SWODY2
SPC AC 011730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT THU MAY 01 2008
VALID 021200Z - 031200Z
...THERE IS A MDT RISK OF SVR TSTMS FROM SERN MO/SWRN IL SWD INTO
ERN TX/LA/NWRN MS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE AREA CENTERED
ALONG THE MS VALLEY...
...SYNOPSIS...
MID AND UPPER LEVEL TROUGH/LOW CENTERED ACROSS THE PLAINS EARLY IN
THE PERIOD IS FORECAST TO MOVE SLOWLY EWD TOWARD THE MO VALLEY WITH
TIME. AS THIS OCCURS...SURFACE COLD FRONT -- TRAILING SSWWD FROM A
LOW INVOF THE MID MO VALLEY -- WILL ALSO PROGRESS EWD/SEWD...MOVING
INTO/ACROSS THE MID MS VALLEY REGION WHILE SHIFTING MORE SLOWLY SEWD
ACROSS THE ARKLATEX REGION AND VICINITY.
ALONG WITH FAVORABLE SHEAR AS A RESULT OF STRONG DEEP-LAYER WIND
FIELD ACCOMPANYING THE UPPER SYSTEM...PERSISTENT NWD FLUX OF
LOW-LEVEL MOISTURE BENEATH FAIRLY STEEP MID-LEVEL LAPSE RATES ALOFT
SHOULD YIELD AN ENVIRONMENT FAVORABLE FOR A POTENTIALLY-SIGNIFICANT
SEVERE WEATHER EVENT -- CENTERED ON THE MID MS VALLEY REGION.
...MS VALLEY REGION FROM SRN WI/ERN IA SWD TO E TX/MS/LA...
THUNDERSTORMS SHOULD BE ONGOING AT THE START OF THE PERIOD ALONG THE
SURFACE FRONT -- LIKELY FROM NRN AND WRN MO SWD TOWARD ERN OK.
THESE STORMS -- AIDED BY MOISTENING/DESTABILIZING ENVIRONMENT AND
FAVORABLE SHER -- WILL LIKELY REMAIN LOCALLY SEVERE THROUGH THE
MORNING. BY EARLY AFTERNOON...COMBINATION OF WARM SECTOR HEATING
AND MOISTENING BENEATH FAVORABLY-STEEP MID-LEVEL LAPSE RATES SHOULD
ALLOW ONGOING STORMS TO INCREASE IN BOTH COVERAGE AND INTENSITY.
THOUGH STRONGEST FLOW ALOFT WILL SPREAD ACROSS NRN PORTIONS OF THE
OUTLOOK AREA...SHEAR MORE THAN SUFFICIENT FOR SUPERCELLS WILL LIKELY
EXTEND ACROSS A LARGE PORTION OF THE WARM SECTOR -- FROM E TX/NRN
LA/WRN MS NWD. ATTM...IT APPEARS THAT THE MOST FAVORABLE
SHEAR/INSTABILITY COMBINATION WILL EXIST BETWEEN 02/21Z AND 03/03Z
FROM ROUGHLY CENTRAL IL/SERN MO SWD ACROSS ERN AR/NWRN MS. ALONG
WITH POTENTIALLY A MORE LINEAR ZONE OF STORMS -- WITH EMBEDDED
ROTATION -- INVOF THE SURFACE FRONT...MORE ISOLATED STORMS ARE ALSO
EXPECTED TO DEVELOP WITHIN THE WARM SECTOR INVOF MORE SUBTLE
BOUNDARIES. GIVEN THE DEGREE OF LOW-LEVEL SHEAR AND DEWPOINTS WELL
INTO THE 60S ACROSS A LARGE AREA...TORNADOES -- A FEW POTENTIALLY
STRONG/LONG-LIVED -- ARE ANTICIPATED. DEGREE OF INSTABILITY ALSO
SUPPORTS LARGE HAIL AND LOCALLY-DAMAGING WINDS WITH
LONG-LIVED/WELL-ORGANIZED STORMS -- BOTH LINEAR AND CELLULAR.
CONVECTION SHOULD CONTINUE SHIFTING EWD ACROSS THE MS VALLEY THROUGH
THE EVENING/OVERNIGHT...AND THOUGH A SLOW DECREASE IN SEVERE THREAT
IS ANTICIPATED WITH THE LOSS OF DAYTIME HEATING...SOME THREAT WILL
LIKELY PERSIST THROUGH 03/12Z.
...IA/SRN WI/NRN IL EWD INTO SRN LOWER MI/NWRN OH...
WHILE LESSER INSTABILITY IS FORECAST ACROSS THIS REGION COMPARED TO
AREAS FURTHER S...SHEAR WILL BE MORE THAN SUFFICIENT FOR
SEVERE/SUPERCELL STORMS. WITH LOW-LEVEL FLOW BACKED NEAR/E OF
SURFACE LOW ACROSS IA DURING THE AFTERNOON...TORNADO THREAT MAY
EXTEND NWWD INTO THIS REGION DESPITE THE LIKELIHOOD OF LESSER
INSTABILITY. OTHER SEVERE/SUPERCELL STORMS WILL LIKELY OCCUR EWD
ACROSS THE MIDWEST/LOWER GREAT LAKES...WHERE PERSISTENT WARM
ADVECTION IS ANTICIPATED.
..GOSS.. 05/01/2008
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