Did You Expect A “Snowmageddon” This Week? What Went Wrong (Hint: It Wasn’t The Forecast)

8pm Thursday…

I’ve wanted to write about this issue for a couple years, but figure now that the weather has calmed down would be a good time.  That’s with memories of snow still fresh in our minds.

By the way, snow showers tonight will return, with ANYONE west of the Cascades possibly seeing something briefly stick.  More likely is a covering of snow on higher hills.  Yet it’s just showers so accumulations will be spotty.  A hill at 1,000′ in one part of town may be bare but 20 miles away at sea level there could be a dusting.  Scattered showers.

After tomorrow midday, snow levels jump back up to around the passes.  This is quite possibly our “last chance” for snow this month.

So did you have the impression we had significant snow on the way this week?  Like a snowfall that could paralyze the metro area and give us a hellish commute?

Here’s the forecast timeline:

About 10 days ago we first put “mixed showers” in our 7 Day Forecast for this past Monday.  Yes, it’s a tough decision whether to throw a snowflake/rain mix into the forecast.  Because viewers and coworkers notice immediately.  Models clearly showed a cool/showery weather pattern, but not one that produces widespread snow.  So seven days ahead of time we forecast those mixed showers with a high of 40 for this past Monday.  For the following 6 days we had a high of 39 to 41 degrees for this past Monday and kept the same forecast.  That’s exactly what happened!

How about Tuesday?  We first forecast “mixed showers” six days ahead of time.  Then we changed it to “flurries and sun” five days ahead of time when it was obvious there wouldn’t be much moisture left that day.  Guess what?  We had flurries, sun, and a little graupel that day.  Highs were always forecast between 35-37.  We hit 40 with the sunbreaks.  Close enough, so for seven days we had a great forecast for Tuesday as well!  No problem so far…

How about Wednesday’s forecast?  This is where things got a bit more intense and we as forecasters were thinking could be the “real deal”.  Models were generally telling us we might have the perfect setup for large regional snow/ice event with cold east wind pouring out of the Gorge.  Or maybe just in the metro area, depending on the model.  Six days ahead of time we had “snow developing” and “snow or freezing rain” in the 7 day Forecast for Wednesday/Thursday forecast with highs at/below freezing.  That would definitely imply something big might be in the works.  For three days we kept that general wording, telling you something like this:

By Saturday, still four days ahead of time, I said this in the blog about Wednesday’s possible “big event”

By Sunday afternoon, the chance of a major event Wednesday was still alive, but on life support.  Some models were pushing the big low offshore farther north, ending our brief cold spell quickly. Our most reliable models (ECMWF & GEM) were saying there would be little or no snow…3 DAYS AHEAD OF TIME!  I wrote this on the blog Sunday evening:

Then by midday Monday it was very clear Wednesday could easily be a non-event.  From my post that day:

TO SUMMARIZE OUR FORECASTING HERE AT FOX12

We nailed the Monday/Tuesday forecasts well ahead of time, calmly letting you know that your “life would continue as normal” through most of this period.  Expect to see snow in the air but not much on the ground at the lowest elevations.

We did indeed indicate Wednesday/Thursday could bring life-altering snow/ice to our area, but backed off drastically 2-3 days ahead of time.  We know that can be the case as we get closer to an event.  Would it have been better to ignore it and then suddenly spring a snowy/ice forecast on you just two days ahead of time?  I don’t think so.  Keep in mind we can’t just leave those last 2-3 days of the 7 Day Forecast blank!  We have to put SOMETHING in there.

WHY THE FEELING THAT A “SNOWMAGEDDON” WAS COMING?

I think it’s a combination of factors:

Today’s connected world:  There is a constant flow of information on TV, smartphones, & the Internet.   Rumors of snow, ice, cold move around in circles and pass through social media instantly.  The volume of information is staggering; we are exposed to far more “snow may be coming” posts/blogs/tweets than even 10 years ago.  Every news/media organization is promoting their brand or business. I think it’s perfectly natural for a person to think “wow, something big must be on the way” when they are seeing so much of this info.  Alert after alert, notifications promoting a newscast, web page, newspaper app, etc…   How could I not think a snowy/hellish commute is headed for Portland?

