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

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…

THE BIG PICTURE

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.

HIGHLIGHTS

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: http://www.whatismyelevation.com/##  Put in your address and it’ll tell you how high up (or how low) you live.

 

TECHNICAL STUFF FOR THE WEATHER GEEKS

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.

wrf_cross_section

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:

rpm_snowaccum_metro

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:

wrf_snow_bymondaypm

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:

ecm_snowendingmondaypm

gfs_snowendingmondaypm

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

57 Responses to Monday Morning Snow: Who Gets It and Who Doesn’t

  1. GTS1K' says:

    31 and all white – for the moment. Started about 9 ish.

    Long time no see.

  2. Prune hill outpost says:

    Rural Washougal (Skamania County) 500 feet. Nice fat flakes snow shower sticking to car and grass.

  3. UW WRF-GFS is saying I might get up to 2″ accumulating snow tonight. Fraser outflow is predicted to interact with a weak onshore flow and cause a convergence zone tonight. I’m not in the most-favored area, but it might wander south or I may get spillover from the area of the main action (which isn’t forecast to be that distant from me). We shall see.

  4. East windstorm in the mix for Thursday??

  5. W7ENK says:

    Woke up to 37° rain this morning, temp bumped up to 39° by the time I reached downtown. Currently it’s 39° with a stiff South wind, and raining pretty hard at the moment. Not one bit of snow or ice mixed in.

    Nailed it!

  6. Mixed rain and snow here. 100 feet elevation on Bainbridge Island, WA. Probably all snow in the hills in the center of the island already.

  7. JohnD says:

    It might not be snowing right where you live but definitely a wintry day overall–rainy-snowy-drippy-cold–and a precursor of things to come! I’m off today and look forward to going out for a snow spotting adventure, starting with the West Hills after while.

  8. Jason Hougak says:

    A nice loop of the 06Z GFS snowfall loop
    http://weather.cod.edu/forecast/

  9. Alohabb says:

    Just too warm for snow today. Try again another day.

  10. Joshua Downtown PDX says:

    Plain old rain downtown right now.

  11. Lee Wilson says:

    1 weather apps says snow/rain,
    one says sleet.
    A third says snow with rain.
    1 weather apps says 36, one states
    And the beta UWX….lies big time at 33.6.

  12. Lee Wilson says:

    Well, all we got was rain while everyone around us got snow.
    Got to love all those microclimates. Lol.

    • muxpux (Longview) says:

      I live up on sandy bend at about 160 feet and had a rain snow mix just now. Chunky rain with a few flakes. I have some geeky photos and footage. But not gonna post it, lol

    • Lee Wilson says:

      Mom lives at 500 feet, but our son is sick…so won’t be venturing out today.

      I was hoping for snow to see how it effects solar power…of course..I’d sweep the panels off though lol.

      Rumors have it that pain else will produce 2x to 4x more power. In cold sunny conditions with snow on the ground.

      Somethingaround the grounds that snow acts like reflectOrson over uv…which solar panels can absorb and use.

      Or the snow acts like a giant prism retracting and redirecting sun light.

      Either way..it’s a cool experiment I want to try.
      And either prove or disprove.
      And posting the results:)

      OR maybe Mark could explain how an why that rumor is false or true.

    • W7ENK says:

      Lee, Mark is a meteorologist. Just a wild guess here, but I’m pretty sure he’s not an Electrical Engineer, nor is he an expert in photovoltaics.

      My good friend in Chiloquin runs his 10 acre property entirely on solar. He suggests tilting your panels facing South at steeper than 45 degrees. This does 2 things: 1) It faces the panels more perpendicular to the lower Wintertime sun angle, and 2) it prevents snow accumulation, which can break the panels if it snows a lot and becomes too heavy. I would imagine it’s also easier to reach to sweep the snow off the panels.

  13. 00Z is epic for a round two mid-month.

  14. 00Z is epic for a round two mid-month.

  15. Washougal1100ft says:

    Snowing for the past twenty minutes 32 and whit out! Hope everyone that wants snow gets to see some tonight and tomorrow!

