SPC AC 011232
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0732 AM CDT TUE APR 01 2008
VALID 011300Z - 021200Z
...NO SVR TSTM AREAS FORECAST...
...UPPER OH VALLEY INTO PA/NY THIS AFTERNOON AND EVENING...
A STRONG MID LEVEL SHORTWAVE TROUGH OVER THE UPPER MS VALLEY AND
GREAT LAKES...AND AN ASSOCIATED SURFACE CYCLONE OVER LAKE
HURON...WILL CONTINUE TO AMPLIFY WHILE MOVING EWD TO QUEBEC AND NEW
ENGLAND BY TONIGHT. A TRAILING COLD FRONT WILL SWEEP EWD ACROSS THE
UPPER OH VALLEY/WRN PA/WRN NY TODAY...AND OFF THE SE NEW ENGLAND AND
MID ATLANTIC COASTS OVERNIGHT. THIS FRONT IS PRECEDED BY A
RELATIVELY MILD AIR MASS THIS MORNING...WITH SURFACE TEMPERATURES OF
56-60 F AND DEWPOINTS IN THE LOW 50S W OF THE APPALACHIANS...AND A
NARROW PLUME OF 55-60 F DEWPOINTS FROM THE ERN CAROLINAS TO
CHESAPEAKE BAY. THESE SEPARATE MOISTURE PLUMES WILL SPREAD NEWD TO
WRN PA/NY AND ERN PA/NJ/SE NY...RESPECTIVELY...WHILE MODEST SURFACE
HEATING OCCURS WITHIN CLOUD BREAKS.
THE PRIMARY LIMITING FACTOR FOR SEVERE STORMS WILL BE MEAGER
INSTABILITY IN ADVANCE OF THE COLD FRONT...WHERE POOR MID LEVEL
LAPSE RATES WILL LIMIT MUCAPE TO AOB 250 J/KG. MOST OF THE BUOYANCY
WILL BE CONFINED TO BELOW THE 500 MB LEVEL...AND IT APPEARS THAT ANY
FRONTAL CONVECTION WILL REMAIN SHALLOW WITH LITTLE LIGHTNING. THERE
IS SOME EARLY INDICATION OF A VERY SHALLOW/WEAK BAND OF SHOWERS
ALONG THE FRONT IN ERN INDIANA/NW OH/SE LOWER MI...AND IT WOULD BE
INTENSIFICATION OF THIS BAND LATER TODAY THAT MAY POSE SOME THREAT
FOR DAMAGING WINDS AS HIGH MOMENTUM AIR IS TRANSFERED TO THE GROUND.
HOWEVER...THE EXPECTED WEAK NATURE OF THE CONVECTION SUGGESTS THAT
THE DAMAGING WIND THREAT IS TOO MARGINAL TO WARRANT A SLIGHT RISK.
...GULF AND SE ATLANTIC COAST STATES TODAY...
A COLD FRONT WILL MOVE SEWD FROM THE LOWER OH VALLEY THIS MORNING TO
THE SRN APPALACHIANS TONIGHT...WHILE THE WRN PORTION OF THE FRONT
ACCELERATES SWD ACROSS TX IN RESPONSE TO PRONOUNCED PRESSURE RISES
IN LATEST SURFACE ANALYSES. THE FRONT IS PRECEDED BY A REMNANT
OUTFLOW BOUNDARY ACROSS CENTRAL MS/AL...NW GA...AND ERN TN. THE
RICHER BOUNDARY LAYER MOISTURE EXISTS FROM MS WWD INTO TX IN ADVANCE
OF THE FRONT...WITH LESSER MOISTURE ACROSS THE INTERIOR SE STATES.
THE STRONGER INSTABILITY IS EXPECTED THIS AFTERNOON IN ADVANCE OF
THE FRONT/DIFFUSE OUTFLOW ACROSS TX/LA...AND WIDELY SCATTERED TO
SCATTERED THUNDERSTORMS SHOULD DEVELOP NEAR THE FRONT AND REMNANT
OUTFLOW. HOWEVER...VERTICAL SHEAR WILL WEAKEN WITH TIME IN THE WARM
SECTOR AS THE PRIMARY SYNOPTIC WAVE MOVES WELL N/NE OF THE GULF
COAST...AND ORGANIZED SEVERE STORMS APPEAR UNLIKELY. INSTEAD...WILL
MAINTAIN LOW HAIL/WIND PROBABILITIES THROUGH THE AFTERNOON TO COVER
THE MARGINAL SEVERE THREAT.
...W TX EARLY WEDNESDAY...
A L0W-LEVEL WAA REGIME IS FORECAST TO RESUME OVER W TX LATE
TONIGHT/EARLY WEDNESDAY AS A 30 KT LLJ DEVELOPS FROM THE RIO GRANDE
VALLEY TO THE EDWARDS PLATEAU. MOISTURE RETURN ABOVE THE SURFACE
AND STEEP MID LEVEL LAPSE RATES MAY RESULT IN SUFFICIENT MID LEVEL
INSTABILITY FOR ISOLATED STORMS WITH MARGINALLY SEVERE HAIL NEAR THE
END OF THE PERIOD.
..THOMPSON/GRAMS.. 04/01/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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