Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 231526
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1026 AM CDT Fri Jun 23 2017

.UPDATE...
Southeast Texas is already off to a hot start this morning with
10 AM CDT heat index values in the mid to upper 90s west of
Interstate 45. Visible satellite imagery shows cumulus cloud
streets streaming northeast across most of the region, with
slightly "cooler" conditions across the extreme eastern counties
where denser cloud cover exists. Aircraft soundings out of Houston
reported 850 MB temperatures around 21 C, which should provide
for daytime highs climbing into the low to mid 90s. The
aforementioned cloud cover will play a big role in just how warm
the region is able to get today... and would not be surprised to
see some upper 90s for areas (especially the western counties)
where cloud cover is able to scour out. No changes are planned to
the ongoing heat advisory, with peak afternoon heat index values
in the 102-109 range this afternoon.

Morning soundings from Corpus Christi and Fort Worth show good
capping around 940-960 MB, which should do a good job suppressing
most convection that attempts to develop once convective
temperatures in the lower 90s are reached around midday. This
capping inversion is not quite as strong on the Lake Charles
sounding and as a result areas east of Interstate 45 may see an
isolated shower (or possibly a thunderstorm) through early
evening. Main change to the forecast was to add an isolated shower
mention to the eastern waters where surface analysis noted an
axis of surface convergence as well as to areas around Galveston
Bay this afternoon based on trends in latest high resolution
guidance. Also updated hourly temperatures and dew points based on
observational trends.

Huffman

&&

.PREV DISCUSSION... /ISSUED 620 AM CDT Fri Jun 23 2017/

AVIATION...
MVFR cigs should lift throughout the morning. An isolated shower
or storm may be possible this afternoon, but chances are far too
low to include in the taf. MVFR cigs may return overnight tonight.
Otherwise, light to moderate southerly wind is expected through
the taf period.  11

PREV DISCUSSION... /ISSUED 448 AM CDT Fri Jun 23 2017/

DISCUSSION...
Warming 850/700mb temps will likely inhibit much in the way of
precip today - especially for portions of the region west of
I-45. Continued southerly flow will persist and am not expecting
the current 75-79F dewpoints to mix out all that much. Warm temps
and high humidity will combine to produce some 107-109 degree
heat indices today...generally along and west of a College
Station-Edna line. Went ahead and issued a heat advsy for that
area this afternoon. Expect 103-107 indices further east.

A weak cool front is forecast to sag into se Tx on Saturday. PW`s
pool to 2-2.3" ahead of the front and 850/700mb temps diminish
whereas capping shouldn`t be much of a concern. Expect
showers/thunderstorms to increase in areal coverage with daytime
heating. With a general weakness situated aloft and light
steering flow, storm motions appear to be less than 7kt so
locally heavy rain appears to be possible. A second concern is
a possible collision of the seabreeze with precip along the front
during the afternoon - which would enhance rain rates & storm
strength where it occurs. Unfortunately this many times is close
to the metro area. Just something we`ll be watching...

Elevated moisture levels, a diffuse front, and a mid/upper level
weakness will linger into at least the early part of next week.
This should provide fairly good chances of shra/tstms each day,
most likely diurnal in nature w/ precip offshore at night
transitioning inland during the day. Same general setup, minus the
surface boundary and maybe not as much resident moisture, will
probably persist for the remainder of the workweek. 47

MARINE...
Moderate southerly winds should slacken some later this morning, but
6-7 foot seas will likely stick around for most if not all of the
day today and into tonight. For this reason, the Small Craft
Advisory was extended for the offshore waters through 3 PM this
afternoon with a SCEC in place after that lasting into tonight.
Winds and seas will continue to slowly diminish into the weekend,
with periods of moderate onshore flow and elevated seas returning
around midweek.

Tides are still elevated tonight with some possible coastal flooding
in the usual areas like Surfside, Blue Water Highway, and Highway 87
at 124 on Bolivar. A Coastal Flood Advisory has been issued for
these areas as high tide is approaching. Tide levels should come
fall below critical levels by mid morning. Astronomical high tides
will be above 2 feet the next few days. The good news is wind/seas
should gradually diminish, but we`ll continue to monitor conditions
for the usual spots prone to elevated water levels. 11

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      96  77  90  73  87 /  10  20  40  40  40
Houston (IAH)              93  77  90  75  87 /  10  20  70  40  70
Galveston (GLS)            89  81  89  81  87 /  10  20  40  40  70

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 6 PM CDT this evening for the following
     zones: Austin...Brazos...Burleson...Colorado...Jackson...
     Washington...Wharton.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 3 PM CDT this
     afternoon for the following zones: Galveston Bay...
     Matagorda Bay.

     SMALL CRAFT SHOULD EXERCISE CAUTION until 10 PM CDT this evening
     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 3 PM CDT this afternoon 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 from 3 PM this afternoon to
     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.

&&

$$

Discussion...14



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