Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 251559 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1059 AM CDT TUE AUG 25 2015

.DISCUSSION...MADE A FEW TWEAKS MAINLY TO EVENING WINDS
WHICH SHOULD GO NEAR CALM ALONG/EAST OF HIGHWAY 281 SOON AFTER
SUNSET IN LIGHT WIND REGIME AHEAD OF APPROACHING BOUNDARY (WIND
SHIFT) ON WEDNESDAY. WILL ALSO LOOK AT ADDING IN PATCHY/AREAS OF
FOG FOR THE RANCHLANDS AND PORTIONS OF THE RURAL RGV BASED ON WHAT
HAPPENED THIS MORNING WITH ANOTHER NIGHT OF LONG-DURATION CALM
WINDS AND CONTINUED HIGH SURFACE MOISTURE.

FOR THE LONG TERM...BEGAN TWEAKING SOME OF THE FORECAST PARAMETERS
TO ADVERTISE A MORE OPTIMISTIC (SUNNY...NO RAIN) SUNDAY WHICH MAY
CARRY INTO MONDAY AT LEAST. ONCE AGAIN...GFS APPEARS TO BE
HANDLING THE SLOW...IF ANY...EROSION OF DRY AIR BETTER THAN OTHER
MODELS AND HAS NOT CHANGED ITS TUNE OVER THE PAST SEVERAL DAYS.
ECMWF HAS GRADUALLY DROPPED RAIN CHANCES FOR THE SUNDAY/MONDAY
PERIOD...ALL BECAUSE THE 500 MB LOW THAT EASES SOUTHWEST INTO THE
WESTERN GULF KEEPS ITS MOIST FLANK IN THE CENTRAL/EASTERN GULF AND
IT WILL BE VERY DIFFICULT TO SEE EVEN ISOLATED (MENTIONABLE) RAIN
ON THE WEST SIDE THROUGH SUNDAY AND PROBABLY MONDAY AS WELL.

MORE ON THIS AS WE GET 12Z GFS AND OTHER DATA IN.
52/BSG

&&

.MARINE...SHADED EVENING/OVERNIGHT WINDS DOWN ESPECIALLY ACROSS
THE GULF WATERS (SUNSET) AND LAGUNA MADRE (03Z OR SO) ALL WHICH
MAY BECOME NEARLY CALM IN LIGHT GRADIENT REGIME. FOR
WEDNESDAY...BOUNDARY WILL PROBABLY ASSIST A PICKUP IN
NORTHEASTERLY WINDS AT FIRST BUT WITH NO ADVECTION NOTHING TOO
NOTEWORTHY. WOULD NOT BE SURPRISED TO SEE A FEW 12 KNOTS GUSTING
17 KNOTS DURING THE AFTERNOON AND EARLY EVENING OVER THE GULF AND
SEAS COULD APPROACH 3 FEET IN A FEW SPOTS BEFORE CONDITIONS SETTLE
DOWN AT NIGHT.
52/BSG

&&

.PREV DISCUSSION... /ISSUED 543 AM CDT TUE AUG 25 2015/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...SOME LIGHT FOG HAS BEEN NOTED...MAINLY IN GRASSY
AREAS...ACROSS THE VALLEY THIS MORNING. HAVE ADDED TEMPO GROUPS
DOWN TO 2SM THROUGH 14Z. OTHERWISE MODEST EASTERLY WINDS AROUND 10
KNOTS WILL CONTINUE TODAY...WITH SKIES REMAINING MOSTLY CLEAR.
VFR CONDITIONS WILL CONTINUE OVERNIGHT TONIGHT...WITH LIGHT WINDS.
SOME LIGHT FOG MAY BE A NUISANCE LATE TONIGHT.

