Area Forecast Discussion
Issued by NWS Brownsville, TX

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS64 KBRO 272335 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
535 PM CST FRI FEB 27 2015

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

&&

.AVIATION...COASTAL TROUGH CONTINUES TO SET UP JUST
OFFSHORE...WHICH WILL BRING CONTINUED LOW CIGS FOR THE REGION
THROUGH THE NEXT 24 HOURS. A BRIEF BREAK HAS ARRIVED THIS
AFTERNOON FOR BRO AND HRL...BUT LOW CLOUDS WILL FILL BACK IN
WITHIN A COUPLE HOURS OF SUNSET. CIGS ALREADY DOWN TO 1000 OFF TO
THE NORTH OF THE REGION...AND THIS PARCEL WILL MOVE INTO THE LOWER
VALLEY LATER THIS EVENING...AND LIKELY CONTINUE THROUGH MOST OF
THE DAY TOMORROW. A FEW VERY LIGHT RAIN SHOWERS AND DRIZZLE MAY
DEVELOP LATER TONIGHT. LIGHT NORTHERLY WINDS WILL GRADUALLY SHIFT
TO THE WEST LATE TONIGHT AND CONTINUE TOMORROW AROUND 10 KNOTS.

&&

.PREV DISCUSSION... /ISSUED 400 PM CST FRI FEB 27 2015/

..FEBRUARY OUT RATHER LION-LIKE THEN MARCH IN LIKE A LAMB BEFORE
ANOTHER LION ROARS IN NEXT WEEK...

SHORT TERM /NOW THROUGH SATURDAY NIGHT/...LATEST SATELLITE AND
OBSERVATION SHOWS THE UPPER TROUGH GRADUALLY DIGGING SOUTH ALONG
THE CA COAST WITH A WEST TO SW FLOW ACROSS SOUTH TEXAS TODAY. AT
THE SURFACE...A BROAD 1042 DAM HIGH PRESSURE IS IN CONTROL OF THE
MORE THAN HALF OF THE EASTERN PORTION OF THE CONUS. THE COLDER AIR
MADE ITS WAY INTO THE CWA OVER THE WESTERN COUNTIES WITH
TEMPERATURES IN THE UPPER 30S WHILE TOWARDS THE EAST IN THE MID
50S. THE SHARP TEMPERATURE GRADIENT IS KEEPING A DRASTIC
TEMPERATURE DIFFERENCE ACROSS THE AREA AND THIS SAME PATTERN WILL
CONTINUE THROUGH THE DAY. HIGHS WILL BE IN THE MID 60S OVER THE
LOWER VALLEY AND SPI. WEST OF HARLINGEN...HIGH TEMPERATURES WILL
RANGE FROM THE MID 50S TO THE MID 40S. THE REST OF TODAY...AS THE
SOUTHWEST FLOW SETS UP ALOFT...THE OVERRUNNING PATTERN WILL INDUCE
LIGHT RAIN AND DRIZZLE INCREASE LATE THIS AFTERNOON AND EVENING.

TONIGHT...THE SOUTHWESTERLY FLOW WILL HELP THE COASTAL TROUGH TO
DEVELOP AND STRENGTHEN OVER THE GULF WATERS WITH COLDER ENCLOSE
AROUND IT. THIS WILL SET UP THE NORTHWEST FLOW AT THE SURFACE MOVING
INTO THE COASTAL AREAS. COLDER AIR MASS WILL FILTER IN LOWERING
TEMPERATURES INTO THE UPPER 40S ALONG THE COAST AND UPPER 30S
TOWARDS THE WEST. DEEPER MOISTURE FROM THE GULF WILL CONTINUE TO
ENHANCE LIGHT SHOWERS ACROSS THE AREA WITH A 30 TO 40 PERCENT
CHANCE.

