495
FXUS64 KBRO 191946
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
246 PM CDT Sat Oct 19 2024

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

.SHORT TERM...
(Tonight through Sunday night)
Issued at 104 PM CDT Sat Oct 19 2024

Key Messages:

- Coastal/Marine Hazards continue through Sunday; High Risk Rip
  Currents, Coastal Flood Potential and Small Craft Advisories.

- Showers and thunderstorms increase in coverage Sunday:
  localized heavy rain possible.

The driving force for the coastal hazards, 1035 mb high pressure
over the Eastern U.S., continues to combine with the broad
circulation of Tropical Storm Nadine producing a long fetch of
strong easterly flow over much of the Gulf of Mexico. This broad
wind flow is directing a building swell train westward impacting
the lower Texas coastal waters through Sunday night. Coastal
flooding potential is highest this evening and tonight with high
tide at 8:22 PM. The combination of the Autumn King tides and the
building swell could push water into the dunes along narrow
beaches making walking and of course driving very difficult to
possibly dangerous. Swimming conditions the rest of today through
Sunday remain dangerous with rip current risk remaining high.

As for sensible weather forecast latest model guidance including
CAMs continue to advertise a few showers moving inland the rest of
the afternoon with increasing chances for rain tonight mainly
over the Gulf and the coastal counties with a good chance of
showers and thunderstorms spreading inland Sunday. First, a surge
of tropical moisture, likely from the northern extent of Tropical
Storm Nadine, moves across the Southwest Gulf of Mexico with
forecast soundings showing pwats nearing 2 inches over the RGV
Sunday. Next this deepening moisture combines with a surface
coastal trough (convergence) and weak diffluence aloft (lift) to
aid in convection development. Subtle CAPE of around 750 J/kg to
allow for isolated thunderstorm which may produce a few downpours.
Probability for moderate rainfall amounts 0.25-1.00 inch is at
40-60%, heavy rainfall over one inch is low 10-30%. Areas that may
see the best coverage and heaviest rainfall Sunday afternoon are
along a band from Kenedy county southwest to Edinburg and McAllen
in Southern Hidalgo county where the sea breeze front (convergence
zone) becomes more defined. Rain chances begin to wane Sunday
evening with instability lowering with the end of daytime heating.

Temperatures and humidity very October like with lows in the 60s
to lower 70s and highs in the mid to upper 80s.

&&

.LONG TERM...
(Monday through next Saturday)
Issued at 104 PM CDT Sat Oct 19 2024

Tropical Storm Nadine is moving across the Yucatan Peninsula
today, and though not much will be left of her on the other side,
some tropical moisture will extend north along the Northeast
Mexican coast and lower Texas coast late this weekend and into
Monday (a 2 inch PWAT tongue will reach to the Rio Grande). That
is the thinking and justification for the residual PoPs in the
forecast for Monday, as portrayed by the NBM, which was used to
initialize this afternoon`s forecast package. Moisture surging
north may get a boost by a sea breeze, and there could be a few
rumbles of thunder for the lower Valley before Monday afternoon
is over. Before moving on, I will mention that wave heights will
remain slightly elevated on Monday, courtesy of an easterly fetch
over the Gulf, and residual elevated rip current risk and minor
beach runup will be possible.

That said, the rest of the work week through early next weekend
should serve up a fairly quiet weather pattern. Mid-level ridging
building upstream will keep any continental weather systems from
reaching our area, and surface high pressure will remain dominant
over the Northwest Gulf. Other than the potential for nearby Gulf
showers and weak afternoon sea breezes, we will see mainly light
to moderate east winds, a mix of clouds and sun (more sun the
latter half) and slightly warmer than average temperatures.

&&

.AVIATION...
(18Z TAFS)
Issued at 1228 PM CDT Sat Oct 19 2024

VFR conditions persist today and tonight, however with Gulf of
Mexico moisture increasing the next 24 hours expect an increase in
clouds and showers or an isolated thunderstorm especially Sunday.
There is a low probability 20-30% of MVFR cloud cover tonight with
a medium chance 50-60% of MVFR ceilings developing Sunday morning.
A light east to east-northeast wind around 10 mph is expected
today and Sunday.

&&

.MARINE...
Issued at 104 PM CDT Sat Oct 19 2024

Now through Sunday night...Pressure gradient between strong high
pressure over the Eastern U.S. and broad circulation around
Tropical Storm Nadine over Belize will continue to drive a
building swell train westward. Small Craft Advisory conditions to
persist with forecast marine models suggesting seas nearing 9 feet
over the outer coastal waters Sunday. As for winds a moderate
easterly flow with occasional gusts 20-25 knots over the open Gulf
Waters can be expected tonight through Sunday. The pressure
gradient remains moderately strong Sunday night with seas
remaining elevated which may result in Small Craft Advisories
being extended.

Monday through Thursday night...Moderate east winds and elevated
seas requiring low end small craft advisories will prevail on the
Gulf Waters through Monday night or Tuesday. The driving factor
will be moderate east winds across a long Gulf fetch. Wave heights
will diminish to moderate around Tuesday as east winds across the
Gulf weaken slightly.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             74  86  72  86 /  20  50  10  20
HARLINGEN               69  85  69  86 /  10  50  10  20
MCALLEN                 71  87  71  89 /  10  60  20  20
RIO GRANDE CITY         68  86  68  88 /  10  50  20  10
SOUTH PADRE ISLAND      77  83  77  83 /  20  40  10  10
BAYVIEW/PORT ISABEL     73  84  72  84 /  20  40  10  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Coastal Flood Advisory until 1 AM CDT Tuesday for TXZ451-454-455.

     High Rip Current Risk through late Monday night for TXZ451-454-
     455.

GM...Small Craft Advisory until 1 AM CDT Tuesday for GMZ150-155-170-
     175.

&&

$$

SHORT TERM...59-GB
LONG TERM....54-BHM
AVIATION...59-GB