SWODY1
SPC AC 061925
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0225 PM CDT TUE OCT 06 2009
VALID 062000Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN/EARLY EVE ACROSS
PARTS OF CNTRL TX INTO THE LWR MS VALLEY...
...20Z UPDATE...
...NORTH CENTRAL GULF STATES/UPPER TENNESSEE VALLEY...
AN AREA OF MID/UPPER FORCING...DOWNSTREAM OF THE VIGOROUS CLOSED
LOW/TROUGH ACCELERATING TOWARD THE GREAT LAKES...APPEARS TO HAVE
PROVIDED SUPPORT FOR SUSTAINED PROMINENT ONGOING STORM CLUSTER NOW
SPREADING ACROSS SOUTH CENTRAL KENTUCKY/MIDDLE TENNESSEE. HOWEVER
...MODELS GENERALLY SUGGEST THAT THIS FORCING WILL WEAKEN THROUGH
THE REMAINDER OF THE AFTERNOON...AND CONVECTIVE ACTIVITY PROBABLY
WILL FOLLOW SUIT. AS CONVECTION CONTINUES EASTWARD...SUPPORTING
MOIST LAYER APPEARS TO BECOME INCREASINGLY ELEVATED/LESS UNSTABLE
...LIKELY RESULTING IN NEARLY NEGLIGIBLE SEVERE POTENTIAL.
IT IS NOT OUT OF THE QUESTION...THOUGH...THAT FORCING ASSOCIATED
WITH ONE OF THE LOW AMPLITUDE UPSTREAM WAVES...ON THE SOUTHERN
FRINGE OF THE STRONGER WESTERLIES...COULD SUPPORT RENEWED UPSCALE
CONVECTIVE GROWTH ACROSS PARTS OF SOUTHERN TENNESSEE/NORTHERN
MISSISSIPPI AND ALABAMA LATER TONIGHT. IF THIS OCCURS...IT PROBABLY
WILL BE ROOTED IN A MOIST LAYER CLOSER TO THE SURFACE...AS
PRE-FRONTAL RETURN FLOW CONTINUES...AND DEEP LAYER FLOW/SHEAR MAY BE
STRONG ENOUGH TO SUPPORT AT LEAST LOW PROBABILITIES FOR SEVERE
WIND/HAIL.
...TEXAS INTO THE LOWER MISSISSIPPI VALLEY...
SLIGHT RISK PROBABILITIES HAVE BEEN MAINTAINED NEAR SURFACE FRONT.
WHILE STORMS HAVE GENERALLY BEEN CONFINED TO A ZONE OF LIFT NORTH OF
THE SOUTHWARD ADVANCING COLD FRONT...A WINDOW OF OPPORTUNITY MAY
STILL EXIST FOR FRONTAL FORCING TO CONTRIBUTE TO STORM DEVELOPMENT
IN THE MODERATELY UNSTABLE PRE-FRONTAL ENVIRONMENT LATE THIS
AFTERNOON. HOWEVER...IT STILL SEEMS PROBABLE THAT ANY SUCH ACTIVITY
WILL BE RELATIVELY SHORT LIVED...WITH THE TENDENCY FOR THE COLD
FRONT TO UNDERCUT STRONGER CONVECTION...AS MID/UPPER RIDGING SLOWLY
BEGINS TO BUILD NORTHWARD ACROSS THE REGION.
..KERR.. 10/06/2009
.PREV DISCUSSION... /ISSUED 1125 AM CDT TUE OCT 06 2009/
...TX INTO LOWER MS RIVER VALLEY...
PRONOUNCED LOW LEVEL WAA MAINTAINING BROKEN BAND OF ELEVATED TSTMS
FROM NWRN TX INTO THE MID SOUTH WILL CONTINUE TO SPREAD ENEWD ACROSS
THE LOWER MS RIVER VALLEY TODAY AS MAIN MID/UPPER LEVEL IMPULSE
LIFTS INTO THE GREAT LAKES. THIS WILL DIMINISH LARGE SCALE ASCENT
ACROSS THE SRN PLAINS...ALTHOUGH EFFECTIVE SURFACE FRONT/WIND SHIFT
WILL CONTINUE SAGGING SWD INTO CENTRAL TX AND INTO NRN LA/NRN MS.
WARM SECTOR WILL REMAIN VERY MOIST WITH PWS IN EXCESS OF 1.5 INCHES
AND SFC DEW POINTS APPROACHING 80F. 12Z SOUNDINGS INDICATE CAPPING
WILL PROVE PROBLEMATIC FOR WARM SECTOR DEVELOPMENT...WITH LOW LEVEL
LIFTING SUPPORTING MORE ELEVATED DEVELOPMENT ATOP SHALLOW SURFACE
COLD LAYER ALONG AND JUST BEHIND THE SURFACE FRONT. DEEP LAYER
SHEAR FROM 45-55 KT SHOULD CONTINUE TO SUPPORT A FEW ORGANIZED
CELLS...INCLUDING SUPERCELLS. TEMPERATURES WILL REMAIN RELATIVELY
WARM AT 500 MB...AROUND MINUS 5 OR 6 C....FROM TX INTO AR AND THE
LOWER MS RIVER VALLEY WHICH MAY LIMIT HAIL GROWTH. HOWEVER
...SUFFICIENT HEATING AND RICH LOW LEVEL MOISTURE SHOULD BOOST
MUCAPE TO AROUND 2500 J/KG IN S CNTRL TX ENE INTO THE ARKLATEX
AND...ALONG WITH STRONG DEEP LAYER SHEAR...STILL SUPPORT A THREAT OF
ISOLATED SEVERE HAIL/WIND.
LATER TONIGHT INTO SWRN TX...LOW LEVEL WAA WILL AGAIN INCREASE ALONG
STRENGTHENING SLY H85 FLOW. ELEVATED TSTM DEVELOPMENT CAN BE
EXPECTED THROUGH THE NIGHT FROM THE RIO GRANDE INTO THE HIGH PLAINS
OF SERN NM/WRN TX WHERE STEEP MID LEVEL LAPSE RATES AND MODEST
EFFECTIVE SHEAR SHOULD SUSTAIN A RISK OF ISOLATED LARGE HAIL.
...MID SOUTH INTO THE TN VALLEY/MIDWEST...
DESPITE AMPLE LARGE SCALE FORCING FOR ASCENT AND STRENGTHENING
DEEP WIND FIELD ASSOCIATED WITH AMPLIFYING UPPER TROUGH...
APPRECIABLE LOW LEVEL DESTABILIZATION SEEMS UNLIKELY AHEAD OF COLD
FRONT GIVEN PREFRONTAL RAIN/CLOUDS AND STRONG CAPPING EVIDENT ON
MORNING SOUNDINGS. COMBINATION OF WEAK ELEVATED INSTABILITY AND
ENHANCED LOW TO MID LEVEL WINDS ATOP RELATIVELY RICH BOUNDARY LAYER
MOISTURE WILL SUPPORT AT LEAST A CONDITIONAL SEVERE RISK...PRIMARILY
IN THE FORM OF ISOLATED STRONG/DAMAGING WINDS AND A NON-ZERO TORNADO
THREAT. OVERALL THREAT APPEARS MARGINAL OVER SUCH A LARGE AREA AND
WILL CONTINUE LOW SEVERE PROBABILITIES ACCORDINGLY.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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