SWODY1
SPC AC 291954
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT WED JUL 29 2009
VALID 292000Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CNTRL AND SRN
HIGH PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE HUDSON VALLEY AND
WRN/CNTRL NEW ENGLAND INTO ERN NC...
...CNTRL/SRN HIGH PLAINS...
CURRENT FORECAST APPEARS ON TRACK WITH ONLY SMALL MODIFICATIONS
MADE. FOR ADDITIONAL NEAR TERM GUIDANCE...SEE MCD 1711 AND WW 635.
...LOWER ELEVATIONS OF THE SRN PLAINS INTO LOWER MS VALLEY...
SEVERE PROBABILITIES AND ASSOCIATED CATEGORICAL SLIGHT RISK HAVE
BEEN DOWNGRADED.
CONSIDERABLE CLOUDINESS AND LINGERING TSTM ACTIVITY HAS LIMITED
DAYTIME HEATING AND RESULTANT AIR MASS DESTABILIZATION FROM ERN OK
INTO AR. FARTHER S OVER CNTRL/ERN TX INTO LA...BOUNDARY LAYER HAS
WARMED THROUGH THE 80S AND WHEN COUPLED WITH DEWPOINTS OF 70-75
F...ENVIRONMENT HAS BECOME MODERATELY UNSTABLE WITH MLCAPE OF
1500-2500 J/KG. THE PRESENCE OF NUMEROUS MESOSCALE BOUNDARIES AND
EWD MIGRATION OF MCV/VORTICITY MAXIMUM FROM CNTRL TX SHOULD SUPPORT
A CONTINUED INCREASE IN STORM COVERAGE ACROSS THE REGION INTO THIS
EVENING. HOWEVER...INSPECTION OF AREA VWP AND PROFILER DATA
INDICATES THAT AMBIENT WIND FIELDS REMAIN RATHER WEAK WHICH WILL
TEND TO LIMIT THE DEGREE OF STORM ORGANIZATION AND THE POTENTIAL FOR
A MORE SUBSTANTIAL SEVERE THREAT. NONETHELESS...ISOLATED WIND/HAIL
WILL REMAIN POSSIBLE WITH THE MORE INTENSE STORMS.
OVERNIGHT...SWLY LLJ IS FORECAST TO STRENGTHEN OVER THE ARKLATEX
WHICH WILL SERVE TO ENHANCE LOW-LEVEL SHEAR. CLUSTERS OF TSTMS WILL
LIKELY BE MAINTAINED OVER THIS AREA WITHIN MOIST AIR MASS...DRIVEN
LARGELY BY THE INTENSIFYING WAA. WHILE SOME STORM ROTATION IS
POSSIBLE...THE PRESENCE OF POOR LAPSE RATES AND CONTINUED WEAK
MID/UPPER-LEVEL WIND FIELDS WILL PRECLUDE A MORE ROBUST SEVERE
THREAT.
...NEW ENGLAND INTO ERN NC...
CLUSTERS OF STRONG/SEVERE TSTMS ARE IN PROGRESS THIS AFTERNOON FROM
THE HUDSON VALLEY/WRN NEW ENGLAND SWD THROUGH SERN VA/ERN NC. WATER
VAPOR IMAGERY AND RADAR DATA INDICATE SEVERAL EMBEDDED
IMPULSES/MCV/S WITH THE PRIMARY SHORT WAVE TROUGH NOW MOVING THROUGH
THE CUMBERLAND PLATEAU AND BLUE RIDGE. THIS SYSTEM IS ACCOMPANIED
BY A BELT OF 40-50 KT SWLY WINDS IN THE MIDLEVELS...AND WHEN COUPLED
WITH 30-35 KT SWLY LLJ...KINEMATIC ENVIRONMENT WILL REMAIN FAVORABLE
FOR EMBEDDED SUPERCELL AND/OR BOWING STRUCTURES CAPABLE OF DAMAGING
WINDS...HAIL AND PERHAPS A TORNADO OR TWO.
..MEAD/ROBINSON.. 07/29/2009
.PREV DISCUSSION... /ISSUED 1128 AM CDT WED JUL 29 2009/
...SYNOPSIS...
