163
FXUS64 KBRO 292343 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
643 PM CDT Mon Apr 29 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 237 PM CDT Mon Apr 29 2024

Key Messages:

- There is a marginal risk for severe thunderstorms this afternoon
  and evening across the Northern Ranchlands.

- A high risk of rip currents along the Lower Texas beaches
  through Tuesday evening.

- Above normal temperatures continue across Deep South Texas.

The short term period will feature low precipitation chances,
partly to mostly cloudy skies, and above normal temperatures
across all of Deep South Texas. Persistent low level southerly to
southeasterly flow across the region has maintained warm and humid
conditions. The 12Z BRO sounding indicated precipitable water
values (PWATs) around 1.5 inches this morning, and GOES-16 Total
Precipitable Water satellite imagery measures PWATs ranging from
1.55 to 1.65 inches across Deep South Texas. Meanwhile, a weak
boundary north of the region will allow for isolated to scattered
showers and thunderstorms to develop late this afternoon and into
tonight.

High res guidance indicates the presence of steep mid-level lapse
rates, modest instability, and sufficient bulk shear values to
support the development of isolated severe thunderstorms with
primarily a hail and damaging wind gust threat, but lack of large
scale forcing will limit this potential. If any severe
thunderstorms were to develop, the best timing would be late this
afternoon and overnight, mainly over the Northern Ranchlands.
However, convective allowing models continue to indicate a mostly
rain/storm-free afternoon and overnight period, with mainly warm
air advection showers developing overnight across portions of Deep
South Texas and the Gulf waters. Isolated to scattered showers
may continue throughout the day on Tuesday, with the development
of isolated thunderstorms possible during the afternoon hours as
instability increases. Isolated thunderstorms may develop off of
the Sierra Madre, but should dissipate before reaching the region
late Tuesday afternoon/evening. Otherwise, a mild and overcast
night is expected tonight and Tuesday night with lows in the 70s.
Highs on Tuesday will range from the upper 70s along the Lower
Texas beaches to mid 90s across the Northern Ranchlands.

&&

.LONG TERM...
(Wednesday through next Monday)
Issued at 237 PM CDT Mon Apr 29 2024

Key Messages:

- Daily low (20-30%) precipitation chances for portions of Deep
  South Texas continue through the end of the week.

- Above normal temperatures persist through the weekend.

Breezy winds will return across Deep South Texas by the start of
the long term period as the pressure gradient tightens in response
to an upper level trough digging into the Rockies. Sustained winds
around 15-20 MPH with gusts up to 30 MPH are likely on Wednesday,
with similar wind speeds expected on Thursday as the trough and
attendant surface features track across the Northern Plains. As
low level southerly to southeasterly flow continues to transport
rich Gulf moisture northward and results in increasing PWATs, weak
disturbances embedded within westerly to southwesterly flow aloft
will result in daily low precipitation chances. The aforementioned
trough will send a cold front southward by the end of the week,
but model guidance continues to struggle with the timing of the
front and the southward extent before stalling.

Unfortunately, this will leave us with above normal temperatures
and humid conditions through the weekend with highs ranging from
the low 80s across the Lower Texas beaches to the mid 90s across
the Northern Ranchlands and lows in the 70s. With the steady
increase of low-level moisture and temperatures, we`ll have to
keep an eye on heat index values mid week. The latest guidance
indicates heat indices will approach 100-106 degrees across most
of the region, including the Mid/Upper Valley and the Northern
Ranchlands, Wednesday through Friday.

&&

.AVIATION...
(00Z TAFS)
Issued at 643 PM CDT Mon Apr 29 2024

Main issue overnight will be low ceilings...with abundant moisture
at or below a sinking inversion flowing in on favorable easterly
flow. Blended guidance along with traditional deterministic
guidance all support a fairly quick developing/lowering ceiling to
low MVFR by or soon after sunset...with further dipping by late
evening, likely to IFR conditions which should continue until 8 or
9 AM Tuesday. Mix-out may be a bit slower later Tuesday morning,
but MVFR, then VFR, conditions return as skies become partly
cloudy (scattered) shortly after noon. Winds gradually veer
southeasterly but speeds remain moderate at best by afternoon.

Only other addition was to add haze (6 miles) with soupy airmass
in place...dewpoints in the mid 70s for all terminals for much of
the night. Would not be surprised to see MVFR visibility at some
point but confidence was too low to include. Winds should preclude
any visibility lower than 3 or 4 miles in a reasonable worst case.

Finally...radar remains quiet this evening and even the convective
allowing models are generally bearish on mentionable thunder in
the overnight forecast...so have left out for now.

&&

.MARINE...
Issued at 237 PM CDT Mon Apr 29 2024

Tonight through Tuesday night...Light to moderate east to
southeast winds and moderate seas will prevail through the period.
Isolated to scattered showers and thunderstorms will be possible
tonight into Tuesday, which may result in higher winds and seas.

Wednesday through Sunday night...A tightening pressure gradient
will result in increased wind speeds on Wednesday, which may
approach Small Craft Exercise Caution to Small Craft Advisory
conditions beginning late Wednesday afternoon into Thursday. Wave
heights will respond and may reach 7-8 feet by Thursday.
Conditions should improve heading into the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             77  90  77  89 /  20  20   0  10
HARLINGEN               74  92  74  92 /  10  20  10  10
MCALLEN                 76  93  77  92 /  10  20   0  10
RIO GRANDE CITY         74  93  75  93 /  20  10   0  20
SOUTH PADRE ISLAND      76  81  76  81 /  20  10  10  10
BAYVIEW/PORT ISABEL     74  87  75  87 /  20  20   0  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk through Tuesday evening for TXZ451-454-455.

GM...None.
&&

$$


AVIATION Update...52-Goldsmith