SWODY1
SPC AC 270540
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1240 AM CDT TUE APR 27 2010
VALID 271200Z - 281200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
AN INTENSE MIDLEVEL LOW CURRENTLY OVER THE LOWER MO VALLEY IS
FORECAST TO EVOLVE INTO AN OPEN WAVE WHILE TRANSLATING SEWD THROUGH
THE TN VALLEY AND EVENTUALLY OFF THE SERN ATLANTIC COAST LATER
TONIGHT. THIS SYSTEM WILL BE ATTENDED BY A CONCENTRATED ZONE OF
90-120 DAM HEIGHT FALLS/12 HR AND A 100+ KT MIDLEVEL JET STREAK AS
IT DIGS SEWD THROUGH THE SERN STATES. AT THE SURFACE...A COLD FRONT
WILL SURGE SEWD THROUGH THE SERN STATES...SERVING AS THE FOCUS FOR
SCATTERED...LOW-TOPPED STORM DEVELOPMENT TODAY INTO THIS EVENING.
OVER THE WRN STATES...A SIMILARLY POTENT AND QUITE COLD /I.E. 500 MB
TEMPERATURES OF -30 TO -32 C/ MIDLEVEL TROUGH WILL MOVE THROUGH THE
PACIFIC NW AND NRN INTERMOUNTAIN REGION...ALONG THE POLEWARD SIDE OF
STRONG MID AND HIGH-LEVEL JET STREAKS. IN THE LOW LEVELS...AN
INTENSIFYING COLD FRONT WILL MOVE FROM THE VICINITY OF THE PACIFIC
NW COAST INTO THE NRN INTERMOUNTAIN REGION...POTENTIALLY SUPPORTING
THE DEVELOPMENT OF A STRONGLY-FORCED CONVECTIVE BAND LATER TODAY
INTO TONIGHT.
...COLUMBIA PLATEAU INTO THE SNAKE RIVER VALLEY...
00Z MODEL GUIDANCE CONTINUES TO SUGGEST THAT WIDESPREAD CLOUD COVER
AND PRECIPITATION WILL INHIBIT THE DESTABILIZATION PROCESS TODAY
ALONG AND AHEAD OF THE SURFACE FRONT. HOWEVER...THE COLD NATURE OF
THE MIDLEVEL TROUGH MAY STILL ALLOW FOR SOME WEAK INSTABILITY TO
DEVELOP BY AFTERNOON WHERE SBCAPE MAY APPROACH A COUPLE HUNDRED
J/KG.
A BAND OF LOW-TOPPED TSTMS WILL BE POSSIBLE LATER TODAY ALONG THE
COLD FRONT AS HEIGHT FALLS/DCVA IN ADVANCE OF THE MIDLEVEL TROUGH
BEGIN TO OVERSPREAD THE WEAKLY UNSTABLE ENVIRONMENT. FORECAST
VERTICAL SHEAR WILL BE QUITE STRONG AND MORE THAN SUFFICIENT TO
SUPPORT EMBEDDED BOWING/MARGINAL SUPERCELL STRUCTURES CAPABLE OF
MAINLY ISOLATED DAMAGING WIND GUSTS. SOME HAIL AND PERHAPS A BRIEF
TORNADO WILL BE POSSIBLE WITH ANY SUSTAINED...ROTATING STORMS INTO
THIS EVENING.
...SRN APPALACHIANS INTO CAROLINAS...
INITIAL COLD FRONTAL SURGE NOW OVER THE WRN ATLANTIC HAS SCOURED
RICHER BOUNDARY LAYER MOISTURE FROM THE REGION WITH DEW POINTS
COMMONLY IN THE 40S TO AROUND 50 F. NONETHELESS...DAYTIME HEATING
COUPLED WITH THE ABOVE-MENTIONED HEIGHT FALLS/DYNAMIC COOLING ARE
EXPECTED TO CONTRIBUTE TO THE DEVELOPMENT OF WEAK CONVECTIVE
INSTABILITY LATER TODAY WITH SBCAPE OF A FEW HUNDRED J/KG. THE
COMBINATION OF FRONTAL CONVERGENCE AND TERRAIN INFLUENCES ARE
EXPECTED TO FOSTER SCATTERED...LOW-TOPPED TSTMS BY AFTERNOON
INITIALLY OVER THE CUMBERLAND PLATEAU...PRIOR TO MOVING/DEVELOPING
EWD THROUGH THE CAROLINAS.
AFTERNOON FORECAST HODOGRAPHS INDICATE THE PRESENCE OF A DEEP WLY
WIND FIELD WITH SUFFICIENT DEEP-LAYER SPEED SHEAR TO SUPPORT
FORWARD-PROPAGATING CONVECTIVE LINE SEGMENTS OR CLUSTERS CAPABLE OF
LOCALLY DAMAGING WIND GUSTS. SOME HAIL WILL ALSO BE POSSIBLE WITH
THE STRONGEST UPDRAFTS INTO THIS EVENING.
..MEAD/GARNER.. 04/27/2010
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