Who Gets Snow Next 2 Days

February 22, 2017

6pm Wednesday…

Today was day #1 of our low snow levels; and it went by somewhat uneventfully with just mixed showers popping up during the afternoon.  In some spots hail or graupel covered the ground.  Check out Corvallis earlier today from Katy Kelly

photo_katie_kelly_corvallis

We are under a cool northerly flow in the upper atmosphere with an upper-level ridge over southern Alaska and a trough right over us.  That pattern continues through Sunday/Monday.

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So we have 4 more days to go in which it’ll be cold enough for snow to stick down to near sea level in the late night or early morning hours (coolest part of the day) IF moisture shows up at the same time.  That’s Thursday-Sunday.  So let’s take it day by day…

THURSDAY:  Looks just like today with a mainly dry morning, then afternoon showers pop up over the hills/mountains and drift out over the valleys.  Because just about all precipitation falls during the midday/afternoon, temperatures will be too warm for sticking snow below 1,000′.  Even at that elevation you’ll be lucky to get a dusting tomorrow afternoon.

SATURDAY:  Should be a dry day with a chilly start then mostly sunny afternoon.  No moisture for snow even though it’ll be cold enough early.

That leaves us with…

FRIDAY:  This day appears to hold the best chance for sticking snow to sea level, mainly the first half of the day (before noon).  That’s because that little “L” (low pressure center) on the satellite picture above will slide down the coastline through the day, picking up moisture and sending it inland over Western Washington and Oregon.  The ECMWF model (surprise!) has been showing this for two days, but other models have now come into agreement with the general plan.  I’m thinking that ANYONE west of the Cascades could see a dusting, but the best chance is north of Salem and west of I-5.  Actually the BEST chance at the lowest elevations may be up on the North Oregon coast where more moisture will be moving south.  Here’s what I’m using on-air:

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Note the ECMWF and WRF-GFS models both hint at snow over the metro area

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As of now it appears unlikely we’ll see sledding in the metro area Friday morning; however I bet all of us will see lots of snow in the air attempting to stick at times.  In this type of situation a mixing southerly wind often dashes our chance for sticking snow at the lowest elevations.   But in this case there will be very little southerly wind since the low is coming at us from the northwest and sliding by to the west.

Another low moves south on Sunday which COULD give us a Friday repeat.  But the atmosphere appears to be slightly warmer which may keep sticking snow up around 1,000′ and higher, or it may be just barely cold enough again…a very close call.  It is very interesting that 41 out of 51 ECMWF ensemble members produce at least 2″ of snow over the Portland area by Sunday afternoon, lending some credibility to the thought that we’ll get at least a little white at some point in the next 4 days.   That 2″ or more would include both Friday and/or Sunday snow combined.

Beyond Sunday, the chance for snow down to 1,000′ or lower goes away for at least a few days, or for good this season…we’ll see.

Chief Meteorologist Mark Nelsen


Great American Solar Eclipse: 6 Months Ahead

February 21, 2017

We’re only 6 months away now from the most anticipated astronomical event of our generation in Oregon.  The total solar eclipse will soon be here; I hope you have a plan to see it.  It will NOT be visible in any cities listed on this map:

markeclipse_2017_a

It’s unlikely the idea that “I’ll just drive down to Madras or Salem for the day” is going to work.  I’m quite confident US 26 over Mt. Hood, US 97 through Central Oregon, or I-5 Eugene to Portland can NOT handle hundreds of thousands of people converging on the center of the state at once and then leaving a few hours later.  Picture that December 14th snowstorm traffic disaster in the metro area, but spread over half the state plus you should add a few hundred thousand cars from California and Washington.  Get the idea???  Most campgrounds and hotels have been booked for months/years within the path of totality.  I have a plan to start camping at a certain somewhat remote mountain lake (lakes) starting Wednesday, 5 days ahead of time.  We’ll see how that works since it’s first come-first serve at that campground.  If that doesn’t work, I have one more backup plan.

