088
FXUS66 KMFR 220709
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1109 PM PST Sun Dec 21 2025

.DISCUSSION...The flood watch for Siskiyou County expired earlier
this evening, with precipitation tapering off overnight. There
were significant rises on rivers, but none reached flood stage.

A Winter Weather Advisory remains in effect overnight for the
Cascades north of Highway 140, with another couple inches of snow
showers possible.

Our area will have a relative break in the action on Monday with
occasional, scattered light showers, mainly west of Interstate 5.

Active weather resumes with rain reaching the coast north of Cape
Blanco during Monday evening. Then, more broadly, moderate to
heavy rain and high elevation snow will be focused on Siskiyou
County late Monday night throughout Tuesday into Wednesday
morning, and Wednesday evening into early Friday. A Winter Storm
Watch has been issued for Siskiyou and Modoc counties above 4500
feet.

Snow levels look to be around 5000 to 6000 feet in southern
Siskiyou County through Tuesday night, which will be above the
major passes. The heaviest precipitation is expected with snow
levels around 4500 feet in southern Siskiyou County late Tuesday
night into early Wednesday and Wednesday night through Thursday.
Precipitation is most likely to decrease in intensity and be
moderate than heavy on Thursday night, but there is also an
expected drop in snow levels to around 3500 to 4000 feet.

Away from Siskiyou County, precipitation will less frequent with
low level rain and potential episodes of advisory level snowfall
in the higher terrain. This includes potential heavy coastal and
Josephine County rain Tuesday night into Wednesday morning.

Winds will also be of note, with a High Wind Watch in effect for
the Shasta Valley and the east side for southerly gusts to 60 mph
Tuesday afternoon into Wednesday morning. Winds also look to be
similarly strong again Wednesday night into early Thursday.

Dry or very nearly dry weather is likely to follow Friday through
next weekend.

&&

.AVIATION...22/06Z TAFs...A moist frontal system is moving east of
the Cascades and will gradually shift southeastward tonight and
Monday morning. This frontal band will shift back north Monday
evening and night.  Meanwhile, a weaker front will push onshore
tonight and spread into areas west of the Cascades overnight and
early Monday.

This pattern is bringing widespread rainfall and higher mountain
snow tonight with a mix of mainly MVFR and IFR conditions in rain
along with widespread mountain obscurations. These conditions are
likely to continue into Monday morning. However, ceilings are
expected to lower to LIFR during breaks in the the precipitation
early Monday morning, especially in in valleys west of the Cascades,
including Medford and Roseburg. Lower ceilings are also expected at
Klamath Falls early Monday morning. These lower ceilings in valleys
are expected to linger into late Monday morning and early Monday
afternoon, then lift and clear to VFR. Then, expect mainly VFR
across the area Monday afternoon.

Monday evening,  MVFR ceilings will develop along the coast as rain
with another front spreads inland. Meanwhile the early frontal band
that shifted southeast of the area will move back north over
portions the area, including eastern Siskiyou, Modoc, southern
Klamath and southern Lake counties. This will bring areas of MVFR to
eastern areas, starting around 04z and later Monday evening.

Freezing levels are currently 4000-5500 feet  from the southern
Oregon Cascades west and 5500-7500 feet east of the southern Oregon
Cascades and over northern California. These levels will lower
tonight and early Monday morning down to 3500-5000 ft across most
the area, with some higher snow levels of 5500-6500 ft in southern
Lake and Modoc counties.

&&

.MARINE...Updated 830 PM PST Sunday, December 21, 2025...Winds and
seas increase overnight into Monday, with very steep seas and
isolated gale force gusts expected by Monday afternoon. Conditions
gradually improve again into Tuesday, then additional fronts, the
strongest of which will move through Wednesday night into Thursday
(gale force winds are possible), will produce periods of gusty winds
and steep to very steep seas through the remainder of the week.
-Spilde

&&

.PREV DISCUSSION... /Issued 925 PM PST Sun Dec 21 2025/

SYNOPSIS...

