Snow Outlook: Monday Evening Update

February 21, 2011

I don’t have a huge amount to add to what I wrote last night, as everything seems to be on track for SOME snow for most of us the next 72 hours.  Here are the graphics I’ll show at 10pm:

All the 00z models are in (except the ECMWF).  They all show progressively colder showers tonight through Thursday.  By Wednesday AM, 850mb temps of -7 or -8 over us, plus southwesterly onshore flow, means snow could stick to the lowest elevations briefly.  Then we play the “how much precipitation and where exactly are the shower bands game”.  That’s how I get the Trace-2″ for Wednesday AM.  Warming Wednesday afternoon (just the sunbreaks inbetween showers) pushes us up around 40 or so.  So whatever falls Wednesday AM will melt in the lowest elevations in the PM.  But as the atmosphere continues cooling and the sun sets Wednesday evening, that sets us up for the best chance for widespread snow showers dumping a good 1-3″ in the lowest elevations through Thursday evening.  Sometime later Thursday, east winds COULD arrive, depending on which model you look at.  If so, that could give a little extra lift, and our RPM model showers healthy showers Thursday when that occurs.  Then it all slides south and we freeze up Thursday night.  The WRF-GFS was real pitiful with precipitation central and western Valley locations through the whole episode…another reason I didn’t go too crazy with snow amounts.

I did check out the cold spell in 1960 (Feb. 27th-29th) that occurred the same time.  Arctic high came in from the NE, 850mb temps to about -10 at PDX and -20 over Spokane.  Lows were 19,24,29 at PDX, highs were 39,42,43 (or something like that for the last day).  So the high temp of 35 and 38 might be low for Friday and Saturday.  I do notice the WRF-GFS is stubbornly pushing us up to 40 on Friday and lower 40s Saturday…might be right on.

Chief Meteorologist Mark Nelsen


Your Posts: How Much Snow This Week?

February 21, 2011

Alright, we’ve seen Bob’s forecast above (very creative!)…6″ at PDX by the time the moisture runs out Thursday night (according to most models), what do YOU think?  Time for everyone to go on record.  Leave discussion in other posts, and I’ll close this around 4pm this evening.  That gives you 5 hours to make a forecast.  I want to see three pieces of info only, nothing else:

1. Snow total from Wednesday morning to Thursday night at PDX.  For example, if we get 1″ one day and 3″ the next day that would be 4″.  We’re not talking snow depth.

2. Highest total we hear of from around 1,000′ either in the West Hills, Sandy, or Mark’s house.

3.  Coldest low temp at PDX, Coldest low temp at HIO (Hillsboro).  That would be between now and Sunday.

By the way, if you’re new to the blog and have not posted a comment in the past, I have to “approve” the comment.  Just wait a few hours and next time I check in I’ll “let it through”.  No need to try 10 times.