Tomorrow’s Snow & Ice: Looking Better! Not as Snowy/Icy

December 7, 2016

11am Wednesday…

I’ve taken a look at all the overnight/morning maps and models.  Several things stick out:

  1. There is good agreement now that moisture doesn’t arrive until midday tomorrow (11am-1pm) in the metro area.
  2. Precipitation forecast is quite a bit lighter than what we were expecting 24 hours ago.
  3. I would hate to be a school administrator in this situation


I’ve gotta tell you, this system coming in tomorrow has a bit of a “bust” potential.  By that I mean there are several signs (as mentioned above and more below) pointing to a lower impact event for our metro area roads and there is also a decent chance some of us in the metro get very little snow OR freezing rain.  Don’t get me wrong, there should still be plenty of icy roads tomorrow and I think freezing rain could be a big issue by tomorrow evening for some areas, but not the “frozen hellish metro area” that I was thinking 24 hours ago.


WINTER STORM WATCH continues from the NWS.  A Watch means conditions are favorable for an event.  This could be converted to either a Winter Storm Warning or Winter Weather Advisory (not as big a deal) later today

Dry and turning extremely windy tonight and Thursday.  Peak gusts 70-80 mph in western Gorge by morning and 40-50 mph eastern metro plus west slopes of West Hills.  The rest of us see gusts 20-35 mph.

Snow arrives in metro area sometime between 11am-1pm.  It could immediately change to an ice pellet or freezing rain mix.

Metro Snow:  Nothing to a dusting far south & southeast metro to 1-3″ way out west of Hillsboro or close to the Gorge.  The rest of us should be in-between.  From Clark County to Longview…similar totals Trace to 3″.

Willamette Valley Snow:  Nothing to 1″ along I-5 Woodburn to Eugene.  A little more west valley, quite possibly no snow east of I-5 (Molalla/Silverton/Lebanon)

Gorge:  Snow arrives midday.  6-10″ possible central/east end, lighter west end.  Lots of freezing rain west end tomorrow evening through Friday AM.  Finally warming late Friday afternoon/evening

Coast Snow:  A little too warm for snow, although could be a brief dusting up around Astoria/Seaside midday…maybe

Metro Freezing Rain:  Regardless of the impact to roads (whether it’s warm enough or not), I think freezing rain will continue on the hills in the metro area and near/in the west end of the Gorge well into Thursday night. It might be just on trees and powerlines as temps hang right around or just below freezing, but that can shut down MAX and cause power outages


There are 3 big reasons I’ve pulled back on the forecast quite a bit:

  1. The “freezer door” is open for the next 24 hours (Columbia River Gorge transporting cold/dry air west of the Cascades), but the freezer dial isn’t set that cold.  I know, this blog posting appears to have just run right off the tracks and into a ravine…but hang on.  We’re starting with a warmer atmosphere than we’ve seen in past big events (January 2016, February 2014, December 2008)
  2.  Midday arrival means roads have a chance to warm up a few degrees.  With the strong wind blowing tonight, we’ll barely get down to freezing, then roads will warm to mainly above freezing by midday.  When the precipitation arrives, temperatures will fall back to around 30-32 for most of the metro area, but not much lower.   It’ll be “tough” to get roads to freeze again.  Sure, snow will accumulate on them.  But once we change to freezing rain, temperatures need to be 30 degrees or below to keep a road frozen.  Got it?  As a result I don’t think every single road will be frozen, like we saw back in early January this year and the February 2014 snow/ice events.  In fact it’s even POSSIBLE that many roads stay clear tomorrow afternoon away from the Gorge and in the central/south metro area
  3. Precipitation intensity is far lighter now on all models.  Lighter precipitation (either snow or freezing rain) means a bit less cooling of the atmosphere due to the dry air overhead.  Less accumulation on roads = fewer travel impacts  Check out the ECMWF total precipitation forecast through tomorrow evening at 10pm:


Wow…Less than 1/2″ precip.  That means even if all snow fell and it all sticks, at most you get 2-4″ in the metro area.  This is through 10pm as well.  The last 6 hours there’s no way it’ll be in the form of snow.  Then take a look at the ECMWF snow forecast:


Notice the WRF-GFS is very similar:


You see the light totals as well.  Your next question may be…why no snow on the east side of the valley and very little in Clark County?  That’s due to temperatures warming in the afternoon up around 2,000-3,000′.  Yes, the fabled warm tongue of air pushing north along the west slopes of the Cascades. Yep, it could be a total snow shutout if you live in Molalla/Oregon City/Silverton/Battle Ground.  It starts too late to stick much midday, but by that time it’s already warming overhead and you miss out on the snow!  Quite possible.

