Area Forecast Discussion
Issued by NWS Brownsville, TX

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 011112 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
612 AM CDT FRI AUG 1 2014

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

&&

.AVIATION...ONLY LIGHT TO MODERATE SOUTHEAST WINDS ARE EXPECTED
TODAY WITH A FLAT PRESSURE GRADIENT OVER THE CWA. DEVELOPING LATE
MORNING LOW CLOUDS MAY PRESENT BRIEF MVFR CEILINGS HOWEVER. A WEAK
FRONT WILL PUSH INTO THE COASTAL BEND AND RIO GRANDE PLAINS TODAY
BUT MOST POTENTIAL CONVECTION FOR THE DAY SHOULD STAY NORTH OF THE
LOWER VALLEY. PWAT LOOKS LIKE IT WILL BE AROUND 1.5 INCHES TODAY
IN THE LOWER VALLEY...AND WHATEVER CONVECTION DOES MANAGE TO POP
UP WILL HAVE TO CONTEND WITH DRY AIR ABOVE THE BOUNDARY LAYER.
THUS...LOOKING FOR MAINLY VFR CONDITIONS WITH LIGHT TO MODERATE
SOUTHEAST WINDS AND MOSTLY SUNNY SKIES...WITH AN EYE ON A POSSIBLE
WEAK SEA BREEZE OR SOME LATE DAY CONVECTION MOVING INTO THE AREA
FROM THE NORTH.

&&

.PREV DISCUSSION... /ISSUED 350 AM CDT FRI AUG 1 2014/

SHORT TERM /NOW THROUGH SATURDAY/...A WEAK COLD FRONT IS DROPPING
SLOWLY SOUTH THROUGH THE HILL COUNTRY AND WILL PUSH INTO SOUTH
CENTRAL TEXAS TODAY WHERE IT SHOULD HANG UP FOR THE NIGHT. A FEW
SHOWERS OR THUNDERSTORMS MAY DEVELOP ALONG THE FRONT WHICH MAY PUSH
SOUTH INTO THE CWA...BUT MOST ACTIVITY IS EXPECTED TO REMAIN NORTH
OF THE POPULATED AREAS OF THE LOWER VALLEY TODAY. A WEAK SEA BREEZE
COULD DEVELOP ALONG THE COAST TODAY...AND ANY CONVERGENCE ALONG THE
SEA BREEZE...COUPLED WITH FRONTAL RELATED CONVECTION...HAS A BETTER
CHANCE OF SUSTAINING ITSELF FARTHER SOUTH. OTHERWISE...HIGH TEMPS
WILL BE ABOVE  NORMAL WITH AMPLE SUN...FILTERED ONLY SLIGHTLY BY MID
TO UPPER LEVEL CLOUDS MOVING INTO THE AREA FROM CONVECTIVE ACTIVITY
OVER NORTHEAST TEXAS. CONDITIONS SHOULD SETTLE DOWN A BIT TONIGHT...
WITH LITTLE FORWARD PROGRESS OF THE FRONT...AND WITH WINDS OVERALL
WEAKENING AND VEERING TO LIGHT EAST. LOW TEMPS WILL BE IN THE MID TO
UPPER 70S.

THE BIG QUESTION IS TO WHAT EXTENT WILL CONVECTION FLARE UP ON
SATURDAY WITH THE FRONT STILL DRAPED ROUGHLY OVER THE NORTHERN
COUNTIES. PWAT VALUES RANGE FROM AN INCH AND A HALF SOUTH OF THE
BOUNDARY TO AROUND TWO INCHES NORTH OF THE BOUNDARY...CERTAINLY
ENOUGH TO SUPPORT THE SCATTERED WORDING NOW IN THE FORECAST FOR
SATURDAY AFTERNOON. LIGHTER WINDS DUE TO LACK OF A STRONG GRADIENT
WILL ALSO NOT INHIBIT SEA BREEZE DEVELOPMENT....WHICH COULD PLAY
INTO THE MIX BY PROVIDING A SECOND BOUNDARY TO INTERACT WITH THE
FRONT. KEPT THE PREVIOUS THINKING ALIVE IN THE INHERITED FORECAST
ALBEIT WITH A SLIGHT INCREASE IN COVERAGE OVERALL SATURDAY. RAIN
FALL EFFICIENCY COULD BE ENHANCED SATURDAY AFTERNOON IF STRONGER
STORMS DEVELOP AND WITH STORM MOVEMENT IN GENERAL EXPECTED TO BE
SLOW. HIGH TEMPERATURES SATURDAY WERE RESTRAINED A DEGREE OR TWO
LOWER OVER THOSE OF TODAY BASED ON SLIGHTLY MORE GENEROUS CLOUD
COVER.

LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
GOOD PATTERN WITH SOME LIMITATIONS FOR SHOWERS AND STORMS...KEPT
RAIN CHANCES ABOVE GUIDANCE THROUGH TUESDAY. BREEZY AND HOT BACK
FOR THURSDAY AND FRIDAY.

SUNDAY...FAIRLY DEEP TROUGHING WILL BE DIGGING INTO THE NORTH
CENTRAL GULF OF MEXICO WITH A JET MAX ON THE WESTERN SIDE OF THE
TROUGH AXIS AIDING IN INCREASING NORTHWESTERLY FLOW AT 300 TO 500MB
WITH NORTHEASTERLY FLOW AROUND 850MB MELDING INTO BROAD CONVERGENCE
AND WHATS LEFT OF THE FRONT CURRENTLY OVER SOUTH CENTRAL TEXAS.
LITTLE EVIDENCE OF ANY REAL AIRMASS CHANGE IS EVIDENT IN THE
BOUNDARY LAYER BUT THE ZONE OF CONVERGENCE AND WEAK FRONTOGENETIC
FORCING FROM THE NORTHEASTERLY PUSH SHOULD AID IN PROVIDING A FAIR
ENVIRONMENT FOR SHOWER AND THUNDERSTORM DEVELOPMENT. 850-700MB
RELATIVE HUMIDITY APPROACHES 70 TO 80 PCT IN THE AFTERNOON UNDER
WEAK DIFFERENTIAL CYCLONIC VORTICITY ADVECTION FROM 300 TO 500 MB.
MID LEVEL LAPSE RATES AND TOTAL INSTABILITY ARE THE ONLY REAL
LIMITING FACTORS AND THAT MAY KEEP TOTAL UPDRAFTS AND PRECIP
COVERAGE LIMITED. DETERMINISTIC PWAT VALUES OF 1.9 TO 2.0 INCHES ON
SUNDAY SUGGEST POTENTIAL FOR EFFICIENT RAINFALL RATES IF
THUNDERSTORMS DEVELOP. LIGHT AMBIENT SFC WINDS OUT OF THE EAST
SOUTHEAST WILL ALSO AID IN DEVELOPING A STRONGER SEABREEZE BOUNDARY
WHICH MAY FURTHER AID IN CONVECTIVE INITIATION. WENT WITH 30 PCT
POPS ACROSS THE SOUTHERN HAL OF THE CWA INCLUDING THE VALLEY...WHICH
IS HIGHER THAN GUIDANCE CONSENSUS BUT APPEARS WARRANTED GIVEN THE
SIGNAL AND THE VALLEYS HISTORY WITH NORTHWEST FLOW EVENTS.

MONDAY THE UPPER LEVEL TROUGH BEGINS TO BREAK OFF AND STRETCH
SOUTHWESTWARD INTO THE WESTERN GULF OF MEXICO. THIS SHIFTS 850/700MB
FLOW TO THE NORTHEAST WITH LIGHT EASTERLY SURFACE FLOW. WEAK DCVA
CONTINUES WITH WEAK LOBES OF VORTICITY RIDING ALONG THE NORTHWEST TO
NORTHERLY UPPER LEVEL FLOW. ECMWF/GFS BOTH SHOW AT LEAST A LITTLE
BIT OF DRIER AIR WORKING INTO THE 700MB LEVEL FROM AIR THAT HAS
PREVIOUSLY SUBSIDED OVER THE CENTRAL GULF OF MEXICO. LIGHT FLOW WILL
AGAIN PROVIDE A GOOD SEABREEZE BOUNDARY. OVERALL 850-700MB RELATIVE
HUMIDITY IS HIGH AND APPEARS HIGH ENOUGH TO CONTINUE A 20 TO 30 PCT
CHANCE OF RAIN...30 PCT IN THE VALLEY...IN THE AFTERNOON HOURS.
AGAIN HIGHER THAN GUIDANCE CONSENSUS BUT WE HAVE GOOD RH AND WIND
PROFILE FOR SEABREEZE CONVECTION AND AN ADDED PUSH WITH THE
NORTHWEST FLOW AND NEARBY UPPER LOW. GFS ENSEMBLE MEAN PRECIPITATION
OUTPUTS ALSO SHOW MORE ACTIVITY THAN STATISTICAL GUIDANCE.

