SPC AC 311257
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0757 AM CDT MON MAR 31 2008
VALID 311300Z - 011200Z
...THERE IS A MDT RISK OF SVR TSTMS TODAY FOR ERN OK...SW MO...WRN
AR...AND NE TX...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK...FROM
CENTRAL TX NEWD TO SE IA/IL...
...SYNOPSIS...
A SURFACE CYCLONE NOW IN KS WILL DEVELOP NEWD ALONG A RETREATING
BAROCLINIC ZONE TO SRN IA BY MIDDAY...EXTREME SW WI THIS
EVENING...AND NRN LOWER MI LATE TONIGHT IN ADVANCE OF THE PRIMARY
MID LEVEL TROUGH NOW EJECTING NEWD FROM CO/NM. SURFACE ANALYSES
CONFIRM THAT THE RICHER LOW-LEVEL MOISTURE IN THE WARM SECTOR WILL
LIKELY BE CONFINED TO AREAS FROM IL/MO/AR/LA WWD INTO OK/TX...WITH
THE ERN EXTENT OF THE MOISTURE LIMITED BY TRAJECTORIES EMANATING
FROM WITHIN THE ERN US SURFACE RIDGE. THESE RELATIVELY DRIER
LOW-LEVEL TRAJECTORIES...ALONG WITH THE LINGERING INFLUENCE OF
YESTERDAY/S CONVECTION ACROSS AR/LA/E TX AND THE ONGOING CONVECTIVE
CLUSTERS IN MO/IA AND NE OK...CAST DOUBT ON THE DEGREE OF
INSTABILITY IN THE WARM SECTOR TODAY FROM CENTRAL MO NEWD TO SE
IA/IL/SRN WI. MEANWHILE...SUBSTANTIALLY GREATER INSTABILITY APPEARS
LIKELY TODAY FROM CENTRAL/ERN OK SWD INTO TX ALONG THE AXIS OF 65-70
F BOUNDARY LAYER DEWPOINTS...ALONG WITH THE GREATER SEVERE STORM
RISK.
...OK/SW MO/AR/CENTRAL AND ERN TX TODAY INTO TONIGHT...
LATEST OBSERVED DATA/CONVECTIVE TRENDS...AND THE MAJORITY OF THE
SHORT TERM MODEL GUIDANCE...SUGGEST THAT THE PRIMARY SEVERE STORM
THREAT CORRIDOR TODAY WILL LIKELY BE CONFINED TO AREAS ALONG AND E
OF I-44 IN MO/OK/WRN AR...WITH A MORE ISOLATED THREAT E OF I-35 IN
SRN OK/TX. THE RESIDUAL PLUME OF STEEP MID LEVEL LAPSE RATES AND AN
UNCONTAMINATED/MOIST BOUNDARY LAYER WILL REMAIN CO-LOCATED TODAY
FROM CENTRAL/ERN OK SWWD INTO CENTRAL/E TX...WHERE MLCAPE VALUES
SHOULD RANGE FROM 1500-3000 J/KG. SOME LOW-LEVEL WARMING/MOISTENING
IS ALSO EXPECTED ACROSS AT LEAST WRN AR INTO SW/CENTRAL MO ON THE
SRN FRINGE OF THIS MORNING/S CONVECTIVE CLUSTER.
EXPECT SEVERE THUNDERSTORMS TO DEVELOP BY MID MORNING TO EARLY
AFTERNOON ALONG THE COLD FRONT MOVING SEWD INTO CENTRAL/NE OK...AND
NE OF THE DRYLINE/COLD FRONT TRIPLE POINT IN CENTRAL OK. THIS
BOUNDARY INTERSECTION SHOULD DEVELOP SWD INTO N TX OVERNIGHT...WITH
THUNDERSTORMS CONTINUING ALONG THE COLD FRONT. OTHER THUNDERSTORM
DEVELOPMENT MAY OCCUR SE OF THE FRONT AND E OF THE DRYLINE DURING
THE DAY FROM NE TX NWD ACROSS ERN OK/WRN AR INTO MO...AND ALONG THE
RESIDUAL BOUNDARY WITH THE NE OK STORMS. THE COMBINATION OF
MODERATE INSTABILITY AND 0-6 KM BULK SHEAR OF AT LEAST 50 KT WILL
SUPPORT A FEW SUPERCELLS WITHIN THE LARGER CONVECTIVE BAND. THE
MORE INTENSE/DISCRETE STORMS WILL BE CAPABLE OF PRODUCING VERY LARGE
HAIL AND A STRONG TORNADO OR TWO THROUGH THIS EVENING...GIVEN A
MOIST BOUNDARY LAYER AND EFFECTIVE SRH AOA 250-300 M2/S2. THE
SEVERE THREAT SHOULD GRADUALLY DIMINISH LATER TONIGHT AS THE
BOUNDARY LAYER COOLS AND THE STRONGER LOW-LEVEL FLOW/SHEAR DEVELOPS
NEWD AWAY FROM THE INSTABILITY AXIS.
...NRN MO/SE IA/IL/SRN WI TODAY...
INSTABILITY WILL LIKELY REMAIN SOMEWHAT LIMITED CLOSER TO THE
SURFACE LOW TRACK...AS A RESULT OF THE ONGOING CONVECTION IN NE
OK/SE KS/SW MO...AND THE PREVIOUSLY MENTIONED DRIER LOW-LEVEL AIR
MASS FROM ERN AR/MO EWD. WIDESPREAD CLOUDS WILL TEND TO LIMIT
SURFACE HEATING ACROSS MOST OF THE AREA...WHILE BOUNDARY LAYER
DEWPOINTS SHOULD RANGE FROM 58-62 F. STILL...VERTICAL SHEAR WILL BE
STRONG AND SUPERCELLS/TORNADOES WILL BE POSSIBLE IF THE SURFACE CAN
WARM A LITTLE MORE THAN CURRENTLY EXPECTED NEAR THE WARM FRONT THIS
AFTERNOON.
...CENTRAL TX THIS AFTERNOON/EVENING...
ISOLATED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE ALONG THE DRYLINE
THIS AFTERNOON ACROSS CENTRAL TX...WHERE MODERATE INSTABILITY AND
DEEP LAYER SHEAR ARE EXPECTED ALONG THE SRN FRINGE OF THE STRONGER
MID LEVEL FLOW. ISOLATED SUPERCELLS WILL BE POSSIBLE...WITH LARGE
HAIL THE PRIMARY THREAT.
..THOMPSON/SMITH.. 03/31/2008
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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