Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 192329

Area Forecast Discussion
National Weather Service Brownsville TX
629 PM CDT Thu Apr 19 2018

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


.AVIATION...A cold front is stalling south of the border with VFR
ceilings and diminishing winds this evening across the Rio Grande
Valley. MVFR ceilings arrive after midnight and continue through
Friday morning with increased moisture and light winds. The
stalled boundary returns as a warm front with increasing
southeasterly winds and VFR ceilings Friday afternoon.


.PREV DISCUSSION... /issued 304 PM CDT Thu Apr 19 2018/

SHORT TERM (Now through Friday Night): A cold front is moving
through Deep South Texas this afternoon with gusty ENE winds and
drier air behind it. Dew points from Zapata to Falfurrias have
dropped into the upper 40s to low 50s with low to mid 60s south of
the front along the Rio Grande. A few showers have developed
along the front, but have maintained 20% PoPs through the evening,
due to environmental soundings showing limited moisture above

Aloft, synoptic flow at 500mb features a deep low over the Southwest
U.S. with broad ridging over the Southern Plains. As the low moves
eastward, weak diffluence and a shortwave trough will move over
South Texas early on Friday. Winds in the low levels will be out of
the east, so moisture will only slowly return across the region.
Model time-heights show very dry air from 850 to 700mb with RH
values ranging from 10 to 30% in the Valley with slightly higher
moisture in the Ranchlands. So, isolated showers and thunderstorms
will be possible, but mainly across the northern counties during the
day. Temperatures during the day will be near normal with highs in
the mid 80s for most locations.

LONG TERM (Saturday through Thursday): 500mb low/trough across
the central United States Saturday will move eastward across
Arkansas and Louisiana Sunday. At the surface...a frontal system
over west Texas Saturday will move eastward Sunday bringing a
weak cold front through the Rio Grande valley Sun morning. Will
mention a slight chance to chance of showers and thunderstorms
across the CWA Saturday before drier air aloft filters into the
area Sat night. Drier and slightly cooler air will filter into the
area on Sunday in the wake of the front. Surface high pressure
will build into the state Monday and provide subsidence across
south TX through Tuesday. A 500mb shortwave trough across the
northern plains Tuesday is progged to move across the Ohio River
valley Wednesday. This will bring another weak cold front through
central TX Wed morning. Low to mid level moisture should increase
Wednesday to warrant a mention of a slight chance of showers
and thunderstorms. The front will likely retreat northward as a
warm front on Thursday.

MARINE (Now through Friday): A cold front is moving through the
coastal waters this afternoon with moderate to strong northeast
winds behind it, mainly affecting the northern waters off the lower
Texas coast. A Small Craft Advisory was issued for the northern
Laguna Madre and Gulf waters out to 60 nm from the Kenedy county
coast through 5 PM CDT. Elsewhere, winds may reach 15 to 20 knots at
times, so small craft should exercise caution. Surface high pressure
will move southeastward across the Mississippi Valley, shifting
winds back to southeast and becoming moderate Friday afternoon.

Saturday through Tuesday...Moderate to strong southeast winds
will prevail across the coastal waters with low pressure across
northwest Texas and surface high pressure across the northeast
United States. Small craft advisories may be needed for the
coastal waters on Saturday. The pressure gradient will weaken
across the western Gulf Sat night through Sun morning before a
weak cold front moves through the lower TX coast Sunday. Winds
will shift to north and increase Sun afternoon. Small craft
advisories will be needed across the coastal waters Sun afternoon.
Moderate to strong north winds Sunday will diminish Sun night as
surface high pressure settles across the western Gulf of Mexico.
Light north winds will prevail across the lower TX coast Monday.
Winds will veer to the east on Tuesday as the surface ridge across
the western Gulf moves eastward.




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