493
FXUS66 KMFR 110534
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
934 PM PST Wed Dec 10 2025

.DISCUSSION...Updated Aviation Discussion.


&&

.AVIATION...11/06z TAFs...Widespread low ceilings and visibilities
are present along the coast, including North Bend, with IFR/LIFR
levels expected through Thursday morning. Then, expect clearing to
VFR in the afternoon. Inland, there are areas of low clouds and fog
in valleys west of the Cascades, including at Medford, Grants Pass
and Montague. Low clouds with MVFR/IFR  are also developing in
Umpqua Valley, including at Roseburg.  These conditions will persist
through Thursday morning then are expected to improve to VFR between
18-21z. Elsewhere, conditions are VFR.

&&

.PREV DISCUSSION... /Issued 252 PM PST Wed Dec 10 2025/

DISCUSSION (Today through Tuesday)...

Key Points:

* Overall, minimal weather impacts through this weekend
* Mostly light rainfall chances expected through tonight
    - No snow expected
* Next widespread chance for precipitation is early next week
    - Could be as early as Sunday
    - Snow: Snow levels are high 6,000+ ft
        - Little to no snow accumulation expected
    - Rain: Mainly for Coastal areas, Cascades, & Umpqua Basin
        - Highest chances for accumulation of at least 0.25"/24hrs
    - Wind: Advisory level wind speeds possible early next week
        - Mainly eastside areas and Shasta Valley

Further Details:

Our weather across the PacNW continues to be dominated by an area
of low pressure over parts of northern British Columbia and high
pressure off the coast of California. This setup is allowing for a
large swath of moisture advection into the region between these
two features. By far and large, all the weather impacts continue
to be north of our forecast area where considerable rainfall has
resulted in significant river rises, especially across Washington.
In other words, we are only expecting light rainfall through
Thursday morning given the location and strength of the high
pressure. Eventually, the ridge of high pressure does break down,
and the orientation shifts to allow this moisture plume to go
farther north into Canada Thursday through Sunday. Through this
stretch, we are expecting dry conditions. There continues to be
uncertainty on the next potential area of low pressure impacting
the region, but it could be as early as Sunday. Deterministic and
ensemble members have a strong signal for rainfall chances
increasing by Monday and continuing through at least middle of
next week. Snow levels are really high early next week, and at
this time very little snowfall is anticipated. Cluster analysis
continues to show a split (ridge vs trough) with 5000mb heights
early next week. This doesn`t lead to high confidence with some of
the exact details. The probability for at least 0.50" of rainfall
over 24hrs is about 40%-80% with higher chances along/near the
coast and Umpqua Basin with decreasing chances elsewhere inland.
Very low chances (0%-30%) for these probabilities on the eastside.
The probability for at least 2.0" of snow over 24 hours is only
around 25% Monday night through Tuesday night for the Cascades
north of Highway 140. Furthermore, most ensemble members don`t
start accumulating snowfall until middle of next week. In other
words, we still have some details to hash out, but early to middle
of next week does look to be the next potential active weather
pattern.

A note on Crater Lake snowfall: the latest Crater Lake has had
zero snow depth was December 26th, 1976. Record keeping began in
1919 for Crater Lake, and we have only had 9 years where we went
into December for the last snow depth of zero. This will be the
10th year, and will likely rank at least 3rd latest ever. In 1958,
we went until December 20th, and in 2008 we went until December
11th.


-Guerrero

MARINE...Updated 200 PM PST Wednesday, December 10, 2025...Seas
remain hazardous to smaller crafts as high and steep swell
persists this evening through tonight. Conditions improve Thursday
evening into the early weekend as high pressure builds and seas
lower.

The next big weather concern will be around Monday as a low
deepens out in the Pacific and models are showing a cold front
swing through the waters to our north. Right now, southerly gales
are looking more probable than not around 60 to 70 percent.

&&

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

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 10 AM PST
     Thursday for PZZ350-370.

&&

$$