Sunday, September 4, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 040555
SWODY1
SPC AC 040554

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1254 AM CDT SUN SEP 04 2011

VALID 041200Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL GULF
COAST...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTHEAST
STATES/UPPER OH VALLEY...

...SYNOPSIS...
AS TROPICAL STORM LEE REMAINS ALONG THE CENTRAL GULF
COAST...POSITIVE TILT UPPER TROUGH WILL BEGIN TO SPLIT AS IT SHIFTS
SLOWLY EASTWARD OVER EASTERN CANADA/GREAT LAKES REGION...WITH
SHOWERS/TSTMS COMMON ALONG/JUST AHEAD OF AN ASSOCIATED COLD FRONT.
IN THE WEST...PREVALENCE OF AN UPPER RIDGE WILL RESULT IN RELATIVELY
BENIGN CONDITIONS WITH RESPECT TO DEEP CONVECTION...SAVE ISOLATED TO
SCATTERED MAINLY AFTERNOON TSTMS ACROSS PORTIONS OF THE SOUTHERN
ROCKIES/FOUR CORNERS AREA.

...CENTRAL GULF COAST...
TROPICAL STORM LEE IS EXPECTED TO SLOWLY DRIFT GENERALLY NORTHWARD
THROUGH THE PERIOD ACROSS SOUTHERN LA...REFERENCE NHC FOR THE LATEST
FORECAST INFORMATION. WITH TS LEE EXPECTED TO GENERALLY MAINTAIN ITS
INTENSITY...A RELATIVELY BROAD ENVELOPE OF ENHANCED
CYCLONIC/GENERALLY SOUTH-SOUTHEASTERLY LOW-LEVEL FLOW WILL PERSIST
ON ITS EASTERN HALF. WEAK/UNCERTAIN DESTABILIZATION PROGRESSIVELY
INLAND WILL LIKELY REMAIN THE PRIMARY LIMITING FACTOR FOR A MORE
CONSIDERABLE TORNADO THREAT. THAT SAID...A CYCLONICALLY PIVOTING
MID-LEVEL DRY SLOT AROUND THE SOUTHERN/EASTERN PERIPHERY OF TS
LEE...OVERSPREADING AREAS SUCH AS FAR SOUTHEAST LA AND SOUTHERN
PORTIONS OF MS/LA AND FL PANHANDLE...COULD BE AN ADDITIONAL FACTOR
IN WHAT SHOULD OTHERWISE BE A DIURNAL ENHANCEMENT TO NEAR-SURFACE
BUOYANCY/POTENTIAL UPDRAFT VIGOR. WHILE THE MAIN TORNADO POTENTIAL
MAY OCCUR DURING THE DAYLIGHT HOURS...STRONG SHEAR/SRH WITHIN THE
LOWEST 1-2 KM WILL SUPPORT THE POSSIBILITY OF ISOLATED TORNADOES
WITH ANY QUASI-SUSTAINED UPDRAFTS/LOW-TOPPED SUPERCELLS THROUGHOUT
THE PERIOD.

...NORTHEAST STATES/UPPER OH VALLEY/APPALACHIANS...
AS PREVIOUSLY DISCUSSED...THE EASTERN CONUS TROUGH SHOULD GRADUALLY
SPREAD EASTWARD/FRAGMENT OVER THE GREAT LAKES REGION/MIDWEST AND
ONTARIO/QUEBEC THROUGH TONIGHT. AN ASSOCIATED COLD FRONT WILL
CONTINUE TO GRADUALLY SPREAD EASTWARD TODAY...ALTHOUGH THE
PERSISTENCE OF SHOWERS/TSTMS AND ASSOCIATED CLOUD COVER MAY
EFFECTIVELY DEFINE THE FRONT A BIT EASTWARD VIA DIFFERENTIAL
HEATING/OUTFLOWS. GIVEN THE ORIENTATION OF THE PARENT UPPER
TROUGH...THE STRONGEST VERTICAL SHEAR WILL TEND TO GENERALLY LAG
/NORTHWESTWARD OF/ THE EFFECTIVE FRONTAL ZONE.
REGARDLESS...INCREASING/CYCLONIC UPPER FLOW AND THE PRESENCE OF A
MOIST/DIURNALLY DESTABILIZING BOUNDARY LAYER SHOULD CONTRIBUTE TO AN
INCREASE IN POTENTIALLY STRONG/SEVERE TSTMS DURING THE
AFTERNOON/EARLY EVENING IN VICINITY OF THE COLD /OR MORE LIKELY
EFFECTIVE/ FRONT. DAMAGING WINDS AND TO A LESSER EXTENT SEVERE HAIL
WILL BE THE PRIMARY CONCERNS...AND THE POSSIBILITY MAY EXIST FOR A
TORNADO ACROSS AREAS SUCH AS NY/NORTHERN NEW ENGLAND.

..GUYER/HURLBUT.. 09/04/2011

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