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  • Updated

Friday, July 30th, 3:50 P.M. 

Happy Friday!

Clouds and a smoky haze kept today a bit cooler than expected, but it was still very warm with highs making it into the mid 90s around the metro area. We are seeing some showers on the radar, but most of the rain is very light and evaporating before it hits the ground. A chance of thunderstorms or light showers will linger tonight, especially over the Cascades.

Saturday brings more high clouds and a smoky haze above with highs in the low 90s. Expect that smoke to stick around on Sunday, but it should have little to no impact on our air quality.

After a couple more 90 degree days on Monday and Tuesday, things cool off midweek. Thursday and Friday bring our first decent chance of showers in over a month and a half!

  • Posted

3:45pm Tuesday...

Very quick post since I'll be on TV from 4-7pm. More info this evening in a longer post between 7:30-9pm. National Weather Service has issued a Winter Storm Watch for many parts of NW Oregon and SW Washington.

It’s been a beautiful sunny day across the entire region…temperatures up into the upper 40s and a calm wind has made for a nice February afternoon.  We expect another clear & cold night with temperatures down into the upper 20s and lower 30s.

Clouds begin to arrive Wednesday afternoon, otherwise another nice day with no rain.   Then our weather gets far more interesting Thursday through the weekend.

Thursday we’ll start with light rain showers, which should turn to steady rain and then a mix of freezing rain/snow late in the day.  From that point through at least Sunday morning, temperatures will be at/below freezing.  That means we’ll be getting snow and freezing rain in the metro area.  Now that were 48+ hours away we’re getting a much better handle on the forecast:

WHAT WE KNOW AT THIS POINT

  • A snowy/icy event (storm?) is likely in at least part of the Portland/Vancouver metro area Thursday night through Saturday
  • This will be a mix of freezing rain and snow, depending on location and time.  For example it’s possible north and east metro gets MANY inches of snow, but west & south gets only a mix or spotty freezing rain.  There’s no guaranteed sledding yet for south & west metro.
  • There is going to be a lot of precipitation available during this time.  Snowy areas could easily get more than 6”
  • There’s a good chance most of the metro area stays frozen Friday morning through Sunday morning.  We might get lucky and have thawing on some roads in parts of metro area Friday and Saturday afternoons.
  • The Gorge and Cascades are going to get hammered.  Several feet are possible for both; high winds + blizzard conditions may occur at some point west end between Troutdale and Bonneville Dam.
  • Snow is unlikely on the coast and south of Woodburn/Salem.  It’s increasingly likely that little/no snow falls in Salem/Albany.  A wintry mix or maybe all freezing rain at times.
  • If we don’t pop out of it with a warming southerly wind Sunday, we definitely will Monday.  This is all about late Thursday through Sunday morning.

THERE IS STILL A CHANCE MODELS PULL THIS WHOLE THING FARTHER NORTH, LEAVING US WITH SNOW ONLY IN CLARK COUNTY AND NEAR/IN GORGE. But that appears to be a small chance now.

Just letting everyone know it’s not a guarantee yet. 

WHAT WE DON’T KNOW YET

  • Exact timing of heaviest freezing rain/snow
  • How many inches we get in any one location
  • How much freezing rain makes it down south of the metro area
  • Will it be one long, continuous storm that shuts down the entire metro area from Thursday night through Saturday evening?  Or do we get one wave Thursday evening, a quiet Friday, then another wave Friday night and Saturday?

Chief Meteorologist Mark Nelsen

  • Posted

Weather is a bit slow this evening...

We've seen some weather action the past few days with three Pacific frontal systems moving across the region. That first one Friday night and Saturday morning was sure a soaker; up to an inch in parts of the metro area. Our October rain total is slowly starting to add up

Western slopes of the Cascades have picked up 7-9" of rain the past month...that has pretty much finished off the fires up there!

Last October was very dry, but we're tracking a bit wetter this year so far

After a very warm start (and warm September!), we've cooled back to normal

What's ahead? Typical October weather...lots of clouds and some showers at times.

A large upper-level ridge is building just west of us. It'll be the main factor in our weather over the next week. It looks about like this right now

By Friday...