You need to be in the shaded area to at least have a brief glimpse of a totally covered sun at midday.  The closer to the center line you are, the longer the eclipse:

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Here’s a great website https://www.greatamericaneclipse.com with even more detailed maps like this one:

tse2017_oregon

 

Chief Meteorologist Mark Nelsen


Wettest February on Record at PDX

February 21, 2017

As of 3pm we have a new February rainfall record in Portland.  We’ve seen 10.04″ (that will keep going up the next few days), which exceeds the old all-time February rain record

rainfall-so-far-this-month_compared-to-normal-or-prev-records

That record was set in the same month we had one of our “Great Floods”.  February 1996 and December 1964 are well-known as the two big flood months across the Pacific Northwest in the past 80 years.

Wondering how this month ranks up with the wettest months on record?  It’s #16 at this point, but as mentioned we have another 7 days to go this month.  Luckily it looks far drier this last week of February:

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We all remember December 2015?  We had another 5″ beyond what we’ve seen this month, luckily we won’t see that repeated.

Chief Meteorologist Mark Nelsen


A Chilly End To February Ahead; Snow For Some

February 19, 2017

9pm Sunday…

Have you noticed the snowflakes in the 7 Day Forecast here at FOX12 or on your weather app?  I’ve got the scoop…

First, We will not be having a snowstorm this week in the lowest elevations of western Oregon or most of SW Washington.  But we should ALL see snowflakes in the air or even and SOME of us will get some snow on the ground.  I don’t think you’ll see me snowblowing a foot of snow in Salmon Creek again:

snow

That said…later this week we’ll be in a weather situation where many of us will see snowflakes.  But this time we won’t have a cold east wind blowing out of the Gorge or a cold air mass to give us a widespread snowstorm.  
Instead we get light showers and clearing periods Wednesday through Friday; it happens to be a colder version of the “showers and sunbreaks” pattern we often see in the winter and spring.  We’ve seen this pattern only two other times this winter…back in early December (it kicked off the fun stuff on the 5th) and on February 6th.  In both of those situations little or nothing fell in the very lowest elevations along I-5.  That includes much of the metro area.  That’s because often in this setup we get a breezy southerly wind coming in off the 50 degree Pacific Ocean, keeping the lowest elevations just a few notches above freezing.  Not always, but maybe 90% of the time.

We can’t predict the sticking snow elevation (the “SNOW LEVEL”) well in these “snow shower” patterns like we have later this week either.  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.

In general, the higher up you live the better chance you have for sticking snow later this week.  Cooler nighttime air, by just a couple of degrees, for Wednesday night and Thursday night means a better chance for sticking snow down below 1,000′.  That’s assuming showers keep going all night as well.  That’s why I think the best window for a dusting down in the lowest elevations is the late night and early morning hours Wednesday night through Friday AM.  Of course as we get closer we’ll refine the forecast and give you more detail…as always.

You can see the general idea just by checking out the ECMWF snow forecast through Saturday:

ecmwf_snowthrusat

See the big empty hole here in the valleys?  And as we saw back on February 6th, models often overdo the lowest elevation snowfall in these marginal setups.  Check out the Cascade snowfall!  It looks like some of the best this season with very low snow levels from Wednesday until further notice

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Here’s the ECMWF ensemble chart from this morning’s run.

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That’s the next two weeks, time goes from left (right now) to right.  Green line is average 850mb temperature for the date (temperature at 4,000′ in celsius), the blue is the operational run and red is average of all the ensemble runs.  This screams a very chilly last week of February and first week of March.  To get sticking snow with onshore flow this time of year we need -7 to -9 at 850mb.  Notice we’re very close to that several times in the next two weeks.  Of course if we lose that onshore flow and get decently heavy showers at some point, it could snow/stick all the way to sea level even as warm as -3 or -4.  So the main message here is that we’ll be flirting with snow in the lowlands several times in the next 2 weeks.  Anything is possible so let’s get the wishcast express loaded up folks!

WishcastingExpress

Chief Meteorologist Mark Nelsen


Are We Done With Winter?

