Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 122351
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
651 PM CDT FRI SEP 12 2014

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

&&

.AVIATION...OUTFLOW BOUNDARIES ARE ENHANCING THUNDERSTORMS OVER
KMFE AND WESTWARD PRODUCING MODERATE TO HEAVY DOWNPOURS AND AS A
RESULT REDUCE VISIBILITIES FOR THE NEXT HALF HOUR. SHOWERS OVER
THE GULF OF MEXICO WILL CONTINUE TO MOVE NORTHWEST AND MOVE CLOSER
TO KBRO AND KHRL IN THE NEXT HOUR. NOT A LOT OF LIGHTING ACTIVITY
AT THIS TIME BUT OCCASIONAL LIGHTNING CAN NOT BE RULE OUT WITH THE
CONVECTION. VISIBILITIES WILL LIKELY BE REDUCE WITH MODERATE SHOWERS.
TEMPO GROUPS HAVE BEEN INCLUDED FOR THIS EVENING. THE TROPICAL WAVE
OVER THE GULF WILL MOVE CLOSER TO OUR AREA TONIGHT INCREASING SHOWER
ACTIVITY OVERNIGHT AND THROUGH THE DAY SATURDAY.

&&

.PREV DISCUSSION... /ISSUED 258 PM CDT FRI SEP 12 2014/

..THE FLASH FLOOD THREAT CONTINUES AS TROPICAL MOISTURE COLLIDES
WITH A COLD FRONT TONIGHT AND SATURDAY...

SHORT TERM /NOW THROUGH SATURDAY NIGHT/...
HAZARDS...
FLASH FLOODING TONIGHT AND SATURDAY IN VALLEY/RIVER COUNTIES
MINOR COASTAL FLOODING SATURDAY AFTERNOON AND EVENING
HIGH SURF SATURDAY
SMALL CRAFT ADVISORY CONDITIONS DEVELOPING TONIGHT AND PERSISTING

RIGHT NOW...
NUMEROUS SHOWERS AND STORMS ARE DEVELOPING IN THE UPPER VALLEY AND
THE RANCH LANDS THIS AFTERNOON. PERSISTENT CLOUD COVER IS HOLDING
TEMPERATURES DOWN IN THE LOWER VALLEY BUT MODIFIED SOUNDINGS SHOW
THE AREA IS STILL MODERATELY UNSTABLE AND ADDITIONAL DEVELOPMENT IS
LIKELY THROUGH MID TO LATE AFTERNOON ALTHOUGH THE MOST SIGNIFICANT
ACTIVITY IS EXPECTED TO BE OVER THE NORTHWESTERN PORTION OF THE CWA
THROUGH THIS AFTERNOON. PRECIPITABLE WATER ESTIMATES RANGE FROM 2.2
TO 2.4 INCHES AND ANY CONVECTIVE CELL WILL BE A TORRENTIAL RAIN
PRODUCER. 15Z ASCAT PASS AND BUOY OBSERVATIONS NEAR THE CORE OF THE
TROPICAL WAVE SHOW A LARGE AREA OF 25 TO 35 KNOT SOUTHEAST WINDS
THAT ARE BUILDING A LONG PERIOD SWELL/FETCH THAT IS FORECAST TO
ARRIVE SATURDAY MORNING.

TONIGHT...
A BRIEF DECREASE IN ACTIVITY IS POSSIBLE THROUGH EARLY EVENING
ALTHOUGH THE ATMOSPHERE WILL REMAIN LARGELY SATURATED AND AT LEAST
SOME DEVELOPMENT IS LIKELY. THE MAIN CORE OF THE 850MB TROUGHING
ARRIVES LATE TONIGHT AND CONVECTIVE BANDING AND SCATTERED TO
NUMEROUS SHOWERS AND STORMS ARE FORECAST. PRECIPITABLE WATER
VALUES WILL LIKELY BE IN THE 2.4 TO 2.5 INCH RANGE AND ANY BANDED
OR TRAINING CONVECTION WILL PRODUCE A FLASH FLOOD RISK AND
CONTINUED THE FLASH FLOOD WATCH STARTING AT MIDNIGHT TONIGHT.
EASTERLY TO SOUTHEASTERLY WINDS OVER THE COASTAL WATERS WILL
INCREASE TO 20 TO 25 KNOTS AS WELL. CONTINUED THE CATEGORICAL
RAINFALL CHANCES AFTER MIDNIGHT FOR ALMOST THE ENTIRE CWA. BEST
CHANCES FOR FLASH FLOODING CONTINUE TO LOOK TO REMAIN IN THE
COUNTIES IN THE FLASH FLOOD WATCH.

