SWODY1
SPC AC 070543
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1243 AM CDT MON SEP 07 2009
VALID 071200Z - 081200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A LARGE UPPER TROUGH WILL CONTINUE PROGRESSING EWD ACROSS THE NWRN
U.S. THIS PERIOD...WITH ASSOCIATED HEIGHT FALLS SPREADING SEWD
ACROSS THE N CENTRAL U.S. WITH TIME. FARTHER E...A WEAKER
TROUGH/LOW IS PROGGED TO DRIFT/LINGER OVER THE MIDWEST/OH VALLEY
REGION. ELSEWHERE...THE FLOW PATTERN ALOFT IS FORECAST TO BE
WEAK/RELATIVELY NONDESCRIPT.
AT THE SURFACE...A COLD FRONT ASSOCIATED WITH THE WRN TROUGH WILL
MOVE EWD ACROSS THE NRN INTERMOUNTAIN REGION...AND THEN SLOWLY
EWD/SEWD INTO THE DAKOTAS/NEB. THIS FRONT SHOULD FOCUS AFTERNOON
CONVECTIVE DEVELOPMENT...BUT ONLY A LOW-PROBABILITY SEVERE THREAT.
...THE DAKOTAS INTO NWRN NEB/ERN WY...
MODEST BOUNDARY-LAYER MOISTURE COMBINED WITH AFTERNOON HEATING
PROGGED ACROSS THE NRN PLAINS SHOULD RESULT IN THE DEVELOPMENT OF
500 TO 1500 J/KG MIXED-LAYER CAPE AHEAD OF THE SLOWLY ADVANCING COLD
FRONT. WITH LARGE-SCALE HEIGHT FALLS/ASCENT OVERSPREADING THIS
REGION...THE FRONT SHOULD FOCUS AFTERNOON STORM DEVELOPMENT -- FROM
THE WRN DAKOTAS SWD INTO NEB...AND SWWD INTO ERN WY. STORMS SHOULD
THEN SPREAD SLOWLY EWD THROUGH THE EVENING...BEFORE WEAKENING
OVERNIGHT.
DESPITE THE ANTICIPATED CONVECTIVE DEVELOPMENT...DEEP-LAYER SHEAR IS
NOT FORECAST TO BE PARTICULARLY SUPPORTIVE OF WELL-ORGANIZED
STORMS...AS STRONGER FLOW ALOFT SHOULD REMAIN WELL TO THE COOL SIDE
OF THE SURFACE FRONT. THEREFORE...WILL MAINTAIN ONLY 5% SEVERE
PROBABILITY ACROSS THIS REGION THIS FORECAST...WITH ONLY A MARGINAL
HAIL/WIND EVENT EXPECTED ATTM.
..GOSS.. 09/07/2009
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