Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 291941

Area Forecast Discussion
National Weather Service Brownsville TX
241 PM CDT Mon May 29 2023


(Tonight through Tuesday night)
Issued at 238 PM CDT Mon May 29 2023

Ongoing seabreeze convection in mainly Kenedy and Willacy counties
is expected to increase in both coverage and intensity during the
remainder of the afternoon and into the evening hours.  CAPEs as
high as 2500 J/kg along with no cap, a seabreeze boundary, and an
approaching mid/upper closed low/vort max in Central TX will produce
scattered convection through this evening across the remainder of
the RGV and Northern Ranchlands. Effective shear values of 30-35 kt
will be enough to possibly produce a few organized strong to
possibly severe storms with damaging winds as the main severe
threat.  Could be some small hail, too.  This scenario is in line
with the latest Day 1 SPC Convective Outlook of Marginal for our
entire CWA this afternoon/evening. Various CAM guidance runs have
also been very consistent with this anticipated convective scenario
this afternoon and evening.  The convection later this evening will
likely have a southward propagation as the closed low/vort max
continues diving southeastward.  Could be strong winds associated
with these southward-moving clusters.

Most of the area remains in a Slight Risk of Excessive Rainfall for
tonight.  PWATs will be close to 1.8-2.0 inches this evening which
is around the 90th percentile. The past few HREF and NBM solutions
still depict 2-4 inches possible with the slower-moving storms (mean
wind from the 12Z BRO sounding this morning was 10 kt or less). Most
of the convection will have either dissipated or pushed south into
Mexico by midnight tonight. Will adjust POPs accordingly, beginning
with chance POPs at the outset and then diminish to 10-20% by

Convection may re-fire on Tue morning across the coastal areas given
the close proximity to the mid-level vort max diving southeastward
across the eastern CWA and adjacent waters and also due to lingering
PWATs close to 1.6-1.7 inches.  Isolated to scattered convection
will be mainly confined to areas east of I-69C on Tue given the
lingering moisture and instability profiles interacting with no cap
and a seabreeze.  Convection should dissipate very quickly by early
Tue evening as stronger subsidence begins to move eastward into the
CWA due to the building mid/upper ridge axis aloft.

Afternoon highs on Tue should be slightly warmer than today given
less cloud cover and lower rain chances.  Did adjust the highs
upward slightly from the latest NBM guidance. For overnight lows,
temps should be a bit lower than the past few days given less cloud
cover and a drying trend.


(Wednesday through next Monday)
Issued at 238 PM CDT Mon May 29 2023

Mid level riding will build overhead Deep South Texas mid to late
week, and as such, rain chances will be less than 10% and
temperatures will gradually increase through the rest of the week.
However, there may be just enough moisture and diurnal heating each
afternoon to support a shower or two, but most areas are expected to
stay dry through Friday.

The mid level ridge will flatten over Deep South Texas into the
weekend as a shortwave trough moves through the Desert Southwest and
into Central Texas, which will help to increase rain chances
Saturday through Sunday. Then rain chances will stick around through
Monday before the mid level ridge tries to build overhead again by
mid week next week.

As for temperatures, highs will generally be in the lower to mid 90s
and lows in the lower to mid 70s. Along the coast, temperatures will
generally remain in the 80s.


(18Z TAFS)
Issued at 1126 AM CDT Mon May 29 2023

Showers have already begun developing along the seabreeze over the
Laguna Madre. Showers and eventually thunderstorms will continue
to develop across many inland locations today given CAPES of at
least 2000 J/kg, no cap, a seabreeze boundary, and an approaching
upper level disturbance across Central TX. Will begin to carry
thunder by 20Z with the main timing window for convection at
21-03Z today. Will indicate possible IFR conditions during this
time window due to strong thunderstorms with heavy rain
potentially affecting all three RGV TAF sites. Convection should
end by midnight in most areas as the airmass continues to
stabilize later tonight.


Issued at 238 PM CDT Mon May 29 2023

Tonight through Tuesday night...The overall gradient will remain
generally weak through Tue night. The thermal gradient in the
afternoon and evening will enhance the winds by at least 5 knots.
Otherwise, seas will remain fairly flat at around 2 feet.

Wednesday through Monday...Overall, marine conditions will stay
fairly benign through the period. Wave heights will remain 1 to 3
feet through the weekend and subside to 1 to 2 feet early next week
with gentle to moderate east-southeast breezes. The chance for some
showers and thunderstorms returns Saturday through Monday.


BROWNSVILLE             72  88  73  88 /  40  30   0   0
HARLINGEN               69  89  70  91 /  40  30   0   0
MCALLEN                 71  91  72  92 /  50  20   0   0
RIO GRANDE CITY         70  92  70  93 /  30  10   0   0
SOUTH PADRE ISLAND      74  84  76  84 /  30  30   0   0
BAYVIEW/PORT ISABEL     71  86  72  87 /  30  30   0   0




LONG TERM....69-Farris
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