492
FXUS66 KMFR 022340
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
340 PM PST Tue Dec 2 2025

...Updated AVIATION discussion for 00Z TAFs...

.DISCUSSION...Key Points:

* Overall, minimal weather impacts through this 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
    - Very high snow levels (6,000ft+)
* Morning fog for westside valleys/low lying areas Wed. morning
* 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:

An upper level ridge has shifted westward to allow meridional flow
today. There will be an area PVA spreading through the region, but
by far and large we are not expecting much--if any--precipitation.
The moisture is lacking in this scenario, and the main impact here
is the cooler airmass advecting in from Canada through Thursday. Fog
and/or freezing fog for westside areas may come to fruition tomorrow
(Wed) morning which could lead to ice accumulation on elevated
surfaces. Not expecting this on the roads but some very isolated
bridges could be impacted, so plan for a little extra commute time
tomorrow and time to heat those vehicles up.

Overall, deterministic/ensemble guidance are in fairly good
agreement with the general pattern this week. We do start to see
some minor discrepancies Thursday night (previously this was Friday)
where some guidance brings in very light QPF. However, this may end
up being clouds without QPF. Regardless, the impacts look to be
minimal in any solution as precipitation would be very light
Thurs/Fri. The much better and more widespread chances starts Friday
night/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) have no
snow accumulation for Crater Lake. In typical fashion, coastal areas
will see the highest 48hr QPF amounts, but the Umpqua Basin and the
Cascades will also be on this list of higher QPF amounts. Crater
Lake could end up with an inch of rainfall over 48 hours given the
high snow levels. At this time, flooding anywhere is unlikely, but
nuisance type flooding with ponding on roadways will likely occur.
Additionally, there may be isolated flood prone areas that have poor
drainage that could see further nuisance type flooding. That being
said, not seeing any notable river rises with this system, and we
are not expecting widespread flooding.

Looking ahead, cluster analysis for 500mb anomalies is split showing
a potential trough in the area Dec 9th-12th which could lead to a
slight risk of both heavy rainfall and a heavy snowfall, but given
the split there is a lot of uncertainty. Additionally, this is
pretty far out and a lot could change, but we are watching this time
period for potential active weather. Soon, we will be able to narrow
down the timing, impacts, and overall hazards. For now, we will wait
for new data and continue to monitor.

&&

.AVIATION...03/00z TAFs...VFR levels are present across most of
northern California and southern Oregon under mid to high levels
clouds, although MVFR ceilings have developed over Roseburg.
Expected fog development in the Umpqua Valley may change if this
ceiling lingers into the night. Northerly flow along the coast may
provide moisture for decreasing levels at North Bend, which may then
be cleared out when winds turn easterly early Wednesday morning. Fog
or freezing fog may also return to the Rogue Valley late tonight or
early Wednesday morning. Anything that develops overnight looks to
clear out late Wednesday morning or early in the afternoon. Other
areas look to remain at VFR levels through the TAF period. -TAD

&&

.MARINE...Updated 200 PM PST Tuesday, December 2, 2025...Breezy to
gusty northerly winds will continue through Thursday morning, with
winds reaching Small Craft Advisory levels from Port Orford
southward. Additionally, long period west swell is peaking today (8
to 9 feet at 16 seconds and combined seas of 8 to 11 feet) and will
persist tonight and Wednesday. Additionally, some areas south of
Gold Beach may see brief Hazardous Seas late tonight into Wednesday.
Conditions are expected to improve by late Thursday. Friday into the
weekend, south winds will develop as a frontal system moves into the
area and seas will increase.

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 4 PM PST
     Wednesday for PZZ356-376.

&&

$$