Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 211953
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
253 PM CDT SUN SEP 21 2014

.SHORT TERM.../NOW THROUGH MONDAY NIGHT/...AFTER TODAY RAIN A BRIEF
REPRIEVE IN THE RAIN FALL IS IN THE OFFERING FOR MONDAY AS DRIER MID
LAYER AIR MOVES INTO SOUTH TEXAS. MODELS HAVE BEEN SOMEWHAT
CONSISTENT ON INDICATING THIS DRIER AIR BUT DIFFER ON THE TIMING AND
HOW FAR SHOW IT REACHES MAKING THE FORECAST CONFIDENCE LOW
ESPECIALLY ACROSS THE RIO GRANDE VALLEY.

NOW AND TONIGHT...COASTAL TROUGH WAS ANALYZED THIS MORNING AND IS
SLOWLY WEAKENING AS IT SHOWS SIGNS OF DRIFTING SOUTH. SCATTERED
SHOWERS HAVE BEEN DEVELOPING PRETTY MUCH ACROSS THE ENTIRE CWA BUT
INTENSITY LEVELS ARE MUCH LESS THAN YESTERDAY DESPITE MORNING
SOUNDING SHOWING PWATS AROUND 2.25 INCHES. EXPECT CONVECTION TO
PERSIST THROUGH THE REMAINDER OF THE AFTERNOON TRACKING IN A SOUTH
TO SOUTHWEST DIRECTION.  THIS SHOULD PLACE THE SOUTHWEST COUNTIES
UNDER THE BEST CHANCE OF RAIN THIS EVENING WITH THE COASTAL WATERS
ALSO SEE THE CHANCE OF RAIN LINGERING WITH THE SOME WEAK RESEMBLANCE
OF THE TROUGH HANGING AROUND. AVERAGE RAINFALL AMOUNTS OF ONE
QUARTER TO ONE HALF CAN BE EXPECTED WITH ISOLATED HIGHER AMOUNTS.
WARM AND MUGGY AFTER THE RAIN WITH CLOUDS SLOWLY ERODING.


MONDAY...UPPER TROUGH OVER THE MIDWEST TO SWING THROUGH THE
TENNESSEE VALLEY BY MONDAY MORNING. SURFACE HIGH PRESSURE BUILDS
ACROSS THE WEAKENING FRONT WHICH MAKES IT TO THE NORTHWEST GULF
MONDAY EVENING. MID LEVEL DRIER AIR TO FILTER INTO THE REGION BUT IT
MAY TAKE MOST OF THE DAY FOR THE DRIER AIR TO MIX INTO THE REGION.
MODELS HAVE BEEN INCONSISTENT ON POP AMOUNTS AND PLACEMENT WITH  MET
AND MAV GUIDANCE CONTINUE TO INDICATE HIGHER RAIN CHANCES IN THE
MORNING THEN TAPERING OFF IN THE AFTERNOON AS THE DRIER AIR MAY
BE SLOWER TO MIX OUT SOME OF THE ABUNDANT SURFACE MOISTURE. TO SAY
THE LEAST THIS IS WILL BE A CHALLENGE AND HAVE KEPT SOME MENTION OF
RAIN IN THE MORNING BUT TRENDED WITH AT LEAST THE GFS MODEL ENDING
THE RAIN CHANCES IN THE AFTERNOON. NAM KEEP SOME RAIN AND MUCH
HIGHER PWATS IN THE AREA THEN DOES THE GFS. TEMPERATURES TO REBOUND
A FEW DEGREES WITH MORE SUNSHINE.

MONDAY NIGHT...THE DRY AIR MAKES ITS FARTHEST SOUTHWARD TRAJECTORY
LATE MONDAY AFTERNOON OR EARLY EVENING. BY TUESDAY MORNING THE
PSEUDO TROPICAL AIR BEGINS TO RETURN. SOME COASTAL SHOWERS MAY
DEVELOP OVERNIGHT AND MAY WORK INLAND AROUND SUNRISE. AGAIN THE NAM
IS THE MOST AGGRESSIVE WITH POPS WITH NOT MUCH OF AIR MASS CHANGE
ACROSS THE LOWER RIO GRANDE VALLEY WITH GFS HINTING AS SOME LOWER
POPS LATE MONDAY NIGHT. INHERITED FORECAST SHOWED THE LOW CHANCE
POPS AND WILL CONTINUE WITH THIS TREND. SLIGHTLY COOLER TEMPERATURES
ACROSS THE NORTHERN ZONES WITH SOME AREAS APPROACHING 70 DUE TO THE
CLEARING SKIES AND SLIGHTLY DRIER AIRMASS. LITTLE TEMP CHANGE IN THE
SOUTH WITH MID TO UPPER 70S.


