Saturday, April 24, 2010

HIGH RISK - Alabama and Mississippi


SPC Convective Outlook, Day One (Saturday 4/24/10)


Tornado Risk


Hail Risk


Severe Wind Risk
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT SAT APR 24 2010

VALID 241200Z - 251200Z

...THERE IS A HIGH RISK OF SVR TSTMS PORTIONS SERN AR...NERN
LA...MS...CENTRAL/NRN AL...

...THERE IS A MDT RISK OF SVR TSTMS ELSEWHERE FROM PORTIONS E TX TO
CENTRAL/NRN LA...AL...WRN GA...TN...SRN/CENTRAL KY...EXTREME SERN
MO...CENTRAL/SRN/ERN AR....

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING MDT RISK...FROM
GULF COAST OF SE TX TO FL PANHANDLE...TO PORTIONS WV/OH...TO
PORTIONS LOWER MO VALLEY REGION...TO E TX....

OUTBREAK OF NUMEROUS SVR TSTMS IS EXPECTED TODAY...GREATEST
CONCENTRATION/INTENSITY OF WHICH SHOULD INCLUDE STG-VIOLENT TORNADO
THREAT AFFECTING MID-SOUTH...MS DELTA REGION...AND TN VALLEY.

...SYNOPSIS...
SPLIT-FLOW PATTERN IN MID-UPPER LEVELS FEATURES CYCLONE INITIALLY
LOCATED OVER CENTRAL HIGH PLAINS...FCST TO MOVE EWD ACROSS KS TO WRN
MO BY 25/00Z AND WEAKEN ALONG WITH ITS SFC MANIFESTATION.
MEANWHILE...STG SHORTWAVE TROUGH AND SPEED MAX ALOFT -- WHICH
COMPRISED MOST OF INITIAL UPPER CYCLONE OVER SWRN CONUS DURING
PREVIOUS FEW DAYS -- IS FCST TO EJECT NEWD FROM CENTRAL TX TO ERN
MO/SRN IL AREA BY 25/00Z...TAKING OVER AGAIN AS PRIMARY 500 MB LOW.
BY THAT TIME...CORRESPONDING SFC CYCLONE WILL FORM ALONG OCCLUSION
TRIPLE POINT E OF ORIGINAL...AND CLOSE TO NEWER MID-UPPER CYCLONE
CENTER. THIS PROCESS WILL RESULT IN REINFORCEMENT/ACCELERATION OF
INITIALLY STALLED FRONTAL SEGMENT NOW OVER SWRN/CENTRAL TX NNEWD
OVER ERN OK. FRONT SHOULD MOVE ACROSS MUCH OF LA...WRN MS AND WRN
PORTIONS TN/KY BY 25/00Z...TO FL PANHANDLE...AL...MIDDLE-ERN TN AND
ERN KY BY END OF PERIOD....WHEN MID-UPPER CYCLONE SHOULD BE OVER NRN
PORTIONS IL/INDIANA...AND SRN LM AREA.

...LOWER MS VALLEY...MID-SOUTH AND TN VALLEY REGIONS...
TSTMS SHOULD BE INCREASING IN COVERAGE/INTENSITY AROUND BEGINNING OF
PERIOD OVER E TX...LA AND ARKLATEX REGION. FOREGOING AIR MASS --
ALREADY MOISTENED/DESTABILIZED FAVORABLY BY PRIOR/OVERNIGHT THETAE
ADVECTION...WILL FURTHER DESTABILIZE AMIDST SFC DIABATIC HEATING.
AMOUNT OF HEATING IS SOMEWHAT IN QUESTION BECAUSE OF POTENTIAL FOR
CLOUD/ANVIL DEBRIS SPREADING DOWNSTREAM IN MID-UPPER LEVELS FROM
EARLY CONVECTION...PERHAPS INCLUDING TEMPORAL EXTENSION OF ACTIVITY
NOW OVER S TX. STILL...AWAY FROM EXISTING CONVECTION...EVERY
REASONABLE SCENARIO INDICATES THAT MLCINH GENERALLY WILL WEAKEN WITH
NWD EXTENT FROM GULF COAST...SUPPORTING EARLY AND RAPID DEVELOPMENT
AND INTENSIFICATION OF TSTMS FROM MID-MORNING THROUGH
MID-AFTERNOON...AND SUSTAINED THREAT SHIFTING EWD AND NEWD ACROSS
OUTLOOK AREA INTO EVENING/OVERNIGHT HOURS.

