Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 060336
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
936 PM CST THU MAR 5 2015

.DISCUSSION...UPDATED TO ACCOUNT FOR TRENDS IN SKY
COVER...WINDS...AND AMBIENT TEMPERATURE. TAKING INTO ACCOUNT THAT
HOURLY TEMPERATURE GRIDS WERE AS MUCH AS 10 DEGREES COOLER THAN
ACTUAL TEMPERATURE...WINDS ARE LOWER THAN FORECAST...AND 00Z MET
MOS GUIDANCE WAS WARMER THAN PREVIOUS...BELIEVE THAT WIND CHILL
ADVISORY WILL NOT BE MET OVERNIGHT. HAVE RAISED OVERNIGHT LOWS AS
WELL WITH WIND CHILLS SEVERAL DEGREES ABOVE ADVISORY CRITERIA.
THEREFORE...HAVE CANCELLED THE WIND CHILL ADVISORY FOR OVERNIGHT.
UPDATE SENT.

&&

.PREV DISCUSSION... /ISSUED 514 PM CST THU MAR 5 2015/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...SKY CONDITIONS ACROSS DEEP SOUTH TEXAS REMAIN VFR WITH
CLOUD DECKS BEGINNING AROUND 3500 FEET AND BROKEN 6000 FEET AND
ABOVE. WITH DEEP COLD AIR ADVECTION IN PLACE AND SOUTHERLY WINDS
BEGINNING AROUND 6000 FEET...BROKEN CLOUD DECKS SHOULD REMAIN AT
THE LEVEL OR ABOVE. STILL SOME POSSIBILITY OF LOWER CLOUDS ACROSS
THE AERODROMES FROM TIME TO TIME TONIGHT...VFR IS FORECAST THE
NEXT 24 HOURS. GUSTY NORTHERLY WINDS UP TO 25 KNOTS CURRENTLY WILL
SLOWLY SUBSIDE THIS EVENING.

PREV DISCUSSION... /ISSUED 254 PM CST THU MAR 5 2015/

SHORT TERM /NOW THROUGH FRIDAY NIGHT/...COLD AIR AT LEAST 7000 FEET
DEEP HAS ALLOWED FOR THE CLOUD DECK TO RISE AND THIN MORE THEN
EXPECTED. ALSO, SURFACE HIGH PRESSURE CONTINUES TO BUILD MORE SOUTH
THEN EAST CONTINUING TO BRING IN DRIER AIR AND PUSHING OUT ALL THE
RAIN SOUTH AND EAST OF THE RIO GRANDE. THIS HAS ALLOW FOR
TEMPERATURES TO INCREASE MORE THAN ANTICIPATED THIS AFTERNOON. WITH
THE SURFACE RIDGE AXIS REMAINING NORTH OF THE TEXAS COAST COLD AIR
ADVECTION ALTHOUGH WEAKENED TO CONTINUE THROUGH AT LEAST EARLY
FRIDAY. THE RIDGE THEN BEGINS TO MOVE EASTWARD LATER FRIDAY INTO
FRIDAY NIGHT.

ANY THREAT OF FREEZING PRECIPIATION HAS ENDED WITH NO RAIN OR
DRIZZLE IN THE FORECAST. GFS HOLDS ON TO SOME LOW POPS IN THE LOWER
VALLEY BUT WITH THE EARLY DEPARTURE OF RAIN AND DEEPER MOISTURE WILL
KEEP THE REGION DRY. IT WILL CONTINUE TO BE COLD THOUGH WITH A
POSSIBLE SHORT DURATION FREEZE ACROSS THE NORTHERN RANCH LANDS WITH
MID TO UPPER 30S ACROSS THE VALLEY. FACTORS TO KEEP US FROM FALLING
TO OR BELOW FREEZING ARE SOME CONTINUATION OF CLOUD COVER AND A
ENOUGH WIND TO KEEP THE ATMOSPHERE MIXED. ANOTHER REASON IS THE
ADDITIONAL WARMING FROM THIS AFTERNOON...UPPER 40S TO LOWER
50S...DUE TO THE THINNER AND HIGHER CLOUD COVER WILL HAVE TO MAKE
TEMPERATURES FALL MORE THEN IF THEY WERE STARTING OFF IN THE UPPER
30S TO LOWER 40S.  THE LOW TEMPERATURES AND RESIDUAL WINDS AROUND 10-
15 MPH OVERNIGHT WILL ALLOW WIND CHILLS TO DIP TO ADVISORY CRITERIA
FOR AT LEAST 2 TO 5 HOURS MAINLY FOR THE EASTERN TWO THIRDS OF THE
CWA. THIS INCLUDES THE MID AND LOWER VALLEY. A WIND CHILL ADVISORY
WILL BE ISSUED TO COVER THIS.

