DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 261242
SWODY1
SPC AC 261240

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0740 AM CDT WED SEP 26 2012

VALID 261300Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE SRN AND CNTRL
PLNS...

...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE OH VLY INTO
THE MID ATLANTIC...

...SYNOPSIS...
WEAK SPLIT FLOW PATTERN WILL CONTINUE OVER THE CNTRL AND ERN
STATES...DOWNSTREAM FROM UT/CO UPR LOW AND ON SRN FRINGE OF QUE/GRT
LKS TROUGH. A SRN STREAM ZONAL JET WILL PERSIST FROM THE SRN
RCKYS/SRN PLNS INTO THE LWR OH VLY/MID ATLANTIC STATES...WHERE IT
WILL MERGE WITH STRONGER BAND OF FLOW MARKING BASE OF QUE TROUGH.

AT LWR LVLS...WRN PART OF FRONTAL ZONE NOW EXTENDING FROM THE LWR
GRT LKS THROUGH NRN/CNTRL IL INTO CNTRL KS SHOULD REMAIN QSTNRY
TODAY...WHILE ERN PART CONTINUES E TO OFF THE NEW ENGLAND CST BY 12Z
THU. SCTD AREAS OF SHOWERS AND TSTMS LIKELY WILL PERSIST INVOF THE
BOUNDARY THROUGH THE PERIOD...WITH ACTIVITY MODULATED BY BOTH
DIURNAL HEATING AND NOCTURNALLY-ENHANCED LLJ. THE GREATEST SFC-BASED
INSTABILITY SHOULD DEVELOP FROM THE SRN PLNS INTO THE OH VLY. WEAKER
BUOYANCY IS EXPECTED OVER THE APPALACHIANS AND MID ATLANTIC
REGION...WHERE SOMEWHAT GREATER DEEP SHEAR WILL EXIST.

...SE CO SE INTO PARTS OF THE SRN PLNS/WRN OZARKS THIS AFTN/EVE...
ONGOING TSTMS ALONG AND S OF STNRY FRONT EXPECTED TO PERSIST THROUGH
AT LEAST MIDDAY FROM ERN PARTS OF KS/OK ENE INTO THE LWR OH
VLY...SUPPORTED BY WAA/MOISTURE TRANSPORT ALONG BROAD WSWLY LLJ.
MOST OF THE ACTIVITY SHOULD REMAIN SUB-SVR...BUT ISOLD MARGINALLY
SVR HAIL OR WIND COULD OCCUR.

SFC HEATING OCCURRING W OF THE ABOVE ACTIVITY SHOULD SUPPORT SCTD TO
NUMEROUS NEW STORMS ALONG OUTFLOW BOUNDARIES OVER NRN/WRN OK AND
SW/S CNTRL KS...AND ALONG DRY LINE IN W TX. OTHER STORMS MAY FORM A
BIT LATER IN THE DAY INTO TNGT IN ZONE OF STRENGTHENING UPSLOPE FLOW
OVER SE CO.

WHILE DEEP SHEAR WILL BE SOMEWHAT WEAKER THAN YESTERDAY /DUE MAINLY
TO DECREASED 700 MB FLOW/...RELATIVELY COOL AIR WILL REMAIN PRESENT
AT MID-LVLS ATOP A MODERATELY MOIST BOUNDARY LAYER. COUPLED WITH
INCREASING UPR DIVERGENCE ASSOCIATED WITH EXIT REGION OF
HIGH-LVL...SRN BRANCH SPEED MAX APPROACHING FROM THE SRN
RCKYS...SETUP MAY YIELD A FEW LONG-LIVED CLUSTERS OF STORMS CAPABLE
OF SVR HAIL/WIND. ISOLD SVR WEATHER MAY PERSIST INTO LATE
EVE...ESPECIALLY IN PARTS OF OK...NW TX...AND PERHAPS SE CO. IN
GENERAL...HOWEVER...STORM STRENGTH SHOULD DIMINISH BY MID EVE.

...MID/UPR OH VLY INTO THE MID ATLANTIC THIS AFTN/EVE...
SEASONABLY STRONG /50 KT/ 700-500 MB UNIDIRECTIONAL WLY FLOW WILL
PREVAIL FROM OH/NRN KY TO THE MID ATLANTIC CST IN BASE OF QUE UPR
TROUGH. INSTABILITY WILL...HOWEVER...REMAIN MODEST RELATIVE TO
POINTS W...OWING LARGELY TO MORE LIMITED BOUNDARY LAYER MOISTURE AND
MID/UPR LVL CLOUD COVER. NEVERTHELESS...SUFFICIENT BUOYANCY LIKELY
WILL DEVELOP TO SUPPORT DEVELOPMENT OF SCTD AREAS OF
DIURNALLY-ENHANCED STORMS IN A NARROW CORRIDOR ALONG THE EFFECTIVE
COLD FRONT...I.E. ALONG COMPOSITE OUTFLOW BOUNDARY THAT ATTM EXTENDS
FROM CNTRL/NRN KY ENE INTO PARTS OF WV/VA/MD.

GIVEN THE STRENGTH OF THE LOW TO MID TROPOSPHERIC WIND FIELD...AND
RELATIVELY STEEP MID LVL LAPSE RATES/RESIDUAL EML...POTENTIAL WILL
EXIST FOR A FEW STORMS WITH SMALL-SCALE BOWS AND POSSIBLY LOCALLY
DMGG WIND. FARTHER N...MORE WIDESPREAD CLOUDINESS AND SOMEWHAT
WEAKER DEEP WIND FIELD EXPECTED TO LIMIT STORM STRENGTH/LONGEVITY
ALONG IMMEDIATE COLD FRONT FROM NRN OH INTO NRN PA/NY...ALTHOUGH
ISOLD STRONG TO SVR GUSTS CANNOT ENTIRELY BE RULED OUT.

..CORFIDI/GRAMS.. 09/26/2012

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