Government organizations prepare for the worst, as they should.  But that worst-case scenario can appear to be THE forecast.  Leading up to a snow event, city leaders, PBOT, ODOT, WADOT, & counties often put out media releases, tweets, hold live news conferences, show off their newest plows, compare sand/salt pile size, etc… It’s a constant feed of “WE’RE GETTING READY FOR SNOW”.  And of course they should always prepare for the worst.  After seeing all this info, it’s easy to think “something big is on the way“.  No one is doing anything wrong here, that’s just how it is.

Some people WANT to see a good snowstorm.  I think plenty of the recent complaints are from people genuinely disappointed we didn’t get a good 2-5″ snow event.  That’s fair, but a forecast of a dusting to 1″ up on the hills doesn’t mean we’re “forecasting snow for Portland” and missed it.

A final one, snow forecast maps from models passed around social media.  I actually didn’t see it much this time around.  It was an issue last February when one local news organization put out a snow map showing 15″ of snow in Portland.  These move around as fast as lightning!  Generally I don’t like to post images more than about 3 days ahead of time.  Notice I didn’t post any snow forecasts for the big Wednesday event here on my blog?  This is why.

What do you think?  What did I miss.  I’ve got a tough skin and would love to see your comments on my Facebook page:  @MarkNelsenWeather

 

Wednesday Evening Update: Snow into edge of metro area

8:45pm Wednesday…

Today turned out pretty much as expected, with a few last minute twists & turns.

1. We saw a rain/snow mix which changed to mainly rain as the cold front moved through during the evening commute
2. Clark county warmed up to around 40 as our “mesoscale” models showed; no snow for most of you up there.
3. No measurable snow for almost all of us.

What was different than expected?

1. Cold Gorge wind was very persistent (surprise!).  Although quite a bit more reasonable compared to a few hours ago, it is still transporting cold continental air westward into the eastern edges of the metro area.  Temperatures are hovering just above freezing in a narrow area along the Columbia River east of I-205
2. Due to that, plus the cooling air overhead, snow has been falling for several hours in the western Gorge, all the way into Camas and Washougal.  Just got a report that two inches have fallen in Bridal Veil, that’s where we should have only seen freezing rain.

Take a look at current temps, only the numbers below 34 degrees plotted below. (click for a better view)

Areas to the right of the yellow line are generally seeing snow.  Mainly or all rain to the left.  Yet in general the snow level west of the Cascades is around 1,500 to 2,000′ right now.  Then how is it snowing down to the Columbia River in Clark and Multnomah counties?  What would typically be about a 1,500′ snow level right near the Gorge and into Camas/Washougal has become “sea level snow” since the last 1,000′ or so are near/below freezing due to that east wind; snowflakes are coming down much lower than one would expect in this pattern.   Due to this, and more precipitation on the way, the NWS has upgraded the western & central Columbia River Gorge to a Winter Storm Warning.  3-6″ likely in these areas.  The pressure difference through the Gorge does continue to weaken and it’s possible at some point Camas/Washougal/Troutdale lose the easterly wind.  If so temps will rise a few degrees.  They sure won’t go down any lower through tomorrow morning.

Through the rest of tonight we’ll see waves of showers moving onshore behind this evening’s cold front.  In general the snow level will remain above 1,000′ through tomorrow morning.  But anyone at/above that elevation in the metro area could see a skiff of snow on the lawn/barkdust/car.  Same setup again tomorrow night and Friday morning.  Beyond that time we’re headed back to a milder weather pattern for the last 1/3 of January.

