Put a fork in it; Winter is over WEST of the Cascades

February 25, 2022

7pm Friday…

Our mild winter is over in the lower elevations west of the Cascades. As I look into the last few days of February and early March, it’s pretty obvious that…

It’s time to put a fork in Winter 2021-2022.This season is finished

What kind of a seemingly ridiculous statement is that?

It means I’m quite confident we’re done with most of our typical winter weather events. But not all! Often early-mid March is included as part of winter in the USA, but that’s not really the case west of the Cascades…we already live in a mild climate where winter is weak sauce anyway. So it doesn’t take much warming to “pull out of winter” here.

First, this winter has been about as average as it gets. No long stretches of cold OR warm. November was much warmer than normal and December slightly cool (warm early, then chilly later). January was about average. February has seen a mix of cool/warm & then very cold. February will go down slightly cooler than average.

Winter Stats
Winter Stats(KPTV)

Rainfall has been about normal, and snow in the northern Oregon and southern Washington Cascades has been near normal as well. Of course, December was a soaker and so was November. Then a ton of rain the first week of January. Since then the faucet has been slowed to a trickle. There IS going to be quite a bit of rain Monday/Tuesday next week, but overall this winter will be remembered for a wet first half and dry second half.

Winter Stats
Winter Stats(KPTV)

Looking at the models for the next 10+ days…

  • 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 (earlier this week), but no big arctic blast.
  • I don’t see a setup for lowland snow west of the Cascades. Even a brief & wet morning snowfall isn’t in the cards. But that can happen in March.

Point #1 on the graphic below is most important; the chance of a widespread snow/ice event that cripples the metro area is down to just about zero. I mean the type of event that shuts down our area for a day or even part of it.

  • Other than the cold spell between Christmas and New Year’s Day, we didn’t have a major freeze this winter. Portland’s low temperature was only 24 (this morning!) We didn’t have any calendar days where it stayed at/below freezing. Both December 27th and January 1st saw high temps of 34.
  • Sure, we can still get a chilly east wind, but no long period of screaming cold easterly wind is likely through the first week of March. That threat goes away for the season by March 10th.
  • Flooding? For the first time in my career, we DID see some significant April flooding in Spring 2018. But otherwise, all of our big floods have occurred during the winter months and not in March.

What could we still see as we head into March?

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

What actions can YOU take at this point?

Get those snow tires off and turn your faucets back on. I just swapped out my tires today and will turn exposed chicken water lines back on tomorrow.

There you go. Basically it’s time to “de-winterize” WEST OF THE CASCADES.

SUMMARY

We transition from late winter to early spring weather over the next 2-3 weeks as temperatures SLOWLY rise and days get longer. We’ve had our “false spring”; 3 days in the 60s! Now it’s back to near normal temps as we head into early-mid March.


Snow Arrives On Time This Morning

February 24, 2022

10am Thursday…

Portland officially received 1/2″ of snow this morning.  That is at the Parkrose NWS office.  Downtown picked up…wait for it…0.1″  That is also an official total. I don’t even know how you measure that.  Melted down, that 1/2″ snow would be just .02″ rain if it would have been above freezing

Looking at the reports around the region, it appears a spot or two did get 1″ up in northern Clark County.  But I see lots of 1/3 to 1/2 inch totals.  You have to admit models did an amazing job with this little system. On timing AND precipitation.  They were very slightly “wetter” during the evening runs last night, all forecasting about 1/2″ with most from Portland north.  That’s what happened.  But even earlier in the day most were forecasting at least a dusting for this morning.  And just as forecast, skies are beginning to clear at 10am and we’ll be up in the lower 40s this afternoon.

It is also (but shouldn’t be) surprising how many traffic accidents and issues are caused by a dusting to 1/2″ snow.  It didn’t help that in this morning’s setup, everything was “perfect”.  Pavement and air temperatures were below freezing, wind was calm (snow wasn’t blowing around), and it was dark.  The thin layer of dry snow is pressed into solid ice by passing vehicles.  If this system had come through at 10am or later, pavement would be too warm for sticking.


