ECMWF Weekly Maps & 18z Ensemble Chart

February 18, 2013

We already have the general idea (from the previous post today) that cooler than average temps are on tap for the next 7-9 days. Then the first wet westerly flow we’ve seen in quite a while.

What about beyond that time? That would be maps #2-4 below. This is the monthly run of the ECMWF split into the next 4 weeks. Could we actually have a mild start to March??? Maybe…maybe.

I’ve included the 18z GFS ensemble chart which says after next Monday-Tuesday we’re headed to milder weather. It also shows the operational model is the coldest in the Sunday-Tuesday period too.

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA

tseries_850t_000-384_Portland

I need to get those forks sharpened…


Monday PM: Rainier Pattern Ahead

February 18, 2013

What a dry weekend, a brief downpour in spots Saturday afternoon but so far that has been about it.  PDX has only seen .05″ rain so far for the weekend, although I expect a few showers as we head towards midnight.  I was up at Skibowl sledding with the kids last night and it was perfect on the mountain too with temps in the mid 20s, stars and moon, and perfectly calm wind.

So what happens this week?  Not much the next 3 days.  A cold system is sliding down the coast right now.  Looks like the cold front is offshore and will drag inland between now and 2am.  Then a colder surface low off the northern tip of Vancouver Island slides down towards California late tonight and tomorrow morning.  That does give us light offshore flow tomorrow, but other than some convective showers (hail or thunder?), no solid precipitation to drag the sticking snow level lower than about 1,500′.  Remember that about a week ago it looked like we might be quite close to snow tomorrow morning.

Our first strong storm system in many weeks moves inland Friday, both the GFS and ECMWF show gusty south/southwest wind with that storm.  Not high winds, but a reminder that part of winter wants to stick around a little longer, or at least reappear briefly.

Behind this system we’ve got a very chilly atmosphere for the weekend.  The models are slightly different beyond Saturday, but in agreement that Saturday itself will see 850mb temps somewhere between -5 and -7 with frequent showers.  This COULD bring brief sticking snow to sea level at nighttime this time of year (the -6 or -7), but there is strong onshore southwest wind the whole time, or at least enough to keep the airmass well-mixed.  Take a look at the surface pattern:

slp_120_0000

That’s a lot of isobars!  As a result I think it’s unlikely we get sticking snow below 1,000′ and then only at night.

Models seem to want to be about the same or slightly warmer on Sunday.  The GFS is sending another storm over us, the ECMWF is more showery between systems.  The ECMWF waits until Monday morning to send another rain/wind producer inland, with another run at 850mb temps around -6 again late Monday and early Tuesday.  The GFS brings back the -6 temps by Sunday evening (it’s faster). 

They both spell out the same result:  If you want snow this weekend or early next week at the lowest elevations, it’s going to be tough to do based on current models/maps.  That could change, so no need to lose hope yet.  If you live at 1,000′ in the West Hills?  Maybe a dusting Saturday and/or Monday morning…maybe.

Or, we may just see all sticking snow remain at/above 1,500!  That could happen; look at the 12z ECMWF and 12z GFS ensemble charts:

tseries_850t_000-360_Portland

tseries_850t_000-384_Portland

Two things I see…

  1. One is that on both models through the next 8-9 days not only are no operational runs showing sub -7 degree temps, but none of all the ensemble members are showing it either.  Pretty good agreement there.  There is still a chance of course that if a surface low were to go to our south or a front stalls we could see sticking snow to sea level, but as of now that isn’t shown on any model.
  2. They both show a general upward trend beyond Tuesday the 26th.  Still below average for a few days, so if you count this week and most of NEXT week as chilly, it’s going to be quite a cool end to February.  But beyond that there may be warming back to normal…maybe.  I could see us ending up with normal precipitation by the end of the month too as a wetter pattern settles in too.

Wait, I think I can smell Winter 2012-2013 finishing up in the oven…is that normal March wet weather ready to be served as a side dish?  Could be…

Chief Meteorologist Mark Nelsen


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