Significant Severe Weather Event Possible 4/8-9/15

[TropicalAnalystwx13]

Severe weather events have been few and far between thus far in 2015, but there are at least short-term signs of that changing as we progress deeper into April. Both the GFS and ECMWF are in agreement that a broad trough will push into the West United States by the start of this upcoming week. Ahead of this trough, a surface low is expected to develop over eastern Colorado, supporting a dryline down into western Texas. Appreciable return flow is expected to support dewpoints well into the 60s as far north as central Kansas by Wednesday evening, and the environment is expected to become extremely unstable within the warm sector. A combination of the aforementioned factors is likely to favor convective initiation along the dryline in south-central Kansas and north-central Oklahoma, with at least a few supercells capable of producing tornadoes possible. One main limiting factor is the presence of a cap due to less-than-impressive forcing, and so the number of severe thunderstorms is in question. If the timing of the trough ejection is quicker than currently being forecast, the potential exists for numerous supercells and a significant tornado outbreak. Activity is expected to spread eastward during the day on Thursday.

This morning's SPC update:

SLIGHTLY MORE WIDESPREAD STORM DEVELOPMENT WILL BE POSSIBLE DURING
THE AFTERNOON ON DAY 5 /WED. 4-8/...AS WEAK HEIGHT FALLS BEGIN AHEAD
OF THE APPROACHING UPPER SYSTEM. WHILE EJECTION OF ANY APPRECIABLE
LEAD WAVE IS NOT EVIDENT ATTM...A LESS SUBSIDENT/MORE NEUTRAL
BACKGROUND LARGE-SCALE UVV SUGGESTS GREATER POTENTIAL FOR CAP
BREACHES/STORM INITIATION -- PRIMARILY ACROSS THE ERN KS/MO/OK
VICINITY. WITH STRONG INSTABILITY AND MODERATELY STRONG SHEAR
EXPECTED...ENVIRONMENT WILL FAVOR SUPERCELLS...AND ASSOCIATED RISK
FOR LARGE HAIL...DAMAGING WINDS...AND POSSIBLE TORNADOES.

WHILE ONGOING CONVECTION OVERNIGHT DAY 5 AND INTO EARLY DAY 6
LIKELY...ASCERTAINING DEGREE AND LOCATION OF SEVERE RISK DAY 6
PRESENTS SOME DIFFICULTY ATTM. WITH THAT SAID...THE ADVANCE OF THE
WRN TROUGH AND ASSOCIATED UVV INTO THE INTO THE CENTRAL PLAINS
DURING THE AFTERNOON AND EVENING WILL PERMIT WIDESPREAD CONVECTIVE
INITIATION -- FOCUSED INVOF THE COLD FRONT FORECAST TO BE ADVANCING
ACROSS ERN KS/CENTRAL OK NEAR PEAK HEATING. WITH SUBSTANTIAL
INSTABILITY LIKELY TO BE PRESENT AND A FAVORABLY SHEARED
ENVIRONMENT...A FAIRLY BROAD AFTERNOON AND EVENING ZONE OF RISK FOR
LARGE HAIL AND DAMAGING WINDS ALONG WITH A FEW TORNADOES IS EVIDENT
-- EXTENDING FROM IL SWWD ACROSS MO/AR INTO SERN KS/ERN OK AND
POSSIBLY INTO N CENTRAL/NERN TX.

[EF-5bigj]

So strong to violent tornadoes are possible?? I'll warn a friend of mine who lives in KS ahead of this event.

[TropicalAnalystwx13]

So strong to violent tornadoes are possible?? I'll warn a friend of mine who lives in KS ahead of this event.

At this point I'm skeptical of a huge outbreak, but several tornadoes, including a few significant ones, may be possible on Wednesday and Thursday.

[EF-5bigj]

We will see how it plays out but I hope there is no large outbreak.

[cycloneye]

The latest is more ominous for day 5.



DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0358 AM CDT SUN APR 05 2015

VALID 081200Z - 131200Z

...DISCUSSION...
APPRECIABLE SPREAD -- EVEN MORE THAN 24 HOURS PRIOR -- IS EVIDENT
AMONGST THE MEDIUM-RANGE MODELS THIS FORECAST...WITH THE GFS
SHIFTING THE WRN TROUGH INTO THE PLAINS FASTER AND WITH MORE OF A
POSITIVE TILT...WHILE THE UKMET AND PARTICULARLY THE ECMWF DEPICT A
SLOWER AND MORE NEUTRAL TO NEGATIVE TILT PROGRESSION. AS A RESULT
OF THESE DIFFERENCES -- AND THE ASSOCIATED VARIANCES IN SURFACE
FEATURE LOCATIONS IN THE DAY 4-5 TIME FRAME...SPECIFICS OF THE
SEVERE WEATHER FORECAST WITH RESPECT TO TIMING/LOCATION REMAIN
DIFFICULT TO ASCERTAIN.

DESPITE TIMING DIFFERENCES WITH RESPECT TO THE MAIN UPPER
LOW/TROUGH...CONFIDENCE HAS INCREASED THIS FORECAST WITH RESPECT TO
SEVERE RISK FOR DAY 4 /WED 4-8/ ACROSS CENTRAL AND ERN OK/ERN KS/MO.
ALL MODELS INDICATE MID-LEVEL HEIGHT FALLS ACROSS THIS AREA...AND
AT LEAST HINTS OF A SUBTLE/EMBEDDED WAVE CROSSING THE REGION NEAR
PEAK HEATING. ATTM...EXPECT RESULTING UVV TO BE SUFFICIENT ATOP THE
EWD-MIXING DRYLINE TO PERMIT CAP WEAKENING SUFFICIENT TO YIELD
ISOLATED TO SCATTERED STORM DEVELOPMENT BY LATE AFTERNOON. WITH A
VERY MOIST BOUNDARY LAYER AHEAD OF THE DRYLINE TOPPED BY STEEP LAPSE
RATES...AND A KINEMATIC ENVIRONMENT FEATURING FLOW THAT VEERS
SUBSTANTIALLY AND INCREASES STEADILY WITH HEIGHT...SHEAR WILL FAVOR
LONG-LIVED SUPERCELLS AND ATTENDANT RISK FOR VERY LARGE
HAIL...DAMAGING WINDS...AND TORNADOES. GIVEN UNCERTAINTY DUE TO
STORM COVERAGE...WILL MAINTAIN ONLY 15% PROBABILITY AREA ATTM --
DESPITE SIGNIFICANT SEVERE WEATHER POTENTIAL WITH ANY STORM THAT
DOES DEVELOP.

THE LIKELIHOOD FOR MORE WIDESPREAD STORMS -- BUT WITH GREATER
UNCERTAINTY IN TERMS OF TIMING AND AREA -- EXISTS DAY 5 /THU 4-9/.
DEEPENING OF THE SURFACE LOW IN THE KS/NEB/IA VICINITY AND ADVANCE
OF A TRAILING COLD FRONT INTO THE CENTRAL/SRN PLAINS WILL FACILITATE
A BROAD ZONE OF STORM INITIATION...GIVEN THE MOIST/FAVORABLY
UNSTABLE AIRMASS EXPECTED. WITH STRONGER FLOW ALOFT AS COMPARED TO
DAY 4 GIVEN PROGRESSION OF THE MAIN MID-LEVEL JET STREAK INTO THE
CENTRAL STATES...SUPERCELL STORMS AND ASSOCIATED RISK FOR VERY LARGE
HAIL...DAMAGING WINDS...AND TORNADOES CAN BE EXPECTED.

MODELS CONTINUE TO DIVERGE DAY 6 AND BEYOND...AND GIVEN THE
INCREASING SPREAD IN SOLUTIONS BETWEEN THEM...LOW CONFIDENCE EXISTS
WITH RESPECT TO EVOLUTION OF SEVERE RISK THROUGH THE SECOND HALF OF
THE PERIOD. THUS...LOW PREDICTABILITY PRECLUDES ATTEMPTS TO
HIGHLIGHT THREAT AREAS BEYOND DAY 5.

..GOSS.. 04/05/2015

[RL3AO]

I think Wednesday has the potential for a couple very strong storms along the dryline in OK/KS. Thursday could be much more widespread as it moves into the Ozarks/Ohio Valley.

Disclaimer: Not an official forecast yada yada...

[TropicalAnalystwx13]

12z GFS supercell composite and crossovers valid at 0z Thursday:

[EF-5bigj]

Well it looks like after a slow start the tornado season will pick up in a big way next week. PDS watch type situation?? Thursday has a 30% severe weather probability.

