD ACROSS THE LOWER OH/TN/LOWER MS VALLEYS INTO THE WRN

   GULF COASTAL REGION BY SUNSET.  THE FRONT WILL THEN CONTINUE RACING

   EWD ACROSS THE GREAT LAKES/OH VALLEY/MID SOUTH/CENTRAL GULF COASTAL

   REGION OVERNIGHT...AND IS PROGGED TO LIE IN LEE OF THE APPALACHIANS

   BY THE END OF THE PERIOD.  BY MID TO LATE AFTERNOON...THE FRONT

   SHOULD DRIVE DEVELOPMENT OF A LINE OF ORGANIZED/FAST-MOVING

   THUNDERSTORMS BRINGING A RISK FOR SEVERE WEATHER -- MAINLY IN THE

   FORM OF WIDESPREAD DAMAGING WIND GUSTS -- TO AN AREA FROM ROUGHLY

   THE MS VALLEY TO THE APPALACHIANS.

 

   ...IL/ERN MO/ERN AR/LA EWD TO THE APPALACHIANS...

   CONVECTION IS PROGGED TO BE ONGOING AT THE START OF THE PERIOD

   ACROSS PARTS OF ERN KS/MO AND EWD INTO THE OH VALLEY...WITHIN A ZONE

   OF WARM ADVECTION WITHIN THE NE QUADRANT OF THE SURFACE LOW.  BY MID

   AFTERNOON...SURFACE COLD-FRONTAL ADVANCE INTO A

   MOISTENING/DESTABILIZING WARM SECTOR SHOULD YIELD CONVECTIVE

   DEVELOPMENT IN THE ZONE OF STRONG/LINEAR LOW-LEVEL ASCENT...WITH

   STORMS THEN EXPANDING BOTH NE AND SW ALONG THE ADVANCING BOUNDARY. 

   GIVEN THE STRONG DEEP-LAYER WIND FIELD ACCOMPANYING THIS SYSTEM

   DRIVING FAST LINE MOTION...RISK FOR NUMEROUS DAMAGING GUSTS IS

   APPARENT.  ISOLATED TORNADOES WILL ALSO BE POSSIBLE WITHIN THE

   LINE...WHILE ISOLATED/MARGINAL HAIL MAY ALSO OCCUR -- MAINLY NEAR

   AND S OF THE OH VALLEY WHERE A MORE UNSTABLE ENVIRONMENT IS

   EXPECTED.

 

   OVERNIGHT...STORMS WILL ADVANCE RAPIDLY EWD ACROSS THE OH/TN VALLEYS

   AND CENTRAL GULF COAST STATES...WITH ACCOMPANYING SEVERE RISK

   EXTENDING EWD TO THE CENTRAL AND SERN APPALACHIANS THROUGH THE END

   OF THE PERIOD.

 

   ..GOSS.. 02/18/2014

[blue60007]

Euro looks more favorable here for severe weather than the NAM. Looks slower/further west. As well, better instability further north.

[Whitelakeroy]

The warm front with these systems are usually modeled too far north.  The models usually like to bring the right up into MI but they tend to get hung up in IN/OH or near the MI border.  Many perfect set ups in the models end up a bit further south.

 

It will be interesting to see how this unfolds.

[hm8]

Kinda surprised with the northern extend of the risk area tbh

[Whitelakeroy]

Kinda surprised with the northern extend of the risk area tbh

Looks to be based on Model output.  It's day 3 so it is what it is.  I wouldn't get my hope high in MI for t-storm (south of I94 maybe).

[Hoosier]

Euro looks more favorable here for severe weather than the NAM. Looks slower/further west. As well, better instability further north.

 

 

At this point I'm still kinda skeptical on how far north the threat gets but the strong forcing and rapid deepening of the surface low is seriously impressive.  Highly anomalous (see my post in the flooding thread about near-record low pressure for February) and I've learned to expect the unexpected when that happens.

