Spring Temps

6pm Monday...

Spring 2019 is in the record books now that May has ended.   Meteorologists consider spring to be March through May in the Northern Hemisphere.  How was it?

In a sentence… WARMER & DRIER THAN AVERAGE IN THE PORTLAND METRO AREA

You may remember the first 10 days of March were very chilly due to leftover snow cover over much of the Pacific Northwest.  But then April and May were significantly warmer than average.  May 2019 and 2018 rank as #4 and #2 warmest on record!   The result = Spring 2019 was #15 warmest out of 80 springs.

This COULD be one effect of a changing global circulation here in the Pacific Northwest (higher upper-level heights); but could be partly cyclical as well.  While speaking with local meteorologists at a Portland Water Bureau meeting last Thursday this subject came up.   It seems we are seeing more up/down movement of the jet stream and fewer stormy periods with strong westerly flow.  This would account for the extra cold/snowy February weather recently with persistent ridging offshore.  Or the shift to ridging directly overhead at times (warm and dry).  This is all anecdotal of course. One local meteorologist feels this has occurred in the past, mentioning similar setups in the 1980s.  Interesting eh?  Regardless, 4 of the top 10 warmest springs have occurred recently; in 2014, 2015, 2016, & 2018.

What about rain?  Of course it’s easy to remember the unusually dry three weeks in late April and early May.  But March was quite dry, and even with a little rain later in May it still ended up below average.

Most interesting is that this is NOT a trend in our area.  Looking back 50+ years the trend is slightly wetter, not drier.

I think these are the three most memorable weather events this spring:

  1. Record cold temps (but sunshine!) in early March.  A rare early March snow-cover east of the Cascades along with easterly wind allowed cold/dry Canadian air farther south than normal.  PDX hit 24 in early March!
  2. Rare (or unprecedented?) April flooding in Willamette Basin.  First time I’ve seen flooding this late in the season.  Did this expand the “flood season” in our area?  Time will tell.
  3. 2nd consecutive year with a long dry spell mid spring.  Around 25 days with little/no rain in our area from 3rd week of April to mid-May.

Looking ahead…

We have seen a series of warm June months as well.  We haven’t seen a “chilly” June since 2014 and looking ahead I wouldn’t be surprised if this happens again in 2019.  The warm May pattern continues into early June on models, but with a brief downturn the mid-late part of this week.  A cool upper-level trough drops into the Pacific Northwest just in time for Friday/Saturday Rose Festival events.  See the ECMWF ensemble 500 millibar heights for tomorrow AM

Then by Friday a cold trough is overhead.  Expect some June snow down to at least Timberline Lodge, could even get a dusting down to Government Camp and those Cascade lakes!

Behind this trough the strongest/warmest (hottest?) ridging of the season develops early NEXT week.  It’s possible we’ll see 90 degrees or higher around Monday-Wednesday next week if this pattern shows up

Rain?  Not a whole lot, but we’ll wet things down a bit Thursday-Saturday.  Possibly as little as .10″ in the driest parts of western valleys to 1″+ in Cascades

And the timing is VERY clear on the ECMWF ensembles.  This is 24 hour rainfall from each of the 51 ensemble members, then the average (in blue) down below.

They all agree on rain Friday/Saturday, then totally dry for several days following.  Obviously late this week isn’t a good time to plan a deck-staining, mowing the lawn, or painting a shed outside.

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