Wind and Cold

February 13, 2011

It’s looking like it will be a winter that started great and ended great, but pretty quiet in the middle.  The models/maps continue to show lots of weather action the next 7+ days.  I’m not working tonight (just finished taxes!), but had to chime in.

First, I should point out I’ve just looked briefly at current satellite/radar imagery and obs (taxes).  The NWS guys tonight have spent far more time looking into things.  That said, the next 24 hours should be real interesting with a complex setup of low pressure systems offshore rotating within a large upper-level trough.  We are on the mild side of the trough with a surface warm front that has now moved north of us.  Models show two good surges of wind along the Coast tomorrow, 1st in the morning, then a 2nd in the afternoon.  But they also clearly hardly know what’s going on offshore.  A well-wrapped low is west of San Francisco, not well modeled, and maybe another developing well west of us.  We’ll see how things work out in the end, but keep a close eye on satellite and buoys (the ones that work at least).

Beyond tomorrow afternoon’s cold front, the next question is…how much Cascade snowfall?  Looks like a good 2 feet to me through Wednesday night or Thursday morning, maybe more.  One thing that’s different then what I saw 2 days ago; the snow level won’t be low enough to talk about snow in the lower foothills (1,000′) until Thursday morning. 

That’s when things start to get a bit messier.  Each run of each model has been a bit different beyond Thursday.  They ALL show the major change with troughing over the West Coast and cold northwest or northerly flow…exactly what we would expect to see at times in a La Nina winter.  Sometimes this pattern brings snow to sea level, but other times it does not.  Generally, in the last two weeks of February or early March, you need to get drier continental air involved to get a widespread snow “event” in the lowest elevations.  Real cold onshore flow rarely does it.  That’s the setup I see through at least Saturday (onshore flow), so I feel confident saying that almost everyone above 500′ should see at least a dusting in the latter half of this week, but there’s a decent chance no snow sticks in the lowest elevations during the next 7 days.  That’s a real general statement of course, but I just want to be a realist.  Remember we had this pattern numerous times in Winter 2007-2008 and no snow officialy fell at PDX, although I think everyone else had at least a dusting at one time or another.  But this IS THE PATTERN you want to see over the next 7-10 days if you want a chance for snow this late in the season.

Now as for President’s Day and Tuesday (just 8 days away!); still looks real interesting with both the GFS and ECMWF indicating some sort of surface low coming down the coastline and interacting with air cold enough to bring snow to the lowest elevations.  That’s going to be something to watch closely.

Chief Meteorologist Mark Nelsen