[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 181242
SWOMCD
SPC MCD 181241
TNZ000-ARZ000-MSZ000-MOZ000-181515-

MESOSCALE DISCUSSION 2000
NWS STORM PREDICTION CENTER NORMAN OK
0741 AM CDT THU AUG 18 2011

AREAS AFFECTED...PORTIONS SRN MO...NRN/ERN AR...EXTREME SWRN
TN...NWRN MS.

CONCERNING...HEAVY RAINFALL

VALID 181241Z - 181515Z

POTENTIAL EXISTS FOR MERGER OF CONVECTIVE CLUSTERS OVER DISCUSSION
AREA THAT THEN WOULD MOVE/SPREAD SEWD THROUGH AT LEAST
15Z...RESULTING IN EXPANSION OF AREA OF 2-3 INCH/HOUR RAIN RATES IN
HEAVIEST CORES.  SHORTER-LIVED EPISODE OF SIMILAR RATES IS LIKELY AT
ANY GIVEN LOCATION AFFECTED BY NEARBY BAND OF TSTMS MOVING EWD ABOUT
20 KT ACROSS OZARKS OF S-CENTRAL MO AND EXTREME NRN AR.

FAVORABLE CAPE AND LIKELIHOOD OF DENSE PRECIP LOADING ALSO MAY
SUPPORT LOCALIZED POTENTIAL FOR DAMAGING WET DOWNBURSTS...BUT
PRIMARY THREAT APPEARS TO BE FROM HEAVY RAIN.

INITIALLY SEPARATE/MESOBETA-SCALE MULTICELLULAR TSTM COMPLEXES HAVE
DEVELOPED OVER PORTIONS NERN AR--
1. BAND OF TSTMS LOCATED BETWEEN SGT-ARG..EXPANDING IN COVERAGE AND
MOVING SEWD ABOUT 20 KT...AND
2. SOMEWHAT LESS-INTENSE BUT WELL-DEFINED CLUSTER INITIALLY FROM MEM
AREA NNWWD TOWARD JBR AND NWD TO JUST S OF MO BOOT-HEEL.  CELLS IN
THIS COMPLEX ARE MOVING SSEWD...BUT OVERALL CLUSTER IS BACKBUILDING
SWWD TOWARD POTENTIAL MERGER ZONE WITH WRN COMPLEX.

PRIND MERGER WILL OCCUR THROUGH 14Z FROM PORTIONS POINSETT/CROSS
COUNTIES SSEWD OVER DELTA ADJACENT TO NRN PORTIONS MS/AR BORDER.
MEANWHILE MO/AR BORDER-AREA BANDS WILL PROCEED EWD ACROSS UNO AREA.
VERY MOISTURE-RICH ENVIRONMENT IS EVIDENT...BASED ON 12Z SGF RAOB
THAT SAMPLED UPSTREAM 850-MB TRAJECTORIES...YIELDING PW BETWEEN
2-2.25 INCHES...MEAN MIXING RATIO NEAR 19 G/KG AND MUCAPE OVER 4000
J/KG.  PW APPEARS SOMEWHAT UNDER-REPRESENTED IN OBJECTIVE/RUC-BASED
MESOANALYSES OVER SRN MO BASED ON THAT RAOB...BUT APPEARS REASONABLE
FARTHER SE OVER ERN AR.

..EDWARDS.. 08/18/2011

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

ATTN...WFO...PAH...MEG...JAN...LZK...SGF...

LAT...LON   34479109 35489161 36639276 37129295 37089179 36899077
            35959033 35278998 34588990 33959001 33889071 34179110
            34479109



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