Saturday, November 29, 2008

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 291253
SWODY1
SPC AC 291250

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0650 AM CST SAT NOV 29 2008

VALID 291300Z - 301200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
AMPLIFICATION OF A LARGE SCALE TROUGH FROM THE CENTRAL PLAINS TO THE
MID MS VALLEY WILL COMMENCE TODAY AS A SERIES OF EMBEDDED SHORTWAVE
TROUGHS EJECT ENEWD FROM THE ARKLATEX...ESEWD FROM THE CENTRAL HIGH
PLAINS TOWARD THE LOWER MS VALLEY...AND SSEWD FROM ALBERTA TO THE
NRN HIGH PLAINS. AN INITIAL WEAK SURFACE CYCLONE WILL PROGRESS
ENEWD TODAY FROM SE MS INTO CENTRAL AL ALONG A STALLED BAROCLINIC
ZONE IN ASSOCIATION WITH THE WEAKENING LEAD WAVE NOW OVER THE
ARKLATEX...WHILE BROADER SYNOPTIC CYCLOGENESIS WILL OCCUR TONIGHT
OVER THE TN VALLEY AS THE HIGH PLAINS SHORTWAVE TROUGH APPROACHES
THE LOWER MS VALLEY. THE PRIMARY THUNDERSTORM THREAT CORRIDOR WILL
BE FROM SE LA/SRN MS ENEWD INTO W/SW GA ALONG THE STALLED FRONT
TODAY INTO TONIGHT.

...SRN LA/MS INTO SRN AL/SW GA THROUGH TONIGHT...
A STALLED BAROCLINIC ZONE S OF I-20 WILL MOVE LITTLE DURING THE DAY
ACROSS AL/GA IN ADVANCE OF THE WEAK SURFACE WAVE...WHILE THE WRN
SEGMENT OF THE FRONT MOVES SEWD ACROSS LA/MS. AN ONGOING BAND OF
CONVECTION ALONG THE FRONT SHOULD PERSIST THROUGH THE DAY AND SPREAD
ENEWD IN CONJUNCTION WITH BOUNDARY LAYER DEWPOINTS IN THE MID 60S
AND DAYTIME HEATING WITHIN CLOUD BREAKS IN THE WARM SECTOR. MUCH
LIKE YESTERDAY...WARM SECTOR INSTABILITY WILL BE RATHER MODEST
/MLCAPE OF 500-1000 J/KG/ OWING TO MID LEVEL LAPSE RATES GENERALLY
AOB 6.5 C/KM...WITH SUFFICIENT DEEP LAYER BULK SHEAR FOR SUPERCELLS.
A COUPLE OF SUPERCELLS AND/OR BOWING LINE SEGMENTS WILL BE POSSIBLE
ALONG THE BAROCLINIC ZONE WHERE LOW-LEVEL ASCENT AND SHEAR WILL BE
STRONGER COMPARED TO THE OPEN WARM SECTOR. HOWEVER...ONLY MODEST
LOW-LEVEL SHEAR MAGNITUDES /COMPARED TO THE INSTABILITY/ SHOULD
LIMIT THE SEVERE STORM THREATS TO ISOLATED DAMAGING WINDS AND
PERHAPS A BRIEF TORNADO...WHILE INSTABILITY COULD BE SUFFICIENT FOR
MARGINALLY SEVERE HAIL IN THE STRONGER STORMS.

THERE WILL BE A TENDENCY FOR INCREASING LOW-LEVEL FLOW/SRH IN THE
WARM SECTOR ACROSS GA/N FL LATE TONIGHT...IN RESPONSE TO PRESSURE
FALLS NEAR AND N OF THIS AREA. VERY MARGINAL INSTABILITY INLAND
WILL CONTINUE TO LIMIT THE DAMAGING WIND/TORNADO THREAT LATE
TONIGHT...THOUGH THIS AREA WILL HAVE TO BE MONITORED CLOSELY FOR
SIGNS OF GREATER INSTABILITY THAN CURRENTLY ANTICIPATED.

..THOMPSON/SMITH.. 11/29/2008

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