000
FXUS64 KBRO 110525
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1225 AM CDT TUE MAR 11 2014

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

&&

.AVIATION...CONVECTION FROM EARLIER THIS EVENING HAS MOVED EAST OF
THE AREA WITH A FEW LIGHT SHOWERS SOUTH OF THE AREA IN NORTHERN
MEXICO. SO...ATTENTION TURNS TO THE REST OF THE NIGHT WITH IFR
CONDS AND BELOW AND POSSIBILITY OF FOG. CIGS WILL STAY FAIRLY LOW
FOR THE REST OF THE NIGHT. PATCHY TO AREAS OF FOG WILL AFFECT THE
AREA TONIGHT. HAVE LIFR IN THE TAFS OVERNIGHT AND VLIFR MAY BE
POSSIBLE IF FOG DEVELOPS ROUGHLY 09-13Z. TOWARDS MID
MORNING...CONDS IMPROVE WITH VFR RETURNING CLOSER TO NOON. WINDS
WILL EVENTUALLY ESTABLISH FROM THE SOUTH IN THE AFTERNOON. TOWARDS
THE END OF THE TAF PERIOD WITH SOUTHEASTERLY WINDS...HIGH MOISTURE
RETURNS WITH LOW CIG/VIS POSSIBLE AT THE TAIL END OF THE TAF OR
SHORTLY THEREAFTER.

&&

.PREV DISCUSSION... /ISSUED 734 PM CDT MON MAR 10 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...THE STRONG 500 MB TROUGH AXIS APPROACHING DEEP SOUTH
TX THIS EVENING WILL BE DRIVING THE CONV OVER THE REGION DESPITE
THE VERY LIMITED CAPE VALUES EVIDENT ON THE LATEST LAPS GRAPHICS.
THIS MAY BRIEFLY REDUCE THE VSBYS AND CEILINGS OVER THE NEXT
SEVERAL HOURS DOWN TO MVFR/IFR LEVELS. THE 00Z BRO SOUNDING SHOWS
A FAIRLY MOIST LOW LEVEL INVERSION PERSISTING INTO THE EVENING
HOURS WHICH WILL ALLOW FAIRLY LOW CEILINGS TO LINGER INTO THE
OVERNIGHT HOURS. HOWEVER AS THE 500 MB TROUGH AXIS CLEARS THE
REGION EARLY TOMORROW MORNING DRIER AIR ALOFT WILL FILTER INTO THE
REGION ALLOWING FOR A RETURN OF VFR CONDITIONS DURING THE LATTER
HALF OF THE UPCOMING TAF PERIOD.

PREV DISCUSSION... /ISSUED 234 PM CDT MON MAR 10 2014/

SHORT TERM.../NOW THROUGH TUESDAY NIGHT/...COASTAL TROUGH
AXIS/REMNANT FRONTAL BOUNDARY PERSISTS ABOUT 60 MILES OFFSHORE
PARALLEL TO THE COAST WITH SOUTHEASTERLY FLOW AT ABOUT 2000 TO 3000
FT OVERRUNNING NORTHWESTERLY FLOW AT THE SURFACE LEADING TO
PERSISTENT RAIN AND DRIZZLE. THE SATURATED LOW LAYERS ALSO HAVE
ALLOWED SOME FOG TO DEVELOP THIS AFTERNOON. THE PARENT UPPER LOW CONTINUES
TO MOVE EASTWARD OVER COAHUILA WITH A LARGE AREA OF UPWARD VERTICAL
MOTION APPARENT ON WATER VAPOR OVER TAMAULIPAS. VISIBLE AND INFRARED
SATELLITE SHOW INCREASING ELEVATED CONVECTIVE DEVELOPMENT
ENCROACHING ON ZAPATA COUNTY AND CONTINUING TO THE SOUTH TOWARDS
MONTERREY.

