Graphic for MPD #0008

MESOSCALE PRECIPITATION DISCUSSION 0008...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
529 AM EST SAT JAN 27 2018

CORRECTED FOR TYPOS IN THE FIRST DISCUSSION PARAGRAPH

AREAS AFFECTED...PORTIONS OF SOUTHEAST TX

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

VALID 271025Z - 271505Z

SUMMARY...RADAR TRENDS/MESOSCALE GUIDANCE ARE BECOMING MORE
BULLISH ON HEAVY RAINFALL BETWEEN HOUSTON AND THE GOLDEN TRIANGLE
OF SOUTHEAST TX.  HOURLY RAIN TOTALS TO 2" WITH LOCAL AMOUNTS TO
4" ARE POSSIBLE.

DISCUSSION...WARM AIR ADVECTION EXISTS EAST OF A WEAK SURFACE LOW
SOUTH OF MATAGORDA BAY.  AN AREA OF DARKENING ON GOES-16 WATER
VAPOR IMAGERY IS SLOWLY ADVANCING FROM THE WEST, POSSIBLY
DEPICTING AN INCOMING SHORTWAVE, WITH INFLECTION POINTS NEAR
COLUMBUS TX AND TO THE SOUTH NEAR OSO BAY/CORPUS CHRISTI.  AN
INVERTED TROUGH IS APPARENT IN THE 10Z SURFACE OBSERVATIONS
EXTENDING INTO GALVESTON BAY, IN THE VICINITY OF INCREASING
THUNDERSTORM ACTIVITY WITH HOURLY RAIN TOTALS IN THE 1-1.5" RANGE
PER RADAR ESTIMATES.  PRECIPITABLE WATER VALUES ARE 1.5-1.6" PER
GPS DATA.  INFLOW AT 850 HPA IS ON SLOW DECLINE, NEAR 20 KTS PER
THE HGX VAD WIND PROFILE.  HOWEVER, REGIONALLY IT REMAINS
CYCLONIC.  EFFECTIVE BULK SHEAR OF 30+ KNOTS EXISTS HERE PER SPC
MESOANALYSES, WHICH ALSO INDICATE 500-1000 J/KG OF MUCAPE, WITH
THE 1000 J/KG CONTOUR JUST SOUTH OF GALVESTON ISLAND.

THE MESOSCALE GUIDANCE, STARTING WITH OLDER HRRR/RAP RUNS, ARE
BECOMING MORE BULLISH ON HEAVY RAINFALL NEAR THE UPPER TX COAST,
WHICH FITS RECENT RADAR TRENDS.  HOURLY RAIN TOTALS UP TO 2", WITH
LOCAL AMOUNTS TO 4", ARE POSSIBLE NEAR/SOUTHEAST OF HOUSTON AS
WELL AS NEAR THE GOLDEN TRIANGLE OF SOUTHEAST TX.  THESE AMOUNTS
WOULD BE QUITE PROBLEMATIC IN THE HOUSTON METRO AREA SHOULD
THUNDERSTORMS MOVE ANY FARTHER NORTHWEST.  THIS MPD, AS WELL AS
SOME OF ITS CONTENT, WAS ISSUED IN COORDINATION WITH THE
HGX/HOUSTON-GALVESTON OFFICE.

ROTH

ATTN...WFO...HGX...LCH...

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

LAT...LON   30439318 29709371 29549429 28949528 29899496
            30439404


Last Updated: 529 AM EST SAT JAN 27 2018