SPC AC 231933
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0233 PM CDT SAT MAY 23 2009
VALID 232000Z - 241200Z
...NO SVR TSTM AREAS FORECAST...
...ERN GULF COAST STATES/FLORIDA...
REMOVED 5 PERCENT WIND LINE FROM THE SW FL WHERE STORM COVERAGE HAS
DECREASED OVER THE LAST 1 TO 2 HOURS AND OUTFLOW HAS SURGED WWD OFF
THE COAST. OTHERWISE...EXTENDED 5 PERCENT WIND LINE A BIT NWD ACROSS
NCNTRL AL AND ERN MS WHERE THE POTENTIAL FOR ROTATING STORMS WILL
INCREASE AS RAINBANDS MOVE NWD LATE THIS AFTERNOON.
...NEB...
EXPANDED 5 PERCENT WIND AND HAIL LINE A BIT EWD ALONG THE I-80
CORRIDOR IN ERN NEB WHERE RUC ANALYSIS SHOWS MODERATE INSTABILITY
/MLCAPE VALUES OF 1000 TO 1500 J/KG/ AND FORECAST SOUNDINGS SHOW
ENOUGH DIRECTIONAL SHEAR FOR A MARGINAL SEVERE THREAT THIS
AFTERNOON.
OTHERWISE...NO CHANGES FROM THE 1630Z OUTLOOK.
..BROYLES.. 05/23/2009
.PREV DISCUSSION... /ISSUED 1050 AM CDT SAT MAY 23 2009/
PRIMARY WESTERLY FLOW ALOFT WILL REMAIN ALONG THE US/CANADIAN BORDER
TODAY...WHILE LOW LEVEL MOISTURE SLOWLY INCREASES ACROSS MOST OF THE
NATION. MEANWHILE...A PERSISTENT SUBTROPICAL LOW NEAR MOB WILL
DRIFT SLOWLY NORTHWARD INTO AL/MS TODAY. SEVERAL AREAS WILL SEE THE
POTENTIAL FOR SCATTERED THUNDERSTORMS DURING THIS PERIOD.
HOWEVER...ORGANIZED SEVERE STORMS ARE NOT ANTICIPATED.
...NORTHEAST STATES...
MORNING VISIBLE SATELLITE SHOWS GENERALLY CLEAR SKIES OVER MUCH OF
NY...AND FROM CENTRAL PA SOUTHWARD INTO THE WESTERN MD/EASTERN WV
PANHANDLE. THESE AREAS WILL SEE STRONG HEATING AND DEWPOINTS IN THE
UPPER 50S TO LOWER 60S. 12Z RAOBS SHOWED RATHER WEAK MID LEVEL
LAPSE RATES AND LOW LEVEL FLOW AOB 20 KT IN MOST AREAS. ISOLATED TO
WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS
AFTERNOON OVER THIS REGION. DEEP LAYER VERTICAL SHEAR MAY BE
SUFFICIENT FOR SOME CONVECTIVE ORGANIZATION AND A RISK OF GUSTY
WINDS AND SMALL HAIL IN STRONGER CELLS. HOWEVER...CURRENT
INDICATIONS ARE THAT COVERAGE OF ANY SEVERE ACTIVITY WILL BE QUITE
LOW AND DOES NOT WARRANT A SLIGHT RISK.
...GULF COAST...
LOW CENTER IS CURRENTLY NEAR MOB AND IS TRACKING SLOWLY INLAND.
LOCAL VAD PROFILES SUGGEST SUBSTANTIAL LOW LEVEL VERTICAL SHEAR IN
THE NORTHWEST QUADRANT OF THE CIRCULATION...BUT SURFACE DEWPOINTS IN
THIS REGION ARE ONLY IN THE MID TO UPPER 60S. A FEW ROTATING
UPDRAFTS WILL BE POSSIBLE WITH A RISK OF AN ISOLATED BRIEF
TORNADO...PRIMARILY ACROSS PARTS OF AL AND THE FL PANHANDLE THIS
AFTERNOON.
...FL...
FARTHER SOUTHEAST...STRONG HEATING AND A VERY MOIST BOUNDARY LAYER
WILL BE PRESENT OVER THE WEST HALF OF THE FL PENINSULA THIS
AFTERNOON. WEAK FLOW AT LOW AND MID LEVELS WILL ALLOW A STRONG
SEABREEZE CIRCULATION TO DEVELOP THIS AFTERNOON AND SPREAD INLAND.
SCATTERED THUNDERSTORMS MAY DEVELOP IN THIS AREA...SOME CAPABLE OF
LOCALLY DAMAGING DOWNBURSTS.
...NEB...
DIFFERENTIAL HEATING ALONG THE EAST EDGE OF WIDESPREAD CLOUDINESS
OVER WESTERN NEB MAY ENHANCE LOW LEVEL CONVERGENCE LATER TODAY FROM
NEAR GLD INTO SOUTHWEST NEB. EASTERLY LOW LEVEL WINDS WILL MAINTAIN
SURFACE DEWPOINTS IN THE 50S OVER THIS REGION AND HELP TO PROMOTE
SCATTERED THUNDERSTORMS. VERTICAL SHEAR IS WEAK...BUT RELATIVELY
STEEP LOW AND MID LEVEL LAPSE RATES MAY PROVIDE SUFFICIENT
UPDRAFT/DOWNDRAFT STRENGTH IN STRONGER CORES FOR HAIL AND GUSTY
WINDS.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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