Ice Storm and Winter Storm in Oregon, January 16 to 21, 2024

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1100 AM PST Tue Jan 16 2024

Updated Aviation discussion.

.UPDATE...Low pressure offshore coming in a little slower than models
predicted. Composite radar shows rain spreading northeast across SW
Oregon as of 11 AM with light precip accumulations in Coos County.
The 12z HRRR seems to be capturing this the best. The depth of the
cold pool, or the freezing level, from the 12z Salem sounding sits
right around 2200 ft, above that temperatures are above freezing.
Forecast is on track with widespread below freezing temperatures.
Freezing rain is expected to start across the southern Willamette
Valley and parts of the Coast Range in the coming hours with it
reaching the Portland/Vancouver metro between 3-4 PM. Once ice
starts accumulating travel will become very difficult, along with
tree damage, and power outages. If you need to travel do so before
the rain begins. -BMuhlestein

&&

.SYNOPSIS...An approaching frontal system will bring widespread rain
and with temperatures below freezing, freezing rain and therefore ice
accumulation impacts are expected across the interior lowlands as
well parts of the lower Columbia River, Columbia River Gorge, and
Washington Cascades. An Ice Storm Warning has been issued as a
result. Snow levels will be on the rise but snow accumulations across
the passes will be enough to warrant a Winter Weather Advisory.
Persistent southwesterly flow after Wednesday will lead to milder
temperatures and rain into the extended.

&&

.SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT...The last night of
extreme cold temperatures continues, with Temperatures as of 1:30AM
right around 20 for most of the Willamette Valley. With a TTD-DLS
gradient of around -12, gusts through the western Columbia River
Gorge remain around 40-50mph; a decrease will be expected Tuesday
morning to around 30-40mph.

Tuesday sees precipitation moving in from the southwest, with
Florence to Eugene seeing precipitation beginning around 11am-12pm,
reaching the Portland metro by around 3-4pm. While the coast just
sees rain and the Coast Range/Cascades mostly see snow, the
Willamette Valley, Cascades/Coast Range foothills, Willapa Hills, and
mountain valleys can expect to see freezing rain as the dominant
precipitation type throughout this event.

The southern Willamette Valley sees freezing rain beginning midday,
though increasing southern winds will be warming temperatures over
the course of Tuesday. Temperatures will become warm enough that
freezing rain will transition to rain by around 4 Tue. With how brief
this period will be, ice accumulations look to remain around
0.10-0.15" in total at Eugene. Ice accumulations increase going
further northward, with around 0.25" in the central Valley near
Salem.

For the northern Willamette Valley/Portland metro area, cold air will
take longer to scour out, with warm southerly winds slowly pushing up
the Valley competing with continuing cold east winds from the Gorge.
At the moment, freezing rain accumulations look to continue from
3-4pm Tue until around 2-3am Wed, bringing somewhere around
0.30-0.40" of ice accumulation over the course of the event. Expect
downed trees and power outages to be a threat with this system.

For the the Columbia River Gorge, expect it to be the last area to
scour out cold air. Expect precipitation to begin as snow, turning
over to mixed wintry precipitation that lasts throughout the rest of
the event, continuing into Wednesday night as a secondary system
arrives Wednesday. Snow, freezing rain, and sleet can all be expected
to be in the mix. While exact totals are difficult to predict as a
result, we're looking at somewhere between 0.30-0.50" of ice
accumulation and 1-3" of snow as a rough forecast.

In the Cascades, snow levels look to be around 4500 feet during this
event. Accumulations look to be somewhere between 10-15 inches from
Tuesday through Wednesday night, with strong winds reducing
visibility at times as well.

Wednesday finally grants us a reprieve from the cold temperatures,
with daytime highs pushing into the mid/upper 40s in the Valley and
50s by the coast. Snow levels will be rising as well, pushing up to
near 6000 feet. While the Gorge continues to see wintry precipitation
due to cold air staying in place, most lowland areas will just see
rain. /JLiu

.LONG TERM...(THURSDAY THROUGH SUNDAY)...Next system approaching the
region from the west on Thu. Warm front will lift north across the
region early in the day. Once it moves north, chance of precipitation
will lower. mainly to south of a Tillamook to Portland line. Will
maintain higher chance of rain to the north, closer to the departing
warm front. Trailing cold front will remain offshore through the
afternoon. As such, will see an uptick of east to southeast winds
across the region. But, at least this will not be frigid winds: cool,
but not frigid. Generally, expect seasonal temperatures for Thu. Not
much change through Fri, as offshore flow continues as front remains
just offshore.

