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