SATURDAY THE HIGH PRESSURE BEGINS TO MOVE EAST WITH SOUTHWESTERLY
FLOW ALOFT. THIS PATTERN WILL CONTINUE TO ENHANCE LIGHT RAIN THROUGH
THE DAY AND INTO SATURDAY NIGHT WITH OVERCAST CLOUD DECK. HIGH
TEMPERATURES WILL BE IN THE MID 50S AS THE COLD AIR MASS IS A BIT
MODIFIED BUT REMAINS IN CONTROL OVER THE CWA. SATURDAY NIGHT...THE
COASTAL TROUGH BEGINS TO LIFT NORTHEAST WITH A MORE PRONOUNCE
SOUTHWEST FLOW WITH HIGH 60 TO 70 DEG DEWPOINTS AS MORE DEEP LOW
LEVEL MOISTURE SURGES NORTHWARD INTO THE CWA. THE CHANCE OF RAIN
INCREASE BEGINNING SATURDAY NIGHT INTO EARLY SUNDAY. LOW
TEMPERATURES SATURDAY NIGHT WILL BE IN THE UPPER 40S TOWARDS THE
WEST AND LOW 60S ALONG THE COAST.

LONG TERM /SUNDAY THROUGH FRIDAY/...IN TWO WORDS? ROLLER COASTER!
IF YOU REMEMBER THE RECENT SHARP CHANGE EARLY THIS WEEK...AND THE
SEVEN SUCH CHANGES IN EARLY 2014...NEXT WEEK IS FOR YOU. WHILE NOT
UNUSUAL FOR SPRING...THE POTENTIAL SHARPNESS OF THE MIDWEEK FRONT
IS WORTHY OF THE FOCUS OF THIS DISCUSSION.

BIG PICTURE-WISE...THE FIRST HALF OF NEXT WEEK IS DOMINATED BY
BUILDING UPPER RIDGE ACROSS THE CENTRAL AND SOUTHERN GULF WHICH
NOSES NORTHWARD INTO DEEP SOUTH TEXAS...WHILE UPPER TROUGH DROPS
INTO SOUTHERN CALIFORNIA EARLY MONDAY AND DAMPENS OUT WHILE
TREKKING EAST TOWARD THE SOUTHERN PLAINS THROUGH TUESDAY. BETWEEN
THESE SYSTEMS...INCREASING LOW LEVEL SOUTHERLIES AND MID LEVEL
SOUTHWESTERLIES WILL BRING THE WARMEST ATMOSPHERE OF THE YOUNG
SPRING...WITH MARCH TRULY COMING IN LIKE A LAMB. BUT...SIMILAR TO
THE SAME TIME IN 2014...THE `LION` WILL EAT THE LAMB ONCE AGAIN
SOMETIME WEDNESDAY AS CROSS-POLAR MID/UPPER FLOW CROSSES THE
CANADIAN PRAIRIES INTO BIG SKY COUNTRY...GENERATING YET ANOTHER
SPRAWLING HIGH WITH TRUE NORTH POLE AIR SET TO RACE DOWN THE
PLAINS TUESDAY AND WEDNESDAY. UPPER LEVEL FLOW RESEMBLES NEARLY
EVERY SHARP CHILLDOWN THIS WINTER...WHICH IS DIFFERENT THAN
TODAY`S TRICKY FORECAST WHERE NORTHEAST FLOW HAS KEPT THE LOWER
VALLEY COOL FOR THE SEASON /UPPER 50S AND 60S/ WHILE WINTER HAS
SET IN FOR THE RIO GRANDE PLAINS...WHERE TEMPERATURES ARE IN THE
UPPER 30S TO LOWER 40S...NEARLY 40 DEGREES BELOW AVERAGE FOR LATE
FEBRUARY.

FOR THE SENSIBLE WEATHER...WHATEVER COOL AIR IS HANGING EARLY
SUNDAY WILL FINALLY BE OVERWHELMED BY INCREASING SOUTH/SOUTHEAST
FLOW AND TEMPERATURES WILL SURGE INTO THE 70S TO AROUND 80 BY
AFTERNOON. HUMIDITY WILL BE NOTICEABLE AS WELL...AND EXPECT
PLANTS/TREES TO SHOW ANOTHER SURGE OF GREENUP WITH THE DEWPOINTS
REACHING WELL INTO THE 60S BY AFTERNOON.

