Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 211949
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
249 PM CDT THU AUG 21 2014

.SHORT TERM /NOW THROUGH FRIDAY NIGHT...WEAK UPPER LEVEL DISTURBANCE
OVER THE WESTERN GULF COAST IS MOVING NORTHWEST INTO MEXICO
ENHANCING SCATTERED CONVECTION OVER THE AREA WHILE ABUNDANT DRY AIR
SHOWN IN THE 12Z KBRO SOUNDING WITH PWATS OF AROUND 1.53 INCHES WERE
OBSERVED. THIS HAS LIMIT THE CONVECTION ACTIVITY OVER DEEP SOUTH
TEXAS AT THIS TIME. SE WINDS HAVE INCREASED AS EXPECTED DUE TO THE
LLJ INCREASING BETWEEN 25 TO 30 KNOTS MIXING TO THE SFC LEADING TO
THIS BREEZE CONDITIONS. KEPT ONLY A LOW 20 PERCENT ACROSS THE LOWER
VALLEY AS A FEW ISOLATED SHOWERS COULD MOVE INTO THE AREA. THE
SOUTHEAST WINDS WILL BEGIN TO LOWER TONIGHT AS THE GRADIENT WEAKENS
AND HIGH PRESSURE SLIGHTLY RETROGRADES WEST. LOW TEMPS WILL STAY IN
THE LOW 80S ACROSS MUCH OF THE CWA. THE DRY AIR EMBEDDED WITHIN THE
PERIPHERY OF THIS HIGH PRESSURE WILL MOVE INLAND FRIDAY LOWERING THE
CHANCE OF SHOWERS EVEN MORE. TEMPERATURES WILL BE ABOVE 100 WEST OF
HWY 281 AND UPPER 90S ALONG THE COAST. HEAT INDEX OR FEEL LIKE
TEMPERATURES WILL BE BETWEEN 108 TO 110. THE PRESSURE GRADIENT WILL
NOT BE AS STRONG FRIDAY ALLOWING FOR SE WINDS TO REMAIN MODERATE
DURING THE DAY.

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
DRIED FORECAST OUT TIL THURSDAY WITH ESPECIALLY DRY AIR OVER GULF OF
MEXICO...BREEZY WINDY THROUGH SATURDAY.

FRIDAY NIGHT INTO SATURDAY GOOD AGREEMENT AMONGST NAM/GFS/ECMWF ON A
SHORTWAVE TROUGH DIVING INTO THE INTERMOUNTAIN WEST AND AIDING IN
AMPLIFYING RIDGING OVER THE MIDWESTERN STATES. THIS SHIFTS THE 500MB
AND ASSOCIATED LOWER LEVEL RIDGING FROM ITS PERCH ON THE NORTHERN
GULF COAST TO THE ARKLATEX REGION. THIS WILL HELP RELAX THE LOW
LEVEL PRESSURE GRADIENT A LITTLE...BUT IT WILL STILL BE STRONG
ENOUGH TO GENERATE PERSISTENT BREEZES AND MAKE SETTING UP A STRONGER
SEABREEZE FRONT DIFFICULT. GFS/NAM MODEL SOUNDINGS ARE DECENT FOR
CONVECTION BUT THE 850/700MB REGION IS PRETTY DRY AND THE LACK OF
EXTRA HELP FROM THE SEABREEZE SHOULD KEEP RAIN CHANCES LIMITED. SREF
AND MOS GUIDANCE AGREE AND THE RUN TO RUN TREND IS DRIER SO PARED
BACK THE SLIGHT CHANCE OF SHOWERS TO A MORE FAVORED ZONE INSIDE OF A
FALFURRIAS SARITA RAYMONDVILLE TRIANGLE. TEMPERATURES WILL BE CLOSE
BUT SLIGHTLY COOLER THAN THE LAST FEW DAYS.

