Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 200545 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1245 AM CDT Fri Oct 20 2017

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

.AVIATION...Light to calm winds with a moist atmosphere and clear
skies may allow for the formation of light fog during the remainder
of the overnight hours. Tomorrow, full VFR will be on display with
light onshore winds and a few clouds.

.PREV DISCUSSION... /issued 642 PM CDT Thu Oct 19 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...VFR conditions will continue through much of the
overnight. Some guidance has been signaling very shallow fog
around sunrise on Friday so MVFR is reflected for all three
sites, though HRL and MFE have the greatest potential for reduced
visibilities. Conditions will quickly improve shortly after
sunrise. Light southeasterly winds can be expected through the end
of the cycle.


PREV DISCUSSION... /issued 247 PM CDT Thu Oct 19 2017/

SHORT TERM (Now through Friday night): The H5 trough continues to
sweep into the western half of the US, with the first wave just now
moving northeast into central Texas. Surface high pressure is
slowly drifting eastward across the eastern US, bringing modest
southeasterly flow to Deep South Texas. Morning sounding showed
moisture is trapped in the lowest 5000 feet, with strong dry air
cap above. Light winds and ample moisture at the sfc will lead to
some patchy ground fog in grassy areas tonight, but if the drier
air can focus llvl moisture closer to the sfc, some more denser
fog might be a possibility for the lower valley around sunrise.
Tomorrow will be similar to today, with dry air capping off around
5 kft, keeping daytime CU field from considerable development.
This will again keep the shower activity to a minimum, and likely
restrict it to the Gulf of Mexico waters.

LONG TERM (Saturday through Thursday): A cold front is still on
track to move through Sunday afternoon, shifting winds to north
and bringing drier, if not significantly cooler, air into the
area. Scattered showers and thunderstorms will develop along the
front, but most of the dynamics will occur farther to the north
with the associated short wave trough. Dry weather will quickly
take over and persist in the wake of the front. Reinforcing high
pressure will arrive on Tuesday as H5 ridging builds upstream,
serving to delay a strong warmup. In general, Sunday through
Wednesday nights will experience good radiational cooling with low
temperatures in the mid 50s, but due to ample sunshine, daytime
high temperatures will get into the 80s, and will remain slightly
above normal.

Now through Friday night: High pressure drifting across the
southeastern US is keeping surface flow easterly across the
northern Gulf. This will begin to increase long period swells
later tonight and tomorrow, with seas reaching 4 feet tomorrow and
5 to 6 tomorrow night, with a period of 8 to 10 seconds. Marine
areas are a bit more unstable, so shower activity will be a bit
more widespread tonight and again tomorrow.

Saturday through Tuesday Night...Moderate southeast winds on
Saturday will be supported by high pressure over the mid-Atlantic
region extending southwest into the Gulf. Slightly elevated seas
will bleed over from Friday night into Saturday, but will decline
Saturday and Saturday night. The winds will weaken Saturday night
into Sunday with the approach of a cold front from upstream. Winds
will turn to moderate north Sunday afternoon and will strengthen
to fresh Sunday night as high pressure behind the front spreads
over the area. Winds will then slowly shift to northeast through
Tuesday night. Seas will build to seven or eight feet offshore
Sunday night through Monday, supporting small craft advisory
conditions on the Gulf. Winds are forecast to remain below 20
knots on the Laguna Madre in the wake of the front, however.
Scattered showers and thunderstorms will develop along and behind
the front Sunday afternoon to Sunday night.



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