Snow Wrap; More Than Expected For Some of Us

January 26, 2021

9pm Tuesday…

That was exciting! All indications were that we’d see a burst of snow/rain moving across the metro area during the mid-late afternoon. But it ended up slightly cooler than expected = more snow coverage.

I was beginning to panic around 3:30-4pm as snow was falling heavily throughout the metro area; fearing a major bust was in progress. At that point it appeared ALL of the metro area could see significant sticking snow. Luckily, (this part worked right), precipitation was lighter and temps didn’t fall as much across most of central/north/east metro. Whew! And precipitation mainly stopped by 5pm putting an end to the event.

Here are the snow totals I have so far. Notice the official Portland total means we don’t have a measurable snowfall yet this winter. There was a TRACE at the Portland NWS forecast office in Parkrose

This is always difficult because two viewers in the same area will report different totals. For example I have a 1/2″ and a 1.5″ for Happy Valley! So 1″ seems good enough. We had no accumulation at KPTV, just off Hwy 26 @ Cornell on the westside. But just a couple miles away in the hills to the northeast someone reported 2″.

IN GENERAL, the white areas saw either nothing, a brief dusting, or less than 1/2″. In those areas the forecast was right on; a snowy afternoon with a brief accumulation anywhere for a short time. That happened in Clark County and a good chunk of Portland east of the Willamette River.

These maps look amazingly similar to the WRF-GFS don’t they? This was the final morning forecast

Alright let’s recap; I’ll go negative first…

THE “BUST” OR WHAT WENT WRONG

  1. I didn’t forecast/expect Salem snow, or light totals around Silverton, Oregon City, or Clackamas county buttes (Happy Valley & Damascus). Total miss there. If only I would have paid attention to that WRF forecast a bit closer! It showed that possibility. But I’ve tended to ignore totals under 2″ due to this model “over-forecasting” light snow events in the past. Maybe that only should apply to onshore flow showers in the future. Lesson learned.
  2. Lower sticking snow in the West Hills than I forecast/expected. Temperatures a couple degrees colder than expected did the trick here. Snowy roads up there after I clearly said CLEAR ROADS METRO AREA for this afternoon
  3. Evaporative cooling was far stronger than I have seen in the past. For the geeks, I couldn’t believe Salem was 39 degrees with a dewpoint of 30 at 1pm, then one our later it was 32/30! Typically you would expect it to drop down to maybe 35-36. That was amazing.
  4. Retweeting a “NO” at the Oregonian referencing their “clickbaity” headline yesterday evening. “Oh how the turntables” was their reply as it began snowing today. So well-played! Lesson learned…you’ll get burned playing with fire kid…

WHAT WENT RIGHT TODAY

Luckily this list is longer…

  1. Models and our forecasts had the general event nailed a couple days ahead of time. A dry morning followed by evaporative cooling leading to snow in the air for just about everyone, but only signficant snow in a few spots
  2. Heaviest snow was right where models showed (and we forecast). All those 2-5″ totals against the Coast Range were impressive! There was no widespread valley snow event.
  3. Much of the central/east/north metro area only saw snow in the air and/or brief and light accumulations. Most models showed this well. I’ll be ignoring the 3km NAM in these marginal events in the future.
  4. There was little to no effect on the evening commute; except up in the West Hills. We didn’t have any sort of December 29, 2009 traffic fiasco; but only 2-4 degrees colder may have done so!
  5. Temperatures rose again after the precipitation moved on north, that was well forecast.

