Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 150035
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
735 PM CDT SUN SEP 14 2014

.DISCUSSION...WINDS AND SEAS CONTINUE TO LOWER AT THIS TIME.
THEREFORE...THE SMALL CRAFT ADVISORY IS NO LONGER IN EFFECT.
THE SHOWER ACTIVITY ALONG THE LOWER AND MIDDLE VALLEY IS
SLOWLY DIMINISHING AS IT MOVES SOUTHWEST. NO OTHER CHANGES
WERE MADE TO THE FORECAST.

&&

.PREV DISCUSSION... /ISSUED 645 PM CDT SUN SEP 14 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...MODERATE TO HEAVY RAIN WILL IMPACT THE MFE TERMINAL
FOR THE NEXT HALF HOUR WITH LOW CIGS. ANOTHER AREA OF SHOWERS NEAR
THE COAST IS MOVING CLOSER TO HRL BUT WILL MOVE SOUTH OF THE
TERMINAL. THIS ACTIVITY WILL DIMINISH BY THIS EVENING WITH LIGHT
AND VARIABLE NORTH TO NORTHEAST WINDS. CIGS WILL BEGIN TO LOWER
AROUND MIDNIGHT TO MVFR CONDITIONS AND POSSIBLE IFR TOWARDS THE
WESTERN COUNTIES OF SOUTH TEXAS. VFR CONDITIONS WILL RETURN EARLY
MONDAY WITH NORTHEAST WIND PREVAILING MONDAY. ISOLATED SHOWERS
WILL BE POSSIBLE IN THE AFTEROON HOURS.

PREV DISCUSSION... /ISSUED 346 PM CDT SUN SEP 14 2014/

SHORT TERM /NOW THROUGH MONDAY NIGHT/...SOMEWHAT TURBULENT UPPER
LEVEL PATTERN IS APPARENT ON WATER VAPOR THIS AFTERNOON. UPPER
RIDGING CENTERED OVER THE NORTH CENTRAL GULF COAST IS WORKING WITH
AN UPPER LEVEL CLOSED LOW OVER THE YUCATAN TO PROMOTE NORTHEAST
FLOW OVER THE REGION BUT THAT IS BATTLING WITH INCREASING
SOUTHWESTERLY FLOW...OUTFLOW FROM MAJOR HURRICANE ODILE OFF THE
BAJA CALIFORNIA PENINSULA TO CREATE AN INTERESTING LOOKING SHEAR
ZONE OVER THE CWA. THIS APPEARS TO BE AT LEAST PARTIALLY
RESPONSIBLE FOR SLOWING THE ADVANCE OF THESE NORTHEASTERLY WINDS
INTO THE CWA THROUGH THIS AFTERNOON WHICH HAS KEPT THE MIDDLE
VALLEY SOCKED IN WITH LOW CLOUDS ALMOST ALL DAY AND KEPT MAX
TEMPERATURES INTO THE MID 80S. THE NORTHEASTERLY WINDS MARK AN
INCREASE IN MOISTURE AND COUPLED WITH THE SUNSHINE THE COASTAL
COUNTIES RECEIVED EARLIER IN THE DAY SEVERAL CLUSTERS OF SHOWERS
AND STORMS ARE BUBBLING UP.

TONIGHT...WITH NO REAL SYNOPTIC FORCING OR LARGE MESOSCALE
BOUNDARIES THE LOSS OF DAYTIME HEATING SHOULD REDUCE THE SHOWER AND
THUNDERSTORM COVERAGE THROUGH THE EVENING. THE FIRST SHOT OF
MOISTURE ASSOCIATED WITH AN ADVANCING TROPICAL WAVE FROM THE GULF OF
MEXICO BEGINS TO ARRIVE EARLY MONDAY MORNING HOWEVER AND KEPT THE
RAIN CHANCES NUDGED UPWARDS AFTER MIDNIGHT ALONG THE IMMEDIATE COAST
UNDER MOSTLY CLOUDY SKIES.

MONDAY...WESTERN HALF OF THE TROPICAL WAVE WILL BE OVER THE REGION
MONDAY WITH THE APEX PROGGED TO BE CROSSING THE COASTLINE MONDAY
EVENING. ABUNDANT MOISTURE AND MODEST SURFACE CONVERGENCE SHOULD
RESULT IN HIGHER COVERAGE OF SHOWERS AND STORMS THAN WE SAW ON
SUNDAY. COVERAGE SHOULD BE HIGHER ALONG THE COAST AND KEPT THE
FORECAST ESSENTIALLY INTACT BLENDING 50 PCT/SCATTERED SHOWERS AND
STORMS IN THE COASTAL COUNTIES TO 30 PCT SCTD SHOWERS AND STORMS
OVER ZAPATA COUNTY IN THE AFTERNOON. DID NUDGE THE 50 PERCENT LINE
INLAND A LITTLE FURTHER BASED ON A LITTLE DEEPER AND RICHER MOISTURE
THAN WAS SHOWN ON PREVIOUS RUNS. WE ARE A LITTLE ABOVE GUIDANCE
WHICH IS TRENDING UPWARD. WITH RICH COLUMN MOISTURE...PWAT VALUES
AROUND 2.2 INCHES ANY SHOWERS/STORMS WILL HAVE EXTREMELY HIGH
RAINFALL RATES. NOT EXPECTING WIDESPREAD CLOUD COVER LIKE TODAY
WHICH SHOULD ALLOW MAX TEMPS TO REBOUND CLOSER TO 90 DEGREES.

