SWODY1
SPC AC 111954
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT TUE OCT 11 2011
VALID 112000Z - 121200Z
...NO SVR TSTM AREAS FORECAST...
...20Z OUTLOOK UPDATE...PLAINS/MISSISSIPPI VALLEY...
IN THE WAKE OF THE VIGOROUS SHORT WAVE TROUGH LIFTING TOWARD HUDSON
BAY...A RESIDUAL NARROW PLUME OF HIGHER PRECIPITABLE WATER LINGERS
ACROSS THE WESTERN GULF COAST NORTHWARD THROUGH THE UPPER GREAT
LAKES. WITHIN THIS CORRIDOR AN AXIS OF STRONGER BOUNDARY LAYER
DESTABILIZATION...CHARACTERIZED BY MIXED LAYER CAPE IN EXCESS OF
1000 J/KG...HAS BECOME A FOCUS FOR INCREASING THUNDERSTORM
DEVELOPMENT ACROSS NORTHEAST TEXAS/EASTERN OKLAHOMA/ WESTERN
ARKANSAS INTO CENTRAL MISSOURI...WHICH WILL LIKELY PERSIST INTO THE
EVENING HOURS. SOME STORMS MAY BE ACCOMPANIED BY GUSTY WINDS...BUT
IN THE PRESENCE OF GENERALLY WEAK DEEP LAYER MEAN FLOW AND
SHEAR...THE RISK FOR SEVERE STORMS ACROSS THIS REGION STILL SEEMS
LOW TO NEGLIGIBLE.
THERMODYNAMIC PROFILES CHARACTERIZED BY STEEPER LOW/MID-LEVEL LAPSE
RATES...AND AT LEAST SOMEWHAT BETTER SEVERE WEATHER POTENTIAL...ARE
GENERALLY CONFINED TO THE VICINITY OF THE LEE SURFACE TROUGH ACROSS
THE PLAINS...WHERE BOUNDARY LAYER DESTABILIZATION IS STILL ONGOING.
MIXED LAYER CAPE MAY APPROACH OR EXCEED 1000 J/KG LATE THIS
AFTERNOON...WITH GREATEST INSTABILITY OVER THE TEXAS SOUTH PLAINS
AND PECOS VALLEY. AS A SHORT WAVE TROUGH CONTINUES TO SHIFT ACROSS
AND EAST OF THE CENTRAL HIGH PLAINS...ISOLATED TO WIDELY SCATTERED
STORM DEVELOPMENT IS EXPECTED...IN THE PRESENCE OF MOSTLY WEAK TO
MODEST DEEP LAYER SHEAR. THIS MAY CONTINUE INTO THE EVENING
HOURS...WITH STRONGEST STORMS CAPABLE OF PRODUCING HAIL AND GUSTY
WINDS. THE POTENTIAL STORM COVERAGE...HOWEVER...IS BECOMING MORE
UNCLEAR...PARTICULARLY ACROSS THE EASTERN TEXAS PANHANDLE AND
WESTERN OKLAHOMA. AND...GIVEN THE MARGINAL NATURE OF THE
ENVIRONMENT AND THE THREAT...SLIGHT RISK PROBABILITIES DO NOT APPEAR
JUSTIFIED AT THE PRESENT TIME.
..KERR.. 10/11/2011
.PREV DISCUSSION... /ISSUED 1127 AM CDT TUE OCT 11 2011/
...CNTRL/SRN PLAINS...
HEIGHT FALLS ASSOCIATED WITH EXIT REGION OF INTENSE UPPER-LEVEL JET
STREAK PROPAGATING FROM THE PACIFIC NW AND CNTRL ROCKIES INTO THE
CNTRL/SRN PLAINS WILL CONTRIBUTE TO AMPLIFICATION OF LARGE-SCALE
TROUGH OVER THE CNTRL CONUS THIS PERIOD. IN THE LOW LEVELS...LEE
TROUGH OVER THE HIGH PLAINS WILL INTENSIFY TODAY AND GRADUALLY
TRANSITION TO A PACIFIC FRONT WHILE PROGRESSING EWD INTO LOWER
ELEVATIONS OF THE GREAT PLAINS.
STEEPENING LOW- TO MIDLEVEL LAPSE RATES WILL COINCIDE WITH A
MOISTENING BOUNDARY LAYER TO SUPPORT AIR MASS DESTABILIZATION TODAY
E OF LEE TROUGH/PACIFIC FRONT. INCREASING HIGH CLOUDS SPREADING EWD
FROM THE ROCKIES MAY TEMPER DAYTIME HEATING AND THE DESTABILIZATION
PROCESS...BUT AFTERNOON MLCAPE VALUES WILL STILL APPROACH 500-1000
J/KG ACROSS THE WARM SECTOR.
WATER VAPOR IMAGERY AND MODEL DIAGNOSTIC FIELDS INDICATE A LEAD
SHORT-WAVE TROUGH OVER ERN PARTS OF CO/NM WHICH WILL CONTINUE EWD.
EXTRAPOLATION OF CURRENT MOTION SUGGESTS THAT THE STRONGER FORCING
FOR ASCENT WILL LIKELY SHIFT E OF THE SURFACE TROUGH/FRONT PRIOR TO
PEAK HEATING. NONETHELESS...THE TRAILING INFLUENCE OF THIS FEATURE
WILL COMBINE WITH LOW-LEVEL ASCENT ALONG INTENSIFYING SURFACE
BOUNDARY TO FOSTER ISOLATED TO WIDELY SCATTERED TSTMS LATER THIS
AFTERNOON INTO EVENING. WHILE ISOLATED SEVERE STORMS CAPABLE OF
HAIL AND GUSTY WIND WILL BE POSSIBLE ALONG THE LENGTH OF THE LEE
TROUGH/PACIFIC FRONT...THE GREATEST POTENTIAL FOR ORGANIZED STORM
MODES --INCLUDING SUPERCELLS-- APPEARS TO BE OVER PARTS OF THE TX/OK
PNHDLS INTO NWRN TX AND WRN OK. HERE...THE EXIT REGION OF MID- AND
HIGH-LEVEL JET STREAKS WILL ENHANCE DEEP-LAYER SHEAR WITHIN A
KINEMATIC ENVIRONMENT EXHIBITING VERTICALLY VEERING WINDS WITH
HEIGHT. LARGE HAIL APPEARS TO BE THE PRIMARY HAZARD...THOUGH
LOCALLY DAMAGING WIND GUSTS WILL BE POSSIBLE...ESPECIALLY AS STORMS
DEVELOP A COLD POOL.
...FAR ERN NC...
WEAK SURFACE LOW OFF THE SC COAST WILL CONTINUE TO DEVELOP NWD ALONG
COASTAL BOUNDARY THIS PERIOD...POTENTIALLY ALLOWING A NARROW AXIS OF
HIGHER THETA-E AIR TO OVERSPREAD THE IMMEDIATE COAST AND THE OUTER
BANKS. SHOULD THIS OCCUR...ISALLOBARICALLY BACKED NEAR-SURFACE FLOW
--AND RESULTANT ENHANCEMENT OF LOW-LEVEL SHEAR-- WILL SUPPORT THE
POTENTIAL FOR BRIEF SUPERCELL STRUCTURES WITH A LOW PROBABILITY RISK
FOR A TORNADO.
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