One last chance for snow for the Christmas holidays: Thursday morning | FOX 12 Weather Blog


1 p.m. Wednesday …

It was a fun ride, if you don’t mind driving in a little snow and / or you didn’t need to go somewhere last week. We saw several small (or large depending on the location) of snow. Of course, the largest and most prevalent was Monday evening through Tuesday morning. Officially, PDX picked up 2.5 ″, which now means it’s the snowiest December since 2008 in the metro area. We were late for a period of cold and snow in December, it has been very mild lately. Although we still haven’t seen an outbreak of cold arctic air across the region.

This cold modified arctic air mass once again swept south and through the gorge into northern Oregon. At noon we are barely above zero in Portland with a cold easterly wind blowing over the east side of town.

This cold easterly wind is not too strong, just about 5 millibars of pressure difference between The Dalles and Portland. Weak sauce… right now things look like this at sea level (black lines, not colors). Cold high pressure area sending easterly wind over northwestern Oregon / SW Washington and a weak area of ​​low pressure developing near Haida Gwaii

4 p.m. Wed29.PNG

This low runs down the coast, like the previous ones, but this time it goes inland NORTH of us. Looks like around 10am Thursday. Do you like my drawing skills in 3rd year?

10 a.m.Thursday30.PNG

We get a relatively strong southerly wind later overnight until the first half of Thursday. This means that the cold arctic air is replaced by a much softer air mass (temporarily). Snow levels rise to around 2,000 ′ at noon. All models support the idea of ​​a quick warm up late at night from South Portland and all along the coast. We’re aiming for a low of 23 in Portland tonight, but it’s before midnight. I expect temperatures to be around 33-34 by 7 a.m. across most of the metro area. Precipitation from this system begins as snow which will accumulate in parts of the Portland metropolitan area to the north. South of Portland I think sticky snow is unlikely (including Salem). Cold air sometimes lasts longer than expected in the Longview / Kalama / Woodland / St. Helens zones in this configuration. I have already seen it. I think this is where a quick 1-2 ″ is most likely.


After around 10 hours, the precipitation changes to light showers, mostly rain in the lower elevations. Most models look like this


  • This is unlikely to be a major snow event in the lower elevations from Portland / Vancouver south, especially after what we have seen in recent days.
  • Sticky snow starts between 5 and 8 a.m. north of the Portland / Vancouver area, but for most of us I don’t expect much buildup on the road due to the rising temperatures. temperatures. The snow will still be in the air for a few hours; it can seem quite snowy. I predict NOTHING AT 1 ″ ACCUMULATION, BETTER CHANCE TO STAY NORTH OF PORTLAND

METRO FOLLOWING ROUTE: Snow / ice patches remaining on the roads due to the overnight frost, maybe a few fresh snow patches, but not a lot. Time up to 32 around 6 a.m.

METRO PM ROUTE: Roads totally clear except for remnants of snow / ice in the hills and possibly northern Clark / Cowlitz counties. Time in the upper 30s.

CTE / SALEM / ALBANY: Roads probably clear and no snow tomorrow

THROAT: Snowy morning, 1 to 4 new snow at noon. I-84 can be icy / snow the first half of the day

The low pressure system and top tier flow are perfect for heavy snowfall in the Cascades and Blue Mountains. Tomorrow is not a good day to travel on I-84 east of La Grande or through the Cascades Passes as you can see in the build-up graph above.

Just like Tuesday evening and this morning, this cold arctic air will try to move up towards the south by Friday morning. But it won’t be that cold. Expect lots of clouds and temperatures just in the mid-30s on Friday. New Years Eve should be perfect in the weather, unless we have scattered patches of ice on the roads. You can see that cold high pressure take back control at 10 a.m. on Friday with more of these lovely hand drawn features. BTW, I think in art class in high school I got a C at best… really! Hmmm …


Friday / Saturday will mark the end of the cold northwest circulation we have been in for nearly two weeks. Here is the aerial view of tomorrow

ecmwf Thursday 30.png

On Monday we returned to an active westerly jet stream again with various model solutions for next week. All are wet.

ecmwf Monday 4th.png

Sometimes we get a big snow / ice event at the end of a cold snap. This is when we get a deep elevation trough offshore and a low level offshore (easterly flow). This does not happen this time. It’s a relatively quick change of southerly wind from Saturday to Monday. When solid precipitation arrives later on Sunday and Monday, it will most likely be rain. But that means even MORE snow in the Cascades. The snowpack is now well above average in many areas of Oregon. Very good news!


It’s over for 2021. I’ll be off Thursday through Sunday, so no blog posts until early next week. Stay safe on the go.

Chief Meteorologist Mark Nelsen

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