SWODY1
SPC AC 042000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT WED APR 04 2012
VALID 042000Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE TX COASTAL AREA INTO
EXTREME ERN TX AND THE LOWER MS VALLEY REGION...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN APPALACHIANS INTO
NC AND SRN VA...
...SRN THROUGH ERN TX...
A FEW STORMS CONTINUE ALONG SEA BREEZE AUGMENTED FRONT ALONG THE TX
COASTAL AREAS. TENDENCY HAS BEEN FOR THIS ACTIVITY TO DEVELOP SWD
WITH TIME...AND AT LEAST ISOLATED DEVELOPMENT REMAINS POSSIBLE INTO
SRN TX. STEEP LAPSE RATES...2000-3000 J/KG MLCAPE...AND 30-40 KT
EFFECTIVE SHEAR WILL SUPPORT A THREAT OF SUPERCELLS WITH LARGE HAIL
AND ISOLATED DAMAGING WIND THE MAIN THREATS INTO THE EARLY EVENING.
THE POTENTIAL EXISTS FOR OTHER STORMS TO DEVELOP FARTHER NORTH FROM
FAR ERN OR NERN TX INTO THE LOWER MS VALLEY REGION THIS EVENING AS
NEXT IN A SERIES OF VORT LOBES ROTATE THROUGH BASE OF UPPER TROUGH
AND BEGINS TO INTERACTS WITH WRN EDGE OF THE INSTABILITY AXIS.
SHOULD THEY DEVELOP...THESE STORMS WILL POSE A RISK FOR ISOLATED
DAMAGING WIND AND HAIL.
...SRN APPALACHIANS THROUGH SRN VA AND NC...
NO SIGNIFICANT CHANGES TO CURRENT FORECAST.
..DIAL.. 04/04/2012
.PREV DISCUSSION... /ISSUED 1128 AM CDT WED APR 04 2012/
...SYNOPSIS...
DEEP-LAYER CYCLONE OVER THE SRN HIGH PLAINS WILL ACCELERATE EWD INTO
THE OZARK PLATEAU THIS PERIOD IN RESPONSE TO THE EWD PROGRESSION OF
MIDLEVEL TROUGH THROUGH THE NWRN CONUS. ELSEWHERE...MID AND
UPPER-LEVEL JET STREAKS OVER ONTARIO INTO THE LOWER GREAT LAKES WILL
PROPAGATE SEWD INTO THE NWRN ATLANTIC...CONTRIBUTING TO LOWERING
HEIGHTS ACROSS CNTRL/SRN NEW ENGLAND AND THE MID-ATLANTIC COAST.
IN THE LOW LEVELS...SURFACE CYCLONE OVER SERN KS WILL DEVELOP EWD
TOWARD THE MS/OH RIVER CONFLUENCE WHILE A TRAILING COLD FRONT
ADVANCES EWD/SEWD INTO THE LOWER MS VALLEY. FARTHER E...BAROCLINIC
ZONE EXTENDING FROM SRN VA SWWD THROUGH NRN KY/CNTRL MO TO THE KS
SURFACE LOW WILL SETTLE SLOWLY SWD IN RESPONSE TO AMPLIFICATION OF
NERN U.S. TROUGH.
...TX COASTAL PLAINS INTO LOWER MS VALLEY THIS AFTERNOON AND
TONIGHT...
RADAR/VISIBLE SATELLITE DATA INDICATE AN OUTFLOW BOUNDARY ASSOCIATED
WITH EXPANSIVE MCS OVER THE N-CNTRL GOM ADVANCING WWD ACROSS THE
UPPER-MIDDLE TX COAST. THIS BOUNDARY WILL LIKELY DECELERATE AND
EVENTUALLY STALL TODAY AS THE ASSOCIATED RESIDUAL COLD POOL BECOMES
INCREASINGLY SHALLOW. 12Z CRP SOUNDING SAMPLED AN ALREADY STRONGLY
UNSTABLE ENVIRONMENT /I.E. MLCAPE OF AROUND 3500 J PER KG/ OWING TO
THE PRESENCE OF A VERY MOIST BOUNDARY LAYER AND STEEP MIDLEVEL LAPSE
RATES. LARGE-SCALE FORCING IS FORECAST TO REMAIN NEGLIGIBLE TODAY
WITH SUBSEQUENT STORM DEVELOPMENT LIKELY CONFINED TO IMMEDIATE
VICINITY OF OUTFLOW BOUNDARY AND STALLED SYNOPTIC FRONT. SUPERCELLS
ARE POSSIBLE GIVEN THE CO-LOCATION OF STRONG INSTABILITY AND 40-50
KT OF DEEP-LAYER SHEAR WITH LARGE HAIL AND DAMAGING WINDS BEING THE
MAIN HAZARDS.
