Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 222051
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
251 PM CST MON DEC 22 2014

.SHORT TERM.../NOW THROUGH TUESDAY NIGHT...
EVERYTHING ON TAP FOR A POTENT COLD FRONT TUESDAY. UPPER TROUGH OVER
THE NORTH AND CENTRAL PLAINS TO DEEPEN AS A 170+ JET STREAKS
SOUTHEASTWARD OVER THE ROCKIES. CYCLOGENESIS TO BE INDUCED OVER THE
WESTERN GULF LATE TONIGHT INTO TUESDAY AS THE NORTHERN JET COMBINES
WITH A MODERATE SUBTROPICAL JET NOSING INTO THE SOUTHWEST GULF.
PRESSURE GRADIENT TO TIGHTEN RAPIDLY TUESDAY WITH STRONG NORTHWEST
WINDS DEVELOPING.

TONIGHT...SKIES HAVE CLEARED AS SOUTHWEST FLOW HAS INCREASED IN
ADVANCE OF THE UPPER TROUGH FEATURE. THE ASSOCIATED COLD FRONT HAS
MOVED INTO NORTHWEST TEXAS AND WILL CONTINUE TO MAKE STEADY
SOUTHWARD PROGRESS. WINDS TO SLACKEN OVERNIGHT WITH STRATUS AND FOG
TO DEVELOP BEFORE OR AFTER MIDNIGHT. LOW CONFIDENCE ON DENSE FOG
WITH BOUNDARY LAYER WINDS INDICATED TO REMAIN STRONG ENOUGH TO LIMIT
ANY MENTION OF FOG BELOW ONE QUARTER MILE. MARINE FOG DEVELOPED
BRIEFLY THIS MORNING AND MAY BE REPEATED SO PUSHED AREAS OF FOG OVER
THE BAY AND INTO THE NEAR SHORE WATERS WHERE SLIGHTLY COOLER WATER
TEMPERATURES RESIDE. LOWS OVERNIGHT WILL BE SLIGHTLY WARMER THEN
LAST FEW NIGHTS WITH MID TO UPPER 50S NORTHWEST TO MID 60S SOUTHEAST.

TUESDAY AND TUESDAY NIGHT...
IMPACT...STRONG WINDS IN WAKE OF POTENT COLD FRONT.

MODELS ARE IN GOOD AGREEMENT MOVING A SURFACE TROUGH THROUGH THE
REGION TUESDAY MORNING THEN SURGING THE COLD FRONT THROUGH THE
REGION EARLY TUESDAY AFTERNOON. PRESSURE GRADIENT STRENGTHENS
THROUGH THE DAY WITH THE STRONGEST WINDS ANTICIPATED LATER IN THE
AFTERNOON AND EVENING AS A BROAD 40-50KNOT JET MAX BETWEEN 925-850MB
MOVES OVERHEAD ON THE BACK SIDE OF A SHARP SHORT WAVELENGTH UPPER
TROUGH. DOWNWARD MOMENTUM TRANSFER UPWARDS OF 45 KNOTS INDICATED BY
LOCAL BUFKIT SOUNDINGS PLACES SOME CONFIDENCE OF POSSIBLE GUSTS NEAR
50 MPH. THE JET MAXIMUM HANGS AROUND OVERNIGHT AND EVEN WITH THE
SUSTAINED WINDS WEAKENING AROUND MIDNIGHT GUSTY PERIODS OF 30-40 MPH
ARE NOT OUT OF THE QUESTION OVERNIGHT. WIND ADVISORIES ARE LIKELY TO
BE ISSUED LATER THIS EVENING OR FIRST THING TUESDAY AND WILL LIKELY
COVER MUCH OF DEEP SOUTH TEXAS WITH THE MID AND LOWER RGV AND
COASTAL AREAS SEEING THE STRONGEST WINDS LAST THE LONGEST. AN SPS
WAS ISSUED EARLIER TO EMPHASIZE THE IMPACT OF THE STRONG WINDS.

AS FOR TEMPERATURES GO...VERY SHARP SLOPE WILL DRY OUT THE
ATMOSPHERE RAPIDLY AND ANY LOW CLOUDS AND FOG IN THE MORNING WILL
QUICKLY GET SHUNTED EASTWARD. INITIALLY DOWNSLOPING CONDITIONS
BEHIND THE SURFACE TROUGH WILL COMPRESS THE LOW LAYERS WHICH WILL
HEAT US UP 5 TO 10 DEGREES ABOVE NORMAL. ONCE THE FRONT PASSES A
STEADY COOL DOWN WILL COMMENCE AND CONTINUE THROUGH THE OVERNIGHT
HOURS. A BLEND BETWEEN THE NAM AND GFS LOOKS WITHIN THE BALL PARK
WITH ONLY A 2-4 DEGREE DIFFERENCE BETWEEN THESE TWO MODELS. THE EC
IS COLDER TUESDAY NIGHT BUT WITH THE STRONGER WINDS ANTICIPATED DO
NOT SEE UPPER 30S TO LOWER 40S BEING REALIZED AT THIS TIME.

