Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 142309 AAA
Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
609 PM CDT Fri Oct 14 2016
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...High pressure aloft will maintain large subsidence
across all of Deep South Texas with mainly VFR conditions through
the next 24 hours. No MVFR cigs are anticipated at the TAF sites
however low probabilities for MVFR ceilings and IFR vsby is noted
over the Western and Northern Ranchlands around sunrise Saturday.
Light southeast to light and variable winds overnight become light
to moderate southeast Saturday.
.PREV DISCUSSION... /issued 304 PM CDT Fri Oct 14 2016/
SHORT TERM (Tonight through Saturday Night): Current water-vapor
satellite imagery shows a short-wave trough moving through NE Texas
at this time. This is temporarily lowering 500-mb heights slightly
but otherwise having no effect over the local area. A stationary
surface front is also analyzed across central TX but will not
approach any nearer. 12Z BRO sounding was quite dry, with
precipitable water of only 1.17", which is in the lowest 25% of
climo values for this date. In spite of this, some low-topped
showers offshore have been riding along on the SSE low-level flow
through the morning but are finally tapering off.
By later tonight and tomorrow, the 500-mb high rebounds eastward over
the area in the wake of the aforementioned shortwave. Subsidence
keeps the column dry, with precipitable water only running 1.1-1.3"
and moisture confined below about 800mb or so. Thus, no precip
through the period is expected except perhaps a few offshore showers
again late tonight.
Nudged tonight`s min temps downward a degree or two in line with
persistence and latest model guidance. Will still be running 4-
6 degrees above normal. For Saturday, max temps should be up a
couple of degrees from today as thicknesses come up slightly, which
was well-reflected in current forecast. This will yield high temps
about 7-10 degrees above normal for mid-October, with Brownsville
flirting with the record high for the date, which is 94F.
LONG TERM (Sunday through Friday): 500 mb ridging will persist
over the RGV from Sunday on through until next Tuesday. The ridging
will then collapse as a strong and deep 500 mb trough axis digs into
the central and eastern portions of the lower 48 states starting
Wednesday. As this trough axis digs over the central states a cold
front will push into Deep South TX late next week potentially
bringing an end to the +90 degree highs as a cooler air mass spreads
southwards from the northern states. The moisture advection ahead of
this 500 mb trough and associated cold front is still somewhat
limited. However enough moisture pools ahead of this front to
warrant some low end pops late next week.
The ECMWF and the GFS models both show good agreement in the
synoptic pattern up through around Tuesday/Tuesday night of next
week. The models then start to diverge quite a bit from Wednesday
on through Friday in the handling of the 500 mb trough axis
digging into the central states. The ECMWF shows a much more
progressive trough axis moving pretty quickly to the east while
the GFS wants to slow down and cut off the trough as a closed low
near the Texas Panhandle region later next week. This results in a
slower southward progression of the cold front in the GFS with a
faster and somewhat milder fropa indicated in the ECMWF.
Will opt for a model blend of the temps and pops through Day 7 as do
not have a preferred model at this time due to timing differences
showing up for the latter half of next week. After a promising start
for model to model consistency yesterday with the ECMWF and the
GFS...confidence in the longer range forecast wording has dropped a
bit today. Confidence is fairly high in the RGV forecast temps
and pops through next Wednesday. Confidence levels then start to
drop for Thursday and Friday as the ECMWF and the GFS diverge in
the timing of the central U.S. trough axis. Hopefully we will see
a little better agreement in the future GFS/ECMWF runs.
MARINE: (Now through Saturday night): An easterly swell of 3-4 ft.
is indicated in current obs from Buoys 42020 and 42002 (200nm out
from Brownsville). With only light-moderate SE winds over the coastal
waters, however, combined seas should not rise much above 4 ft.
before possibly subsiding later on Saturday. Isolated showers
for the outer waters again late tonight, then rain-free
Sunday through Wednesday Night...Surface ridging will remain in
place over much of the Gulf of Mexico and the Gulf Coast on
through early next week. This will maintain fairly steady and
light/moderate southeasterly winds through Tuesday night with a
little more easterly flow developing Wednesday/Wednesday night
with the approach of the cold front next week. Seas will remain
fairly benign due to the light to moderate onshore flow pattern.
So do not expect any SCA conditions through the first half of next
week. The marine conditions during the latter half of next week
will be a little trickier due to the divergent solutions shown by
the GFS and the ECMWF models. If the GFS verifies with the slower
fropa the lower Texas coastline may not see SCA conditions until
Friday. If the ECMWF solution verifies with a faster progress of
the cold front...SCA could develop as quickly as early Thursday
.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL 73 89 75 92 / 10 10 10 0
BROWNSVILLE 73 93 73 94 / 10 10 0 0
HARLINGEN 70 94 72 94 / 10 10 10 0
MCALLEN 73 97 74 96 / 10 10 0 0
RIO GRANDE CITY 71 94 73 98 / 10 10 0 0
SOUTH PADRE ISLAND 80 85 80 86 / 10 10 10 0
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