SWODY1
SPC AC 261231
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0631 AM CST THU FEB 26 2009
VALID 261300Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE MID MO/MID MS
RIVER VALLEY INTO THE MID SOUTH/AR/SERN OK...
...MID MO/MID MS RIVER VALLEYS INTO THE MID SOUTH/AR/SERN OK...
FAST MOVING...LOW-AMPLITUDE SHORTWAVE TROUGH WILL CONTINUE EWD
ACROSS THE CENTRAL PLAINS THIS AFTERNOON AND THE MID/UPPER MS RIVER
VALLEY LATER TONIGHT. ASSOCIATED SURFACE LOW DEVELOPING OVER WRN KS
EARLY THIS MORNING WILL LIKEWISE TRAVERSE ENEWD INTO THE IL/MO/IA
TRI-STATE REGION BY EARLY THIS EVENING...BEFORE LIFTING NEWD ACROSS
SRN LOWER MI OVERNIGHT. EARLY MORNING SURFACE ANALYSES INDICATED
COMPLEX SETUP WITH ARCTIC FRONT ESTABLISHED FROM THE NRN GREAT LAKES
INTO THE NRN HIGH PLAINS...AND A STATIONARY FRONT ERODING FROM THE
ERN GREAT LAKES TOWARDS LOW CENTER OVER NWRN KS. IN ADDITION...WARM
FRONT ALONG LEADING EDGE OF RETURNING GULF MOISTURE IS BECOMING
BETTER DEFINED ACROSS NRN KS INTO THE MID SOUTH. EXPECT WARM FRONT
WILL CONSOLIDATE/BECOME BETTER DEFINED THROUGH THE DAY FROM NRN IL
INTO ERN IA/NWRN MO...WITH STRONG SURFACE COLD FRONT CONTINUING SEWD
IN WAKE OF LOW CENTER THROUGH THE PERIOD.
SEVERE THREAT WILL LIKELY EVOLVE IN TWO MODES/AREAS DURING THE
PERIOD. THE FIRST OF WHICH IS ALREADY UNFOLDING OVER ERN NEB INTO
WRN-SRN IA/NERN KS/NWRN MO WHERE STRONG LOW LEVEL WAA IS LIFTING
PARCELS TO LFC/S BENEATH VERY STEEP MID LEVEL LAPSE RATES. 12Z
SOUNDINGS FROM OAX/SGF/TOP ALL INDICATE 500+ MUCAPE AND 35+ KT
EFFECTIVE SHEAR. ALTHOUGH ACTIVITY WILL REMAIN ROOTED WELL ABOVE
STABLE SURFACE...EVEN WITHIN DEVELOPING WARM SECTOR...VERY STEEP
LAPSE RATES AND 40-50 KT EFFECTIVE SHEAR WILL SUPPORT LARGE HAIL AND
ELEVATED SUPERCELLS ACROSS THIS REGION BEGINNING LATER THIS MORNING
AND CONTINUING ENEWD THROUGH MUCH OF THE DAY. FORECAST SOUNDINGS
INDICATE THIS ACTIVITY WILL LIKELY REMAIN ELEVATED AS IT DEVELOPS
ENEWD ACROSS THE MID MS RIVER VALLEY TODAY. HOWEVER...SHEAR WILL
REMAIN QUITE STRONG AND TRACK OF SURFACE LOW INTO NRN IL SUGGESTS
SURFACE-BASED THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH THE
DAY ALONG AND SOUTHEAST OF THE LOW.
SECOND AREA OF SEVERE THUNDERSTORMS IS EXPECTED TO DEVELOP ALONG THE
COLD FRONT FROM PORTIONS OF S-CENTRAL/SERN MO OR SRN IL INTO SERN OK
LATER THIS EVENING/OVERNIGHT. FORECAST SOUNDINGS MAINTAIN CAPPING
ALONG THE FRONT FOR MUCH OF THE DAYLIGHT HOURS...ALTHOUGH LOW
PROBABILITIES FOR SEVERE THUNDERSTORMS REMAIN WARRANTED OVER ERN KS
INTO NERN OK/SWRN MO IN CASE CAP DOES BREAK DURING THE DAY. MORE
LIKELY SCENARIO...WHICH IS SUPPORTED BY ALL THE OPERATIONAL
MODELS...IS FOR CAP TO WEAKEN ALONG FRONT AS IT INTERACTS WITH
RICHER GULF MOISTURE AND DEEP ASCENT BEGINS TO OVERSPREAD IT TOWARDS
06Z. BY THIS TIME...FRONT SHOULD EXTEND FROM SRN IL INTO SERN OK.
THIS ACTIVITY WILL HAVE THREAT OF NOT ONLY LARGE HAIL...BUT ALSO
SOME RISK OF WIND DAMAGE AND/OR ISOLATED TORNADOES AS STORMS ROOT IN
OR VERY NEAR THE BOUNDARY LAYER AND SHIFT SEWD ACROSS THE MID SOUTH
OVERNIGHT. ALTHOUGH STORMS NEAR AND WEST OF THE MID SOUTH MAY
REMAIN SEVERE INTO THE DAY 2 FORECAST PERIOD...SEVERE THREAT IS
EXPECTED TO DIMINISH WITH EWD EXTENT AS STORMS OVERSPREAD MORE OF
THE OH RIVER VALLEY AND CENTRAL KY/MIDDLE TN INTO EARLY FRIDAY
MORNING.
..EVANS.. 02/26/2009
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