Chief Meteorologist Mark Nelsen

First Snow & Rain Moving Through At Midday

11am Wednesday…

So far things are going about as planned weatherwise.  Temps dropped to below freezing for most of us last night.  As of 11am all parts of the Willamette Valley up into Kelso/Longview are above freezing, a gusty east (cold) wind is blowing out of the Gorge, and a bit of “downsloping” southeasterly wind has arrived in the Cascade foothills, central Willamette Valley, and Clark county.

Now the first band of snow and rain is passing overhead.  I’ve seen reports of snow in St. Johns, McMinnville, but just rain in central Portland.  A mix in Beaverton too.  Looks like McMinnville was able to get a dusting as that passed overhead:

WHAT’S HAPPENING AS OF MIDDAY?

At 4am the balloon sounding over Salem said “all snow”; the air was below freezing all the way up through the atmosphere.  But that has changed; there is a huge storm that has developed off the coastline.

We are on the east side of that storm, which means strong south and southeast wind developing in the lowest few thousand feet of the atmosphere.  The air just above the surface up to around 3,000′ is warming quickly.  That continues until a cold front passes overhead around sunset (the sharp back edge to the cloud cover).  So for the next couple of hours it’ll be a rain/snow mix until temps get a bit warmer overhead.  As you can see the temperatures down here at ground level are too warm to allow snow to stick and we’ll remain above freezing through tonight.

All the mesoscale models (with better terrain and resolution) say no sticking snow in metro area tonight, including Clark county.   The WRF-GFS model was perfect showing temperatures rising up to around 40 or higher in a weird sort of southeasterly “downslope” wind flow up there.  Here’s the snow forecast through 4am

and the NAM-NEST model is similar, this is ending at 1am

The mixed precipitation should change to all rain as the main cold front band passes overhead 3-7pm.  After that it’s frequent showers tonight.

SUMMARY FOR LOWLANDS WEST OF THE CASCADES

• Mixed rain/snow continues at times through early afternoon, changing to mainly rain.  Although a mix likely continues up in northern Clark County and maybe Columbia County around Scappoose and St. Helens.
• Mainly rain showers tonight, although mixing with snow on hills.
• Could see a trace to 1″ eastern metro hills up around 1,000′ and above.  1-3″ above 1,000′ possible any of the Cascade foothills (east of Battle Ground, Camas, Sandy, Silverton etc…)
• Freezing is unlikely in metro area tonight.  But just like the last few nights, there could be spots where breaks in clouds allow some local freezing.  If it happens most likely it’ll be west metro areas.
• Scattered light showers Thursday, still mixing with snow at/above 1,000′

 

COLUMBIA RIVER GORGE

A bit more complicated here because a shallow layer of cold air isn’t going anywhere.  This isn’t quite the typical situation since the real cold air is only about 2,000′ thick.  But since it’s not a real warm atmosphere overhead there should be no problem keeping precipitation type as snow from Bonneville Dam eastward.  There’s a very narrow area at the west end of Gorge that will see freezing rain late this afternoon/evening.  That’s from near Corbett/Cape Horn east to about Multnomah Falls.  Then back to a snow/rain mix later tonight in those areas.  So east of Multnomah Falls or Bonneville, expect a Trace to 4″ in the Gorge.  The trace would be out near The Dalles…just not that much precip to work with.

 

 

Bright Sunshine Today; But How Close Will Snow Get To Us Wednesday?

Noon Tuesday…

Last night’s forecast worked out well for the most part.  There was a dusting of snow in spots, even down to sea level.  I picked up 1.5″ at 1,000′ at home, and of course nothing measurable fell in Portland.  This continues to be a snowless winter (officially) in Portland.  By the way, someone was complaining about that yesterday on Twitter.  You know we’ve had three consecutive winters with significant snow in Portland.  It would be nothing unusual if we get no snow the rest of the season.

