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000
FXUS64 KBRO 182310 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
610 PM CDT SAT MAY 18 2013

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

.AVIATION...NO CHANGES WERE NEEDED TO THE PREVIOUS TAF FORECAST
PACKAGE. PREVIOUS DISCUSSION:

GENERALLY A BROKEN RECORD FORECAST INTO SUNDAY AFTERNOON. SLOWLY
DEVELOPING/MOVING UPPER LEVEL TROUGH ACROSS THE NORTHERN PLAINS
WILL ENHANCE THE SEMI-PERMANENT PRESSURE GRADIENT BETWEEN THE LEE
OF THE SIERRA MADRE AND THE WESTERN GULF FOR ONE MORE DAY. THAT
MEANS GUSTY SOUTH/SOUTHEAST WINDS FROM MID TO LATE MORNING THROUGH
EARLY EVENING WITH SUSTAINED VALUES RAMPING INTO THE LOW-MID 20S
AND GUSTS AT OR ABOVE 30 KNOTS FOR A FEW HOURS...FOLLOWED BY THE
NOCTURNAL DROP TOWARD BUT NOT BELOW 10 KNOTS OVERNIGHT.

AS FOR CLOUDS...DRY AIR WITHIN THE INVERSION ENSURES RAPID MIX-OUT
OF THE LATE NIGHT THROUGH EARLY MORNING SOUP...WHICH WILL FLIRT
WITH THE IFR/MVFR BOUNDARY AT 1K FEET BETWEEN 06Z AND 13Z. ONCE
MIXED...SCATTERED TO OCCASIONALLY BROKEN CIRRUS PREVAILS THOUGH
HIGH LEVEL DRYING APPEARS SUNDAY AFTERNOON.

LAST BUT NOT LEAST...SMOKE FROM THE LAST OF AGRICULTURAL BURNING IN
YUCATAN STATE WILL CONTINUE ON A TRAJECTORY TOWARD THE VALLEY AND
SHOULD LEAD TO HIGH MVFR VISIBILITY RESTRICTIONS UNDER THE
INVERSION OVERNIGHT AND EARLY MORNING AS HAZE/MIST. VISIBILITY
SHOULD RISE ABOVE THRESHOLDS NEAR THE GROUND...BUT HAZE ALOFT
LOOKS TO BE IN THE CARDS FOR SUNDAY WHICH COULD RESTRICT
VISIBILITY A LITTLE IN THE MIXING LAYER...3 TO 5K FEET OR SO...ON
APPROACH.
&&

.PREV DISCUSSION... /ISSUED 157 PM CDT SAT MAY 18 2013/

SHORT TERM /NOW THROUGH SUNDAY NIGHT/...SUMMER SWELTER HAS ARRIVED
FOR THIS WEEKEND AS TEMPERATURES AND HUMIDITY WILL BE MORE LIKE LATE
JUNE AND EARLY JULY THAN MID MAY. THAT SAID...THE PAST SEVERAL YEARS
HAVE HAD STRETCHES IN MAY THAT WERE SIMILAR IF NOT HOTTER...AND THE
BIGGEST DIFFERENCE BETWEEN NOW AND JULY IS THE GENERAL STRENGTH OF
THE SOUTHERLY FLOW WHICH OWES TO DEEPENING SURFACE LOW PRESSURE
AHEAD OF DEVELOPING UPPER TROUGH SLIDING ACROSS THE CENTRAL AND
NORTHERN PLAINS. IN ADDITION TO THE WINDS...HAZY SKIES AND MODERATE
TO UNHEALTHY AIR QUALITY COURTESY OF THE LAST OF THE AGRICULTURAL
BURNING IN YUCATAN DON`T TYPICALLY COME WITH LATE JUNE/JULY HEAT.

SUBTLE CHANGES IN THE MID/UPPER FLOW INTO EARLY MONDAY WILL DO
LITTLE TO AFFECT SENSIBLE WEATHER...WHICH WILL CONTINUE TO FEATURE
SULTRY NIGHTS WITH LOW CLOUDS QUICKLY DEVELOPING AND BECOMING
OVERCAST BY MIDNIGHT OR SO...BOOKENDING A HAZY HOT AND BREEZY DAY ON
SUNDAY.  THE SUBTLE CHANGE...WHICH INVOLVES A FLATTENING 500 MB
RIDGE AND VEERING WINDS ABOVE 700 MB TOWARD THE NORTHWEST...SHOULD
REDUCE THE AMOUNT OF CIRRUS ON SUNDAY AFTERNOON COMPARED WITH THIS
(SATURDAY) AFTERNOON.

