SWODY3
SPC AC 190728
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0128 AM CST WED DEC 19 2007
VALID 211200Z - 221200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
UPPER AIR PATTERN IS FCST TO REMAIN PROGRESSIVE THROUGH REMAINDER
PERIOD ACROSS CONUS. INITIAL SHORTWAVE TROUGH NOW OVER SRN CA AND
NRN BAJA SHOULD MOVE ACROSS SRN CONUS THROUGH DAY-2...THEN OFFSHORE
CAROLINAS/GA/FL EARLY IN THIS PERIOD. MUCH STRONGER/UPSTREAM WAVE
IS EXPECTED TO DEVELOP OVER ERN PACIFIC FROM PHASING SHORTWAVE
TROUGHS AND SPEED MAXIMA...THEN MOVE INLAND TO GREAT BASIN AND NRN
ROCKIES DAY-2. BY 22/00Z...OPERATIONAL WRF/SPECTRAL AND MOST SREF
MEMBERS AGREE STRONGLY ON GENERAL PATTERN OF SYNOPTIC TROUGH FROM
DAKOTAS SSWWD ACROSS NM...WITH SOME POTENTIAL FOR CLOSED LOW TO FORM
FROM NRN STREAM SHORTWAVE TROUGH ACROSS EITHER NRN PLAINS OR
ADJACENT CANADIAN PRAIRIES. HOWEVER...CONSIDERABLE VARIATION IS
EVIDENT AMONGST VARIOUS GUIDANCE PACKAGES ON MOST PERTINENT SECTOR
OF MID-UPPER SYSTEM...NAMELY WITH STRENGTH/TIMING OF SHORTWAVE
MOVING THROUGH BASE OF TROUGH CROSSING SRN HIGH PLAINS DURING LATTER
HALF OF PERIOD. OPERATIONAL WRF/SPECTRAL REPRESENT WEAK/STRONG
EXTREMES RESPECTIVELY WITH THIS WAVE...WITH ECMWF AND MOST SREF
MEMBERS MORE REASONABLY SHOWING MDT AMPLITUDE PERTURBATION AND WEAK
SFC CYCLOGENESIS ALONG COLD FRONT.
SFC COLD FRONT SHOULD MOVE ACROSS CENTRAL/SRN PLAINS DURING
PERIOD...EXTENDING BY 22/12Z FROM UPPER MS VALLEY SSWWD ACROSS
OZARKS TO ARKLATEX AND S-CENTRAL TX.
..W GULF COASTAL PLAIN...
SOME SVR POTENTIAL MAY DEVELOP NEAR END OF PERIOD...AS COLD FRONT
BEGINS TO IMPINGE ON NRN/NWRN PORTIONS OF RETURN FLOW IN MOIST
SECTOR. MAIN UNCERTAINTIES FOR THIS FCST INVOLVE
STRENGTH/POSITIONING OF FAVORABLE LARGE SCALE SUPPORT ALOFT
DISCUSSED ABOVE...AS WELL AS OF RICHEST BOUNDARY LAYER MOISTURE.
UNCHARACTERISTICALLY...OPERATIONAL WRF APPEARS TO BE WEAKER WITH
RETURN FLOW THAN 00Z SPECTRAL AND SEVERAL SREF MEMBERS. VERTICAL
SHEAR PROFILES ARE EXPECTED TO STRENGTHEN CONSIDERABLY ACROSS MOIST
SECTOR AHEAD OF UPPER TROUGH...SO AT LEAST MRGL SVR PROBABILITIES
ARE WARRANTED. HOWEVER...MORE AGGRESSIVE OUTLOOK IS PRECLUDED ATTM
BY APPARENT HORIZONTAL DISPLACEMENT BETWEEN STRONGEST LIFT AND MOST
FAVORABLE MOISTURE BEFORE END OF PERIOD.
.EDWARDS.. 12/19/2007
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