Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 171118 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
618 AM CDT Sun Mar 17 2024

...New AVIATION...

.SHORT TERM...
(Today through Monday)
Issued at 344 AM CDT Sun Mar 17 2024

Severe threat early this morning was much more limited to the brush
country to western ranchlands in the BRO CWA and running out of
steam fairly quickly compared to last night, with the strongest
cells across Zapata County and north into the CRP CWA. This
coincided with a passing shortwave in the southwesterly flow aloft
rather well, with some lingering convective activity following, but
behaving.

As a Rex Block pattern continues to set up across the west, with a
ridge across the Pacific NW and a cut-off low across the Desert SW,
expect the active pattern to continue into the new week, with a
series of shortwaves and perturbations in the mostly southwesterly
flow sliding through Deep South Texas every 12 to 18 hours or so.

At the surface, a weak and slow-moving cold front continues to
gradually work south, potentially through the RGV by the afternoon,
with highs reaching into the upper 70s and low 80s. Some CAM
guidance suggest a couple of roaming thunderstorms with the front
early to mid afternoon from north to south with the frontal
boundary. MUCAPE does top 2k J/kg by the afternoon, with bulk shear
over 50 kts, a steep lapse rate, and a limited to non-existent cap
across the ranchlands into Starr and Hidalgo counties by mid to late
afternoon. The big questions become if that is enough time for the
atmosphere to recharge enough after the activity early this morning
and will the front outrun the best instability as it heads south,
cutting off most convective initiation.

If storms do develop, there may be couple of strong cells, with
damaging winds and some hail. By the early evening and overnight, a
much more stable setup takes shape with more shower activity than
thunderstorms expected. Some much needed additional, but mostly
light, rain is possible through Monday with overrunning
precipitation and a better surge of northerly winds, especially
along the coast by mid-morning through the afternoon. Below normal
highs are also anticipated, only reaching the mid to upper 60s for
most, with a few low 70s across the mid to lower valley. Some
guidance would drop temperatures a little further, into the low to
mid 60s for most.

&&

.LONG TERM...
(Monday night through Saturday)
Issued at 344 AM CDT Sun Mar 17 2024

A mainly dry weather pattern is expected during the long-term
forecast period with a Rex Block over western North America breaking
down giving way to a more zonal flow pattern aloft. Behind the
passage of a cold front on Monday, a broad 1025 mb surface high
pressure system is expected to build into the region from the north.
This feature will support plenty of subsidence overhead and thus
mainly dry weather for the long-term period.

Wednesday-Thursday is the timeframe that we have to continue to
monitor for the potential for another round of showers and
thunderstorms. Multiple global deterministic forecast models are
indicating shower and thunderstorm prospects increasing
Wednesday- Thursday in response to a nearby low pressure system
and associated frontal boundary. Given the continued uncertainty
at this time stamp, have only low grade PoPs for
showers/thunderstorms Wednesday- Thursday of next week.

A warming trend is expected to take place during the long-term
period with temperature anomalies initially starting off cooler than
normal before climbing to warmer than normal levels by the end of
the period.

&&

.AVIATION...
(12Z TAFS)
Issued at 616 AM CDT Sun Mar 17 2024

MVFR and IFR conditions continue across the RGV this morning in
the wake of overnight convection and ahead of a slowly approaching
weak frontal boundary. Northerly winds arrive during the afternoon
and evening, with a chance of thunderstorms this afternoon into
early this evening, potentially transitioning to light rain or
showers after or just beyond this TAF period. Some VFR breaks may
be possible later this morning or early this afternoon, depending
on the frontal boundary, with confidence too low to stray from
MVFR at this time.

&&

.MARINE...
Issued at 344 AM CDT Sun Mar 17 2024

Now through Monday...A cold front gradually works south into this
afternoon and evening with a few more thunderstorms possible into
this afternoon, mainly north of Port Mansfield. Northerly winds
generally remain light until mid Monday morning, with a stronger
blast of northeasterly flow and reinforcing high pressure bringing
adverse marine conditions to the lower Texas coast. Additional light
rainfall is possible through Monday. Small Craft Advisories will
likely be needed Monday morning into the long term period.

Monday Night through Saturday...Adverse marine conditions are
expected to be ongoing into the long- term period Monday night and
possibly into Tuesday. Following the passage of a cool fropa,
winds will shift out of the northeast and become gusty at times.
With sustained winds between 20-30 kts and seas between 7-10 feet,
a Small Craft Advisory will likely be taking place Monday
evening/night before ending Tuesday morning/afternoon.

Marine conditions will once again become favorable after Tuesday
with a return to light to moderate winds and seas. Showers and
thunderstorms are possible in the Wednesday through Thursday
timeframe.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             83  68  72  62 /  30  30  30  10
HARLINGEN               82  64  71  58 /  30  30  30  10
MCALLEN                 83  66  70  59 /  30  40  40  10
RIO GRANDE CITY         81  63  69  57 /  20  40  50  10
SOUTH PADRE ISLAND      75  67  70  64 /  30  20  20  10
BAYVIEW/PORT ISABEL     78  66  71  61 /  30  20  20  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

SHORT TERM...56-Hallman
LONG TERM....23-Evbuoma
AVIATION...56-Hallman


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