Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 280608 AAC
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
108 AM CDT THU AUG 28 2014

.DISCUSSION...RADAR SHOWS A NEAR SURFACE CIRCULATION CENTER ABOUT
35 MILES EAST OF SOUTH PADRE ISLAND AND 1 AM. SURFACE OBSERVATIONS
SUGGEST AN ELONGATED SURFACE TROUGH EXTENDING EAST SOUTHEASTWARD
ABOUT 150 MILES INTO THE GULF OF MEXICO WHICH IS SUPPORTED BY
INFRARED SATELLITE IMAGES OF A MID LEVEL CENTER DISPLACED ABOUT 75
TO 100 MILES EAST OF THE RADAR CENTER. THE DEEPEST CONVECTION IS
OFF THE KENEDY COUNTY COAST THIS MORNING AND THAT AREA LOOKS AS IF
IT MAY MOVE ONSHORE IN THE NEXT FEW HOURS. GOES SATELLITE DERIVED
WINDS AND WATER VAPOR AS WELL AS THE SYSTEMS OVERALL RAGGED
APPEARANCE CONTINUE TO SHOW THE SYSTEM IS STRONGLY SHEARED AND NHC
LOWERED THE PROBILITY OF DEVELOPMENT INTO A SELF SUSTAINING
TROPICAL DEPRESSION TO 10 PERCENT BEFORE LANDFALL WHICH APPEARS SPOT ON
GIVEN THE CURRENT CONDITIONS AND THE SYSTEMS RAGGED CURRENT
APPEARANCE. PRESSURE FALLS AT BUOY 20 HAVE STOPPED AND WINDS THERE
HAVE DECREASED A BIT. WILL STILL BE WATCHING THE SYSTEM THOUGH FOR
A FLARE UP AT THE NORMAL DIURNAL MAXIMUM BETWEEN 3 AND 6 AM THAT
MAY INCREASE RAINFALL AMOUNTS AS IT MOVES ON SHORE. FORECAST RIGHT
NOW LOOKS ABOUT RIGHT...WILL BE FOCUSING ON THE ELONGATED TROUGH AND
THE DEEPENING EASTERLY FLOW OVER THE NEXT 36 HOURS IN THE MORNING
FORECAST PACKAGE AS THE GENERAL TROUGHINESS WILL LIKELY MEANDER
AROUND THE COAST FOR A DAY OR TWO. /68-JGG/

&&

.PREV DISCUSSION... /ISSUED 1225 AM CDT THU AUG 28 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...LOW PRESSURE CENTERED ABOUT 100 MILES OFFSHORE
CONTINUES TO DRIFT WESTWARD THIS MORNING AND LOW MOISTURE WILL
INCREASE MARKEDLY AS IT MOVES ONSHORE. THE FIRST REPORTS OF 1500
FT CIGS ARE STARTING ALONG THE IMMEDIATE COAST AND EXPECT THOSE
WILL BE A LITTLE INTERMITTENT FOR THE NEXT FEW HOURS BEFORE
BECOMING MORE PREVAILING AT AROUND 2000FT IN THE COASTAL COUNTIES
BY SUNRISE AND SPREADING WESTWARD THROUGH THE DAY AMID SHOWERS AND
STORMS. CONVECTIVE INTENSITY WILL PICK UP IN THE AFTERNOON HOURS.
FORECASTING PREVAILING MVFR CONDITIONS IN THE EVENING AS EASTERLY
ONSHORE FLOW PULLS IN VERY RICH LOW LEVEL MOISTURE. CONDITIONS
WILL PROBABLY FLUCTUATE MORE THAN NORMAL WITHIN INDIVIDUAL
PERTURBATIONS ASSOCIATED WITH THE CONVECTIVELY INDUCED LOW
PRESSURE SYSTEM. /68-JGG/

PREV DISCUSSION... /ISSUED 637 PM CDT WED AUG 27 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...MOSTLY CLEAR SKIES CONTINUE THIS EVENING...AS THE MAIN
TROPICAL LOW REMAINS NEARLY STATIONARY JUST OFFSHORE. CLOUD COVER
THROUGH THE FIRST HALF OF THE NIGHT WILL BE LIMITED TO CIRRUS.
SOME OF THE TROPICAL SHOWERS AND THUNDERSTORMS WILL BEGIN TO DRIFT
INLAND LATE OVERNIGHT...REACHING THE KBRO AND KHRL SITES. ONCE
DAYTIME HEATING ARRIVES...SHOWERS AND THUNDERSTORMS ARE EXPECTED
TO BECOME MORE NUMEROUS AREAWIDE. WITH RAIN CHANCES ABOVE 50
PERCENT...HAVE SHIFTED TAFS TO VC PRECIPITATION WITH TEMPO
THUNDERSTORM GROUPS.

