Snow Storm Delivers in Metro Area

February 20, 2018

11:30pm…

I’ve been on the air all but one hour since 5pm…a long night!

But oh it’s been nice…models did EXCELLENT showing a burst of snow moving through SW Washington and NW Oregon between 4pm-10pm.   We couldn’t see it most of the time because the Portland radar had died, but neat nonetheless

3.5″ is the final total from Portland NWS office.  That’s the heaviest snowfall we’ve seen beyond Valentines Day since a late February snowstorm in 1993.  It’s very rare to see heavy snow this late in the season.  Our 1-4″ forecast last night, which we changed to 2-5″ today, turned out just fine.  It appears most parts of the metro area were in the 2-4″ range.  Of course hills saw more, and as expected very little fell south of the metro area.  We forecast Trace-1″ for Salem and Albany, but unfortunately you didn’t even get that!

 

Chief Meteorologist Mark Nelsen


4:30pm Update: Commute Begins With Wet Roads

February 20, 2018

You may remember this graphic from last night?

Mark Road Condition Forecast

The good news is that the commute HAS begun with just wet roads (best scenario so far).  The few schools that decided to continue on with their day scored with no transportation issues.  That said, a school administrator couldn’t have won with today’s conditions…heavy snow at starting time, but supposedly melting during the day?  Risky move.  But at least we’re past that now.

The temperature part of today’s forecast has been perfect.  Check out 4pm temps with relatively “warm” conditions on the west/south metro but hanging just within a degree or two of freezing in the city and east/north metro.

web_metrotemps

The sun sets in just over an hour and at that time temps should drop at least a couple degrees.  An easterly breeze in the Gorge right now should increase a bit and spread across those already cool areas on the map above.  The result is that we should have no problem getting snow to stick after 6pm or so, especially central/east/north metro.

But what about precipitation?  Bad news, the Portland radar died around 2pm and is out of commission.  The NWS hopes to have it running again by 6pm.  The Ocean Shores radar in SW Washington does show an area of heavy showers moving down into NW Oregon right now.  This is on the north side of a little low pressure area spinning down into NW Oregon.  This low moves down just to our south the next 8 hours.  The burst of heavier snow showers models have been anticipating should occur during this time.   Note the latest HRRR model forecast of snowfall:

hrrr_snow_portland_9

Interesting that it looks similar to most morning forecasts showing the heavier stuff north/central/east metro.

So we are sticking with our 2-5″ snowfall forecast in the metro area between now and midnight.  A Winter Storm Warning continues for the metro area north to Longview, the Coast Range, and Columbia River Gorge.  May the snow odds be in your favor!

Mark Warnings Winter Weather Lowlands

Chief Meteorologist Mark Nelsen


Noon Update: Roads Clear In Most of Metro Area Through The Afternoon

February 20, 2018

Noon Tuesday…

I just checked all the ODOT road sensors and they show pavement temps rising, between 33 and 42 in the metro area.  Those are sensors embedded IN the pavement.   That explains why just about all roads/streets (except in the hills) are wet.  That’s different than an air temperature sensor of course.

Here are the regular air temps at noon:

web_metrotemps (3).jpg

  • For the schools that decided NOT to cancel you’ll be fine through 3-4pm.  We knew temps would stay above freezing during the day and that is happening now.

Snow intensity has lightened up quite a bit.  Combine that with temperatures creeping up toward the forecast high in the mid 30s and we’re in good shape for lowland travel in most of the metro area through at least 3-4pm…maybe through the early part of the commute if we get lucky.

Again, as mentioned in the previous two posts we expect snow intensity to pick up sometime after 5pm and temperatures drop.  That’s when roads will likely turn snowy again.

Chief Meteorologist Mark Nelsen

 


Snow Arrives Early…Snowy Day Ahead

February 20, 2018

10am Tuesday…

Surprise!  Just like the rest of you I looked out the window this morning and saw snow falling…about 8 hours ahead of schedule.  Meteorologists don’t like that.

Obviously moisture has arrived earlier than expected, although so far it has been light.  Most models DO seem to have caught on and it appears the heavier snow projections from yesterday will end up as reality.

Current temps are right around freezing in the lowlands, but below freezing in the Gorge and near/above 1,000′

web_metrotemps (2)

So here’s what I see from this point forward:

  1. Light snow will fall during the day, then pick up in intensity (possibly quite heavy) during the evening commute.  I think heaviest snow will still be somewhere between 5-10pm.
  2.  Roads are mainly wet in the lowest elevations and WILL LIKELY STAY THAT WAY THROUGH THE LATE-AFTERNOON.  It’s late February and unless snow just starts dumping out of the sky, the increasing sun angle gives just enough “heat” to keep roads ice-free during daylight hours.
  3. Temperatures stay ABOVE FREEZING through late afternoon as well…that will help with #1.
  4. During the evening commute, an increasing easterly wind (cool air) plus heavier snowfall will turn all roads snowy in the metro area at some point.  For sure by 8pm or so.