Models fairly consistent with bringing another rather strong low off
the north Pac and swinging that low to the northeast into western
British Columbia Fri and Sat. So, front will slowly push inland later
Fri into Sat, with rain, and snow for the Cascades. Unsettled
weather continues into next week, with more rain and mountain snow.

&&

.AVIATION...18Z TAFs: Forecast generally on track with a slight
delay with onset of pcpn. Low off the central Oregon coast with
associated warm front approaching the south Oregon coast. The
warm front forecast to lift northward across region later today.
As such, will see increasing mid and high clouds later this am,
with CIGS lowering to lower VFR in the afternoon into early
evening, with widespread MVFR and pockets of IFR CIGS Tue night
into early Wed am.

Precipitation will spread northward, across Lane County between
19Z and 22Z, with that moving northward through early evening.
However, with cold air in lowlands, this will fall as a mix of
sleet and snow initially, then turn to freezing rain. As warm air
spreads into the region from south to north tonight, will see
threat of freezing rain end, generally at KEUG around 00-03Z Wed,
KSLE around 06Z, and KPDX around 12Z Wed. However, offshore
flow (east winds) maintains cold air, with freezing rain likely
lasting well into Wed am in Columbia River Gorge.

PDX AND APPROACHES...Warm front approaches from the south, will
see CIGS lower to low VFR later today, with generally MVFR after
04Z Wed. Precipitation starts around 22Z Tue, with mix of sleet
or snow. Brunt of the ice accumulation expected from 00Z-06Z, then
tapers off with. Fortunately will be slowly rising temperatures
overnight. Appears will rise above 32 deg F 10-12Z Wed
/mh /Rockey

&&

.MARINE...High pressure inland will maintain east to southeast
winds on the waters this am. Gusty east wind to 20 kt possible
just downwind of the larger gaps in the coastal terrain. Seas
stay at 5 to 7 ft today.

Active weather pattern returns to the region today and tonight.
Low pres over the north Pac will push a warm front northward
across the coastal waters today and tonight. Winds will pick up
behind the front, with gusts to 35 kt on the waters to south of
Cape Falcon. As such, will maintain Gale Warning on the coastal
waters from Cape Falcon southward. To the north, gusts not as
strong, so will maintain Small Craft Advisory in that area. Seas
will come up a bit with the winds, generally to 10 to 12 ft.
Trailing cold front will push onshore on Wed.

Next system arrives on Thu, with another warm front lifting
northward across the region, with the trailing cold front arriving
on Fri. Gradients not quite a potent, and seem to be more favoring
east to southeast flow. So, potential of gales not quite as
favorable with such a pattern. Still, winds likely 20 to 25 kt.
with seas gradually building back to the mid-teens. Active weather
continues into the weekend.			 /Rockiga

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Ice Storm Warning from 2 PM this afternoon to 4 AM PST Wednesday
     for Central Willamette Valley-Coast Range of Northwest
     Oregon-Greater Portland Metro Area.

     Ice Storm Warning until 10 PM PST this evening for Central Coast
     Range of Western Oregon-South Willamette Valley.

     Ice Storm Warning from 4 PM this afternoon to 4 AM PST Wednesday
     for Lower Columbia.

     Wind Advisory until 7 PM PST this evening for Greater Portland
     Metro Area.

     Winter Weather Advisory from 1 PM this afternoon to 10 PM PST
     Wednesday for Cascades in Lane County-Northern Oregon
     Cascades.

     Ice Storm Warning from 4 PM this afternoon to 10 AM PST
     Wednesday for Central Columbia River Gorge-Upper Hood River
     Valley-Western Columbia River Gorge.

WA...Ice Storm Warning from 2 PM this afternoon to 4 AM PST Wednesday
     for Greater Vancouver Area.

     Ice Storm Warning from 4 PM this afternoon to 4 AM PST Wednesday
     for I-5 Corridor in Cowlitz County.

     Ice Storm Warning from 4 PM this afternoon to 10 AM PST
     Wednesday for Central Columbia River Gorge-South Washington
     Cascade Foothills-South Washington Cascades-Western
     Columbia River Gorge.

     Winter Weather Advisory from 4 PM this afternoon to 4 AM PST
     Wednesday for Willapa Hills.

PZ...Small Craft Advisory until 7 AM PST Wednesday for Coastal waters
     from Cape Shoalwater WA to Cape Falcon OR out 10 NM-
     Columbia River Bar.

     Gale Warning until 7 AM PST Wednesday for Coastal waters from
     Cape Foulweather OR to Florence OR out 10 NM.Coastal waters
     from Cape Foulweather OR to Florence OR from 10 to 60 NM.

     Small Craft Advisory until 7 AM PST Wednesday for Waters from
     Cape Shoalwater WA to Cape Falcon OR from 10 to 60 NM.

&&

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