SWODY1
SPC AC 310555
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CDT THU JUL 31 2008
VALID 311200Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS UPPER MIDWEST...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ERN NY AND NEW
ENGLAND...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CAROLINAS AND NERN
GA...
...SYNOPSIS...
IN MID-UPPER LEVELS...NRN STREAM PATTERN FCST TO BE DOMINATED BY
SHORTWAVE PERTURBATIONS NOW OVER QUE/ONT BORDER REGION AND OVER SRN
SASK/NERN MT. ERN TROUGH -- WITH EMBEDDED UPPER LOW -- SHOULD
CONTINUE EWD ACROSS SRN QUE AND PORTIONS NRN NY AND NEW ENGLAND.
ASSOCIATED SFC FRONT/TROUGH WILL MOVE EWD FROM HUDSON VALLEY REGION
ACROSS NEW ENGLAND DURING DAY. TRAILING PORTION OF THIS WEAK
FRONTAL ZONE -- REINFORCED/MODULATED BY CONVECTIVE OUTFLOWS -- WILL
LIE QUASISTATIONARY FROM SRN KY OR NRN TN SWWD ACROSS ARKLATEX
REGION TOWARD NRN COAHUILA.
MEANWHILE...TROUGH ALOFT WILL MOVE EWD ACROSS CANADIAN
PRAIRIES...SRN PORTION BRUSHING ND/NRN MN. ASSOCIATED SFC COLD
FRONT WILL MOVE EWD OVER NRN MN...SEWD ACROSS DAKOTAS...AND SWD OVER
CENTRAL HIGH PLAINS...WITH LATTER PORTION DECELERATING/STALLING LATE
IN PERIOD. WEAK/ATTACHED FRONTAL-WAVE LOW SHOULD MOVE EWD OR ESEWD
FROM SD ACROSS MN/IA BORDER REGION...FOLLOWING WARM FRONTAL ZONE
THAT WILL BE DRIFTING N.
...UPPER MIDWEST...
CONDITIONAL SVR POTENTIAL EXISTS EARLY IN PERIOD WITH CONVECTIVE
COMPLEX EVOLVING AND MOVING SEWD FROM ERN DAKOTAS...ASSOCIATED WITH
GROWING MCS THAT IS OVER CENTRAL/SRN ND AS OF THIS WRITING. IF
ASSOCIATED COLD POOL DEVELOPS SUFFICIENT DEPTH AND PRESSURE
PERTURBATION ON MESOBETA SCALE...MCS MIGHT CONTINUE UNABATED SEWD
ACROSS OUTLOOK AREA WITH RELATIVELY CONTINUOUS WIND/DERECHO
POTENTIAL. IF THIS SCENARIO LOOKS MORE LIKELY BY 13Z OUTLOOK
UPDATE...SIGNIFICANT HAIL PROBABILITIES MAY NEED REDUCTION...AND
WIND PROBABILITIES BOOSTED...ACROSS OUTLOOK AREA.
FOR NOW...MORE PROBABLE SCENARIO IS FOR MCS TO DEVOLVE DURING
MID-LATE MORNING...RELATED OUTFLOW/DIFFERENTIAL HEATING ZONE
BLENDING WITH SYNOPTIC WARM FRONT OVER NRN IA OR SRN MN AS PRIMARY
FOCUS FOR AFTERNOON/EVENING SVR POTENTIAL INCLUDING SUPERCELL RISK.
