SWODY1
SPC AC 240517
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1217 AM CDT THU SEP 24 2009
VALID 241200Z - 251200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PATTERN WILL CHANGE LITTLE THROUGH THURSDAY WITH A CUTOFF UPPER LOW
PREVAILING OVER THE CENTRAL U.S. ALONG WITH AN UPPER RIDGE OVER THE
SERN STATES. COLD FRONT WILL ADVANCE THROUGH THE REMAINDER OF THE
NERN STATES AND MID ATLANTIC IN ASSOCIATION WITH UPPER TROUGH
AMPLIFYING ACROSS SERN CANADA AND NEW ENGLAND. WEAK SURFACE BOUNDARY
WILL LINGER FROM NRN NEB OR SRN SD THROUGH THE MID MS VALLEY REGION.
...MIDDLE MO RIVER VALLEY...
MOIST AXIS WITH UPPER 50S TO LOW 60S BOUNDARY LAYER DEWPOINTS WILL
PERSIST NORTH OF WEAK SURFACE BOUNDARY FROM SERN SD THROUGH SRN MN
AND NRN IA BENEATH NERN PERIPHERY OF THERMAL TROUGH ASSOCIATED WITH
UPPER LOW CIRCULATION. POTENTIAL WILL EXIST FOR THE ATMOSPHERE TO
DESTABILIZE IN VICINITY OF MOIST AXIS WHERE SUFFICIENT DIABATIC
WARMING OCCURS. HOWEVER...STEEPER MID LEVEL LAPSE RATES WILL LIKELY
REMAIN SW OF LOW LEVEL MOIST AXIS AND CLOSER TO UPPER LOW CENTER.
NET RESULT IS THAT ONLY MARGINAL SURFACE BASED INSTABILITY IS
EXPECTED. VORTICITY MAXIMA ROTATING AROUND UPPER LOW WILL LIKELY
CONTRIBUTE TO DEVELOPMENT OF CONVECTION WITHIN ZONE OF MODEST BUT
DEEP CONVERGENCE OVER THE MIDDLE MO RIVER VALLEY AREA. ELY DEEP
LAYER VERTICAL SHEAR OF 25-30 KT WILL SUPPORT MULTICELLS. ISOLATED
STORMS COULD BECOME CAPABLE OF PRODUCING SMALL TO MARGINALLY SEVERE
HAIL AND GUSTY WINDS FROM LATE AFTERNOON THROUGH EARLY EVENING.
OVERALL THREAT APPEARS TOO MARGINAL TO WARRANT MORE THAN 5% HAIL
PROBABILITIES.
..DIAL/SMITH.. 09/24/2009
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