.LONG TERM...TUESDAY THROUGH SUNDAY NIGHT/...
IN THE EARLY PART OF THE LONG TERM...UPPER LEVEL TROUGH ALONG THE
EAST COAST OF THE CONUS BEGINS TO INTERACT WITH RIDGE ACROSS THE
DESERT SW AND THE CENTRAL PLAINS. BROAD SURFACE HIGH PRESSURE BEHIND
THE UPPER TROF WILL KEEP AN EASTERLY FLOW ACROSS THE GULF WATERS
INTO DEEP SOUTH TX THROUGH MOST OF THE WEEK. THE LATEST GFS/NAM
MODEL RUNS SHOW AN AREA OF DRY AIR IN THE MID LEVELS MOVING TOWARDS
THE SOUTHWEST TUESDAY IN THE AFTERNOON AND TUESDAY NIGHT AS THE
FRONT/BOUNDARY GETS CLOSER. STILL SOME LINGERING MOISTURE ALONG THE
RIO GRANDE WILL POSSIBLY INITIATE A FEW ISOLATED SHOWERS ESPECIALLY
RIGHT ALONG THE RIO GRANDE. THE PRECIPITABLE WATER VALUES WERE 2.3
INCHES FOR TODAY WHICH IS STILL 2 TO 3 STANDARD DEVIATIONS ABOVE
NORMAL FOR SEPTEMBER AND BOTH MODELS KEEP PWATS VALUES FOR TUESDAY
AND WEDNESDAY IN THE 1.8 TO 2 IN RANGE WHICH WILL HELP WITH THIS
ACTIVITY TO DEVELOP TUESDAY AFTERNOON. WEDNESDAY THE SAME PATTERN
PREVAILS WITH RICH MOISTURE IN THE AREA AS THE EASTERLY FLOW REMAINS
SURGING MOISTURE INTO THE CWA. KEPT INHERITED 20 TO 30 PERCENT FOR
WEDNESDAY AFTERNOON.


THURSDAY THROUGH SATURDAY...AN MID LEVEL LOW DEVELOPS OVER THE
NORTHERN GULF COAST AND GRADUALLY MIGRATES WESTWARD INTO THE WESTERN
GULF COAST THURSDAY INTO FRIDAY WITH ABUNDANT MOISTURE. THIS WILL
ENHANCE THE POTENTIAL FOR MORE SHOWERS AND THUNDERSTORMS THURSDAY
AND FRIDAY. KEPT THE 30 TO 40 PERCENT POPS INTACT ACROSS MUCH OF THE
CWA. TEMPERATURES THROUGH THE WEEK WILL REMAIN IN THE MID TO UPPER
80S ACROSS THE AREA DUE TO THE ABUNDANCE IN CLOUD COVER LIMITING THIS
TEMPS TO REACH ABOVE 90S. NOW...BY NEXT WEEKEND...A TROPICAL WAVE
DEVELOPS OVER THE NORTHERN GULF WHICH HELPS PUSH THE DRY AIR FURTHER
SOUTH QUICKLY INTO THE CWA ESPECIALLY OVER THE WESTERN COUNTIES. LEAN
TOWARDS LESS POPS ACROSS THE WEST EARLY SATURDAY AND SUNDAY EVEN MORE
AS THE MODELS SHOW THIS TROPICAL WAVE BEEN TRANSPORTED NE INTO THE SE
PLAINS SUNDAY. WITH LESS CLOUD COVER EXPECT TEMPS TO INCREASE INTO THE
LOW TO MID 90S SATURDAY AND SUNDAY.


&&

.MARINE...NOW THROUGH MONDAY NIGHT...PRESSURE GRADIENT HAS
STRENGTHEN THIS AFTERNOON AS A LOW PRESSURE TROUGH HAS FORMED JUST
OFF THE LOWER TEXAS COAST. MONDAY AND MONDAY NIGHT EXPECT THIS
GRADIENT TO STRENGTHEN ANOTHER NOTCH AS HIGH PRESSURE BUILDS INTO
THE NORTHERN GULF AND COMBINES WITH THE SOUTHWARD MOVING TROUGH.
WINDS TO RANGE IN THE EXERCISE CAUTION VALUES WITH SEAS TO BUILD
WITH A PERSISTENT EAST FLOW DEVELOPING OVER THE NORTHERN GULF.
MARGINAL SMALL CRAFT ADVISORY CONDITIONS FOR BOTH WINDS AND SEAS ARE
ANTICIPATED MONDAY.

TUESDAY THROUGH SUNDAY NIGHT...BROAD HIGH PRESSURE OVER THE NORTHERN
GULF WILL KEEP A LIGHT TO MODERATE EASTERLY FLOW ONSHORE THROUGH
THE LONG TERM FORECAST. THE WINDS WILL REMAIN LIGHT KEEPING SEAS
AROUND 2 TO 4 FEET OR LESS. NO SMALL CRAFT ADVISORY EXPECTED AT
THIS TIME. THE MAIN IMPACT WILL BE THE SHOWER ACTIVITY WHICH WILL
CONTINUE THROUGH THE PERIOD AS THERE IS ABUNDANT MOISTURE IN THE
AREA. THIS ACTIVITY WILL PRODUCE VERY HEAVY DOWNPOURS AND
OCCASIONAL LIGHTNING. EXPECT A SLIGHTLY NE FLOW EARLY TUESDAY AS
DRY AIR FILTERS INTO THE AREA DIMINISHING THE CHANCE OF RAIN
ACROSS THE CWA FOR A DAY. RAIN RETURNS EARLY WEDNESDAY AS THE
MOISTURE REMAINS CONCENTRATED OVER DEEP SOUTH TEXAS.


&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  79  90  78  89 /  20  20  20  20
BROWNSVILLE          77  91  76  91 /  20  20  20  20
HARLINGEN            77  92  75  92 /  20  20  20  20
MCALLEN              77  92  74  92 /  20  20  20  20
RIO GRANDE CITY      76  93  74  92 /  20  10  10  20
SOUTH PADRE ISLAND   80  88  79  88 /  20  20  20  20

&&

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

$$

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