Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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801
FXUS64 KHGX 261515
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1015 AM CDT Mon Sep 26 2016

.UPDATE...
No major changes were made to the previous forecast. Showers and
thunderstorms are currently focused offshore and well to the west
over Central Texas. Showers and thunderstorms should get going
across SE Texas early this afternoon once we reach convective
temps. With PWs remaining over 2" across much of the area, some of
these storms may produce locally heavy rainfall. Highs are
forecast in the 80s this afternoon. 11

&&

.PREV DISCUSSION... /ISSUED /

AVIATION...
Messy forecast for the first 12 hours of the 26/12Z TAFs with a
mix of LIFR to VFR ceilings across the Southeast Texas terminals
and a weak frontal boundary moving across the region. Main
aviation concerns will be timing for these ceilings and scattered
SHRA/TSRA today both ahead and with the cold front.

Morning surface analysis shows a poorly defined cold front
stretching from South Texas into northwestern Louisiana and this
boundary will continue to move south into the Gulf through the
day. Low clouds currently impacting CLL/UTS/CXO/IAH will gradually
improve through the morning, but expect CLL/UTS to hang on to MVFR
ceilings through 18Z as low level moisture remains trapped beneath
a post-frontal inversion. Easterly low level flow ahead of this
frontal boundary has allowed some drier air over southwestern
Louisiana to move into the region, keeping the terminals rain-free
this morning. Model guidance is fairly consistent in developing
SHRA/TSRA with daytime heating today, but a fairly persistent BKN-
OVC deck around FL150 looks to keep convective temperatures (low-
mid 80s) from being reached until early to mid afternoon near the
terminals. Have pushed onset of SHRA/TSRA back a few hours as a
result, with rain continuing into the evening hours as a weak
disturbance over South Central Texas and the frontal boundary move
across the area. Concerned that coverage may be a bit overdone
with most model guidance not appearing to have a great handle on
some of the drier air that moved in from the east and have low
confidence on timing for any terminal impacts this afternoon or
if TS will actually occur near the terminals. Loss of heating as
well as forcing from the front/disturbance will result in dry
conditions through the remainder of the TAF period.

Otherwise, light east/northeasterly winds around 5 knots this
morning are expected to become northerly and increase to near 10
knots behind the cold front. May see a few MVFR ceilings develop
overnight behind the front, but confidence is not high enough to
include in the TAFs attm.

Huffman

PREV DISCUSSION... /ISSUED /

DISCUSSION...
Storms near the coast have waned and storms over the Hill Country
expanding west with mid level troughing from HOU-CLL and mid level
ridging from LFK-BPT-BYY. This is currently placing most of SETX
in weak subsidence. VWP showing SFC-8kft of E to NE winds. This
may bode poorly for rain chances this morning until we warm up
to 80-81 degrees. Have lowered pops in the short term but by 10a-
noon temperatures should be high enough and able to overcome the
subsidence with the abundant moisture in place for scattered
showers and thunderstorms to develop. Still some questions on
where storms may develop along the frontal boundary this
afternoon. At 4 am front looks to be along a line from Longview to
Waco to Junction with ridging having helped to back our winds to
the northeast and shifting low level convergence into the Gulf.
In addition lowering cigs across the north and central counties with
some light-moderate fog. The clouds will persist today given the
moisture present but the lower cigs should improve by mid morning
or so and transition over to CU and abundant high clouds so we
should struggle to get to the mid 80s.

This afternoon scattered precip develops as front sags southward
and by 3 to 6 pm should be close to the Highway 59 corridor
probably pushing offshore tonight/early Tuesday. Scattered storms
will be possible through the evening hours and may have to keep an
eye out for a cluster of storms to develop to the southwest of
Houston where heavier rains may occur. Could also see a waterspout
near the coast and some tropical funnels near the coast. The
storms should wind down tonight then possibly redevelop Tuesday
morning over the southern counties though primarily showers.
During the afternoon Tuesday some isolated thunderstorms south of
the I-10 corridor before dry air finally wins out and blankets the
region.

Wednesday through Saturday should be very pleasant with lows in
the mid 50s to lower 60s and highs in the 80s. This will bring our
long record stretch of 70 or greater temperatures at IAH to an
end. The current record stands at 112 days in a row with 106 days
set back in 1991 ending 09/18.

Guidance still keeping the tropical system to the eastern
Caribbean turning north and through day well outside of the Gulf
of Mexico and potentially along or east of the Eastern Seaboard.

45

MARINE...
Outflow from thunderstorms yesterday has served as a focus for
showers and thunderstorms early this morning, with greatest coverage
south and southwest of Matagorda Bay where the outflow intersects a
coastal trough. Expect scattered showers and thunderstorms to
continue across the coastal waters through the remainder of the day
and into the overnight hours as coastal convergence and
aforementioned boundaries (and any others from subsequent storms)
result in continued development. Stronger storms will be capable of
heavy rainfall reducing visibilities to 1 nautical mile or less at
times and locally enhanced winds/waves. Low level shear is slightly
stronger than yesterday and forecast lapse rates are not quite as
steep which will help mitigate against a greater waterspout threat,
but still cannot rule out an isolated waterspout along the coast
today with deep tropical moisture in place.

A weak front stretching from south central Texas towards the
ArkLaTex early this morning will push across Southeast Texas during
the day, reaching the coastal waters on Tuesday. Shower and
thunderstorm coverage is expected to focus along this front as it
moves south, with drier air behind the front ending rain chances for
the coastal waters by Wednesday night. Northeast winds behind the
front may reach caution criteria early Tuesday morning, with light
northeast flow expected to persist over much of the upcoming week.
May see another brief window for caution flags on Thursday as a
reinforcing front moves into the Gulf. Otherwise, expect seas
generally in the 2-4 ft range through mid-week.

Huffman

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      81  67  83  65  87 /  30  20  10   0   0
Houston (IAH)              85  71  85  68  88 /  50  30  20   0   0
Galveston (GLS)            85  76  84  75  85 /  40  40  20  10   0

&&

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

$$

Discussion...11



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