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000
FXUS64 KBRO 050530
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1130 PM CST WED DEC 4 2013

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

&&

.AVIATION...SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE
LOW CLOUDS AND FOG ACROSS THE RIO GRANDE VALLEY AND DEEP SOUTH
TEXAS. A MIX OF IFR/LIFR/VLIFR CEILINGS/VISIBILITIES PERSIST
ACROSS THE AREA. THE FORECAST IS TRICKY WITH LIGHT WINDS AT BRO
AND GUSTY WINDS AT MFE. LIGHT WINDS WILL ALLOW VISIBILITIES TO
DROP TO A MILE OR LESS AT THE TAF SITES...WITH PATCHY DENSE FOG A
POSSIBILITY. HOWEVER...LOCATIONS WHERE THE WINDS REMAIN A LITTLE
STRONGER...LOW CEILINGS WILL BE THE MAIN CONCERN. FOG AND LOW
CEILINGS WILL IMPACT RIO GRANDE VALLEY TAF SITES THROUGH MID
MORNING. VFR CEILINGS EXPECTED TO DEVELOP BY LATE MORNING ON
THURSDAY.

&&

.PREV DISCUSSION... /ISSUED 702 PM CST WED DEC 4 2013/

DISCUSSION...UPDATED FOR LATEST MARINE DISCUSSION BELOW.

MARINE...DENSE SEA FOG IS DEVELOPING ACROSS THE LAGUNA MADRE AND
THE NEAR SHORE GULF WATERS THIS EVENING. SATELLITE IMAGERY ALONG
WITH SURFACE OBSERVATIONS AND SOUTH PADRE ISLAND WEB CAMS SHOW
DENSE SEA FOG FORMING ALONG THE COAST. THEREFORE...THE DENSE FOG
ADVISORY HAS BEEN PUSHED UP FOUR HOURS AND IS NOW IN EFFECT FOR
THE LAGUNA MADRE AND THE LOWER TEXAS GULF WATER OUT 20 NM EAST OF
PADRE ISLAND THROUGH 8 AM THURSDAY.

PREV DISCUSSION... /ISSUED 549 PM CST WED DEC 4 2013/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...FOG AND LOW CLOUDS WILL BE AN ISSUE AGAIN TONIGHT. A
MIX OF VFR/MVFR CONDITIONS WILL PREVAIL ACROSS THE RIO GRANDE
VALLEY THIS EVENING. LIGHT SOUTH WINDS AT 5 TO 10 MPH...WITH
ADVECTION TYPE FOG FORMING OVER AND MOVING IN FROM THE GULF.
VISIBILITIES WILL DROP TO A MILE OR LESS AT THE TAF SITES...WITH
PATCHY DENSE FOG A POSSIBILITY. LIGHTER WINDS OVER INLAND AREAS
SHOULD ALLOW FOR DENSER FOG FORMATION THERE. IFR AND EVEN LIFR
CONDITIONS POSSIBLE FROM A FEW HOURS BEFORE DAWN UNTIL BURN OFF.
VFR CEILINGS EXPECTED TO DEVELOP BY MID TO LATE MORNING ON
THURSDAY.

PREV DISCUSSION... /ISSUED 249 PM CST WED DEC 4 2013/

SHORT TERM.../NOW THROUGH THURSDAY NIGHT/...FOG AND LOW CLOUDS WILL
AGAIN BE AN ISSUE TONIGHT. WINDS SPEEDS WILL REMAIN LIGHT FROM THE
SOUTH AT 5 TO 10 MPH...WITH ADVECTION TYPE FOG FORMING OVER AND
MOVING IN FROM THE GULF. VISIBILITY WILL DROP TO A MILE OR LESS
ACROSS THE LOWER VALLEY...WITH PATCHY DENSE FOG A POSSIBILITY.
LIGHTER WINDS OVER INLAND AREAS WILL BREED DENSER FOG CONDITIONS
THERE.