.LONG TERM...WEDNESDAY THROUGH MONDAY NIGHT...STRONG UPPER TROUGH
OVER THE CENTRAL PLAINS EARLY IN THE LONG TERM MIGRATES EAST AS HIGH
PRESSURE BUILDS ACROSS DEEP SOUTH TEXAS AND THE RGV. PRESSURE
GRADIENT STRENGTHENS DURING THE DAY WITH DAYTIME MIXING WHICH WILL
ALLOW FOR GUSTY WINDS TO DEVELOP WEDNESDAY DURING THE DAY WITH DRY
AIR INFILTRATING ALOFT AND AT THE LOWER LEVELS OF THE ATMS. DUE TO
THE LACK OF CLOUD COVERAGE ACROSS THE CWA BUT AN ABUNDANCE SUNSHINE
WILL BE IN PLACE...THE TEMPERATURES WILL WARM
UP INTO THE MID 60S ACROSS MOST OF THE CWA. HOWEVER...DUE TO THE
INCREASE GUSTY WINDS EXPECTED DURING THE DAY...WINDCHILL OR FEEL
LIKE TEMPS WILL RANGE FROM THE MID TO UPPER 50S THROUGH THE MORNING
HOURS AND INTO THE MID 50S BY THE AFTERNOON. BACK EARLY THURSDAY
MORNING...LOWER THICKNESS VALUES AND A TREND OF LOWER 850 MB TEMPS
ON BOTH MODELS SUGGESTS COOLER TEMPERATURES FOR EARLY THURSDAY
RANGING FROM THE MID TO LOW 40S AND CLOSER TO 35 DEGREES ALONG THE
RANCHLANDS OVER THE NORTHERN COUNTIES. THE WINDS WILL NOT BE A BIG
OF AN ISSUE AS THE GRADIENT WILL WEAKEN KEEPING LIGHT WINDS THROUGH
THE NIGHT. WITH THE HIGH PRESSURE SHIFTING EAST...THE WINDS BACKING
SW TO S BY THURSDAY AFTERNOON. DRY THROUGH THE COLUMN FOR CHRISTMAS
DAY AND SOUTHERLY FLOW WILL ALLOW TEMPS TO RETURN TO THE 70S BY THE
AFTERNOON HOURS.

ANOTHER TROUGH DEVELOPS LATE WEDNESDAY INTO THURSDAY ENTERING THE PAC
NORTHWEST AND DIGGING SOUTHEAST THURSDAY. THERE ARE SOME DIFFERENCES
IN THE MODELS WITH THIS FEATURED NOT COMPLETELY RESOLVED YET. THE GFS
AND ECMWF SHOW THE TROUGH DEVELOPING WITH A SECONDARY SHORTWAVE ENERGY
TRAILING BEHIND IT WHICH WILL EVENTUALLY AMPLIFY THE TROUGH ENTERING
INTO THE WEEKEND TIME FRAME. BY FRIDAY GFS HAS SOME OF THE ENERGY
LIFTING TOWARDS THE CENTRAL PLAINS. WHILE THE ECMWF IS A BIT SLOWER AND
FURTHER SOUTH WITH THE TROUGH AXIS OVER THE FOUR CORNER REGION. LATER
INTO SATURDAY...MOST OF THE ENERGY IS LIFTED NORTHEAST WITH A FRONT
ARRIVING INTO SATURDAY WHILE THE ECMWF IS ARRIVING EARLY SUNDAY.
REGARDLESS OF THE DIFFERENCES...THERE IS A GOOD POTENTIAL FOR
OVERRUNNING PATTERN TO DEVELOP ALONG THE CWA. THIS WILL ENHANCE THE
POTENTIAL FOR RAIN AND CLOUDS LATE FRIDAY NIGHT INTO SATURDAY AND
CONTINUING THROUGH MOST OF THE WEEKEND. LEAN TOWARDS THE FRONTAL
PASSAGE SATURDAY AFTERNOON INTO EARLY SUNDAY INCREASING NORTHERLY
WINDS ACROSS THE AREA. TEMPERATURES WILL LOWER TO THE 60S DURING THE
DAY SATURDAY AND IN THE 40S BY SUNDAY MORNING. THE PROGRESSIVE
PATTERN CONTINUES INTO THE FOLLOWING WEEK AS ANOTHER SYSTEM ENTERS
THE PACIFIC COAST MONDAY. THIS WILL KEEP THE SOUTHWEST TO WESTERLY
WIND ALOFT WHILE SURFACE HIGH PRESSURE SHIFTS EASTWARD. THIS WILL
KEEP AN EASTERLY ONSHORE FLOW ACROSS THE AREA STRENGTHENING THE
OVERRUNNING PATTERN AND AS A RESULT INCREASING THE CHANCE OF RAIN.
WEAK COASTAL LOW DEVELOPS ALONG THE COAST AND LIFTS NORTHEAST
MAINTAINING THE MOISTURE CONTENT IN THE AREA WITH CLOUDY CONDITIONS
AND LIGHT TO MODERATE RAIN SHOWERS. TEMPERATURES WILL REMAIN IN THE
LOW 70S.

