Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 240537
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1137 PM CST MON FEB 23 2015

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

&&

.AVIATION...THE CAA FROM THE NORTH IN THE WAKE OF THE FROPA EARLY
MON MORNING WILL MAINTAIN THE LOW STRATUS DECK IN PLACE THROUGH THE
OVERNIGHT HOURS INTO EARLY TUES MORNING. NAM FORECAST SOUNDINGS
MAINTAIN A FAIRLY SATURATED AND STRONG LOW LEVEL INVERSION
THROUGHOUT TONIGHT INTO EARLY TUESDAY MORNING WHICH WILL IN TURN
KEEP THE GENERAL IFR CEILINGS IN PLACE FOR MUCH OF THE CURRENT TAF
PERIOD. FORECAST WINDS ALOFT WILL THEN START SHIFTING AROUND FROM
THE WEST STARTING LATE TUES WHICH WILL ENTRAIN IN SOME DRIER AIR
WHICH COULD IMPROVE CEILINGS BACK TO VFR LEVELS LATE IN THE CURRENT
TAF PERIOD. THE CEILINGS COULD BE ALSO BE IMPROVED DUE TO THE SHIFT
OF THE SURFACE WINDS FROM THE E-NE TUES AFTERNOON AND EVENING WHICH
MAY HELP WARM UP THE LOWER LEVELS OF THE ATMS LATE TUES PUSHING THE
CEILINGS UP TO MVFR/VFR LEVELS.

&&

.PREV DISCUSSION... /ISSUED 853 PM CST MON FEB 23 2015/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...THE CAA FROM THE NORTH IN THE WAKE OF THE FROPA
EARLY THIS MORNING WILL MAINTAIN THE LOW STRATUS DECK IN PLACE
THROUGH THE OVERNIGHT HOURS INTO EARLY TUES MORNING. NAM FORECAST
SOUNDINGS MAINTAIN A FAIRLY SATURATED AND STRONG LOW LEVEL
INVERSION THROUGHOUT TONIGHT INTO EARLY TUESDAY MORNING WHICH WILL
IN TURN KEEP THE MVFR/IFR CEILINGS IN PLACE FOR MUCH OF THE
CURRENT TAF PERIOD. FORECAST WINDS JUST OF THE SURFACE WILL START
SHIFTING AROUND FROM THE WEST STARTING LATE TOMORROW WHICH WILL
START ENTRAINING DRIER AIR WHICH COULD IMPROVE CEILINGS BACK TO
VFR LEVELS LATE IN THE CURRENT TAF PERIOD.

PREV DISCUSSION... /ISSUED 416 PM CST MON FEB 23 2015/

SHORT TERM /NOW THROUGH TUESDAY NIGHT/...CLASSIC OVERRUNNING
SCENARIO NOW IN EFFECT...WITH VISIBLE SATELLITE IMAGERY SHOWING HIGH
CIRRUS MOVING FROM WEST-SOUTHWEST TO EAST-NORTHEAST OVER LOW STRATUS
HEAVILY INFLUENCED BY MODERATE TO BREEZY NEARLY NORTHERLY WINDS.
KBRO DOPPLER RADAR SHOWS LIGHT PRECIPITATION OVER THE CENTRAL AND
EASTERN PORTIONS OF THE BRO CWFA AND ADJACENT COASTAL WATERS...WITH
SURFACE OBSERVATIONS SHOWING LIGHT FOG AND REDUCED VISIBILITIES FOR
MUCH OF DEEP SOUTH TEXAS AND THE RIO GRANDE VALLEY.