The forecast is very tricky Saturday through the middle of next week. That's due to the ridge wanting to move just slightly farther west and "flatten" a bit. That leaves the door open to weak systems moving by to the north. Basically we may get clipped by several waves of clouds and light rain showers. You can see one moving by Sunday

The morning ECMWF model (pictured here) really flattened the ridge and carved out a cool upper-level trough. This would be a setup to bring light snow down below 5,000' in the Cascades. But other models and even some ensemble members of this model keep a stronger ridge closer to us. We'll see. I think the main point is that we're probably not headed into a warm and sunny 7-10 days, but also no sign of stormy weather either. Just a typical mix of clouds, showers, and occasional sunny days. The ECMWF ensembles show temps cooling a bit more the next 10+ days; that would be normal for late October

Speaking of cooler temps, La Nina is now into the MODERATE category in the equatorial Pacific. Forecasters are confident this will be the case for upcoming Winter 2020-21. I'm working on the general winter outlook and should have it finished up next week. I'm feeling very confident we should see quite a bit more action than last winter. Remember how boring it was? Almost no storms and no lowland snow until mid-March! To whet your appetite a bit...take a look at the past 20 winters in Portland.

And farther back in time...seems like we have leveled off the past three decades a bit. Last winter finished off the 2010s decade; a new weather decade starts this winter. Snow measurements were taken at the NW corner of PDX up until 1996, then moved to Parkrose (near Sandy Blvd) for the past 24 years.

Last winter was very mild, some of my annuals from the previous summer made it through.

My banana bushes/tree, which most winters die down to the ground, made it to the 2nd story roofline by late August!

In fact last winter EVERY SINGLE DAY made it to at least 40 degrees for a high. It's been 18 years since we've seen a winter without a 30-something degree day.

  • Posted

Today has been another fantastic early spring day; sunshine with temperatures reaching into the 50s.  That will change tomorrow as a cold upper-level trough drops down along the West Coast.  The result is a wet & cool Friday.  In fact you may even see some snowflakes mixed in.  The sticking snow level will be around 2,000' tomorrow.

Models have come into better agreement on what happens beyond.  A surface low lingers off the Oregon coastline through Saturday, pulling cool/cold Canadian air south into the Pacific Northwest.   At the same time lots of moisture in the form or snow/rain showers will be rotating around the upper-level trough overhead.   This is what I'm thinking for Saturday in the Portland metro area; some "conversational snow".  I doubt any snow Saturday will affect your life.  Certainly far less than the current COVID-19 cancellations.

Snow Spring Headlines

Saturday night and Sunday almost all the moisture pulls south and skies start to clear out.  By Monday/Tuesday we're back into a nice spring weather pattern; sunshine with afternoon highs into the 50s or even 60.

Sure, models agree on the basic progression of weather the next 4-5 days.  But how much precipitation shows up?  And how much cold air comes in from the east?  Those are the big questions.    Trends the past 24-48 hours suggest less precipitation than earlier expected.  More obvious is models getting warmer and warmer as we approach this event.  2-3 days ago the GFS/ECMWF were at least down around -8 degC at 850mb (or much colder in the case of the GFS).  Now they both bottom out around -5 to -6!  Without cold air coming in from the east, that doesn't produce lowland snow.

Some models have backed off on precipitation totals for Saturday.  The ECMWF was very wet last night but ensemble average shows less than 0.50" now.  Of course if temperatures were below freezing from tomorrow night through Saturday afternoon that could produce 5" of snow.  But that's not happening.

ecmwf-ensemble-KPDX-indiv_qpf_24-4014400

All of our modeling shows very reasonable (for mid-March) temperatures between 36-42 degrees during the daytime Saturday.  That's cold enough to see snow in the air, but definitely not any significant sticking.  Basically a non-event in the lowest elevations.  If you live up around 1,000' and above, I think a Trace to 2" is very likely at some point between Friday night and Sunday morning.  Still, even up there it'll be tough to get any snow on roads during the day, it would only stick at night.

Put this all together and I feel the latest NAM-3KM is a pretty good representation of what to expect Saturday.  Some white on the hills, and maybe even briefly in the lowest elevations, but this likely ends up similar to our other 3 "close calls" this season

nam-nest-conus-portland-total_snow_10to1-4273600

I know it's a brief post, but as you can imagine it's been a crazy day in the news business.  I'm off work Friday and Saturday, that's my "weekend".  But if something more significant (widespread snow) shows up I'll be on Facebook and Twitter and possibly shoot out another blog post.

