537
FXUS64 KBRO 191958
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
258 PM CDT Thu Sep 19 2024

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

.SHORT TERM...
(Tonight through Friday night)
Issued at 234 PM CDT Thu Sep 19 2024

Persistence will be the main guidance for the short-term forecast.
Synoptic pattern across the CONUS remain in a highly amplified omega
block pattern with strong mid-level ridge anchored over Texas and
north Mexico. The ridge maintains the near to slightly above normal
high temperatures and with a persistent southeast fetch of Gulf
moisture dew points remain elevated in the 76-81 degree range. As we
know the combination of heat and humidity (high dew point air)
allows for the "feel like" temperatures to soar well over 100
degrees. This will be the case for Friday afternoon as it has been
most of the week. WPCs experimental heat risk shows a moderate risk
for all areas of Deep South Texas, except the immediate coastline.
With this said, expect another SPS for heat to be issued Friday to
cover heat indices in the 106-110 range with a few locations
touching 111-113 for an hours or two.   Overnight conditons also
remain rather persistent with warmer than normal low temperature,
courtesy of elevated dew points, with fair skies and light winds
making for muggy conditions tonight and again Friday night.

As for rain chances, the stubborn ridge and no significant
disturbance is limiting shower and thunderstorm coverage. Model
guidance does show a widespread of probability of 5-45 percent and
blend of NBM and Consall narrows the range to a more seasonal 15-30
percent.  Differential heating and weak sea-breeze will be the
forcing and lifting mechanism to fire off the isolated convection
for the late morning through the afternoon.


&&

.LONG TERM...
(Saturday through next Thursday)
Issued at 234 PM CDT Thu Sep 19 2024

Midlevel high pressure will remain over Deep South Texas through
the period. As a trough in the four corners lifts into the Great
Lakes into early next week, the ridge axis will move eastward off
the eastern US coast and flatten over our region. At the surface,
high pressure will remain over the northern Gulf coast into the SE
US. Rain chances will be somewhat limited thanks to the ridging
overhead through this weekend, though isolated seabreeze showers
and thunderstorms will be possible through the weekend (generally
20- 30%). As we head in the workweek, this ridge begins to
breakdown and a weak coastal trough develops allowing rain to
increase slightly (25-45%), with the bulk of the activity
remaining along the seabreeze and offshore.

Things get interesting as we head into midweek. The National
Hurricane Center is monitoring an area for potential tropical
development in the Northwestern Carribean Sea. Current projected
movement is north or northwest over the northwestern Carribean or
southern Gulf with a 40% chance of tropical development (medium) in
the next 7 days. This entity will be a major driver in the forecast
from Wednesday onwards. Will continue to run with the NBM for the
middle to end of next week which has the aforementioned trough moving
westward and increasing moisture from the Gulf that will increase
rain chances (40-60%) for Wednesday and Thursday. Because of the
high uncertainty of the development, strength and movement of the
disturbance, the forecast is likely to continue to evolve over the
coming days.

Temperatures throughout the period will remain near normal with
highs in the low to mid 90s. Any rain or thunderstorm activity early
in the afternoon, especially as we head into the middle of next week
could keep temperatures just below normal for affected areas.
Overnight lows will remain generally in the low to mid 70s. While
Heat Advisories are not likely through the period, elevated heat
indices on Saturday could warrant a Special Weather Statement.

&&

.AVIATION...
(18Z TAFS)
Issued at 1232 PM CDT Thu Sep 19 2024

Main aviation impact this afternoon will be isolated showers and
thunderstorms associated with the sea breeze with best chances
from 18-23Z accompanying a primarily southeast flow. Flight
categories are forecast to remain primarily VFR this afternoon and
overnight outside of the convection. There is medium (30-40%)
probability of patches of MVFR to IFR ceilings at KMFE starting
as early as 8Z and lasting through 15Z, cloud bases at KMFE may
drop briefly below 1000 feet as was the case Thursday morning.
Daytime convection is forecast again Friday with PROB30s in place
for 16z at KHRL and KBRO to highlight uncertainty in spatial and
temporal coverage of isolated and scattered showers.

&&

.MARINE...
Issued at 234 PM CDT Thu Sep 19 2024

Now through Friday night...Favorable marine conditions persist
over the Laguna Madre and the Gulf waters through Friday.
Pressure gradient remains weak over the Gulf of Mexico as broad
surface high pressure remains centered over the northern Gulf.
Light Southeast wind and slight seas observed over the Lower Texas
coastal waters are expected to persist through the period.
Isolated showers or thunderstorms are possible.

Saturday through Tuesday...Light to moderate winds and light seas
are expected the period with seas of 1 to 2 feet. There is a slight
chance of showers and thunderstorms daily, which may result in brief
periods of elevated winds and seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             80  92  79  91 /  10  30  10  40
HARLINGEN               76  92  75  92 /   0  30   0  40
MCALLEN                 80  97  79  96 /  10  30   0  30
RIO GRANDE CITY         78  95  77  94 /  20  10  10  20
SOUTH PADRE ISLAND      82  88  81  87 /  20  30  20  30
BAYVIEW/PORT ISABEL     78  90  77  89 /  10  30  10  20

&&

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

$$

SHORT TERM...59-GB/69-HK
LONG TERM....68-McGinnis
AVIATION...59-GB/69-HK