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000
FXUS64 KBRO 122006
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
306 PM CDT Fri Apr 12 2024

...New SHORT TERM, LONG TERM, MARINE, FIRE WEATHER...

.SHORT TERM...
(Tonight through Saturday night)
Issued at 306 PM CDT Fri Apr 12 2024

Flat subtropical 500 mb ridge controls the situation for much of
the weekend, building into the RGV from northern Mexico by mid
afternoon Saturday and continuing through Saturday night. As the
ridge builds, downstream surface ridge also strengthens across the
central,then eastern, Gulf with a broad southeasterly flow on its
backside, covering the entire forecast area. This is the "classic"
Valley Wind Machine pattern...but with no additional surface
features outside of the lee-side trough east of the Sierra Madre,
expect only breezy to marginally windy conditions. This will
change a bit by Monday as stronger winds arrive, courtesy of
deepening low pressure moving into the southern Plains. More on
those details in the long-term discussion.

In terms of sensible weather...the persistent southeasterly low
level flow will gradually moisten up the lower part of the
column...but it will take some time to be fully realized...most
likely beginning Sunday. Until then...expect periods of thicker
cirrus overnight (though stars will be viewable through them) and
sunshine filtered through cirrus on Saturday with the first lower
cumulus clouds making their appearance for the first time since
this past Tuesday. Temperatures will be comfortable again
tonight...dropping to just a touch below seasonal averages (60 to
65) even though southeast winds won`t lay down completely.

Highs on Saturday will rise into the mid to upper 80s..perhaps
touching 90 out west where slightly drier air remains. Saturday
night will see similar winds (around 10 mph or so) with moistening
low levels presenting a better opportunity for more low clouds,
especially after midnight. This combination will keep temperatures
from falling as much...and mid 60s ranchlands to around 70 lower
Valley should do it.

&&

.LONG TERM...
(Sunday through next Friday)
Issued at 306 PM CDT Fri Apr 12 2024

The long term period will feature a gradual warming trend, breezy
winds, and rain-free conditions. Unsettled weather will return
towards the end of the work week.

The upper level pattern will begin to transition from upper level
ridging to southwesterly flow Sunday into Sunday night as an upper
level trough digs into the Desert Southwest. Persistent low level
southerly flow will aid in allowing moisture to steadily return,
resulting in a warm and breezy afternoon. The pressure gradient will
continue to tighten early next week in response to the upper level
trough/low and attendant surface features tracking across the
Plains, which will result in sustained southerly winds around 25-30
MPH and gusts upwards of 35 MPH Monday and Tuesday. Probabilistic
guidance indicates there is a medium to high chance (60% or greater)
of wind gusts greater than 35 MPH, and a low to medium chance (30-
60%) of wind gusts greater than 40 MPH. Wind headlines for portions
of the Rio Grande Valley and the Gulf waters will likely be needed.
Temperatures will steadily warm each afternoon, with highs in the
90s expected by Tuesday for most of the region. The exception will
be along the Lower Texas beaches and near the immediate coast, where
highs should only warm into the 80s. A weak cold front will approach
the region towards the end of the long term period, which will bring
low rain chances across portions of the region beginning late
Thursday evening or Thursday night.

&&

.AVIATION...
(18Z TAFS)
Issued at 1228 PM CDT Fri Apr 12 2024

Situation continues to be a wind forecast through midday Saturday,
which will make takeoffs and landings a bit tricky due to
enhancement from late morning through afternoon thermals both
today and again on Saturday.

Winds have already picked up to 17+ knots this afternoon with
gusts at or above 23 knots at times...direction from the east-
southeast...and expect the usual east to west decrease through mid
evening. Speeds will remain near 10 knots overnight so no fog/mist
expected. Gradient continues to tighten on Saturday and direction
will veer toward the more traditional southeast (i.e. 150 degrees)
as surface ridge nudges farther east into the Gulf...a quicker
rise by mid morning toward 20 knots which will become likely after
1 PM Saturday.

As for clouds...patchy cirrus will be the rule through mid morning
Saturday. Introduced few-scattered low VFR cumulus by 10 AM
Saturday due to increasing (but well mixed) low level
moisture...but with plenty of mid level dry air mixing down not
expecting a broken sky on Saturday.

&&

.MARINE...
Issued at 306 PM CDT Fri Apr 12 2024

Now through Saturday Night...Marine layer will begin to be felt as
humidity over the water rises (dewpoints well into the 60s by
Saturday afternoon)...and this will help neutralize stronger winds
over land and keep the Gulf around 15 knots through Saturday. As
the gradient tightens and we lose the marine layer overnight,
winds should rise into the 15-20 knot range (Caution). The onset
of stronger winds well offshore Saturday afternoon/evening will
help raise seas to 5 feet or higher...mainly offshore but
potentially spreading nearshore after midnight.

Laguna Madre will be fairly copacetic overnight but winds should
pick up quickly by mid morning. Question will be how much. Current
forecast nudges just over advisory levels (20 knots) for a few
hours from late morning through mid afternoon...and caution is a
certainty at this point. Laguna winds on Saturday night will
diminish once again but not as much as this evening with the
increased cloud cover keeping mixing going...but speeds should
hold just below advisory levels by mid evening.

Sunday through Thursday night... An enhanced pressure gradient will
result in breezy winds through most of the extended period. Seas
will build in response, with the highest wave heights expected
Monday night into Tuesday. Small Craft Should Exercise Caution to
Small Craft Advisory conditions will prevail along the Laguna Madre
on Sunday, and all of the Gulf waters Monday through Tuesday night.
Conditions will improve on Wednesday.

&&

.FIRE WEATHER...
Issued at 306 PM CDT Fri Apr 12 2024

Rest of today: Fire Danger conditions
(https://weather.gov/rgv/mapcolors#fire, search on Fire Danger)
are right in line and have freshened the statement. We are right
on the edge of Red Flag conditions in the Hidalgo/Brooks corridor
and a very short fused warning may be needed until 5 or 6 PM...but
sustained winds tend to be holding below 20 mph. That said...gusts
can matter...and 30+ mph gusts can quickly spread an active
wildfire so extreme caution is still urged.

Saturday: Consensus of model guidance and continued drying surface
conditions suggest dewpoints..and hence humidity...will be several
ticks lower than the default blended models. Therefore...have
adjusted them downward from Jim Hogg through Zapata and northern
Starr and RH dips accordingly into the mid to upper 20s. Expect
another Fire Danger Statement for these areas, while higher
humidity farther east (30s to 40s) should reduce the threat. Of
course, continued dry fuels and gusty winds can still cause
issues...so Fire Weather may remain a concern elsewhere except
near the coast.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             66  81  70  84 /   0   0   0   0
HARLINGEN               62  84  67  87 /   0   0   0   0
MCALLEN                 64  86  69  89 /   0   0   0   0
RIO GRANDE CITY         63  88  67  92 /   0   0   0   0
SOUTH PADRE ISLAND      70  76  71  77 /   0   0   0   0
BAYVIEW/PORT ISABEL     65  81  68  83 /   0   0   0   0

&&

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

$$

SHORT TERM...52-Goldsmith
LONG TERM....22-Garcia
AVIATION...52-Goldsmith