-- Discussion containing changed information from previous version are highlighted. --
696
FXUS64 KBRO 252318
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
618 PM CDT Tue Jun 25 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Wednesday night)
Issued at 325 PM CDT Tue Jun 25 2024

Key Messages
* Late June heat continues through Wednesday, with hot humid
  afternoons and sultry overnights and early mornings

The atmospheric pattern through Wednesday night will feature a
quick resurgence of the "La Canicula" (the "dog days")
ridge...the strong summer ridge centered over southwest
Texas/southeast New Mexico/northern Chihuahua and Coahuila states
and extending across much of Texas. La Canicula has been largely
absent for most of the past ten days...and will only be around for
a few more as the ridge will eventually stretch east-west across
the southern U.S. by Friday, when the deeper easterly flow will
reappear and support deeper moisture return. More on this in the
long term discussion.

Unlike prolonged and searing heat situations with La Canicula,
this shorter duration event, following the beneficial rainfall
from June 18-23, will have less general effect on heating due to
evapotranspiration (which can keep temperatures from rising too
much). At the same time, however, that moisture still in the
ground percolates into above average dewpoint temperatures, which
have been hanging in the 75 to 80 range even from late morning
through early afternoon. That should be the case again Wednesday.

So...the only remaining question is will there be sufficient
duration of heat index values at or above 111, particularly
along/east of the I69C-US281 corridor? At this point, hourly
forecasts fall just short, so will likely handle with special
weather statements to cover the few locations and brief duration
of 111 or higher (Heat Advisory criteria). Any slight increases in
temperature or dewpoint (or both) would nudge over the criteria
line, so will need to monitor closely.

Other than temperatures...with the area being under La Canicula
and associated dry air, expect very limited sea breeze activity on
Wednesday. Still have 20 percent chances (left as showers) east of
the IH-69C corridor and west of Laguna Madre between late morning
and mid afternoon, but there will be only temporary impact on
temperatures.

&&

.LONG TERM...
(Thursday through next Tuesday)
Issued at 325 PM CDT Tue Jun 25 2024

Starting off with the tropics, NHC currently has a 20 percent chance
of tropical development over the Bay of Campeche over the course of
the next 7 days. However, due to the forecasted presence of a mid-
level ridge, most tropical impacts are likely to be south of Deep
South Texas and the Rio Grande Valley. Most of the tropical impacts
based on the current model trends would bring it into Veracruz.
However, increase in rain chances, seas, and dangerous rip currents
are possible for the lower Texas coast around Sunday into Monday.

The mid-level ridge looks to remain in place over the duration of
the long term forecast period, meanwhile the onshore flow at the
surface will help to bring in more tropical moisture over the area.
Models continue to try to produce some convection with the seabreeze
passage. A more normal summer time pattern when there is plenty of
tropical moisture for the atmosphere to work with. Considering the
rise in PWAT values towards the end of the week above 2 inches with
some values close to 2.3 to 2.4 around Friday which would be very
high for late June.

As for the temperatures, high temperatures are expected to be in the
range of mostly 90s, with the upper 90s in the Upper Rio Grande
Valley, while high temperatures in the mid 90s are more likely for
the rest of the region. Meanwhile the heat indices will tip toe
towards Heat Advisory, but are not expected to meet it at this time.
As for the low temperatures, the lows are expected to be mostly in
the 70s, but a few places could get into the 80s.

&&

.AVIATION...
-- Changed Discussion --
(00Z TAFS)
Issued at 617 PM CDT Tue Jun 25 2024

Through 00z Thursday....VFR conditions are expected to persist
through the entirety of the 00z TAF cycle. There may be a few MVFR
clouds around tonight and on Wednesday.

Winds will continue out of the southeast between 5-15 kts through
the 00z TAF period.
-- End Changed Discussion --

&&

.MARINE...
Issued at 325 PM CDT Tue Jun 25 2024

Tonight through Wednesday night...Fairly copacetic conditions
through the period, especially compared with most of the past
week. Seas will continue at 2, perhaps 3 feet in the Gulf with
modest winds...generally 10 knots by day and 10 to 15 knots and
gusty overnight. Laguna Madre conditions flip as usual with sea
breeze enhanced gustiness Wednesday afternoon into early evening
before falling back to around 5 knots from 2-3 AM through 9-10
AM...perfect for early morning fishing.

May see isolated showers in the Gulf overnight each day but
general dry atmosphere will keep coverage fairly low.

Thursday through Next Tuesday...Light to moderate winds and low to
moderate seas will prevail through next Tuesday. While favorable
conditions will start off the period, conditions will soon become
adverse on Friday due to some possible tropical activity to the
south leading to some higher winds and seas that will require Small
Craft Exercise Caution through the weekend and into the next early
work week. After, that favorable conditions do return to the area.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             80  94  80  93 /   0  10  10  40
HARLINGEN               77  95  77  95 /   0  10   0  40
MCALLEN                 80  96  79  95 /   0  10   0  30
RIO GRANDE CITY         78  95  77  93 /  10   0   0  20
SOUTH PADRE ISLAND      83  87  82  88 /   0  10  10  30
BAYVIEW/PORT ISABEL     79  91  79  91 /   0  10   0  30

&&

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

$$

SHORT TERM...52-Goldsmith
LONG TERM....64-Katz
AVIATION...23-Evbuoma