Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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005
FXUS64 KHGX 172350
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
550 PM CST Fri Nov 17 2017

.AVIATION...
Could see one more round of mainly MVFR ceilings develop overnight with
S to SSW winds 10-15 knots and occasionally gusty under a tightened
pressure gradient. The gusty winds will shift to the SW and W tomorrow
morning ahead of a cold front that will quickly works its way through
the area during the afternoon through very early evening hours. Winds
will stay gusty behind the front as they shift to the NW. Any ceilings
that developed tonight will lift and break - if not ahead of the front,
then definitely behind the front as drier air moves into the area. VFR
into tomorrow evening with weakening winds around the CLL and UTS areas
but staying on the breezy/windy side closer to the coast.  42
&&

.PREV DISCUSSION... /ISSUED 350 PM CST Fri Nov 17 2017/

DISCUSSION...
Daytime heating has allowed for some mixing in the
lower levels, dragging some of the higher wind speeds located
within the first few kilometers of the atmosphere, down to the
surface. This warming has also help to erode the thicker cloud
deck that was present earlier this morning. Strands of cumulus
clouds still linger over much of the region this afternoon.

Overnight, low level clouds will develop around 2,000 feet and PWs
will fall to around one inch. Forecast soundings still holding on to
a fairly strong cap at 850 mb across the region as well. Although
winds and wind gusts should lower early this evening, winds speeds
will stay elevate around 10 mph overnight. These faster wind speeds
should allow for a break from patchy fog tonight. Low temperatures
should remain in the upper 60s to lower 70s along the coast.

Saturday will bring the next cold front of the season which should
help drop temperatures to below normal climatology for this time of
year. Still a little uncertainty with the exact timing of the front,
but the models have been coming into more agreement in the more
recent model runs. The spread in the timing between the ECMWF and
the GFS has narrowed, and what was once a six hour discrepancy
has lessened, with the GFS solution making it to the coast
slightly faster. The pressure gradient will begin to tighten as
the trough enters the northern zone of our forecast area around
18Z Saturday. We should see most of the precip move through SE TX
between 18-00Z Saturday, clearing the coast shortly after 00Z.
With the model soundings significantly capped as the front pushes
through the region, decided to keep thunder out of the forecast
and only anticipating showers at this time. This system will not
bring much in terms of total rainfall with most of the
accumulation along the coast, but it will leave gusty winds in its
wake.

Both models show the wind shift to out of the north/northwest by 00Z
Sunday. Therefore, gusty conditions will prevail Saturday evening
behind the front especially along the coast, evident in the
forecast soundings. Will have to continue to monitor trends in the
models, as we could be flirting with wind advisory criteria
Saturday night into Sunday along the coast and specifically for
Galveston County. Behind the front cool and dry conditions will
prevail. The ECMWF is trending temperatures a few colder  in
comparison to GFS. Leaned the forecast a little on the warmer side
closer to the GFS solution, based on consistency over the last
few model runs.

Additionally, depending on the timing of the cold front Saturday,
Saturday high temperatures could flirt with record values. The table
below contains both the normal and record temperature values for
Saturday November 18th. Behind the front high temperatures will
reach into the mid to upper 60s Sunday with low temperatures Sunday
night into Monday in the 40s to low 50s along the coast.

High pressure builds in behind the front and a warming trend will follow,
before the next cold front arrives late Tuesday into early
Wednesday. PWs rise to 1.00 to 1.25 inches on Tuesday as the next
front pushes through the region. Most of the precip with this
system will again be concentrated along the coast and over the
Gulf waters. This system will act to provide a reinforcing shot of
cooler air, which will leave high temperatures Wednesday and
Thursday in the mid 60s to low 70s, with lows in the 40s to mid
50s.

Hathaway

Climate...
       Normal and Record Temperature Values for November 18th
Site  Date   Normal     Normal        High Max        High Min
              High       Low         Temp Record     Temp Record
GLS  11/18     71         53         84 in 2016       73 in 1985
HOU  11/18     72         53         86 in 1973       73 in 1985
IAH  11/18     72         51         84 in 1973       74 in 1985
CLL  11/18     70         50         84 in 1986       71 in 1985

Hathaway

MARINE...
Expect onshore winds to increase to caution conditions tonight as
the surface pressure gradient tightens. The cold front should push
off of the coast sometime Saturday evening. Strong offshore winds
will develop behind the front with advisory conditions expected
Saturday night and Sunday. The thermal gradient right behind the
front will help lead to gusts to gale after the frontal passage
Saturday night. These could persist into Sunday morning but this
will depend upon the thermal gradient. Onshore winds return by
Monday. Another front is expected off of the coast Tuesday evening.

FIRE...
Elevated fire weather conditions are expected to develop for Sunday
and Monday as a very dry airmass moves over Southeast Texas. Even
though minimum relative humidity values will drop to between 25 and
30 percent area wide on Sunday afternoon and 30 to 40 percent most
areas on Monday, winds will likely be on the light side--probably 5
to 10 mph away from the coast on Sunday and under 10 mph on Monday.
Most concerned for Sunday with the drier conditions and winds
possibly reaching to between 10 and 15 mph in the coastal areas.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      67  79  45  66  41 /  20  20   0   0   0
Houston (IAH)              69  84  48  67  43 /  10  20   0   0   0
Galveston (GLS)            71  82  55  66  54 /  10  30  10   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION through late tonight 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...Waters from Freeport to the
     Matagorda Ship Channel from 20 to 60 NM...Waters from High
     Island to Freeport from 20 to 60 NM.

&&

$$

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