SPC AC 241940
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0240 PM CDT SUN MAY 24 2009
VALID 242000Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF NE PA...NJ...SE
NY AND SRN NEW ENGLAND...
...NE PA/SE NY/NJ/SRN NEW ENGLAND...
EXTENDED THE SLIGHT RISK AREA WEST INTO NE PA AND EAST INTO CT WHERE
AN EAST TO WEST BOUNDARY EXISTS. SFC DEWPOINTS IN THE LOWER 60S
F...MLCAPE VALUES IN THE 1500 TO 2500 J/KG RANGE AND 0-3 KM LAPSE
RATES EXCEEDING 7.5 C/KM ACCORDING TO THE RUC SHOULD SUPPORT A
THREAT FOR ISOLATED DAMAGING WIND GUSTS. IN ADDITION...THE
INSTABILITY AND RELATIVELY STEEP MID-LEVEL LAPSE RATES SHOULD BE
SUFFICIENT FOR LARGE HAIL ESPECIALLY ACROSS NJ...SE NY AND CT WHERE
INSTABILITY IS LOCALLY MAXIMIZED.
...MAINE...
STRONG CELLS ARE LOCATED JUST AHEAD OF A SHORTWAVE TROUGH NEAR THE
CANADA-U.S. BORDER IN NERN MAINE. STRONG VERTICAL SHEAR AND STEEP
MID-LEVEL LAPSE RATES SHOWN BY THE RUC SHOULD BE SUFFICIENT FOR AN
ISOLATED LARGE HAIL THREAT. ALTHOUGH THE STRONGER CELLS ARE NOW JUST
EAST OF THE MAINE STATE-LINE...REDEVELOPMENT COULD OCCUR OVER THE
NEXT 1 TO 2 HOURS MAINLY IN AROOSTOOK COUNTY.
...FLORIDA...
REMOVED 5 PERCENT HAIL AND WIND PROBABILITIES ALONG THE WEST COAST
OF FLORIDA IN STABILIZED AIRMASS BEHIND SEA BREEZE BOUNDARY.
ELSEWHERE...NO CHANGE TO THE PREVIOUS OUTLOOK.
..BROYLES.. 05/24/2009
.PREV DISCUSSION... /ISSUED 1051 AM CDT SUN MAY 24 2009/
ANOTHER DAY OF RELATIVELY WEAK FLOW ALOFT AND INCREASING LOW LEVEL
MOISTURE IS EXPECTED ACROSS THE UNITED STATES TODAY. THIS WILL LEAD
TO NUMEROUS AREAS OF SCATTERED THUNDERSTORMS...BUT ONLY ISOLATED
REGIONS WHERE PARAMETERS SUGGEST A RISK OF STRONG/SEVERE STORMS.
...PA/NY/NJ/CT/MA...
WEAK SURFACE COLD FRONT IS SAGGING SOUTHWARD ACROSS NY THIS MORNING.
SOUTHWESTERLY LOW LEVEL WINDS AHEAD OF THE FRONT ARE SLOWLY
TRANSPORTING 60S DEWPOINTS INTO REGION...WHILE GENERALLY CLEAR SKIES
HELP TO DESTABILIZE AIRMASS. AFTERNOON MLCAPE VALUES AT OR ABOVE
1000 J/KG ARE LIKELY. SCATTERED SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO INTENSIFY ALONG THE FRONT BY MID AFTERNOON AND TRACK
SOUTHEASTWARD. SOUTHERLY ONSHORE FLOW OVER MA/CT WILL LESSEN
INSTABILITY AND LIKELY WEAKEN STORMS AS THEY MOVE INTO THAT AREA.
HOWEVER...THREAT FOR ISOLATED SEVERE STORMS CAPABLE OF HAIL AND
DAMAGING WINDS WILL LIKELY PERSIST THROUGH THE EARLY EVENING AS FAR
SOUTH AS CENTRAL NJ. REFER TO SWOMCD NUMBER 861 FOR FURTHER
DETAILS.
...FL...
MORNING VISIBLE SATELLITE IMAGERY SHOWS CLEAR SKIES OVER ALL OF THE
FL PENINSULA THIS MORNING. SURFACE DEWPOINTS IN THE 70S AND 500MB
TEMPERATURES AOB -10C WILL YIELD AFTERNOON MLCAPE VALUES OVER 2000
J/KG. WEAK FLOW AT ALL LEVELS WILL PROMOTE SEABREEZE CIRCULATIONS
AND LIKELY RESULT IN WIDESPREAD THUNDERSTORMS BY EARLY AFTERNOON.
DEGREE OF INSTABILITY AND AVAILABILITY OF SOME DRY AIR ALOFT SUGGEST
A RISK OF HAIL AND GUSTY WINDS IN STRONGER CORES. REFER TO SWOMCD
NUMBER 860 FOR FURTHER DETAILS.
...WY/SD/NEB...
WIDESPREAD CLOUDS ARE IN PLACE THIS MORNING OVER EASTERN WY AND
WESTERN SD/NEB. SLOW EROSION OF CLOUDS IS EXPECTED FROM THE WEST
TODAY...LEADING TO RELATIVELY STEEP LOW LEVEL LAPSE RATES AND
MODERATE INSTABILITY OVER EASTERN WY. MODEL GUIDANCE IS IN GOOD
AGREEMENT THAT SCATTERED THUNDERSTORMS WILL DEVELOP IN THIS CORRIDOR
AND MOVE EASTWARD INTO WESTERN SD/NEB PANHANDLE BY LATE AFTERNOON
AND EVENING. WINDS ALOFT ARE RATHER WEAK...BUT SHOW A VEERING
PROFILE WHICH MAY BE SUFFICIENT FOR A FEW ORGANIZED/SEVERE
STORMS...ESPECIALLY IF THEY CAN INTERACT WITH A WEAK REMNANT
BOUNDARY EXTENDING FROM SOUTHEAST MT INTO THE BLACK HILLS.
...SOUTH TX...
AMPLE MOISTURE OVER THE MOUNTAINS OF MEXICO WILL LIKELY RESULT IN
SCATTERED AFTERNOON THUNDERSTORMS SPREADING ACROSS THE LOWER RIO
GRANDE VALLEY. FORECAST SOUNDINGS SUGGEST WEAK BUT SUFFICIENT DEEP
LAYER VERTICAL SHEAR FOR ISOLATED STORMS TO BECOME STRONG THIS
AFTERNOON AND EVENING ACROSS DEEP SOUTH TX. GUSTY WINDS AND HAIL
ARE POSSIBLE IN THE STRONGEST STORMS.
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