Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 031023
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
423 AM CST TUE MAR 3 2015

.SHORT TERM /NOW THROUGH WEDNESDAY/...

RELEVANT FEATURES... AN UPPER LEVEL CLOSED LOW OFF THE SOUTHERN
CALIFORNIA COAST IS EMBEDDED IN A LARGE POSITIVELY TILTED TROUGH
OVER MOST OF THE WESTERN CONUS. MEANWHILE A SOUTHWESTERLY JET OFF
THE WESTERN CANADA COAST IS AMPLIFYING TROUGHING OVER THE
NORTHWESTERN US WHICH IS HELPING SHIFT EVERYTHING SLOWLY EASTWARD
DESPITE PRETTY STRONG JET ENERGY EAST OF THE PARENT TROUGH WITH
250MB SPEEDS INCREASING FROM 125 TO 165 KTS FROM NORTHERN MEXICO
INTO NEBRASKA AND KANSAS. THIS IS KEEPING A BROADLY DIVERGENT
PATTERN IN PLACE OVER SOUTH TEXAS WITH COLD AIR DAMMED AGAINST THE
SIERRA MADRES FROM THE LAST FRONT BEING OVERRUN BY INCREASING SOUTH
AND SOUTHEASTERLIES RESPONDING TO THE NEXT SYSTEM. THE RESULT IS
PLENTY OF THICK LOW OVERCAST AND FOG WITH COASTAL TROUGHING OVER THE
WESTERN GULF AND SURFACE TROUGHING OVER SOUTH TEXAS LEADING TO
RELATIVELY LIGHT WINDS. A DENSE FOG ADVISORY WILL REMAIN IN EFFECT
THROUGH MID MORNING TODAY.

TODAY...SOUTHEAST WINDS ARE EXPECTED TO MAKE IT TO THE SURFACE BY
MID TO LATE MORNING. DRYING FROM SOUTHWESTERLY 850MB WINDS SHOULD
HELP LOW CLOUDINESS CLEAR OUT AND LET TEMPERATURES RISE WARMER THAN
WE HAVE SEEN THE LAST FEW DAYS. WITH A STRONG SEA SURFACE
TEMPERATURE GRADIENT ALONG THE COAST CLOUDS AND FOG MAY HOLD ON
THROUGH THE LATE MORNING OR AFTERNOON ON THE ISLAND AND KEPT THAT IN
THE FORECAST. FURTHER INLAND SKIES SHOULD BECOME PARTLY TO MOSTLY
CLOUDY AS TEMPERATURES RISE INTO THE MID 70S TO LOW 80S.

TONIGHT...THROUGH THE NIGHT THE CLOSED LOW EJECTS AROUND THE BASE OF
THE PARENT TROUGH INTO WEST TEXAS AND 850/925MB FLOW INCREASES. THIS
WILL HELP KEEP WIND SPEEDS UP THROUGH THE NIGHT AND WILL PROBABLY
HELP DEVELOP A LOW LEVEL INVERSION THAT WILL HELP CLOUD COVER
ORGANIZE AND INCREASE THROUGH THE NIGHT. MILD TEMPERATURES ARE
FORECAST...WITH LOWS IN THE MID TO LOWER 60S AMID INCREASING SURFACE
MOISTURE.

WEDNESDAY...WEAK SURFACE TROUGHING WILL PERSIST THROUGH THE MORNING
OVER THE GENERAL AREA OF LAREDO WITH A STRONG RESIDUAL TERRAIN
INVERSION KEEPING A CAP ON DEEP CONVECTION/SHOWERS DESPITE
INCREASING SFC HEATING AND MOISTURE. DOWNSLOPING SOUTHWESTERLIES
SHOULD ALLOW SKIES TO CLEAR OUT AND TEMPERATURES WILL WARM UP LIKELY
INTO HE MID TO LOWER 80S. THERE WILL PROBABLY BE A WINDOW OF SOME
FOG FORMATION AROUND PADRE ISLAND AND THE IMMEDIATE COAST WHEN WIND
SPEEDS SLACKEN IF A SEA BREEZE TYPE CURRENT IS ABLE TO FORM FROM THE
60 DEGREE WATER TO THE 80 DEGREE LAND. A SMALL CHANCE OF
SHOWERS/STORMS DEVELOPS OVER THE FAR NORTHERN RANCHLANDS MAINLY TO
PROVIDE SOME TIMING WIGGLE ROOM TO THE ADVANCING FRONT. /68-JGG/