Snow Flurries, Or A Bit More For Some of Us Thursday A.M.

February 23, 2022

3pm Wednesday…

A quick blog post to update you on our snow chances tomorrow morning. This evening and tonight we’ll start clear and see temperatures drop into the 20s again as the east wind dies down.  We will all see calm wind by sunrise.

A very weak “BC Slider” system (more like Alberta Slider) is dropping south out of Canada late tonight and early Thursday morning.  Models have been showing this for several days, and we’ve been expecting just a few flurries.  That still appears to be the case.   But if we get anything more than flurries, temperatures are cold enough that snow could stick anywhere in the region.  

If it was normal weather (mild), we’d be calling for sprinkles or a shower tomorrow morning.  But keep in mind that sometimes that turns into a couple hours of showers.  Would you even notice?  Would any of us notice the difference between sprinkles and .05″ of rain?  Not really.  But for tomorrow that could make a huge difference between a few flurries in the air and snow-covered roads

Right now I’m seeing a mix of just flurries or up to 1/2″ snow during the Thursday morning commute on all our different models

So make sure you are paying attention if you plan to head out on the roads before 9am tomorrow.

I’m only concerned about the first few hours of the day; the system quickly moves out of here and we’ll be partly cloudy or mostly sunny beyond noon.  Temperatures quickly warm into the 30s and lower 40s by afternoon.


Tonight Will Be Coldest Night of Winter For Some of Us

February 22, 2022

7:30pm Tuesday…

Quite a change today! All sunny in the metro area and much of the Willamette Valley, but cold/dry modified arctic air has flooded into the Pacific Northwest. This will remain in place through tomorrow, and to a lesser extent Thursday too. We struggled into the mid-upper 30s in the metro area. Portland’s high of 37 was the coldest since New Year’s Day, but not a record cold high temp for the date.

(KPTV)

Notice it wasn’t quite as cold away from the Gorge. But very cold in Central Oregon! Teens there after a weekend in the upper 50s to 60.

Cold Weather

Dewpoints have dropped down to around 10 in the metro area. The current value of 8 means it’s the driest airmass we’ve seen in 2.5 years in the metro area. We had an early season “arctic blast” back in late October 2019 that brought dewpoints down below 5 degrees in Portland. That’s skin-cracking dry! When the air is this dry, and wind is calm, the temperature can drop WAY down at night.

Easterly wind has backed off a little this evening, and I expect calm conditions by sunrise for about 1/2 of the metro area. We KNOW it’ll be cold everywhere tonight. In the windy areas (Troutdale, Camas, Gresham, Parkrose etc…) temperatures will “only” get down to 25-27 degrees. Then the spots that go completely calm should drop down into the teens. Maybe as low as 15 in the coldest outlying areas. The low temperatures so far this winter

It seems reasonable that the wind should at least go briefly calm at PDX airport tonight, allowing temps down into the lower 20s. We’re going for 22 at that location and this should be the coldest night of this cold spell. That’s because a few clouds show up tomorrow night, then the airmass warms after tomorrow

IF we make it below 23, it’ll be the coldest February temperature in Portland since the February 2014 cold snap. That one involved a very cold Gorge wind plus snow.

Tomorrow should be great with sunshine once again, but east wind backing off. Much calmer conditions for many of us. I’m watching Thursday morning closely since a disturbance dropping down out of Canada could give us flurries. Some models are totally dry, others produce those flurries. At this point there’s no indication that we could even get 1/2″. There’s a very good chance we just stay dry. The evening GRAF model keeps trying for flurries at 7am Thursday

Cold Weather

Then the airmass starts modifying under strong late February sunshine Friday and Saturday.

That’s it for now…stay warm tonight!


