Wednesday, October 20, 2010

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 200844
SWOD48
SPC AC 200844

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0344 AM CDT WED OCT 20 2010

VALID 231200Z - 281200Z

...DISCUSSION...
EJECTING SWRN CONUS LOW...DESCRIBED IN DAY-2/DAY-3 OUTLOOKS...IS
EXPECTED TO CONTINUE MOVING NEWD ACROSS CENTRAL PLAINS WITH GEN
WEAKENING TREND...MAIN QUESTION BEING...HOW WEAK? CONSIDERABLE
VARIATION IS EVIDENT BY THIS PERIOD IN MREF AND DETERMINISTIC PROGS
OF AMPLITUDE/TILT OF THIS PERTURBATION...AND RELATED CHARACTER OF
LOW-LEVEL MASS FIELDS. SOME SVR MAY BE POSSIBLE DAY-4/22ND-23RD
FROM COLD-CORE REGION OF THIS SYSTEM OVER NEB SWD ACROSS PORTIONS
SRN PLAINS...HOWEVER POTENTIAL IS TOO CONDITIONAL TO ASSIGN 30%
PROBABILITY AREA ATTM.

GEN AGREEMENT EXISTS ON UPSTREAM PATTERN WITHIN AND JUST AHEAD OF
STG/ZONAL NERN PAC JET BY DAY-5/24TH-25TH...LED BY AMPLIFYING SERN
CONUS SHORTWAVE MOVING FROM AZ/NM ACROSS TX AND NRN MEX. AS
USUAL...MAIN UNCERTAINTIES THIS FAR OUT LIE IN CRUCIAL DETAILS.
MOST MREF MEMBERS ARE 6-12 HOURS AHEAD OF 00Z/120 HOUR ECMWF 500 MB
FCST OVER TX...WHICH ITSELF IS SLIGHTLY AHEAD OF OPERATIONAL
SPECTRAL/UKMET. LOW-LEVEL RESPONSE TO THIS PERTURBATION APPEARS
NEBULOUS IN MANY PROGS...AND IT MAY IMPEDE SIGNIFICANT LOW-LEVEL
MOISTURE RETURN TO LARGER/MORE INTENSE SYNOPTIC-SCALE TROUGH
EVOLVING OVER NRN/CENTRAL PLAINS REGION DAYS 6-7/25TH-27TH.

..EDWARDS.. 10/20/2010

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