384  
FXUS64 KBRO 250521 AAB  
AFDBRO  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE BROWNSVILLE TX  
1121 PM CST SAT FEB 24 2018  
   
DISCUSSION
 
UPDATED FOR LATEST AVIATION DISCUSSION BELOW.  
 

 
   
AVIATION
 
SATELLITE IMAGES AND SURFACE OBSERVATIONS ACROSS DEEP  
SOUTH TEXAS LATE THIS EVENING INDICATES MAINLY MID TO HIGH LEVEL  
CLOUDS OVER THE AREA WITH SOME PATCHES OF LOWER MVFR DECKS. LIGHT  
TO MODERATE SOUTHEAST TO SOUTH WINDS CONTINUE ACROSS THE REGION  
THIS EVENING. EXPECT VFR CONDITIONS TO PREVAIL ACROSS THE AREA FOR  
THE NEXT SEVERAL HOURS UNTIL LOW CLOUDS AND PATCHY FOG DEVELOP AND  
EXPAND. A WEAK COLD FRONT WILL MOVE INTO THE NORTHERN RANCHLANDS  
TONIGHT AND LOW TO MID LEVEL MOISTURE WILL INCREASE AHEAD OF THE  
BOUNDARY. EXPECT MVFR TO NEAR IFR CONDITIONS TO DEVELOP WITH LOW  
CLOUDS/FOG LATE TONIGHT INTO EARLY SUNDAY MORNING. IN  
ADDITION...SHOWERS AND THUNDERSTORMS WILL DEVELOP ACROSS PORTIONS  
OF THE NORTHERN RANCHLANDS TONIGHT AND POSSIBLY MOVE INTO THE RIO  
GRANDE VALLEY EARLY SUNDAY MORNING. LIGHT TO MODERATE WINDS AND  
MVFR CEILINGS ARE EXPECTED TO LINGER INTO EARLY SUNDAY AFTERNOON.  
BRIEF VFR CONDITIONS MAY BE POSSIBLE BY MID TO LATE AFTERNOON  
BEFORE LOW CEILINGS RETURN LATE IN THE PERIOD.  
 

 
   
PREV DISCUSSION
 
/ISSUED 554 PM CST SAT FEB 24 2018/  
 
DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.  
 
AVIATION...SATELLITE IMAGES AND SURFACE OBSERVATIONS ACROSS DEEP  
SOUTH TEXAS EARLY THIS EVENING INDICATE SOME MID TO HIGH LEVEL  
CLOUDS OVER THE AREA. EXPECT VFR CONDITIONS TO PREVAIL ACROSS  
THE AREA THIS EVENING WITH BREEZY SOUTHEAST TO SOUTH WINDS  
GRADUALLY DIMINISHING AFTER SUNSET. A WEAK COLD FRONT WILL MOVE  
INTO THE NORTHERN RANCHLANDS TONIGHT AND LOW TO MID LEVEL MOISTURE  
WILL INCREASE AHEAD OF THE BOUNDARY. EXPECT MVFR TO NEAR IFR  
CONDITIONS TO DEVELOP WITH LOW CLOUDS/FOG LATE TONIGHT INTO EARLY  
SUNDAY MORNING. IN ADDITION...SHOWERS AND THUNDERSTORMS WILL  
DEVELOP ACROSS PORTIONS OF THE NORTHERN RANCHLANDS TONIGHT AND  
POSSIBLY MOVE INTO THE RIO GRANDE VALLEY EARLY SUNDAY MORNING.  
LIGHT TO MODERATE WINDS AND MVFR CEILINGS ARE EXPECTED TO  
LINGER INTO EARLY SUNDAY AFTERNOON.  
 
