SWODY3
SPC AC 270747
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0147 AM CST WED FEB 27 2008
VALID 291200Z - 011200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
IN MID-UPPER LEVELS...PROGRESSIVE SERIES OF SHORTWAVES WILL CONTINUE
TO PENETRATE WRN NORTH AMERICAN MEAN RIDGE. SHORTWAVE TROUGH -- NOW
EVIDENT IN MOISTURE CHANNEL IMAGERY OVER NERN PACIFIC BETWEEN
130W-140W -- IS EXPECTED TO DIG SEWD DAY-2 OVER NWRN MEX. SEPARATE
UPPER LOW INITIALLY OVER SERN GULF OF AK IS EXPECTED TO MOVE SEWD
ACROSS CANADIAN PRAIRIES AND DAKOTAS DAY-2...THEN ACROSS GREAT LAKES
TO QUE THIS PERIOD. MEANWHILE...ANOTHER PERTURBATION -- CURRENTLY
OVER N-CENTRAL PACIFIC ABOUT HALFWAY FROM HI-AK -- IS EXPECTED TO
MOVE SEWD ACROSS CANADIAN ROCKIES/NRN HIGH PLAINS REGION EARLY IN
PERIOD...THEN RAPIDLY SEWD TO OH VALLEY AND INTO BASE OF GREAT LAKES
TROUGH BY 1/12Z.
AT SFC...CYCLONE PRECEDING LEAD NRN STREAM SHORTWAVE TROUGH SHOULD
MOVE SEWD OVER CANADIAN SHORES OF UPPER GREAT LAKES...THEN EWD
TOWARD LOWER ST LAWRENCE VALLEY. TRAILING COLD FRONT IS EXPECTED TO
MOVE SEWD INTO AR AND CENTRAL TX BEFORE STALLING/WEAKENING LATE IN
PERIOD.
..ARKLATEX...E TX TO LOWER MS VALLEY...
MORNING CONVECTION MAY DEVELOP OVER OZARKS REGION AND BUILD SWWD
ACROSS ARKLATEX WITH TIME. STRONG LOW LEVEL WAA IN ADVANCE OF NRN
STREAM PERTURBATION WILL ALSO BE ASSOCIATED WITH LEADING EDGE OF
ELEVATED/RETURN FLOW REGIME EARLY IN PERIOD. FCST SOUNDINGS BEFORE
18Z...HOWEVER...SHOW ONLY VERY WEAKLY BUOYANT LAYER...THROUGH
INSUFFICIENT DEPTH TO SUPPORT MORE THAN VERY BRIEF/ISOLATED THUNDER
POTENTIAL.
THROUGH REMAINDER DAY...CONTINUING WARM/MOIST ADVECTION SHOULD
COMBINE WITH DIABATIC HEATING TO FURTHER DESTABILIZE AIR MASS AHEAD
OF COLD FRONT. STRONGLY CURVED LOW LEVEL HODOGRAPHS WILL DEVELOP
AND FAVOR AT LEAST MRGL SVR THREAT. MAIN CONCERNS PRECLUDING
CATEGORICAL SVR OUTLOOK THIS SOON ARE TWOFOLD...
1. LOW LEVEL AIR MASS MODIFICATION OVER GULF...FOLLOWING CURRENT
STG/COLD FROPA -- WILL BE INCOMPLETE. DEW POINTS 50S F MAY REACH
INTO PORTIONS AR BY 1/00Z...BASED ON AIR MASS MODIFICATION
CLIMATOLOGIES AND SREF MOISTURE GUIDANCE...WITH LOW 60S OVER PARTS
E-CENTRAL/SE TX.
2. STRONGEST ISALLOBARIC FORCING...AND ASSOCIATED BACKED FLOW AND
ENHANCEMENTS TO LOW LEVEL CONVERGENCE...WILL REMAIN WELL NE OF AREA
ACROSS GREAT LAKES. FRONTOLYTIC REGIME IS EXPECTED THIS FAR S...SFC
WINDS BECOMING WEAKER AND MORE VARIABLE WITH TIME...ESPECIALLY OVER
TX PORTION OF WARM SECTOR.
STILL...MLCAPES NEAR 500 J/KG MAY DEVELOP AND SUPPORT POTENTIAL FOR
SOME TSTMS WITH HAIL OR GUSTS NEAR SVR LEVELS. MESOSCALE BOUNDARIES
MAY DICTATE ANY ENHANCED AREAS OF SVR POTENTIAL WITHIN CURRENT
BROADER/MRGL PROBABILITIES. ADDITIONAL TSTMS MAY DEVELOP DURING
EVENING AND OVERNIGHT IN SEWD MOVING LINE...ALONG/AHEAD OF COLD
FRONT...ACROSS LOWER MS VALLEY REGION.
.EDWARDS.. 02/27/2008
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