SWODY1
SPC AC 081245
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0645 AM CST SUN NOV 08 2009
VALID 081300Z - 091200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A SERIES OF LOW AMPLITUDE UPPER LEVEL DISTURBANCES WILL CONTINUE TO
MOVE EWD AROUND THE BASE OF A CLOSED LOW POSITIONED OVER THE GULF OF
AK...AND THEN PROGRESS RAPIDLY EWD WITHIN A BELT OF STRONG WLY FLOW
ALOFT OVER THE NWRN-N CENTRAL STATES. MEANWHILE...A TROUGH
POSITIONED OVER NRN MEXICO THIS MORNING IS FORECAST TO LIFT NEWD
INTO THE SRN PLAINS DURING THE NEXT 24 HRS...AND BEGIN TO PHASE WITH
THE STRONGER WESTERLIES LOCATED TO ITS N. FARTHER TO THE S OVER THE
GULF OF MEXICO...HURRICANE IDA WILL MOVE NWD TOWARD THE COASTS OF
LA/MS /REFERENCE LATEST NHC GUIDANCE FOR DETAILS/.
...SOUTH TX...
A MOIST BOUNDARY LAYER AIRMASS /I.E. MID 60S SURFACE DEWPOINTS/
RESIDES AHEAD OF AN UPPER LEVEL TROUGH MOVING ACROSS NRN MEXICO THIS
MORNING. RECENT LIGHTNING DATA INDICATE A CLUSTER OF STRIKES HAS
BEEN OCCURRING IMMEDIATELY DOWNSTREAM OF THE MEXICAN TROUGH. AS THE
TROUGH CONTINUES TO APPROACH S CENTRAL TX...STORM COVERAGE MAY
INCREASE SLIGHTLY THROUGH THE AFTERNOON AS MID LEVEL TEMPERATURES
COOL AND SURFACE HEATING TAKES PLACE. FORECAST SOUNDINGS CONTINUE TO
SHOW MARGINAL LAPSE RATES/BUOYANCY AND DECREASING VERTICAL WIND
SHEAR PROFILES WITH TIME...WHICH SHOULD PRECLUDE A SEVERE WEATHER
THREAT FROM DEVELOPING.
...PACIFIC NORTHWEST...
A COLD MID LEVEL AIRMASS WILL CONTRIBUTE TOWARD A STEEP LAPSE RATE
ENVIRONMENT OVER THE PAC NW...AND AID IN THE DEVELOPMENT OF 100-200
J/KG OF MUCAPE ALONG THE WA/ORE COASTLINE. WLY LOW TO MID LEVEL FLOW
WILL BE FAVORABLY ORIENTED WITH COASTAL MOUNTAINS THROUGH MUCH OF
THE AFTERNOON...PROVIDING A SOURCE OF LIFT FOR STORM DEVELOPMENT.
AFTER 00Z...MODEL GUIDANCE INDICATES DECREASING LAPSE RATES...AS
WELL AS WIND FIELDS WHICH BACK IN RESPONSE TO AN APPROACHING S/W
TROUGH OVER THE PACIFIC /RESULTING IN DECREASING MESOSCALE ASCENT/.
THUS...LIGHTNING POTENTIAL MAY MOVE OFFSHORE AND ACCOMPANY THE
APPROACH OF THE NEXT UPPER DISTURBANCE ENTERING THE REGION TOWARD
12Z/MONDAY.
...SOUTH CENTRAL PLAINS LATE TONIGHT...
S/W TROUGH LOCATED INVOF THE BIG BEND REGION THIS MORNING IS
FORECAST TO LIFT NEWD ACROSS THE SRN AND CENTRAL PLAINS TONIGHT.
MEANWHILE...SLY LOW LEVEL FLOW AHEAD OF A SWD SAGGING SURFACE COLD
FRONT WILL MAINTAIN MODEST BOUNDARY LAYER MOISTURE OVER SRN KS/NRN
OK /MAINLY LOW-MID 50S SURFACE DEWPOINTS/. COMBINATION OF LARGE
SCALE ASCENT WITH THE EJECTING SRN STREAM TROUGH AND FRONTAL FORCING
ALONG THE COLD FRONT WILL AID IN LOW LEVEL SATURATION ABOVE FRONTAL
INVERSION AND BENEATH MODERATELY STEEP MID LEVEL LAPSE
RATES...YIELDING MUCAPE VALUES AROUND 500 J/KG. THIS SHOULD BE
SUFFICIENT FOR ELEVATED THUNDERSTORM DEVELOPMENT MAINLY AFTER
06Z...BUT WEAK LAPSE RATES AND EFFECTIVE BULK SHEAR APPEAR TO BE
UNFAVORABLE FOR LARGE HAIL.
..GARNER/CORFIDI.. 11/08/2009
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