TONIGHT...WEAK INVERTED SURFACE TROUGHINESS SETS UP OVER THE WESTERN
GULF OF MEXCIO. WITH THE 500 MB FLOW OVERHEAD REMAINING FROM NEARLY
THE WEST AND SURFACE WINDS FROM NEARLY THE NORTH...LIGHT RAIN AND
FOG SHOULD CONTINUE...ESPECIALLY BEFORE MIDNIGHT. LOW TEMPERATURES
SHOULD FALL INTO THE UPPER 30S TO NEAR 40 DEGREES...NOT UNLIKELY
GIVEN THE FACT THAT DEWPOINT TEMPERATURES ARE STEADILY FALLING INTO
THAT RANGE EARLY MONDAY AFTERNOON.

TUESDAY...INVERTED SURFACE TROUGH PERSISTS AND MOVES CLOSER TO THE
COASTLINE OF THE LOWER TEXAS COAST. SLIGHTLY DRIER AIR WILL WORK
FROM WEST TO EAST ACROSS THE BRO CWFA...AND THIS...COMBINED WITH THE
TROUGH...SHOULD HELP TO LIMIT PRECIPITATION MAINLY ALONG AND EAST OF
THE HIGHWAY 281/INTERSTATE 69C CORRIDOR...INCLUDING THE LOWER TEXAS
COASTAL WATERS. RETAINED INHERITED TEMPERATURES IN THE 50S...AND
THIS COULD BE THE WEAKEST ASPECT OF THE FORECAST WITH ADJUSTMENTS
POSSIBLY NEEDED DOWNWARD SOMETIME DURING THE NEXT 18 HOURS.

LONG TERM /WEDNESDAY THROUGH MONDAY/...THE SPRING ROLLER COASTER
GETS RESTARTED THROUGH THE PERIOD AS A CHILLY START TO WEDNESDAY
IS ERASED BY WARMING SUNSHINE INTO THURSDAY BEFORE ANOTHER FRONT
OOZES...OR SWEEPS...ACROSS THE VALLEY THURSDAY EVENING WITH AT
LEAST ONE COOL TO COLD DAY TO CLOSE THE WORK WEEK. MARCH LOOKS TO
COME IN LIKE A LAMB AFTER FEBRUARY`S LION-LIKE END...WHICH WILL
ENSURE THAT THE MONTH TILTS JUST BELOW THE LONG TERM AVERAGE.

PATTERN-WISE...POTENT SHORT WAVE RIPS ACROSS EAST TEXAS EARLY
WEDNESDAY AND WILL TAKE THE GRAY CHILL WITH IT. NORTHWEST WINDS
FOLLOWING THE LOW BRING A PACIFIC-SOURCED AIR MASS INTO THE VALLEY
AFTER SUNRISE...AND GUSTS COULD REACH 30+ MPH IN SPOTS KEEPING A
CHILLY EDGE TO TEMPERATURES DESPITE INCREASING SUNSHINE. THOSE
WINDS WILL QUICKLY DIMINISH BY AFTERNOON...AND WITH FULL SUNSHINE
AND COMPRESSION EXPECT READINGS TO RISE TO JUST BELOW SEASONAL
NORMS...NEAR 70...BY 3 PM OR SO.

A CLEAR AND QUIET OVERNIGHT WITH WINDS QUICKLY VEERING TO THE EAST
WILL ALLOW TEMPERATURES TO CRASH EARLY THEN SLOW THEIR DROP
SOMEWHAT. STILL SHOULD BE A BIT CHILLIER THAN GUIDANCE THURSDAY
MORNING ESPECIALLY WHERE WINDS GO SLACK. WE MAY HAVE TO WATCH FOR
RADIATION AND PERHAPS A HINT OF ADVECTION FOG NEAR THE COAST EARLY
THURSDAY...BUT INCREASING EAST WINDS SHOULD MIX THINGS OUT NICELY
WITH TEMPERATURES IN MOST AREAS REBOUNDING INTO THE UPPER 60S TO
LOWER 70S BETWEEN SYSTEMS.

