SWODY2
SPC AC 111738
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1238 PM CDT MON AUG 11 2008
VALID 121200Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS N TX TO NWRN AL...
...SYNOPSIS...
MID-UPPER LEVEL SHORTWAVE TROUGHS NOW OVER NRN QUE ARE FCST TO DIG
SWD WITH CLOSED LOW DEVELOPING OVER SRN QUE BY ABOUT 13/06Z. AS
THAT OCCURS...UPPER LOW NOW INVOF NYC IS FCST TO MOVE EWD ACROSS SRN
NEW ENGLAND...DEVOLVE INTO OPEN-WAVE TROUGH...THEN EJECT NEWD ACROSS
NOVA SCOTIA DAY-2. UPPER LOW -- NOW EVIDENT IN MOISTURE CHANNEL
IMAGERY OVER SWRN AB -- SHOULD MOVE ESEWD THEN EWD ACROSS SASK THIS
PERIOD. GEN NWLY-WNWLY FLOW PATTERN DOMINATES MID-UPPER LEVELS
ACROSS MUCH OF CONUS S OF THOSE LOWS. THIS BELT WILL CUT THROUGH
MEAN RIDGE NOW OVER UPPER MS VALLEY AND MB...RESULTING IN CLOSED
UPPER HIGH OVER NERN MB. SHORTWAVE TROUGH -- NOW PIVOTING ESEWD
PERIOD. NAM FCST OF SMALL/CLOSED LOW OVER MN BY 12/18Z IS
FAR-OUTLYING/LOW-CONFIDENCE PROG...NOT SUPPORTED BY LATEST
SPECTRAL...ECMWF...NGM OR GREAT MAJORITY OF SREF MEMBERS.
AT SFC...DIFFUSE AND CONVECTIVELY MODULATED FRONTAL ZONE SHOULD
LINGER FROM E GULF COASTAL PLAIN WNWWD TOWARD NRN TX.
WEAK/FRONTAL-WAVE LOW -- EVIDENT ATTM OVER RED RIVER REGION NNE OF
MCV NEAR MWL -- IS EXPECTED TO MOVE EWD ALONG FRONTAL ZONE FROM
ARKLATEX REGION ACROSS LOWER MS VALLEY. WEAK SFC LOW AND
FRONTOGENESIS MAY OCCUR OVER MN IN IMMEDIATE ADVANCE OF SHORTWAVE
TROUGH ALOFT...WITH BOUNDARY EXTENDING SWWD TOWARD ERN KS.
...NE TX TO MID SOUTH...
SCATTERED-NUMEROUS TSTMS ARE EXPECTED TO DEVELOP NEAR AND E OF SFC
LOW...AND E OF MCV NOW OBSERVED ON VIS IMAGERY OVER N-CENTRAL TX.
STG-SVR GUSTS ARE POSSIBLE...ALONG WITH MRGL SVR HAIL AND PERHAPS A
TORNADO OR TWO. POTENTIAL EXISTS THROUGHOUT PERIOD -- SPREADING W-E
-- BUT SHOULD BE MAXIMIZED DURING AFTERNOON/EVENING AND INVOF
DIFFUSE FRONTAL ZONE...WHERE COMBINATION OF DIURNALLY-BOOSTED
BUOYANCY...LOW LEVEL CONVERGENCE AND SRH EACH ARE EXPECTED TO BE
MAXIMIZED. FCST SOUNDINGS SUGGEST MODEST MID-UPPER LEVEL
FLOW...WEAKENING WITH SWD EXTENT...BUT ADEQUATE TO SUPPORT 30-40 KT
EFFECTIVE SHEAR. ENLARGED LOW LEVEL HODOGRAPHS ARE EXPECTED IN
FRONTAL ZONE WHERE SFC WINDS WILL BE BACKED...CONTRIBUTING TO
POTENTIAL FOR BRIEF/HEAVY-PRECIP SUPERCELL AND BOWING STRUCTURES.
...CENTRAL HIGH PLAINS...
WIDELY SCATTERED TSTMS IN CLUSTERS MAY DEVELOP ACROSS ERN PORTIONS
CO/MN AND PERHAPS SERN WY AND NEB PANHANDLE DURING AFTERNOON...IN
FAVORABLY MOIST ENVIRONMENT MADE INCREASINGLY UNSTABLE THROUGH
DIURNAL HEATING. ALTHOUGH LOW-MIDLEVEL WINDS WILL BE WEAK...STG
DIRECTIONAL SHEAR AND UPPER FLOW WILL SUPPORT SOME STORM
ORGANIZATION...WITH STG-SVR GUSTS POSSIBLE INTO WELL-MIXED SUBCLOUD
LAYER. WEAKER AND MORE NLY AMBIENT FLOW COMPONENT...COMBINED WITH
POTENTIAL FOR PROPAGATION INTO STRONGER
MOISTURE/BUOYANCY...INDICATES CLUSTER OF CONVECTION MAY MOVE SWD
ACROSS ERN NM DURING AFTERNOON/EVENING HOURS. ACTIVITY MAY PRODUCE
STG-SVR GUSTS...ESPECIALLY OVER ERN PORTION WHERE HOTTER AND MORE
DEEPLY MIXED BOUNDARY LAYER WILL CHARACTERIZE PRE-STORM AIR MASS.
...UPPER MS VALLEY TO CENTRAL LOW PLAINS...
SCATTERED TSTMS MAY DEVELOP IN NNE-SSW ALIGNED BAND CLOSE TO FRONTAL
ZONE AS ASSOCIATED LOW LEVEL CONVERGENCE COMBINES WITH
RICH/EVAPOTRANSPIRATIVELY-AIDED MOIST LAYER AND STG AFTERNOON
HEATING. A FEW ORGANIZED MULTICELLS ARE POSSIBLE IN KINEMATIC
ENVIRONMENT CHARACTERIZED BY STG VEERING WITH HEIGHT UNDER NW FLOW
ALOFT...BUT WEAK LOW-MIDLEVEL WINDS. ISOLATED HAIL/GUSTS NEAR SVR
LEVELS ARE POSSIBLE.
..EDWARDS.. 08/11/2008
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