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000
FXUS64 KBRO 130506
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1206 AM CDT THU MAR 13 2014

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

&&

.AVIATION...VFR THROUGH THE PERIOD. SFC HIGH PRESSURE WILL MOVE
FROM CENTRAL TEXAS TO LOUISIANA TODAY WHICH WILL AID IN SWITCHING
THE WINDS FROM THE NORTH EARLY IN THE TAF PERIOD TO THE EAST BY
THE AFTERNOON. A FEW CUMULUS CLOUDS WILL BE POSSIBLE IN THE LATE
AFTERNOON HOURS BUT OTHERWISE SKIES WILL BE CLEAR.

&&

.DISCUSSION...UPDATED FOR LATEST MARINE DISCUSSION BELOW.

&&

.MARINE...WITH WINDS AT BUOY 42020 STILL FIRMLY WITHIN SCA
CRITERIA AND KOPM WITH LIGHTER WINDS...HAVE EXTENDED 20 TO 60 NM
OFFSHORE WATERS TILL 12Z AND WILL LET 0 TO 20 NM NEARSHORE WATERS
EXPIRE AT 1 AM.

&&

.PREV DISCUSSION... /ISSUED 652 PM CDT WED MAR 12 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...NORTH WINDS ARE GRADUALLY DECREASING ACROSS THE
AREA WITH A FEW GUSTS UP TO 20 KNOTS CONTINUING THROUGH SUNSET.
LIGHT NORTHERLY WINDS WILL PREVAIL TONIGHT WITH VFR CONDITIONS
ACROSS THE AREA. A BROKEN DECK WILL POSSIBLY DEVELOP OVER KBRO
TONIGHT BUT CONDITIONS REMAIN VFR. THE NORTH WINDS WILL REMAIN
BETWEEN 10 TO 15 KNOTS THURSDAY AND GRADUALLY SHIFT EAST AND
SOUTHEAST BY THE AFTERNOON HOURS. THE SE WINDS WILL DECOUPLE IN
THE LATE AFTERNOON HOURS.

PREV DISCUSSION... /ISSUED 214 PM CDT WED MAR 12 2014/

SHORT TERM /NOW THROUGH THURSDAY NIGHT/...MORE TRANQUIL CONDITIONS
FORECAST FOR THE SHORT TERM AFTER THE FRONT RACED THROUGH EARLIER
THIS MORNING. WITH SFC HIGH PRESSURE DROPPING INTO TEXAS
TONIGHT...WINDS WILL QUICKLY FALL TO LIGHT FROM THE NORTH OVERNIGHT.
CLEAR SKIES WILL ALLOW TEMPS TO FALL INTO THE 40S AREAWIDE. TOMORROW
THE SFC HIGH BEGIN TO SHIFT OFF TO THE EAST...ALLOWING ONSHORE FLOW
TO RETURN SLOWLY. WINDS WILL REMAIN LIGHT...WITH A SLOW INCREASE OF
SFC DEWPOINTS THROUGH THE AFTERNOON.

LONG TERM /FRIDAY THROUGH WEDNESDAY/...
SOUTH TO SOUTHEASTERLY LOW LEVEL WINDS ON FRIDAY WILL INCREASE
MOISTURE IN THE BOUNDARY LAYER AMID A FAIRLY BREEZY AND WARM
AFTERNOON WITH HIGHS AROUND 80 EXCEPT RIGHT AT THE COAST. ADDED A
CHANCE FOR SHOWERS UNDER THE 750MB INVERSION IN THE MORNING HOURS ON
FRIDAY. ON SATURDAY 700 TO 800MB WINDS SHIFT SOUTHWESTERLY
INCREASING CAPPING BUT LOW LAYER MOISTURE INCREASES TO THE POINT
THAT ISOLATED SHOWERS WILL BE POSSIBLE DURING THE DAY...MAINLY
HIGHWAY 281 AND EASTWARD AND REFLECTED THAT IN THE NEW FORECAST.

BETTER AGREEMENT IN THE 12Z SUITE AMONGST THE GFS AND ECMWF
REGARDING THE WEEKEND/EARLY NEXT WEEK SYSTEM. GFS/ECMWF AND GFS
ENSEMBLE MEMBERS ARE IN PRETTY GOOD AGREEMENT WITH A FRONTAL PASSAGE
IN THE SUNDAY DAYPART...LIKELY BEFORE NOON. THE GFS AND ECMWF BOTH
DEVELOP WEAK TROUGHING IN THE NORTHWESTERN BAY OF CAMPECHE SUNDAY
MORNING IN RESPONSE TO DIVERGENCE PRODUCED BY A JET MAXIMUM ON THE
EAST SIDE OF THE MAIN UPPER TROUGH OVER NORTHWESTERN MEXICO. THIS
SHIFTS OUR SURFACE WINDS MORE SOUTHEASTERLY AND PRODUCES A SORT OF
CONFUSED LOWEST 150MB FLOW. THE NEXT RESULT APPEARS TO BE WEAKENED
BOUNDARY LAYER CONVERGENCE ALONG THE FRONT ITSELF AS IT MOVES THROUGH
THE REGION.

