Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 111723 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1223 PM CDT FRI APR 11 2014

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

.AVIATION...SATELLITE IMAGES AND SURFACE OBSERVATIONS INDICATE
CLEAR SKIES ACROSS THE CWA EARLY THIS AFTERNOON. WEST TO NORTHWEST
FLOW ALOFT WILL CONTINUE TO PROVIDE SUBSIDENCE ACROSS THE RIO
GRANDE VALLEY THE REST OF THE AFTERNOON INTO TONIGHT. VFR
CONDITIONS WILL PREVAIL THE REST OF THE AFTERNOON THROUGH THIS
EVENING AS A RESULT. EXPECT MVFR CONDITIONS TO DEVELOP TONIGHT AS
LOW LEVEL MOISTURE INCREASES ACROSS THE COASTAL SECTIONS AND MOVES
INLAND.
&&

.PREV DISCUSSION... /ISSUED 641 AM CDT FRI APR 11 2014/
DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...THE CIRRUS DECK THAT COVERED MOST OF DEEP SOUTH TEXAS OVERNIGHT HAS
CLEARED OUT LEAVING BEHIND CLR SKIES. THE 00Z BRO SOUNDING SHOWS A
VERY DRY ATMS IN PLACE OVER THE AREA AS SOUTHEASTERLY LOW LEVEL FLOW
RETURNS TO THE AREA. EXPECT SOME SCT SC DECKS TO FORM UP LATER THIS
AFTERNOON AS THE DAYTIME HEATING INTERACTS WITH THE RETURNING LOW
LEVEL MOISTURE MOVING IN OFF OF THE GULF OF MEX. THE FORECAST
SOUNDINGS FROM BOTH THE NAM AND GFS MODELS INDICATE SOME BETTER
POTENTIAL FOR LOW CLD DECKS TO FORM UP LATER TONIGHT THROUGH EARLY
SATURDAY MORNING. WILL MAINTAIN A MENTION OF THIS IN THE LATTER
PORTION OF THE CURRENT TAF PACKAGE. UNTIL THEN GENERALLY EXPECT VFR
CONDITIONS TO PREVAIL FOR THE LOWER RGV AIRPORTS.

PREV DISCUSSION... /ISSUED 337 AM CDT FRI APR 11 2014/
SHORT TERM /TODAY THROUGH SATURDAY/...500 MB TROFFING WILL BE ON
THE INCREASE OVER THE WESTERN AND CENTRAL STATES THROUGHOUT TODAY
AND SAT. THIS WILL BUILD A SERIES OF SURFACE LOWS ACROSS THE
CENTRAL PLAINS STATES WHICH WILL IN TURN MAINTAIN STEADY WAA AND
SURFACE MOISTURE RETURN OVER DEEP SOUTH TX THROUGHOUT THE SHORT
TERM. THIS STEADY WAA WILL ALLOW TEMPS TO REMAIN NEAR OR A LITTLE
ABOVE CLIMO THROUGH SATURDAY. THE INCREASING LOW LEVEL MOISTURE
VALUES WILL LIKELY RESULT IN A LITTLE MORE CLD COVER LATER TONIGHT
INTO SAT. SO WILL GO WITH A LITTLE COOLER HIGH TEMPS SAT DUE TO
THE REDUCED DIURNAL HEATING.

THE LOW LEVEL MOISTURE RETURN WILL NOT BE ENOUGH TO WARRANT ANY
SIGNIFICANT POPS THROUGHOUT THE SHORT TERM AS THE MID AND HIGHER
LEVELS OF THE ATMS REMAIN PRETTY PARCHED

THE PGF WILL BE PRETTY DECENT AS THE SURFACE LOWS OVER THE CENTRAL
PLAINS STATES DEVELOP. THIS WILL RESULT IN SOME BREEZY/WINDY
CONDITIONS MAINLY DURING THE AFTERNOON HOURS TODAY AND TOMORROW.
HOWEVER THE WIND STRENGTH DOES NOT APPEAR STRONG ENOUGH TO REQUIRE
AND WIND ADVISORIES AT THIS TIME. /60/

THE FORECAST TEMPS THROUGH THE SHORT TERM PERIOD ARE BASICALLY A
ROUGH 50/50 BLEND OF THE MAV AND MET NUMBERS. THE MAV AND MET ARE IN
PRETTY GOOD AGREEMENT FOR HIGHS TODAY AND LOWS TONIGHT. FOR SAT THE
MAV HAS A COOL BIAS VERSUS THE MET AND WILL LEAN A LITTLE MORE
TOWARDS THE WARMER MET HERE.

LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
THROUGH SUNDAY AN UPPER TROUGH WILL BE DIGGING INTO THE CENTRAL
PLAINS REGION INTENSIFYING SURFACE LOW PRESSURE OVER TEXAS AND
OKLAHOMA. THAT WILL INCREASE OUR LOW LEVEL WINDS LEADING TO A
FAIRLY BREEZY DAY ON SUNDAY. FOR NOW THE MAXIMUM GRADIENT SETS UP
OVERNIGHT SATURDAY AND BEGINS TO RELAX ON SUNDAY LEADING TO MORE
OF A 20 TO 30 MPH GUSTS DAY THAN A 30 TO 40 MPH DAY. TEMPERATURES
WILL BE WARM WITH CURRENT MAXES IN THE MID TO UPPER 80S IN THE
VALLEY AND ABOVE 90 WEST OF HIGHWAY 281. RAINFALL CHANCES HOLD OFF
AMID TERRAIN GENERATED CAPPING BUT THE PERSISTENT SOUTHEASTERLIES
WILL HAVE INCREASED HUMIDITY AND LOW MOISTURE MAKING THE DAY FEEL
STICKIER THAN THE LAST FEW.

SUNDAY NIGHT THE 00Z ECMWF DISPLAYS PARTICULARLY DIFFLUENT 300/500MB
FLOW OVER THE WESTERN GULF OF MEXICO AHEAD OF A WEAK LEADING SHORT
WAVE TROUGH. THE LOCATION OF THE BEST LIFT AND MARGINAL
THERMODYNAMIC ENVIRONMENT WILL LIKELY PREVENT CONVECTIVE DEVELOPMENT
OVER THE REGION AND KEPT THE FORECAST DRY. HOWEVER GIVEN ITS
PROXIMITY THIS FEATURE WILL BE WORTH WATCHING TO SEE IF IT DIGS A
LITTLE FURTHER SOUTH IN SUBSEQUENT MODEL RUNS.

THE MAIN LONGER WAVE TROUGH MOVES INTO THE PLAINS MONDAY AND A COLD
FRONT SURGES SOUTH THROUGH THE DAY. BEST TRACE OF THE SOURCE AIRMASS
FOR THIS FRONT IS IN WESTERN CANADA WHERE ITS AROUND 20 TO 30
DEGREES F. EXPECT THE SHALLOW COLD AIRMASS TO OUTRUN THE 40KM GLOBAL
MODEL RESOLUTION AND SPED THE FRONT UP A BIT...CURRENTLY THINKING
MORE MIDDAY MONDAY THAN LATE AFTERNOON/EVENING. WITH THE SHALLOW
FRONTAL BOUNDARY WELL AHEAD OF THE BEST MID LEVEL ASCENT PRE FRONTAL
CONVECTION APPEARS UNLIKELY WITH RESIDUAL 750MB CAPPING BUT THERE
SHOULD BE PLENTY OF 1000-700MB MOISTURE AND ELEVATED INSTABILITY FOR
SHOWERS AND THUNDERSTORMS BEHIND THE FRONT AS WELL AS STRATIFORM
RAIN AS 700MB SOUTHWESTERLIES OVERRUN THE COLD AIRMASS. WIND SPEEDS
ON THE DETERMINISTIC GFS/ECMWF ARE QUITE STRONG WITH AN IMPRESSIVE
PRESSURE GRADIENT AHEAD OF THE BUILDING PLAINS 1028MB HIGH AND WILL
NEED TO MONITOR FOR WIND ADVISORY/GALE WARNING TYPE CONDITIONS AS
THE EVENT APPROACHES.