PREV DISCUSSION... /ISSUED 309 PM CDT WED AUG 27 2014/

SHORT TERM.../NOW THROUGH THURSDAY NIGHT/...SURFACE LOW IS LOCATED
ABOUT 150 MILES ENE OF BROWNSVILLE AS OF 2 PM TODAY. SCATTERED
CONVECTION CONTINUES TO DEVELOP AROUND THE LOW WITH ISOLATED SHOWERS
ACROSS THE COASTAL COUNTIES ALONG THE QUASI-STATIONARY SEA BREEZE.
THE LOW CONTINUES TO TRACK WSW AROUND THE PERIPHERY OF THE MID TO
UPPER RIDGE OVER SOUTHERN STATES. THIS WILL DIRECT THE LOW TOWARDS
THE LOWER TX COAST TONIGHT AND OVER THE RGV THURSDAY.

FOR TONIGHT...MODELS SUGGEST THE UPPER LEVEL WINDS TO WEAKEN WHICH
COULD RESULT IN DEEP CONVECTION INCREASING AROUND THE CENTER OF THE
LOW. NOT ANTICIPATING ANY SIGNIFICANT TROPICAL DEVELOPMENT BUT A
WARM ADVECTION RAIN EVENT COULD EVOLVE OVERNIGHT. PWATS APPROACH
2.25 INCHES AND LIGHTER WINDS WOULD SUGGEST CONVECTION TO INCREASE
OVER THE WARM GULF AND MOVE WESTWARD ALONG THE COAST AFTER MIDNIGHT.
THE LAST FEW NIGHTS ISOLATED CONVECTION CLUSTERS HAVE PRODUCED VERY
HEAVY RAINFALL AMOUNTS OVER THE OPEN GULF. DO NOT SEE ANY REASON WHY
THIS SHOULD NOT OCCUR AGAIN ESPECIALLY WITH THE SHEAR WEAKENING.
LOCALLY HEAVY RAIN WILL BE MENTIONED WITH AMOUNTS OVER THE NEXT
12-24 HOURS /THROUGH THURSDAY NIGHT/ RANGING FROM 1/2 TO 2 INCHES
WITH LOCALLY HIGHER AMOUNTS OF 3 TO 5 INCHES. AT THIS TIME WILL
PLACE THE HIGHER RAIN AMOUNTS AND HIGHER POPS ACROSS THE COASTAL
COUNTIES. MODELS ARE IN GOOD AGREEMENT INCREASING POPS OVERNIGHT
WITH NAM THE MOST AGGRESSIVE WITH RAINFALL AMOUNTS AND PWAT VALUES.

AS WE MOVE INTO THURSDAY AND THURSDAY NIGHT SURFACE LOW MOVES INLAND
AND UPPER DIVERGENT FLOW INCREASES ALONG AND EAST OF THE SHEAR LINE
MOVING ALONG THE TEXAS COAST. AT THE SURFACE LOW LEVEL WINDS TURN
MORE SOUTHEAST SURGING ADDITIONAL MOISTURE INTO THE REGION. MODELS
ARE PUSHING PWATS BETWEEN 2.5 AND 3 INCHES BY 00Z FRIDAY. RAIN
CHANCES GO UP ANOTHER NOTCH WITH LIKELY POPS ALONG AND EAST OF
HIGHWAY 281/69C. HEAVY RAIN IS LIKELY AND AS MENTIONED ABOVE SOME
AREAS MAY SEE SIGNIFICANT RAINFALL WHERE THE SHOWERS AND STORMS
TRAIN OVER THE SAME LOCATIONS. UPPER FLOW WILL BE LIGHT SO STORMS
WILL BE SLOW MOVING AS WELL. DO NOT ANTICIPATE A FLASH FLOOD WATCH
WITH THE GROUND VERY PARCHED AND WILL BE CAPABLE OF RECEIVING A LOT
OF WATER. FLASH FLOOD GUIDANCE FOR ONE HOUR RANGES FROM 3.5 TO 5.7
INCHES...4 TO 6 INCHES FOR 3 HOURS AND 5 TO 7.5 INCHES FOR 6 HOURS.

TEMPERATURES ON THURSDAY WILL BE SLIGHTLY LOWER BUT COULD BE EVEN
LOWER THEN FORECAST IF RAIN AND CLOUDS DO NOT ABATE MUCH DURING THE
DAY. IN ANY CASE, A REPRIEVE OF 95-105 INTO THE 88-94 DEGREE RANGE
WILL BE NICE.