SUNDAY THE 500MB RIDGE AXIS WILL BE A LITTLE FURTHER NORTH BUT THE
OVERALL SYNOPTIC PATTERN IS EXPECTED TO BE CLOSE TO SUNDAY. LOW
LEVEL MOISTURE WILL LIKELY REMAIN A LITTLE TOO LOW FOR MUCH IN THE
WAY OF PRECIP WITH 850/700MB FLOW SOURCING IN THE CURRENTLY RATHER
DRY WESTERN GULF OF MEXICO AND THE LOW LEVEL PRESSURE GRADIENT WILL
STILL BE A LITTLE TOO STRONG FOR SEABREEZE CONVECTION. PLAYED THE
TEMPS AND POPS SIMILAR TO SATURDAY IN THE NEW FORECAST WITH A DRY
VALLEY AND SMALL AREA OF THE RANCHLANDS THAT MAY POP A LATE
AFTERNOON SEABREEZE SHOWER.

MONDAY THE RIDGE MOVES TO THE MID MISSISSIPPI VALLEY WITH LOW LEVEL
WIND SPEEDS DECREASING MORE NOTICEABLY AND ORIENTING MORE EAST TO
WEST. HIGH TEMPERATURES WILL BE A TOUCH COOLER...ALTHOUGH STILL IN
THE MID/UPPER 90S TO LOW 100S. MID LEVEL CONVERGENCE IN THE AREA
WILL BE LOWER WITH THE RIDGE MOVING AHEAD BUT WHEN GFS/ECMWF SHIFT
THE LOW TO MID LEVEL FLOW MORE EASTERLY IT ONLY ADVECTS IN STILL
RELATIVELY DRY AIR. AMSU/SSMI BLENDED PRECIPITABLE WATER
ESTIMATES...GOES SOUNDER... ND CURRENT WEATHER OVER THE BAY OF
CAMPECHE APPEAR TO SUPPORT THAT CONCEPT WITH A FAIRLY DRY 850MB
LAYER ACROSS THAT ENTIRE REGION SO KEPT THE VALLEY DRY WITH ANOTHER
SMALL AREA OF SEABREEZE SHOWERS OVER THE RANCHLANDS GIVEN THE
UNUSUALLY DRY AIRMASS TO OUR SOUTHEAST.

TUESDAY A REINFORCING PACIFIC JET MAX BEGINS TO DIG WESTERN US
TROUGHING A LITTLE FURTHER EAST AND SOUTH WHICH APPEARS TO FLATTEN
THE EASTERN US RIDGE. THIS LEADS TO DEEPER MORE EASTERLY FLOW OVER
THE REGION BUT STILL ONLY DRAWS IN THE DRY AIR FROM THE CENTRAL GULF
AND DOES NOT REALLY APPEAR TO INCREASE PRECIP CHANCES MUCH. WINDS
WILL BE FAIRLY LIGHT OUT OF THE EAST WITH TEMPERATURES MODERATED
SLIGHTLY BY THE EASTERLY FLOW. KEPT POPS A LITTLE BELOW GUIDANCE
CONSENSUS FEELING THAT CLIMATOLOGY MAY BE PLAYING TOO BIG A ROLE AT
THAT RANGE COMPARED TO OUR CURRENT ABNORMALLY DRY AIRMASS.

WEDNESDAY GFS/ECMWF STILL DIFFER IN THE PROGRESSION OF THE MID LEVEL
SHORTWAVE THAT MOVES OVER THE PLAINS IN RESPONSE TO THE PREVIOUS
DAYS EVENTS BUT THE 12Z ECMWF DID TREND CLOSER TO THE GFS. SET UP
THE FORECAST BASED ON A SYNOPTIC SOLUTION CLOSER TO THE GFS ENSEMBLE
WHEREAS THE ECMWF FLATTENS AND DEEPENS RIDGING IN A WAY TO USHER IN
MUCH RICHER EASTERN GULF MOISTURE AND GFS BRINGS IN AT LEAST A
LITTLE HIGHER MID/LOW LEVEL RH VALUESBUT NOT QUITE AS MUCH IN TERMS
OF RICHNESS AND DEPTH. WIND SPEEDS SHOULD BE FAVORABLE FOR A SEA
BREEZE BUT I SUSPECT THAT LEE TROUGHING WILL BE STRONGER THAN
FORECAST IN DAY 7 GUIDANCE AND BUMPED WIND SPEEDS UP A BIT. WENT
WITH A NEARLY VALLEY WIDE 20 POP. /68-JGG/