MAX TEMPS WILL DROP ON TUESDAY INTO THE MID TO UPPER 70S. QUICK
COLUMN DRYING WILL LEAD TO PLENTY OF LOW ANGLE APRIL SUNSHINE BUT
COLD ADVECTION THROUGH THE DAY ON TUESDAY SHOULD BE A SIGNIFICANT
ENOUGH PLAYER TO BE CONSIDERED. UNDERCUT GUIDANCE CONSENSUS SLIGHTLY.

PLAINS RIDGING SHIFTS BACK TO ITS FAVORED NORTH CENTRAL
GULF/SOUTHERN GULF STATES POSITION BY WEDNESDAY INTO THURSDAY AND
SOUTHEASTERLY RETURN FLOW WILL ONCE AGAIN BEGIN RECHARGING LOW LEVEL
RH/MOISTURE ON STEADY BREEZES. MAX TEMPS WILL WARM BACK UP INTO THE
LOW TO MID 80S THROUGH THURSDAY AND FRIDAY. GFS/ECMWF DIFFER ON THE
LARGE SCALE PATTERN THURSDAY INTO FRIDAY WITH THE GFS SHOWING A MID
LEVEL SHORTWAVE AND BROADLY DIFFLUENT UPPER FLOW WITH INCREASING
SOUTHEAST LOW LEVEL WINDS WHILE THE ECMWF IS QUICKER TO AMPLIFY
DESERT SOUTHWEST RIDGING AND KEEPS TROUGHING FURTHER TO THE NORTH.
RUN TO RUN CONSISTENCY AND AVAILABLE GLOBAL ENSEMBLE MEMBERS SUPPORT
THE GFS SOLUTION AND USED THE BASIC CONCEPT FOR THE FORECAST WHICH
RESULTED IN A RETURN OF SLIGHT SHOWER AND THUNDERSTORM CHANCES FOR
THURSDAY AND THURSDAY NIGHT. DRY CONDITIONS RETURN FOR FRIDAY.
/68-JGG/

MARINE...
TODAY THROUGH SATURDAY...ALTHOUGH THE PGF WILL REMAIN PRETTY STRONG
OVER THE LOWER TX BAY AND GULF WATERS THROUGH SATURDAY...THE
RELATIVELY COOL BAY AND GULF WATER TEMPS WILL LIKELY LIMIT THE
DOWNWARD MIXING OF THE S-SE LOW LEVEL FLOW OVER THE AREA. SO FOR
TODAY WILL MENTION ONLY SCEC CONDITIONS FOR THE MARINE AREAS. EXPECT
A SIMILAR PATTERN TO PREVAIL ON SATURDAY. ANOTHER LIMITING FACTOR
SHOWING UP ON SATURDAY WILL BE THE BETTER CLD COVER POTENTIAL. IF WE
HAVE MORE COVERAGE OF LOW LEVEL MARINE CLD LAYERS FOR BOTH THE BAY
AND GULF WATERS...THIS MAY ALSO HELP INHIBIT THE DOWNWARD MIXING OF
THE STRONGER SOUTHERLY WINDS ALOFT.

SUNDAY THROUGH TUESDAY...
BREEZY SOUTHEAST WINDS WILL LIKELY LEAD TO EXERCISE CAUTION
CONDITIONS ON SUNDAY AND SUNDAY NIGHT. A COLD FRONT WILL SWEEP
ACROSS THE LOWER TEXAS COASTAL WATERS ON MONDAY AND STRONG NORTH TO
NORTHWEST WINDS WILL PRODUCE AT LEAST SMALL CRAFT ADVISORY
CONDITIONS WITH GALE CONDITIONS POSSIBLE. SEAS WILL TRANSITION FROM
LOW TO MODERATE ON SUNDAY TO ROUGH BY MONDAY AFTERNOON. STRONG WINDS
ARE EXPECTED TO CONTINUE THROUGH MONDAY NIGHT BEFORE GRADUALLY
DECREASING BY TUESDAY AFTERNOON AND BEGINNING TO SHIFT TO THE EAST.
ROUGH SEAS ARE EXPECTED MOST OF THE DAY AND EVENING TUESDAY.
&&

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

$$

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