098
FXUS66 KMFR 060000
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
400 PM PST Wed Feb 5 2025

.Update AVIATION and MARINE Discussions...

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.AVIATION...06/00Z TAFs...Generally VFR conditions prevail across
the region with areas of MVFR and terrain obscurations due to
scattered showers. Showers are focused along and west of the
Cascades and freezing levels are low across much of the area.
Under the heavier, more persistent shower activity, colder air is
being dragged down to the surface and resulting in accumulating
snow. This is happening most frequently in the Illinois and Shasta
Valleys and east of the Cascades. Shower activity will diminish
overnight, but never come to an end. IFR/LIFR conditions are
expected to return tonight to areas that aren`t influenced by
showers, including Medford. Otherwise, a mix of MVFR/VFR
conditions will prevail through the TAF period. /BR-y

&&

.MARINE...Updated 400 PM Wednesday, February 5, 2025...Broad low
pressure resides off the coast of Washington and northern Oregon.
South winds will maintain steep seas, with very steep seas north of
Cape Blanco through this evening. Winds and seas decrease tonight as
low pressure weakens into Thursday. Gusty north winds and steep seas
return Thursday night into Friday as the low pressure center swings
inland, then relatively calm conditions are expected through the
rest of the weekend. High pressure may return early next week, along
with gusty north winds and steep seas, especially south of Cape
Blanco. -BPN/BR-y

&&

.PREV DISCUSSION... /Issued 305 PM PST Wed Feb 5 2025/

DISCUSSION...The previous discussion is pasted below, and the
latest update is found above this. Please view the WSWMFR for
latest updates on the new products starting tomorrow afternoon.

Update...Uncertainty for valley floor snowfall is high (based on low,
moderate, and high values) for the next round of snowfall Thursday
afternoon through Friday morning. One of the reasons for this
uncertainty is the fact models are not initializing correctly. For
example, some of the models "think" there is very little to no
snowfall on the ground for the Rogue Valley, and this is leading to
incorrect analysis of future outcomes because we have several inches
still in place across the valley and a foot in some areas. There is
also high spread in the snowfall output from trace amounts to 8.0+
inches for forecast snowfall Thurs-Fri. We are confident enough to
say amounts will likely be higher than a trace, but lower than 8
inches. The probability for Medford to receive 1.0" or greater in
24hrs of snowfall is around 70 percent, while the probability to see
4.0" or greater in 24 hours is 21%. Our confidence for Medford is
highest around 2 to 4 inches of snowfall Thursday afternoon through
Friday morning. That said, there is likely to be highly variable
amounts across the valley at varying elevations. The key here is
that any further snowfall will only make travel and road conditions
worse since roads are already nasty in some areas. Additionally,
snow melt will likely lead to icy and dangerous road conditions
where we have snow melt. Extreme caution should be used during any
travel over the next couple of days across most of the forecast
area.

Previous Discussion...An upper low is located off the
Washington and Oregon coasts. This is bringing cold and unstable
air to the area. Shortwave disturbances will move around the low
and into the area today and Thursday, resulting in areas of low
elevation and mountain snow, especially near and west of the
Cascades and extending into northern/eastern Klamath County.
Through Thursday morning, the main concern will be around
additional snow in showers as a couple disturbances move through
the area. Snow levels will be down to lower valley floors and may
even be down to beaches at times this morning as showers move into
western portions of the area. Then snow levels may rise to 1000
to 2000 feet in the afternoon before lowering again to lower
valley floors. Even as snow levels rise in the afternoon, showers
moving in may drop snow levels back to lower valley floors or
bring graupel to western valleys. Models and satellite/radar
trends indicate shower activity will be most concentrated from the
coast into the coastal mountains through early this morning, then
increase in intensity and coverage during the day and evening,
spreading into to the Cascades and eastward. Also with showers,
there is a slight chance for lighting, especially for the coast
waters and coast locations.

As a low pressure system approaches the northern California coast
and moisture moves up into the area, a second round of showers is
likely Wednesday night into Thursday morning. The exact position
of this band of showers is uncertain but overall, expect this band
to be located over western portions of the area, mainly from the
coast into the coastal mountains and extending into portions of
Josephine, western Siskiyou and the Southern Oregon Cascades.

Given this cold and showery pattern, we have added winter weather
advisories (NPWMFR) to many areas from the Southern Cascades west
and into portions of Siskiyou and Klamath counties. We have also
continued the winter storm warning over the coastal mountains,
where shower activity is likely to be greatest. Please see the
WSWMFR for details. Travelers are encouraged to stay up to date with
the current weather and road conditions and delay travel if
possible, for areas most affected. If you must travel, be prepared
for winter travel conditions.

Next, attention shifts to a frontal band of precipitation that
arrives Thursday afternoon into Thursday night as a low pressure
system moves onshore over northern California. Models and
ensembles support slight rise in snow levels to 2000 to 3000 feet
during the day Thursday but given this pattern, cold air may be
slow to move out, especially for areas in southwest Oregon. So
snow levels may remain lower for some locations. We will continue
to monitor the track and timing of this system and where the main
band of precipitation sets up. Models and ensembles then indicate
this low will track inland Thursday night across northeast
California while a trough deepens off the coast of southern
Oregon. This will result in cold air advection into areas west of
the Cascades, with lowering snow levels. Meanwhile the band of
moderate precipitation will remain over the area, with the
heaviest precipitation likely for northern California. Some areas
in Coos and northwest Douglas counties may remain mostly dry
while ongoing precipitation is expected for areas south and east.
Additional winter weather headlines are possible during this
period with moderate to heavy snow possible from the Cascades east
and Siskiyou south and areas of moderate snow possible west of
the Southern Oregon Cascades. With the low is expected to track
northeastward into southeast Oregon and northwest Nevada, expect
continued precipitation into Friday morning. We will continue to
monitor this storm with the next set of model runs. Please watch
for additional updates.

A broad upper trough and cold air mass may settle over the area
late Friday into Saturday with areas of light showers. Much colder
temperatures are expected Friday night into Saturday and again
Saturday night. The National Blend of Models supports temperatures
in the single digits east of the Cascades and in the teens to low
30s for west of the Cascades (except for even cooler temperatures
around 10 to 20 degrees for valleys in Siskiyou County).

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 10 AM PST Thursday for ORZ023>026-
     029>031.

     Winter Weather Advisory from 4 PM Thursday to 10 AM PST Friday
     for ORZ023>030.

CA...Winter Storm Warning until 10 AM PST Thursday for CAZ080>085.

     Winter Weather Advisory from 4 PM Thursday to 10 AM PST Friday
     for CAZ080>082-084-085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 4 AM PST Thursday
     for PZZ356-376.

     Hazardous Seas Warning until 4 AM PST Thursday for PZZ350-370.

&&

$$