366
FXUS64 KBRO 161127 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
627 AM CDT Mon Sep 16 2024

...New AVIATION...

.SHORT TERM...
(Today through Tuesday)
Issued at 255 AM CDT Mon Sep 16 2024

The biggest story for today is the potential for another round of
showers and thunderstorms to impact the area. There is still plenty
of moisture in the environment and instability as well that will
foster a favorable environment for convective development. These
showers and thunderstorms that do develop will have the potential to
produce heavy rainfall as well. Should any showers and thunderstorms
bring heavy rainfall train to the same areas, there is the
possibility that some minor flooding could occur. By the evening
hours, rain chances are expected to drastically decrease. Tomorrow,
rain chances become more isolated with better chances occurring
along the coast with the seabreeze during the afternoon.

As for the temperatures, the expected cloud coverage for today
should keep the high temperatures a bit cooler than normal with the
highs being in the upper 80s to low 90s. As for tomorrow, the high
temperatures for Tuesday start to warm back up more as the cloud
coverage is expected to be less, allowing for the temperatures to
warm back up to the lower 90s for the region. The low temperatures
on the other hand, will are expected to be about normal in the 70s
for tonight.

&&

.LONG TERM...
(Tuesday night through Sunday)
Issued at 255 AM CDT Mon Sep 16 2024

Overall, the extended period looks to feature slightly above normal
temperatures for deep south Texas. A series of unseasonably potent
shortwave troughs will dig into southern California, allowing the
swath of below normal 500mb geopotential height field to expand
eastward. However, the area of below normal 500mb height field
across the southeast U.S. will also expand westward into the
Appalachian Mountains. The result is for a neutrally tilted omega
block to become positively tilted along an axis from Great Bend, TX
into the Upper Peninsula of Michigan. In other words, deep South
Texas and the RGV will likely see continued late summer warmth
through the start of astronomical fall, which begins on the morning
of Sunday, September 22. For reference, typical daytime highs are in
the 91-94 range, while overnight lows are around 73-76. The ridging
regime with weakly forced mesoscale and synoptic environment means
that the main rainfall and convective chances will likely come from
local sea breeze boundaries. This means that on most days, PoPs will
generally remain below slight chance (less than 15 percent) west of
I-69C/US-281 corridor, with a slight to low chance PoP (15 to 25
percent) along and east of it. Temperatures wise, with dew points
remaining elevated in the mid to upper 70s, ensemble guidance shows
elevated probabilities of apparent temperatures AOA 105 degrees on
Wednesday and Thursday. The experimental WPC heat risk tool
currently shows pockets of moderate (level 3 of 4) heat risk on
Wednesday and more widespread moderate heat risk on Thursday.
Remember that the dry bulb or ambient air temperature does not tell
the full story of what it feels. For instance, a normal high ambient
temperature of 93 and dew point of 78 yields a heat index of 109,
enough to trigger a SPS for warm conditions for our CWA.

Heading into the weekend, the amplitude of the positively tilted
omega block begins to wane, but that could also well be a function
of forecast uncertainty. Indeed, the apparent temperature difference
between the 75th and 25th percentile of the National Blend of Models
increases into the 7-10 degree range for this weekend. So the jury
remains out on whether the RGV can start astronomical autumn (this
Sunday) with a break from the oppressive summer heat. Stay tuned.

&&

.AVIATION...
(12Z TAFS)
Issued at 622 AM CDT Mon Sep 16 2024

Mostly VFR conditions are expected for the duration of the TAF
period. Light southeasterly winds are expected to persist through
the duration of the TAF cycle as well. More convection is expected
to occur today with TEMPO and PROB30 groups being used to estimate
the timing. Showers and thunderstorms today are expected to bring
MVFR ceilings and reduced visibilities. Some showers and
thunderstorms are capable of producing heavy rainfall and could
further reduce visibilities to IFR, but confidence was not high
enough to include in the TAF package.

&&

.MARINE...
Issued at 255 AM CDT Mon Sep 16 2024

Today through Tuesday...Mostly favorable conditions are expected
through Tuesday with light to moderate southeasterly winds and low
seas. Isolated showers and thunderstorms are possible and could
produce periods of heavy rainfall and locally enhanced winds and
seas.

Tuesday night through Sunday....Outside of any convection,
favorable marine conditions (light to moderate winds and light
seas) are expected to prevail Tuesday night through Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             88  77  91  78 /  70  30  40  10
HARLINGEN               89  74  92  75 /  70  10  40   0
MCALLEN                 91  77  95  79 /  70  20  30   0
RIO GRANDE CITY         88  75  92  76 /  80  30  30  10
SOUTH PADRE ISLAND      86  80  87  82 /  70  40  30  10
BAYVIEW/PORT ISABEL     87  76  89  77 /  70  30  30  10

&&

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

$$

SHORT TERM...64-Katz
LONG TERM....Chai
AVIATION...64-Katz