252
FXUS64 KBRO 130535 AAC
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1235 AM CDT Mon May 13 2024

...New AVIATION...

.UPDATE...
Issued at 712 PM CDT Sun May 12 2024

Mesoscale Analysis: As of 7:15 PM CDT, latest radar scans depict
a couple of thunderstorm cells moving eastward from the Mexico
plateau towards our CWA. The first cell is just to the west of
Zapata County. The second batch of showers and thunderstorms are
just southwest of Starr and Hidalgo Counties. These showers and
storms are associated with a shortwave overhead. Given the
upstream activity already in place and an environment with CAPE
values in excess of 2,000 J/kg, these showers and storms should
maintain it`s momentum as they work their way into our forecast
area this evening. The biggest question is whether or not we get
additional development as the aforementioned shortwave works its
way in the region and how severe/strong these storms become.
Currently, these storms are still rather shallow with cloud (echo)
tops ranging between 30,000-50,000 feet. Will continue to monitor
radar trends and update accordingly.

That said, we have bumped up PoPs to 20-30% to reflect a slight or
isolated chance for a shower or thunderstorm this evening/tonight.
We`ve also adjusted the WX grids accordingly. The rest of the
going forecast remains on track. See previous discussion.

&&

.SHORT TERM...
(Tonight through Monday night)
Issued at 212 PM CDT Sun May 12 2024

Slight rain chances are in the forecast for late tonight, Monday
morning and Monday afternoon with an elongated mid-level
disturbance passing over Texas. Not all models are showing much in
the way of rain with this weak disturbance, but last nights
disturbance did produce isolated activity which provides added
confidence in the consensus NBM solution to maintain 20 percent
tonight and Monday. The atmosphere remains conditionally unstable
with a strong low level cap (stronger eastern counties) and
elevated MUCape of 3000+ J/kg. As the disturbance passes overhead
some model point soundings show a weakening of the cap and the
instability being tapped. Although, SPC has a marginal risk of
Severe Thunderstorms after 12Z Monday, if the cap is broken
tonight, any thunderstorm that develops over NE Mexico or
"homegrown" will have some potential to go severe. Main threats
will be hail with 3-6km lapse rates 7.5-8C with wind a secondary
threat if organization of isolated cells in clusters occur. The
low probability (20%) for strong to severe thunderstorms continues
Monday which is highly dependent on the track and speed of the
mid-level disturbance.

The other element of concern Monday is the Heat.  Southerly winds
and elevated 850mb tempeatures of 24-25C to allow for ambient
temperatures to climb 5-10 degrees above normal. The daily records
at Brownsville (96F, 2011) and Harlingen (98, 2011) may be
approached. Dewpoints also are expected to bump up in the range of
75-79 degrees, especially along and east of I-69C, which when
combining with surface temperatures heat index values range from 111-
114F for 2-5 hours Monday afternoon. With this said, will be
contemplating a Heat Advisory for the Mid and Lower RGV. Farther
west a dryline may work into the far western counties which may
temper down the heat indices (105-110F) with highs to reach into the
lower 100`s.  Low`s tonight and Monday night remain elevated in the
75-80 degree range continuing the muggy conditions.

&&

.LONG TERM...
(Tuesday through next Sunday)
Issued at 212 PM CDT Sun May 12 2024

A stationary front situated over Deep South Texas looks to shift
north Wednesday, as weak upper level ridging and southeasterly
low-level flow return to the region. Enhanced forcing associated
with a mid-level shortwave combined with increased instability and
surface moisture could support isolated showers and thunderstorms
Wednesday, with rain chances topping out around 30%.

An upper-level trough looks to moves into the region Thursday,
supporting the development of a surface low pressure system over
North Texas, with a cold front extending across Central Texas.
Additionally, increased forcing over Deep South Texas could again
support a 20-30% chance of showers and Thunderstorms Thursday
ahead of the cold front. The cold front looks to stall to the
north Friday, before possibly pushing into Deep South Texas on
Saturday.

High temperatures in the mid to upper 90s Tuesday and Wednesday
look to warm slight, remaining in the upper 90s to just above 100
through the remainder of the period. Overnight low temperatures
are also expected to warm slightly through the period, starting in
the low to mid 70s Tuesday night, climbing to the mid 70s to low
80s by Wednesday night. The potential passage of a cold front
Saturday could seas slightly cooler temperatures return next
weekend, however confidence is low on if or when the front would
pass.

The combination of warm temperatures and increased humidity
Thursday could support heat indices around 112 for eastern
portions of the CWA. However, any showers or thunderstorms that do
develop Thursday could keep temperatures slightly cooler. Either
way, heat advisories may be needed Thursday afternoon for the
eastern most counties.

&&

.AVIATION...
(06Z TAFS)
Issued at 1227 AM CDT Mon May 13 2024

Low MVFR stratus and light southeast winds prevail across Deep
South Texas early this morning. BRO radar indicates some isolated
convection northeast of HRL. These showers and thunderstorms will
continue to move to the northeast and are not expected to impact
the RGV aerodromes. Otherwise, MVFR ceilings should remain in
place through the overnight hours. There could be brief instances
of IFR ceilings as well late tonight. Ceilings are expected to
improve to VFR levels mid to late morning. MVFR ceilings may
return late in the period at BRO, around 04Z.

&&

.MARINE...
Issued at 212 PM CDT Sun May 12 2024

Tonight through Monday night...The moderate southerly flow
across the coastal waters persists or weakens slightly over the next
12-24 hours with weak high pressure over the Gulf and a cold front
moving into Central Texas. The associated developing surface low
pressure over North Texas is forecast to lift quickly northeast
tonight and Monday also allowing for a weaker southerly wind. Seas
to respond Monday by subsiding slightly with a range of 2-4 feet for
the period.

Tuesday through next Sunday...A surface high pressure system over
East Texas looks to support light to moderate easterly winds and
moderate seas Tuesday. As the surface high shifts over the
northern Gulf on Wednesday, tightening pressure gradients along
the lower Texas coast will likely support stronger southeasterly
winds over the Laguna Madre and nearshore Gulf waters, possibly
necessitating Small Craft Should Exercise Caution headlines or
Small Craft Advisories. Pressure gradients look to weak Wednesday
night as the surface high moves further offshore, allowing light
to moderate winds and slight to moderate seas to persist through
the remainder of the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             78  93  78  91 /  10  10   0  20
HARLINGEN               75  93  74  93 /  10  10   0  10
MCALLEN                 78  97  77  96 /  10  10   0  20
RIO GRANDE CITY         76  97  75  96 /  10  10  10  20
SOUTH PADRE ISLAND      79  85  79  84 /  10  10   0  10
BAYVIEW/PORT ISABEL     77  89  76  89 /  10  10   0  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory from 1 PM this afternoon to 7 PM CDT this evening
     for TXZ251-253>255-353.

GM...None.
&&

$$

UPDATE/MESOANALYSIS....23-Evbuoma
SHORT TERM...59-GB
LONG TERM....60-BE
AVIATION...63-KC