REST OF THE AFTERNOON...EXPECTING THE LOW LAYER SOUTHEASTERLIES TO
WEAKEN AS THE UPPER LOW APPROACHES AND THE LIGHT RAIN AND DRIZZLE
MAY LET UP A LITTLE THROUGH 2 TO 3 PM. THE LINE OF SHOWERS AND
ISOLATED THUNDERSTORMS OVER MEXICO THOUGH SHOULD INCREASE IN
COVERAGE AND INTENSITY WITH TIME AND PUSH INTO THE WESTERN EDGE OF
THE CWA THROUGH THE SAME TIMEFRAME AND MOVE TOWARDS THE UPPER AND
MIDDLE VALLEY LATE THIS AFTERNOON/EARLY THIS EVENING.

TONIGHT...A PERIOD OF ENHANCED SHOWERS WITH A FEW THUNDERSTORMS IS
EXPECTED THROUGH THE EVENING HOURS WITH SOME RESIDUAL STRATIFORM
RAIN OCCURRING AS WELL. AS THE UPPER LOW MOVES OVERHEAD COASTAL
TROUGHING WEAKENS AND THE SURFACE FLOW BECOMES COUPLED TO LEE
TROUGHING OVER NEW MEXICO AHEAD OF THE NEXT STORM SYSTEM. THIS
ALLOWS WINDS TO BECOME EASTERLY AND ONSHORE AND SEND HIGHER
DEWPOINTS INTO THE AREA...SO EXPECTING FOG DEVELOPMENT
TONIGHT...WITH DENSE FOG POSSIBLE...ESPECIALLY NEAR THE COAST.

TUESDAY...WITH THE UPPER LEVEL LOW CLEARING AMID CONVERGENCE ALOFT
WE SHOULD SEE A VERY QUICK DRYING AND CLEARING BY LATE MORNING ON
TUESDAY WITH QUITE A BIT OF SUNSHINE IN THE AFTERNOON AND
TEMPERATURES REBOUNDING INTO THE UPPER 70S TO LOW 80S EXCEPT RIGHT
AT THE ISLAND WHERE COLD WATER TEMPERATURES WILL KEEP IT COOLER.
PREDOMINANT WIND OUT OF THE SOUTH TO SOUTHEAST SHOULD ALSO BEGIN TO
ESTABLISH BY MIDDAY AS THE AREA BREAKS OUT OF THE PERSISTENT LOW
CLOUDS AND DRIZZLE THAT HAS GRIPPED IT FOR THE LAST SEVERAL DAYS.
/68-JGG/

LONG TERM /WEDNESDAY THROUGH MONDAY/...THE CHANGEABLE WEATHER
PATTERN CONTINUES THROUGH THE WEEK..THOUGH THE SENSIBLE WEATHER
WILL BE MORE TYPICAL OF SPRING THAN OF THIS WINTER WHICH HAS
FEATURED NO FEWER THAN EIGHT `SHARP CHANGE` DROPS IN TEMPERATURE
/30 OR MORE DEGREES FROM ONE DAY TO THE NEXT/...AS WE HEAD TOWARD
THE WEEKEND AND INTO EARLY NEXT WEEK.

THE BIG PLAYER IS ON WEDNESDAY...AS A SHORT WAVE SLIDES ACROSS THE
FRONT RANGE OF THE COLORADO ROCKIES AND INTO THE MEAN LONG WAVE
TROUGH ACROSS THE MISSISSIPPI VALLEY AND HELPS BRING A SURGE OF
NORTHERLY FLOW ALONG WITH A 1030 HIGH INTO NORTH TEXAS. UNLIKE
RECENT EVENTS...THE ATMOSPHERE WILL REMAIN DRY WITH PERHAPS A BAND
OF STRATOCU ALONG THE FRONT. THE DRY SURGE WILL ALLOW DRY TO SUPER
ADIABATIC MIXING FROM 925 MB TO THE SURFACE...SOMETHING WE
TYPICALLY SAW DURING LATE WINTER AND EARLY SPRING 2013 BUT HAVE
RARELY SEEN SO FAR THIS YEAR. WINDS JUST OFF THE DECK ARE FORECAST
TO REACH 28 KNOTS AND SEE LITTLE REASON WHY THEY WON`T MIX DOWN IN
THE WARMING MARCH SUNSHINE. THUS...HAVE BUMPED SUSTAINED WINDS TO
THE EDGE OF ADVISORY (26 KNOT) LEVELS FOR A 3-6 HOUR PERIOD FROM
MID MORNING (RANCHES) TO MID AFTERNOON (VALLEY). AS FOR
TEMPERATURES...THE MARCH SUN ANGLE WILL TEMPER THE COLD ADVECTION
AND AFTERNOON HIGHS SHOULD BE ABLE TO REACH INTO THE LOWER OR EVEN
MID 70S NEAR THE RIVER AND CLOSE TO 70 ACROSS THE RANCHLANDS...IN
LINE WITH THE 12Z GUIDANCE PACKAGE.

