Snow Outlook: No Need For Sleds In The City

Here’s our “snow forecast” for the next 24 hours here in the metro area:

As you can see I’m not real excited for any signficant snow here in the lowest elevations.  I envision the morning commute as mainly clear, but snowy spots on the side roads up in the hills (close to and above 1,000′).  This is a classic “get excited for snow and then the letdown” event.

If you’re a kid (or teacher) looking for a snow day, that appears unlikely unless your school is higher up like Skyline, Yacolt, Vernonia, Sandy, or Corbett.  Even in those areas, I bet a 2 hour delay is far more likely.

Here is the 00z RPM snow forecast just out:

11pm update…

Busy evening, that cluster of showers pushed sticking snow all the way down to the Valley floor, a good indication that ANYONE could see a dusting tonight as showers continue streaming inland.  I adjusted the forecast above just slightly, but still feel we won’t see widespread accumulations.  Will PQR (the Portland Forecast Office) see measurable snow?  I think it’s unlikely; we’ll see.  Official Portland snow accumulation measurements are taken there, near NE Sandy and 122nd in Parkrose.

Why don’t I expect more snow than those amounts above?

1. There isn’t a ton of moisture moving inland the next 10 hours.  Maybe .20″ at best, which means 1-2″ in the higher hills where everything will stick.

2.  Onshore flow is keeping the lowest 1,000′ of the atmosphere above freezing.  That won’t change during the night as southwesterly wind continues.  Sure, with clearing in between showers your backyard temp could drop as low as 30, but as soon as a shower with its mixing winds moves overhead the temp pops back up to around 35 degrees.  Sticking snow is just about guaranteed near/above 1,000′ with the KPTV Tower temps showing the freezing level is right near that level.  It’ll stay there the rest of the night before rising a bit tomorrow.

I should point out that if we get an unexpected cluster of showers, it could easily stick anywhere.  But I see no reason to think that will occur.

Tomorrow night looks interesting with steady precipitation spreading inland with the next system.  It will likely start as just about all snow, then transition to rain all areas below 1,500′ by daybreak Thursday.  I think we could see an inch or two (after midnight) on the higher hills before we change over.  We have tomorrow to worry about that though.

After that, lots of mountain snow and cold valley rain, but I don’t see us getting near snow again as we head into Christmas Week. 

Chief Meteorologist Mark Nelsen