Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 170513 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1213 AM CDT Sun Mar 17 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Sunday night)
Issued at 255 PM CDT Sat Mar 16 2024

A cut-off low over the Desert Southwest will promote southwesterly
flow aloft over Deep South Texas through the short term period. A
shortwave moving moving overhead tonight will provide additional
forcing.  At the surface, southeasterly flow has allowed warm and
humid air to return to the region this afternoon, this will support
CAPE values reaching >1500 J/kg this evening, as well as PW values
around 1.5”. The combination of the moisture, instability and
forcing look to provide an environment favorable for convection,
especially the western half of the CWA. Model soundings from the 18z
run of the RAP are showing shear and thermodynamic profiles that
could support the development of severe thunderstorms over the
western most counties. The Storm Prediction Center’s day one
convective outlook has a Slight risk over northwestern portions of
Zapata and Jim Hogg counties, and a Marginal Risk over the
remainder of of Zapata and Jim Hogg counties, as well as Starr,
Brooks, and northwestern portions of Hidalgo and Kenedy counties.
The primary threat is expected to be damaging hail and wind, however
a very limited tornado threat is also possible. Additionally, some
heavy rain is possible with these storms, and the Weather Prediction
Center has a marginal risk for excessive rainfall for parts of
Zapata, Jim Hogg, Brooks, Kenedy and Hidalgo counties.

A general thunderstorm threat continues further east, however
stronger CIN and lower CAPE values are forecast closer to the coast,
which will limit the severe potential. A cold front currently
situated over South/Central Texas is expected to move through Deep
South Texas Sunday. Additional isolated to scattered showers and
thunderstorms are possible through the day Sunday. Rain chances
decrease, behind the front Sunday night, however potential for some
light rain or an elevated thunderstorm looks to stick around as a
weak overrunning setup looks take hold.

Low temperatures tonight are expected to drop into the upper 60s to
low 70s. Temperatures are expected to climb back to the low 80s
Sunday, ahead of the front. Sunday night, temperatures are expected
to fall to the upper 50s to mid 60s behind the front.

&&

.LONG TERM...
(Monday through next Saturday)
Issued at 255 PM CDT Sat Mar 16 2024

The long term forecast pattern will start off with a Rex Block being
set up between a cut-off low over the Desert Southwest and a ridge
over the Pacific Northwest that will last through the mid-week. This
will allow for an active pattern to persist over Deep South Texas and
the Rio Grande Valley as a series of shortwaves will move through
the area due to the southwesterly flow aloft. However, with this
active pattern there is a great potential for much needed rainfall
to occur. PWAT values through the period remain high in the range of
1.6 to 1.8 through Thursday, before they drop off on Friday.

The downside to this active weather pattern is that there is the
potential for more severe weather to occur. Mid-week looks to be a
key time for the long term forecast period as storms coming off the
Mexican plateau move towards Zapata, Starr, and Hidalgo counties.
The primary threat with these kind of storms are the large hail.
Overrunning showers or isolated thunderstorms are possible for Monday
and Tuesday. With the onshore flow, there will be plenty of moisture
to help fuel these developing storms.

&&

.AVIATION...
(06Z TAFS)
Issued at 1209 AM CDT Sun Mar 17 2024

A mixed bag of MVFR and IFR conditions possible overnight with
any remaining VFR expected to diminish. Current convective
activity setting up west and northwest of the RGV, with tall CB
and large hail. Confidence remains lower in this activity reaching
into the RGV, but will continue to monitor for any AMDs. Another
round of convection is possible Sunday afternoon with the advance
of a weak and slow-moving cold front. Patchy fog may be possible
as well near daybreak today and again this evening.

&&

.MARINE...
Issued at 255 PM CDT Sat Mar 16 2024

Tonight through Sunday Night...Showers and thunderstorms are
possible over the Gulf waters and Laguna Madre tonight through
tomorrow night. The best rain chances are tonight, with
probabilities decrease through the day Sunday, and only limited rain
Chances by Sunday night. Otherwise, generally favorable conditions
are expected to continue through the short term. Light to moderate
southeasterly flow will continue tonight and into the day Sunday,
however a cold front late Sunday morning into Sunday afternoon will
slowly shift wind more northeasterly. Winds look to begin increasing
late Sunday night into early Monday morning, and adverse conditions
requiring a Small Craft Advisory or Small Craft Should Exercise
Caution headline are possible near the end of the period.

Monday through Next Saturday...A hazardous start on Monday with
elevated winds and seas that will require a Small Craft Advisory
with 30 knot winds possible for the nearshore Gulf waters and Laguna
Madre. However conditions will start to improve moving into Tuesday.
Winds turn towards the east then southeast during the week leaving a
favorable pattern through next Saturday. Showers and thunderstorms
are possible through Thursday, with gusty winds and hail possible.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             67  73  61  71 /  20  30  10  10
HARLINGEN               64  72  58  71 /  20  20  10  10
MCALLEN                 66  72  59  72 /  30  30  10  10
RIO GRANDE CITY         63  71  56  70 /  30  50  20  10
SOUTH PADRE ISLAND      67  70  64  68 /  10  20  10  10
BAYVIEW/PORT ISABEL     65  72  61  71 /  10  20  10  10

&&

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

$$

SHORT TERM...60-BE
LONG TERM....64-Katz
AVIATION...56-Hallman


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