That’s it for tonight. This was our last “close call” for now. Notice the ECMWF ensembles show mile conditions most of the next two weeks. Sure, wet and cool at times, but not many hints of lowland snow

For tonight, most of us remain above freezing with lots of cloud cover. There might be a few icy spots high in the West Hills or in some outlying areas IF we get some clearing. But I think that’ll be patchy

Chief Meteorologist Mark Nelsen


Noon Tuesday: Snow Arriving In Coast Range and Western Willamette Valley

January 26, 2021

We’re heading into “prime time” now. All the action for the lower elevations west of I-5 will be from now through sunset or so (5-7pm). My thinking hasn’t changed. Models that were forecasting little/no snow appear to still be on track and “It’s Happening!” where they have been expecting snow. Snowing all through Coast Range now and into the lowland areas west of Salem & McMinnville too

PRECIPITATION

Precipitation spreads into the Willamette Valley and metro area next two hours and continues through the evening.

Depending on location in metro area, that precip will be rain/snow mix, or all snow. The all snow areas would be west of the West Hills (possibly at KPTV) in the western half of metro area.

THIS MEANS IT’LL GET EXCITING THIS AFTERNOON AS SNOW FLIES THROUGH THE AIR IN SPOTS, ESPECIALLY WEST METRO.

WHAT ABOUT STICKING SNOW?

Almost all sticking snow should be in far western metro, from Hillsboro and North Plains westward. But it will also stick up on Chehalem Mtn, maybe Cooper Mtn, and possibly at top of West Hills too. Expect a Trace to 3″ in these spots. Of course this includes all western valley locations from Sheridan to McMinnville, Yamhill, Forest Grove, Banks, Vernonia. I could even see a dusting in Newberg (maybe) and Amity. South Salem hills? Possibly.

Of course, if it comes down hard enough, even at 35 degrees it could stick somewhere else but it won’t last long and precipitation would need to be quite heavy.

THERE SHOULD BE NO EFFECT ON EVENING COMMUTE IN METRO AREA

After 7pm or so the precipitation dies down, plus changes to mainly rain since it’ll be warming a bit overhead.

Again, the “main action” today is 1pm-7pm. I think this HRRR model best represents what we are thinking for snow accumulation.

And the WRF-GFS; notice it gives a dusting to parts of far west metro area, West Hills, and south Salem hills. This is all reasonable.

Notice the lack of snow, even in the hills, on the east side of Willamette Valley and Clark County. That’s due to much lighter precipitation in those areas, but a few degrees warmer. And in parts of east metro the easterly wind gives a little too much “mixing” to get temps down to 33 to get that snow to stick. Yes, Banks at 300′ has a far better chance getting 1-2″ today than Sandy at 1,000′.

I’ll be on TV all through the evening, so probably no blog posts, but make sure you are following me on Facebook @marknelsenweather and Twitter @MarkNelsenKPTV. I’ll have some updates there.

Chief Meteorologist Mark Nelsen


Snowy Afternoon & Evening Tuesday, But Only For Some In Lowlands

January 25, 2021

6pm Monday…

We have one more “close call” with snow late tomorrow afternoon & evening, then continued cool and wet through the first few days of February.  Tomorrow will be dry through early afternoon, with a gusty east wind picking up after noon.  Temperatures reach the lower 40s. Then a wet weather system moves inland the 2nd half of the day. I expect precipitation to start sometime right after noon in the Coast Range and central Willamette Valley, then spread north into the metro area around 4pm. That leads to…

TUESDAY AFTERNOON & EVENING HIGHLIGHTS

  • THE VAST MAJORITY OF THE METRO AREA & LOWLANDS WILL NOT SEE STICKING SNOW TOMORROW AFTERNOON
  • BUT EXPECT A SNOWY MESS THROUGH THE COAST RANGE LATE TOMORROW AFTERNOON & EVENING. Watch out if you are headed that way! At least 3″ of snow is likely over Wilson River and Sunset Summits. Possibly down into the Van Duzer corridor between Lincoln City and Willamina as well.
  • Where the precipitation is heavier (far west metro up against Coast Range) we see a decent chance for at least a dusting.  That’s anywhere west of Hillsboro or North Plains.  It’s possible Forest Grove, Banks, Chehalem Mtn. pick up more than a trace.  Timing is 4pm-10pm.
  • We think there won’t be enough precipitation and/or temperatures won’t be cold enough for sticking snow (or even in the air) for just about all other areas.
  • Whatever happens will be done by midnight, then it’s back to light showers for Wednesday with temperatures in the 40s

TECHNICAL INFO

Models are in better agreement this evening. The general idea is that dewpoints drop into the 20s by midday due to a mild downsloping easterly wind (heading toward low pressure offshore). Temperatures with good mixing move into the 41-45 degree range in the lowlands. Then as precipitation arrives, evaporative cooling drops everyone at least a few degrees.

