Sneakerwave in Oregon, February 25 to 26, 2024

Area Forecast Discussion
National Weather Service Medford OR
858 PM PST Sat Feb 24 2024

.SHORT TERM...Tonight through much of the day Sunday, dry weather
will persist across the area. Overnight, areas of low clouds and
fog are expected, mainly in the Umpqua Basin and Coquille valley
with isolated low clouds/fog in the Grants Pass area, Illinois
Valley and lower Klamath River valley. Otherwise, expect high
clouds to begin moving into the area late tonight and Sunday
morning, ahead of a strong cold front. However, temperatures will
remain warmer than normal Sunday afternoon. Then as the front
moves down into the area Sunday night and Monday, a cold and wet
pattern will be in store, with rain, snow and gusty winds across
the area.

Models remain on track showing this front moving north to south
across the area late Sunday night through Monday afternoon.
Precipitation will spread into northwest portions of the area
including Coos and Douglas Counties and the Southern Oregon
Cascades Sunday evening, then gradually spread across much of the
area Sunday night into Monday morning. This front will gradually
exit to the south late Monday afternoon with an upper trough
moving in place behind it. As this front tracks southward, snow
levels will lower from 5000 to 6000 feet Sunday evening down to
2000 to 4000 feet Monday. Moist onshore westerly flow will bring
heaviest snow to the southern Oregon Cascades and western
foothills in Douglas County. Models continue to show moderate to
heavy snow across these areas. The National Blend of Models
indicates a 70 to 100% chance of at least 4 inches of snow in the
Cascades and over foothills in eastern Douglas County Sunday night
through Monday afternoon and a 50 to 80% chance for 6 inches or
more of snow. Additional moderate snow arrives across the Cascades
and foothills with showers Monday evening and night. Forecast
storm totals (Sunday night through Monday evening) over the
Cascades and western foothills in eastern Douglas County are
around 8 to 18 inches. Areas of moderate snow (around 4 inches)
are also possible across northern Klamath County, especially north
of Chiloquin, on Monday morning as the front moves across this
area. Elsewhere, snowfall amounts will be generally light, to
locally moderate over higher mountains.

Behind the front, a cold and showery airmass will move into place
late Monday through Monday night. Light snow showers are expected
down to around 1000 to 1500 feet elevation Monday evening and
night but impacts will be limited in valleys and across lower
mountains west of the Cascades due to warmer ground temperatures
and light showers. One area to watch is Canyon Mountain on I-5
which may see a mix of rain and snow Monday afternoon then snow
showers, generally light, late Monday into Monday night. This area
has a 30-35% chance of an inch of snowfall but with warmer ground
temperatures, snow may quickly melt. Of note, as flow aloft turns
northwest Monday evening/night showers will be most favored along
the coast, into Douglas County and the southern Oregon Cascades,
especially over mountains and northwest slopes.

Gusty winds will also be a concern Sunday night and Monday,
especially over the higher mountains and east of the Cascades.
Gusty winds combined with snowfall in the Cascades will result in
very low visibilities at times. East of the Cascades, moderate to
strong gusty winds expected over the mountains and into the Summer
Lake area. These winds will lower Monday evening and night but
remain breezy.

Along with the colder airmass Monday night into Tuesday morning,
expect low temperatures, near or below freezing in many inland
valleys west of the Cascades.

A showery and cold airmass lingers on Tuesday, then additional
systems will impact the area late Wednesday through Saturday. See
the discussion below for more details.

&&

.AVIATION...25/00Z TAFs...VFR conditions prevail through the
evening.  Fog is anticipated in the Umpqua Basin with LIFR ceilings
and visibilities overnight.  Things should clear out by the late
morning hours as the sun mixes things out.  VFR ceilings and
visibilities will continue for most of Sunday before rain and snow
arrives after 0Z Monday.

-Smith

&&

.MARINE...Updated 230 PM Saturday February 24, 2024...North winds
will continue steep wind driven seas tonight. Conditions improve
briefly Sunday, then a strong cold front will bring gusty northwest
winds and steep seas Sunday night into Monday. Current forecast
outcomes suggest steep seas across all waters, with winds peaking at
25 knots and waves of 10 to 13 feet at 12 to 14 seconds expected in
all waters. Winds will ease Monday night into Tuesday, but
persistent west swell is expected to sustain steep seas for all
waters. Another strong front will bring strong south to southwest
winds and steep to very steep seas Wednesday into Thursday. These
conditions are likely to be present in all waters to end the week
and continue into the weekend. -Spilde/Miles

&&

.PREV DISCUSSION... /Issued 311 PM PST Sat Feb 24 2024/

SHORT TERM...Tonight through Monday night...Our current much
warmer than normal afternoon with mostly sunny skies will lead to
another similar night with low clouds and fog developing in most
portions of the Umpqua, Coquille, Illinois, lower Rogue, and
Klamath River valleys. The stratus will again gradually dissipate
during Sunday morning. It will be nearly as warm as today on
Sunday afternoon, but southwest winds will become locally breezy
and clouds will increase from the west and the northwest.

