804
FXUS64 KBRO 281930
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
230 PM CDT Sun Apr 28 2024

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

.SHORT TERM...
(Tonight through Monday night)
Issued at 225 PM CDT Sun Apr 28 2024

Key Messages:

* Stagnant, tropical environment remains in place through the
  short-term period (warm to very warm, humid, and hazy)

* Day-to-day chances, albeit low/ of an isolated shower or
  thunderstorm through Monday night

Latest MSAS surface analysis and satellite imagery reveals a weak
surface low/shortwave trough over the forecast area under a
scattered to broken deck of strato-cumulus clouds this afternoon.
Just to the west, is a weakening cold front that`s expected to
wash out and transition to a dryline later this afternoon/evening.
Steep mid-level lapse rates on the order of 7-8 C/km, surface-
based and most unstable CAPE (SBCAPE/MUCAPEs) in excess of 2,000
J/kg, showalter values indicating a very unstable environment with
values between -3 to -7 coupled with this weak meso-scale feature
in place over the area would suggest the potential for showers
and thunderstorms to develop this afternoon.

However, per the 12z KBRO sounding from this morning, the
atmosphere is strongly capped with a strong surface inversion in
place at about 900 mb. Given the unfavorable jet structure
overhead and weak winds aloft on top of the lack of a lifting
mechanism at the surface suggests that shower and thunder activity
will be severely inhibited over the area through the day today.
That said, have maintained low grade (20%) PoPs over the northern
half of the area or across the Northern Ranchlands this afternoon
into tonight to account for the low but non-zero probability/risk
of there being an isolated/rogue shower or thunderstorm
developing. The Storm Prediction Center (SPC) in Norman, Oklahoma
in it`s SWODY1 has maintained the northern half of our CWA under a
General Outlook for thunderstorms through today.

For tonight, continued onshore flow will allow for marine layer
influences to increase. This will result in an increase in low
clouds tonight. With clouds preventing any long wave outgoing
radiation to take place, tonight will be another warm and muggy
one with overnight lows projected to hold in the low to mid/upper
70s with similar dewpoint values. Southeast winds should be
elevated enough to prevent the development of widespread fog.
However, there could be patches of mist around tonight especially
in areas where the winds are not strong enough.

Though winds are not expected to be as strong, Monday will serve
as a rinse and repeat from today with warm to very warm, humid,
and at times hazy conditions continuing under partly cloudy to
mostly cloudy skies in a likely capped environment. Despite the
lack of a lifting mechanism and unfavorable winds/jet dynamics
aloft, instability parameters will be in place to support maybe an
isolated/rogue shower or thunderstorm on Monday, especially
during the afternoon hours with max differential surface heating.
Similar to today, have low grade (20-30%) PoPs in the grids to
reflect this low, but non-zero probability/risk. The Storm
Prediction Center`s (SPC`s) SWODY2 has the entire CWA or all of
Deep South Texas under a General Outlook for thunderstorms on
Monday and a Marginal (Level 1 out of 5) Risk for severe
thunderstorms over our extreme northwestern sections (i.e.
northern Zapata, northern Jim Hogg, and northwest Brooks Counties)
for Monday. High temperatures are progged to be in the upper 80s
to low/mid 90s on Monday.

Monday night will feature another warm and muggy night with
overnight low temperatures in the lower to mid/upper 70s (similar
to tonight) with similar dewpoint values.

&&

.LONG TERM...
(Tuesday through next Sunday)
Issued at 225 PM CDT Sun Apr 28 2024

Key messages will remain muted for the long term. Mid-level flow
will remain unamplified for the most part. No deep troughs to the
west. Nonetheless, minor disturbances may move over the Sierra
Madres and across South Texas from time to time. This will show up
in the forecast as regular (daily) mention of isolated to
scattered convection out west.