  16. Washougal1100ft says:

    Has been snowing hard for the past twenty minutes enough to cover everything. At 32 and sticking hope everyone gets to see some snow tomorrow!

  17. Jake-(Gresham) says:

    Car was freezing over in Damascus when I left work. I suspect East of the Metro area may get sticking snow briefly tonight before things mellow out and all melts in time for the commute. I doubt we break the dome however. This is all too weak. Just my 2 cents.

  18. Alohabb says:

    And a rain shower comes through and temp rises to 37.

    Aloha 37 now

  19. Max in Fairview says:

    PDX last update showed 35 with DP 31. Getting cold fast.

  20. Boring 550ft says:

    It’s currently 31° at my location in Boring. Been clear skies the past few hours and things are getting iced over. All I need is some precipitation!

  21. Alohabb says:

    Now 35 temp and 34 dew point in aloha. Clear skies, dry roads….. sure close to a snow event to me.

  22. This might be a good sign! I live down by Fairview Lake which is pretty close to sea level and came home to a 1/8″-1/4″ inch accumulation of ice on the cars. Ground is still wet, but I’m hoping that this turns out into at least some snow. It’s 34 right now which is warmer than it was earlier but colder than I was expecting by now

  23. JohnD says:

    Just got around to reading the afternoon NWS AFD. Way more bullish than Mark’s renditions. Nothing untypical in that regard though.

  24. High Desert Mat says:

    Thanks for the update Mark. As we all know things can change and can surprise us. I remember the winter of ’03-’04, the mets around town kept saying it would warm up the next day for a week. It didn’t happen and the east winds just kept a blowin’. We know you’ll be right Mark, but does it have to be all the time? Lol

    • Washougal1100ft says:

      I sure do remember that it snowed on and off for week and every day they would say it’s going to warm up and it ended up taken a week or so ! Computers can be wrong and they can’t always judge Mother Nature!

  25. W7ENK says:

    HRRR shows no snow accumulation in The Dome next 18 hours.

    It concurs with Mark’s RPM (above).

    Even NWS is backing off on the snow idea now, raised SL to 700 feet.

    • Sapo says:

      Yeah. Although 33 degree rain is unlikely in this scenario, especially in heavier precip. But tomorrow is somewhat of a non-event, with a decent band of precip 6-7 AM producing some wet snow, and that’s about it.

  26. JohnD says:

    If you like snow in your backyard, you don’t live in Portland. And if you do, we all know that there are so many intricacies involved for it to happen. And between events, you typically must wait a very long time. So–amid the need for perennial emotional detachment–we resume the waiting period.

    Still, you don’t hang your hat on one non event. This still could be a long and interesting winter overall. Perhaps that hoped for anomalous year–like we remember.

  27. kcteach says:

    Down to 39.2 from 41 an hour ago in SW Gresham. Very partial clearing right now. Hoping for some cooling prior to precip tonight.

  28. Alohabb says:

    I bet more happens than thought. I’m aloha my temp has fallen from 46 to 41 in the hour I’ve been home

  29. Sapo says:

    Nope Mark, you’re wrong. 1-3″ above 700 feet, just a trace anywhere below. It must be true, it says so in our winter weather advisory.

  30. Anonymous says:

    Been snowing off and on in Sandy since 3 and it’s about 32°. Hope it doesn’t get much colder or we’ll have to deal with icy roads as well. Will there still be moisture on the roads Tuesday morning for an icy commute?

  31. Andy says:

    37 deg here in Jefferson, OR…with some clearing…could we possibly get colder than forecasted?

  32. Paul D says:

    Both of those snow flakes are going to cripple the area!

  33. kcteach says:

    first time ever??

  34. Andy says:

    Hail shower, down to 40 deg. Jefferson Or.

  35. Jason Hougak says:

    NWS has 1-3″ tonight, 2-5″ tomorrow and 1-3″ for Monday night in the Cascade Foothills. I sure hope this pans out. Had a nice groupel shower blow through an hour ago and dust the ground. It has cleared off since and all my work activity has caused a chill to develop. Better get that woodstove blazing.

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