OTHERWISE...A WEAK WESTERLY ZONAL FLOW AT THE MID LEVEL WILL BACK TO
SOUTHWEST OVER THE NEXT 36 HOURS AS TROUGHING OVER THE WEST DEEPENS
INTO THE EAST SIDE OF AN OMEGA BLOCK OVER THE EASTERN PACIFIC. THE
BENIGN CONDITIONS AND CAPPING INVERSION WILL SUPPORT TEMPERATURES
WELL ABOVE NORMAL FOR THIS TIME OF THE YEAR...IN THE 60S TO NEAR 70
TONIGHT...AND HIGH TEMPERATURES WELL INTO THE 80S TOMORROW. LIGHT
WINDS WILL SHIFT TO SOUTHEAST THURSDAY NIGHT WITH A FEW SHOWERS
POSSIBLE ACROSS THE NORTHERN TIER BY MIDNIGHT...BECOMING A CHANCE OF
RAIN BY DAWN WITH THE IMMINENT ARRIVAL OF AN ARCTIC COLD FRONT.
OVERNIGHT LOWS COULD BE AFFECTED ACROSS THE NORTHERN TIER...WHERE
THEY COULD DIP INTO THE 40S BY DAWN.

LONG TERM/FRIDAY THROUGH WEDNESDAY/...A MUCH COLDER WEEKEND IS AHEAD
FOR THE RIO GRANDE VALLEY AND DEEP SOUTH TEXAS AS AN UPPER LEVEL
RIDGE OVER THE WEST COAST EXTENDS WELL NORTH INTO CENTRAL
ALASKA...WHILE A LARGE POSITIVELY TILTED TROUGH IS LOCATED OVER
THE CONUS. SEVERAL SHORTWAVES ROTATE THROUGH THE FLOW AND PUSH A
COUPLE OF COLD FRONTS SOUTH ACROSS THE PLAINS AND THROUGH
TEXAS...ALLOWING COLD ARCTIC AIR TO SURGE SOUTH.

FIRST FRONT MOVES SOUTH ACROSS THE REGION EARLY FRIDAY
MORNING...ENTERING THE NORTHERN RANCHLANDS AFTER MIDNIGHT AND
PUSHING THROUGH BROWNSVILLE BY MIDMORNING. HAVE MAINTAINED A MENTION
OF THUNDER WITH THE PASSAGE OF THE FRONT AS LIFTING WITH THE FRONT
AND SOME INSTABILITY COULD LEAVE TO CONVECTION. COLD AIR BEHIND THE
FRONT WILL SURGE IN FRIDAY...DROPPING TEMPERATURES THROUGHOUT THE
DAY...WITH HIGH TEMPS REACHED DURING THE EARLY MORNING HOURS. EXPECT
AFTERNOON TEMPERATURES IN THE 40S INLAND AND SLIGHTLY HIGHER
RIGHT ALONG THE COAST. OVERCAST SKIES AND MODERATE WINDS WILL KEEP
TEMPERATURES FROM DROPPING BELOW FREEZING FRIDAY NIGHT...WITH LOWS
RANGING FROM THE MID 30S ACROSS THE NORTHERN RANCHLANDS TO AROUND
40 CLOSER TO THE RIO GRANDE RIVER. STRONG NORTHERLY WINDS COMBINED
WITH THE COLDER TEMPERATURES FRIDAY AFTERNOON WILL RESULT
TEMPERATURES "FEELING" 40 TO 50 DEGREES COLDER THAN TEMPERATURES
THURSDAY AFTERNOON...WITH ACTUAL TEMPERATURES 30 TO 40 DEGREES
COLDER. FRIDAY NIGHT WIND CHILL VALUES WILL DIP JUST BELOW THIRTY
DEGREES ACROSS PORTIONS OF THE NORTHERN RANCHLANDS WITH WIND
CHILLS IN THE LOWER 30S ELSEWHERE. WILL HAVE TO KEEP AN EYE ON
THESE AS LATER RUNS COULD SHOW WIND CHILLS APPROACHING ADVISORY
LEVEL.

