Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 250234 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
934 PM CDT SUN MAY 24 2015

.DISCUSSION...LATEST BRO RADAR SHOWS WEAKEN CONVECTION OVER
NORTHEASTERN MEXICO. CURRENT WATER VAPOR SATELLITE IMAGERY
CONTINUES TO SHOW DRIER AIR ALOFT AND DUE TO THE LACK OF SHORT
TERM MODEL SUPPORT FOR OVERNIGHT CONVECTION...MADE A QUICK UPDATE
TO LOWER POPS AND REMOVE THE MENTION OF THUNDERSTORMS TONIGHT.
ALSO MADE A FEW MINOR SHORT TERM ADJUSTMENTS TO SKY AND WINDS
GRIDS THROUGH LATE TONIGHT AND LOWER POPS SLIGHTLY FOR MONDAY
MORNING. NO OTHER CHANGES NEEDED.

&&

.PREV DISCUSSION... /ISSUED 706 PM CDT SUN MAY 24 2015/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE
MOSTLY CLEAR SKIES ACROSS DEEP SOUTH TEXAS THIS EVENING. BRO
RADAR IS SHOWING VERY LIMITED ACTIVITY WITH ALL OF THE CONVECTION
WELL SOUTH OF THE RIO GRANDE RIVER OVER NORTHEAST MEXICO. VFR
CONDITIONS WILL CONTINUE ACROSS THE RIO GRANDE VALLEY THIS
EVENING WITH MVFR CEILINGS DEVELOPING AFTER MIDNIGHT. HIGH END
MVFR/LOW END VFR CEILINGS WILL PREVAIL AFTER 14Z WITH BRIEF
PERIODS OF MVFR CONDITIONS IN AND AROUND ANY CONVECTION. SHOWERS
AND THUNDERSTORMS ARE POSSIBLE LATE MONDAY MORNING INTO THE
AFTERNOON HOURS AS ANOTHER UPPER LEVEL DISTURBANCE MOVES CLOSER TO
SOUTHERN TEXAS. WILL CONTINUE TO MENTION VCTS AFTER 17Z FOR ALL
VALLEY TAF SITES.

PREV DISCUSSION... /ISSUED 312 PM CDT SUN MAY 24 2015/

SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...OUTFLOW FROM THE EARLY
MORNING CONV RESULTED IN A MORE STABLE ATMS THAT COVERED DEEP SOUTH
TX TODAY. THE LAPS CAPE VALUES FOR MOST OF THE MORNING AND MIDDAY
HOURS WERE GENERALLY PRETTY LOW AND HAVE NOT STARTED TO REBOUND
UNTIL THIS AFTERNOON WITH THE HIGHEST CAPE VALUES LOCATED OUT WEST
OVER HIDALGO AND STARR COUNTIES. DAYTIME HEATING MAY DESTABILIZE THE
ATMS OUT WEST ENOUGH TO FORCE SOME SCT CONV INTO THE LATE AFTERNOON
AND EVENING HOURS. THE LATEST VSBL SATL IMAGERY SHOWS SOME CU FIELDS
DEVELOPING ALONG AND WEST OF THE OLD HIGHWAY 281 CORRIDOR WITH
GENERALLY CLEAR SKIES PREVAILING OUT WEST. WITH THE LOSS OF THE
DAYTIME HEATING BELIEVE THAT ANY CONV THAT FORMS WILL DIE DOWN
PRETTY QUICKLY. SO WILL POST UP 20% POPS EAST AND 30% WEST FOR THE
REST OF THIS AFTERNOON INTO THE OVERNIGHT HOURS.

FOR MEMORIAL DAY...THE NEXT 500 MB TROUGH SWINGS ACROSS TX WHICH
WILL INCREASE THE MID AND UPPER LEVEL SUPPORT FOR MORE ORGANIZED
CONV. THE NAM/GFS AND ECMWF GUIDANCE TEND TO KEEP MOST OF THE HIGHER
QPF AMOUNTS CONCENTRATED TO THE NORTH OF THE DEEP SOUTH TX WITH THE
RGV REMAINING ON THE SOUTHERN FRINGES OF THE BETTER QPF FIELDS. THE
ECMWF IS STILL THE WETTEST OF THE THREE SHORT RANGE MODEL SETS
KEEPING SOME CHC POPS A LITTLE FURTHER SOUTHWARDS INTO OUR AREA.
THIS SOLUTION LOOKS FAIRLY REASONABLE ESPECIALLY IF DEEP SOUTH TX
GETS A LITTLE BETTER PVA MOVING OVER THE REGION.

SO WILL TREND MORE TOWARDS THE ECMWF FOR POPS ON MON AS MY
CONFIDENCE OF A TOTALLY DRY FORECAST FOR THE RGV IS FAIRLY LOW AT
THIS TIME. SINCE THE PEAK QPF FROM THIS SYSTEM APPEARS TO BE
SHIFTING FURTHER EAST TOWARDS THE ARKLATEX AREA WILL HOLD OFF ON
A NEW FFA AT THIS TIME.

