000
FXUS64 KBRO 230226 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
926 PM CDT TUE JUL 22 2014

.DISCUSSION...
QUIET WEATHER CONDITIONS CONTINUED OVER THE FORECAST AREA AT MID-
EVENING...THANKS TO THE CONTINUED PRESENCE OF A POWERFUL...NEARLY
600 DAM...RIDGE AT 500MB CENTERED OVER SOUTHERN COLORADO. WITH A
CONTINUED DRY BOUNDARY LAYER INDICATED BY THE EVENING KBRO
SOUNDING (PRECIPITABLE WATER VALUES BELOW NORMAL FOR LATE JULY)...
WATER VAPOR IMAGERY SHOWING A STREAM OF DRY MID-LEVEL AIR (FOR
LACK OF A BETTER TERM)...AND LACK OF ANY SIGNIFICANT SYNOPTIC
SCALE FORCING...THIS TREND IS EXPECTED TO CONTINUE OVERNIGHT.

AS WINDS CONTINUE TO DIMINISH THIS EVENING...STRATUS IS EXPECTED
TO RETURN TO PARTS OF THE FORECAST AREA UNDER THE SUBSIDENCE
INVERSION. BECAUSE OF THIS...SOME CHANGES HAVE BEEN MADE TO THE
SKY COVER GRIDS IN THE ONGOING FORECAST.

A LOOK AT THE LATEST OBSERVATIONAL AND HIGH-RESOLUTION MODEL DATA
OVER THE NEXT 18 HOURS OR SO INDICATES LITTLE SIGNIFICANT CHANGE
IN THE OVERALL WEATHER PATTERN FOR OUR AREA. WE ARE WATCHING A
MOSTLY MID- AND UPPER-LEVEL LOW...AND ITS ASSOCIATED WEAK SURFACE
REFLECTION...HANGING OUT NEAR MOBILE BAY (ALABAMA) THIS EVENING.
THIS FEATURE IS EXPECTED TO SHIFT WESTWARD OVER THE NEXT 24 HOURS
OR SO AND BRING THE POSSIBILITY OF CONVECTION BACK TO OUR AREA BY
THE START OF THE LONG TERM PORTION OF THE FORECAST.

UNFORTUNATELY FOR US...THE LOW WILL BE FIGHTHING THE UPPER RIDGE
AND IT LOOKS LIKE THIS FEATURE WILL BE SOMEWHAT STRETCHED OR
SHEARED AS IT HEADS TOWARD OUR CORNER OF THE WORLD. STILL
THOUGH...LOW-LEVEL MOISTURE IS EXPECTED TO DEEPEN WITH
PRECIPITABLE WATER VALUES PEAKING AROUND THE 2 INCH MARK. THIS MAY
RESULT IN AN ENHANCEMENT OF THE SEABREEZE BY THE TIME THURSDAY
ROLLS AROUND.

IN THE MEANTIME...I HAVE ADJUSTED FORECAST PRECIPITATION
PROBABILITIES TO LESS THAN 15 PERCENT THROUGH TOMORROW EVENING. WE
MAY SEE SOME STREAMER-TYPE SHOWER DEVELOPMENT...MAINLY OVER THE
MARINE/COASTAL AREAS...BETWEEN MIDNIGHT AND SUNRISE THURSDAY.

IN ADDITION...SOME ADJUSTMENTS HAVE BEEN MADE TO THE DIURNAL
TRENDS PRESENT IN THE HOURLY TEMPERATURE/DEWPOINT GRIDS BASED ON
OBSERVED TRENDS. THIS MAY RESULT IN SOME MINOR CHANGES TO FORECAST
LOW AND HIGH TEMPERATURES. PRELIMINARY NUMBERS ARE GIVEN BELOW FOR
YOUR PERUSAL.