PREV DISCUSSION... /ISSUED 307 PM CST SAT FEB 24 2018/  
 
SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT): WINDS CONTINUE TO GUST  
BETWEEN 40 AND 45 MPH ACROSS PORTIONS OF CAMERON COUNTY AND  
BETWEEN 30 AND 35 MPH ACROSS PORTIONS OF HIDALGO COUNTY THIS  
AFTERNOON. WILL CONTINUE THE WIND ADVISORY FOR THE COASTAL  
COUNTIES OF DEEP SOUTH TEXAS THROUGH THE REST OF THE AFTERNOON.  
THE WINDS WILL DIMINISH EARLY THIS EVENING AS THE STRONG LOW LEVEL  
JET ACROSS THE LOWER TX COAST LIFTS NORTHWARD AND THE PRESSURE  
GRADIENT BEGINS TO RELAX AS A WEAK COLD FRONT MOVES INTO SOUTH  
TEXAS. MAIN CONCERN TONIGHT IS THE CONVECTIVE POTENTIAL ACROSS THE  
NORTHERN RANCHLANDS AND UPPER RIO GRANDE VALLEY AS THE FRONT  
MOVES INTO THE NORTHERN AND WESTERN PORTIONS OF THE CWA LATE  
TONIGHT. THIS MORNING THE HRRR WAS PROGGING THUNDERSTORMS  
DEVELOPING ACROSS PORTIONS OF JIM HOGG AND BROOKS COUNTIES TONIGHT  
BUT THE LATEST HRRR IS INDICATING SOUTHERN PORTIONS OF HIDALGO  
COUNTY BEFORE MIDNIGHT. WITH LACK OF MID LEVEL MOISTURE AND A  
STRONG LOW LEVEL THERMAL INVERSION ACROSS THE LOWER RGV...WILL  
KEEP BEST RAIN CHANCES ACROSS THE NORTHERN RANCHLANDS AND UPPER  
RGV TONIGHT WHERE SHOWERS OR THUNDERSTORMS ARE MORE FAVORABLE FOR  
DEVELOPMENT. WITH FAIRLY DECENT STORM RELATIVE HELICITY ACROSS THE  
AREA...WILL MENTION GUSTY WINDS... SMALL HAIL...AND HEAVY  
RAINFALL WITH STRONG THUNDERSTORMS ACROSS THE NORTHERN AND WESTERN  
PORTIONS OF THE CWA TONIGHT.  
 
THE FRONT WILL LIKELY STALL SOMEWHERE OVER DEEP SOUTH TX LATE  
TONIGHT INTO SUNDAY. WILL LIKELY SEE SCATTERED SHOWERS AND  
ISOLATED THUNDERSTORMS ACROSS EASTERN PORTIONS OF THE CWA SUN  
AFTERNOON WHERE SURFACE INSTABILITY WILL LIKELY BE HIGHER WITH  
LIGHT SOUTHERLY WINDS ACROSS THE LOWER RGV. THE FRONT TRIES TO  
MOVE ACROSS THE LOWER TX COAST SUN NIGHT AND OFFSHORE EARLY MON  
MORNING WITH A CONVECTIVE BOUNDARY ACROSS SOUTHEAST PORTIONS OF  
THE CWA SUN NIGHT. WILL KEEP HIGHER POPS ACROSS SOUTHERN AND  
EASTERN PORTIONS OF THE CWA SUN NIGHT AS DRIER AIR FILTERS INTO  
THE NORTHERN AND WESTERN PORTIONS.  
 
LONG TERM (MONDAY THROUGH SATURDAY): A CHANGEABLE SPRING-LIKE  
PATTERN FITTINGLY DOMINATES THE COMING WORK WEEK, INCLUDING JUST  
ABOUT EVERYTHING FROM WELCOME RAIN EARLY TO A HEAT SPIKE AND WIND  
MACHINE IN THE MIDDLE, AND PERHAPS THUNDERSTORMS SEPARATING THE  
VERY WARM/HOT DAY FROM A WARM BREEZY AND MUCH DRIER DAY TO FOLLOW  
AS MARCH ARRIVES, THEN BACK TO SOME CLOUDS AND PERHAPS A LITTLE  
RAIN TO START THE NEXT WEEKEND.  
 
THE CHANGEABLE WEATHER COMES COURTESY OF A SUBTLE CHANGE IN THE  
STEERING PATTERN T THROUGH THE WEEK. THOUGH SOUTHWEST FLOW STILL  
PREVAILS AT 500 MB INTO MID WEEK, THE SUBTROPICAL RIDGE THAT HAS  
DOMINATED THE GULF OF MEXICO AND KEPT FLORIDA BEAUTIFUL AND SOUTH  
TEXAS BREEZY TO WINDY AND GENERALLY WARM/HUMID WILL FLATTEN A BIT  
AND BEGIN TO SHIFT WEST, AND BY LATE WEEK THIS RIDGE AXIS IS  
CENTERED OVER VERACRUZ. AT THE SAME TIME, TROUGHING DEVELOPS ALONG  
THE MID ATLANTIC COAST, WITH NORTHWEST STEERING FLOW REACHING  
FLORIDA AND BRINGING A LONG-AWAITED FRONT THROUGH MOST OF THE  
PENINSULA. WHY DOES THIS MATTER? IT *COULD* BE THE START OF A  
TREND TOWARD DRIER FRONTS AND CONTINUED WARMER THAN NORMAL  
TEMPERATURES HEADING DEEPER INTO MARCH, WHICH IS PART OF THE  
SPRING PATTERN EXPECTED TO DRY OUT AND EVENTUALLY HEAT UP (IN A  
MORE NOTABLE WAY) THE RIO GRANDE VALLEY. STAY TUNED.  
 
