246  
FXUS64 KBRO 211137 AAA  
AFDBRO  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE BROWNSVILLE TX  
637 AM CDT SUN OCT 21 2018  
   
DISCUSSION
 
UPDATED FOR LATEST AVIATION DISCUSSION BELOW.  
 

 
   
AVIATION
 
MUCH BALLYHOOED RAIN STARTING TO STREAM ACROSS  
CAMERON COUNTY THIS MORNING, REINFORCING DEGRADED AVIATION  
CONDITIONS AT THE TAF SITES, ESPECIALLY BRO AND HRL. LOOK FOR  
IFR/MVFR CEILINGS AND ALSO PERIODIC VISIBILITY RESTRICTIONS IN  
MIST AND PATCHES OF RAIN. A COASTAL TROUGH REMAINS IN PLACE, WITH  
SOME MODELS HINTING AT A SHARPENING ALONG THE TROUGH AXIS AND A  
WESTWARD TOPPLING OF THE APEX OVER THE LOWER VALLEY, MAINTAINING  
LOWER CEILINGS AND ELEVATED/INCREASING RAIN CHANCES THROUGH THE  
DAY AND INTO THIS EVENING. SURFACE WINDS WILL BE MOSTLY MODERATE  
NORTH.  
 

 
   
PREV DISCUSSION
 
/ISSUED 429 AM CDT SUN OCT 21 2018/  
 
SHORT TERM (NOW THROUGH MONDAY): WITH THE MODELS MOSTLY HOLDING  
THE COASTAL TROUGH OFFSHORE TODAY, THE THREAT OF FLASH FLOODING  
ACROSS THE AREA HAS DIMINISHED. MOST QPF ESTIMATES ARE BELOW FF  
GUIDANCE. THUS, TRIMMED THE ONGOING WATCH BACK A SKOSH, CUTTING OUT  
BROOKS COUNTY, AND PROBABLY COULD HAVE TRIMMED MORE, BUT OPTED TO  
LET THE NEXT SHIFT HAVE A LOOK AT THE SITUATION. THAT SAID, RAIN  
CHANCES THE NEXT 36 HOURS REMAIN FAIRLY HIGH, BUT ANTICIPATE MORE OF  
THE LIGHT RAIN TYPE. THAT'S NOT TO SAY ISOLATED MODERATE TO HEAVY  
SLOW MOVING RAINERS COULDN'T TRACK ACROSS THE SOUTHEAST CORNER OF  
THE CWA, PRODUCING LOCALIZED FLOODING HERE AND THERE. HIGH TEMPS IN  
THE SHORT TERM WILL BE HELD IN THE 60S AND 70S UNDER MOSTLY CLOUDY  
TO OVERCAST SKIES, WITH OVERNIGHT LOWS IN THE 50S AND 60S. WINDS  
WILL BE LIGHT TO MODERATE FROM THE NORTH.  
 
THE APEX OF THE OFFSHORE CONVERGENT ZONE WILL NOSE FARTHER NORTH ON  
MONDAY, TAKING MUCH OF THE PRECIP POTENTIAL WITH IT, LEAVING WEAK  
LOW PRESSURE JUST OFFSHORE. THE THREAT OF HEAVY RAINFALL WILL  
FURTHER DIMINISH, THOUGH MOISTURE WILL REMAIN ELEVATED WITH  
PRECIPITABLE WATER OVER TWO INCHES AND ENOUGH OF A LOW LEVEL  
INVERSION TO KEEP MOSTLY CLOUDY TO OVERCAST SKIES IN THE SHORT TERM  
FORECAST. MOISTURE FROM HURRICANE WILLA IN THE EASTERN PACIFIC MAY  
TRACK CLOSE TO (RGV PLAINS) OR POSSIBLY OVER THE UPPER VALLEY WITH  
TIME, BUT UNCERTAIN AS TO ANY RAIN POTENTIAL FROM THAT SOURCE IN THE  
SHORT TERM RIGHT NOW.  
 