Chief Meteorologist Mark Nelsen

  • Posted

7pm Sunday…

Hope you are enjoying the Super Bowl on FOX12 or anything else you are up to this Sunday evening.  I’m on a bit later tonight, around 8:30pm or so once The Masked Singer finishes up.  That gives some time for a quick blog post to let you know what’s up weatherwise for this first week of February

Quite a change today from the low 60s Friday.  We only hit 45 today and we’ll spend most of Monday in the 30s and lower 40s.  A cold upper-level trough is passing over the Pacific Northwest this evening.  Earlier we saw a few scattered showers pop up in the chilly airmass, producing a mix of rain, hail, and graupel.  Those were driven by the increasing February sun angle producing surface warming that bubbled up into the cold air above.  Now that the sun has set, we’re finished with those.

KPTV 2017 Default Earth

We’ll likely remain dry through about midnight.  With partly cloudy skies temperatures fall down to around freezing most areas west of the Cascades too.

Models are in pretty good agreement that the line of showers offshore moves inland after midnight.  These will be light showers, but with temps around freezing ANYONE COULD SEE A BRIEF DUSTING OF SNOW west of the Cascades.  That said, some of us will be slightly above freezing = no sticking snow.  Other areas may get a rain/snow mix, then partial clearing AFTER the showers pass by could lead to a wet road freezing.

The result will be a random mix of four road conditions west of the Cascades for the morning commute in the lowlands from Longview to Eugene:

  1. Dry roads: where showers don’t pass overhead
  2. Snow-dusted roads: snow showers have passed over w/temps near/below freezing
  3. Icy roads: snow/rain showers pass by, then skies clear = black ice forms
  4. Wet roads: snow/rain showers pass by, but temps remain above freezing

All of these could occur within just a few miles of each other so tomorrow morning is definitely the type of morning to keep an eye on your car thermometer and morning weathercasts (here on FOX12 of course!)

And of course I could see a few school delays as well.  But this is not a “widespread snow” sort of weather setup.

Snow Tonight Forecast 1

What are models saying?  They don’t do very well with this real marginal/light precipitation setup so you can’t look at any one specific location and claim it will/won’t snow and stick right there.  But you can get a general idea.  Here’s our GRAF model, the lightest color indicates 0.2″ to 1″ in this case.

GRAF Snow Accumulation

The WRF-GFS thinks most showers go south, a little better chance in south Willamette Valley = no snow for most

or_snow24.36.0000

And the HRRR, just a very light dusting in spots

hrrr_snow7am

The message in general is the same…almost all of us will see our day progress as normal Monday, but a few wake up to a dusting of white.

Tomorrow should be a GREAT day…partly cloudy with a bright blue sky.  Chilly start and end but around 45 mid-late afternoon.  Tuesday will be similar, although lots of us will start in the mid-upper 20s.  I’ll go 28 at PDX for Tuesday morning.  Once again we can’t seem to reach the cold nights we saw back in November.

Winter Coldest Day Each Year

A weak ridge of high pressure sits overhead Wednesday-Friday, bringing a mild south wind and rainy weather those days.

Models are still going for a little cooling next weekend, although nothing that would bring snow close to sea level again.  By next Sunday all models are bringing an upper-level ridge close to us again.  The GFS ensembles shown here for:

gfs_sunday9th

But just 10 days away (Wednesday the 12th), the GFS is trying to bring very cold troughing down over us

m500za_f240_bg_NA

The GEM (Canadian) says nope, ridging is much closer

gem_wed12th

The ECMWF agrees with the GEM, keeping temps relatively mild, but a little on the cool side through mid-February

ecmwf-ensemble-KPDX-daily_tmin_tmax_ecmwf-0644800

We may dry out a bit too with a closer ridge.  ECMWF ensemble average (for Salem) shows only 1.5″ rainfall during the next two weeks.  Operational (blue line) only around an inch.

ecmwf-ensemble-KSLE-indiv_qpf-0644800

By the way, 3 of the past 6 Februarys we’ve seen significant snow in Portland.  We’ll see what happens this month, but nothing suggests we’ll see measurable snow in the first 10 days of the month.