FOR FRIDAY AND FRIDAY NIGHT SURFACE HIGH PRESSURE IN CONTROL WITH
SOME RESIDUAL MID AND HIGH CLOUDINESS AND A LIGHT NORTH WIND DURING
THE DAY. A COLD START OF THE DAY SHOULD END UP COOL TO MILD BUT
STILL WELL BELOW NORMAL WITH SUFFICIENT HAZY SUNSHINE TO WARM US
INTO THE MID 50S. TRENDED WITH THE WARMER GFS BUT IF CLOUDS THIN
MORE THEN EXPECTED TEMPS MIGHT EXCEED THESE VALUES. MODEL GUIDANCE
HOLDING ONTO SOME CHANCE POPS FOR FRIDAY BUT DO NOT SEE ANY SIGNALS
FOR ISENTROPIC LIFT AND THE WESTERN UPPER TROUGH LOOKS TO HAVE
LITTLE INFLUENCE ON OUR WEATHER AT THIS TIME. WILL KEEP FORECAST DRY
WITH ZERO POPS. MOISTURE RETURN IS NOT TAP FOR FRIDAY AS WIND VEER
EASTERLY AND THE INCREASE OF CLOUDS WILL BATTLE THE FORECAST LOWS.

LONG TERM /SATURDAY THROUGH WEDNESDAY/...THE FORECAST PERIOD WILL
BEGIN WITH A SOUTHWEST FLOW ALOFT AND A WEAK 500MB LOW OVER BAJA
CALIFORNIA AND NORTHWEST MEXICO...WITH A RIDGE OVER THE WEST COAST.
THIS WILL RESULT IN OVERRUNNING CONDITIONS ACROSS DEEP SOUTH AND...
ALONG WITH A NORTHEAST SURFACE FLOW...LOW LEVEL MOISTURE WILL RENAIN
STUBBORNLY PARKED OVER THE AREA EVEN AS CENTRAL TX TENDS TO BECOME
DRIER. TEMPS WILL REMAIN WELL BELOW NRML THROUGH THE WEEKEND...WITH
HIGH TEMPS ON SATURDAY IN THE LOWER 60S. LOW TEMPERATURES SATURDAY
NIGHT WILL RANGE FROM 45 ACROSS THE NORTHERN RANCHLANDS TO THE MID
50S NEAR THE COAST.

THE GFS AND ECMWF BOTH SUPPORT THE UPSTREAM LOW EJECTING OUT TO WEST
TX BY SUNDAY...WITH DIVERGENCE AT THE MID LEVEL INDUCING INSTABILITY
OVER NORTHEAST MEXICO AND THENCE DEEP SOUTH TEXAS. RAIN CHANCES WILL
REMAIN ROBUST FROM SATURDAY NIGHT THROUGH MONDAY AS THE TROUGH EDGES
SLOWLY EAST TOWARD THE TEXAS PANHANDLE THROUGH SUNDAY...WITH THE
ADDED SUPPORT OF ADDITIONAL HIGH PRESSURE MAKING ITS WAY INTO THE
SOUTHEAST UNITED STATES. NORTHEAST WINDS WILL STRENGTHEN SUNDAY
NIGHT INTO MONDAY...AS WILL RAIN CHANCES OVER THE NORTHWEST GULF
EXTENDING BACK TOWARD THE LOWER TEXAS COAST...WHICH WILL REMAIN NON
NEGLIGIBLE. HIGH TEMPS SUNDAY WILL BE IN THE 60S WITH LOWS SUNDAY
NIGHT IN THE 50S.

