Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 280142
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
842 PM CDT FRI MAY 27 2016

.UPDATE...
The thunderstorm complex that`s slowly pushed across the region
all day today has finally reached the Upper Texas coast and is
expected to continue to move into the Gulf through the remainder
of the evening hours. Harris County FWS gages have shown rain
rates in the 1-1.5"/hour range this evening and an additional 1-2"
of rain (with isolated higher amounts) will be possible as the
line clears the region. The main forecast update to retrend the
forecast based on latest observational data and drop the Flash
Flood Watch as the majority of the rain has pushed south of the
watch area. Have also added patchy fog where recent rainfall and
light winds will contribute to fog development. Already seeing a
few sites (College Station, Bryan, and Brenham) with visibilities
of 6 miles or less.Drier conditions are expected by early Saturday
morning, with overnight lows in the upper 60s to low 70s.

Huffman

&&

.PREV DISCUSSION... /ISSUED /

AVIATION...
Today`s MCS nearing the coast at this time. However there are some
concerns with the west end of this line...which appears to be back
building further west. But having said that, it does look like the
entire line is continuing to slowly translate south. Will continue
to carry TSRA for IAH and points south. For sites to the north, we
are seeing IFR CIGS. Extrapolating the timing for the back edge of
the clouds has CLL clearing at/around 02Z, then to the I-45 corri-
dor at/around 06Z. Was on the fence about POPS for tomorrow after-
noon, but did opt for VCSH/VCTS at most sites given the trends the
last few days. 41

PREV DISCUSSION...

The latest water vapor imagery shows the upper level low over
CO/KS border with its trough axis stretching into central Texas.
Thunderstorm activity has formed north of a strong outflow
boundary which has become more oriented on the boundary and
training along it. Overall motion of the line of storms is to the
SE but individual storms are moving ENE/NE. This has allowed for
some hourly rain rates near 2-3 inches an hour over some of the
same areas that flooded last night and yesterday. Storms should
track into Houston over the next couple of hours before moving
east. The HRRR 18z run seems to have a decent handle on the
current evolution and pushes the convection towards the coast.
This really depends on whether storms become more organized and
cold outflow can push the boundary south. HRRR seems to fast with
this motion compared to current trends. Could see scattered storms
continue through the evening and slowly transition east out of SE
Texas by midnight.

Upper level ridging builds over SE Texas this weekend and into
early next week. Precipitable water values drop to under 1.5
inches so may only see an isolated storm with day time heating
each of Saturday and Sunday. Moisture increase back again late
Monday into Tuesday which will support higher rain chances as the
ridge breaks down. For the middle of next week the upper level
pattern becomes more amplified with an upper level trough forming
over the plains. A frontal boundary works south as well which will
be a focus for more thunderstorm activity. There may also be a
couple of week short wave troughs that move over the area to help
support thunderstorm activity. The 3 to 4 day break from heavy
rainfall should allow for much needed runoff and receding of
flooding. We will likely need to monitor the extended forecast
next week for another heavy rainfall threat.

MARINE...
Very strong onshore winds persisting across the coastal waters today
and expecting this pattern to linger through the rest of the aftn on
into the early evening hours as the associated line of storms across
SE TX moves offshore. These storms are forecast to move off to the E
and SE this evening with light/brief offshore winds in its wake.

However, onshore winds will be returning to the marine waters tomor-
row ow and will be prevailing the rest of this holiday weekend. With
the weather less active, winds and seas should also be lower.

The persistent fetch from Gulf combined with the strong onshore flow
have helped raise tide levels to near 3.3 feet above MLLW this aftn.
With the winds decreasing tonight, tides should follow suit as well.
41

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      70  88  73  86  71 /  20  30  10  20  20
Houston (IAH)              72  89  73  88  71 /  60  30  10  20  10
Galveston (GLS)            80  85  78  84  77 /  60  20  10  20  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until 10 PM CDT this evening FOR THE
     FOLLOWING ZONES: Brazoria...Chambers...Galveston...
     Matagorda.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 1 AM CDT Saturday FOR
     THE FOLLOWING ZONES: Galveston Bay...Matagorda Bay.

     SMALL CRAFT SHOULD EXERCISE CAUTION until 7 AM CDT Saturday FOR
     THE FOLLOWING ZONES: Coastal waters from Freeport to the
     Matagorda Ship Channel out 20 NM...Coastal waters from High
     Island to Freeport out 20 NM.

     Small Craft Advisory until 10 PM CDT this evening FOR THE
     FOLLOWING ZONES: Waters from Freeport to the Matagorda Ship
     Channel from 20 to 60 NM...Waters from High Island to
     Freeport from 20 to 60 NM.

     SMALL CRAFT SHOULD EXERCISE CAUTION until 7 AM CDT Saturday FOR
     THE FOLLOWING ZONES: Waters from Freeport to the Matagorda
     Ship Channel from 20 to 60 NM...Waters from High Island to
     Freeport from 20 to 60 NM.

&&

$$

Discussion...14


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