SWODY1
SPC AC 010057
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0757 PM CDT THU JUL 31 2008
VALID 010100Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS IA...NERN
MO...IL...WRN INDIANA...
...SYNOPSIS...
IN MID-UPPER LEVELS...NRN STREAM PATTERN FEATURES BROAD ANTICYCLONIC
FLOW AROUND MEAN RIDGE FROM CENTRAL ROCKIES TO CANADIAN HIGH PLAINS.
DOWNSTREAM LOW AND ACCOMPANYING POSITIVELY-TILTED TROUGH OVER
CENTRAL/NRN PORTIONS SASK SHOULD LIFT NEWD AWAY FROM CONUS...EXCEPT
FOR VORTICITY LOBE CALVING OFF SERN FRINGES OF TROUGH OVER SRN
MB/FAR WRN ONT. THIS FEATURE SHOULD MOVE SEWD TO NEAR N SHORE OF LS
BY 12Z. FARTHER DOWNSTREAM...CONVECTIVELY INDUCED/REINFORCED
SHORTWAVE PERTURBATION -- ASSOCIATED WITH PRIOR MCS -- WAS EVIDENT
IN MOISTURE CHANNEL IMAGERY AND VWP DATA FROM LM SWWD ACROSS NRN
IL...AND IS FCST TO CONTINUE SEWD TOWARD WRN PA...OH/WV BORDER AND
NERN KY THROUGH REMAINDER PERIOD. UPPER LOW OVER SRN QUE SHOULD
CONTINUE MOVING SLOWLY EWD/NEWD...WHILE ASSOCIATED TROUGHING
CONTINUES TO MOVE EWD OVER NEW ENGLAND.
AT SFC...COLD FRONT IS ANALYZED FROM OCCLUSION TRIPLE-POINT LOW
INVOF BOS...WSWWD ACROSS SRN PA TO ANOTHER LOW OVER NWRN OH/NERN
INDIANA...ASSOCIATED WITH REMAINS OF EARLY MCS. OUTFLOW BOUNDARY
ARCS SWWD ACROSS N-CENTRAL INDIANA...NRN IL AND ERN IA...BECOMING
DIFFUSE NWWD TO SWD MOVING FRONTAL ZONE EVIDENT OVER NRN IA AND
E-CENTRAL/SERN NEB. COLD FRONTS WILL CONTINUE TO MOVE SWD ACROSS
MID-ATLANTIC AND CENTRAL LOW PLAINS REGIONS...WHILE WRN SEGMENT OF
PLAINS FRONT STALLS ACROSS WRN KS AND ERN CO. WEAK/RESIDUAL FRONTAL
ZONE EXTENDS FROM NRN COAHUILA NEWD THROUGH LOW OVER DFW
METROPLEX...SERN OK...CENTRAL/NERN AR. THIS BOUNDARY SHOULD MOVE
LITTLE THROUGH REMAINDER PERIOD...WHILE BECOMING MORE DIFFUSE AMIDST
MULTITUDE OF SMALL SCALE CONVECTIVE OUTFLOWS.
...MIDWESTERN OUTLOOK AREA...
PER MESOSCALE DISCUSSION 1982...CONDITIONAL POTENTIAL EXISTS FOR
DIURNAL CONVECTION TO DEVELOP ALONG ZONALLY ALIGNED SEGMENT OF
BOUNDARY ACROSS NRN IA. MLCAPES 2000-4000 J/KG...AND ROUGHLY 40 KT
EFFECTIVE SHEAR...WOULD SUPPORT SVR POTENTIAL AND POSSIBLE
DOWNSHEAR/UPSCALE CONTINUATION OF ACTIVITY WITH LARGE HAIL AND
STG-SVR GUSTS POSSIBLE. ADDITIONAL DEVELOPMENT MAY OCCUR ALONG AND
N OF THIS BOUNDARY OVERNIGHT ACROSS MID/UPPER MS VALLEY REGION AS
WELL...ALTHOUGH MOST GUIDANCE REASONABLY INDICATES LACK OF ROBUST
LLJ BY AROUND 06Z IN WAKE OF SHORTWAVE TROUGH ASSOCIATED WITH
EARLIER MCS...WITH ABOUT 20-25 KT 850 MB FLOW AND STG WLY COMPONENT
THERETO. HOWEVER...PRESENCE OF SOME LARGE SCALE ASCENT IS EXPECTED
TO DEVELOP ASSOCIATED WITH LOW LEVEL WAA...ALONG WITH SUBTLE
MIDLEVEL ASCENT AHEAD OF WEAK PERTURBATION EVIDENT OVER CENTRAL SD
ATTM. SPECTRAL/ECMWF GUIDANCE RESOLVED THAT FEATURE AND PROGS ITS
SEWD MOTION ACROSS IA OVERNIGHT. VERY RICH LOW LEVEL MOISTURE --
E.G. MEAN MIXING RATIOS 15-18 G/KG IN OAX/DVN RAOBS -- INDICATE HIGH
THETAE INFLOW AIR WILL BE AVAILABLE TO ANY ACTIVITY THAT DOES
DEVELOP...WHETHER FROM CURRENT AREA OF AGITATED SHALLOW CONVECTION
OR LATER TONIGHT.
...SERN CONUS...
LINE OF STG-SVR TSTMS SHOULD FINISH MOVING OFFSHORE WITHIN NEXT
HOUR...BEHIND WHICH CONSIDERABLE STABILIZATION AND LACK OF
CONVERGENCE SHOULD REDUCE SVR THREAT SUBSTANTIALLY. REF REMAINDER
WW 784 AND RELATED MESOSCALE DISCUSSIONS FOR MORE DETAILED NEAR-TERM
INFORMATION. OTHERWISE...PULSE/MULTICELL DAMAGING GUST POTENTIAL
WWD ACROSS SRN APPALACHIANS AND MID-SOUTH REGIONS IS MORE SPORADIC
AND TIED STRONGLY TO DIURNAL HEATING PROCESSES. AS SUCH...REMAINING
SVR THREAT WILL DIMINISH MARKEDLY AFTER APPROXIMATELY 03Z.
...NRN MN...
FAVORABLE DEEP-LAYER SPEED SHEAR WILL PERSIST TO SUPPORT ISOLATED
STG-SVR TSTMS ACROSS THIS REGION FOR A FEW MORE HOURS...PER INL RAOB
AND RUC FCST SOUNDINGS. MODIFICATIONS TO THOSE SOUNDINGS SUGGEST
THAT DIABATIC COOLING OF NEAR-SFC LAYER WITH TIME WILL RESULT IN
GRADUAL DIMINISHMENT OF DAMAGING GUST POTENTIAL AT SFC...ALTHOUGH
HAIL THREAT MAY PERSIST SOMEWHAT LONGER.
..EDWARDS.. 08/01/2008
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