792
FXUS64 KBRO 050438 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1038 PM CST Wed Dec 4 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Thursday night)
Issued at 251 PM CST Wed Dec 4 2024

An area of low pressure along or just inland of the Coastal Bend
with its associated frontal boundary stretching south just off the
Texas coast. The low lifts northeast across the NW Gulf tonight
filling in as it moves along the northern Gulf coast Thursday while
the frontal boundary extends southwest becoming draped across the
County Warning Area (CWA). Clouds linger and lower overnight with
some patchy fog potentially reforming by sunrise. Lows not as cool
with upper 50s to near 60 north and west and low to mid 60s for the
Mid and Lower RGV. Near 70 degrees looks on the mark for SPI.

For the coastal beaches tonight will keep any coastal flood
statements or advisories nil at this time. Offshore pressure
gradient weakens with winds and seas continuing to lower. The local
coastal flood matrix with a predicted MHHW water level of 0.3
maintain water levels just below statement levels during the high
tide cycle of 8 PM-Midnight. A high risk of rip currents will be
maintained through Thursday.

Surface high pressure builds north of the front and weak mid-level
ridging moves over Texas Thursday providing a temporarily reprieve
of total overcast an grey conditions. Rain chances do not go away
completely Thursday with only slight chances, mainly along the coast
and the Lower RGV expecting a 20% chance for most of the daytime
hours. Farther west, and in most of the CWA, some breaks in the
overcast Thursday allow for temperatures to warm up a bit with model
consensus in the upper 60s to near 70 for the Northern Ranchlands to
mid 70s for the RGV. Rain chances go up substantially Thursday night
with the mid-level ridge being pushed east as a an upper low
settling. Weak disturbances and overall increasing ascent within
the southwest flow, deep moisture and the frontal boundary nearby
should be sufficient for likely Pops of 60% areawide Thursday night.
Rainfall amounts of around one-tenth of inch is showing up in the
latest QPF with low-medium probability (20-40%) of higher amounts
0.25 inch or greater after midnight Thursday night/Friday morning.

&&

.LONG TERM...
(Friday through next Wednesday)
Issued at 251 PM CST Wed Dec 4 2024

The overall pattern for the long term starts with a closed low over
AZ. Early in the weekend, the low will become a positively tilted
trough and dig south, bringing southwesterly flow aloft to deep
south Texas. This will keep temperatures mild and bring unsettled
weather, in tandem with the meandering coastal low in the western
Gulf. The interactions between these systems will bring chances of
rain. QPFs daily through Sunday are as high as 0.25 inches,
primarily along the coast, although low confidence in forcing
mechanism timing leaves us with low to moderate PoPs (20-50%) Friday
through Sunday.

For festivities planning, rain chances this weekend - especially
overnights and along the coast - are elevated. Guidance disagrees on
when the chance of rain is highest. Right now, Friday has the
highest agreement between models in the sense of... It Could Rain.
The highest chance is in the northern ranchlands (50%), with a low
chance in the Lower Vally (20-30%). Showers may be brief but heavy
pop-ups.

To begin the workweek, the trough formerly over AZ will eject a cold
front - likely to be dry - although confidence in speed, depth, and
trajectory between guidance is not high. ECMWF guidance moves the
front much quicker than North American/GEFS. GEFS is anticipating
much less moisture loss following fropa, which will play a factor
in the high temperatures reached early next week. Following the
front early next week, a benign pattern with surface high pressure
is expected for the remainder of the period keeping temperatures
mild and rain chances low.

High uncertainty in temperatures for the beginning of the period.
Models on Friday are all over the place - NAM expecting around 60,
Euro expecting mid 60s, NBM expecting around 70, GFS expecting 80.
The location of the coastal trough on Friday and Saturday will be
the biggest factor in the temperatures felt early in the period. The
coastal low parking offshore will bring northerly flow, keeping
temperatures mild, however if the low situates itself inland (like
GFS anticipates), southerly flow will dominate and rise
temperatures. A majority of the models don`t anticipate the high to
drop below 60, nor rise much beyond 77.

&&

.AVIATION...
(06Z TAFS)
Issued at 1028 PM CST Wed Dec 4 2024

MVFR conditions are currently occuring at local airports due to
low cloud ceilings (between 1100 and 1500 feet) that remain over
the area. Overnight, conditions are are expected to become IFR
between 08z-10z and there is the potential for ceilings to get
down to LIFR during intermittent periods between 09-14z. There
could also be some patchy fog or mist in addition to the lower
ceilings. Winds are expected to be light and variable this evening
into tonight, shifting to a more northerly direction and slightly
increasing (around 5-8 knots) between 06z and 09z. There is a
small window of LLWS (25-30 knots) at around 2000-3000 ft from 04z
to 06z above the inversion particularly at BRO, but confidence
was too low to include in the TAF package. Conditions should
return to MVFR by 14-16z.

&&

.MARINE...
Issued at 251 PM CST Wed Dec 4 2024

Tonight through Thursday night...pressure greater remains strong
over the Gulf waters with a low pressure area analyzed just inland
of the Texas coastal Bend. Buoy 42020 continues to observer Small
Craft Advisories (SCA) conditions with South winds of 20-25 knots
and seas 10-11 feet as of Noon. Pressure gradient is expected to
weaken later this afternoon as the low fills in and lifts northeast
over the NW Gulf tonight. Seas will be slow to subside ahead of the
diminishing winds and the SCA for the Gulf waters will be extended
until at least 10 PM. Thursday and Thursday night a frontal boundary
to be draped across the coastal waters most of Thursday before
dropping just south of the waters tomorrow night. High pressure
builds to the north and east of the region providing moderate north
to northeast winds and a moderate sea. Although not anticipating
SCA`s Thursday night, there is a low probability (10-30%)of seas
exceeding 6 feet after midnight (Thursday night/Friday morning).
Scattered to widespread showers to continue through the period.

Friday through next Wednesday...Moderate to light northeasterly flow
Friday morning will diminish through the day and leave favorable
conditions for Friday night. Showers reducing visibility and
degrading conditions temporarily are possible through the weekend,
as high as 70% on offshore waters on Friday and decreasing to 30-40%
through Monday. A cold front is expected to move through early next
week, which could again increase winds and elevate seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             66  75  66  78 /  10  40  50  50
HARLINGEN               62  75  61  74 /  10  20  60  50
MCALLEN                 63  75  62  71 /   0  10  60  40
RIO GRANDE CITY         60  72  58  68 /   0  10  70  50
SOUTH PADRE ISLAND      69  74  70  76 /  20  50  60  50
BAYVIEW/PORT ISABEL     65  74  65  76 /  10  40  60  50

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Small Craft Advisory until 8 AM CST Thursday for TXZ455.

     High Rip Current Risk through Thursday afternoon for TXZ451-454-
     455.

GM...Small Craft Advisory until 8 AM CST Thursday for GMZ150-155-170-
     175.

&&

$$

SHORT TERM...59-GB
LONG TERM....69-HK
AVIATION...55-MM