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Area forecast discussion
National Weather Service Houston/Galveston Texas
645 am CDT Thu Sep 21 2017

Aviation.../12z taf/
radar imagery showing that showers are beginning to develop along
the coast again but perhaps not quite as much as yesterday. GOES
16 10.3-3.9 micron difference channel showing clearly where low
stratus begins and ends. This is mainly north of kela to kcxo to
k6r3 where obs also show IFR ceilings. Ceilings are transient at
times so likely see a mix of IFR/MVFR/VFR for kcll/kuts/kcxo taf
sites. Houston terminals south to the coast remain VFR with patchy
fog surrounding them. Think these areas will largely remain VFR
except for maybe later in the morning as shower activity begins.
Tafs keep mention of thunderstorms in the vicinity but begin ts around 16-17z per latest
hrrr and WRF model runs. Convection should end 22z to 01z this
evening. Sref low ceiling probabilities are highest west of the
area overnight into Friday morning but low visibility
probabilities still higher from kcll to kuts. Fog may be an issue
but could hinge on how much rain falls across the area and
clearing overnight.

Overpeck



&&

Previous discussion... /issued 337 am CDT Thu Sep 21 2017/

Discussion...
the pattern over southeast Texas early this morning consisted of
an upper low pressure trough that extended from the mid Atlantic
coast through Louisiana into our area. An upper level high
pressure ridge was across north and central Texas and bordered the
northern and western portions of the forecast area. An abundance
of moisture was present south of the Interstate 10 but mainly off
of the coast into south Texas. Models show that this moist airmass
will push northward this morning. Given the unstable airmass do
expect isolated showers currently occurring along and off of the
coast to spread inland and become more widespread this morning and
afternoon. Model forecast soundings show the potential for locally
heavy rainfall given that pws reach 2.0 to 2.1 inches and
k-indices reach to between 34 and 36. There is also the potential
for isolated strong storms as cape values will reach to between
2800 and 3300 during the mid and late afternoon period.

The shower and thunderstorm coverage should decrease on Friday
and Saturday as the upper level high pressure ridge builds
overhead from the west. A combination of an approaching upper
trough and a weakening of the ridge will lead to a more unstable
airmass beginning on Sunday. This in turn will lead to increasing
rain chances through the first half of the week.

40

Marine...
light to moderate southeast winds and seas around 3 feet are
forecast to persist along the Upper Texas coast through at least
the next week. Scattered showers and a few thunderstorms will be
possible this morning through today as higher moisture moves
inland from the Gulf. Showers and a few thunderstorms will be
possible each day going into next week with the best chances in
the morning for the coastal areas. Tide levels will likely be
about a half foot above normal through the rest of the week with
maybe a slight increase to 1 foot above normal over the weekend.

Overpeck

&&

Preliminary point temps/pops...
College Station (cll) 92 73 92 72 92 / 50 30 20 10 20
Houston (iah) 89 73 91 72 90 / 50 30 20 10 30
Galveston (gls) 89 78 90 78 89 / 40 30 20 10 20

&&

Hgx watches/warnings/advisories...
Texas...none.
GM...none.
&&

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