Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 271125 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
625 AM CDT THU AUG 27 2015

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

&&

.AVIATION...VFR CONDITIONS EXPECTED THROUGH THE NEXT 24 HOURS AS
DRY AIR CONTINUES TO MOVE INTO THE REGION. EAST WINDS WILL RISE TO
10 TO 12KTS LATE THIS MORNING AND CONTINUE THROUGH SUNSET...BEFORE
FALLING TO LIGHT FROM THE SOUTHEAST.

&&

.PREV DISCUSSION... /ISSUED 403 AM CDT THU AUG 27 2015/

SHORT TERM /NOW THROUGH FRIDAY/...SIGNIFICANT ATMOSPHERIC REGIME
CHANGE HAS ARRIVED...AS ESTIMATED PW VALUES FROM GOES IMAGERY
CURRENTLY AROUND 1.2 INCHES...WITH VALUES UNDER 1 INCH JUST TO THE
NE. DRY AIR WILL MIX DOWN TO THE SFC DURING THE AFTERNOON TODAY
AND AGAIN TOMORROW...WHICH WILL HOLD HEAT INDEX VALUES BELOW 105
TODAY AND ONLY AROUND 100 AT PEAK HEATING ON FRIDAY.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...THE ATMOSPHERE AT
THE BEGINNING OF THE LONG TERM STARTS OUT EXCEPTIONALLY DRY THEN
SLOWLY MOISTENS UP AT THE LATTER END OF THE PERIOD. DEEP SOUTH
TEXAS WILL BE SITUATED BETWEEN MID/UPPER LEVEL HIGH PRESSURE TO
OUR WEST AND A MID LEVEL TROUGH JUST TO OUR EAST. THIS WILL
MAINTAIN A NORTH TO NORTHWEST /DRY/ FLOW BETWEEN 800 TO 250MB MUCH
OF THE PERIOD. GFS FORECAST PRECIPITABLE WATER VALUES START OFF
70-90 PERCENT BELOW NORMAL AND ONLY REACH NORMAL VALUES OF AROUND
1.75 INCHES NEXT WEDNESDAY. SURFACE FLOW TO REMAIN SOUTHEAST BUT
DRY AIR ALOFT TO MIX OUT THE SHALLOW LAYER OF MOSITURE AIR AT THE
SURFACE UNTIL THE DEPTH OF THE MOISTURE INCREASES BEGINNING
MONDAY.

MODELS DIFFERENCES ARE SLIGHT BUT COULD BE SIGNIFICANT DEPENDING
ON THE PLACEMENT OF THE MID LEVEL TROUGH OVER THE DEEP SOUTH AND
THE WESTERN GULF. THE ECMWF IS THE FARTHEST WEST WITH THE TROUGH
AXIS WITH GFS FARTHER EAST ON THE 00Z RUN THEN WHAT WAS PROGGED
YESTERDAY. THE UPPER RIDGE OVER THE DESERT SOUTHWEST TO REMAIN
ANCHORED WITH A RIDGE TO SET UP SHOP OVER THE MIDWEST AND
NORTHEAST WHICH SHOULD SLOWLY ALLOW THE TROUGH IN THE SOUTH TO
DRIFT EVER SO SLOWLY WESTWARD. BOTH EC AND GFS MODEL POP GUIDANCE
IS LOWER TODAY THAN YESTERDAY WHICH WOULD FAVOR TO LOWER POPS
ACROSS THE BOARD AT LEAST THROUGH TUESDAY WHEN ALL MOISTURE FIELDS
INDICATE LIMITED MOISTURE. NOT UNTIL WEDNESDAY DO MODELS FAVOR
SUFFICIENT MOISTURE DEPTH AND THE CLOSER PROXIMITY OF THE TROUGH
TO FAVOR A BETTER CHANCE OF RAIN. THE LATEST FORECAST HAS TRENDED
LOWER WITH POPS USING A MODEL BLEND BUT FAVORING A HIGHER
PERCENTAGE OF THE DRIER GFS. TEMPERATURES SHOW LITTLE CHANGE WITH
THE DRY ATMOSPHERE WITH A LARGER DIURNAL RANGE THEN NORMAL BUT
BECOMING NARROW WITH TIME AS THE DEW POINTS RISE AS WE MOVE INTO
NEXT WEEK. DAYTIME HIGHS REMAIN NEAR NORMAL WITH OVERNIGHT LOWS
STARTING OFF BELOW NORMAL AND RISING NEAR NORMAL AT THE END OF THE
FORECAST PERIOD.

MARINE...NOW THROUGH FRIDAY...WEAK RIDGING CONTINUES TO PROVIDE
TRANQUIL CONDITIONS ACROSS THE LOCAL MARINE LOCATIONS. SEAS WILL
REMAIN 2 FEET OR LESS THROUGH THE NEXT 36 HOURS...WHILE ONSHORE FLOW
CONTINUES AROUND 10 KNOTS.

FRIDAY NIGHT THROUGH MONDAY...WEAK SURFACE HIGH PRESSURE TO REMAIN
ANCHORED OVER THE NORTHEAST GULF WITH WEAK LOW PRESSURE SURFACE
TROUGHING ACROSS THE SOUTHWEST GULF AND THE BAY OF CAMPECHE. THIS
WILL MAINTAIN A LIGHT TO LOW END MODERATE SOUTHEAST FLOW AND
SLIGHT SEA THROUGH THE WEEKEND. AN ISOLATED SHOWER OR
THUNDERSTORM MIGHT SHOW UP IN THE FAR OFFSHORE WATERS SUNDAY WITH
A SLIGHT INCREASE MONDAY.

&&

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

$$

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