000
FXUS64 KBRO 201924
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
224 PM CDT Sat Apr 20 2024

...New SHORT TERM, LONG TERM, MARINE...

.SHORT TERM...
(Tonight through Sunday night)
Issued at 121 PM CDT Sat Apr 20 2024

This morning`s scattered showers and thunderstorms, associated with
a weak disturbance embedded within the flow aloft, has come to an
end as of early this afternoon as the disturbance exits to the east.
Low level easterly to southeasterly flow will continue to transport
Gulf moisture across the region this afternoon, allowing for
precipitable water values to remain around or above the 90th
percentile for this time of year. The 12Z BRO sounding measured a
PWAT value of 1.73 inches, and most high res guidance indicates
PWATs should remain high through tonight. Meanwhile, a cold front,
currently moving across the Texas Hill Country, is expected to make
its way toward Deep South Texas late this evening as an upper level
disturbance tracks across much of the state this afternoon through
tonight.

Although we`ll have high moisture content in place ahead of
the cold front, the better forcing for ascent will be located well
north of the region which may limit the overall potential for strong
to severe thunderstorms as the cold front approaches tonight.
However, high res model soundings reveal MUCAPE values ranging from
1500-2000 J/kg across the Rio Grande Valley and closer to 2000-2500
J/kg across the Northern Ranchlands, mid-level lapse rates ranging
from 7-8 C/km, and 0-6 km shear around 30 knots. This would support
at least a limited threat for severe thunderstorms tonight with
primarily a damaging wind and hail threat, primarily across the
Northern Ranchlands and Rio Grande Plains. HREF members continue to
vary in solutions on precipitation and thunderstorm coverage for
tonight into early Sunday morning, but are in general agreement on
the onset of precipitation across the Northern Ranchlands beginning
around or after 9 PM and after midnight for the RGV.

Scattered showers and isolated thunderstorms will linger through the
morning and early afternoon hours across the Rio Grande Valley as
warm, humid air rises above the southward moving cold front. The
combination of lingering precipitation, cloud cover, and arrival of
brisk north winds should result in a noticeably cool Sunday across
all of Deep South Texas. High temperatures will top out in the upper
60s across the Northern Ranchlands and low 70s across the RGV, with
the high temperature likely occurring during the morning hours.
Guidance indicates temperatures will steadily fall through the
afternoon into the 60s with the arrival of the cooler airmass. Wind
gusts around 20-30 MPH will be likely beginning by mid to late
Sunday morning, and should begin to subside by the evening hours as
the pressure gradient slackens. Low temperatures will fall into the
mid 50s across the Rio Grande Plains into the low 60s across the Rio
Grande Valley Sunday night into Monday morning. Additional light
precipitation cannot be ruled out Sunday night, mainly over the RGV.

For the Lower Texas beaches, a moderate to high risk of rip currents
is likely beginning Sunday due to increasing seas.

&&

.LONG TERM...
(Monday through next Saturday)
Issued at 121 PM CDT Sat Apr 20 2024

The general forecast trend for the long term...starts off cool
and damp Monday followed by a drier and warmer period. Models are
in good agreement with the center of a cool surface ridge over
the Arklatex Monday morning with Sunday`s frontal boundary not to
far south over the Gulf. Persistent northeast surface winds and
mid-level overrunning (S-SW winds at 800-700mb) producing a
thick overcast and providing a lingering chance of light rain
maintains below normal temperatures. Model guidance is suggesting
highs only 69-74 across Deep South Texas which is 15-20 degree
below mid April averages. Probability of any location seeing
high temperatures over 75 degrees Monday are only 10-15 percent.

One more cool morning Tuesday, upper 50s to lower 60s, before
this cool shot departs and a warming trend commences. 500mb ridge
builds over the Rockies and spreads eastward over Texas Thursday
and over the Western Gulf of Mexico Friday and Saturday. Surface
winds return from the Southeast Tuesday morning with the surface
high pressure settling along the East Coast. Pressure gradient is
moderate at best through Thursday with a tightening of the
gradient Friday and Saturday as the next upstream storm system
takes shape. All model guidance warms up high and low temperatures
near normal Wednesday, going above normal Thursday through
Saturday.

&&

.AVIATION...
(18Z TAFS)
Issued at 1227 PM CDT Sat Apr 20 2024

The latest radar and satellite imagery depict the morning
convection has exited the region, with the exception being over
the offshore Gulf waters. VFR to MVFR conditions are currently
observed across the region, with conditions expected to improve
to VFR and persist through the early evening hours. Breezy south
to southeast winds with gusts around 25-30 knots will prevail
through the evening hours as well in response to an approaching
cold front and upper level disturbance.

Prior to the arrival of any convection, MVFR/IFR ceilings will
overspread all the TAF sites after 01-03Z as low level flow
transports Gulf moisture. High res guidance indicates the onset of
any SHRA/TSRA for the terminals is after 07-08Z, with scattered
coverage expected for the remainder of the TAF period. While a
strong or severe thunderstorm cannot be ruled out near the
terminals, the greater potential will be north of the terminals.
Otherwise, lightning, gusty winds, and small hail are the main
threats with any activity. MVFR/IFR ceilings will prevail through
the period and winds should shift to the north around 12-13Z, with
gusts increasing to around 25 knots by 16-17Z.

&&

.MARINE...
Issued at 121 PM CDT Sat Apr 20 2024

Now through Sunday night...Generally favorable marine conditions are
expected through tonight, although there will be a potential for
scattered showers and thunderstorms ahead of and along a cold front.
Increasing winds and building seas in wake of the frontal passage
will result in Small Craft Exercise Caution conditions beginning
early Sunday morning and Small Craft Advisory conditions along the
Laguna Madre and Gulf waters by mid to late Sunday morning through
the end of the period. Additional scattered showers and isolated
thunderstorms will be possible through Sunday night.

Monday through Saturday...Adverse weather conditions are expected
at the beginning of this period (Monday morning) with a steady
improvement Monday afternoon as surface high pressure settles over
the northwest Gulf. By Tuesday, surface ridge is expected to be
well east of the Texas coast with veering winds becoming light and
seas becoming slight. Thereafter, Wednesday and Thursday light to
moderate southeast winds with a modest gradient across the
western Gulf. Pressure gradient begins to strengthen Friday and
Saturday as the next storm system moves into the Central Plains.


&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             73  74  65  72 /  30  50  30  30
HARLINGEN               71  71  60  73 /  30  40  20  30
MCALLEN                 70  72  61  73 /  40  40  20  30
RIO GRANDE CITY         68  69  59  70 /  50  40  20  30
SOUTH PADRE ISLAND      72  73  67  70 /  30  50  30  30
BAYVIEW/PORT ISABEL     72  72  64  72 /  30  40  30  20

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory from 7 AM to 10 PM CDT Sunday for GMZ130-
     132-135.

     Small Craft Advisory from 7 AM Sunday to 7 AM CDT Monday for
     GMZ150-155-170-175.

&&

$$

SHORT TERM...22-Garcia
LONG TERM....59-GB
AVIATION...22-Garcia