Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 222017

Area Forecast Discussion
National Weather Service BROWNSVILLE TX
317 PM CDT Sat Oct 22 2016

.SHORT TERM (Tonight through Sunday Night): Beautiful day in-
progress across the Rio Grande Valley and Deep South Texas with
temperatures generally in the low 80s F and dewpoints in the 40s
and 50s. High- pressure ridging in place for the moment both
surface and aloft. Both features will be shifting eastward over
the next 24 hours, however, as a relatively weak mid-level trough
currently over NW Mexico moves in our direction. High clouds are
already streaming over the area ahead of this trough, and will
continue to gradually thicken and lower for much of the short-
term. Migration of the surface high eastward will also cause
surface winds to veer back to the SE by tonight, which will in
turn start bringing back more humid air from the Gulf of Mexico.
Dewpoints will be back into the 60s most areas tomorrow (perhaps
mixing out into the upper 50s far NW), and then up toward 70 for
the coastal zones by early Monday morning.

For tonight, if cirrus does thicken up as expected, radiational
cooling should be limited somewhat, even with light and variable
winds.  Kept inherited mention of some patchy fog for the northern
ranchlands and brush county, but trimmed back areal coverage to keep
out of the RGV as it doesn`t appear that RH`s will approach 100%
there.  Going into Sunday, overall moisture increases somewhat from
west to east with the approaching trough, but H7-H5 layer remains
stubbornly dry.  Raised max temps about 2 degrees across the board
for Sunday, but still held about 2-3 degrees below latest MOS
guidance. Despite the main vort max associated with the upper trough
moving into central TX and a trailing lobe of vorticity moving
through the CWA Sunday afternoon and into the evening, still keeping
PoP`s silent at 10%.  None of the models/blends putting out much of
anything in the way of QPF through early Monday.  With the higher
dewpoints and cloud cover in place, min temps on Monday recover
back to the low 70`s for the SE half of the CWA with some upper 60`s
in the NW.

.LONG TERM (Monday through Saturday):Not too many change to the
forecast as models generally remain in good agreement. A 500mb
high will be centered over the Gulf...with surface high pressure
over the Southern CONUS to start the long term. This will allow
for deeper layer southeasterly flow which will usher moisture
back into the RGV. Meanwhile...a upper level short wave will move
across central TX and provide just enough forcing to generate
showers and some thunderstorms. Have only adjusted some POP
coverage...but was not overly confident to increase amounts. As
the short wave moves away...the 500mb ridge will flatten and
elongate back over the Deep South Texas.

Moisture will stick around for Tuesday and Wednesday as well as
another 500mb storm system moves through the Northern Plains.
This system will cause an already flattened ridge of high pressure
aloft to retreat westward and build over the Desert Southwest. A
few showers or thunderstorms or two will be possible with the
ridge pulled back to the west. But activity will be spotty and
more seabreeze/diurnal in nature.

By late in the period...the ridge will expand back over the
Valley...effectively shutting off the precip chances for Thursday
and Friday. Temperatures will also be warmer than normal with the
high centered overhead. By Saturday...some models are hinting at
an upper level inverted trough moving southwestward around the
periphery of the high pressure system over the Southern Gulf of
Mexico. This ushers moisture back towards the RGV. Models do
differ slightly on how far north the moisture reaches and have
only added slight chance POPs to the southern Valley near the



Now through Sunday night: Moderate ENE winds currently reported
from Buoy 020 will veer to SE by around midnight tonight and
remain at moderate strength. Combined seas down to 3-4 ft. today
and should generally trend down to the 3 ft. range this evening as
ENE swells from the Gulf continue to subside. No adverse marine
conditions expected through Sunday night.

Monday through Thursday: Surface high pressure will generally
remain over the Southern CONUS and Northern Gulf waters through
the forecast period. This will keep low to moderate ENE to E winds
in place. Seas will start out low early in the period...with wave
generally 2 to 3 feet. However...with a prolonged periods of
easterly winds...swells will slowly develop from the ENE through
the week...with moderate seas of 3 to 5 feet expected.


BAYVIEW/PORT ISABEL  69  85  74  86 /   0  10  10  20
BROWNSVILLE          68  86  73  88 /   0  10  20  20
HARLINGEN            65  87  71  89 /   0  10  20  30
MCALLEN              65  88  72  90 /   0  10  20  30
RIO GRANDE CITY      63  88  69  89 /   0  10  10  20
SOUTH PADRE ISLAND   76  84  78  85 /   0  10  10  10




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