743
FXUS66 KMFR 160150
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
550 PM PST Mon Dec 15 2025

...Updated the Aviation Section...

.AVIATION...16/00Z TAFs...A cold front is nearing the Cascades early
this evening, and will continue eastward across the area tonight.
This is producing a wide range of conditions with light to moderate
rain, local (mainly coastal) IFR, and mainly VFR, but also
occasional MVFR with areas of mountain obscuration.

Overnight into Tuesday morning, areas of low level wind shear are
expected east of the Cascades, particularly in northern Klamath
County and Lake County, including Lakeview. Low level winds aloft in
that area are expected to be west-southwest at 35 to 50 knots.
Meantime, behind the front, west side valley LIFR/IFR will develop
after 04Z and again become widespread. East of the Cascades,
ceilings are likely to lower to MVFR.

Rain will taper off overnight. But, the next weather system will
reach the Curry County coast by 18Z Tuesday morning, and begin
another episode of rain and mountain obscuration across our area
through Tuesday night with variable heights of predominantly IFR and
MVFR overcast skies.

&&

.MARINE...Updated 100 PM PST Monday, December 15, 2025...The first
round of south gales north of Cape Blanco is winding down this
afternoon. Very steep and hazardous seas will remain elevated, but
become less steep as they transition to swell dominated this evening
and persist through much of Tuesday. The next front is expected late
day Tuesday, bringing another round of southerly gales that quickly
switch to the northwest, and remain strong, late Tuesday night. This
will build seas again, becoming very steep and hazardous Tuesday
night across all waters, with gales expected north of Cape Blanco.

Winds ease late Wednesday morning, but seas will remain steep
through Wednesday night. Another, more persistent front will take
aim at the coast late Wednesday night/early Thursday morning,
bringing a longer duration of strong winds. Strong gales are likely
with this system, with a 20-40% chance of storm force (>55kt) gusts
possible north of Cape Blanco on Thursday morning. Winds will
gradually ease from north to south late Thursday night into Friday
morning, but seas are likely to remain steep to very steep through
Friday. Moderate to heavy rain will accompany each front this week.
/BR-y

&&

.PREV DISCUSSION... /Issued 219 PM PST Mon Dec 15 2025/

DISCUSSION...The first in a series of fronts is moving into the
area bringing rain to the coast and coastal mountains and gusty
winds. Strongest north of Cape Blanco. Precipitation will spread
farther inland, with winds increasing east of the Cascades. The bulk
of the precipitation will be along the coast, coastal mountains and
Cascades. Satellite image and radar are showing moderate to
occasionally heavy precipitation with a few lightning strikes which
is partially being aided by an upper level jet moving towards
southwest Oregon. Isolated thunderstorms should remain confined to
the south Oregon coast and inland in Curry and western Josephine
County into early this evening.

Most of the Rogue Valley could end up dry during the day
Monday with not much more than occasional showers late this
afternoon and early evening due to the non-favorable southwest flow.
East of the Cascades will likely get little to rainfall, but it will
be windy into early this evening.

More fronts will follow the rest of the week into next weekend
bringing more rain, moderate to strong winds and higher elevation
mountains snow. Detail`s on the timing mentioned below could vary
with each individual storm, so be on the lookout for updates to the
forecast in the days to come.

A second and stronger system will arrive Tuesday night into
Wednesday brining moderate to heavy rain to the coast, coastal
mountains and Cascades. Moderate to occasionally strong winds are
possible at the coast. Not all of the ingredients are there for a
winds to reach high wind warning criteria at the coast, but they do
for east of the Cascades, especially near and at the ridges.
guidance shows 700 mb winds between 60-70 kts Tuesday night through
Wednesday morning, then decreasing some Wednesday afternoon. Given
the above, the High Wind Watch has been upgraded to a High Wind
Warning for the higher terrain in Lake, Modoc and potions of Klamth
County. At the same time a Wind advisory has been issued to cover
the remainder of Lake, Modoc and to include more of Klamath County.
Please see NPWMFR for more details.

