285
FXUS64 KBRO 162010
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
310 PM CDT Sun Jun 16 2024

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

.SHORT TERM...
(Tonight through Monday night)
Issued at 243 PM CDT Sun Jun 16 2024

Key Messages:

* The National Hurricane Center (NHC) has upgraded the potential
  for tropical cyclone development over the Bay of Campeche to a
  30% chance over the next couple of days and a HIGH (70%) chance
  over the next 7 days.

* Showers and thunderstorms are expected to develop over at least
  parts of Deep South Texas as early as Monday

* Hazardous Marine conditions are expected to develop as early as
  Monday Night

The short term forecast period will feature the onset of what is
expected to be a potentially high impact weather event this week
over Deep South Texas and the Rio Grande Valley. All eyes are
focused on the southwestern Gulf of Mexico and the potential for
tropical cyclone development in the days ahead. Latest satellite
and radar observations show a large disorganized area of showers
and thunderstorms over Central America, the Yucatan Peninsula, and
adjacent waters of the northwestern Caribbean. The latest
Tropical Weather Outlook from the National Hurricane Center (NHC)
has upgraded the potential for tropical cyclone development over
the Bay of Campeche to a 30% chance over the next couple of days
and a HIGH (70%) chance over the next 7 days.

With the local forecast area situated in an area of weakness between
two anomalously strong ridge complexes, one being a strengthening or
emerging 594-600 dam sub-tropical heat dome over the eastern U.S.
and another heat ridge to our west over central/western Mexico and
parts of the Desert Southwest, deep tropical moisture that resulted
in a deluge over parts of Florida last week will shift westward this
week. Through Monday night or the short term period, deep tropical
moisture will be pulled into the region from this developing
tropical system. Between this evening and Monday evening, dewpoint
(Td) temperatures, integrated water vapor transport (IVT), and
precipitable water (PWAT) values are expected to increase. In fact,
PWATs are expected to increase from ~1.5 inches this
afternoon/evening to 2 inches or so by Monday night. That said,
shower and thunderstorm chances will begin to expand and increase in
coverage and probability from east to west beginning on Monday.

Through tonight, not much is expected. Latest MSAS surface analysis,
radar, and satellite observations show rain with some embedded
thunder well offshore. This activity through tonight is expected to
largely remain offshore. There could be a shower or perhaps a
thunderstorm reach the coastal areas, particularly from I-69E and
points east tonight. Have low grade (20-30%) PoPs through tonight to
reflect this potential/risk. Otherwise, expect for another warm and
muggy night with overnight lows in the mid 70s to near 80F.

During the day on Monday, the combination of peak sfc based
differential heating and the continued influx of tropical moisture
amid onshore winds, will result in the potential for some diurnal
showers and thunderstorms. Coverage looks to be isolated to
scattered at best. Have 20-40% chance PoPs across much of the CWFA
with categorical PoPs from the coastal areas into the Gulf Waters.
The latest convective outlook from the Storm Prediction Center (SPC)
has much of the area, basically outside of Zapata County, under a
general outlook/risk for thunderstorms on Monday. Otherwise, expect
for another very warm to hot and humid day across the area with
daytime highs ranging from the mid 90s east to lower 100s west.
Increased cloud coverage on Monday is the main reason for the
slightly cooler temperatures compared to today. Nonetheless, with
the increase in dewpoint (Td) temperatures, another Special Weather
Statement (SPS) may be necessary for Monday with forecast heat
indices ranging between 105-11F degrees.

Monday night will be another warm and muggy one with overnight lows
in the mid 70s to near 80F.

&&

.LONG TERM...
(Tuesday through next Sunday)
Issued at 243 PM CDT Sun Jun 16 2024

Key Messages:

* Tropical Cyclone Development in SW Gulf now at 70 percent

* Increasing Rain Chances with Periods of Heavy Rainfall Mid to
   Late Week

* Substantial Beneficial Rainfall Likely with Areas of Flooding
  Possible

The most imminent element and highest confidence of the long term
forecast is the substantial increase of atmosphere moisture and
the chance of rain with a good likelihood of heavy rainfall and
potential flooding concerns. The other concern of course is the
potential Tropical Cyclone development in the Gulf of Mexico. NHC
continues to gradually bump up probabilities (30% in 2 days, 70% 7
days) for an area of disturbed over Central America and Southern
Mexico which is expected to drift into the Bay of Campeche Monday
or Tuesday. Current, projections is for this potential tropical
entity to move into Central Mexico Gulf coast sometime Wednesday.
Another spin up low pressure area is shown by the deterministic
models to form over the southcentral Gulf next Friday or Saturday
and drift northwest next Weekend. There is a lot uncertainty with
this second entity.

