DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 281228
SWODY1
SPC AC 281226

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0726 AM CDT FRI SEP 28 2012

VALID 281300Z - 291200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
A SERIES OF LOW AMPLITUDE SHORTWAVE TROUGHS WILL PROGRESS GENERALLY
EWD FROM THE CENTRAL PLAINS TO THE CENTRAL APPALACHIANS AND SRN NEW
ENGLAND...AROUND THE PERIPHERY OF AN AMPLIFYING TROUGH OVER THE
GREAT LAKES AND SRN ONTARIO/QUEBEC. AT THE SURFACE...A WEAK LOW
WILL DEVELOP SLOWLY ENEWD FROM NRN MD/ERN PA TO THE SE NEW ENGLAND
COAST IN ADVANCE OF THE WEAKENING LEAD SHORTWAVE TROUGH OVER ERN PA
AND A SEPARATE UPSTREAM WAVE OVER THE LOWER OH VALLEY. A DIFFUSE
SURFACE FRONT EXTENDS WSWWD FROM THE MID ATLANTIC TO KY/TN...WITH
THE WRN EXTENT OF THE FRONT INTO OK/TX MASKED BY PRIOR CONVECTIVE
OUTFLOWS.

...MID ATLANTIC TO THE SRN NEW ENGLAND COAST TODAY...
THE SURFACE WARM SECTOR WILL BRUSH THE SRN NEW ENGLAND COAST AS THE
WEAK SURFACE WAVE DEVELOPS ENEWD...WITH WEAK INSTABILITY POSSIBLE
INLAND. LOW-LEVEL VERTICAL SHEAR WILL BE SUFFICIENT FOR ROTATING
STORMS ALONG THE NRN EDGE OF THE WEAK INSTABILITY ACROSS SRN NEW
ENGLAND LATER TODAY...THOUGH THE POOR INSTABILITY AND SOMEWHAT
MODEST SRH WITHIN THE WARM SECTOR BOTH SUGGEST THAT ANY TORNADO RISK
WILL BE MARGINAL AT BEST.

OTHERWISE...THE UPSTREAM SHORTWAVE TROUGH OVER THE LOWER OH VALLEY
WILL IMPACT VA/NC THIS AFTERNOON. THOUGH LOW-LEVEL MOISTURE AND
MIDLEVEL LAPSE RATES WILL BE RATHER MODEST...SURFACE HEATING IN
CLOUD BREAKS COULD ALLOW MLCAPE TO INCREASE TO 500-1000 J/KG BY
EARLY AFTERNOON TO THE E OF THE THICKER CLOUDS. SOME INCREASE IN
UNIDIRECTIONAL DEEP-LAYER SHEAR COULD SUPPORT THE DEVELOPMENT OF
LINE SEGMENTS WITH A MARGINAL RISK FOR DAMAGING WINDS THIS
AFTERNOON.

...CENTRAL/S TX THROUGH TONIGHT...
A MOISTURE PLUME EMANATING FROM THE REMNANTS OF TC MIRIAM OFF THE
SRN BAJA COAST WILL CONTINUE TO SPREAD NEWD ACROSS MEXICO TOWARD
SW/CENTRAL TX. MEANWHILE...RICHER LOW-LEVEL MOISTURE /LOW-MID 70S
DEWPOINTS/ AND PW VALUES AOA 2.25 INCHES WILL ALSO SPREAD NWD FROM
THE WRN GULF INTO S TX. A GRADUAL INCREASE IN CONVECTION IS
EXPECTED THROUGH THIS AFTERNOON ACROSS THE EDWARDS PLATEAU /AS WELL
AS THE MIDDLE TX COAST/...AND STORM CLUSTERS WILL SPREAD ROUGHLY EWD
OVERNIGHT ACROSS S CENTRAL TX. LOCALLY HEAVY RAINFALL WILL BE THE
PRIMARY CONCERN WITH SLOW-MOVING/ PRECIPITATION-EFFICIENT
STORMS...THOUGH VEERING WINDS WITH HEIGHT AND SOME HODOGRAPH
CURVATURE COULD SUPPORT A FEW WEAK ROTATING STORMS WITHIN THE LARGER
CLUSTERS. STILL...POOR LAPSE RATES AND GENERALLY MARGINAL VERTICAL
SHEAR SUGGEST THAT THE RISK FOR SEVERE STORMS WILL BE QUITE SMALL.

..THOMPSON/GARNER.. 09/28/2012

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