Area Forecast Discussion
Issued by NWS Brownsville, TX

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853
FXUS64 KBRO 250559
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1259 AM CDT Sat Mar 25 2017

.DISCUSSION...Updated for latest aviation discussion below.

&&

.AVIATION...Current METARs and GOES-16 fog difference product show
patches of MVFR CIG`s drifting up from the south and over the RGV
terminals at times. SREF probabilities indicate more cloud
coverage inland, so will lean that way in the TAF`s (with
prevailing MVFR at MFE at least for the next few hours).
Discounting the more pessimistic GFS MOS for now, which hints at
some IFR conditions around sunrise, but will continue to monitor.
VFR should take hold from mid-morning onward with light to
moderate winds and perhaps a few high clouds. Winds may shift to W
or SW at MFE for a few hours around mid-day as a surface trough
passes, but confidence not too high on this yet and duration
should be fairly short, at any rate.

&&

.PREV DISCUSSION... /issued 656 PM CDT Fri Mar 24 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Gusty south to southeast winds will continue over the
next couple of hours before decoupling shortly after sunset. The
strong gradient is expected to lessen overnight as the storm
system across Oklahoma moves east towards the Ohio River Valley.
Meanwhile, weak surface troughing will set up over the region on
Saturday with winds much lighter by comparison. Low level moisture
is lower given the dry air that has moved into the region, and
although low clouds could form, VFR conditions should prevail
through the period.

PREV DISCUSSION... /issued 253 PM CDT Fri Mar 24 2017/

SHORT TERM (Now through Saturday night): Low pressure area
continues to sweep across the Texas, pushing a weak cold front out
ahead of it. Prefrontal trough in our region has slowly decreased
winds, and is starting to bring drier air and heating into the
western valley. Capping has kept the shower activity well to the
north of our area as expected, and will keep things stable through
the next 36 hours. Weak H5 ridging sets up for tomorrow behind
today`s trough, while more dry air draws into the Western valley
during the day. Highs will reach the low to mid 90s out west in
the drier air, while the western valley remains in the upper 80s
in the more humid regime.

LONG TERM (Sunday through Friday): The next in a series of short
wave troughs will move out over the southern Plains on Sunday;
upstream pressure falls will be enough to support locally
stronger winds, but there won`t be enough push to get a front
past the dry line in West Central Texas. Mid level ridging will
take hold over the Plains again on Monday in the up until now
rapidly evolving mid level pattern across the southern United
States.

A more interesting and deeper trough will dive down the West
Coast Monday into Tuesday, bottoming out as a mid level low over
the Four Corners on Tuesday and Wednesday. This will bring spokes
of energy and upper Pacific moisture over the Sierra Madres of
Mexico and mainly into Central Texas on Wednesday, with the low
sinking into New Mexico. The low will eject east Wednesday, with
stronger weather ahead of it. The progression is a little faster
than it was 24 hours ago, but a front will still try to push
through on Thursday. The GFS has a little bit of energy aloft in
the trough axis, but the forecast sounding looks capped Thursday
morning and very dry air will accompany the wind shift, with PWAT
dropping by half an inch to around half an inch and leaving little
else to work with at the surface. Relative humidity values will
plummet Thursday with the arrival of the drier air, and will
remain depressed on Friday, resulting in a dry heat. Model
guidance is advertising highs well into the 90s on Wednesday
ahead of the front, even near the century mark for MFE, though
still hedged a little lower in the forecast for now. To sum up:
warm, breezy and dry for much of the long term.

MARINE:
Now through Saturday night: Winds have dropped off offshore thus
afternoon as the sfc wind decouple from the llvl jet, but continue
to race northward closer to shore. Seas remain agitated, running 8
to 10 feet offshore and 6 to 7 feet close to shore. Small Craft
Advisories remain in effect for the Gulf waters through at least
7PM for all zones, and may need to be extended for the Gulf waters
if seas don`t relax as quickly as forecast. Better marine
conditions forecast tomorrow as high pressure briefly moves across
the northwest Gulf. Winds will remain 10 to 15 knots, which will
allow seas to drop to 4 to 5 feet. Seas remain agitated Saturday
night and southeast winds reestablish and begin to rise.

Sunday through Wednesday: Pressure will decrease over the plains
Saturday, resulting in stronger southeast winds late Saturday into
Sunday and Sunday night. Seas will build by Sunday under fresh
southeast winds. winds and seas will improve Monday and Monday
night as the next ridge moves into the plains. A vigorous short
wave/cut off low will move into the four corners region Tuesday.
Southeast winds will subsequently ramp up to above 20 knots on
the Gulf Tuesday through Wednesday, with near 20 knots on the
Laguna Madre also. Wave heights will build to between 6 and 8
feet offshore late Tuesday night into Wednesday. Hence, except
for a brief improvement Monday into Monday night, marine
conditions will not be ideal, with small craft exercise caution
to small craft advisory conditions a possibility much of the
time.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory until 6 AM CDT early this morning for
     GMZ170-175.

&&

$$

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