Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 210230
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
930 PM CDT Tue Jun 20 2017

.UPDATE...
No changes to previous watch/warning configurations.

At 00z, the LCH sounding showed PW values near 1.90 inches while
the CRP sounding is a bit drier at 1.70 inches. 850 mb moisture
was increasing from the east and the edge of the deeper moisture
extended from about Tyler to Port Bolivar. At 500 mb, an expansive
upper ridge extended east into western MS but last night, the GFS
was a bit stronger with the ridge so perhaps the influence of this
feature will be less than anticipated. With a weaker ridge,
perhaps TS Cindy could be tugged a bit further north before
reaching the TX coast. At 300 mb, a pocket of 25-30 knots will
still provide some shear and could hinder intensification.

Tropical Storm Cindy remains nearly stationary over the north
central Gulf. The storm is expected to begin moving NW overnight.
Showers and thunderstorms will begin to move into the coastal
waters and could encroach on the coast prior to sunrise. Rain
chances will likely increase through the day with higher rain
chances Wednesday night into Thursday. A Flash Flood Watch may be
required for parts of the area for Wednesday night.

Previous forecast has a good handle on things so no significant
changes planned.  43

&&

.PREV DISCUSSION... /ISSUED 644 PM CDT Tue Jun 20 2017/

AVIATION...
Impacts from TS Cindy should begin to affect KGLS this evening as
wind gusts will be likely during showers from rain bands. One band
was shown by radar to be moving into the Upper Texas coastal
waters at 2330Z and may affect KGLS by 03Z. Winds should increase
during the day on Wednesday after about 14Z for the inland sites.
Gusts will range from just over 20 knots well inland at KCLL and
KUTS to near 30 knots at KGLS at the coast. Ceilings will possibly
lower to near MVFR by the late afternoon on Wednesday.

40

PREV DISCUSSION... /ISSUED 349 PM CDT Tue Jun 20 2017/

DISCUSSION...
Newly upgraded Tropical Storm Cindy continues to dominate the
forecast as it meanders over the Central Gulf. The new advisory
drifts the track a bit more to the west, necessitating the upgrade
of the tropical storm watch area to a tropical storm warning. The
expectation for primary threat to the area continues to be for
heavy rainfall along and east of the track`s expected center,
which may cause some limited flooding threat. Some minor impacts
from wind gusts and elevated tidal levels may be seen in parts of
the Bolivar Peninsula as well. More details can be found in issued
tropical products.

NEAR TERM [Through Tonight]...

Weather continues to be hot and largely dry across Southeast Texas
today while Tropical Storm Cindy continues to try to organize well
offshore. Radar has shown some showers trying to develop along a
coastal boundary from Liberty County southwest through Brazoria
County towards Matagorda Bay. For the most part, these showers have
been isolated, light, and short-lived. However, near Matagorda Bay,
these showers have been a bit more successful.

These showers should come to an end this evening, but overnight look
for rain chances over the offshore waters to increase as the
circulation of Cindy continues to draw nearer. Over land, expect
scattered clouds to become a bit more dominant overnight, but
don`t expect temperatures to fall below the middle to upper 70s
thanks to high dewpoints.

SHORT TERM [Wednesday Through Thursday Night]...

The caveat right up front: This portion of the forecast is going
to be very dependent on the precise track of Cindy. A deviation in
track to the left or right will move impact areas accordingly.

Now, much of the morning should continue as past days have.
The key harbinger of change will be increasing clouds from the
southeast as Cindy moves closer to the area. Most should stay dry
Wednesday morning with most outer rains still offshore - however,
immediate coastal areas may start to see increased showers begin
to pop up. Rainfall potential will increase through the afternoon,
with the prime time for rain occurring Wednesday night into
Thursday morning. Some heavy rains will obviously be possible,
with the highest threat along and east of the storm`s center.
As of the current forecast track for the storm, this will put the
heaviest rain east of the Houston metro, from the coast up towards
Livingston. It`s worth noting that Cindy`s lopsided appearance
means that the rainfall gradient on the west side of the center is
likely to be very sharp, with the difference between solid rain
totals and very little rain not likely to be separated by a great
distance. Because of this, will hold off on any flash flood
watches for now to gain some more confidence on where the heaviest
rain is likely to fall.

Cindy`s center will continue to move north through Thursday and
Thursday night, before a northern stream trough passing through
the Great Lakes will draw what`s left of the storm to the
northeast through Louisiana. As it does so, rain chances will draw
down, but continue to linger into Thursday night. It probably goes
without saying, but high temperatures will be noticeably cooler
with cloudy skies and rain keeping temperatures down. Overnight,
though, these factors will also keep low temperatures elevated,
suppressing the diurnal curve in temperatures.

LONG TERM [Friday Through Tuesday]...

Friday and Friday night look a bit drier as Cindy accelerates
away from the region. But this trend does not look to be terribly
long lived as the upper trough that takes the storm away will dig
into the Eastern US, and help a cold front slide into the area.
There is considerable uncertainty in exactly how this front will
behave, but for now models suggest it may stall out in the general
vicinity of the coast, and could provide a focus for continued
rainy activity into early next week. Previous guidance had also
brought in a surge of very high moisture - about 2.3 inches of
precipitable water - as well, which alerted to potential that
Cindy may be a predecessor event for later high rainfall. The GFS
has since backed off of that, but still keeps precipitable water
around or above 1.75 inches with weak to non-existent capping,
which could allow for some very rainy showers and storms. With
strong focus put on Cindy, simply want to highlight the fact that
continued showers and storms may be possible.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      74  91  75  87  76 /  10  20  40  60  40
Houston (IAH)              78  88  77  86  78 /  10  50  80  70  60
Galveston (GLS)            81  85  80  86  83 /  20  70  80  70  50

&&

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

GM...Small Craft Advisory from 7 AM Wednesday to 6 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 Wednesday 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 6 PM CDT Thursday for the following
     zones: Waters from Freeport to the Matagorda Ship Channel
     from 20 to 60 NM.

&&

$$

Discussion...43



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