BY AFTERNOON...VERY STG INSTABILITY SHOULD DEVELOP WITHIN AND S OF
WARM FRONTAL/DIFFERENTIAL HEATING ZONE...WITH STG SFC HEATING AND
FRONTAL CONVERGENCE TO YIELD WEAK CINH. EXPECT EVAPOTRANSPIRATIVELY
AIDED SFC DEW POINTS COMMONLY UPPER 60S TO LOW 70S F BY MID-LATE
AFTERNOON BENEATH 7-8 DEG C/KM MIDLEVEL LAPSE RATES...CONTRIBUTING
TO MLCAPES IN 3000-4000 J/KG RANGE. ALTHOUGH SFC WINDS ARE NOT FCST
TO BE PARTICULARLY STG...DIRECTIONAL SHEAR IS. RELATIVELY BACKED
FLOW INVOF BOUNDARY SHOULD YIELD LOOPED HODOGRAPHS...AS WELL AS
ENHANCED STORM-RELATIVE INFLOW IN NARROW CORRIDOR. DISCRETE
SUPERCELLS WOULD HAVE POTENTIAL FOR DAMAGING HAIL GIVEN THEIR
INTERNAL FORCING AND LARGE AMBIENT BUOYANCY. INSTABILITY GRADIENT
WILL BE FAVORED CORRIDOR FOR MOTION OF ANY SUBSEQUENT/NOCTURNAL
MCS...EXPANDED UPSCALE OR RE-INTENSIFIED FROM EARLIER ACTIVITY.
ASSOCIATED WIND THREAT MAY EXTEND AS FAR SE AS SRN WI AND NRN IL BY
END OF PERIOD.
...SERN CONUS...
RELATIVE CONCENTRATION OF PULSE/MULTICELL EVENTS -- PRIMARILY
DAMAGING DOWNBURST WINDS -- MAY DEVELOP DURING AFTERNOON AS CINH
WEAKENS...NEAR AND E OF WEAK LEE-SIDE TROUGH. SCATTERED-NUMEROUS
TSTMS IN CLUSTERS ARE POSSIBLE. SFC DEW POINTS COMMONLY 70S F --
WITH SOME POCKETS MIXED INTO UPPER 60S -- COMBINED WITH STG DIABATIC
HEATING SHOULD BE SUFFICIENT TO OVERCOME WEAK LAPSE RATES ALOFT.
RESULT SHOULD BE MLCAPES 1500-2500 J/KG ATOP STEEP THERMAL LAPSE
RATS IN SUBCLOUD LAYER. FCST SOUNDINGS SUGGEST SHALLOW INVERTED-V
PROFILE CHARACTERISTIC OF WELL-MIXED ENVIRONMENTS AND SUPPORTING
DOWNDRAFT ACCELERATION. COLD POOL ORGANIZATION AND OUTFLOW
BOUNDARIES WILL STRONGLY INFLUENCE THREAT WITHIN OUTLOOK AREA.
...NERN CONUS...
WEAK CONVERGENCE INVOF FRONT/TROUGH...DIURNAL HEATING...AND
FAVORABLE MOISTURE SHOULD SUPPORT POTENTIAL FOR SCATTERED LATE
MORNING THROUGH LATE AFTERNOON TSTMS WITH RISK FOR SVR HAIL AND
DAMAGING GUSTS. CONDITIONAL SUPERCELL POTENTIAL ALSO EXISTS WITHIN
SRN FRINGE OF STRONGEST FLOW ALOFT -- ESPECIALLY CENTRAL NEW ENGLAND
NNEWD ACROSS WRN MAINE WHERE LOW LEVEL VEERING WITH HEIGHT SHOULD BE
MORE PRONOUNCED. HOWEVER...PRESENCE OF SUFFICIENT DESTABILIZATION
APPEARS MORE QUESTIONABLE/CONDITIONAL WITH NWD EXTENT.
...TN-TX...
FRONTAL ZONE WILL CONCENTRATE CONVECTIVE POTENTIAL DURING
AFTERNOON...AND MAY BE ENHANCED BY DIFFERENTIAL HEATING OVER TN/KY
AREA -- S OF LARGE/PERSISTENT AREA OF PRECIP AND CLOUDS PRESENTLY
UNDERWAY AND LIKELY TO PERSIST THROUGH MUCH OF REMAINDER OF MORNING.
LOCALIZED AREAS OF ENHANCED PULSE/MULTICELL POTENTIAL MAY DEVELOP
INVOF STRONGER BOUNDARIES OR THEIR INTERSECTIONS...HOWEVER
COMBINATION OF SUCH MESOSCALE UNCERTAINTIES AND WEAKNESS OF
DEEP-LAYER WIND FIELDS PRECLUDES CATEGORICAL OUTLOOK ATTM.
..EDWARDS/SMITH.. 07/31/2008
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