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


 

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.

wrfsnow_ending10amtuesday

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

ecm_snowmonday4pmtoTuesday4pm

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

nam3km_snowending4amTuesday

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.

web_temperature_ORWA (1)

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.

gfsthursdayamlowlocations

The GEM now agrees as well, even farther north

gemthursdayamlowlocations

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

111 Responses to Snow Outlook: Monday Midday Update

  1. K says:

    On the bright side– this event has cemented how pathetic our area really is in terms of weather. We’ve, in the past year, missed out on two major snowstorms, two major windstorms, and several atmospheric rivers. That’s just sad. Now let’s add another two snowstorms onto the list.

  2. Evan -- Cedar Mill says:

    Meanwhile, some parts of Astoria have snowy roads 🤦‍♂️🤦‍♂️

  3. Evan -- Cedar Mill says:

    Cold air my @$$. Nearing 40F.

    • W7ENK says:

      The “cold air” never made it here, it’s still hung up 100 miles to our North. This is literally the exact same airmass we’ve been stewing in since New Years.

  4. Evan -- Cedar Mill says:

    Still baffled as to how the NWS has 1-3 in for Portland…

    • Andrew says:

      It seems unlikely but certainly could happen. cold air can linger longer than expected. some models support a longer transition. I agree that 3 inches feels unrealistic. But a quick inch isn’t out of realm of possibility, albeit with fairly quick melting.

      • W7ENK says:

        Seriously, what part of “the cold air never made it here” are you having trouble comprehending? The cold air never made it here! It got hung up around Centralia, and has since retreated back up to Olympia. There is no cold air here to linger, this is the same airmass that’s been in place for two weeks, and it’s the same airmass that is going to shove North up toward BC tomorrow, giving the overrunning precip to the Puget Sound basin, and thus a snowstorm. We will be too warm from the get go, BECAUSE THE COLD AIR NEVER MADE IT THIS FAR.

        THAT is the most disappointing part of this whole thing. The cold never made it here, thus our opportunity for sticking snow on the Valley floor never materialized. Holding out hope at this point is just plain ridiculous.

  5. JohnD says:

    So is it absolutely, positively forgone re the track of Wed’s. storm? Absolutely zero chance of it coming inland more to the south as models indicated days ago? Or at least stall during its northerly migration? No doubt Mark will elucidate at some point today.

    • Andrew says:

      The model consistency between GFS and Euro over last 48 hours suggests it’s fairly set in stone. Speed of system and intensity of moisture is still somewhat wait and see. But I think general storm track is largely indisputable at this point, unfortunately.

  6. W7ENK says:

    Clouds parted, the Sun peaked through, and the temperature in Downtown Portland near instantaneously shot up to 39 degrees.

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