Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 111743
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1243 PM CDT FRI JUL 11 2014

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

&&

.AVIATION...LATEST SATELLITE IMAGERY SHOWS THE MID LEVEL TROUGH
CONTINUING TO MOVE NORTHWEST BUT ABUNDANT CLOUD COVER PERSIST
OVER DEEP SOUTH TEXAS. MVFR CLOUDS WILL GRADUALLY ERODE IMPROVING
TO VFR CONDITIONS BY THIS AFTERNOON WITH SOUTHEAST WINDS INCREASING
WITH GUSTS UP TO 20 TO 25 KNOTS. DRY AIR WILL MOVE INTO THE AREA
LIMITING ANY POTENTIAL FOR RAIN TONIGHT AND SATURDAY BUT LOW LEVEL
MOISTURE WILL AID FOR SCT TO BKN DECK POSSIBLE IN THE MORNING HOURS.
EXPECT LIGHTER SOUTHEAST WINDS AFTER SUNSET AND PREVAILING THROUGH
EARLY SATURDAY.

&&

.PREV DISCUSSION... /ISSUED 714 AM CDT FRI JUL 11 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...AS THE 500 MB TROUGH AXIS THAT BROUGHT THE RAINFALL TO
DEEP SOUTH TX YESTERDAY MOVES FURTHER WEST THE ATMOSPHERE OVER THE
REGION WILL CONTINUE TO DRY OUT LOWERING THE PROBABILITY FOR LOW
CLDS. SO WILL MENTION MAINLY HIGH LEVEL CLD COVER IN THE CURRENT
TAF SET AND WILL MAINTAIN VFR CONDITIONS FOR ALL OF THE RGV
AIRPORTS THROUGH 12Z SATURDAY.

PREV DISCUSSION... /ISSUED 407 AM CDT FRI JUL 11 2014/

SHORT TERM /NOW THROUGH SATURDAY/...THE 500 MB TROUGH AXIS THAT
BROUGHT THE WIDESPREAD CONV TO THE REGION YESTERDAY WILL BE SHIFTING
FURTHER WEST TODAY AND SATURDAY. AS THIS TROUGH AXIS MOVES FURTHER
WEST THE DEEPER LAYER MOISTURE LEVELS WILL DECREASE OVER THE REGION
WHICH WILL RESULT IN LOWER RAIN CHANCES TODAY AND SATURDAY. SHORT
RANGE GUIDANCE FROM THE NAM/GFS AND ECMWF ALSO POINTS TOWARDS MUCH
LOWER RAIN CHANCES AS THE WEEKEND APPROACHES. THIS MORNINGS RADAR
REFLECTIVITY SHOWS SOME LINGERING SHOWER ACTIVITY. SO WILL MAINTAIN
SOME MENTION OF 20% POPS THROUGHOUT THE MORNING HOURS AND WILL DROP
THEM DOWN TO SILENT 10S FOR THIS AFTERNOON THROUGH SATURDAY. AS THE
TROUGH AXIS MOVES AWAY FROM THE AREA STEADILY AND THE MOISTURE
LEVELS DECREASE EXPECT SUNSHINE TO GRADUALLY INCREASE ALLOWING THE
TEMPS TO WARM UP SLOWLY THROUGH TOMORROW.

THE MAV AND MET TEMPS AND POPS ARE IN PRETTY GOOD AGREEMENT
THROUGHOUT THE SHORT TERM AND WILL GO CLOSE TO A MODEL BLEND BETWEEN
THE 3 MODELS THROUGH SATURDAY.

LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
HOT AND DRY WITH RELATIVELY LIGHT WINDS THROUGH MOST OF THE
WEEK...POSSIBLY BECOMING MORE UNSETTLED BY NEXT WEEKEND.

FAIRLY LIGHT ZONAL FLOW WILL CONTINUE INTO THE EARLY PORTION OF THE
LONG TERM PERIOD. WEAK SURFACE AND LOW LEVEL RIDGING CONTINUES OVER
THE EASTERN GULF OF MEXICO BUT WITH THE WEAK UPPER FLOW OVER THE
CENTRAL CONUS NO REAL MID CONTINENTAL OR LEE TROUGHING FORMS AND OUR
SURFACE PRESSURE GRADIENT AND RESULTING WINDS STAY PRETTY LIGHT OUT
OF THE SOUTHEAST. AFTERNOON ENHANCEMENTS FROM THERMAL TROUGHING IN
THE LEE OF THE SIERRA MADRE AND THE LAND SEA THERMAL DIFFERENCE WILL
PUT SOME GUSTINESS INTO THE AFTERNOON AND EXPECT AT LEAST SOME
DEGREE OF SEABREEZE WIND SHIFT WILL DEVELOP AS WELL.
OTHERWISE...LOWER ATMOSPHERIC RELATIVE HUMIDITY AND MOISTURE CONTENT
IS LOW...AND GENERALLY DRY WEATHER IS FORECAST.