East wind will be very strong tomorrow and it appears it’ll continue through tomorrow night in the Gorge and east metro area. Check out the WRF-GFS for 4am Friday…that easterly flow will still be going near/in the Gorge


As a result I don’t expect a sudden warmup in the metro area until early Friday.  Luckily we aren’t starting out extremely cold so by the Friday morning commute it’s likely roads away from the West Hills and Gorge should be just fine.

I know it’s a long post so let’s wrap it up with a few questions…

  1. WILL SCHOOL GET CANCELLED TOMORROW?  Wow, that’s an extremely tough call.  If administrators don’t cancel and snow covers many roads and/or ice at 3pm that’s a problem.  If they DO cancel and most roads remain wet at 3pm…they don’t win either.  Sorry folks, no good answer on this one
  2. WILL THERE BE POWER OUTAGES TOMORROW EVENING/NIGHT?  Possibly in the hills and east metro area (especially east of I-205) with ice accumulating on trees/powerlines, definitely in the Gorge, but they all have generators out there!
  3. IS THERE A BIG FREEZE AHEAD?  No, this morning PDX dropped to 27 and it’ll only drop to around freezing or upper 20s in outlying areas tonight.

Chief Meteorologist Mark Nelsen







Major Winter Storm Ahead

December 6, 2016

5pm Tuesday…

The National Weather Service has issued a Winter Storm Watch for ALL of Western Oregon from the Coast Range to the Valleys FOR THURSDAY.


So here we go folks…at this point it appears that Thursday we’ll see the biggest snow/ice event we’ve seen since early February 2014.  Yes, we’ve gone two winters without a major snow/ice event.  Although we DID have an all day icy/snow episode early last January that gave us 1″ of snow.

What’s going on?  It’s our classic snow/ice storm pattern:

  1. Cold and dry air is moving in now, and by tomorrow at this time the freezer door will be wide open.  That means east wind gusts 40-50 mph as that cold/dry air pours out of the Gorge from Eastern Washington.
  2. Thursday morning a low pressure system slides north along the coastline, pushing abundant moisture OVER THE TOP of the cold air mass in place
  3. The air mass should be cold enough to support some mix of frozen precipitation (snow or freezing rain) all day in the Metro area, Gorge, & Kelso/Longview.
  4. Likely cold enough for brief snow than freezing rain for at least the first part of the day in the Willamette Valley.

This should give you a good idea of what we’re expecting…




Once cold air is stuck in the Columbia River Gorge, it’s extremely difficult to modify (warm) that air mass.  It takes several days IF we don’t get a warming westerly wind.  And as of this evening no model shows a warming west wind in the Gorge Friday.  So I think the Gorge will see the worst weather…likely blizzard conditions Thursday as the snow falls heavily.


Of course you all want to know…“how much snow am I going to get at my house?”.  The short answer is that we don’t know yet, but it’s fair to say in the metro area 1″-5″ is reasonable and a Trace-4″ in the Willamette Valley.  That’s a real rough guess.

Except for the Gorge and Cascades, that snow forecast is a real problem.  That’s because above-freezing air will be moving in up around 2,000-4,000′.  Once that occurs, then it’ll just be freezing rain and/or ice pellets until the temperature at the ground goes above freezing.  And warmer air above will arrive at different times in different parts of the valley.  So let’s say it remains as all snow all day Thursday for you…probably 5-7″ of snow!  But if the changeover happens quickly, you might only get a dusting.  Generally, the closer to the Coast Range you are (due to cold air piling up against eastern slopes) and closer to the metro area/Gorge, the better change you’ll hang on to the snow longer.  Of course models have a tough time predicting snow totals to start, but this really screws up those snow maps!  Our RPM, not usually a good performer in these east wind snow events, just shows very light totals before changeover, even in the metro area:


