Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 200535
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1135 PM CST Sun Nov 19 2017

.AVIATION...
VFR for the 20/06Z TAFs with lots of cirrus streaming across the area
overnight. Light N to NE winds tonight will shift around to the S and
SE during the day tomorrow. Could see some lower clouds develop across
parts of the area tomorrow night and on into Tuesday morning.  42
&&

.PREV DISCUSSION... /ISSUED 744 PM CST Sun Nov 19 2017/

UPDATE...
With quiet weather, the forecast is on track - the only tweaks
needed this evening are to more seamlessly trend observational
trends in with the forecast. GOES-16 shows some high cirrus
streaming into the area to join contrails over the area as we are
downstream of a subtle upper shortwave trough. This isn`t likely
to have an extremely significant impact on the sensible weather
beyond maybe keeping radiational cooling overnight from peak
efficiency, but it is somewhat interesting to compare the
character of these clouds with those over the Southwestern Gulf
and Eastern Great Lakes/Mid-Atlantic in the Nighttime
Microphysics RGB product.

Luchs

PREV DISCUSSION... /ISSUED 306 PM CST Sun Nov 19 2017/

NEAR TERM [Through Tonight]...

Since I cannot take my AWIPS workstation outside in the cool
crisp fall air to enjoy, I`m left writing my discussion looking
out the window at it. But at least I have a window to look out to
see some thin cirrus moving across the sky. Satellite imagery
shows this as well and water vapor imagery showing a weak short
wave trough enhancing the cloud cover. High pressure over Texas
today will move east over the Tennessee river valley tonight. Axis
of high pressure will still support calm winds tonight. Cirrus
may be an issue for the low temperature forecast but do not think
it will be that thick enough to make an impact. Look for
temperatures Monday morning in the upper 30s to low 40s for much
of the area.

SHORT TERM [Monday Through Tuesday Night]...

Short range models are in pretty good agreement with some weak
return flow on Monday going into Tuesday. Rain chances increase
mainly in the Gulf and just along the coast on Tuesday. Vorticity
from a trough now approaching the Pacific NW should continue its
movement around the upper level ridge and reach Texas late
Tuesday. A cold front will be moving into the area about the same
time so will keep some low end rain chances in the forecast. Best
chances of rain and higher rainfall totals should remain off the
Gulf coast. The cold front should push off the coast by Wednesday
morning with high pressure building over the Plains.

LONG TERM [Wednesday Through Sunday]...

Surface high pressure should remain over the area in some shape
or fashion through the end of the week. This will allow for
temperatures to be about 5 degrees below normal for Thanksgiving.
You can be thankful we will not have any record breaking high
temperatures that day or even record high minimum temperatures.
Temperatures then push maybe 5 degrees above normal for the
holiday weekend as upper level ridge begins to expand over the
Desert SW and Southern Rockies causing 500mb height rises. Even
then, the NW flow aloft may help push a weak front through the
area next Sunday taking the edge off those slightly above normal
temperatures.

Overpeck

MARINE...

The winds have steadily diminished this afternoon. This in turn
has led to subsiding seas as well. Expect the small craft advisory
that was in effect between 20 and 60 nm offshore of the coast to
end at 4:00 PM. With the surface high pressure ridge over North
Texas expected to build into East and Southeast Texas, winds and
seas should continue to diminish. Onshore winds will return on
Monday. Still looks like a cold front will move off of the coast
late Tuesday. Caution or advisory conditions are possible behind
this front Tuesday night and Wednesday.

The low water advisory will continue through the remainder of
this afternoon. Water levels in some locations of Galveston Bay
were down to one foot below the predicted levels. With diminishing
winds, should see the water levels to begin returning to near
normal levels this evening.

FIRE WEATHER...

Elevated fire weather conditions will continue through the
remainder of this afternoon. Some locations have seen the relative
humidity values to drop to around 25 percent so far this
afternoon. However, wind speeds have dropped below 15 mph and many
of the driest locations were already below 10 mph. On Monday the
lowest relative humidity values should range from 35 to 40
generally north of the Interstate 10 corridor. With easterly and
then southeasterly winds developing, the elevated fire weather
threat should diminish as the afternoon progresses.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      42  67  51  74  50 /   0   0  10  10  10
Houston (IAH)              41  67  52  74  54 /   0   0  10  20  10
Galveston (GLS)            55  67  61  74  60 /   0  10  10  30  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until midnight CST tonight
     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.

&&

$$

25/42



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