Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 181736 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1236 PM CDT THU SEP 18 2014

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

&&

.AVIATION...LIGHT TO MODERATE SOUTHERLY FLOW TO MAINTAIN ABUNDANT
LOW LEVEL MOISTURE AOB 5000 FEET THROUGH ALL OF DEEP SOUTH TEXAS.
EXPECTING PREDOMINATE THROUGH THE REMAINDER OF THE AFTERNOON AND
OVERNIGHT. WEAK INVERSION SETS UP BY SUNRISE FRIDAY AND LOW CLOUDS
TO FORM. MVFR CIGS ARE ANTICIPATED AS THE CUMULUS FIELD
REGENERATES AND WILL PERSIST THROUGH THE MORNING HOURS. A FEW
SHOWERS MAY DEVELOP WITHIN THE CUMULUS STREAK BUT SHOULD BE SHORT
LIVED AND CIRCUMNAVIGABLE.

&&

.PREV DISCUSSION... /ISSUED 607 AM CDT THU SEP 18 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...THIN CIRRUS CONTINUES TO DRIFT SOUTH OVER THE CWA
THIS MORNING...WHILE LOW CU HAS RESULTED IN TEMPO MVFR CEILINGS AT
BRO ON LIGHT SOUTHEAST WINDS. MAY SEE MORE TEMPO MVFR CONDITIONS
FOR THE LOWER VALLEY THROUGH THE MORNING...BUT WINDS WILL PICK UP
THROUGH THE DAY AND THE WEAK ELEVATED INVERSION SHOULD LIFT...
ALLOWING VFR CONDITIONS TO RETURN. WILL STILL SEE SCT TO BKN
CLOUD STREETS THIS AFTERNOON HOWEVER. NO OTHER AVIATION ISSUES
SEEN FOR THE DAY. CLOUDS SHOULD THIN OUT TONIGHT WITH LOSS OF
DAYTIME HEATING...WITH LOW CLOUDS MOVING IN AGAIN FRIDAY MORNING
ON LIGHT WINDS.

PREV DISCUSSION... /ISSUED 403 AM CDT THU SEP 18 2014/

SHORT TERM /TODAY THROUGH FRIDAY/...THE LARGE SCALE MID LEVEL RIDGE
OVER THE WEST WILL SHIFT EAST INTO THE PLAINS AS THE REMNANTS OF
ODILE REMAIN OVER THE SOUTHWEST U.S....DECAY AND BECOME ABSORBED.
THE INCREASING STABILITY PROVIDED BY THE RIDGE...PLUS THE CURRENT
ABSENCE OF EXTRA MOISTURE FROM THE SOUTHWEST GULF...WILL PROVIDE
MORE SETTLED CONDITIONS LOCALLY IN THE SHORT TERM. NONETHELESS...
SURFACE MOISTURE POOLING ALONG AN OLD BOUNDARY OVER NORTHEAST TX...
COUPLED WITH DIVERGENCE ALOFT OVER THAT AREA TODAY...WILL KEEP
THINGS MORE ACTIVE TO THE NORTH. SOME RESIDUAL CONVECTION COULD MAKE
IT TO THE NORTHERN TIER COUNTIES TONIGHT...AND THUS KEPT POPS A
SKOCHE HIGHER THERE AS A RESULT. OVERALL...MOISTURE WILL REMAIN
ELEVATED LOCALLY...WITH PWAT REMAINING AROUND TWO INCHES THROUGH THE
LONG TERM.

TODAY...A SLIGHTLY STRONGER SOUTH TO SOUTHEAST FLOW WILL DEVELOP...
WITH A WEAK SEA BREEZE POSSIBLE...FAVORING A FEW MORE SHOWERS OVER
KENEDY AND MAYBE BROOKS COUNTIES. HIGH TEMPERATURES WILL CHECK IN
CLOSE TO NORMAL...OR JUST A DEGREE OR TWO ABOVE. A FEW EXTRA MORNING
LOW CLDS WILL YIELD TO A MIX OF CLOUDS AND SUN LATER THIS MORNING.
MOISTURE CONTENT WILL REMAIN ELEVATED THOUGH...WITH PWATS AROUND 2
INCHES...SO ANY SHOWERS OR TSTMS WILL CONTINUE TO BE EFFICIENT RAIN
MAKERS AND COULD PRODUCE ONE HALF TO ONE INCH OF PRECIP IN A SHORT
AMOUNT OF TIME.