As has been mentioned several times, despite any tropical cyclone
develop the moisture content of the overall atmosphere across the
Western Gulf of Mexico and South Texas is very likely to increase
substantially as spokes of energy rotates around the Central
American Gyre (CAG) sending deep tropical moisture north and west
between ridges along the both the Pacific and Atlantic coast.
Although details on where the heaviest rain may fall and how much
may accumulate over the next 3-7 days is highly uncertain, there is
increasing confidence in the model consistency of an extended period
of widespread rainfall some of which will be heavy and producing
potential flooding.  Showers and thunderstorms will be efficient
rainmakers as GFS/ECMWF as well as ensemble models indicating
specific humidity and pwats at 3-4 standard deviations from normal.
Wednesday and Thursday continue to be the days with most extensive
rainfall but any band or cluster of showers/thunderstorm Tuesday
through next Saturday can easily produce 2-4 inch/hr rainfall rates.
Conservatively, general rainfall amounts over the next 7 days may
range 3 to 7 inches (WPC QPF) with locally higher amounts. No flood
Watches are imminent with antecedent soils very dry and can receive
a good amount of water. However, if these wet conditions do
materialize and the potential for excessive rainfall may lead to
areas of flooding. WPC Excessive Rainfall Outlook (ERO) has a
marginal to slight risk for rainfall exceeding Flash Flood Guidance
Tuesday-Thursday for all or portions of Deep South Texas.

Coastal and local beaches will be highly likely to see a long period
of hazardous conditons as the pressure gradient strengthens over the
Gulf and the entrainment of showers and thunderstorms.  High rip
current risk, coastal flooding, high surf and gale force gusts are
all possible with periodic advisories or warnings through next
weekend.

Temperature forecast will be a "Nothing Burger" for once with the
increased cloud cover and rainfall allowing temperatures to stay
near or drop below normal.

&&

.AVIATION...
(18Z TAFS)
Issued at 1218 PM CDT Sun Jun 16 2024

Through 18z Tuesday....VFR conditions are expected to prevail
through the entire 18z TAF cycle under a FEW-SCT deck of cumulus to
stratocumulus clouds with bases ranging between 3,000-6,000 feet AGL
and unrestricted visibilities.

The chance for showers and thunderstorms increase towards the end
of the TAF period (Monday afternoon/evening) as deep tropical
moisture connected to a developing tropical system in the
Southwestern Gulf continues to advect into the region.

Onshore winds are expected to continue out of the east-southeast
between 7-15 kts through the 18z TAF period. There could be
occasional gusts between 20-25 kts during the afternoon and
evening hours.

&&

.MARINE...
Issued at 243 PM CDT Sun Jun 16 2024

Tuesday through Sunday...Marine conditions will be deteriorating
through the week and likely remaining adverse to hazardous next
weekend as winds, seas as well as showers and thunderstorms
increase. One and possibly a second tropical low pressure area
could form and pass over the southwestern and central Gulf of
Mexico respectively. NHC is monitoring possible tropical cyclone
development over the Bay of Campeche Tue/Wed and another potential
tropical low next Fri/Sat in the South Central Gulf. The first
potential cyclone low has a 30% of development in next 2 days and
70% in the next 7 days. A tightening pressure gradient between the
overall lower pressure over the Southern Gulf and Southern Mexico
to combine with high pressure extending into the northern Gulf to
produce a fresh to strong easterly fetch of winds across much of
the Gulf of Mexico. An Extended period of Small Craft Advisories
is likely from Tuesday through at least Friday mainly due to
elevated seas/swells with a medium probability (40-60%) of seas
exceeding 10 feet. Strongest winds Wednesday, Wed night and
Thursday may gust near gale force at times. Stay tuned to the
latest marine forecast for any possible Tropical cyclone
advisories, Watches or Warning through the next week.

(Tonight through Monday Night): Marine conditions are
expected to gradually deteriorate and become more and more adverse
through Monday night. A potential developing tropical cyclone over
the Southwestern Gulf will help to enhance the pressure gradient.
This will result in light east-southeast winds becoming more
moderate on Monday and Monday evening. Increased ocean swells from
higher winds and seas over the middle parts of the Gulf of Mexico
will result in higher seas Monday into Monday night. SCEC conditions
are possible for the Gulf Waters as early as Monday and Small Craft
Advisory (SCA) conditions are possible for the Gulf Waters as early
as Monday night. Lastly, a MODERATE RISK of rip currents are
expected at the local beaches on Monday.


&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             80  94  81  92 /  30  60  50  80
HARLINGEN               76  95  78  93 /  20  50  40  70
MCALLEN                 80  98  80  96 /  10  30  20  60
RIO GRANDE CITY         79  99  78  95 /   0  10  10  40
SOUTH PADRE ISLAND      83  87  83  87 /  50  60  60  80
BAYVIEW/PORT ISABEL     80  91  80  90 /  40  60  50  80

&&

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

$$

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