Area Forecast Discussion
Issued by NWS Brownsville, TX

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

000
FXUS64 KBRO 080015
AFDBRO

Area Forecast Discussion
National Weather Service BROWNSVILLE TX
615 PM CST Wed Dec 7 2016

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

&&

.AVIATION...A stationary front is located over the Lower Rio
Grande Valley with satellite and surface observations indicating
ceilings of 1000ft and below in the Northern Ranchlands to around
5000ft along the Rio Grande this evening. As the front moves
southward late tonight as a cold front, winds will increase along
with lowering ceilings. MVFR to IFR conditions are expected all
day Thursday with briefly LIFR possible in the Brownsville area
with fog development ahead of the front overnight. Warm air aloft
riding over cold air at the surface will lead to light rain or
drizzle throughout the day.

&&

.PREV DISCUSSION... /issued 311 PM CST Wed Dec 7 2016/

SHORT TERM (Tonight through Thursday Night):Surface low pressure
across the lower Texas coast this afternoon will continue to provide
warmer temperatures across the coastal sections of the CWA this
evening with cooler temps across the western and northern portions.
A strong push of high pressure across western Canada bringing a mix
of polar and arctic cold air will filter into the central and
southern plains tonight reaching the northern ranchlands late
tonight and the Rio Grande valley early Thursday morning. This
shallow cold air will allow overrunning conditions to develop late
tonight into Thursday as warm and moist air aloft moves across the
colder air at the surface. This will provide a chance of light
rain/drizzle/mist developing across deep south TX late tonight into
Thursday. High temperatures for Thursday will likely be at midnight
tonight with lows for tonight being Thursday morning as temperatures
fall during the morning hours and holding steady Thursday afternoon.
The pressure gradient will increase across the coastal sections
Thursday and strong to very strong north winds will develop across
the coastal sections of Cameron...Willacy and Kenedy counties as a
result. Have issued a wind advisory for the coastal counties for
Thursday through Thursday evening. Winds will diminish Thurs night
but temperatures will continue to fall Thurs night providing wind
chill values in the 30s across most of the area.

LONG TERM (Friday through Wednesday): A cold and blustery start
to the work/school day can be expected Friday morning as high
pressure settles into the region. This arctic high pressure air
mass will moderate the amount of cold air that it brings into the
RGV...with any subfreezing temps remaining north of the region.
Even so...it will not be uncommon to see morning lows in the mid
30s across the Northern Ranchlands to start the day...with temps
being warmer in the Lower RGV and coastal areas.

Winds will also remain elevated for a while behind the cold front
given that the strong surface pressure gradient. Wind chill
values will remain above any advisory criteria levels...but will
still be in the upper 20s to mid 30s for much of the areas.
However...winds will be steadily decreasing through the day
Friday. As far as precipitation chances...light rain will
continue to linger through the day.

By late Friday into Saturday...coastal troughing will develop
along the frontal boundary. This will allow for northeast/onshore
winds to run-up over the colder air mass in place and bring
clouds and light rainfall/drizzle through the first half of the
weekend...mainly along coastal areas. Temperatures will begin to
moderate.

The pattern shifts late Saturday and into early Sunday as the high
pressure system over the Texas and the Plains shifts east as the
next storms system quickly move out of the Rockies and deepens in
the Central Plains. This will allow southerly flow to return and
temps will warm on Sunday...with a brief break from the rain.

However...the storm system in the Plains will drag another cold
front towards the region Sunday night into Monday. There are
timing difference between long term models with the GFS having a
slightly faster solution than the ECMWF. Have opted to go with a
more blended time. Either way...this FROPA will not be nearly as
cold and only bring small rainfall chances. Onshore flow and high
pressure will return to round out mid week.

MARINE:

Tonight through Thursday night: Seas were near 2 feet
with south to southeast winds near 8 knots at buoy020 this
afternoon. Light east winds will prevail across the coastal waters
tonight before a surge of high pressure builds across the lower
Texas coast Thursday. Winds will shift to the north and increase
Thursday morning with gusts to near gale force developing late
Thurs morning into Thurs afternoon. Strong to very strong north to
northeast winds will prevail across the western Gulf of Mexico
Thursday. Have upgraded the Gale watch to a Gale warning for all
of the Laguna Madre Thursday morning through Thursday evening and
for the offshore waters Thursday morning through Thursday night as
the pressure gradient will remain extremely strong across the
coastal waters Thursday night.

Friday through Monday: Although Gale Force conditions should be
ending to start the day Friday. However...given the strength of
the surface pressure gradient as an arctic high pressure settles
over North TX...northerly winds will still be strong...at least
near 25 Knots. High seas exceeding 10 feet will be likely Friday
morning as well. A SCA will likely be need for the Laguna Madre
and Gulf Waters for the rest of the day Friday. The gradient will
relax Saturday and winds will become more moderate...however seas
may still remain elevated offshore. By Sunday more moderate marine
conditions will return and advisories are not expected.
However...another cold front may approach late Sunday night into
Monday.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory from 6 AM Thursday to midnight CST Thursday night
     for TXZ251-256-257.

GM...Gale Warning from 6 AM Thursday to midnight CST Thursday night
     for GMZ130-132-135.

     Gale Warning from 6 AM Thursday to 6 AM CST Friday for GMZ150-
     155-170-175.

&&

$$

This product is also available on the web at:
HTTP://WEATHER.GOV/RGV

65/60



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.