DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 071253
SWODY1
SPC AC 071250

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT MON SEP 07 2009

VALID 071300Z - 081200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
THE MID LEVEL TROUGH OVER THE PAC NW AND NRN ROCKIES WILL CONTINUE
TO PROGRESS EWD TO THE NRN HIGH PLAINS BY TONIGHT...ALONG WITH AN
ASSOCIATED COLD FRONT. ELSEWHERE...A DIFFUSE MID LEVEL CYCLONIC
SHEAR AXIS EXTENDS SWD FROM THE NRN HIGH PLAINS TO NM...AND A WEAK
CLOSED LOW IS DRIFTING EWD OVER INDIANA/KY/OH TO THE S OF THE MAIN
BELT OF WESTERLIES. SOME CONCENTRATION OF THUNDERSTORMS WILL OCCUR
AROUND THE SRN/ERN PERIPHERY OF THE OH VALLEY CLOSED LOW...AND NEAR
THE OUTER BANKS OF NC IN CONJUCTION WITH A WAVE ON THE STALLED
BAROCLINIC ZONE. OTHERWISE...MORE SCATTERED DIURNAL CONVECTION IS
EXPECTED ACROSS THE N CENTRAL GULF COAST...S FL...AND THE
SRN/CENTRAL ROCKIES AREA. POOR LAPSE RATES AND/OR WEAK FLOW WILL
GENERALLY PRECLUDE A THREAT FOR ORGANIZED SEVERE STORMS FROM THE SRN
ROCKIES TO THE GULF COAST AND OH VALLEY.

...NRN HIGH PLAINS THIS AFTERNOON INTO TONIGHT...
MODERATE INSTABILITY IS EXPECTED IN ADVANCE OF THE SURFACE COLD
FRONT IN ND THIS AFTERNOON/EVENING...AND SWD ALONG THE LEE TROUGH
INTO WRN NEB. THE COMBINATION OF DAYTIME HEATING AND BOUNDARY LAYER
DEWPOINTS NEAR 60 F SPREADING NWD BENEATH AN ELEVATED MIXED LAYER
PLUME WILL SUPPORT AFTERNOON MLCAPE VALUES IN THE 1000-1500 J/KG
RANGE. VERTICAL SHEAR WILL REMAIN RATHER WEAK ALONG THE LEE TROUGH
AND E OF THE COLD FRONT THROUGH THIS EVENING...THUS DIURNAL
CONVECTION THAT FORMS ALONG THESE BOUNDARIES SHOULD BE MULTICELL IN
CHARACTER...WITH AN ATTENDANT THREAT FOR ISOLATED LARGE HAIL AND
DAMAGING GUSTS. ELEVATED CONVECTION IS EXPECTED TO DEVELOP/PERSIST
OVERNIGHT ON THE IMMEDIATE COOL SIDE OF THE FRONT WHERE LOW-MID
LEVEL ASCENT WILL BE GREATEST. A MARGINAL SEVERE STORM THREAT WILL
ALSO PERSIST OVERNIGHT WITH THESE STORMS IN A NARROW CORRIDOR WHERE
DEEP LAYER VERTICAL SHEAR INCREASES IN THE PRESENCE OF MUCAPE OF
500-1000 J/KG.

..THOMPSON/GARNER.. 09/07/2009

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.