Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 280505 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1105 PM CST THU NOV 27 2014

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

&&

.AVIATION...BRO ASOS AND VISUAL CONFIRMATION INDICATES THAT FOG
IS FORMING WITHIN PARTS OF THE RIO GRANDE VALLEY AND DEEP SOUTH
TEXAS...ESPECIALLY WITH DEWPOINT DEPRESSIONS DECREASING. ADDED
FORMATION A COUPLE OF HOURS FROM NOW BASED UPON THIS TREND...AND
INCREASED FOG DENSITY BASED UPON OBSERVATIONS FROM LAST NIGHT...
WHEN 1/2SM FG AND 1/4SM FG WAS OBSERVED FOR SEVERAL HOURS AT BRO
AND HRL. ADJUSTED TIMING AND INTENSITY FOR FOG AT MFE AS WELL...
WITH RESULTS NOT AS SEVERE AS BRO/HRL...WHERE LIFR CONDITIONS WILL
OCCUR IF THE DENSER FOG FORMATION PANS OUT. TOMORROW...VFR WILL
PREVAIL UNDER PARTLY CLOUDY SKIES AND MODERATE SURFACE WINDS.
WINDS AROUND 10 KNOTS TOMORROW NIGHT SHOULD PRECLUDE ANY FORMATION
OF FOG AND ALLOW VFR TO KEEP GOING THROUGH THE OVERNIGHT HOURS.

&&

.PREV DISCUSSION... /ISSUED 1012 PM CST THU NOV 27 2014/

DISCUSSION...ISSUED AN UPDATED FORECAST FOR TONIGHT/S LOW
TEMPERATURES ACROSS DEEP SOUTH TEXAS AND THE RIO GRANDE VALLEY.
SURFACE OBSERVATIONS ACROSS THE REGION INDICATED THAT DEWPOINT
TEMPERATURES WERE A COUPLE OF DEGREES HIGHER THAN THE EXPECTED
MINIMUMS FOR THE OVERNIGHT HOURS TONIGHT. THUS...INCREASED LOW
TEMPERATURES BY TWO DEGREES ACROSS THE ENTIRE BRO CWFA. ALSO...
BRO ASOS ALREADY HAS 1/4SM FG...AND WITH AMBIENT TEMPERATURES
HEADING TOWARDS THE DEWPOINT ACROSS THE MAJORITY OF THE CWFA...
STARTED THE FOG A LITTLE EARLIER IN THE FORECAST TONIGHT. WITH
WINDS BECOMING LIGHT TO CALM TONIGHT AND A RELATIVELY MOIST
ATMOSPHERE IN PLACE...INCOMING SHIFT MAY NEED TO WEIGH THE
POSSIBILITY OF A DENSE FOG ADVISORY FOR PORTIONS OF THE RIO
GRANDE VALLEY AND DEEP SOUTH TEXAS.

PREV DISCUSSION... /ISSUED 527 PM CST THU NOV 27 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...CUMULUS FIELD IS CLEARING FROM EAST TO WEST AND SHOULD
BE COMPLETELY GONE WITHIN THE NEXT HOUR OR SO. EXPECT WINDS TO BE
LIGHT OVERNIGHT...WHICH SHOULD ALLOW THE FORMATION OF LIGHT FOG
FOR A FEW HOURS NEAR SUNRISE FRIDAY MORNING. WINDS WILL INCREASE
TO MODERATE LEVELS TOMORROW UNDER PARTLY CLOUDY SKIES. OVERALL...
ONLY A FEW MINOR ADJUSTMENTS MADE TO THE PREVIOUS SET OF TAFS. PURE
VFR SHOULD PREVAIL THROUGH A MAJORITY OF THE NEXT 24 HOURS.

PREV DISCUSSION... /ISSUED 257 PM CST THU NOV 27 2014/

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...SURFACE RIDGING
OVER THE CENTRAL U.S. WILL STEADILY SHIFT EASTWARD ALLOWING FOR A
RETURN OF WAA OVER DEEP SOUTH TX THROUGHOUT THE SHORT TERM PERIOD.
THIS WILL ALLOW THE SURFACE DEWPOINTS TO ALSO START REBOUNDING AS
THE FLOW STARTS COMING OFF OF THE GULF OF MEX. THE RETURNING
MOISTURE WILL COMBINE WITH LIGHT SURFACE WINDS LATER TONIGHT TO
ALLOW THE POTENTIAL FOR SOME PATCHY FOG. THE 12Z BRO SOUNDING WAS
STILL VERY PARCHED THIS MORNING WITH A PWAT OF 0.46 INCHES. EVEN
WITH THE RETURNING SURFACE MOISTURE LEVELS DO NOT EXPECT ENOUGH
MOISTURE ADVECTION TO ALLOW MUCH OF A POTENTIAL FOR POPS OR EVEN
MUCH IN THE WAY OF CLD COVER.

THE MAV...MET AND ECMWF SHORT TERM TEMP GUIDANCE IS IN BETTER
AGREEMENT VERSUS YESTERDAYS RUNS. THE MAV IS NOT SHOWING THE COOL
BIAS THAT IT INDICATED YESTERDAY. SO WILL GO WITH A GENERAL BLEND OF
THE SHORT TERM TEMP GUIDANCE FOR HIGHS AND LOWS.

