Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 191743
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1243 PM CDT FRI SEP 19 2014

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

&&

.AVIATION...LATEST SATELLITE AND RADAR TRENDS SHOW SOME ISOLATED
SHOWERS DEVELOPING ALONG THE COAST AND MOVING NORTHWARD. S WINDS
ARE STARTING TO SHIFT SE AND THE TREND WILL CONTINUE INTO KHRL
AND KMFE AND THE WESTERN AREAS ALLOWING FOR MORE CONVECTION TO
INITIATE CLOSE TO THE TERMINALS. TEMPO GROUPS HAVE BEEN INCLUDED
MENTIONING THE BEST TIMING FOR THE CONVECTION. THIS ACTIVITY WILL
BEGIN TO LOWER WITH THE LOSS OF DAYTIME HEATING WITH VFR CONDITIONS
PREVAILING OVERNIGHT AND LIGHT TO VARIABLE WINDS. THE SE WINDS WILL
BEGIN TO INCREASE AFTER 15Z TOMORROW WITH ANOTHER POSSIBLE ROUND OF
SHOWERS DEVELOPING SATURDAY AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 728 AM CDT FRI SEP 19 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...THE ATTENTION FOR CONV TRENDS HAS SHIFTED FROM THE
NORTH TO THE WEST AS THE CONV TO OUR NORTH HAS DISSIPATED WHILE AN
APPARENT MCS HAS FIRED UP OVER NORTH CENTRAL MEXICO AND IS MOVING
EAST TOWARDS THE WESTERN PORTIONS OF THE BRO CWA. ALTHOUGH IT IS
IMPRESSIVE ON SATELLITE AT THIS TIME AM NOT SURE THAT IT WILL MAKE
IT OVER THE MOUNTAINS OF MEXICO INTACT. REGARDLESS DAYTIME HEATING
LATER TODAY WILL INTERACT WITH TROPICAL MOISTURE LINGERING OVER
THE AREA TO GENERATE UP SOME SCT CONV ACROSS THE REGION DURING THE
LATE MORNING AND AFTERNOON HOURS. WITH THE LOSS OF THE DAYTIME
HEATING LATER THIS EVENING THE CONV WILL DIMINISH. EXPECT GENERAL
MVFR/VFR CONDITIONS TO PREVAIL FOR THE MOST PART WITH BRIEF
REDUCTIONS OF CEILINGS/VSBYS CUE TO SCT CONV.

SOME PATCHY SHALLOW GROUND FOG WILL AFFECT ALL OF THE LOWER RGV
AIRPORTS THIS MORNING REDUCING VSBYS DOWN FOR A FEW HOURS.

PREV DISCUSSION... /ISSUED 406 AM CDT FRI SEP 19 2014/

SHORT TERM /TODAY THROUGH SATURDAY/...REMNANT DEEP LAYER TROPICAL
MOISTURE FROM ODILE REMAINS IN PLACE IN THE OVERALL 500 MB RIDGE
AXIS THIS MORNING FROM SOUTHERN NEW MEXICO THROUGH CENTRAL AND
EASTERN TEXAS. THIS MOISTURE PLUME WILL LIKELY ROTATE SLOWLY AROUND
THE SOUTH CENTRAL PLAINS STATES AS THE MID LEVEL TROFFING OVER NEW
MEXICO PUSHES NORTHEAST AROUND THE TOP OF THE RIDGE AXIS. THIS MAY
EDGE A LITTLE BETTER MOISTURE VALUES BACK INTO DEEP SOUTH TX
POSSIBLE PUSHING OUR PWAT VALUES BACK UP TO >2 INCHES WHICH COULD
INCREASE OUR CONV POTENTIAL A BIT AS DAYTIME HEATING DESTABILIZES
THE ATMS A BIT MORE. MAV AND MET GUIDANCE ARE IN GOOD AGREEMENT
THROUGHOUT THE SHORT TERM TRENDS WITH THE ECWMF COMING QUITE A BIT
WETTER FOR TODAY. SINCE THE ECMWF IS THE OUTLIER MODEL WILL GO
CLOSER TO A MAV/MET POPS BLEND THROUGH SATURDAY.

