DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 110602
SWODY1
SPC AC 110600

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT THU OCT 11 2012

VALID 111200Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS KS/OK BORDER AREA TO
EXTREME WRN PORTIONS KY/TN...

...SYNOPSIS...
IN MID-UPPER LEVELS...SPLIT-FLOW PATTERN FCST THROUGH PERIOD OVER
PORTIONS WRN/CENTRAL CONUS...RELATED TO PRONOUNCED CYCLONE ALOFT NOW
LOCATED INVOF CENTRAL CA COASTAL WATERS. ASSOCIATED LOW IS FCST TO
PIVOT SEWD JUST OFFSHORE THROUGH FIRST HALF OF PERIOD...THEN MOVE
ASHORE AROUND 12/00Z. CYCLONE WILL TURN ENEWD THROUGH REMAINDER
PERIOD...ITS CENTER REACHING SERN SIERRAS BY 12/12Z. STG SHORTWAVE
TROUGH CURRENTLY OVER LOWER GREAT LAKES AND INTERIOR MID-ATLC
REGIONS SHOULD MOVE RAPIDLY ENEWD OVER ERN NEW ENGLAND BY START OF
PERIOD. HOWEVER...BROADLY CYCLONIC FLOW WILL BE MAINTAINED TODAY
OVER UPPER MIDWEST/GREAT LAKES REGIONS AS ANOTHER PERTURBATION --
NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER ERN MB AND SRN/CENTRAL
SK -- MOVES ESEWD ACROSS UPPER GREAT LAKES AND AMPLIFIES. RELATED
TROUGH SHOULD REACH ST LAWRENCE VALLEY AND SRN ONT BY 12/12Z.

AT SFC...QUASISTATIONARY FRONTAL ZONE NOW OVER ERN/CENTRAL/SWRN TX
IS EXPECTED TO MOVE NWD AS WARM FRONT THROUGH PERIOD...REACHING
PORTIONS WRN/SRN AR AND NERN OK/SERN KS BY 12/00Z. WRN SEGMENT OF
THIS BOUNDARY WILL BE OVERTAKEN ACROSS CENTRAL/WRN KS BY COLD FRONT
NOW MOVING SEWD OVER SD. DIFFUSE DRYLINE SHOULD DEVELOP ALONG NWRN
RIM OF GULF RETURN-FLOW DURING DAY...EXTENDING FROM TX PANHANDLE
SSWWD OVER SERN NM BY LATE AFTERNOON. WEAK FRONTAL-WAVE LOW MAY
DEVELOP ALONG COLD FRONT BETWEEN WARM-FRONTAL INTERSECTION AND
DRYLINE OVERNIGHT...AS COLD FRONT DECELERATES OVER NRN OK AND TX
PANHANDLE.

...KS/OK BORDER AREA TO EXTREME WRN PORTIONS KY/TN...
SCATTERED TSTMS ARE FCST TO DEVELOP DURING 12/03Z-12/012Z TIME FRAME
IN W-E OR WNW-ESE ALIGNED CORRIDOR PARALLEL TO AND NEAR SFC FRONTAL
ZONE. MAIN CONCERN WILL BE LARGE HAIL. THIS ACTIVITY WILL BE
SUPPORTED BY SWATH OF 30-40 KT 850-MB SWLYS AND WARM FRONTAL
FORCING...ALONG WITH RELATED MOISTURE TRANSPORT AND ISENTROPIC
ASCENT TO LFC. FAVORABLY STEEP MIDLEVEL LAPSE RATES UNDERLAIN BY
INCREASING THETAE WILL YIELD MUCAPE VALUES 1000-2000 J/KG ACROSS
THIS CORRIDOR...AMIDST 35-45 KT EFFECTIVE SHEAR MAGNITUDES. THIS
REGION ALSO SHOULD EXPERIENCE LARGE-SCALE ASCENT BENEATH
RIGHT-ENTRANCE REGION OF ROUGHLY 100-KT 250-MB JET MAX SHIFTING
ESEWD ACROSS NRN MO/IL/INDIANA. INITIAL DEVELOPMENT MAY OCCUR LATE
EVENING OVER OZARKS REGION AND MOVE EWD...WITH DISCRETE/BACKBUILDING
EVOLUTION FARTHER W ACROSS KS/OK BORDER REGION OVERNIGHT.
ADDITIONAL ACTIVITY MAY MOVE INTO THIS REGION FROM DIURNAL/DRYLINE
CONVECTIVE REGIME...THOUGH THAT POTENTIAL IS MORE CONDITIONAL.

