974
FXUS66 KMFR 040005
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
405 PM PST Wed Dec 3 2025

.Updated AVIATION Discussion...

&&

.AVIATION...04/00z TAFs...VFR conditions prevail with some mid-high
level clouds streaming north to south over the area. Persistent mid-
high level clouds will likely limit fog development and extent
tonight, but LIFR conditions most likely in the Umpqua Basin and
Illinois Valley late tonight. Here in the Rogue Valley, if fog does
develop, it`s more likely to be shortlived and right around/before
sunrise. VFR conditions will prevail for all other areas through the
TAF period. A weak front will sag southward along the coast early
Thursday, bringing lowering ceilings and light rain between 15-18z.
/BR-y

&&

.PREV DISCUSSION... /Issued 207 PM PST Wed Dec 3 2025/

DISCUSSION...

Key Points:

* Overall, minimal weather impacts through early next week
* By far and large, mostly dry conditions expected through Fri
* Next widespread chance for precipitation is mainly Saturday
    - Could be as early as Friday and lingering into Sunday
    - Very high snow levels (6,000ft+)
    - See note at end of discussion on Crater Lake snow
* Signs pointing towards active weather around Dec 9th-12th
    - Heavy rain (west of Cascades) and heavy snow (Cascades)
* King Tides are this weekend, but not expecting impacts/hazards

Further Details:

A ridge of H5 high pressure continues over the Pacific allowing
northerly to northwesterly flow aloft to dominate the region. The
ridge will slowly flatten out by Friday which will allow for more of
a westerly flow pattern through the weekend. Overall, deterministic
and ensemble guidance continues to be in fairly good agreement with
the general pattern this week. We do start to see some minor
discrepancies tomorrow where some guidance brings in light QPF.
However, this may end up being clouds without QPF, but recent trends
have showed an increase in measurable precipitation. Regardless, the
impacts look to be minimal in any solution as precipitation would be
very light through tomorrow night. The much better and more
widespread chances starts Friday/Saturday and continues through
Sunday morning. The result will be rainfall for most areas as snow
levels are 6K+ feet. For perspective, several ensemble members (both
GFS and Euro) continue to show no snow accumulation for Crater Lake.
In typical fashion, coastal areas will see the highest 48hr QPF
amounts, but the Umpqua Basin (especially higher elevations around
Douglas County) and the Cascades will also be on this list of higher
QPF amounts. Crater Lake could end up with close to an inch of
rainfall over 48 hours given the high snow levels. At this time,
flooding anywhere is unlikely, and we are not seeing any notable
river rises with this system.

Looking ahead, cluster analysis for 500mb anomalies is still split
on a potential trough in the area Dec 10th-12th (as early as the
9th). 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 PM PST Wednesday, December 3,
2025...Advisory level north winds will maintain steep seas south
of Cape Blanco through Thursday morning. Long period, swell
dominated seas will persist north of Cape Blanco. Winds swing
around to the west and southwest late Thursday into Friday, and
the resulting wind seas will combine with ongoing swell to produce
steep seas through 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 Thursday to 4
     PM PST Saturday for PZZ350-370.

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

&&

$$