 

SNOW STORM TOTALS

This is the first late February snowstorm (extremely rare) we have seen in the metro area since 1995.

How much snow will fall?  We forecast 1-4″ last night.  With the earlier start plus more moisture, that forecast needs to go up, especially in the hills where snow will accumulate all day long.  Temps a few degrees above freezing during the day will limit how much we get in the lowest elevations between now and 5pm.

  • 2-5″ should be a good forecast for most of the metro area up to Kelso/Longview,
  • Up to 8″ could fall up around 1,000′ in the West Hills, Chehalem Mtn, Mt. Scott, and the west end of the Gorge.  Actually anywhere above 500′ or so in Clark County could see a solid 6″

Check out the morning model forecasts…all give us a solid 2″ (or more)

 

AT THE COAST:  Expect light accumulation during the day, then maybe 1/2″ tonight as temperatures cool.  A little above freezing out there until after sunset

COAST RANGE:  A snowy day…2-6″ likely

WILLAMETTE VALLEY:  Right now a southerly breeze has pushed everywhere south of Wilsonville up above freezing.  So little or no accumulation during the daytime.  After sunset a wind switch should drop you down to around freezing, so expect TRACE to 1″ Woodburn/Salem/Albany.

 

Enjoy this rare late February snowstorm!

I’ll be at work all afternoon and evening and of course we’ll be on the air regularly

Chief Meteorologist Mark Nelsen


Quick Evening Snow Update

February 19, 2018

9:45pm Monday

All evening models except ECMWF are in.  A few additional thoughts, although make sure you read the HIGHLIGHTS section on the previous post.

  1. Only the WRF-GFS and RPM give us little or no snow.  They are quite dry showing almost no precip…thus little/no snow.
  2. All other models give us an inch or so to as much as 5-6″.  Confidence has grown that we’ll have some sort of widespread coverage of 1-2″ at least.  This will likely be the most widespread snow event of the winter.  It should also be the first snow in the Willamette Valley south of the metro area.  Here are the latest numbers (ECMWF is from this morning).

Snow Model Accumulation Several

3. Wind is light much of the day, then east wind starts pouring out of the Gorge in the evening as the low pressure moves by offshore.  It’s not a big mid-winter type strong easterly wind, but enough to transport dry air over us.  That helps drop us to freezing and below during the evening/overnight hours.

Of course the huge question is about the evening commute.  I think whenever the heavier snow decides to show up, that’s when things may grind to a halt within an hour or so.  And we’re not confident on that timing.  Our freeways are over-capacity for the population that lives here.  So I think we all know it won’t take long to bring things to a halt.  You see the BEST CASE and WORST CASE scenarios below.  I’m inclined to think this might be like the January event last year where much of the commute was okay (wet)  but then things ground to a halt right around 6:30-7:00pm.  The really bad event last year (December 14th) was when the snow showed up on already-frozen roads at 2-3pm.  I think that is unlikely tomorrow.  The heavy snowfall appears to show up well after 4pm.

Mark Road Condition Forecast

Snow Cold Look Ahead Forecast 2

So tomorrow is a day to keep a close eye on radar (hopefully it doesn’t break down) and temperatures.  I’ll be on at 5, 6, 8 (FOX12 PLUS) , 9 (FOX12 PLUS), 10, & 11…shouldn’t be hard to find me!

Chief Meteorologist Mark Nelsen


Widespread Snow Likely Tuesday Evening & Night

February 19, 2018

2:00pm Monday…

Last night the clouds didn’t clear out as expected so we just dropped to freezing or a bit below in the metro area.  Lots of icy streets but it appears it wasn’t a total ice-pocalypse for the morning commute.

Today we’re under a dry flow of air from the north which is giving us lots of sunshine but chilly temps…a good 10 degrees below average.  We’ll end up around 40 or so.

We have an almost perfect sticking snow setup for the lowlands with two disturbances coming straight down from the north the next 3 days.  They pick up a bit of moisture once they move over the coastal waters offshore, then generate snowfall in mainly Western Oregon and SW Washington.  The one issue (if you want lots of snow) is that it’s late February and daytime heating is “strong” for late winter.   This DOES keep us from having an all-day snow/ice event where roads stay frozen…you know, continuous-coverage type snow event for TV folks.  Roads just don’t stay frozen/icy the whole day this time of year…whew!

I see two good chances for lowland snow before a slight warm up Friday night and into the weekend lifts sticking snow levels back up into the foothills.  1st is tomorrow afternoon through early Wednesday morning, the 2nd is early Thursday morning.