[RL3AO]

Fairly significant backtracking from the models. They have become more progressive with the trough and no longer eject a negatively tilted trough into the plains. Thursday still looks favorable to severe weather, but maybe not as widespread as originally thought.

GFS for Thursday evening

Yesterday's run

Today's run

[TropicalAnalystwx13]

Fairly significant backtracking from the models. They have become more progressive with the trough and no longer eject a negatively tilted trough into the plains. Thursday still looks favorable to severe weather, but maybe not as widespread as originally thought.

GFS for Thursday evening

Yesterday's run

Today's run

Yep. Although, to be fair, I'm not sure why so much hype was lent to Thursday to begin with. Lesser instability, stronger but more unidirectional shear, and concerns about morning crapvection never had me impressed. That being said, there is still a small area across northern Illinois that looks favorable for at least a brief period of supercells Thursday afternoon.

Wednesday continues to look more favorable to me. Less forcing reduces my concerns about conglomeration, and more directional shear should favor supercells as the primary storm mode. There is still some model variance, with the GFS offering the least impressive setup, the ECMWF offering the most impressive setup, and the NAM serving as a middle ground. The combination of an extremely unstable environment and sufficient shear leads me to believe that even though we may only see a few tornadoes, some of those tornadoes may be significant, and I even wouldn't rule out a violent tornado (especially if the ECMWF is to be believed; 0-3km SRH of 600m2/s2 along the central KS-OK border).

I haven't checked ECMWF, but the GFS is showing a much more pronounced trough crossing the central Plains by the weekend. Busier times ahead, at least in the short term...

[apocalypt-flyer]

Looks like the moisture should be there for several days over the course of the next fortnight - question is how the timing aloft is going to pan out.

As for Thursday, SPC went with ENH, going to be interesting to see how things are going to go over the course of the next two days.

[TropicalAnalystwx13]

Latest SPC Day 2:

...CENTRAL PLAINS INTO LOWER MISSOURI VALLEY...
MODELS CONTINUE TO SUGGEST THAT A SMALLER SCALE...BUT SIGNIFICANT
...SHORT WAVE PERTURBATION WILL PRECEDE OR DEVELOP AHEAD OF THE MAIN
UPPER TROUGH...EAST OF THE CENTRAL ROCKIES...BEFORE PROPAGATING
EASTWARD ACROSS THE PLAINS THROUGH THE MIDDLE MISSISSIPPI/LOWER OHIO
VALLEY DURING THIS PERIOD. IT APPEARS THAT FORCING ASSOCIATED WITH
THIS FEATURE MAY CONTRIBUTE TO THE INITIATION OF CONVECTION RATHER
EARLY...PRIOR TO TYPICAL PEAK LATE AFTERNOON HEATING...AND BEFORE
THE MORE SUBSTANTIVE STRENGTHENING OF LOW-LEVEL FLOW FIELDS
ASSOCIATED WITH THE ANTICIPATED CYCLOGENESIS. STILL..DEEP LAYER
SHEAR SHOULD BE STRONG ENOUGH FOR ORGANIZED CONVECTION...INCLUDING
SUPERCELLS AND AN EVOLVING STORM CLUSTER...IN THE PRESENCE OF
SIZABLE CAPE.

THE SURFACE FRONT/DRYLINE INTERSECTION NEAR THE KANSAS/OKLAHOMA
BORDER AREA MAY PROVIDE THE INITIAL FOCUS FOR THIS EARLY
DEVELOPMENT...BEFORE ACTIVITY SPREADS EAST NORTHEASTWARD ACROSS AND
NORTHEAST OF THE MISSOURI OZARKS THROUGH THE REMAINDER OF THE
AFTERNOON AND EVENING...WITH THE RISK FOR LARGE HAIL AND DAMAGING
WIND GUSTS.

THEREAFTER...TRAILING OUTFLOW...WESTWARD TOWARD THE SURFACE
FRONT/DRYLINE INTERSECTION...IS EXPECTED TO PROVIDE THE FOCUS FOR
PERHAPS THE MOST SUBSTANTIVE/CONCENTRATED NEW THUNDERSTORM
DEVELOPMENT. BY EARLY EVENING THIS SHOULD COINCIDE WITH
STRENGTHENING SOUTHERLY LOW-LEVEL FLOW...AND ENLARGING LOW-LEVEL
HODOGRAPHS...AS THE MAIN SURFACE LOW BEGINS TO DEVELOP EAST OF THE
HIGH PLAINS. THIS MAY BE ACCOMPANIED BY AN INCREASED RISK FOR
SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL AND A COUPLE OF
TORNADOES. INITIALLY ROUGHLY NEAR THE CENTRAL AND EASTERN
KANSAS/OKLAHOMA BORDER AREA...THIS ACTIVITY IS EXPECTED TO SPREAD
NORTHEASTWARD/EASTWARD TOWARD THE LOWER MISSOURI VALLEY...BEFORE
GRADUALLY WEAKENING WEDNESDAY NIGHT.

