Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 080600
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1200 AM CST Thu Dec 8 2016

.AVIATION...
A cold frontal passage through sunrise with swaths of light rain
or drizzle occurring just ahead of the boundary. Primarily MVFR
ceilings...with occasional IFR...will persist through the morning
as moisture remains trapped within the lower level post-frontal
inversion. Strong northerlies in the front`s wake...with 20-30
knot near surface winds mixing down to around 15-20kt...gusts to
25 knots during the afternoon hours. 31

&&

.PREV DISCUSSION... /ISSUED 855 PM CST Wed Dec 7 2016/

DISCUSSION...
Cold front to our north is still on schedule to move across Southeast
Texas overnight. Some southwest to northeast moving showers and rain
have developed across parts of the area this evening, and expect this
to continue as the front moves into the area. Activity should gradually
decrease in coverage behind the front, and look for cooling temperatures
and strengthening north winds during the day tomorrow. Our counties
that will be under wind advisories along with our coastal waters that
will be under small craft advisories and gale warnings all look good
for tomorrow. Everything looks good in the forecast, and only minor
tweaks to the grids have been made this evening.  42

PREV DISCUSSION... /ISSUED 610 PM CST Wed Dec 7 2016/

AVIATION...
Local aircraft soundings depicting a couple of lower level
inversions that support recent obs of primarily MVFR
ceilings...with periods of IFR anticipated. MVFR/IFR conditions
will be the overnight theme as the region falls downstream of a
cold frontal boundary that is now passing south of the Red River
Valley. This cold front will be traveling through the area from
around midnight (CLL) through sunrise (GLS)...strong northerly
winds following in its wake. Drizzle...or light rain...may occur
mainly across the metro and southern terminals ahead of this front
.quickly clearing out with the front`s passage. Moisture trapped
under the low level post-frontal inversion will be slow to lift
through the afternoon. Daytime MVFR decks with late afternoon
into early evening clearing to VFR and a slight weakening of that
once stout...brisk north wind. 31

PREV DISCUSSION... /ISSUED 349 PM CST Wed Dec 7 2016/

DISCUSSION...
Surface analysis at 21Z shows the much discussed cold front
slicing through Oklahoma and Texas Panhandle. A dissipating cold
front was off the coast and responsible for trapping moisture in a
frontal inversions over much of SE Texas. This has allowed for low
clouds and patchy fog to continue through the afternoon. Patchy
fog and low clouds will likely continue tonight as warm advection
increases over the frontal surface. Latest NAM/GFS show subtle
isentropic lift at 295K which will contribute to light
showers/drizzle through the overnight. Rainfall amounts are not
expected to be much but could get up to a tenth of an inch in a
few locations. The cold front should push off the coast around
10-12Z Thursday which should slowly allow for rain chances to end
through the morning.

Cold front will bring a much colder Canadian airmass into SE
Texas. Winds will be quite strong especially along the coast and
offshore. Wind advisory will be needed for the coast and Gale
warnings for the marine areas. Temperatures will fall at first
into the 40s/50s but remain fairly steady during the afternoon.
Temperatures should continue to drop into the 30s and 20s Thursday
night. Winds will slowly decrease overnight and cloud cover may
linger through Friday morning. Low temperatures Friday morning
should reach sub freezing mainly north of Houston. The main
problem may be lingering cloud cover which could hold temperatures
a couple of degrees warmer. Cold advection will be strong so there
is enough confidence that a freeze warning may need to be issued
for Friday morning for areas basically from Columbus to Katy to
Cleveland. Northern Harris County could see temperatures right at
freezing but will be close. Temperatures should be in the
mid/upper 30s south of that line. The other issue to be aware of
is that winds will still be breezy at times overnight which means
minimum wind chill values will be in the 20s for much of the area.

In the extended forecast, look for a broad trough to persist
across much of the central U.S. and Canada. Moisture will begin to
return to the area from the Gulf late Saturday into Sunday
allowing for another warm advection/isentropic lift rain event.
Rain chances have increased slightly for Sunday as short wave
trough moves across the Plains. GFS is faster than the ECMWF with
this feature and as such slightly faster with another frontal
passage. Front should push through Sunday night into Monday
morning as high pressure builds into the Plains.

The ECMWF holds onto the trough more than the GFS with McFarland
like pattern next Tuesday and Wednesday. This allows for another
1040mb high to push into the Plains by Wednesday morning with
another strong cold front pushing through the area. GFS has no
such front or high pressure at this time. Forecast leans a bit
more on the ECMWF given the upper level pattern evolution. This
could allow for more chilly temperatures for the end of next week.

Overpeck

MARINE...
As per coordination with surrounding offices, have upgraded the Gale
Watch to a Warning for all of Thurs with this package. A strong cold
front will be moving off the coast late tonight/early Thurs morning,
with very strong N/NE developing in its wake. Sustained winds in the
wake of the front will increases to 25-35 kts with higher gusts. SCA
conditions will prevail over the bays Thurs/Thurs Night.

There might be some impact on Thurs for the more north-to-south ship
channels as water is pushed out of the bays. The N/NE wind direction
is currently in the forecast...and not expecting any low water
advisories at this time.

The strong offshore flow will be decreasing and shifting to the east
Friday as the surface high moves off to the east. A moderate onshore
flow is forecast for Saturday...but winds will be increasing back to
near SCEC/SCA criteria for Sat night/Sun as the gradient tightens in
response to the next storm system moving across the Southern Plains.
The winds will diminish on Sunday night ahead of another front early
Monday. 41

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      42  44  30  47  35 /  40  20  10   0  10
Houston (IAH)              50  52  33  49  35 /  60  20  10   0   0
Galveston (GLS)            54  56  41  51  47 /  50  40  10   0  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory from 6 AM to 6 PM CST Thursday for the following
     zones: Brazoria...Chambers...Galveston...Harris...Jackson...
     Matagorda.

GM...Small Craft Advisory from 6 AM Thursday to midnight CST Thursday
     night for the following zones: Galveston Bay...Matagorda
     Bay.

     Gale Warning from 6 AM Thursday to midnight CST Thursday night
     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.

&&

$$

Discussion...42
Aviation/Marine...31



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