SWODY1
SPC AC 020600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT THU SEP 02 2010
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SRN PLAINS TO UPPER
GREAT LAKES REGION...
...SYNOPSIS...
PROGRESSIVE NRN STREAM WILL CHARACTERIZE UPPER-AIR PATTERN THIS
PERIOD...FEATURING RIDGING MOVING EWD ACROSS PAC NW...AND STG
SHORTWAVE TROUGH NOW ANALYZED OVER SRN SK AND ERN MT. THIS
PERTURBATION IS FCST TO MOVE ESEWD ACROSS UPPER MS VALLEY TO UPPER
GREAT LAKES REGION WHILE AMPLIFYING. BY 3/12Z...THIS TROUGH SHOULD
EXTEND SWD ACROSS MID MS VALLEY FROM CLOSED LOW OVER LS. RELATED
SFC COLD FRONT...ANALYZED ATTM FROM ERN SD ACROSS WRN NEB AND NERN
CO -- WILL SWEEP SEWD ACROSS CENTRAL/SRN PLAINS AND MUCH OF MS
VALLEY. BY 3/00Z...FRONT SHOULD EXTEND ROUGHLY ALONG
MQT...PIA...SGF...OKC...CDS...HOB. BY END OF PERIOD...FRONT SHOULD
REMAIN PROGRESSIVE NEAR CLE...BWG...MEM...DAL...MRF. EFFECTIVE
FRONTAL ZONE MAY BE SHUNTED SEWD AND SWD FROM PROGGED SYNOPTIC
POSITIONS...PARTICULARLY FROM MID MS VALLEY INTO SRN PLAINS DURING
AFTERNOON/EVENING...BY CONVECTIVE OUTFLOWS. MID-LATE AFTERNOON
DRYLINE SHOULD EXTEND FROM FRONTAL INTERSECTION OVER EXTREME ERN TX
PANHANDLE OR WRN OK...SSWWD OVER PERMIAN BASIN REGION.
...SRN PLAINS TO UPPER GREAT LAKES REGION...
SCATTERED-NUMEROUS AFTERNOON TSTMS FCST TO DEVELOP INVOF SFC FRONT
FROM WI SWWD ACROSS MO TO OK...PERHAPS INTO PORTIONS ERN TX
PANHANDLE AND NW TX ALONG THAT SEGMENT OF FRONT NEAR DRYLINE.
PREDOMINANT MODE SHOULD BE QUASI-LINEAR...WITH SOME DISCRETE TSTMS
EARLY IN CONVECTIVE CYCLE. MAIN THREAT ALL ALONG THIS CORRIDOR
SHOULD BE DAMAGING GUSTS.
ISOLATED TO WIDELY SCATTERED SVR HAIL ALSO MAY OCCUR...PRIMARILY
WITH ANY RELATIVELY DISCRETE ACTIVITY. STRONGEST MID-UPPER LEVEL
WINDS AND DEEP-TROPOSPHERIC SHEAR WILL BE FROM MID MS VALLEY REGION
NEWD...WHERE 40-50 KT 500 MB FLOW IS EXPECTED...ALONG WITH 30-40 KT
EFFECTIVE SHEAR MAGNITUDES. PREFRONTAL/DIABATIC HEATING AT
SFC...AND DEW POINTS UPPER 60S TO 70S F...SHOULD OFFSET MODEST LAPSE
RATES ALOFT TO YIELD MLCAPE IN 1500-2500 J/KG RANGE.
MEANWHILE...GREATEST OVERALL CAPE AND LOW-LEVEL LAPSE RATES SHOULD
BE OVER SRN PLAINS SECTOR OF OUTLOOK WHERE LOW-LEVEL AND DEEP-LAYER
FLOW EACH WILL BE WEAKER. STRONG SFC HEATING OF PRECONVECTIVE AIR
MASS WILL YIELD DEEPLY MIXED BOUNDARY LAYERS SUITABLE FOR STG-SVR
DOWNDRAFTS...WHILE PRESENCE OF MID 60S TO LOW 70S F SFC DEW POINTS
HELPS TO BOOST MLCAPE PAST 3000 J/KG OVER MUCH OF AREA. ACTIVITY
SHOULD UNDERGO NET SHIFT SWD ACROSS RED RIVER REGION AMIDST
COMBINATION OF WSWWD DISCRETE PROPAGATION...AND WEAK NWLY MEAN FLOW.
FCST SOUNDINGS ALSO SUGGEST SUFFICIENT POST-FRONTAL MOISTURE AND
INSTABILITY TO SUSTAIN SOME THREAT FOR SFC-BASED/STG-SVR TSTMS AFTER
FROPA...FROM OZARKS SWWD TO NEAR ERN BORDER OF TX PANHANDLE.
HOWEVER...LACK OF CONVERGENCE AND EVENTUAL OUTFLOW-DOMINANCE OF
FRONTAL ACTIVITY WILL LIMIT SUCH POTENTIAL WITH TIME FROM LATE
AFTERNOON INTO EVENING.
...CENTRAL/NRN MN...
WIDELY SCATTERED TSTMS MAY PRODUCE OCNL HAIL NEAR SVR LEVELS.
COLD MIDLEVEL TEMPS -- I.E. -18 TO -20 DEG C -- ARE FCST TO MOVE
OVHD DURING AFTERNOON IN CLOSE PROXIMITY TO DEVELOPING MID-UPPER
CYCLONE. MEANWHILE...MLCINH WILL BECOME MINIMAL BECAUSE OF
COMBINATION OF RESIDUAL BOUNDARY LAYER MOISTURE...DIABATIC SFC
HEATING TO OFFSET CAA...AND LIFT INVOF COLD/OCCLUDED FRONTAL
SEGMENT. POTENTIAL IS EXPECTED TO DIMINISH AFTER DARK AS COOLING
ALOFT MOVES E OF AREA AND OVER MORE STABLE LOW-LEVEL AIR MASS.
...NC OUTER BANKS/TIDEWATER REGION...
WITH CENTER OF HURRICANE EARL CURRENTLY EXPECTED TO PASS E OF OUTER
BANKS...SECTOR LIKELY TO CONTAIN MOST FAVORABLE KINEMATIC PROFILES
FOR SUPERCELLS SHOULD REMAIN OFFSHORE. REF NHC ADVISORIES FOR
LATEST TRACK/INTENSITY FCSTS FOR THIS SYSTEM.
...NRN NY...NRN NEW ENGLAND...
QUASISTATIONARY FRONTAL ZONE AND LOW-LEVEL WAA MAY SUPPORT TSTM
POTENTIAL FROM SERN ONT EWD ACROSS AREA N OF ADIRONDACKS TO
N-CENTRAL MAINE...PERHAPS BRUSHING EXTREME NRN PORTIONS NY/VT/NH
DURING MID-AFTERNOON HOURS. LACK OF MORE ROBUST DEEP-LAYER
FLOW...AND PROGS OF MOST CONVECTION BEING ON CANADIAN
SIDE...PRECLUDE UNCONDITIONAL SVR PROBABILITIES ATTM.
..EDWARDS/STOPPKOTTE.. 09/02/2010
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