005
FXUS64 KBRO 261956
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
256 PM CDT Thu Sep 26 2024

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

.SHORT TERM...
(Tonight through Friday night)
Issued at 103 PM CDT Thu Sep 26 2024

Key messages:

* High risk for rip currents and minor coastal flooding associated
  with distant swells from Hurricane Helene.
* A noticeably more refreshing air mass will make for a comfortable
  evening and overnight.
* Plentiful sunshine and seasonable temperatures are on tap on
  Friday albeit with gusty conditions at times.

Cold front has pushed south of the international border this
morning. While it is more of a dew point front, there will be a
noticeable change in air mass especially by this evening. Already,
we are seeing dew points in the 60s across the region, partially
helped by the mixing of drier air from the top of the boundary
layer. Gusty north or northwest winds will subside and become
light overnight tonight as the boundary layer decouples. Patchy
fog could develop in some of the climatologically favored locales
as overnight lows approach crossover but any fog that does develop
should be localized and transient so no impacts are expected.
Forecast wise, expect widespread mid to upper 60s away from the
immediate coast and I-2/US-83 corridor. As for the latter,
temperatures should bottom out in the 69 to 73 range. If we do 71
or lower at Brownsville overnight tonight as forecast, it would be
the coolest reading at KBRO since Apr 23, when we reached a low
of 69.

Friday looks to be a pleasant late September day by RGV standards
with plentiful sunshine, near seasonable temperatures and dew
points in the 60s. Locations west of the I-69C/US-281 corridor are
likely to see dew points dip into the 50s during the afternoon
hours. Expect highs in the low to mid 90s, except mid to upper 80s
across the coastal zones and SPI. Our region will be in the
middle between a 592 decameter (dam) high centered over New
Mexico and a deepening vertically stacked upper low across the
southeast US associated with Hurricane Helene. The result is
subsidence across our region leading to a rain free Friday. High
clouds associated with Hurricane John impacting southwest Mexico
could stream into our region late Friday afternoon to make for a
vibrant sunset.

Quiet weather continues into Friday night and it looks to be very
similar to the prior night except overnight lows should be a
couple of degrees warmer, mainly in the 67-74 range.

Otherwise, the main concern for our region through Friday night
would be the high risk for rip currents as well as minor coastal
flooding associated with the distant swells from Hurricane Helene.
The main window of concern for minor coastal flooding is
overnight tonight around the hours surrounding astronomical high
tide at 342 AM CDT, when wave runup is expected to approach the
dunes. For more details about Helene including the latest
advisories and track, visit nhc.noaa.gov.

&&

.LONG TERM...
(Saturday through next Thursday)
Issued at 103 PM CDT Thu Sep 26 2024

A large H5 low will be centered over the Lower Ohio River Valley
initially, and will subsequently scoot east. Ridging over the
Rockies and High Plains will form a counterpoint to the low,
leaving deep South Texas and the RGV in a relatively quiet weather
area between the two. A weak remnant frontal boundary will be in
the vicinity. The upshot is that the CWA will see drier air and a
lack of rainfall Saturday and Sunday.

I used the NBM to initialize the forecast. Mid-level ridging will
move overhead from the west by Tuesday, supporting a mix of
clouds and sun and mostly light to moderate onshore winds. That
said, Gulf moisture may also begin to increase early next week, at
least for the Lower RGV. Moisture will have a tough time pushing
very much farther inland than that (the Lower RGV), but it`s
enough to bring a mention of showers into the forecast for Tuesday
through Thursday.

High temperatures will be mainly in the mid 90s through the
forecast. Drier air will help keep heat index values below 100
degrees. Low temperatures will be in the upper 60s to near 70 most
mornings. Coastal hazard threats from Helene will be mostly
dissipated by this weekend with a return of lower wave heights,
and thus coastal flooding and rip current concerns will be
lessened. Long range forecasts hint at a potential tropical system
of interest late in the long term, still outside the long term
window, but will need to keep an eye on the West to Northwest
Caribbean mid to late next week for possible development.

&&

.AVIATION...
(18Z TAFS)
Issued at 1204 PM CDT Thu Sep 26 2024

A cold front has passed through the region and VFR conditions
will prevail through the TAF period at all aerodromes. Behind the
front winds will remain between 10 and 15 kts with gusts to
around 20 kts through this afternoon. Winds will decrease this
evening becoming light and variable.

&&

.MARINE...
Issued at 103 PM CDT Thu Sep 26 2024

Tonight through Friday night...A Small Craft Advisory is in
effect for our offshore Gulf waters between the mouth of the Rio
Grande and Baffin Bay from 20 to 60 nm through 1 PM CDT Friday
with waves of 4-8 ft, locally higher across the outermost waters.
Winds gusting 20-25 mph, locally 30 mph this afternoon will begin
to subside this evening, falling to 10-15 mph overnight and
staying below 20 mph through Friday night.

Saturday through Tuesday night...we expect light to moderate winds
and low to moderate seas through Tuesday night. A few showers will
return to the forecast on Tuesday.

Worth a mention: In the Western Caribbean an area of low pressure
could form by the middle of next week. Environmental conditions are
expected to be conducive for slow development thereafter, while the
system moves generally northwestward. Low (20 percent) formation
chances through 7 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             71  90  72  92 /   0   0   0   0
HARLINGEN               67  92  68  94 /   0   0   0   0
MCALLEN                 71  95  72  97 /   0   0   0   0
RIO GRANDE CITY         69  92  69  95 /   0   0   0   0
SOUTH PADRE ISLAND      77  86  77  88 /   0   0   0   0
BAYVIEW/PORT ISABEL     71  89  70  90 /   0   0   0   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk through late Friday night for TXZ451-454-
     455.

      from 10 PM CDT this evening through Friday morning for TXZ451-
     454-455.

GM...Small Craft Advisory until 1 PM CDT Friday for GMZ170-175.

&&

$$

SHORT TERM...68-McGinnis
LONG TERM....54-BHM
AVIATION...68-McGinnis