AS QUICKLY AS THE WINDS CRANK UP THEY`LL DROP SHARPLY OVERNIGHT
WEDNESDAY UNDER MOSTLY CLEAR SKIES AS THE HIGH BRIEFLY SETTLES
ACROSS THE VALLEY. WITH DEWPOINTS FALLING PERHAPS INTO THE LOWER
30S IN SOME AREAS EXPECT A QUICK DROP AFTER SUNSET...WITH MORNING
LOWS THURSDAY RANGING THROUGH THE 40S. WOULD NOT SURPRISE TO SEE
SOME UPPER 30S IN WIND PROTECTED RANCH/RURAL AREAS...BUT NOT
FORECASTING JUST YET.

THURSDAY SHOULD HAVE ENOUGH SUNSHINE INLAND...ALONG WITH RETURN
EASTERLY FLOW TO MODIFY TEMPERATURES QUICKLY INTO THE 60S TO LOWER
70S. MODEL SOUNDINGS DO SHOW A DEVELOPING DECK AROUND 4000 FEET IN
ALONG HIGHWAY 77 AND PERHAPS NUDGING FARTHER WEST TO HIGHWAY 281
OR SO...AND THIS WILL HAVE TO BE WATCHED TO SEE IF TEMPERATURES
ARE CAPPED A FEW DEGREES BELOW CURRENT FORECAST. THAT SAID...THE
CURRENT FORECAST IS ALREADY 10-12 DEGREES BELOW AVERAGE...SO
SITUATION SHOULD BE COVERED.

MODERATION CONTINUES FRIDAY AND SATURDAY AS SOUTHERLY LOW LEVEL
FLOW ARRIVES AHEAD OF THE NEXT UPPER LEVEL SYSTEM DIGGING TOWARD
NORTH MEXICO BEHIND A STRENGTHENING FULL LATITUDE TROUGH ALONG
THE EAST COAST. FOR NOW...HAVE BROUGHT A CONSIDERABLE CLOUDY
PERIOD /THOUGH THE RIO GRANDE PLAINS COULD SEE SUNSHINE
FRIDAY/...WITH TEMPERATURES RIGHT AROUND AVERAGE DURING THE DAY
/UPPER 70S EAST TO LOWER 80S WEST / AND A BIG ABOVE AVERAGE AT
DAYBREAK WITH THE CLOUD COVER.

