Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 201431 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
931 AM CDT MON APR 20 2015

.DISCUSSION...ALLOWED FOR THE DENSE FOG ADVISORY TO EXPIRE AS
STRONG APRIL FRONT HAS MOVED THROUGH THE REGION. NORTHEAST WINDS
HAVE INCREASED WITH GUSTS NEAR 30 KNOTS OR 35 MPH AT BROWNSVILLE.
LIGHT RAIN IS DEVELOPING WITH A WEAK OVERRUNNING PATTERN
DEVELOPING IN WAKE OF THE FRONT. THE RAIN MAY INCREASE IN COVERAGE
AND INTENSITY LATER TODAY AND TONIGHT AS A SURFACE FRONT DEVELOPS
NEAR THE COAST AND THE FRONT PULLS UP STATIONARY JUST SOUTH OF THE
RIO GRANDE RIVER.

&&

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

&&

.MARINE...THE PRESSURE GRADIENT HAS STRENGTHEN SUFFICIENTLY AND
OFFSHORE BUOYS AND TCOON SITES HAVE INDICATED WINDS EXCEEDING
SMALL CRAFT ADVISORY LEVELS. HAVE ISSUED AN ADVISORY FOR BOTH THE
LAGUNA MADRE AND THE OFFSHORE WATERS UNTIL 4 PM THIS AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 658 AM CDT MON APR 20 2015/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...THE COLD FRONT HAS MOVED SOUTH OF THE RIO GRANDE
VALLEY THIS MORNING. THE LATEST SURFACE OBSERVATIONS AND
SATELLITE IMAGES INDICATES PATCHY FOG AND LOW CLOUDS ACROSS THE
SOUTHERN PORTIONS OF DEEP SOUTH TEXAS. WILL MENTION A TEMPO FOR
LINGERING LOW VISIBILITIES AND CEILINGS. MVFR CONDITIONS EXPECTED
TO DEVELOP BY LATE MORNING WITH VFR CONDITIONS THIS AFTERNOON.
ISOLATED TO SCATTERED CONVECTION ALSO IS ANTICIPATED TO DEVELOP
ALONG AND BEHIND THE FRONT. HAVE REMOVED THE PREVIOUS MENTION OF
VCTS DUE TO LOW CONFIDENCE BUT WILL MENTION/MAINTAIN THE
SHRA/VCSH THROUGH THE TAF PERIOD.

PREV DISCUSSION... /ISSUED 457 AM CDT MON APR 20 2015/

SHORT TERM /NOW THROUGH TUESDAY/...

A COLD FRONT CURRENTLY EXTENDING FROM NEAR LAREDO TO SOUTH OF
KINGSVILLE AND INTO THE GULF WATERS. THE FRONT WILL MOVE SOUTH INTO
THE NORTHERN RANCHLANDS IN THE NEXT COUPLE OF HOURS AND INTO THE RIO
GRANDE VALLEY JUST AFTER SUNRISE. THE COMBINATION OF LIGHT AND
VARIABLE SURFACE WINDS AHEAD OF THE APPROACHING COLD FRONT AND
ELEVATED SURFACE HUMIDITY VALUES HAS RESULTED IN PATCHY FOG ACROSS
PORTIONS OF DEEP SOUTH TEXAS THIS MORNING. SURFACE OBSERVATIONS
INDICATE VISIBILITIES VARY BETWEEN A HALF MILE TO 5 MILES ACROSS
MOST OF THE AREA. HOWEVER...WEB CAMERAS AT SOUTH PADRE ISLAND AND
SURFACE OBSERVATIONS AT PORT ISABEL INDICATE DENSE FOG HAS
DEVELOPED. HAVE ISSUED A DENSE FOG ADVISORY FOR COASTAL CAMERON AND
COASTAL WILLACY COUNTIES ALONG WITH THE LAGUNA MADRE AND THE LOWER
TEXAS GULF WATERS OUT TO 20 MILES OFFSHORE UNTIL 9 AM. THE DENSE FOG
SHOULD DISSIPATE AS THE COLD FRONT PUSHES SOUTH OF THE LOWER TEXAS
COASTLINE LATER THIS MORNING.