Today we’ve transitioned to just a few scattered showers with lots of sunbreaks.  GOES-17 image shows the breaks between the clouds

One part of the forecast I missed was a very thin layer of subfreezing arctic air that slipped into the eastern Columbia River Gorge last night.  Temps fell into the 20s as far west as Hood River.  In fact it was less than 1,000′ thick at that location; Parkdale stayed warmer than the lower valley.  I see some accidents along I-84 Hood River to The Dalles due to snow/ice on freeway.  There might be some brief thawing this afternoon with a brief westerly wind back in place for a few hours.

WHAT’S AHEAD?

There is a good chance we get no measurable snow in the next 48 hours for the vast majority of the metro area. 

Why?  Probably too “warm” for almost all of us.

Models have been pushing tomorrow’s strong weather system farther offshore and north the past two days.   We get our big snow/ice events in the metro area when cold air surges in from the Gorge and moisture runs over the top of that cold air.  With the system tomorrow now well forecast to be north of our latitude, we don’t get a significant push of cold air from the east.  Strong southerly wind, not just at the surface but a couple thousand feet overhead, overwhelms the cooling coming in from the east.  As of midday, there is only one model trying to produce snow west of the Cascades, and it has been the most unreliable lately.

So here’s what I think is most likely tomorrow through Thursday morning:

• No snow at the coastline or anywhere south of the metro area.  That means no snow for Woodburn, Molalla, Salem, Albany etc…
• During the afternoon hours tomorrow (with temps between 36-42 degrees) precipitation arrives.  It’ll probably be a rain/snow mix in the metro area.  Best chance for an all snow start would be north of the Columbia River (Clark County).  There is the slightest chance it sticks up there, but temperatures would have to fall 5 degrees or more.
• It’s unlikely we get any sticking in the metro area from the Columbia River south.  It might even be tough to get sticking snow up on the West Hills, Mt. Scott, Chehalem Mtn.
• Temperatures remain above freezing tomorrow night, unless rain showers end and a few spots clear out.  Then we’d get the usual “wet roads turn icy” in spots.  We saw that in Washington County this morning.
• Thursday we’ll see scattered showers, although snow level remains relatively low, around 1,500′ in the afternoon…more Cascade and foothill snow!

MOST IMPORTANT:  We will know by midday tomorrow (if not earlier) for sure since we’ll see what temperatures/dewpoints are doing and if we’re actually getting any cold air out of the Gorge.  If we get to late morning and there’s no cold air pouring out of the west end of the Gorge then it’s over, even for Clark County.

Columbia River Gorge

It’ll be cold enough for snow tomorrow afternoon/night/Thursday AM east of Multnomah Falls, but there won’t be a ton of moisture to work with.  Expect 1-4″ snow from tomorrow afternoon (maybe not until late) through Thursday morning.  Western Gorge will warm quickly like the metro area.  Maybe just brief snow/freezing rain late tomorrow afternoon around Cape Horn, Corbett…etc.  It’ll depend on the temperature.

DISCUSSION

Only the #Sad GFS model is hanging on to snow chances tomorrow afternoon/evening.  The dependable ECMWF and WRF-GFS say forget it.  The reasoning is clear; I’ve never seen significant snow with 1) No cold arctic air in place + 2) isobar orientation forecast.  The low pressure center offshore is too far north.  There isn’t any strong pull of cold air from the east on all models except the GFS.  Check out ECMWF snow forecast

And even better, the WRF-GFS.  When we’ve had marginal situations, there is at least a hint of SOMETHING across the lower elevations.

Brian MacMillan and I were just discussing that we’ve never seen a significant snow event when this model doesn’t even have a hint of snow at the lower elevations.  Yes, even in the busted forecasts (surprise snow!) there has been some sort of hint.  You can see why in the surface map for 4pm (colors are temperature at ~2,500′) tomorrow, above freezing at that elevation plus very little cold wind coming through the Gorge.

Then check out the cross-section over Portland.  The “0” line is the freezing level.  Time runs the opposite of what you’d expect.  4am this morning right side, 4pm Friday afternoon left side.  Highlighted along the bottom in yellow is 1pm to 10pm tomorrow. Far too much mild southeasterly flow overhead to bring snow close to sea level.

