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000
FXUS64 KBRO 130528
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1228 AM CDT MON MAY 13 2013

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

&&

.AVIATION...RAIN SHOWERS CONTINUE TO DEVELOP AND MOVE ACROSS
NORTHERN MEXICO AND INTO THE LOWER/MIDDLE RIO GRANDE VALLEY.
ALTHOUGH COVERAGE HAS BEEN ON THE WANE THE LAST 1-2 HOURS...STILL
EXPECT SHOWERS TO IMPACT KBRO/KHRL OVER THE NEXT SEVERAL HOURS.
CIG/VIS WILL BE PREDOMINATELY VFR OUTSIDE HEAVIER SHOWERS WHERE
BRIEF MVFR CONDS CAN BE EXPECTED. THROUGH THE DAY MONDAY...PRECIP
COVERAGE SHOULD BE A LITTLE LESS WITH DIFFLUENCE WEAKENING AND
MOISTURE SLIGHTLY DECREASING. MONDAY EVENING...RAIN SHOWERS AND
ISOLATED TSTORMS SHOULD ONCE AGAIN DEVELOP OVER THE HIGHER TERRAIN
OF NORTHERN MEXICO AND MOVE INTO THE RIO GRANDE VALLEY.

&&

.PREV DISCUSSION... /ISSUED 621 PM CDT SUN MAY 12 2013/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...RAIN SHOWERS ARE EXPECTED TO PERSIST IN HIDALGO COUNTY
THROUGH THE NEXT SEVERAL HOURS POSSIBLY EXPANDING INTO CAMERON
COUNTY THROUGH THE NEXT 3 TO 4 HOURS. VISIBILITY WILL BE
PREDOMINANTLY VFR OR HIGH MVFR WITH THE RARE DROP TO IFR BRIEFLY
POSSIBLE IN HEAVIEST SHOWERS. CONVECTION NEAR HBV/BKS SHOULD BEGIN TO
DECREASE IN THE NEXT TWO HOURS. PREVAILING VFR CIG EXPECTED
BRIEFLY LOWERING IN HEAVIEST SHOWERS TO MVFR. OCCASIONAL LIGHTNING
STRIKES WILL BE POSSIBLE IF THE LARGER AREA OF ACTIVITY OVER NUEVO
LEON MOVES INTO SOUTH TEXAS....WHICH IS POSSIBLE THROUGH MIDNIGHT. A
GENERAL DECREASE IN PRECIP COVERAGE IS EXPECTED AFTER MIDNIGHT.
WINDS WILL BE LIGHT THROUGH THE OVERNIGHT.

ADDITIONAL SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE THROUGH THE
MORNING AND AFTERNOON WITH THE BEST OVERALL PROABABILITY AFTER 21Z
BUT TOO CONDITIONAL FOR TAF MENTION ATTM. PREVAILING VFR WITH
MODERATE NORTHEAST WINDS EXPECTED AMONG BKN TO OVC MID CLOUDS.
/68-JGG/