[Stebo]

NAM is a bit more ominous especially across the OH Valley, it brings up around 600 J/kg of MLCAPE into the region with the amount of shear in place this would be sufficient to get things to potentially go tornadic. The GFS is slightly lower, but not by much and both models have been inching these numbers upward as we have approached the potential

 

A couple of choice graphics from the NAM:

 

 

[snowlover2]

Small day 2 slight risk added for hail which includes west central MO.

 

 

 

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1055 AM CST TUE FEB 18 2014

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SERN KS INTO CNTRL MO...

...CNTRL PLAINS/MID MS VALLEY/LOWER OH VALLEY...

STRONG MID-LEVEL HEIGHT FALLS...ON THE ORDER OF 150M/12HR...WILL
DEVELOP ACROSS THE CNTRL HIGH PLAINS LATE IN THE PERIOD AS 500MB
SPEED MAX IN EXCESS OF 80KT DIGS ACROSS THE 4-CORNERS REGION INTO
THE TX PANHANDLE. AS THIS FEATURE APPROACHES THE SRN ROCKIES...SFC
WARM FRONT SHOULD RESPOND AND ADVANCE NWD ACROSS THE RED RIVER INTO
NRN OK BY 20/00Z. STRENGTHENING LOW LEVEL WARM ADVECTION ATOP THIS
NWD-ADVANCING BOUNDARY SHOULD INDUCE ELEVATED CONVECTION ACROSS ERN
KS/MO DURING THE LATTER HALF OF THE PERIOD.

LATEST MODEL GUIDANCE SUGGEST 60F SFC DEW POINTS WILL OVERSPREAD THE
WARM SECTOR AS FAR NORTH AS I-40 BY EVENING. THIS MOISTURE SHOULD
SPREAD ATOP RETREATING COOLER LOW LEVEL AIR MASS OVER ERN KS/MO
LIKELY BEING LIFTED NEAR 850MB AS LLJ STRENGTHENS IN EXCESS OF 50KT.
FORECAST SOUNDINGS SUGGEST MID-LEVEL LAPSE RATES...APPROACHING 7.5
C/KM...WILL OVERSPREAD KS WHICH SHOULD SUPPORT MUCAPE AROUND 1500
J/KG ALONG A CORRIDOR FROM SERN KS INTO CNTRL MO. SOUTH OF THIS
ZONE...STRONG CAP ACROSS OK/AR SHOULD PREVENT DEEP CONVECTION FROM
DEVELOPING ACROSS THESE STATES. HAIL SHOULD ACCOMPANY MOIST DEEP
CONVECTION ACROSS THIS REGION AS STRONGLY SHEARED UPDRAFTS SHOULD
ROTATE DUE TO CLOUD LAYER SHEAR OF 80-90KT. LARGE
HAIL...POTENTIALLY THE SIZE OF GOLF BALLS...CAN BE EXPECTED WITH
STORMS THAT DEVELOP DURING THE LATTER HALF OF THE PERIOD.

 

[Thunder Road]

Kinda surprised with the northern extend of the risk area tbh

 

Yup.  I suppose we could get SVR-criteria wind gusts up here with the squall line, but in general I agree.  Even with all the melting happening today and tomorrow, there will still be a lot of snow on the ground Thursday morning in these parts.

[Chicago Storm]

LOT

 

THERE REMAINS STRONG ASCENT AHEAD OF THE LOW...WITH CONSIDERABLE
LLVL SHEAR IN THE LOWEST 0-3KM AGL THUR. WITH MIDLVL CAPE PROGGED
ARND 300-400J/KG...HAVE MAINTAINED THE MENTION OF THUNDER...AND IT
IS CONCEIVABLE THAT SOME OF THE STORMS COULD BECOME STRONG. SPC HAS
CONTINUED THE SLIGHT RISK FOR SEVERE WEATHER THUR...MAINLY ALONG AND
EAST OF A PONTIAC TO GARY LINE. THE MAIN THREAT FROM THUNDERSTORMS
LOOKS TO BE WIND...HOWEVER GIVEN HOW LOW THE FREEZING LEVEL WILL
BE...AND WITH THE SHEAR IN THE LLVLS...IT IS POSSIBLE FOR AN
ISOLATED TORNADO.