Generally the highest resolution models, which have the best topography, are forecasting no snow in the lowest elevations over and east of I-5. That’s because temperatures don’t drop down close to freezing tomorrow afternoon. That’s partly due to a breezy easterly wind (keeping air stirred up) and/or very light precipitation in those areas. There is no cold airmass east of the Cascades heading our way; the Columbia River Gorge is not “in play” this time around.

But west of I-5? Specifically close to the Coast Range? Cool air piles up a bit more, wind is light, and precipitation is much heavier. That can drag snow all the way down to the valley floor. Sometimes I’ve called this the “Forest Grove Effect”. I first noticed it early in my career. It can be breezy & 36-40 degrees in Portland. Yet calm, snowing, & 32-33 degrees way out against the Coast Range. I think that’ll be the case 24 hours from now. At this moment the HRRR shows this best…I like the temperatures for 5pm as well.

But the GRAF and RPM also forecast no snow. The contour pictured here is the 18z GRAF; it did very well with yesterday’s “event”. By the way, the ECMWF is accumulating snow for us with temps above 35 degrees…unlikely.

The (usually) reliable WRF-GFS at 1.33km resolution can see all the hills. It says forget it for anyone east of I-5, even up at 1,000′ or higher! This event is about LOCATION, not so much ELEVATION.

Regardless what happens in the late afternoon through early evening, slightly warmer air overhead should change anything to mainly rain showers after 10pm. Although there won’t be much precipitation by that time anyway. I’m guessing PDX goes from 43 tomorrow afternoon, down to 37-39 at 5-7pm, then back up to 39-40 by late evening.

We’ll see how this all plays out!

Chief Meteorologist Mark Nelsen


A Cool Week Ahead; Snow Level Low Again Tuesday Evening

January 24, 2021

9pm Sunday…

Today generally worked out about as expected; no snow in the lowlands. There was plenty of “chunky rain” on my drive to work at 1-2pm. Models did well showing temperatures holding steady or even dropping as the day wore on.

Sticking snow level was all over the place. From around 200-300′ way out westside near Banks

to 2,000′ or a bit higher east of Rhododendron at mid-afternoon

This really points out how important precipitation intensity can be to snow level forecasts in these marginal snow setups.

Steady precipitation has ended for most of the area, and now it’s on to very spotty showers tonight through Monday in the post-frontal cool airmass. GRAF model says less than .10″ for most of us along I-5 through sunset Monday. There’s not going to be much of anything falling out of the sky tonight and Monday

Since temperatures are just a few degrees above freezing and wind is light, any clearing could lead to icy roads. This is far more common than snow in our climate. So keep a close eye on your car thermometer tomorrow morning as you head out and of course Andy & Tony have you covered on FOX12 OREGON. Of course if skies don’t clear much, we won’t have to worry about icy roads. I think it’ll be real spotty. A summary of the next 24 hours…

TUESDAY & BEYOND

An active weather pattern continues through the end of the month, and at least into the first days of February. But it’s not a strong westerly jet stream running right into the Pacific Northwest. Rather a series of cold upper-level troughs that drop down along the coastline, or into the Eastern Pacific. #1 is approaching now; will be right over us Monday

That one heads down through the Desert Southwest Tuesday/Wednesday while #2 settles in just offshore

Then by Saturday/Sunday, #2 has moved east of us and a larger/deeper low (#3) is plopped down in the Gulf of Alaska. This wouldn’t be quite as chilly for us since the cold air is dumping out over the northeast Pacific. It’s a long path over the mild ocean from Alaska to the Pacific Northwest!

