SWODY1
SPC AC 300526
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1226 AM CDT THU AUG 30 2007
VALID 301200Z - 311200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
ACTIVE NRN STREAM PATTERN WILL CONTINUE TODAY AND
TONIGHT...DOWNSTREAM FROM PERSISTENT RIDGING THAT WILL EXTEND FROM
4-CORNERS HIGH NWD OVER CANADIAN ROCKIES. POSITIVELY TILTED
SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER
UPPER GREAT LAKES SWWD TO CENTRAL PLAINS -- IS FCST TO MOVE EWD AND
BECOME MORE DIFFUSE OVER NERN CONUS...WHILE MAIN VORTICITY LOBE
EJECTS ENEWD OVER/OFFSHORE LABRADOR. MEANWHILE...UPSTREAM SPEED MAX
PRESENTLY OVER FAR NRN PORTIONS SASK/MB IS FCST TO DIG
SEWD...RESULTING IN ANOTHER PROGRESSIVE SHORTWAVE TROUGH MOVING OVER
MUCH OF NRN ONT...JAMES BAY AND LS REGIONS DURING THIS PERIOD.
DIFFUSE MID/UPPER TROUGH WILL LINGER OVER SRN/ERN TX...WITH EWD
EXTENSION DEVELOPING ALONG GULF COAST.
AT SFC...COLD FRONT -- INITIALLY ASSOCIATED WITH LEAD TROUGH -- WILL
MOVE SEWD OFF MID-ATLANTIC AND NEW ENGLAND. FRONTAL ZONE WILL
BECOME BROAD AND DIFFUSE FARTHER SW ACROSS CAROLINAS...ARKLATEX
REGION AND SRN HIGH PLAINS. THIS WILL OCCUR AS NLY FLOW COMPONENT
PREDOMINATES ACROSS MUCH OF WRN/CENTRAL GULF COAST STATES AND SRN
APPALACHIANS...W THROUGH N OF WEAK SFC CYCLOGENESIS PROGGED OVER FL
PANHANDLE. LOW LEVEL MOISTURE WILL REMAIN ALONG AND N OF COLD FRONT
NEAR AND S OF OH VALLEY SWD ACROSS AR...SUPPORTING POTENTIAL FOR
DIURNAL GEN TSTM THREAT ON BOTH SIDES OF FRONT.
..NERN CONUS...
TSTMS MAY MOVE ACROSS PORTIONS MAINE...AND PERHAPS NRN VT/NH...EARLY
IN PERIOD AND ATOP RELATIVELY STABLE BOUNDARY LAYER REMAINING FROM
NOCTURNAL DIABATIC COOLING. ANY SUCH ACTIVITY MAY LEAVE BEHIND
DIFFERENTIAL HEATING ZONE AHEAD OF COLD FRONT THAT MAY ACT AS FOCUS
FOR LATER DEVELOPMENT. LOW-MIDLEVEL VERTICAL SHEAR IS EXPECTED TO
WEAKEN SUBSTANTIALLY WITH SWWD EXTENT ALONG/AHEAD OF FRONT IN NEW
ENGLAND...WHILE BUOYANCY STRENGTHENS DUE TO INCREASINGLY FAVORABLE
LOW LEVEL MOISTURE AND STRONGER AND MORE PERSISTENT SFC
INSOLATION...AWAY FROM ANY CLOUD/PRECIP DEBRIS. ALTHOUGH WEAK LOW
LEVEL FLOW IS PROGGED INVOF FRONT...HEATING OF HIGH THETAE AIR MASS
AND WEAK FRONTAL FORCING SHOULD BE SUFFICIENT TO REMOVE SBCINH FROM
MIDDAY THROUGH AFTERNOON. MAIN CONVECTIVE MODES WILL BE
MULTICELLULAR AND LINE SEGMENTS...WITH STRONGER STORMS PRODUCING
GUSTS NEAR SVR CRITERIA.
..ORE...
LONG FETCH OF SWLY FLOW ALOFT WILL CONTINUE...SE OF BROAD MID/UPPER
VORTEX LOCATED OVER ERN GULF OF AK. NO SIGNIFICANT MID/UPPER
PERTURBATIONS ARE EITHER PROGGED TO MOVE OVER THIS AREA...OR ARE
EVIDENT UPSTREAM IN MOISTURE CHANNEL IMAGERY...
ALTHOUGH WEAK/BROAD PERTURBATION NOW NEAR CENTRAL/NRN CA COAST
SHOULD LIFT NEWD ACROSS NV. HOWEVER...STRENGTHENING MIDLEVEL
GRADIENT WIND WILL ENHANCE DEEP-LAYER SHEAR PROFILES OVER THIS AREA
THROUGHOUT AFTERNOON. MEANWHILE...SFC AIR MASS WILL
HEAT/DESTABILIZE...BENEATH BROAD AREA OF MID 40S TO MID 50S F
LOWER-ELEVATION SFC DEW POINTS. BY LATE AFTERNOON...EXPECT
FAVORABLY STEEP LAPSE RATES...WEAKENING CINH AND HEATING OF HIGHER
TERRAIN TO SUPPORT TSTM DEVELOPMENT. SCATTERED TO WIDELY
SCATTERED...HIGH BASED TSTMS WILL MOVE NEWD OVER WELL MIXED BOUNDARY
LAYERS OF LOWER ELEVATIONS AND POSE RISK OF ISOLATED HAIL AND
STG-SVR GUSTS. POTENTIAL SHOULD WANE CONSIDERABLY AFTER ABOUT 03Z
AS DIABATIC SFC COOLING INTENSIFIES.
.EDWARDS/CROSBIE.. 08/30/2007
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