FOR TEMPS WILL GO ON THE LOWER SIDE OF MAV/MET GUIDANCE AS EXPECT
MID AND HIGH LEVEL DEBRIS CLD COVER FROM CONV TO OUR NORTH TO ADVECT
DOWN SOUTH TODAY AND TOMORROW WHICH MAY HELP LIMIT THE DAYTIME
HEATING A BIT.

LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
SPOTTY RAIN CHANCES CONTINUE...NO REAL FOCUS TO INCREASE
COVERAGE/INTENSITY APPARENT FOR NOW THOUGH.

SATURDAY NIGHT INTO SUNDAY THE 300/500MB TROUGHING RETREATS WESTWARD
WITH 850-700MB HUMIDITY VALUES AROUND 70 TO 80 PERCENT. WEAK DCVA
PERSISTS...PART OF THE REMNANTS OF EAST PAC HURRICANE ODILE WITH A
WEAK ADVANCING EASTERLY WAVE AS WELL. PULLED A SLIGHT CHANCE OF GULF
COAST SHOWERS INLAND IN THE AFTERNOON SUNDAY INCREASING TO AROUND 30
PERCENT. THIS REMAINS BELOW GUIDANCE CONSENSUS BUT CONDITIONS STILL
APPEAR TO SUPPORT A FAIRLY WEAK SEABREEZE FRONT WITH RELATIVELY LOW
LAND/SEA THERMAL GRADIENT WHICH IS EXACERBATED BY CLOUD COVER FROM
HIGH COLUMN RH VALUES AND THE CONVERGENCE ASSOCIATED WITH THE
EASTERLY WAVE IS VERY WEAK.

MONDAY THE WAVE MOVES INLAND AND LEAVES BEHIND A SLIGHTLY DRIER LOW
LEVEL COLUMN...ALBEIT STILL PRETTY MOIST. THERE IS HOWEVER LESS MID
LEVEL DCVA/LIFT AND SURFACE CONVERGENCE. CONTINUED THE CWA WIDE
AFTERNOON SLIGHT CHANCE TSRA/SHRA POPS WITH A CIRCLE OF 30 PCT JUST
INSIDE OF A RAYMONDVILLE/HEBBRONVILLE/FALFURRIAS CIRCLE WHERE SEA
BREEZE ORIENTED CONVERGENCE SHOULD MAXIMIZE.

TUESDAY MID LEVEL CONVERGENCE INCREASES AS A TROUGH DIGS INTO THE
SOUTHEASTERN CONUS. THIS EXTENDS THE SOUTHWESTERN US RIDGE EASTWARD
OVER THE AREA AND SQUASHES THE BEST 850/700MB MOISTURE TO THE
SOUTHERN HALF OF THE CWA. OVERALL MOISTURE DEPTH AND RICHNESS EVEN
IN THE WETTER AREAS IS FAIRLY LOW AND JUST WENT WITH A SLIGHT CHANCE
POP OVER THE VALLEY IN THE AFTERNOON FOR ISOLATED SEABREEZE
CONVECTION WHICH GIVEN THE THERMAL/MOISTURE PROFILES IS STILL
POSSIBLE.

