Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 242039
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
239 PM CST WED DEC 24 2014

.SHORT TERM /NOW THROUGH THURSDAY NIGHT/...SURFACE HIGH PRESSURE
OVER THE MEXICAN STATES OF CHIHUAHUA AND COAHUILA WILL MOVE ACROSS
DEEP SOUTH TEXAS TONIGHT...TRACKING EAST OF THE REGION CHRISTMAS
DAY. PLEASANT BUT COLD TONIGHT WITH WINDS DIMINISHING AND SKIES
IN THE MOST PART REMAINING MOSTLY CLEAR. SOME HIGH CLOUDS TO THE
SOUTH ARE SEEN DRIFTING NORTH BUT BELIEVE SUBSIDENT NORTHWEST FLOW
ALOFT WILL KEEP CLOUD COVER LIMITED. THIS WILL SET UP AN EXCELLENT
RADIATIONAL COOLING EVENT WITH GUIDANCE ONCE AGAIN GOING RATHER
COLD WITH SOME INDICATION OF A LIGHT FREEZE ACROSS THE NORTHERN
RANCH LANDS. HAVE LOWERED TEMPERATURES FROM THE PREVIOUS FORECAST
BUT KEPT TEMPERATURES JUST ABOVE FREEZING. IF EVERYTHING COMES
TOGETHER FOR THIS RADIATIONAL EVENT CHRISTMAS MORNING COULD BE THE
COLDEST OF THE FALL/WINTER SEASON THUS FAR.

CHRISTMAS DAY...AS MENTIONED HIGH PRESSURE WILL SHIFT EASTWARD
THURSDAY AFTERNOON WITH SOUTH WINDS RETURNING RATHER QUICKLY.
EXPECT A MILD DAY WITH THE SOUTH WINDS INCREASING AND BECOMING
QUITE BRISK IN THE AFTERNOON. MODEL PROJECTIONS SHOW 925-850MB
BETWEEN 25-35 KNOTS WITH MODEL GUIDANCE SHOWING WINDS OF 20-25
MPH AT THE SURFACE ALONG AND EAST OF THE 69C/69E CORRIDORS.
TEMPERATURES REBOUND TO NEAR 70 AND MAY INCH ABOVE THE 70 DEGREE
MARK.

THURSDAY NIGHT...PRESSURE GRADIENT STRENGTHENS AS NEXT UPPER
TROUGH MOVES INTO THE ROCKIES AND THE 4 CORNERS REGION. HIGH
PRESSURE OVER THE GULF WILL COMBINE WITH THE LOWER PRESSURES
DEVELOPING A LOW LEVEL SOUTHERLY JET OF 30-45KNOTS. SURFACE WINDS
WILL NOT BE AS WINDY BUT BREEZY CONDITIONS AT TIMES CAN BE
EXPECTED. AS A RESULT OF THE RAPID WARM AIR ADVECTION CLOUDS WILL
BE ON THE INCREASE AND TEMPERATURES TO REBOUND RATHER QUICKLY.
LOWS OVER NIGHT WILL BE MUCH WARMER THAN CHRISTMAS EVE AND ARE
FORECAST TO BE 15 TO 20 DEGREES WARMER.

.LONG TERM /FRIDAY THROUGH TUESDAY/...SOUTH SOUTHEAST RETURN FLOW
WILL BRING LOW CLOUDS AND A FEW SHOWERS NORTH ALONG THE COAST
FRIDAY MORNING...AS A TIGHT PRESSURE GRADIENT BETWEEN RETREATING
HIGH PRESSURE OVER THE SOUTHEAST UNITED STATES AND LOWER PRESSURE
UPSTREAM OVER NEW MEXICO CONTINUES. DAY TIME HIGH TEMPS WILL BE
IN THE MID 70S. WHILE A MID LEVEL TROUGH HANGS BACK OVER THE FOUR
CORNERS FRIDAY NIGHT...WITH LOW TEMPS ACROSS THE CWA MAINLY IN
THE 60S...THE UNDERLYING SURFACE LOW PRESSURE SYSTEM IN NEW MX
WILL TRANSLATE NORTHEAST TOWARD THE UPPER MIDWEST...LEAVING HIGH
PRESSURE FROM THE PACIFIC NORTHWEST TO FILL IN FROM BEHIND. A COLD
FRONT WILL GAIN DEFINITION ACROSS CENTRAL TEXAS ON SATURDAY...
REACHING THE NORTHERN RANCH LANDS AROUND SUNSET. IN THE MEAN
TIME...MOISTURE WILL POOL OVER THE AREA ON SATURDAY...PRODUCING
CLOUDY SKIES AND HIGH TEMPS MAINLY IN THE 70S EXCEPT FOR ROUGHLY
THE NORTHWEST CORNER OF ZAPATA COUNTY WHERE COOLER AIR MOVING
SOUTH MAY HAVE AN IMPACT LATE IN THE DAY.

