Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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758
FXUS64 KHGX 212351
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
651 PM CDT Thu Sep 21 2017

.AVIATION...
Some changes with the 00Z TAFS - lowered CIGS/VIS a bit for to-
night/early Fri morning for some sites and added the mention of
VCSH for most sites tomorrow afternoon. Widespread showers this
afternoon should give way to clearing skies,light winds and wet
grounds across the area tonight. These conditions will be favo-
rable for the development of some patchy fog/low clouds tonight
through sunrise tomorrow morning...in particular locations just
north of IAH. While most models are drying things out tomorrow,
still not confident enough to not mention at least VCSH for the
afternoon hours tomorrow. Of note, NAM is the lone outlier, and
has a slug of 2" PWs moving in from the west tomorrow afternoon.
41

&&

.PREV DISCUSSION... /ISSUED 332 PM CDT Thu Sep 21 2017/

Scattered to numerous slow moving showers and thunderstorms
continue across Southeast Texas this afternoon as a disturbance
moves eastward across the area. The slow moving activity and
precipitable water values above 2 inches have brought locally
heavy rainfall to the area resulting in several
advisories/warnings. At one point, a Harris County Flood Warning
System rain gage (Cypress Creek at Huffmeister) had rainfall rates
of 0.48 inches in 5 minutes and 0.80 inches in 10 minutes. Expect
decreasing coverage/intensity late this afternoon through early
this evening. The area remains on the southern fringes of ridging
both at the surface and aloft, and enough heating should allow for
some mainly daytime shower and thunderstorm development over the
next several days. But compared to today, expect to see much less
coverage for the end of the week and over the weekend with lower
precipitable water values. Still looking at an eventual increase
in rain chances next week as mid/upper level ridging edges
eastward and a western U.S. trough gradually works its way toward
the east. Will be carrying higher rain chances as we head on into
the middle to end of the week when the trough and associated slow
moving cold front begin to work their way toward our area. Will
need to keep a close eye on model trends over the next several
days as some have precipitable water values approaching a very
high 2.50 inches under the persistent onshore flow ahead of the
slow moving boundary. This potential heavy rain event is still
many days away, and a lot can change with the models. Obviously,
our area does not need to see another significant rainfall event
as the Harvey recovery continues. 42

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      73  91  72  92  72 /  30  20  10  20  10
Houston (IAH)              73  91  72  90  73 /  30  20  10  20  10
Galveston (GLS)            80  89  78  89  80 /  30  20  10  20  10

&&

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

$$



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