Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 241952
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
252 PM CDT Sun Mar 24 2024

...New SHORT TERM, LONG TERM, MARINE...

.SHORT TERM...
(Tonight through Monday night)
Issued at 132 PM CDT Sun Mar 24 2024

* A Fire Weather Danger Statement has been issued for Zapata, Jim
  Hogg, and Starr Counties for the risk of elevated fire weather
  concerns from Noon to 8 Pm CDT on Monday.

* A Wind Advisory remains in effect for Cameron, Willacy, and Kenedy
  Counties till 7 Pm CDT.

* A Small Craft Advisory remains in effect for the Laguna Madre till
  8 PM CDT this evening and for the Gulf Waters (0-60 nm) till 1 PM
  CDT on Monday (see Marine section below for more details).

* A High Rip Current Statement remains in effect till 7 PM CDT
  Monday (see Marine section below).

Main weather concerns in the immediate near term is the continued
strong southerly winds and the resultant adverse effects on marine
conditions, followed by the elevated risk for fire potential
following the passage of a cold front on Monday.

Latest surface analysis reveals a tight pressure gradient over the
area this afternoon. This tight pressure gradient happens to be the
byproduct of a mammoth sub-580 mb storm system over the central
Rockies/Plains and its trailing cold front approaching the area from
the west , and a surface high pressure system in place to our east
over the Gulf of Mexico. Increased mixing heights this afternoon
tapping into low level jet (H850) winds of 30-40 mph has resulted in
these strong winds mixing down to the surface. Couple all of this
with local topographic/climate effects and the "Valley Wind Machine"
has been activated at least across parts of the area this afternoon.
Winds have been out of the south-southeast 20-35 mph with gusts
between 40-55 mph. Current wind gusts at KBRO, KHRL, and KMFE are 49
mph, 43 mph, and 42 mph, respectively. Peak winds of 53 mph, 49 mph,
and 42 mph have occurred so far at these sites, respectively. The
pressure gradient is expected to relax some later this evening and
especially overnight which will result in these gusty southerly
winds decreasing. For tonight, it will still remain breezy at times
with gust ranging between 20-35 mph, but in decreasing fashion as
time evolves. Outside of that, the weather will remain dry with
continued subsidence from the influences of a high pressure system
to our east. Tonight will be mild with overnight lows progged to be
in the mid 60s to lower 70s.

Dry and tranquil weather conditions will persist on Monday with
noticeably calmer winds. A surface trough/secondary southern stream
low pressure system and cold front will be approaching the local
forecast area from the west. Before the cold fropa, highs will have
a chance to climb into the mid/upper 80s to low 90s, giving way to a
very warm day on Monday. Cold front sweeps over the area during the
day on Monday. This cold front will be moisture starved, so not
expecting any precipitation with it. Additionally, this cold front
has origins from the Pacific, so not expecting a notable airmass
change. Nonetheless, cooler and drier air will be advecting into the
region during the day on Monday. Across our western zones (i.e.
Zapata, Jim Hogg, and Starr Counties), relative humidity values are
expected to drop between 15-25%. This coupled with 20ft winds
between 10-15 mph with gusts between 20-25 mph will support an
elevated risk for wildfire concerns during the afternoon/evening
hours on Monday. That said, a Fire Weather Danger Statement has been
issued from Noon-8 PM CDT on Monday for Zapata, Jim Hogg, and Starr
Counties.

Monday night will remain dry and with north-northwesterly winds,
overnight low temperatures will fall into the mid 50s to lower
60s.

&&

.LONG TERM...
(Tuesday through next Sunday)
Issued at 132 PM CDT Sun Mar 24 2024

A dry forecast is in store throughout the extended forecast
period. A full latitude trough axis stretching from the Upper
Midwest into the Southern Plains and Mexico will be in place at
the beginning of the period on Tue morning. At the surface, there
will be a dry post-frontal airmass slowly sagging through the
CWA. A shortwave rounding the base of this full latitude trough
axis will result in a surge of high pressure across the Western
Gulf and result in cooler and drier conditions across our CWA Tue
night into Wed night. Overnight lows through Thu morning will
generally be in the 50s except 60s along the immediate coast.
Highs will generally be in the upper 70s to lower 80s on Tue and
Wed.

Moderating temperatures are expected to begin by Thu afternoon as
our CWA finally gets on the back edge of the departing surface
ridge axis. This will allow easterly flow to begin to develop and
slowly boost temperatures, mainly across inland locations.
Through the remainder of the forecast period from Fri into next
weekend, a more typical late March synoptic pattern will prevail.
This will entail large-scale prevailing south to southeast
gradient flow due to persistent Lee-side low pressure and high
pressure across the Northern and Northeast Gulf. Could be
borderline wind advisory conditions for the coastal counties on
Fri and possibly into Sat. A warming trend will continue during
this latter part of the extended period given this persistent
moderate to occasionally strong south to southeast flow.

&&

.AVIATION...
(18Z TAFS)
Issued at 1202 PM CDT Sun Mar 24 2024

Through 18z Monday.....VFR to MVFR ceilings are expected through
Monday morning thanks to some marine layer influences due to the
southerly winds (onshore flow regime) in place ahead of an
approaching cold front. Late Monday morning and to a greater extent
by Monday afternoon, ceilings should return to VFR as the cold fropa
will allow for a winds to shift out of the west-northwest and drier
airmass to filter into the region eliminating the presence/influence
of the marine layer.

Strong south-southeast winds 20-30 kts, gusting up to 40 kts amid a
tight pressure gradient will continue through this evening before
diminishing late this evening and tonight. Following the passage of
a cold front, south-southeast winds will shift out of the west-
northwest between 10-15 kts late Monday morning into Monday
afternoon.

&&

.MARINE...
Issued at 132 PM CDT Sun Mar 24 2024

Tonight through Monday Night...Strong southerly winds 20-30 kts,
gusting to 35-40 kts associated with a tight pressure gradient has
resulted in adverse marine conditions. These winds are expected
to diminish later this evening and tonight. A Small Craft Advisory
remains in effect for the Laguna Madre till 8 PM CDT and for the
Gulf Waters till 1 PM CDT Monday for seas between 6-9 feet.
Afterwards, Small Craft Exercise Caution Statements will be needed
for the Gulf Waters for seas between 4-6 feet into Tuesday as
winds weaken and marine conditions gradually get better.

Tuesday through Sunday...High pressure will continue to build
across the coastal waters through Thu morning as a potent
shortwave rounds the base of a full latitude trough axis. Return
flow albeit weak will begin on Thu and then slowly strengthen on
Fri and into the weekend. For now, will keep conditions below
small craft advisory thresholds for all but the Laguna Madre for
the Fri-Sun period.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             72  90  62  82 /   0   0   0   0
HARLINGEN               69  90  57  83 /   0   0   0   0
MCALLEN                 69  90  59  84 /   0   0   0   0
RIO GRANDE CITY         65  89  56  83 /   0   0   0   0
SOUTH PADRE ISLAND      70  81  65  73 /   0   0   0   0
BAYVIEW/PORT ISABEL     70  87  61  78 /   0   0   0   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory until 7 PM CDT this evening for TXZ251-254-255-351-
     354-355-451-454-455.

     High Rip Current Risk through Monday evening for TXZ451-454-455.

GM...Small Craft Advisory until 8 PM CDT this evening for GMZ130-132-
     135.

     Small Craft Advisory until 1 PM CDT Monday for GMZ150-155-170-
     175.

&&

$$

SHORT TERM...23-Evbuoma
LONG TERM....80-MB
AVIATION...23-Evbuoma


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