Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 100511 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1211 AM CDT THU APR 10 2014

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

&&

.AVIATION...LOW LEVEL MOISTURE WILL INCREASE A BIT AS
SOUTHEASTERLY WINDS INCREASE BUT CONTINUING TO FORECAST VFR
THROUGH THE TAF PERIOD...SOME SCATTERED LOW CLOUDS AROUND SUNRISE
TODAY BUT NOT ANTICIPATING A CEILING. LOW LEVEL WINDS WILL
INCREASE AND APPROACH 2000/3000 FT WIND SHEAR CRITERIA BUT SHOULD
START TO MIX TO THE SURFACE SUFFICIENTLY TO AVOID THAT DEGREE OF
SHEAR. BY MID MORNING SOUTH TO SOUTHEASTERLY WINDS AT 20 TO 25
KNOTS...GUSTS 30 TO 35 KNOTS THROUGH THE LATE MORNING AND
AFTERNOON. WINDS WILL STAY UP AT 10 TO 15 KNOTS AFTER SUNSET WITH
GUST SPEEDS DECREASING. /68-JGG/

&&

.PREV DISCUSSION... /ISSUED 624 PM CDT WED APR 9 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...CLOUD COVER WILL BE LIMITED THIS EVENING AND OVERNIGHT
TO HIGH CIRRUS STREAMING OVERHEAD. CLOUD COVER ALOFT WILL CONTINUE
TOMORROW...WITH LOWER CU FIELD DEVELOPING GENERALLY DURING THE
AFTERNOON BTWN 3000 AND 4000. BREEZY CONDITIONS CURRENTLY WILL
SLACKEN OFF TO AROUND 10 KNOTS OVERNIGHT. SOUTHEAST WINDS WILL
AGAIN INCREASE INTO THE UPPER TEENS WITH GUSTS AROUND
25KTS...ESPECIALLY DURING THE AFTERNOON.

PREV DISCUSSION... /ISSUED 142 PM CDT WED APR 9 2014/

SHORT TERM /NOW THROUGH THURSDAY NIGHT/... MID LEVEL RIDGE TO
FLATTEN OUT THE NEXT 24 HOURS AS WEAK SHORTWAVE MOVES SOUTHEAST
OUT OF THE ROCKIES INTO THE CENTRAL PLAINS. MAIN WEATHER IMPACT IN
THE SHORT TERM WILL BE WIND AS THE PRESSURE GRADIENT STEADILY
STRENGTHENS.

TONIGHT...WITH THE GRADIENT STRENGTHENING UNDERWAY THIS AFTERNOON
AND PRESSURES LOWERING ACROSS THE TX PANHANDLE TONIGHT WIND WILL
BE SOMEWHAT DELAYED IN DECOUPLING THIS EVENING. MAYBE NOT UNTIL
MIDNIGHT WILL WE SEE WINDS DROP BELOW 10 KNOTS. THIS WILL ALLOW
FOR TEMPERATURES TO BE SLOW IN FALLING INITIALLY BUT WITH DEW
POINT RECOVERY DELAYED TEMPERATURES TO FALL ONCE AS THE WINDS
ABATE. THE WINDS TO LIMIT RADIATIONAL COOLING EVEN WITH CLEAR
SKIES WHICH RESULTS IN AT LEAST A 5 TO 10 DEGREE WARM UP OVER THIS
MORNING.

THURSDAY...LOW PRESSURE CONTINUES TO FALL OVER THE PLAINS AS
SHORTWAVE MOVES INTO THE ROCKIES. SOUTHEAST FLOW TO GATHER SOME
STEAM WITH BREEZY TO WINDY CONDITIONS DEVELOPING MID TO LATE
MORNING. WINDS BETWEEN 925-850MB ARE NOT SEEN TO EXCEED 30 KNOTS
SO DO NOT ANTICIPATE WIND ADVISORY CONDITIONS ALTHOUGH MAV MET
GUIDANCE ARE APPROACHING THE THRESHOLD OF 26 KNOTS. MOISTURE
RETURN IS LIMITED TO THE BOUNDARY LAYER BELOW 925H WITH VERY DRY
AIR STILL RESIDING WELL THROUGH THE ATMOSPHERIC COLUMN. FEW-SCT
CUMULUS TO PROVIDE MOSTLY SUNNY TO PARTLY CLOUDY SKIES. TEMPS
WARM UP NICELY AND MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE
PREVIOUS FORECAST OF NEAR TO SLIGHTLY ABOVE AVERAGE LOOKING ON
TRACK FOR MID 80S EAST TO LOWER 90S WEST.

