Wednesday, May 4, 2011

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 040759
SWOD48
SPC AC 040759

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 AM CDT WED MAY 04 2011

VALID 071200Z - 121200Z

...DISCUSSION...
MODELS DEPICT A WNWLY FLOW REGIME FROM THE PACIFIC NW INTO THE MID
ATLANTIC ON SAT/D4 WITH PERHAPS AN EMBEDDED DISTURBANCE MOVING
QUICKLY EWD SOMEWHERE BETWEEN THE NRN PLAINS INTO THE OH VALLEY. BY
THIS TIME...LOW LEVEL MOISTURE WILL HAVE BEGUN TO RETURN NWD FROM
THE SRN PLAINS INTO THE LOWER MO VALLEY. ELEVATED THUNDERSTORMS MAY
BE ONGOING SAT MORNING OVER PORTIONS OF IA/MO/IL/IND...SHIFTING EWD
AS A LOW LEVEL JET VEERS. SEVERITY OF THIS CONVECTION WILL DEPEND ON
THE STRENGTH OF ANY UPPER SUPPORT...BUT AS PREVIOUSLY ALLUDED
TO...PREDICTABILITY IS NOT HIGH AT THIS TIME.

BY SUN/D5...THERE IS STRONG EVIDENCE THAT A LARGE UPPER TROUGH WILL
BEGIN TO TAKE SHAPE ACROSS THE WRN STATES WITH AN 80+ KT MID LEVEL
JET DIGGING SWD ALONG THE W COAST. THE BOUQUET OF MREF SOLUTIONS AS
WELL AS DETERMINISTIC MODELS SHOW LITTLE AGREEMENT ON D5 WITH HOW
QUICKLY AND HOW FAR S THIS TROUGH WILL DEVELOP. THIS WILL HAVE AN
IMPACT ON THE PROBABILITY OF SEVERE CONVECTION OVER THE SRN/CNTRL
HIGH PLAINS NEAR THE DRYLINE WHERE CAPPING WILL BE A CONCERN...AND
ALSO WITH POSSIBLE NOCTURNAL CONVECTION FOCUSED OVER NEB/IA/MO/IL
OVERNIGHT WITH A SWLY LOW LEVEL JET. BOTH THESE AREAS HAVE
POTENTIAL...BUT NOT ENOUGH TO INTRODUCE ANY SEVERE AREAS WITH SUCH
UNCERTAINTY.

FOR THE REMAINDER OF THE PERIOD MON/D6 TO WED/D8...THERE WILL LIKELY
BE A SEVERE THREAT EACH DAY ALONG THE DRYLINE ACROSS THE CNTRL/SRN
PLAINS...AND PERHAPS EXTENDING EWD FROM A SURFACE LOW/WARM FRONT
ACROSS THE MIDWESTERN REGION AS THE UPPER TROUGH...AND/OR PIECES OF
THE TROUGH EMERGE OVER THE REGION.

SEVERE AREAS BEGINNING SUN/MAY 8TH AND LASTING THROUGH ABOUT MAY
10TH ARE LIKELY FORTHCOMING FOR MUCH OF THE CNTRL U.S. AS THE EVENT
NEARS AND PREDICTABILITY INCREASES.

..JEWELL.. 05/04/2011

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