Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 272327 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
627 PM CDT Thu Apr 27 2017

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

.AVIATION...Visible satellite imagery shows a lowered deck of
cloudiness moving onshore...and MVFR ceilings are expected through
the overnight hours. Moderate winds right now will become breezy a
few hours before sunrise Friday morning...and will increase even
further to windy levels after sunrise. Thus...a wind advisory may
be needed for the BRO and HRL aerodromes tomorrow.

.PREV DISCUSSION... /issued 304 PM CDT Thu Apr 27 2017/

SHORT TERM (Tonight through Friday Night):Broad 500mb trough
across the country this afternoon will deepen across the western
United States Friday. Surface low pressure across northwest Texas
will allow the weak frontal boundary across the Rio Grande valley
this afternoon to retreat northward as a warm front. Southeast winds
across the CWA tonight will veer to the south Friday as a surface
trough/dryline moves into west central TX Fri afternoon. This will
result in above normal temperatures Friday and with dewpoints in the
lower 70s across the coastal sections...heat index values will range
from 105 to 110 degrees across the eastern portions of the CWA Fri
afternoon. With the tight pressure gradient across the lower TX
coast Friday...breezy conditions will prevail across the eastern
portions of the CWA. With little in the way of low to mid level
moisture across the area through Fri rain chances are
expected through the short term.

LONG TERM (Saturday through Thursday):Another day of very hot
temperatures expected across the Rio Grande Valley and Deep South
Texas on Saturday as flow at 750 to 850 mb remains out of the
west southwest and 850 mb temps still look to push into the 23 to
27C range. This flow will bring hot and dry air thanks to
downsloping and compressional heating off the Sierra Madre.
Temperatures expected to push well past the 100 degree mark once
again Saturday afternoon, nudging towards the Highway 77 corridor.
Think that there may be enough southeasterly flow Saturday
afternoon to keep temperatures a few degrees cooler across the
lower Valley and along the coast. Breezy conditions redevelop by
late Saturday morning and continue through the afternoon hours
across the lower Valley and and along the coast. Latest guidance
continue show winds staying just below advisory levels, with
sustained winds of 24 knots at BRO and HRL and 25 knots at PIL.

Shortwave trough over the desert southwest on Saturday lifts
northeast across the southern plains, pushing a cold front
south across Texas.  The cold front is expected to enter
the northern reaches of the CWA around midnight and push
through the Valley around sunrise, bringing a noticeably
cooler day, with afternoon temperatures 10 to 15 degrees
lower than Saturday. There is some moisture pooling with
the front, but moisture remains limited, with a deep dry
layer aloft. The lift from the front along with the minimal
moisture, may be  enough to produce a few showers right along
the coast and over the coastal waters (where moisture will be
the greatest), so kept pops on the low end.  Elevated fire weather
conditions expected to develop behind the front Sunday afternoon
as dry air moves in on moderate and gusty northwest winds,
dropping RH values into the 12 to 25 percent range across much of
the inland areas. Areas of greatest concern remain the western
counties, but would not be surprised for that line to shift
eastward. Sunday night looks to be the coolest of the week as
skies clear and temperatures fall into the mid to upper 50s across
much of the area. The slight cool down is only temporary with
temperatures rebounding quickly as we move into the new week and
onshore flow resumes, with highs well into the 90s by Tuesday.

Model guidance brings another cold front through the area during
the late Wednesday into Thursday time frame, bringing our next
chance of rain and slightly cooler temperatures.

MARINE (Tonight through Friday night): Seas were near 6 feet with
east winds near 12 knots at buoy020 early this afternoon. Moderate
to strong southeast winds will prevail across the coastal waters
tonight with low pressure across northwest Texas and high pressure
across the eastern Gulf of Mexico. Will word SCEC for the far
offshore waters tonight. The pressure gradient will increase
slightly across the lower Texas coast Friday and winds will veer to
the south and increase slightly. Small craft advisories will be
needed for the Laguna Madre and offshore waters Friday. Strong
southeast to south winds will prevail across the western Gulf of
Mexico Fri night and small craft advisories will likely need to be
extended for the offshore waters.

Saturday through Monday: Unfavorable marine conditions prevail
through the weekend and into early Monday before improving. Strong
southeasterly winds expected Saturday ahead of an approaching cold
front with seas building to 8 to 10 feet due to increased swells.
Small craft advisories are likely Saturday into Saturday night for
all lower Texas coastal waters. Winds diminish briefly late
Saturday night ahead of the approaching front Sunday morning,
before shifting to the north and increasing in the wake of the
front, resulting in another round of Small craft advisories for
Sunday afternoon and night. Conditions begin to improve going into
Monday as high pressure over the area slides east, allowing winds
to relax and seas to subside.



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