&&

.MARINE...NOW THROUGH TUESDAY...
PATCHY DENSE MARINE FOG MAY DEVELOP OVER THE LAGUNA MADRE AND NEAR
SHORE WATERS TONIGHT IN ADVANCE OF TUESDAY STRONG COLD FRONT. LIGHT
WINDS AND COOLER WATER TEMPERATURES NEAR THE COAST LINE WILL
INITIATE FOG DEVELOPMENT WITH SOME UNCERTAINTY IF VISIBILITIES DROP
BELOW ONE HALF MILE. IN ANY CASE LIGHT WINDS AND LOW SEAS ARE
FORECAST THROUGH TONIGHT WITH RAPIDLY DETERIORATING MARINE
CONDITIONS TUESDAY. A SHARP COLD FRONT IS EXPECTED TO SWEEP ACROSS
THE LOWER TEXAS COAST DURING THE DAY TUESDAY BRINGING VERY STRONG
WINDS AND RAPIDLY ROUGHENING SEAS. WIND SPEEDS WILL INCREASE THROUGH
THE AFTERNOON PRODUCING FREQUENT GALE FORCE GUSTS ON THE LAGUNA
MADRE AND NEARSHORE WATERS AND SUSTAINED WINDS NEAR GALE FORCE ON
THE OFFSHORE WATERS. AN OCCASIONAL GUST APPROACHING STORM FORCE
CANNOT BE COMPLETELY RULED OUT WITH THIS SYSTEM TUESDAY NIGHT AS THE
GRADIENT MOVES OVER THE LOWER TEXAS COAST. SEAS TO EXCEED TEN FEET
BY TUESDAY EVENING AND REMAIN VERY HIGH INTO WEDNESDAY MORNING. GALE
WATCH REMAINS IN EFFECT AND WILL LIKELY BE UPGRADED TO A GALE
WARNING LATER TONIGHT OR FIRST THING TUESDAY MORNING. MARINERS ARE
URGED TO MONITOR THE LATEST FORECASTS AND FACTOR THIS POTENTIALLY
DANGEROUS SYSTEM INTO YOUR PLANS.

WEDNESDAY THROUGH MONDAY...THE FRONT CONTINUES TO MOVE FURTHER SOUTH
AND IS EXPECTED TO MAKE IT ACROSS THE GULF WATERS BY THIS EVENING.
THIS WILL INCREASE WINDS AND SEAS DURING THE NIGHT INTO EARLY
MORNING. A SCA HAS BEEN ISSUED DUE TO THIS HAZARDOUS CONDITIONS.
IT IS EXPECTED TO IMPROVE BY MID MORNING SATURDAY WITH LOWERING
SEAS AND WINDS. THE POTENTIAL FOR RAIN INCREASES INTO SATURDAY
NIGHT WITH WINDS SHIFTING NORTHEAST TO EAST AS A WEAK BOUNDARY
LIFT NORTHWARD.


&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  65  78  48  62 /  10  10  10   0
BROWNSVILLE          64  80  47  63 /  10  10  10   0
HARLINGEN            62  78  45  63 /  10  10   0   0
MCALLEN              62  77  48  64 /  10   0   0   0
RIO GRANDE CITY      56  75  46  64 /  10   0   0   0
SOUTH PADRE ISLAND   66  77  51  63 /  10  10  10   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...GALE WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY NIGHT FOR
     GMZ130-132-135-150-155-170-175.

&&

$$

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