THE END OF THE WEEKEND REMAINS A BIT MUDDLED. ONLY CHANGE WAS TO
TRIM BACK RAIN CHANCES TO KEEP THE VALLEY DRY SATURDAY...WITH A
GRADUAL INCREASE INTO SUNDAY. SUNDAY`S TEMPERATURES A BIT OF
TRICKY CALL AND COULD DEPEND ON IF AND HOW MUCH RAIN FALLS. THE
ATMOSPHERE LOOKS `SEASONAL` SO UPPED VALUES A FEW DEGREES BUT
STILL A SHADE BELOW THE WARMER GFS. A QUICK LOOK TOWARD ST.
PATRICK`S DAY /NEXT MONDAY/ SHOWED BETTER AGREEMENT BETWEEN THE
ECMWF AND GFS...BUT STILL UNCERTAINTY AS TO HOW THE EASTERN U.S.
TROUGH EVOLVES WITH THE JUST ARRIVED 12Z ECMWF CUTTING OFF A LOW
IN THE SOUTHEAST U.S. AND THE GFS WITH A SINGLE-PHASE MID LATITUDE
JET. BOTH RUNS INDICATE PLENTY OF SUNSHINE WHICH WAS IN THE
FORECAST...AND WOULD ALLOW TEMPERATURES TO RISE TO NEAR 80 SHOULD
IT VERIFY. HAVE LEFT JUST SHORT FOR NOW GIVEN LOWER THAN AVERAGE
HEIGHTS/THICKNESS/850 TEMPS BUT PLENTY OF TIME TO ADJUST SINCE
CONFIDENCE ON DETAILS IS LOW.

MARINE...NOW THROUGH TUESDAY NIGHT...PATCHY DENSE FOG APPEARS POSSIBLE NEAR
THE COAST THIS AFTERNOON AND TONIGHT. OTHERWISE MODERATE WINDS AND
SEAS ARE EXPECTED OUT OF THE NORTHWEST CLOSE TO THE COAST AND
POSSIBLY OUT OF THE EAST ON THE FAR OFFSHORE WATERS WHERE THE MAIN
COASTAL TROUGH AXIS/RESIDUAL FRONT IS LOCATED. THIS BOUNDARY SHOULD
WASH OUT TONIGHT AMID LIGHT EASTERLY WINDS WITH SEAS REMAINING LOW
TO MODERATE. BETTER CONDITIONS ARE EXPECTED BY MID MORNING TUESDAY
INTO TUESDAY NIGHT WITH MODERATE EAST WINDS SHIFTING TO THE SOUTH
AMID LOW TO MODERATE SEAS LASTING THROUGH TUESDAY NIGHT.

WEDNESDAY THROUGH SATURDAY: HAZARDS ARE FRONT-LOADED WITH THE
STRONG FRONT EARLY WEDNESDAY. WITH ONLY MARGINAL COLD/DRY
ADVECTION AND THE STILL CHILLY /UPPER 50S/ NEARSHORE WATERS ALONG
WITH PAST EXPERIENCE WITH THESE TYPES OF FRONTS BELIEVE SITUATION
WILL NOT REACH GALE CRITERIA. COULD BE A GUST OR TWO TO 35+ KNOTS
RIGHT ALONG THE FRONT BUT CURRENT FORECAST CAPS GUSTS AT 33 KNOTS
FOR THE SIX HOUR LATE MORNING/AFTERNOON WINDOW AND WILL LET THE
FORECAST RIDE. SEAS/WAVES WILL CRANK UP QUICKLY TO 8 FEET OR
HIGHER BEHIND THE SURGE...AND TIMING OCCURRING BETWEEN 9 AND 11
AM MAKES EARLY MORNING OFFSHORE FISHING EXPEDITIONS A DANGEROUS
RISK WITH A RACE TO RETURN TO PORT BEFORE THE SLAM.

A ROUGH AFTERNOON WEDNESDAY WILL GRADUALLY MODERATE OVERNIGHT AND
CONDITIONS WILL IMPROVE FURTHER DURING THE DAY THURSDAY OVER THE
GULF. WINDS CRASH QUICKLY OVER LAGUNA MADRE OVERNIGHT
WEDNESDAY...SO A ONE DAY POSTPONEMENT NOT A BAD IDEA FOR THOSE
PLANNING TO STAY ON THE BAY.

THEREAFTER...LIGHT TO MODERATE WINDS...15 KNOTS OR LESS...AND
SLIGHT SEAS...3 FEET OR LESS...WILL DOMINATE THE LATE WEEK/EARLY
WEEKEND PERIOD WITH ZONAL FLOW AND GENERALLY DRY AIR TO KEEP ANY
THREAT OF RAIN AWAY.

&&

.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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