Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 280002 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
702 PM CDT MON APR 27 2015

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

&&

.AVIATION...NORTHWEST WINDS TO SLACKEN OFF OVERNIGHT NEARING CALM
CONDITIONS PRIOR TO A REINFORCING SURGE OF HIGH PRESSURE EXPECTED
AROUND SUNRISE TUESDAY. THE LIGHTER WIND AND A VERY SHALLOW
MOISTURE LAYER MAY ALLOW FOR BRIEF PATCHY IFR TO MVFR FOG TO
DEVELOP WITH BETTER CHANCES AT KBRO AND KHRL. TIMES OF THE LOWEST
PROBABLE VISIBILITIES BETWEEN 09-13Z. OTHERWISE, ONLY A STREAM OF
HIGHER CLOUDS EXPECTED OVER DEEP SOUTH TEXAS TONIGHT AND TUESDAY.
NORTHWEST TO NORTH WINDS INCREASE TUESDAY WITH HIGH PRESSURE BUILD
INTO THE REGION. SUSTAINED WINDS OF 15 TO 20 KNOTS AND GUSTS UP TO
30 KNOTS ARE ANTICIPATED.

&&

.PREV DISCUSSION... /ISSUED 340 PM CDT MON APR 27 2015/

SHORT TERM /NOW THROUGH TUESDAY NIGHT/...LATEST VAPOR IMAGERY SHOWS
AN UPPER LEVEL LOW OVER THE TEXAS PANHANDLE. THE WEAK COLD FRONT
THAT MOVED THROUGH DEEP SOUTH TEXAS THIS MORNING HAS PUSHED WELL
EAST OF THE LOWER TEXAS GULF WATERS THIS AFTERNOON. MUCH DRIER AIR
CONTINUES TO FILTER INTO THE REGION THIS AFTERNOON WITH DEWPOINTS
FALLING INTO THE LOWER 50S AT ZAPATA AND HEBBRONVILLE. EXCEPT FOR
STREAMING HIGH LEVEL CLOUDS OVERHEAD COURTESY OF SOUTHWEST FLOW
ALOFT...THE DRIER AIRMASS HAS ERODED AWAY MOST OF THE LOW CLOUDS.
THE GUSTY NORTH WINDS HAS PUSHED THE PERSISTENT HAZE OVER THE REGION
THE PAST FEW DAYS TO SOUTH INTO THE GULF OF MEXICO AND GIVE THE AREA
A BREAK OF THE AGRICULTURAL BURNING SMOKE. TEMPERATURES WILL REMAIN
IN THE UPPER 80S TO AROUND 90 FOR THE REST OF THE AFTERNOON.

THE 500MB LOW WILL MOVE EASTWARD OVER NORTHERN TEXAS TONIGHT...THE
ARKLAMISS REGION TUESDAY AND OVER THE TENNESSEE RIVER VALLEY TUESDAY
NIGHT. THE PRESSURE GRADIENT WILL RELAX TONIGHT RESULTING IN LIGHT
WINDS OVERNIGHT. SOME HAZE MAY DRIFT BACK ACROSS THE COASTAL AREAS
LATER TONIGHT DUE TO THE LIGHT WINDS. OTHERWISE...MOSTLY CLEAR SKIES
WILL ALLOW FOR TEMPERATURES TO FALL INTO THE LOW TO MID 60S.

A SURGE OF HIGH PRESSURE/ANOTHER COLD FRONT WILL APPROACH DEEP SOUTH
TEXAS LATE TONIGHT/NEAR SUNRISE TUESDAY. BREEZY NORTH WINDS WILL
PREVAIL ACROSS DEEP SOUTH TEXAS THROUGH THE DAY ON TUESDAY. HIGH
TEMPERATURES WILL BE BELOW NORMAL TUESDAY WITH HIGH TEMPERATURES
RANGING FROM THE UPPER 70S TO AROUND 80. OVERNIGHT LOW TEMPERATURES
WILL FALL INTO THE 50S...EXCEPT AROUND 60 NEAR THE COAST...TUESDAY
NIGHT. DRY CONDITIONS WILL PREVAIL ACROSS THE REGION FOR THE NEXT
36 HOURS.