Snow levels will be between 7000-8000 feet Tuesday, then lowering
between 4500-5500 feet Wednesday. Therefore we`ll see rain change
over to snow late Tuesday night into Wednesday morning with 3-5
inches possible up towards Willamette Pass, and 2-4 inches around
Diamond and Crater Lake by late Wednesday morning.

Precipitation will gradually diminish later Wednesday morning
through the afternoon and we`ll catch a relative break in the action
from Wednesday afternoon into most of Wednesday night.

A stronger storm will arrive Thursday and last through Thursday
night bringing another round of moderate to heavy precipitation and
strong winds. Strong winds will be a concern Thursday, especially
east of the Cascades where some of the guidance shows 700 mb winds
between 70-80 kts over a large chunk of real estate east of the
Cascades. It`s also worth noting, strong winds east of the Cascades
could be of longer duration (12-18 hours).

Although not as high of a concern, moderate to strong winds will be
a concern in the Shasta Valley. However the wind direction in the
Shasta Valley has a westerly component which could put a cap on the
magnitude of the winds. Guidance shows the Medford to Redding
gradient between 8-9 mb. So it`s something we`ll have to keep a
close watch on.

The coast is another story. Current gradients between Arcata and
North Bend peak out at almost 10 mb Thursday afternoon and night
which is significant enough for high winds, and guidance shows an
enhanced area of strong winds close to 70 kts Thursday afternoon
from about Cape Blanco north.

Thre`s good agreement the storm that arrives Thursday will have an
atmospheric river (AR) component, with a long fetch of moisture
extending southwest towards 160W, with the source region coming from
the tropics. Additionally, there is favorable upslope flow along the
coastal mountains and Cascades. The net result could be a prolonged
period (24-36 hours) of heavy precipitation for these areas along
with moderate to occasionally heavy rainfall elsewhere. Given the
lack of rain the last few weeks, rivers are pretty low, but they
will come up over time and we could be looking at potential flooding
on the Coquille towards the end of the week. Another factor that
could put a cap on the flooding concerns is little to no snowpack.
Therefore there will be no additional contribution from snowmelt
going into the rivers. Another item worth noting is there are some
indications the core of heavier precipitation could shift north of
the Umpqua Divide for a brief period of time Thursday afternoon into
Thursday night before shifting south over southern Oregon and
Northern California Friday. Keep in mind the details could change,
so keep a eye out for updates in the days to follow.

Looking into next week leading up to Christmas Holiday, there`s
strong evidence that`s being supported by the ECMWF, GEFS ensemble
means and clusters, we`ll be heading into a colder and wet pattern
with storms originating from the Gulf of Alaska as we get towards
the following weekend through at least Christmas Day.

These typically result in colder temperatures, and precipitation
with lower snow levels. The pattern shows below normal 500 mb
anomalies with a stronger upper troughing in the western U.S. with
ridging and above normal 500 mb anomalies in the northeastern part
of the U.S. The anomalies being shown are pretty significant this
far out which is unusual since they tend to "wash out" and lean more
towards climatology.

This is a almost the opposite of the pattern we have experienced for
almost the last three weeks, with stronger ridging in the western
part of the U.S. and deep upper troughing in the northeastern part
of the U.S. In other words, the switch basically gets flipped as the
overall pattern changes. -Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 10 PM Tuesday to 4 PM PST Wednesday for
     ORZ030-031.

     Wind Advisory from 10 PM Tuesday to 4 PM PST Wednesday for
     ORZ029>031.

CA...High Wind Warning from 10 PM Tuesday to 4 PM PST Wednesday for
     CAZ085.

     Wind Advisory from 10 PM Tuesday to 4 PM PST Wednesday for
     CAZ085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 4 PM PST Tuesday
     for PZZ350-356-370-376.

     Hazardous Seas Warning from 4 PM Tuesday to 4 AM PST Wednesday
     for PZZ356-376.

     Gale Warning from 4 PM Tuesday to 4 AM PST Wednesday for PZZ350-
     370.

&&

$$