Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 142356 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
556 PM CST SUN DEC 14 2014

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

&&

.AVIATION...VFR CURRENTLY AT THE LOCAL TAF SITES. CONDITIONS ARE
BREEZY AND GUSTY FROM THE SOUTH SOUTHEAST WITH A FEW INNOCUOUS LOW
CLOUDS. MUCH LESS IN THE WAY OF MID AND UPPER CLOUDS TODAY AS AN
UPPER DISTURBANCE OVER THE SOUTHERN PLAINS EXITS TO THE EAST AND
DRIER AIR MOVES INTO SOUTH TEXAS FROM THE WEST. THE PRESSURE
GRADIENT WILL FLATTEN TONIGHT...RESULTING IN LIGHT WINDS UNDER
MOSTLY CLEAR SKIES. A WEAK SURFACE INVERSION WILL BE POSSIBLE.
WINDS WILL BE STRONG ENOUGH TO BRING IN MARINE CLOUDS HOWEVER...
WITH MVFR CEILINGS DEVELOPING LATE IN THE NIGHT. THE DROP IN WIND
SPEED COULD RESULT IN FOG ACROSS THE NORTHERN RANCH LANDS AND
BRUSH COUNTRY...WITH LIGHT PATCHY STUFF POSSIBLY EXTENDING TO MFE
AND HRL BY DAWN. VISIBILITY SHOULD BE LESS OF AN ISSUE THAN
CEILINGS FOR THE TAFS SITES. NONETHELESS...WINDS WILL DIE DOWN
MUCH MORE INLAND...AND LARGER AREAS OF THICKER FOG MAY DEVELOP...
THUS REQUIRING A WATCH ON THE FOGS SPREAD TOWARD THE LOWER VALLEY.
SOUTH SOUTHEAST SURFACE WINDS WILL INCREASE BY MID MORNING NEAR
THE COAST...FREEING THOSE AREAS FROM ANY FOG AND/OR LOW CIGS...
WITH A RETURN TO VFR. A WEAK FRONT WILL MOVE INTO THE AREA LATE
MONDAY...WITH MORE WIDESPREAD AND THICKER FOG POSSIBLE MONDAY
NIGHT.

&&

.PREV DISCUSSION... /ISSUED 234 PM CST SUN DEC 14 2014/

LONG TERM /TUESDAY THROUGH SATURDAY/...
FRONT WILL BE WORKING SLOWLY ACROSS THE AREA FROM NORTH TO SOUTH
DURING THE DAY ON TUESDAY. SOUTHWEST FLOW ALOFT SHOULD ALSO SUPPORT
SOME COASTAL TROUGHING COMBINING WITH THE PRESSURE/TEMPERATURE
STRUCTURE OF THE FRONT. WINDS AT 700-850 MB WILL BE OUT OF THE SOUTH TO
SOUTHEAST SUPPORTING SOME MODEST OVERRUNNING AND MOISTURE/WARM AIR
ADVECTION AND KEPT LOW GRADE SHOWER CHANCES IN THE FORECAST THROUGH
THE DAY. KEPT THE EXISTING TEMPERATURE STRUCTURE WHICH KEEPS A LARGE
GRADIENT OF TEMPERATURES ACROSS THE CWA...MID 60S NORTH...NEAR 80
SOUTH. WITH THE ACTUAL AIR MASS CHANGE POSSIBLY NOT QUITE REACHING
THE RGV.

RIDGING REESTABLISHES OVER THE WEST CENTRAL GULF OF MEXICO ON
WEDNESDAY AND WORKS WITH LEE TROUGHING AND A DEVELOPING
TROUGH/CYCLONE OVER THE PLAINS TO PRODUCE A BREEZY TO WINDY DAY.
TEMPERATURES SHOULD ALSO WARM UP A BIT...BUT FOR WINDS AND TEMPS DID
CHEAT COOLER AND LIGHTER EXPECTING THAT SOME RESIDUAL COASTAL
TROUGHINESS WILL HANG ON. SYNOPTIC OVERCOMING SHOULD CLEAR THAT UP
BUT SUSPECT IT WILL TAKE SLIGHTLY LONGER THAN GLOBAL MODEL GUIDANCE
SUGGESTS.

THURSDAY AN UPPER LOW BEGINS CUTTING ACROSS NORTHERN MEXICO WITH
GULF RIDGING SHIFTING TO NEAR THE FLORIDA COAST. WIND SPEEDS WILL
BACK DOWN A BIT BUT THERE WILL BE A FAIRLY BROAD JET MAXIMUM TO THE
EAST OF THE NORTHERN MEXICO UPPER LOW AND SOUTH TEXAS LOOKS TO BE IN
A MODESTLY DIVERGENT SECTION OF THAT JET MAXIMUM. KEPT A SLIGHT
CHANCE OF SHOWERS IN THE FORECAST OWING TO THIS...MAINLY IN THE FORM
OF ELEVATED MID LEVEL SHOWERS IN THE AFTERNOON AND LIGHT LOW LEVEL
ACTIVITY IN THE MORNING.

