Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 211725 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1225 PM CDT SUN SEP 21 2014

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

&&

.AVIATION...ON GOING CONVECTION EARLY THIS AFTERNOON TO PERSIST
THROUGH THE AFTERNOON HOURS DRIFTING STEADILY SOUTH TO SOUTHWEST.
THE THREE TAFS SITES WILL HAVE DECENT CHANCES OF SEEING ONE OR TWO
HOURS OF +TSRA WITH TEMPO MVFR CIGS AND VSBY. AS THE ATMOSPHERE
STABILIZES AROUND SUNSET CONVECTION TO WANE AND FLYING CONDITIONS
IMPROVE. WEAK COASTAL LOW PRESSURE TROUGH IS PROVIDING A LIGHT
NORTHERLY FLOW WEST OF THE COAST TODAY. A MORE NORTHEAST FLOW IS
EXPECTED OVERNIGHT.

&&

.PREV DISCUSSION... /ISSUED 635 AM CDT SUN SEP 21 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...PATCHY FOG MAY CAUSE MODEST VISIBILITY RESTRICTIONS IN
THE EARLY MORNING HOURS BEFORE OPENING UP TO PREVAILING VFR FOR THE
REST OF THE DAY. SPOTTY SHOWERS AND A THUNDERSTORM WILL LIKELY
PERSIST UNTIL AROUND 18 TO 20Z WHEN DRIER MID LEVEL NORTHEASTERLIES
SHOULD GREATLY REDUCE COVERAGE. MOSTLY CLEAR SKIES AND PREVAILING
VFR FORECAST OVERNIGHT AS WELL.

PREV DISCUSSION... /ISSUED 428 AM CDT SUN SEP 21 2014/

SHORT TERM /NOW THROUGH MONDAY/...AREA REMAINS IN DEEP AND RICH
COLUMN MOISTURE PER OBS AND SATELLITE ESTIMATES. UPPER LEVEL
TROUGH OVER THE CENTRAL PLAINS WILL BEGIN CHANGING THAT LATE THIS
AFTERNOON. ISOLATED TO SCATTERED SHOWERS CONTINUE THROUGH THE
EARLY MORNING HOURS AND EXPECT SUNRISE WILL SPARK A NEW ROUND OF
SHOWERS AND STORMS.

TODAY...BEST RAIN CHANCES WILL BE DURING THE MORNING HOURS AND SHIFT
TO THE WEST AND SOUTHWESTERN PORTIONS OF THE CWA THROUGH THE DAY.
KEPT AT LEAST SOME CHANCE IN EVERYWHERE BUT KEPT THE 30S AND 40S
CONFINED MORE TO THE AREA WEST OF HIGHWAY 281. BY 3 TO 4 PM MUCH
DRIER 850-700MB AIR AND UPPER CONVERGENCE SHOULD RESULT IN A
NOTICEABLE DROPOFF IN COVERAGE AND INTENSITY. THIS SHOULD ALSO
REDUCE CLOUD COVER IN THE LATE AFTERNOON.

TONIGHT...LINGERED A SLIGHT CHANCE OF SHOWERS ALONG THE RIVER WEST
OF THE VALLEY TONIGHT FOR ANY LINGERING/MEANDERING SIERRA MADRE
INITIATED CONVECTION BUT THE VALLEY SHOULD BE DRY WITH UPPER
CONVERGENCE AND DRY MID TO LOWER LEVELS.

