Area Forecast Discussion
Issued by NWS Brownsville, TX

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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
FXUS64 KBRO 251155

Area Forecast Discussion
National Weather Service BROWNSVILLE TX
655 AM CDT Tue Oct 25 2016

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


.AVIATION...Upper level clouds will move across the area with
increasing moisture rotating around a ridge of high pressure over
Baja California. With easterly winds prevailing, low level
cumulus field will develop late this morning. Confidence is low on
rain chances, but an isolated shower cannot be ruled out through
early afternoon.


.PREV DISCUSSION... /issued 415 AM CDT Tue Oct 25 2016/

SHORT TERM (Now through Wednesday): A weak short wave continues
to move east across the ARKLATEX overnight as another 500mb trough
moves across the Southern Rockies and approaches the Panhandles
region. Meanwhile...Deep South Texas remains between two areas of
high centered towards Baja Mexico and a weaker
ridge centered over the Gulf.

The aforementioned 500mb trough will pass across Northern Texas
today through Wednesday. Mid to upper level moisture associated
with it will increase cloud cover across the RGV today. Low to mid
level flow remain onshore...however flow aloft at the 500mb level
will continue to be northerly. A few isolated showers will be
possible to day...however given the dry layer of air
expect that any development will be limited to the influence of a
sea breeze.

A similar setup can be expected for Wednesday...however most
moisture will be confined to the lower level with increasingly
drier air aloft. The POPs/precip amounts for Wednesday may even be
too optimistic. Temperatures will continue to range a few degrees
above normal for both highs and lows.

LONG TERM (Wednesday Night through Monday): A 588 decameter
height center will be over Northwest Mexico and portions of the
Desert Southwest Wednesday night, part of a more expansive ridge
extending north into Canada. A positive tilt short wave trough
will dig across the midwest while high press over the Southeast
United States extends into the Northwest Gulf. Showers may develop
to the south over the Gulf Thursday, moving up toward the lower
Texas Coast Thursday night and Friday.

Temperatures during the period will run five to ten degrees above
normal, with ridging providing mid level subsidence. That will
mean mid to upper 80s and even some lower 90s during the day and
mid to upper 60s to near 70 at night. The GFS temperatures are a
bit more modest then those of the ECMWF. Used a model blend in
arriving at the final numbers.

Guidance for pops indicated numbers near climo for this time of
year, which is essentially for a slight chance of rain each day.
With ridging shifting slowly east toward and over the area, the main
source of rain will necessarily be the Gulf, and unsettled weather
will continue there into the weekend. The GFS tries to develop a
weak surface low over the Western Caribbean or Southwest Gulf Wed
night, which does have a tendency to occur (nightly), with the main
impact to enhance convection chances farther north along the coast.

Moving to late in the week and into the weekend, mid level
ridging will continue to edge east over all of Texas and into the
Lower Mississippi Valley. Temperatures will continue above normal
and persistent high pressure over the North Gulf will maintain an
easterly wind.

In summary, upstream ridging will block any serious weather threat
from the west, while activity over the Gulf will be more inclined to
show up on the doorstep as Gulf based shower or diurnal sea breeze
activity. Without a strong focusing mechanism or lift, rainfall, if
any, will remain fairly light. Temperatures will be around five to
ten degrees warmer than normal.

Now through Wednesday...Light to moderate SE to E winds and low
to moderate seas will continue through the next 36 hours as broad
surface high pressure centered over the northern Gulf remains in
control. Some shower activity could be noted through mid morning
and again overnight into Wednesday.

Wednesday night through Saturday...High pressure over the
Southeast United States will nose into the North Gulf Wednesday
night, and when combined with lower pressure to the south, will
result in a large scale anticyclonic flow over the Gulf that will
generate light east winds across the Lower Texas Coastal Waters
and moderate to fresh east winds farther east. There should be
some swell in local seas as a result. The GFS favors developing
lower pressure over the Southwest Gulf on Thursday, which will
back local winds to northeast temporarily. H5 ridging will build
over Texas Thursday, and stronger high pressure developing over
the North Gulf will tend to overpower lower pressure to the south,
veering winds to east again Thursday night through Saturday.
Convective activity will tend to develop and move into the area
through the period. Swells may contribute to wave heights enough
Saturday and Sunday to warrant small craft should exercise caution
conditions offshore.




This product is also available on the web at:

69/54 is the U.S. government's official web portal to all federal, state and local government web resources and services.