LONG TERM...FRIDAY THROUGH WEDNESDAY NIGHT...
WEAK TROPICAL LOW CURRENTLY OVER WESTERN GULF COAST WILL BE OVER
THE CWA BY THE BEGINNING OF THE LONG TERM FORECAST WITH ABUNDANT
MOISTURE TO ENHANCE CONVECTION THROUGH THE WEEKEND. THE GFS/NAM
SHOW AN INCREASE ON THE PRECIPITABLE WATER OF 2.47 INCHES FRIDAY
AS THE DEEP TROPICAL MOISTURE MOVES OVER THE AREA. THIS WAVE WILL
ENHANCE SHOWERS AND THUNDERSTORMS ACROSS THE RGV FRIDAY THROUGH
SATURDAY. WITH THIS ABUNDANT MOISTURE AND THE UPPER LEVEL SUPPORT
FROM THIS WEAK LOW...EXPECT THIS ACTIVITY TO PRODUCE LOCALLY HEAVY
RAIN WITH 2 TO 3 INCHES WITH THE STRONGEST STORMS. BEST POTENTIAL
WILL FRIDAY AFTERNOONS AND OVERNIGHT...WITH SOME ADDITIONAL
ACTIVITY SATURDAY...BUT FARTHER INLAND. ACTIVITY SHOULD DECREASE
SUNDAY AND MONDAY AND TEMPERATURES AND HEAT INDEX VALUES CREEP
BACK UP A COUPLE OF DEGREES. TREND IN TEMPERATURES EACH DAY WILL
CONTINUE TO BE ABOVE NORMAL THROUGH THE LONG TERM.

AN UPPER LEVEL TROUGH MOVING ALONG THE CANADIAN BORDER DURING THE
WEEKEND WILL DEEPEN LEE SIDE TROUGH OVER THE CENTRAL PLAINS SUNDAY
AFTERNOON INCREASING SOUTHEAST WINDS ACROSS THE CWA. EXPECT BREEZE
AFTERNOON SUNDAY. DRY AIR MASS BEHIND THE TROPICAL WAVE WILL MOVE
INTO THE AREA MONDAY SUPPRESSING THE CHANCE OF RAIN. THE RH VALUES
BETWEEN 1000 TO 500 MB DROPS TO BELOW 45 PERCENT. A MORE ZONAL UPPER
LEVEL FLOW DEVELOPS ACROSS THE WESTERN AND SOUTHERN PORTION OF TEXAS
WITH GFS CONTINUING TO SHOW A TROPICAL WAVE MOVING ACROSS THE
YUCATAN PENINSULA AND INTO THE BAY OF CAMPECHE LATE MONDAY INTO
TUESDAY. INCREASE POPS TO 20 PERCENT OVER THE GULF WATERS BY
TUESDAY. THERE WERE NO OTHER SIGNIFICANT CHANGES IN THE LONG TERM
FORECAST.

MARINE...NOW THROUGH THURSDAY...
THE SURFACE LOW IS LOCATED ABOUT 150 MILES ENE OF PORT ISABEL THE
PERSISTENT MODERATE WINDS CIRCULATING AROUND THE LOW ARE ALLOWING
FOR THE SEAS/SWELLS TO INCREASE. MARGINAL SMALL  CRAFT ADVISORY SEA
HEIGHTS ARE ANTICIPATED TONIGHT AND EARLY THURSDAY AS THE LOW
APPROACHES THE COAST BY SUNRISE THURSDAY. WINDS TO TURN E-SE
THURSDAY NIGHT AT LIGHT TO MODERATE LEVELS. SOME RESIDUAL SWELL TO
CONTINUE BUT A SUBSIDING TREND IS FORECAST. THE ONLY FLY IN THE
OINTMENT WILL BE THE INCREASE IN SHOWERS AND THUNDERSTORMS WHICH
COULD ALLOW FOR LOCALLY HIGHER WINDS AND SEAS WHICH MIGHT PERSIST
THROUGH THURSDAY NIGHT. THANK YOU TO NESDIS AND CRP FOR THE
COORDINATION.

FRIDAY THROUGH TUESDAY NIGHT...WEAK TROPICAL WAVE OVER THE GULF
OF MEXICO WILL BE INLAND BY FRIDAY ENHANCING THE CONVECTION OVER
THE GULF WATERS THROUGH SATURDAY. THIS ACTIVITY WILL KEEP SEAS
ERRATIC AND A ELEVATED CLOSE TO 4 TO 5 FEET. SEAS WILL BUILD
MONDAY THROUGH TUESDAY AS PRESSURE GRADIENT STRENGTHEN AND
INCREASE SEAS CLOSE TO 6 FEET. ANOTHER WAVE WILL MOVE INTO THE
GULF WATERS BY NEXT WEEK INCREASING THE CHANCE OF RAIN ONCE AGAIN.

&&

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

$$

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