MONDAY BEGINS WITH A WEAK 500 MB SHORT WAVE/SHEAR AXIS WHICH HELPS  
TO DEVELOP A WEAK BUT IMPORTANT COASTAL TROUGH JUST EAST OF THE  
LOWER TEXAS COAST. THE GFS WAS INITIALLY THE MOST BULLISH ON THIS  
SOLUTION, BUT THE 12Z DETERMINISTIC ECMWF CAME AROUND COMPLETELY  
TODAY AND GIVEN THAT THE POTENTIAL FOR LIGHT BUT NOTABLE RAINS  
ESPECIALLY ACROSS THE POPULATED RGV MAKES SENSE GIVEN THE BIG  
PICTURE, ESPECIALLY SINCE SUNDAY'S FRONT HAS MINIMAL SOUTHWARD  
PUSH OF DRIER AIR AFTER REACHING THE RANCHLANDS. WITH LEFTOVER  
SUBTROPICAL MOISTURE IN THE MIX HAVE PUSHED UP QPF A FEW NOTCHES,  
WITH POTENTIAL FOR AREA-WIDE .25 TO .5 INCHES ACROSS THE POPULATED  
RGV. TEMPERATURES WILL BE A BIT TRICKY; LOW CLOUDS/LIGHT RAIN AND  
NORTHEAST FLOW SHOULD HOLD READINGS IN THE SOUPY MID 60S TO AROUND  
70 FOR THE VALLEY, BUT WITH DRIER AIR AND FILTERED SUNSHINE  
FARTHER NORTH AND WEST THE MID 70S ADVERTISED BY THE ECMWF IS IN  
LINE AS WELL.  
 
WINDS CONTINUE TO VEER TO THE EAST MONDAY NIGHT BUT LIGHT (5 KNOTS  
OR LESS) AND EVENTUALLY TO LIGHT SOUTHEAST BY DAYBREAK TUESDAY.  
WITH ONLY SLIGHT DROPS IN TEMPERATURE BUT MORE IMPORTANTLY  
DEWPOINTS CATCHING UP/REMAINING FOR 100 PERCENT HUMIDITY, FOG,  
WHICH HAS BEEN A DOMINANT WEATHER ELEMENT THIS WINTER ON THE EDGE  
OF TRANSITIONS FROM COOL/COLD TO WARM, LOOKS LIKELY TO  
DEVELOP. FOLLOWED WFO CORPUS' LEAD AND ADDED "AREAS" MENTION TO  
ENTIRE REGION EXCEPT FOR OUTER COASTAL WATERS, WITH SLOW  
DISSIPATION TUESDAY ALONG THE IMMEDIATE COAST WHERE MARINE LAYER  
WILL KEEP WINDS SUPPRESSED SOME.  
 
AS FOR THOSE WINDS ON LAND, QUICK RETURN TO SOUTH/SOUTHEAST FLOW  
WITH A PICKUP TO NEAR 30 KNOTS AT 850 WILL GET THE VALLEY WIND  
MACHINE BACK IN GEAR - THOUGH NOT AS CRAZY AS TODAY'S VERSION  
WHICH HAS PUMPED LONG DURATIONS OF 30 TO 34 MPH GUST 40 TO 50 MPH  
ACROSS THE LOWER VALLEY. AS DEEPER MOISTURE QUICKLY SCOOTS NORTH,  
EXPECT A MIX OF AFTERNOON SUN AND CLOUDS IN MOST AREA, AND WITH  
RAPID LOW LEVEL WARMING LOW TO MID 80S SEEM LIKE A SURE BET,  
PERHAPS A FEW UPPER 80S SNEAKING IN ACROSS PARTS OF HIDALGO AND  
STARR COUNTY.  
 
