SPC AC 301609
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1109 AM CDT WED SEP 30 2009
VALID 301630Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OF THE CENTRAL
PLAINS...
...CENTRAL PLAINS...
STRONG/COLD TROUGH CONTINUES EWD ACROSS ROCKIES INTO THE HIGH PLAINS
TONIGHT. RATHER COMPLEX SURFACE PATTERN WITH THE PRIMARY COLD FRONT
FROM WRN WY SWD THRU ERN UT INTO NRN AZ. IN RESPONSE TO ONGOING
VIGOROUS LARGE SCALE ASCENT AND MID LEVEL COLD ADVECTION ACTIVE BAND
OF CONVECTION/SURFACE TROUGH HAS DEVELOPED SWD FROM E OF RWL TO WRN
CO THIS MORNING...ACCOMPANIED BY WINDS TO NEAR SVR LEVELS.
A RATHER DISORGANIZED AREA OF LOW PRESSURE OVER WY EXPECTED TO
CONSOLIDATE INTO A CENTER TO LEE OF CENTRAL ROCKIES AND MOVE EWD
TONIGHT ALONG KS/NE BORDER. SLY LOW LEVEL JET HIGH PLAINS WILL
INCREASE TO 60KT OR GREATER TONIGHT AS TROUGH AND 70-80KT MID LEVEL
JET APPROACH FROM THE WEST.
GULF MOISTURE RAPIDLY RETURNING FROM SRN PLAINS AND IN CONCERT WITH
A STEEP EML SPREADING EWD WILL PROVIDE A FAVORABLE CONDITIONAL
ENVIRONMENT FOR SEVERE STORMS. THE PRIMARY CAVEAT WILL BE THE
SUFFICIENT WEAKENING OF THE CURRENT STRONG CAP TO ALLOW SURFACE
BASED STORM INITIATION.
IT NOW APPEARS THAT THE PRIMARY THREAT INTO THE EVENING WILL BE WITH
THE STRONG ASCENT AND COLD ADVECTION THAT IS FORCING THE CURRENT
ACTIVE CONVECTION CENTRAL ROCKIES AS IT ROTATES NEWD INTO HIGH
PLAINS OF NEB/SWRN SD. WHILE MOISTURE WILL BE LIMITED THE
COMBINATION OF VERY STEEP LAPSE RATES...DCAPES OF 1000 J/KG OR
GREATER AND 50KT OF SHEAR...SUPPORTS WIND DAMAGE POTENTIAL WITH
STORMS BY LATER THIS AFTERNOON.
FURTHER S ALONG THE DRY LINE WHICH SETS UP THRU WRN KS INTO TX
PANHANDLE...THE CAP WILL WEAKEN WITH STRONG HEATING...BUT MODEL
SOUNDINGS INDICATE THERE LIKELY WILL STILL BE SUFFICIENT INHIBITION
TO PRECLUDE STORM INITIATION. HAVE THUS REDUCED SOME THE THREAT OF
SEVERE STORM COVERAGE IN KS THRU THE EVENING. HOWEVER WITH THE
SHEAR AND STEEP MID LEVEL LAPSE RATES IN PLACE...ANY STORM THAT IS
ABLE TO FORM OFF THE DRY LINE COULD BECOME QUICKLY SEVERE WITH A
LARGE HAIL AND DAMAGING WIND THREAT.
OVERNIGHT ELEVATED THUNDERSTORMS EXPECTED TO INCREASE IN COVERAGE
AND POTENTIAL SEVERITY ACROSS THE CENTRAL PLAINS. AGAIN THE PRIMARY
THREAT WILL BE LARGE HAIL...HOWEVER A MORE ORGANIZED WIND DAMAGE
THREAT COULD SPREAD EWD ACROSS NE WHERE LARGE SCALE ASCENT WILL BE
GREATEST AHEAD AND N OF THE TRACK OF SURFACE LOW.
...CENTRAL ROCKIES...
WITH THE COLD FRONT NOW ENTERING WRN CO...POTENTIAL FOR A FEW
STRONG/SEVERE WIND GUSTS WILL PERSIST THRU THE AFTERNOON. STEEP
LAPSE RATES AND STRONG UPPER JET WILL ENHANCE WIND POTENTIAL WITH
ANY THUNDERSTORM THAT DEVELOPS VICINITY AND AHEAD OF COLD FRONT.
..HALES/JEWELL.. 09/30/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
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