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

Area Forecast Discussion
National Weather Service Portland OR
131 PM PST Tue Jan 16 2024

.SYNOPSIS...An approaching frontal system will bring widespread
freezing rain to inland areas below roughly 1500 ft, snow across the
high Cascades, and rain elsewhere. An Ice Storm Warning remains in
effect for much of the region through this evening and into
Wednesday morning. For midweek on, expect a return to climatological
conditions with milder temperatures and rain into the extended.

&&

.DISCUSSION...TONIGHT THROUGH MONDAY...Satellite and radar as of
1 PM shows an area of low pressure near 43N/130W sending a stratus
shield northeast with a few hundredths of an inch of precipitation
accumulating in SW Oregon. Temperatures across SW Washington, NW
Oregon remain in the mid to 20s. The warm sector will overrun the
cold pool that currently sits in the interior lowlands and freezing
rain with start accumulating in the coming hours. Ice accumulations
will increase the closer one gets to the Columbia River Gorge which
is the source of the cold air drainage and the area in which the
cold pool is deepest. The current Ice Storm Warnings remain in place
throughout the region for significant ice accumulations.

The freezing rain will start in the southern Willamette Valley but
according to the HRRR the depth of the cold air in this area is
fairly shallow. Near Creswell it's only 1200 ft and 1600 ft near
Eugene. It won't take long for the warm southwesterly flow to scour
out the cold air but there will still be a few hours of freezing
rain so ice accumulations in that zone which reaches as far north as
Albany will see a range of 0.05 to 0.25" of ice with the higher
amounts to the north.

This will be the trend areawide, the closer you get to the source
i.e. the Gorge, the greater the ice accumulations. The cold pool
will scour out and once a site climbs above freezing it will remain
above freezing and freezing rain will transition to rain. The
exception will be sheltered pockets on the east side of the Coast
Range around Lees Camp and Timber. The cold air will be trapped and
ice accumulations will persist into the overnight hours.

The Greater Portland/Vancouver metro will see ice accumulations
between 0.25-0.50" of ice through late Tuesday night, early
Wednesday morning. The Columbia River Gorge will hold onto mixed
precipitation through Wednesday and into parts of Thursday as the
next system quickly approaches which will maintain east winds through
the Gorge.

In the Cascades snow levels will sit around 4500 feet and
accumulations between 10-20 inches from Tuesday through Wednesday
night is likely. Strong winds across the crest will reduce
visibility at times.

Daytime highs on Wednesday will push 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.

Beyond Wednesday and into early next week, expect a return to
climatological temperatures with multiple rounds of precipitation
from an active NE Pacific. Persistent southwesterly flow will
maintain higher snow levels producing primarily rain across much of
the Cascades. -BMuhlestein

&&

.AVIATION...00Z TAFs: Precipitation on track with (most) models.
HRRR, RAP simulated radar seems best at this time. Not a whole lot
of changes to the forecast at this point with associated warm
front lifting northward across region tonight. Will see CIGS
lowering to lower VFR in the afternoon into early evening, with
widespread MVFR and pockets of IFR CIGS Tue night into early Wed
morning.

Precipitation continues to move northward, already across Lane
County with that moving northward reaching by 00Z Wed. With cold
air in lowlands, this will fall mainly as freezing rain though may
see a mix of sleet and snow initially. As warm air spreads into
the region from south to north tonight, will see threat of
freezing rain end, generally at KEUG around 03Z Wed, KSLE around
06Z, and KPDX around 12Z Wed. However, lighter offshore flow (east
winds) maintains cold air, with freezing rain likely lasting well
into Wed am near and 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. IFR not out of the question after 12Z Wed with HREF
probabilities and model soundings indicating such.

Precipitation expected around 00Z mainly as freezing rain with
possibly a mix of sleet or snow to start. The brunt of the ice
accumulation expected from 00Z-06Z with 0.15 to 0.20 inch, then
up to 0.10 06-12Z Wed. Fortunately will be slowly rising
temperatures overnight. Appears will rise above 32 deg F 10-12Z
Wed /mh /Rockey

&&

.MARINE...Low pres over the north Pac will push a warm front
northward across the coastal waters tonight. Winds will pick up
behind the front as the low approaches the coast, 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 14 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 with system following similar track to
recent systems.
/mh

&&

.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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