SWODY1
SPC AC 241251
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0751 AM CDT SUN AUG 24 2008
VALID 241300Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CNTRL/NRN HI PLNS...
...SYNOPSIS...
RIDGE WILL PERSIST OVER THE FOUR CORNERS THIS PERIOD AS STRONG NE
PACIFIC TROUGH PROGRESSES E INTO BC/WRN WA. DOWNSTREAM TROUGH NOW
OVER ONTARIO AND THE UPR GRT LKS WILL BE REINFORCED BY IMPULSE NOW
APPROACHING LK SUPERIOR. THE TROUGH SHOULD REACH SRN QUEBEC BY 12Z
MONDAY. ELSEWHERE...WV LOOP SHOWS A DISTURBANCE NOW OVER NW WY/SRN
MT THAT SHOULD CONTINUE E/SE AROUND NERN FRINGE OF UPR RIDGE LATER
TODAY/TONIGHT. FINALLY...T.D. FAY EXPECTED TO REMAIN MORE OR LESS
STNRY OVER SRN MS AS SYSTEM CONTINUES TO MERGE WITH WEAK UPR
DISTURBANCE THAT MOVED SE ACROSS AR/LA EARLIER TODAY.
...CNTRL HI PLNS...
LEE TROUGH WILL BECOME BETTER ESTABLISHED OVER THE CNTRL HI PLNS
TODAY AS LARGE SCALE TROUGH APPROACHES THE PACIFIC NW. ASSOCIATED
INCREASE IN LOW LVL SSELY FLOW WILL ALLOW UPR 50S TO LOW 60S F
DEWPOINTS TO SPREAD NNW THROUGH WRN NEB...SW SD...AND ERN WY BENEATH
NERN FRINGE OF RCKYS EML. COUPLED WITH STRONG SFC HEATING...EXPECT
AFTN SBCAPE ACROSS REGION TO RANGE FROM 1500 TO 2500 J/KG.
EML WARM LAYER AND ABSENCE OF LOW LVL FORCING LIKELY SHOULD KEEP THE
PLNS FREE OF DEEP CONVECTION THROUGH MUCH OF THE DAY. BUT
HEATING...WEAK UPSLOPE COMPONENT TO FLOW...AND ASCENT ASSOCIATED
WITH WY/MT IMPULSE SHOULD SUPPORT SCTD AFTN STORMS OVER HIGHER
TERRAIN JUST TO THE WEST. THIS ACTIVITY SHOULD MOVE/DEVELOP SE INTO
THE PLNS BY EVE...BEFORE SUBSEQUENTLY WEAKENING AS BOUNDARY LAYER
COOLS AND UPR IMPULSE CONTINUES E BEYOND AXIS OF GREATEST LOW LVL
INSTABILITY.
20 KT WNWLY MID LVL WINDS ATOP 15-20 KT SSELY NEAR-SFC FLOW COULD
SUPPORT A FEW ORGANIZED STORMS/MARGINAL SUPERCELLS. THESE COULD
YIELD LARGE HAIL...LOCALLY DMGG WIND...AND PERHAPS A BRIEF TORNADO.
...CNTRL GULF CST...
VWP AND RAOB DATA SHOW THAT DEEP WIND FIELD WITH FAY HAS WEAKENED
OVERNIGHT...AND WINDS OVER AL/MS AND LA SHOULD CONTINUE TO SLOWLY
WEAKEN TODAY. A MID LVL DRY SLOT HAS OVERSPREAD PARTS OF AL AND THE
FL PANHANDLE AS SYSTEM INTERACTED WITH MID LATITUDE IMPULSE THAT
CROSSED AR/LA. ASSOCIATED EROSION OF DEEP CLOUD FIELD WILL ALLOW
FOR MORE SUBSTANTIAL SFC HEATING IN SE QUADRANT OF REMNANT LOW LVL
CIRCULATION THAN HAS BEEN THE CASE IN RECENT DAYS. WHILE THIS MAY
SUPPORT DEVELOPMENT OF BANDS/CLUSTERS OF DIURNALLY- ENHANCED
CONVECTION/POSSIBLE STORMS...WARM 700-500 MB TEMPERATURES SHOULD
LIMIT COVERAGE/STRENGTH.
EXTRAPOLATION OF CURRENT PATTERN SUGGEST THAT SOME MID LVL COLD
ADVECTION COULD OVERSPREAD THE CNTRL GULF CST THIS EVE AND TONIGHT
AS PART OF FORMER AR/LA IMPULSE THAT IS NOW OVER THE NW/N CNTRL GULF
ROTATES NEWD. THIS FEATURE APPEARS...IN PART...TO BE RESPONSIBLE
FOR TSTMS NOW OVER THE GULF S OF LA...AND COULD ENHANCE THE
POTENTIAL FOR EVE/OVERNIGHT STORMS IN SRN MS/SRN AL AND THE FL
PANHANDLE. MODERATE DEEP SHEAR WILL EXIST ACROSS THAT REGION AT
THAT TIME...ALTHOUGH THE MAGNITUDE OF THE LOW LVL DIRECTIONAL
COMPONENT WILL BE REDUCED RELATIVE TO WHAT IT HAS BEEN INVOF FAY IN
RECENT DAYS. NEVERTHELESS...GIVEN RICH MOISTURE
AVAILABILITY...PARTS OF THE CNTRL GULF CST REGION COULD REQUIRE
UPGRADE TO CATEGORICAL SVR RISK LATER TODAY IF IT BECOMES APPARENT
THAT SUSTAINED DISCRETE STORMS WILL INDEED OCCUR THIS EVE/OVERNIGHT.
...NE OH/NW PA INTO WRN/CNTRL NY...
GLANCING INFLUENCE OF UPR IMPULSE REINFORCING ONTARIO TROUGH WILL
ENHANCE UVV ACROSS THE LWR GRT LKS REGION LATER TODAY. A NARROW
AXIS OF MODEST INSTABILITY LIKELY WILL DEVELOP ALONG ASSOCIATED
COLD FRONT...BUT WEAK MID LVL LAPSE RATES WILL LIMIT SBCAPE TO
GENERALLY AROUND 1000 J/KG. SCTD STORMS SHOULD FORM ALONG THE FRONT
AND LK BREEZE BOUNDARIES OVER PARTS OF OH...PA AND NY. WEAK
DEEP SHEAR WILL FAVOR PULSE/MULTICELL STRUCTURES. RELATIVELY STEEP
LOW LVL LAPSE RATES MAY SUPPORT A THREAT OF ISOLD STRONG WIND GUSTS
THROUGH EARLY EVENING.
..CORFIDI/JEWELL.. 08/24/2008
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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