990
FXUS66 KMFR 080543
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
943 PM PST Sun Dec 7 2025

.Updated AVIATION and MARINE Discussions...

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.AVIATION...08/06z TAFs...Plenty of cloud cover is resulting in a
variety of conditions across the region with widespread terrain
obscurations present. Not much change in overall conditions is
expected into Monday morning. Areas of precipitation are bringing a
mix of LIFR/IFR conditions along the coast, MVFR conditions in the
Umpqua Basin and Illinois Valley, and VFR conditions for the
remainder of the region. Depending on any level of clearing this
overnight, LIFR conditions could develop in West Side Valleys, but
cloud cover is expected to be persistent enough to at least limit
development and extent of these LIFR conditions.

Moderate to strong winds aloft will result in mountain wave
turbulence along and east of the Cascades with stronger winds near
and at the ridges. /BR-y

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.MARINE...Updated 800 PM PST Sunday, December 7, 2025...South winds
will persist overnight, with steep seas continuing north of Cape
Blanco into Monday morning. Conditions worsen late Monday morning as
southerly winds increase, especially north of Cape Blanco, and steep
seas spread to all areas. Advisory level conditions are expected
through Tuesday, and winds could approach gales late Monday into
early Tuesday north of Cape Blanco. Conditions improve around mid-
week as winds ease and seas become swell dominated.

&&

.PREV DISCUSSION... /Issued 346 PM PST Sun Dec 7 2025/

DISCUSSION...While a very heavy rain/flooding event is expected
to materialize to our north through midweek, our forecast area in
SW Oregon and NorCal will largely dodge those threats. We`ll
explain the reasons for that below. Please continue to follow NWS
Portland and Seattle for the details on how much rain and the
associated flooding risks up there.

Currently, a weak disturbance is moving through our area today,
and is bringing a little light rain/drizzle from the
Siskiyous/Cascades north/west to the coast. A few drips may also
occur in Siskiyou County. Amounts so far though, as of 1 pm PST,
have been generally light -- 0.01-0.10" in most areas, but 0.34"
at Charlotte Ridge RAWS and up to 0.59" at Burnt Ridge RAWS. Snow
levels are generally around 7000 feet. Expect mostly intermittent
light rain/drizzle to continue tonight across NW sections of the
CWA. Meanwhile, SE areas like Alturas and even most areas east of
the Cascades in Oregon will stay dry.

On Monday, a deep plume of subtropical moisture, or atmospheric
river, will gather over the Pacific and become directed into
British Columbia, Washington and NW Oregon. This will set the
stage for the prolonged period of heavy rainfall for our neighbors
to the north. Our forecast area will be largely spared of the
impacts though. This is primarily due to the strength of an upper
level high centered near 30N and 130W (off the California Coast).
This high will remain strong enough to deflect most of that moist
plume off to our north. The main source of uncertainty has been
the strength of this high and just how far south the moist plume
could jog Monday night to Wednesday. Models are trending farther
north (at least in terms of QPF) compared to yesterday. 12Z GEFS
solutions have come more in line with the ECMWF and now show very
little rain even here in Medford with rain shadowing significantly
impacting amounts south of Roseburg. Favored areas along the
coast and over to the Cascades as well as north of Roseburg along
the Douglas/Lane County border still could see amounts of 1-3
inches during that time period, but we`re not concerned about
flooding. We issued a Hydrological Outlook yesterday to raise
awareness of the risks, but we`ll allow that to expire this
evening.

One thing that continues to be shown is a fairly strong gradient
and mid-level jet (55-65kt) across the Cascades that could lead
to stronger winds east of the Cascades in Oregon and north of
Highway 140 beginning Monday night and continuing through Tuesday
evening. Not completely sure these strong winds aloft mix down to
the surface, but could at the higher terrain and locally
channeled valleys like around Summer Lake. As such, have gone
with a wind advisory for those locations 7 pm PST Monday through
10 pm PST Tuesday for gusts up to 50 mph.

After Wednesday, the upper ridge off the California coast is expected
to amplify and that should push the front well off to our north
and bring a period of dry weather to most, if not all, of the
area Thursday into the weekend. Slight chance PoPs remain along
the coast, but wouldn`t be surprised to see these fall out of the
forecast. Some guidance breaks down the ridge over the weekend
with a front reaching the coast sometime Saturday night, but most
hold this front off until later in the weekend or early next week.
This will maintain the milder pattern through at least mid-month.
-Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 7 PM Monday to 10 PM PST Tuesday for ORZ030-
     031.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 10 AM Monday to 1
     PM PST Tuesday for PZZ356-376.

     Small Craft Advisory until 1 PM PST Tuesday for PZZ350-370.

&&

$$