SWODY1
SPC AC 091626
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1126 AM CDT SUN SEP 09 2007
VALID 091630Z - 101200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
A BROAD UPPER TROUGH WILL RESIDE ALONG NRN TIER OF STATES TODAY.
EMBEDDED WITHIN THIS TROUGH...SEVERAL WEAKER PROGRESSIVE SHORTWAVES
WILL EXIST. AT THE SFC...A SLOW MOVING COLD FRONT EXTENDING FROM THE
SRN ROCKIES INTO THE GREAT LAKES WILL CONTINUE TO PROGRESS EWD
THROUGH THE OHIO VALLEY AND THE NRN APPALACHIANS/SRN NEW ENGLAND
THROUGH TONIGHT SUPPORTED BY A SHORTWAVE TROUGH MOVING THROUGH THE
OHIO VALLEY. FURTHER WEST...THE FRONT IS EXPECTED TO BECOME
STATIONARY ACROSS THE SRN PLAINS/LOWER MS VALLEY AND SRN/CENTRAL
ROCKIES AS PRESSURE FALLS COMMENCE AHEAD OF A SHORTWAVE TROUGH
MOVING THROUGH THE NRN ROCKIES. GENERALLY WEAK VERTICAL SHEAR AND/OR
LAPSE RATES WILL LIMIT THE SVR POTENTIAL WITH ANY TSTMS THAT OCCUR
ACROSS THE CONUS TODAY.
..NRN APPALACHIANS/SRN NEW ENGLAND...
AHEAD OF A SHORTWAVE TROUGH OVER OHIO...A SFC WAVE HAS DEVELOPED
OVER CENTRAL PA. A WARM/MOIST AND UNSTABLE AIRMASS WILL BE IN PLACE
TO THE EAST OF A CLOUD SHIELD AND SOUTH OF A STATIONARY BOUNDARY
ACROSS SRN NEW ENGLAND...FROM ERN PA/SERN HALF OF NY INTO PARTS OF
WRN CT/WRN MA. ACROSS THIS AREA...MODEST UNIDIRECTIONAL WIND
PROFILES /30 KTS ON THE REGIONAL VWP DATA/ ASSOCIATED WITH
APPROACHING SHORTWAVE WILL OVERSPREAD THE AREA THIS AFTERNOON.
THEREFORE SOME LINEAR ORGANIZATION IS POSSIBLE WITH ANY TSTMS THAT
DEVELOP. HOWEVER...GENERALLY WEAK LAPSE RATES /AROUND 6 C/KM/ NOTED
ON THE 12Z REGIONAL SOUNDINGS SHOULD LIMIT UPDRAFT STRENGTH AND
POTENTIAL FOR A MORE ORGANIZED SVR WIND THREAT.
..NWRN TX EWD INTO THE LOWER MS VALLEY...
ALONG A CONVECTIVE AIDED FRONTAL BOUNDARY EXTENDING FROM NEAR ABI
ENEWD TO NEAR MEM...MODEST CONVERGENCE AND DAYTIME
HEATING/DESTABILIZATION SHOULD AID IN NEW DEVELOPMENT OR
STRENGTHENING OF ONGOING CONVECTION THIS AFTERNOON. GENERALLY WEAK
WIND FIELDS /AOB 10 KTS THROUGH THE TROPOSPHERE/ WILL SUPPORT PULSE
TYPE TSTMS WITH HVY RAIN THE MAIN THREAT. AN ISOLATED WET MICROBURST
MAY OCCUR WHERE CELL MERGERS LOCALLY ENHANCE UPDRAFT STRENGTH.
..SRN/CENTRAL ROCKIES AND HIGH PLAINS...
A COLD FRONT PUSHED WEST INTO THE HIGHER TERRAIN EARLY THIS MORNING
AND RESIDES ALONG THE ERN EDGE OF THE CONTINENTAL DIVIDE AT MIDDAY.
STABLE/COOL AIR OVER THE HIGH PLAINS/FRONT RANGE WILL CONTINUE TO BE
REINFORCED BY WIDESPREAD LOW CLOUD COVER AND ONGOING LGT/MOD
PRECIPITATION...DESPITE PRESSURE FALLS EXPECTED TO OCCUR AHEAD OF A
PROGRESSIVE SHORTWAVE TROUGH OVER THE NRN ROCKIES. THEREFORE...THE
BEST INSTABILITY IS EXPECTED TO REMAIN ALONG THE HIGHER TERRAIN FROM
CENTRAL CO SWD INTO SCENTRAL NM WHERE MLCAPE VALUES FROM 500-1000
J/KG ARE EXPECTED BY MID AFTERNOON. ALONG THIS INSTABILITY AXIS
ACROSS NM...UPPER FORCING AHEAD OF A VORT LOBE MOVING OUT OF SERN AZ
MAY SUPPORT AN ISOLATED SVR WIND/HAIL THREAT. FURTHER
NORTH...STEEPER LOW-MID LEVEL LAPSE RATES AND STRONGER WIND FIELDS
/ASSOCIATED WITH THE APPROACHING NRN ROCKIES UPPER TROUGH/ WILL
EXIST OVER CENTRAL CO THIS AFTERNOON AND POSSIBILITY THE IMMEDIATE
FOOTHILLS LATE TODAY. HOWEVER...LIMITED INSTABILITY /SBCAPE LESS
THAN 500 J/KG SHOULD ALSO LIMIT THE SVR THREAT.
..ERN NC...
T.S GABRIELLE HAS NOW MOVED ACROSS THE SRN OUTER BANKS OF NC.
DESPITE THE FACT THAT ALL OF THE DEEP CONVECTION REMAINS SOUTH OF
THE CENTER OF CIRCULATION...AN ISOLATED TSTM MAY STILL DEVELOP IN
THE L.F QUADRANT OF THE SYSTEM AS IT PROGRESSES NWD THROUGH TONIGHT
/SEE NHC FOR OFFICIAL TRACK FCST/. MARGINAL LOW LEVEL VERTICAL SHEAR
WILL PRECLUDE ANYTHING MORE THAN A VERY LOW PROBABILITY OF A
TORNADO.
.CROSBIE/HALES.. 09/09/2007
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