ISC GRIDS HAVE BEEN SENT AND SHOULD BE POSTED TO THE INTERNET. AN
UPDATED TEXT FORECAST PRODUCT WILL BE ISSUED SHORTLY. /53/

&&

.PREV DISCUSSION... /ISSUED 645 PM CDT TUE JUL 22 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...
GUSTY SE-S WINDS SHOULD DIMINISH AFTER SUNSET...ALLOWING WIND SPEEDS
AROUND 5 KTS TO AGAIN BE SEEN ACROSS THE REGION OVERNIGHT.  AS THIS
OCCURS...AREAS OF STRATUS SHOULD AGAIN BE SEEN UNDER THE SUBSIDENCE
INVERSION.  SIMILAR TO THE PAST COUPLE OF MORNINGS...THE THICKEST
STRATUS SHOULD BE SEEN FOR A FEW HOURS AROUND 23/1200 UTC COASTWARD
FROM THE IH-69C/US-281 CORRIDOR.  ADDITIONALLY...LIGHT WINDS AND
LIMITED LOW-LEVEL MOISTURE MIGHT ALLOW A FEW PATCHES OF BR TO BE
SEEN OVER N JIM HOGG AND BROOKS COUNTIES.  RIGHT NOW...I`LL KEEP
FLIGHT CATEGORIES VFR WITH ONLY SCTD COVERAGE EXPECTED.  ANY
STRATUS/BR SHOULD LIFT AROUND 23/1500 UTC AS MECHANICAL MIXING
INCREASES OVER THE REIGON.  /BUTTS/

PREV DISCUSSION... /ISSUED 343 PM CDT TUE JUL 22 2014/

SHORT TERM /NOW THROUGH WEDNESDAY NIGHT/...600 DAM MID LEVEL
RIDGING IS CENTERED BROADLY OVER THE SOUTHWEST UNITED STATES AND THE
SOUTHERN HIGH PLAINS...AND WILL REMAIN A DOMINANT FACTOR IN THE WX
PATTERN FOR THE NEXT SEVERAL DAYS. WITH RIDGING UPSTREAM...TEMPS FOR
THE CWA WILL TEND TO REMAIN AT OR ABOVE NORMAL...AND RAINFALL WILL
TEND TO BE SUPPRESSED...EXCEPT FOR THE POSSIBILITY OF ISOLD CONV FED
BY ONSHORE BREEZES NEAR THE LOWER TEXAS COAST. IN ADDITION...A WEAK
MID LEVEL LOW OVER THE FLORIDA PANHANDLE WILL DRIFT SLOWLY WEST...
REACHING THE NORTHWEST GULF WEDNESDAY NIGHT. A FEW MARINE BASED
SHOWERS/THUNDERSTORMS MAY DEVELOP AS A RESULT...JUSTIFYING AN OVERT
MENTION IN THE MARINE FORECAST...BUT SILENT MENTION FOR NOW FOR ANY
INLAND LOCATIONS IN THE SHORT TERM.

LOOK FOR MOSTLY CLEAR SKIES TONIGHT WITH LOW TEMPERATURES IN THE
UPPER HALF OF THE 70S DECADE...I.E.75 TO 79 OR 80...PLUS LIGHT
SOUTHEAST TO SOUTH WINDS. THE LOW TEMPS WILL BE A FEW DEGREES ABOVE
THE AVERAGE OF AROUND 75. MARINE MOISTURE AND CLOUDS WILL MOVE
ASHORE OVERNIGHT...WITH PARTLY CLOUDY MORNING SKIES NEAR THE COAST
BECOMING PARTLY CLOUDY TO MOSTLY SUNNY WITH A MODERATE ONSHORE WIND.
FORECAST PWAT OF AN INCH AND A HALF ALONG WITH DRIER AIR ALOFT WILL
PRECLUDE ANY SIGNIFICANT CHANCE OF RAIN ON WEDNESDAY. HIGH TEMPS
WILL RANGE FROM AROUND 90 AT THE COAST TO THE MID 90S JUST INLAND TO
THE CENTURY MARK OR SLIGHTLY HIGHER FARTHER INLAND WEST OF U.S. 281.
HEAT INDEX VALUES WILL BE AROUND 105 FOR INLAND AREAS. ANOTHER MILD
NIGHT WILL BE ON TAP WEDNESDAY NIGHT WITH MOSTLY CLEAR TO PARTLY
CLOUDY SKIES...LIGHT ONSHORE WINDS AND LOW TEMPS WELL INTO THE 70S.
THE AFOREMENTIONED MID LEVEL LOW WILL ARRIVE OVER THE NORTHWEST GULF
AND A FEW SHOWERS OR THUNDERSTORMS MAY DEVELOP OFFSHORE. ON THE
WHOLE HOWEVER...SIGNIFICANT WEATHER WILL BE ABSENT IN THE SHORT TERM
WITH PERSISTENCE HOLDING SWAY...AND A FLEETING CHANCE OF SHOWERS
WEDNESDAY NIGHT...CONTINUING INTO THURSDAY AND THE LONG TERM
BELOW. /54/

