SWODY1
SPC AC 260550
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1250 AM CDT FRI SEP 26 2008
VALID 261200Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE UPPER MS
VALLEY...
...UPPER MS VALLEY REGION...
BELT OF STRONGER WLYS WILL PERSIST OVER THE NRN PLAINS THIS PERIOD.
A SHORTWAVE TROUGH OVER THE NRN ROCKIES WILL ADVANCE INTO THE UPPER
MS VALLEY FRIDAY AFTERNOON AND PROVIDE IMPETUS FOR A COLD FRONT TO
ADVANCE SEWD THROUGH THE NRN PLAINS AND MN. MODIFIED CP AIR WITH
UPPER 50S TO NEAR 60 DEWPOINTS WILL PERSIST IN PRE-FRONTAL WARM
SECTOR BENEATH 7.5-8C/KM MID-LEVEL LAPSE RATES. BOUNDARY LAYER
WARMING WILL CONTRIBUTE TO FURTHER DESTABILIZATION WITH AXIS OF 1500
J/KG MLCAPE PROBABLE IN ADVANCE OF FRONT. THE BOUNDARY LAYER SHOULD
REMAIN CAPPED UNTIL MID-AFTERNOON WHEN DIABATIC HEATING AND FRONTAL
FORCING AUGMENTED BY APPROACHING SHORTWAVE TROUGH SHOULD WEAKEN
CONVECTIVE INHIBITION SUFFICIENTLY FOR STORMS TO DEVELOP. LARGELY
UNIDIRECTIONAL SWLY BULK SHEAR OF 30-40 KT WILL SUPPORT POTENTIAL
FOR A FEW ORGANIZED STORMS INCLUDING UPDRAFT ROTATION...BUT ACTIVITY
SHOULD EVENTUALLY EVOLVE INTO LINE SEGMENTS. ISOLATED DAMAGING WIND
AND LARGE HAIL WILL BE THE MAIN THREATS THROUGH MID EVENING.
...ERN NC THROUGH MID ATLANTIC REGION...
VERTICALLY STACKED UPPER LOW IS FORECAST TO SLOWLY WEAKEN AS IT
DRIFTS SLOWLY WNWWD INTO A MORE STABLE BOUNDARY LAYER OVER THE WRN
CAROLINAS. MARITIME TROPICAL AIR WILL LIKELY BE ADVECTED WWD ABOVE A
SHALLOW STABLE LAYER REINFORCED BY ONGOING RAIN...BUT THE TRUE
COASTAL FRONT WILL LIKELY REMAIN ACROSS ERN NC NWD INTO SERN VA. THE
ADVECTION OF 70S DEWPOINTS INLAND SHOULD RESULT IN 500-1000 MUCAPE
IN WARM SECTOR...ESPECIALLY WHERE ANY HEATING OCCURS. HODOGRAPHS
WILL BE SUFFICIENT TO MAINTAIN A THREAT FOR AN ISOLATED TORNADO OR
TWO...BUT TREND SHOULD BE FOR LOW LEVEL WIND FIELDS TO GRADUALLY
WEAKEN AS THE UPPER LOW DRIFTS WWD.
..DIAL/GRAMS.. 09/26/2008
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