PREV DISCUSSION... /ISSUED 429 PM CDT SUN MAY 12 2013/

DISCUSSION...LARGER AREA OF RADAR RETURNS BUILDING TO THE
SOUTH AND SOUTHWEST OF THE AREA WITH LIGHT PRECIP STARTING TO MOVE
INTO STARR AND HIDALGO COUNTY. AN AREA OF DIFFLUENCE AND A
DEPARTING SPEED MAX APPEAR TO BE THE SOURCE AND IT IS LIKELY BEING
GENERATED AT ABOUT 8000 TO 10000 FT PARTIALLY ASSISTED BY
ISENTROPIC FRONTAL OVERRUNNING. ELEVATED INSTABILITY IN THIS
REGION IS MODEST...ABOUT 200 TO 500 J/KG SO A FEW BOLTS OF
LIGHTNING ARE POSSIBLE AND HAVE BEEN OBSERVED OVER THE LAST HOUR.
MORE ISOLATED TO SCATTERED SHOWERS ARE FORMING IN NORTHERN BROOKS
AND KENEDY COUNTY WHERE SURFACE MOISTURE IS DEEPER IN AN AREA OF
LOW CONVERGENCE. THOSE SHOWERS ARE LIKELY SURFACE BASED WITH ABOUT
800 J/KG OF CAPE TO WORK WITH SO A FEW BOLTS OF LIGHTNING WILL BE
POSSIBLE THERE AS WELL...THAT ACTIVITY WILL REMAIN POSSIBLE FOR
ABOUT ANOTHER 2 TO 3 HOURS UNTIL THE BOUNDARY LAYER STABILIZES.
THE AREA OF PRECIP TO THE SOUTH WILL PROBABLY MAKE DECENT INROADS
OVER THE NEXT FEW HOURS AS THE BEST GUESS FROM COMBINING
RAP/NAM/GFS AND WATER VAPOR IS THE DIVERGENCE WILL STAY STRONG
ENOUGH TO PRODUCE PRECIP THROUGH ABOUT 06Z. PWATS REMAIN ELEVATED
AT 1.5 TO 1.7 SO ANY SHOWERS SHOULD BE PRETTY EFFICIENT RAINFALL
PRODUCERS WITH HOURLY RAINFALL RATES OF 0.50 INCHES THE NORM IN
THE MORE CONCENTRATED SHOWERS AND HEAVIER THUNDERSHOWERS PRODUCING
1.00 TO 1.50 INCH RAINFALL RATES. THE GOING FORECAST SEEMS TO HAVE
A SOLID HANDLE AND NO SIGNIFICANT CHANGES APPEAR NEEDED. /68-JGG/

PREV DISCUSSION... /ISSUED 143 PM CDT SUN MAY 12 2013/

SHORT TERM /NOW THROUGH MONDAY NIGHT/...LOW PRESSURE SYSTEM
CENTER OVER BAJA CA UNDERNEATH THE SUBTROPICAL JET IS KEEPING THE
DIFFLUENT FLOW ALOFT ACROSS SOUTH TEXAS WITH A COUPLE OF
PERTURBATIONS MOVING ACROSS THE CWA TONIGHT AND MONDAY. THIS WILL
FAVOR THE REDEVELOPMENT OF SHOWERS AND AN ISOLATED THUNDERSTORM
LATE INTO THE EVENING. AT THIS TIME THERE IS SOME INITIATION RIGHT
ALONG AND EAST OF THE SIERRA MADRE BUT IT IS FAR WEST THAT WILL
NOT REACH THE CWA AT THIS TIME. THE CLOUDS ARE BEGINNING TO BREAK
ALLOWING FOR MORE SUN TO REACH THE SURFACE WHICH IN TURN RISE
TEMPS INTO THE UPPER 80S SIMILAR TO YESTERDAY. EXPECT THE
TEMPERATURES TO CONTINUE TO TREND A FEW DEGREES HIGHER FOR THE
INTO MONDAY ACROSS THE RIO GRANDE VALLEY. EXPECT A BREAK IN THE
RAINFALL THROUGH MUCH OF THE AFTERNOON AND REDEVELOPMENT IN THE
EVENING CONTINUING INTO THE NIGHT AS THE WINDS VEER EAST AND THE
PERTURBATION WITHIN THE FLOW FAVORS THE CONDITIONS FOR SHOWERS TO
REORGANIZED. MOST OF THE RAIN IS EXPECTED TO IMPACT THE
COMMUNITIES ALONG THE BORDERLINE. THE CLOUD COVER WILL LOWER AND
SPREAD ACROSS MUCH OF THE CWA KEEPING LOW TEMPERATURES CLOSE TO
THE 70S WITH MOST OF THE LOCATIONS TO THE NORTH IN THE MID TO
UPPER 60S. THE MOISTURE IN THE AREA IS ABUNDANT WITH THE 12Z KBRO
SOUNDING SHOWING PWAT VALUE UP TO 1.69 INCHES. THE EASTERLY FLOW
AT THE SURFACE WILL PREVAIL THROUGH THE NIGHT OVER THE GULF WATERS
FEEDING GULF MOISTURE INLAND. THIS EASTERLY/SE WINDS CONTINUE AS
THE SURFACE HIGH PRESSURE OVER THE NORTHERN PART OF THE GULF OF
MEXICO EXPANDS. HIGH TEMPERATURES WILL BE IN THE MID TO UPPER 80S
ONCE AGAIN MONDAY WITH CHANCE OF RAIN REPEATING ALONG THE BORDER
ONCE AGAIN AS THE TROUGH GRADUALLY BEGINS TO LIFT NORTHEASTWARD.

