SWODY1
SPC AC 281954
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT TUE JUN 28 2011
VALID 282000Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY ACROSS
THE SERN STATES INTO THE CAROLINAS AND VA...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF ERN CO AND WRN
KS...
...THERE IS A SLGT RISK OF SVR TSTMS PARTS OF NY AND PA...
...SRN PLAINS ACROSS LOWER MS VALLEY INTO CAROLINAS...
PRIMARY ADJUSTMENTS ARE TO SUPPRESS MAIN SEVERE THREAT SWD ACROSS MS
AL AND GA ALONG AND AHEAD OF LARGER-SCALE CONVECTIVE OUTFLOW
BOUNDARY. ENVIRONMENT TO THE SOUTH OF THE BOUNDARY REMAINS
MOIST/UNSTABLE WITH MLCAPE OF 2000-3000 J/KG.
REGION OF MAINLY PULSE SEVERE STORMS IS CONTINUING FROM SERN GA INTO
CENTRAL NC ALONG AND SOUTHEAST OF A SUBTLE SURFACE BOUNDARY.
FARTHER TO THE NORTH AND WEST...SLIGHT RISK EXPANDED WWD WHERE
STORMS ARE DEVELOPING ALONG A LOW LEVEL CONVERGENCE ZONE NEAR THE
LEE OF THE APPALACHIANS.
ISOLATED SEVERE STORM DEVELOPMENT IS ALSO POSSIBLE OVER PARTS OF
SERN OK WHERE CONVERGENCE...INSTABILITY...AND SHEAR IS ENHANCED IN
THE WAKE OF THE DOWNSTREAM MCS. THERE IS UNCERTAINTY IF THE CAP
WILL BREAK...BUT AREA WILL NEED TO MONITORED FOR POSSIBLE STORM
DEVELOPMENT.
ELSEWHERE...NO MAJOR CHANGES ARE NECESSARY.
..WEISS.. 06/28/2011
.PREV DISCUSSION... /ISSUED 1131 AM CDT TUE JUN 28 2011/
...GULF COAST STATES...
CONVECTIVE OUTFLOW ASSOCIATED WITH MULTIPLE NOCTURNAL CONVECTIVE
SYSTEMS IS EXPECTED TO SERVE AS THE FOCUS FOR RENEWED TSTM
DEVELOPMENT TODAY. DOWNSTREAM AIR MASS ACROSS MS/AL/GA IS QUITE
MOIST WITH PW VALUES GREATER THAN 1.75 INCHES...AND MIDLEVEL LAPSE
RATES OF 7-7.5 C/KM WERE OBSERVED BY 12Z JAN/BMX/FFC SOUNDINGS.
WHEN COUPLED WITH DAYTIME HEATING...EXPECT ENVIRONMENT TO BECOME
MODERATELY TO STRONGLY UNSTABLE BY AFTERNOON WITH MLCAPE OF
2000-3500 J/KG. THOUGH VERTICAL SHEAR WILL REMAIN RATHER
WEAK...ROBUST COLD POOL DEVELOPMENT WILL ALLOW FOR THE SWD
PROPAGATION OF MULTIPLE STORM CLUSTERS TOWARD THE GULF COAST. HAIL
AND CORRIDORS OF WIND DAMAGE WILL BE THE PRIMARY HAZARDS.
...MID ATLANTIC AND SERN ATLANTIC STATES...
SATELLITE-DERIVED PW IMAGERY AND GPS PW DATA INDICATE THE PRESENCE
OF A VERY MOIST AIR MASS IN PLACE E OF THE APPALACHIANS. AND WHILE
MIDLEVEL LAPSE RATES ARE WEAKER THAN POINTS TO THE SW/W...ABUNDANT
SUNSHINE SHOULD SUPPORT RAPID BOUNDARY LAYER WARMING WITH A
RESULTANT STEEPENING OF LOW-LEVEL LAPSE RATES AND MLCAPE INCREASING
TO 1500-3000 J/KG. WEAK MIDLEVEL HEIGHT FALLS COMBINED WITH HEATING
ALONG THE HIGH TERRAIN AND CONVERGENCE ALONG LEE TROUGH AND
DEVELOPING SEA BREEZE CIRCULATIONS WILL FOSTER NUMEROUS TSTMS THIS
AFTERNOON. STORMS WILL LIKELY CONGEAL INTO MULTIPLE CLUSTERS WITH
THE POTENTIAL FOR DAMAGING WET MICROBURSTS THROUGH THIS EVENING.
...CNTRL HIGH PLAINS...
MIDLEVEL HEIGHTS WILL BUILD ACROSS THE REGION TODAY IN ADVANCE OF
INTENSE UPSTREAM SYSTEM WHICH WILL MOVE ONTO THE CA COAST.
HOWEVER...A DEVELOPING LEE TROUGH WILL SERVE TO MAINTAIN AN AXIS OF
50S F BOUNDARY LAYER DEWPOINTS BENEATH EML...RESULTING IN AFTERNOON
MLCAPE OF 1000-2000 J/KG. STRONG HEATING INVOF LEE TROUGH IS
EXPECTED TO SUFFICIENTLY ERODE CAP SUCH THAT ISOLATED TO WIDELY
SCATTERED TSTMS APPEAR LIKELY BY LATE AFTERNOON/EARLY EVENING.
GIVEN A KINEMATIC ENVIRONMENT FEATURING VERTICALLY VEERING WIND
PROFILES AND 40-45 KT OF WLY/NWLY SHEAR...SETUP WILL FAVOR THE
DEVELOPMENT OF HIGH-BASED SUPERCELLS CAPABLE OF DAMAGING WINDS AND
HAIL.
...NORTHEAST...
FORCING FOR ASCENT/HEIGHT FALLS ATTENDANT TO MIDLEVEL SYSTEM
APPROACHING FROM THE W COUPLED WITH FRONTAL ASCENT WILL SUPPORT THE
DEVELOPMENT OF SCATTERED TSTMS ALONG COLD FRONT PROGRESSING EWD
THROUGH REGION TODAY. VISIBLE SATELLITE IMAGERY SHOWS THAT
CLOUDINESS IS DECREASING WHICH SHOULD ALLOW FOR STRONGER DAYTIME
HEATING TO OCCUR WITHIN THE MOIST PRE-FRONTAL WARM SECTOR WITH
MLCAPE INCREASING TO 1000-1500 J/KG. VERTICAL SHEAR WILL ALSO
GRADUALLY INCREASE AS MIDLEVEL HEIGHT GRADIENT TIGHTENS... RESULTING
IN AN ENVIRONMENT SUPPORTIVE OF WIDELY SCATTERED SEVERE STORMS.
HAIL AND LOCALLY DAMAGING WIND GUSTS WILL BE THE PRIMARY HAZARDS
THIS AFTERNOON AND EVENING.
...NRN INTERMOUNTAIN REGION...
MIDLEVEL HEIGHTS WILL GRADUALLY LOWER THROUGH THE D1 PERIOD AS
INTENSE MID AND UPPER-LEVEL TROUGH EDGES EWD. HOWEVER...IT APPEARS
THE TERRAIN INFLUENCES WILL LARGELY SERVE AS THE FOCUS FOR DIURNAL
STORM DEVELOPMENT. GIVEN THE STEEP LAPSE RATES IN PLACE...PW VALUES
OF AROUND .75 INCH AND 40-45 KT OF DEEP SWLY SHEAR...SETUP WILL
FAVOR THE DEVELOPMENT OF A FEW SEVERE STORMS CAPABLE OF DAMAGING
WINDS AND HAIL.
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