LONG TERM /WEDNESDAY THROUGH MONDAY/...DRY AND STABLE 500 MB
RIDGING WILL FOLLOW ON THE HEELS OF THE CLOSED LOW THAT WILL BE
MOVING OVER THE SOUTH CENTRAL PLAINS STATES EARLY THIS WEEK. THE
RIDGE AXIS WILL THEN SHIFT STEADILY EASTWARDS THROUGH THE LATTER
HALF OF THIS WEEK. THIS WILL ALLOW FOR THE NORTHERLY SURFACE WINDS
TO LINGER INTO WED AND WED NIGHT. AS THE 500 MB RIDGE AND THE
ASSOCIATED SURFACE RIDGE MOVES FURTHER EAST EXPECT THE SURFACE
FLOW TO SHIFT BACK FROM THE SOUTHEAST DURING THE LATTER HALF OF
THE WEEK WHICH WILL ALLOW FOR THE SURFACE WAA TO INCREASE AND FOR
THE DEWPOINTS TO REBOUND LATE IN THE FORECAST PERIOD. DESPITE THE
INCREASE IN THE LOW LEVEL DEWPOINTS LATE THIS WEEK DEEP LAYER
MOISTURE WILL REMAIN PRETTY LIMITED OVER THE REGION. THIS IN
COMBINATION WITH THE SUBSIDENT FLOW GENERATED BY THE 500 MB RIDGE
AXIS WILL KEEP THE CONV CHCS PRETTY LOW THROUGH DAY 7. HOWEVER
LONGER TERM GUIDANCE BRINGS ANOTHER STRONG 500 MB TROUGH ACROSS
CENTRAL AND NORTHERN TEXAS EARLY NEXT WEEK POSSIBLY BRING POPS
BACK INTO THE PICTURE.

THE ECMWF AND GFS MEX MOS GUIDANCE ARE IN PRETTY CLOSE AGREEMENT
FOR MAX/MIN TEMPS THROUGH NEXT MON. BOTH MODEL SETS KEEP POPS IN
THE SINGLE DIGITS ALSO THROUGH DAY 7. RUN TO RUN CONSISTENCY WITH
THE GFS MEX MOS GUIDANCE IS PRETTY STEADY ALSO. SO WILL OPT FOR A
GENERAL MODEL BLEND THROUGH DAY 7 FOR TEMPS. OVERALL FORECAST
CONFIDENCE IS WELL ABOVE AVERAGE AT THIS TIME.

MARINE...NOW THROUGH TUESDAY NIGHT...MODERATE NORTHWEST WINDS
PREVAIL ALONG THE LOWER TEXAS COASTAL THIS AFTERNOON. BUOY 42020
CURRENTLY REPORTING NORTHWEST WINDS AROUND 17 KNOTS WITH GUSTS OF
21 KNOTS AND SEAS OF 2.6 FEET. EXERCISE CAUTION CONDITIONS
EXPECTED OVER THE GULF WATERS FOR THE NEXT SEVERAL HOURS DUE TO
THE ELEVATED WINDS. THE PRESSURE GRADIENT RELAXES TONIGHT BEFORE A
SURGE OF THE HIGH PRESSURE ARRIVES LATE TONIGHT/TUESDAY MORNING.
THIS WILL RESULT IN INCREASING WINDS AND SEAS TUESDAY AND TUESDAY
NIGHT. SMALL CRAFT ADVISORY CONDITIONS LIKELY ON ALL THE LOWER
TEXAS COASTAL WATERS TUESDAY DUE TO STRONG WINDS AND BUILDING
SEAS.

WEDNESDAY THROUGH SATURDAY...THE NORTHERLY POST FRONTAL GRADIENT
WILL START TO WEAKEN ON WEDNESDAY AND THURSDAY AS THE SURFACE
RIDGING STARTS SHIFTING FURTHER EAST. THE SOUTHEAST FLOW WILL
RETURN TOWARDS THE END OF THE WEEK BUT WILL REMAIN FAIRLY WEAK.
SOME MARGINAL SCA CONDITIONS MAY PERSIST INTO WED ACROSS THE GULF
WATERS DUE TO THE LINGER NORTHERLY SURFACE WINDS. WITH THE RETURN
OF THE SOUTHEASTERLY LOW LEVEL FLOW FAIRLY LOW SEAS SHOULD PREVAIL
THROUGH THE LATTER HALF THE WEEK KEEPING CONDITIONS BELOW SCA
LEVELS FOR THE BULK OF THE EXTENDED RANGE CWF PERIOD.

HYDROLOGY...RUN OFF FROM RECENT HEAVY RAINS OVER NORTHEAST MEXICO
IS PUSHING UP THE RIVER LEVELS OF THE LOWER PORTIONS OF THE RIO
GRANDE AT THE SAN BENITO GAGE. NO RIVER FLOODING IS EXPECTED AT
THIS TIME. A CREST OF 51.4 FEET IS EXPECTED AT THE SAN BENITO
RIVER GAGE AROUND 1 AM FRIDAY MORNING. FLOOD STAGE AT THE SAN
BENITO GAGE IS 55.0 FEET.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY FOR WINDS FROM 7 AM TO 8 PM CDT TUESDAY FOR
     GMZ130-132-135.

     SMALL CRAFT ADVISORY FROM 7 AM TUESDAY TO 7 AM CDT WEDNESDAY FOR
     GMZ150-155-170-175.

&&

$$

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