LATER TODAY INTO TONIGHT...MODEL GUIDANCE INDICATES THAT A VORTICITY
MAXIMUM WILL ROTATE THROUGH SRN PERIPHERY OF UPPER LOW ACROSS THE
RED RIVER VALLEY AND INTO THE LOWER MS VALLEY. FORCING ASSOCIATED
WITH THIS FEATURE WILL LIKELY CONTRIBUTE TO AN INCREASE IN TSTM
COVERAGE ACROSS PORTIONS OF SERN TX AND LA THIS EVENING...COINCIDENT
WITH THE EWD DESTABILIZATION OF THE AIR MASS IN THE WAKE OF THIS
MORNING/S MCS. VERTICAL SHEAR WILL BE SUFFICIENTLY STRONG TO
SUPPORT EMBEDDED BOWING AND SUPERCELL STRUCTURES WITH AN ASSOCIATED
THREAT FOR DAMAGING WINDS AND HAIL.
...CNTRL APPALACHIANS TO SERN VA/NC COASTS THIS AFTERNOON AND
EVENING...
12Z REGIONAL SOUNDINGS SHOWED STEEP MIDLEVEL LAPSE RATES OF 7.0-7.5
C/KM WHICH WILL COMBINE WITH MODEST BOUNDARY LAYER MOISTURE AND
DAYTIME HEATING TO BOOST AFTERNOON MLCAPE VALUES TO 1000-1500 J/KG.
LOW-LEVEL UPLIFT ALONG THE FRONT COUPLED WITH THE INCREASING HEIGHT
FALLS ATTENDANT TO LARGE-SCALE TROUGH MENTIONED ABOVE...AND A WEAK
IMPULSE TRANSLATING ESEWD INTO THE CNTRL APPALACHIANS WILL GIVE RISE
TO WIDELY SCATTERED TSTMS THIS AFTERNOON INTO EVENING. A TIGHTENING
MIDLEVEL HEIGHT GRADIENT WILL RESULT IN STRENGTHENING VERTICAL SHEAR
TODAY...NAMELY E OF THE APPALACHIANS WHERE THE POTENTIAL WILL EXIST
FOR ORGANIZED STORM MODES. SEVERE HAIL AND DAMAGING WIND GUSTS WILL
BE THE PRIMARY HAZARDS THROUGH EARLY-MID EVENING BEFORE STORMS
WEAKEN WITH THE COOLING/STABILIZATION OF THE BOUNDARY LAYER.
...SERN KS INTO THE MID SOUTH...
TSTMS ARE EXPECTED TO DEVELOP THIS AFTERNOON FROM THE VICINITY OF
SURFACE LOW EWD ALONG AND S OF SURFACE FRONT AS DEEP-LAYER ASCENT
INCREASES AHEAD OF SRN PLAINS LOW. ISOLATED OCCURRENCES OF
MARGINALLY SEVERE HAIL AND LOCALLY DAMAGING WIND GUSTS WILL BE
POSSIBLE OWING TO THE DEVELOPMENT OF MODERATE INSTABILITY /I.E.
AFTERNOON MLCAPE OF 1000-1500 J/KG. GENERALLY WEAK VERTICAL SHEAR
IS EXPECTED TO LIMIT STORM ORGANIZATION AND AN ATTENDANT ORGANIZED
SEVERE WEATHER THREAT. THEREFORE...THE CATEGORICAL SLIGHT RISK HAS
BEEN REMOVED.
...AL/NWRN GA...
WEAK MIDLEVEL LAPSE RATES AND MODEST BOUNDARY LAYER MOISTURE CONTENT
WILL LIMIT THE DEGREE OF DESTABILIZATION WITH AFTERNOON MLCAPE
REMAINING AOB 1000-1500 J/KG. MOREOVER...REGION WILL REMAIN
DISPLACED TO THE E OF STRONGER TROPOSPHERIC WIND FIELD ASSOCIATED
WITH SRN PLAINS LOW WHICH WILL REGULATE THE STRENGTH OF VERTICAL
SHEAR. ISOLATED SEVERE STORMS REMAIN POSSIBLE...BUT HERE TOO THE
POTENTIAL FOR AN ORGANIZED SEVERE WEATHER EPISODE APPEARS TOO LOW TO
WARRANT A CATEGORICAL SLIGHT RISK.
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