OTHERWISE...WITH LOW LEVEL THICKNESS...1000-500 MB THICKNESS...850
TEMPERATURE...ETC. PRETTY MUCH STATUS QUO EXPECT NEARLY THE SAME
SURFACE TEMPERATURE AND HUMIDITY ON SUNDAY AS THEY WERE ON FRIDAY
AND TODAY. THIS MEANS HIGHS IN THE 90S EXCEPT JUST OVER 100 ACROSS
THE ZAPATA PLAINS...LOWER 80S AT THE BEACHES...AND FEELS LIKE
TEMPERATURES A LITTLE OVER 100 IN ALL AREAS EACH AFTERNOON.
NIGHTTIME TEMPERATURES WILL FALL INTO THE UPPER 70S TOWARD THE COAST
BY MID EVENING AND HOLD ALL NIGHT...WITH LOWER TO MID 80S WELL
INLAND BY MIDNIGHT FALLING INTO THE 70S BEFORE DAYBREAK.

AS FOR AIR QUALITY...VALUES FOR FINE PARTICULATE
MATTER...DUST/HAZE/SMOKE ETC...PASSED 100 THIS MORNING MID VALLEY
WHICH PUTS HIDALGO/WESTERN CAMERON/STARR IN UNHEALTHY FOR SENSITIVE
GROUPS.  EXPECT SIMILAR CONDITIONS ON SUNDAY WITH NOTHING TO CHANGE
THE TYPE OF AIR MASS AND THE LONG FETCH COMING FROM THE YUCATAN.
WHILE THE WIND TRAJECTORY BRINGS THE PARTICULATES...THE STRENGTH OF
THE WIND MIXES THEM TO A DEGREE AND SHOULD KEEP VALUES FROM RISING
INTO MORE DANGEROUS TERRITORY.  FOR MORE...SURF TO
HTTP://TCEQ.TEXAS.GOV AND CLICK ON "AIR".

LONG TERM /MONDAY THROUGH SATURDAY/...A LARGE CLOSED LOW/TROUGH WILL
BE POSITIONED FROM THE MIDWEST TO THE FOUR CORNERS AT THE
BEGINNING OF THE LONG TERM. THE TROUGH WILL BE SLOW IN MOVING EAST
WITH THE TROUGH AXIS NOT MOVING EAST OF TEXAS UNTIL EARLY THURSDAY.
A HOT AND INCREASINGLY UNSTABLE ATMOSPHERE WILL SET UP OVER SOUTH
TEXAS THROUGH MIDWEEK BUT MOISTURE WILL BE THE LIMITING FACTOR TO
PROVIDE ANY HIGHER THEN THE SLIGHT CHANCE OF THUNDERSTORMS THAT IS
ALREADY IN THE FORECAST ANYTIME FROM TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT. BEST CHANCES STILL REMAIN IN THE WESTERN HALF OF
THE CWA WHERE MODEL GUIDANCE CONTINUES TO FAVOR THIS AREA. AS
MENTIONED IN PREVIOUS DISCUSSION...INITIATION OF CONVECTION IS
LIKELY OVER CENTRAL TEXAS WHERE A QUASI-STATIONARY FRONT IS
PROGGED TO BE LOCATED OR OVER THE LEE SIDE OF THE SIERRA MADRE.
WEST TO NORTHWEST FLOW COULD ALLOW FOR SOME CONVECTION TO WORK ITS
WAY INTO AND POSSIBLE THROUGH PORTIONS OF DEEP SOUTH TEXAS. MODELS
REMAIN PERSISTENT ON THIS SCENARIO BUT GUIDANCE POPS REMAIN RATHER
LOW WITH MOISTURE DEPTH LIMITED UP TO 800MB. ONCE THIS TROUGH AXIS
PASSES TO THE EAST AND STRONG 500MB HIGH BUILDS BACK NORTH FROM
MEXICO THE THREAT FOR THUNDER AND ANY CHANCE OF RAIN ENDS. THE
LATTER HALF OF THE FORECAST PERIOD REMAINS DRY.

