Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 292337
SWOMCD
SPC MCD 292337
LAZ000-MSZ000-TXZ000-300200-

MESOSCALE DISCUSSION 1844
NWS STORM PREDICTION CENTER NORMAN OK
0537 PM CST TUE NOV 29 2016

AREAS AFFECTED...PORTIONS OF SOUTHERN LA...SOUTHEAST TX...AND FAR
SOUTHERN MS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 292337Z - 300200Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...A RISK FOR SEVERE THUNDERSTORMS MAY GRADUALLY INCREASE
THROUGH THE EVENING HOURS...AND THIS INCLUDES A RISK FOR TORNADOES.
WHILE NOT IMMEDIATELY LIKELY...WATCH ISSUANCE MAY BE NEEDED DURING
THE NEXT FEW HOURS.

DISCUSSION...RICH MOISTURE ACCOMPANYING A GULF-MODIFIED AIR MASS
CONTINUES TO BE TRANSPORTED INTO THE LOWER SABINE VALLEY AND POINTS
EASTWARD AS LOW-LEVEL SOUTHERLIES ARE WELL ESTABLISHED OVER A BROAD
PORTION OF THE WESTERN GULF COAST AND VICINITY. SURFACE DEWPOINTS
AROUND 70-72F ARE ESTABLISHED ACROSS THE AREA...WITH EVEN RICHER
MOISTURE OFFSHORE. AS SUCH...A MODERATELY UNSTABLE AIR MASS IS IN
PLACE...WITH MLCAPE AROUND 1500-2500 J/KG AND LITTLE MLCINH.

WHILE AMPLE MID/HIGH-LEVEL FLOW IS SUPPORTING EFFECTIVE SHEAR AROUND
50-55 KT IN SUPPORT OF CONDITIONAL SEVERE POTENTIAL...LARGE-SCALE
ASCENT MAY REMAIN QUITE LIMITED. AS SUCH...THERE IS SUBSTANTIAL
UNCERTAINTY REGARDING CONVECTIVE EVOLUTION DURING THE EVENING HOURS.
ONE POSSIBLE SCENARIO WOULD BE FOR CONVECTION TO CONTINUE DEVELOPING
ALONG A REMNANT FRONTAL ZONE EXTENDING NORTHEAST/SOUTHWEST FROM
WEST-CENTRAL LA TO SOUTHEAST TX...AND THIS ACTIVITY COULD SLOWLY
SPREAD EASTWARD. WITH DEEP SHEAR VECTORS MAINTAINING AT LEAST SOME
BOUNDARY-PARALLEL COMPONENT...THIS ACTIVITY MAY EXHIBIT MORE
QUASI-LINEAR/CONVECTIVE-CLUSTER MODES. FURTHERMORE...THERE IS SOME
POSSIBILITY THAT WEAK WARM ADVECTION FARTHER EAST COULD ENCOURAGE
MORE SUSTAINED CONVECTION ACROSS PORTIONS OF SOUTHERN LA/SOUTHERN
MS. THIS LATTER ACTIVITY MAY HAVE MORE OF A PROPENSITY TO BECOME
SUPERCELLULAR...AND ESPECIALLY BE SUPPORTED LATER THIS EVENING AS
EVEN RICHER MOISTURE SPREADS ONSHORE.

GIVEN AMPLE DEEP SHEAR SUPPORTING ORGANIZED CONVECTIVE STRUCTURES...
AND GIVEN SUFFICIENT LOW-LEVEL SHEAR -- ESPECIALLY EASTWARD INTO
SOUTH-CENTRAL LA AND ADJACENT SOUTHERN MS -- THE RISK FOR ALL SEVERE
HAZARDS INCLUDING THE POTENTIAL FOR TORNADOES COULD EXIST. HOWEVER...
THE TIMING OF THE MORE SUBSTANTIAL INCREASE IN THE SEVERE RISK IS
UNCERTAIN. ULTIMATELY...BY MID/LATE EVENING...A GREATER SEVERE RISK
COULD EVOLVE.

..COHEN/HART.. 11/29/2016

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...JAN...LIX...LCH...

LAT...LON   30129395 30459404 31109345 31209229 31059082 30139087
            29919319 30129395



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