Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 282350 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
550 PM CST FRI NOV 28 2014

.DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW. /53/

&&

.AVIATION...
PRIMARY AVIATION CONCERNS FOR THE 29/0000 UTC TAF PACKAGE
CONTINUE TO INVOLVE OVERNIGHT LOW CIGS/VSBY RESTRICTIONS...AND
GUSTY WINDS SATURDAY.

BOUNDARY LAYER WINDS ARE EXPECTED TO INCREASE ACROSS THE REGION THIS
EVENING AS A MID-LEVEL DISTURBANCE APPROACHES FROM THE W. S WINDS AT
925MB/850MB SHOULD APPROACH 30-40 KTS BETWEEN 29/0600-0900 UTC.
THESE TRAJECTORIES SHOULD BRING A PLUME OF LOW-LEVEL GULF MOISTURE
ALONG THE MX COAST AND INTO S TX OVERNIGHT.  BOUNDARY LAYER MOISTURE
SHOULD BE DEEPEST AT TERMINALS BETWEEN THE US-281 AND IH-69E/US-77
CORRIDORS.

MY INITIAL THOUGHTS ARE FAIRLY CONSISTENT WITH THE ONGOING FORECAST.
MECHANICAL MIXING IN THIS LAYER (AND JUST ABOVE A FORECAST SHALLOW
THERMAL INVERSION) SHOULD LARGELY INHIBIT THE DEVELOPMENT OF
FG...AND INSTEAD ALLOW FLIGHT CATEGORIES TO BE REDUCED (PRIMARILY)
DUE TO LOW CIGS. WILL MAINTAIN THE ONGOING TREND IN THE TAFS FOR
NOW AND WAIT FOR THIS EVENING`S KBRO SOUNDING TO SEE HOW THINGS
ARE EVOLVING.

THE LOW CIGS/VSBYS SHOULD CONTINUE THROUGH 29/1500 UTC OR SO...WHEN
MECHANICAL MIXING AIDS IN IMPROVING FLIGHT CATEGORIES. THIS
SHOULD ALSO RESULT IN STRONG/GUSTY SE WINDS THROUGH 30/0000 UTC.
GUSTS BETWEEN 25 AND 30 KTS WILL BE POSSIBLE THROUGH MUCH OF
SATURDAY. /53/

&&

.PREV DISCUSSION... /ISSUED 311 PM CST FRI NOV 28 2014/

SHORT TERM /NOW THROUGH SATURDAY NIGHT/...MAIN IMPACTS IN THE SHORT
TERM WILL BE FOG POTENTIAL OVERNIGHT AND BREEZY CONDITIONS ON
SATURDAY...

SHORTWAVE TROUGH ACROSS THE BAJA MEXICO REGION WILL MOVE EASTWARD
INTO NORTHERN MEXICO SATURDAY WHICH WILL HELP STRENGTHEN LEE
TROUGHING TO OUR WEST AND WITH HIGH PRESSURE RIDGING ACROSS THE AREA
INTO THE GULF OF MEXICO...SFC AND LOW LEVEL WINDS WILL STRENGTHEN
OVERNIGHT INTO SATURDAY. LOW LEVEL JET WILL FORM AFTER SUNSET
REACHING 35 KNOTS AROUND 2K FEET. THIS WILL HELP DRAW UP LOW LEVEL
MOISTURE AND MAY ACTUALLY HINDER FOG FORMATION. HOWEVER THE NAM IS
HINTING AT A STRONG INVERSION ACROSS THE AREA WITH WINDS AT THE SFC
LESS THAN 6 KNOTS IN PARTS OF THE AREA. BELIEVE PATCHY FOG IS
POSSIBLE IN MOST FOG PRONE AREAS /MAINLY NORTH OF THE VALLEY AND
ACROSS LARGE GRASSY AREAS/ BUT DO NOT BELIEVE WIDESPREAD OR DENSE
FOG WILL BE LIKELY DUE TO TURBULENCE AROUND THE INVERSION LAYER.

AS WE HEAD INTO SATURDAY...CLOUDS AND PATCHY FOG SHOULD BEGIN TO
BREAK BY MID MORNING ALLOWING THE LOW LEVEL WINDS TO MIX TO THE
SURFACE. BREEZY CONDITIONS SHOULD BEGIN AFTER 9AM WITH GUSTS 25-30
MPH POSSIBLE IN THE LATE MORNING AND AFTERNOON HOURS...THE STRONGER
OF THE WINDS WILL BE CLOSER TO THE COAST AND COASTAL WATERS. HIGHS
WILL BE A DEGREE OR TWO WARMER WITH MIXING AND WARM AIR
ADVECTION...REACHING CLOSE TO 80 ACROSS THE MAJORITY OF THE AREA.

BY SATURDAY NIGHT THE MID LEVEL DISTURBANCE WILL BE CROSSING THE
TEXAS BIG BEND LATER IN THE NIGHT. SURFACE WINDS WILL DECREASE AFTER
SUNSET AS THE NOCTURNAL INVERSION SETS UP BUT SHOULD REMAIN ELEVATED
ACROSS THE COAST AND PERHAPS AROUND THE LAGUNA MADRE. LOW LEVEL JET
SETS UP AGAIN AND SURFACE WINDS ARE A LITTLE HIGHER OVERNIGHT AS
COMPARED TO TONIGHT SO NO BIG CONCERNS FOR FOG. SKIES WILL BECOME
MOSTLY CLOUDY OVERNIGHT AND WILL HOLD SILENT POPS ACROSS THE COASTAL
COUNTIES AND COASTAL WATERS AS A FEW STREAMER SHOWERS MAY DEVELOP
AND IMPACT THE COASTAL WATERS. WITH WARM AIR ADVECTION AND EXPECTED
CLOUD COVER...LOWS WILL JUST FALL TO THE LOWER/MIDDLE 60S. /55/