A SLOW WARMING TREND WILL CONTINUE SUNDAY INTO EARLY NEXT WEEK...BUT
NEAR NORMAL TEMPERATURES WON`T REALLY BE BACK UNTIL WEDNESDAY OR
THURSDAY. RAIN CHANCES WILL CONTINUE THROUGH MID WEEK AS THE MID
LEVEL TROUGH WILL BE SLOW TO EJECT. IN FACT...THERE IS SOME HINT
THAT WEST COAST RIDGING WILL TOPPLE EAST TOWARD THE FOUR CORNERS...
HELPING TO CUT OFF THE UPPER WEAKNESS OVER NORTH CENTRAL MEXICO. THE
RELATED DIVERGENCE WOULD SUPPORT PRESSURE DECREASES OVER THE WEST
GULF WHILE HIGHER PRESSURE STILL CONTROLLED THE NORTH GULF...LEADING
TO A BROAD INVERTED TROUGH AND NORTHEAST TO NORTH WINDS...LOCKING IN
LOW LEVEL MOISTURE AND THE ASSOCIATED COOL...CLOUDY CONDITIONS.

MARINE...
NOW THROUGH FRIDAY NIGHT...GALES TO CONTINUE UNTIL 6 PM WITH A
FEW GALE FORCE GUST CONTINUING ACROSS THE SOUTHERN WATERS. SMALL
CRAFT ADVISORIES TO REPLACE THE GALE WARNING AND WILL CONTINUE FOR
THE LAGUNA UNTIL MIDNIGHT HOWEVER THE GULF WILL SEE HAZARDOUS SEAS
CONTINUING MOST OF FRIDAY WITH AT LEAST SOME PERSISTENT NORTH
WIND. MARINE CONDITIONS CONTINUE TO IMPROVE FRIDAY NIGHT.

SATURDAY THROUGH MONDAY...MODERATE WINDS AND SEAS WILL PREVAIL
SATURDAY MORNING. HIGH PRESSURE WILL BE CENTERED OVER THE LOWER
MISSISSIPPI VALLEY...BUT THE GRADIENT OVER THE NORTHWEST GULF WILL
BE REASONABLE WITH LIGHT TO MODERATE NORTHEAST WINDS. THE STATUS QUO
WILL PREVAIL THROUGH SUNDAY WITH LIGHT TO MODERATE NORTHEAST WINDS
AND LOW TO MODERATE SEAS...WHEN ADDITIONAL HIGH PRESSURE WILL ARRIVE
IN THE SOUTHERN UNITED STATES...EXTENDING SOUTHWEST INTO THE LOWER
MISSISSIPPI VALLEY AND EAST TEXAS. THIS WILL TIGHTEN THE GRADIENT A
BIT AND WILL INCREASE NORTHEAST WINDS INTO THE MODERATE TO FRESH
CATEGORY LATE SUNDAY INTO SUNDAY NIGHT. LOW END SMALL CRAFT ADVISORY
CONDITIONS WILL BE POSSIBLE OFFSHORE MONDAY DUE TO WINDS...BUT SEAS
ON THE GULF WILL ALSO BUILD TO SEVEN FEET MONDAY AFTERNOON AND
EVENING.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY FOR WINDS UNTIL 3 AM CST FRIDAY FOR GMZ130-
     132-135.

     SMALL CRAFT ADVISORY UNTIL 6 PM CST FRIDAY FOR GMZ150-155-170-
     175.

&&

$$

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