High Surf Advisory 9, NWS Brownsville, TX

Area Forecast Discussion
National Weather Service Brownsville TX
307 PM CST Sun Nov 17 2024

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

.SHORT TERM...
(Tonight through Monday night)
Issued at 245 PM CST Sun Nov 17 2024

Key Messages:

* First of two cold fronts pass through the region on Monday; drier
  airmass change, but still warmer than normal temps expected on
  Monday

* Isolated showers and thunderstorms possible Monday morning into
  Monday afternoon

* Adverse to hazardous marine conditions expected through Monday
  evening

Latest forecast models continue to advertise cyclogenesis taking
place through this evening/tonight across northern Mexico and
western Texas. A tightening pressure gradient courtesy of this
brewing mid-latitude cyclone to our west-northwest and a large 1020
hpa sfc high over the southeastern U.S., has cranked up the "Valley
Wind Machine" here across the region with gusty south-southeast
winds. As of this update, peak wind gusts so far have been 45 mph in
McAllen (KMFE), and 36 mph in both Brownsville (KBRO) and Harlingen
(KHRL). While most of the kinematics/wind energy will be to our
northwest (i.e. across West Texas), the low level jet (LLJ) winds
between 850-925 mb are expected pick up later this evening/tonight.
H850 LLJ winds have been sampled between 40-50 kts later this
evening/tonight. Despite the decreasing mixing heights, some of
these winds could mix down to the sfc and wind gusts up to 45 mph
are possible in spots later on. Have issued a Wind Advisory for the
entire area (all of Deep South Texas and the Rio Grande Valley) this
evening through tonight from 7 PM CST to 5 AM CST Monday to account
for this potential. According to multiple models including DESI and
NBM, wind gusts of over 40 mph for 2 or more hours are possible
within this time period.

Winds are expected to wane Monday morning ahead of the cold fropa.
The cold font is rather weak and will be weakening upon its
approach. That said, not much of a thermal airmass change following
the passage of the cool front on Monday. Humidity levels, however,
will drop off signaling a drier airmass with dewpoints expected to
fall between 30-60F degrees across the northwestern half of the
area, and relative humidity values between 15-45% across the same
areas by Monday evening. Daytime high temperatures will still climb
to warmer than normal levels for mid November with values topping
out in the mid 80s to near 90F.

Shower and thunderstorm chances will range between 20-50% from IH-
69C and points east with the greatest chance being near the coast
and offshore Monday morning into Monday afternoon in association with
the cool front. Coverage will be isolated given the weak instability
in place (i.e. SBCAPE values up to 1,000 J/kg, MLCAPE values up to
300 J/kg, weak midlevel lapse rates of 5-6 C/km, and Showalter
values near 0).

Monday night will be mild with warmer than normal temperatures.
Overnight lows will range between the mid 50s northwest to near 70F
over SE Cameron County.

&&

.LONG TERM...
(Tuesday through next Sunday)
Issued at 245 PM CST Sun Nov 17 2024

An upper-level trough over the Central Plains will shift towards
the Great lakes through the first half of the period. At the same
time, a weak shortwave rotating through the back side of the
trough will help drive a strong cold front south across the Plains
and through Deep South Texas on Wednesday. Cool and dry northerly
surface flow from this weeks earlier cold front is expected to
still be in place Wednesday, severely limiting rain chances along
Wednesday’s front. However, the front is expected to bring
increased wind speeds and colder temperatures to the area.

Upper level ridging is expected to build over the western US
through the later half of the period, allowing southeasterly
surface flow to return by Friday, and supporting a gradual warming
trend going into the weekend.

The strongest winds are expected to be along the coast, with
gusts limited to around 20 knots further inland. NBM probabilities
for sustained wind speeds 30 MPH or gusts above 40 MPH are less
than 5%. As such, wind advisories do not look likely Wednesday.
Fire weather, however, does look to be a concern. With dry air
moving into the region earlier this week, some drying of the fuels
are expected. While observed fuel moisture values are currently
in the above normal category, they are forecast to become dry by
the start of the period, at least for western portions of the CWA.
With low RH values and dry fuels across the western counties,
wind speeds will likely be the limiting factor for fire weather.
NBM probabilities are near zero for for wind speeds high enough to
warrant a Red Flag Warning, and around 50% for wind speeds high
enough to warrant a Fire Danger Statement.

