SWODY1
SPC AC 271552
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1052 AM CDT WED MAY 27 2009
VALID 271630Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM SOUTH TX INTO THE LOWER
AND MIDDLE MS VALLEYS...
MORNING U/A ANALYSIS SHOWS BROAD CYCLONIC FLOW ALOFT ACROSS THE
SOUTHERN PLAINS AND LOWER/MID MS VALLEY...WITH 500MB WIND SPEEDS
GENERALLY AOB 30 KNOTS. A SURFACE COLD FRONT HAS PUSHED SOUTHWARD
THROUGH OK AND INTO CENTRAL TX...LEAVING AN ARC OF MOIST/UNSTABLE
AIR FROM SOUTH TX INTO LA...THEN NORTHWARD INTO IL/IND. THESE
REGIONS WILL BE THE THREAT AREA FOR STRONG/SEVERE STORMS TODAY.
...SOUTH TX...
INTENSE THUNDERSTORMS ARE CURRENTLY OCCURRING ALONG A SAGGING
SURFACE BOUNDARY NORTH OF CRP. THIS ACTIVITY WILL MOVE OFFSHORE
EARLY THIS AFTERNOON...LEAVING AN EXTREMELY UNSTABLE AIRMASS ACROSS
DEEP SOUTH TX. FORECAST SOUNDINGS ALONG AND SOUTH OF THE BOUNDARY
INDICATE A RATHER WEAK CAP AND THE RISK OF REDEVELOPMENT OF
SCATTERED CONVECTION DURING PEAK HEATING. STORMS MAY INITIALLY FORM
OVER THE MOUNTAINS OF MEXICO AND SPREAD EASTWARD TOWARD THE
LRD/CRP/BRO AREAS. DEEP LAYER VERTICAL SHEAR PROFILES WOULD FAVOR
SUPERCELL STORM STRUCTURES WITH A RISK OF VERY LARGE HAIL AND
DAMAGING WINDS IF THIS SCENARIO UNFOLDS.
OTHER STORMS MAY DEVELOP THIS AFTERNOON AND EVENING OVER PARTS OF
SOUTHWEST TX AND PROPAGATE SOUTHEASTWARD DOWN THE RIO GRANDE VALLEY
OVERNIGHT. THESE STORMS COULD ORGANIZE INTO AN MCS WITH A RISK OF
ISOLATED SEVERE STORMS.
...LOWER MS VALLEY...
AMPLE MOISTURE AND INSTABILITY ARE PRESENT THIS MORNING OVER MUCH OF
THE LOWER MS VALLEY WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.
RELATIVELY STRONG DAYTIME HEATING WILL LEAD TO A STRONGLY UNSTABLE
AIRMASS BY AFTERNOON WITH MLCAPE VALUES OVER 3000 J/KG. VERTICAL
SHEAR IS WEAK...AND LARGE SCALE FORCING MECHANISMS ARE HARD TO
IDENTIFY. NEVERTHELESS...IT APPEARS LIKELY THAT AT LEAST SCATTERED
THUNDERSTORMS WILL DEVELOP ALONG THIS CORRIDOR WITH A RISK OF HAIL
AND DAMAGING WINDS IN THE STRONGER CORES.
...MID MS VALLEY...
VISIBLE SATELLITE IMAGERY SHOWS GENERALLY CLEAR SKIES OVER SOUTHEAST
MO/SOUTHERN IL. THIS AREA WILL ALSO BECOME QUITE UNSTABLE BY
AFTERNOON WITH MLCAPE OVER 3000 J/KG AND LITTLE CAP. SCATTERED
THUNDERSTORMS ARE EXPECTED TO DEVELOP BY EARLY AFTERNOON OVER MO AND
SPREAD EASTWARD INTO PARTS OF IL/IND/KY BY EVENING. THIS REGION MAY
EXPERIENCE SLIGHTLY STRONGER LARGE SCALE FORCING AS REMNANT
CIRCULATIONS FROM OVERNIGHT CONVECTION OVERSPREAD THE AREA. THIS
MAY IN TURN HELP FOCUS STORMS AND LEAD TO WIDELY SCATTERED SEVERE
STORMS.
...FL...
SCATTERED STRONG STORMS WITH A RISK OF WET MICROBURSTS AND HAIL WILL
BE POSSIBLE ONCE AGAIN OVER THE CENTRAL AND SOUTHERN FL PENINSULA
THIS AFTERNOON. NORTH FL IS IN THE WAKE OF A MID LEVEL SHORTWAVE
TROUGH...AND MAY SEE LOWER COVERAGE OF STORMS THAN THE LAST FEW
DAYS.
..HART/GRAMS.. 05/27/2009
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