Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 230950
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
450 AM CDT Wed Aug 23 2017

.SHORT TERM (Today through Thursday)...

Things are quiet across SE TX this evening, with low temperatures
falling into the upper 70s to low 80s along the coast and mid 70s
further inland. Skies will become partly cloudy by sunrise, as
showers and thunderstorms begin to bubble over the coastal waters
and eventual push inland.

Expecting a fairly saturated airmass to be in play Wednesday with
forecast soundings showing PWs ranging between 1.90-2.10 inches.
This moist airmass can also be seen on the GOES-16 precipitable
water imagery, moving in from the east. Essentially two features are
going to dictate our chance for showers and thunderstorms Wednesday.
The most recent runs of the RAP13, Texas Tech WRF, and HRRR show
development beginning between 12-14Z over the bays and nearshore
waters before pushing onshore by late morning associated with the
seabreeze and day time heating. Additionally, an early season cold
front which is currently draped across the Red River region and
southwestward into Hill Country, will continue to move
southeastward towards SE TX. Precip associated with this frontal
boundary will attempt to push into our northern counties mid-day
Wednesday, but global models such as the ECMWF and GFS show a
majority of these showers and thunderstorms diminishing before
making it into the region. Although there could still be some
isolated lingering convection associated along this boundary.

By Wednesday afternoon, model solutions highlight the best precip
coverage over the southeastern section of our CWA and extending
along the coastline. Moving into the late afternoon early evening
hours, shower and thunderstorm development should shift northward
and across the I-10 corridor. Additional convection could be
triggered off of lingering outflow boundaries sent out from the
initial early day storms. Gusty winds can also be expected with
stronger storms, with showers and thunderstorms potentially
lingering for a few hours after sunset.

Thursday could see slightly more coverage than Wednesday, with the
main driving force behind the precip associated with the progression
of the seabreeze and daytime heating. Wednesday and Thursday will
again be warm, with Wednesday being the hotter of the two.
Wedneday`s high temperatures will reach into the low to upper 90s
further inland, with Thursday`s high temperatures in the low to mid
90s. Low temperatures through early Friday morning will also be near
normal for this time of year.

Hathaway

&&

.LONG TERM (Friday through Tuesday)...

The driver of the long term forecast again remains on the tropical
disturbance made up of the remnants of Harvey. As of 1AM CT, NHC has
a 100% chance of tropical cyclone formation over the next five days,
and a 90% chance over the next 48 hours. This area of broad low
pressure is currently located over the eastern Bay of Campeche,
though there is no sign of a closed circulation as of yet. With the
environment primed for development, a tropical depression or
tropical storm is very likely to form today or tonight. This system
will continue to move to the northwest across the western Gulf of
Mexico today.

A large concern lies in how the global models are handling the
potential track of this system. With the aid in steering provided by
the TUTT low currently located over the northern Gulf, the 00Z ECMWF
and GFS show the system slowing down and meandering over the
northwestern Gulf along the mid to upper Texas coastline before
eventually tracking eastward late Saturday. To account for these
potential slower solutions, bumped up PoPs beginning Friday
morning to account for the heavy rainfall threat possible with
this tropical disturbance, capping the PoPs at 80% for now.

While there is still substantial uncertainty in the motion and
speed of this system, which should become clearer once defining a
closed circulation center, there is still significant potential
for high rainfall totals which could lead to extensive flooding.
The likelihood for the heavier rainfall looks to begin early
Friday and last into late Monday. Keeping PoPs on the higher side
between 60- 80% for now to account for this threat. Also, kept
with the WPC rainfall totals through this extended period.

Regardless of the low certainty in how the track of this system will
prevail... Now is the time to make sure you have your hurricane
preparedness plans ready to go and supplies prepared.

Hathaway

&&

.MARINE...

Light to occasionally moderate winds, combined with low seas will
continue through tonight. The National Hurricane Center continues
to indicate the remnants of Harvey will very likely develop into a
tropical depression or tropical storm today or tonight as it moves
northwestward across the western Gulf of Mexico, possibly reaching
the northwestern Gulf coast late Friday. Deteriorating conditions
(increasing winds and building seas) can be expected across the
upper Texas coastal waters as this system organizes/intensifies
and heads toward the coast with tropical storm conditions
currently in the forecast Thursday night through Saturday.
Significant changes are possible with this forecast, and mariners
are strongly urged to closely monitor the latest forecast over the
next several days. 42

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      99  75  95  75  91 /  30  30  40  30  40
Houston (IAH)              96  77  94  77  87 /  40  20  40  40  60
Galveston (GLS)            91  82  90  81  88 /  40  20  40  60  70

&&

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

$$

Short/Long...08
Aviation/Marine...42



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