SWODY2
SPC AC 280600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT WED APR 28 2010
VALID 291200Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE SRN AND
CNTRL PLAINS INTO THE UPPER MS VALLEY...
...SYNOPSIS...
THE BROAD UPPER TROUGH NOW MOVING INTO THE WRN U.S. WILL CONTINUE
SLOWLY EWD THROUGH THURSDAY. AT LEAST A COUPLE OF IMPULSES
ORIGINATING WITHIN THE UPPER TROUGH WILL EJECT NEWD THROUGH THE
CNTRL PLAINS AND UPPER MS VALLEY DURING THE DAY. A STRONGER IMPULSE
IS FORECAST TO EJECT INTO THE SRN AND CNTRL PLAINS LATER THURSDAY
NIGHT. MODEL CONSENSUS IS THAT A SURFACE LOW INITIALLY OVER NEB
EARLY THURSDAY WILL LIFT NEWD INTO MN DURING THE DAY IN ASSOCIATION
WITH EJECTING SHORTWAVE TROUGH. THIS WILL FORCE A COLD FRONT SEWD
THROUGH ERN NEB AND NRN KS DURING THE AFTERNOON. FARTHER SOUTH A
DRYLINE WILL RESIDE ACROSS WRN TX...OK AND NWD INTO KS. A LEE
CYCLONE WITH TRAILING PACIFIC FRONT WILL SHIFT EWD THROUGH SRN
KS/WRN OK THURSDAY NIGHT IN ASSOCIATION WITH AN IMPULSE MOVING
THROUGH BASE OF UPPER TROUGH. THIS FRONT WILL OVERTAKE THE DRYLINE
ACROSS THE SRN/CNTRL HIGH PLAINS.
...CNTRL PLAINS THROUGH UPPER MS VALLEY AREA...
SURFACE RIDGE WILL MAINTAIN ELY-NELY TRAJECTORIES OVER THE NRN GULF
AND DELAY MORE SIGNIFICANT GULF BOUNDARY LAYER MODIFICATION UNTIL
WEDNESDAY NIGHT. THIS WILL RESULT IN ONLY PARTIALLY MODIFIED GULF
AIR WITH DEWPOINTS IN THE 50S TO AROUND 60 ADVECTING NWD INTO THE
CNTRL PLAINS AND UPPER MS VALLEY BENEATH ERN PERIPHERY OF STEEPER
LAPSE RATE PLUME. THESE PROCESSES AND DIABATIC WARMING WILL
CONTRIBUTE TO 800-1200 J/KG MLCAPE. EWD ADVECTION OF THE EML PLUME
ABOVE THE MODEST MOIST AXIS WILL LIKELY RESULT IN A CAP TO SURFACE
BASED STORMS. MOST LIKELY AREA OF INITIATION WILL BE WITHIN ZONE OF
DEEPER ASCENT ALONG COLD FRONT FROM ERN NEB AND WRN IA DURING THE
AFTERNOON...THOUGH AN ISOLATED STORM OR TWO CANNOT BE RULED OUT
ALONG THE DRYLINE ACROSS KS. ADDITIONAL STORMS MAY EVENTUALLY
BACKBUILD SWD INTO KS AS THE COLD FRONT OVERTAKES THE DRYLINE AND AS
THE SLY LOW LEVEL JET STRENGTHENS TO IN EXCESS OF 60 KT. VERTICAL
SHEAR IN EXCESS OF 60 KT WILL SUPPORT ORGANIZED STORMS INCLUDING
SUPERCELLS. HOWEVER...STORMS SHOULD EVENTUALLY GROW UPSCALE INTO
LINES ALONG THE SEWD ADVANCING COLD FRONT.
...SRN PLAINS...
THREAT IN THIS AREA IS MORE CONDITIONAL DUE TO LOWER PROBABILITY OF
THUNDERSTORM INITIATION. THE ATMOSPHERE WILL BECOME MODERATELY
UNSTABLE DURING THE AFTERNOON AS PARTIALLY MODIFIED GULF AIR ADVECTS
NWD BENEATH STEEP LAPSE RATES ASSOCIATED WITH EML PLUME. HOWEVER...A
STOUT CAPPING INVERSION WILL EXIST OVER MUCH OF THE WARM SECTOR. IN
WAKE OF IMPULSE MOVING THROUGH THE CNTRL PLAINS AND UPPER MS VALLEY
REGION...DRYLINE CONVERGENCE WILL NOT BE PARTICULARLY PRONOUNCED.
HOWEVER...HEATING AND MIXING ALONG THIS BOUNDARY MIGHT BE SUFFICIENT
TO INITIATE AN ISOLATED STORM OR TWO. IF A STORM DEVELOPS IT WOULD
RAPIDLY BECOME SUPERCELLULAR GIVEN THE STRONG VERTICAL SHEAR IN
PLACE. GREATER PROBABILITY FOR STORM INITIATION WILL OCCUR LATER
THURSDAY NIGHT WHEN THE PACIFIC FRONT ACCOMPANYING A SPEED MAX
MOVING THROUGH BASE OF UPPER TROUGH OVERTAKES THE DRYLINE.
MODELS ALSO INDICATE STORMS MAY DEVELOP TOWARD THE END OF THIS
PERIOD WITHIN WARM ADVECTION REGIME FROM ERN PARTS OF THE SRN PLAINS
INTO THE LOWER MS VALLEY COINCIDENT WITH SURGE OF RICHER GULF
MOISTURE.
..DIAL.. 04/28/2010
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