A rare late season cold blast arrives Monday evening

February 20, 2022

7pm Sunday…

Just like the person that swoops in to take your parking spot at the very last moment, winter has decided to make a (brief) comeback this week. It won’t be around long, but you sure will notice a change in the weather! Really cold stuff is on the way. The highlights for those of you not into lots of weather talk…

HIGHLIGHTS

  • Light rain showers turn to mixed rain/snow showers overnight in the lowlands of SW Washington and NW Oregon.
  • Sticking is unlikely for just about all of us below 1,000′, but a heavy shower could drop a “barkdusting” anywhere. Study up kids, I think a snow day is unlikely and the morning commute should be “normal”!
  • Light showers and sunbreaks continue through early afternoon Monday with temperatures into the lower 40s
  • A strong easterly wind suddenly shows up between 4-8pm Monday all across the metro area and temperatures drop…brrr! Easterly gusts 30-35 mph are possibly anywhere as cold/dry air descends off the Cascades.
  • At the same time, skies turn mainly clear and showers end by sunset.
  • Clear, cold, & windy is the story tomorrow night through Tuesday. Lows in the 20s, highs in the 30s. This will be the coldest we have seen since the week between Christmas and the New Year.
  • Wednesday will be colder & calmer in the morning. Some areas west of the Cascades will dip into the upper teens. Even in the city I expect lower 20s in calm areas.
  • IF you took off your snow tires already, no reason to panic, roads should be mainly (or all?) clear this week
  • IF you have turned your outdoor faucets or water lines on…drain them again. I just did that with my exposed chicken/duck water lines.
  • This is NOT really pipe-busting cold, just similar to what we’ve already experienced this winter. And I expect all days we’ll see temps rise above freezing with sunshine.
  • Normal weather is back by Friday at the latest…Highs into the 40s and then 50s next weekend.

DETAILS

I almost “cancelled” winter on-air and in a (still in draft mode) blog post last Tuesday. I had the fork ready and almost hit PUBLISH, but then noticed the ECMWF model was suddenly showing a sharp upper-level trough digging south over us about a week out in time (for tomorrow/Tuesday). So I figured I would give it one more day. Good move. On Wednesday the Euro looked the same! But GFS/GEM models were having none of that, forecasting mild this week. Now the GFS was trying for a winter return regularly from early January through mid February…way out in time, the weather geeks are used to that. But this was the first time the Euro tried to push cold/dry arctic air south over us within the 7 day forecast. Apparently it was right and here we are! Not much changed in the last 4 days while I took a little mini-vacation, except other models have turned colder like the Euro and now all are in agreement.

So the two questions in this pattern are always: How cold? & Could it snow to sea level? The answer is “quite cold” for late February, and no, little or no snow in the valleys.

First, check out the northern flow over us at 500mb right now. There are two “shortwaves” sliding south. One is the first dotted line, bringing cold showers today. The 2nd is heading south now

(KPTV)

That 2nd one arrives overhead tomorrow evening. The coldest airmass overhead follows this 2nd wave.

(KPTV)

Sticking snow isn’t a guarantee at sea level until the cold air flows in tomorrow night behind that wave. 850 millibar temps (temp in C at 4,000′) are “only” -5 to -6 tomorrow, typically not cold enough in onshore flow to bring snow to sea level. It’s only on Tuesday that the coldest air arrives overhead. All models agree on -9 to -10 at 850mb over Salem by Tuesday afternoon. But at the surface we’re totally dry long before the coldest air arrives; that’s common in our climate. In fact showers will likely be gone by 7pm tomorrow. The WRF-GFS tries to give some hilltop dustings tomorrow morning…seems reasonable. This pattern is excellent for Cascade snow, Mt. Hood will end up with a much needed 18-24″ by the time it dries out tomorrow evening.