&&

.MARINE...
NOW THROUGH FRIDAY NIGHT...SOUTHEAST WINDS WILL PREVAIL
THROUGH THE SHORT TERM PERIOD WITH SLIGHT CHANCE OF SHOWERS OVER THE
GULF WATERS IN THE AFTERNOON. SMALL CRAFT ADVISORY IS IN EFFECT OVER
THE LAGUNA MADRE THROUGH THE EVENING. CONDITIONS IMPROVE TONIGHT BUT
WINDS PICK UP AGAIN FRIDAY BUT PRESSURE GRADIENT WILL NOT BE AS
STRONG AS TODAY WITH POSSIBLE SCEC OVER THE LAGUNA AND THE NEAR
SHORE WATERS. SEAS WILL REMAIN UP TO 5 FEET OVER THE GULF WATERS BUT
WILL BEGIN TO LOWER TO AROUND 4 FEET INTO TOMORROW AS THE WINDS
BEGIN TO DECREASE.

FRIDAY NIGHT THROUGH TUESDAY...
BREEZY SOUTHEAST WINDS ARE EXPECTED TO PREVAIL THROUGH SUNDAY BEFORE
BECOMING LIGHTER AND MORE SOUTHEASTERLY MONDAY AND TUESDAY. CURRENT
FORECASTS SUGGEST WIND SPEEDS BELOW ADVISORY CRITERIA HOWEVER FOR
THE ENTIRE PERIOD FRIDAY NIGHT THROUGH TUESDAY BUT PERIODS OF
MODERATE SEAS AND SMALL CRAFT EXERCISE CAUTION LEVEL WINDS WILL BE
POSSIBLE.

&&

.FIRE WEATHER...ON FRIDAY DRY AIR EMBEDDED WITHIN THE HIGH PRESSURE OVER THE
GULF WILL MOVE INLAND. RH VALUES BETWEEN 1000 TO 500 MB LOWER TO
AROUND 30 TO 25 PERCENT. IN ADDITION...THE SE WINDS WILL BEGIN TO
INCREASE IN THE AFTERNOON WITH GUST UP TO 20 MPH. DUE TO THE DRY
FUELS IN THE WESTERN COUNTIES AND MODERATE TO STRONG SE WINDS
INCREASING...FIRE WEATHER CONDITIONS WILL NOT BE ELEVATED TO
CRITICAL OVER THE WESTERN COUNTIES BUT COULD ENHANCE FIRE DANGER MAY
BE ISSUED AS THE DRY CONDITIONS CONTINUE OVER THE AREA. THE
PRECIPITABLE WATER VALUES HAVE ALSO LOWER TO AROUND 1.5 INCHES.
MINIMUM RH VALUES FOR TOMORROW RANGE FROM 25 TO 30 PERCENT
ESPECIALLY FOR ZAPATA...JIM HOGG AND WESTERN STARR COUNTIES. RH
RECOVERIES FOR THE WESTERN COUNTIES REMAIN IN THE LOWER 80 PERCENT
WITH A FEW LOCATIONS ALONG THE RIVER REMAINING IN THE 70 PERCENT
RANGE.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  81  95  80  94 /  10  10  20  10
BROWNSVILLE          79  96  78  96 /  10  10  10  20
HARLINGEN            79  99  77  99 /  10  10  10  20
MCALLEN              79 101  79 101 /  10   0  10  10
RIO GRANDE CITY      79 102  79 102 /  10   0  10  10
SOUTH PADRE ISLAND   81  91  80  89 /  20  10  20  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY FOR WINDS UNTIL 8 PM CDT THIS EVENING FOR
     GMZ130-132-135.

&&

$$

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

SHORT TERM...TORRES
LONG TERM...GIBBS
UPPER AIR/GRAPHICAST...BILLINGS






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