The WRF-GFS does a little better:


It shows the heavier snowfall up against the Coast Range AND down into the Valley.  Supposedly Clark County gets left out…r.i.g.h.t…  See the problem here?  I guarantee the next run of the same model will look different.  It’s still almost 2 days out and we’re going to see some last-minute twists and changes in the forecast the next day or so.  There is still time to figure things out.  We do know there is plenty of moisture coming in from Thursday morning through Friday morning.  Check out the RPM rain forecast!  If it’s all snow, you can get about 10″ of snow for each 1″ of rain.  You can see the possibility in the Gorge can’t you?  Theoretically 20″ of snow could fall (and has in past snow storms there!)


Of course once we get into the cold air then we look for a warming south or westerly wind to bring those temps above freezing.  Now that the unreliable GFS model has come around to the ECMWF on timing (morning start Thursday), we can compare them a bit more closely.  The GFS brings a deep low up toward the NW Washington coastline, turning our wind gusty southerly Thursday evening/night.  The ECMWF barely gives us a breath of southerly wind late Thursday night and never gets rid of the easterly gradient in the Gorge!  That’s due to a much weaker low just offshore, with the main low center much farther west.  For now I’m going with a slow warmup like the more reliable ECMWF.  That means it’s still frozen in the Gorge Friday morning and we ever so slowly warm up Thursday night and Friday in the metro area.

To sum it up:

I’m quite confident that a big storm is coming for the Gorge and much of the metro area.  Thursday will be one of those days you may not make it into work or school.  Friday is a question mark…there could still be a lot of snow/ice left around.

More tomorrow!  Chief Meteorologist Mark Nelsen


Light Snow Showers Tonight

December 5, 2016

6pm Monday…

That was exciting earlier today; I think we all saw the snow and it appears just about all lowland areas stayed in the ZERO-1″ range we forecast.  It’s rare to get this lowland snow shower pattern just right.

So where do we go from here?  Basically the moisture supply dwindles tonight and tomorrow, so showers taper off and become more widely scattered.


With temps creeping back down close to freezing, a heavy snow shower COULD dump a dusting of snow just about anywhere.  That said, I bet 80% of us in the lower parts of the metro area end up with bare ground in the morning.  The RPM model paints that picture well…only scattered spots get 1/2″ or more, up in the hills


There is an additional issue.  Lots of wet roads.  In such a chilly air mass, any clearing sky could lead to icing on any exposed surface.  That means your local street could be icy during the morning commute.  OR, it could be icy from 1-3am, cloud cover moves in, and the ice melts.  In general I think we’ll be more cloudy than clear overnight so I didn’t hit the icy streets to hard in the forecast.

To summarize, our GO GUIDE covers it:


Give yourself a bit of extra time to check conditions (temperatures) before you head out Tuesday morning.  Then plan on some bright sunshine in the afternoon.  Well-deserved sunshine I think!

Chief Meteorologist Mark Nelsen


Post your Monday morning snow totals

December 5, 2016

Did you get snow at your home (or work) today?  Some of us did, a lot of us didn’t.  If you got 1/2″ or more put it in the comments below like this:


We just need your location and depth, and elevation if you know it.

Keep weather discussion on the previous or future postings.


9am: No Sticking Snow For Most Today

December 5, 2016

Good Morning!

As I mentioned yesterday, if we don’t get heavy enough precipitation to drag down the snow level, the snow level will stay higher today (read in previous post).  That’s exactly what has happened.  Only .10-.15″ precipitation for PDX, Vancouver, & Hillsboro.  In fact Troutdale has only seen a trace!  As a result we’re at the lower end of that ZERO-1″ I forecast in the lowest elevations.  It’s been a mix of rain/snow showers, and the cool atmosphere can’t overcome the breezy/mixing southerly wind we were expecting as well.

This has screwed up the hilltop snow forecast.  I expected 1-3″ up around 1,000′ and above.  The lack of heavy precipitation is putting us at the lower end of that for sure.  So far at 1,000′ at my home (east of Troutdale) I have just a dusting.

