Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 231139 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
639 AM CDT Mon May 23 2022

.DISCUSSION...Updated for latest aviation discussion below.

&&

.AVIATION...VFR to MVFR should prevail for the next few hours. Low
clouds and mist being reported at EBG, north of MFE, which could
briefly drift into aerodrome. VFR ceilings then expected for the
middle part of the day, with winds gradually veering to SE.
Thunderstorms become the main aviation concern by early this
evening, with greatest coverage between about 02-08Z. These
thundershowers may bring temporary MVFR ceilings and visibilities,
or even brief IFR in heavier downpours. Timing of specific impacts
will be better refined with future TAF updates.

&&

.PREV DISCUSSION... /issued 438 AM CDT Mon May 23 2022/

SHORT TERM (Now through Tuesday):  Active short-term period in
store.  Current water-vapor imagery shows a short-wave trough aloft
moving from Chihuahua into Coahuila state in Mexico.  The approach
of this trough, interacting with a stationary boundary that will
gradually begin to retreat northward as a warm front within the next
24 hours, should act to produce another round of showers and
thunderstorms from later today into the overnight period.  Model
trends have been for a little bit later timing in our CWA, with
general consensus for best PoPs from 02-08Z.  The shortwave is
likely to produce an MCS of sorts as it approaches, and model
guidance still differs a bit on its motion.  00Z GFS takes it
roughly across EWX`s area, with NAM more across CRP`s area just to
our north.  Other CAM`s also vary somewhat with placement and
intensity, so couldn`t get too specific in the grids just yet.

SPC has placed the entire area under a Marginal risk of severe
storms through 12Z Tuesday, with strong wind gusts the main
threat...possibly marginally severe hail as well.  This makes sense,
as the area will be in the left-exit region of a modest (~70KT) jet
at H25, along with 0-6km bulk shear increasing to 40-50KT across the
northern tier counties and MUCAPE values of 2,000-3,000 J/kg.  The
SPC Slight risk area also clips NW Zapata County.

Precipitable water values are also progged to climb to near 1.75"
ahead of the shortwave, which would lie in the 75th-90th percentile
from BRO (and in the higher end of that range out west), so we also
have a Marginal risk of excessive rainfall across the area through
tonight.  Will again need to keep an eye on the Zapata area where
radar estimates of up to 2-3" of rainfall fell yesterday, with a
localized flooding report or two.

MCS should be scooting offshore by around daybreak Tuesday, with a
slightly drier column filtering in behind it and the aforementioned
warm front.  There may be enough remnant moisture for a few showers
and thunderstorms, though coverage should wane through the day,
especially in the mid/Lower RGV.  Temps should also climb back into
the low-mid 90s everywhere except along the coast, with heat index
values reaching 100-105F for a few hours.

Finally, have extended the Rip Current Statement through 12Z
Tuesday, as easterly longer period (8-10 sec) swell continues, per
obs at Buoys 42020 and 42002 and latest NWPS guidance.

LONG TERM (Tuesday Night through Sunday): A large mid level trough
with a closed mid level low will move through the central CONUS
Tuesday night into Wednesday, bringing a wet and unsettled start to
the long term period for Deep South Texas. A weak shortwave moving
through the base of the trough Tuesday night could help support some
shower and thunderstorm development during the overnight hours...but
that will depend on how the potential convection on Tuesday leaves
the atmosphere over Deep South Texas for Tuesday night. The ECM is a
bit more gung-ho with the PoPs due to the higher amount of available
moisture and instability, where as the GFS is showing less moisture
and a stronger convective cap.

The next cold front will approach Deep South Texas on Wednesday
evening and provide another focus for shower and thunderstorm
development along and ahead of its frontal boundary. The atmosphere
will likely be primed to support the development of strong to severe
thunderstorms along the front...with forecast soundings showing
above average PWATs (precipitable water), impressive CAPE, moderate
shear, and impressive DCAPE values. Biggest threat with these storms
is looking like the potential for strong to damaging winds and some
hail. SPC has all of Deep South Texas in a Marginal Risk for severe
weather for this period. Overall rainfall amounts with this activity
are expected to be a little higher than the previous forecast, with
0.25 to 0.5 of an inch possible for much of the area.

A mid level ridge will build in from the west on Thursday night
heading into Friday as the deep trough pushes east. Subsidence from
this ridge along with the slightly drier air behind the front will
help keep the rest of the forecast generally rain-free.

Temperatures will be closer to normal on Wednesday, before the front
on Wednesday night drops temperatures below. Then as mid level
ridging and drier conditions take over for the latter part of the
forecast, a warming trend will commence into the Memorial Day
weekend.

MARINE: Now through Tuesday... Have extended the current SCA for
the offshore Gulf waters only through 15Z today, after
collaboration with CRP. Longer period (8-10 sec) easterly swell
continues, per obs at Buoys 42020 and 42002. Guidance gradually
diminishes the wave heights through mid-day. Freshening easterly
breezes may require Small Craft Exercise Caution (SCEC) conditions
for portions of the coastal waters this afternoon as well. After
a stationary front retreats northward as a warm front by this
evening, SE winds increase again, with SCA conditions likely to
return for Tuesday. Scattered thunderstorms later this afternoon
into Tuesday morning may also produce locally strong winds and
rough seas.

Tuesday Night through Sunday...Hazardous marine conditions
are expected Tuesday night as moderate to strong southeasterly winds
set up across the lower Texas waters and build seas into mid week.
Small Craft Advisories will likely carry over into Tuesday night.
Then SCEC conditions will linger into Thursday in advance of and
briefly behind the next cold front. Showers and thunderstorm
activity will persist into mid week, with stronger storms expected
with the front Wednesday night into Thursday morning. Then the
pressure gradient will strengthen into the weekend, bringing SCEC
or even SCA conditions for Memorial Day weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  87  77  91  77 /  20  40  20  10
BROWNSVILLE          91  78  92  79 /  20  30  10  10
HARLINGEN            91  76  94  77 /  30  40  20  20
MCALLEN              94  77  94  77 /  30  50  20  20
RIO GRANDE CITY      94  76  96  75 /  50  50  20  20
SOUTH PADRE ISLAND   82  78  84  78 /  10  30  10  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk through Tuesday morning for TXZ451-454-455.

GM...Small Craft Advisory until 10 AM CDT this morning for GMZ170-175.

&&

$$

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