Mark Snow PDX February

Chief Meteorologist Mark Nelsen

  • Posted

3pm Saturday…

Nothing is more relaxing than a day off work, sitting by the fire, perusing the latest maps/models and meteorological info.  What could be better???  Isn’t that what everyone does?

I’ll be back at work tomorrow, but nowadays everything we need to make forecasts is available online (free or behind a paywall) and can be done from home.  It wasn’t like that 29 years ago when I first began forecasting in Portland.

Today has been a great day for skiing in the mountains.  I see 15-21″ new snow has fallen since Friday morning on Mt. Hood, most of that since sunset Friday.  The problem is high winds.  At 1pm Mt. Hood Meadows closed down after putting lifts on standby for an hour or so.  It’s just too exposed up there in the middle of a storm.  This is a four day long storm folks.  Tomorrow’s wind could be similar as another wave of heavy snow arrives.  By the time the snow tapers off Tuesday morning, we can expect another 3 to 5 feet!  Here’s one snow forecast from a weather forecast model (WRF-GFS) through 4am Monday

wrf_snowthroughMondayAM

We’ve got very large waves on the coastline and some occasional downpours in the lower elevations, but neither is too noteworthy since we’re in the middle of the storm season.

What you really want to know about is lowland snow for next week right?  Now that we’re within 2-5 days of this lowland “snow chance episode”, we’re getting a clearer picture of what’s ahead.

I see two specific periods in which there is a decent chance at least parts of the lowlands west of the Cascades will see sticking snow.  

  1. Monday evening/night
  2. Wednesday (or possibly Wednesday into Thursday)

Notice I didn’t mention tomorrow, tomorrow night, Monday daytime, or Tuesday?  That’s because it’s too warm tomorrow (40s), slightly too warm with strong southwesterly wind Sunday night (snow unlikely to stick much below 1,000′ along I-5 corridor), and a bit too warm Monday (36-40 degree day).  Then Tuesday will likely be dry, or mainly dry and 35-40 degrees too.  That’s why I’m thinking your lives should continue as normal during those times.

MONDAY EVENING/NIGHT

Increasing rain/snow mix Monday afternoon may change to all snow from the metro area south to Eugene around sunset and beyond.  If temps drop down to 32-33 degrees that evening and moisture keeps coming down, this could be a setup for a sloppy 1-3″ snow somewhere between Portland and Eugene.  Everything has to work out just right for this to happen.  So it’s just a chance for now.  But you should be thinking there’s a possibility at least part of this area (including Portland/Salem/Albany) could get sloppy/snowy roads Monday evening/night.  It’s still over two days away so tomorrow we should have a much better idea.  If something fun/snowy is going to happen in the lowlands, this is the first chance.

WEDNESDAY NEXT WEEK

This is our classic setup for a real snow or snow/ice storm.  If enough cold air pours out of the Gorge and into the metro area (and north), we could be left with a snowy/windy/frozen day in Portland.  Of course that extends east into the Gorge as well.  One of those days where most/all schools shutdown and it’s tough to get around.  A real snow day is a possibility.   Models are forecasting a dusting to 6″ (at the high end).  This is why I don’t show snow forecast maps from models many days ahead of time; totally irresponsible and then they get passed around on social media.  Three days ago they were throwing around numbers like 10-20″.  There are strong hints that the cold air may not extend south of the metro area.  It’s quite possible Salem/Albany get little or no snow out of this second event.  And nothing at the coastline.

BEYOND WEDNESDAY

It’s very clear that this week’s flirtation with snow/ice/cold is a one shot deal.  All models swing us back into the mild “split jet stream” setup we’ve seen all winter by next weekend and beyond.   Two of our models have a mild south wind and end of freezing conditions by Thursday morning.