You may remember my rant about snow level forecasting in these showery patterns.  We’re doing people a disservice by implying we have more accuracy than we do (in this pattern).  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:


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


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.


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′.  There you go…rant over for now.


  1. Snow showers or snow/rain showers continue.  Some maybe be heavy this afternoon with a rumble of thunder if we get some sunbreaks inbetween.  Hail or ice pellets are possible too.
  2. NO ACCUMULATION AT THE LOWEST ELEVATIONS…HIGHWAYS REMAIN TOTALLY CLEAR unless we get hail/ice pellets out of a heavy shower suddenly in just one location.  Evening commute should be fine.
  3. A Trace to 2″ is still possible at/above 1,000′…more the higher you go


Snow showers continue, could be a dusting on the hills overnight, but nothing likely in the lowest elevations.  Assuming we stay mostly cloudy, I don’t think leftover wet roads freezing are a problem, but I’ll look at that more closely this afternoon.

Chief Meteorologist Mark Nelsen




Monday Morning Snow: Who Gets It and Who Doesn’t

December 4, 2016

3pm Sunday…

It’s a  refreshing day out there with partly cloudy skies and just a few light showers.  I came over the Coast Range midday and not a snowflake, or even snow-dusted tree in sight.  Very nice.  But tomorrow morning/midday will be far different.  So glad we never forecast snow (or anything close to it) for Sunday here at FOX12.

Let’s jump right into the highlights for all of you that just want to know what to expect tomorrow without the hype or technical details…


We will not be having a snowstorm tomorrow in the lowest elevations of western Oregon or most of SW Washington.  But we should ALL see snowflakes in the air or even briefly heavy snow falling and SOME of us will get some snow on the ground.

We can’t predict the sticking snow elevation (the “SNOW LEVEL”) well in these “snow shower” patterns like we have tomorrow.  No matter how often someone tells you it’s going to snow down to 750′, or 500′, or 250’…forget that nonsense…I generally stick to 1,000′ increments in these situations nowadays.  That’s because (for example) heavy showers in one location could drag the snow level down to 300′, yet just light showers 10 miles away don’t drop snow at 1,000′!  I’ve seen that happen many times.


Partly cloudy skies tonight with a few light rain/snow showers as temps cool into the mid 30s

  • Between 4-9am a batch of snow showers move through NW Oregon and SW Washington (during the commute)
  • Lowest elevations of all the I-5 corridor cities (including Portland): expect ZERO-1″ accumulation during that time.  If the showers are heavy enough, up to 1″, if it’s just light stuff that doesn’t drag enough cool air down for “stickage”, then forget it…just flakes in the air or a dusting on grass/cars.
  • Up around 1,000′ and above expect 1-3″ snow during that time.  < Pretty confident on this.

I expect no big traffic issues on major highways/freeways in the metro area, I think the AM Commute should be okay in the cities and lowest elevations.  MAYBE some slush up at Sylvan on Hwy 26 briefly if the showers are heavy enough.

There will be snowy/slushy roads up around 1,000′.  Or at lower elevations in central/northern Clark county where the showers will be heavier.  Possibly Scappoose/St. Helens as well.

Regardless of what happens during the AM Commute, afternoon/evening temps remain well above freezing so lowland roads will be bare and that dusting to 1″ will have melted.  It’s unlikely we get a sudden freezing in the evening hours there.  Of course there could still be leftover snowy/slushy spots up around 1,000′ and above.

COAST:  Too warm, just rain/snow showers mixed

GORGE:  I-84 (near sea level) remains clear, hills up around 1,000′ get snow just like westside though

COAST RANGE SUMMITS:  Snowy at times, especially early.  First icy driving of the year.  A little better early/mid afternoon with warming temps.

We dry out tomorrow night and Tuesday

A GREAT TOOL FOR CHECKING YOUR ELEVATION I love this one:  Put in your address and it’ll tell you how high up (or how low) you live.



