Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 251724 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1124 AM CST Tue Feb 25 2020

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

&&

.AVIATION...Low clouds and fog rapidly lifting across the 3
airport sites and LIFR conditions should become VFR by or shortly
after 19Z. VFR persist through the afternoon with light winds with
a return of MVFR to IFR conditions prior to a cold front passage
between 04-06Z. Ceilings to gradually lift overnight with VFr
return by sunrise while winds increase to strong and gusty levels
as the strong high pressure builds in from the north. Gusts of
25-30 knots expected overnight and Wednesday.


&&

.PREV DISCUSSION... /issued 700 AM CST Tue Feb 25 2020/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...The morning low clds and fog, due to the combination
of light surface winds and pretty elevated low level dewpoints, is
resulting in LIFR conditions at both the BRO and HRL airports this
morning. Vsbys are a little better at the MFE airport, however
pretty low ceilings have also spread inland there producing LIFR
conditions. Warming temps later this morning should help mix out
the low vsbys and ceilings allowing for a return of MVFR/VFR
conditions throughout the late morning and afternoon hours. As the
cold front moves through the region late tonight, a drier NW-N low
level flow will build in over the area likely maintaining VFR
conditions throughout 12Z Wed.

PREV DISCUSSION... /issued 333 AM CST Tue Feb 25 2020/

SHORT TERM (Now through Wednesday): Areas of dense fog have
developed across mainly the eastern portions of Cameron and Willacy
counties this morning due to calm winds and narrow dew point
depressions for these areas. These conditions are expected to
continue through early this morning. Light south-southeast winds at
the surface under a nearly zonal flow aloft will dominate Deep South
Texas and the Rio Grande Valley ahead of the approaching cold front.
Temperatures will be similar to yesterday, with highs reaching the
the low to mid 80s for most areas. The front is expected to reach
Zapata, Jim Hogg and Starr counties early this afternoon and
progress steadily southeastward through the evening, bringing breezy
northerly winds to the region. The influx of moisture with the
southeast flow ahead of the front will allow for slight rain chances
mainly across Cameron and Willacy counties along the front through
isentropic lifting tonight, but rainfall amounts are expected to
remain minimal with generally one to two hundredths possible.

Temperatures will drop into the upper 40s in the northern
ranchlands, with lower 50s for the rest of Deep South Texas and the
Rio Grande Valley early Wednesday morning. Cool, dry airmass
settling into the region on Wednesday will allow skies to clear to
partly cloudy conditions and temperatures to reach a pleasant range
of lower to mid 60s. Winds will remain breezy throughout the day
with low relative humidity. A Fire weather watch has been posted
Wednesday for the entire CWA with expected relative humidities
lowering into the 15 to 30 percent range and 20 foot winds, the
limiting factor, indicated to be 15 to 20 mph. However, with 850-
925mb winds of 25 to 35 knots, gusty conditions can be expected.
Have decided to keep the watch for now, but will possibly need to
upgrade to a Red Flag Warning if winds are expected to increase with
new model runs.

LONG TERM (Wednesday Night through Monday): High pressure
settles across the Southern US through the rest of the week and
into the weekend. Low pressure develops across the Southern Plains
and North Texas Sunday into Monday as high pressure heads east
across the Southeast. Very dry air aloft arrives by Wednesday
night and holds through the rest of the week. Southerly flow
returns mid-weekend, allowing low-level moisture to return. Rain
chances into Monday remain below 10 percent at this time. Overall,
very comfortable day time conditions are expected Thursday into
Saturday, with cooler nights and mornings.

Temperatures Wednesday night are expected to free fall under clear
skies and light winds into the 30s, with a few typically cooler
locations like Zapata and Armstrong potentially hitting freezing
or slightly below. Radiational cooling keeps overnight lows below
normal through the rest of the week with near perfect stargazing
skies for Deep South Texas. High temperatures on Thursday struggle
to get into the upper 60s and rebound into the low to mid 70s on
Friday. As low-level southerly flow returns over the weekend,
expect warmer nights and a few more clouds across the sky. Highs
return to normal on Saturday, the 80s on Sunday, and mid 80s to
near 90 degrees by Monday. Expect breezy to windy conditions
Sunday into Monday due to the strengthening pressure gradient.

MARINE (Now through Wednesday): Areas of dense marine fog have
developed across portions of the Laguna Madre and the nearshore Gulf
waters overnight. These conditions are expected to continue through
early this morning. Otherwise, fairly benign marine conditions
expected today with light to moderate southeast winds and low seas
ahead of approaching cold front. The cold front will bring hazardous
marine conditions due to very strong northerly winds behind the
front late tonight and into early Wednesday morning. Hence, a Gale
Warning has been issued across the Gulf waters out 60 nm along with
a Small Craft Advisory for the Laguna Madre for this time period.

Wednesday Night through Monday: High pressure builds across the
Gulf of Mexico through the rest of the week before heading east
over the weekend. Elevated seas subside through the end of the
week, with very favorable marine conditions Thursday night into
Saturday night. As southerly flow increases across the lower Texas
coast due to low pressure developing across North Texas, expect
seas to build through Sunday morning, becoming hazardous Sunday
afternoon through Monday.

FIRE WEATHER...A cool, very dry airmass will settle into the region
on Wednesday behind the cold front with breezy northerly winds.
Winds will remain breezy throughout the day with very low relative
humidity. A Fire weather watch has been posted Wednesday for all of
Deep South Texas and the Rio Grande Valley with expected relative
humidities lowering into the 15 to 30 percent range and 20 foot
winds, the limiting factor, indicated to be 15 to 20 mph. However,
with 850-925mb winds of 25 to 35 knots, gusty conditions can be
expected. This watch may need to be upgraded to a Red Flag Warning
if winds are expected to increase with new model runs.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Fire Weather Watch from Wednesday morning through Wednesday
     afternoon for TXZ248>257-351-353.

GM...Small Craft Advisory from midnight tonight to noon CST Wednesday
     for GMZ130-132-135.

     Gale Warning from midnight tonight to noon CST Wednesday for
     GMZ150-155-170-175.

&&

$$

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