THIS PRODUCES A NEW FLY IN THE OINTMENT FOR THE FORECAST. GFS MODEL
FORECAST SOUNDINGS SHOW SUBSTANTIAL CAPPING IN PLACE EARLY SUNDAY
MORNING THAT IS ELIMINATED BY STRONG LIFTING FROM THE APPROACHING
UPPER LOW BY LATE AFTERNOON SUNDAY BUT THAT FORCING COMES RIGHT AS
THE FRONT ARRIVES AND MAY BE TOO LATE TO ALLOW FOR SURFACE BASED
THUNDERSTORM DEVELOPMENT. IF THE FRONT IS A LITTLE SLOWER...AMPLE
INSTABILITY AND SHEAR...WITH 0-6KM SHEAR VALUES AROUND 45KTS AND
MLCAPE VALUES AROUND 2000 J/KG WOULD NEED TO BE MONITORED...BUT AT
THE CURRENT TIME IT APPEARS THE MOST LIKELY SCENARIO PRODUCES
ELEVATED CONVECTION/THUNDERSTORMS THAT WOULD HAVE SIGNIFICANTLY LESS
AVAILABLE INSTABILITY. FOR THE FORECAST CONTINUED A SLIGHT CHANCE OF
THUNDERSTORMS FROM SUNDAY MORNING THROUGH MONDAY EVENING BUT
EFFECTIVELY LOWERED POPS A BIT AS 700MB OMEGA FORCING APPEARS FAIRLY
SHORT LIVED...NEARER TO THE FRONT AND ONLY THROUGH MONDAY MORNING
WITH A MODEST FRONTAL OVERRUNNING SIGNATURE AND 300K AND 305K
CONDENSATION PRESSURE DEFICITS AND ISENTROPIC CHARTS NOT SUGGESTING
WIDESPREAD PRECIP. CONTINUED AT LEAST SLIGHT CHANCES FOR RAIN/RAIN
SHOWERS THROUGH MONDAY NIGHT AS AT LEAST SOME COASTAL TROUGHING AND
LOW LEVEL CONVERGENCE/FRONTAL OVERRUNNING LOOKS TO BE AVAILABLE BUT
COVERAGE MAY BE MORE LIMITED. TEMPERATURES WILL BE MODERATED BY
MODEST NORTHEASTERLY ONSHORE FLOW/COLD ADVECTION DESPITE AT LEAST
SOME SUNSHINE AND KEPT HIGHS CLOSE TO 70 TO 75.

TUESDAY THROUGH WEDNESDAY RIDGING REESTABLISHES OVER THE
SOUTHEASTERN US AND WE RETURN TO WARM AND HUMID SOUTHEASTERLY FLOW.
RAIN CHANCES APPEAR LOW THROUGH THIS TIMEFRAME AND 12Z ECMWF/GFS ARE
IN BETTER AGREEMENT WITH THE OVERALL SYNOPTIC PATTERN IN THIS PERIOD
THAN IN PRIOR RUNS. /68-JGG/

FRIDAY THROUGH SUNDAY...
REASONABLY FAVORABLE MARINE CONDITIONS ARE FORECAST FRIDAY AND
SATURDAY WITH MODERATE SOUTHEAST WINDS EASING AND SHIFTING TO THE
EAST AND SOUTHEAST ON SUNDAY. A COLD FRONT IS EXPECTED TO PUSH
ACROSS THE LOWER TEXAS COAST SUNDAY MORNING PRODUCING STRONG NORTH
WINDS AND ROUGH SEAS WITH SMALL CRAFT ADVISORIES LIKELY ON SUNDAY.

MARINE...
OW THROUGH THURSDAY NIGHT...THE COLD FRONT HAS RACED THROUGH...WITH
NORTH WINDS OF 25 TO 30 KNOTS PRETTY COMMON. THE GALE WARNING
EXPIRES AT 4PM...AS FREQUENT GAL GUSTS WILL HAVE DEPARTED WITH THE
FRONT. SMALL CRAFT ADVISORIES WILL BE IN EFFECT FOR A SHORT PERIOD
FOR THE LAGUNA MADRE FOR RESIDUAL 20 KNOT WINDS...WHILE GULF WATERS
ADVISORIES WILL COTNINUE THROUGH THIS EVENING...MAINLY FOR ELEVATED
SEAS STILL ABOVE 7 FEET. AFTER SUNSET...THE SFC HIGH MOVES INTO
TEXAS AND THE NW GULF...QUICKLY LOWERING WINDS TO NEAR CALM. ONSHORE
FLOW RETURNS TOMORROW AS THE SFC HIGH MOVES EAST...WITH WINDS
REMAINING AROUND 10 KNOTS. SEAS WILL CONTINUE TO RELAX...FALLING
BELOW 5 FEET BY THE AFTERNOON.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...HIGH RIP CURRENT RISK THROUGH THIS AFTERNOON FOR TXZ256-257.

GM...SMALL CRAFT ADVISORY UNTIL 7 AM CDT THIS MORNING FOR GMZ170-175.

     SMALL CRAFT ADVISORY UNTIL 1 AM CDT EARLY THIS MORNING FOR
     GMZ150-155.

&&

$$

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HTTP://WEATHER.GOV/RGV

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