Friday, March 20, 2009

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 200829
SWOD48
SPC AC 200828

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0328 AM CDT FRI MAR 20 2009

VALID 231200Z - 281200Z

...DISCUSSION...

LATEST MEDIUM-RANGE GUIDANCE REMAINS IN REMARKABLY GOOD AGREEMENT IN
THE EVOLUTION OF A POWERFUL SYNOPTIC SYSTEM OVER THE CNTRL U.S. ON
D4 /MON MAR 23RD/. ALOFT...AN INTENSE MID/UPPER-LEVEL LOW WILL
SHIFT EWD FROM THE CNTRL ROCKIES INTO THE CNTRL PLAINS WHILE AN
ASSOCIATED SURFACE CYCLONE DEVELOPS FROM THE CNTRL HIGH PLAINS NEWD
INTO THE CNTRL PLAINS BEFORE OCCLUDING. BOUNDARY LAYER MOISTURE
QUALITY STILL APPEARS SOMEWHAT QUESTIONABLE WITH DEWPOINTS REMAINING
LARGELY IN THE 50S. HOWEVER...THE PRESENCE OF STEEP LAPSE
RATES...STRONG DYNAMIC FORCING AND STRENGTHENING WIND FIELDS WILL
LIKELY FOSTER NUMEROUS SEVERE STORMS /INCLUDING SUPERCELLS/ ALONG OR
AHEAD OF DRYLINE OR PACIFIC FRONT OVER THE CNTRL AND SRN PLAINS.

BOUNDARY LAYER MOISTURE IS EXPECTED TO IMPROVE AHEAD OF PACIFIC
FRONT OVER LOWER ELEVATIONS OF THE SRN PLAINS INTO OZARK PLATEAU BY
D5 /TUE MAR 24TH/. WHILE PRIMARY UPPER LOW/VORTICITY MAXIMUM AND
ASSOCIATED SURFACE LOW ARE FORECAST TO DEVELOP NEWD TOWARD THE UPPER
MIDWEST...MODEL GUIDANCE SUGGESTS A SECONDARY VORTICITY MAXIMUM/JET
STREAK ROTATING THROUGH THE LARGE-SCALE TROUGH BASE OVER THE SRN
PLAINS. GIVEN THE INCREASING MOISTURE/INSTABILITY AND CONTINUED
STRONG WIND FIELDS...POTENTIAL WILL EXIST FOR ANOTHER ORGANIZED
SEVERE WEATHER EPISODE FROM ERN PARTS OF OK/TX INTO PORTIONS OF AR
AND PERHAPS SRN MO AND NRN LA.

THEREAFTER...MODEL DIFFERENCES BEGIN TO ARISE IN THE EVOLUTION OF
THE UPPER-LEVEL PATTERN. MOREOVER...CONSIDERABLE TSTM ACTIVITY OVER
THE PREVIOUS TWO DAYS MAY POTENTIALLY DISPLACE THE EFFECTIVE WARM
SECTOR FURTHER TO THE S/SE THAN WHAT CURRENT GUIDANCE INDICATES.
NONETHELESS...IT DOES APPEAR THAT MODERATELY STRONG WIND FIELDS WILL
BE MAINTAINED ACROSS THE GULF COAST REGION IN CLOSE PROXIMITY TO A
MOIST AND UNSTABLE AIR MASS. AS SUCH...THE POTENTIAL FOR SEVERE
WEATHER WILL LIKELY CONTINUE THROUGH THE REMAINDER OF THE EXTENDED
PERIOD. HOWEVER...GIVEN THE UNCERTAINTY IN THE DETAILS...NO
ADDITIONAL SEVERE WEATHER AREAS WILL BE DELINEATED ATTM.

..MEAD.. 03/20/2009

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