SWODY2
SPC AC 190453
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1153 PM CDT FRI APR 18 2008
VALID 201200Z - 211200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
LARGE UPPER TROUGH CURRENTLY OVER SRN BRITISH COLUMBIA WILL AMPLIFY
OVER THE WRN STATES THROUGH EARLY SUNDAY. A SRN BRANCH SHORTWAVE
TROUGH CURRENTLY OFF THE CA COAST IS FORECAST TO EJECT NEWD INTO THE
CNTRL AND NRN PLAINS. VEERING DEEP LAYER FLOW IN WAKE OF SHORTWAVE
TROUGH EJECTING NWD ALONG ERN PERIPHERY OF UPPER LOW WILL PROVIDE
IMPETUS FOR A COLD FRONT TO SURGE EWD AND SEWD THROUGH THE NRN AND
CNTRL PLAINS. FARTHER EAST...THE CUTOFF UPPER LOW WILL DRIFT SLOWLY
EAST INTO VA AND THE CAROLINAS.
...NRN PLAINS AREA...
BOUNDARY LAYER MOISTURE IN THIS REGION WILL REMAIN LIMITED WITH
DEWPOINTS IN THE UPPER 30S TO LOW 40S EXPECTED. HOWEVER...PRESENCE
OF STEEP 850-500 MB LAPSE RATES AND SURFACE HEATING WILL CONTRIBUTE
TO MARGINAL INSTABILITY WITH MLCAPE BELOW 500 J/KG EXPECTED. STRONG
BOUNDARY LAYER HEATING AND MIXING AND LARGE SCALE ASCENT ATTENDING
NWD EJECTING SHORTWAVE TROUGH WILL SERVE TO WEAKEN ANY CAP. STORMS
ARE EXPECTED TO DEVELOP ALONG FRONT BY EARLY EVENING AS IT SURGES
EWD INTO THE WRN DAKOTAS THEN SHIFT EWD OVERNIGHT. ISOLATED STRONG
WIND GUSTS AND HAIL WILL BE POSSIBLE WITH THE STRONGER STORMS. WILL
MAINTAIN 5% SEVERE PROBABILITIES FOR THIS REGION. HOWEVER...AT THIS
TIME IT APPEARS THE OVERALL SEVERE THREAT SHOULD REMAIN LIMITED BY
MARGINAL INSTABILITY.
...NC THROUGH MID ATLANTIC...
UPPER TROUGH AND ITS ATTENDANT OCCLUDED SURFACE LOW WILL DRIFT EAST
INTO VA...MD AND NC DURING THE DAY. SCATTERED STORMS WILL LIKELY
PERSIST WITHIN ZONE OF ASCENT ALONG LOW LEVEL CONFLUENCE BAND FROM
PARTS OF ERN NC NWWD THROUGH PARTS OF THE MID ATLANTIC. WEST OF THIS
BAND ACROSS CNTRL NC AND CNTRL VA...COLD MID LEVEL TEMPERATURES WITH
-18 TO -20C AT 500 MB WILL CONTRIBUTE TO NEAR 7C/KM MID LEVEL LAPSE
RATES. AS THE BOUNDARY LAYER WARMS...MLCAPE NEAR 500 J/KG WILL BE
POSSIBLE. ADDITIONAL STORMS WILL LIKELY DEVELOP IN THIS REGION AS
THE BOUNDARY LAYER DESTABILIZES. SOME OF THIS ACTIVITY MIGHT BECOME
CAPABLE OF PRODUCING HAIL DURING THE AFTERNOON BEFORE SUBSIDING
OVERNIGHT.
..DIAL.. 04/19/2008
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