WEDNESDAY ANOTHER WEAK 850MB EASTERLY WAVE BEGINS TO MOVE ONSHORE
WITH A MODEST MID LEVEL SHORTWAVE PROJECTED TO ALSO MOVE OVERHEAD
FROM THE NORTHWEST IN THE 00Z GFS RUN...IT IS MUCH LESS APPARENT ON
THE ECMWF RUN. WENT WITH A CWA WIDE 20 PCT POP AND 30S FROM  HIGHWAY
77 WESTWARD AND SOUTH OF HBV/BKS 30 MAINLY IN DEFERENCE TO THE
ARRIVAL OF HIGHER LOW LEVEL MOISTURE AND THE WEAK CONVERGENCE OF THE
850MB WAVE. EASTERLY 850/700MB FLOW KEEPS MOISTURE PUMPING INTO THE
AREA KEEPING SLIGHT RAIN CHANCES IN THE FORECAST OVERNIGHT WEDNESDAY
INTO THURSDAY AND WENT WITH A MORE WIDESPREAD 30 POP ON THURSDAY
GIVEN 850/700MB RH PROJECTIONS AND WEAK CONVERGENCE FROM 850MB WAVES
THE TIMING OF WHICH WILL BE DIFFICULT AT THAT RANGE. MAINLY THE 30
POP IS IN DEFERENCE TO THE AVAILABLE MOISTURE AND THE EFFECT OF
DAYTIME HEATING ON OUR CONVECTIVE POTENTIAL. POPS EVEN THROUGH THIS
PERIOD REMAIN BELOW GUIDANCE CONSENSUS BUT FEEL COMFORTABLE WITH
THAT GIVEN THE CLIMO TENDENCY OF SEPTEMBER TO BE WET POSSIBLY
BIASING THE GUIDANCE COUPLED WITH NO PARTICULARLY STRONG EASTERLY
WAVES ON THE HORIZON. THE TENDENCY TOWARDS NORTHWESTERLY FLOW ABOVE
500MB HOWEVER WOULD BE A POSITIVE TOWARDS RAINFALL/THUNDERSTORM
PRODUCTION AND ANY REAL UPTICK IN COVERAGE/INTENSITY WILL PROBABLY
BE TIED TO MODEST SHORTWAVES THAT WORK IN AMONGST THAT FLOW...NONE
OF WHICH ARE RELIABLY APPARENT IN GLOBAL MODEL GUIDANCE THROUGH 00Z SO
WILL PLAY IT MORE CONSERVATIVE PRECIP WISE FOR NOW.

ANOTHER MID CONTINENT TROUGH/CLOSED LOW DROPS INTO THE CENTRAL
PLAINS BY FRIDAY. AT FIRST GLANCE THIS SYSTEM DOESNT APPEAR TO
GREATLY IMPACT OUR WIND OR MOISTURE FIELD BUT HISTORICALLY THESE
GENERATE AT LEAST SOME SOUTHWESTERLY 700MB FLOW WHICH WOULD DRY AND
WARM THAT LAYER AND LIMIT CONVECTIVE POTENTIAL SO NUDGED POPS LOWER
THAN THERMODYNAMIC PROFILES IN OPERATIONAL MODEL GUIDANCE AND MOS
SUGGEST. LITTLE REAL TEMPERATURE CHANGE APPEARS LIKELY DURING THE
PERIOD WITH NO FRONTS MAKING MUCH OF A CHARGE THROUGH THE NEXT 7
DAYS. /68-JGG/

MARINE...TODAY THROUGH SATURDAY...BROAD SURFACE RIDGING OVER THE
SOUTHEAST STATES AND THE GULF OF MEXICO WILL MAINTAIN FAIRLY LOW
WINDS AND SEAS ACROSS THE LOWER TX BAY AND GULF WATERS TODAY WITH A
GENERAL E-SE WIND FLOW PREVAILING. NO SCA CONDITIONS EXPECTED
THROUGH SATURDAY.

SATURDAY NIGHT THROUGH WEDNESDAY...
LIGHT TO MODERATE SOUTHEAST WINDS ARE FORECAST TO SHIFT TO THE EAST
SATURDAY NIGHT INTO SUNDAY AND PERSIST THROUGH WEDNESDAY. A MODEST
INCREASE IN WIND SPEED IS EXPECTED TUESDAY AND WEDNESDAY BUT VALUES
ARE CURRENTLY FORECAST TO REMAIN BELOW EXERCISE CAUTION LEVELS. THE
EASTERLY WINDS WILL HOWEVER BUILD A RELATIVELY LONG FETCH OVER THE
CENTRAL GULF OF MEXICO AND WAVE HEIGHTS WILL LIKELY BEGIN TO
INCREASE BY WEDNESDAY POSSIBLY APPROACHING EXERCISE CAUTION OR
ADVISORY LEVELS. LOW TO MODERATE SEAS ARE FORECAST HOWEVER SATURDAY
NIGHT THROUGH TUESDAY.

&&

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

$$

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