THURSDAY NIGHT...WINDS WILL BE SLOW IN DIMINISHING WITH PRESSURE
GRADIENT REMAINING STEADY STATE ALL NIGHT. PARTIAL DECOUPLING WILL
ALLOW FOR WINDS TO DROP TO BETWEEN 10 AND 15 KTS OVERNIGHT. TEMPS
WILL BE MILD WITH THE INCREASE IN LOW LEVEL MOISTURE AND THE
STEADY WINDS. ANOTHER 5 DEGREES ADDED TO THURSDAY MORNING LOWS
PUSHING VALUES SLIGHTLY ABOVE NORMAL. NOT ANTICIPATING FOG
DEVELOPMENT ESPECIALLY WITH THE STRONGER WINDS BUT SOME PATCHY
GROUND FOG MAY FORM IN THE PREDAWN HOURS WHEN WINDS REACH THERE
MINIMUM.

LONG TERM /FRIDAY THROUGH TUESDAY/...A LARGE SCALE MID LEVEL RIDGE
RESIDING UPSTREAM IN THE SHORT TERM WILL ERODE AND FLATTEN...SUCH
THAT A MUCH WEAKER RIDGE WILL BE IN PLACE OVER THE SOUTHWEST UNITED
STATES BY FRIDAY. A SOUTHERN STREAM MID LEVEL LOW OVER THE EAST
PACIFIC WILL DRIFT EAST...ROTATING JUST NORTH OF AN UNDERLYING JET
STREAK...ARRIVING OVER SOUTHERN CALIFORNIA ON FRIDAY. HOWEVER...
SENSIBLE WEATHER FOR THE CWA WILL CHANGE GRADUALLY THROUGH THE
WEEKEND...RETAINING NEAR NORMAL TEMPERATURE CHARACTERISTICS WHILE
CLOUDINESS INCREASES IN A PERSISTENT GULF RETURN FLOW WHILE SOUTH
WEST CAPPING FLOW INCREASES WITH THE APPROACH OF THE UPPER LOW FROM
THE WEST.

AS THE SOUTHERN LOW OPENS INTO A TROUGH SATURDAY WHEN APPROACHING
WEST TEXAS...RIDGING WILL BUILD OVER THE WEST COAST INTO CANADA...
AND A MID LEVEL TROUGH WILL PLUNGE SOUTH FROM CANADA...DIVING ACROSS
THE PLAINS ON SUNDAY AND TAPPING INTO ARCTIC SOURCE HIGH PRESSURE
WHICH WILL REACH THE VALLEY ON MONDAY. WEATHER CONCERNS WILL NOT
REALLY DEVELOP UNTIL MONDAY AS THE ATMOSPHERE WILL REMAIN DRY UNTIL
A FOCUSING MECHANISM IS ABLE TO TAKE ADVANTAGE OF THE POTENTIAL
ENERGY. THE CANADIAN TROUGH WILL ELONGATE SOUTH OVER TEXAS...
LEAVING ADDITIONAL ENERGY FARTHER TO THE NORTH...BUT PHASING WITH
THE SOUTHERN STREAM TROUGH AS THEY BOTH MOVE OVERHEAD ON MONDAY.

