National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS64 KBRO 182335 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
635 PM CDT Thu Apr 18 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Friday night)
Issued at 237 PM CDT Thu Apr 18 2024

The short term period will feature mostly rain-free conditions and
above normal temperatures. The exception will be tonight, where
there will be a brief period for showers, and potentially isolated
thunderstorms, across portions of Deep South Texas. The latest
radar and satellite imagery depict rain-free conditions and a
steady influx of clouds across Deep South Texas. Temperatures will
continue to warm into the upper 80s and low 90s through the
afternoon hours, with temperatures steadily falling into the 70s
tonight.

Persistent southerly to southeasterly flow in the lower levels of
the atmosphere will aid in increasing low level moisture content
from the Gulf of Mexico, while southwesterly flow aloft will aid
in mid and high level moisture content from the Pacific Ocean.
Model guidance indicates precipitable water values will steadily
increase upwards of 1.5 inches, which is around the 75th to 90th
percentile for this time of year. As moisture content, and cloud
cover, increase overnight, a weak mid-level shortwave will
approach the region and bring a low chance of isolated showers and
thunderstorms across portions of the region tonight. Although
most guidance keeps the best potential for strong thunderstorms
well to our north, model soundings reveal mid-level lapse rates
around 7.5-8 C/km, which could support an isolated thunderstorm or
two. Any activity will likely dissipate before daybreak on
Friday. In addition to the potential for low rain chances across
portions of the region, the influx of low level moisture and low
surface winds may yield patchy fog across portions of the Northern
Ranchlands and the Gulf waters tonight.

Friday will feature a gradual clearing of cloud cover through the
mid to late morning hours, and another warm afternoon with high
temperatures ranging from the upper 70s along the Lower Texas
beaches to upper 90s across the Northern Ranchlands. Another
round of patchy fog will be possible Friday night across portions
of the region. Lows will once again fall into the 70s region wide.

&&

.LONG TERM...
(Saturday through next Thursday)
Issued at 237 PM CDT Thu Apr 18 2024

Key Messages:

* Showers and thunderstorms remain a possibility Saturday night
  through Sunday as a cold front sweeps over the area.

* Big airmass change to the cooler and drier side in the wake of the
  cold front Sunday and Monday.

* Temperatures and humidity levels attempt to rebound Tuesday
  through Thursday of next week.

The main weather concern during the long-term forecast period
continues to focus on the risk/potential for showers and
thunderstorms Saturday night through Sunday.

We start off the long-term period on Saturday where we`ll see
another very warm and humid day before the big weather change. On
the western flank of a departing sfc high pressure system to our
east, southeasterly winds will continue to advect moist and warm air
in the region. This will allow for daytime high temperatures to rise
into the upper 80s to lower 90s across much of Deep South Texas
(cooler near/along the coast). Subsidence amid continued influences
from the sfc high will allow for another dry and tranquil weather
day on Saturday.

Deterministic forecast models and ensembles continue to advertise
the potential for showers and thunderstorms developing Saturday
night through Sunday in response to a cold front that`s progged to
sweep across the region. Models remain rather dispersed as far as
the areal/spatial and temporal extent of showers and storms Saturday
night into Sunday. That said, have 20-50% chance Pops to reflect a
low to medium confidence on the threat/risk of showers and storms at
this time stamp. As we sort out the more salient details with future
model iterations, will have a better handle regarding this threat.

With surface-based CAPE (SBCAPE) via the latest 12z runs sampled in
excess of 1,000 J/kg, 0-6 km bulk shear values sampled between 30-45
kts, showalter values between 0C to -4C denoting a moderately to
very unstable/buoyant airmass in place, and mid-level lapse rates
between 7-8 C/km, it`s certainly plausible that some storms could
become strong to severe Saturday night through Sunday. With a
weak/unfavorable jet structure support, a lot will depend on the
forward momentum/strength of the frontal boundary and to what extent
any ongoing upstream convective activity to our north will be able
to hold together as it shifts into our region as there will likely
need to be some forcing mechanism to help offset a cap that will be
in place in what will likely be a conditionally unstable environment
during this timeframe. Currently, the Storm Prediction Center (SPC)
in Norman, Oklahoma has our cwa designated under a general outlook
for thunderstorms.

Depending on where the front is positioned, there could be another
round of showers and storms Sunday afternoon/evening and maybe again
during the day on Monday. The front is expected to be far south
enough to result in a notable airmass change to the cooler and drier
side Sunday and Monday, however. Daytime highs are progged to be in
the mid 70s to near 80F both days with dewpoint values in the 60s.

Tuesday through Thursday, temperatures and humidity levels attempt
to rebound once again as the aforementioned cold front lifts
northward over the area as a warm front or quasi-stationary front.

&&

.AVIATION...
(00Z TAFS)
Issued at 629 PM CDT Thu Apr 18 2024

VFR conditions are expected to give way to MVFR ceilings overnight
with southeasterly winds diminishing after sunset. Isolated
thunderstorms are roaming in between HRL and BRO and may diminish
or continue to miss both aerodromes over the next couple of hours.
AMDs may be needed if anything further develops. Additional
showers or very isolated thunderstorms may reach MFE early this
evening as well.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             74  89  74  87 /  10   0   0   0
HARLINGEN               72  93  72  89 /  10   0   0   0
MCALLEN                 75  95  75  92 /  20   0   0  10
RIO GRANDE CITY         74  95  73  93 /  20   0   0  10
SOUTH PADRE ISLAND      74  80  74  79 /  10   0   0   0
BAYVIEW/PORT ISABEL     72  87  73  85 /  10   0   0   0

&&

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

$$

SHORT TERM...22
LONG TERM....23
AVIATION...56-Hallman