SWOMCD
SPC MCD 292330
ARZ000-LAZ000-TXZ000-300100-
MESOSCALE DISCUSSION 2181
NWS STORM PREDICTION CENTER NORMAN OK
0530 PM CST SUN NOV 29 2009
AREAS AFFECTED...PARTS OF NE TX...SRN AR...NRN LA
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 292330Z - 300100Z
AN INTENSIFYING STORM OR TWO IS POSSIBLE EARLY THIS EVENING. SEVERE
PROBABILITIES...INCLUDING PERHAPS EVEN THE POSSIBILITY OF A
TORNADO...STILL SEEM RATHER LOW...BUT TRENDS WILL CONTINUE TO BE
MONITORED.
A BAND OF CONVECTION CONTINUES TO EVOLVE WITHIN A CONFLUENT
LOW-LEVEL FLOW REGIME...NEAR A SURFACE FRONT SLOWLY ADVANCING TOWARD
THE ARKLATEX REGION. MORE DISCRETE THUNDERSTORMS ARE ALSO FORMING
NEAR SHREVEPORT...IN RESPONSE TO BROADER SCALE FORCING FOR ASCENT
WITHIN A MOIST PRE-FRONTAL ENVIRONMENT CHARACTERIZED BY MIXED LAYER
CAPE AROUND 500 J/KG. THIS IS OCCURRING BENEATH A STRENGTHENING
DIVERGENT UPPER FLOW...WHICH WILL CONTINUE TO SUPPORT CONVECTION
INTO/THROUGH THE EVENING HOURS...GRADUALLY DEVELOPING EASTWARD
TOWARD THE LOWER MISSISSIPPI VALLEY. ALTHOUGH GENERALLY WEAK LAPSE
RATES APPEAR TO LIMIT THE POTENTIAL INTENSITY OF BOTH UPDRAFTS AND
DOWNDRAFTS...MODELS INDICATE THE PRESENCE OF A NARROW BELT OF
STRONGER WEST SOUTHWESTERLY 850 MB FLOW /AROUND 30 KTS/ SHIFTING
EASTWARD NEAR THE LOUISIANA/ARKANSAS BORDER. THIS MAY CONTRIBUTE TO
A WINDOW OF OPPORTUNITY FOR A STRENGTHENING ISOLATED SUPERCELL OR
TWO THROUGH AT LEAST THE 02-03Z TIME FRAME...BEFORE THE SEVERE
THREAT BECOMES INCREASINGLY NEGLIGIBLE ONCE AGAIN WITH BOUNDARY
LAYER STABILIZATION.
..KERR.. 11/29/2009
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...JAN...LZK...SHV...FWD...
LAT...LON 32409566 33259475 33719377 34059279 34109264 33799153
33349156 32829179 32659209 32329299 31969383 31699471
31859535 32409566
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