IN THE WAKE OF THE FRONT...COOLER AIR WILL FILTER INTO DEEP SOUTH
TEXAS TODAY WITH HIGH TEMPERATURES IN THE UPPER 70S TO AROUND 80
DEGREES. SHOWERS AND ISOLATED THUNDERSTORMS ARE POSSIBLE ALONG AND
BEHIND THE FRONT THIS MORNING. SPC HAS THE AREA OUTLINED FOR A
MARGINAL RISK UNTIL 7 AM THIS MORNING THEN A GENERAL THUNDERSTORM
RISK FOR TODAY AND TONIGHT. RAIN CHANCES LINGER ACROSS THE DEEP
SOUTH THIS AFTERNOON AND TONIGHT AS WEAK OVERRUNNING PATTERN
DEVELOPS. WILL MENTION ISOLATED THUNDER ALONG THE RIO GRANDE RIVER
THIS AFTERNOON DUE TO SOME ELEVATED INSTABILITY. LOW TEMPERATURES
TONIGHT WILL RANGE FROM THE MID 60S ACROSS THE NORTHERN RANCHLANDS
TO THE LOWER 70S ALONG THE COAST. HIGH TEMPERATURES WILL BE IN
THE LOW TO MID 80S ACROSS MUCH OF DEEP SOUTH TEXAS ON TUESDAY.
RAIN CHANCES INCREASE AGAIN ON TUESDAY AS THE WEAK FRONT BOUNDARY
MOVES NORTH OF DISSIPATES ACROSS THE AREA.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...DEEP SOUTH TX WILL BE
UNDER THE INFLUENCE OF A 500 MB RIDGE AXIS STARTING AT MIDWEEK
WITH A BROAD 500 MB CLOSED LOW CENTERED OVER THE GREAT LAKES AND A
CLOSED LOW DIGGING INTO THE SOUTHWESTERN STATES. THIS RIDGE AXIS
WILL STRENGTHEN STEADILY AS THE SOUTHWESTERN STATES CLOSED 500 MB
LOW PUSHES FURTHER EAST. AS THE RIDGE AXIS STRENGTHENS THE BETTER
PVA EJECTING OUT FROM THE CLOSED LOW TO OUR WEST WILL TEND TO PUSH
FURTHER NORTH MISSING THE RGV RESULTING IN LOWER POPS DURING THE
LATTER HALF OF THE WORK WEEK. THE INCREASING 500 MB RIDGING WILL
ALLOW THE TEMPS TO PUSH WELL ABOVE CLIMO FOR LATE APRIL AFTER
TUES.

OVERALL TEMPS AND POPS IN THE LONGER RANGE PERIOD WILL BE A
GENERAL BLEND OF THE ECMWF AND THE GFS NUMBERS. PRETTY GOOD
AGREEMENT EXISTS BETWEEN THE TWO MODELS THROUGH DAY 7 WITH THE
ECMWF HAVING A SLIGHT WARMER BIAS. OVERALL FORECAST CONFIDENCE IS
ABOVE AVERAGE AT THIS TIME FOR THE LONGER RANGE WORDING.

MARINE...NOW THROUGH TUESDAY...BOUY 42020 CURRENTLY REPORTING VERY
LIGHT NORTH NORTHEAST WINDS WITH SEAS SLIGHTLY ABOVE 2 FEET. THE
COMBINATION OF LIGHT AND VARIABLE SURFACE WINDS AHEAD OF A COLD
FRONT APPROACHING DEEP SOUTH TEXAS AND ELEVATED SURFACE HUMIDITY
VALUES WILL RESULT IN AREAS OF DENSE COASTAL FOG. A DENSE FOG
ADVISORY IS IN EFFECT UNTIL 9 AM FOR THE LAGUNA MADRE AND THE LOWER
TEXAS GULF WATERS OUT TO 20 MILES OFFSHORE. THE COLD FRONT CURRENTLY
MOVING ACROSS THE LOWER TEXAS GULF WATERS...WILL PUSH SOUTH OF THE
RIO GRANDE RIVER SHORTLY AFTER SUNRISE. THE PRESSURE GRADIENT WILL
STRENGTHEN LATER TODAY RESULTING IN NORTHEAST WINDS NEARING 20 KNOTS
ACROSS THE GULF WATERS. SMALL CRAFT EXERCISE CAUTION CONDITIONS
LIKELY TODAY FOR THE LAGUNA MADRE AND GULF WATERS.

TUESDAY NIGHT THROUGH FRIDAY...PERSISTENT SURFACE RIDGING OVER THE
GULF OF MEX WILL MAINTAIN A LIGHT TO MODERATE SOUTHEAST SURFACE
FLOW OVER THE LOWER TX BAY AND GULF WATERS. NO SCA CONDITIONS
EXPECTED THROUGH NEXT FRIDAY.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 PM CDT THIS AFTERNOON FOR
     GMZ130-132-135.

     SMALL CRAFT ADVISORY UNTIL 4 PM CDT THIS AFTERNOON FOR GMZ150-
     155-170-175.

&&

$$

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