SWODY1
SPC AC 191253
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0753 AM CDT FRI SEP 19 2008
VALID 191300Z - 201200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
THE PRIMARY BELT OF MID LEVEL WLYS WILL REMAIN OVER SRN CANADA
THROUGH TONIGHT...WITH A WEAKER SRN STREAM FROM NRN CA TO THE SRN
PLAINS/LOWER MS VALLEY AND SERN STATES. WITHIN THIS SRN
STREAM...ONE SHORTWAVE TROUGH IS MOVING EWD OFF THE SE ATLANTIC
COAST...A SECOND WAVE IS MOVING EWD FROM THE SRN PLAINS TOWARD THE
LOWER MS VALLEY...AND A THIRD WAVE IS APPROACHING NW CA. THE
PRIMARY THUNDERSTORM THREAT AREAS ACROSS THE CONUS WILL RESIDE
DOWNSTREAM FROM THE LATTER TWO TROUGHS OVER THE MS VALLEY AND GREAT
BASIN. ELEVATED THUNDERSTORMS ACROSS NRN MN THIS MORNING SHOULD
DECREASE GRADUALLY THROUGH MIDDAY AS A WARM ELEVATED MIXED LAYER
SPREADS EWD FROM THE NRN PLAINS...IN ADVANCE OF A SURFACE COLD
FRONT.
A WEAK SURFACE TROUGH AND RELATIVE MAXIMUM IN LOW-LEVEL MOISTURE
ACCOMPANY THE MID LEVEL TROUGH MOVING EWD FROM AR/LA TO MS. DESPITE
MODEST MID LEVEL LAPSE RATES...DAYTIME HEATING WITHIN CLOUD BREAKS
WILL CONTRIBUTE TO THE DEVELOPMENT OF MLCAPE IN THE RANGE OF 500-750
J/KG AND MINIMAL CONVECTIVE INHIBITION. VERTICAL SHEAR COULD BE
SUFFICIENT FOR A FEW ORGANIZED MULTICELL CLUSTERS TODAY ACROSS
MS...THOUGH THE POOR LAPSE RATES AND RELATIVELY WEAK LOW-MID LEVEL
FLOW SHOULD LIMIT ANY SEVERE STORM THREAT.
WIDELY SCATTERED THUNDERSTORMS CAN BE EXPECTED LATER TODAY INTO
EARLY TONIGHT INVOF THE FOUR CORNERS IN CONJUNCTION WITH DAYTIME
HEATING AND SEVERAL DIFFUSE MID LEVEL TROUGHS FROM NV TO CO. A
STRONGER TROUGH WILL MOVE INLAND FROM NRN CA/ORE TO NV/ID BY
TONIGHT. ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL BE
POSSIBLE IN THE ZONE OF ASCENT DOWNSTREAM FROM THIS TROUGH FROM NRN
NV INTO SW ID...WHERE LOW-MID LEVEL MOISTURE AND LAPSE RATES WILL
BECOME SUFFICIENT FOR WEAK BUOYANCY.
..THOMPSON/CROSBIE.. 09/19/2008
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