Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 190853

Area Forecast Discussion
National Weather Service Brownsville TX
353 AM CDT Wed Apr 19 2017

.SHORT TERM (Now through Thursday): So good. The pesky
500 mb trough that developed over central and south Texas Sunday
night through early Tuesday apparently got a nice convective
"push" into the western Gulf early Tuesday morning, and drier flow
aloft from the north made for a pleasant afternoon and especially
evening across the entire region later Tuesday. Clear skies and
nearly calm winds have allowed temperatures to dip into the 60s in
most areas as of 3 AM and lower to mid 60s will probably be the
rule by daybreak with just some passing cumulus. Have added patchy
fog for most areas for the 4 AM to 9 AM window with light winds,
100 percent humidity, and better soil moisture over the past few
days particularly across the Upper Valley and ranchlands where
several inches of rain fell since Sunday.

Today`s (Wednesday`s) forecast is still a tad tricky, though. In the
big picture, the deepest moisture remains along the east side of the
shearing trough, and with 500 mb ridge oozing in from the west there
is no chance for organized convection.  On the smaller scale,
however, a pocket of moisture up to 700 mb or so slides southwest
along the shear axis and reaches the Lower and perhaps Mid Valley
this afternoon. Combined that with light winds and a sea breeze
pickup by early afternoon and would not be surprised to see isolated
showers and perhaps afternoon thunderstorms, initially near the
coast but clearing the beaches and favoring areas mainly between US
281 and 77. Not enough to stop an outdoor event and most areas
should see nothing, but something still worth a small mention.  More
sunshine and a cleaner air mass should easily allow temperatures to
reach the upper 80s to lower 90s area-wide, still a few ticks above
the mid April average.

Any mid to late afternoon action will end quickly this evening, with
mainly clear skies and light winds returning. Could end up being a
carbon copy of early this morning, so lowered temperatures a hair
though not as `cool` as we`ll be by daybreak today, and kept the
patchy fog mention mainly north of the Valley.

On Thursday, as the upper ridge builds in, so will a few more
notches on the afternoon temperature as low level southerly flow
begins to pick up and atmosphere overall begins to warm.  Capped at
90 to 94 in most areas (hottest along the Rio Grande in Starr
County). Plenty of sunshine though nothing more than fair weather
cumulus, lifting fairly high (7K feet) by afternoon. Got beach
plans? This is your day.

.LONG TERM (Thursday Night through Tuesday): 500mb ridge across
northern Mexico and southwest Texas Thursday into Friday will
provide subsidence across south TX through the rest of the week
before a 500mb low/trough across the central United States Friday
moves eastward Saturday bringing a weak cold front through the CWA
late Sat afternoon into early Sat evening. Moisture is progged to
pool along and ahead of the front and this will provide a slight
chance to chance of showers and thunderstorms across deep south
TX Saturday into Sat night. Surface high pressure will build into
south TX Sunday in the wake of the front bringing drier and
slightly cooler air across the CWA. Above normal temperatures
Friday and Saturday will fall below Sunday before returning to
near normal Monday. Above normal temperatures...especially across
the western portions of the CWA...will return through the rest of
the forecast period with surface high pressure across the TX coast
Monday moving eastward and low pressure developing across the TX
panhandle. A weak 500mb trough is progged to develop across
northern Mexico Tuesday but rain chances are not expected until
possibly Wednesday across the western portions of the CWA.

.MARINE (Now through Thursday): While Monday and Tuesday morning
were touch and go (and not good at all early Tuesday) for
boating/fishing trips into the Gulf, much better conditions are
likely within 60 nm of the coast to close out the week. Still will
need to watch for isolated storm development from mid morning to
early afternoon in all waters, then just the outer waters during
the afternoon which is still closest to the shear axis. Fair
weather arrives everywhere this evening and Thursday looks like
the best day of the week.

That`s because light flow and reduced swell have briefly improved
seas to slight to locally moderate (around 3 feet) which will
continue through the period.  Winds will hang near 10 knots today in
all areas - perhaps a little pickup over Laguna Madre this
afternoon. A slight increase on Thursday as gradient begins to pick
up, but mainly over Laguna Madre and still no more than 15 knots
during the afternoon.

Thursday night through Sunday...Moderate southeast winds will
prevail across the coastal waters Thurs night with low pressure
across west Texas and high pressure across the northeast Gulf of
Mexico. Winds will veer to the south Friday with low pressure
across the TX panhandle. The pressure gradient will increase
across the lower TX coast Fri night before a weak cold front
moves into central TX. Moderate to strong southeast winds Fri
night will diminish Saturday before the front moves through the
coastal waters late Sat afternoon. Winds will shift to the north
and increase in the wake of the front Sat night. Strong north
winds should prevail across the western Gulf of Mexico Sat night
into Sunday. Small craft advisories will be needed for the
offshore waters Fri night...for all of the coastal waters Sat
night and for the offshore waters Sunday.

BAYVIEW/PORT ISABEL  85  70  85  73 /  20   0   0  10
BROWNSVILLE          86  70  88  72 /  20  10   0  10
HARLINGEN            87  68  90  71 /  20   0   0  10
MCALLEN              90  69  92  72 /  20  10   0  10
RIO GRANDE CITY      90  68  93  71 /  10   0   0  10
SOUTH PADRE ISLAND   81  74  80  74 /  20  10   0  10



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