MONDAY...WITH UPPER CONVERGENCE AND NORTHEASTERLY AND DRY 850-700MB
FLOW CONTINUING KEPT THE RAIN CHANCES OUT OF THE FORECAST MONDAY
AMID MODEST EASTERLY LOW LEVEL WINDS. A WARM AND MOSTLY SUNNY DAY IS
FORECAST.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...NEXT WEEK 500 MB
TROFFING WILL DIG DOWN OVER THE EASTERN AND SOUTH EASTERN STATES
WITH A POTENTIAL CLOSED LOW CUTTING OFF OVER THE SOUTHEASTERN
STATES ON OR AFTER TUESDAY. THIS CUT OFF LOW WILL REMAIN FAIRLY
STATIONARY OVER THE SOUTHEASTERN STATES THROUGHOUT MUCH OF NEXT
WEEK WITH ANOTHER 500 MB TROUGH AXIS DIGGING ACROSS THE CENTRAL
PLAINS STATES THURS WHICH WILL LIKELY PULL THIS CUT OFF LOW
FURTHER NORTH. MSL FIELDS OVER THE GULF COAST AND THE GULF OF MEX
INDICATES THAT AN OLD FRONTAL BOUNDARY WILL REMAIN STATIONARY NEAR
OR OVER THE GULF OF MEX THROUGHOUT MUCH OF NEXT WEEK. TO THE NORTH
OF THIS BOUNDARY MORE LIMITED MOISTURE VALUES ARE EVIDENT WHILE TO
THE SOUTH OF THIS BOUNDARY DEEPER LAYER TROPICAL MOISTURE REMAINS
POOLED OVER MUCH OF THE SOUTHERN GULF OF MEX AND CENTRAL AND
SOUTHERN MEXICO.

BOTH THE ECMWF AND GFS MODELS MAINTAIN SOME OVERALL POPS FOR THE
RGV DUE TO THE CLOSE PROXIMITY OF THE OLD FRONTAL BOUNDARY AND THE
DEEPER LAYER MOISTURE. THE GFS IS A BIT WETTER THAN THE ECMWF
SINCE THE GFS MAINTAINS A BIT MORE OF AN SIGNAL FOR SOME TYPE OF
COASTAL SURFACE TROFFING NEAR THE LOWER TX COASTLINE IN THE LONGER
TERM VERSUS THE ECMWF. ACCORDINGLY HAVE OPTED FOR A BLEND OF THE
TWO MODEL SETS FOR POPS THROUGH DAY 7.

SINCE CAA WILL BE FAIRLY WEAK OR NON EXISTENT IN THE LONGER TERM
PERIOD AND EXPECT FAIRLY ABUNDANT CLD COVER DUE TO THE HIGHER
MOISTURE VALUES OVER THE GULF...EXPECT OVERALL TEMP TRENDS TO BE
FAIRLY STATIC WITH NO DRASTIC SWINGS NEXT WEEK. SO WENT WITH A
GENERAL BLEND OF THE ECMWF AND MEX MOS HIGH AND LOW TEMPS.

OVERALL CONFIDENCE IN THE FORECAST IS ONLY AVERAGE TODAY DUE TO
DIFFERENCES IN THE HANDLING OF THE DEEPER LAYER MOISTURE FIELDS
OVER THE GULF IN THE GFS AND ECMWF. ALSO LARGER DIFFERENCES START
SHOWING UP BETWEEN THE GFS AND THE ECMWF IN THE 500 MB FIELDS ON
AND AFTER THURS.

MARINE...NOW THROUGH MONDAY...MODERATE EAST WINDS ARE FORECAST
THROUGH THE PERIOD. WIND SPEEDS MAY APPROACH EXERCISE CAUTION LEVELS
ON MONDAY. LOW SEAS WILL BECOME MORE MODERATE ON MONDAY.

MONDAY NIGHT THROUGH THURSDAY...BROAD SURFACE RIDGING OVER THE
EASTERN STATES WILL INTERACT WITH AN STATIONARY FRONT IN THE GULF
OF MEX TO MAINTAIN A LIGHT TO MODERATE E-NE SURFACE FLOW ALONG THE
LOWER TX COASTLINE. THIS WILL KEEP BOTH THE BAY AND GULF SEAS MORE
CHOPPY THAN USUAL. HOWEVER NO SCA CONDITIONS EXPECTED THROUGH
THURS.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  90  79  90  78 /  30  10  10  20
BROWNSVILLE          90  78  91  75 /  40  10  10  20
HARLINGEN            91  77  92  75 /  40  10  10  20
MCALLEN              91  77  92  75 /  40  10  10  20
RIO GRANDE CITY      91  77  93  74 /  40  20  10  20
SOUTH PADRE ISLAND   89  81  88  79 /  30  10  10  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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