To wrap it up…my gut feeling is we see light rain tomorrow afternoon/evening, maybe with some snowflakes mixed in.  But that’s it.  Hopefully the midday/evening runs of GFS model come back to reality and get rid of the snow chance for good.  Sorry kids!

I’ll be on TV starting at 4pm today…see you there.

Chief Meteorologist Mark Nelsen

 

Snow Outlook: Monday Midday Update

Noon Monday…

Ah, the curse of the onshore southwesterly wind.  As mentioned yesterday, we almost never get anything significant snow-wise in the lower elevations with onshore-flow showers.  That’s why I went with nothing in the valleys for this morning and a trace to 1″ up around 1,000′.  But even that TRACE forecast was a bit aggressive in the metro area.  Sticking snow was mainly north of the metro area (Rainier, Longview, Kalama etc…) in the hills.  Nothing in the West Hills or at my home @1,000′.  A non-event for all of us in Portland.

By the way:  I recommend you follow me on Facebook (search for me @MarkNelsenWeather) and Twitter (@MarkNelsenKPTV)  I post updates there more frequently than on this blog.  Much quicker to do that than an expansive blog posting.  Especially when things change quickly and I’m on-air.

Right now a weather system moving into southwest Oregon is spreading steady light rain or light snow (depending on your elevation) across the area.  I’ve got all snow here at home, and it’s just barely sticking at 34 degrees.  The steady precipitation continues through this evening and then goes back to light showers by 10pm or so.  Those light showers continue through Tuesday.

HIGHLIGHTS

• THE EVENING COMMUTE WILL REMAIN CLEAR ALL AREAS BELOW 1,000′  from Longview to Eugene.
• A bit of cooling mean snow showers will stick a bit lower, with a dusting possible on the hills around the metro area later this evening/overnight.
• Up around 1,000′, expect a Trace to 1″ snow, maybe up to 2″ closer to 1,500′.

TUESDAY MORNING COMMUTE SHOULD BE CLEAR.  But patchy areas of snow on the ground, mainly on hills.  Expect some snowy roads up around 1,000′.  That’s the top of the West Hills, Chehalem Mtn, and Mt. Scott.

The rest of Tuesday we’ll see scattered showers and sunbreaks, more dry than wet/white.

TUESDAY EVENING’S COMMUTE WILL BE ALL OR MAINLY DRY

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DISCUSSION

Onshore flow continues tonight and Tuesday, but as the system passes by to our south this evening colder air is pulled in overhead.  That should drop sticking snow lower, but then there won’t be much moisture left for snow showers tonight.  Technically ANY ELEVATION could see a dusting tonight.  But no models are showing significant or life-altering snowfall in the lowlands.  The WRF-GFS thinks it’ll be juicy enough for 2″ top of West Hills and Chehalem Mtn, but notice the lowlands stay all clear.

ECMWF agrees that Tuesday morning should be a non-event for 95% of us in the cities

And NAM-Nest3km is #SAD for the next 24 hours…

There is an arctic front tantalizingly close to us.  That’s the leading edge of very cold/dry Canadian air.  If that moved over us right now, this snow/rain mix would change Portland to a snowy, gridlocked mess.  BUT, it’s stalled up north around Seattle west of the Cascades and Hermiston/Boardman east of the Cascades.

That boundary won’t get any closer through tomorrow because the surface low moving into eastern Oregon this afternoon/evening pulls in more westerly flow behind it.  Too bad…it could have been great!

850mb temperatures fall to around -8 to -9 by Tuesday morning on the back side of this system, cold enough for sea level snow.  But again, models are saying we run out of moisture.  Still, that’s partly the reason I say any elevation could get a dusting of snow late tonight or tomorrow morning.

WHAT ARE WE SEEING FOR LATER WEDNESDAY AND/OR THURSDAY?

