660
FXUS64 KBRO 211925
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
225 PM CDT Fri Jun 21 2024

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

.SHORT TERM...
(Tonight through Saturday night)
Issued at 216 PM CDT Fri Jun 21 2024

Key Messages:

- There is a 50% chance of tropical development near the Bay of
Campeche over the next 48 hours.

- Minor coastal flooding due to elevated seas and tides, as well as
a high risk of rip currents, will continue through Saturday night.

Deep South Texas will remain in an unsettled weather pattern through
the short term period as an area of low pressure translates westward
from the Bay of Campeche towards Southeastern Mexico. Meanwhile, the
mid/upper level ridge centered over the Northeast US earlier this
week will continue to shift toward the Southern Plains late this
afternoon and evening. While the broad area of low pressure is in
the general location of where Tropical Storm Alberto developed
earlier this week, a more westward track is likely as the ridge
builds over the Southern Plains. This scenario would keep our
highest precipitation chances mainly over the Rio Grande Valley and
Gulf waters, as the subsidence associated with the ridge will not
be quite as strong.

The latest probabilities from the National Hurricane Center indicate
there is a 50% chance of tropical cyclone development over the next
48 hours. Should any further development occur tonight, it is
possible a tropical depression could develop over the weekend.
Despite any tropical development, the main impacts for Deep South
Texas would be locally heavy rainfall, increasing seas, and a high
risk of rip currents along Lower Texas beaches. Given the beneficial
rainfall most of Deep South Texas received earlier this week, any
locally heavy rain may result in minor flooding issues. Isolated
instances of flash flooding cannot be ruled out, especially in low-
lying areas or flood-prone areas. Overall, rainfall amounts will
range from around 0.5" across the Northern Ranchlands to around 1.5"
across the Rio Grande Valley (locally higher amounts close to 2")
through Saturday night.

For the Lower Texas beaches, a high risk of rip currents will
continue through at least Saturday night. Wave heights are expected
to slowly decrease tonight, but may increase slightly once again on
Saturday with the westward movement of the area of low pressure.
Minor coastal flooding issues may develop once again and a Coastal
Flood Advisory may be needed. Otherwise, the combination of
increased cloud cover and rain chances will result in slightly below
normal temperatures for mid June, ranging from the low 90s across
the Northern Ranchlands to mid to upper 80s across the Rio Grande
Valley. Low temperatures will be mostly in the 70s region wide, with
low 80s along the immediate coast.
&&

.LONG TERM...
(Sunday through next Friday)
Issued at 216 PM CDT Fri Jun 21 2024

Key Messages:

_ Tropical Low (possible cyclone)approaching Tamaulipas Coast Sunday
- Heavy Rain Potential Sunday
- Coastal/Marine Impacts Possible Sunday/Monday
- Back to typical June Weather Tuesday-Friday

The Sunday and Monday forecast is highly dependent on the future
track and strengthening of the tropical disturbance expected to
move into the Bay of Campeche/Southern Gulf waters tonight or
early Saturday. NHC has a 50 and 60 percent chance of tropical
cyclone development in the next 2 to 7 days respectively. For the
latter portion of the long term mid-level ridging to dominate and
drive the forecast trends.

Sunday trends on the wetter side as moisture surges over the RGV.
All deterministic models show significant POPs as the available deep
tropical moisture converges along a low pressure trough and moves
inland. Precipitable water  values once again climb in the 2-2.5+
inch range which will provide the opportunity for heavy rainfall. At
this time, average WPC QPF values for Sunday range from 0.5-1 inch
(less over the northern Ranchlands).  Can not rule out higher
amounts up to 2 inches in isolated thunderstorms or training of
heavier showers.  With this said, only the counties of Cameron,
Willacy, Hidalgo and Starr are within the day 3 Excessive Rainfall
outlook issued by WPC. Not anticipating a Flood Watch, however
nuisance street and low-lying flooding is possible especially with
areas that received more than 3 inches earlier this week.
Temperatures Sunday are likely to be below normal in mid 80s to
lower 90s as clouds and rain keep insolation limited.

Residual high moisture content and differential heating Monday
should be sufficient for another round of scattered showers and a
few thunderstorms.  Rain chances may be a bit robust as the mid-
level ridge becomes established over Texas and the Desert SW so
there may be some adjustments to trend lower on the POPs in the next
few days. Near normal temperatures are expected with lows in the 70s
and highs in the 90s.

Tuesday-Friday look to trend near seasonal conditions with the mid-
level ridge strengthening over the Desert SW and a mid-level low
pressure trough shown to move over the north-central Gulf of Mexico.
This places Deep South Texas in a weak shear zone with modest low
level moisture and increasing subsidence in the mid-levels. Forecast
temperatures are likely to trend up while isolated sea breeze
convection are possible mainly east of I-69C.

Coastal impacts on Sunday due to the tropical entity moving toward
the Southern Tamaulipas/northern Veracruz coast will also be
highly dependent on future strengthening. In any case, worse case
scenario would be coastal flood advisories especially at the high
tide cycle and high risk of rip currents. At least a moderate
risk of rip currents is likely for Monday and Tuesday.

&&

.AVIATION...
(18Z TAFS)
Issued at 1228 PM CDT Fri Jun 21 2024

The latest radar and satellite observations reveal mostly VFR
conditions and widely scattered SHRA/isolated TSRA across the
region this afternoon. Expect these trends to continue through the
evening hours as low level easterly to southeasterly flow
transports tropical moisture across the region. Precipitation
chances increase late tonight into tomorrow as the broad area of
pressure over the Bay of Campeche translates west northwestward
toward Southeastern Mexico. Scattered showers and isolated
thunderstorms will likely persist by mid morning Saturday through
the afternoon/evening hours. Locally heavy rain may result in
reduced visibility at the terminals. Otherwise, MVFR ceilings will
return around 14-16Z.

&&

.MARINE...
Issued at 216 PM CDT Fri Jun 21 2024

Tonight through Saturday night...Moderate northeast to east winds
and elevated seas will prevail through the period and result in
Small Craft Exercise Caution to Small Craft Advisory conditions over
the Gulf of Mexico and Laguna Madre. Scattered to numerous showers
and isolated thunderstorms will remain likely through the period the
airmass remains unsettled. The NHC currently has a 50% chance of
tropical development near the Bay of Campeche over the next 48
hours, which could result in higher winds and seas than currently
forecast.

Sunday through Friday...Latest models continue to show a weaker
and less broad tropical low pressure area moving over the
Southern Gulf waters. This translates into a smaller wind field
with lower winds and lower seas. Conditions on Sunday look to in
the exercise caution to low end small craft advisory level as the
tropical entity approaches the Mexican coast about 300 miles
south of the mouth of the Rio Grande. As high pressure builds over
the northern Gulf the remainder of the week winds and seas will
be trending lower with light to moderate winds and slight seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             78  88  78  90 /  80  80  90  90
HARLINGEN               75  88  76  90 /  60  80  80  90
MCALLEN                 76  87  77  90 /  60  80  70  90
RIO GRANDE CITY         76  87  76  89 /  50  80  60  90
SOUTH PADRE ISLAND      81  85  81  86 /  80  80  90  90
BAYVIEW/PORT ISABEL     78  88  79  89 /  80  80  80  90

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Coastal Flood Advisory until 7 PM CDT this evening for TXZ351-
     354-355-451-454-455.

     High Rip Current Risk through Sunday morning for TXZ451-454-455.

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

GM...Small Craft Advisory until 7 PM CDT this evening for GMZ150-155-
     170-175.

&&

$$

SHORT TERM...22
LONG TERM....59
AVIATION...22