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National Weather Service Forecast Discussion

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844
FXUS64 KHGX 201804
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1204 PM CST Sat Dec 20 2025

...New DISCUSSION, MARINE...

.KEY MESSAGES...

- Long stretch of unseasonably warm weather with temperatures
  10-20 degrees above normal.

- A weak, backdoor front will help keep Sunday from being quite as
  warm as other days, and also bring an outside shot at some
  showers and a stray thunderstorm.

- Daily chances for sea fog (and inland fog) will become the main
  weather concern, especially across the bays and coastal areas.
  The main threat for fog will be during the nighttime and early
  morning hours, especially tonight through Monday morning.

&&

.DISCUSSION...
Issued at 1150 AM CST Sat Dec 20 2025

Onshore flow has return and should remain in place throughout the
next seven days while a midlevel ridge over Baja California
gradually migrates eastward towards Texas. Heights within this ridge
are anticipated to reach 586-590 dam, which is particularly high for
December. A weak backdoor cold front should push into the northern
half of our cwa on Sunday, though most model guidance anticipates it
stalling out around I-10/the coastal plains before subsequently
lifting north. We could see some spares showers during the day and a
few isolated storms, along with a slight cool down for temperatures,
all be it small. In all, we`re still expecting highs in the
70s/lower 80s with lows in the upper 50s/lower 60s. This puts
temperatures around 10-20 degrees above normal for December.

Water temperatures are still in the upper 50s/lower 60s across the
nearshore waters/bays. Dewpoints are already in the upper 60s/lower
70s over the gulf waters and with this uninterrupted stretch of
onshore flow, it is very likely that we`ll see fog on the daily in
some capacity with sea fog being the primary concern for our
mariners (in addition to inland radiation fog). Tonight, Sunday and
early Monday will likely see the worst of the sea fog, with SHREF &
HREF probabilities for fog greatest during this period. REFS is also
showing a strong signal for fog as well, especially over the waters.
Wind direction does lean a tad unfavorable given the slight westerly
component, though otherwise confidence is high in sea fog. As
mentioned before, we`ll likely see the lowest visibilities during
this dusk-dawn period with patches to areas of sea fog in the
coastal waters and bays filling inland with radiation fog as the
night progresses.

Timing the end of the fog is still tricky, since no large wx systems
are on the horizon to wipe out the sea fog/radiation fog in one go,
thus we`ll have to wait for water temperatures to gradually warm up
(from advection & downwelling) till it`s near or above dewpoints.
RTOFS still has around a 1-4 degree difference between the dewpoints
and water temperatures by Monday morning. By Tuesday morning, this
gap is around a 0-2 degree difference. SREF still shows a signal for
sea fog at this point, though on the whole trending downward with
respect to probabilities. While this is all contingent on the speed
at which water temperatures warm these next few days, the bigger
picture suggest the worst visibility reductions through Monday
morning, with lingering patches for Monday night/Tuesday and beyond.

03

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 533 AM CST Sat Dec 20 2025

Some sites may see MVFR cigs through around 15Z this morning, but
skies are expected to scatter out later in the morning and
afternoon. S-SE winds will increase to 10-15 kts with gusts up to
around 25 kts today, and relax to around 5 kts later tonight. The
main hazards for this TAF period are IFR-MVFR cigs/vis developing
tonight into Sun morning as moisture increases over the region
and areas of fog develop. Some locations could even have
conditions lower to LIFR early Sun morning. Fog is expected to
gradually burn off around 14-15Z. Conditions will be slower to
improve for sites closer to the bays due to sea fog.

Cotto

&&

.MARINE...
Issued at 1150 AM CST Sat Dec 20 2025

Onshore flow continues today ahead of a weak backdoor cold front,
which is expected to push into SE Texas on Sunday but stall out
before it can reach the Gulf waters. Some isolated to scattered
showers/storms could develop along/ahead of it. With any breaks in
rainfall, we`ll have to watch out for patches to areas of sea fog
with dense pockets possible tonight Sunday morning. Sea fog will
continue to be a daily risk into next week, especially during the
dusk-dawn hours. There are no significant fronts or weather systems
on the horizon that will clear out sea fog, so we`ll have to wait
for water temperatures to gradually rise enough to put an end to sea
fog.

03

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  58  72  55  77 /   0  10   0   0
Houston (IAH)  67  79  65  78 /   0  10  10  20
Galveston (GLS)  65  72  64  70 /   0  20  30  30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

DISCUSSION...03
AVIATION...Cotto
MARINE...03

NWS HGX Office Area Forecast Discussion