Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 212339 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
539 PM CST SUN DEC 21 2014

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

&&

.AVIATION...WITH WEAK HIGH PRESSURE IN THE REGION...WIND FLOW AT
THE SFC WILL REMAIN LIGHT AND VARIABLE TONIGHT. CIGS CONTINUE TO
FLUCTUATE BETWEEN 1000 AND 2000 FEET...WITH BRIEF THINNING AT KMFE
DUE TO A PASSING MIDLEVEL CLOUD DECK. CIGS ARE FORECAST TO LOWER
SLIGHTLY OVERNIGHT BACK DOWN TO AROUND 700 FEET...WITH SOME LIGHT
BR DEVELOPING AFTER MIDNIGHT. ON MONDAY...LLVL WINDS ARE FORECAST
TO SHIFT TO THE SOUTHWEST AROUND 10KTS IN THE MORNING. THIS WILL
BRING A QUICKLY DRYING ATMOSPHERE TO SOUTH TEXAS...WHICH WILL HELP
TO QUICKLY THIN OUT CLOUD COVER BY MIDMORNING.

&&

.PREV DISCUSSION... /ISSUED 252 PM CST SUN DEC 21 2014/

SHORT TERM /NOW THROUGH MONDAY NIGHT...LATEST WATER VAPOR IMAGERY
SHOWS THE MID LEVEL TROUGH AXIS MOVING ACROSS THE BIG BEND REGION.
RIGHT REAR QUAD JET DYNAMICS...MOISTURE ASSOCIATED WITH A
SOUTHWEST FLOW ALOFT AND A WEAK COASTAL TROUGH CONTINUES TO
PROVIDE CLOUDY SKIES ACROSS DEEP SOUTH TEXAS THIS AFTERNOON.
BROWNSVILLE RADAR CURRENTLY INDICATES AREAS OF LIGHT RAIN AND
DRIZZLE CONTINUES ACROSS WILLACY AND CAMERON COUNTIES EXTENDING
INTO THE LOWER TEXAS COASTAL WATERS. THE INCREASE IN CLOUD COVER
WILL KEEP TEMPERATURES IN THE 60S THROUGH THE REST OF THE THIS
AFTERNOON.

RAIN CHANCES BEGIN TO DECREASE THIS EVENING AS THE MID LEVEL TROUGH
SWINGS THROUGH THE AREA LATER TONIGHT. LIGHT NORTH TO NORTHEAST
WINDS WILL GRADUALLY VEER TO SOUTH LATER TONIGHT. ATMOSPHERIC
PROFILES INDICATE THAT DRIER AIR IN THE MID LEVELS WILL FILTER INTO
THE REGION...ESPECIALLY ACROSS THE WESTERN COUNTIES. LOW LEVEL
MOISTURE NEAR THE SURFACE...DRIER AIR ALOFT AND LIGHT WINDS WILL
SUPPORT THE DEVELOPMENT OF FOG LATER TONIGHT. WILL MENTION PATCHY
FOG TONIGHT WITH AREAS OF FOG DEVELOPING ALONG AND WEST OF I-69C/US
HWY 281 DUE TO PARTIAL CLEARING AND BETTER RADIATIONAL COOLING.
OTHERWISE...EXPECT PARTLY CLOUDY TO MOSTLY CLOUDY SKIES TONIGHT WITH
LOW TEMPERATURES GENERALLY RANGING FROM 55 TO 60 DEGREES.

FOG WILL LIFT BY MID MORNING AS SOUTH TO SOUTHWEST INCREASE AND MID
LEVEL DRIER AIR MIXING DOWN TO THE SURFACE. PARTLY CLOUDY SKIES CAN
BE EXPECTED BY MONDAY AFTERNOON WITH HIGH TEMPERATURES SEVERAL
DEGREES ABOVE NORMAL...IN THE UPPER 70S TO AROUND 80 DEGREES. A
STRONG COLD FRONT ACROSS CENTRAL TEXAS MONDAY EVENING WILL SURGE
SOUTHWARD MONDAY NIGHT. PATCHY FOG WILL BE POSSIBLE ACROSS THE AREA
AGAIN MONDAY NIGHT AS WINDS BECOME LIGHT AHEAD OF THE APPROACHING
FRONT. OVERNIGHT LOW TEMPERATURES WILL RANGE FROM THE UPPER 50S
ACROSS THE RANCHLANDS TO THE MID 60S ALONG THE COAST. THE STRONG
COLD FRONT IS EXPECTED TO REMAIN NORTH OF THE DEEP SOUTH TEXAS
THROUGH THE SHORT TERM FORECAST PERIOD.

