Friday, March 6, 2009

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 070047
SWODY1
SPC AC 070044

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0644 PM CST FRI MAR 06 2009

VALID 070100Z - 071200Z

...THERE IS A SLGT RISK OF SVR TSTMS TONIGHT ACROSS PARTS OF THE E
CNTRL PLAINS AND MIDDLE MISSISSIPPI VALLEY....

...IMMEDIATE LEE OF THE SOUTHERN ROCKIES...
WEAK THUNDERSTORM STORM ACTIVITY HAS BEEN ONGOING THE PAST FEW HOURS
NEAR THE SANGRE DE CRISTO MOUNTAINS...WHERE STEEPENING LAPSE RATES
WITH THE HEATING OF THE HIGHER TERRAIN HAS SUPPORTED WEAK
DESTABILIZATION. FAVORABLE OROGRAPHIC FORCING BENEATH DIVERGENT
UPPER FLOW DOWNSTREAM OF AN UPPER TROUGH ACROSS THE INTERMOUNTAIN
WEST HAS SUPPORTED CONVECTIVE DEVELOPMENT...BUT THIS HAS BEEN
MINIMIZED BY LIMITED MOISTURE AVAILABILITY. WHILE IT SEEMS MOST
PROBABLE THAT ACTIVITY WILL DIMINISH BY OR SHORTLY AFTER SUNSET...IT
IS POSSIBLE THAT LARGE-SCALE FORCING MAY BE SUFFICIENT TO MAINTAIN A
COUPLE OF STORMS FOR AN HOUR OR TWO AFTER NIGHTFALL.

...CENTRAL PLAINS THRU OHIO VALLEY...
EAST OF THE ROCKIES...SUBTROPICAL RIDGING REMAINS STRONG ACROSS MUCH
OF THE SOUTH CENTRAL AND SOUTHEASTERN STATES. COUPLED WITH
WARM...MIXED BOUNDARY LAYER AIR ADVECTING EAST NORTHEASTWARD OFF THE
PLATEAU REGION...THIS IS CAPPING A WEAK LOW-LEVEL MOISTURE RETURN
OFF THE WESTERN GULF OF MEXICO. AN EXCEPTION EXISTS ALONG A WEAK
SURFACE BOUNDARY ACROSS THE TEXAS PANHANDLE...WHICH HAS
STALLED...AND ALREADY APPEARS TO BE LIFTING NORTHWARD. LOW-LEVEL
WARM ADVECTION ALONG THE BOUNDARY MAY BE SUPPORTING DEVELOPMENT...
BUT HEATING TO CONVECTIVE TEMPERATURES IS PROBABLY THE MOST
PROMINENT FORCING...AND THESE STORMS MAY BE FAIRLY SHORT-LIVED.

THE PRIMARY FOCUS FOR CONVECTIVE DEVELOPMENT TONIGHT STILL APPEARS
TO BE A QUASI-STATIONARY LOWER/MID TROPOSPHERIC FRONT EXTENDING WEST
SOUTHWEST OF THE OHIO VALLEY...THROUGH THE CENTRAL PLAINS...NEAR THE
CREST OF THE SUBTROPICAL RIDGE. LOW-LEVEL MOISTURE RETURN TO THE
VICINITY OF THIS BOUNDARY...COINCIDENT WITH STEEPENING ISENTROPIC
ASCENT...AIDED BY AT LEAST WEAK FRONTOGENETIC FORCING...AND
STRENGTHENING DIVERGENT UPPER FLOW IN THE RIGHT ENTRANCE REGION OF
AN INTENSIFYING HIGH-LEVEL JET...IS EXPECTED TO SUPPORT WEAK TO
MODERATE DESTABILIZATION. THE STRONGEST DESTABILIZATION...WITH MOST
UNSTABLE CAPE GENERALLY ON THE ORDER OF 500-1000 J/KG SEEMS MOST
LIKELY ACROSS PARTS OF NORTH CENTRAL/NORTHEAST KANSAS THROUGH
NORTHERN MISSOURI...ACCOMPANIED BY INCREASING STORM COVERAGE AFTER
06Z. IT IS POSSIBLE THAT FORCING ON THE NOSE OF A NOCTURNALLY
STRENGTHENING LOW-LEVEL JET COULD SUPPORT THE INITIATION OF STORMS
AS EARLY AS THE 03-06Z TIME FRAME...A BIT FARTHER TO THE
WEST...ACROSS PARTS OF WESTERN/CENTRAL KANSAS.

STORMS ARE EXPECTED TO BE BASED ABOVE A NEAR SURFACE STABLE LAYER.
HOWEVER...GIVEN A FAVORABLE THERMODYNAMIC ENVIRONMENT ALOFT...
STRONG SHEAR WITHIN THE ELEVATED INFLOW LAYER...AND THROUGH THE
CONVECTIVE LAYER...WILL ENHANCE THE RISK FOR LARGE HAIL IN THE MOST
VIGOROUS STORMS. ALTHOUGH LOW-LEVEL TEMPERATURE/DEW POINT SPREADS
WILL BE INITIALLY LARGE...THE RISK FOR DAMAGING WIND GUSTS STILL
APPEARS LOW.

..KERR.. 03/07/2009

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