THE GFS AND ECMWF ARE IN FAIRLY GOOD AGREEMENT NOW WITH A MONDAY
FROPA...WITH THE GFS A LITTLE FASTER IN BRINGING THE FRONT THROUGH
IN THE MORNING AS OPPOSED TO THE ECMWF IN THE AFTERNOON. THE ECMWF
ACTUALLY BRINGS A PRIMARY FRONT THROUGH EASTERN TEXAS IN THE A.M.
WITH A QUICK-ON-THE-HEELS REINFORCING SHOT SEALING THE DEAL FOR DEEP
SOUTH TEXAS AND THE RGV BY AFTERNOON. CONFIDENCE IS ABOVE AVERAGE TO
THAT POINT. BOTH MODELS FOCUS DEEP MOISTURE AHEAD OF THE FRONT...
YIELDING A QUARTER INCH TO A HALF INCH OF QPF FOR THE DAY. THE ECMWF
FAVORS THE AFTERNOON FOR THE MAIN EVENT WHILE THE GFS IS ABOUT SIX
HOURS FASTER...BRINGING THE FRONT THROUGH THE LOWER VALLEY LATE
MORNING TO EARLY AFTERNOON. BOTH MODELS TRY TO CONCENTRATE QPF OVER
THE NORTHEAST MEXICAN PLAINS AS OROGRAPHIC LIFT COMES INTO PLAY
ALONG THE SIERRA MADRES. THE GFS GUIDANCE IS CLOSE TO THE 30 PERCENT
POPS THAT WERE RETAINED FOR MONDAY...WITH THUNDER INCLUDED DUE TO
THE COORDINATED TIMING OF THE MID LEVEL SUPPORT. THE GFS FORECAST
SOUNDING FOR BRO AT 18Z ON THE 14TH FOCUSES 1.88 INCHES OF PWAT
AHEAD OF THE FRONT AND A DISAPPEARING CAP...ALTHOUGH OTHER
INSTABILITY INDICATORS OF SIGNIFICANCE APPEAR MORE ELUSIVE.

IN ANY CASE...THE RESULT IS GOOD CONTINUITY WITH THE INHERITED
FORECAST. BOTH MODELS SUGGEST A RATHER QUICK CLEARING OUT AND
DRYING OUT MONDAY NIGHT INTO TUESDAY WITH A MODERATE COOL DOWN.
NEAR NORMAL TEMPERATURES MONDAY WILL DROP BY 5 TO 10 DEGREES TO
SLIGHTLY BELOW NORMAL MONDAY NIGHT...TUESDAY AND TUESDAY NIGHT.

MARINE...
NOW THROUGH THURSDAY NIGHT...PRESSURE GRADIENT TO STEADILY
INCREASE THE NEXT 24 TO 36 HOURS AS HIGH PRESSURE SETTLING ACROSS
THE GULF SOUTH STATES INTERACTS WITH DEEPENING CENTRAL PLAINS LOW
PRESSURE. WINDS FAVORABLE MARINE CONDITIONS CONTINUE THROUGH
SUNRISE THURSDAY THEN SOUTHEAST WINDS PICK ACROSS THE LAGUNA MID
TO LATE MORNING. SMALL CRAFT ADVISORIES MAY BE NECESSARY AS THE
WINDS APPROACH 20 KNOTS. THE STRONGER GRADIENT DOES NOT REACH ALL
THE WAY OUT OVER THE GULF WATERS UNTIL THURSDAY NIGHT WHEN THE
GRADIENT PEAKS. EXPECTING A SLOW BUT STEADY INCREASE IN WINDS AND
SEAS INTO FRIDAY MORNING WITH MARGINAL SMALL CRAFT ADVISORY
CONDITIONS.

FRIDAY THROUGH SUNDAY...BROAD HIGH PRESSURE OVER THE NORTHWEST
GULF WILL INITIALIZE THE LONG TERM FORECAST BY INTERACTING WITH
LOWER PRESSURE INLAND TO BRING ABOUT LIGHT TO MODERATE SOUTHEAST
WINDS AND LOW TO MODERATE SEAS. THE TREND WILL CONTINUE INTO THE
WEEKEND. SOUTHEAST WINDS OVER THE GULF...ESPECIALLY THE OFFSHORE
WATERS... WILL OFTEN HOVER IN THE 15 TO 20 KNOT RANGE DUE TO
SYNOPTIC SCALE FORCING...AND WILL MAINTAIN EXERCISE CAUTION TO LOW
END ADVISORY CONDITIONS. WINDS WILL DECREASE SUNDAY NIGHT TO
MONDAY MORNING AS LOWER PRESSURE AHEAD OF A COLD FRONT APPROACHES
FROM THE NORTH. EXCEPT FOR ISOLATED STREAMER SHOWERS SUNDAY
MORNING..RAIN CHANCES WILL BE LOW TO NEARLY NONEXISTENT THROUGH
SUNDAY NIGHT.

&&

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

$$

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