WRF-GFS Snow Forecast
WRF-GFS Snow Forecast(KPTV)

Check out the cross-section from the WRF-GFS. Look at the dramatic arrival of easterly wind late tomorrow afternoon/evening

(KPTV)

Green colors are high relatively humidity and clear = dry. Quick drying as the cold air starts pouring in (circled). I think this next graphic is even more interesting. It shows the dry air coming right over the Rockies and surging over the Cascades from 4am Monday through 10am Wednesday. Dewpoints may drop to zero or even a bit blow west of the Cascades. That’s harsh on plants and our skin, especially combined with wind. A similar event February 16th-19th 2006 dropped dewpoints to -7 at PDX; I remember “scorched” looking Douglas Firs in several spots around town and on my own trees. Peak gust with that dry air was 50 mph at PDX!

(KPTV)

I think gusts to 50 mph with this event are unlikely since pressure gradient isn’t as strong, but it IS interesting the WRF-GFS shows much stronger wind in Clark County than we’d typically see with this setup. That tells me we’ve got a nice downsloping wind tomorrow evening coming off the Cascades. I think the wind arrival may be quite abrupt like during the Labor Day Windstorm in 2020.

COLD AIR: It’s interesting that 3 historic late-season cold snaps in our area (1960, 2006, 2011) all saw 850mb temps bottom out between -9 and -11 at 850mb (on Salem soundings). The same is coming up Tuesday/Wednesday. Nice consistency. For some reason the Euro has tended to be colder forecasting surface temps only around freezing Tuesday and Wednesday. That seems too cold with no snow cover, although a high only around freezing did happen in that 2011 event under sunshine. Right now we’re forecasting 36 and then 38 for highs those two days. That seems reasonable. Record low high temperatures are 34 for Tuesday and 39 Wednesday; I think we can break that 2nd record…if the wind doesn’t die down too much. For lows, with such a dry airmass and totally clear skies Monday and Tuesday nights, theoretically we should be able to see some upper teens in outlying areas and 20-25 in the city. But that will depend on calm conditions. I’m thinking there will be far too much wind tomorrow night for us to get crazy cold, but the record low is only 27 Tuesday. We should be able to beat that one. Wednesday morning’s record is 24 and we can probably do that at PDX if the wind goes calm. IF we don’t get cloud cover early Thursday morning, low 20s should be doable for one more day…maybe a 3rd record low temperature then. We will see. Here’s the Euro ensemble forecast low/high temps the next 15 days. This time of year the cold doesn’t stick around long, well, except in 2019. That one kept going into early March.

(KPTV)

That’s it for now, throw on an extra blanket for the next few days!


A very dry February, plus a cool (or cold?) spell next week

February 16, 2022

9pm Wednesday…

This has been another uneventful week weather-wise. A mix of clouds, sun, and just some sprinkles/showers here and there.

Of course, February has been very dry, just .26″ so far this month. Just 12 days to go!

(KPTV)

I’ve been curious, wondering if a dry February means anything for March. Basically, what’s the chance that we could turn wet? I found the 5 driest Februarys in Portland’s history (records go back to 1940 at PDX). Notice we are still about 1/2″ below the driest February on record (.72″ in a chilly February 1993). So it’s POSSIBLE we have a record dry February, but that would require less than 1/2″ rain in 12 days. We will see… The other driest Februarys were 1964, 1988, 2013, & 2001.

(KPTV)

Then I looked at the 10 driest Februarys and what happened the following March. I’ve assumed that most of those turn wet, but that’s not the case. 3 of them DID turn wet. 3 were just a bit drier than normal, nothing too dramatic. But 4 stayed very dry (1941, 1964, 2013, & 2020). That leaves 7 generally drier than average, and 3 wetter. That implies we have a better chance of staying dry plus there’s sure no guarantee that we’re about to get soaked.