WILL START TRENDING DOWN THE POPS ON MON NIGHT AS THE 500 MB TROUGH
OVER CENTRAL TX LIFTS OUT QUICKLY TO THE NE ALLOWING DRIER AND MORE
STABLE AIR TO MOVE INTO THE REGION.

LONG TERM /TUESDAY THROUGH SATURDAY/...THE MODEL CONSENSUS HAS
SCALED BACK ON POPS SLIGHTLY FOR THE MIDDLE PART OF THE UPCOMING
WEEK. LOOKS THERE WILL BE A TEMPORARY LULL ON TUESDAY AS THE MID
LEVEL PATTERN IS INITIALLY ZONAL AND LOOSE. THAT SHOULD RESULT IN
LIGHT TO MDT SOUTHEAST WINDS AND A MIX OF CLOUDS AND SUN WITH HIGH
TEMPS IN THE UPPER 80S TO LOWER 90S. A FEW STORMS MAY DEVELOP NEAR
THE MEXICAN MOUNTAINS TUESDAY NIGHT...BUT ALL IN ALL THEY SHOULD
LEAVE THE CWA ALONE AS A SLIGHTLY MORE STABLE RIDGE BUILDS OVER TX
GOING INTO WEDNESDAY. TUESDAY NIGHT LOW TEMPS WILL STAY WARM BETWEEN
75 AND 80.

SIMILAR WEATHER IS EXPECTED ON WEDNESDAY AS THE TEMPORARY H5 RIDGE
OVER TEXAS HOLDS ON FOR ANOTHER DAY. ANOTHER MID LEVEL TROUGH WILL
BEGIN TO APPROACH FROM THE FAR WEST WITH ENOUGH DESTABILIZATION TO
KICK OFF SOME CONVECTION OVER THE BIG BEND WEDNESDAY NIGHT AS THE
RIDGE SHIFTS EAST. THE TROUGH WILL REMAIN SHALLOW AS IT MOVES EAST
OVER THE SOUTHERN HIGH PLAINS WHILE AN UPPER HIGH STAYS OVER THE
NORTHWEST GULF. THUS...UPSTREAM NOCTURNAL CONVECTION WILL BE MORE
ACTIVE THE LATTER HALF OF THE WEEK...BUT CERTAINTY REMAINS LOW THAT
MUCH WILL MAKE IT INTO THE CWA. THE HIGH HEIGHT CENTER OVER THE WEST
CENTRAL GULF AND SURFACE HIGH PRESSURE BRINGING RELATIVELY DRIER AIR
INTO THE AREA WILL HELP BALANCE THE EFFECTS TO THE WEST.

THE ECMWF IS MORE ROBUST IN DEVELOPING CONVECTION IVOF THE BIG BEND
THURSDAY NIGHT...TRYING TO PUSH ANOTHER QLCS SOUTH AND EAST INTO THE
AREA THURSDAY NIGHT AND FRIDAY...WITH SOME REGENERATION OVER THE MID
AND UPPER VALLEY FRIDAY NIGHT. THE GFS...THOUGH...DOESN`T HAVE THAT
SIGNAL. OTHERWISE...MODERATE SOUTHEAST WINDS WILL BE ON TAP ALONG
WITH SEASONAL TEMPERATURES...THOUGH SLIGHTLY WARMER THAN AVERGAE AT
NIGHT.

MARINE /TONIGHT THROUGH MONDAY NIGHT/...THE LATEST REPORT FROM
BUOY020 INDICATES A SE WIND AT 17G21KT WITH SWELLS NEAR 6.6 FEET.
WILL EXTEND THE SCA FOR THE GULF WATERS THROUGH THE OVERNIGHT HOURS
INTO MONDAY AS EXPECT THE PGF THE REMAIN FAIRLY STRONG THROUGH
MEMORIAL DAY. THE PGF WILL THEN START TO DECREASE TOMORROW NIGHT
ALLOWING FOR THE WINDS AND SEAS TO DECREASE A BIT.

TUESDAY THROUGH THURSDAY...LOW END SMALL CRAFT ADVISORY CONDTIONS
DUE TO SEAS MAY STILL BE IN PLAY TUESDAY MORNING...BUT THE OVERALL
TREND WILL BE TOWARD MODERATE SOUTHEAST WINDS AND SLIGHTLY LOWER
SEAS...WITH SMALL CRAFT EXERCISE CAUTION CONDITIONS MORE THE RULE
ON THE GULF WEDNESDAY AND THURSDAY. OTHERWISE...HIGH PRESSURE WILL
REMAIN IN CONTROL OVER THE NORTHEAST GULF...NOSING WEST INTO THE
NORTHWEST GULF AND COMBINING WITH LOWER PRESSURE OVER THE SOUTHERN
HIGH PLAINS TO MAINTAIN THE SYNOPTIC PATTERN AND ASSOCIATED
FORCING.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...HIGH RIP CURRENT RISK THROUGH MONDAY EVENING FOR TXZ251-256-257.

GM...SMALL CRAFT ADVISORY UNTIL 7 PM CDT MONDAY FOR GMZ150-155-170-
     175.

&&

$$

THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT:
HTTP://WEATHER.GOV/RGV

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