Latest SPC Day 3:

...GREAT LAKES REGION SSWWD INTO TX...
WIDESPREAD MORNING CONVECTION IS FORECAST ACROSS THE MIDWEST REGION
IN A ZONE OF WARM ADVECTION AHEAD OF THE SURFACE CYCLONE AND
ASSOCIATED/ADVANCING UPPER SYSTEM. WHILE RESIDUAL CONVECTION/CLOUD
COVER COULD ALTER THE LOCATION OF -- OR EVEN HINDER DEVELOPMENT OF
-- THE NEXT ROUND OF AFTERNOON/EVENING STORMS AHEAD OF THE ADVANCING
SYSTEM...IT APPEARS ATTM THAT AMPLE DESTABILIZATION WILL OCCUR AHEAD
OF THE FRONT IN THE WAKE OF PRIOR PRECIPITATION.

PRESUMING THIS INDEED OCCURS...STORM INITIATION WILL BECOME LIKELY
DURING THE AFTERNOON ALONG AND AHEAD OF THE FRONT FROM ERN IA/SRN
WI/IL SWWD ACROSS THE LOWER MO VALLEY/OZARKS/ARKLATEX REGIONS.
THOUGH SOME QUESTIONS EXIST WITH REGARD TO THE THERMODYNAMICS...A
FAVORABLE KINEMATIC ENVIRONMENT IS A MUCH GREATER CERTAINTY...AND
THUS EXPECT DEVELOPING STORMS TO QUICKLY ORGANIZE. STORM MODE
REMAINS DIFFICULT TO DISCERN ATTM...HOWEVER EXPECT SUPERCELL MODE TO
EXIST -- AT LEAST INITIALLY -- WHICH THUS SUPPORTS INTRODUCTION OF
AN SIGNIFICANT SEVERE-WEATHER AREA AND ENHANCED CATEGORICAL RISK
ACROSS IL/ERN MO AND VICINITY...WHERE LARGE HAIL AND DAMAGING WINDS
APPEAR LIKELY ALONG WITH A FEW TORNADOES. SEVERE RISK WILL SPREAD
EWD ACROSS THE MID MS/OH VALLEYS INTO THE EVENING...WITH STORMS
LIKELY TO PERSIST ALONG/AHEAD OF THE FRONT THROUGH THE OVERNIGHT
HOURS.

[EF-5bigj]

There are tornado warnings in IN right now and the trough hasn't even touched that area. I don't know if that bodes well for Wed-thur

[TropicalAnalystwx13]

NWS Wichita excerpt for tomorrow:

STILL LOOKING AT A SIGNIFICANT SEVERE WEATHER EVENT FOR PORTIONS OF
SOUTH CENTRAL KANSAS FOR WED AFTERNOON INTO WED EVENING...AS BULGE
IN THE DRYLINE PUSHES INTO AREAS JUST TO THE WEST OF THE KICT AND
KHUT METRO AREAS. INITIAL SHORTWAVE PUSHES OUT INTO THE PLAINS FOR
THE EARLY AFTERNOON HOURS WED WHICH WILL HELP STORMS DEVELOP. BULK
SHEAR OF 45-50 KTS AND MLCAPE VALUES OF 2200-2500 J/KG SUGGESTS ANY
STORM THAT DEVELOPS WILL RAPIDLY BECOME SEVERE. NOT EXPECTING STORMS
TO BE WIDESPREAD...WITH MORE DISCRETE/ISOLATED SUPERCELLS. BUT
CERTAINLY THINK THERE IS A SIGNIFICANT THREAT OF VERY LARGE HAIL OF
2 INCHES OR GREATER AND DAMAGING STRAIGHT WINDS. 0-3KM SHEAR ALSO
SUGGESTS A TORNADO THREAT...ESPECIALLY AS LOW LEVEL JET INCREASES
AND SURFACE WINDS VEER SOME FORM THE SOUTH TO SOUTHEAST BY AROUND 23-
24Z. 0-8KM SHEAR SUGGESTS ANY TORNADO THAT DEVELOPS...MAY END UP
STAYING ON THE GROUND FOR AWHILE...WITH A POSSIBLE STRONG TORNADO.

