Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 041155 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
655 AM CDT FRI SEP 4 2015

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

&&

.AVIATION...500 MB RIDGING WILL BE STRENGTHENING OVER DEEP SOUTH
TX OVER THE NEXT 24 HOURS WHICH WILL TRIM BACK THE CONV POTENTIAL.
SHORT TERM MODEL TRENDS INDICATE THAT THE BETTER TROPICAL MOISTURE
VALUES WILL REMAIN POOLED ALONG AND EAST OF THE LOWER TX COASTLINE
THROUGHOUT THE UPCOMING TAF PERIOD. DAYTIME HEATING AND SEA BREEZE
EFFECTS MAY DEVELOP ISOLD CONV LATER TODAY NEAR THE RGV AIRPORTS.
BUT BELIEVE THE OVERALL CONV COVERAGE WILL BE PRETTY LIMITED TODAY
AND WILL NOT HAVE TOO MUCH OF AN IMPACT ON AVIATION OPERATIONS.
EXPECT VFR CONDITIONS TO PREVAIL FOR THE RGV AIRPORTS FOR THE
NEXT 24 HOURS.

&&

.PREV DISCUSSION... /ISSUED 351 AM CDT FRI SEP 4 2015/

SHORT TERM /TONIGHT THROUGH SATURDAY/...THE LATEST IR/WV SATL
IMAGERY AND LIGHTNING DATA INDICATES THAT THE NAM HAS INITIALIZED
PRETTY WELL ON THE POSITION OF THE 500 MB TROUGH AXIS THAT HAS
BROUGHT THE CONV TO THE REGION OVER THE LAST SEVERAL DAYS. SATL
IMAGERY INDICATES THAT THE TROUGH AXIS IS LOCATED TO OUR SOUTH OVER
NORTHEAST MEXICO. THE LATEST NAM GUIDANCE PUSHES THIS 500 MB FEATURE
FURTHER WEST THROUGH THE SHORT TERM AND GRADUALLY WEAKENS IT THROUGH
SAT ALLOWING 500 MB RIDGING TO REBUILD OVER THE AREA. DEEP LAYER
MOISTURE NEAR THE LOWER TX COASTLINE AND OVER THE WESTERN GULF WILL
WEAKEN ALSO AS THE RIDGE AXIS STRENGTHENS. EXPECT THE CONV POTENTIAL
TO STEADILY DIMINISH OVER THE SHORT TERM PERIOD AS THE MOISTURE
LEVELS DECREASE. HOWEVER ENOUGH MOISTURE MAY LINGER NEAR THE REGION
TODAY TO ALLOW FOR SOME ISOLD DAYTIME HEATING/SEA BREEZE DRIVEN CONV
TO FIRE. SO WILL MAINTAIN A SLGT CHC INLAND TODAY AND WILL KEEP THE
SLGT CHC CONFINED TO THE GULF WATERS ON SAT.

AS THE ATMS DRIES OUT AND STABILIZES FRI AND SAT WILL ALLOW FOR
SLIGHTLY WARMER HIGH TEMPS ON SAT WITH SOME 100 DEGREE READINGS
CREEPING BACK INTO THE WESTERN COUNTIES WITH 90S ELSEWHERE.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...THE FORECAST IN
THE EXTENDED PERIOD CURRENTLY APPEARS SOMEWHAT TAME. H5 RIDGING
WILL STAY ANCHORED UPSTREAM...EVEN BUILDING SLIGHTLY OVER THE
WEEKEND. RAIN CHANCES WILL TREND DOWN TO SLIGHT OR LESS THROUGH
MID WEEK. THE RIDGE WILL ULTIMATELY WEAKEN TOWARD THE END OF THE
PERIOD HOWEVER FROM A COUPLE OF INFLUENCES. THE FIRST WILL BE
PERSISTENT NORTHERN STREAM TROUGHING OVER THE NORTHWEST THAT WILL
FINALLY SUCCEED IN FLATTENING THE RIDGE AROUND MID WEEK. THE OTHER
INFLUENCE WILL BE WEAK H5 TROUGHING OVER THE EASTERN SEABOARD
WHICH WILL SAG SOUTH INTO THE GULF OF MEXICO. THESE TWO INFLUENCES
WILL CAUSE THE RIDGE TO RETREAT WEST AND EVEN EVENTUALLY DISAPPEAR
LATE NEXT WEEK. A COLD FRONT WILL PUSH INTO NORTH TEXAS WEDNESDAY
NIGHT AND THENCE INTO SOUTH CENTRAL TEXAS THURSDAY AND
FRIDAY...THOUGH APPARENTLY LACKING ENOUGH PUNCH TO SERIOUSLY
THREATEN DEEP SOUTH TEXAS.

LOOKING AT THE LONG TERM GUIDANCE FOR THE GFS AND ECMWF...DO NOT
SEE SIGNIFICANT DIFFERENCES. TEMPERATURES WILL CONTINUE TO RUN
SLIGHTLY ABOVE NORMAL DAY AND NIGHT. POPS WILL REMAIN CLOSE TO
CLIMATOLOGICAL NORMS...THOUGH SLIGHTLY DRIER OVER THE WEEKEND...
AND SLIGHTLY WETTER LATER IN THE WEEK...ESPECIALLY THE ECMWF.
AFTERNOONS WILL BECOME PTLY CLOUDY...ESPECIALLY OVER EASTERN
SECTIONS...BUT MORNINGS AND LATE EVENINGS TO OVERNIGHTS SHOULD BE
GENERALLY MOSTLY CLEAR.

MARINE...
TONIGHT THROUGH SATURDAY...WEAK SURFACE RIDGING OVER THE GULF OF
MEXICO WILL PERSIST ON INTO THE WEEKEND MAINTAINING FAIRLY LIGHT
S-SE WINDS ACROSS THE MARINE AREAS AND FAIRLY LOW SEAS. NO SCA
CONDITIONS EXPECTED THROUGH SATURDAY.

SATURDAY NIGHT THROUGH TUESDAY...BROAD SURFACE HIGH PRESSURE
WILL SUSTAIN PERSISTENT LIGHT TO MODERATE SOUTHEAST WINDS AND LOW
TO MODERATE SEAS AS THE FORECAST TRANSITIONS INTO THE LONG TERM.
H5 RIDGING BUILDING UPSTREAM WILL TEND TO DEFLECT ANY NORTHERN
TRACK SYSTEMS AWAY FROM THE SOUTHERN PLAINS...AND ANY WEAK LEE
SIDE OR SOUTHERN PLAINS/WEST TEXAS SURFACE TROUGHING WILL HAVE A
MINIMAL IMPACT ON THE PRESSURE GRADIENT.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  91  80  92  79 /  20  20  10  10
BROWNSVILLE          93  78  94  78 /  20  10  10  10
HARLINGEN            94  78  97  78 /  20  20  10  10
MCALLEN              98  81  99  80 /  20  20  10   0
RIO GRANDE CITY      99  78 100  78 /  20  10  10   0
SOUTH PADRE ISLAND   87  81  88  81 /  20  20  10  10

&&

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

$$

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

SHORT TERM...60
LONG TERM...54
GRAPHICAST/UPPER AIR...58


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