MESOSCALE PRECIPITATION DISCUSSION 0114
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
958 PM EDT WED APR 12 2017

AREAS AFFECTED...WESTERN TX...EXTREME SOUTHEAST NM

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 130157Z - 130657Z

SUMMARY...CONGEALING OF MCS ACROSS TRANS-PECOS REGION OF TX/SE NM
WITH INCREASING CONVECTIVE COVERAGE AND RAINFALL EFFICIENCY POSING
POSSIBLE FLASH FLOODING THROUGH EARLY OVERNIGHT HOURS.

DISCUSSION...GOES-E/16 IR LOOP DENOTES INCREASING EXPANSION OF
LARGE MCS CANOPY WITH EMBEDDED OVERSHOOTING TOPS BEGINNING TO
ORIENT IN LINEAR FASHION ACROSS SE NM AND CENTRAL AND EASTERN
PORTIONS OF THE W TX PANHANDLE.  WV LOOP SHOWS THE EMBEDDED
SHORTWAVE THAT HAS BEEN SUPPORTING BROAD SCALE ASCENT DUE TO DPVA
WILL CONTINUE TO LIFT ENE INTO THE LOWER CAPROCK THROUGH THE NIGHT
AND PROVIDE BEST UPPER LEVEL ASCENT DYNAMICS FOR THE GROWING MCS
AS A WHOLE.  ADDITIONALLY...STRENGTHENING SOUTHERLY JET ENHANCED
TO 60-70KTS BY THE UPSCALE/CONVECTIVE GROWTH WILL LEAVE THE AREA
OF CONCERN IN THE RIGHT ENTRANCE ALLOWING FOR FURTHER UPPER LEVEL
EVACUATION ALONG WITH AROUND 50-70 DEGREES OF DIFFLUENCE BETWEEN
IT AND THE SUBTROPICAL JET ACROSS THE BIG BEND INTO CENTRAL TX
CURRENTLY. 

IT IS EXPECTED THAT THE EVACUATION ALOFT WILL HELP ENHANCE THE LOW
LEVEL FLOW WITH RAP FORECASTS CONTINUING TO STRENGTHEN A COMPACT
SELY LLJ WITH FLOW TO 30KTS INITIALLY CRANKING TO 40-45KTS PEAK
NEAR 07-08Z.  THIS WILL INTERFACE WITH THE EXPANDING CONVECTIVE
LINE ACROSS THE SOUTHERN PECOS RIVER VALLEY WHERE THERE IS SOME
REMAINING INSTABILITY...THOUGH THIS COMBINATION IS LIKELY TO
SUPPORT FORWARD PROPAGATION AND MORE OF A SQUALL LINE...BUT WITH
INCREASE MST FLUX...INITIAL RATES OF 1.5-2"/HR FOLLOWED BY BROAD
SHIELD PRECIPITATION FOR AN HOUR OR TWO AFTERWARD MAY ALLOW FOR
TOTALS TO EXCEED THE LOWER FLASH FLOOD GUIDANCE IN THE VICINITY OF
THE LOWER PECOS TOWARD 04-07Z. 

FURTHER NORTH...UNDER THE BEST DPVA AND DIFFLUENCE ALOFT ACROSS
THE LOWER CAPROCK TOWARD I-20 THERE SHOULD BE A MAINTENANCE OF THE
MCS BUT CURRENT LOW LEVEL ENVIRONMENT AND LESS STEEP LAPSE RATES
THERE IS LIMITED INSTABILITY SUGGESTIVE OF ONLY SMALL ISOLATED
ELEVATED CONVECTION WITHIN THE LARGER BROAD MODERATE SHIELD
PRECIPITATION. WITH HIGH FFG VALUES THE THREAT HERE IS MORE
LIMITED PARTICULARLY LATER IN THE EVENING/EARLY OVERNIGHT HOURS. 
IN THE SHORT-TERM HOWEVER...ONGOING ACTIVE CONVECTION WITH WEAK
OVERSHOOTING TOP POKING THROUGH THE CIRRUS SHIELD PER GOES-16 MESO
VIS/IR...AND MEAN CELL MOTIONS TRACKING WITH THE SHORTWAVE...THERE
MAY BE SOME SHORT-TERM TRAINING AND CELL MERGERS ACROSS SE NM INTO
GAINES/ANDREWS/WINKLER AND ECTOR COUNTIES.

ACROSS THE DAVIS RANGE...THERE IS SOME SUGGESTION BY RECENT HRRR
RUNS AND SATELLITE TRENDS THAT THE TAIL END OF THE MCS/SQUALL LINE
WILL TRAIL BACK TOWARD UPSTREAM HEIGHT FALLS STILL PROGRESSING
ACROSS THE HIGHER PLATEAU OF N CHIHUAHUA...AND WITH SOUTHERLY FLOW
AND BEST REMAINING INSTABILITY...THESE CELLS MAY BE A BIT STRONGER
AND ORIENT MORE E-W ACROSS PRESIDIO/BREWSTER
COUNTIES...POTENTIALLY SETTING UP A TRAINING CORRIDOR.  WHILE THIS
IS OF THE LOWEST CONFIDENCE TO COME TO FRUITION...IT MAY ALSO POSE
THE GREATEST THREAT FOR FLASH FLOODING GIVEN TERRAIN/LOWER FFG
VALUES WITH RATES OVER 1.5"/HR.

GALLINA

ATTN...WFO...EWX...LUB...MAF...SJT...

ATTN...RFC...WGRFC...

LAT...LON   33720110 32900066 31190083 29760162 29780226
            29410270 28930304 29190393 29670464 30160484
            30610486 32420417 33010355 33380292