Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 060510 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1110 PM CST FRI FEB 5 2016

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

&&

.AVIATION...LOW LEVEL MOISTURE IS ERODING OVER THE UPPER VALLEY
AND CLOUDS MAY CLEAR ALL AIRPORTS BEFORE 9Z. THIS MAY ALLOW FOR
SOME FOG FORMATION HOWEVER HIGH PRESSURE IS BRIDGING A COLD FRONT
MOVING THROUGH THE WESTERN HILL COUNTRY AND THIS MAY KEEP THE
TEMPERATURE DEW POINT DEPRESSION SPREAD WIDE AS DRIER AIR FILTERS
INTO THE REGION. IN ANYCASE, VFR SHOULD PREVAIL WITH ONLY TEMPO
MVFR FOR VSBY IF FOG DEVELOPS. ONCE THE FRONT MOVES THROUGH AROUND
SUNRISE NORTHWEST WINDS INCREASE WITH GUSTS OF 20-25 KNOTS THIS
AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 529 PM CST FRI FEB 5 2016/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...A PLUME OF LOW LEVEL MOISTURE HAS THICKENED OVER SOUTH
TEXAS. EXPECT CEILINGS TO DECREASE THIS EVENING AS WINDS DIMINISH
AND THE BOUNDARY LAYER SATURATES. CEILINGS MAY BRIEFLY DIP INTO
MVFR TERRITORY LATE IN THE EVENING TO AFTER MIDNIGHT. PATCHY LIGHT
FOG WILL ALSO BE POSSIBLE IN THIS LIGHT WIND ENVIRONMENT. MODERATE
TO FRESH NORTHWEST WINDS WILL DEVELOP BY MID MORNING HOWEVER AS A
COLD FRONT ARRIVES AND IS BACKED UP BY SURFACE HIGH PRESSURE AND A
SHARP DROP IN DEW POINTS. THE TEMP/DEW POINT SPREAD WILL INCREASE
AND SKIES WILL OPEN UP THROUGH THE DAY. GUIDANCE SUPPORTS LITTLE
IMPACT TO AVIATION INTERESTS OVERALL...HOWEVER.

PREV DISCUSSION... /ISSUED 250 PM CST FRI FEB 5 2016/

SHORT TERM /NOW THROUGH SATURDAY NIGHT/...THE 500 MB SHORT WAVE
OVER THE EASTERN ROCKIES WILL DIVE FURTHER SOUTHEAST TODAY AND
TONIGHT. THIS TROUGH WILL MOVE EAST PRETTY QUICKLY MOVING OVER THE
LOWER MISS RIVER VALLEY DURING THE DAY TOMORROW. THIS WILL PULL A
COLD FRONT THROUGH THE RGV LATE TONIGHT THROUGH AROUND SUNRISE SAT.
OVERALL MOISTURE VALUES WITH THIS 500 MB TROUGH AND COLD FRONT
REMAIN PRETTY LIMITED. WILL MAINTAIN ONLY SOME SLGT CHC POPS NEAR
THE COASTLINE EXTENDING OUT INTO THE LOWER TX GULF WATERS. THE CAA
IN THE WAKE OF THIS FRONT WILL BE PRETTY DECENT. HOWEVER DAYTIME
HEATING TOMORROW WILL HELP MODERATE THE AFTERNOON HIGHS BACK UP INTO
THE 70S. THE STRONG N-NW LOW LEVEL FLOW WILL THEN WEAKEN QUICKLY
TOMORROW EVENING INTO SAT NIGHT WHICH WILL ALLOW FOR MUCH BETTER
RADIATIONAL COOLING CONDITIONS TO KICK IN THEN.

THE MET AND MAV GUIDANCE ARE COMING IN THE COOLEST AND WETTEST OF
THE THREE SHORT TERM MODEL SETS WHILE THE ECMWF IS THE DRIEST AND
WARMEST. WILL LEAN A LITTLE CLOSER TO THE DRIER AND WARMER ECMWF
NUMBERS AS AM A BIT SCEPTICAL OF THE PCPN POTENTIAL FOR ANY
INLAND SITES IN THE RGV.

SOME PATCHY FOG WILL BE POSSIBLE TONIGHT AHEAD OF THE FRONT AS
ENOUGH LOW LEVEL MOISTURE MAY OCCUR IN COMBINATION WITH THE
LIGHTERLY SURFACE WINDS. THE SURFACE DEWPOINTS HAVE NOT HAD ENOUGH
TIME TO REBOUND TODAY SO DO NOT EXPECT ANY DENSE FOG.

