Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 311755
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1255 PM CDT SUN AUG 31 2014

.DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

&&

.AVIATION...MORE SHOWERS AND THUNDERSTORMS ARE DEVELOPING ALONG
THE COASTAL COUNTIES PRODUCING BRIEF DOWNPOURS AND OCCASIONAL
CLOUD TO GROUND LIGHTNING. EXPECT THIS ACTIVITY TO CONTINUE TO
IMPACT IN THE NEXT FEW HOURS KHRL AND KBRO. HOWEVER...KMFE MAY
SEE MORE ACTIVITY AFTER 19Z. THE CONVECTION BEGINS TO DIMINISH
AFTER 00Z AS WE LOOSE OF DAYTIME HEATING BUT ABUNDANT DEBRI CLOUD
CAN BE EXPECTED WITH VFR CONDITIONS. AFTER MIDNIGHT MVFR CIGS
ARE POSSIBLE AGAIN TONIGHT OVER MFE BUT SHOULD STAY LOW END VFR
FOR KHRL AND KBRO. BRIEF SHOWERS WILL BE POSSIBLE IN THE EARLY
MORNING HOURS WITH LIGHT SOUTHEAST WINDS.


&&

.PREV DISCUSSION... /ISSUED 702 AM CDT SUN AUG 31 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...THE MORNING CONV HAS BEEN MORE LIMITED TODAY AND HAS
BEEN HOLDING NEAR THE COASTLINE MOVING TO THE NORTH. THE ATMS
REMAINS PRETTY MOIST AND UNSTABLE TODAY. BELIEVE THAT THE CONV
TRENDS WILL BE SIMILAR TO YESTERDAY MORNINGS WITH THE BULK OF THE
CONV AFFECTING THE RGV AIRPORTS THROUGHOUT THE MORNING AND EARLY
AFTERNOON HOURS WITH THE CONV DYING DOWN IN THE EVENING AND
OVERNIGHT HOURS AS THE AIRMASS STABILIZES SOMEWHAT. SO WILL
MENTION PREDOMINANT VFR CONDITIONS DURING MOST OF THE UPCOMING TAF
PERIOD WITH BRIEF REDUCTIONS OF VSBYS AND CEILINGS DUE TO THE
PASSING CONV. SOME BRIEF MVFR CONDITIONS MAY BE POSSIBLE FOR THE
RGV AIRPORTS BUT DID NOT INCLUDE AN ACTUAL MENTION OF THIS WITH
THE 12Z TAF ISSUANCE.

PREV DISCUSSION... /ISSUED 425 AM CDT SUN AUG 31 2014/

SHORT TERM /NOW THROUGH MONDAY/...THE 500 MB TROUGH REMAINS IN
PLACE OVER DEEP SOUTH TEXAS TODAY. DEEP LAYER TROPICAL MOISTURE
AND INSTABILITY REMAINS IN PLACE OVER THE REGION WITH THE 00Z BRO
SOUNDING SHOWING A PWAT OF 2.45 INCHES AND A CAPE OF 3433 J/KG.
THIS SHOULD ALLOW FOR ANOTHER ROUND OF CONV TODAY. THE LATEST KBRO
RADAR REFLECTIVITY INDICATES SCATTERED RW/TRW EXTENDING FROM NEAR
SP1 DOWN ALONG THE MEXICAN COASTLINE NEAR TAMPICO. ALL THIS
ACTIVITY HAS BEEN MOVING UP NORTH. THE ACTIVITY TODAY IS LESS
ORGANIZED AND INTENSE VERSUS WHAT WAS GOING ON OVER THE AREA EARLY
YESTERDAY MORNING. THIS INDICATES THAT THE ATMS MAY BE STABILIZING
A BIT OR THAT THE 500 MB TROFFING IS STARTING TO WEAKEN.

SHORT RANGE GUIDANCE INDICATES THAT THE 500 MB TROFFING WILL BE
GRADUALLY WEAKENING THROUGHOUT TODAY AND TOMORROW. THIS WILL RESULT
IN A GRADUAL DECREASE IN OVERALL CONV TRENDS THROUGH MON. ENOUGH
TROPICAL MOISTURE MAY LINGER INTO TOMORROW TO COMBINE WITH DAYTIME
HEATING AND SEA BREEZE EFFECTS TO MAINTAIN A SLGT CHC OF POPS. WILL
LEAN TOWARDS A BLEND OF THE MET AND ECMWF POP GUIDANCE WHICH IN A
LITTLE BETTER AGREEMENT VERSUS THE GFS MAV GUIDANCE WHICH SEEMS DRY
OUT THE ATMS A LITTLE TOO FAST ON MON.

