SWODY1
SPC AC 300558
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT TUE SEP 30 2008
VALID 301200Z - 011200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
HIGHLY AMPLIFIED/MERIDIONAL LARGE SCALE UPPER FLOW PATTERN WILL
PREVAIL THROUGH THE PERIOD OVER THE CONUS. AS AN UPPER RIDGE
DOMINATES THE WESTERN STATES...A DOWNSTREAM DIGGING UPPER JET WILL
CONTINUE TO DEEPEN THE LONGWAVE TROUGH OVER THE EASTERN CONUS. IN
ASSOCIATION WITH THIS UPPER TROUGH...A COLD FRONT WILL TRANSITION
EASTWARD ACROSS THE APPALACHIANS/MID ATLANTIC REGION...WITH THE
SOUTHERN PORTION OF THE FRONT ADVANCING SOUTH-SOUTHEASTWARD ACROSS
THE SOUTHEAST/GULF COAST STATES.
...MID ATLANTIC STATES/APPALACHIANS TO CAROLINAS...
AS THE UPPER TROUGH SHIFTS EASTWARD OVER THE GREAT LAKES...STEADY
LARGE SCALE HEIGHT FALLS ARE EXPECTED OVER THE REGION AS SEVERAL LOW
AMPLITUDE SHORTWAVE TROUGHS PIVOT EAST-NORTHEASTWARD OVER THE OH
VALLEY AND CENTRAL/NORTHERN APPALACHIANS THROUGH THE PERIOD. IN
ASSOCIATION WITH A LEAD MID LEVEL IMPULSE AND THE ADVANCING COLD
FRONT...AT LEAST ISOLATED SHOWERS/TSTMS AND AMPLE CLOUD COVER SHOULD
BE SPREADING EASTWARD TOWARD THE APPALACHIANS VICINITY THROUGH
DAYBREAK THIS MORNING...WITH ADDITIONAL HIGH LEVEL CLOUD COVER
SPREADING NORTHWARD VIA A SOUTHERN STREAM IMPULSE OVER THE EASTERN
GULF/SOUTHEAST STATES. IN THE WAKE OF THIS EARLY DAY ACTIVITY...THE
APPROACH OF A SECONDARY MID LEVEL FEATURE AND DIURNAL
DESTABILIZATION SHOULD BE FAVORABLE FOR AN UPSWING IN TSTM
COVERAGE/INTENSITY ALONG THE COLD FRONT AND/OR LEE TROUGH DURING THE
AFTERNOON. IN SPITE OF FAVORABLE KINEMATICS BENEATH
CYCLONIC/MODERATELY STRONG FLOW ALOFT...QUESTIONS REGARDING CLOUD
COVER/EARLY DAY PRECIPITATION AND SUBSEQUENT DESTABILIZATION/WAKE
REDEVELOPMENT PRECLUDES A CATEGORICAL SLIGHT RISK AT THIS TIME.
NEVERTHELESS...PENDING SUFFICIENT HEATING/SURFACE BASED
DESTABILIZATION THIS AFTERNOON...COOL PROFILES ALOFT /-13 TO -18C AT
500 MB/ AND STEEP MID LEVEL LAPSE RATES WILL BE CONDUCIVE FOR SEVERE
HAIL WITH THE STRONGEST TSTMS...IN ADDITION TO STRONG WIND GUSTS.
VERTICAL SHEAR ON THE ORDER OF 30-35 KT WILL BE FAVORABLE FOR THE
DEVELOPMENT OF MULTICELLS/LINE SEGMENTS...AND PERHAPS A FEW
SUPERCELLS ACROSS THE MID ATLANTIC REGION.
...SOUTH FL...
DESTABILIZATION TODAY MAY BE SOMEWHAT TEMPERED IN THE WAKE OF
OVERNIGHT SHOWERS/TSTMS ACROSS THE SOUTHERN HALF OF THE FL...BUT THE
EASTWARD TRANSITION OF A MID LEVEL IMPULSE/ASSOCIATED SURFACE LOW
WILL CONTINUE TO FOCUS TSTMS ALONG A WEAK BAROCLINIC ZONE ACROSS
SOUTH FL TODAY. PROVIDED MODEST HEATING/CLOUD BREAKS...SUFFICIENT
VERTICAL SHEAR MAY FAVOR SOME STRONG/PERHAPS ISOLATED SEVERE TSTMS
THROUGH THE AFTERNOON. ISOLATED DAMAGING WIND GUSTS AND/OR A BRIEF
TORNADO/WATERSPOUT WILL BE POSSIBLE.
..GUYER/HURLBUT.. 09/30/2008
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