It's been a while since I've posted a blog. After getting hired as the weather forecaster for EOA.TV in December 2020, I featured my winter outlook on their platform the following year. But I didn't give myself enough time to share it across G-Weather, even though I had predictions for both the east and west side. Since then, I have begun releasing extended forecasts for them five times a week - rather than just one. I was able to earn my high school diploma early, so I've had much more time for all things weather this past year! Before I get to my fifth annual outlook, I want to go over my accuracy from last winter.
The main takeaway through the months of November and March were correct, the weak La Niña brought slightly higher snowfall amounts than usual with temperatures near normal. Portland was 0.78 degrees above normal on average, while La Grande was 0.39 degrees below. Although, I didn't think we would see as much rainfall. There were 24.36 inches reported in Portland between November and March - over 5 inches of my mean prediction. Not as significant in La Grande with 10.3 inches, but still roughly 1 inch above the mean that I came up with. You can't forget that cool and wet spring, which I should've extended the outlook into because April brought rare snow to Portland bringing the season total to 6.3 inches - roughly 2 inches above average. It also increased the snowpack, bringing La Grande's season total to 56.9 inches through May - roughly 10 inches above average. Trying to predict timing was a mixed bag. I correctly predicted the first dusting of snow in La Grande being in October, in fact it happened on the 13th - nearly two weeks after I released the outlook. Although Portland didn't see a dusting until December 8th, when I thought it was going to happen in November. But that possibility diminished when November had temperatures 3.3 degrees above average in Portland. In fact, it was also 3 degrees above in La Grande - which delayed my projection for the first widespread snow from November to December. November became the warmest and rainiest month region wide, unlike my prediction of January in Portland and February in La Grande. Things quickly changed the second half of December as I anticipated, arctic air spilled in from Canada between Christmas and New Year's. That allowed for the first widespread snow of 1 to 6 inches throughout Portland with highs generally in the 30's and lows in the 20's. 10 to 20 inches of snow reported through La Grande with highs generally in the 20's with lows in the 10's, although New Year's Day brought the morning low down to 22 below zero. That was the coldest and snowiest part of the season region wide, which became the most accurate projection of my outlook. Although we got more spotty snow accumulations in February, nothing widespread due to the lack of precipitation - opposite of what I thought. Despite that, we still managed to receive slightly above average precipitation in the entirety of the season. Good thing it wasn't as dry as I projected, the rain helped set up a better wildfire season! Now onto this winter....
We're going into a triple La Niña, which has only been recorded twice in the past 72 years - 1975 through 1976 and 2000 through 2001. Both years have produced only dustings of snow in Portland, although the previous year that they came out of are not comparable to this past season - other than being a double La Niña. Different story in La Grande, 1974 through 1975 is very similar to what we just came out of and that brings 51.5 inches of snow the following season with 15.2 inches of precipitation between October and April. I'm very confident in using those as a mean this season, bringing the snow range from 36 to 67 inches across the Grande Ronde Valley. Why such a big range? Keep in mind, Union and Wallowa are polar opposites. Union is usually the warmest area, while Wallowa is the coldest and La Grande is somewhere in between. In fact, the mean snow year brings 67.1 inches to Wallowa and 36.4 inches to Union - how perfect is that? As for Portland, there is not one particular year that is close enough to represent the mean. I had to combine 1971 through 1972, 1972 through 1973, 2017 through 2018 and 2018 through 2019 just to get bits and pieces of this past season. The year that follows those seasons brings anywhere from a dusting to 7 inches of snow, bringing the mean to 3.5 inches of snow with 27.6 inches of precipitation between October and April. Those are the best numbers that I can come up with, especially knowing that triple La Niña years haven't produced much snow. Although I shortened the range between 1 and 6 inches across the Willamette Valley since there wasn't enough data to support the possibility of no measurable snow. That would bring near to below average snowfall west of the cascades and near to above average snowfall east of the cascades, which would be slightly less than last season. The highest temperatures and precipitation should average out during the first half of the season, before the lowest settle in the second half. That would bring slightly lower temperatures and precipitation than last season in Portland, although slightly more in La Grande. Now onto specifics....
October looks to bring less precipitation than normal, according to shorter range models that I use on a day-to-day basis. Long range models believe that it could even be the one month the remainder of the calendar year that brings below average precipitation. In fact, the set of years that I chose from that month received rainfall from 2.55 inches below average to 0.79 inches above average. ECMWF Seasonal forecast model projects rainfall this October from 1 inch below average to 0.25 inches above average. It's clear that October won't be wet, the mean from all the data sets brings 0.62 inches below average. I'll place my rainfall range between 0.5 inches and 1.5 inches below average. Using the same data, October will feature the first snowflake in La Grande - but will wait to reach Portland until November as La Grande receives the most amount of snow this calendar year. Both months will feature near to slightly above normal temperatures, but precipitation will be higher in November with averages near to slightly above normal. December looks the warmest and rainiest. Record data received rainfall that month from 1.38 inches below average to 4.16 inches above average, while temperatures ranged from 1.4 degrees above average to 4.0 degrees above average. ECMWF projects rainfall this December from 0.25 inches above average to 2 inches above average, while temperatures range from 1 degree above normal to 2.5 degrees above normal. The rainfall mean from all the data sets gives 1.26 inches above average, so I'll place the rainfall range between 1 and 2 inches above average. The temperature mean is roughly 2.23 degrees above average, so I'll place the range between 2 and 3 degrees above average. January begins with slightly above average temperatures and precipitation, dropping near to slightly below into February. During that transition period, the snowiest part of the season should take place. March will feature the coldest month. Record data from that month ranged temperatures from 3.5 degrees below average to 0.4 degrees below average, while ECMWF projects between 0.25 degrees below average to 1 degree above average. The mean is roughly 0.79 degrees below average, so I'll place the range between 0.5 to 1.5 degrees below average. Data suggests the last snowflake will be in March for Portland and in April for La Grande. There isn't much else to point out, April will be near to slightly below normal in precipitation and temperatures. The Climate Prediction Center shows the chance of La Niña downgrading to 54 percent during the period of January and March. 2001 transitioned from La Niña to ENSO-Neutral during the period of February and April, while 1976 did so during the period of April and June. Based on that, there is reason to believe that we could see a transition to ENSO-Neutral late this winter and into spring as conditions are turning drier and colder. But with the lack of precipitation, that could negatively impact fire conditions next summer as temperatures warm. Definitely not a slam dunk, but something to think about as much of the precipitation will end earlier than last year.
Weeks of work later and that's what I came up with! Are you hoping for cold and snow? As Rob Grimes from PDX WX Analysis would say, "C'MON!!!!" - Gabe Curtis, EOA.TV's Official Forecaster and Creator of G-Weather
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