Area Forecast Discussion
Issued by NWS Brownsville, TX

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
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 43 44 45 46 47 48 49 50
000
FXUS64 KBRO 170530 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1130 PM CST Thu Nov 16 2017

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

&&

.AVIATION...Broad high pressure over the northwest Gulf will
support light south southeast winds the rest of tonight with
initially mostly clear skies and VFR conditions. Low cloudiness may
develop inland in the pre-dawn hours of Friday, with the MFE
terminal having a better chance at MVFR ceilings from 4 am to 8 am.
Patchy fog may develop late tonight, especially in areas where the
dew points can persist in the upper 60s to near 70 degrees, however,
the latest model guidance has backed off from the slightly stronger
fog signal that had been suggested earlier. South southeast winds
will become moderate and gusty from late Friday morning to late
afternoon as pressure falls upstream tighten the gradient. Skies
will be mostly sunny to partly cloudy with VFR conditions.

&&

.PREV DISCUSSION... /issued 518 PM CST Thu Nov 16 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Light south southeast winds will prevail tonight,
with GFS model guidance keeping conditions better than the more
pessimistic NAM, which wants to bring in MVFR ceilings and
lower, MVFR visibility after midnight through dawn, but more for
HRL and MFE than BRO. Conditions will improve Friday after
sunrise, and south southeast winds will become moderate and gusty
from late morning to late afternoon under a mix of clouds and sun.

PREV DISCUSSION... /issued 317 PM CST Thu Nov 16 2017/

.Much Cooler temperatures expected this Sunday...

SHORT TERM (Tonight through Friday Night): Another warm day across
much of deep South TX. Temperatures ranged from the middle to
upper 80s with the warmer spots being along the I-69C/HWY 281
corridor this afternoon. A few more clouds around, but overall a
nice day. There have been some very isolated light showers from
time to time in response to a decaying wave as well as a remnant
frontal boundary across the area. This activity will remain weak
and isolated in coverage at best as mid and upper levels remain
dry.

Overnight tonight expect almost a carbon copy from previous nights.
Mild conditions with perhaps some patchy ground fog developing,
especially across the northern Ranchlands and upper Rio Grande
Valley. That said, there is a bit more uncertainty overnight in
terms of fog. There will be an uptick in surface winds, which may
keep things mixed enough to limit the development in some locations.

Friday looks like a fairly nice day overall. It will be another warm
one with temperatures possibly nearing record territory as the upper
high briefly builds back into the region. Another clue that it will
be a warm one is the H85 Temp anomaly, which should end up as high
as around 4-7 deg C on the warm side. With strong surface
heating, the atmosphere will be very well mixed, which should lead
to a breezy afternoon.

LONG TERM (Saturday through Thanksgiving Day): A pretty sharp and
deep 500 mb trough will dig across the central and eastern
portions of the lower 48 states this weekend. The passage of this
trough axis will bring a pretty significant cold front through the
RGV late Sat/early Sun. Overall moisture levels ahead of this next
cold front are pretty minimal. So will maintain only some 20%
pops mainly near the coastline and offshore for late Sat Night.
After this fropa a series of 500 mb short waves will dig across
the lower 48 states throughout next week which will erode away the
broad ridge axis over the Mex/U.S. border region and will
increase broad troffing. A stronger short wave will then push
through the south central Plains states late Tues/early Wed
pulling another relatively dry cold front through the region
allowing for a reinforcing shot of cooler Canadian air.

The GFS and ECMWF show pretty good agreement in the overall
synoptic pattern until next Mon. The two models then start
diverging with the ECMWF closing off the southerly end of the 500
mb trough over the western Gulf Coast with the GFS trying to cut
off this trough axis much further east near Florida later next
week. This results in the GFS showing a general warmer solution
for much of next week versus the ECMWF. Will lean closer to the
warmer ECMWF numbers on Sat as expect an increased potential for a
heat spike ahead of the approaching cold front. Daily record
highs may be threatened across the entire RGV on Sat.

After the fropa late Sat, will go with a general model blend for
temps through Day 7. Overall confidence in the longer range
forecast is only average due to the increasing model differences
showing up in the broad pattern.

MARINE (Now through Friday Night): Light to moderate southeasterly
winds and seas generally under 3 feet expected through tonight. Low
pressure is forecast to develop on Friday across the plains, which
will increase winds close to Small Craft Advisory thresholds late
Friday. Seas are expected to build to as high as 5-6 feet before
rounding out the short term.

Saturday through Tuesday Night...The approach and passage of the
cold front late Sat/early Sun will result in pretty dramatic
changes across the lower TX marine areas with much stronger
northerly surface flow dominating the region from late Sat into
Sun. The pressure gradient will then weaken pretty quickly from
Sun Night into Tues Night as the center of the surface ridge
shifts pretty quickly east allowing for a return of a light to
moderate E-SE flow. Strong SCA to borderline Gale conditions will
be very likely immediately after the fropa late Sat/Sun.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

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

63


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