-- Discussion containing changed information from previous version are highlighted. --
823
FXUS64 KBRO 251749
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
1249 PM CDT Sat May 25 2024

...New AVIATION...

.SHORT TERM...
(Today through Sunday)
Issued at 343 AM CDT Sat May 25 2024

Key Messages:

- Excessive, Dangerous, Record-Breaking Heat Likely today and Sunday
  with Triple digit highs for Brownsville, Harlingen, and McAllen.
- Heat Indices between 110-120F Saturday, 112-122F Sunday.
- High Risk for Rip Currents continue through Sunday.

.Short term...500mb ridge holding strong over north Mexico and South
Texas and with latest deterministic models showing the center of the
heat dome nearing the Rio Grande Sunday and Monday. The extreme heat
is only expected to go up albeit, just a few more degrees
maintaining the threat of records being broken.  Persistence is the
best forecast with Excessive Heat Warnings and overnight Heat
Advisories in place today and likely continuing tonight and
repeating Sunday. To avoid any confusion will not issue additional
heat advisories or warnings and let today`s hazards run their course
before reissuing for Saturday night and Sunday.

As the center of the 595dm subtropical ridge edges north the next 24-36
hours, 500mb heights and 1000-500mb thicknesses tick upward
supporting an increase in ambient temperatures of 1-3 degrees
Sunday. All the latest guidance support this slight bump up in highs
and in some cases overnight lows.  One thing that is for sure not
change is the heat indices as the persistent moderate to strong
pressure gradient continues to provide a breezy and gusty southeast
to south flow keeping dew points elevated.

The persistence moderate to fresh southeast wind over the Gulf of
Mexico continue to drive a moderate swell train towards the lower
Texas coast. Rip Current procedure suggest a continuation of a High
Rip Current Risk through Sunday.

&&

.LONG TERM...
(Sunday night through Friday)
Issued at 343 AM CDT Sat May 25 2024

Mid to upper level ridging centered over Mexico will continue to
provide strong subsidence across Deep South Texas and the Rio Grande
Valley. Dangerous heat will persist through early next week with
triple-digit temperatures and heat indices as steady low level
southerly to southeasterly flow will maintain elevated dew points.

High temperatures will likely reach around 100 degrees along the I-
69E corridor to near 110 degrees across the Rio Grande Plains on
Memorial Day. Heat indices will range from 112 to 122 degrees across
the region Monday afternoon. Record high temperatures will likely be
tied or broken across the area on Memorial Day. Overnight
temperatures will remain warm with lows in the upper 70s across the
Northern Ranchlands to the low to mid 80s across the Rio Grande
Valley.

The very warm nights and dangerously hot days will cause heat
illnesses for anyone who is not acclimated to the heat or does not
take proper precautions against the heat. The NWS HeatRisk tool
indicates an extreme risk of heat-related impacts to those spending
any time outdoors.

The 500 mb ridge is expected to weaken slightly and allow for the
passage of some upper level disturbances/shortwaves. The best rain
chances will be Monday evening/night as some convection may develop
over the high terrain of Mexico/Sierra Madre and drift towards the
Rio Grande Plains. Will lean towards the NBM for pops through the
extended. Slightly lower high temperatures and more seasonable heat
indices are expected Tuesday through Friday.

&&

.AVIATION...
-- Changed Discussion --
(18Z TAFS)
Issued at 1248 PM CDT Sat May 25 2024

Through 18z Sunday....As of this update, VFR-MVFR conditions were
taking place at the terminals under mostly sunny skies and with some
haze in the area, particularly over KHRL and KMFE restricting
visibilities down to 5-6 statute miles. Haze reducing vsbys down to
MVFR levels is the main concern this afternoon into this evening.
Otherwise, expect mainly VFR conditions to take over under mostly
sunny skies.

Similar to the past couple of night, a rinse and repeat trend will
continue. Clouds are expected to increase in coverage and lower in
elevation tonight which will bring flight categories back down to
MVFR. There could be some patchy mist/haze around too. During the
day on Sunday, clouds will once again scour out/clear giving way to
a return to mainly VFR ceilings. There could be some haze around
reducing visibilities down to MVFR levels.

Winds will remain out of the southeast 10-15 kts with gusts between
20-25 kts through much if not all of the 18z TAF cycle. The one time
where gusts may diminish will be tonight.
-- End Changed Discussion --

&&

.MARINE...
Issued at 343 AM CDT Sat May 25 2024

Today through Sunday: The enhanced pressure gradient over the
Gulf of Mexico persist through Sunday. Surface ridge remains over
the Gulf and is combining with the persistent thermal low over NE
Mexico and S Texas maintaining moderate to fresh southeast winds
and a moderate sea state. Expect winds to approach but remain just
shy of Small Craft Advisory criteria of 20 kts on the Laguna
Madre during the day shifting over the Gulf overnight. A moderate
sea with a moderate swell period will continue over the Gulf
waters this weekend.

Sunday night through Friday...Moderate winds and seas will prevail
through the period. Small Craft Exercise Caution conditions will
continue through the upcoming week along the Laguna Madre and Gulf
waters due to an enhanced pressure gradient. A brief period of Small
Craft Advisories will possible during the afternoon hours as wind
speeds increase.

&&

.CLIMATE...

Record Daytime Highs (F) for Saturday May 25, 2024

Brownsville 97 in 2018 (Forecast high 100)
Harlingen 97 in 2018 (Forecast high 100)
McAllen 103 in 1989 (Forecast high 103)

Record High Minimums (F) for tonight (May 26)

Brownsville 81 in 2000 (Forecast low 83)
Harlingen 80 in 2000 (Forecast low 80)
McAllen 81 in 2017 (Forecast low 81)

Record Daytime Highs (F) for Sunday May 26, 2024

Brownsville 97 in 2018 (Forecast high 100)
Harlingen 99 in 2018 (Forecast high 101)
McAllen 102 in 2017 (Forecast high 105)

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
BROWNSVILLE             82 101  82  98 /   0   0   0   0
HARLINGEN               79 101  80 101 /   0   0   0  10
MCALLEN                 81 105  82 104 /   0   0   0  10
RIO GRANDE CITY         81 108  80 106 /   0   0  10  10
SOUTH PADRE ISLAND      83  89  83  88 /   0   0   0   0
BAYVIEW/PORT ISABEL     81  95  80  95 /   0   0   0   0
-- End Changed Discussion --

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
TX...Excessive Heat Warning until 7 PM CDT this evening for
     TXZ248>255-353.

     Heat Advisory until 7 PM CDT this evening for TXZ351-354-355.

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

GM...None.
-- End Changed Discussion --
&&

$$

SHORT TERM...59-GB
LONG TERM....63-KC
AVIATION...23-Evbuoma