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  • Updated

Friday, July 30th, 12:30 P.M. 

After a warm start to the day, temps will soar close to 100° in the Portland metro area this afternoon/early evening. We are keeping an eye on some clouds and showers over the Cascades this afternoon. I can't rule out the chance for a brief shower or thunderstorm in the metro area or central valley this afternoon and evening.

High pressure will slowly back off over the weekend, but we will still have a southerly wind overhead. Thin smoke and high elevation clouds will be possible at times, and isolated storms could fire up during the afternoons & evenings along the Cascades and east of the mountains. Highs should trend back into mid 90s to upper 80s Saturday and Sunday.

High pressure will continue to inch away from the Pacific Northwest next week, resulting in cooler temperatures. Afternoon highs will slowly trend back down into the 80s, with overnight lows in the upper 50s and low 60s. 

  • Posted

7pm Monday...

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.

What's ahead?

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:

  1. 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.
  2. Numerous members of each model's ensembles were forecasting this at one point too.
  3. For a few days it was looking like something might be up for late this week...or by the 8th at the latest.
  4. 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.
  5. 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

  • Posted

Our mild winter has been limping along for weeks. As I look into the last week of February and early March on our various models, it’s pretty obvious that

It’s time to put a fork in Winter 2019-2020.  This season is finished

So what kind of a statement is that?

It means I’m quite confident we’re done with most of our typical winter weather events.  But not all!  Read on…

First, this winter (December 1st to now) is running 5th warmest on record at PDX.  Those records extend back to 1940.  Spokane is 11th warmest out of 140, and Baker City is experienced its third warmest winter.  Olympia is at #4.  So not a record warm winter, but definitely at the upper end for many spots.

Looking at the models for the next 10-14 days…

  1. I don’t see an outbreak of cold arctic air.  For that matter I don’t see unusually chilly air for this time of year.   We have not seen a region-wide arctic air-mass descend across the Pacific Northwest since December 2013!  Sure, some cold-air intrusions to some areas at times, but no big arctic blast.
  2. I don’t see a setup for lowland snow west of the Cascades.  I thought we might be close next Monday, but the GFS model has finally caved in to the milder Euro/GEM models.

Point #1 on the graphic below is most important; the chance of a widespread snow/ice event in the metro area is dwindling quickly.  I mean the type of event that shuts down our area for a day, or even part of it.

Mark Winter is Over1

  • Other than the cold spell Thanksgiving Weekend that dropped the metro area into the low-mid 20s, we haven’t seen a hard freeze this winter.  It’s too late for that now (considering current forecast models).
  • Sure, we can still get a chilly east wind, but in late February and early March we don’t get long periods of the screaming cold easterly wind.
  • As for flooding, for the first time in my career we DID see some significant April flooding last spring.  But otherwise all of our big floods have occurred during the winter months.

What could we still see as we head into March?

We have seen March windstorms in the past and even one April event a couple years ago.   And of course in recent year’s we’ve seen close calls with snow in March.  Although it’s still far more rare than December-February snow.

Mark Winter is Over2

What actions can YOU take at this point?   Get those snow tires off and turn on the water to the chicken coop (I need to do that).

Mark Winter is Over3

There you go.  Basically it’s time to “de-winterize”.

To summarize:

We transition from late winter to early spring weather over the next 2-3 weeks as temperatures gradually rise.

Chief Meteorologist Mark Nelsen

  • Posted

These first 10 days of December have been mild; quite a turnaround from that cold Thanksgiving week.

web_PDXTemp_13days

Of course we’ve been on the dry side since early October too.  Both Oregon/Washington saw a dry fall.  Take a look at the precipitation percent of normal for the past 60 days

anomimage

I do see three wet days ahead.  A Pacific system moves inland tomorrow afternoon followed by lots of post-frontal showers in the colder airmass Thursday and Friday.  There are hints we could see vigorous showers Thursday with maybe hail or thunder.  Then I see another somewhat “splitty” jet stream setup this weekend and part of next week.  That’s a return to weak systems.  You can see the upper-level system heading into California on Tuesday

gfs_tuesday

All models advertise strong southwesterly flow of some sort later NEXT week (about 10 days out).  The GFS 500 millibar heights and anomaly for Friday the 20th…

gfs_fri20th

What I don’t see, at least during the next 10 days, is any setup for lowland snow or a freeze.  I’m sure not going to bother putting on my snow tires for now.  Maybe next week.

Snow levels will vary between 2,000-6,000′ in the next 10 days.  Probably lowest this weekend.  Notice not a single one of 51 ECMWF ensemble members produces snow in Portland through Christmas Eve either!  Leading up to the Thanksgiving cold spell there were multiple ensemble members hinting that we might see some snow fun.  But you see nothing here.

ecmwf-ensemble-KPDX-indiv_snow_24-5979200

I’ve also been noticing the consistency in those ensembles for 850mb temps (temp in Celsius around 4,000′) through the next two weeks.  Not a single member down below -6; that’s when I start getting interested in lowland snow setups.

tseries_850t_000-360_Portland

The last time we saw snow in December was Christmas Eve 2017.  You may remember a couple hours of light snow, followed by a bunch of freezing rain.  It was a “Silver Christmas Morning” in 2017.

December Snow PDX 2017

To summarize

  1. There’s no sign of lowland snow or a hard freeze in the next 10 days, possibly longer
  2. That means we’ll make it at least 2/3rds of the way through December without snow
  3. We can’t see much beyond that point, although there are no hints of anything a little farther out.  It’s too early to know if we’ll be close to snow or ice for Christmas Week

Chief Meteorologist Mark Nelsen