This doesn’t tend to be a HUGE snow producer for the Cascades (until next weekend) since a lot of the energy is headed to our south. The Sierra Nevada pick up many feet more snow than the Cascades this week.

So the big question is…could we see another close call for lowland snow? Possibly, but it’s a stretch just like today.

One thing we know isn’t in play; there’s no source of cold air to the east. I don’t see a setup this week that would bring in 20-30 degree air through the Gorge with moisture riding over the top for a widespread snow event. What I DO see is another “close call” Tuesday afternoon/evening. As a Pacific frontal system moves toward the West Coast (2nd jet stream image above), most energy heads south. But we get the leftovers as a band of precipitation swings north over us. There will be a relatively strong surface low well offshore too. The GRAF model shows the precipitation moving over the Willamette Valley Tuesday afternoon/evening with heaviest precipitation from Salem south and west. That’s because the precipitation band is moving away from the main storm center and weakening. There are hints that MAYBE the west side of the Willamette Valley up against the Coast Range could score snow to relatively low elevations…maybe.

This model and the ECMWF produce about .20-.30″ liquid precipitation. But temperatures remain above freezing through the Valley on both. GRAF gives hints the far westside of Willamette Valley might get something. But nothing for most of us…like today

The WRF-GFS says forget it as well; all the sticking snow is right up against the east side of the Coast Range. Total snow ending at 4pm Tuesday…It could be quite a snow dump up in the Coast Range!

ECMWF tries a little harder, but temperatures are 33-38 degrees through the entire “event”.

Luckily we’ve got another day to see if models warm up a few degrees as they did this time around. There WILL be an gusty east wind blowing through the Gorge, but there’s no cold air source eastside as I mentioned. So that doesn’t help us. Models are insisting dewpoints drop down into the 20s Tuesday just ahead of the precipitation too; allowing the 40-42 degree midday temps to drop down close to freezing a few hours later with evaporative cooling. I’m a bit skeptical.

Beyond Tuesday, snow levels lift a bit. It appears Wednesday through next weekend they will be in the 1,500′-3,000′ range. No sign of rain in the Cascades and it’s going to stay cool in the valleys.

I will have some time to blog again tomorrow evening, sometime after 5-6pm. Hopefully things become a bit more clear at that time. That should allow us to either swing toward NO SNOW in the valley (most likely) or SOME OF US WILL GET A LITTLE TUESDAY P.M.

Chief Meteorologist Mark Nelsen


Sunday Morning Forecast Still On Track; Flakes Mixed In Rain For Most of Us

January 23, 2021

6pm Saturday…

I’m not at work today, busy getting all the snow preps done! Just kidding, I left my snow shovel at work for a promo shoot. I’ve been confident I won’t need it tomorrow morning, even at 1,000′. I don’t shovel an inch or so…

This little “event” coming up late tonight and tomorrow morning has been solid forecast-wise for four days! Nothing has changed in either models or our thinking. The previous post is still valid.

Sunday Highlights

  • We will all wake up (west of the Cascades) to rain or a mix of snow/rain at the lowest elevations. Precipitation arrives sometime after 3am…timing has moved up a bit.
  • If you live near/above 1,000′, there’s a decent chance you get at least a dusting on the ground. If you live below 1,000′ IN THE METRO AREA, I’d be surprised if anything sticks. The “1,000 ft” is an approximation, we can’t actually forecast snow level with precision more than 500-1,000′. See rant below…
  • Whatever happens will be done by noon, then temps rise a few degrees (up to around 40 or so) and steady rain changes to light afternoon showers. Nothing interesting happens the 2nd half of the day
  • If you live in the lowest elevations (90% of us), your life should continue as normal tomorrow. Except for that COVID thing, but you know what I mean. Normal for these times.
  • If you live well above 1,000′ (like 1,500′ or higher), you’ll have some nice snow to enjoy tomorrow! Probably 1-4″ up there. This includes northern Clark County foothills, the hills above Scappoose and St. Helens, and above Kalama, Longview etc…

