Friday, January 27, 2012

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 270535
SWODY1
SPC AC 270533

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1133 PM CST THU JAN 26 2012

VALID 271200Z - 281200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM SC TO THE DELMARVA...

...EAST COAST...

STRONG HEIGHT FALLS...ON THE ORDER OF 120-150KT...WILL OVERSPREAD
MUCH OF THE MIDDLE ATLANTIC REGION EARLY IN THE PERIOD AHEAD OF
PROGRESSIVE UPPER TROUGH. SWD EXTENT OF LARGE SCALE FORCING IS
EXPECTED TO CLIP THE NRN FL PENINSULA DURING THE PRE-DAWN HOURS WITH
SHALLOW FRONTAL CONVERGENCE EXPECTED TO SERVE AS THE PRIMARY
MECHANISM FOR POTENTIAL CONVECTIVE DEVELOPMENT ACROSS THE PENINSULA
LATER IN THE DAY.

LEADING EDGE OF STRONG DCVA WILL COINCIDE WITH SFC FRONTAL POSITION
ACROSS WRN VA...SWD INTO SC AT 12Z. IN RESPONSE TO THIS FEATURE
LATEST GUIDANCE SUGGESTS LLJ WILL INCREASE MARKEDLY ACROSS THE
MIDDLE ATLANTIC WITH 60-70KT SLY 850MB WINDS EXPECTED EAST OF THE
SRN/CNTRL APPALACHIANS. OF PARTICULAR CONCERN WILL BE THE POTENTIAL
FOR ROBUST THUNDERSTORM DEVELOPMENT WITHIN A STRONGLY SHEARED
ENVIRONMENT THAT WOULD SEEM SUPPORTIVE OF DEEP ROTATING
UPDRAFTS...OR AT LEAST FAVORABLE FOR AN ORGANIZED SQUALL LINE ALONG
ADVANCING COLD FRONT.

GREATEST PLUME OF MOISTURE CURRENTLY EXTENDS ACROSS THE CNTRL/ERN
GULF IN CONJUNCTION WITH DEEPER CONVECTION THAT EXTENDS SWWD TOWARD
THE YUCATAN PENINSULA. ALTHOUGH THIS PLUME WILL NOT EXTEND INTO THE
CAROLINAS PRIOR TO FRONTAL PASSAGE IT DOES APPEAR A GRADUALLY
MOISTENING WARM SECTOR WILL RESULT IN SBCAPE VALUES ON THE ORDER OF
500 J/KG PRIOR TO CONVECTIVE OVERTURNING. FORECAST SOUNDINGS
SUGGEST A SQUALL LINE COULD CERTAINLY EVOLVE BY DAYBREAK ALONG THE
COLD FRONT AND DAMAGING WINDS WOULD BE THE PRIMARY SEVERE THREAT
WITH THIS ACTIVITY. AN ENHANCED TORNADO THREAT WILL BE NOTED WITH
ANY DISCRETE SUPERCELLS THAT MANAGE TO EVOLVE AHEAD OF THE LINE
DESPITE THE SOMEWHAT MARGINAL LAPSE RATES/INSTABILITY AS BOUNDARY
LAYER WILL BE FAIRLY MOIST AND STRONGLY SHEARED.

FARTHER SOUTH...IT/S NOT ENTIRELY CLEAR HOW ORGANIZED CONVECTION
WILL BE AS IT SPREADS ACROSS THE FL PENINSULA...THOUGH ACTIVITY
COULD BE SOMEWHAT STRONGER ACROSS NRN REGIONS AND ALONG THE WEST
COAST EARLY. IN THE ABSENCE OF MEANINGFUL LARGE SCALE FORCING AND
MARGINAL LAPSE RATES IT APPEARS ANY SEVERE STORMS THAT DEVELOP
ACROSS FL SHOULD REMAIN SOMEWHAT ISOLATED.

..DARROW/HURLBUT.. 01/27/2012

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