A COASTAL TROUGH SETS UP OVER THE WESTERN GULF OF MEXICO AND
DRIFTS NORTHEAST THROUGH THE DAY SATURDAY. SURFACE INVERSION
STRENGTHENS UP TO 10 TO 12C OVER THE AREA IN THE WAKE OF THE
FRONT...KEEPING A THICK CLOUD DECK AND OVERCAST SKIES. TROUGH AXIS
REMAINS OFFSHORE AS DO THE GREATEST PRECIP CHANCES...BUT
MAINTAINED MENTION OF LIGHT RAIN AND DRIZZLE THROUGH SUNDAY. THERE
IS AN OUTSIDE CHANCE OF SOME WINTRY PRECIP EARLY SATURDAY ACROSS
THE NORTHERN RANCHLANDS WITH A SHALLOW SATURATED LAYER THAT MAY
FALL BELOW FREEZING...HOWEVER NO ACCUMULATIONS ARE EXPECTED AND
HAVE NOT INCLUDED IN THE FORECAST AT THIS TIME. TEMPERATURES
SATURDAY REMAIN WELL BELOW NORMAL WITH HIGHS IN THE UPPER 30S TO
LOWER 40S ACROSS THE NORTHERN RANCHLANDS TO THE MID TO UPPER 40S
FURTHER SOUTH AND LOWS IN THE MID TO UPPER 30S NORTH OT THE LOWER
40S SOUTH. WIND CHILLS REMAIN IN THE 30S.

A SLIGHT REPRIEVE IS GRANTED ON SUNDAY AS TEMPERATURES WARM UP
SLIGHTLY...BUT THE WARM UP IS SHORT LIVED AS ANOTHER COLD FRONT
MOVES ACROSS THE REGION ON MONDAY. LAST FEW MODEL RUNS HAVE
INDICATED THAT THIS SECONDARY SURGE OF HIGH PRESSURE WOULD MOVE
FURTHER SOUTH INTO TEXAS BEFORE LIFTING NORTHEAST THAN THE ONE ON
FRIDAY...BRINGING COLDER OVERNIGHT TEMPS AND DRIER CONDITIONS. HAVE
KEPT TEMPS ABOVE FREEZING ACROSS THE NORTHERN COUNTIES BUT CANNOT
RULE OUT FREEZING TEMPERATURES MONDAY NIGHT AND TUESDAY NIGHT. WIND
CHILLS LOOK TO DROP INTO THE MID TO UPPER 20S MONDAY NIGHT AND
TUESDAY NIGHT ACROSS THE NORTHERN RANCHLANDS AND INTO THE UPPER 20S
TO LOWER 30S FURTHER SOUTH...WHICH WOULD MEET WIND CHILL ADVISORY
CRITERIA FOR SOME OF THE REGION.

MARINE...
NOW THROUGH THURSDAY NIGHT...HIGH PRESSURE COVERING THE GULF WILL
INTERACT WITH LOWER PRESSURE INLAND AND UPSTREAM TO PRODUCE LIGHT TO
MODERATE SOUTH WINDS AND MODERATE SEAS FOR THE LOWER TEXAS COASTAL
WATERS THROUGH THURSDAY NIGHT. HIGH DEW POINT AIR WILL MOVE ACROSS
COOLER SHELF WATERS OVER THE NEAR SHORE GULF OF MEXICO WATERS
TONIGHT. THIS WILL PRODUCE DENSE SEA FOG. THIS SEA FOG WILL REDUCE
VISIBILITIES TO ONE QUARTER MILE OR LESS TONIGHT THROUGH THURSDAY
MORNING.

FRIDAY THROUGH MONDAY...STRONG COLD FRONT IS EXPECTED TO CROSS THE
LOWER TEXAS COASTAL WATERS ON FRIDAY FOLLOWED BY ANOTHER FRONTAL
PASSAGE ON MONDAY. HAZARDOUS MARINE CONDITIONS ARE EXPECTED TO
DEVELOP QUICKLY IN THE WAKE OF THE FRONT WITH WIND GUSTS TO GALE
CONDITIONS AND BUILDING SEAS. SMALL CRAFT ADVISORY CONDITIONS WILL
OCCUR FRIDAY THROUGH SATURDAY WITH A GALE WATCH OR WARNING A
POSSIBILITY. MARINE CONDITIONS IMPROVE BRIEFLY ON SUNDAY BUT
QUICKLY DETERIORATE WITH THE PASSAGE OF THE NEXT FRONT MONDAY.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...DENSE FOG ADVISORY UNTIL 8 AM CST THURSDAY FOR TXZ251-256-257.

GM...DENSE FOG ADVISORY UNTIL 8 AM CST THURSDAY FOR GMZ130-132-135-
     150-155.

&&

$$

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

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