The Winter Storm Watch has been upgraded to a Winter Storm Warning
for the Cascade Foothills, Cascades, Siskiyou Mountains, and
northern Klamath County late Sunday evening into late Monday
night. The heaviest snowfall is expected late Sunday night through
Monday morning. The snow level will be at 5500 feet as snow
begins late Sunday evening, but steadily decrease to around 3500
feet before sunrise Monday, 2500 feet Monday afternoon, then as
low as 1500 feet as snow tapers off late Monday night. Snowfall
will be lighter, generally up to 5 inches, but may reach advisory
level amounts for other higher terrain locations in our area.

Also, a Wind Advisory has been issued for northeast Siskiyou, and
much of Modoc and Lake counties from Monday morning through
Monday evening. Southwest to West winds at 20 to 35 mph will gust
at 30 to 50 mph.

Late Monday night into early Tuesday morning, lingering flurries
may produce a skiff of snow down to 1000 feet.

LONG TERM...Tuesday(2/27) through Saturday(3/2)...Despite
upper level ridging building in overhead, showers will linger along
the coast and across the Umpqua Basin Tuesday as continuing
onshore flow keeps moist air flowing into the region. Snow levels
through the day are expected to remain around or just above 2000
feet, so while precipitation should be light, we can not rule out
some light snow over the I-5 passes between Grants Pass and
Canyonville, or over the Cascade passes along and north of Crater
Lake. Travel impacts should be negligible.

A warm front will then push north through the area and ridging will
continue to build in aloft Tuesday night into Wednesday, but with
limited moisture, shower activity will remain isolated to scattered.
Meanwhile, snow levels will quickly rise, reaching 4000 feet by
Wedensday morning. Again, precipitation amounts will be light, so no
major impacts are expected.

The big story then begins late Wednesday. A very broad and strong
upper level trough over the Gulf of Alaska will dig southeast and
intensify, approaching the coast of the Pacific Northwest by
Wednesday night, then slowly but surely moving into and passing
through the region Thursday through Saturday. The general pattern
during this time, including the strength, track, and timings of this
trough, is in near universal agreement across the model suites, so
confidence is high that we will have an impactful multi-day event.
The devil is of course in the details, and in our area, a few
hundred feet of elevation change will make all the difference in
terms of snow, and this will be the primary focus of forecast
efforts over the coming days, especially as low-elevation snow
remains a potential threat.

Winds will begin increasing at the coast Wednesday afternoon, with
gusty southwest winds then spreading to the rest of the area
Wednesday night into Thursday morning, with the cold front itself
finally passing through the forecast area Thursday afternoon.
Forecasted pressure gradients and model mid-level wind fields ahead
of the front suggest that winds will be a concern, particularly
along the coast, over the ridgelines, across the East Side, and in
the Shasta and Rogue valleys. Meanwhile, moisture transport values,
wile not exceedingly strong, are strong enough to suggest a good
shot of precipitation from Wednesday night until the front passes
Thursday afternoon (with the likely exception of the Medford area,
where systems such as these typically underperform due to downsloping
effects off the Siskiyous).

This front will introduce a cold air mass to the area that is more
typical of early January than early March. Snow levels will begin
around 5000 feet as precipitation spreads across the area Wednesday
night and Thursday morning, but will quickly lower behind the front,
reaching 1000 to 2000 feet by Thursday night, and may drop even
lower Friday into Saturday. The bulk of precipitation will have
fallen by the time snow levels bottom out, but with the trough still
offshore and approaching, showers will be an ongoing feature for the
remainder of the extended term, and snow could easily reach valley
floors, and may even been seen at the coast. Amounts in these lower
elevations should be light, and with warm ground temperatures may
not stick around long, while over the Cascades, Klamaths, and the
high terrain of the East Side could pick up 2 to 3 feet of new snow
through Saturday.

This event still remains several days out, and several forecast
changes are possible in the coming days. We will be keeping a sharp
eye on this event as it approaches, and in the meantime, preliminary
preparations should be made considering the higher potential for
widespread wind impacts, as well as impactful winter conditions for
significant portions of the area, including potentially down to the
West Side valley floors. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 7 AM to 10 PM PST Monday for ORZ031.

     Beach Hazards Statement from 2 AM PST Sunday through Sunday
     afternoon for ORZ021-022.

     Winter Storm Warning from 10 PM Sunday to 1 AM PST Tuesday for
     ORZ025-027-028.

     Winter Storm Warning from 10 PM Sunday to 1 AM PST Tuesday for
     ORZ030.

CA...Wind Advisory from 7 AM to 10 PM PST Monday for CAZ084-085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 10 PM PST this
     evening for PZZ356-376.

     Small Craft Advisory until 10 PM PST this evening for PZZ350-
     370.

&&

CC