Area Forecast Discussion
Issued by NWS Brownsville, TX

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063
FXUS64 KBRO 211135 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
635 AM CDT Tue May 21 2024

...New AVIATION...

.SHORT TERM...
(Today through Wednesday)
Issued at 304 AM CDT Tue May 21 2024

594dm Subtropical Ridge anchored over N Mexico and South Texas to
maintain the above seasonal heat and keep our region rain free
today through Wednesday. 850mb temperatures of 22-24C, dew points
in the upper 70s to upper 60s support heat indices in the 110-115
range for all areas with except to the coast and Island counties.
A heat advisory will be issued from 1-6 PM to cover the dangerous
heat today. Another heat advisory is possible Wednesday with no
substantial change to the airmass or the position of strength of
the 500mb ridge. No relief overnight with minimums also remaining
above normal with mid 70s to 80 degrees as low as they go with a
modest southeast breeze and some increasing overnight cloudiness
keep any radiational cooling at a minimum or zero. Otherwise,
morning lower clouds break up fairly quickly each mid to late
morning with plenty of afternoon and early evening Sun along with
some afternoon gustiness. Also, hazy skies persist with
agricultural fires from southeast Mexico continue to spread north
with the southeasterly flow. Local air quality will be impacted
with AQI in the `Unhealthy for Sensitive groups" forecast for the
RGV including the lower coast today and Wednesday.

&&

.LONG TERM...
(Wednesday Night through Monday)
Issued at 304 AM CDT Tue May 21 2024

Building heat will be the main concern during this portion of the
total forecast. The BRO CWFA will remain on the northern periphery
of 500 mb high pressure centered over Mexico, resulting in well
above normal daytime high and overnight low temperatures. A HEAT
ADVISORY is a near certainty daily beginning on Thursday, and an
EXCESSIVE HEAT WARNING cannot be ruled out entirely beginning on
Friday, with areal coverage of the WARNING likely being the key
factor each day as to whether or not it is issued.

Additionally, the presence of the 500 mb high will result in dry
weather, with no precipitation anticipated. However, beyond the
end of the Long Term period, on Tuesday night and Wednesday, some
model guidance suggests that the passage of a mid-level shortwave
may generate a wave of strong to severe thunderstorms through Deep
South Texas and the Rio Grande Valley with welcome/needed rainfall
at that time.

&&

.AVIATION...
(12Z TAFS)
Issued at 629 AM CDT Tue May 21 2024

Patches of MVFR ceilings along with light fog and haze producing
MVFR visibility at times are expected to lift and dissipate by 15Z
or shortly after. VFR conditions prevail this afternoon and early
evening before the low level marine layer works back into the
region providing moisture for developing MVFR ceilings later
Tuesday evening and continuing Wednesday morning. Increasing
southeast winds later today to produce wind gusts to 25 knots.


&&

.MARINE...
(Today through Wednesday)
Issued at 304 AM CDT Tue May 21 2024

A moderate pressure gradient persist over the Lower Texas coastal
as a high pressure ridge extends from Florida to the SW Gulf of
Mexico. Moderate to locally fresh southeast winds and slight to
moderate seas can be expected today through Wednesday.

(Wednesday Night through Monday)
High pressure over the Gulf of Mexico will interact with thermal
low pressure over Mexico to produce an enhanced pressure gradient
along the Lower Texas Coast through the period. Small Craft Should
Exercise Caution and/or Small Craft Advisory is likely to be
needed daily to account for the breezy winds and elevated seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             97  81  96  81 /   0   0   0   0
HARLINGEN               97  77  98  78 /   0   0   0   0
MCALLEN                101  80 101  80 /   0   0   0   0
RIO GRANDE CITY        103  79 104  78 /   0   0   0   0
SOUTH PADRE ISLAND      87  82  86  81 /   0   0   0   0
BAYVIEW/PORT ISABEL     94  79  94  79 /   0   0   0   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory from 1 PM this afternoon to 6 PM CDT this evening
     for TXZ248>255-353.

GM...None.
&&

$$

SHORT TERM...59-GB
LONG TERM....66-Tomaselli
AVIATION...59-GB