015
FXUS64 KBRO 261150 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
645 AM CDT Sun May 26 2024

...New AVIATION...

.SHORT TERM...
(Today through Monday) Issued at 307 AM CDT Sun May 26 2024

Key Messages:

* Excessive, Dangerous, Record-Breaking Heat Likely again today
* Triple digit highs expected for Brownsville, Harlingen, and
  McAllen today; Heat Indices will range between 115-124 degrees
* Extreme risk of heat related impacts to anyone spending time
  outdoors and not taking the necessary precautions
* High Risk for Rip Currents expected through Monday

A mid to upper-level ridge anchored over Mexico will continue to
provide strong subsidence across Deep South Texas and the Rio Grande
Valley through the period. Dangerous heat will persist through
Memorial Day with triple-digit temperatures for most inland
locations. Due to steady southeast surface flow, dew points climbing
into the 70s, will support elevated heat index values, which will
encroach eastward. Temperatures and dew points are expected to
increase few degrees today and tomorrow as subsidence strengthens.

Mid-level dry air should mix down this afternoon and again tomorrow
afternoon, so made some slight adjustments to the temperature and
dewpoint grids. These changes should keep daytime high temperatures
and dewpoints a little more realistic and more inline of what has
been observed the past two days. This is also close to the latest
HREF 2m apparent temperature probabilities.

Persistence is the best forecast with Excessive Heat Warnings and
overnight Heat Advisories in place for today and likely continuing
tonight and repeating Monday. To avoid any confusion will not issue
additional heat advisories or warnings and let today`s hazards run
their course before reissuing for tonight and Monday.

Some convection may develop over the higher terrain of Mexico/Sierra
Madre and drift towards the Rio Grande Plains Monday afternoon as a
weak shortwave traverses around the periphery of the 500 mb. The
Storm Prediction Center /SPC/ has most of Deep South Texas in a
general thunderstorm outlook for Monday.

The persistence moderate southeast winds over the Gulf of Mexico
will continue to drive a moderate swells towards the Lower Texas
Coast through the period. Therefore, a continuation of a High Rip
Current Risk is expected through Monday.

&&

.LONG TERM...
(Monday night through Saturday) Issued at 307 AM CDT Sun May 26 2024

Key Messages:

- Well above normal temperatures continue through next weekend.
- Medium probability (40-70%) of Heat Advisories everyday.

Latest model trends continue to indicate the center of the
subtropical ridge getting shunted slightly to the south- southwest
as a series of shortwaves track west to east across the Southern
Plains late Tuesday-Friday. This should allow for a minor lowering
of daytime temperatures but don`t be fooled, temperatures and heat
indices will remain well above normal and day to day heat advisories
have a medium (40-70%) probability of occurring each afternoon. The
Experimental NWS Heat Risk Index continues to show Major to Extreme
(4-5 out of 5) risk of heat-related impacts providing increase
confidence in the forecast. Overall, high temperatures to range from
near 90 at the local beaches to 105 inland west. Overnight lows do
not show any significant downward trend with a range of 76-82
degrees.

Rain chances  continue to be limited to far western counties Monday
and Tuesday evenings as the weakening ridge and the mid-level
disturbances may trigger isolated Sierra Madre Convection. Model
consensus remains consistent with only 10-20 percent pops over the
the western Ranchlands including portions of Starr County and < 10%
everywhere else. Moisture remains shallow with exception to the
Monday and Tuesday evening out west where some depth to the moisture
profile is the indicator for the isolated convection chances.

A more pronounced upper trough moving through the northern and
Central Plains next weekend shows a front moving into Central Texas
which may aid in trending down the temperatures another notch while
providing a slighlty better chance of rain.

&&

.AVIATION...
(12Z TAFS) Issued at 637 AM CDT Sun May 26 2024

A mix of VFR/MVFR ceilings and moderate southeast winds prevail
across Deep South Texas early this morning. Latest satellite imagery
indicates some low cloud decks south of the Rio Grande Valley over
Mexico, drifting northward. In addition, current surface
observations suggest some light haze has developed across portions
of the area. Therefore, will mention TEMPO wording through around
15Z for MVFR ceilings and/or visibilities. VFR conditions should
return to all RGV aerodromes by mid to late morning. Some
intermittent visibility reductions are possible through the period,
as haze/mist could briefly drop visibility to 5 to 6 miles, though
confidence is too low to include in the remainder of TAF period.
Moderate winds early this morning will increase and become gusty
later this morning into the afternoon. Low clouds with MVFR ceilings
should return later this evening.

&&

.MARINE...
Issued at 307 AM CDT Sun May 26 2024

(Today through Monday): An enhanced pressure gradient along the
Lower Texas coast will maintain moderate to fresh southeast winds
and moderate seas. Expect winds to approach but remain just shy of
Small Craft Advisory criteria of 20 knots on the Laguna Madre during
the day shifting over the Gulf waters overnight.

(Monday night through Saturday): A persistent light to moderate
southeast flow and moderate sea regime is indicated for Monday night
through next weekend. Broad surface ridging over the Gulf waters and
modest low pressure troughing extending from the NE Mexico through
the Southern plains to maintain the modest onshore flow and steady
state wave profile. Not anticipating any significant rainfall but
can not rule out a few streamer showers leading into next weekend.

&&

.CLIMATE...
Issued at 307 AM CDT Sun May 26 2024

Record Highs for today May 26, 2024

Brownsville 98 in 1928 (Forecast high 99)
Harlingen 100 in 1924 (Forecast high 101)
McAllen 102 in 2017 (Forecast high 104)

Record Highs for Monday May 27, 2024

Brownsville 99 in 1973 (Forecast high 100)
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             99  82  98  81 /   0   0   0   0
HARLINGEN              101  80 100  78 /   0   0  10  10
MCALLEN                104  82 104  81 /   0   0  10  10
RIO GRANDE CITY        108  81 106  80 /   0  10  20  20
SOUTH PADRE ISLAND      89  83  88  83 /   0   0   0  10
BAYVIEW/PORT ISABEL     96  81  95  80 /   0   0   0  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 11 AM CDT this morning for TXZ248>255-351-
     353>355.

     Excessive Heat Warning from 11 AM this morning to 9 PM CDT this
     evening for TXZ248>255-351-353>355.

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

GM...None.
&&

$$

SHORT TERM...63-KC
LONG TERM....59-GB
AVIATION...63-KC