CONVECTIVE OUTLOOK WILL AGAIN BE RATHER MESSY WITH EXTENSIVE DEEP
MOIST CONVECTION ALONG PERIPHERY OF BROAD GREAT LAKES MID/UPPER
LEVEL TROUGH. MORNING SOUNDINGS/GOES IMAGERY INDICATE DEEP MOISTURE
ARCING AROUND THIS TROUGH WITH PW/S FROM 1.5-2.25 INCHES. GIVEN
ABUNDANT MOISTURE...DIURNAL HEATING WILL SUPPORT LARGE AREAS OF
MODERATE OR HIGHER INSTABILITY AND WIDELY SCATTERED STRONG/SEVERE
THUNDERSTORMS ONCE AGAIN. PRIMARY FOCI FOR MORE ORGANIZED
THUNDERSTORM AREAS WILL LIKELY BE TIED TO SHORTWAVE TROUGHS ROTATING
AROUND LARGE TROUGH...NOW MOVING INTO THE CENTRAL APPALACHIANS AND
BUILDING SEWD ACROSS THE CENTRAL/SRN HIGH PLAINS.
...APPALACHIANS INTO THE NORTHEAST...
MORNING SATELLITE IMAGERY SUGGESTS MODERATE TO STRONG HEATING HAS
COMMENCED WITHIN MOSTLY CLEAR SKIES ACROSS ERN NC/VA NWD INTO NJ.
THIS SHOULD STEEPEN LOW LEVEL LAPSE RATES AND BOOST INSTABILITY
AHEAD OF MAIN IMPULSE MOVING ACROSS THE CENTRAL APPALACHIANS LATE
THIS MORNING. REGION WILL REMAIN UNDER FAIRLY STRONG SWLY MID LEVEL
FLOW...WHICH IS EXPECTED TO SUPPORT ORGANIZED CONVECTION AS STORMS
INTENSIFY. ISOLATED DEVELOPMENT IS ALREADY OCCURRING EARLY THIS
AFTERNOON OVER PORTIONS OF THE MID ATLANTIC...POSSIBLY ASSOCIATED
WITH SUBTLE IMPULSE EJECTING NEWD ACROSS PA THIS MORNING. MORE
WIDESPREAD/ROBUST DEVELOPMENT SHOULD INCREASE LATER THIS AFTERNOON.
ACTIVITY WILL LIKELY EVOLVE INTO SUPERCELLS AND FAST MOVING/SMALL
BOW ECHOES WITHIN GENERALLY UNIDIRECTIONAL WIND PROFILES WITH
PRIMARY THREAT OF DAMAGING WINDS. HOWEVER... MARGINALLY SEVERE HAIL
AND POTENTIAL FOR A TORNADO OR TWO WILL ALSO ACCOMPANY PERSISTENT
SUPERCELL STRUCTURES. THREAT MAY PERSIST THROUGH THE EVENING INTO
PORTIONS OF WRN NEW ENGLAND ASSOCIATED WITH 50+ KT LLJ FORECAST TO
OVERSPREAD THE HUDSON VALLEY.
...CENTRAL/SRN HIGH PLAINS SEWD TOWARDS THE MID SOUTH...
CLUSTERS OF STORMS SHOULD PERSIST AHEAD OF MID LEVEL VORT MAX/MCV
NOW SHIFTING ACROSS CENTRAL TX TODAY...AS WELL AS POSSIBLE SUBTLE
WAVES MOVING ACROSS NERN TX/SERN OK AND SHIFTING SEWD ACROSS SWRN KS
THIS MORNING. OVERALL WEAK DEEP LAYER SHEAR AND MODEST LAPSE RATES
SHOULD LIMIT STORM ORGANIZATION AND PERSISTENT SEVERE THREAT.
HOWEVER...SIMILAR TO PAST SEVERAL DAYS...A FEW CLUSTERS OF SEVERE
MAY ACCOMPANY THIS ACTIVITY. ADDITIONAL...LIKELY MORE
ROBUST...DEVELOPMENT IS EXPECTED TO EVOLVE OVER THE HIGH PLAINS
REGION AND SPREAD SEWD THROUGH THE EVENING/OVERNIGHT IN THE FORM OF
ONE OR MORE MCSS. LARGE HAIL...AND POSSIBLY A TORNADO OR TWO SHOULD
ACCOMPANY INITIAL DEVELOPMENT INVOF THE HIGH PLAINS WHERE NWLY FLOW
ALOFT SUPPORTS SUPERCELL STRUCTURES. HOWEVER...WIND DAMAGE AND
ISOLATED HAIL THREATS CAN BE EXPECTED AS ACTIVITY EVOLVES INTO MCSS
THIS EVENING.
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