227
FXUS64 KBRO 270530 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1230 AM CDT Mon May 27 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Monday night)
Issued at 237 PM CDT Sun May 26 2024

Key Messages:

* Excessive, Dangerous, Record-Breaking Heat Monday
* High Rip Risk through Monday
* Marginal Severe Weather Risk Northwest portions Monday
  afternoon/evening

There will be little relief from the frying pan heat in the short
term. Mid-level ridging (595 dam) anchored over Mexico will provide
strong subsidence across deep South Texas and the Rio Grande Valley.
Dangerous heat will persist Monday with triple-digit temperatures
(up to 109 in the Upper Valley) for most non-coastal locales. Due to
steady southeast surface flow, dew points poking well into the 70s
will support elevated heat index values ranging from 115 to 120
degrees for a few hours Monday afternoon. This would support an
excessive heat warning. Record high temperatures may be tied or
broken (see climate section below). Looked at the NBM and also
looked at mixing in the ConsShort but the results were similar.

Tonight and Monday night temperatures will remain warm with lows in
the upper 70s across the Northern Ranchlands to the lower 80s across
the Lower Rio Grande Valley. Interestingly, SPC now places portions
of the RG Plains, Brush Country, and Upper Valley in a marginal
severe risk for late Monday afternoon/evening. Looking at the
models, a promising source will be earlier initiating convection
over South Texas that propagates south into the Northern sections of
the CWA. Outflows could contribute to follow-on storms. Convection
moving out of the Sierra Madre Oriental Range is also an ongoing
possibility. In any case, isolated stronger storms could deliver
large hail and strong, damaging winds from Monday afternoon into the
late evening. Though storms tend to move smartly along, brief
downpours could result in a quick inch of rain.

&&

.LONG TERM...
(Tuesday through next Sunday)
Issued at 237 PM CDT Sun May 26 2024

Key Messages:

-Well above seasonal temperatures will continue through the long
term forecast period
-More Heat Advisories are likely for each day for the duration of
the long term forecast period.

While the current model trend have continued to show the center of
the subtropical ridge move slightly to the south-southwest as a
group of shortwave troughs move towards the east starting on Tuesday
and continuing through Friday. While this will allow for the
temperatures to come down by a degree or two. High temperatures are
still going to be in the range of upper 90s along the coast and the
barrier island, while triple digits will persist over the rest of
the region. Looking at the experimental HeatRisk tool, a mixture of
Major to Extreme heat risk is present Tuesday through Saturday.
Considering that surface winds remain out of the southeast through
next Sunday, plenty of humidity will flow into the region. The
combination of the heat and the humidity will allow the heat indices
to rise. The current model analysis shows that the heat indices will
be in the range of 109 to 113. However most of Deep South Texas and
the Rio Grande Valley has more heat indices closer to 111 to 113.

Even at night, the temperatures are expected to be hot. As low
temperatures are expected to be in the range of upper 70s to low 80s
through out the region. Since there will be still plenty of humidity
at night the heat indices will still be high. Based on the current
model analysis the nightly heat indices are expected to be in the
range of low 80s to low 90s.

As for the rain chances, they remain very limited at best. Isolated
showers are possible on Tuesday for Starr and Zapata, but after that
point, the rain chances drop off. Most of the long term forecast
period is pretty expected to be rain free.

&&
 Moderate to breezy southeast winds will scatter out the low
clouds by mid day Monday.


.AVIATION...
(06Z TAFS)
Issued at 1225 AM CDT Mon May 27 2024


A mix of VFR/MVFR ceilings and light to moderate southeast winds
prevail across Deep South Texas early this morning. Widespread MVFR
ceilings are expected to develop overnight. Low cloud decks then
should decrease after sunrise, with VFR conditions returning to
all RGV aerodromes by mid-morning. Some intermittent visibility
reductions are possible through the period, as haze/mist could
briefly drop visibility to 5-6 miles, though confidence is too low
to include in the TAF. Light winds overnight will increase and
become gusty later this morning into the afternoon.

&&

.MARINE...
Issued at 237 PM CDT Sun May 26 2024

Tonight through Monday night...Mostly moderate southeast breezes
and moderate to slightly enhanced wave heights will prevail
through the forecast. High pressure over the Gulf will provide the
driving force for the seasonal winds. Small craft may at times
need to exercise caution.

Tuesday through Next Sunday...Light to moderate onshore flow with
moderate seas are generally expected to continue through next
weekend. However a locally enhanced pressure gradient will pick up
starting on Wednesday that will result in a period of Small Craft
Exercise Caution for the Laguna Madre. Then on Friday the winds and
seas will pick up resulting in the need for Small Craft Exercise
Caution for the Laguna Madre and Gulf waters. A low end Small Craft
Advisory cannot be ruled out at this point either.

&&

.CLIMATE...

Record Highs for Monday May 27, 2024

Brownsville 99 in 1973 (Forecast high 99)
Harlingen 100 in 2018 (Forecast high 101) *A break in the climate
records
McAllen 107 in 1973 (Forecast high 104)

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             82  96  81  95 /   0   0   0  10
HARLINGEN               79  98  79  97 /  10   0   0  10
MCALLEN                 81 101  81 100 /  10  10  10  10
RIO GRANDE CITY         80 102  78 102 /  20  10  10  10
SOUTH PADRE ISLAND      82  87  82  87 /  10   0   0  10
BAYVIEW/PORT ISABEL     80  93  80  93 /  10   0   0  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 11 AM CDT this morning for TXZ248>255-353.

     Excessive Heat Warning from 11 AM this morning to 8 PM CDT this
     evening for TXZ248>255-353.

     Heat Advisory until 8 PM CDT this evening for TXZ351-354-355.

     High Rip Current Risk through this evening for TXZ451-454-455.

GM...None.
&&

$$

SHORT TERM...54-BHM
LONG TERM....64-Katz
AVIATION...63-KC