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...AN ELONGATED AND
DEEP 500 MB TROUGH WILL DIG ACROSS MUCH OF THE LOWER 48 STATES WED
NIGHT AND THURS. THE SOUTHERN END OF THE TROUGH AXIS WILL SHEAR
OFF FROM THE REST OF THE TROUGH AND WILL CLOSE OFF NEAR THE BAJA
CALIFORNIA PENINSULA. AS THE NORTHERN PORTION OF THIS TROUGH AXIS
PUSHES EAST OVER THE GREAT LAKES REGION AND THE NORTHEASTERN
STATES THE PASSAGE OF THE TROUGH WILL PUSH A VERY STRONG COLD
FRONT THROUGH DEEP SOUTH TX LATE WED NIGHT/EARLY THURS MORNING. IN
THE WAKE OF THE FRONT A COLD CANADIAN AIRMASS WILL SETTLE OVER
DEEP SOUTH TX THURS THROUGH SAT. ALTHOUGH THE CAA WILL NOT RESULT
IN ANY FREEZING TEMPS AT THIS TIME...THE COMBINATION OF THE
SUSTAINED CAA AND THE STRONG NORTHERLY FLOW WILL SET THE STAGE FOR
A PROLONGED PERIOD OF LOW WIND CHILL VALUES OVER THE REGION DURING
THE LATTER HALF OF THIS WEEK. THE SUSTAINED CAA WILL ALSO BE
HELPED ALONG BY PERSISTENT COASTAL SURFACE TROFFING IN THE WAKE OF
THE FROPA WHICH WILL LIKELY MAINTAIN THICK LOW LEVEL CLD COVER AND
PERSISTENT POPS ON INTO THIS UPCOMING WEEKEND. THE COASTAL
TROFFING WILL LIKELY LOOSEN ITS GRIP OVER DEEP SOUTH TX LATER THIS
WEEKEND. BUT THE DISSIPATION OF THIS SURFACE FEATURE WILL THEN BE
FOLLOWED QUICKLY BY THE BAJA CALI 500 MB LOW WHICH WILL THEN OPEN
UP AND MOVE EASTWARDS OVER TX SUN AND MON. THE COMBINATION OF THIS
SERIES OF 500 MB AND SURFACE LOWS/TROUGHS WILL LIKELY HOLD THE
CLD COVER AND RAIN CHCS IN PLACE ON INTO THE WEEKEND WHICH WILL
TEND TO HOLD BACK ANY SERIOUS WARMING OF TEMPS THROUGH THE
EXTENDED RANGE PERIOD.

PRETTY GOOD AGREEMENT SHOWS UP BETWEEN THE GFS AND ECMWF THROUGH
AROUND FRI. THE MODELS THEN START DIVERGING FROM SAT THROUGH MON
WITH THE ECMWF HOLDING ONTO THE 500 MB CLOSED LOW OVER THE BAJA
CALI PENINSULA MUCH LONGER THAN THE GFS. FOR TEMPS AND POPS THESE
DIFFERENCES SHOW UP WITH THE GFS MEX MOS HOLDING ONTO THE COLDER
TEMPERATURES LONGER VERSUS THE ECMWF. WILL LEAN TOWARDS THE COLDER
GFS SOLUTION SINCE THE HIGHS ADVERTISED BY THE ECMWF THIS WEEKEND
LOOK A LITTLE TOO WARM CONSIDERING THE PERSISTENT CLD COVER AND
RAIN CHCS.

&&

.MARINE /NOW THROUGH WEDNESDAY...DENSE FOG IS EXPECTED TO
CONTINUE AT LEAST THROUGH MID MORNING ACROSS THE LOWER TEXAS
COAST. SOUTH WINDS WILL GRADUALLY BECOME STRONGER THROUGH THE DAY
TODAY AND TUESDAY NIGHT. WIND SPEEDS WILL GRADUALLY DECREASE
THROUGH WEDNESDAY IN ADVANCE OF A FRONT ARRIVING AFTER DARK
WEDNESDAY.

WEDNESDAY NIGHT THROUGH SATURDAY...MAJOR CHANGES ARE EXPECTED WED
NIGHT/THURS MORNING AS THE NEXT MAJOR COLD FRONT ARRIVES. MSL
FIELDS AFTER THE FROPA ARE VERY TIGHTLY PACKED ON THURS AND
ACCORDINGLY EXPECT A VERY STRONG POTENTIAL FOR GALE CONDITIONS FOR
BOTH THE BAY AND GULF WATERS FROM LATE WED NIGHT THROUGH THURS.
THE PGF WILL THEN RELAX A LITTLE BIT FRI AND SAT WHICH WILL ALLOW
THE WINDS AND SEAS TO DECREASE SOMEWHAT. HOWEVER SCA CONDITIONS
WILL LIKELY PERSIST ESPECIALLY FOR THE GULF WATERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  73  67  80  42 /  20  10  10  50
BROWNSVILLE          76  66  84  39 /  20  10  10  50
HARLINGEN            78  68  86  39 /  20  10  10  50
MCALLEN              80  67  87  38 /  20  10  10  50
RIO GRANDE CITY      80  64  88  40 /  20  10  10  50
SOUTH PADRE ISLAND   69  66  75  46 /  20  10  10  50

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...DENSE FOG ADVISORY UNTIL 10 AM CST THIS MORNING FOR TXZ250-251-
     253>257.

GM...DENSE FOG ADVISORY UNTIL 10 AM CST THIS MORNING FOR GMZ130-132-
     135-150-155-170-175.

     GALE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING
     FOR GMZ130-132-135-150-155-170-175.

&&

$$

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

SHORT TERM...68
LONG TERM...60
GRAHICAST/UPPER AIR...67



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