Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 241037 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
437 AM CST Fri Nov 24 2017

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


.AVIATION...VFR TAFs. Aside from scant high cirrus drifting down
from the north later today, quiet conditions will prevail as broad
high pressure remains in place over the region. Light winds will
stabilize from the south southeast later today as pressure falls
over the Texas Panhandle provide a weak but undeniable gradient.


.PREV DISCUSSION... /issued 337 AM CST Fri Nov 24 2017/

..Warmer With Continued Abundant Sunshine Today...

SHORT TERM (Today through Saturday): Little has changed since
Thursday, and will therefore piggy back somewhat on the previous
forecast as deep south Texas and the Rio Grande Valley will tend to
remain under the influence of high pressure at the surface and mid
level ridging to the west. This pattern, coupled with a very dry
atmosphere, will support a rain free forecast and limited cloud
cover. After a nippy start this morning temperature wise, with a lot
of readings in the 40s, the day will warm well into the 70s, and to
near 80 in some spots. A weak south wind will develop tonight, with
some recovery in dew points, and low temperatures will rise into the
50s. By Saturday, high temperatures will again be in the 80s, above
normal by a margin of around 10 degrees, but still well under any
record high values for the day. The tail end of a cold front
stretching across the southern U.S. will push into south central
Texas by Saturday, under a transiting plains short wave trough, but
any local effects will be attenuated and deferred into the long term
period. Run to run consistency has been pretty good with short term
temperatures overall, though the models do have slight differences,
seemingly more so with high temps. Went with a blend with above
normal confidence.

LONG TERM (Saturday Night through Thursday): The long term period
will begin with the aforementioned very weak surface frontal
boundary pushing through the area. With the parent wave east of
our region (and spatially similar to the last system) much of the
forcing will be offshore. Still, models do show some very weak QPF
signal late Saturday and Sunday. Continued to keep the forecast
dry for now, however, if the trend continues we may need to bump
POPs slightly for this timeframe in subsequent forecasts.

Sunday looks just slightly cooler, however, as the surface high
builds east by Monday, southeasterly return flow will help bump
temperatures back into the 80s. Aloft, northwesterly flow
eventually gives way to zonal or perhaps southwesterly flow by

If you`ve been following over the last few days you will know we
have been advertising a cold front boundary passage by midweek. It
is still looking as if that will happen. The GFS is starting to
converge on the initial EURO idea of a closed low across the west
and a slower, less progressive flow. There are still some spatial
disagreements in terms of exact placement of the upper low as
well as eventual evolution of the upper ridge over Mexico,
however, confidence is increasing that another cold front will
push through Wednesday...albeit appears to be much weaker than
initially thought. Due to this, kept temps in the long term
warmer than prior forecasts and left some mention of POPs.

Looking just a bit further into the crystal ball, the GFS 5-wave
is finally showing signs of a potential Arctic intrusion across
much of the US sometime shortly after the start of December.
Details this far in advance are of course murky at best, but
perhaps some hope for those patiently awaiting something other
than mostly above average temperatures. Speaking of, again,
mainly above average temperatures through this period.



(Today through Saturday): Light to moderate winds, generally from the
south, and low to moderate seas will prevail in the short term.
Broad high pressure covers the northwest Gulf while a 590 dam high
height center remains over the Baja California area, extending north
into the western fourth of the country. Light winds and low seas
will start the forecast today. A short wave trough, associated
loosely with a faster moving trough over the Great Lakes, will move
through the western ridge and into the high plains today and
tonight, supporting pressure falls over the Texas Panhandle region
and slightly stronger, moderate strength winds tonight and Saturday.
Since high pressure will fill in over the southern Plains rather
quickly later on Saturday, the stronger marine winds will be
temporary, and no hazardous marine conditons will be present during
the short term.

(Saturday Night through Thursday): Light winds and seas can be
expected through the weekend. A weak cold front will push into
the region late Saturday or early Sunday, however, no impacts to
seas expected. The only marine issue in the long term looks to be
a cold frontal boundary midweek, which should increase winds and
seas to at least SCEC thresholds, however, the overall trend has
been a weaker frontal passage with a general decrease in forecast
winds/seas from prior forecasts.





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