TONIGHT...IT WILL BE WARM AND MUGGY TONIGHT WITH SOME PATCHY STRATUS
DEVELOPING ALONG THE COAST...AND EVEN PATCHY LIGHT FOG INLAND...WITH
LIGHT ONSHORE WINDS. LOW TEMPS WILL CHECK IN FROM 75 TO 80...A FEW
DEGREES ABV NRML DUE TO THE ELEVATED DEW POINTS. ONGOING CONVECTION
OVER CENTRAL TEXAS MAY FIND ITS WAY DOWN THE RIO GRANDE PLAINS AND
INTO THE UPPER VALLEY OVERNIGHT.

FRIDAY...HIGH PRESSURE PUSHING WEST OVER TEXAS WILL FOCUS A BOUNDARY
NORTH OF THE AREA...AND CONVECTION MOVING SOUTH MAY CLIP THE UPPER
VALLEY THURSDAY NIGHT AND CONTINUE INTO THE UPPER WESTERN REACHES
EARLY FRIDAY MORNING. OTHERWISE...THE DAY WILL AGAIN BEGIN WITH BKN
LOW CLOUDS GIVING WAY TO A MIX OF CLOUDS AND SUN WITH LIGHT TO MDT
SOUTHEAST WINDS AND NEAR TO SLIGHTLY WARMER THAN NORMAL HIGH TEMPS.

LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
LITTLE CHANGE TO PREVIOUS FORECAST...MAXES HELD BACK BY SOIL
MOISTURE...MODEST DISORGANIZED RAIN CHANCES CONTINUE AMID AMPLE
COLUMN MOISTURE.

FRIDAY NIGHT INTO SATURDAY MID AND UPPER LEVEL RIDGING PERSISTS TO
THE WEST WHILE A SHORTWAVE TROUGH PASSES THROUGH THE EASTERN GULF OF
MEXICO KEEPING A VERY LIGHT EAST TO SOUTHEAST SURFACE FLOW IN PLACE
WITH NO REAL NORTH CENTRAL GULF SURFACE RIDGING IN PLACE. THE REGION
KEEPS HIGH COLUMN AND LOW LEVEL MOISTURE BUT LACKS MUCH OF A
FOCUSING MECHANISM. WITH NEARSHORE GULF OF MEXICO WATER TEMPS IN THE
MID 80S AND SURFACE MAX TEMPS REDUCED TWO TO THREE DEGREES BY
INCREASED SOIL MOISTURE THE SEABREEZE FRONT WILL TEND TO BE MORE
DIFFUSE AS WELL...DESPITE A LIGHT ONSHORE WIND REGIME. EXPECT THAT
THERMAL GRADIENT WILL BE A LITTLE TOGETHER BY SATURDAY BUT MID LEVEL
SUBSIDENCE WILL LIMIT INSTABILITY AND KEEP COVERAGE LOWER. WENT WITH
THE INHERITED 20 TO 30 PCT POPS WHICH IS BELOW GUIDANCE CONSENSUS.

MID LEVEL RIDGING SPREADS EASTWARD ON SUNDAY WITH NO OTHER REAL
SYNOPTIC LEVEL CHANGES EVIDENT IN THE GLOBAL MODEL GUIDANCE. THERE
ARE HINTS OF VERY WEAK EASTERLY WAVES...WHICH MAKES SENSE IN LATE
SEPTEMBER...BUT NOTHING TO REALLY FOCUS LOW LEVEL CONVERGENCE OR
MOISTURE. WENT WITH A SLIGHT CHANCE AFTERNOON POP AND WARMED MAXES
UP ABOUT A DEGREE FROM THE INHERITED FORECAST.

