SWODY2
SPC AC 010559
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT THU MAY 01 2008
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS E TX TO SWRN MS...NNEWD TO
PORTIONS ERN IA...SRN WI AND SWRN LOWER MI...
...SYNOPSIS...
MID/UPPER LEVEL CYCLONE -- INITIALLY EVIDENT IN MOISTURE CHANNEL
IMAGERY FROM ERN GREAT BASIN REGION TO NRN ROCKIES -- IS FCST TO
EVOLVE/CONSOLIDATE INTO DISTINCT CLOSED/OCCLUDING LOW BY START OF
DAY-2 PERIOD...CENTERED OVER WRN/CENTRAL NEB. CYCLONE ALOFT IS
EXPECTED TO FILL AND MOVE SLOWLY EWD OR ENEWD TOWARD MID/UPPER MS
VALLEY THROUGH 3/12Z. ALTHOUGH MOST OPERATIONAL AND SREF PROGS NOW
MAINTAIN CLOSED CYCLONE THROUGH END OF PERIOD...CONSIDERABLE SPREAD
STILL DEVELOPS AFTER 3/00Z REGARDING TRACK...AS SYSTEM INTERACTS
WITH TROUGHING THAT WILL EXTEND SWD FROM LARGER UPPER CYCLONE
RETROGRADING ACROSS HUDSON BAY.
AT SFC...INITIAL/OCCLUDED LOW BENEATH UPPER VORTEX SHOULD WEAKEN
EARLY IN PERIOD...FOLLOWED BY DEEPENING AND OCCLUSION OF
TRIPLE-POINT LOW THAT WILL BE LOCATED INVOF WRN/NRN IA AT 2/12Z. BY
END OF PERIOD...NEW LOW SHOULD DEVELOP AT WARM/COLD FRONT
INTERSECTION INVOF NRN LM OR NRN LOWER MI. TRAILING COLD FRONT IS
FCST TO MOVE EWD ACROSS MID/UPPER MS VALLEY REGION...WHILE
OVERTAKING DRYLINE ACROSS CENTRAL AND NRN TX. WARM FRONT IS FCST TO
DRIFT NWD ACROSS ERN IA AND OVER PORTIONS SRN WI...SRN LM AND SRN
LOWER MI.
...MO/IL TO W GULF COASTAL PLAIN AND SRN MS...
SVR POTENTIAL MAY BE ONGOING FROM DAY-1...PRIMARILY ASSOCIATED WITH
BAND OF TSTMS ALONG OR IMMEDIATELY AHEAD OF SFC COLD FRONT FROM
WRN/CENTRAL IA SSWWD ACROSS WRN/CENTRAL MO...NWRN AR...AND SOME
PORTIONS ERN OK. EARLY-PERIOD BACKBUILDING SWWD ACROSS RED RIVER
INTO NRN/CENTRAL TX IS MORE UNCERTAIN AND CONDITIONAL...BECAUSE OF
CONCERNS OVER COUNTERBALANCING EFFECTS OF STRONGER CAPPING AND
WEAKER FRONTAL LIFT COMPARED TO FARTHER N.
POTENTIAL CONVECTIVE COVERAGE AND INTENSITY EACH SHOULD INCREASE
DURING DAYLIGHT HOURS FROM ARKLATEX REGION EWD ACROSS LOWER MS
VALLEY AMD NNEWD ACROSS ERN MO/IL REGION...AS COMBINATION OF MOIST
ADVECTION AND SFC DIABATIC HEATING EACH BOOST BOUNDARY LAYER THETAE
AND MLCAPES...WHILE WEAKENING CINH. SFC DEW POINTS MID 60S F -- NOW
PRESENT OVER DEEP S TX -- SHOULD EXTEND NWD AT LEAST AS FAR AS ERN
MO AND SRN IL BY 2/18-3/00Z TIME FRAME.
AS WITH MANY SUCH SYSTEMS...STRONGEST DEEP-LAYER WIND PROFILES WILL
BE OVER NRN PORTION OF WARM SECTOR...WHILE STRONGEST DIURNAL
HEATING...MOISTURE AND BUOYANCY WILL BE FARTHER S.
HOWEVER...VERTICAL SHEAR WILL BE FAVORABLE FOR ORGANIZED SVR JUST
ABOUT ANYWHERE ALONG AND JUST AHEAD OF FRONTAL ZONE BETWEEN E
TX....CENTRAL LA AND S-CENTRAL MS NWD. FURTHERMORE...DEEP-LAYER
SHEAR PROFILES WILL SUPPORT TORNADIC SUPERCELLS WITH ANY SUSTAINED
AND RELATIVELY DISCRETE DEVELOPMENT THAT MAY OCCUR AHEAD OF PRIMARY
BAND OF CONVECTIVE FORCING. FOCI FOR SUCH DEVELOPMENT ARE UNCLEAR
ATTM AND PROBABLY WILL BE MESOBETA SCALE OR SMALLER IN NATURE --
E.G. DIFFERENTIAL HEATING BOUNDARIES OR DEEP HCR FEATURES -- E OF
WHAT IS LEFT OF ELEVATED MIXED LAYER PLUME...WHERE CAPPING IS
RELATIVELY WEAK DURING AFTERNOON. SVR POTENTIAL SHOULD SHIFT EWD
ACROSS LOWER/MID MS VALLEY INTO PORTIONS MS AND WRN TN/KY/SRN
INDIANA BEFORE WEAKENING NOCTURNALLY.
...IA TO NRN INDIANA AND LOWER MI...
SMALL WEDGE OF RELATIVELY CONCENTRATED SVR POTENTIAL -- INCLUDING
SUPERCELLS/TORNADOES -- MAY DEVELOP DURING AFTERNOON OVER AREA
ESE-ENE OF SFC LOW AND INVOF WARM FRONT. DURATION AND MAGNITUDE OF
LOW LEVEL DESTABILIZATION WILL STRONGLY INFLUENCE COVERAGE/INTENSITY
OF CONVECTION OVER THIS REGION...WITH GREATEST SVR PROBABILITIES
SHIFTING EWD FROM IA ACROSS NRN IL/SRN WI REGION BETWEEN 2/18-3/00Z
TIME RANGE. ENOUGH UNCERTAINTY REMAINS ATTM TO KEEP ONLY MRGL
PROBABILITIES FOR CATEGORICAL RISK AREA. RELATIVE MIN IN TORNADO
AND SVR WIND POTENTIAL IS FCST OVER SRN LM WHERE RELATIVELY
COOL/STABLE BOUNDARY LAYER IS FCST ABOVE COLD LAKE WATERS.
POCKETS OF CLEARING MAY COMBINE WITH UPPER 50S TO LOW 60S F SFC DEW
POINTS TO CONTRIBUTE TO MLCAPES 500-1000 J/KG. STRONGEST LOW LEVEL
SHEAR SHOULD BE IN REGION OF BACKED FLOW ALONG WARM FRONT...AND JUST
E-SE OF TRIPLE-POINT LOW IN MOIST SECTOR. IN THOSE AREAS...FCST
SOUNDINGS SHOW SOME WEAKNESSES IN SPEED SHEAR AND IRREGULARITIES
WITH DIRECTIONAL SHEAR...HOWEVER LOW LEVEL HODOGRAPHS SHOULD BE
LARGE. SVR RISK MAY EXTEND AS FAR NE AS CENTRAL/ERN LOWER PENINSULA
OF MI...BUT SHOULD WEAKEN AFTER DARK AS BOUNDARY LAYER COOLS.
..EDWARDS.. 05/01/2008
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