Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 151743
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1243 PM CDT Tue Aug 15 2017


.AVIATION...
A few showers still going on over Liberty/Chambers county and
extending off to the east with greater coverage and becoming TSRA.
VFR at the area terminal at 17z with SW winds 5-13kts. Expect
winds to back to the south and south-southeast this afternoon and
relax slightly loosing the gusty character of a few hours ago.
An isolated shower or thunderstorm may be possible near IAH/HOU
this afternoon but chances look low enough to hold off on mention
of VCSH/VCTS for now. Overnight some patchy MVFR CIGS should
redevelop after 09z mainly for CLL/UTS with the possibility of
some light fog at CXO/LBX. Streamer showers before sunrise should
dot the coastal areas and by mid to late morning expand inland to
SGR/HOU/IAH with lighter winds than today. Will mention VCSH IAH
southward starting 14-16z.
45

&&

.PREV DISCUSSION... /ISSUED 1151 AM CDT Tue Aug 15 2017/

UPDATE...
Streamer showers this morning appeared considerably more healthy
on radar than previous days. At 1145am, this has mostly come to an
end except around Liberty and Chambers counties. Visible satellite
shows clouds streets are in place across much of the area, but
are pretty dampened except around and a bit to the north of
Galveston Bay, where there`s a bit more vertical growth. This
presentation would seem to support the going thought of having
the best convective potential in this portion of the area,
dropping off to the west. Did sharpen up the PoP gradient a little
more to reflect trends in short range models, but stopped short of
going dry in the Houston Metro just yet, keeping slight chances
there. Otherwise, the forecast is largely on track, needing only
cosmetic tweaks to better flow with the obs.

Luchs

PREV DISCUSSION... /ISSUED 653 AM CDT Tue Aug 15 2017/

AVIATION.../12Z TAF/
Surface analysis shows enough of a pressure gradient for moderate
southerly winds today. Only MVFR conditions are at KCLL and KCXO
with low cloud decks and patchy fog. Looking forward, each TAF
looks like a repeat of yesterday and think persistence forecast
make sense. Based on GOES 16 derived PW, there is a moisture
gradient across the area with highest moisture over far E Texas.
There should be a few showers this morning along the coast which
should spread NE of KGLS. Think showers miss Houston area
terminals but could become close enough that a VCSH may be needed.

Overpeck

PREV DISCUSSION... /ISSUED 357 AM CDT Tue Aug 15 2017/

DISCUSSION...
The main item of concern over the next few days will be the heat.
From today through Sunday afternoon heat indices will likely
reach to between 104 and 107 and there could be an hour or two
where the heat indices reach to between 108 and 110, especially
Friday and over the weekend. To help exacerbate the situation,
nighttime low temperatures are only expected to fall into the
upper 70s well inland and around 80 toward the coast and bays. The
heat indices will be just under advisory criteria today but will
reassess today.

Some relief could be found with isolated to scattered showers and
thunderstorms. The upper level ridge of high pressure that extended
across southern and central Texas and over the northern Gulf
coastal areas 500 mb up to 200 mb has a weakness in place over SE
Texas and the NW Gulf early this morning. However, the models show
some indication that the ridge will try and push the weakness
eastward a bit today. With PWs near 2 inches over the far NW Gulf
of Mexico working its way into the coastal counties east of
Freeport, think that the best chances for showers and
thunderstorms today will be over the eastern set of counties. The
coverage will depend upon high strong the ridge develops overhead.

During the next few days, an upper low that was over the Yucatan
early this morning will work its way westward toward the lower TX
coast and Mexico. As it does so, the upper level ridge will
reassert itself over the forecast area and help to suppress all
but isolated showers and thunderstorms on Wednesday. By Thursday
an inverted upper trough will extend northward form the upper low
into SE Texas. This should help generate better coverage of
scattered showers and thunderstorms mainly Thursday afternoon.
Best chances will be over the eastern areas where model PWs were
slightly higher. The upper level ridge is then expected to build
back overhead the area from the east starting on Friday. However,
daily isolated showers and thunderstorms will be possible through
the weekend. The GFS and ECMWF both showed an upper level system
moving westward across the northern Gulf of Mexico into the upper
Texas coastal areas late Monday into Tuesday. The timing, location
and coverage of any resulting showers and thunderstorms is
difficult to ascertain at this time but there could be an increase
in rain chances for the start of the work week.

40

MARINE...
Southerly winds should continue for the next several days into the
weekend. The low level jet may be stronger each night which will
allow for slightly higher winds each of the next couple of nights.
This means winds around 15 knots can be expected at night across the
Upper Texas Coastal waters. Winds drop back down closer to 10 knots
during the day. Seas will persist at 3 to 4 feet and then slowly
drop to 2 to 3 feet for the end of the week.

Tide levels look to be about a half foot above normal or less. Tide
levels should remain near these levels for the week with little
change in winds.

Overpeck

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      99  78  98  78  99 /  10  10  20  10  10
Houston (IAH)              96  80  95  80  96 /  20  10  20  10  30
Galveston (GLS)            90  84  91  83  91 /  20  10  20  10  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

Discussion...25
Aviation/Marine...45



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