Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 230921

Area Forecast Discussion
National Weather Service Brownsville TX
421 AM CDT Fri Aug 23 2019

.SHORT TERM (Today through Saturday): Today should be very similar
to yesterday. Hot and somewhat breezy conditions expected once
again. Similar to yesterday, diurnal convection can be expected
along the sea breeze from late morning through the afternoon hours,
generally along and east of I69C/Highway 281. CAMs, especially the
ARW show this very well. Offshore and along the coastal counties
there may be a streamer shower or two between now and sunrise. Not
expecting much rainfall with this activity.

The big picture shows a mid level vort and surface trough across the
western Gulf. This will keep POPs relatively high offshore through
much of the short term period. We`ll need to watch areas across the
upper valley/western tier counties toward the end of the short term
period. There appears to be a slightly higher QPF signal in rather
close proximity. An upper level vort develops across northern Mexico
coupled with some subtle surface troughing.
This will likely produce convection, however, whether or not this
drifts into Deep South TX is still up in the air. With the slightly
lower winds and increasing humidity values, fire weather concerns
continue to decrease.

.LONG TERM (Saturday Night through Thursday): The long term period
begins with the tropical wave/mid-level trough pushing into the
northwestern Gulf and mid level riding overhead, keeping conditions
hot and humid for deep South Texas through the weekend. On Sunday,
the ECMWF has a shortwave trough moving through the Southern Plains
with a 500 mb low pinching off the base of this trough and
eventually nudging into deep South Texas by evening. This feature
also brings a 500 mb vorticity max and precipitable water values
around 2 inches to our CWA, therefore increasing our rain chances.
In contrast, the GFS has a weaker shortwave trough and keeps its
axis offshore. Have gone with a blend of these two solutions with
a slight bias towards the wetter GFS solution for now, making
Sunday our best chance for showers and thunderstorms for the long
term period.

On Monday afternoon, models agree that a 500 mb high centered over
the Desert Southwest region begins to slide in behind the shortwave
trough. Ridging aloft will help to keep conditions hot and mostly
dry. However, with residual moisture overhead, have gone with a
slight chance of showers and thunderstorms each day to account for
possible sea breeze development.

In summary, not much has changed from the previous package, except
for the slight increase of PoPs on Sunday.


.MARINE (Today through Saturday): Mariners can expect generally the
same conditions as the last several days, except maybe a little less
wind. Light to moderate winds are expected for the Gulf waters,
which will produce seas of 3 to 4 feet. For the Laguna, during the
daylight hours expect winds of 15 to perhaps 20 knots, so we`ll
likely need to keep cautionary headlines in the coastal waters
product(s). That said, minimal SCEC is currently  anticipated as
winds remain lights with the closer proximity of the surface trough
just offshore. Showers/Tstorm chances remain across the Gulf waters,
especially beyond 20 nautical miles. With the aforementioned surface
trough, diurnally driven pockets of convection are expected to
develop, especially where moisture quality is maximized.

Saturday Night through Thursday...In general, a weak to moderate
surface pressure gradient will lead to moderate south/southeasterly
flow and moderate seas through the period. Small craft exercise
caution conditions may be needed across the Bay each
afternoon/evening, possibly across the near-shore waters, as well.
Showers and thunderstorms continue to be possible each day with
ample environmental moisture over the western Gulf waters.


BAYVIEW/PORT ISABEL  92  80  94  80 /  30  20  20  10
BROWNSVILLE          97  81  96  81 /  30  20  20  10
HARLINGEN            98  79  98  79 /  30  10  20  10
MCALLEN             102  81 102  82 /  20  10  20  10
RIO GRANDE CITY     103  80 102  81 /  10  10  20  20
SOUTH PADRE ISLAND   86  82  86  81 /  30  20  30  10




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