Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 121732 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1232 PM CDT SAT APR 12 2014

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

&&

.AVIATION...DEEPENING LOW PRESSURE OVER THE SOUTHERN HIGH PLAINS
IS KEEPING THE GRADIENT TIGHT AND BREEZY...GUSTY SOUTH SOUTHEAST
WINDS ALIVE THIS AFTN. HEATING IS DEVELOPING A BKN FIELD OF LOW
CU OVER THE EASTERN HALF OF THE CWA INCLUDING THE TAF SITES. THE
BRO MORNING SOUNDING SHOWS A STRONG INVERSION WITH A BASE AROUND
3800 FT...SO CLOUD HEIGHTS SHOULD MIX OUT TO VFR CONDITIONS FOR
THE AFTN. GUIDANCE SHOWS CEILINGS DECREASING TO AROUND 1000 FT
LATE THIS EVE...WITH FLUCTUATIONS BETWEEN MVFR AND IFR CONDITIONS
POSSIBLE. MODERATE SOUTH SOUTHEAST WINDS WILL CONTINUE...BUT THERE
IS A SIGNAL FOR PATCHY FOG IN THE GUIDANCE...SO INCLUDING IT FOR
THE RANCH LANDS AND BRUSH COUNTRY AROUND U.S. 281 FOR A FEW HOURS
BEFORE DAWN SUNDAY. SIMILAR CONDITIONS ON SUNDAY WILL RESULT IN
ANOTHER ROUND OF BREEZY WINDS AND CEILINGS LIFTING TO BKN VFR
BY AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 632 AM CDT SAT APR 12 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...IR SATL IMAGERY AND SURFACE OBS INDICATES THAT HIGH
LEVEL CIRRUS CONTINUES TO SPREAD OVER THE AREA FROM WEST TO EAST.
CLOSER TO THE SURFACE PATCHY AREAS OF STRATUS ARE FORMING UP
ACROSS THE AREA. AS THE SOUTHEAST LOW LEVEL FLOW CONTINUES TO
BRING IN HIGHER MOISTURE VALUES IN OFF OF THE GULF OF MEX EXPECT
THE POTENTIAL FOR SOME MVFR CEILINGS TO PERSIST THROUGH THE EARLY
MORNING HOURS TODAY. AFTER SUNRISE THE LOW LEVEL MIXING WILL
INCREASE AS THE DAYTIME HEATING AND SURFACE WINDS INCREASE. THIS
WILL INCREASE THE CEILINGS BACK UP TO NEAR VFR LEVELS THROUGHOUT
THE LATE MORNING AND AFTERNOON HOURS. MVFR/IFR CEILINGS WILL
LIKELY RETURN ONCE AGAIN AFTER SUNSET TODAY AS THE MOIST LOW LEVEL
INVERSION REFORMS SAT NIGHT. THE KBRO VWP SHOWS SOME 40 TO 45 KNOT
SOUTHERLY WINDS AT AND BELOW 2 KFT. AM NOT SURE HOW LEGITIMATE
THESE VALUES ARE AS THEY COULD BE BIRD CONTAMINATED. WILL HOLD OFF
ON MAINTAINING THE MENTION OF LLWS AND WILL ALLOW THE DAY CREW TO
TAKE A LOOK AT THE 12Z BRO SOUNDING TO SEE HOW STRONG THE LOW
LEVEL WINDS ACTUALLY ARE. USED A BLEND OF THE GFS AND NAM GUIDANCE
AS A BASIS FOR THE 12Z TAF SET AS BOTH MODELS WERE IN PRETTY GOOD
AGREEMENT IN BRINGING IN LOWER CEILINGS THIS MORNING THROUGHOUT
SATURDAY MORNING.

PREV DISCUSSION... /ISSUED 419 AM CDT SAT APR 12 2014/

SHORT TERM /TODAY THROUGH SUNDAY/...THE BROAD AND DEEP 500 MB
TROUGH AXIS THAT IS EXPECTED TO DEEPEN OVER THE WESTERN AND CENTRAL
PLAINS STATES TODAY AND TOMORROW WILL MAINTAIN A PRETTY STRONG PGF
OVER THE AREA AS A SERIES OF SURFACE LOWS DEVELOP OVER THE CENTRAL
PLAINS STATES. AS A RESULT OF THE MODERATE S-SE LOW LEVEL FLOW OVER
THE AREA THE MOISTURE LEVELS OVER THE RGV WILL GRADUALLY INCREASE
RESULTING IN HIGHER RH`S AND THICKENING CLD COVER. WAA WILL ALSO
CONTINUE AS A RESULT OF THE PERSISTENT SOUTHERLY LOW LEVEL FLOW OVER
THE AREA. ALTHOUGH THE THICKENING CLD COVER WILL TEND TO HOLD DOWN
THE DIURNAL HEATING A BIT.

DESPITE THE RETURN OF THE LOW LEVEL MOISTURE WITH THE S-SE WINDS
DEEP LAYER MOISTURE AND INSTABILITY REMAINS PRETTY LIMITED THROUGH
TOMORROW. THIS IN COMBINATION WITH THE COLD FRONT AND THE 500 MB PVA
REMAINING CONFINED GENERALLY WELL NORTH OF DEEP SOUTH TEXAS EXPECT
POPS TO REMAIN IN THE 5 TO 10 % RANGE THROUGHOUT TODAY AND TONIGHT.
WILL INCLUDE SOME 20 % POPS MAINLY ALONG THE COASTLINE DURING THE
DAY SUNDAY AS A LITTLE DEEPER LAYER MOISTURE EDGES INTO THE REGION
THEN.

