SWODY1
SPC AC 191959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT WED SEP 19 2007
VALID 192000Z - 201200Z
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL HIGH PLAINS...
..SYNOPSIS...
LARGE SCALE PATTERN INCLUDES MEAN TROUGH OVER WRN STATES AND
POSITIVELY TILTED RIDGING FROM NERN MEX NEWD UP OH VALLEY TO
MID-ATLANTIC/NEW ENGLAND. BROAD MID/UPPER CYCLONE OFFSHORE FMY WILL
CONTINUE DRIFTING WWD OR NWWD...CONTRIBUTING TO FL GEN THUNDER
POTENTIAL. FARTHER W...ANOMALOUSLY DEEP/LARGE MIDDLE-UPPER LEVEL
CYCLONE -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER NWRN CA --
IS FCST TO CONTINUE DIGGING SWD DOWN CA COAST BEFORE DECELERATING
LATE IN PERIOD IN GENERAL VICINITY MRY.
AT SFC...CYCLONE OVER N-CENTRAL/NERN NV IS EXPECTED TO MOVE LITTLE
THROUGH REMAINDER PERIOD. WARM FRONTAL ZONE EXTENDS EWD FROM THERE
ACROSS UT/ID BORDER AREA...W-CENTRAL WY...SERN WY...NERN
CO...W-CENTRAL/CENTRAL KS. WARM FRONT SHOULD CONTINUE
MOVING/REFORMING NWD ACROSS CENTRAL/NRN ROCKIES AND CENTRAL GREAT
PLAINS THROUGH OVERNIGHT HOURS.
..CENTRAL HIGH PLAINS...
TSTMS HAVE DEVELOPED OVER SWRN KS IN FAVORABLY MOIST/UNSTABLE
ENVIRONMENT JUST S OF WARM FRONT...WITH ADDITIONAL INITIATION
POSSIBLE AS FAR NW AS EXTREME ERN CO AS STG HEATING AND AT LEAST
MRGL LOW LEVEL CONVERGENCE CONTINUE TO ERODE CINH. MOST FAVORABLE
BUOYANCY/SHEAR OVERLAP WILL REMAIN INVOF WARM FRONT...WHERE LOW
LEVEL FLOW WILL REMAIN RELATIVELY BACKED...ENHANCING STORM-RELATIVE
INFLOW...LOW LEVEL HODOGRAPHS/SRH...AND LIFT. POTENTIAL EXISTS FOR
SUPERCELL HAIL/WIND EVENTS AND PERHAPS TORNADOES IN WARM FRONTAL
ZONE...WHERE LARGEST BOUNDARY LAYER SHEAR LOWEST LCL ARE MOST LIKELY
TO BE JUXTAPOSED. BOTH LOW-LEVEL AND DEEP-LAYER SHEARS WILL
DIMINISH WITH SWD EXTENT...INDICATING SVR POTENTIAL WILL DO LIKEWISE
AND BE MORE DISORGANIZED SWD INTO TX PANHANDLE.
REF SPC MESOSCALE DISCUSSION 1981...WW 672...AND SUBSEQUENT
MESOSCALE DISCUSSIONS AS THEY ARRIVE...FOR NEAR-TERM GUIDANCE ON
THIS HAZARD. SOME OF THIS ACTIVITY MAY PERSIST AFTER DARK WITH HAIL
BECOMING MAIN CONCERN...HOWEVER...STRONGER LOW LEVEL FORCING RELATED
TO WAA AND MOIST ADVECTION SHOULD SHIFT FARTHER N OVER NRN PLAINS.
..NRN PLAINS...
STRENGTHENING LLJ IS EXPECTED AFTER DARK...AS BOUNDARY LAYER
DECOUPLES AND SFC WARM FRONT REPOSITIONS NWD. THIS PROCESS SHOULD
INCLUDE SUFFICIENT LOW LEVEL WAA/MOIST ADVECTION TO STEEPEN
LOW-MIDLEVEL LAPSE RATES ABOVE FRONTAL LAYER...DEEPEN BUOYANT LAYER
ALOFT...AND MOISTEN BASE OF CAPE PROFILE. AS ELEVATED MUCINH
WEAKENS...CONTINUING ISENTROPIC ASCENT WILL HOIST PARCELS TO LFC IN
SOME LOCALES...RESULTING IN WIDELY SCATTERED TSTMS IN CLUSTERS.
FAVORABLE EFFECTIVE BULK SHEAR AND ELEVATED MUCAPES 5000-1000 J/KG
MAY SUPPORT ORGANIZED CONVECTION WITH ISOLATED LARGE HAIL POSSIBLE.
..NRN CA...
VERY COLD AIR ALOFT WILL HELP TO OFFSET WEAK BOUNDARY LAYER THETAE
AND CONTRIBUTE TO POTENTIAL FOR SHALLOW TSTMS THROUGH REMAINDER
AFTERNOON/EVENING. HAIL IS POSSIBLE...AND MINI-SUPERCELL WITH
BRIEF/SMALL TORNADO CANNOT BE RULED OUT EITHER...ALTHOUGH STRONGEST
COOLING/ASCENT ALOFT MAY NOT JUXTAPOSE WELL WITH BELT OF STRONGEST
MIDLEVEL WINDS WHERE DEEP-LAYER SHEAR WOULD BE MOST FAVORABLE.
.EDWARDS.. 09/19/2007
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