THE TRICKY PART OF THE FORECAST ARRIVES THURSDAY NIGHT AND FRIDAY.
ANOTHER ARCTIC-SOURCED SURFACE HIGH DIVES INTO THE PLAINS AS WEAK
500 MB SHEAR AXIS SLIDES ACROSS SOUTH TEXAS. UNLIKE TODAY`S
PLUNGE...THE UPPER LEVELS ARE NOT AS CONDUCIVE TO BRINGING A GOOD
CHUNK OF THE SURFACE HIGH SOUTH VS. EAST. THAT SAID...GLOBAL
MODELS HAVE A VERY DIFFICULT TIME HANDLING MESOSCALE DENSITY
FEATURES ESPECIALLY IN VERY COLD AIR MASSES...TODAY BEING A
CLASSIC EXAMPLE (JUST TWO DAYS AGO...THE GFS MODEL WAS INDICATING
DAYTIME TEMPERATURES IN THE 60S!). THAT SAME GFS IS HINTING AT A
`NOSE` OF HIGH PRESSURE SPOKING DOWN INTO THE LEE OF THE SIERRA
MADRE WHICH WOULD AID WEAK COASTAL TROUGHING. IT`S TOO EARLY TO
LOOK AT A FULL NAM-12 TO SEE IF IT MIGHT (CORRECTLY??) BACK WINDS
TO THE NORTH/NORTHWEST BY EARLY FRIDAY BUT THAT ANSWER LIES
WITHIN THE SCOPE OF REASON THIS FAR OUT.

SO...THIS IS WHEN I WISH I HAD A CONFIDENCE (BOOM/BUST) SCENARIO
TO PLAY WITH RATHER THAN A `LEAN`. THE BOOM SCENARIO (SHALLOW COLD
DIVE) WOULD SUGGEST DAYTIME TEMPERATURES FRIDAY STRUGGLING THROUGH
THE UPPER 40S/LOWER 50S WITH `FEELS LIKE` TEMPERATURES NEAR 40.
THE CAUTIOUS...MOST PRAGMATIC FORECAST IS FOR DAYTIME TEMPERATURES
SOMEWHERE IN THE 50S TO PERHAPS LOWER 60S AS WEAK OVERRUNNING AND
STRATUS/PATCHY NUISANCE LIGHT RAIN DEVELOPS. WITH A NUMBER OF
END-OF-MONTH ACTIVITIES SETTING UP THURSDAY-SUNDAY...THIS FORECAST
HAS A LOT OF EYES ON IT...SO STAY TUNED IS THE WATCHWORD FOR
THURSDAY NIGHT THROUGH FRIDAY NIGHT.

SATURDAY WILL BE A TRANSITION DAY ANY WAY WE LOOK AT IT AS THE
MAIN SURFACE HIGH SLIDES INTO THE OHIO VALLEY AND ANOTHER UPPER
TROUGH BEGINS DEVELOPING ACROSS THE NEVADA/CALIFORNIA REGION.
INCREASINGLY STRONG SOUTHERLIES BY AFTERNOON SHOULD ERODE WHATEVER
CHILL IS LEFT AND BRING 60S BACK INTO THE FOLD...STILL A BIT BELOW
AVERAGE BUT MUCH IMPROVED ON FRIDAY. AND THE VALLEY WIND MACHINE
RETURNS IN EARNEST SUNDAY AS THE TROUGH DIGS INTO THE WEST WHILE
BUMPING SOUTHWEST FLOW ACROSS TEXAS...ENSURING NOTICEABLY HIGHER
SURFACE HUMIDITY AND A GOOD BET FOR SOUTHERLIES AT 20 TO 30 MPH
WITH HIGHER GUSTS ALONG WITH TEMPERATURES FINALLY RETURNING ABOVE
AVERAGE AND LIKELY ABOVE 80 AT MANY LOCATIONS (AVERAGE ON MARCH 1
IS 75 TO 78 ACROSS THE RGV). NEXT MONDAY IS A CRAPSHOOT AT THIS
POINT...THE DEEPENING TROUGH ON THE GFS KEEPS THE WARM/HUMID AND
BREEZY WEATHER GOING WHILE THE ECMWF BRINGS THE TROUGH FARTHER
EAST MORE QUICKLY...PUSHING THE NEXT FRONG THROUGH LATE MONDAY
WITH A MODEST COOL DOWN BEFORE SUNSET. POPULATED WITH THE MODEL
BLEND FOR THE TIME BEING UNTIL AN ANSWER IS REVEALED...WHICH COULD
BE THE SLOWER TROUGH (GFS) OR A FASTER OPEN WAVE (ECMWF).