We have a big problem forecasting how much snow we get tomorrow afternoon through early Wednesday…models have widely varying snow totals and also put the heavier stuff in different places.  Check out 7 different models showing total snow accumulation by 4am Wednesday.  Blue on most of them is 2″ (or more). See the issue?  You can click on each individually for a larger view.

The big message here is that SOME AREAS BETWEEN OLYMPIA AND EUGENE SHOULD GET A GOOD 2″ OR MORE SNOWFALL BY WEDNESDAY AM.  But SOME AREAS WILL ONLY GET A DUSTING TO 1/2″.  Each model is slightly different in the placement of precipitation.  Note the one that shows 4-6″ snow centered on metro area.

If this was all rain none of you would notice; we’d just forecast increasing rain showers Tuesday afternoon through Tuesday night.  Would any of us care if we got .05″ rain instead of .30″?  Nope!  We wouldn’t even notice, it would just be a little wet.  But when that falls in the form of snow that’s the difference between a dusting and 3″!  Suddenly it matters!  You see the forecast problem now don’t you?

But I get paid to make a forecast and prepare you for the possibilities, so here’s what I’m thinking this afternoon:

  1. Light snow showers develop most areas west of the Cascades tomorrow afternoon, then pick up in intensity after 6pm or so.
  2. Temperatures likely hover near/above freezing through early evening, so MOST LIKELY roads will be mainly wet through the evening commute.
  3. Dropping temps and increasing snowfall should turn many roads snowy by late evening.  No, we don’t know exactly when; it depends on snow intensity and how warm it gets during the daytime.
  4. Expect 1/2″ to 3″ in the western lowlands from Longview to Eugene.
  5. Many roads/areas will have fresh snow on the ground for Wednesday AM commute, then thaw during the day (travel just fine during day).  Wednesday may be a Snow Day for many areas west of the Cascades.

 

COULD TUESDAY EVENING’S COMMUTE TURN INTO A HELLISH EVENING WITH TRUCKS & CARS STUCK ON FREEWAYS…LIKE LAST WINTER?

YES,  That is a “worst-case” scenario at this point, not likely but possible.  If snow starts falling heavily during the evening commute, temps could immediately drop to 32 degrees and we could have a fiasco.  How to avoid?

  • EVERYONE should have chains, studded tires, and/or 4 wheel drive vehicle available for use tomorrow evening just in case this happens.  Otherwise please don’t get on roads/highways if they turn snowy.
  • Hopefully transportation agencies have learned quite a bit from last year.  For example I would hope salt is in place to keep interchanges, ramps, & bridges clear this time.  (personal opinion ahead)… The de-icer used in the past doesn’t seem to do much; in both storms last year highways just froze up.  Why do we soak our highways in thousands of gallons of chemical if it freezes anyway? …(end opinion) Remember some of you stuck at I-84/I-5 interchange for 6 hours?  Same on approaches to Marquam Bridge and Sylvan Hill.  Bad memories we don’t need to repeat…

 

WHAT ABOUT SCHOOLS TOMORROW?

With a little daytime heating I think we’re fine until sunset in most lowland locations.  But administrators should be keeping a close eye on noon/early PM temperatures and radar.  I’ll be doing the same.

COAST?

Snow showers all day tomorrow.  Not much stickage since temps will be above freezing, but after dark maybe a little on roads.  I could see a Trace to 1″ anywhere along the coastline, with more in the Coast Range of course.

GORGE?

Same as western lowlands, although drier in the eastern Gorge, farther removed from moisture.

That’s the update for now, of course I’ll be keeping a close eye on things in case for some reason timing suddenly speeds up (morning snow!) or models turn much heavier with the snowfall.

Good times ahead!

Chief Meteorologist Mark Nelsen


Snow Ends, Cold Night Ahead

February 18, 2018

11:45pm…

Did we say ZERO to 1/2″ in the lowest elevations?  Well it ended up as ZERO to 3″ in the lowest elevations of the metro area and Willamette Valley.  Quite a wide variety of snow totals…here’s the final snow map, I’ll add in a few numbers tomorrow.

Snow Totals Metro Area

That disturbance really dumped the heavier stuff on the eastside and then up into Clark County.  West and south metro were left out again.  Salem had nothing, except in the hills.  So in reality most of the western valleys of Oregon had very little.

So officially at the NWS office we now have two measurable snowfalls this season (Christmas Eve and Presidents Day “Eve”), plus one Trace (Valentine’s Day).  Nice holiday lineup.  What’s coming on St. Patrick’s Day?

Enjoy the bright sunshine tomorrow and drive carefully the next 10 hours as roads freeze up.

Chief Meteorologist Mark Nelsen