Incredible Series of Weather Events for the Inland NW

Thus far the Fall of 2022 has been an unusually mild one. For the Spokane area, the period from September 1st through October 31st was the 3rd warmest on record and the warmest since 1952. 

It was also the warmest October on record for Spokane, by a relatively impressive 0.5°F. 

And this is despite a transition to a slightly cooler and wetter pattern for a cooler stretch of weather between the 21st and the 26th. 

And it wasn't just Spokane that set records. According to data from the Climate Toolbox, it was the warmest September-October across much of the the Inland Northwest between the years of 1979-2015. 

This weather pattern was a direct result of an anomalously strong and persistent ridge of high pressure over the West Coast of the US with the upper level jet stream or storm track bottled up over southern Alaska and the Yukon. 

Mean Jet Stream Position for 9/1/2022-10/30/2022

Positive height anomalies centered over SW Canada and the Pacific Northwest show how this pattern deviated from the normal jet position. 

So why are we showing you this? Well first off  it will likely be the warmest and mildest weather we will see at least until next spring, but that's not the big news. The big news is we are headed for a major transition in our weather pattern. And this will be a direct result of the jet stream taking a dive to our south...in fact well to our south. But before we get there we have some very active weather to get through. 

Weather enthusiasts usually have to wait a while for a high-impact event to come along.  That's what makes this upcoming set of weather events so impressive.  We won't be able to give a ton of detail to each event or this blog would run on forever.  So we'll try to hit the high points.

The first act will be the snow.  This will be the first snow of the season for many lowland locations in the Inland NW.  The precursor is already in place, namely, a cold atmosphere.  That is complements of the very slow cold front that moved through the region on Monday and Tuesday and has left an unstable and cool trough located over the area this evening (11/2/2022). 

Jet Position 11/2/2022 5pm

 This has lowered our temperatures aloft to well-below freezing now, so snow will be the predominant precipitation type when the next storm arrives tomorrow night.  

Here is what the upper level jet looks like for tomorrow evening. The deep trough located over the Inland Northwest this evening will quickly be replaced by more stable and moisture-laden air mass with the jet gradually tracking to our north. 

Jet position 5 pm Thursday 11/3/2022

And here's the resultant precipitation forecast from the GFS for early Friday morning:

Precipitation Forecast for 5am Friday 11/4/2022

Now some of the computer models are forecasting a heavy snow event for a few locations, most notably the Idaho Panhandle and Northeast Washington.  

24 hour snow forecast ending Thursday 11am 11/4/2022

But the issue that these models don't really account for is that;

1. The surface air temperatures won't be all that cold. Most locations will be right around freezing by the time the precipitation begins on Thursday night and hold somewhat steady through the night.  
2. The ground temperatures are still considerably warmer than freezing, since it's only early November.  

So while some folks in these areas could get some impressive snowfall, it will be the wet, heavy type and shouldn't accumulate on roads very easily, if at all. The problem with warm fronts is that warmer air follows the snow.  And in this case, the warmer air will melt all of the snow by Friday night and change any remaining precipitation to rain.  So take your "first snow" pictures quickly.

Our snow storm is followed by a strong wind storm Friday night as the cold front comes marching through.  An impressively strong 160 knot jet stream will be right over our area Friday night and Saturday morning.  This is not good news.

Jet Position Saturday morning 11/5/2022

Meanwhile, a strong surface low will be deepening (i.e. getting stronger) as it tracks across southern British Columbia.  This pattern is well known for strong damaging winds in our area.  Many locations will see wind gusts of 45-50 mph and a few gusts to 60 mph are possible.

Surface weather map and precipitation forecast for 11pm 11/4/2022

The biggest fly in the ointment could be a non-meteorological factor: tree leaves.  Our mild fall has meant that the deciduous trees are decidedly late in losing their leaves.  This could have implications for both the snow and the wind.  If the temperature is just right (not to warm or too cold), wet snow will stick to the leaves, adding considerable weight to branches that aren't accustomed to it.  The resulting tree damage could temporarily block roads and cause power outages.  

 Tree damage from a moderate October snowfall in 2019 with fully leafed trees. 

The same goes for the strong winds.  Trees with leaves tend to "catch" more of the wind, which could also increase the tree damage and power outages.

Our Saturday will still be windy, but mostly dry.  This will serve as the breather between the weather systems.  And it doesn't last long.  The next Pacific storm will follow a different track, moving by to our south.  This track favors heavier snow for the Cascade folks (Omak and  Wenatchee) and less snow for other locations.  And the snow won't change to rain with this pattern.  Also in the image below, you can see all of the thin black lines, or isobars,  over the Idaho Panhandle and northeast Washington.  That means cold, brisk northeasterly winds as an arctic air mass pushes in from Canada.

The resulting snow totals could be rather impressive for the Cascades.  The GFS forecast is pretty impressive, and the ECMWF forecast (not shown) is equally significant.  

The GFS Ensemble (think of this as the average of 30 different perturbations or varieties of the initial GFS model) also points to heavy snow potential for north-central Washington.

Remember, this is still 4-5 days out.  The forecast keeps changing, so we wouldn't hang our hat on this scenario at this point.  Everyone in the Inland Northwest should keep checking the forecast updates over the next couple of days.

The last act in this string of weather events will be the unusually cold conditions.  We have much higher confidence of this than snow amounts or wind speeds.  The cause of this pattern shift will be the upper level jet plunging well south of the area with the air mass coming out of the Yukon or Northwest Territories. 

Jet position for Monday 11/7/23

Daytime temperatures will remain below freezing for many locations next Monday through Wednesday (if not longer), with nighttime temperatures in the 20s and teens.  Here's is the high temperature forecast from the ECMWF ensemble for Tuesday:

In case you were wondering, yes some of these forecast values are record cold highs for the date. The record cold high for 11/7 is 32°F set in 2017 and we have a forecast of 33°F. The forecast for 11/8 is 30°F with the record for the date being 26°F set in 1945. 

So there you have it.  A Thursday night snow storm chased by a Friday night wind storm  and then followed by yet another snowstorm for Sunday night.  The end of the story will be a very good chance of seeing an unusually early arctic cold snap next week.  Remember, November is still an autumn month although it won't feel much like it. And by the way, the latest 8-14 day outlook isn't giving much of a chance of breaking out of this cold pattern anytime soon.