...SRN HIGH PLAINS...
DIABATIC HEATING...STEEP LOW-LEVEL LAPSE RATES...DRYLINE LIFT...AND
INCREASING BOUNDARY-LAYER MOISTURE SHOULD LEAD TO WEAKENING CINH AND
INCREASING TSTM POTENTIAL THROUGH AFTERNOON. ACTIVITY ALSO MAY
DEVELOP OVER MOUNTAINS OF SRN NM AND MOVE NEWD INTO REGIME OF
INCREASING LOW-LEVEL MOISTURE WITH EWD EXTENT AND WITH TIME.
ALTHOUGH LOW-LEVEL FLOW WILL BE RELATIVELY WEAK...BENEATH RIDGING
ALOFT...FAVORABLY STG UPPER-LEVEL WINDS ARE FCST INVOF BROAD
SUBTROPICAL JET BRANCH THAT WILL BE GRADUALLY STRENGTHENING WITH
TIME. BUOYANCY MAY BE LIMITED SOMEWHAT BY EFFECTS OF CLOUD COVER
ALOFT...BOTH IN TERMS OF MID-UPPER LEVEL LAPSE RATES AND SOMEWHAT
MUTED PACE OF SFC HEATING. 30-40 KT EFFECTIVE SHEAR MAGNITUDES WILL
SUPPORT SOME STORM ORGANIZATION...WITH MULTICELLULAR MODES BEING
DOMINANT AND TRANSIENT SUPERCELL EVOLUTION POSSIBLE. ATTM...SVR
POTENTIAL APPEARS TOO UNCERTAIN IN COVERAGE FOR MORE THAN MRGL
PROBABILITIES.

...PORTIONS AZ/SERN NV/SRN UT...
WIDELY SCATTERED TO SCATTERED TSTMS SHOULD DEVELOP OVER PORTIONS NRN
AZ...SRN UT AND SRN NV...AND PERHAPS OVER PARTS OF E-CENTRAL/SERN
AZ...DURING AFTERNOON. ACTIVITY MAY PERSIST INTO EVENING. ISOLATED
LARGE HAIL AND STG-SVR GUSTS MAY OCCUR FROM MOST INTENSE CELLS.
STRENGTHENING DEEP-LAYER ASCENT IS FCST ACROSS MUCH OF THIS
CORRIDOR...IN TERMS OF BOTH LOW-LEVEL FORCING NEAR EWD-MOVING PAC
FRONT AND LARGE-SCALE LIFT/COOLING ALOFT AHEAD OF INCREASINGLY
PROGRESSIVE CYCLONE. PLUME OF RELATIVELY MAXIMIZED LOW-LEVEL
MOISTURE NOW LOCATED OVER LOWER CO RIVER VALLEY REGION SHOULD SHIFT
EWD...WITH MOIST ADVECTION AND SFC DIURNAL HEATING CONTRIBUTING TO
AFTERNOON BUOYANCY. WELL-MIXED SUBCLOUD LAYERS WILL SUPPORT GUSTY
TSTM WINDS...BENEATH SUFFICIENTLY STG FLOW ALOFT FOR 35-40 KT
EFFECTIVE SHEAR MAGNITUDES.

..EDWARDS/GUYER.. 10/11/2012

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