Along the eastern portion of the CWA, higher winds will likely
satisfy the requirements for elevated fire weather conditions,
however higher soil moisture and RH values may limit the
likelihood of any fire weather concerns.

High temperatures are expected to be in the mid to upper 80s
Tuesday, falling to the mid 70s to low 80s on Wednesday then
slowly returning to the mid 80s to low 90s by the end of the
period. Likewise, low temperatures in the mid 50s to low 60s
Tuesday night are expected to fall into the mid 40s to low 50s
Wednesday night and slowly climbing to the upper 60s to mid 60s by
the end of the period.

&&

.AVIATION...
(18Z TAFS)
Issued at 1145 AM CST Sun Nov 17 2024

Through 18z Monday....

The main aviation weather items for the 18z TAF cycle includes:

* Low VFR to MVFR cigs through the period

* Strong, gusty south-southeast winds through the period; peak
  timing of strongest winds (peak wind gusts between 30-40 knots)
  later this evening/tonight between 03z-10z

As of this update, GOES-16 visible satellite imagery showed a
persistent SCT-BKN deck of cumulus and stratocumulus clouds
streaming from northeast Mexico into Deep South Texas. These clouds
have ceilings/bases ranging between 2,000-4,000 feet AGL. Through
the 18z TAF period, expect for low VFR to MVFR cigs to persist. The
greatest chance for MVFR clouds will be tonight.

The other story through the TAF period will be the winds. A
tightening pressure gradient and strengthening low level jet (LLJ)
will result in gusty south-southeast winds through the period. South-
southeast winds 15-20 knots gusting up to 30 knots this afternoon
will increase later this evening/tonight 20-25 knots will gusts
between 30-40 kts. The best window for the strongest winds look to
be between 03z-10z. Around daybreak on Monday, winds are expected to
subside some with gusts ranging between 20-30 knots.

&&

.MARINE...
Issued at 245 PM CST Sun Nov 17 2024

Tonight through Monday night...Adverse to hazardous marine/coastal
conditions are expected to continue through Monday night with
deteriorating marine conditions expected to this evening/tonight.
Breezy south-southeasterly winds through tonight will result in
increased wave heights over the Gulf and the Bay becoming rough. A
Small Craft Advisory remains in effect for the Laguna Madre and the
Gulf Waters through 6 PM CST Monday. A High Risk for Rip Currents is
in place along the Lower Texas Coast beaches this evening through
Monday.

Tuesday through next Sunday...Marine conditions are expected to
briefly improve Tuesday, however the arrival of another cold front
Wednesday is expected to bring increased winds to the Laguna Madre
and Gulf waters. This will again lead to increased seas along the
Lower Texas Coast, and will likely require additional Small Craft
Advisories through the day Wednesday. Conditions are expected to
begin improving Wednesday night in the wake of the cold front,
with favorable conditions returning by Thursday and continuing
through the remainder of the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             78  89  71  85 /   0  20  20   0
HARLINGEN               75  89  64  87 /   0  30  10   0
MCALLEN                 78  90  65  89 /  10  20  10   0
RIO GRANDE CITY         75  88  60  87 /  10  10   0   0
SOUTH PADRE ISLAND      79  83  75  81 /   0  30  30   0
BAYVIEW/PORT ISABEL     76  88  69  83 /   0  30  20   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory from 7 PM this evening to 5 AM CST Monday for
     TXZ248>255-351-353>355-451-454-455.

     High Rip Current Risk from 6 PM CST this evening through Monday
     afternoon for TXZ451-454-455.

GM...Small Craft Advisory until 6 PM CST Monday for GMZ130-132-135-
     150-155-170-175.

&&

SHORT TERM...23-Evbuoma
LONG TERM....60-BE
AVIATION...23