First Alarm Weather Days Next Week; First winter snow chance in the lowlands

On January 31, 2025By Littum

It’s been nice while it lasted! I’ve been on my bike this month more than any winter month in the past. Which stable weather pattern with cold nights in the 20s and sunny afternoons up about 50 °. Now it is changing and it is really clear that we are flirting with low-height-snare chances much of the first 7-10 days in February.

Key points

Clouds arrive tomorrow, then a rainy day Friday will be followed by scattered showers on Saturday and Sunday.
Over the weekend, Sticking Snow should remain on/over 1,000 ′ in the I-5 corridor. But in the lowest heights (including coastline) you can see snow in the air, especially Sunday, and Splats on your windshield
Scattered showers continue on Sunday night to Wednesday, possibly male of a great deal of Tuesday/Wed.
Expect spotted light accumulation of snow under the coldest parts of each day (night over + morning commuter)
There is a good chance that we will get school delays and stains with snow/ice on some ways of the mornings.
This is not a widespread snow and “Frozen City” event as last January or February 2023.
We do not expect an “Arctic freezing” (heights below 32 ° in Portland) through at least Tuesday/Wednesday

And here is our current 7-day forecast. Note that I am most interested in Monday-Wednesday Morning, and thus the first Alarm Weather Days (Morning)

Today we have tied the record for all the time (back to 1940) for consecutive dry days in January. 17 this year! What a stretch of fantastic and refreshing weather.

However, this is not a record dry January … We probably end up with approx. 1/2 of normal rainfall.

What’s the there ahead

Prognosis models are in excellent conformity tonight; Pretty good for 4-7 days out in time. They all agree that low level with over -level falls down. The euro model Saturday morning shows the cool western stream over us over our heads, this is 500 millibar, about 18,000 ′

Between that time and Wednesday, the cold trough falls south and actually backs away from the coastline slightly towards Wednesday. This is Evening GFS model during these 5 days

In this setup we get scattered showers moving on land throughout the period. We know from previous experience that in order to get Sticking Snow to the sea surface (or valley floor) in this pattern, we need 850 millibar -temps (in ° C) down to -7 to -9 °. For guaranteed that sticks down to the ground surface, you need -9 to -10. In a well -mixed atmosphere, this means that cascade pass temperatures are down about 20 ° (F). Here is Monday Morning on the latest GFS model

The red line is around -10, note that the coldest air remains west of us over the open sea. The blue line is the boundary of the cold/dry Arctic air mass, it remains well north of us through Monday, although there may be some “leakage” of the cold air mass later Tuesday and Wednesday down eastern Washington/Oregon. Models disagree about it a little. Therefore, at this point I do not expect a large freezing.

And the reason we just go for light showers in the 72 hours from late Sunday to Wednesday? Check rainfall during that time … less than 1/2 ″!

The Evening Save model and former ECMWF were the same … quite dry during this period. In case you wonder how much snow you could squeeze out of 1/2 ″ rain? On average approx. 5 ″. So if you read that model literally (you shouldn’t do it) you can say “If every shower was snow and stuck at any time of the day, the maximum snowfall we could get during these 3 days would be 5 ″

Of course, much of the time is over freezing, so it doesn’t happen … You get the idea. This is why we continue to talk showers instead of widespread snowfall early next week.

That’s it for this evening, the weather team will record a brand new podcast tomorrow night; It should be out Friday morning by the latest. In these podcasts we take a deep dive in the expected models and other weather geese. We have a brand new team member that we also introduce! You can find them here:

Then I have a new blog post on Friday night … probably before 7 p.m. 20.