COASTAL FLOODING: BEACH CAMS SHOW BEACH RUN UP AT HIGH TIDE, AND  
WITH FRESH NORTHEAST WINDS AND BUILDING SEAS FORECAST FOR TODAY,  
WITH TIDES RUNNING A FOOT ABOVE ASTRONOMICAL, OPTED TO POST A  
COASTAL FLOOD STATEMENT THROUGH HIGH TIDE AT AROUND 1:30 PM THIS  
AFTERNOON.  
 
LONG TERM (MONDAY NIGHT THROUGH SATURDAY): LOOKS LIKE UNSETTLED  
WEATHER WILL REMAIN IN THE PICTURE THROUGH THE MIDDLE PART OF THE  
WEEK, THEN AN INCREASINGLY DRIER, MORE STABLE, AND SOMEWHAT WARMER  
PATTERN KICKS IN FOR THE LATTER PORTION OF THE WEEK.  
 
00Z RUNS OF GFS AND NAM BOTH A LITTLE MORE STUBBORN IN HANGING  
ON/REFORMING THE COASTAL TROUGH/LOW A LITTLE LONGER THAN PRIOR  
RUNS. MONDAY NIGHT, THE ATMOSPHERIC COLUMN IS PROGGED TO REMAIN  
NEARLY SATURATED, BUT WITH LITTLE UPPER-LEVEL SUPPORT, QPF REMAINS  
ON THE MODEST SIDE (ONLY A 0.1" OR SO) EVEN INTO TUESDAY. LOOKS  
LIKE A COOL START TO THE LONG-TERM AS WELL, IN ADDITION TO THE  
DAMPNESS, AS THE SURFACE TROUGH MAINTAINS N-NW WINDS AT THE  
SURFACE, WITH MORNING LOWS RANGING FROM THE MID-50S FAHRENHEIT NW  
TO THE LOW 60S NEAR BROWNSVILLE. GULF OF MEXICO 500-MB HIGH  
"TRIES" TO BACK INTO THE AREA TUESDAY, BUT HAS A TOUGH TIME MAKING  
HEADWAY AS THE TROUGHING OVER THE GREAT BASIN PHASES WITH THE  
REMNANT UPPER CIRCULATION FROM CURRENT TROPICAL STORM WILLA TO  
MAINTAIN LIGHT SW FLOW. THUS, SHOWER CHANCES CONTINUE.  
 
BOTH GFS AND ECMWF INDICATE THAT THE WILLA REMNANT MOISTURE/UPPER  
CIRCULATION WILL BE CAUGHT UP IN THE MID-LATITUDE FLOW AND MOVE UP  
OVER SOUTHERN/CENTRAL TEXAS. SOME DIFFERENCES IN TIMING AND  
AMPLITUDE OF THE PROGRESSION, THOUGH. GFS MOVES WHAT'S LEFT OF  
WILLA QUICKLY ACROSS SOUTH TEXAS ON WEDNESDAY, WITH DRIER AIR  
QUICKLY MOVING IN BEHIND IT OVERNIGHT. ECMWF DAMPENS IT OUT MORE,  
WITH A SLOWER PROGRESSION...BUT WITH A PATH MORE OVER DEEP SOUTH  
TEXAS...FROM ROUGHLY 06-18Z THURSDAY. BOTH MODELS, HOWEVER, KEEP  
THE BULK OF THE PRECIPITATION TO THE NORTH OF OUR CWA. DIDN'T MAKE  
MANY CHANGES TO THE POP'S IN THIS PERIOD, DUE TO THE TIMING  
UNCERTAINTY. SCATTERED SHOWERS WITH A FEW THUNDERSTORMS WOULD SEEM  
TO BE A GOOD BET.  
 
