Area Forecast Discussion
Issued by NWS Brownsville, TX

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

FXUS64 KBRO 131117 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
617 AM CDT Tue Mar 13 2018

.DISCUSSION...Updated for latest aviation discussion below.

.AVIATION...VFR is expected to continue through the next 24 hours.
The higher cloudiness approaching from the west-northwest has
tapered off and has been replaced with a 7k to 8k deck moving
north out of Mexico. This level of cloud cover should prevail
during the TAF period but will likely bounce up and down a couple
thousand feet. Surface winds will be generally light and veer.

.PREV DISCUSSION... /issued 359 AM CDT Tue Mar 13 2018/

SHORT TERM (Now through Wednesday):  Deep South Texas and the Rio
Grande Valley will be dominated at the surface by high pressure and
by a west-northwest to east-southeast flow at the 500 mb level. The
mid-level flow will aid in advecting significant cloudiness out of
Mexico, which will combine with a northeast to east flow at the
surface to hold temperatures at below normal levels through the
forecast period. Despite the widespread cloud cover, no measurable
rainfall is likely.

LONG TERM (Wednesday Night through Monday): Still only a couple
of shots at rain in the long-term forecast, and even those are
questionable. Models in reasonable enough consensus regarding a
mid-level shear axis passage on Thursday to maintain slight
chance to chance (favoring coastal and offshore areas) of showers.
The dryline may push into at least western portions of the CWA
each afternoon from Friday through Sunday. In concert with another
shear axis/vort max progged to be in the area by both the GFS and
ECMWF, this may be enough for a few showers on Sunday, mainly
across the northern tier. However, poor column moisture depth (up
to 850mb, tops) will be a limiting factor. After near-normal max
temps on Thursday, also expecting much warmer values
(approximately 8-12 deg above normal) from Friday through at least
Sunday. Have continued the prior forecast`s lean toward toward
the somewhat warmer ECM temps, as sustained southerly flow ahead
of the dryline should continue the WAA over the eastern CWA, with
possible downslope warming effects behind the dryline further
west. Afternoons will also be breezy from Thursday through Sunday
(though not as windy as forecast previously), as the pressure
gradient remains enhanced due to a couple episodes of
cyclogenesis in the lee of the Rockies.

As might be expected, some more significant differences in model
solutions emerge at the tail-end of the period, due to slightly
different handling of the next upstream, deep upper low dropping
into position offshore of California early next week. GFS brings a
dry, Pacific front slowly through South Texas on Monday, whereas
the ECMWF brings a more Canadian-sourced front through on Tuesday
with at least a slight chance of showers. Will keep PoP`s silent
through Monday for now.

MARINE (Now through Wednesday):  Buoy 42019 reported northeast winds
around 10 knots gusting to around 14 knots with seas slightly over
3.5 feet with a period of 7 seconds at 02 CDT/07 UTC. Surface high
pressure building and persisting over the western Gulf of Mexico
will produce light to moderate winds and low to moderate seas for
the Lower Texas Coast during the forecast period. Small Craft
Exercise Caution and Small Craft Advisory are not anticipated to
be needed.

Wednesday Night through Sunday: Cyclogenesis in the lee of Rockies
will act to maintain an elevated pressure gradient across the
coastal waters, yielding moderate to occasionally fresh breezes
across the Lower Texas Coastal Waters. However, with the mid-
latitude storm track trending a bit further north, winds should be
held below Small-Craft Advisory criterion, though periods of SCEC
may occur, especially on Thursday. Seas initially at 2-3 ft.
Wednesday night gradually build to 5 or perhaps 6 ft. far offshore
by Thursday night as the SSE fetch is maintained. Seas then relax
to 3-4 ft. from Friday through the end of the period in response
to the slightly loosened pressure gradient.



This product is also available on the web at:
HTTP://WEATHER.GOV/RGV is the U.S. government's official web portal to all federal, state and local government web resources and services.