BREEZY WARM WEATHER CONTINUES OVERNIGHT TUESDAY INTO EARLY  
WEDNESDAY AS REGION IS SANDWICHED BETWEEN WHAT'S LEFT OF  
SUBTROPICAL RIDGE AND APPROACHING (BUT LIFTING) SHORTWAVE TROUGH  
MOVING THROUGH THE SOUTHWEST U.S. LOWS SHOULD BE IN THE LOWER 70S  
(UPPER 60S RANCHLANDS) BUT COULD BE A TAD HIGHER IF LOW CLOUDS  
SCOOT IN, ESPECIALLY ACROSS THE RGV. THIS SETS US UP FOR A  
"CLASSIC" WIND MACHINE/HEAT SPIKE DAY ON WEDNESDAY. EXPECT 40-45  
MPH GUSTS ACROSS THE US 77/IH 69E CORRIDOR BY LATE MORNING THROUGH  
AFTERNOON, AND WITH ATMOSPHERE QUITE WARM FOR LATE FEBRUARY,  
TEMPERATURES SHOULD ACHIEVE UPPER 80S TO PERHAPS 90 IN A FEW SPOTS  
GIVEN AMPLE SUNSHINE. FARTHER WEST, WEST TO SOUTHWEST FLOW AT 850  
BRINGS THE DOWNSLOPE, AND SURFACE WINDS GO LIGHT. GUIDANCE FAIRLY  
CONSISTENT ON 90 TO 95 ALONG/WEST OF US 281-IH 69C WITH HIGHEST  
TEMPERATURES NEAR FALCON DAM. WOULD NOT RULE OUT THE YEAR'S FIRST  
CENTURY MARK READINGS EITHER; GUIDANCE OFTEN LATE TO CATCH ON AND  
HAS TO DEAL WITH LATE WINTER CLIMATOLOGY WHERE OUTLIERS ARE VERY  
DIFFICULT TO NAIL DOWN. FOR NOW, WENT 92 TO 95 FROM MCALLEN  
THROUGH ZAPATA, BUT WOULD NOT BE SURPRISE TO SEE THIS END UP IN  
THE 96 TO 100 RANGE.  
 
THE AFOREMENTIONED SHORTWAVE TROUGH RIPS THROUGH TEXAS WEDNESDAY  
NIGHT, WITH A QUICK MOVING WIND SHIFT/FRONT SURGING THROUGH DEEP  
S. TEXAS AT SOME POINT. GFS/ECMWF IN EXCELLENT AGREEMENT WITH A  
MID EVENING TO MIDNIGHT PASSAGE FOR THE RANCHES, AND A MIDNIGHT TO  
3 AM OR SO PASSAGE FOR THE VALLEY. WHILE THIS IS LIKELY TO CHANGE  
A BIT, THE TIMING OF ANY PRECIPITATION (INCLUDING THUNDER) WILL  
ULTIMATELY BE AN HOUR OR TWO (NOT A FULL SIX HOURS AS CURRENTLY  
FORECAST) BEFORE REFRESHINGLY DRY AIR SWEEPS IN. THURSDAY LOOKS  
MAINLY SUNNY WITH PASSING CIRRUS; THE ECMWF IS A BIT DRIER BUT THE  
GFS CAME TOWARD THIS SOLUTION WITH THE 12Z RUN. TEMPERATURES WILL  
STILL BE WARM BUT DEWPOINTS WILL BE MUCH LOWER, AND WE MAY NEED  
TO WATCH COMBO OF AFTERNOON RH AND WIND FOR POTENTIAL WILDFIRE  
SPREAD ISSUES AS WE GET CLOSER TO THE EVENT.  
 
CLOUDS GRADUALLY INCREASE FRIDAY BUT STILL SHOULD BE ENOUGH  
SUNSHINE AND STILL COMFORTABLE HUMIDITY WITH LIGHTER  
EAST/NORTHEAST WINDS TO MAKE A GREAT END TO THE WORK WEEK.  
SATURDAY REMAINS UNCERTAIN FOR NOW; RETAINED THE IDEA OF SOME  
LIGHT RAINS FOR THE RIO GRANDE VALLEY WITH FAIRLY DEEP LOW LEVEL  
MOISTURE (TO 800 MB) AS WEAK SHORT WAVE SLIDES THROUGH THE FLAT  
RIDGE, WHICH WILL BE CENTERED OVER VERACRUZ.  
 
MARINE: SEAS WERE GENERALLY 5 TO 7 FEET WITH SOUTH TO SOUTHEAST  
WINDS 15 TO 20 KNOTS OFFSHORE THE LOWER TEXAS COAST THIS  
AFTERNOON. WINDS WILL DIMINISH ACROSS THE COASTAL WATERS TONIGHT  
AS A WEAK COLD FRONT MOVES INTO SOUTH TEXAS LATE TONIGHT AND THE  
PRESSURE GRADIENT WEAKENS ACROSS THE LOWER TX COAST. SEAS WILL  
REMAIN HIGH OFFSHORE SO WILL EXTEND THE SMALL CRAFT ADVISORY FOR  
THE 20-60NM WATERS THROUGH MIDNIGHT BUT THE NEARSHORE WATERS  
SHOULD BE BELOW SCA CRITERIA SO WILL REPLACE WITH SCA WITH SCEC  
AFTER 6 PM. LIGHT TO MODERATE SOUTHEAST WINDS WILL PREVAIL ACROSS  
THE LOWER TX COAST AFTER MIDNIGHT TONIGHT. WINDS SHOULD REMAIN  
LIGHT FROM THE SOUTH ACROSS THE COASTAL WATERS SUNDAY AS THE FRONT  
LIKELY STALLS NEAR THE COASTAL BEND SUN AFTERNOON. THE FRONTAL  
BOUNDARY TRIES TO MOVE OVER THE LOWER TX COAST SUN NIGHT AND MOVE  
OFFSHORE EARLY MON MORNING AS A CONVECTIVE BOUNDARY. WINDS ARE  
EXPECTED TO SHIFT TO THE NORTH AND NORTHEAST ACROSS THE NORTHERN  
COASTAL WATERS EARLY MON MORNING AS A RESULT.  
 
