SWODY1
SPC AC 111226
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0726 AM CDT SUN SEP 11 2011
VALID 111300Z - 121200Z
...NO SVR TSTM AREAS FORECAST...
...MID ATLANTIC REGION THIS AFTERNOON...
A NRN STREAM SHORTWAVE TROUGH WILL AMPLIFY OVER THE CANADIAN PRAIRIE
PROVINCES THROUGH TONIGHT...WHILE DOWNSTREAM HEIGHT FALLS PROMOTE
EVOLUTION INTO AN OPEN WAVE AND EWD MOVEMENT OF THE CLOSED LOW
CURRENTLY OVER THE OH/MS VALLEYS. AHEAD OF THE EWD MOVING
TROUGH...RESIDUAL BOUNDARY LAYER DEWPOINTS IN THE 60S ACROSS THE MID
ATLANTIC REGION WILL COMBINE WITH DAYTIME HEATING TO SUPPORT MLCAPE
VALUES APPROACHING 1500 J/KG. A WEAK SURFACE LEE TROUGH WILL HELP
FOCUS THUNDERSTORM DEVELOPMENT THIS AFTERNOON FROM SE PA SWD INTO MD
ALONG THE INSTABILITY AXIS. DEEP-LAYER SPEED SHEAR WILL BE
SUFFICIENT FOR SOME RISK OF SUPERCELLS...THOUGH LOW-LEVEL FLOW/SHEAR
IS EXPECTED TO REMAIN WEAK. A FEW STORMS COULD PRODUCE MARGINALLY
SEVERE HAIL AND STRONG OUTFLOW WINDS...BUT THE SEVERE STORM RISK
DOES NOT APPEAR TO WARRANT A SLIGHT RISK AT THIS TIME.
...AZ THIS AFTERNOON/EVENING...
A CLOSED LOW WILL REMAIN QUASI-STATIONARY NEAR THE SRN CA COAST
THROUGH THE PERIOD. A BELT OF 30+ KT SWLY MIDLEVEL FLOW WILL BE
MAINTAINED FARTHER TO THE E OVER AZ...ALONG WITH A PW PLUME WITH
VALUES NEAR 1 INCH. THUNDERSTORMS WILL AGAIN BE POSSIBLE THIS
AFTERNOON ALONG AND S OF THE RIM WITHIN THE MOISTURE PLUME...WHERE
WEAK-MODERATE INSTABILITY AND EFFECTIVE BULK SHEAR OF 25-30 KT WILL
SUPPORT A FEW ORGANIZED MULTICELLS/MARGINAL SUPERCELLS WITH AN
ATTENDANT RISK FOR STRONG GUSTS AND MARGINALLY SEVERE HAIL.
..THOMPSON/HURLBUT.. 09/11/2011
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