SPC AC 132001
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0301 PM CDT THU MAY 13 2010
VALID 132000Z - 141200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN GREAT LAKES
REGION/OH VALLEY SWWD INTO AR...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF CENTRAL TX AND
INTO THE MID RIO GRANDE VALLEY...
...SRN GREAT LAKES/OH VALLEY REGION INTO SRN MO/NRN AR...
STORMS HAVE REMAINED MORE ISOLATED AND LESS ROBUST THAN PREVIOUSLY
EXPECTED ACROSS MOST OF THE OUTLOOK AREA...DESPITE AMPLE
HEATING/MODERATE DESTABILIZATION. ATTM...EVEN VISIBLE SATELLITE
IMAGERY DOES NOT IMPLY ROBUST DEVELOPMENT...WITH THINKING ATTM THAT
UPPER RIDGING MAY BE HINDERING A MORE WIDESPREAD SEVERE EVENT.
THUS...HAVE GENERALLY SCALED BACK SEVERE WEATHER PROBABILITIES.
HAVING SAID THAT...THREAT FOR LOCALLY-DAMAGING WINDS...HAIL...AND AN
ISOLATED TORNADO OR TWO STILL REMAIN LIKELY...AS THE EWD PROGRESSION
OF THE SURFACE STORM SYSTEM CONTINUES THROUGH THE PERIOD.
HAVE ALSO EXTENDED THE SLIGHT RISK AREA FARTHER SWWD ACROSS NRN AND
WRN AR...WHERE A RELATIVELY ORGANIZED CLUSTER OF STRONG/OCCASIONALLY
SEVERE STORMS HAS EVOLVED.
...TX...
EARLIER/STRONG CONVECTION OVER CENTRAL TX HAS DIMINISHED...WITH ONLY
SUB-SEVERE CONVECTION PERSISTING AT THIS POINT.
HOWEVER...ADDITIONAL HEATING/DESTABILIZATION SHOULD ALLOW SOME
RE-INTENSIFICATION OF STORMS THIS AFTERNOON. STORMS MAY ALSO
DEVELOP FARTHER SW TOWARD THE MID RIO GRANDE VALLEY...AND POSSIBLY
SPREAD EWD OFF THE HIGHER TERRAIN OF NRN MEXICO ONTO THE U.S. SIDE
OF THE BORDER.
WHILE SHEAR SHOULD WEAKEN SOMEWHAT WITH TIME...MULTICELL CLUSTERS
MAY BECOME SEVERE -- WITH HAIL AND PERHAPS LOCALLY GUSTY WINDS
POSSIBLE.
..GOSS.. 05/13/2010
.PREV DISCUSSION... /ISSUED 1122 AM CDT THU MAY 13 2010/
...SOUTHERN GREAT LAKES AND OH VALLEY...
A BROAD UPPER TROUGH REMAINS OVER THE NORTHERN PLAINS AND ROCKIES
TODAY...WITH FAST SOUTHWESTERLY MID LEVEL FLOW FROM THE SOUTHERN
PLAINS INTO THE GREAT LAKES. SEVERAL CLUSTERS OF OVERNIGHT
CONVECTION LEFT A SERIES OF PRE-FRONTAL OUTFLOW BOUNDARIES EXTENDING
FROM NORTHEAST IL INTO SOUTHEAST MO...THEN SOUTHWESTWARD ACROSS AR
INTO SOUTHEAST OK. THE MAIN COLD FRONT THEN EXTENDS SOUTHWESTWARD
ACROSS CENTRAL TX. ALL OF THESE BOUNDARIES ARE LIKELY TO PLAY A
ROLE IN CONVECTIVE DEVELOPMENT LATER TODAY...WITH THE CORRIDOR OF
GREATEST SEVERE RISK EXTENDING ACROSS MUCH OF IND/OH INTO WESTERN
PA.
PRESENT INDICATIONS ARE THAT STRONG HEATING WILL CONTINUE ACROSS
MUCH OF IND...WHERE SURFACE DEWPOINTS HAVE RISEN THROUGH THE 60S.
SCATTERED THUNDERSTORMS WILL LIKELY FORM IN THIS REGION BY EARLY
AFTERNOON AND TRACK QUICKLY EAST-NORTHEASTWARD INTO OH AND
EVENTUALLY WESTERN PA. VERTICAL SHEAR PROFILES IN THIS REGION SHOW
SUFFICIENT EFFECTIVE SHEAR FOR SUPERCELL STRUCTURES. SOUTHERLY LOW
LEVEL WINDS /OR EVEN SOUTHEASTERLY NEAR THE SURFACE WARM FRONT/ ARE
FAVORABLE FOR THE RISK OF TORNADOES THROUGH THE AFTERNOON. HAVE
INCREASED THE TORNADO PROBABILITIES ALONG THE WARM FRONT TO ACCOUNT
FOR THIS RISK. OTHERWISE...CLUSTERS OF STORMS INCLUDING BOWS/LEWPS
WILL POSE A THREAT OF RATHER WIDESPREAD DAMAGING WIND AND HAIL.
...TX...
LARGE CLUSTER OF STRONG THUNDERSTORMS PERSISTS OVER NORTH CENTRAL
TX. DIURNAL HEATING TO THE SOUTHEAST OF THE CLUSTER MAY EVENTUALLY
HELP TO STRENGTHEN THE UPDRAFTS AND LEAD TO INITIATION ALONG
ASSOCIATED OUTFLOW BOUNDARIES. THEREFORE...HAVE MAINTAINED SLIGHT
RISK ACROSS THE REGION. MAIN RISK APPEARS TO BE LARGE HAIL AND
LOCALLY DAMAGING WINDS.
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