SINCE THE CONV COVERAGE IS LESS TODAY VERSUS YESTERDAY WILL NOT
MENTION ANY LOCALLY HEAVY RAINFALL FOR TODAY. ALSO BELIEVE THAT THE
POTENTIAL FOR MINOR NUISANCE FLOODING WILL BE MUCH LOWER TODAY
VERSUS YESTERDAY.

AS THE 500 MB TROFFING GRADUALLY WEAKENS OVER THE REGION HIGH TEMPS
WILL START TO INCREASE STEADILY AS THE RIDGING REBUILDS OVER THE
AREA. WILL GO WITH A MAV/MET/ECMWF MODEL BLEND FOR TEMPS THROUGHOUT
THE SHORT TERM AS ALL ARE REFLECTING A GENERAL WARM UP THROUGH
MON.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY NIGHT/...UNSETTLED WEATHER
RETURNS TO THE RIO GRANDE VALLEY AND DEEP SOUTH TEXAS TUESDAY
THROUGH THURSDAY AS DEEP TROPICAL MOISTURE INCREASES ACROSS THE
REGION. THE INCREASE IN MOISTURE IS ASSOCIATED WITH A TROPICAL WAVE
IN THE SOUTHWESTERN GULF OF MEXICO. PRECIPITABLE WATER VALUES CLIMB
TO BETWEEN 2 TO 2.3 INCHES BY LATE TUESDAY...WHICH WILL SUPPORT A
GOOD CHANCE OF SHOWERS AND THUNDERSTORMS TUESDAY THROUGH LATE WEEK.
HOWEVER...THE BEST OPPORTUNITY OF WIDESPREAD CONVECTION APPEARS TO
BE ON WEDNESDAY AS PRECIPITABLE WATERS REACH 2.4 INCHES
/ESPECIALLY NEAR THE COAST/ AND WITH MEAN RELATIVE HUMIDITY VALUES
AROUND 80 PERCENT AT 1000-500MB. ALSO WITH THE HIGH PRECIPITABLE
WATER VALUES ACROSS THE AREA...LOCALLY HEAVY RAINFALL IS
POSSIBLE.

THE LATEST MODEL GUIDANCE CONTINUES TO INDICATE THAT A WEAK SURFACE
LOW WILL DEVELOP ALONG THE TROPICAL WAVE AS THIS FEATURE MOVES
BETWEEN TAMPICO AND VERACRUZ IN MEXICO. THE NATIONAL HURRICANE
CENTER CURRENTLY HAS A 50 PERCENT CHANCE OF DEVELOPMENT AS THIS
SYSTEM MOVES ACROSS THE SOUTHWESTERN GULF OF MEXICO. PLEASE REFER
TO THE LATEST STATEMENTS AND OUTLOOKS FROM THE NATIONAL HURRICANE
CENTER CONCERNING THE PROGRESS OF THIS TROPICAL WAVE.

HIGH TEMPERATURES WILL RANGE FROM THE LOW 90S ALONG THE BEACHES TO
THE MID TO UPPER 90S ACROSS THE WEST ON TUESDAY. TEMPERATURES WILL
BE BELOW NORMAL WEDNESDAY AND THURSDAY COURTESY OF THE INCREASE IN
CLOUD COVER AND RAIN CHANCES. TEMPERATURES WILL BEGIN TO INCREASE
AGAIN FRIDAY AND INTO THE WEEKEND AS HIGH PRESSURE BUILDS ACROSS
THE REGION AND RAIN CHANCES DECREASE.

MARINE...NOW THROUGH MONDAY...SURFACE RIDGING OVER THE WESTERN GULF
WILL MAINTAIN FAIRLY LIGHT TO MODERATE SE WINDS ACROSS THE LOWER
TEXAS BAY AND GULF WATERS.  BAY AND GULF SWELLS WILL HOLD FAIRLY
STEADY WITH NO SCA CONDITIONS.

MONDAY NIGHT THROUGH THURSDAY NIGHT...THE PRESSURE GRADIENT BEGINS
TO STRENGTHEN ON TUESDAY AS HIGH PRESSURE OVER THE NORTHERN GULF
INTERACTS WITH A TROPICAL WAVE IN THE SOUTHWEST GULF. THE TROPICAL
WAVE WILL BRING AN INCREASE IN RAIN CHANCES ACROSS THE COASTAL
WATERS BY TUESDAY. INCREASING SWELL ACTIVITY IN THE SOUTHWESTERN
GULF OF MEXICO FROM THIS TROPICAL WAVE MAY RESULT IN SOME SMALL
CRAFT ADVISORY CONDITIONS IN THE GULF FROM LATE TUESDAY THROUGH
THURSDAY.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

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

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