LONG TERM /TUESDAY THROUGH SUNDAY/...LOW TO MID LEVEL MOISTURE IS
PROGGED TO REMAIN HIGH ACROSS SOUTHWEST TEXAS TUESDAY WITH THE
PESKY 500MB LOW ACROSS NORTHWEST MEXICO AND THE 500MB RIDGE ACROSS
THE WESTERN GULF OF MEXICO. THE RIDGE IS EXPECTED TO WEAKEN ACROSS
THE STATE WEDNESDAY AS THE UPPER LOW/TROUGH FINALLY EJECTS INTO
THE SOUTHERN PLAINS. WITH THAT SAID...THE RAIN CHANCES ACROSS THE
AREA WILL DIMINISH TUESDAY INTO WEDNESDAY AS SUBSIDENCE INCREASES
ACROSS WEST TX AS THE TROUGH MOVES EASTWARD AND AN UPPER RIDGE
BUILDS ACROSS THE SOUTHWEST UNITED STATES IN ITS WAKE. THE 500MB
RIDGE ACROSS THE SOUTHERN PLAINS FRIDAY WILL PROVIDE VERY WARM AND
RELATIVELY DRY CONDITIONS THROUGH THE REST OF THE FORECAST PERIOD
AS A RESULT EVEN AS A SHORTWAVE TROUGH DEVELOPS ACROSS THE NORTH
CENTRAL U.S. SUNDAY.

MARINE...
NOW THROUGH SUNDAY NIGHT...A FEW SHOWERS OVER THE FAR
NORTHEAST PORTION OF THE COASTAL WATERS WILL CONTINUE TO MOVE E AND
PRODUCE MODERATE DOWNPOURS AND POSSIBLE GUSTY WINDS. EXPECT A BREAK
IN THE CLOUDS IN THE AFTERNOON WITH A CHANCE OF SHOWERS TO REDEVELOP
IN THE EVENING AS THE UPPER LEVEL SYSTEM OVER THE COAST OF BAJA CA
REMAINS IN THE AREA SENDING PERTURBATIONS TOWARDS SOUTH TEXAS AND
MEXICO. SEAS WILL REMAIN LOW WITH THE EXCEPTION OF DISRUPTION OF THE
CONDITIONS DUE TO DOWNPOURS FROM THE CONVECTION. CONDITIONS WILL
CONTINUE ON AND OFF AND REDEVELOP INTO MONDAY NIGHT. NO SCA OR SCEC
AT THIS TIME FOR THE SHORT TERM FORECAST.

TUESDAY THROUGH FRIDAY...MODERATE SOUTHEAST WINDS SHOULD PREVAIL
ACROSS THE COASTAL WATERS TUESDAY BEFORE THE PRESSURE GRADIENT
INCREASES ACROSS THE WESTERN GULF OF MEXICO WEDNESDAY. MODERATE TO
STRONG SOUTHEAST WINDS WILL PREVAIL ACROSS THE LOWER TEXAS COAST
WEDNESDAY AS A RESULT. THE GRADIENT IS PROGGED TO WEAKEN SLIGHTLY
SO MODERATE SOUTHEAST WINDS SHOULD PREVAIL ACROSS THE WESTERN GULF
THROUGH THE REST OF THE WEEK.

&&

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

$$

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