MONDAY INTO TUESDAY THE UPPER LEVEL RIDGE BEGINS TO RETREAT WESTWARD
AS TROUGHING DEVELOPS ALONG THE SOUTHEASTERN US COAST. A STRONGER
EASTERLY WAVE SIGNAL ALSO IS APPARENT IN THE GUIDANCE MONDAY AND
TUESDAY WITH SFC-500MB HUMIDITY VALUES INCREASING. THE CONVERGENCE
ALONG THE WAVE AND THE INCREASE IN MOISTURE FROM PERSISTENT 850MB
EASTERLIES KEEPS AT LEAST SOME CHANCE OF SHOWERS OR STRAY STORMS IN
THE FORECAST THROUGH WEDNESDAY...INCLUDING THE OVERNIGHT PERIODS FOR
MUCH OF THE CWA. PEAKED THE CHANCES MONDAY AFTERNOON ALONG THE COAST
AS THE LEADING EDGE OF A TROPICAL WAVE EVIDENT WITH REASONABLE
TIMING CONTINUITY BETWEEN THE GFS/ECMWF ARRIVES. THE AFOREMENTIONED
FRONT APPEARS WEAKER IN THE 00Z GUIDANCE AND THE REINFORCING TROUGH
WHICH HAD BEEN PRESENT IN PREVIOUS GLOBAL MODEL RUNS IS MUCH FURTHER
NORTH AND LESS ORGANIZED SO FEEL A LITTLE BETTER ABOUT NOT SEEING A
STRONG COLD FRONT APPROACH THE AREA. DID CONTINUE A SMALL NORTHERLY
WIND SHIFT OVER THE AREA TUESDAY NIGHT BUT A TRUE AIRMASS CHANGE
LOOKS FAIRLY UNLIKELY AS THE SYSTEM WASHES OUT. COULD ENHANCE
RAINFALL CHANCES WHICH FURTHER LED TO A SORT OF BROAD BRUSH 20 PCT
POP EACH 6 HOUR PERIOD THROUGH THE END OF THE LONG TERM FORECAST.

EXPECT THAT LATER FORECAST CYCLES WILL BE ABLE TO LOCK IN ON SOME OF
THE SMALLER SCALE DETAILS AND EXACT PLACEMENT OF THE FRONT AND WE
WILL BE ABLE TO REMOVE SOME OF THE 20 POP PERIODS AND REPLACE A FEW
WITH 30 OR 40 PCT CHANCES AS IT DRAWS CLOSER. SLOWLY WARMED MAX
TEMPERATURES UP THROUGH ABOUT MONDAY CLOSER TO MEX/ECX CONSENSUS
ANTICIPATING SLIGHTLY LESS SOIL MOISTURE HOLDING AFTERNOON MAXES
BACK. /68-JGG/

MARINE...
TODAY THROUGH FRIDAY...SEEMINGLY PERENNIAL HIGH PRESSURE OVER THE
GULF WILL SUPPORT LIGHT TO MODERATE ONSHORE WINDS AND LOW TO MDT
SEAS IN THE SHORT TERM. CONVECTION WILL MOVE OUT OVER THE NORTHWEST
GULF FROM NORTHEAST TEXAS TODAY AS MOISTURE AND ENERGY ASSOCIATED
WITH THE REMNANTS ODILE OVER NORTHWEST MEXICO RIDE OVER A SURFACE
BOUNDARY HANGING ACROSS THE NORTH GULF. THIS ACTIVITY SHOULD STAY
NORTH OF THE AREA HOWEVER AND THE LOCAL RADAR IS GENERALLY QUIET
THIS MORNING. THE FORECAST CALLS FOR LIGHT TO MODERATE SOUTHEAST OR
SOUTH SOUTHEAST WINDS AND SEAS OF 2 TO 4 FEET...WITH MAINLY ISOLATED
GULF CONVECTION.

FRIDAY NIGHT THROUGH TUESDAY...
LIGHT TO MODERATE SOUTHEASTERLY WINDS ARE EXPECTED TO BECOME MORE
EASTERLY AND EVENTUALLY NORTHEASTERLY SUNDAY NIGHT INTO TUESDAY.
SEAS SHOULD REMAIN LOW TO MODERATE. NO WIDESPREAD AREAS OF SHOWERS
OR THUNDERSTORMS OR EXERCISE CAUTION LEVEL CONDITIONS ARE CURRENTLY
FORECAST.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  90  79  90  81 /  20  10  20  10
BROWNSVILLE          92  78  91  79 /  20  10  30  10
HARLINGEN            94  77  92  79 /  20  10  20  10
MCALLEN              95  78  94  79 /  20  10  20  10
RIO GRANDE CITY      95  77  94  79 /  20  10  30  20
SOUTH PADRE ISLAND   87  80  88  81 /  20  10  20  20

&&

.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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