This graphic summarizes it well

Tomorrow night and Monday we’ll see very light showers; could be mixed at times, but leftover wet roads freezing in a few spots Monday morning MIGHT be a bigger issue. I’ll tackle that tomorrow

SOME OTHER INFO

Latest ECMWF snow forecast looks the same as it has for the past few days

This will be the first test of IBM’s 4km (higher resolution) GRAF model for us. Actually it nailed the 1/2″ last March, but this is the longer range version (to 3 days) that came out last summer. It says “FORGET IT” in the lowest elevations.

The “reliable for the past 20+ years” WRF-GFS (UW) is reasonable…a bit of snow most areas above 1,000′. But all lowest elevations…forget it. I’ve noticed it tends to “over snow” these marginal events. So we’ll see if hills around Happy Valley and central Clark county picks up measurable snow… This is the highest resolution model we have for our area. 1.33km! This means grid spacing is so tight that the model’s terrain includes features not seen in coarser resolutions. You can see Chehalem Mtn, the West Hills, outer SE metro area buttes, and south Salem hills. Note this one can also clearly “see” the Gorge. Little or no snow on I-84 in the Gorge tomorrow.

Just taking a look at the text data from ECMWF says we’re coolest before midnight with the partly cloudy skies we’re seeing now, then a light southerly breeze plus cloud cover means temps actually rise a bit toward sunrise. Precipitation is quite light on this model as well. Only .10 to .20″ by noon, that’s not going to drag the snow level down very far. NOTE THAT TYPICALLY THE -3 to -4 850mb temps would mean a sticking snow level up around 2,000′. We’re lucky to see sticking snow below that elevation briefly tomorrow morning.

WE CAN’T FORECAST SNOW LEVELS IN 100′ INCREMENTS

You may remember my rant about snow level forecasting in the past. I cringed when the NWS folks issued a Winter Weather Advisory for elevations ABOVE 700′ in the metro area for Sunday. I have no problem with NWS; they all work hard and do a great job. But when is the last time you heard a Mt. Hood snow forecast of “3,700′ tomorrow”. Or “expect a 4,300′ snow level dropping to 2,700′ late this evening”. We don’t, and shouldn’t in this case either. That’s because snow level is also highly dependent on precipitation intensity. Heavier precipitation = lower snow levels generally. So don’t read the Winter Weather Advisory as “you won’t get sticking snow at 600′ but will at 800 ft”. Instead, I wouldn’t be surprised if some neighborhood gets sticking snow (somewhere) to 500′ Sunday morning, but somewhere else you get nothing at 1,000′. That’s why I use the “near and above 1,000 ft.” terminology.

So insert your eyeroll here and “oh geez, Mark is throwing a fit about THIS again?” One example below is from a blog post in 2016. Setup was a bit different, but same issue


We’re doing people a disservice by implying we have more accuracy than we do.  

This morning is a perfect example of why forecasters (and the NWS) shouldn’t be forecasting snow level in increments below 1,000′ in a snow shower pattern.  A snapshot at 8:30am:  Staley’s Jct. on U.S. 26 west of Banks…elevation 200 feet.  A snowy road and maybe a half inch on the ground:

us26-at-staleys-junction3_pid2985

At the SAME ELEVATION, but 15 miles east on the west side of Beaverton…all bare and wet with no snow in sight:

26bethany_pid524

Then over on the eastside of the metro area just above Sandy…at 1,200′.  NO SNOW. The white stuff is left over from yesterday’s hail/graupel showers.

us26-at-firwood-rd_pid2331

So what was the “snow level” at 9am???  Under the heavy showers it was near sea level, where very little precipitation fell it was higher, up around 1,500′.  