[Stebo]

IWX

 

THREAT FOR SEVERE WEATHER STILL LOOMS THURSDAY AFTERNOON/EVENING BUT
VERY QUESTIONABLE DESPITE IMPRESSIVE KINEMATICS EXPECTED. 850 MB
JET OF 60 TO 80 KTS AND 0-1KM HELICITY IN EXCESS OF 500 WITH OVER 60
KTS OF SHEAR IN THE SAME LAYER. IN ADDITION...LEFT FRONT QUAD OF 130
KT JET STREAK WILL BE ARRIVING NEAR OR JUST BEHIND THE FRONT.
INSTABILITY PARAMETERS NOT AS IMPRESSIVE BY NORMAL CONVECTIVE
STANDARDS...BUT CONSIDERING WE ARE TALKING MID FEBRUARY...SHOWALTER
VALUES NEAR OR JUST BELOW ZERO AND MID LEVEL LAPSE RATES OF 6.5 TO
LOCALLY AS HIGH AS 8 C/KM ARE DEFINITELY ATTENTION GRABBING. AS
WOULD BE EXPECTED...SFC DEWPTS WON`T BE EXTREME BUT SURGE OF UPR 40
TO AROUND 50 F MAKES A RUN FOR SE AREAS IN THE 21Z THUR TO 02Z FRI
RANGE. LOOKING BACK AT CIPS ANALOGS...AT MOST A HANDFUL OF SEVERE
EVENTS HAVE OCCURRED THIS FAR NORTH OVER THE WINTER MONTHS. THE
INTERESTING POINT OF THESE WAS THERE WAS GENERALLY NO SNOWPACK IN
PLACE. WHILE WE WILL BE WORKING ON OUR SNOWPACK ACROSS THE AREA OVER
THE NEXT COUPLE DAYS AND MOST AGGRESSIVELY THURSDAY...WILL BE
INTERESTING TO SEE POTENTIAL IMPACTS WITH POSSIBLE STRUGGLE BETWEEN
WAA AND THE MELTING SNOWPACK/RESULTANT BOUNDARY LAYER CONDITIONS.
REGARDLESS...THE THREAT STILL EXISTS FOR A LINE OF LOW TOPPED
SHOWERS/STORMS TO SWEEP THROUGH LATE THURS AFTN INTO THE EVENING
ESPECIALLY ACROSS SE PORTIONS OF THE AREA. SPC DAY3 OUTLOOK HAS
ENTIRE FORECAST AREA IN SLGT RISK WITH HIGHEST PROBS JUST GRAZING
FAR S SECTIONS WITH GREATER FOCUS INTO CENTRAL INDIANA/OHIO.
OVERNIGHT SHIFT ADDED WIND MENTION TO HWO AND FOR THE TIME BEING
THIS WILL WORK WITH CONTINUED MONITORING AS WE DRAW CLOSER TO THE
EVENT.

[Stebo]

Another NAM run another inch upward in instability, 4km NAM is even higher with instability.

 

 

If this type of instability is realized, it will be a very busy day. By the way, those CAPE values are with a 62 to 67/60 to 63 surface temperature/dew point range in IL/KY, so we aren't talking about unreasonable surface conditions.

[Hoosier]

Risk area almost unchanged from the old day 3 outlook

 

...