ONCE THIS FEATURE DOES MOVE THROUGH, PRECIPITATION CHANCES ARE  
EXPECTED TO EFFECTIVELY END (ESPECIALLY COMPARED WITH THOSE OF  
LATE), AS A MID- LATITUDE TROUGH TO THE NORTH FLATTENS THE FLOW  
ALOFT TO ZONAL BY FRIDAY. PRECIPITABLE WATER TUMBLES BACK DOWN TO  
AROUND 1.5" OR SO. FURTHER DRYING IS INDICATED FOR NEXT WEEKEND,  
AS VERY DRY NW FLOW ALOFT ARRIVES AFTER A SHEAR AXIS MOVES  
THROUGH ON SATURDAY.  
 
TEMPERATURES SHOULD MODERATE SOME AFTER TUESDAY, BUT STILL REMAIN  
WELL BELOW NORMAL THROUGH AT LEAST THURSDAY, WITH MID-UPPER 70S  
(NOT BAD!) COMMON IN THE MID/LOWER RGV. IF THE ADVERTISED DRYING  
LATE IN THE WEEK DOES OCCUR, TEMPS COULD CLIMB BACK TO NEAR OR  
JUST SLIGHTLY ABOVE NORMAL. LEANED ON THE WARMER SIDE OF GUIDANCE  
FOR NEXT SATURDAY AS THE DRYING PATTERN LOOKS REALISTIC.  
 
MARINE (NOW THROUGH MONDAY): COASTAL TROUGHING ALONG A WEAK STATIONARY  
FRONT IS SUPPORTING DEGRADED MARINE CONDITIONS IN THE SHORT TERM.  
THE TIGHTER PRESSURE GRADIENT BETWEEN THE TROUGH AND HIGHER PRESSURE  
OVER THE NORTHWEST GULF IS PRODUCING FRESH TO STRONG NORTHEAST  
WINDS, WHICH SHOULD CONTINUE THROUGH THE NEXT 36 HOURS, ALONG WITH  
ELEVATED WAVE HEIGHTS. SMALL CRAFT SHOULD EXERCISE CAUTION TO LOW  
END SMALL CRAFT ADVISORY CONDITIONS WILL CONTINUE ON THE LAGUNA,  
WITH MORE CERTAIN SMALL CRAFT ADVISORY CONDITONS ON THE GULF WATERS.  
IT LOOKS LIKE THE FRONTAL BOUNDARY WILL PUSH NORTH BY MONDAY, BEING  
REPLACED OFFSHORE BY AN AREA OF LOW PRESSURE, ULTIMATELY ALLOWING  
FOR SOMEWHAT WEAKER WINDS.  
 
MONDAY NIGHT THROUGH FRIDAY: SMALL CRAFT ADVISORY CONDITIONS (BOTH  
WIND AND SEAS) MAY TO BE ONGOING MONDAY EVENING FOR THE GULF  
WATERS, AS STRONGER NE WINDS NORTH OF THE ONCE-AGAIN REINVIGORATED  
COASTAL TROUGH WILL BE IN PLACE. SAID SURFACE LOW IS FORECAST TO  
FINALLY LIFT AWAY FROM THE LOWER TEXAS COAST AS TUESDAY WEARS ON.  
AGITATED SEAS PROBABLY WILL BE SLOW TO SUBSIDE, HOWEVER, WITH  
HAZARDOUS CONDITIONS LINGERING INTO TUESDAY NIGHT. A MORE MODERATE  
NORTHERLY WIND, AND CONSEQUENTLY MODERATE SEAS OF 3-5 FT., SHOULD  
PREVAIL FROM WEDNESDAY THROUGH FRIDAY.  
 

 
   
BRO WATCHES/WARNINGS/ADVISORIES
 
 
TX...FLASH FLOOD WATCH THROUGH MONDAY MORNING FOR TXZ251-253>257-351-  
353.  
 
GM...SMALL CRAFT ADVISORY FOR WINDS UNTIL MIDNIGHT CDT TONIGHT FOR  
GMZ130-132-135.  
 
SMALL CRAFT ADVISORY UNTIL 1 PM CDT MONDAY FOR GMZ150-155-170-  
175.  
 

 
 

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