THE MAV...MET AND ECMWF TEMPS THROUGHOUT THE SHORT TERM PERIOD ARE
IN PRETTY GOOD AGREEMENT AND WILL LIKELY GO CLOSE TO A 50/50 MODEL
BLEND OF THE MAV AND MET FOR HIGHS AND LOWS THROUGH TOMORROW. THE
NAM IS A LITTLE WETTER VERSUS THE MAV ON SUNDAY AFTERNOON AND WILL
LEAN TOWARDS THIS MODEL FOR POPS THROUGH THE SHORT TERM.

ALTHOUGH THE PGF WILL BE PRETTY DECENT AS THE SURFACE LOWS OVER THE
CENTRAL PLAINS STATES DEVELOP THIS WEEKEND. AT THIS TIME DO NOT
EXPECT ANY WIND ADVISORY CONDITIONS.

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY NIGHT/...THE MAIN FORECAST
ISSUES IN THE LONG TERM WILL BE THE COLD FRONTAL PASSAGE MONDAY AND
THE ASSOCIATED SHOWERS AND THUNDERSTORMS. A STRONG COLD FRONT
LOCATED ACROSS THE TEXAS PANHANDLE SUNDAY EVENING WILL QUICKLY MOVE
SOUTHWARD INTO CENTRAL TEXAS BY MONDAY MORNING. EXPECT OVERNIGHT LOW
TEMPERATURES SUNDAY NIGHT IN THE 70S WITH PATCHY FOG POSSIBLE NEAR
THE COAST. MOISTURE POOLS AHEAD OF THE FRONT WITH PRECIPITABLE WATER
VALUES OVER 1.6 INCHES. RAIN CHANCES BEGIN TO INCREASE AROUND DAWN
MAINLY ACROSS THE NORTHERN RANCH LANDS. PRECIPITABLE WATERS INCREASE
TO AROUND 1.80 INCHES AHEAD OF THE COLD FRONT. FRONTAL FORCING WILL
ALLOW SHOWERS AND THUNDERSTORMS TO DEVELOP ACROSS THE AREA ON
MONDAY. HEAVY RAIN ALONG WITH FEW STRONG THUNDERSTORMS ARE POSSIBLE
BUT NO SEVERE WEATHER IS ANTICIPATING AT THIS TIME. HIGH TEMPS ON
MONDAY WILL BE IN THE MID TO UPPER 80S UNDER MOSTLY CLOUDY SKIES.

THE COLD FRONT MOVES THROUGH THE RIO GRANDE VALLEY AND DEEP SOUTH
TEXAS MONDAY AFTERNOON WITH SHOWERS AND THUNDERSTORMS LINGERING
ACROSS THE AREA THROUGH MONDAY EVENING. HIGH PRESSURE BUILDS ACROSS
THE AREA MONDAY NIGHT INTO TUESDAY. GOOD COLD AIR ADVECTION EXPECTED
IN THE WAKE OF THE FRONT WITH NORTH WINDS OF 20 TO 25 MPH AND HIGHER
GUSTS DEVELOPING MONDAY NIGHT. OVERNIGHT LOW TEMPERATURES MONDAY
NIGHT WILL FALL INTO THE UPPER 40S ACROSS THE NORTHERN RANCH LANDS
WITH MID 50S NEAR THE COAST. TUESDAY WILL BE COOLER AS DRY AIR AND
NORTH WINDS CONTINUE ACROSS THE REGION. SURFACE HIGH PRESSURE MOVES
TO THE EAST ON WEDNESDAY ALLOWING WINDS TO VEER TO THE EAST THEN
SOUTHEAST. THIS WILL RESULT IN TEMPERATURES GRADUALLY WARMING
THROUGH THE WEEK.

MARINE...TODAY THROUGH SUNDAY...ALTHOUGH THE PGF WILL REMAIN
PRETTY STRONG OVER THE LOWER TEXAS BAY AND GULF WATERS THROUGH
SUNDAY...THE RELATIVELY COOL BAY AND GULF WATER TEMPS WILL LIKELY
LIMIT THE DOWNWARD MIXING OF THE S-SE LOW LEVEL FLOW OVER THE
AREA. SO FOR NOW WILL ONLY MENTION ONLY SCEC CONDITIONS FOR THE
MARINE AREAS. ANOTHER LIMITING FACTOR FOR TODAY WILL BE THE
INCREASING CLD COVER. MORE LOW LEVEL MARINE CLD LAYERS FOR BOTH
THE BAY AND GULF WATERS WOULD ALSO HELP INHIBIT THE DOWNWARD
MIXING OF THE STRONGER SOUTHERLY WINDS ALOFT.

SUNDAY NIGHT THROUGH WEDNESDAY NIGHT/...A COLD FRONT ARRIVES
MONDAY AFTERNOON RESULTING STRONG WINDS AND ROUGH SEAS. SMALL
CRAFT ADVISORIES WILL BE NECESSARY WITH EVEN A SHORT DURATION OF
GALE CONDITIONS MONDAY NIGHT AS WIND GUSTS NEAR GALE FORCE. HIGH
PRESSURE WILL BE SLOW TO MOVE EAST ALLOWING ADVERSE MARINE
CONDITIONS TO PERSIST THROUGH TUESDAY NIGHT. MARINE CONDITIONS
IMPROVE ON WEDNESDAY AS HIGH PRESSURE MOVES EAST.

&&

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

$$

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