A punch of slightly higher ops farther east will occur Friday
into Friday night with a weak surface cold front not too far away
to the north. The dryline will hang out over West Texas. Did I
mention a cold front? Moving south late in the week will be a weak
cold front, driven by a Plains storm system, stalling out just to
the north of the County Warning Area Friday into Saturday, then
moving slowly back north. Slightly stronger southeast winds
Wednesday and Thursday ahead of the front may agitate Gulf wave
heights and push rip current risk into the high category
Wednesday night through Friday.

Seasonably above average temperatures will prevail with the
region just north of a semi-permanent subtropical summer ridge.
Lows will trend several degrees above average with highs a few
degrees warmer than typical. Partly to mostly cloudy skies will
dominate the local skies.

&&

.AVIATION...
(18Z TAFS)
Issued at 1233 PM CDT Sun Apr 28 2024

Through 18z Monday....

Key Messages:

* VFR-MVFR ceilings expected to continue through today.

* MVFR-IFR ceilings are expected to develop tonight.

* Ceilings expected to improve to at least MVFR levels on Monday.

* Southeast winds, gusty at times, are expected to weaken this
  afternoon into this evening.

As of this update, VFR to MVFR conditions were taking place at the
terminals under a SCT-OVC deck of strato-cumulus clouds as indicated
on the latest GOES-16 Visible Channel with ceilings ranging between
2,500-4,000 feet AGL. Latest surface analysis reveals a weak low
pressure area over the area this afternoon. However, the latest
forecast model and satellite trends indicate some clearing off to
the west thanks to the strong April sun angle and rather weak
upper level divergence taking place. This should allow for some
improving sky coverage into the middle parts of this afternoon.
That said, flying conditions due to ceilings could waffle back and
forth between VFR to MVFR today.

As we shift towards tonight, forecast models are suggesting
marine influences to increase with increasing low level clouds
(low stratus) from the Gulf. With plenty of low level moisture in
place, MVFR to IFR conditions are expected to develop and take
over the TAF sites tonight.

As we shift into Monday, any MVFR to IFR ceilings/clouds are
expected to improve to at least MVFR conditions.

Moderate to at times gusty winds out of the southeast 10-15 kts this
afternoon are expected to weaken as the day progresses as the
surface pressure gradient continues to weaken. Tonight into Monday,
southeast winds are expected to be at around 10 kts.

&&

.MARINE...
Issued at 225 PM CDT Sun Apr 28 2024

Tonight through Monday Night....Adverse to hazardous marine
conditons will continue particularly for the Gulf Waters till
Monday as seas/wave heights will range between 6-9 feet. Hence, a
Small Craft Advisory remains in effect till 7 AM CDT Monday for
the Gulf Waters (0-60 nautical miles out). A High Risk for Rip
Currents will remain in effect to 7 PM CDT Monday evening. During
the day on Monday and through Monday evening, Small Craft Exercise
Caution (SCEC) conditions will remain in place over the Gulf
Waters with seas/wave heights between 4-6 feet.

Tuesday through Friday night...Moderate to fresh southeast
breezes will prevail through the long term. With those winds will
come moderate to occasionally elevated wave heights. Thus, expect
here and there small craft should exercise caution to low end
small craft advisory conditions. Synoptically, high pressure over
the North Gulf will interact with lower pressure upstream to
maintain a gradient supportive of moderate to fresh winds.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             77  89  77  90 /  10  10  20  20
HARLINGEN               74  90  75  93 /  10  20  20  20
MCALLEN                 77  92  77  94 /  10  20  20  20
RIO GRANDE CITY         74  92  75  93 /  10  30  10  20
SOUTH PADRE ISLAND      76  80  77  81 /  10  10  20  20
BAYVIEW/PORT ISABEL     75  85  75  88 /  10  10  20  20

&&

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

GM...Small Craft Advisory until 5 PM CDT this afternoon for GMZ130-
     132-135.

     Small Craft Advisory until 7 AM CDT Monday for GMZ150-155-170-
     175.

&&

$$

SHORT TERM...23-Evbuoma
LONG TERM....54-BHM
AVIATION...23-Evbuoma