Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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458
FXUS64 KHGX 250908
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
408 AM CDT Thu Aug 25 2016

.DISCUSSION...
Infrared satellite imagery early this morning shows high clouds
overspreading the region from the east, as a plume of tropical
moisture pushes into Southeast Texas. Similar to the past few
mornings, low stratus was beginning to develop across portions of
Central Texas. Slightly less certain about how far east these low
clouds will expand this morning with higher clouds moving
overhead, but expect most locations north of Highway 59 to
experience at least patchy fog.

For today, patchy fog will lift by mid-morning with daytime
heating. As has happened the past few mornings, visibilities may
fall below 2 miles in isolated locations. Only planning on
highlighting this hazard in the Hazardous Weather Outlook for now,
but will continue to monitor for any dense fog advisories.
Additionally, the KHGX radar shows isolated showers across the
coastal waters this morning. Expect this activity to continue,
expanding inland later this morning as a plume of 2+ inch
precipitable water air arrives from the east.

Southeast Texas still remains on the western periphery of an
upper ridge over the southeastern US, but shortwaves lifting
across the Southern Plains have allowed for the center of the
ridge to shift away from the region with mid-level heights having
fallen 2 decameters over the past 24 hours per 00Z radiosonde
observations. Increasing moisture and decreasing subsidence will
result in greater shower and thunderstorm coverage today. Expect
highest coverage (40-50 PoPs) south and east of the Highway 59
corridor, closer to where the deeper moisture resides with (30-40
PoPs) north and west of the Highway. Unlike the past few days,
shower and thunderstorm activity will not necessarily be relegated
to the daytime hours but look to continue for most of the region
overnight as weak disturbances moving west under the upper ridge
slide across the region. Otherwise, expect afternoon temperatures
in the upper 80s to low 90s today with overnight lows falling into
the 70s.

A stronger disturbance looks to approach the region during the
day on Friday, resulting in scattered to numerous showers and
thunderstorms. Some of these thunderstorms may be capable of brief
heavy rain and gusty winds. Additionally, given the buoyant,
tropical airmass in place across the region Friday into the
weekend cannot rule out tropical funnels inland or a waterspout or
two along the coast. Finally, cloud cover and rain during the day
Friday will cause many locations to struggle to get out of the 80s
during the afternoon.

The upper disturbance is expected to cutoff from the main flow
Friday into Saturday, with widespread rain chances continuing this
weekend as the cutoff low stalls along the Texas coast. Height
falls associated with this upper low look to induce a weak surface
low/trough over the northwestern Gulf of Mexico, which may provide
a focusing mechanism for rainfall. Upper level winds/ jet dynamics
are not terribly impressive on Saturday and Sunday (part of the
reason why the low stalls along the coast), but model guidance is
fairly consistent on bringing a relative wind speed max (20-30
knots) across the northwestern Gulf and Southeast Texas Saturday
into Sunday.

This (albeit weak) upper level lift combined, enhanced low level
convergence from the surface low/trough in close proximity to the
coast, and deep tropical moisture with 2.2-2.4 inch forecast
precipitable water values raise concerns for at least a locally
heavy rain threat for areas along and south of Interstate 10 this
weekend. Total model QPF during for Saturday and Sunday generally
ranges between 1-3 inches total owing to different placements of
the surface low/trough, and placement of this surface feature
will be critical to if or where a locally heavy rain threat
materializes. Have highlighted best rain chances along the coast
during this time, but isolated to scattered showers and
thunderstorms will be possible farther inland this weekend
especially with daytime heating. Otherwise, rain and cloud cover
should keep afternoon temperatures in the upper 80s to near 90.

The upper low looks to wobble south into South Texas on Monday as
ridging expands across the Southern Plains and ArkLaTex, but may
result in a locally heavy rain threat continuing (especially for
southwestern/ western counties) as it exits the region. Mainly
daytime isolated to scattered thunderstorms will remain possible
on Tuesday and Wednesday with near normal temperatures around 90
degrees expected early to mid next week.

Huffman

&&

.MARINE...
High pressure over the eastern U.S. and lower pressures over the
southwest Gulf of Mexico will produce a light east wind today
through the weekend. The prolonged easterly fetch should produce
slightly elevated tides over the weekend.

An area of low pressure will enter the eastern Gulf of Mexico
early next week. There is a great deal of uncertainty with regard
to the movement and intensity of this feature. Mariners are urged
to keep up the latest forecast. 43

&&

.TROPICS...
The National Hurricane Center is continuing to monitor Invest
99L, a broad area of low pressure northwest of Puerto Rico early
this morning. Satellite imagery shows a largely disorganized area
of showers associated with this feature, with increasingly
favorable conditions for tropical cyclone development as Invest
99L moves towards the Bahamas this weekend. As of now, there are
no forecast impacts from Invest 99L for Southeast Texas with 00Z
model guidance keeping this disturbance well east of the region.
However, with no well-defined center for model guidance to latch
on to, fluctuations in forecast track and intensity of any cyclone
that develops from 99L are expected over the next few days.

As a reminder, late August through early October is the
climatological peak of the hurricane season. Southeast Texans
should make sure they keep up with the forecast and hurricane
preparedness regardless of whether or not a system is in or
approaching the Gulf of Mexico.

Huffman

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      92  74  89  74  91 /  30  20  50  20  40
Houston (IAH)              91  75  89  74  90 /  40  30  60  20  40
Galveston (GLS)            88  79  88  79  87 /  30  50  60  40  50

&&

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

$$

Discussion...14
Aviation/Marine...43



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