Heavy Snow and Winter Weather in Washington, February 14 to 15, 2024

Area Forecast Discussion
National Weather Service Portland OR
255 PM PST Wed Feb 14 2024

.SYNOPSIS...Vally rain and mountain snow through Thursday. Impactful
snow also expected in the Columbia River Gorge, east of Multnomah
Falls, and for the Upper Hood River Valley. Low probabilities for
accumulating snow across the lowlands from Portland/Vancouver metro
area northward tonight. Mostly dry Friday, but breezy east winds
likely. Showers return this weekend into early next week, with
temperatures warming to near seasonable normals.

&&

.SHORT TERM (THROUGH FRIDAY NIGHT)...

Key Points:

 * Heavy snow is expected for the Cascades (1 to 2 ft), Columbia
River Gorge (4 to 8 inches) and the Upper Hood River Valley (8 to 16
inches) beginning this afternoon and continuing through Thursday.
Travel could be very difficult, including blowing snow with gusts
up to 50 mph in the Gorge.

 * Wet snow is expected for the northern Oregon to south Washington
Cascade foothills, Coast Range mountains of Northwest Oregon, and
the Willapa Hills. Around 2 to 6 inches of snow is expected, except
up to 10 to 12 inches above 2000 ft north of HWY 26.

 * Generally rain is expected below 500 feet for the lowlands with
periods of wet snow possible tonight north of Wilsonville. Best
chances of accumulating snow of 1 to 2 inches are areas north and
east of Interstate 205, as well as elevations above 500 feet, and
the eastern slopes of the Coast Range in western Washington County.

 * Strongest east winds through the Columbia River Gorge and across
the Portland metro are expected late Friday morning through Friday
night with gusts possibly gusting up to 45-50 mph across the east
PDX metro.

A low pressure system around 999 mb, currently centered about 250
miles west of Coos Bay, is expected to move northeast and slowly
weaken as it nears the Long Island peninsula of SW Washington
Thursday morning. The initial wave of precipitation has pushed north
to the Columbia River as of 2 PM Wednesday. No indications of any
lowland snow as temperatures warmed into the mid 40s across the
Portland metro this afternoon. Dewpoints in the upper 20s, though
are increasing into the lower 30s as the moisture arrives so appears
it will be difficult for any snow that does fall to accumulate below
500 feet. As we have been messaging, this scenario has been the most
likely outcome. High resolution models from 12Z this morning have
also moved away from the worse case scenarios of impactful snowfall
in the lowlands. There remains one model (GFS) that wants to bring
colder temperatures and snow to the valley floor, but the latest run
(18Z) has backed off from its higher amounts from earlier. So, will
maintain the Winter Weather Advisory for the Portland/Vancouver
metro area north through the lower Columbia and I-5 corridor into
Cowlitz County, but have lowered snowfall amounts to up to 1 inch.
Do think the best time for snowfall would be late tonight into early
Thursday morning during a period of more intense precipitation rates
that is currently forecast to occur (between 10 PM and 4 AM).

The surface low is then expected to rapidly weaken off the
Washington coast on Thursday while a frontal band brings another
round of precipitation to the forecast area, especially from the
central Oregon coast to the central Oregon Cascades. This is
expected to bring another burst of heavy snow to the mountains above
3500 ft, mainly from Mt Jefferson southward through Thursday night.

Conditions becoming mostly dry on Friday as upper level heights
build and low-level offshore flow increases. Pressure gradients
between KTTD-KDLS are currently forecast to increase to around -8 to
-9 mb by Friday afternoon. Typically see east winds gusting to 60
mph in the Columbia River Gorge and up to 45-50 mph across eastern
Portland metro area. Precipitation associated with a front offshore
is likely to remain there through most of the day Friday, but PoP
increases Friday night although QPF amounts likely remain on the
lighter side as upper level flow becomes split and the front likely
shears apart.  /Hartsock

.LONG TERM (SATURDAY THROUGH WEDNESDAY)...
Broad upper level troughing continues over the NE Pacific into the
weekend while a shortwave lifts another round of precipitation to
the Pacific NW on Saturday. There is decent model agreement for a
developing low pressure system west of the north CA coast on Sunday.
Where that low eventually moves is still quite uncertain. Most
ensemble members tend to keep some showers around through the
weekend and into early next week. But, no indications of any heavy
precipitation in the long range forecast. Temperatures likely remain
on the cool side for Saturday, but the NBM indicates at least a 75%
chance that highs warm back up to near normals (lower 50s). Snow
levels are likely to rise to around 5000 ft. Overall, not seeing
any signals for impactful weather through the middle of next week.
/DH

