SWODY1
SPC AC 180540
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1240 AM CDT FRI MAR 18 2011
VALID 181200Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A ZONAL FLOW REGIME WILL BEGIN TO AMPLIFY ACROSS THE WRN U.S. AS AN
INTENSE UPPER LEVEL JET NOSES INTO CA AND THE WRN GREAT BASIN. TO
THE E...A LOW AMPLITUDE UPPER TROUGH WILL MIGRATE FROM THE GREAT
LAKES INTO NEW ENGLAND THROUGH THE PERIOD...WITH MINOR UPPER RIDGING
ACROSS THE PLAINS. AT THE SURFACE...A COLD FRONT WILL SAG SWD ACROSS
THE OH/TN VALLEY WWD INTO THE SRN PLAINS. AHEAD OF THIS FRONT...ONLY
MARGINAL LOW LEVEL MOISTURE WILL BE AVAILABLE DUE TO LESS THAN
OPTIMAL SURFACE TRAJECTORIES ORIGINATING FROM A SURFACE HIGH ALONG
THE CNTRL/ERN GULF COAST.
...OZARKS INTO THE LOWER OH VALLEY...
AT LEAST ISOLATED ELEVATED THUNDERSTORMS ARE EXPECTED TO BE ONGOING
OVER PORTIONS OF ERN KS INTO CNTRL/SRN MO THIS MORNING WITH WEAK
WARM ADVECTION ATOP A SURFACE BOUNDARY. WHILE MID TO UPPER LEVEL
LAPSE RATES MAY FAVOR SOMEWHAT VIGOROUS CONVECTION...OVERALL
EFFECTIVE SHEAR WILL BE MARGINAL FOR ELEVATED SEVERE...ALTHOUGH
SMALL HAIL MAY OCCUR. AS HEATING OCCURS DURING THE DAY...AND LIFT
OCCURS ALONG THE FRONT...CAPPING IS EXPECTED TO ERODE WITH ONGOING
SHOWERS AND STORMS TRANSITIONING TO SURFACE BASED FROM NRN AR EWD
INTO KY AND TN. STEEPENING LOW LEVEL LAPSE RATES FROM NRN AR/SRN MO
EWD INTO KY AND TN...AS WELL AS 20-30 KT MEAN FLOW MAY FAVOR AN
OCCASIONAL STRONG TO SEVERE WIND GUST. ANY THREAT SHOULD DECREASE
DURING THE EVENING.
...NWRN TX/SWRN OK...
THERE IS SIGNIFICANT UNCERTAINTY IN REGARD TO CONVECTIVE COVERAGE
LATER TODAY OVER NWRN TX AND FARTHER N INTO WRN OK...BUT WILL
MAINTAIN LOW END CONDITIONAL SEVERE PROBABILITIES FOR HAIL/WIND FOR
NWRN TX.
WITH W TO SWLY SURFACE FLOW AND STRONG HEATING...AN AXIS OF VERY
STEEP LOW TO MID LEVEL LAPSE RATES WILL MATERIALIZE BY LATE
AFTERNOON ACROSS SW TX...EXTENDING NEWD OVER NWRN TX WHERE HIGHS
WILL APPROACH 90 F. MEANWHILE...A COLD FRONT WILL SAG SWD INTO THE
AREA...ENHANCING LOW LEVEL CONVERGENCE. A FEW RELATIVELY HIGH BASED
THUNDERSTORMS THUS MAY OCCUR OVER NWRN TX WITH A MARGINAL WIND/HAIL
THREAT. IT IS UNCLEAR IF ANY CONVECTION WILL DEVELOP NWD WITH TIME
AS A SELY LOW LEVEL JET INCREASES...BUT ANY STORMS THAT DO FORM INTO
THE TX PANHANDLE OR WRN OK WOULD HAVE A HAIL THREAT. HOWEVER...GIVEN
MARGINAL MOISTURE IN PLACE AND POTENTIAL CAPPING ISSUES OVERNIGHT
WILL NOT EXPAND PROBS NWD AT THIS TIME.
..JEWELL/STOPPKOTTE.. 03/18/2011
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