477
FXUS64 KBRO 171730 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1230 PM CDT Mon Jun 17 2024

...New AVIATION...

.SHORT TERM...
(Today through Tuesday)
Issued at 304 AM CDT Mon Jun 17 2024

This portion of the total forecast is expected to be the start of
the much-discussed and much- anticipated significant
precipitation event for Deep South Texas and the Rio Grande
Valley. The latest Tropical Weather Outlook from the National
Hurricane Center lists a 60% chance of tropical formation over the
southwestern Gulf of Mexico through the next 48 hours, and a 70%
chance of tropical formation over the southwestern Gulf of Mexico
through the next seven days. As this potential tropical system,
combined with steadily-deepening tropical moisture (with
precipitable water values ranging between 2 and 2.5 inches), moves
towards the western coast of the Gulf of Mexico,
isolated/scattered showers and thunderstorms today and tonight
will become scattered to numerous on Tuesday across the BRO CWFA.

Temperature-wise, above normal values are forecast for today and
tonight, with daytime highs on Tuesday cooled to more near normal
levels due to increased cloudiness and rain chances. Heat indices do
not suggest a HEAT ADVISORY during the short term forecast period,
so will cover the indices with a SPECIAL WEATHER STATEMENT today and
tomorrow.

Finally, slightly more adverse marine conditions, courtesy of an
increase in winds and building of seas, will lead to an elevated
risk of rip currents at the local beaches today through Tuesday.

&&

.LONG TERM...
(Tuesday night through Sunday)
Issued at 304 AM CDT Mon Jun 17 2024

Key Messages:

* Tropical Cyclone Development in the SW Gulf remains at 70 percent

* Increasing Rain Chances with Periods of Heavy Rainfall around Mid
  through Late Week.

* Substantial Beneficial Rainfall Likely with Areas of Flooding
  Possible

Confidence remains high with increasing atmospheric moisture and
the chances of rain increasing leading to periods of heavy rainfall
and potential flooding concerns in the long term forecast period.
The potential development of a tropical cyclone in the SW Gulf of
Mexico has increased to 60 percent within the next 48 hours and 70
percent within the next 7 days, though the system will not be around
that long. Currently the system is located over the Central America
and Southern Mexico, but is expected to move into the Bay of
Campeche either today or tomorrow. Current model guidance still
shows the center of this system moving into Central Mexico late
Wednesday into Thursday. The model guidance does still show that
there is another spin up that forms towards the end of the long term
forecast period as well, however confidence is not high on the
second system at this point.

Moving into the main event of the long term forecast period, the
long awaited rainfall that is highly anticpated for Deep South Texas
and the Rio Grande Valley. The moisture content of the atmosphere
over the Western Gulf of Mexico and Deep South Texas is very likely
to increase drastically as deep tropical moisture is transported
north and west between the ridges along the Pacific and Atlantic
coast. By the start of the long term forecast period the PWATS over
the region are around 1.9 inches based on the GFS and the NAM,
however the ECMWF has PWATS at 2.1 inches. PWATS continue to rise
through the day on Wednesday eventually reaching its peak on
Wednesday night at a value of 2.9 inches. The current total QPF is
in the range of about 4 to 7 inches. While the soils are very dry
and could take up quite a lot of rainfall, there is still the
concern that some flooding could take place if heavy rain fall is
persistent enough. WPC currently has a marginal to slight risk for
Excessive Rainfall Tuesday through Thursday for parts or all of Deep
South Texas and the Rio Grande Valley.

Expect many hazards to be in effect for the beaches during the long
term forecast period as well. An enhanced pressure gradient is going
to strengthen the southeasterly flow that will in turn build even
greater swell. The result of this will be an increase in Rip Current
risk, coastal flooding, high surf, and possible gale force gusts.

Lastly, the temperatures for the long term forecast period. With the
expected cloud coverage from the rain, high temperatures are not
expected to be too hot and actually close to normal. As such the
high temperatures are expected to be in the range of upper 80s to
low 90s. While the low temperatures are expected to be mostly in the
70s, with a few places getting into the 80s.

&&

.AVIATION...
(18Z TAFS)
Issued at 1227 PM CDT Mon Jun 17 2024

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

The main concern during the 18z period will be the risk for showers
and thunderstorms developing (mainly during the afternoon and
overnight hours). Forecast models continue to suggest the
potential for showers and thunderstorms developing later this
evening/tonight and then again during the day on Tuesday. These
showers and thunderstorms are associated with a plume of deep
tropical moisture advecting from a developing tropical cyclone
over the Southwestern Gulf of Mexico. Any storms that do move over
a TAF site will have the capabilities of briefly reducing cigs
and/or visibilities down to IFR levels. Showers and storms will be
isolated through tonight becoming more isolated to scattered
during the day on Tuesday. Have Prob30 groups in the TAFs to
reflect this potential. Otherwise, expect for VFR conditions to
prevail.

Winds will be out of the east 7-15 kts through this afternoon into
this evening with occasional gusts between 20-25 kts. Winds will
subside tonight out of the east at 5-10 kts. During the day on
Tuesday, winds are expected to shift out of the northeast at 5-10
kts.

&&

.MARINE...
Issued at 304 AM CDT Mon Jun 17 2024

Today through Tuesday...This portion of the total marine forecast
is highly dependent on the area of disturbed weather over Central
America, the Yucatan Peninsula, the waters of the northwest
Caribbean Sea and southern Gulf of Mexico, and the possible future
development and movement of a tropical system within it. Overall,
Small Craft Should Exercise Caution (SCEC) and Small Craft
Advisory conditions (SCA) are anticipated along the Lower Texas
Coast through the period, with SCEC likely needed today, and SCA
needed tonight through Tuesday.

Tuesday night through Sunday...Marine conditions are expected to be
Hazardous Tuesday night and remain that way through the work week,
with Saturday starting to see some improving conditions. An enhanced
pressure gradient will generate moderate southeast winds and seas.
Small Craft Advisory conditions are expected to be present Tuesday
night through early Saturday for the Gulf waters. While hazardous
conditions are expected to come to an end a little sooner for the
Laguna Madre.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             80  92  78  89 /  50  80  80  90
HARLINGEN               76  93  75  88 /  30  80  80  90
MCALLEN                 79  95  78  87 /  20  70  60  90
RIO GRANDE CITY         78  96  77  84 /  10  50  50  80
SOUTH PADRE ISLAND      83  87  80  86 /  60  80  90  90
BAYVIEW/PORT ISABEL     79  90  77  87 /  50  80  80  90

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk from 7 PM CDT this evening through Tuesday
     evening for TXZ451-454-455.

GM...None.
&&

$$

SHORT TERM...66-Tomaselli
LONG TERM....64-Katz
AVIATION...23-Evbuoma