LONG TERM /TUESDAY THROUGH SUNDAY/...THE TRANSITION TO A MORE
PROGRESSIVE 500MB FLOW AS WE MOVE INTO WINTER TO RESULT IN TWO
FRONTAL PASSAGES IN THE SHORT TERM. MODEL GUIDANCE IS IN FAIR
AGREEMENT WITH TIMING AND SENSIBLE WEATHER ASPECTS SO LITTLE
CHANGE IN THE FORECAST WAS CHANGED.

THE FIRST FRONT MAKES ITS MARK ON THE AREA TUESDAY AS A SHARP MID
LEVEL TROUGH DEVELOPS OVER THE CENTRAL AND SOUTHERN PLAINS. STRONG
SHORTWAVE TROUGH MOVING RAPIDLY SOUTHEAST THROUGH THE ROCKIES TO
COMBINE WITH THE SUBTROPICAL JET INDUCING SURFACE CYCLOGENESIS IN
THE WESTERN GULF. AS THE PREVIOUS SHIFT MENTIONED A TIGHT PRESSURE
GRADIENT SETS UP BETWEEN THE SURFACE LOW AND HIGH PRESSURE DIVING
INTO THE SOUTHERN PLAINS. THE FRONT SURGES SOUTH INTO THE NORTHERN
RANCHLANDS SHORTLY AFTER SUNRISE AND RACES SOUTH MOVING OFF THE
LOWER COAST BEFORE NOON. THE MAIN FEATURE WITH THIS FRONT WILL BE
THE WINDS. BOTH THE 12Z ECMWF AND GFS ARE ADVERTISING 35-45 KNOTS
WINDS AT THE 925-850MB LEVEL. WINDS ADVISORY CRITERIA...SUSTAINED
WINDS 30+MPH G40+...LOOKS TO BE REACHED FOR AT LEAST A FEW HOURS
TUESDAY AFTERNOON HOURS AS THESE WINDS TRANSLATE TO THE SURFACE. ANY
YARD DECORATIONS WILL NEED TO BE SECURED BY MONDAY NIGHT TO PROTECT
THEM FROM BLOWING THROUGH THE NEIGHBORHOOD. THE COLD AIR ADVECTION
WILL BE STOUT BUT WITH THE SOURCE REGION NOT FROM CANADA DO NOT
EXPECT ANYTHING EXTREME. 850MB TEMPS DO HOWEVER DROP BETWEEN 0-4C BY
WED AM SO I DO ANTICIPATE TEMPERATURES TO FALL THROUGH THE AFTERNOON
AFTER REACHING LOW TO UPPER 70S PRIOR TO THE FRONT MOVING THROUGH.
ANY RESIDUAL CLOUDS AND COASTAL SHOWERS WILL BE QUICKLY WHISKED AWAY
TO THE EAST AS DRY AIR INFILTRATES THE REGION LEAVING MOSTLY CLEAR
SKIES BY SUNSET TUESDAY.

TUESDAY NIGHT AND WEDNESDAY...HIGH PRESSURE WORKS ITS WAY INTO THE
RGV WITH A DRY AND CHILLY AIRMASS SETTLING IN. CLEAR SKIES AND DRY
AIR ALONG WITH DIMINISHING WINDS TO ALLOW TEMPS TO FALL INTO LOW TO
MID 40S WHICH WILL MAKE IT THE COOLEST NIGHT IN DECEMBER. LOW 850MB
TEMPERATURES OF 0-2C TO KEEP TEMPERATURES SLIGHTLY BELOW NORMAL
CHRISTMAS EVE DAY EVEN WITH FULL SUNSHINE. LIGHT TO MODERATE NORTH
WINDS WILL MAKE THE LAST DAY OF SHOPPING QUITE COMFORTABLE.