February 15, 2017

10pm Wednesday…

It’s only February 15th, but this is the time of year folks often ask me if we’re “done with winter”.  If you have lived west of the Cascades for long, you know that yes, in general we don’t get big winter weather events after mid February (snow/ice/flooding).  I don’t think I’ve seen significant freezing rain, flooding, or day-long snowstorms after about February 20th while working here in Portland.  That goes all the way back to 1991!  BUT, that doesn’t mean it can’t happen.

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Lots of you took the poll in the past few days (previous post).  Looks like a majority of you think we’re either totally done with snow or we’ll only see a little in the hills.  63% of you say that there will not be any more measurable snow at the lowest elevations here in the city.  History says you are most likely right.  Take a look at what we’ve seen AFTER FEBRUARY 20TH in Portland during the past “generation”.  That’s considered to be 25 years.

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Yes, we’ve only seen measurable snow (that late in the season) 4 out of those 25 years.  So the odds are very much against additional snow.  Keep in mind this is at the official observing location out at the Parkrose NWS.  Obviously if you live at any elevation above that you know we’ve seen 1, 2, or even 4″ during some of those events!  Remember March 2012?  Quite a few inches in mid-March that year, plus coastal and valley snow.  But that was the exception.  In March Portland has seen measurable snow in only 4 of the past 50!

There is a tendency to see late season cold events or late season snow in La Nina winters, which we are now in.  So it would be quite premature to pull out the fork at this point and declare winter over.  That said, I’m quite confident we’re well past the worst winter has to offer.  Don’t take the studded snow tires off quite yet…give it another couple of weeks.

By the way, February has been a big soaker, about 3 times our typical rainfall so far:

rainfall-so-far-this-month_compared-to-normal-or-prev-records

It’s the wettest February since I was just 30 years old…a long time ago.  More rain coming…

Chief Meteorologist Mark Nelsen

 


Poll: Are We Done With Snow in Portland?

February 13, 2017

The past few days have definitely given the feeling that “the worst of winter is over”.  This happens every February in our mild climate; you’ve probably noticed this if you’ve lived here for awhile.

I can tell you that it’s extremely rare to get freezing rain in the Portland metro area after mid-February.  In fact during the 26 years I’ve been forecasting here in PDX, I’ve never seen freezing rain after Valentine’s Day anywhere in the metro area.  I have seen it maybe twice or three times in the western Gorge in early March, but even that is quite rare.  So we’re done with the ice threat in the lowlands west of the Cascades.

But snow?  What do you think…are we done with it in Portland this year?  Let’s vote:

I’ll give you my thoughts on possible snow the rest of the season on Wednesday.

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Two Nice Days Ahead, Then Wet

February 12, 2017

11pm Sunday…

A very slow weather night and mainly slow week ahead as we creep through the final stretch of winter west of the Cascades.

High pressure has settled overhead, giving us another dry day.  East wind has that “end of winter” feel too, not nearly as strong as what we have seen in December and January.   Even the temperature chart shows the last 4 days of 50+ weather are the longest stretch since around Thanksgiving…winter is losing it’s bite!

marktemp_last13days

Tomorrow’s high temps will be around 50 in the metro area under mostly sunny skies, same thing for Valentine’s Day too.

The rain is definitely coming back though, that’ll be Wednesday night and Thursday as a southwesterly flow sits over us for about 36 hours.  This won’t be a flooding event like the last one, I expect less than 2″ in the lowlands during that time.  You can see the precipitation forecast numbers from both the GFS & ECMWF are similar:

One final note; a hiker turned up missing this afternoon while hiking just west of Multnomah Falls.  Almost all those trails are still in “winter mode” which means tons of snow/ice/downed trees across them and most are shaded from the sun until those higher sun angles of March.  Remember that out in the Gorge it has been cooler with the last ice storm occurring less than a week ago!  This is the one year every generation where you shouldn’t be hiking in the Gorge until we get a widespread melt in March.  It’s not a good idea to attempt hiking through the snowiest/iciest conditions we’ve seen in the Gorge in 30+ years.  Give it time to melt…

Chief Meteorologist Mark Nelsen