Here we are...it's February and tomorrow is Groundhog Day. Already!
Of course it has been a very dark winter across the USA. I, like almost all of you, have never experienced such a depressing period. Thousands dying every day due to the pandemic, plus all the political drama and civil unrest through early January. That has added to the gloomy mood.
But weather? It's as if time has stood still west of the Cascades. November was a typical late fall month; temperatures near average and normal rainfall. December & January? Warmer and a bit wetter than average. So all three months have been quite similar; like we've been in a "perpetual fall" since November.
Each year I present a recap of the past winter weather at an Oregon AMS meeting. So far I only have TWO "events" to talk about; a brief wind/rain storm and then a close call with snow. That's it.
First the numbers:
Of course Portland International Airport is affected by the "urban heat island", so overnight lows are warmer than they used to be; always keep that in mind when we talk PDX temps. The period December 1st through January 31st is the 3rd warmest on record. #2 was last year! This also makes it the warmest La Niña on record at PDX...through January 31st. A quick check shows Salem, Redmond, & Pendleton were near their warmest on record as well; in the top 7-16 for each.
Check out the 50 degree day count since winter started on December 1st
You probably have some annual plants from last summer that still haven't died? That's because we've only seen light freezing in the urban/suburban areas. PDX hasn't dropped below 27 degrees
The run of mild storms with relatively high snow levels has been tough on the lowest elevations of the ski areas; and our water supply. It was back up to 43 with a few sprinkles at Government Camp today where there is less than 2 feet of snow on the ground. Very little snow remains on the ground below 3,000' in the northern Oregon Cascades. And most of Oregon has below average snowpack on the ground...
Things have gone downhill...here's the map one month ago. Too much rain at low-mid elevations instead of snow.
By the way, this IS exactly what we would expect in a gradually warming climate. In 10-30 years this should be the normal...if climate experts are correct. Plenty of winter precipitation, but higher snow levels.
The first 7-10 days of February remain mild, maybe with some temperatures a bit below average NEXT week...maybe. A cold upper-level trough offshore moves overhead tomorrow afternoon through Wednesday morning. Snow levels will dip down to around 1,000-1,500' tomorrow night and Wednesday morning. We'll be in a showery airmass with onshore flow, but I could see some spots in that elevation band picking up a dusting Wednesday morning.
Upper-level ridging builds offshore Wednesday and on into early next week. That will give us much drier weather; but not totally dry since it'll be a "dirty" ridge. In this case, weather systems will be riding over the top of the ridge. Expect plenty of clouds and showers/sprinkles from time to time.
Over the past 5-6 days, models have been toying with the idea of the ridge strengthening and pushing farther north. That would open the door to cold arctic air pushing south. Several thoughts on that:
- Each of the 3 operational forecast models I keep a close eye on (GFS/GEM/ECMWF) went full on "arctic blast mode" at some (or several) point/s late last week. Generally out in the day 10-15 range. The afternoon GFS model does just that.
- Numerous members of each model's ensembles were forecasting this at one point too.
- For a few days it was looking like something might be up for late this week...or by the 8th at the latest.
- By yesterday, models had all decided this probably wasn't in the works at least through February 10th, although some sort of close call with lowland snow might be in the cards next week.
- This was never within the 7 day period, so of course we sure didn't mention it on-air.
This is very similar to what we just went through in late January. What looked like a promising cold spell fell apart many days ahead of time. We ended up with 3-4 hours of snow and accumulation in some areas and then our mild winter resumed. It's not that models are "terrible", but anything beyond a week is just a general guide. Stick to ensembles that far out...
The ensemble forecast from both the latest ECMWF & GFS show mild temperatures for at least the first 10 days of this month
These are averages from all the ensemble members, so of course a few members (or the operational model itself) can be much colder or warmer. But that's far out in time.
IF we are going to get a significant cold spell this winter, there's only 3-4 weeks for that to happen. That leaves 2-3 weeks beyond the February 10th date I just referenced. It's not a hopeless cause, but time is running out on Winter 2020-21 west of the Cascades.
Chief Meteorologist Mark Nelsen