Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 211011
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
511 AM CDT Wed Jun 21 2017

.DISCUSSION...
Tropical Storm Cindy may be exhibiting more subtropical
characteristics as the bulk of the main convection remains well
displaced into southern Louisiana from the main 995 mb low located
roughly 200 miles from Vermilion Parish coastline (220 miles
southeast of Galveston Island). Water vapor imagery depicting a
nice swath of dry air rotating along the backside of Cindy`s
circulation and wrapping around her east side...significantly
scouring out precipitation. The official forecast has TS Cindy
making landfall in the Sabine River Valley region (Texas-Louisiana
state line) sometime just past midnight Thursday morning...or
less than 24 hours from now. Western upper ridging will work in
nudging Cindy more east of west...with an Appalachian region mid-
upper trough trending to pull Cindy up to the north-northeast.
Buoy observations have certainly verified the existence of a
tropical storm as persistent sustained 40-45 knot observations
have occurred across the north central Gulf this morning. The main
threat from Cindy will be rainfall and WPC has placed our extreme
southeastern CWA (Galveston Bay, Chambers/Liberty Counties) under
a slight risk for excessive rainfall today. Winds will be the
secondary threat...especially across the southeastern third of the
CWA...marine locations surrounding Galveston Bay and points
offshore east of a Freeport line. Northeasterlies along Cindy`s
western periphery will pick up this afternoon with 20 to 30 mph
sustained magnitudes...with occasional gusts to 40 to 50 mph over
eastern Galveston...Liberty and Chambers counties from this
afternoon through mid to late Thursday morning (i.e., extreme
southeastern forecast area). Taking an eastern storm track into
account...with the model ensemble...has placed an average 1 to 3
inches of storm total rainfall over those communities along and
east of the Interstate 45 corridor. Feeder bands wrapping around
Cindy as she becomes an inland remnant low Thursday afternoon
through Friday could put down an additional 2 to 4 inches in a
short amount of time so going with a local 4 to 6 inches is not
out of the question for the eastern forecast area (although very
isolated in nature). The lack of any recent significant rainfall
has kept soil moisture relatively low...on average about 50% capacity
in the lower 10 cm layer. Thus...with the WGRFC`s Flash Flood
Guidance of 3 to 6 hour 4-6 inch totals...feel any 24 to 48 hour
flooding threat will be very localized in nature.

There is a good possibility that southeastern Texas picks up more
rainfall over the weekend than over the next couple of days with
Cindy...of course assuming she follows the aforementioned Sabine
River Valley track. Texas falls within a general height weakness
channel between the Bermuda ridge and a northwestern Mexico ridge.
The elements of a broad trough axis (left behind in Cindy`s wake)
within an unstable (lower sfc-3km 7 to 7.5 C deg/km lapse rates)
and very moist environment (2 inch pwats)...when throwing in a
sluggishly southern-sagging backdoor boundary...has this weekend`s
weather pattern adjective pegged at `unsettled`. This first
weekend of Summer `17 will kick off overcast/humid with light
east-southeast winds as mornings warm from the sticky lower 80s
into the lower 90s by early afternoon. Areawide inland low end
rain chances on Saturday will increase to more moderate rain
chances focused across the southern half of the forecast area
Sunday. The only positive will be that overcast and intermittent
rain/storms will regulate maxTs to around 90 F...the negative
(other than the rain) will be that weekend heat indices will range
in the 99 to 104 F range.

The next work week`s synoptic weather pattern will undergo little
change...southwestern Desert SW ridging and eastern CONUS troughing
still places the region in that inflection point between the waves.
Higher daytime POPs will be be centered about the Gulf Coast as
this is where the higher moisture/theta e ridging will be located
during peak heating. Convective temperatures in the middle 80s
should be easily achieved with upper 80 F afternoon temperatures
forecast each subsequent day from Monday onward. Overcast...more
periodic rain with a damp ground...should regulate late period
warming to the 80s for the majority of the daytime hours. High
morning humidity will maintain mean low to mid 70 minTs with mid
to late afternoon 50 to 60 %RH values equating to heat indices in
the middle to upper 90s. Hello Summer! 31

&&

.MARINE...
Tropical storm force winds will be moving into the coastal waters
generally east of Freeport during the day today and persist into the
overnight hours until Tropical Storm Cindy moves inland. This is
forecast to occur later tonight...possibly near the Tx/La border
(though always subject to revisions until it actually does so).
No change in the warning/advisory configurations.

Winds: 20-30kt north winds currently in the Gulf east of Freeport.
Elevated rigs just off to the east are seeing some gusts between 40-
50kt. West of Freeport, elevated winds/seas also persist, just not
quite as high.

Tides/seas: Currently running from 1/2 to 1 foot above normal. A 7-
11 foot 10 second swell has filled in across the coastal waters. We
are currently coming in and around Galveston Bay. The combination of
the 2 have produced some decent wave run up along area beaches.
Webcams show water/waves almost to the Seawall in Galveston - so
suspect the usual more prone locations like Highway 127/87 on
Bolivar, etc might be seeing some water close to the road. We are
coming out of high tide now so we`ll probably see some improvement
this morning. The next high tide along the beaches will be around
1230pm, although not quite as high, but it`ll be worth keeping an
eye on. Later tonight, I`d anticipate water levels to start pushing
out of northern parts of the bays as offshore flow increases. We may
need a low water advisory in parts of the bay and Houston Ship
Channel. While at the same time keeping an eye on north facing
shorelines of Galveston Island and Bolivar where the water may pile
up. Complicated scenario...

As Cindy moves inland, winds will gradually back to the west on
Thursday then to the south Thursday night. Moderate onshore winds
will then persist into the weekend.  47

&&

.AVIATION...
Increased winds will obviously be the main aviation hazard
today/tonight for the metro and coastal airports. Otherwise...mainly
VFR conditions should persist for much of the day until we start
seeing some precip approach from the east & southeast later in the
day and overnight. Cigs will then transition down into MVFR
territory.  47

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      91  74  91  76  93 /  10  30  60  40  30
Houston (IAH)              88  76  86  77  92 /  30  70  70  40  50
Galveston (GLS)            84  78  85  82  90 /  60  80  70  50  60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Tropical Storm Warning for the following zones: Chambers...
     Galveston...Harris...Liberty.

     Coastal Flood Advisory until 11 AM CDT this morning for the
     following zones: Brazoria.

GM...Small Craft Advisory until 9 PM CDT Thursday for the following
     zones: Coastal waters from Freeport to the Matagorda Ship
     Channel out 20 NM...Matagorda Bay.

     SMALL CRAFT SHOULD EXERCISE CAUTION until 7 AM CDT this morning
     for the following zones: Coastal waters from Freeport to
     the Matagorda Ship Channel out 20 NM...Matagorda Bay.

     Tropical Storm Warning for the following zones: Coastal waters
     from High Island to Freeport out 20 NM...Galveston Bay...
     Waters from High Island to Freeport from 20 to 60 NM.

     Small Craft Advisory until 9 PM CDT Thursday for the following
     zones: Waters from Freeport to the Matagorda Ship Channel
     from 20 to 60 NM.

&&

$$

Discussion...31



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