   DAY 2 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   1251 AM CST WED FEB 19 2014   VALID 201200Z - 211200Z   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE ERN HALF   OF THE U.S. FROM THE MS VALLEY EWD TO THE APPALACHIANS...AND THE   GREAT LAKES SWD TO THE GULF COAST...   ...SYNOPSIS...   A STRONG MID-LEVEL TROUGH INITIALLY MOVING INTO THE PLAINS STATES IS   FORECAST TO SHIFT EWD ACROSS THE PLAINS THROUGH THE AFTERNOON...AND   THEN ACROSS THE MS/OH VALLEYS/UPPER GREAT LAKES OVERNIGHT AS IT   BEGINS TO TAKE ON A NEGATIVE TILT.   AT THE SURFACE...A DEEPENING LOW IS FORECAST TO MOVE NNEWD FROM THE   SERN KS VICINITY TO LK SUPERIOR BY THE END OF THE PERIOD...WHILE A   STRONG/TRAILING COLD FRONT SWEEPS QUICKLY EWD -- CROSSING THE MS   VALLEY THROUGH THE AFTERNOON AND THEN ACROSS THE APPALACHIANS   THROUGH THE END OF THE PERIOD.  THIS FRONT WILL FOCUS A LINE OF   STRONG/SEVERE STORMS FROM AFTERNOON INTO THE OVERNIGHT HOURS.   ...OH/MID AND LOWER MS VALLEYS ACROSS TN INTO THE DEEP SOUTH...   SIMILAR TO THE FORECAST OVER THE PAST COUPLE OF DAYS...A FAIRLY   WIDESPREAD SEVERE WEATHER EPISODE APPEARS LIKELY DAY 2 -- PRIMARILY   THURSDAY AFTERNOON AND EVENING AND INTO THE EARLY MORNING HOURS OF   FRIDAY -- AS A STRONG COLD FRONT AND ASSOCIATED/POWERFUL UPPER STORM   SYSTEM MOVE ACROSS THE CENTRAL AND INTO THE ERN CONUS.   STRONG SLY LOW-LEVEL WINDS ADVECTING MOISTURE NWD WILL SUPPORT   MODEST DESTABILIZATION /GENERALLY AROUND 500 J/KG MIXED-LAYER CAPE/   ALONG THE FRONT...LEADING TO EVENTUAL INITIATION/EXPANSION OF A   FRONTAL LINE OF THUNDERSTORMS.  BY LATE AFTERNOON...A NEARLY   SOLID/FAST-MOVING LINE OF CONVECTION SHOULD STRETCH FROM THE SRN   UPPER GREAT LAKES VICINITY SSWWD INTO THE CENTRAL/WRN GULF COASTAL   REGION -- ACCOMPANIED BY A RISK FOR FAIRLY WIDESPREAD DAMAGING WIND   GUSTS.  IN ADDITION...GIVEN WINDS EXPECTED TO INCREASE   RAPIDLY/SIGNIFICANTLY ABOVE THE SURFACE...A FEW EMBEDDED TORNADOES   WILL BE POSSIBLE WITHIN THE LINE -- PARTICULARLY WITHIN A ZONE IN   THE MID OH/TN VALLEY VICINITY.  LIMITED INSTABILITY SHOULD LIMIT   SEVERE HAIL RISK HOWEVER...PARTICULARLY N OF THE GULF COAST STATES.   OVERNIGHT...STORMS SHOULD REMAIN WELL ORGANIZED/SEVERE AS THEY MOVE   QUICKLY EWD TOWARD/INTO THE APPALACHIANS -- AFTER WHICH SOME   DISRUPTION OF OVERALL STORM INTENSITY/SEVERE RISK MAY OCCUR.   ..GOSS.. 02/19/2014

[LouWX]

Surprised this isn't getting more action. Pretty substantial wind threat with this squall line it appears with LEWP spin ups possible.

Everyone is still hung up on winter I guess? No doubt it appears there's plenty of that left starting next week.

[Hoosier]

SPC giving the snowpack some weight and has chopped of the northern part on the new day 2 outlook.

 

.....