SUMMARY FOR WESTERN LOWLANDS: LONGVIEW TO SALEM INCLUDING PORTLAND

  • SUNDAY EVENING & NIGHT:  Rain showers change to rain/snow showers mixed overnight into Monday morning.  Little or no sticking at lowest elevations and no freezing.  Trace-1″ up around 1,000′.  Maybe a few inches up around 1,500′  Monday morning commute should be perfectly normal, except some snowy roads up around 1,000′ and above.
  • MONDAY DAYTIME: Scattered light rain showers turning to steady afternoon rain.  Mixing w/snow by sunset and possibly changing to all snow and sticking later…beyond 7pm.  Yes, I’ll keep a close eye on this so we can avoid a 2pm, 4pm, 6pm etc… jammed freeway surprise.   Zero to 3″ late Monday evening through the night.  Best chance south of Portland.  Yes, I also realize zero to 3″ sounds ridiculous.  I’ll narrow it down tomorrow afternoon.  Some models keeping all the snow from Salem south at this point.
  • TUESDAY:  Partly cloudy, a flurry or two.  Areas that have snow-covered roads from Monday night would be icy.  But where it doesn’t snow Monday night, both commutes Tuesday will be fine.

METEOROLOGY BEHIND THE FORECAST

This weather pattern is a lot of work, but for a weather geek like me it’s nice to have something interesting ahead.  That’s after 2.5 months of “meteorological melancholy” since Halloween.  I took one day away from the weather maps/models yesterday then jumped back online this morning.  One message sticks out:  The GFS has been terrible leading up to this event, constantly pushing in cold arctic air too fast plus too intense.  I had a feeling that was the case but looking back at maps 2-3 days ago that’s very clear.  Other models have turned a little milder but they were never crazy with the arctic air to start with.  In fact it’s now clear no arctic air moves into the Portland metro area until it gets pulled in through the Gorge Wednesday.  For the geeks this has gone from what could have been an epic event to a typical (somewhat) brief midwinter snow/ice episode with no arctic blast.

That surface low moving by to the north Sunday night gives us far too much onshore flow for lowland sticking snow, even with 850mb temps down around -7/-8, especially since showers appear to dwindle to almost nothing by Monday morning.  I think Monday morning will be a non-event for 95% of us; some grass on some lawns/barkdust here and there but any real snow (1/2″ or more) up around 1,000′ and above. Tuesday’s forecast is easy because the surface low passing through Oregon Monday night is gone.  We’re left with -8/-9 at 850mb and flat gradient.  That should allow us to climb up around 36-40 degrees (assuming ground is bare).  But about that Monday low…

The ECMWF came in this morning going gangbusters with precipitation Monday evening.  It sends the surface low from Florence to La Grande, throwing up around .60″ precipitation over south/east metro!  A light northerly breeze at the same time = possible sticking snow.  The 18z RPM gives us maybe an inch of snow.

RPM_72_SNOW_18z

ECMWF (snowiest) says 2-4″ at least.  This is 12 hour precipitation from 4pm Monday to 4pm Tuesday.  I guarantee this will shift north or south on future runs.

ecm_precipmonday4pm-tuesday4am

Reliable WRF-GFS says band of precip stays mainly south; hosing metro area with little or no snow, but 2-3″ Salem to Eugene.

wrfsnowmonday4pm-Tuesday4pm

As for the 2nd event, both GFS and ECMWF are bringing a very deep low close to the coast, far enough north to put Salem/Albany pretty much out of the running for snow/ice.  Check out the WRF-GFS pressure pattern midday Wednesday…a tad windy in the Gorge maybe?  Strong south wind on the central/south coastline the same time.

wrf_wednesdaypmpressure

That 2nd event is far out in time so I’m sure this will be changing as we get closer.

So remember, the first real chance of lowland snow (for some of us, not all) is Monday evening/night, other than that you’re in the clear.  That’s it for now.

Chief Meteorologist Mark Nelsen

  • Posted

6pm Wednesday…

So far this winter we’ve seen very mild conditions, no lowland snow in Portland, and hardly any storminess.  Sure, we're getting some sticking down around 1,000' east of Portland this evening (Sandy, Estacada), but no snow down into the lowlands.

Now it seems increasingly likely that SOMETHING is in the works along the I-5 corridor for next week.   Some sort of snow/ice/cold “event” may be on the way. Maybe even out to portions of the coastline.