[WeatherGuesser]

The two current TOR Warnings are outside the risk area.

One WAY outside, in CA.

[EF-5bigj]

That supercell in KY is pretty impressive.

[WeatherGuesser]

And passing a munitions dump.

[EF-5bigj]

Nocturnal supercells in KS right now.

[TropicalAnalystwx13]

SPC Day 1:

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT WED APR 08 2015

VALID 081200Z - 091200Z

...THERE IS AN ENH RISK OF SVR TSTMS FROM A PORTION OF OK THROUGH
SERN KS...MO INTO WRN IL...

...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE SRN AND
CNTRL PLAINS INTO THE MID MS VALLEY AND OH VALLEY REGIONS...

...THERE IS A MRGL RISK OF SVR TSTMS FROM A PORTION OF THE SRN AND
CNTRL PLAINS THROUGH THE MID MS AND OH VALLEYS...

...SUMMARY...
SEVERE STORMS ACCOMPANIED BY A RISK FOR VERY LARGE HAIL...DAMAGING
WIND AND A FEW TORNADOES ARE EXPECTED ACROSS PARTS OF THE CENTRAL
PLAINS AND LOWER MISSOURI VALLEY WEDNESDAY AFTERNOON AND EVENING.
OTHER STRONG TO SEVERE STORMS MAY DEVELOP OVER A PORTION OF THE OHIO
VALLEY.

...SYNOPSIS...

A LOW-AMPLITUDE PROGRESSIVE SYNOPTIC REGIME WILL CHARACTERIZE THE
UPPER PATTERN WEDNESDAY. UPPER TROUGH NOW MOVING TOWARD THE GREAT
BASIN AREA WILL REACH THE CNTRL HIGH PLAINS WEDNESDAY EVENING. AN
UPPER JET STREAK APPROACHING THE NRN BAJA SHOULD REACH THE SRN
PLAINS DURING THE AFTERNOON.

AT SFC A QUASI-STATIONARY FRONT NOW EXTENDS FROM THE OH VALLEY WWD
TO A SFC LOW OVER NRN MO...SWWD INTO NWRN OK AND THE TX PANHANDLE.
WRN PORTION OF THIS BOUNDARY WILL LIFT NWD AS A WARM FRONT INTO
SRN/CNTRL KS LATER WEDNESDAY AFTERNOON AS A LEE LOW BECOMES
ESTABLISHED OVER THE CNTRL HIGH PLAINS. DRYLINE WILL SHARPEN FROM
SWRN KS INTO THE ERN TX PANHANDLE...SWD THROUGH WRN TX AND MIX EWD
INTO WRN OK BEFORE RETREATING WWD DURING THE EVENING. A PACIFIC
FRONT WILL EVENTUALLY MERGE WITH THE DRYLINE FROM KS THROUGH WRN TX
WEDNESDAY NIGHT.

...SRN AND CNTRL PLAINS THROUGH THE LOWER MO VALLEY...

PARTIALLY MODIFIED GULF AIR IS IN PLACE OVER THE SRN PLAINS...AND
LOW-LEVEL LOW TO MID 60S F DEWPOINTS SHOULD CHARACTERIZE MUCH OF THE
WARM SECTOR DURING THE AFTERNOON. THE 00Z WED RAOBS INDICATE AN EML
WITH STEEP LAPSE RATES HAS ALREADY ADVECTED ABOVE MUCH OF THIS
REGION...AND DIABATIC WARMING OF THE BOUNDARY LAYER SHOULD BOOST
MLCAPE TO 2500-3500 J/KG WEDNESDAY AFTERNOON. ELEVATED STORMS MAY
DEVELOP EARLY IN THE PERIOD NORTH OF THE STALLED FRONT FROM ERN KS
INTO MO...AND SOME OF THIS ACTIVITY MAY POSE A THREAT FOR LARGE
HAIL. CURRENT INDICATIONS ARE THAT MOST OF THE WARM SECTOR WILL
REMAIN CAPPED MUCH OF THE DAY. SOME MODEL SOLUTIONS INITIATE STORMS
BY EARLY AFTERNOON FROM NRN TX INTO OK...BUT THIS ACTIVITY MIGHT BE
MID-LEVEL CONVECTION ROOTED ABOVE THE CAP AND DEVELOPING IN RESPONSE
TO THE SRN-STREAM JET STREAK.