Oh boy, how the mighty have fallen…yesterday the ECMWF was pushing a deep surface from off the Oregon coastline far north to Vancouver Island.  I wasn’t sure if that was the correct solution, but now it appears that will be the case.  Check out ensemble low locations from this morning’s GFS run.  This is Thursday 4am.

The GEM now agrees as well, even farther north

Low pressure moving that far to the north offshore means southerly wind can overcome cold easterly flow out of the Gorge quickly.  If we didn’t already have cold air in place, this wouldn’t be considered a “snow setup” for the metro area.

What does this mean for our snow chances later Wednesday and Thursday?

1. Whatever happens snow-wise is going to be brief (less than 24 hours, maybe only 6 hours)
2. We are not going to be locked into a frozen/snowy Portland for long; if at all, and south of the metro area you can forget about snow.
3. There is even a chance we get nothing out of this event…we’ll see.
4. We may get a brief snow (Trace-4″) later Wednesday/Wednesday night in the metro area at best.
5. There MAY be an issue with Wednesday evening’s commute.  More on this tomorrow.

That’s it for today.  I’ll post again tomorrow midday.   I’ll be on six evening newscasts today (4,5,8,9,10,11) and fresh model info will be coming in during most of those.  You can find me there.

Chief Meteorologist Mark Nelsen

Snow For Some of Us Monday/Tuesday

5:30pm Sunday…

Apparently there is some sort of important football game on FOX12 right now, so no 5pm show this evening…good time for a blog post!  And joking about the big game of course.  I’ll be on live TV with fresh model info at 8/9pm on FOX12Plus and 10/11pm on 12.  See you then.

BIG PICTURE:  Some, but not all of us, will see some white on the ground within the next 48 hours.  The forecasts below apply to all areas from Longview to Albany in the western valleys of SW Washington/Oregon.  Including Portland, Vancouver, Salem of course.

THIS EVENING / TONIGHT

1. Showers mix with snow as temperatures drop
2. ANYONE could see a dusting on the barkdust I suppose.  But for most of us in the lowest elevations/cities it won’t be quite cold enough for sticking snow and/or the showers will be too light to drop the snow level much below 1,000′.
3. We’re talking off/on showers tonight.  I don’t think I’ve ever seen widespread snowfall in this setup.

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MONDAY A.M. COMMUTE

NOTHING TO DUSTING IN THE LOWLANDS.  UP TO 1″ SNOWFALL NEAR 1,000′,  2″ UP AROUND 1,500′

• Since it’s showery, many of us will wake up to nothing or just the “white on barkdust” stuff at best.
• Some school delays are likely in the highest areas (top of West Hills?, northern Clark County, Cowlitz County?).  Rest of the kids can plan on normal school hours
• Some roads will be slushy or have light snow on them at/above 1,000′
• MAIN HIGHWAYS/FREEWAYS WILL BE CLEAR FOR A.M. COMMUTE
• There is a small chance a wet road freezes somewhere tonight if a local temperature drops to freezing.  Keep a close eye on your car thermometer tomorrow morning!

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DAYTIME & EARLY EVENING MONDAY

• Continue your normal Monday life…
• Roads/highways all clear with high temp 38-40 in afternoon, slushy snow left on roads up near/above 1,000′
• Scattered showers change to steady rain/snow mix at times, especially Portland south.  But little/no sticking snow below 1,000′

 

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MONDAY NIGHT THROUGH TUESDAY AM COMMUTE

1. BETTER CHANCE FOR LOWLAND DUSTING OR LIGHT ACCUMULATION, especially from Portland south to Eugene.   Cooler temps + showers continuing = better for snow.
2. First guess (will update tomorrow of course) is a dusting to 2″ on the ground at the lowest elevations for Tuesday AM commute.  Mainly south and east of Portland (more moisture, slightly higher elevations = better chance for sticking snow).  Salem could end up with an inch or two Tuesday morning, but nothing around Vancouver or downtown Portland for example.

