Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 072149

Area Forecast Discussion
National Weather Service Houston/Galveston TX
349 PM CST Wed Dec 7 2016

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.



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 advi-
sories 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


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


TX...Wind Advisory from 6 AM to 6 PM CST Thursday for the following
     zones: Brazoria...Chambers...Galveston...Harris...Jackson...

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

     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.



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