If we don’t get heavy showers tomorrow morning, there could easily be nothing accumulating anywhere below 1,000′ due to a marginally cold atmosphere (only -5 to -6 at 850mb), breezy/mixing southerly wind, and no cold air mass already in place.  Let’s pretend it’s the old days (like 1995-2000), and we don’t have these high-resolution models:  I’d just be forecasting “sticking snow above 1,000′, with no accumulation likely in the lowest elevations”.   When I look at the WRF-GFS cross-section, that’s very marginal for snow.  I prefer to see the “zero” line (32 degrees F) a bit closer to sea level with that well mixed southerly flow setup.  Again, if we don’t get heavy showers this is going to be a non-event in the metro area.


I think our RPM model’s forecast of snow accumulation pretty much represents what I’m forecasting on-air tonight and in the highlights above:


The heavier stuff is over the hills and higher terrain of the metro area.  Do not read maps like this too “literally”.  By that I mean (for example), you shouldn’t think the northern part of Lake Oswego could see 1/2″ but the south side gets an inch.  Models aren’t that great yet.  That model data is then contoured by a separate program too, introducing other issues.  The general idea is that we’re not getting a big snow event tomorrow, but it’ll be a close call for many of us and there will probably be plenty of two-hour school delays in the hills.

For some reason the WRF-GFS model from the UW is very bullish on Clark County snow:


It also thinks 2″ is going to fall over Portland’s central/eastside areas.  I doubt that will happen.  Forecasting exact snow amounts any day is tricky, but forecasting them off of randomly placed showers is a bit crazy.

You can also see on the map above what I talked about with snow level forecasting.  Lighter showers in the higher elevations southeast of Oregon City produce almost no snow in those hills up around Redland near 1,000′, yet 2″ at PDX near sea-level.  You get the idea hopefully…don’t read too much into any one model in this sort of pattern.  It IS notable that both the GFS and ECMWF generate almost nothing over us:



So there you have it.  We do dry out Tuesday and Wednesday, and on Wednesday we’ll get a strong and very cold east wind.  That sets us up for some sort of freezing rain and/or snow event by Thursday morning in the Gorge, and likely in a good part of the metro area too.  The good news is that upper-level westerly flow is resuming with lots of wet weather just beyond with onshore flow.  That’s going to dispatch the cold air coming through the Gorge relatively quickly.  I think it’s a 1 day event for the metro area Thursday.  It COULD last into Friday in the Gorge…we’ll see.

Chief Meteorologist Mark Nelsen

A Busy Weather Week Ahead: Low Elevation Snow Update

December 3, 2016

10am Saturday…

I’ve been checking all the latest maps/models and meteorological goodies over my morning drink.  Doesn’t everyone else wake up on a Saturday morning and do that as well???

December-February is winter as far as meteorologists are concerned, and west of the Cascades just about all our winter weather (snow/ice/big storms) occurs in December/January most years.  Right on schedule, next week will be our first wintry week of the season with a:  1) strong cold front Sunday morning,  2) marginal snow event for the lowlands Monday, and 3) possibly a widespread snow/ice event in the metro area and (for sure) Gorge Thursday.  Beyond that we’ll most likely warm up again.


A strong cold front will pass through the region very early Sunday morning.  In fact by the time you wake up it’ll already be down around 40 degrees and there may even be snow mixed in up in the hills, but no sticking below 1,500′.  Then at midday the rain stops and skies break open to sunshine.  Sunday afternoon looks great!  Partly cloudy and mainly/all dry with light wind.  Last chance to hang your Christmas lights in dry and comfortable weather for a while.  Late Sunday night and the first part of Monday is when it gets real interesting.  A “cluster” of showers moves inland, right after skies have cleared overnight.  At this point it’s marginally cold enough to get sticking snow down to the lowest elevations west of the Cascades.  But if we get a burst of heavy enough showers, we could easily get some of that snow to stick down here at the valley floor.  Very tough call in these situations.  If you want it to snow, we have the overnight cooling to help us, yet we also have a mixing southerly wind that tends to keep the snow level off the valley floor.  Models are in very good agreement showing .15″ to .30″ precipitation during this time.  That would be enough for 1-3″ snow accumulation if it all made it to the ground.  That’s very unlikely in the lowest elevations.  But I’m not paid to just see-saw back and forth over what may or may not happen…this is what I think is most likely…