 

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WEDNESDAY

I still think we have some sort of larger “snow event” coming for some part of the western valleys of Oregon & SW Washington, but details are very uncertain.  Will it just be a 12 hour snowfall with only 1-2″ and then we warmup?  Or a 24 hour long fiasco with the metro area frozen under several inches Wednesday afternoon through sometime Thursday?  We don’t know yet; but it’s still three days away.

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COLUMBIA RIVER GORGE

No cold east wind through the Gorge until Tuesday night so I-84 should be in good shape most of that time.  Just 1-2″ each 24 hours above river level.  But that very cold and strong east wind arrives Wednesday!  Prepare for some sort of snow/ice event later Wednesday-Friday, especially central/east part

OREGON & SW WASHINGTON COAST

Cold showers tonight through Tuesday midday.  At any time a vigorous shower could dump hail or snow, even down to the beaches.  We could briefly see “white sandy beaches”.   But highs each afternoon in the upper 30s would melt that quickly during the day.

Trace -2″ possible anywhere along the beaches if a heavy shower passes by.  That’s either tonight or tomorrow night.

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DISCUSSION

The forecast for tonight through tomorrow afternoon is simple.  It’s the cold onshore flow weather pattern.  Arctic air has moved out over the ocean, picked up moisture, and that comes inland as cold rain or snow showers.  This pattern almost never produces notable lowland snow.  But I have seen it bring an inch or two around Kelso/Longview since it tends to be a bit wetter up there.  And anywhere with some elevation helps.  Notice I don’t specifically mention 500′ or 1,000′ much.  That’s because there is no specific elevation where it does/doesn’t snow.  Heavy showers can drag sticking snow to sea level, but if only light showers pass over a hill at 1,200′ there may be no snow sticking even up there!  850mb temps tomorrow are marginal for lowland snow anyway.  -6 to -7 often doesn’t get snow to sea level with onshore flow.   Models agree, forecasting essentially nothing through midday tomorrow:

Tomorrow night is a bit tricker.  That surface low is still expected to move right across central Oregon, spreading steady precipitation across the Willamette Valley.   The arctic front, boundary of very cold continental air, will be up around Kelso/Longview and down to around The Dalles east of the Cascades.  No model forecasts it to slide farther south.  Because of that, the ECMWF thinks it’ll be too warm for much snowfall tomorrow evening/night even under that steady precip.  WRF-GFS thinks it’ll be significantly colder (it’s based on what seems to be a cold-biased GFS).  My gut feeling is we may not see much snowfall tomorrow night and Tuesday, but I put it in the forecast based on an abundance of caution.   You see the lack of snow in the Euro forecast 4pm Monday to 4pm Tuesday.  This 18z run backed off more than the 12z

Then the “aggressively snowy” WRF-GFS below.  We’ll see if this goes away in three hours when evening run comes in.

Finally, what to do about Wednesday/Thursday?  It’s still three days away, but there are doubts whether it’s really going to be a major player or not.  The GEM and ECMWF are now saying we get brief easterly flow in the metro area then transition to southerly surface wind within 12 hours or so.  That’s because they are swinging the deep low far north offshore.  You need to keep the surface low west or southwest of PDX to keep the cold Gorge wind pumping air into the western valleys of Oregon & SW Washington.  But the GFS is a perfect setup for a major snow event.  Huge easterly flow through the Gorge and deep low to our southwest.  This is Wednesday afternoon

A neat tool nowadays is to compare ensemble surface low pressure locations.  All 21 members from the GFS; general agreement low is southwest of us Thursday 4am.  Snowstorm Wednesday PM through Thursday midday in this case.

Yet the 51 members of the 18z ECMWF say forget it…we’re outta here and heading north!  All of 1-2″ snow is done in Portland by Thursday morning in this case.

That’s plenty for now.  Enjoy watching the snowflakes fall the next 24 hours…at least we’ll all see some in the air!

Chief Meteorologist Mark Nelsen

A Bit Too Much Snowy/Stormy Mountain Weather & Lowland Snow Update

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

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.

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.

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

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.

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