BY MONDAY NIGHT INTO TUESDAY A FAIRLY IMPRESSIVE TROUGH DIGS INTO
THE EAST CENTRAL UNITED STATES WITH NORTHWESTERLY FLOW AT 250 TO
500MB APPROACHING FROM THE NORTHWEST. GFS/ECMWF BOTH INITIATE
CONVECTION WELL TO THE NORTH OF THE AREA TUESDAY AFTERNOON BUT THE
NORTHWESTERLY FLOW DOES NOT QUITE MAKE IT INTO THE REGION. WITH
FAIRLY MARGINAL AVAILABLE MOISTURE AND WARM MID LEVEL TEMPERATURES
PRODUCING WEAK LAPSE RATES KEPT THE FORECAST DRY BUT IT WOULD NOT BE
TOTALLY OUT OF THE QUESTION TO GET A DISSIPATING CLUSTER OR LINE OF
SHOWERS/STORMS APPROACHING THE AREA BASED ON THE ADVERTISED SETUP.

THE FLOW WEAKENS ALOFT AGAIN AND BECOMES MORE ZONAL THROUGH
WEDNESDAY WITH ONE MORE WARM AND HUMID DAY WITH RELATIVELY LIGHT
WINDS. A REINFORCING SHORTWAVE TROUGH DIGS INTO TEXAS AND ARKANSAS
THROUGH THURSDAY AFTERNOON AND A LOW LEVEL CYCLONE SPINS UP IN
RESPONSE IN THE LEE OF THE SIERRA MADRE. THIS SIGNIFICANTLY
INCREASES LOW LEVEL WINDS AND SHOULD PUT US BACK INTO THE BREEZY TO
WINDY CATEGORY AND INCREASED FORECAST WIND SPEEDS...ESPECIALY IN THE
AFTERNOON...QUITE A BIT WITH THIS PACKAGE. SOUTHWESTERLY 700MB WINDS
INCREASE CAPPING DESPITE A SLIGHT INCREASE IN 850MB LAYER
MOISTURE/HUMIDITY AND CONVECTIVE CHANCES APPEAR LOW.

BY FRIDAY HOWEVER THE MAIN UPPER LEVEL WAVE AND MID LEVEL ASCENT
MOVES CLOSE ENOUGH TO BEGIN GENERATING CONVECTION OVER THE HILL
COUNTRY AND COASTAL PLAIN...CLOSER THAN ADVERTISED ON TUESDAY...AND
MOVES INTO THE AREA AMID A MORE FAVORABLE UPPER LEVEL PATTERN.
SUSPECT WITH THE SOUTHWESTERLIES ALOFT WE WILL NEED TO GET THE
TROUGH A LITTLE CLOSER FOR CONVECTION...BUT DID ADD A SLIGHT CHANCE
OF SHOWERS AND STORMS FRIDAY AFTERNOON INTO FRIDAY EVENING WHICH
LOOKS TO MARK THE START OF A NEW PERIOD OF MORE UNSETTLED WEATHER. /68-JGG/

MARINE...NOW THROUGH SATURDAY...
SURFACE RIDGING OVER THE GULF OF MEXICO AND THE SOUTHEASTERN
STATES WILL MAINTAIN A FAIRLY STEADY MODERATE S-SE SURFACE FLOW
THROUGHOUT THE WEEKEND. THE EXPECTED WINDS AND SEAS WILL REMAIN
BELOW SCA LEVELS THROUGHOUT THE SHORT TERM.

SATURDAY NIGHT THROUGH WEDNESDAY...
FAVORABLE MARINE CONDITIONS ARE FORECAST THROUGH THE WEEKEND AND
INTO NEXT WEEK WITH MODERATE TO OCCASIONALLY LIGHT SOUTH TO
SOUTHEAST WINDS AND LOW TO MODERATE SEAS.

&&

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

$$

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