MONDAY NIGHT...THE BACKSIDE OF THE TROPICAL WAVE BEGINS TO CROSS THE
COAST LINE LEADING TO ANOTHER SLIGHT INCREASE IN MOISTURE. EXPECT
THE MOISTURE INCREASE WILL BALANCE OUT THE LOSS OF DAYTIME HEATING
AND KEPT DECENT RAIN CHANCES...ABOUT 30 TO 50 PERCENT...IN THE
FORECAST DURING THE OVERNIGHT PERIOD WITH MORE SHOWERS THAN
THUNDERSTORMS LIKELY GIVEN EXTREMELY WARM COLUMN TEMPERATURES AND
MODEST INSTABILITY.

LONG TERM /TUESDAY THROUGH SUNDAY/...F THERE`S A `NORMAL` MID SEPTEMBER PATTERN FOR THE RIO GRANDE
VALLEY..THIS WEEK AND PROBABLY INTO THE WEEKEND IS IT. DAILY AVERAGE
RAINFALL PEAKS THIS WEEK...GENERALLY AT 0.18 TO 0.22 INCHES PER DAY
FOR THE 30 YEAR CYCLE /1981-2010/ FOR MOST LOCATIONS IN THE REGION
AND THIS MAY WELL WORK OUT ON THE WHOLE FOR THE NEXT SEVEN
DAYS...HENCE THE 7 DAY ACCUMULATED RAINFALL OUTLOOK OF 1 TO 2+
INCHES FOR THE REGION.

FOR THE PERIOD AS A WHOLE...WILL MAINTAIN THE ELEVATED RAIN CHANCES
AND CONTINUE TO LEAN TIMING TOWARD LATE NIGHT/EARLY MORNING NEAR THE
COAST AND MID MORNING THROUGH EARLY EVENING INLAND...WITH SOME
NUANCE THROUGH MID WEEK.  FOR NEXT WEEKEND...WILL BECOME A BIT MORE
PESSIMISTIC EARLY AS THERE`S LITTLE TO BUDGE THE DEEP MOISTURE OUT
OF THE REGION AND MAY HOLD ONTO THE LOWEST CHANCES FOR SUNDAY FOR
NOW...BUT EVEN THAT MAY BE A BIT MORE WISHFUL THINKING THAN REALITY.
AT THIS POINT...UNTIL THE FIRST `REAL` AUTUMN COLD FRONT SWEEPS
THROUGH...MOST DAYS WILL HAVE SOME SHOWER/STORM ACTIVITY SOMEWHERE.

FOR THE SENSIBLE WEATHER...NO CHANGES TO TUESDAY`S FORECAST FOR
NOW...THOUGH WOULD BE QUITE PLAUSIBLE TO SEE HIGHER RAIN CHANCES AND
AN UPWARD NUDGE OF PRECIP ACCUMULATION WITH SURFACE LOW EDGING BY
PRECEDED BY WEAKENING UPPER LEVEL DISTURBANCE MOVING UNDER THE
PANCAKE 500 MB RIDGE. FOR WEDNESDAY...THE GFS HINTS AT A SLIGHTLY
DRIER POCKET IN THE 800-500 MB LAYER WITH THE ECMWF HANGING ON TO
DEEPER MOISTURE BEHIND THE FIZZLING WAVE. RATHER THAN GET
CUTE...WILL ALSO HANG ONTO THE MID RANGE CHANCE FOR NOW.

AS FOR THE TAIL END OF THE WORKWEEK...BROAD AND FAIRLY DEEP (FOR MID
SEPTEMBER) EASTERN U.S. 500 MB TROUGH NUDGES A BIT FARTHER SOUTH AND
WEST AND HELPS TO THICKEN MOISTURE ALONG SHEAR AXIS THAT
DEVELOPS/EDGES ALONG A NORTHWEST-SOUTHEAST LINE FROM WEST TEXAS TO
THE MID TEXAS GULF COAST THURSDAY AND FRIDAY. THAT MOISTURE OOZES
INTO SOUTH TEXAS THURSDAY AND COVERS ALL OF THE RGV/DEEP SOUTH TEXAS
ON FRIDAY WITH ENHANCED LIFT AROUND 700 WHERE WINDS CHANGE DIRECTION
FROM THE LOW LEVEL SOUTHEASTERLIES TO THE NORTHWEST ON THE BACKSIDE
OF THE TROUGH. REGARDING THE BACKSIDE NORTHWEST FLOW...TYPICALLY
DRY BUT NOT THIS TIME AS WE`LL BE INJECTING THE REMNANTS OF
EASTERN PACIFIC HURRICANE ODILE INTO THE MIX WHICH SHOULD ALSO
HELP SEED THE UPPER LEVELS THOUGH THICK CIRRUS COULD AFFECT
HEATING JUST A BIT.

