DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 251719
SWODY2
SPC AC 251717

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1217 PM CDT TUE SEP 25 2012

VALID 261200Z - 271200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
CHAOTIC SPLIT-FLOW PATTERN WILL PERSIST OVER CONUS THROUGH DAY-2...S
OF TRAIN OF HIGH-AMPLITUDE SHORTWAVES FROM AK TO ERN CANADA.
INTENSIFYING SHORTWAVE TROUGH AND RELATED SPEED MAX -- NOW EVIDENT
IN MOISTURE CHANNEL IMAGERY OVER NWRN ONT AND ERN AB -- IS FCST TO
PIVOT CYCLONICALLY ACROSS LS REGION THROUGH REMAINDER
DAY-1...REACHING ERN LOWER MI AND NRN WI BY 26/12Z. PERTURBATION
THEN SHOULD TURN EWD AND GRADUALLY WEAKEN...MOVING ACROSS SERN ONT
AROUND 27/00Z AND OVER NEW ENGLAND BY 27/12Z. MEANWHILE...MID-UPPER
CYCLONE NOW ANALYZED OVER UT SHOULD DRIFT EWD TO WRN CO BY START OF
PERIOD. GRADUAL FILLING OF LOW WILL PERSIST INTO DAY-2 AS IT
REMAINS NEARLY CUT OFF FROM NRN-STREAM FLOW BELT. AS SUCH...FEATURE
SHOULD MOVE LITTLE FROM ITS WRN CO POSITION UNTIL DAY-3...WHILE
BECOMING OPEN-WAVE TROUGH.

SFC COLD FRONT -- ANALYZED FROM NRN LOWER MI SWWD ACROSS IA TO SWRN
KS -- IS FCST TO MOVE TO CENTRAL/ERN NY...CENTRAL/SRN OH...SRN
MO...NRN/WRN OK AND NRN PORTIONS TX PANHANDLE BY 27/00Z. SEGMENT OF
FRONT W OF MS RIVER SHOULD BECOME QUASISTATIONARY DURING LATTER HALF
OF PERIOD...PERTURBED MAINLY BY CONVECTIVE PROCESSES. BY LATE
AFTERNOON...DIFFUSE DRYLINE SHOULD SET UP FROM N-CENTRAL/NERN TX
PANHANDLE SSWWD ACROSS LOWER PECOS/PERMIAN BASIN REGION OF W TX AND
EXTREME SERN NM. THIS DRYLINE WILL RETREAT WWD ACROSS SRN HIGH
PLAINS DURING LOCAL EVENING HOURS.

...CENTRAL/SRN HIGH PLAINS TO OZARKS AND LOWER OH VALLEY...
WIDELY SCATTERED TO SCATTERED TSTMS SHOULD DEVELOP DURING AFTERNOON
INVOF FRONT...NRN SEGMENT OF DRYLINE...AND OVER SERN CO/NERN NM
AREA...POST-FRONTAL UPSLOPE REGIME. THOUGH WELL-REMOVED FROM
STRONGEST MID-UPPER WINDS...AT LEAST MRGL/CONDITIONAL SVR THREAT
EXISTS WITH THIS ACTIVITY. SOME OF THESE TSTMS MAY AGGREGATE INTO
MULTICELLULAR MCS DURING EVENING WITH COLD-POOL DRIVEN FORWARD
PROPAGATION. HOWEVER...MESOSCALE FACTORS MOST SUITABLE FOR SUCH
EVOLUTION REMAIN TOO UNCERTAIN TO HIGHLIGHT GREATER CONCENTRATION OF
UNCONDITIONAL SVR THREAT ATTM.

GREATEST LOW-LEVEL MOISTURE WILL BE LOCATED IN AND N OF SFC FRONTAL
ZONE...WHERE RELATIVELY BACKED SFC WINDS WILL ADVECT MOISTURE WWD
AND UPSLOPE OVER PORTIONS SWRN KS...SERN CO AND POSTFRONTAL
PANHANDLES. STRONGLY HEATED...WELL-MIXED AND DEEP BOUNDARY LAYER IS
EXPECTED ALONG AND S OF FRONT OVER OK AND TX PANHANDLE...IN SUPPORT
OF STG/ISOLATED SVR GUSTS. STEEP LOW-MIDDLE LEVEL LAPSE RATES AND
STRONGER DEEP SHEAR N OF FRONT...LATTER BEING AIDED BY ELY FLOW
COMPONENT...ALSO WILL CONTRIBUTE TO TSTM ORGANIZATION AND SOME HAIL
POTENTIAL.

...INLAND MID-ATLC AND ADJOINING APPALACHIANS...
WIDELY SCATTERED TO SCATTERED TSTMS MAY DEVELOP DURING AFTERNOON
ALONG/AHEAD OF SFC COLD FRONT. ACTIVITY PRIMARILY SHOULD BE
LOW-TOPPED IN NATURE GIVEN PRONOUNCED WEAKNESSES IN LAPSE RATES
ALOFT EVIDENT IN FCST SOUNDINGS. WHEN JUXTAPOSED ABOVE PREFRONTAL
SFC DEW POINTS GENERALLY LOW-MID 60S F OVER LOWER
ELEVATIONS...MLCAPE LESS THAN 500 J/KG RESULTS IN MUCH OF THIS
CORRIDOR. NONETHELESS...EXPECT STRENGTHENING OF BOTH WINDS ALOFT
AND DEEP-LAYER SPEED SHEAR...AS MID-UPPER SHORTWAVE TROUGH APCHS.
THIS SUPPORTS MRGL UNCONDITIONAL PROBABILITIES ATTM...PRIMARILY IN
FORM OF FOR DAMAGING GUSTS APCHG SVR LIMITS.

RELATIVE MIN IN SVR PROBABILITIES MAY EXIST BETWEEN THIS CORRIDOR
AND WRN AREA...MOST LIKELY OVER PORTIONS LOWER-MIDDLE OH VALLEY
WHERE DEEP-LAYER FLOW AND NEAR-FRONTAL LIFT APPEAR RELATIVELY WEAK
IN PROGS. HOWEVER...IT IS TOO SOON TO CARVE OUT SPECIFIC AREA WHERE
TSTMS NEAR FRONT ARE LIKELY TO REMAIN SFC-BASED YET FAIL TO OFFER AT
LEAST MRGL GUST OR HAIL POTENTIAL.

..EDWARDS.. 09/25/2012

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