SWODY1
SPC AC 291941
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0241 PM CDT TUE JUN 29 2010
VALID 292000Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS FAR SERN VA...PARTS OF
THE CAROLINAS TO NERN GA...
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN ORE TO WRN MT...
...NERN GA/SC/SRN NC...
SLIGHT RISK HAS BEEN EXPANDED WSWWD ACROSS SRN NC...THE REST OF NRN
SC INTO NERN GA WHERE OBJECTIVE ANALYSES INDICATED MLCAPE 2000+ J/KG
HAS DEVELOPED IN LEE OF THE SRN APPALACHIANS TO THE SRN ATLANTIC
COAST. FARTHER NE...THE SLIGHT RISK AREA HAS BEEN REMOVED/SEVERE
WIND PROBABILITIES REDUCED ACROSS MUCH OF SERN VA...WITH GREATER
SEVERE WEATHER THREAT EXPECTED SWD WHERE INSTABILITY IS HIGHER AND
CONVERGENCE STRONGER ALONG PRE-FRONTAL BOUNDARY. EARLY AFTERNOON
SURFACE ANALYSIS SHOWED THE PRE-FRONTAL WIND SHIFT EXTENDING FROM
NERN NC SWWD INTO CENTRAL SC AND NRN GA. ALTHOUGH DEEP LAYER SHEAR
REMAINS WEAK /AOB 20 KT/ PER AREA WSR-88D VADS ACROSS THIS
REGION...TSTMS DEVELOPING ALONG THE PRE-FRONTAL WIND SHIFT AND ALSO
MOVING EWD OFF THE SRN APPALACHIANS INTO MODERATE INSTABILITY WILL
CONTINUE TO FAVOR PULSE-TYPE STORMS WITH SOME CLUSTERING POSSIBLE
WHERE STORM MERGERS TAKE PLACE.
...ERN ORE TO WRN MT...
EARLY AFTERNOON RADAR MOSAIC/SATELLITE IMAGERY/LIGHTNING DATA SHOWED
A FEW STORMS DEVELOPING OVER THE HIGHER TERRAIN OF CENTRAL ID/SWRN
MT. JUST WEST OF THIS DEVELOPMENT/CLOUDINESS...OBJECTIVE ANALYSES
INDICATED AIR MASS HAS BECOME MODERATELY UNSTABLE /MLCAPE UP TO 1500
J PER KG/ ALONG AND EAST OF THE COLD FRONT WHICH AT 19Z EXTENDED
FROM FAR NWRN MT SSWWD INTO ERN ORE. GIVEN THESE TRENDS AND
EXPECTED TSTM DEVELOPMENT ALONG AND E OF THE COLD FRONT WHERE THE
AIR MASS IS MOST UNSTABLE AND SUFFICIENTLY SHEARED /40-50 KT/ FOR A
SEVERE THREAT...NO CHANGES TO THE OUTLOOK ARE REQUIRED.
..PETERS.. 06/29/2010
.PREV DISCUSSION... /ISSUED 1054 AM CDT TUE JUN 29 2010/
...NRN ROCKIES AREA THIS AFTERNOON INTO EARLY TONIGHT...
A MIDLEVEL TROUGH W OF BC/WA/ORE WILL MOVE EWD/INLAND THROUGH
TONIGHT...WITH STRONG GRADIENT FLOW MAINTAINED ALOFT OVER THE PAC NW
AND NRN ROCKIES. A BAROCLINIC ZONE ACCOMPANYING THE MIDLEVEL TROUGH
WILL DRIFT EWD ACROSS ERN ORE/NW ID/NW MT THROUGH THE PERIOD. STEEP
MIDLEVEL LAPSE RATES AND A PLUME OF 0.75-1.00 INCH PW VALUES HAVE
SPREAD NNEWD FROM THE GREAT BASIN TO THE NRN ROCKIES IN ADVANCE OF
THE FRONT. DAYTIME HEATING WITHIN/W OF THE MOISTURE/CLOUD PLUME
WILL CONTRIBUTE TO AFTERNOON MLCAPE VALUES OF 500-1000 J/KG...AND
SUFFICIENTLY WEAK CONVECTIVE INHIBITION TO ALLOW THUNDERSTORM
DEVELOPMENT. EFFECTIVE BULK SHEAR IN EXCESS OF 40 KT WILL FAVOR
SMALL BOWING SEGMENTS AND A COUPLE OF SUPERCELLS WITHIN A BROKEN
BAND OF STORMS ALONG THE FRONT LATER THIS AFTERNOON INTO EARLY
TONIGHT. DAMAGING WINDS AND LARGE HAIL WILL BE THE MAIN SEVERE
THREATS.
...TIDEWATER AREA TO THE NRN GULF STATES THIS AFTERNOON...
A COLD FRONT WILL CONTINUE TO DRIFT SEWD ACROSS VA/CAROLINAS AND THE
NRN GULF COAST STATES THIS AFTERNOON. A WARM/MOIST BOUNDARY LAYER
IN ADVANCE OF THE FRONT WILL AGAIN CONTRIBUTE TO MODERATE
INSTABILITY /MLCAPE VALUES AOA 2000 J PER KG/...IN AN ENVIRONMENT OF
WEAK VERTICAL SHEAR S OF THE MAIN BELT OF WLYS. THE ENVIRONMENT
WILL SUPPORT A BROKEN BAND OF THUNDERSTORMS ALONG THE FRONT THIS
AFTERNOON/EVENING FROM THE TIDEWATER REGION SWWD ACROSS THE
CAROLINAS INTO THE NRN GULF STATES. THE THREAT FOR DAMAGING
DOWNBURSTS WILL BE SOMEWHAT GREATER ACROSS THE SLIGHT RISK AREA
COMPARED TO THE SEE TEXT AREA AS A RESULT OF GREATER INSTABILITY AND
CLOSER PROXIMITY TO THE SRN FRINGE OF THE MIDLEVEL WLYS ON THE SRN
PERIPHERY OF THE ONTARIO/QUEBEC CLOSED LOW.
...CENTRAL MAINE EARLY THIS AFTERNOON...
MARGINAL INSTABILITY REMAINS IN A NARROW CORRIDOR E OF THE COLD
FRONT ACROSS INTERIOR MAINE WHERE SURFACE TEMPERATURES HAVE WARMED
INTO THE 70S TO NEAR 80 F WITH DEWPOINTS IN THE 60S. LAPSE RATES
ALOFT ARE RATHER POOR...BUT STEEPENING LOW-LEVEL LAPSE RATES AND
EFFECTIVE BULK SHEAR NEAR 40 KT COULD SUPPORT A FEW STORMS CAPABLE
OF PRODUCING ISOLATED STRONG WIND GUSTS. REFER TO MD 1157 FOR
ADDITIONAL INFORMATION.
...TX COAST...
TC ALEX APPEARS TO BE STRENGTHENING OVER THE WRN GULF OF MEXICO AND
IS FORECAST TO MAKE LANDFALL IN NE MEXICO WEDNESDAY EVENING. IT
APPEARS THE MORE FAVORABLE AREA FOR OUTER BAND SUPERCELLS AND
TORNADOES WILL REMAIN OFFSHORE THROUGH THIS PERIOD...THUS WILL NOT
INTRODUCE ANY SEVERE PROBABILITIES IN THIS UPDATE.
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