077
FXUS66 KMFR 041203
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
403 AM PST Thu Dec 4 2025

.DISCUSSION...Updated Aviation Discussion.


&&

.AVIATION...04/12z TAFs...LIFR/IFR in fog will persist in valleys
west of the Southern Oregon Cascades this morning, lifting to VFR
in the late morning. A weak front will move into the area today,
with periods of light rain expected along the coast, into the Umpqua
and southern Oregon Cascades this afternoon and tonight.
Low clouds will spread inland late this afternoon and this evening,
with MVFR and IFR developing along the coast inland to the Cascades.
From the southern Oregon Cascades west, ceilings are expected to
lower overnight to IFR/LIFR with IFR visibilities. Mountain
obscurations are likely. Areas of MVFR ceilings may spread east of
the Cascades and into portions of northern California late Thursday
night.


&&

.PREV DISCUSSION... /Issued 313 AM PST Thu Dec 4 2025/

DISCUSSION...

Key Points:

* A warm front moving over the ridge will bring chances for light
  rain to northern portions of the area today, with light rain
  likely Friday as a cold front moves inland.

* Breezy to gusty winds are expected across the mountains and
  east of the Cascades Friday afternoon into Friday night.

* Expect continuing chances for light precipitation this weekend.
  Then additional rain moves into the area Monday into Tuesday as
  another front moves into the region.

* King Tides are this weekend, but not expecting impacts/hazards.

* Signs point towards a potential for more significant and active
  weather Dec 10-12th
    - Heavy rain (west of Cascades) and heavy snow (Cascades)

Today through Sunday:

The upper level ridge over the Pacific will flatten as low
centered over the Aleutian Islands sends a shortwave trough and
front into the region. A warm front will gradually move into the
Pacific Northwest today. This front will be centered north of the
area, but will bring chances for light rain to portions of
southwest Oregon, mainly along the coast, Douglas County and into
northern Klamath and Lake counties. Then as a cold front
approaches early Friday and gradually moves inland Friday and
Friday night, this will bring increasing chances for light
precipitation across the area. Models and guidance indicate breezy
to gusty winds over the mountains and east of the Cascades on
Friday as well. This may bring some local impacts to higher
mountains with gusts of 30 to 45 mph possible late Friday. Snow
levels will be high around 7000+ feet through Friday, lowering
behind the front to 5500 to 6500 feet Friday night across
southwest Oregon.

On Saturday, the National Blend of Models supports lingering
chances for light showers, with best chances (50-80%) along the
coast, into Douglas County and the southern Oregon Cascades. Snow
levels may drop to 5000 to 6000 feet across southwest Oregon and
6500 to 7000 feet across northern California on Saturday. So, this
may result a dusting of snow to higher mountains in the Southern
Oregon Cascades.

This pattern continues into Sunday. Another shortwave trough and
frontal system are expected to move into the region from the
northwest on Sunday and Sunday night, bringing additional chances
for generally light precipitation. Snow levels are expected to
range between 6000 to 7000 feet during the day Sunday and into
Sunday night.

Next week:

Another, stronger front is forecast to move into the region early
next week. Models and ensembles show this system moving inland
over the Pacific Northwest Monday and Tuesday. Deterministic
models and ensembles show highest chances for moderate to heavy
precipitation staying north of the area during this period, with
generally light precipitation affecting southwest Oregon and low
chances for precipitation across northern California. Snow levels
are high during this period, so expect precipitation to fall
mainly as rain.

Looking further ahead, cluster analysis for 500mb anomalies is
still split on a potential trough in the area Dec 10th-12th. This
could lead to a slight risk of both heavy rainfall and heavy
snowfall, but given the split (trough vs ridge) there is a lot of
uncertainty. Additionally, this is pretty far out in the future,
and a lot could change, but we are watching this time period for
potential active weather. We will continue to monitor and refine
the details in the coming days. Snow pack is really low for this
time of year. The average (1991-2020) snow depth for today (Dec
3rd) at Crater Lake is is normally 28.0", but we are sitting at
zero. It will likely take a few systems to get back to normal, but
this potential system next week would be a good start.

MARINE...Updated 200 AM PST Thursday, December 4,
2025...Advisory level north winds will maintain steep seas south
of Cape Blanco into this afternoon. Long period, swell dominated
seas will persist north of Cape Blanco. Winds shift to west
Thursday evening then southwest on Friday, and the resulting wind
seas will combine with ongoing swell to produce steep seas. Then
steep, west seas are expected on Saturday. Gusty south winds and
additional steep seas may develop Saturday night into Sunday.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 4 PM this
     afternoon to 4 PM PST Saturday for PZZ350-370.

     Small Craft Advisory until 4 PM PST Saturday for PZZ356-376.

&&

$$