A high impact winter storm will likely bring two waves of
snowfall to the region with the first arriving Tuesday into
Wednesday. Winds will also be strong in the Shasta Valley and east
of the Cascades Tuesday night into Wednesday morning. The storm
will persist Thursday and Friday before conditions quiet down
during the weekend.

DISCUSSION...

The heavy rain has let up some as there gaps starting to show on
KMAX`s reflectivity plot. Rain has been heavy indeed, although no
reports of areal flooding yet. Rivers have also undergone some
quick rises and exceeded forecasts, although all are still
forecast to remain below flood stage.

A deep low in the Pacific and atmospheric river will remain in the
region with the AR shifting to the south a bit during Monday,
giving our area a brief break from the heavy rain. There will be
some showers around as a cold front and some colder air pushes in
from the Pacific. Snow levels will drop in this area down to 4000
feet, although the warm moist air from the AR will remain to the
south east and keep snow levels up to 6600 feet around Modoc
County.

By Tuesday, wind direction becomes more southerly and the leading
edge of the AR begins to target Siskiyou County on Tuesday. This
is when snow accumulation intensity should start to pick up at
around 4500 feet with and up to 6500 feet in Modoc County. Some
deterministic models suggest winds up the Sacramento Valley will
be 65 knots, which suggests the orographic lift should be pretty
intense Tuesday night into Wednesday morning.

Other than rain and snow, winds will probably be pretty intense
in the Shasta Valley. The 700 mb flow, which is usually a good
predictor of these strong winds, is due south around 55 knots
around 6Z Wednesday. Therefore, we feel pretty confident high
winds will occur there. Model BUFR soundings near Fort Rock(FRO)
also show lapse rates around 9 to 8 between 800 and 700mb.
Therefore, we feel pretty good the winds mixing and impacting
higher terrain or even the surface with a weaker inversion.

By Wednesday, morning models want to eject a weaker surface low
through our forecast area. This varies by intensity depending on
what model you look at, although the ECMWF Ensemble(ENS) shows
about half the members pushing a low through our forecast area.
once that happens, one would think winds would die down by later
Wednesday morning. Once this low moves through precipitation
intensity should decrease in some areas on Wednesday, although it
looks like Mt. Shasta City will see plenty of rain and snow
continue through Wednesday.

One last round of weather will hit the region Thursday into
Friday morning as the upper trough starts to progress eastwards.
Snow levels will be a tad bit lower around 4000 feet with 5000
feet farther east. Again, strong southerly flow will enhance
orographic lift in southern Siskiyou County and produce some heavy
snow accumulation there into Friday.

Once the trough departs the region, guidance is very confident in
high pressure building over the region Friday and Saturday.

-Smith

MARINE...Updated 230 PM PST Sunday, December 21, 2025...Somewhat
improved conditions persist into this evening, though showers and
occasionally lower visibility will persist. Winds and seas increase
overnight into Monday, with very steep seas and isolated gale force
gusts expected by Monday afternoon. Conditions gradually improve
again into Tuesday, then additional fronts, the strongest of which
will move through Wednesday night into Thursday (gale force winds
are possible), will produce periods of gusty winds and steep to very
steep seas through the remainder of the week. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Watch from Tuesday afternoon through late Tuesday
     night for ORZ029>031.

     Winter Weather Advisory until 4 AM PST Monday for ORZ027-028.

CA...Winter Storm Watch from late Monday night through Friday morning
     for CAZ080-082>085.

     High Wind Watch from Tuesday afternoon through late Tuesday
     night for CAZ081-084-085.

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

     Small Craft Advisory from 10 PM Monday to 10 PM PST Tuesday for
     PZZ350-370.

     Hazardous Seas Warning from 10 AM to 10 PM PST Monday for PZZ350-
     356-370-376.

     Small Craft Advisory until 10 PM PST Tuesday for PZZ356-376.

&&

$$