SWODY1
SPC AC 010059
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0759 PM CDT WED SEP 30 2009
VALID 010100Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS KS...WRN OK AND ERN
PANHANDLE OF TX...
...SYNOPSIS...
UPPER AIR PATTERN ACROSS CONUS FEATURES HIGH-AMPLITUDE TROUGHS...ONE
FROM MT TO NRN NM...AND ANOTHER EXTENDING SWD FROM LOW OVER QUE
ACROSS MID-ATLANTIC STATES. FORMER TROUGH IS FCST TO CONTINUE
MOVING EWD ACROSS HIGH PLAINS OVERNIGHT. RELATED SFC CYCLONE --
INITIALLY ANALYZED OVER NERN CO -- IS FCST TO EJECT NEWD ACROSS NEB
OVERNIGHT...WHILE COLD FRONT INITIALLY OVER W-CENTRAL AND N-CENTRAL
CO MOVES SEWD OVER WRN KS AND TX PANHANDLE. WARM FRONT WILL LIFT
NWD ACROSS MORE OF ERN/N-CENTRAL KS AND SWRN/S-CENTRAL NEB. DRYLINE
WAS ANALYZED AT 23Z FROM WARM FRONT INTERSECTION OVER SWRN NEB SWD
ACROSS W-CENTRAL KS THEN SSWWD OVER ERN OK PANHANDLE...E-CENTRAL TX
PANHANDLE...TO NEAR SERN CORNER NM. TX PORTION IS EXPECTED TO
RETREAT NWWD SLIGHTLY BEFORE STALLING OVERNIGHT...WHILE KS PORTIONS
REMAINS QUASISTATIONARY UNTIL OVERTAKEN BY COLD FRONT.
...CENTRAL/SRN PLAINS...
ISOLATED TO WIDELY SCATTERED TSTMS HAVE FORMED AHEAD OF DRYLINE FROM
CENTRAL KS SWWD ACROSS PERMIAN BASIN REGION OF SW TX. MOST
FAVORABLE SVR THREAT FROM NEARLY SFC-BASED CONVECTION SHOULD BE IN
AND NEAR WW 750. REF WW 750 AND RELATED MESOSCALE DISCUSSIONS FOR
ADDITIONAL NOWCAST INFO ON SVR THREAT FROM CENTRAL KS TO ERN TX
PANHANDLE.
GIVEN LACK OF MORE ROBUST NEAR-SFC MOISTURE AND DIURNALLY DRIVEN
CHARACTER OF ONGOING/SFC-BASED CONVECTION...MODIFIED 00Z RAOBS FROM
OUN...DDC AND LBF INDICATE BOOST IN BUOYANCY PROVIDED BY SFC MOIST
ADVECTION WILL BE OFFSET BY DIABATIC COOLING. THIS PROCESS SHOULD
KEEP MLCINH STG E OF NARROW CORRIDOR WITHIN WHICH STG-SVR TSTMS ARE
ONGOING ATTM AHEAD OF DRYLINE. CURRENT ACTIVITY LARGELY MAY
DIMINISH DURING NEXT COUPLE HOURS AS A RESULT.
HOWEVER...ADDITIONAL STG-SVR CONVECTION MAY DEVELOP OVERNIGHT -- IN
TWO POSSIBLE MODES:
1. ELEVATED MCS OVER PORTIONS LOWER-MID MO VALLEY REGION EWD OVER
PORTIONS IA/NRN MO...PERHAPS EMBEDDED WITHIN BROADER BAND OF PRECIP
THAT WOULD BE ALIGNED NEARLY PARALLEL TO ARC OF SFC WARM FRONT...AND
100-200 NM TO ITS NE. SUCH ACTIVITY IS PROGGED BY
RUC...SPECTRAL...OPERATIONAL WRF AND SEVERAL SREF
MEMBERS...DEVELOPING NEAR NOSE OF 45-55 KT LLJ...IN REGIME OF STG
MOISTURE ADVECTION/TRANSPORT AND RELATED ISENTROPIC ASCENT TO LFC.
MAIN CONCERN WITH ANY SUCH ACTIVITY WILL BE HAIL.
2. PRE COLD-FRONTAL LINE LATE IN PERIOD...PROGGED BY SEVERAL SREF
MEMBERS AND OPERATIONAL WRF FROM S-CENTRAL KS SWWD ACROSS
CENTRAL/SWRN OK AND PERHAPS PORTIONS NW TX. ISOLATED GUSTS/HAIL
NEAR SVR LEVELS IS POSSIBLE...WITH ALIGNMENT OF CONVECTION NEARLY
PARALLEL TO MEAN DEEP-LAYER FLOW VECTOR.
..EDWARDS.. 10/01/2009
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