LONG TERM /SUNDAY THROUGH FRIDAY/...THE BROAD 500 MB FLOW PATTERN
WILL BE TRANSITIONING FROM A SOMEWHAT ZONAL PATTERN ON SUNDAY TO A
BROAD RIDGING PATTERN MON AND TUES WITH THE RIDGING STARTING TO
SHIFT EAST AND FLATTENING OUT SOMEWHAT THURS AND FRI. 500 MB
TROFFING WILL BE DIGGING ACROSS THE UPPER MIDWEST AND THE
GREAT LAKES REGIONS ON MON WHICH WILL PUSH A COLD FRONT THROUGH
DEEP SOUTH TX LATE MON AFTERNOON AND EVENING. ANY CAA IN THE WAKE
OF THIS FRONT WILL BE PRETTY SHORT LIVED WITH THE SURFACE FLOW
SHIFTING AROUND FROM THE E-SE WED NIGHT AS THE SURFACE HIGH SHIFTS
FURTHER EAST. WAA WILL THEN PERSIST OVER THE REGION THURS AND FRI
AS THE SURFACE RIDGE REMAINS POSITIONED FURTHER EAST. THE FAIRLY
FAST MID LEVEL FLOW WILL LIKELY KEEP ANY DECENT MOISTURE ADVECTION
PRETTY LIMITED THROUGHOUT THE UPCOMING LONGER RANGE PERIOD. SO
WILL LIKELY MAINTAIN SOME MENTION OF 20 TO 30 % POPS MAINLY OVER
THE MARINE AND COASTAL REGIONS THROUGH THURS. SIGNIFICANT RAINFALL
IS NOT EXPECTED OVER THE LONGER RANGE PERIOD. PRETTY LOW QPF
AMOUNTS ARE EXPECTED.

WITH SOME FORM OF WEAK TO MODERATE 500 MB RIDGING PREVAILING FOR
MUCH OF THE LONGER TERM PERIOD EXPECT OVERALL TEMP TRENDS TO
REMAIN NEAR OR ABOVE CLIMO FOR LATE NOV FOR THE MOST PART. THE
EXCEPTION DURING THE LONGER TERM PERIOD WILL BE TUES AFTER THE
FROPA WHEN TEMPS WILL BE BELOW CLIMO. WILL GO WITH A GENERAL BLEND
OF THE GFS/ECMWF FOR LONG TERM TEMPS. RUN TO RUN CONSISTENCY WITH
THE GFS MEX MOS WILL IS PRETTY STABLE OVER THE LAST SEVERAL RUNS
BOTH FOR TEMPS AND POPS. THE LATEST ECMWF RUN IS IN PRETTY GOOD
AGREEMENT WITH THE GFS 500 MB FIELDS UP THROUGH AROUND WED. THE
AGREEMENT IN THE 500 MB PATTERN THEN BECOMES MORE HAZY FOR THURS
AND FRI. OVERAL CONFIDENCE IN THE LONGER RANGE FORECAST WORDING IS
GENERALLY ABOVE AVERAGE DESPITE THE WIDER MODEL DISAGREEMENT LATER
NEXT WEEK. /60/

MARINE /NOW THROUGH SATURDAY NIGHT/...HIGH PRESSURE WILL SETTLE OVER
THE NORTHWEST AND NORTH GULF THE NEXT COUPLE OF DAYS AS LOWER
PRESSURE DEVELOPS OVER THE CENTRAL PLAINS WITH LEE TROUGHING
STRETCHING INTO NORTHERN MEXICO. THE RESULT WILL BE SOUTH
SOUTHEAST WINDS STRENGTHENING FROM LIGHT TO BREEZY. SMALL CRAFT
EXERCISE CAUTION CONDITIONS WILL BE POSSIBLE ON THE GULF
TONIGHT... WITH POSSIBLE LOW END SMALL CRAFT ADVISORY CONDITIONS
ON THE BAY AND ON THE GULF SATURDAY. AS STRONGER WINDS DEVELOP...A
FEW COASTAL SHOWERS MAY DEVELOP AND MOVE NORTH ALONG THE COAST
SATURDAY NIGHT WITH SMALL CRAFT ADVISORIES POSSIBLE SATURDAY NIGHT
AS WELL. /55/

SUNDAY THROUGH WEDNESDAY...THE PGF MAY BE STRONG ENOUGH SUN AND
SUN NIGHT TO RESULT IN NEAR SCA CONDITIONS DUE TO STRONG SE MARINE
WINDS. THE PGF WILL THEN WEAKEN MON WITH THE APPROACH OF THE COLD
FRONT FROM THE NORTH. THEN CONDITIONS WILL LIKELY DEGRADE ONCE
AGAIN MON NIGHT INTO TUESDAY MORNING IN THE WAKE OF THE FROPA AS
STRONGER N-NE WINDS BUILD OVER THE GULF WATERS. SCA CONDITIONS MAY
BE POSSIBLE BRIEFLY LATE MON NIGHT/EARLY TUES MORNING BUT SCEC
CONDITIONS MAY BE MORE LIKELY. THE PGS THEN WEAKENS ONCE AGAIN
TUES NIGHT INTO WED ALLOWING FOR CALMER MARINE CONDITIONS TOWARDS
THE END OF THE CWF PERIOD. /60/

&&

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

$$

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

SHORT TERM... BUTTS
LONG TERM... TOMASELLI
PSU/GRAPHICAST... MARTINEZ





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