Alright, I’ll be on TV tomorrow evening at 5/10/11pm, taking a close look at Monday and Tuesday. Likely a couple more “near misses” for those days.

Chief Meteorologist Mark Nelsen


Sunday Morning: First Snow Sighting Of Winter For Many of Us

January 21, 2021

6pm Thursday…

If you haven’t left the lowlands this winter, most likely you also haven’t seen a single snowflake. February is less than 10 days away! That’s unusual in our climate. Typically we have a close call or two, if not real sticking snow, by this point in the winter. Not this year, it’s been very mild. But if you are up before 10am Sunday, it appears there’s a decent chance you will at least SEE snowflakes in the air. Sledding in the lowlands? Unlikely.

For the short attention span (TLDR) folks…

Winter Weather Highlights

  • Between 4-8am Sunday, precipitation arrives across NW Oregon and SW Washington. Most likely it’ll be a rain/snow mix in the lowest elevations (where most of us live)
  • There’s a decent chance it falls as mainly snow for at least a few hours 7am-10am, even in the lowest elevations. It could get very exciting weather-wise for a few hours!
  • Temperatures remain ABOVE freezing Saturday night and Sunday = little or no sticking. If it falls heavily enough, it might briefly accumulate on cars/barkdust etc…
  • IF you live up around 1,000′ and above, there’s a better chance your neighborhood turns totally white for a few hours.
  • IF you live around 1,500′ and above, expect 1-3″ Sunday morning through midday. There are no spots in the metro area that low.
  • Highways/roads will remain snow-free Sunday in the metro area, except at/above 1,000′ where they could briefly turn snow covered.

THIS SHOULD BE A “CONVERSATIONAL SNOW” EVENT FOR THE LOWEST ELEVATIONS. That means everyone will be talking about it; plus posting Instagram/Facebook pictures of their dog/cat/pig/chicken/duck running wildly about outside, but it won’t affect our lives otherwise.


TECHNICAL DETAILS

A cool upper-level trough (the first of several) is sliding down north to south along the West Coast. This system is headed for California and far enough offshore that we’re seeing almost no showers inland. A mainly dry and cool airmass settles over us Friday & Saturday. Drier air filtering in from Canada gives us LOTS of sunshine Saturday; enjoy that day after a cold start. We’re not getting a “cold blast of air” by any means, just a bit colder.

By Saturday night another cold upper-level trough is sliding south along the BC coastline. A cold front then moves inland midday Sunday. Here’s a loop from the ECMWF model showing the movement from 1am to 7pm Sunday. Not exactly a “storm” eh? All models have been showing this scenario for several days and all agree on the timing; pretty good for 3-5 days ahead of time.

Freezing levels Sunday morning will be up around 2,000′ or so with this system, which typically means we might see snowflakes down to maybe 1,000′ and just a rainy Sunday morning in the lowlands. But a few things are different Sunday morning which should bring those flakes lower:

  1. Overnight cooling, while minimal, means this system comes in at the coldest time of day
  2. No significant “warming” onshore wind. There’s no cold/dry wind blowing out of the Gorge, but there’s no push of warmer air before 10am either. It should be mainly calm Sunday morning, at least for a few hours.
  3. There are signs we get a burst of heavier precipitation between 7-10am. Heavier precip = better chance for flakes to survive a longer fall through the atmosphere

These all point to a setup where snowflakes may survive falling all the way down to the valley floors west of the Cascades (less likely along the coastline) for a few hours Sunday morning. The reliable WRF-GFS model from UW shows the above freezing temps through Saturday night. At 4am it’s in the mid-upper 30s in Portland. This isn’t a setup where precipitation arrives at sunrise after a frozen night.

