806
FXUS64 KBRO 151944
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
244 PM CDT Sun Sep 15 2024

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

.SHORT TERM...
(Tonight through Monday night)
Issued at 242 PM CDT Sun Sep 15 2024

Latest model suite continue to indicate a robust unsettled weather
patterning persisting Tonight through Monday. Deep layer moisture
(SFC-300mb) and  weak impulses emanating from the Pacific Ocean and
Gulf of Mexico linger over the forecast region producing scattered
to numerous showers and isolated thunderstorms. Last night and this
morning Soundings indicated record values pwats (2.69, 2.42 inches
respectively) which is pretty impressive for September. WPC has
expanded the Day 1 Marginal Risk for Excessive rainfall Outlook to
cover all of the CWA with exception of the NE portions of Kenedy
county. The heaviest rain thus far today has occurred over the
Northern and Western Ranchlands where 1-3 inches have fallen. Flash
Flood Guidance started out rather high in these areas, thus no
immediate concerns of flooding at this time.

As for the rest of today and tonight, convergence zone setting up
from Cameron to Brooks county with a broken band of heavier showers
and isolated thunderstorms. CAM and even deterministic blends show a
continuing high chance of rain through the evening and overnight
hours. Probability of seeing 1/2-1 inch of rain over the next 6-12
hours is low to medium or 20-40% (10-20% or 2 inches) with the
counties bordering the Rio Grande (Starr, Hidalgo, Cameron) having
the best chances. Pockets of 2-4 inches is not out of the question
through Monday with some nuisance flooding possible where heavy rain
rates occur.

Moisture remains deep and robust Monday before models show more
influence from the mid level ridge building over Texas suppressing
the moisture  late in the day and tomorrow night. Rain chances
remain robust Monday before  tapering off after sunset. Additional
rainfall amounts of 1/2-1+ inches is possible.  At this time, WPC
does  not have the CWA under any Excessive Rainfall outlook but this
may change depending on what occurs over the next 12 hours.

The thick cloud cover and rainfall is doing a number on temperatures
today and will likely impact highs tomorrow. I lowered NBM highs for
Monday by a degree or two and this may not be enough looking at what
has happened today. Forecast highs Monday currently are in the 86-89
degree range.  Overnight are expected to remain elevated as dew
points will be in the 75-81 degree range.  Any "cooler" temperatures
will likely  be brief and occur where rain cooled conditions
develop. These areas are likely to warm back up to match the dew
points maintaining the oppressive humid conditions.

&&

.LONG TERM...
(Tuesday through next Sunday)
Issued at 242 PM CDT Sun Sep 15 2024

Global deterministic forecast models and ensembles continue to
depict a 591 dam heat dome/ridge building over northeastern Mexico
into Deep South Texas through the extended. This will yield slightly
warmer/hotter than normal temperatures during the long-term period
with mainly dry/rain-free conditions in place. Over the past week,
forecast models have trended and favored more ridging developing
over the region.

Atmospheric moisture content will be lower compared to previous
days/weeks with precipitable water (PWAT) values between 1.5-2.0
inches. Despite the lower values, it should be adequate enough to
support a rogue or isolated chance for a shower or thunderstorm
nearly each day. Subsidence, however, with the aforementioned mid-
level ridging in place, will help to keep things mostly suppressed
during the period. That said, expect for mainly dry or rain-free
conditions to prevail through the long-term period with an isolated
chance for a shower or storm nearly each day.

Temperature anomalies will run slightly warmer/hotter than mid-late
September standards through the extended. High temperatures are
expected to be in the mid to upper 90s for much of the region and
for much of the period. Moderate HeatRisk can be expected for the
most part through the extended. There could be areas of major
HeatRisk developing, especially in the Wednesday-Friday timeframe.
Heat indices are expected to range between 105-111F on Tuesday and
again on Saturday (slightly lower values on Sunday). Heat indices
are progged to range between 108-115F Wednesday through Friday. That
said, Special Weather Statements (SPS) to Heat Advisories may be
needed during the expected.

&&

.AVIATION...
(12Z TAFS)
Issued at 616 AM CDT Sun Sep 15 2024

Mostly VFR conditions are expected at all the TAF sites. However,
with isolated to scattered rain chances over the region, there is
the possibility of MVFR conditions. There is the possibility of
some IFR visibilities as any shower or thunderstorm could be
capable of producing heavy rainfall. Light to moderate
southeasterly winds are expected at all TAF sites.

&&

.MARINE...
Issued at 242 PM CDT Sun Sep 15 2024

Tonight through Monday night...Pressure gradient remain weak over
the Gulf of Mexico as surface high pressure remains centered over
the western Gulf and a stationary front remains draped across the
northeast Gulf of Mexico. Light Southeast wind and slight seas
observed over the Lower Texas coastal waters are expected to persist
through the period.  Main impact on the coastal waters will be
scattered to numerous showers and isolated thunderstorms.  Heavy
rainfall, poor visibility within the heavy rainfall and possible
waterspouts as well as lightning is possible within the unsettled
weather conditions.

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

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             77  87  77  92 /  70  70  10  40
HARLINGEN               75  89  74  93 /  50  70   0  40
MCALLEN                 77  89  78  97 /  70  70  10  30
RIO GRANDE CITY         75  86  75  93 /  80  70  10  30
SOUTH PADRE ISLAND      80  86  81  88 /  70  60  20  30
BAYVIEW/PORT ISABEL     75  87  76  91 /  60  60  10  30

&&

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

$$

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