CURRENT THINKING IS THAT SFC-BASED STORMS WILL INITIATE ALONG THE
DRYLINE-FRONT INTERSECTION OVER NCNTRL OK OR SCNTRL KS BY LATE
AFTERNOON...WHILE OTHER MORE ISOLATED ACTIVITY MAY DEVELOP FARTHER
SW FROM THE ERN TX PANHANDLE INTO WRN TX WITHIN ZONE OF DEEP MIXING
ALONG THE DRYLINE. DEEP-LAYER SHEAR PROFILES WILL STRENGTHEN TO
40-50 KT WITH APPROACH OF THE MID-LEVEL JET STREAK SUPPORTIVE OF
SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL. THREAT FOR
TORNADOES /A COUPLE OF WHICH COULD BE STRONG/ WILL ALSO INCREASE BY
LATE AFTERNOON INTO THE EARLY EVENING AS THE LLJ STRENGTHENS IN
ASSOCIATION WITH DEEPENING LEE LOW. ACTIVITY IS EXPECTED TO DEVELOP
NEWD THROUGH THE MID MS VALLEY AREA DURING THE EVENING WITH A
CONTINUED THREAT FOR LARGE HAIL...DAMAGING WIND AND A FEW TORNADOES.
GIVEN THE POTENTIAL FOR SIGNIFICANT SEVERE...AN UPGRADE TO MODERATE
RISK MIGHT BE NEEDED IN LATER UPDATES ONCE MORE CONFIDENCE IS GAINED
REGARDING STORM COVERAGE/EVOLUTION.

...OH VALLEY AREA...

STORMS ARE EXPECTED TO DEVELOP ONCE AGAIN WITHIN THE MODERATELY
UNSTABLE WARM SECTOR OVER THE OH VALLEY GENERALLY ALONG AND SOUTH OF
THE QUASI-STATIONARY FRONT AS THE BOUNDARY LAYER DESTABILIZES.
EFFECTIVE-SHEAR PROFILES FROM 30-40 KT WILL SUPPORT STORM
ORGANIZATION INCLUDING POTENTIAL FOR BOTH MULTICELLS AND SUPERCELLS
WITH DAMAGING WIND AND LARGE HAIL THE MAIN THREATS.

..DIAL/GLEASON.. 04/08/2015

[cycloneye]

Moderate Risk issued



DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1155 AM CDT WED APR 08 2015

VALID 081630Z - 091200Z

...THERE IS A MDT RISK OF SVR TSTMS FROM PARTS OF NRN OK AND SE KS
INTO WRN AND SRN MO...

...THERE IS AN ENH RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA
FROM CNTRL OK ENE INTO SRN IND...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ABOVE AREAS
FROM NW TX TO THE CNTRL APPALACHIANS...

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE ABOVE AREAS
FROM SW TX THROUGH THE OH VLY TO NRN NC...

...SUMMARY...
VERY LARGE HAIL...DAMAGING WIND AND TORNADOES ARE EXPECTED OVER
PARTS OF THE CENTRAL PLAINS AND LOWER MISSOURI VALLEY THIS AFTERNOON
AND EVENING. OTHER STRONG TO SEVERE STORMS MAY DEVELOP FROM PARTS
OF TEXAS NORTHEASTWARD INTO THE OHIO VALLEY AND CENTRAL
APPALACHIANS.

...SYNOPTIC SETUP...
PROGRESSIVE SPLIT FLOW WILL PREVAIL OVER THE CNTRL AND ERN STATES
THROUGH THU...DOWNSTREAM FROM DEAMPLIFYING LARGER-SCALE TROUGH NOW
OVER THE GRT BASIN. THE GRT BASIN TROUGH SHOULD REACH THE CNTRL HIGH
PLNS BY 12Z THU AS A LWR-AMPLITUDE SRN BRANCH DISTURBANCE NOW
CROSSING NRN BAJA ACCELERATES ENE TO FAR W TX THIS EVE AND INTO ERN
OK EARLY THU.