MONDAY THROUGH THURSDAY: A RATHER YUCKY BOATING DAY MONDAY WITH  
OCCASIONAL RAIN/SHOWERS AND A NUISANCE STIFF NORTHEAST WIND, ALONG  
WITH MIXED SEAS (WIND CHOP AND SOME SWELL) UP TO 5 FEET EXPECTED.  
A BIT BETTER FOR EARLY MORNING FISHING TUESDAY EXCEPT FOR  
POTENTIAL DENSE FOG (RADATION/SEA FOG COMBO) THAT COULD DELAY  
TRIPS FOR THOSE CONCERNED WITH LOW VISIBILITY, WITH WINDS LIGHT  
AND SEAS MODERATE TO START THE DAY. LAGUNA WINDS WILL PICK UP SOME  
TUESDAY AFTERNOON, AND CAUTION/ADVISORY CONDITIONS FOR WINDS  
POSSIBLE BUT WILL BE DETERMINED BY STRENGTH OF THE MARINE LAYER.  
 
WINDS WILL PICK UP TUESDAY NIGHT IN ALL AREAS (A BIT LESS OVER THE  
NEARSHORE WATERS DUE TO REMAINING MARINE LAYER) AND WITH 850 MB  
FLOW POSSIBLY REACHING 40 TO 45 KNOTS ADVISORY CONDITIONS (WIND  
AND PERHAPS SEAS) MAY DEVELOP OFFSHORE, CONTINUING WEDNESDAY WITH  
20 KNOT SUSTAINED WIND LIKELY IN BOTH AREAS. EVEN THE NEARSHORE  
COULD SEE 20 KNOT WINDS FOR A TIME, ESPECIALLY MID MORNING THROUGH  
MID AFTERNOON.  
 
A BRIEF LULL IN WINDS BEFORE SHIFTING NORTHWEST/NORTH LATE  
WEDNESDAY NIGHT AND CONTINUING THURSDAY. WITH MINIMAL COLD AIR  
ADVECTION OVER A MARINE LAYER, EXPECTING SUSTAINED WINDS OVER THE  
NEARSHORE WATERS THURSDAY TO BE AROUND THE EDGE OF CAUTION (15 TO  
20 KNOTS) WITH A BETTER OPPORTUNITY OVER LAGUNA MADRE. SEAS WILL  
HOLD AT MODERATE TO CAUTION (6 FOOT) LEVELS THOUGH NORTHWEST FLOW  
SHOULD DROP VALUES A BIT NEARSHORE FOR THURSDAY.  
 
CLIMATE: THE HEAT HAS DOMINATED FEBRUARY, AND AFTER TODAY ALL  
PRIMARY LOCATIONS (BROWNSVILLE, HARLINGEN, MCALLEN) WILL BE  
SOMEWHERE BETWEEN 5 AND 5.5 DEGREES ABOVE THE MONTHLY AVERAGE.  
WITH ABOVE TO SLIGHTLY ABOVE AVERAGE TEMPERATURES THROUGH MONDAY,  
THEN A LAST HURRAH OF HEAT TUESDAY AND ESPECIALLY WEDNESDAY, 6  
DEGREES ABOVE AVERAGE FOR THE MONTH IS NOT OUT OF THE REALM OF  
POSSIBILITY. THAT *COULD* TIP THE SCALES TO A WINTER (DECEMBER-  
FEBRUARY) JUST *ABOVE* AVERAGE - SOMETHING THAT SEEMED UNHEARD OF  
WHEN JANUARY ENDED. WE'LL DO THE NUMBERS IN A FEW DAYS.  
 

 
   
BRO WATCHES/WARNINGS/ADVISORIES
 
 
TX...NONE.  
GM...SMALL CRAFT ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR GMZ170-175.  
 

 
 

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