328
FXUS66 KMFR 042238
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
238 PM PST Thu Dec 4 2025

.DISCUSSION...The battle zone between dry and wet will be SW
Oregon and northern California for at least the next week. Model
guidance is near unanimous in showing a strong, moist upper level
jet and ARs directed into British Columbia and portions of the
PacNW (especially northern Oregon and Washington) through next
Thursday. But, strong high pressure aloft currently situated
between 30 and 40N and around 140W will gradually drift ESE during
this time period and will serve to deflect most of the heaviest
precipitation associated with the jet to our north. At times,
however, shortwave disturbances will allow for frontal systems to
wag to the south and bring some rain to our area. With the main
activity/fronts remaining to the north, this should also keep
temperatures above normal for early December and snowfall will be
limited in the mountains.

One such system is expected to come over the top the offshore
ridge on Friday, with a slug of moderate to perhaps briefly heavy
precipitation focused in Coos and Douglas counties, especially the
coast and coast ranges, but also the Cascades and adjacent west
side foothills. Snow levels are up around 9000 feet Friday, so
precipitation will be rain, even at the higher mountains. Most
likely rain amounts in those areas will be 0.50-1.50 inches,
perhaps slightly higher in areas of higher orographic enhancement
(NNW-facing slopes of Cascades). But, this isn`t the type of flow
that brings a lot of rain to the Rogue/Illinois valleys, so
amounts drop off significantly, to around 0.10-0.25 of an inch.
South and east of the Cascades, some places won`t measure any
rainfall, but a few hundredths here and there will be the general
rule, again aside from any NNW-facing terrain enhancement. Models
are showing a mid-level jet of 45-50 kt around 700 mb late Friday
afternoon/night and this could bring gusts up to 45 mph over the
higher terrain and the East Side (Summer Lake region) then. We
don`t think this will affect a large area, so we aren`t putting up
a wind advisory, but hunters or others venturing into the
mountains should be aware of potentially gusty winds. Gradually,
snow levels fall to 5500-6000 feet by Saturday morning, but
precipitation should be tapering off or ending by then. Some light
rain/drizzle has the highest probability of persisting along the
coast and into the Umpqua Basin during Saturday.

After a break Saturday/Saturday night, the next disturbance will
move over the top and into WA/OR Sunday. This will bring a renewed
risk of moderate precipitation across N&W sections of the CWA,
once again with most, if not all, precipitation staying to the
north of the OR/CA border. We don`t currently predict any
measurable rainfall here in Medford, but there could be a
0.10-0.30 of an inch from the coast to the Umpqua Divide/Cascades.

The Pacific fire hose will continue to wag back and forth Tuesday
through Thursday with models showing a warm front shifting north
of the area and snow levels once again rising above 8000 feet. The
force field still appears to be the OR/CA border, with
precipitation really struggling to reach into NorCal during the
stretch. Right now, we can expect some minor rises on area creeks,
streams and rivers across N&W sections of the CWA (up around
Roseburg and north/west), but since they`re running low for this
time of year, we don`t expect flooding. Most significant impacts
from the rain will be to our north.

Beyond that, model clusters/ensembles are generally split between
the upper ridge moving onshore into the SW late next week and then
into the nation`s midsection over the weekend or upper ridging
holding in the SW longer. If the pattern is more progressive, upper
troughing over the north Pacific/Gulf of Alaska could head in our
direction Fri/Sat. Right now, about 20-40% of the membership show
a colder solution with the potential for lower snow levels.
However, more likely, some semblance of the upper ridge remains
over the SW with a shift in the storm track slightly southward
with time. This is likely due to some blocking expected
downstream. This brings better odds for precip here, but with
temps remaining near to above normal. CPC 8-14 day forecast is
showing this scenario with better odds for above normal temps
continuing through Week 2, but also a higher probability of above
normal precip. Since there are many scenarios and plenty can
change between now and then, we`d recommend checking back for
updates! -Spilde

&&

04/18z TAFs...VFR will prevail for most areas this afternoon. A
weak front is crossing through the area today, with periods of
light rain expected along the coast and into the Umpqua and
southern Oregon Cascades this afternoon and tonight. Low clouds
will spread inland late this afternoon and this evening, with MVFR
and IFR developing along the coast inland to the Cascades. From
the southern Oregon Cascades west, ceilings are expected to lower
overnight to IFR/LIFR with IFR visibilities. Mountain obscurations
are likely. Areas of MVFR ceilings may spread east of the
Cascades and into portions of northern California late Thursday
night. Lower flight conditions will continue through at least
Friday morning. -BPN

&&

.MARINE...Updated 200 PM PST Thursday, December 4, 2025...North
winds will transition towards the south and west today and tonight
as a front passes through the area. The combination of residual
north wind seas and new south/west wind seas will result in
somewhat chaotic seas today into Friday. Then, gusty south winds
and west swell will produce continued steep seas Saturday night
into Sunday. Conditions remain unsettled through the first part of
next week, with several passing fronts bringing periods of gusty
south winds and continued steep combined seas. -BPN

&&

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

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 4 PM this
     afternoon to 4 PM PST Saturday for PZZ350-370.

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

&&

$$

MAS/BPN