DAY 2 CONVECTIVE OUTLOOK    NWS STORM PREDICTION CENTER NORMAN OK  1111 AM CST WED FEB 19 2014    VALID 201200Z - 211200Z    ...THERE IS A SLGT RISK OF SVR TSTMS OH/MID AND LOWER MS VALLEYS  INTO THE TN VALLEY AND DEEP SOUTH...     ..SYNOPSIS    AN INTENSE TROUGH WILL SHIFT EWD OUT OF THE PLAINS THURSDAY  AFTERNOON AND ACROSS THE MID MS AND OH VALLEYS/SRN GREAT LAKES  REGION BY 12Z FRIDAY. AT THE SURFACE...ASSOCIATED LOW IN THE  VICINITY OF WRN MO AT THE BEGINNING OF THE PERIOD WILL RAPIDLY  INTENSIFY AND LIFT NEWD TOWARD THE UPPER GREAT LAKES. THUNDERSTORMS  ARE EXPECTED TO INCREASE ALONG AN EWD ADVANCING COLD FRONT DURING  THE EARLY AFTERNOON...WITH A DAMAGING WIND THREAT EXTENDING ROUGHLY  ALONG THE I-70 CORRIDOR FROM SRN IL INTO SRN OH SOUTHWARD ACROSS THE  OH/TN VALLEYS INTO THE DEEP SOUTH INTO THE OVERNIGHT HOURS.      ..MID AND LOWER MS VALLEY...OH/TN VALLEY INTO THE DEEP SOUTH    DESPITE WARMING TEMPERATURES THE LAST FEW DAYS...SUBSTANTIAL SNOW  PACK REMAINS ACROSS PARTS OF NRN IL...SRN LOWER MI AND NRN IND/OH.  WHILE THE INTENSIFYING SFC LOW AND APPROACHING SHORTWAVE IMPULSE  WILL LEAD TO STRONG DEEP LAYER FLOW ACROSS THIS REGION...THE  LINGERING SNOW PACK WILL LIMIT SEVERE POTENTIAL NORTH OF THE I-70  CORRIDOR DUE TO A NEAR SURFACE STABLE LAYER AND WEAK BUOYANCY  LIMITING CONVECTIVELY ENHANCED WIND POTENTIAL.    FURTHER SOUTH...ESPECIALLY TOWARD THE LOWER OH AND TN VALLEY...THE  QUALITY OF THE WARM SECTOR AIRMASS AND LOW LEVEL THERMODYNAMICS  /UPPER 50S F DEWPOINTS...0-3 KM LAPSE RATES NEAR 7.0 DEG C PER KM  AND MUCAPE APPROACHING 1000 J PER KG/ SHOULD BE SUFFICIENT TO  SUPPORT MORE ROBUST THUNDERSTORM UPDRAFTS INTO THE EVENING HOURS.  ADDITIONALLY...THE STRENGTH OF LOW LEVEL WIND FIELDS /50+ KT JUST  OFF THE SFC/ COUPLED WITH A FAST MOVING QLCS COULD LEAD TO  WIDESPREAD DAMAGING WINDS ACROSS PARTS OF FAR SRN IND...PARTS OF  WRN/CNTRL KY INTO PORTIONS OF WRN/MIDDLE TN. STRONG LOW LEVEL SPEED  SHEAR COULD LEAD TO A FEW TORNADOES AS WELL.    THUNDERSTORMS WILL CONTINUE TO DEVELOP SOUTHWARD ALONG/JUST AHEAD OF  THE SFC COLD FRONT INTO THE LOWER MS VALLEY WHERE BETTER MOISTURE  AND A WARMER AIRMASS WILL RESIDE. HOWEVER...THIS AIRMASS WILL NOT BE  JUXTAPOSED WITH BETTER KINEMATIC FIELDS AS THE SFC LOW AND SHORTWAVE  TROUGH CONTINUE TO LIFT NEWD. ADDITIONALLY...FORECAST SOUNDINGS  INDICATE A DRY/WARM LAYER AROUND 700 MB WHICH COULD INITIALLY HINDER  UPDRAFT ORGANIZATION/STRENGTH UNTIL AFTER DARK. BUT...STEEP LOW  LEVEL LAPSE RATES AND A FAST MOVING LINE OF STORMS WILL STILL POSE A  DAMAGING WIND THREAT AS THE LINE TRACKS EWD ACROSS THE DEEP SOUTH  OVERNIGHT.    ..LEITMAN/DARROW.. 02/19/2014   

[Whitelakeroy]

Surprised this isn't getting more action. Pretty substantial wind threat with this squall line it appears with LEWP spin ups possible.