BALMY...EVEN MUGGY...CONDITIONS ARRIVE SUNDAY NIGHT AND
TEMPERATURES WILL ONLY DROP BACK INTO THE MID TO UPPER 60S BY
DAYBREAK MONDAY...SETTING THE STAGE FOR 80S FOR ALL BUT THE COAST
WITH INCREASING SOUTHERLY `WIND MACHINE` WITH GUSTS EXCEEDING 25
MPH BY NOON.

AS THE DISSIPATING TROUGH EDGES CLOSER TO TEXAS...SURFACE PRESSURE
WILL FALL ALONG THE LEE OF THE SIERRA MADRE MONDAY NIGHT AND
TUESDAY AND KICK UP 850-925MB WINDS TO 35 TO 45 KNOTS. THESE WINDS
WILL TRANSLATE DOWN ENOUGH TO KEEP FOG AT BAY BUT ALSO HOLD
TEMPERATURES UP...WITH LOWS BY TUESDAY MORNING UNLIKELY TO DROP
BELOW 70 IN MANY AREAS...A SURE SIGN THAT SPRING WEATHER WILL
ULTIMATELY PREVAIL. THAT SAME FLOW SHOULD VEER TO THE
WEST/SOUTHWEST BY AFTERNOON BRINGING THE FIRST TRUE COMPRESSIONAL
WARMING AFTERNOON OF THE YOUNG SPRING TO THE MID/UPPER
VALLEY...AND WILL SEE OUR FIRST COVERAGE OF 90+ TEMPERATURES FROM
HIDALGO/BROOKS THROUGH ZAPATA COUNTY. ALONG HIGHWAY 77...WINDS
COULD EDGE TOWARD ADVISORY (30 MPH SUSTAINED) LEVELS BETWEEN 9 AM
AND 4 PM...SOMETHING TO KEEP AN EYE ON WHILE WINDS WILL DROP
NOTICEABLY ALONG/WEST OF HIGHWAY 281.

THEN COMES THE FUN. AFTER ANOTHER BALMY TUESDAY NIGHT/EARLY
WEDNESDAY WITH TEMPERATURES 10 DEGREES ABOVE AVERAGE...THE POLAR
SLAM ARRIVES. TIMING IS VIRTUALLY IMPOSSIBLE THIS FAR OUT...BUT
PERSISTENCE OF THE GFS AND NOW THE ECMWF COMING AROUND TO A DEEPER
AND FASTER SOLUTION...BELIEVE TIMING WILL SETTLE IN SOMETIME
BETWEEN NOON AND 6 PM. GFS MOS STRUGGLING MIGHTILY WITH A MORNING
TEMPERATURE RISE (EQUATIONS DON`T INCLUDE THREE-HOURLY
TEMPERATURE FORECASTS) AND WITH A WARM START...LIGHTER WINDS...AND
SOME PRE-FRONTAL SUNSHINE EXPECT HIGHS TO END UP NEAR CURRENT
FORECAST VALUES...UPPER 70S TO LOWER 80S...BEFORE THE BIG CRASH.

THAT CRASH /MIGHT/ COME WITH A BROKEN LINE OF THUNDERSTORMS MAINLY
ACROSS THE LOWER VALLEY AS MOISTURE POOLS AND IS LIFTED RIGHT
ALONG THE FRONT. CONFIDENCE NOT HIGH BUT INTRODUCED 20 PERCENT TO
BE SAFE. THE FRONT WILL SWEEP THROUGH AND TEMPERATURES WILL CRASH.
MODEL BLENDS TOSSED OUT FOR THIS PARTICULAR EVENT...AND LEANED
TOWARD THE GFS SLAM WITH TEMPERATURES CRASHING INTO THE UPPER 40S
TO LOWER 50S BY SUNSET. SHOULD GFS BE ON TARGET...THESE NUMBERS
COULD BE TOO HIGH SO STAY TUNED. AS WEAK DISTURBANCE TRAVERSE THE
SOUTHWEST FLOW ABOVE THE COLD DOME...EXPECT SOME MEASURABLE
RAINFALL FROM LATE AFTERNOON THROUGH EARLY THURSDAY MORNING.
GFS GUIDANCE BRINGS LOW TO HIGH 30S ACROSS THE REGION AND WIND
CHILLS AS LOW AS THE MID TO HIGH 20S. DIDN`T GO QUITE THAT COLD
JUST YET BUT SEE NO REASON TO DEVIATE MUCH WITH ECMWF...OVERALL
PATTERN...AND EXPERIENCE ADDING TO THE CONFIDENCE.