INTENSE VERTICAL WIND PROFILES WILL SPREAD ACROSS BROAD WARM/MOIST
SECTOR TODAY...MUCH OF WHICH ALREADY IS IN PLACE ACROSS MUCH OF
LA...MS AND COASTAL AL. THIS AIR MASS WILL SPREAD INLAND TOWARD TN
VALLEY AS CONVECTION/PRECIP NOW OVER TN/AL/GA SHIFTS NEWD. SFC DEW
POINTS WILL BE 70S INVOF GULF COAST...TRANSITIONING TO UPPER 60S AS
FAR N AS TN AND LOW-MID 60S TO OH VALLEY. WEAKENING LAPSE RATES
ALOFT AND BUOYANCY WITH NWD EXTENT...FROM TN VALLEY TO OH VALLEY AND
GREAT LAKES...RENDER PROGRESSIVELY MORE CONDITIONAL NATURE TO SVR
THREAT...THOUGH KINEMATIC PROFILES WILL BECOME FAVORABLE OVER VERY
LARGE AREA S OF GREAT LAKES BY EVENING/OVERNIGHT HOURS.

MULTIPLE CONVECTIVE EPISODES AND STORM MODES ARE EXPECTED IN THIS
SITUATION...AGGREGATE OF WHICH SHOULD YIELD DENSE CONCENTRATION OF
SVR EVENTS BY END OF PERIOD ACROSS MDT/HIGH CATEGORICAL RISK AREAS.
THOUGH DISCRETE/CYCLIC TORNADIC SUPERCELLS ARE MOST POTENTIALLY
DANGEROUS THREAT...ESPECIALLY OVER HIGH RISK AREA...CLUSTERED AND
QUASI-LINEAR CONVECTIVE ELEMENTS WITH EMBEDDED BOW/LEWP FORMATIONS
AND SUPERCELLS ALSO APPEAR PROBABLE. STRENGTHENING DEEP-LAYER WINDS
AND RELATED FAST STORM MOTIONS PORTEND LONG TRACKS FOR SUPERCELLS
AND FOR SOME OF THEIR TORNADOES...AS WELL AS FOR SWATHS OF DAMAGING
WIND WITH ANY BOW/LEWP FEATURES. THIS SUPPORTS RATHER ROBUST
PROBABILITIES FOR ALL SEVERE MODES.

PARAMETER SPACES IN FCST SOUNDINGS OVER HIGH RISK AREA -- SHIFTING
NEWD FROM LATE MORNING THROUGH AFTERNOON -- INCLUDE 50-60 KT LLJ
SUPPORTING VERY LARGE HODOGRAPHS WITH 0-1 AND 0-1 KM SRH 300-600
J/KG. ALSO EXPECT 50-60 KT EFFECTIVE SHEAR MAGNITUDES BENEATH
110-140 KT 250 MB JET MAX AND 60-90 KT 500 MB WINDS...POTENTIALLY
JUXTAPOSED WITH MLCAPE 1500-2500 J/KG.

SUPERCELL/TORNADO THREAT MAY CARRY INTO EVENING/OVERNIGHT HOURS OVER
CENTRAL/SRN APPALACHIANS REGION AND WRN GA BEFORE DIMINISHING.

...IA...MO VALLEY REGION...
SCATTERED STG-SVR TSTMS ARE EXPECTED TO DEVELOP ACROSS THIS AREA
INVOF LARGE CYCLONE ALOFT...AS STEEP MID-UPPER LEVEL LAPSE RATES
COLLOCATED WITH BROAD AREA OF LOW-LEVEL CONVERGENCE AND
DIABATIC/DIURNAL DESTABILIZATION OF BOUNDARY LAYER. MAIN CONCERN
WILL BE SVR HAIL...THOUGH POTENTIAL FOR DAMAGING GUSTS EXISTS. SVR
POTENTIAL SHOULD WANE SIGNIFICANTLY AFTER SUNSET.

..EDWARDS/GARNER.. 04/24/2010

CLICK TO GET WUUS01 PTSDY1 PRODUCT

NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
CURRENT UTC TIME: 0614Z (1:14AM), RELOAD THIS PAGE TO UPDATE THE TIME

1 comment:

Storm Chasing Mikey said...

Amazing setup today Mike. Be safe.