725
FXUS66 KMFR 032204
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
304 PM PDT Fri May 3 2024

.SHORT TERM...Through Monday morning...An approaching low pressure
system is already bringing rainfall to the Oregon coast. Rainfall
will continue through the night over Coos, Curry, and western
Douglas counties. Precipitation will steadily move eastward across
the area through Saturday. Coastal areas will see about 2 to 3
inches of rainfall while west side valleys will get between half an
inch and an inch of rain. Klamath and Modoc counties will get
similar amounts of rainfall while Lake County will generally get
half an inch of rain or less. The heaviest amounts will be late
tonight through early Saturday morning.

This system is bringing unseasonably cold air aloft, which will
bring snow levels down from their current 8000 feet to 3000 feet by
Saturday morning. While most snowfall will remain over higher
terrain, the amount of moisture and the fast drop in snow levels
will bring periods of heavy snow to the Cascades and to western
Siskiyou County. Currently, 4 to 6 inches of snow are expected at
elevations above 4000 feet for the Cascades and Siskiyou ranges,
with a 20-30% chance of more than 6 inches over the Cascades by
Sunday morning. Additionally, high resolution guidance shows a 40-
80% chance of snowfall rates of 1 inch per hour Saturday morning.
Due to the dangerous travel conditions that these conditions are
expected to make, a Winter Weather Advisory is in place for parts of
western Siskiyou County from 2 AM to 11 AM on Saturday and for the
Cascades from 2 AM to 11 PM on Saturday.

This system will also bring elevated winds, especially across
elevated terrain east of the Cascades. A Wind Advisory is in place
for higher terrain in Lake County from Saturday at 5 AM through 5
PM. Gusty winds reaching over 40 mph are expected in this time,
while wind gusts could still exceed 30 mph in other areas of
Klamath, Lake, and Modoc counties.

One final impact from this system will be a drop in nighttime
temperatures from Saturday to Sunday. Temperatures will drop to the
high teens to mid 20s for areas east of the Cascades. Below freezing
temperatures are also possible west of the Cascades, although right
now only the Shasta and Scott valleys look to be significantly below
freezing. A Freeze Watch is in place for those valleys on Sunday
morning, but below freezing temperatures are possible for the Rogue
and Illinois valleys as well. Future guidance will help determine if
additional products will be needed, bur right now that looks
unlikely.

The effects of the system continue through Sunday, but are most
likely limited to post-frontal showers over the Oregon coast and the
Cascades. Cool daytime temperatures will continue and nighttime
temperatures look to warm from Saturday night`s levels. -TAD

.LONG TERM DISCUSSION...Models continue to show a front moving
across the area on Monday with high chances (60 to 100 percent)
across most the area. Precipitation amounts with this front on
Monday will be mainly light with some moderate amounts (0.25 inches
or more) over the Cascades, coastal mountains and along the coast.
Snow levels will range from 4000 to 5500 feet. Additionally, models
and ensembles support a slight chance (20%) for thunderstorms Monday
afternoon across portions of southwest Oregon, including Coos,
Douglas, Klamath and Lake Counties. Brief downpours and gusty winds
may occur with any thunderstorms that develop. Then, moist, onshore
flow will allow for lingering showers on Tuesday, especially across
southwest Oregon zones with lesser chances across Northern
California. High pressure builds into the area Wednesday and remains
in place through the end of the wee. This will bring drier and much
warmer weather. By Friday, high temperatures will likely be in the
80s for valleys west of the Cascades and in the 70s for valleys east
of the Cascades.

&&

.AVIATION...03/18Z TAFs...Prevailing VFR this morning will drop back
to MVFR with local IFR cigs/vsbys as a potent cold front moves in,
with periods of moderate to occasionally heavy precipitation this
afternoon. VFR will prevail elsewhere inland through late this
afternoon/early this evening.

The front will spread moderate precipitation across the rest of the
west side tonight, reaching east of the Cascades Saturday morning.
Expect widespread MVFR conditions and local IFR in rain with higher
terrain obscured in rain/snow. A rapid drop in freezing levels will
occur overnight (~09-15Z) from west to east and especially around
12Z Saturday morning near the Cascades. Rain will change to snow
down to as low as 2500 feet with brief heavy snow in the mountains,
reducing visibility to LIFR at times. Breezy south winds are
expected with the front too, with peak gusts in the 40-50 mph range.
Despite the increasing winds, low level wind shear is not a concern
at this time.

Conditions should improve a bit behind the front with precipitation
becoming more showery, but still with a good amount of MVFR
ceilings/visibility through tomorrow morning. -Spilde/BPN

&&

.MARINE...Updated 200 PM Friday, May 3, 2024...A cold front will
move through today into this evening with moderate to heavy rain,
gusty south winds and steep seas. Following the front, seas will
remain steep, dominated by fresh short period west swell through
tonight. Showers continue with a slight chance of thunderstorms
(20%) on Saturday. West seas trend less steep Saturday afternoon
through Sunday. Another front arrives Sunday night into Monday with
the potential for gusty south to southwest winds followed by
building west-northwest seas into Tuesday. After that, we expect
high pressure to build in mid-late next week with a thermal trough
strengthening along the coast. This will bring a return of stronger
north winds and steep seas, highest south of Cape Blanco.
-Spilde/BPN


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 2 AM to 11 PM PDT Saturday above
     4000 feet for ORZ027-028.

     Wind Advisory from 5 AM to 5 PM PDT Saturday for ORZ030-031.

CA...Winter Weather Advisory from 2 AM to 11 AM PDT Saturday above
     4000 feet for CAZ080.

     Freeze Watch from late Saturday night through Sunday morning for
     CAZ080-081.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT this
     evening for PZZ350-356-370-376.

&&

$$

TAD/CC/BPN