PREV DISCUSSION... /ISSUED 404 AM CDT TUE AUG 25 2015/

SHORT TERM /TODAY THROUGH WEDNESDAY/...A MUCH DRIER AIR PARCEL
HAS SPREAD INTO SOUTH TEXAS FROM THE NE DURING THE PAST 12 HOURS.
PW VALUES ESTIMATED FROM SATELLITE DATA AROUND 1.5 INCHES. RIDGING
ALOFT CONTINUES TO BUILD ACROSS THE REGION...AND THESE FACTORS
WILL LEAD TO A MOSTLY SUNNY DAY WITH TEMPERATURES SOARING INTO THE
UPPER 90S AND LOWER 100S. HAVE GONE ABOVE MOST ALL GUIDANCE...AS
ALL HAVE BEEN CONSISTENTLY UNDERFORECASTING HIGHS.

WHILE THE RIDGE TRIES TO BUILD...THE LARGE TROUGH ACROSS THE EASTERN
US CONTINUES TO DIRECT IMPULSES SOUTHWARD ALONG THE MISSISSIPPI
RIVER. MODELS ARE PICKING UP ON ONE OF THESE IMPULSES WRAPPING
AROUND THE RIDGE INTO SOUTH TEXAS DURING THE DAY WEDNESDAY. MOISTURE
WILL INCREASE ALONG WITH IT...BUT WILL NOT BE A SIGNIFICANT SURGE.
BUT WITH SOME INSTABILITY AND INCREASED MOISTURE...THE SEABREEZE
SHOULD HAVE ENOUGH STRENGTH TO SPARK SOME SHOWERS AND THUNDERSTORMS
WEDNESDAY AFTERNOON. SCATTERED SHOWERS WILL ALSO HELP HOLD TEMPS
DOWN A BIT DURING THE DAY...TAPERING 2 TO 4 DEGREES FROM TUESDAY`S
HIGHS.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...500MB RIDGE ACROSS
THE WESTERN UNITED STATES AND 500MB TROUGH ACROSS THE EASTERN U.S.
WEDNESDAY WILL ALLOW DRIER AIR ACROSS THE SOUTHEAST U.S. TO FILTER
INTO SOUTH TEXAS WED NIGHT INTO THURSDAY AS A WEAK FRONTAL
BOUNDARY MOVES INTO THE NORTHERN GULF OF MEXICO. THE NORTHEAST
FLOW ALOFT WILL PROVIDE SUBSIDENCE ACROSS THE CWA THROUGH THE REST
OF THE WEEK BEFORE A 500MB LOW DEVELOPS WITH THE SHEAR AXIS ACROSS
THE GULF OF MEXICO FRIDAY. THE MODELS APPEAR TO BE BETTER IN
AGREEMENT WITH THIS FEATURE...WEAKER PER THE GFS...MOVING WESTWARD
INTO SOUTH TEXAS THROUGH THE WEEKEND INTO EARLY NEXT WEEKEND. WILL
RAISE POPS SLIGHTLY...MAINLY ACROSS THE COASTAL
SECTIONS...SATURDAY AND SUNDAY AND MENTION A SLIGHT CHANCE TO
CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH MONDAY.

MARINE...
NOW THROUGH WEDNESDAY...WITH FAIRLY WEAK SURFACE RIDGING
PREVAILING OVER THE GULF OF MEX EXPECT THE MSL FIELD TO REMAIN
FAIRLY RELAXED. THIS WILL RESULT IN MODEST WINDS AND LOW SEAS
THROUGH TOMORROW NIGHT WITH NO ADVISORIES.

WEDNESDAY NIGHT THROUGH SATURDAY...LIGHT EAST WINDS WILL PREVAIL
ACROSS THE COASTAL WATERS WED NIGHT INTO THURSDAY WITH SURFACE
HIGH PRESSURE ACROSS THE EAST-CENTRAL UNITED STATES EXTENDING
INTO THE NORTHWEST GULF OF MEXICO. WINDS WILL BE LIGHT AND
VARIABLE ACROSS THE COASTAL WATERS FRIDAY AS THE PRESSURE GRADIENT
WEAKENS ACROSS THE LOWER TEXAS COAST. A WEAK FRONTAL BOUNDARY
DRAPED ACROSS THE SOUTH CENTRAL U.S. SATURDAY WILL ALLOW WINDS TO
VEER TO THE SOUTHEAST AND SOUTH BUT REMAIN LIGHT.

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

$$

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


&&

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

$$

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


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