BOTTOM LINE? PERSISTENT SPRING WARMTH ON HOLD FOR THE NEXT WEEK
AND LIKELY BEYOND.

MARINE...NOW THROUGH TUESDAY NIGHT...BUOY 42020 REPORTED NORTH
WINDS AROUND 25 KNOTS GUSTING TO AROUND 29 KNOTS WITH SEAS SLIGHTLY
UNDER 8 FEET WITH A PERIOD OF 7 SECONDS AT 14 CST/20 UTC. THE PRE-
DAWN MONDAY MORNING PASSAGE OF A COLD FRONT CONTINUES TO PRODUCE
SMALL CRAFT ADVISORY WINDS AND SEAS ALONG THE LOWER TEXAS COAST
RIGHT NOW. THESE CONDITIONS SHOULD PERSIST UNTIL AROUND MIDNIGHT
TONIGHT...WITH WINDS AND SEAS IMPROVING AFTERWARDS AND THROUGH
TUESDAY AS A WEAK INVERTED SURFACE TROUGH OF LOW PRESSURE BRIEFLY
DEVELOPS OVER THE WESTERN GULF OF MEXICO. HOWEVER...LOW PRESSURE
FORMING ALONG THE LOWER TEXAS COAST AND THE APPROACH OF AN
ASSOCIATED COLD FRONT WILL LEAD TO INCREASING WINDS AND BUILDING
SEAS TUESDAY NIGHT...WITH A RETURN TO SMALL CRAFT ADVISORY AT THAT
TIME.

WEDNESDAY THROUGH SATURDAY: A QUICK SHOT OF 20 KNOT AND GUSTY
WIND BEHIND THE DEVELOPING LOW AND EAST TEXAS SHORT WAVE WILL MAKE
FOR A ROUGH GO FOR BOATERS/FISHERS EARLY...BUT THINGS COULD
IMPROVE NICELY BY AFTERNOON...TOO LATE FOR MOST. THURSDAY IS
PROBABLY THE ONE DECENT DAY OF THE WEEK AT LEAST FOR THE MORNING
WITH A BRIEF REPRIEVE OF LIGHT WINDS/SLIGHT SEAS.

THAT WON`T LAST MORE THAN 6-12 HOURS AS THE AFOREMENTIONED LATE
WEEK FRONT SURGES THROUGH. NO MATTER HOW THE SITUATION
EVOLVES...NORTH TO EAST WINDS RISING TOWARD OR OVER 20 KNOTS
BECOMING MORE LIKELY THURSDAY NIGHT INTO FRIDAY...WITH WAVES
QUICKLY RETURNING TO 5-7 FEET OR HIGHER WITH THE STRONGER FETCH.
TIDAL ISSUES MAY NEED TO BE WATCHED THOUGH ASTRONOMICAL TIDES ARE
NOT OF GREAT CONCERN. CONDITIONS WILL REMAIN UNSETTLED FRIDAY
NIGHT INTO SATURDAY WITH 15-20 KNOT SUSTAINED WINDS AND HIGHER
GUSTS AS FLOW VEERS FROM NORTHEAST TO EAST/SOUTHEAST.WRKARF

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 4 AM CST TUESDAY FOR GMZ150-155-170-
     175.

&&

$$

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