&&

.AVIATION...An area of low pressure will continue to track
northeast through the forecast period bringing variable flight
conditions to all terminals. Lingering LIFR and IFR conditions
from this morning are starting to mix out as winds within the warm
front increase. Easterly winds will persist through the Columbia
River Gorge impacting K4S2, KTTD and KPDX, while southerly winds
will begin in the Willamette Valley south of KUAO.

Snowfall in the Columbia River Gorge and around K4S2 is expected
this evening and during the overnight hours. Coastal sites and
those from KUAO south will see rain. In the northern Willamette
Valley however, east winds out of the gorge have the potential to
cool the atmospheric column enough to produce flurries and/or
light snow accumulation (an inch or less) at KHIO, KTTD, and KPDX
into Thursday morning. Persistent low level stratus is expected
across the region through the next 24 hours regardless of
precipitation type.

Note that the observations in Newport (KONP) are currently limited
to winds, temperature and pressure. Time of restoration is
unknown.

PDX AND APPROACHES...East winds will increase through the
afternoon with peak gusts this evening. Rain is expected to be
the dominant precipitation type but east winds through the gorge
could cool the atmospheric column enough to bring a brief
transition to snow. Accumulations, if any, will be light.
-BMuhlestein

&&

.MARINE...Low pressure currently over 44N/128W will slowly track
northeast into the overnight hours. As the low occludes while
approaching the coastline there will be favorable dynamics in the
southeast and northwest quadrants of the storm to push wind gusts
into Gale Force criteria. Have upgraded the Hazardous Seas
Warning to a Gale Warning until 2 AM tonight. The low will decay
and winds will diminish. Seas will build into the the 12-15 ft
range within strongest winds and decay by Thursday morning to sub
10 ft. Because the low will track right over the waters and move
onshore somewhere between Astoria and Garibaldi there will be
considerable differences in the wind field; east winds over the
northern waters and southwest to west over the central and
southern waters.

Conditions will ease throughout the day Thursday before ramping
back up overnight into Friday. An area of low pressure currently
tracking across the northeast Pacific will start to veer northeast
into the Gulf of Alaska early Friday morning. The low will send a
warm front across the coastal waters throughout the day but will
remain well enough to the west that winds will keep an offshore
component to them into Saturday. The cold front will fall apart
before it reaches the coastal waters but Gales past 40 nm remain
a concern going into Friday evening.

Conditions are currently forecasted to diminish below Advisory
criteria at the start of next week. -BMuhlestein

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Winter Weather Advisory until 4 PM PST Thursday for Coast Range
     of Northwest Oregon.

     Winter Weather Advisory from 8 PM this evening to 4 PM PST
     Thursday for Greater Portland Metro Area-Lower Columbia.

     Winter Weather Advisory until 10 PM PST Thursday for Northern
     Oregon Cascade Foothills.

     Winter Storm Warning until 10 PM PST Thursday for Cascades in
     Lane County-Central Columbia River Gorge-Northern Oregon
     Cascades-Upper Hood River Valley-Western Columbia River
     Gorge.

WA...Winter Weather Advisory until 4 PM PST Thursday for Willapa
     Hills.

     Winter Weather Advisory from 8 PM this evening to 4 PM PST
     Thursday for Greater Vancouver Area-I-5 Corridor in Cowlitz
     County.

     Winter Storm Warning until 10 PM PST Thursday for Central
     Columbia River Gorge-South Washington Cascade Foothills-
     South Washington Cascades-Western Columbia River Gorge.

PZ...Small Craft Advisory until 10 AM PST Thursday for Columbia River
     Bar.

     Small Craft Advisory until 4 PM PST this afternoon for Coastal
     waters from Cape Shoalwater WA to Florence OR out 60 NM.

     Gale Warning until 2 AM PST Thursday for Coastal waters from
     Cape Shoalwater WA to Florence OR out 60 NM.

     Hazardous Seas Warning from 2 AM to 10 AM PST Thursday for
     Coastal waters from Cape Shoalwater WA to Florence OR out
     60 NM.

&&

www.weather.gov/portland

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