682
FXUS66 KMFR 050550
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
950 PM PST Tue Feb 4 2025

.Updated AVIATION Discussion...

&&

.AVIATION...05/06Z TAFs...The steadier precipitation has moved east
out of the area this evening. Showers are developing over the marine
waters and moving onshore as the air mass becomes more unstable with
colder air moving in aloft. Even so, with all the snow and moisture
here in portions of the Rogue Valley, fog is forming this evening
and restricting visibility to 1/4 of a mile at Grants Pass and
Medford. Expect some showers to move in overnight and this could
break up the fog. Also worth noting is that snow levels will remain
low overnight and any showers tonight could bring some additional
light snow accumulations, including at Medford and Roseburg.

Along the coast and over the marine waters, showers with possible
thunderstorms are expected through the TAF period with conditions
varying from VFR to brief periods of IFR. Guidance shows
precipitation will mostly be rain, however, if showers are heavy
enough, this could drag colder air towards the surface, resulting in
a brief period of a rain/snow mix, all snow or even small
hail/graupel with reduced visibilities under these heavier showers.

East of the Cascades, ceilings and visibilities improved to VFR this
evening and should remain that way mostly through the period. South
winds will increase Wednesday afternoon with peak gusts near 30 kts.
-Spilde/BR-y

&&

.PREV DISCUSSION... /Issued 904 PM PST Tue Feb 4 2025/

DISCUSSION...We have cancelled the winter weather advisories and
warnings that were out for earlier today, but the winter
headlines remain in place west of the Cascades as a cold core
upper trough pinwheels out around or just beyond 130W off the
PacNW coast. The front that brought the widespread moderate to
heavy precipitation over the area the last couple of days is
finally pushing off to the east. Radar is still showing some snow
falling across Modoc and Lake counties this evening, but this
should end (mostly) in the next couple of hours. Now, the colder
air is taking hold and skies are clearing in many areas behind it.
This will allow temperatures to drop this evening and overnight,
so any wet, slushy roads are likely to turn icy, including many
west side valleys. Please slow down and use extra caution if
traveling tonight into Wednesday morning. With all the rain that
has occurred in Modoc County the last few days, the Pit River at
Canby is around 11.0 feet this evening and is in major flood
stage. We adjusted the river flood warning to reflect this latest
trend. It is expected to remain in major flood Wednesday night
into Thursday, then gradually fall during Friday and reach below
flood stage Saturday morning. To put this in perspective, Alturas
already has had 3.25 inches in just the 1st 4 days this month.
Normal for the entire month of February in Alturas is only 1.09
inches!

Multiple shortwave disturbances will rotate around the cold upper
low offshore and move onshore tonight through Wednesday night.
This will bring cold showers just about everywhere from the coast
to the Cascades. In addition to the winter headlines that were
already up for the west side, we`ve added a few Winter Weather
Advisories for the coast and the valleys just inland since
showers in these areas could be rather persistent. The convective
nature of the showers could result in isolated lightning strikes
over the marine waters and also the coast later tonight into
Wednesday. Since the air mass is cold, this could bring small
hail/graupel. This may seem benign, but if showers are persistent
enough, the graupel could cover roadways and cause slippery
conditions. Snow levels will be generally near or above 500 feet
at the coast, but we couldn`t rule out a burst of snow in a
heavier shower. Showers will focus on the higher terrain of the
coast ranges/western Douglas Counties where Winter Storm Warnings
are up for elevations above about 1500 feet. In these situations,
we often see lower snow levels SW of Grants Pass, specifically in
the Illinois Valley, so we have a winter weather advisory out
there for 1-4 inches of snow. Passes north of Grants Pass are also
likely to see some snow accumulations, so if you h ave travel
plans on I-5, please prepare for wintry travel. Some of these
showers could move across Jackson County too, but have held off
any products for now to see how the showers develop. We may need
to add an advisory here as well. Showers look most likely here
Wednesday afternoon when snow levels are shown to rise to around
1500-2000 feet and temps peaking in the upper 30s/near 40F. But,
would be surprised if precip fell as anything but snow/graupel.
While brief accumulation is possible in a heavier shower, best
chance is above 1500 feet.

MARINE...Updated 830 PM Tuesday, February 4, 2025...Broad low
pressure resides off the coast of Washington and northern Oregon.
South winds will increase Wednesday morning as a weak front passes
through the region, resulting in a period of steep seas. Winds
decrease Wednesday night as low pressure weakens into Thursday,
and seas will lower below advisory levels by Thursday morning.
Sub- advisory conditions are generally expected through the
weekend, though there could a brief period of advisory level
winds/steep seas on Friday. /BR-y

PREV DISCUSSION... /Issued 455 PM PST Tue Feb 4 2025/

Updated Aviation Discussion.

