SPC AC 280452
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1152 PM CDT THU SEP 27 2012
VALID 281200Z - 291200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A HUDSON BAY LOW WILL DRIFT TOWARDS THE ERN GREAT LAKES...WITH A
SERIES OF UPPER DISTURBANCES ACROSS THE KY/TN VALLEY AND NORTHEAST
PHASING WITH THE BROADER UPPER TROUGH. MEANWHILE...A SURFACE FRONT
WILL CONTINUE TO SAG SWD INTO THE MID ATLANTIC...EXTENDING THROUGH
CNTRL TX. AN UPPER RIDGE INITIALLY CENTERED OVER AB/SK WILL SHIFT
EWD TOWARDS MB AND WRN ONT OVERNIGHT. MEANWHILE...AN UPPER LOW OVER
THE GULF OF ALASKA WILL PROGRESS SEWD TOWARDS THE CANADIAN/PACIFIC
NORTHWEST COAST...WHILE A WEAK LOW LINGERS OVER ERN MT.
...SERN CO/NERN NM/PORTIONS OF THE OK/TX PANHANDLES...
SIMILAR TO THE PAST FEW DAYS...WIDESPREAD SHOWERS AND THUNDERSTORMS
ARE EXPECTED TO OCCUR ALONG A SWD SAGGING FRONT ACROSS N TX...WITH
CLOUD COVER GENERALLY HINDERING STRONGER SURFACE-BASED
DESTABILIZATION. HEIGHT RISES WILL LIKELY FURTHER SUPPRESS ROBUST
UPDRAFTS. HOWEVER...WEAK UPSLOPE FLOW ACROSS THE SANGRE DE CRISTOS
AND LINGERING STEEP MID-LEVEL LAPSE RATES MAY SUPPORT ISOLATED
DIURNALLY-DRIVEN STRONG STORMS.
...KY/TN VALLEYS...MID ATLANTIC AND COASTAL NORTHEAST...
A SUBTLE NY/PA VORT MAX WILL QUICKLY TRANSLATE EWD INTO NEW ENGLAND
THROUGH THE MORNING...WITH ASSOCIATED LOW-LEVEL WARM ADVECTION
OCCURRING ACROSS THE COASTAL NORTHEAST. WITH AT LEAST WEAK
INSTABILITY BUT MODEST LOW-LEVEL SHEAR...BRIEF ROTATION AND/OR A
TORNADO WILL BE POSSIBLE...WITH TORNADIC POTENTIAL QUICKLY
DECREASING THROUGH THE AFTERNOON AS THE INITIAL WAVE MOVES OFFSHORE.
MEANWHILE...A SERIES OF CNTRL/SRN PLAINS UPPER WAVES WILL CONTINUE
EWD...REACHING THE KY/TN VALLEYS AND SUPPORTING ONGOING CONVECTION
AT 12Z/FRI. CLOUD COVER WILL LIKELY INITIALLY LIMIT STRONGER SURFACE
BASED-HEATING/DESTABILIZATION...THOUGH A FEW STORMS MAY BE CAPABLE
OF DMGG WINDS AND HAIL WHERE BREAKS IN THE CLOUDS CAN OCCUR. ACROSS
THE PIEDMONT OF VA/NC...SPARSER CLOUD COVER AND DIURNAL HEATING WILL
CONTRIBUTE TO STEEPENING LOW-LEVEL LAPSE RATES THROUGH THE
AFTERNOON. AS CONVECTION INCREASES ACROSS THE CNTRL APPALACHIANS AND
PROGRESSES EWD...A SEMI-ORGANIZED COMPLEX OF THUNDERSTORMS MAY
EVOLVE...WITH EVAPORATIVE COOLING/PRECIPITATION LOADING CONTRIBUTING
TO STRONG TO SEVERE WINDS.
..HURLBUT/KERR.. 09/28/2012
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z