SPC AC 041250
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT THU JUN 04 2009
VALID 041300Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CNTRL AND SRN HI
PLNS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF ORE AND ADJACENT
STATES...
...SYNOPSIS...
LITTLE OVERALL CHANGE EXPECTED ACROSS THE LWR 48 THIS PERIOD AS
ELONGATED TROUGH PERSISTS OVER S CNTRL/SE CANADA...AND UPR LOW OFF
THE CA CST EDGES SLOWLY EWD. STRONG SHORTWAVE IMPULSE NOW OVER SK
WILL CONTINUE SE INTO NRN MN BY 12Z FRI. FARTHER S...A SERIES OF
DISTURBANCES IN WEAKER CYCLONIC FLOW OVER THE CNTRL AND SERN U.S.
SHOULD EVOLVE INTO A TROUGH OVER MS/AL. W OF THIS EVOLVING
SYSTEM...SLIGHT HEIGHT RISES WILL PREVAIL OVER THE CNTRL/SRN HI
PLNS.
AT THE SFC...COLD FRONT ASSOCIATED WITH SK IMPULSE WILL ACCELERATE
SE ACROSS THE NRN PLNS/UPR MS VLY...WHILE WEAK SFC LOW NOW OVER
MS/AL REDEVELOPS SLOWLY E/NE INTO GA AND THE CAROLINAS. WEAKENING
COLD FRONT JUST NW OF THE LOW LIKELY WILL BE DRAWN INTO THE
CIRCULATION OF THE LOW. THE FRONT WILL MAKE MINIMAL SWD PROGRESSION
IN VA...BUT WILL MOVE STEADILY ESE ACROSS THE TN VLY/GULF CST
STATES.
...CNTRL/SRN HI PLNS...
A WEAK LEE TROUGH WILL BEGIN TO DEVELOP TODAY OVER THE CNTRL/SRN HI
PLNS AS EXPANSIVE SFC RIDGE CENTERED OVER THE NRN PLNS/UPR MS VLY
EDGES ESEWD. SE FLOW AHEAD OF TROUGH WILL BE OF CONTINENTAL
ORIGIN...WITH SFC DEWPOINTS ONLY IN THE 40S TO LOW 50S F. MODERATE
WNW TO NWLY MID LVL FLOW WILL...HOWEVER...MAINTAIN EML ACROSS
REGION. AS A RESULT...STRONG SFC HEATING SHOULD BOOST SBCAPE TO AOA
1000 J/KG.
DESPITE WEAK HEIGHT RISES...DIFFERENTIAL HEATING/TERRAIN
CIRCULATIONS SHOULD SUPPORT DEVELOPMENT OF ISOLD TO SCTD AFTN/EVE
STORMS FROM CNTRL/SE WY S/SE INTO CO...NE NM...AND THE WRN TX
PANHANDLE. ALTHOUGH LOW LVL WINDS WILL BE LIGHT...AMPLE DEEP SHEAR
WILL BE PRESENT FOR SUPERCELLS WITH LARGE HAIL AND LOCALLY DMGG
WIND. A LIMITED SVR THREAT MAY CONTINUE INTO LATE TONIGHT OVER NE
CO...WRN NEB...AND NW KS...WHERE A SMALL CLUSTER OR TWO OF STORMS
MAY PERSIST IN EXIT REGION OF STRENGTHENING/MOISTENING LLJ.
...ORE AND PARTS OF ADJACENT STATES...
DIFFLUENT LEFT EXIT REGION OF PERSISTENT HI-LVL JET STREAK ON ERN
SIDE OF OFFSHORE LOW WILL RESIDE OVER ORE AND ADJACENT PARTS OF NRN
CA/WRN ID/SRN WA TODAY. THIS AREA WILL CONTINUE TO COINCIDE WITH
MAX PW AXIS...WITH AVERAGE VALUES REMAINING CLOSE TO 1 INCH. BKN
CLOUD COVER WILL SOMEWHAT LIMIT SFC HEATING. BUT SUFFICIENT
DESTABILIZATION SHOULD OCCUR TO SUPPORT DIURNAL INTENSIFICATION OF
EXISTING STORMS...AND ADDITIONAL STRONG DEVELOPMENT...BY EARLY AFTN.
SHEAR PROFILES WILL BE FAVORABLE FOR FORWARD-PROPAGATING
/NW-DEVELOPING/ LINE SEGMENTS WITH LOCALLY DMGG WIND AND HAIL. A
FEW SUPERCELLS COULD ALSO OCCUR BEFORE STORM MERGE INTO BKN
LINES/CLUSTERS BY EARLY EVE.
...SERN U.S...
LEAD IMPULSE ASSOCIATED WITH EVOLVING TROUGH OVER THE GULF CST
STATES HAS ALREADY MOVED INLAND ACROSS THE WRN FL PANHANDLE/SRN AL.
SATELLITE LOOPS SUGGEST THAT OVERALL CIRCULATION WILL CONTINUE TO
SLOWLY STRENGTHEN TODAY/TONIGHT. ALTHOUGH ASSOCIATED MID/UPR LVL
FLOW IS EXPECTED TO REMAIN WEAK...A CURRENT OF ENHANCED...MOIST SWLY
850 MB FLOW...WITH SPEEDS AROUND 30 KTS...WILL PREVAIL IN WARM
SECTOR OF MS/AL SFC WAVE. CLOUDS/SHOWERS LIKELY WILL LIMIT LOW LVL
LAPSE RATES. BUT IF SMALL...DISCRETE OR SEMI-DISCRETE SHOWERS/WEAK
STORMS DO INDEED DEVELOP...A CONDITIONAL THREAT WOULD EXIST FOR A
BRIEF TORNADO OR TWO FROM NRN FL/GA NE INTO THE CAROLINAS.
FARTHER S...A FEW STRONG AFTN MULTICELLS WITH WET MICROBURSTS COULD
OCCUR OVER CNTRL FL...IN AREA OF STRONGER SFC HEATING ON SRN FRINGE
OF UPR CIRCULATION.
...UPR MS VLY...
A BAND OR TWO OF VIGOROUS BUT LOW-TOPPED STORMS MAY ACCOMPANY COLD
FRONT MOVING INTO NE ND/NRN MN LATE TODAY. ALTHOUGH WIND FIELD WILL
BE FAVORABLE FOR BOWING SEGMENTS...RELATIVELY WEAK LOW LVL LAPSE
RATES AND SMALL TEMPERATURE-DEWPOINT SPREADS SUGGEST THAT ANY DMGG
WIND THREAT WILL REMAIN LOW.
..CORFIDI/GARNER.. 06/04/2009
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