DISCUSSION...The snow that is falling in west side valleys this
afternoon is finer and not as wet as the snow yesterday. Current
radar shows a line of showers in Northern California that expands
through central Josephine County through the Cascades as the front
moves slightly to the northwest. From this morning around 10 AM
through tonight at 10 PM, overall 3-6 inches is expected in the
areas that are under the Winter Storm Warning with 2-5 inches for
areas under the Winter Weather Advisory, which includes the Rogue
and Illinois Valleys. Please see the WSWMFR for more information.
The precipitation is looking to move eastward between 5-7 PM to
east of the Cascades. there is also still a Flood Warning in
effect for the Pit River through 10 PM tonight, and the latest
updates show a steady increase with snow melt today.

The next topic of concern is falling temperatures tonight. Everyone
will see colder temperatures tonight. Starting at the coast, these
will be where the warmest temperatures will be found in the low 30s.
Incoming showers will prevent this area from cooling as much, so
there is a lower chance for freezing temperatures at the coast
tonight, which means a Freeze Warning will not be issued for the
coast tonight. Areas west of the Cascades will otherwise see mid-
/upper 20s for overnight lows. This has been slightly increased in
this forecast because the snow cover and heavier cloud cover will
make it hard to see as much cooling. With freezing temperatures will
in the forecast, this will mean that whatever is still on roads from
yesterday`s snowfall and the new snowfall today could freeze. Please
remember that bridges and overpasses will freeze faster.

With this colder air, snow levels will fall across the board tonight
and this could mean snow at the coast. Stronger showers could bring
the snow to the coast faster which would surpass the need for
freezing temperatures at the surface. For now there is more
agreement that there will either be snow or rain in the mix, but
sleet is a potential with steeper lapse rates as well.

The main update for today includes new a new Winter Weather Advisory
and Winter Storm Warning. From 4 AM Wednesday- 4 AM Thursday, a
Winter Storm Warning will be in effect for parts of southern Douglas
County, the Kalmiopsis Wilderness and portions of the Marble and
Siskiyou mountains. Overall 3-8 inches are possible with up to 16
inches in higher terrain of Northern California.

A Winter Weather Advisory will also be in effect tomorrow at 4 AM
through Thursday at 4 AM for the Eastern Douglas County foothills
and for portions of the Cascades. Overall looking at 4-8 inches with
up to 12 inches possible in higher terrain, including near Crater
Lake. There is a 30-50% probability to see half an inch per hour
snowfall rates through Wednesday afternoon. -Hermansen

AVIATION...05/00Z TAFs...The back edge of the steady
precipitation is just east of Grants Pass and the high res models
suggest precipitation at the Medford Airport will diminish towards
2z with visibility and ceilings gradually increasing. While
visibilities will improve, ceilings will likely not get much better
than MVFR this evening and tonight.

Farther northwest, north of Cape Blanco, VFR conditions are expected
through the TAF period with convective showers moving in early this
evening. Guidance shows precipitation will be rain. However, in the
convective showers are moderate to heavy, this could drag colder air
towards the surface and North Bend could experience a brief period
of rain/wet snow mix of just snow with reduced visibility. Right now
confidence is not high enough to include the snow and lower
visibility in the TAF, but will be monitored closely. Additionally,
a colder air mass will move in late tonight into Wednesday resulting
in increasing instability that could bring an isolated thunderstorm
or two at North Bend.

East of the Cascades, steady moderate snow, at Klamath Falls will
continue into this evening, with ceilings and visibilities improving
towards 5z as snow tapers off and ends, and ceilings should improve
to VFR late this evening until the end of the TAF period. South
winds will increase Wednesday afternoon with peak gusts near 30 kts.
-Petrucelli

MARINE...Updated 200 PM Tuesday, February 4, 2025...Broad low
pressure resides off the coast of Washington and northern Oregon.
South winds increase as a weak front rotates around the south side
of the low into the Oregon coast early Wednesday. Winds decrease
Wednesday night as low pressure weakens into Thursday. Then, weak
high pressure builds into the coastal waters through Friday. North
winds gradually increase through the weekend as a thermal trough
develops. Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning from 4 AM Wednesday to 4 AM PST Thursday
     for ORZ023-024.

     Winter Weather Advisory until 10 AM PST Wednesday for ORZ021>025-
     027.

CA...Winter Storm Warning from 4 AM Wednesday to 4 AM PST Thursday
     for CAZ080.

PACIFIC COASTAL WATERS...Small Craft Advisory from 4 AM Wednesday to
     4 AM PST Thursday for PZZ350-356-370-376.

&&

$$