But as precipitation starts falling, look how surface temp drops to 33-36 degree range

Then 10am

That’s pretty much a snow sounding; at/below freezing except for the lowest 500′ or so. By 1pm Sunday, the cold front has passed, mixing (warming) the lowest layer of the atmosphere with a southwest or westerly wind. At that point we’ll just see rain or mixed rain/snow showers. It appears we have .25 to .50″ precipitation to work with, enough for 1-3″ in higher elevations where this falls as snow and sticks.

Models ALWAYS struggle with predicting snow totals in these marginal events. This morning’s ECMWF model continues the “little or no sticking snow” idea; you need to be up/above 1,000′ (or 1,500′) to make a snowman this time around

Note the coarse resolution here. I’ve purposely left it “unsmoothed” so you can see the model resolution. It doesn’t see the West Hills or Chehalem Mtn. at this 9 kilometer resolution. It also doesn’t “see” the Columbia River gap between Woodland and Longview, thus painting a bunch of snow for Kalama, Rainier, Longview, & St. Helens. It “thinks” the hills of Columbia county OR just merge into the hills above Kalama & Woodland. Higher resolution models (4km & lower) DO show those features, but we don’t have those today. They run just 72 hours out in time and only cover to 4am Sunday.

Alright, so that’s your first “big snow chance” for this season. That was a joke, it’s not a big snow chance. We MIGHT be close again early next week (either Monday morning or Tuesday night), but we can discuss later.

I still want to be clear that this is the not the beginning of a cold/snowy weather pattern. Sure, we’ll be getting more regular frost and overnight freezing. But no sign of an arctic blast through at least the first few days of February.

I probably won’t post tomorrow considering how minor this event will be; time to get out and enjoy the wintry outdoors. I’ll definitely be back with an update Saturday.

Chief Meteorologist Mark Nelsen


Warm Winter Records & Low Elevation Snow Thoughts

January 19, 2021

7pm Tuesday…

Just a brief post this time around to assist in your weekend planning.

It has been another mild day…back in the 50s. Hard to believe it took until January 19th to see our first frost of the new year too! We dropped to 31 in Portland this morning.

From the beginning of meteorological winter (December 1st) to this point, Portland has never seen so many 50+ degree days! It’s a record that goes back 80+ years. Salem hasn’t seen this many in 100+ years, same thing at Astoria. Even in Central Oregon, Redmond has seen more 50 degree days than any winter (so far) in the past 30 years. It’s truly been a mild winter to remember…so far.

The general plan continues the same through the next 8-10 days. Warm upper-level ridging is replaced by cool upper-level troughs dropping down over us Thursday, Sunday, and possibly next Tuesday. Beyond that time the troughing either weakens or shifts farther west = slightly warmer which would mostly eliminate the main chance for low-elevation snow. So for January it appears our “big chance” near the valley floor will be Sunday-Tuesday. But don’t get out the sleds yet…

In case that was already enough technical talk for you, I think these two graphics cover it well:

What we DON’T expect…

and what we DO expect…

For the rest of this month, it appears your plants are safe from a big arctic freeze. That’s still not in the cards. Just looking at the next two weeks (Euro model ensemble high/low average) you can see we “bottom out” Sunday through Tuesday, then rise back to around average again late next week. We may not be headed into a prolonged period of cooler than average weather. We’ll see.

Alright, how are we looking for Sunday at this point?

As you can see above, I think there’s a good chance that we may wake up to rain/snow mix even at the lowest elevations. But all models show temps near/above freezing that morning with a light southerly flow; we’re not going to have a snowy metro area locked in snow Sunday.

If you live at/above 1,000′ it could be a nice little 1-3″ snow event Sunday. Best bet would be northern Clark county hills along with higher parts of Columbia county (St. Helens/Scappoose) and Coast Range (Vernonia). Maybe central/eastern Gorge too. Possibly a dusting to an inch in Portland’s West Hills…maybe.

We will cover all this in more detail as we get closer…we’re still five days away.

Chief Meteorologist Mark Nelsen