459
FXUS64 KBRO 091123
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
623 AM CDT Mon Sep 9 2024

...New AVIATION...

.SHORT TERM...
(Today through Tuesday)
Issued at 454 AM CDT Mon Sep 9 2024

Key Messages:

* Morning commute to be impacted by moderate to heavy rainfall in
  Brownsville; evening commute could also be impacted as well

* A Tropical Storm Watch is in effect for the coastal and island
  portions of Cameron and Willacy Counties till Tuesday evening

* A Tropical Storm Watch is in effect for the Laguna Madre from Port
  Mansfield to the mouth of the Rio Grande River, the Gulf of Mexico
  waters from 0 to 60 nautical miles offshore from Port Mansfield to
  the mouth of the Rio Grande River, and 20 to 60 nautical miles
  offshore from Port Mansfield to Baffin Bay till Tuesday evening

* A Flood Watch is in effect for Cameron, Willacy, and Kenedy
  Counties till Wednesday morning

* A Small Craft Advisory remains in effect for the Laguna Madre from
  Port Mansfield to Baffin Bay and the nearshore Gulf Waters 0 to 20
  nautical miles of Port Mansfield till 7 PM CDT Tuesday

* A Coastal Flood Advisory, a High Surf Advisory, and a High Risk
  for Rip Currents remains in effect through Tuesday evening

A multi-hazard event, from coastal flooding and high risk for rip
currents to breezy, potentially tropical storm force winds and
inland areal/flash flooding is set to take shape through the
short term forecast period amid a developing tropical
cyclone/potential tropical cyclone six (PTC6) churning near the
western Gulf of Mexico coast. Per the latest 1 AM CDT Advisory
from the National Hurricane Center (NHC), this developing tropical
system was located about 320 miles south-southeast from the mouth
of the Rio Grande River, moving north-northwest at 5 mph. This
system has a central minimum pressure of 1003 millibars with max
sustained winds of 50 mph. Latest surface analysis, satellite, and
radar data show the tropical system (PTC6`s) rain bands just to
the east-southeast of Brownsville. Trends suggest that moderate to
heavy rainfall associated with these bands will begin arrive over
Brownsville just before sunrise in the next hour or so. That
said, expect for conditions to begin to rapidly deteriorate over
the next couple of hours as these rain bands make their way
inland, especially over/near Brownsville. This will have impacts
on the morning commute. Through today, expect for rounds or waves
of rain showers, some which will be moderate to heavy at times.

The tropical system is expected to remain offshore over the Gulf
Waters as it tracks north-northeastward. In fact, model trends over
the past 24 hours has favored an eastward shift in the track. That
said, this storm will be in close enough proximity and broad
enough to still pose impacts across Deep South Texas and the Rio
Grande Valley over the next 24 to 48 hours. Heavy rainfall,
including the potential for localized flooding and hazardous
marine/coastal conditions will be the main threats. Winds will be
more of a lesser concern or secondary threat. Our immediate
coastal areas as well as areas over the Gulf Waters will be at
greatest risks from impacts from this tropical system.

Given the anomalously high atmospheric moisture content with PWATs
ranging between 2.5-3 inches, which is +1 to +3 STDEVs above normal,
rainfall output and efficiency will undoubtedly be strong.
Additionally, given the wet antecedent conditions from past rains,
the potential for flooding exists, especially over areas that
experience repeated instances or training of heavy rainfall. That
said, localized flooding is possible. The Weather Prediction
Center (WPC) has parts of the area under a Marginal to Slight Risk
for Excessive rainfall in it`s Day 1 (today) and Day 2 (Tuesday)
Excessive Rainfall Outlook (ERO), with the Slight Risk confined
along the coastal counties (i.e. generally along and east of
between I-69C and I-69E) and the Marginal Risk further inland
(i.e. along/west of I-69C). In all, anywhere from 3 to 6 inches of
rainfall with locally higher amounts up to 10 inches can be
expected by Wednesday morning. The highest QPF will be located
over/along our coastal areas, especially near Brownsville
(southeastern Cameron County). A Flood Watch has been hoisted for
all of Cameron, Willacy, and Kenedy Counties till Wednesday
morning.

The other major concern will be hazardous marine/coastal conditions
through at least Tuesday night, likely persisting beyond. An
enhanced pressure gradient associated with the developing tropical
system (PTC6) will result in breezy north-northeast winds 10-20
mph gusting as high as 30-45 mph with the highest gusts expected
over the Gulf waters. These conditions will lead to high seas
between 5-10 feet today increasing to 10-17 feet Tuesday/Tuesday
night, coastal flooding, high risk for rip currents, and high
surf. That said, a Small Craft Advisory, Coastal Flood Advisory,
High Surf Advisory, and High Risk for Rip Currents are in effect
through Tuesday evening or till 7 PM CDT Tuesday for Kenedy,
Willacy, Cameron Island Counties or areas near/along the beach.

