East Wind Season Ends…It’ll Be Back in 8 Months

March 6, 2017

Those of you that live in the usual east wind spots have probably noticed…our old friend disappeared a couple of weeks early this year!  I doubt anyone is complaining.  The combination of a very windy period in December and January along with the coldest winter in 30+ years in the metro area made it especially difficult winter.  Heating bills were HUGE in January which didn’t help our bank accounts.

We can track the wind season-by-season by counting the number of days where gusts (from the east) exceeded 25 mph at Troutdale.  That location is just outside the west end of the Gorge and has a 24 hour a day reliable wind instrument.  I would use Crown Point or Corbett, but then we lose readings due to power outages and during ice storms…missing the strongest wind days.

Check out the past few years:

capture

A few notes:

  • As mentioned, combining the large number of days with the extra cold temps = extra miserable.  At least those other 3 big years saw afternoon temps rise into the 30s and 40s consistently, instead of 25-35 regularly this January.
  • January 13th-18th was the coldest/windiest period we have seen since just before the February 1996 flood.  Troutdale gusted 50+ for 4 days straight.  Corbett gusted over 80 mph several times; that sensor hadn’t seen a gust over 78 mph in the same location in at least 10 years.
  • During that period, high temperatures were in the 25-30 degree range at Troutdale and 20-25 range up around Crown Point and Corbett…brrr!
  • The wind suddenly “stopped” President’s Day weekend and we haven’t seen it since that time.  That’s because the past two weeks we’ve gone into a more “typical” La Nina winter pattern of cool showers and weather systems coming at us from the west or northwest.  That kills high pressure east of the Cascades = less wind.  Note the 3 previous La Nina winters (on the chart above) saw just 40-41-48 days instead of the 69 days this year.  El Nino winters tend to give us more east wind due to more stagnant high pressure overhead.  This was a very different La Nina winter than those years.

Now keep in mind that the wind doesn’t totally disappear for the next 8 months.   Anytime we get strong high pressure overhead (unusually warm weather) April through October we get at least some wind, but generally gusts stay under 50 mph.  And personally I love those rare 20-30 mph breezes in June/July/August that blow all night long.  During heat waves that can keep temperatures out in the western Gorge in the 60s/70s at night; it feels like tropical breezes at that point.

Chief Meteorologist Mark Nelsen


Snow Totals: How Much Did You Get?

March 6, 2017

snowflake

9am Monday…

As expected some spots saw snow and some did not.  IF YOU RECEIVED MORE THAN 1/2″ SNOW, then put it in the comments below.  In this case it’s especially important that you put in your elevation too.  At least within 500′ if possible.  Just looking for 3 bits of information:

SNOW
LOCATION
ELEVATION

I’ll start,

2.0″ –  Corbett – 1050′


March 2017 is a March 2012 Redux So Far

March 5, 2017

9:30pm Sunday…

This month sure seems similar to March 2012.  That year we saw a series of close calls with low elevation snow through the 3rd week of the month.  Officially we only received 0.8″ in Portland very close to sea level that March.  But up around 1,000′ there were 3 periods in which significant snow fell.  That month I had 21″ at 1,000′ at home in the far eastern metro area spread through the month (unrelated to cold Gorge wind).  There was also a record-setting late season wet snowfall in the southern Willamette Valley on the 21st.  Remember this viewer pic?  Not quite the spring break they imagined…

springbreak

Now so far we’ve had less snowfall than 5 years ago, but the pattern wants to continue quite chilly.   In fact this is the exact same weather pattern we saw the first half of December, January, & February.  But this time we are heading into spring and we don’t have a cold east wind to deal with that could bring a widespread snow storm to the metro area…whew!

For the folks who just want to know if they’ll have a snow day tomorrow?  The short answer is NO in the lowlands, but a couple of properly placed heavy snow showers 4-9am hitting a few hills could easily give us a bunch of 2 hour delays…we’ll see.  Regardless, but noon all areas below 1,000′ should be around 40 degrees or above…it can’t last long.

marksnow_upcominginmetroarea

Check out the 500 millibar height map for midweek, that’s flow in the upper atmosphere up around 18,000′.  gfs_namer_084_500_vort_ht  Our old friend the Alaskan Upper High is back.  Flow is coming down from the north on the backside of that high then converging with westerly flow and moving right into the Pacific Northwest.  This general setup gave us the big snowstorm in January and led to numerous close calls and ice storms through the winter.  As I mentioned, at least this time of year there is no cold air east of the Cascades (50+ the last few days at The Dalles) as the increasing sun angle kills low-level cold airmasses quickly.

All of us should see snow in the air the rest of tonight and tomorrow morning, but the limiting factor once again is the persistent onshore flow of mild marine air off the Pacific Ocean at the lowest elevations.  The Eugene to Olympia pressure gradient is pretty strong this evening, over 7 millibars.  That should equate to gusts 20-30 mph.  This means a mixing southerly breeze continues through tomorrow morning and most of the time that’ll keep the snow level up in the hills.  But any heavy batch of snow showers can easily dump snow right down to sea level since it’s so cold overhead.  To summarize, my gut feeling is most of the metro area will not be white at 7am tomorrow.  Once we get past 9-10am temperatures will definitely be too warm for sticking snow below 1,000′.  And for all you “window-licking wishcasters” out there…stop reading those snow accumulation maps!  Most of the time the mesoscale models and to a lesser extent the global models have been far too aggressive with low elevation snow in these onshore flow setups…I think we’ve seen it for every event this cold season.  It’s not that the model itself is bad, it’s just how the developers have chosen to represent snow in the algorithms, it may not be optimized for this setup.  Look at 850/925mb temps, precipitation intensity, and amount of mixing wind to start.  A lower dewpoint helps too.

Beyond tomorrow it looks wet, wet, wet…yuck.  Hard to find a dry day to work outside this week!  So it goes with a La Nina March…

Chief Meteorologist Mark Nelsen


Another “Flirtation” With Snow In Lowlands

March 2, 2017

11pm Thursday…

Let’s do it again!  If we’re going to have a cold and wet start to March, at least we can add some variety and bring in some snowflakes to the lowlands again.  Saturday through Monday (especially Sunday/Monday) we’ll be back to cold showers and sunbreaks just like last weekend.

marksnow_upcominginmetroarea

This is nearly a repeat of what we saw about a week ago.  One difference = there is more onshore flow this time, and the calendar has advanced a week further away from winter.  Meanwhile the thermal profile of the atmosphere overhead is similar to last week.  This tells me there’s no greater chance for sticking snow this time around, and probably less so along the coastline due to the stronger onshore flow.  As a result I think it’s unlikely we get measurable snow in most of the very lowest elevations west of the Cascades.  Of course with a heavy shower at the right time of day anyone could see a brief dusting; but most likely it just won’t affect your life down here.  More “conversational” snow for most of us in the lowlands.  It’ll look pretty as it falls too of course.

Now if you live up close to or above 1,000′ some sticking snow is possible at almost anyt time from Saturday through Monday.  And up around 1,500′ this could easily be a 5-10″ snowfall again…winter doesn’t let go as easily up in the foothills!

I’m headed to the annual Pacific Northwest Weather Workshop in Seattle this weekend so I won’t be back at work until Sunday PM.

Enjoy the snowflakes!

Chief Meteorologist Mark Nelsen