TEMPERATURES START OFF HOT WITH THE WARMEST 850MB TEMPERATURES OF
THE WEEK RUNNING 23-25C. AS THE TROUGH MOVES INTO TEXAS AND
HEIGHTS AND THICKNESS LOWER TEMPERATURES DROP OFF INTO THE UPPER
TEENS TO AROUND 20C BY THURSDAY. SURFACE TEMPS FOLLOW THIS TREND
WITH THE MAX TEMPS PEAKING MONDAY AND LOWERING TO NORMAL BY MID
WEEK. OVERNIGHT LOWS TO REMAIN RATHER WARM AND SULTRY WITH
SOUTHEAST WINDS NOT ABATING MUCH AT LEAST INTO WEDNESDAY.

MARINE...THIS AFTERNOON THROUGH SUNDAY...STATUS QUO HERE AS
WELL...WITH THE USUAL FLIP-FLOP OF STRONGER WINDS ACROSS THE GULF
AND LIGHTER WINDS ACROSS THE LAGUNA MADRE OVERNIGHT BECOMING
STRONGER ACROSS THE LAGUNA MADRE AND SOMEWHAT LIGHTER OVER THE
DEEPER GULF WHERE THE MARINE LAYER SHOULD BE ABLE TO OVERCOME
SYNOPTIC FORCING PROVIDED BY THE LOW PRESSURE TROUGH...WHICH NEVER
REALLY STRENGTHENS OWING TO THE STEADY STATE CONDITION OF THE
CENTRAL/NORTHERN PLAINS UPPER LOW.

THUS...EXPECT ANOTHER ROUND OF SMALL CRAFT ADVISORY/WINDS FOR LAGUNA
MADRE WATERS ON SUNDAY...WITH CAUTION CONDITIONS AT MOST DURING THE
DAY ACROSS THE OPEN GULF WATERS.  FOR TONIGHT AND SUNDAY
NIGHT...EXPECT SURFACE WINDS TO EDGE CLOSE TO ADVISORY LEVELS BUT
REMAIN JUST BELOW.  WINDS IN THE 850-925 LAYER SIT IN THE 25-29 KNOT
RANGE TONIGHT WHICH...WHEN COMBINED WITH WATER TEMPERATURES AT OR A
FEW DEGREES LOWER THAN AMBIENT AIR SHOULD PROVIDE A RARE NOCTURNAL
MARINE LAYER TO KEEP SUSTAINED WINDS IN THE 16-18 KNOT RANGE WITH A
FEW GUSTS UP TO 20-23 KNOTS OR SO.  SUNDAY NIGHT COULD PUSH ACROSS
THE 20 KNOT SUSTAINED THRESHOLD AS LOW LEVEL WINDS INCREASE A COUPLE
KNOTS WITH THE SURFACE TROUGH STRENGTHENING JUST A TAD.  FOR
NOW...HAVE WORDED AS `NEAR 20 KNOTS`.

SEAS HAVE RISEN TOWARD 5 FEET THIS AFTERNOON OFFSHORE AND EXPECT
VALUES TO MAINTAIN OR RISE A LITTLE MORE OVERNIGHT. DID NOT POP A 6
FOOT FORECAST JUST YET BUT WILL NEED TO MONITOR OVER THE NEXT COUPLE
OF DAYS.

MONDAY THROUGH THURSDAY...THE FIRST HALF OF THE WEEK TO REMAIN
NEAR SCEC LEVELS OR EVEN PERIODS OF SMALL CRAFT ADVISORY
ESPECIALLY ACROSS THE LAGUNA. THE GRADIENT STRENGTHENS A BIT
MONDAY AND TUESDAY WITH A LOW PRESSURE TROUGH MOVING INTO TEXAS.
THE TROUGH AXIS MOVES ALONG THE UPPER GULF COAST WEDNESDAY WITH
SOME SLACKENING OF THE GRADIENT. THE TROUGH MOVES EAST THURSDAY
AND HIGH PRESSURE BUILDS IN FOR THE WEEKEND WITH WINDS AND SEAS
LOWERING SLIGHTLY.
&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY FOR WINDS UNTIL 7 PM CDT THIS EVENING FOR
     GMZ130-132-135.
&&

$$

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