Everyone is still hung up on winter I guess? No doubt it appears there's plenty of that left starting next week.

After a couple more weeks cold and I will watch 'Twister' and get into severe weather mode.  Snow still dominating my mind right now. 

[Stebo]

 

SPC giving the snowpack some weight and has chopped of the northern part on the new day 2 outlook.

 

.....

DAY 2 CONVECTIVE OUTLOOK    NWS STORM PREDICTION CENTER NORMAN OK  1111 AM CST WED FEB 19 2014    VALID 201200Z - 211200Z    ...THERE IS A SLGT RISK OF SVR TSTMS OH/MID AND LOWER MS VALLEYS  INTO THE TN VALLEY AND DEEP SOUTH...     ..SYNOPSIS    AN INTENSE TROUGH WILL SHIFT EWD OUT OF THE PLAINS THURSDAY  AFTERNOON AND ACROSS THE MID MS AND OH VALLEYS/SRN GREAT LAKES  REGION BY 12Z FRIDAY. AT THE SURFACE...ASSOCIATED LOW IN THE  VICINITY OF WRN MO AT THE BEGINNING OF THE PERIOD WILL RAPIDLY  INTENSIFY AND LIFT NEWD TOWARD THE UPPER GREAT LAKES. THUNDERSTORMS  ARE EXPECTED TO INCREASE ALONG AN EWD ADVANCING COLD FRONT DURING  THE EARLY AFTERNOON...WITH A DAMAGING WIND THREAT EXTENDING ROUGHLY  ALONG THE I-70 CORRIDOR FROM SRN IL INTO SRN OH SOUTHWARD ACROSS THE  OH/TN VALLEYS INTO THE DEEP SOUTH INTO THE OVERNIGHT HOURS.      ..MID AND LOWER MS VALLEY...OH/TN VALLEY INTO THE DEEP SOUTH    DESPITE WARMING TEMPERATURES THE LAST FEW DAYS...SUBSTANTIAL SNOW  PACK REMAINS ACROSS PARTS OF NRN IL...SRN LOWER MI AND NRN IND/OH.  WHILE THE INTENSIFYING SFC LOW AND APPROACHING SHORTWAVE IMPULSE  WILL LEAD TO STRONG DEEP LAYER FLOW ACROSS THIS REGION...THE  LINGERING SNOW PACK WILL LIMIT SEVERE POTENTIAL NORTH OF THE I-70  CORRIDOR DUE TO A NEAR SURFACE STABLE LAYER AND WEAK BUOYANCY  LIMITING CONVECTIVELY ENHANCED WIND POTENTIAL.    FURTHER SOUTH...ESPECIALLY TOWARD THE LOWER OH AND TN VALLEY...THE  QUALITY OF THE WARM SECTOR AIRMASS AND LOW LEVEL THERMODYNAMICS  /UPPER 50S F DEWPOINTS...0-3 KM LAPSE RATES NEAR 7.0 DEG C PER KM  AND MUCAPE APPROACHING 1000 J PER KG/ SHOULD BE SUFFICIENT TO  SUPPORT MORE ROBUST THUNDERSTORM UPDRAFTS INTO THE EVENING HOURS.  ADDITIONALLY...THE STRENGTH OF LOW LEVEL WIND FIELDS /50+ KT JUST  OFF THE SFC/ COUPLED WITH A FAST MOVING QLCS COULD LEAD TO  WIDESPREAD DAMAGING WINDS ACROSS PARTS OF FAR SRN IND...PARTS OF  WRN/CNTRL KY INTO PORTIONS OF WRN/MIDDLE TN. STRONG LOW LEVEL SPEED  SHEAR COULD LEAD TO A FEW TORNADOES AS WELL.    THUNDERSTORMS WILL CONTINUE TO DEVELOP SOUTHWARD ALONG/JUST AHEAD OF  THE SFC COLD FRONT INTO THE LOWER MS VALLEY WHERE BETTER MOISTURE  AND A WARMER AIRMASS WILL RESIDE. HOWEVER...THIS AIRMASS WILL NOT BE  JUXTAPOSED WITH BETTER KINEMATIC FIELDS AS THE SFC LOW AND SHORTWAVE  TROUGH CONTINUE TO LIFT NEWD. ADDITIONALLY...FORECAST SOUNDINGS  INDICATE A DRY/WARM LAYER AROUND 700 MB WHICH COULD INITIALLY HINDER  UPDRAFT ORGANIZATION/STRENGTH UNTIL AFTER DARK. BUT...STEEP LOW  LEVEL LAPSE RATES AND A FAST MOVING LINE OF STORMS WILL STILL POSE A  DAMAGING WIND THREAT AS THE LINE TRACKS EWD ACROSS THE DEEP SOUTH  OVERNIGHT.    ..LEITMAN/DARROW.. 02/19/2014   

