SWODY1
SPC AC 010530
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 AM CDT FRI AUG 01 2008
VALID 011200Z - 021200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS GREAT LAKES/OH VALLEY
REGIONS TO MID MS VALLEY...
...SYNOPSIS...
MORE HIGHLY AMPLIFIED UPPER AIR PATTERN FCST TO DEVELOP ACROSS NRN
HALF OF CONUS...AS WRN MEAN RIDGE FURTHER AMPLIFIES AND TROUGHING
DEEPENS OVER GREAT LAKES. LATTER PROCESS WILL BE AIDED BY SEWD
MOVEMENT AND STRENGTHENING OF SHORTWAVE TROUGH -- NOW BREAKING OFF
SERN END OF SASK TROUGH...AND EVIDENT IN MOISTURE CHANNEL IMAGERY
INVOF MB/ONT BORDER. BY 2/12Z...STG SHORTWAVE TROUGH SHOULD EXTEND
FROM SRN ONT SWWD TO SSWWD ACROSS WV. BY 2/00Z...ASSOCIATED SFC
COLD FRONT -- NOW MOVING SWD OVER IA AND CENTRAL PLAINS -- SHOULD
REACH SRN ONT...WRN OH...SRN IL...AND CENTRAL MO...BECOMING
QUASISTATIONARY WWD ACROSS CENTRAL KS...THEN DIFFUSE WARM FRONT OVER
W-CENTRAL/W KS AND E-CENTRAL/NERN CO.
BY 2/12Z...NWRN FRINGE OF HIGH PLAINS WARM FRONTAL SEGMENT WILL
BUILD/MOVE NWD AND LINK WITH LEE-SIDE SFC LOW INVOF SWRN ND/SERN
MT/NWRN SD. THIS LOW SHOULD DEVELOP IN RESPONSE TO MID-UPPER
SHORTWAVE TROUGH NOW APCHG BC/WA COAST...AND FCST OVER CANADIAN
ROCKIES BY END OF PERIOD. OCCLUDED FRONTAL ZONE SHOULD EXTEND NWD
FROM SFC LOW ACROSS WRN ND OVER SERN SASK AT THAT TIME...WITH COLD
FRONT SWWD OVER WRN WY.
...GREAT LAKES/OH VALLEY REGIONS TO MID MS VALLEY...
SCATTERED TSTMS EXPECTED TO DEVELOP ALONG/AHEAD OF FRONT OVER LOWER
MI/NWRN OH/ERN INDIANA AREA DURING AFTERNOON. PATTERN FAVORS
RELATIVELY CONCENTRATED DAMAGING WIND PROBABILITIES ACROSS OH WHERE
ACTIVITY MAY CONSOLIDATE INTO QUASI-LINEAR OR BOWING CONVECTIVE
SYSTEM AND MOVE SEWD TOWARD WV. FCST THERMODYNAMIC PROFILES SUGGEST
PLUME OF FAVORABLY RICH LOW LEVEL MOISTURE WILL ADVECT EWD ACROSS
THIS REGION FROM SFC THROUGH 850 MB...COMBINING WITH SFC DIABATIC
HEATING TO BOOST MLCAPES INTO 2000-3000 J/KG RANGE
INDIANA/OH...DECREASING EWD INTO PA. STG WLY COMPONENT OF BOUNDARY
LAYER FLOW AHEAD OF FRONT WILL ACT TO REDUCE CONVERGENCE AND
HODOGRAPH SIZE...BUT ALSO...WILL YIELD NEARLY UNIDIRECTIONAL
DEEP-LAYER WIND PROFILES. MEANWHILE...DEEP-LAYER SPEED SHEAR IS
FCST TO STRENGTHEN THROUGHOUT DAY ALONG AND JUST AHEAD OF SFC FRONT
AS TROUGH ALOFT APCHS AND HEIGHT GRADIENTS TIGHTEN...BENEATH NRN
PORTION OF STRONGLY DIFFLUENT UPPER WINDS.
LOW LEVEL MOISTURE AND MID-UPPER LEVEL LAPSE RATES ARE EXPECTED TO
INCREASE WITH WWD EXTENT ALONG TRAILING PORTION COLD FRONT...AT
LEAST INTO CENTRAL MO. HOWEVER...OFFSETTING FACTORS INCLUDE
WEAKENING CONVERGENCE WITH WWD EXTENT. CAPPING WILL LIMIT
CONVECTIVE COVERAGE/DURATION DURING MOST FAVORABLE THERMODYNAMIC
PERIOD OF LATE AFTERNOON. ANY TSTMS THAT CAN DEVELOP MAY BRIEFLY
PRODUCE HAIL OR STG-SVR DOWNBURSTS.
...NRN HIGH PLAINS...LATE PERIOD...
COMBINATION OF MOIST AND WARM ADVECTION WILL INCREASE LOW LEVEL
THETAE THROUGHOUT LATTER HALF OF PERIOD AHEAD OF SFC LOW AND COLD
FRONT...AND ALONG AND N OF SFC WARM FRONT. DESPITE RATHER SCANT SFC
MOISTURE...HIGH-BASED TSTMS WITH STG WINDS MAY DEVELOP OVER
CENTRAL/ERN MT DURING AFTERNOON. MORE PLAUSIBLE SCENARIO IS FOR
ELEVATED TSTMS TO FORM LATE IN PERIOD FROM ERN MT ACROSS WRN ND.
STEEP LOW-MIDLEVEL LAPSE RATES AND FAVORABLE DEEP-LAYER SHEAR WILL
SUPPORT CONDITIONAL HAIL AND STG-SVR GUST POTENTIAL WITH SOME OF
THIS ACTIVITY. MAIN CONCERN WILL BE QUALITY/BREADTH OF SUPPORTIVE
MOISTURE RETURN FIELD.
...SERN CONUS...
ONGOING ACTIVITY HAS SHUNTED COLLECTIVE OUTFLOW BOUNDARY WELL S OF
RESIDUAL/WEAKENING FRONTAL ZONE. FORMER BOUNDARY...ALONG WITH SEA
BREEZE FRONTS AND NEWER OUTFLOWS DURING PERIOD...SHOULD BE PRIMARY
FOCI FOR DEVELOPMENT FROM SRN ATLANTIC COASTAL PLAIN WWD ACROSS GULF
COASTAL STATES...INTO ARKLATEX REGION. ALTHOUGH LOW LEVEL FLOW AND
DEEP-LAYER SHEAR EACH ARE EXPECTED TO BE RATHER WEAK...SEVERAL
RELATIVELY DENSE CONCENTRATIONS OF MULTICELLULAR TSTMS ARE LIKELY TO
EVOLVE AND CONCENTRATE MRGL SVR WIND POTENTIAL DURING AFTERNOON.
..EDWARDS/SMITH.. 08/01/2008
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