CHRISTMAS EVE AND CHRISTMAS DAY...ANOTHER CHILLY NIGHT IS IN STORE
AS SURFACE HIGH PRESSURE TO REMAINS OVERHEAD. CLEAR, CALM AND DRY
TO TRANSLATE INTO AN EXCELLENT RADIATIONAL COOLING EVENT WITH
MINIMUMS LOWERING ANOTHER 2 TO 4 DEGREE OVER WEDNESDAY AM. HIGH
PRESSURE DOES SHIFT EAST CHRISTMAS AND WINDS RETURN TO THE SOUTHEAST
HOWEVER WARM AIR ADVECTION WILL BE SLOW TO DEVELOP AND ALL GUIDANCE
HAS RESORTED TO A SLOWER INCREASE TEMPERATURES RECOVERING TO NEAR
SEASONAL NORMALS OF UPPER 60S TO NEAR 70.

FRIDAY THROUGH SUNDAY...TEMPERATURES CONTINUE TO RECOVER FRIDAY AS
SOUTHEAST WINDS INCREASE WITH THE SURFACE RIDGE EXTENDING ACROSS THE
GULF AND THE NEXT UPPER TROUGH DEVELOPING UPSTREAM OVER THE
NORTHWEST STATES. BROAD UPPER TROUGH STRENGTHENS NEXT WEEKEND WITH
THE NEXT FRONT PUNCHING THROUGH DEPP SOUTH TEXAS SATURDAY. BOTH EC
AND GFS ARE IN GOOD AGREEMENT WITH AN EARLY SATURDAY MORNING
PASSAGE. ONLY SLIGHT MOISTURE RECOVERY INDICATED WITH BEST MOISTURE
HUGGING THE COASTAL REGIONS. WILL KEEP RAIN CHANCES MINIMAL ALONG
THE COAST AT THIS TIME. HIGH PRESSURE IS A BIT STRONGER WITH THIS
THIS FRONT AROUND 1035MB AND 1000-500MB THICKNESSES ARE RATHER LOW
SO WILL MAINTAIN PREVIOUS FORECASTERS TEMPERATURES WHICH MATCH UP
PRETTY WELL WITH THE LATEST GUIDANCE.

MARINE...NOW THROUGH MONDAY NIGHT... LATEST MARINE OBSERVATIONS
INDICATE EAST-NORTHEAST WINDS AROUND 12 KNOTS ACROSS THE LOWER
TEXAS COASTAL WATERS WITH SEAS NEAR 4 FEET AT BUOY 42020. A WEAK
GRADIENT WILL MAINTAIN LIGHT EAST TO NORTHEAST WINDS AND LOW TO
MODERATE SEAS THROUGH THIS EVENING. STRENGTHENING LOW PRESSURE
ACROSS THE PLAIN STATES WILL ALLOW WINDS TO BECOME SOUTHEAST LATER
TONIGHT AND SOUTH ON MONDAY. WINDS WILL ALSO BECOME MODERATE
MONDAY AFTERNOON INTO MONDAY NIGHT AHEAD OF A STRONG COLD FRONT.
THE STRONG FRONT IS EXPECTED TO REMAIN NORTH OF THE LOWER TEXAS
COASTAL WATERS THROUGH THE FORECAST PERIOD.

TUESDAY THROUGH FRIDAY. STRONG SHARP COLD FRONT IS EXPECTED
TUESDAY BEFORE NOON. SURGING NORTH WINDS TO REACH GALE FORCE FOR A
FEW HOURS TUESDAY AFTERNOON WITH GALE FORCE GUSTS LIKELY INTO THE
EARLY EVENING HOURS OFFSHORE. SEAS TO RESPOND RAPIDLY EXCEEDING 10
FEET BEFORE SUNSET TUESDAY. NORTH TO NORTHWEST WINDS TO SLOWLY
DIMINISH TUESDAY NIGHT BUT REMAINING AT SCA LEVELS THROUGH AT
LEAST WEDNESDAY MORNING AS HIGH PRESSURE REMAINS JUST NORTH OF THE
COASTAL WATERS. WINDS DO TAPPER OFF WEDNESDAY PM AND BECOME LIGHT
WED NIGHT. SOUTHEAST WINDS RETURN FOR CHRISTMAS DAY AS THE SURFACE
RIDGE SHIFTS EAST. NEXT FRONT IS SCHEDULED FOR SATURDAY AND IS
EXPECTED TO BE WEAKER THEN TUESDAYS FRONT.

&&

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

$$

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

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