It’s still too far out (5-7 days) to know how things will play out in detail, but now that we’re getting closer it’s fair to make these statements:

  1. Some (or a large) part of western Oregon and/or western Washington lowlands will likely get a significant snowfall (2-4″+) within the next 8 days.
  2. There is also a decent chance for hard freezing conditions (below 25 degrees) sometime beyond Tuesday.  That’s from at least the metro area north up into Washington, and of course east of the Cascades plus Gorge.  That said, it already happened earlier this winter at Thanksgiving.  So your pipes/faucet covers should be in good shape.
  3. Start planning ahead… “what if there is some sort of significant snow/ice event the middle of next week?”.  Somewhere in the Tuesday-Thursday time-frame. How would you deal with it if that’s the case?  If we get lucky nothing happens, but at least you can be prepared.

At this point, we are not able to make statements like this:

 I expect a, (6″? 8″? 10″?)  snowfall over the Portland metro area next Wednesday, or Thursday” or “I expect a snowstorm in late January or February

Portland will be a frozen hellish white mess Tuesday through Friday next week

Snow Portland Preview

WHAT ARE WE SEEING RIGHT NOW?

All models are in good agreement forecasting the general weather pattern for the next 7 days.  They all agree that a series of systems drop into the Pacific Northwest on cool northwesterly flow through Sunday.   That’s valley rain and mountain snow.  Expect a MAJOR snow storm on Mt. Hood Friday night and Saturday, then again Saturday night and Sunday.  First big weekend on Mt. Hood with all resorts fully open (Skibowl opens tomorrow) + 1-2 feet snow + tons of traffic = big mess possible Hwy 26 & 35 Saturday/Sunday.  Friday afternoon through Sunday evening should feature 2-4 feet of snow up there…

7 Day Forecast Cascades Mt Hood Government Camp

Then Sunday through Tuesday an especially cold upper-level trough (big dip in jet stream) drops south through western Canada.  Here’s Sunday:

gfs_sundayam

Then next Tuesday… 6 days from now.  Models generally agree to this point

gfs_tuesdayam

Notice that very cold low is sitting up there in southern British Columbia.  When we get our big arctic blasts, a low like that drops directly overhead on its way south and east.  No model is forecasting that to happen early-mid next week. That’s what happened Thanksgiving weekend, but of course the airmass was not nearly so cold early in the season.  In this setup, which models agree on up to this point, we generally see cold “onshore flow” showers.  Wind at sea level is coming in from the southwest or west, off the 50 degree ocean.  In this case the air is taking a very short trajectory from western Canada out over the cold water and coming onshore as snow showers.  This is the classic setup for lots of snow on hilltops and a slush mix in the lowest elevations.  If you live at 1,000′ this can give you big snow.  But this isn’t how we get our big “Portland shuts down” sort of snow events.  That’s why we have mixed snow/rain showers in Monday’s forecast and then mainly flurries for Tuesday.

2 of 3 main long-range models (GEM & ECMWF) say we still have weak onshore flow (although very cold onshore flow!) Tuesday.  Bitterly cold arctic air is poised just north of us at that point.  Of course the crazy GFS is still blasting in cold air Tuesday, but at least it has been backing off on that time-wise. A couple days ago it has the “arctic front” (leading edge of cold north & east wind) coming through late Sunday.  Now it’s doing that Tuesday.  It’s been unreliable for the really cold stuff so far in this event.  So at this point the most likely scenario is that we’re going to be flirting with low elevation snow Monday/Tuesday, but the showery/slushy stuff; no frozen/hellish commute issues.  You get the idea with the ECMWF snowfall forecast through Tuesday:

ECMWF Snow Accumulation

Beyond Tuesday?  Of course we’re talking 7 days out in time, but models are hinting we could see a classic snow/ice storm setup somewhere west of the Cascades.  ALL models agree that an approaching system from the west will pull cold/dry arctic air south & west from Washington and through the Gorge.  Then moisture rides over that cold air…a classic!  But will it be a relatively brief snow/ice event after Tuesday or a historic drawn-out snow storm?  It’s too far out in time and both are possible.  Luckily we have many days to figure it out.  The reason I have confidence that we’re going to see at least SOMETHING is the ensembles from the different models.  43 of 51 ECMWF ensemble members show at least 2″ snow around Wilsonville (I chose a location along I-5 corridor) by next Friday.  You don’t often see such good agreement among the ensembles, clearly a spike around next Wednesday/Thursday.

ecmwf-ensemble-KUAO-indiv_snow_24-8484800

Stay tuned!

Chief Meteorologist Mark Nelsen