  • Rainy start Sunday, then dry and partly cloudy, no sticking snow below 1,500
  • During Monday AM commute, EVERYONE WILL SEE SNOW IN THE AIR as snow showers arrive before sunrise
  • If you live ABOVE 1,000′, expect 1-2″ snow on the ground by mid-morning
  • If you live in the higher hills around town (West Hills/Mt. Scott/Sylvan) near 1,000′, expect a trace to 1″
  • At the surface (where most of us live) a dusting is possible, maybe even up to 1″ on the lawns/barkdust
  • I DON’T EXPECT MAJOR IMPACTS TO THE A.M. COMMUTE ON HIGHWAYS/FREEWAYS, but probably very slow as we all gawk at the snow
  • SOME SNOW WILL GET ON ROADS HIGHER UP IN HILLS (for sure above 1,000′)
  • Monday afternoon commute will be uneventful with temperatures in the upper 30s and scattered light showers

So obviously we’re all going to really excited about seeing the first snow of the season, but a bunch of snow accumulating on metro highways is pretty unlikely in this pattern.

Note the different model snow forecasts.  It’s important not to read these too “literally” because the terrain of the model may not match the actual terrain.  For example, notice on all three there is significant snow on I-5 between Longview and Woodland.  That’s because the narrow gap the Columbia River cuts through the hills isn’t resolved on this resolution model, so it just thinks the hills continue right across the low areas.  The West Hills, Chehalem Mtn, and south Salem hills show up nicely on the WRF-GFS (middle image) though.  The same thing happens in the Gorge.  Most models (unless they have less than 5 km resolution) just see the Gorge as a low mountain pass.  Thus Cascade Locks may be seen as a 2,000′ pass instead of at sea level, similar setup for Hood River too.




Whatever happens the first half of Monday, by afternoon it’ll just be snow/rain showers in the lowest elevations as temperatures “warm” up to 40 or so.

We might have a leftover flurry Monday night or Tuesday, but for now it looks like far less moisture available.  Beyond that time we go into dry and cold for a couple of days.


On Wednesday a cold east wind starts blowing out of the Gorge and that sets us up for what we call a “transition event”.  Here in the lowlands of Western Oregon and SW Washington there are two ways we get snow (generally).  The first is the showers flowing onshore like Monday which involves no cold/dry continental air coming in from the east.  On Monday the lower elevations of the Gorge have the same weather we do in the western valleys.   This first situation rarely provides much snow and it’s always a real marginal situation.  I don’t think I’ve ever seen it below 30-32 degrees in this pattern.

The 2nd way we get snow is when cold air is in place (often via cold air moving in from the Gorge) and then moisture returns from the west overhead.  This typically is at the end of a cold period.  That pattern is how we get our big/significant snow/ice storms.  That setup is coming either Wednesday night or Thursday.  And this far out details are very much subject to change.

By Wednesday night a very strong east wind will likely be blowing through the Gorge and out into the metro area.  10-12 millibars easterly gradient = brrrr!  That’s the usual gusts to 100 at Vista House and 70 mph in most of the usual windy settlements at the west end.  At the same time a warmer front is approaching.  Check out the WRF-GFS map for late Wednesday night and you can see thick cold air dammed up in the Eastern Gorge, pouring out the west end:


I’ve been around this block a few times…that setup, along with a bunch of precipitation arriving, screams SNOW STORM IN THE GORGE and/or ICE STORM FOR PART OF THE GORGE.  Or most likely a combo.  If the air is cold enough, this could be a snow/ice event in the metro area too.  We won’t really know the details of that until Wednesday when the colder air is in place.


  • Some sort of significant snow/ice storm is likely in the Gorge either late Wednesday night or Thursday
  • It MAY be cold enough for snow and/or freezing rain in at least parts of the metro area too
  • Whatever happens will most likely occur overnight Wednesday night into Thursday

Stay tuned!

Tonight I’ll be out in Seaside for the Providence Festival of Trees.  It’s a great event to raise money for the Providence Seaside Hospital Foundation.  Stop by and say hello if you see me.  Just don’t shake my hand…I think I have some sort of cold coming on…poor timing…

Chief Meteorologist Mark Nelsen