SWODY1
SPC AC 071954
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT FRI OCT 07 2011
VALID 072000Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MO VALLEY AREA
SWWD INTO THE TX HIGH PLAINS AREA...
...ERN NEB SSWWD INTO PARTS OF W TX...
LITTLE CHANGES APPEAR NEEDED TO PRIOR FORECASTS...WITH CU/CONVECTION
SLOWLY RAMPING UP FROM ERN NEB SSWWD INTO THE TX PANHANDLE. EXPECT
THIS SLOW RAMP-UP TO CONTINUE...AS MODEST HEATING CONTINUES INVOF
THE SURFACE BOUNDARY BUT WITH OVERALL SPEED OF DEVELOPMENT LIKELY TO
REMAIN MODULATED BY WEAK SHORT-WAVE RIDGING ALOFT -- AND THUS
BACKGROUND/WEAK LARGE-SCALE SUBSIDENCE -- CONTINUING.
WITH TIME...A FEW STRONGER DEVELOPING UPDRAFTS -- AIDED BY STRONG
FLOW ALOFT/AMPLE SHEAR -- WILL LIKELY EVOLVE...WHICH SUPPORTS
CONTINUATION OF THE SLIGHT RISK FORECAST FOR ISOLATED DAMAGING WINDS
AND HAIL...AND POSSIBLY A TORNADO OR TWO LATER THIS EVENING. STORMS
-- AND PERHAPS LOW-END SEVERE THREAT -- CAN BE EXPECTED THROUGH THE
END OF THE PERIOD.
..GOSS.. 10/07/2011
.PREV DISCUSSION... /ISSUED 1126 AM CDT FRI OCT 07 2011/
...MIDDLE MO VALLEY INTO THE SRN HIGH PLAINS...
STRONG SHORT-WAVE TROUGH OVER THE LOWER CO VALLEY WILL PROGRESS
ENEWD THROUGH THE FOUR-CORNERS REGION WITH A CLOSED MIDLEVEL
CIRCULATION EVENTUALLY FORMING OVER THE CNTRL ROCKIES BY SAT
MORNING. THIS PATTERN EVOLUTION WILL RESULT IN AN INCREASE IN
HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT GRADUALLY SPREADING ACROSS
THE SRN HIGH PLAINS OVERNIGHT. IN THE LOW LEVELS...WEAK LEE CYCLONE
OVER SWRN KS WILL INTENSIFY IN PLACE THROUGH THE D1 PERIOD WHILE
ATTENDANT BAROCLINIC ZONE REMAINS QUASI-STATIONARY FROM SERN SD/NERN
NEB SWWD THROUGH WRN KS AND INTO WRN TX. THIS BOUNDARY WILL SERVE
AS THE FOCUS FOR STRONG-SEVERE TSTM DEVELOPMENT LATER THIS AFTERNOON
INTO EARLY SAT.
THOUGH LARGE-SCALE FORCING FOR ASCENT WILL REMAIN MINIMAL
TODAY...12Z REGIONAL SOUNDINGS SUGGEST THAT AS TEMPERATURES WARM
INTO THE 80S...THE CAP WILL BECOME QUITE WEAK WITH AFTERNOON MLCAPE
VALUES INCREASING TO 500-1500 J/KG. SUSTAINED CONVERGENCE ALONG
BAROCLINIC ZONE IS EXPECTED TO FOSTER SCATTERED TSTMS BY MID-LATE
AFTERNOON INITIALLY NEAR THE NEB-KS BORDER WITH ACTIVITY EXPANDING
NEWD INTO THE MID MO VALLEY. GIVEN THE PRESENCE OF 40-50 KT DEEP
SWLY SHEAR /ALIGNED PARALLEL TO THE SURFACE FRONT/...ENVIRONMENT
WILL SUPPORT BOTH SUPERCELL AND LINEAR STRUCTURES WITH THE PRIMARY
HAZARD BEING DAMAGING WINDS. HOWEVER...THE RISK FOR A TORNADO OR
TWO WILL INCREASE THIS EVENING OWING TO STRENGTHENING LOW-LEVEL
SHEAR IN ASSOCIATION WITH DEVELOPING NOCTURNAL LLJ.
FARTHER S...A SEPARATE AREA OF TSTMS WILL BECOME MORE PROBABLE AFTER
08/00-03Z OVER THE TX PNHDL AS HEIGHT FALLS/DYNAMIC FORCING INCREASE
AHEAD OF MIDLEVEL SYSTEM MOVING THROUGH THE SRN ROCKIES. WITH
TIME...THESE STORMS MAY LINK WITH ONGOING STORMS OVER CNTRL PLAINS
WITH ACTIVITY GRADUALLY SPREADING EWD INTO SAT MORNING. HERE...
INCREASING BOUNDARY-LAYER MOISTURE WILL ALIGN WITH STRENGTHENING
LOW- AND DEEP-LAYER SHEAR WITH SETUP BECOMING FAVORABLE FOR EMBEDDED
SUPERCELL STRUCTURES. MARGINAL INSTABILITY...GRADUALLY INCREASING
CONVECTIVE INHIBITION /DUE TO TIME OF DAY/...AND POTENTIAL FOR
MULTIPLE STORM MODES WILL LIMIT A MORE WIDESPREAD SEVERE WEATHER
EVENT. HOWEVER...ISOLATED OCCURRENCES OF DAMAGING WINDS AND LARGE
HAIL WILL BE POSSIBLE...AS WILL A TORNADO OR TWO.
...UPPER MS VALLEY...
DEEP-LAYER CYCLONE OVER THE WRN DAKOTAS WILL LIFT NNEWD INTO MB WITH
TRAILING COLD FRONT PROGRESSING EWD INTO THE UPPER MS VALLEY.
THOUGH BOUNDARY-LAYER MOISTURE CONTENT WILL CONTINUE TO INCREASE
TODAY AHEAD OF THE FRONT...DECREASING MIDLEVEL LAPSE RATES AND
LARGE-SCALE FORCING FOR ASCENT WILL TEND TO LIMIT TSTM COVERAGE AND
INTENSITY. NONETHELESS...A STRONG SWLY WIND FIELD WILL BE
MAINTAINED ALONG FRONTAL ZONE...SUGGESTING A RISK FOR LOCALLY
DAMAGING WIND GUSTS WITH ANY STORMS THAT DEVELOP.
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