THURSDAY NIGHT INTO FRIDAY THE AFOREMENTIONED UPPER LOW MOVES
QUICKLY ACROSS CENTRAL TEXAS FORMING A SURFACE CYCLONE TO THE
NORTHEAST OF THE REGION. ECMWF/GFS SHOW DIFFERENCES IN THE PLACEMENT
OF THE 500 MB VORTICITY MAXIMUM AND THE ULTIMATE LOCATION OF THE
SURFACE LOW. THE ECMWF USES THE NATURAL BAROCLINICITY OF THE GULF
COAST TO GENERATE A CYCLONE TRACK FROM JUST SOUTH OF HOUSTON
EASTWARD INTO THE MOBILE/NEW ORLEANS AREA WHERE THE GFS KEEPS THE
FEATURE FURTHER NORTH INTO THE ARKLATEX. PREFER THE ECWMF SOLUTION
BUT THE ACTUAL IMPACT ON SENSIBLE WEATHER HERE DEPENDENT ON THE
DIFFERENCES SHOULD BE MODEST. COLD FRONT ARRIVES DURING THE DAY ON
FRIDAY WITH A CHANCE OF SHOWERS AND POSSIBLY A THUNDERSTORM. EXPECT
THAT ANY THUNDER WILL BE CONFINED TO THE IMMEDIATE FRONTAL SLOPE AND
THE BEST LARGE SCALE ASCENT STAYS TO THE NORTH ON DETERMINISTIC AND
ENSEMBLE PROJECTIONS SO MOST OF THE RAIN/DISTURBED WEATHER SHOULD
STAY TO THE NORTH. GUSTY NORTHWEST WINDS ARE FORECAST THROUGH FRIDAY
NIGHT INTO SATURDAY MORNING AS THE FRONT MOVES THROUGH. WENT WARMER
THAN GUIDANCE ON TEMPERATURES...CLOSE TO THE INHERITED FORECAST AS
THE AIR MASS SOURCE REGION FOR THIS FRONT IS EASTERN NEW MEXICO...SO
NOT AN ARCTIC AIR MASS BY ANY STRETCH...LIKELY WILL PREVENT A
SHOCKING CHANGE IN TEMPERATURE AS A RESULT.

HIGH PRESSURE TAKES OVER IN THE CENTRAL PLAINS SATURDAY AND SUNDAY
SHIFTING OUR WINDS TO THE EAST WITH A DRYING COLUMN. SHOULD BE
RELATIVELY WARM AND PLEASANT THROUGH THAT PERIOD WITH LITTLE IF ANY
RAIN CHANCE.  BEYOND THAT HOWEVER GFS/ECMWF SHOW ANOTHER ANOMALOUSLY
STRONG UPPER LEVEL LOW APPROACHING THE AREA BY MONDAY INTO TUESDAY.
TOO EARLY TO HAVE MUCH OF A BEAD ON ANTICIPATED WEATHER BUT A MORE
ACTIVE PERIOD OF WEATHER...MAINLY IN THE PRECIPITATION CATEGORY
WOULD BE POSSIBLE IF THE SYNOPTIC PICTURE HOLDS CLOSE TO CURRENT
PROJECTIONS. /68-JGG/

MARINE...NOW THROUGH MONDAY NIGHT...MODERATE WINDS ARE EXPECTED
THROUGH THE REMAINDER OF TODAY AND TONIGHT FOR THE LOWER TEXAS GULF
WATERS AND SEAS WILL GRADUALLY BUILD TO AROUND 5 FEET BY THIS
EVENING. SMALL CRAFT ARE ADVISED TO EXERCISE CAUTION THROUGH TONIGHT
FOR THE GULF WATERS. WINDS WILL RELAX MONDAY AND SEAS WILL SLOWLY
SUBSIDE WITH THE APPROACH OF THE NEXT COLD FRONT.

TUESDAY THROUGH THURSDAY...
A COLD FRONT WILL BE WORKING NORTH TO SOUTH ACROSS THE AREA MONDAY
BUT MAY NOT QUITE PRODUCE ADVISORY LEVEL WINDS AS IT STALLS OVER THE
LOWER TEXAS COAST. A FAIRLY LONG NORTHEASTERLY FETCH WILL LIKELY
PRODUCE SOME INCREASED SWELL ON TUESDAY THOUGH REGARDLESS OF WHAT
THE FINAL WIND SPEEDS ARE. WINDS WILL SHIFT FAIRLY QUICKLY BACK TO
THE SOUTHEAST ON WEDNESDAY TO EXERCISE CAUTION LEVELS AND STAY CLOSE
TO THOSE LEVELS THROUGH THURSDAY AMID MODERATE SEAS.

&&

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

$$

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