Monday, April 30, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 301957
SWODY1
SPC AC 301954

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT MON APR 30 2007

VALID 302000Z - 011200Z

..THERE IS A SLGT RISK OF SVR TSTMS MUCH OF SOUTH TEXAS...

..THERE IS A SLGT RISK OF SVR TSTMS PARTS OF CENTRAL AND EASTERN
OKLAHOMA...

..THERE IS A SLGT RISK OF SVR TSTMS PARTS OF UPPER MISSISSIPPI
VALLEY...

..SYNOPSIS...
PRIMARY BELT OF WESTERLIES FROM PAC NW ACROSS NRN ROCKIES RIDGE THEN
ESEWD ACROSS GREAT LAKES. UPPER LOW CAUGHT IN WEAKER SRN BRANCH
DRIFTING NEWD INTO WRN OK THIS EVENING WHILE UPSTREAM TROUGH
APPROACHES SRN CA BY LATER TONIGHT.

..SRN PLAINS...
ONGOING SEVERE MCS OVER SCENTRAL TX EXPECTED TO INTENSIFY DURING
REMAINDER OF AFTN. PRIMARY SEVERE THREAT WILL BE ALONG LEADING EDGE
OF LARGE COLD AIR OUTFLOW THAT HAS SPREAD S AND SW ACROSS CENTRAL
TX. 20KT OF LOW LEVEL SHEAR COUPLED WITH 40KT OF DEEP LAYER SHEAR
WILL BE SUFFICIENT FOR NOT ONLY MULTICELLULAR SEVERE BUT ALSO
ISOLATED SUPERCELLS GIVEN MLCAPES AOA 2000 J/KG IN THE WARM SECTOR.
BRIEF TORNADOS WILL BE POSSIBLE THRU THE EVENING ASSOCIATED WITH ANY
SUPERCELL THAT DEVELOPS VICINITY OF THE OUTFLOW BOUNDARIES.

A PLUME OF HIGHER MID/UPR 60 DEWPOINTS AND INSTABILITY HAVE SPREAD
NWD THRU ERN OK AHEAD OF A WEAK MID LEVEL VORT MAX TO THE SW OF OKC.
WHILE SHEAR OF 20-30KT IS MARGINAL FOR SEVERE...MLCAPES AOA 2000
J/KG ALONG AND E OF N/S SURFACE BOUNDARY TO THE E OF OKC WILL BE
SUFFICIENT FOR A FEW MULTICELLULAR SEVERE EVENTS. PRIMARY THREAT OF
LARGE HAIL AND WET MICRO BURSTS WILL DIMINISH TOWARD SUNSET.

..UPPER MS VALLEY...
THE ELEVATED THUNDERSTORMS DURING THE MORNING TO THE N OF FRONTAL
BAND EXTENDING FROM SURFACE LOW SERN SD EWD TO SRN WI WILL GRADUALLY
BECOME NEAR SURFACE BASED DURING THE AFTERNOON. STRONG SURFACE
HEATING ACROSS IA TO S OF FRONTAL ZONE WITH TEMPERATURES TO NEAR 90F
HAVE GENERATED STEEP LOW LEVEL LAPSE RATES AND MLCAPES UP TO 1000
J/KG IN WARM SECTOR. POTENTIAL FOR HAIL AND DOWNBURSTS WINDS WILL
INCREASE ALONG AND JUST TO S OF FRONTAL ZONE EWD ACROSS SRN MN/NERN
IA AND INTO SRN WI. MARGINAL DEEP LAYER SHEAR SHOULD LIMIT THE
EXTENT OF SEVERE THAT WILL DEVELOP...ALTHOUGH THREAT WILL LIKELY
CONTINUE AFTER DARK TOWARD LM.

..NERN CO...
STEEP LAPSE RATES OF 9C/KM AND CONVERGENCE ALONG FRONTAL ZONE
SETTLING SEWD INTO NERN CO...WILL BE SUFFICIENT WITH THE RATHER
LIMITED MOISTURE FOR A FEW STRONG/SEVERE STORMS THIS AFTERNOON.
ALTHOUGH MLCAPES GENERALLY LESS THAN 1000 J/KG...HIGH BASES AND
STEEP LAPSE RATES SUPPORT BOTH HAIL AND ISOLATED DOWNBURSTS FROM THE
HIGH BASED STORMS.

.HALES.. 04/30/2007

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