LONG TERM /SUNDAY THROUGH FRIDAY/...INHERITED LONG TERM PORTION
WAS QUIET AND THAT TREND REMAINS SO FOR THIS FORECAST CYCLE. DEEP
SOUTH TEXAS AND THE RIO GRANDE VALLEY WILL BE CAUGHT BETWEEN DEEP
500 MB TROUGHINESS MOVING SLOWLY THROUGH THE EASTERN HALF OF THE
UNITED STATES...WITH 500 MB RIDGING GRADUALLY MOVING OFF THE COAST
OF CALIFORNIA AND INTO THE DESERT SOUTHWEST. PERSISTENT NORTHWEST
TO SOUTHEAST MID-LEVEL FLOW OVER THE BRO CWFA WILL ENSURE DRY
WEATHER THROUGHOUT THE ENTIRE FORECAST PERIOD...AIDED BY VERY DRY
AIR WITHIN THE REGION. ONLY EVENT IN THE LONG TERM FORECAST PERIOD
WORTH ANY CONCERN WILL BE MONDAY...WHEN A WEAK COLD FRONT PASSES
THROUGH THE BRO CWFA...REINFORCING THE DRY AIR ALREADY IN PLACE.
20-FOOT WINDS MAY INCREASE ENOUGH THAT WILDFIRE ACTIVITY MAY BE A
CONCERN ON THIS DAY...AND SUCCESSIVE SHIFTS WILL NEED TO WATCH FOR
THE POSSIBILITY OF A RED FLAG WARNING AT THIS TIME.

MARINE...NOW THROUGH SATURDAY NIGHT...SURFACE OBSERVATIONS AND
BUOY DATA INDICATE THAT A MODERATE SE FLOW CONTINUES ACROSS THE
LOWER TX BAY AND GULF WATERS THIS AFTERNOON. THE SURFACE FLOW WILL
DECOUPLE A BIT LATER TONIGHT AHEAD OF THE APPROACHING COLD FRONT.
THIS WILL ALLOW THE MARINE WINDS AND SEAS TO DECREASE SOME. AFTER
THE COLD FRONT CLEARS THE MARINE AREAS EARLY TOMORROW MORNING
EXPECT SCA CONDITIONS TO DEVELOP PRETTY QUICKLY ACROSS THE GULF
WATERS DURING THE DAY SAT. THE PGF OVER THE BAY WATERS WILL LIKELY
REMAIN JUST BELOW SCA LEVELS IN SCEC TERRITORY. THE SCA CONDITIONS
WILL BE PRETTY SHORT LIVED AS THE GRADIENT FLOW WILL WEAKEN PRETTY
QUICKLY SAT NIGHT ALLOWING THE WINDS AND SEAS TO DECREASE.

SUNDAY THROUGH FRIDAY...DESPITE THE PASSAGE OF A COLD FRONT
THROUGH THE LOWER TEXAS COASTAL WATERS ON MONDAY...SURFACE HIGH
PRESSURE WILL PREVAIL OVER THE WESTERN GULF OF MEXICO THROUGH A
MAJORITY OF THE LONG TERM FORECAST PERIOD. LIGHT TO MODERATE WINDS
AND LOW TO MODERATE SEAS ARE LIKELY...WITH SMALL CRAFT EXERCISE
CAUTION AND SMALL CRAFT ADVISORY NOT ANTICIPATED TO BE NEEDED.

FIRE WEATHER...THE EXPECTED RH VALUES FOR SAT AFTERNOON PLUMMET
INTO THE TEENS ACROSS THE WESTERN TWO THIRDS OF THE REGION IN THE
WAKE OF THE EARLY MORNING COLD FRONT. THE EXPECTED LOW LEVEL WINDS
TOMORROW AFTERNOON COULD PUSH INTO RED FLAG WARNING CRITERIA
ESPECIALLY ACROSS THE WESTERN PORTIONS OF THE REGION. WILL MAINTAIN
THE FIRE WEATHER WATCH IN PLACE FOR THE AFTERNOON FORECAST ISSUANCE.
A RED FLAG WARNING REMAINS A STRONG POSSIBILITY FOR AT LEAST A
PORTION OF THE RGV AND DEEP SOUTH TX TOMORROW AFTERNOON.

BRO WATCHES/WARNINGS/ADVISORIES...
TX...FIRE WEATHER WATCH FROM SATURDAY MORNING THROUGH SATURDAY
     EVENING FOR TXZ248>257.

GM...SMALL CRAFT ADVISORY FROM 8 AM TO 6 PM CST SATURDAY FOR GMZ150-
     155-170-175.

$$

THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT:
HTTP://WEATHER.GOV/RGV


&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  54  71  46  70 /  10  10   0   0
BROWNSVILLE          52  73  44  71 /  10  10   0   0
HARLINGEN            50  74  41  72 /  10  10   0   0
MCALLEN              50  74  42  74 /  10  10   0   0
RIO GRANDE CITY      48  72  38  75 /  10  10   0   0
SOUTH PADRE ISLAND   57  67  52  67 /  10  10   0   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...FIRE WEATHER WATCH FROM 11 AM CST SATURDAY THROUGH SATURDAY
     EVENING FOR TXZ248>257.

GM...SMALL CRAFT ADVISORY FROM 8 AM TO 6 PM CST SATURDAY FOR GMZ150-
     155-170-175.

&&

$$

THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT:
HTTP://WEATHER.GOV/RGV

54/59...AVIATION


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