LONG TERM /SATURDAY THROUGH THURSDAY NIGHT/...FORECAST REMAINS
ON TRACK THIS WEEKEND AND INTO MONDAY WITH FEW CHANGES MADE DURING
THIS TIME FRAME. DIFFERENCES IN THE MODELS BEGIN TO CREEP IN TO
THE FORECAST TUESDAY THROUGH THURSDAY NIGHT WITH CONFIDENCE LOW
DURING THIS PORTION OF THE LONG TERM.

SFC HIGH PRESSURE WILL DOMINATE THIS WEEKEND WITH SOUTHEASTERLY
FLOW...MILD TEMPERATURES...AND INCREASING MOISTURE. IT WILL BE  A
LITTLE BREEZY SATURDAY WITH WINDS RELAXING FOR SUNDAY. A WEAK MID
LEVEL DISTURBANCE WILL TRACK ACROSS NORTHERN MEXICO AND ACROSS SOUTH
TEXAS SUNDAY. A FEW SHOWERS ARE POSSIBLE AHEAD OF THIS FEATURE
SUNDAY BUT SHOULD MOSTLY BE RELEGATED ACROSS THE COASTAL WATERS. A
WEAK FRONTAL BOUNDARY WILL REACH CENTRAL TEXAS MONDAY MORNING WITH
STREAMER SHOWERS POSSIBLE ACROSS THE COASTAL WATERS SUNDAY NIGHT
POSSIBLY MOVING INTO THE COASTAL COUNTIES MONDAY. AS THE FRONT SAGS
INTO SOUTH TEXAS...ENOUGH CONVERGENCE COULD SPARK A FEW SHOWERS
AHEAD OF THE FRONT AS WELL WHICH WILL ACCOMPANY THE FRONT INTO DEEP
SOUTH TEXAS TUESDAY.

FROM THIS POINT FORWARD THE FORECAST GETS A LITTLE MURKY. BOTH THE
GFS AND ECMWF MOS SHOW DECENT COOLING BEHIND THIS FRONT WITH HIGHS
DROPPING INTO THE UPPER 60S/LOWER 70S TUESDAY. THE ECMWF SHOWS A
REINFORCING SHOT OF COOLER AIR WEDNESDAY WHICH LASTS INTO THURSDAY
WHEREAS THE GFS SHOWS WARMING WITH EAST/SOUTHEAST WINDS RETURNING
WEDNESDAY/THURSDAY WITH HIGHS AROUND 10 DEGREES WARMER THAN THE
ECMWF. LOOKING AT THE MID LEVELS...GFS MAINTAINS SOUTHWESTERLY FLOW
DURING THIS TIME FRAME WITH A DISTURBANCE TO OUR WEST. ECMWF IS
TRENDING TOWARDS HIGHER HEIGHTS ACROSS OUR AREA BUT MAINTAINS
NORTHWESTERLY FLOW IMPLYING SOME COLD AIR ADVECTION. WILL EDGE
TOWARDS THE GFS DUE TO CONSISTENCY AND THE FACT THAT THE ECMWF MAY
BE TRENDING TOWARDS A INCREASING ZONAL FLOW IN LATER RUNS WITH LESS
COLD AIR ADVECTION. WILL SHOW A SLIGHT WARMING TREND WEDNESDAY AND
THURSDAY AND REMAIN IN THE MIDDLE OF THE FORECAST ENVELOPE KEEPING A
LITTLE MORE WEIGHT ON THE GFS SIDE.

MARINE /TONIGHT THROUGH FRIDAY NIGHT/...A GENERAL LIGHT TO
MODERATE ONSHORE FLOW WILL PREVAIL TONIGHT EVENTUALLY SHIFTING TO
THE SE ON FRI AND FRI NIGHT. THE PGF REMAINS FAIRLY WEAK UNTIL FRI
NIGHT WHEN THE GRADIENT MAY STRENGTHEN UP ENOUGH TO PUSH
CONDITIONS UP CLOSE TO SCEC CRIT.

SATURDAY THROUGH TUESDAY...WINDS SATURDAY AND SATURDAY
NIGHT WILL BE MODERATE TO STRONG AS A MID LEVEL DISTURBANCE
APPROACHES FROM THE WEST. EXERCISE CAUTION IS ALMOST CERTAIN DURING
THIS TIME PERIOD AND SMALL CRAFT ADVISORIES ARE CERTAINLY POSSIBLE.
THIS FEATURE WILL WEAKEN AND PASS BY SUNDAY WITH WINDS AND SEAS
RELAXING TO MODERATE LEVELS SUNDAY AND MONDAY. A WEAK COLD FRONT IS
EXPECTED TUESDAY MORNING WITH SOUTHEAST WINDS BECOMING NORTHEASTERLY
BEHIND THE FRONT AND A SLIGHT UPTICK IN WINDS AND SEAS BUT RIGHT NOW
LOOKS TO REMAIN BELOW EXERCISE CAUTION LEVELS.

&&

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

$$

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