Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 172325 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
625 PM CDT Tue Apr 17 2018

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

.AVIATION...VFR is prevailing right now, but MVFR is expected to
develop overnight as winds diminish to moderate levels and low
stratus forms. Tomorrow, VFR will return as the day progresses,
with slightly weaker winds anticipated due to the approach of a
weak cold front from the north.
&&

.PREV DISCUSSION... /issued 309 PM CDT Tue Apr 17 2018/

SHORT TERM (Now through Wednesday Night): Satellite imagery was
showing mostly clear skies across the forecast area amidst quasi-
zonal flow aloft and a tight low level pressure gradient due to
lee surface troughing. Wind speeds had been just below advisory
criteria for coastal locations through the late morning hours but
have issued a wind advisory for the coastal counties until 7 pm
this evening as winds have crept up to advisory levels. Overnight
tonight, the pressure gradient will remain fairly tight but weaken
somewhat, however winds will diminish somewhat more due to the
loss of daytime heating than anything else. Additionally, moisture
continues to increase from east to west amidst moderate low level
onshore flow. Dew points have crept back up in the upper
50s/lower 60s for many of the lower/mid valley locations. The
increased moisture will lead to the development of low clouds over
the lower/mid valley after midnight tonight. Clouds will thicken
sufficiently along the coastal counties tonight/Wednesday morning
so that those areas most likely will stay at least mostly cloudy
through the day. Mid and upper valley locations will see much more
sun than the coast on Wednesday. Highs Wednesday afternoon look
to range from the mid 80s at the coast to the mid 90s out west.
Wednesday will not be nearly as breezy as today due to a weakening
low level pressure gradient.

Overnight Wednesday night, additional moisture increase associated
with a very weak cold front approaching from the north will lead to
slight chances of showers and possibly a thunderstorm over the
entire region. Overnight low temperatures will remain on the warm
side with upper 60s/lower 70s area-wide.

LONG TERM (Thursday through Tuesday): The synoptic pattern for
the beginning of the long term period will feature a mid-level
trough digging across the Southwest U.S. with another trough
moving across the Northeast. A surface low in the mid-Atlantic
will bring a weakening cold into South Texas on Thursday with
slight northeast winds slowly veering back to the southeast on
Friday. The main impacts with this front will be isolated showers
and storms. Friday into Saturday a surface low will develop across
North Texas and track eastward, bringing another front through the
area early on Sunday. Ahead of the front, showers and
thunderstorms will be possible with a very low chance of a few
stronger storms, especially in the northern areas. Models show a
substantial capping inversion on Saturday, but if the upper-level
trough and surface low track a bit further south, chances will
increase across our area.

Temperatures each day will be around normal to slightly above
normal with highs in the 80s to low 90s in the Upper Valley and
ranchlands. Behind the front Saturday night into Sunday, slightly
cooler temperatures will be felt early next week.

MARINE (Now through Wednesday night): Latest observation from buoy
42020 as of 1:30 pm CDT showed low end Small Craft Advisory
conditions in place with SSE winds of 18G23KT and seas 7 ft. These
conditions will prevail over the waters through the evening and
overnight with slowly improving marine conditions Wednesday morning.
Small Craft will still need to exercise caution through the day on
Wednesday as seas will remain agitated from ongoing winds. Marine
conditions will be more ideal Wednesday night and winds/seas
continue to subside.

Thursday through Sunday: A weak cold front is expected to
dissipate across the northern areas of Deep South Texas, with
another cold front expected on Sunday. Moderate winds and seas are
expected through the short term with Small Craft Exercise Caution
conditions Friday night through Saturday and again Sunday and
Monday.
&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory until 7 PM CDT this evening for TXZ251-254>257.

GM...Small Craft Advisory for winds until 10 PM CDT this evening for
     GMZ130-132-135.

     Small Craft Advisory until 7 AM CDT Wednesday for GMZ150-155-170-
     175.
&&

$$

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