AT THE SFC...APPROACH OF UPR IMPULSES WILL BE ACCOMPANIED BY
DEEPENING/CONSOLIDATION OF LEE LOW OVER SE CO LATER TODAY. THE LOW
SHOULD TRACK ENE ALONG FRONT NOW STALLING OVER NRN OK/SRN KS INTO NW
MO BY THE END OF THE PERIOD. WAVY STNRY/WARM FRONT EXTENDING E FROM
THE LOW...AUGMENTED IN PLACES BY MCS OUTFLOW...WILL BE A FOCUS FOR
PERIODIC STRONG TO SVR TSTMS THROUGH EARLY THU...WITH OTHER STORMS
LIKELY TO FORM LATER TODAY INTO TNGT NEAR THE SFC LOW...AND MORE
ISOLD ACTIVITY SSW ALONG TRAILING DRY LINE.

...MID OH VLY TO CNTRL APPALACHIANS TODAY INTO TNGT...
AREA VWP DATA AND DIURNAL HEATING SUGGEST THAT SW OH SQLN WILL
CONTINUE MAINLY ESE...WITH A CONTINUING RISK FOR SVR WIND/MARGINALLY
SVR HAIL /REF WW 229/. SYSTEM COULD CONTINUE AND/OR PARTIALLY
RE-DEVELOP E OF THE WV MTNS INTO WRN/SRN VA...WITH A CONTINUING RISK
FOR LOCALLY DMGG WIND W AND S OF STALLING BACK-DOOR FRONT.

...MID-MS TO MID OH VLY TODAY/TNGT...
PERSISTENT WAA/MOISTURE TRANSPORT ATOP STALLED FRONT/CONVECTIVE
OUTFLOW IS LIKELY TO YIELD EPISODIC STORMS DEVELOPMENT THROUGH THU
MORNING FROM PARTS OF MO EWD INTO IND/KY. WITH SATELLITE AND RAOB
DATA INDICATING ONLY WEAK DISTURBANCES IN SW FLOW
ALOFT...DEVELOPMENT WILL MOST STRONGLY BE MODULATED BY /1/ DIURNAL
HEATING TODAY...AND /2/ NOCTURNAL ENHANCEMENT OF LLJ TNGT. AMPLE
BUOYANCY /BOOSTED BY EML/ AND DEEP WSWLY SHEAR WILL BE PRESENT FOR
SUPERCELLS...WITH THE STORMS LIKELY EVOLVING INTO COMPLEX
LINES/CLUSTERS POSING A RISK FOR SVR HAIL...DMGG WIND...AND
ESPECIALLY DURING EARLY STAGES OF STORM DEVELOPMENT...TORNADOES.

...SRN/CNTRL PLNS INTO OZARKS LATE THIS AFTN THROUGH EARLY THU...
CONDITIONS MAY BECOME INCREASINGLY FAVORABLE FOR A FEW
LONGER-LIVED...DISCRETE OR SEMI-DISCRETE SUPERCELLS THIS EVE THROUGH
LATE TNGT NEAR AND ENE OF SFC WAVE TRACKING ENE ACROSS S CNTRL KS
AND ADJACENT NRN OK/W CNTRL MO. GIVEN THAT THE LOW-LVL FLOW LIKELY
WILL APPRECIABLY/STRENGTHEN GIVEN BOTH TIME OF DAY AND THE
FAVORABLY-TIMED APPROACH OF BAJA JET MAX...THE CORRESPONDING
INCREASE IN LOW-LVL HODOGRAPH LENGTH AND CURVATURE COULD YIELD AN
ENHANCED RISK FOR A STRONG TORNADO OR TWO. MORE ISOLD TSTMS WITH A
RISK FOR VERY LARGE HAIL AND A COUPLE TORNADOES ARE EXPECTED SSW
ALONG DRY LINE INTO W CNTRL TX.

...LWR MO VLY EWD TO LWR GRT LKS TODAY THROUGH EARLY THU...
SOME RISK ALSO WILL EXIST THROUGH THE PERIOD FOR SCTD SMALL
CLUSTERS/BANDS OF ELEVATED STORMS WITH A POTENTIAL FOR SVR HAIL
FARTHER N OF SFC WAVE AND STNRY/WARM FRONT...WITH ACTIVITY ROOTED
INTO THE 850-700 MB LAYER TAPPING THE PERSISTENT EML ASSOCIATED WITH
THE FAST WSWLY MID-LVL FLOW.

..CORFIDI/MOSIER.. 04/08/2015