THIS TYPE OF PATTERN CAN FAVOR DECENT UPSLOPE RAINS ACROSS NORTHERN
MEXICO WHICH WOULD AT LEAST BE A FEW DROPS IN THE BUCKET ACROSS
FALCON AND PERHAPS AMISTAD RESERVOIR. IT MAY ALSO PUSH HIGHER
CHANCES TO THE RIO GRANDE PLAINS...BUT FOR NOW WILL PAINT WITH A
BROAD BRUSH AND INCREASE CHANCES TO 40/50 THURSDAY AND FRIDAY WITH
CONTINUED DIURNAL VARIATION...THOUGH NOT QUITE SO BLACK AND WHITE
WITH SO MUCH MOISTURE AROUND.

AS FOR SATURDAY...AS SHEAR AXIS FADES AWAY DRY AIR SHOULD BEGIN TO
SLIDE INTO THE ATMOSPHERE ABOVE 500 MB...BUT WITH PLENTY OF LOW
LEVEL MOISTURE AROUND PREFER TO KEEP MORE MENTIONABLE PRECIPITATION
AND WILL RAISE CHANCES HERE AS WELL...FAVORING MORE AFTERNOON
ACTIVITY INLAND AND LESS TOWARD/OVER THE COAST. SUNDAY COULD BE
DRIER STILL...BUT STILL A BIT CONCERNED ABOUT RESIDUAL LOW LEVEL
MOISTURE ENOUGH TO KICK OFF ISOLATED ACTIVITY TOWARD THE COAST. FOR
NOW...WILL RAISE CHANCES FROM 10 TO 20 PERCENT EAST/CENTRAL BUT
THAT`S ABOUT ALL.

MARINE...
NOW THROUGH MONDAY NIGHT...
A SMALL CRAFT ADVISORY REMAINS IN EFFECT THROUGH THIS EVENING FOR
RESIDUAL ROUGH SEAS. AN IMPROVEMENT IN CONDITIONS IS FORECAST
TONIGHT BUT NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
DEVELOP LATE TONIGHT INTO MONDAY AS ANOTHER TROPICAL WAVE APPROACHES
FROM THE EAST. PREVAILING WINDS AND SEAS SHOULD REMAIN MODERATE
THROUGH MONDAY NIGHT.

TUESDAY THROUGH FRIDAY: OUTSIDE OF SCATTERED TO LOCALLY NUMEROUS
THUNDERSTORMS...ESPECIALLY DURING THE DIURNALLY FAVORED TIMES FROM
MID EVENING TO MID MORNING...LIGHT WINDS AND SLIGHT SEAS WILL BE THE
RULE.

BY SATURDAY...WINDS AND ESPECIALLY SEAS MAY BEGIN TO PICK UP
AS FAIRLY STRONG SEPTEMBER SURFACE HIGH ALONG THE EAST COAST
BROADENS ITS SOUTHERN PERIPHERY WHICH SHOULD HELP SWELLS ALONG. AT
MOST COULD SEE CAUTION CONDITIONS FOR 6 FOOT SWELLS AND PERHAPS A
PERIOD OF 15-20 KNOT WIND.

CLIMATE...AS MENTIONED IN MORNING WEB BRIEFING AND PUBLIC
INFORMATION STATEMENT...THE 3 TO 5 INCHES OF VALLEY WIDE RAINFALL
FROM FRIDAY THROUGH EARLY THIS MORNING PUSHED MONTHLY TOTALS INTO
THE 5 TO NEARLY 9 INCH RANGE...OR A FEW TICKS ABOVE NORMAL /4 TO 6
INCHES/ WITH MORE THAN HALF THE MONTH TO GO.  BY THE END OF THIS
WEEK...SOME AREAS WILL LIKELY BE AT OR OVER 10 INCHES FOR THE
MONTH...WHICH WILL PUT SEPTEMBER 2014 ON PACE TO BE WETTER THAN
SEPTEMBER 2013 AND PERHAPS START TO CHALLENGE SEPTEMBER
2010...THOUGH THERE`S A LONG WAY TO GET TO SOME OF THOSE NUMBERS.

&&

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

$$

THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT:
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