TUESDAY SEES SIMILAR CONDITIONS...SLIGHTLY MORE DRY AIR WORKS IN
FROM THE EAST AND LOWER LEVEL RH DROPS A BIT BUT BOTH GFS AND
ESPECIALLY ECMWF SHOW THE UPPER LEVEL LOW MOVING SOUTHWEST AND
GIVING THE AREA BETTER MID LEVEL ASCENT. FEEL LESS CONFIDENT ABOUT
THIS DAY BUT DID AGAIN INCLUDE A 30 PCT AFTERNOON POP IN THE
FORECAST. DRIER LOW LEVEL AIR AND PERSISTENT POOR MID LEVEL LAPSE
RATES AGAIN THE MAIN LIMITING FACTOR TO THE ODDS OF SHOWERS/STORMS
DEVELOPING BUT THERE ARE SEVERAL FAVORABLE FACTORS AS WELL.

BEGAN TO STEP DOWN THE POPS WEDNESDAY AND WEDNESDAY AFTERNOON AS THE
UPPER LOW WEAKENS AND LOW LEVEL WINDS SHIFT BACK TO THE SOUTHEAST AS
RIDGING INCREASES OVER THE GULF OF MEXICO. ECMWF HOLDS ONTO STRONGER
MID LEVEL TROUGHING WHICH WILL NEED TO BE WATCHED TO POSSIBLY
ENHANCED PRECIP CHANCES BUT LEANED WITH GFS AND GFS ENSEMBLES DRIER
APPROACH WHICH HAS GOOD RUN TO RUN CONSISTENCY. STILL ENOUGH LOW
LEVEL MOISTURE TO EEK OUT A SLIGHT CHANCE POP EAST OF HIGHWAY 281
BUT DOWN FROM THE LAST SEVERAL DAYS.

BETTER AGREEMENT THURSDAY AND FRIDAY OF MID GULF RIDGING
RETURNING...A DRIER OVERALL COLUMN AND A RESURGENCE OF HOT
TEMPERATURES AND BREEZY SOUTHEAST WINDS. LITTLE CHANGE TO INHERITED
FORECAST IN TERMS OF THE OVERALL SIGNAL WITH A DRY FORECAST AND HIGH
TEMPERATURES RETURNING TO THE 105 WEST 95/98 COASTAL TREND SEEN FOR
MUCH OF THE SUMMER. /68-JGG/

MARINE...
NOW THROUGH SATURDAY...LIGHT TO MODERATE SOUTHEAST WINDS WILL
PREVAIL TODAY...WITH LOW SEAS...AS A FLAT PRESSURE FIELD COVERS THE
NORTHWEST GULF. WINDS WILL WEAKEN TONIGHT AND SATURDAY...BECOMING
EAST...AS A WEAK FRONTAL BOUNDARY SAGS SOUTH INTO THE AREA AND HANGS
UP. THE MAIN CONCERN WITH THE BOUNDARY WILL BE THE POTENTIAL FOR
MARINE SHOWERS AND THUNDERSTORMS...WHICH WILL MAINLY AFFECT THE
NORTHERN ZONES LATE TONIGHT...BUT MAY DEVELOP FARTHER SOUTH ON
SATURDAY.

SUNDAY THROUGH WEDNESDAY...
LIGHT WINDS AND LOW SEAS ARE GENERALLY FORECAST THROUGH TUESDAY. THE
ONLY POTENTIAL PITFALL FOR MARINERS WILL BE ISOLATED TO SCATTERED
SHOWERS THAT WILL BE POSSIBLE IN THE VICINITY OF A WEAK STATIONARY
FRONT EXPECTED TO REMAIN IN THE AREA THROUGH MONDAY OR TUESDAY.
SOUTHEASTERLY WINDS WILL INCREASE TUESDAY AND ESPECIALLY WEDNESDAY
LIKELY TO EXERCISE CAUTION LEVELS ON THE LAGUNA IN THE AFTERNOON
WITH MORE MODERATE CONDITONS AND MODERATE SEAS ON THE GULF OF
MEXICO.

&&

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

$$

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

54/68/58




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