SATURDAY...
SURFACE FRONT PUSHES IN FROM THE NORTH EARLY SATURDAY AND
SHOULD WORK WITH THE CORE OF THE TROPICAL WAVE TO PRODUCE WIDESPREAD
RAIN AND THUNDERSTORMS. 12Z GUIDANCE SUITE IS A LITTLE MORE
SUGGESTIVE OF THE FRONT HAVING A STRONGER DRYING INFLUENCE ON THE
LOWER ATMOSPHERE AND REDUCES QPF VALUES...BUT BELIEVE BASED ON
AVAILABLE MOISTURE AND THE TRAJECTORY OF WINDS THAT IT WILL ACTUALLY
PRODUCE AN OVERRUNNING EFFECT AND INCREASE RAINFALL COVERAGE ONCE IT
PASSES SO KEPT POPS HIGH. THE CORE OF HEAVIEST RAINFALL POTENTIAL
SHIFTS FROM THE SOUTHEAST COASTAL REGIONS TO AROUND STARR/ZAPATA
COUNTY BY LATER IN THE AFTERNOON. SEA STATE ANALYSIS AND WAVE
GUIDANCE PROJECTS 8 TO 10 SECOND SWELL ARRIVES BY 9 TO 10 AM AND
THAT WILL LIKELY PRODUCE MARGINAL HIGH SURF ADVISORY CONDITIONS. WE
WILL BE IN LOW TIDE EARLY IN THE DAY SATURDAY BUT ALSO HOISTED A
COASTAL FLOOD ADVISORY FOR CAMERON AND WILLACY COUNTIES FOR THE
EVENING HIGH TIDE WHICH SHOULD BE COLLOCATED WITH LONG PERIOD SWELL
AND WATER WILL LIKELY APPROACH AND BRIEFLY EXCEED THE DUNE LINE.

SATURDAY NIGHT...
TROPICAL WAVE AND TROUGHING MOVE INLAND REDUCING LOW LEVEL
CONVERGENCE AS THE FRONT ALSO BECOMES MORE DIFFUSE. WE RETAIN A
LARGE AMOUNT OF MOISTURE SO ANY WEAK CONVERGENCE WILL BE ABLE TO
PRODUCE ISOLATED TO SCATTERED SHOWERS AND STORMS SO KEPT POPS IN
THE 30 TO 40 PCT RANGE BUT DID START A MODEST DRYING TREND
CONSIDERING THE LACK OF FORCING FROM THE TWO SYSTEMS BY THE
EVENING. /68-JGG/

LONG TERM /SUNDAY THROUGH THURSDAY/...EASTERLY WAVE AND WEAK SFC
LOW WILL MOVE ACROSS FLORIDA AND INTO THE GULF ON SATURDAY...AND
THEN DRIFT ACROSS THE GULF BELOW RIDGING OVER THE NORTHERN MEXICAN
COAST. IN THE MEANTIME...CONDITIONS NEAR THE COAST AND OVER THE
GULF WILL REMAIN UNSETTLED AS DEEP TROPICAL MOISTURE CONTINUES TO
PROVIDE FUEL FOR CONVECTION. BY THE TIME THE LOW GETS TO THE WEST
GULF...RIDGING UPSTREAM WILL BE AMPLIFYING...LEAVING THE SURFACE
LOW STUCK OVER SOUTH TEXAS...WHERE MILDLY UNSETTLED WEATHER WILL
CONTINUE. HIGH TEMPERATURES WILL REMAIN AT OR SLIGHTLY ABV NORMAL
DURING THE LONG TERM...WHILE LOW TEMPS WILL BE NEAR NORMAL. ISOLD
TO SCTD SHOWERS AND THUNDERSTORMS WILL BE THE RULE FOR THE WEEK...
ESPECIALLY NEAR THE COAST.

MARINE...
NOW THROUGH SATURDAY NIGHT...A TROPICAL WAVE IS PRODUCING
RELATIVELY STRONG WINDS OVER THE WESTERN GULF OF MEXICO. THIS IS
EXPECTED TO GENERATE A LONG PERIOD SWELL WITH ROUGH SEAS THAT WILL
ARRIVE BY EARLY SATURDAY MORNING. THE WAVE WILL ALSO INCREASE
EASTERLY WINDS TONIGHT TO MARGINAL ADVISORY CONDITIONS AND A SMALL
CRAFT ADVISORY HAS BEEN ISSUED FOR ALL GULF WATERS THROUGH LATE
TONIGHT AND SATURDAY. ROUGH SEAS WILL REMAIN POSSIBLE THROUGH
SATURDAY NIGHT.

SUNDAY THROUGH TUESDAY...SLIGHTLY LOWER SEAS WILL PREVAIL ON
SUNDAY...FOUR TO SIX FEET...AS THE LONG PERIOD SWELL GENERATOR IN
THE BAY OF CAMPECHE...THE LOW PRESSURE AREA AND ITS ASSOCIATED
NORTHWARD EXTENDING TROUGH...WEAKENS AND MOVES TOWARD...IF NOT
INLAND...ALONG THE NORTHEAST MEXICAN COAST. SEAS SHOULD STABILIZE
AT MODERATE AFTER SUNDAY...WITH LIGHT TO MODERATE ONSHORE WINDS.
FLY IN THE OINTMENT FOR NEXT WEEK WILL BE LOW PRESSURE AREA
TRACKING WEST TO EAST ACROSS THE NORTH GULF...AND ITS POSSIBLE
DEVELOPMENT.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...FLASH FLOOD WATCH FROM MIDNIGHT CDT TONIGHT THROUGH SATURDAY
     EVENING FOR TXZ248-252>257.

     COASTAL FLOOD ADVISORY FROM NOON SATURDAY TO 4 AM CDT SUNDAY FOR
     TXZ256-257.

     HIGH SURF ADVISORY FROM 3 AM TO 7 PM CDT SATURDAY FOR TXZ256-257.

GM...SMALL CRAFT ADVISORY FROM 1 AM TO 7 PM CDT SATURDAY FOR GMZ150-
     155-170-175.

&&

$$

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