THURSDAY STARTS FLAT OUT MISERABLE BUT RAIN SHOULD END AND CLOUDS
GRADUALLY THIN...LIFT...OR DISSIPATE THROUGH AFTERNOON WHICH
SHOULD ALLOW STRONGER SUN TO PUSH TEMPERATURES BACK TOWARD OR
ABOVE 50...STILL UP TO 25 DEGREES BELOW AVERAGE FOR MARCH 5. TO
CLOSE THE WORK WEEK...MODELS DIVERGE A BIT WITH GFS DEVELOPING
FLAT NORTHWEST FLOW AND INCREASING SUNSHINE WHILE ECMWF CUTS OFF
ENERGY ACROSS BAJA WITH SPOKES POSSIBLY ENHANCING COASTAL LIFT AND
PERHAPS SOME LIGHT RAIN/SHOWERS BEGINNING FRIDAY. ANSWER MAY LIE
IN BETWEEN...SO KEPT HIGHS ON THE COOL-ISH SIDE WITH A GOOD DEAL
OF CLOUDS.

BOTTOM LINE?  KEEP THE WINTER...AND SUMMER...CLOTHES CLOSE BY!

MARINE...NOW THROUGH SATURDAY NIGHT...THE BROAD HIGH PRESSURE ACROSS
THE MID WEST WHICH BROUGHT THE COLD FRONT ACROSS THE AREA WILL MAINTAIN A
STRONG EASTERLY FETCH OVER THE GULF WATERS. THIS WILL INCREASE SEAS WITH
SCA IN EFFECT THROUGH MUCH OF THE DAY AND CONTINUING THROUGH THE WEEKEND.
AT THIS TIME...SEAS WILL BE BUILDING BETWEEN 6 TO 8 FEET TONIGHT AND TO
10 FEET BY SATURDAY. SEAS LOWER TO 7 FEET BY THE END OF THE SHORT
TERM.

SUNDAY THROUGH WEDNESDAY: SOUTHEAST FLOW BEGINS TO TAKE
HOLD SUNDAY BUT MARINE LAYER AND GENERALLY WEAK GRADIENT SHOULD
KEEP THINGS UNDER CONTROL. THAT CHANGES SUNDAY NIGHT AND
MONDAY...WITH 15 TO 20 KNOT WINDS LIKELY AND SEAS BUILDING TO 4-5
FEET. MARINE LAYER WILL KEEP WINDS IN CHECK MONDAY...BUT THAT WILL
BE GONE MONDAY NIGHT AND TUESDAY AS SYNOPTIC
FORCING...STRENGTHENING SURFACE TROUGH...AND 35 TO 45 KNOT JET
ENOUGH TO PUSH 20-25 KNOT SOUTHERLIES AND 7 FOOT WAVES INTO THE
WATER MONDAY NIGHT...CONTINUING TUESDAY.

CONDITIONS SHOULD STAY RATHER DIFFICULT TUESDAY NIGHT AND SHOULD
BRIEFLY LAY DOWN WEDNESDAY BUT NOT LONG ENOUGH BEFORE THE SLAM
ARRIVES. EXPECT GALE FORCE `NORTHER GUSTS SOMETIME WEDNESDAY AND
ESPECIALLY WEDNESDAY NIGHT AS LOCAL SEAS BUILD TO 12 FEET...AND
WARNINGS MORE THAN LIKELY AT SOME POINT DURING THAT PERIOD.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 3 AM CST SATURDAY FOR GMZ150-155-170-
     175.

&&

$$

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

64/64


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.