SWOMCD
SPC MCD 120540
TXZ000-120845-
MESOSCALE DISCUSSION 2373
NWS STORM PREDICTION CENTER NORMAN OK
1140 PM CST TUE NOV 11 2008
AREAS AFFECTED...PORTIONS SE TX.
CONCERNING...HEAVY RAINFALL
VALID 120540Z - 120845Z
INCREASINGLY DENSE AND ORGANIZED BAND OF HEAVY RAIN PRODUCING TSTMS
IS EXPECTED TO PERSIST AS IT MOVES SLOWLY EWD ACROSS MID-UPPER TX
COASTAL PLAIN...INCLUDING HOU METRO AREA. RATES 2-3 INCHES/HOUR
WILL BE COMMON IN STRONGEST CORES EMBEDDED IN THIS BAND. SOME
BACKBUILDING AND TRAINING OF ECHOES WILL ENHANCE HEAVY RAIN THREAT
LOCALLY.
CONVECTIVE BAND WAS EVIDENT AT 05Z FROM SAN JACINTO COUNTY SWWD TO
DEWITT COUNTY...MOVING EWD APPROXIMATELY 15 KT ON N END AND DRIFTING
EWD ON S END. SFC MESOANALYSIS INDICATED OLD BUT STILL WELL-DEFINED
OUTFLOW BOUNDARY -- PRODUCED BY MORNING-AFTERNOON MCS -- NOW NEARLY
STATIONARY FROM SWRN LA SWWD ACROSS BPT AREA...CURVING WWD-NWWD
ACROSS SWRN PORTIONS HOU METRO AREA. THIS BOUNDARY INTERSECTS
ONGOING CONVECTIVE BAND OVER NWRN FT BEND COUNTY. FAVORABLY MOIST
MARINE ENVIRONMENT CHARACTERIZES INFLOW LAYER AIR MASS S OF OUTFLOW
BOUNDARY...WITH SFC DEW POINTS LOW 70S F AND 1.5-1.75 INCH PW. SLAB
OF THIS AIR WILL CONTINUE TO BE LIFTED ISENTROPICALLY OVER RESIDUAL
COLD POOL IN SUPPORT OF ELEVATED CONVECTION WITH HEAVY RAIN N OF
OUTFLOW BOUNDARY -- FROM SAN JACINTO COUNTY EWD TOWARD SRN PORTION
SABINE RIVER -- WITH ELEVATED MUCAPES 500-1000 J/KG. HIGH BOUNDARY
LAYER THETAE SHOULD HELP TO MAINTAIN CAPE 1000-1500 J/KG ROOTED AT
OR VERY NEAR SFC S OF OUTFLOW BOUNDARY. LARGE SCALE ASCENT ALOFT
SHOULD INCREASE DURING NEXT SEVERAL HOURS...AS SHORTWAVE TROUGH
APCHS FROM SW TX...AND AREA REMAINS UNDER RIGHT ENTRANCE REGION OF
100-120 KT 250 MB JET MAX. IR AND MOISTURE CHANNEL IMAGERY INDICATE
STRONGLY DIFLUENT UPPER FLOW ASSOCIATED WITH INCREASINGLY PRONOUNCED
BAROCLINIC LEAF SIGNATURE.
ALTHOUGH HEAVY RAIN WILL PRESENT GREATEST OVERALL HAZARD WITH THIS
ACTIVITY...ISOLATED DAMAGING GUSTS OR BRIEF/SMALL QLCS SPINUP ALSO
ARE POSSIBLE...ESPECIALLY WITH ANY LEWP/BOW FEATURES THAT CAN
DEVELOP WITHIN CONVECTIVE BAND. GUST POTENTIAL WILL DECREASE WITH
NEWD EXTENT FROM HOU AREA AS RESIDUAL/NEAR-SFC COLD POOL DEEPENS AND
BECOMES MORE STABLE.
..EDWARDS.. 11/12/2008
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...LCH...HGX...CRP...EWX...
LAT...LON 29179747 29799609 30249561 30699525 30579381 30219385
29469499 28989694 29179747
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