SWODY1
SPC AC 181623
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1023 AM CST WED NOV 18 2009
VALID 181630Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A MID LEVEL CLOSED LOW POSITIONED OVER THE STL AREA AT 12Z IS
FORECAST TO LIFT NWD THROUGH THE DAY IN RESPONSE TO A S/W TROUGH
EMERGING OUT OF THE PAC NW. AT THE SURFACE...AN OCCLUDED FRONT WAS
LOCATED FROM GA NWD INTO THE MID OH VALLEY REGION...AND THEN W
ACROSS IL/IND TOWARD A LOW PRESSURE CENTER OVER ERN MO. E OF THE
OCCLUDED FRONT...A HIGH PRESSURE CENTER OVER NEW ENGLAND EXTENDED
S-SWD TOWARD SC...WHICH WAS MAINTAINING A COOL BUT MOIST LOW LEVEL
AIRMASS ACROSS THE REGION.
...UPPER OH RIVER VALLEY...
AS THE UPPER LOW BEGINS TO LIFT NWD THROUGH THE NIGHT...LARGE SCALE
FORCING FOR ASCENT AND LOW LEVEL MASS FIELDS ARE EXPECTED TO
INCREASE...WITH AN EWD SURGE IN THE OCCLUDED FRONT FORECAST TO OCCUR
OVER THE UPPER OH RIVER VALLEY REGION. INCREASING MOISTURE TRANSPORT
ABOVE A COOL/STABLE SURFACE AIRMASS OCCURRING IN CONJUNCTION WITH
STEEPENING MID LEVEL LAPSE RATES WILL RESULT IN A FAVORABLE
ENVIRONMENT FOR THUNDERSTORM DEVELOPMENT LATE THIS AFTERNOON THROUGH
THE OVERNIGHT PERIOD. HOWEVER...ELEVATED INSTABILITY AND EFFECTIVE
BULK SHEAR VALUES APPEAR TO BE TOO WEAK TO SUPPORT A SEVERE WEATHER
THREAT.
...APPALACHIAN MTNS SWD INTO THE CAROLINA COASTAL PLAIN...
A WEDGE FRONT EXTENDS EWD FROM THE OCCLUDED FRONT OVER GA TO A
LOCATION ALONG THE SC/NC COAST. VISIBLE SATELLITE IMAGERY REVEALS
WIDESPREAD STRATUS PRESENT N OF THE WEDGE FRONT...WHICH WILL IMPEDE
SURFACE BASED DESTABILIZATION THROUGH THE DAY. HOWEVER...NWD
TRANSPORT OF MOISTURE ABOVE THE STABLE SURFACE AIRMASS WILL FAVOR
SHOWERS AND ISOLATED THUNDERSTORM DEVELOPMENT THROUGH THE
AFTERNOON/EVENING. AS THE LARGE SCALE PATTERN BECOMES MORE
PROGRESSIVE TONIGHT...MODEL GUIDANCE INDICATES THE WEDGE/COASTAL
FRONT WILL ATTEMPT TO LIFT NWD THROUGH NC. FORECAST SOUNDINGS
INDICATE THAT LOW LEVEL SHEAR PROFILES WILL BE FAVORABLE FOR UPDRAFT
ROTATION. HOWEVER...A SHALLOW STABLE LAYER CONTINUES TO BE
DEPICTED...WHICH WILL PRECLUDE THE INTRODUCTION OF A TWO PERCENT
TORNADO AREA AT THIS TIME.
..GARNER/EVANS.. 11/18/2009
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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.
No comments:
Post a Comment