Winds will be the other concern, but again, more of a secondary
risk/threat, especially for areas inland. As mentioned, north-
northeast winds will be sustained between 10-20 mph with gusts
between 30-45 mph. The strongest of winds will be offshore in
closer proximity to the tropical system. Given the situation, a
Tropical Storm Watch is in effect for the Gulf Waters. It`s
important to note that this storm could experience rapid
intensification given the very warm sea surface temperatures
(SSTs), which are in the 80s.

Temperatures are expected to run cooler than normal today and on
Tuesday given the copious amounts of cloud cover and rainfall.
Highs are progged to mainly be in the 80s across Deep South Texas
and the Rio Grande Valley. Nights will continue warm and humid
with lows in the low to mid 70s.

&&

.LONG TERM...
(Tuesday night through Sunday)
Issued at 454 AM CDT Mon Sep 9 2024

Key Messages:

* Unsettled weather pattern looks to continue with day-to-day
  chances for showers and storms

* Temperatures will attempt to trend warmer

* Hazardous marine conditions to start will become more
  favorable late week into next weekend

The weather pattern during the long term forecast period looks to
remain unsettled. Global deterministic models/ensembles continue
to depict day-to-day diurnal chances for showers and thunderstorms
through the period. Continued high atmospheric moisture content
coupled with increased instability along a sea breeze, will result
in day-to-day chances for showers and storms.

An uptrend in temperatures are expected during the long term period
with high temperatures returning back into the 90s and overnight
lows in the mid 70s to near 80F.

&&

.AVIATION...
(12Z TAFS)
Issued at 622 AM CDT Mon Sep 9 2024

Through 12z Tuesday....

Key Aviation IDSS Messages for the 12z TAF period:

* Deteriorating flying conditions to take place this morning onward

* Mainly MVFR/IFR conditions expected through today

* Breezy north to northeast winds will persist through the 12z TAF
  period

Deteriorating flying conditions are expected to continue through
this morning. The latest GOES-East and Doppler radar imagery depicts
the first rain bands over the southeastern portions of the area
(i.e. Cameron and Willacy Counties). These rain bands are connected
to Potential Tropical Cyclone Six (PTC6) as it continues to
develop over the western Gulf of Mexico coast. As of this update,
VFR conditions were taking place at KMFE with MVFR conditions
taking place at KBRO and KHRL under a SCT-OVC deck of cumulonimbus
and strato-cumulus clouds with bases between 700-3,000 feet AGL
and unrestricted visibilities. Expect for MVFR-IFR conditions to
become more of the prevailing flight categories as rain bands
associated with PTC6 continue to increase. Heavy rainfall is
possible, especially over KBRO and KHRL through today and into
tonight.

North to northeast winds 10-20 kts with gusts as high as 25 kts are
expected to persist through the 12z TAF cycle.

&&

.MARINE...
Issued at 454 AM CDT Mon Sep 9 2024

Today through Tuesday night....Multiple hazardous marine/coastal
conditions are expected through the short term period or through
Tuesday night. An enhanced pressure gradient from the developing
tropical cyclone will result in breezy north-northeast winds between
10-20 kts with gusts up to 35 kts. This will lead to high/rough seas
and a high risk for rip currents. A Small Craft Advisory is in
effect, in addition to a High Risk for Rip Currents, a High Surf
Advisory, and a Coastal Flood Advisory through Tuesday evening.

Wednesday through Monday....The period will start off with continued
hazardous marine conditions. However, as the tropical system pulls
aways, marine conditions are expected to return or become more
favorable through the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             79  76  82  76 /  90  90  90  60
HARLINGEN               78  73  82  74 /  90  70  90  50
MCALLEN                 81  74  86  77 /  80  70  80  40
RIO GRANDE CITY         83  72  88  74 /  60  60  60  30
SOUTH PADRE ISLAND      83  79  83  79 /  90  90 100  80
BAYVIEW/PORT ISABEL     81  75  83  74 /  90  80  90  70

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Tropical Storm Watch for TXZ354-355-454-455.

     Flood Watch through Wednesday morning for TXZ251-254-255-351-354-
     355-451-454-455.

     Coastal Flood Advisory until 7 PM CDT Tuesday for TXZ451-454-455.

     High Rip Current Risk through Tuesday evening for TXZ451-454-455.

     High Surf Advisory until 7 PM CDT Tuesday for TXZ451-454-455.

GM...Tropical Storm Watch for GMZ130-132-150-170-175.

     Small Craft Advisory until 7 PM CDT Tuesday for GMZ135-155.

&&

$$

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