(KPTV)

COOLER WEATHER AHEAD

Models are advertising the strong ridge just west of us in the eastern Pacific to generally remain in the same place the next 7+ days. But one relatively small change could have a big impact on our weather next week. The current view:

Jet Stream Right Now
Jet Stream Right Now(KPTV)

Then next Tuesday. See the change? Ridge is still there…

Jet Stream Next Tuesday
Jet Stream Next Tuesday(KPTV)

But the ridge has amplified north a bit in the Eastern Pacific, allowing a sharp upper-level trough to drop south out of Canada. This is a very cold pattern for us. Now this is the ECMWF model, and other models are not as deep/sharp with the cold trough dropping in over us. But they do all have some sort of cooler system dropping south Sunday-Monday. How chilly might we get in this setup in late February? 850mb temps forecast from the ECMWF drops Portland down to around -9 to -11! GEM model is significantly warmer and the GFS is in-between.

It’s possible to have high temperatures in the 30s as the ECMWF shows (coldest since Christmas Break), or just a weak push of chilly easterly wind Tuesday/Wednesday might just keep us around 45 degrees (no big deal). It seemed prudent not to go “whole hog” on a big blast of cold air early next week for now. This is our forecast this evening:

7 Day Forecast Temps
7 Day Forecast Temps(KPTV)

So…after our false spring weather of last week, it appears “winter” is on life support now, but wants to make one last push to stay relevant early next week. We will see how things play out. Regardless, the much drier than normal weather continues through NEXT week too. Maybe another half-inch rainfall by next Friday at best. It does look good in the Cascades though! Check out the snow for the all-important President’s Day Weekend

(KPTV)

I will be off through Sunday, but if something really good is in the works (snow!) I’ll get a blog post out Sunday. Chief Meteorologist Mark Nelsen


Record February “Heat” Today

February 11, 2022

7pm Friday…

If you live in the Portland/Vancouver metro area, you’ve just experienced the warmest February day in 27 years!

We expected today to be “warm” across the metro area, but temperatures soared well past our 62-degree high-temperature forecast. PDX Airport officially hit 67 degrees, breaking the daily record high. Notice the entire metro area was extremely warm for the month of February

Warm February 11th
Warm February 11th(KPTV)

Aurora’s 69 is the warmest official temperature I’ve seen in NW Oregon or SW Washington today. This next graphic shows the top 15 warmest days on record at PDX. By the way, PDX records go back to late 1940…about 80 years. You can see the last time we were this warm (in February) was in 1995.

Warm February 11th
Warm February 11th(KPTV)

Now look at those dates a bit more closely…notice anything? The warmest 16 days in February have all been in the 2nd half of the month. That means this is the earliest we’ve been this warm. Now check out the regional high temperatures today

Warm February 11th
Warm February 11th(KPTV)

Several things stick out…a warm coastline for sure. Actually I thought we’d see more easterly wind surface earlier on the coastline for more mid-upper 60s. Only Tillamook was “crazy warm”. Although that may happen in more spots out there tomorrow, it’ll be a fantastic Saturday on the beaches.

See those valley temperatures? Eugene barely broke out of the low-level inversion and Roseburg stayed in clouds/fog all day. So here in the north Willamette Valley we had the perfect setup with the easterly wind coming down into the lowlands. I expect a similar setup tomorrow except warmer temperatures down around Eugene/Roseburg and a few notches cooler in the metro area.

Some other records today, all in the metro area except Salem.

Warm February 11th
Warm February 11th(KPTV)

It is interesting that the atmosphere overhead was NOT in record territory today. Here’s a plot showing 850mb temperatures (around 5,000′) over Salem the last few decades. This is from the twice-daily balloon launches. The black line is average for any one day during the year. Makes sense because an average temperature up around 5,000′ this time of year is right around 32 degrees (0 degC on this graph). The red squiggles above each represent the highest (warmest) value observed on any one day. Today is the red dot I’ve highlighted in yellow. A good 5 degrees below record values this time of year…just over +10 degC.

Warm February 11th
Warm February 11th(KPTV)

That’s it for now…enjoy your weekend!