LONG TERM /THURSDAY THROUGH TUESDAY/...PICKING UP FROM THE SHORT
TERM...THE AFOREMENTIONED UPPER TROUGH CONTINUES TO ELONGATE AND
SHEAR OUT AS IT MOVES WEST-SOUTHWEST INTO SOUTH TEXAS/NORTHERN
MEXICO THURSDAY INTO THURSDAY NIGHT...WITH 12Z GFS/00Z ECMWF EACH
SHOWING THE WAVE RECONSTITUTING ACROSS NUEVO LEON BY LATE FRIDAY
NIGHT INTO SATURDAY. AT THAT POINT...THE RIDGE REBUILDS FROM
NORTHEAST TO SOUTHWEST AND PUSHES FAIRLY DEEP DRY AIR FROM EAST
TEXAS WELL SOUTH...COVERING THE VALLEY BY SUNDAY AND ENSURING A
SUNNY AND HOT WEEKEND CONTINUING RIGHT INTO EARLY NEXT WEEK.

FOR THE SENSIBLE WEATHER...THE BEST BET FOR SOME COVERAGE OF
THUNDERSTORMS IS ON THURSDAY AS THE FRONT LOBE OF THE SHEARING
WAVE REACHES THE AREA...ALONG WITH JUST ENOUGH MOISTURE IN THE
500-850 MB LAYER TO ALLOW CONVECTIVE GROWTH ON WHAT SHOULD BE A
DECENT SEA BREEZE AFTER A CALM MORNING WITH A HINT OF A
CONVERGENCE-ENHANCING WEAK LAND BREEZE. BECAUSE THE WAVE IS
WEAKENING AND DEEP MOISTURE NOT OVERLY IMPRESSIVE...NOT TO MENTION
UNCERTAINTY IN EXACTLY HOW THINGS WILL SHAPE UP TWO DAYS FROM
NOW...HAVE HELD CHANCES AT 20 PERCENT BUT ADJUSTED TIMING AND
MOVEMENT TO ACCOUNT FOR CLIMATOLOGY /EARLY MORNING COAST...MID
MORNING TO EARLY AFTERNOON ALONG HIGHWAY 77...AND MID TO LATE
AFTERNOON FARTHER WEST/. WOULD NOT BE SURPRISED TO SEE CLOSER TO
40 PERCENT COVERAGE...ALONG WITH THE USUAL POCKETS OF NUISANCE
FLOODING AND SOME DECENT CLOUD TO GROUND LIGHTNING WHERE STRONGER
CELLS FORM.

CONDITIONS BRIEFLY GO QUIET THURSDAY EVENING BEFORE WE ATTEMPT A
REPEAT ON FRIDAY. MODEL GUIDANCE TRENDS DOWN FRIDAY OWING TO LESS
VERTICAL MOTION AND MID LEVEL DRYING...ESPECIALLY ON THE GFS...BUT
PROXIMITY OF VORTICITY CENTER AND STILL UNCERTAINTY ON HOW MUCH
SOUTH/SOUTHEAST FLOW CAN REGENERAGE GIVES PAUSE TO REMOVING
CHANCES ALTOGETHER AT THIS POINT. CERTAINLY COVERAGE WILL BE LOWER
WITH 20 PERCENT ON AVERAGE PER COUNTY...AT BEST.

WITH THE INCREASED POTENTIAL OF RAIN AND MORE CLOUD COVER HAVE
NUDGED TEMPS DOWN IN LINE WITH GUIDANCE TRENDS. NEEDLESS TO SAY
AREAS THAT SEE MIDDAY RAINS COULD STRUGGLE TO SEE THE CENTURY MARK
OR EVEN REALIZE FORECAST HIGHS /UPPER 90S/...AND HAVE ACCOUNTED
FFOR SOME OF THIS IN THE CAMERON/WILLACY FORECAST DURING THE EARLY
AFTERNOON THURSDAY. SLIGHT DOWNWARD NUDGING FRIDAY AS WELL BUT
WITH NO ATTEMPT TO TIME OUT DIPS DUE TO RAIN.