DUE TO A FILLING...YET STILL VIABLE MID LEVEL TROUGH OVER FAR WEST
TEXAS...SOUTHWEST FLOW ALOFT WILL CAP THE ATMOSPHERE OVER SOUTH
TEXAS AS THE FRONT MOVES THROUGH THE CWA...REACHING THE COAST AROUND
OR AFTER MIDNIGHT. TEMPERATURES WILL DECREASE TO THE MID 40S ACROSS
THE BRUSH COUNTRY AND RANCH LANDS...AND THE MID 50S ALONG LOWER
VALLEY. CLOUDY SKIES WILL PREVENT SIGNIFICANT RADIATIONAL HEAT LOSS
WITH LIGHT RAIN ACROSS THE SELF SAME SOUTHEAST CORNER OF THE CWA.
SUNDAY WILL BE COOL WITH HIGHS IN THE 50S AND 60S. SUNDAY NIGHT WILL
BE COLDER THAN SATURDAY NIGHT...AND MORE LIKE IT WILL BE TONIGHT...
WITH LOW TEMPERATURES MAINLY IN THE 40S. A WARMUP INTO THE 60S WILL
OCCUR ON MONDAY AS WINDS VEER TO EAST AND MOISTURE EDGES INTO THE
CWA. ANOTHER MID LEVEL TROUGH WILL DESCEND OUT OF THE PACIFIC
NORTHWEST SUNDAY INTO MONDAY...MOVING SOUTH AND OPENING THE WAY
FOR COLDER CANADIAN AIR TO SINK SOUTH FROM CANADA.

&&

.MARINE...
NOW THROUGH THURSDAY NIGHT...SMALL CRAFT ADVISORY CONDITIONS
PERSIST OVER THE NEAR AND FAR OFFSHORE WATERS WITH MARGINAL WINDS
OVER THE LAGUNA MADRE. WINDS TO DIMINISH BY THIS EVENING AS HIGH
PRESSURE BEGINS TO BUILD TOWARD THE LOWER TEXAS COAST. SOUTHEAST
WIND RETURN RATHER RAPIDLY CHRISTMAS DAY AND INCREASING STEADILY
THROUGH THURSDAY NIGHT. EXERCISE CAUTION VALUES ON THE BAY AND
OFFSHORE ARE ANTICIPATED THURSDAY AFTERNOON...WITH SMALL CRAFT
ADVISORY CONDITIONS POSSIBLE OFFSHORE THURS NIGHT AS THE PRESSURE
GRADIENT STRENGTHENS IN RESPONSE TO AN UPPER LEVEL TROUGH MOVING
OVER THE ROCKIES.

FRIDAY THROUGH SUNDAY...1027 MB HIGH PRESSURE CENTERED OVER THE
SOUTHEAST UNITED STATES WILL EXTEND SOUTHWEST INTO THE NORTHWEST
GULF OF MEXICO FRIDAY...NOT ONLY BRINGING MOISTURE NORTH ALONG THE
NORTHEAST MEXICAN COAST IN THE FORM OF LIGHT ISOLATED STREAMER
SHOWERS... BUT ALSO INTERACTING WITH A LOW PRESSURE SYSTEM MOVING
OUT OF THE FOUR CORNERS AREA...THEREBY CONTINUING LOW END SMALL
CRAFT ADVISORY CONDITIONS ON THE GULF THROUGH THE DAY. THE SOUTH
SOUTHEAST WINDS WILL DECREASE FRIDAY NIGHT AS HIGH PRESSURE FROM
THE PACIFIC NORTHWEST FILLS INTO THE UPSTREAM LOW...WHILE AT THE
SAME TIME REPRESENTING A COLD FRONTAL BOUNDARY MOVING INTO WEST
TEXAS. WINDS WILL FURTHER DECREASE SATURDAY...BUT BY AROUND
MIDNIGHT THE COLD FRONT WILL PUSH OFFSHORE...SHIFTING WINDS TO
NORTH. WINDS WILL TOP OUT AT AROUND 20 KNOTS SUNDAY AFTERNOON...
WITH BORDERLINE SMALL CRAFT ADVISORY CONDITIONS....WITH THOSE
WINDS DECREASING TO MODERATE SUNDAY NIGHT AS HIGH PRESSURE SPREADS
OVER THE AREA.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  40  71  60  75 /   0   0   0  10
BROWNSVILLE          40  71  59  76 /   0   0   0  10
HARLINGEN            38  71  57  77 /   0   0   0  10
MCALLEN              38  71  56  77 /   0   0   0  10
RIO GRANDE CITY      37  71  51  77 /   0   0   0   0
SOUTH PADRE ISLAND   45  71  65  74 /   0   0   0  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS EVENING FOR GMZ150-155-
     170-175.

&&

$$

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