Friday, December 25, 2020

Dec. 24 20

 Area Forecast Discussion

Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 250540
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1140 PM CST Thu Dec 24 2020

.AVIATION [06Z TAF Issuance]...

No changes from previous as high pressure builds down from the
Plains. Light west winds overnight should become more NW early
tomorrow as a weak secondary push of cold/dry air filters into
the region from the north. Light/variable winds will return by
tomorrow night as another surface high settles over the state.
Otherwise, VFR conditions will persist. 41

&&

.PREV DISCUSSION... /ISSUED 310 PM CST Thu Dec 24 2020/

SHORT TERM [Tonight and Friday]...
Dry, cool conditions continue with a northwest flow aloft. Winds
should decouple quickly around sunset and provide for good
radiational cooling with clr skies and low dewpoints in place.
Areas north of an Edna-Liberty line will probably see a light
freeze. The Houston metro area within the Beltway will likely be
spared, but cannot rule out a few spotty outlying areas. Warmer
tomorrow with a more westerly component to the llvl winds. Have
60-65F (east-to- west) and sunny skies in the fcst, but future
shifts may end up needing to bump them up a few degrees.

47

LONG TERM [Friday Night Through Thursday]...
With high pressure to the east...light onshore flow will continue
over the weekend...with airmass gradually becoming more humid. A
weak cold front will approach on Sunday then stall out over
northern portions of the forecast area on Monday. This boundary
could provide convergence and lift to support a few rain showers
along and just north of the boundary...so low chances of rain look
good for Monday...especially central and northern portions of the
forecast area...not so much toward the coast.

The front lifts north of the area by Tuesday...with stronger
onshore flow and much warmer more humid air mass advecting in.
Will likely see a more impressive cold front...and associated
stronger short wave trough at upper levels...pushing across the
area Tuesday night and Wednesday. This will provide our best
chance of more widespread rain for this forecast period...with
showers and thunderstorms likely along the front. Models are in
pretty good agreement in timing of this feature...although since
several days out this could change. Main synoptic models have cold
front crossing the area from NW to SE...pushing off the coast Wed
morning...with colder...drier conditions returning Wednesday
night and Thursday as cold front pushes east.

18

MARINE... Winds/seas are beginning to settle down, but will need
to continue the SCA`s for the remainder of the day/evening. Bays
can likely be dropped for the evening update and Gulf waters
possibly be replaced by caution flags. Also extended the low water
advsy thru the evening with several locations still below the -1
MLLW criteria. May need another one for Galveston Bay around the
next low tide cycle Fri morning.

Surface high pressure over south Tx moves ewd into the Gulf on Fri.
Light onshore flow should resume Fri night then strengthen early
next week ahead of the next storm system. Might need SCA`s again in
the Gulf by Mon night or Tue. The next front is forecast to push
thru the waters Tue night or Wed morning. 47

FIRE WEATHER...
Currently seeing dry, windy conditions meeting Red Flag criteria
in some spots with relative humidities in the upper teens and
lower 20s...and wind gusts 20 to 30 mph. Fuels not particularly
dry however. Still elevated fire danger for sure for the rest of
the afternoon. Winds will diminish tonight. Will be dry again
tomorrow...low relative humidities...but very light winds with
high pressure parked over the area. Over the weekend will start to
see warmer...more humid conditions as winds become onshore.

18

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      33  62  38  68  50 /   0   0   0   0   0
Houston (IAH)              34  62  41  67  52 /   0   0   0   0   0
Galveston (GLS)            42  59  52  65  59 /   0   0   0   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Low Water Advisory until 9 AM CST Friday for the following
     zones: Galveston Bay...Matagorda Bay.

&&

$$

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