They did add a hatched area from I-64 to I-40 and from MS river to just East of I-65. This is also the area where the best collocation of instability and shear. 

[Hoosier]

MUCAPE values look decent enough for a severe threat even into the Lakes (given impressive dynamics) but it's the SBCAPE/MLCAPE values that are pitiful.  Those values are likely being heavily influenced by the snowpack so if the models are overestimating the effects of the snowpack then we could see an axis of modest SBCAPE/MLCAPE make it farther north.

[Stebo]

MUCAPE values look decent enough for a severe threat even into the Lakes (given impressive dynamics) but it's the SBCAPE/MLCAPE values that are pitiful.  Those values are likely being heavily influenced by the snowpack so if the models are overestimating the effects of the snowpack then we could see an axis of modest SBCAPE/MLCAPE make it farther north.

I agree, another thing that is being overlooked is a hail potential too, wet bulb zeros are around 8000 to 8500' up here. Unlike wind, hail isn't as dependent upon SBCAPE especially if you have sufficient to good MUCAPE and mid-level shear.

[Indystorm]

This will be a very interesting test case to see if the snowpack does enhance low level stability per SPC in constrast to upper level kinematics.  Like Stebo mentioned, hail and heavy rain can be considerable risks for the more northern regions with wind in the Ohio River valley.  Post frontal wind speeds aside, KY looks prime.

[chase_stormz]

If we're going to see any kind of semi-discrete action tomorrow, it is going to occur in the Paducah, KY to Madisonville, KY to Owensboro, KY to Evansville, IN area just South and East of the surface low pressure. I'm not a big fan of the veering surface winds but I'd give it a narrow window of a shot with the incredible dynamics. The shear is off the chart so there's always that chance. There will also be somewhat of a tornado threat as the entire thing becomes a major QLCS mainly in the bow/comma heads. I'm honestly expecting quite a few of those kinds of tornadoes tomorrow along with numerous damaging wind reports. 

[Hoosier]

18z NAM has 700-500 mb lapse rates of 8 C/km in part of the warm sector tomorrow.

[chase_stormz]

18z NAM has 700-500 mb lapse rates of 8 C/km in part of the warm sector tomorrow.

 

Wow! Not to shabby for February! That would really enhance the hail threat IF we were to see any semi-discrete cells develop at the onset. 

[Hoosier]

Wow! Not to shabby for February! That would really enhance the hail threat IF we were to see any semi-discrete cells develop at the onset. 

 

 

Yeah that is really good for this time of year. 

 

As long as it doesn't appear like temps/dews are going to underperform, think there's a reasonably good chance of an outlook upgrade. 

[Chicago Storm]

Odds are the SPC will have to pull the slight risk back NW deeper into IL/IN once again.

...And add on to the hatched area up to a Terre Haute line.

[A-L-E-K]

LOT has severe in p&cs up to I80