AS MENTIONED ABOVE...THE WEEKEND LOOKS DRY...AND DAYTIME TEMPERATURES
WE`VE SEEN MONDAY/TODAY WILL BE THE RULE AS 1000-500 MB
THICKNESS/850-1000 THICKNESS/LOW LEVEL TEMPERATURE FIELDS SUGGEST
WIDESPREAD 100-102 READINGS MAINLY WEST OF HIGHWAY 281...98 TO 100
BETWEEN 77 AND 281...AND MID 90S ELSEWHERE. EVEN DRIER AIR MAKES A
MOVE ON THE VALLEY FOR MONDAY AND TUESDAY AS THE ATMOSPHERIC
COLUMN COOLS A SHADE DESPITE A CONTINUING SOUTH/SOUTHEAST LOW AND
MID LEVEL FLOW AS THE UPPER RIDGE ELONGATES FROM THE CENTRAL
ROCKIES THROUGH THE EAST CENTRAL GULF. JUST A FEW TWEAKS TO THAT
PART OF THE FORECAST. /52/

MARINE...
TONIGHT THROUGH WEDNESDAY NIGHT...LIGHT TO MODERATE SOUTHEAST TO
SOUTH WINDS AND SEAS WILL PREVAIL AS HIGH PRESSURE DOMINATES ACROSS
THE GULF. ISOLATED MARINE SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE
FROM MID TO LATE WEEK AS AN UPPER DISTURBANCE MOVES WEST ACROSS THE
NORTHWEST GULF AND THEN INLAND OVER NORTH MEXICO.

THURSDAY THROUGH SUNDAY: LIGHT WINDS/SLIGHT SEAS THURSDAY AND
FRIDAY AS THE SHORT WAVE TEMPORARILY DISRUPTS THE PERSISTENT
SOUTH/SOUTHEAST WIND FLOW. FOR SATURDAY AND
SUNDAY...SOUTH/SOUTHEAST WINDS RETURN BUT MARINE LAYER WILL KEEP
THEM IN CHECK ACROSS THE GULF EACH DAY...AND ONLY ENOUGH OOMPH
ACROSS THE LAGUNA TO SUGGEST CAUTION /15-20 KNOTS/ BY SUNDAY ONLY.
/54/

OF INTEREST TO BOATERS/FISHERS AND SWIMMERS/SURFERS IN THE
NEARSHORE GULF WATERS IS THE REFRESHING CHILL. THIS MORNING`S SURF
AT SPI WAS A SPRING-LIKE 75...AND 70S HAVE BEEN DOMINANT THROUGH
JULY. THE REASON? PERSISTENT UPWELLING OF COLDER SUB-SURFACE WATER
DRIVEN BY THE PARALLEL LONGSHORE CURRENT...WHICH IN TURN IS DRIVEN
ATMOSPHERICALLY BY THE STABLE AND HIGHLY AMPLIFIED UPPER LEVEL
PATTERN THIS MONTH WHICH HAS BROUGHT SPRINGLIKE COMFORT TO THE MID
ATLANTIC/MIDWEST WHILE SOUTH/WEST TEXAS RUNS A FEW DEGREES ABOVE
ALREADY HOT NORMALS. THE PATTERN HAS ALLOWED RELATIVELY STRONG LOW
PRESSURE SYSTEMS TO TRAVERSE THE NATION`S MIDSECTION AND HAS
ELIMINATED THE BROAD BERMUDA TO THE DEEP SOUTH CENTERED SURFACE
RIDGE...WHICH FAVORS MORE PERSISTENT EASTERLY FLOW AND HENCE
WARMER GULF WATERS ALL THE WAY TO THE TEXAS COAST.

THE NEXT TWO WEEKS SHOW NO SIGN OF THIS PATTERN CHANGING...SO
EXPECT MORE 70S IN THE SURF UNTIL FURTHER NOTICE. /52/

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  79  93  78  93 /  10  10  10  20
BROWNSVILLE          78  95  78  95 /  10  10  10  20
HARLINGEN            77  97  76  97 /  10  10  10  20
MCALLEN              79 100  77  99 /  10  10  10  20
RIO GRANDE CITY      78 101  78 101 /  10  10  10  20
SOUTH PADRE ISLAND   80  89  80  91 /  10  10  20  20

&&

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

$$

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

SHORT TERM FORECASTER... BUTTS
LONG TERM FORECASTER... SPEECE