Our First Spring “Mini Heat Wave” Sunday & Monday

March 9, 2018

5pm Friday

Today was a pleasant day with just a few sprinkles here and there.  Of course the first week of March has been cool across the West, leftovers of the cool troughing that has lingered over us (or just offshore) since the middle of February.  But get ready for MUCH warmer temperatures the next 3 days.

Spring in our area (March through May) is typically a series of wet or mainly wet days interspersed with a few dry days.  Occasionally from now through May we’ll see a period of temperatures well above average; a spring “heat wave”.  Obviously it isn’t really hot and sure isn’t a real heat wave, but just much warmer than the average high for the date.  This is going to happen Saturday through Monday, especially Sunday-Monday.  Our average high is in the mid 50s in the middle of March, and we’ll be a good 10-15 degrees warmer than that.

Why so warm?  Several reasons:

  1. A cold and deep storm out in the Eastern Pacific will push warm air north along the West Coast

2. Easterly “offshore” wind will be blowing through the Gorge and over the Cascades.  This time it won’t be a cold wind (except mornings east metro and western Gorge).  An offshore wind in March helps warm us up a bit and dries out the airmass nicely.

3. Lots of sunshine.  Saturday will be mainly sunny, although during the late afternoon & evening skies WILL cloud up as a weak disturbance passes overhead.  Sunday should be totally sunny.  Monday starts sunny but skies cloud up in the afternoon.

How warm could we get?  850mb temps (temp in Celsius around 4,000′) peak out around +6 to +8 on Sunday and +8 to +10 on Monday.  Past cases say that if everything is perfect, this setup in March could give us high temperatures in the lower 70s.  But in the case of this weekend I don’t think it’ll be “perfect”.  Lots of clouds arrive midday/afternoon Monday.  So for now we don’t have a 70 in the forecast.  Still, highs between 65-70 are quite deluxe for March 11th/12th!

This won’t last long, we’re headed back to typical cool showers Tuesday and beyond.  Model agreement is good on this.  Check out the sharp change beginning Tuesday on the ECMWF ensemble forecast for Portland

TO SUMMARIZE

  • Enjoy our first real warm spring weekend!
  • It won’t be totally sunny Saturday & Monday, but you’ll enjoy the warmest temperatures we’ve seen so far this season with ample sunshine.
  • Record highs are unlikely, although Monday will be close.

SOME OF US WON’T ENJOY THE WARM TEMPS AS MUCH

If you live in the eastern metro area close to the Gorge, or in the western Gorge, the east wind will blow the next 3 days.  Sure, it won’t be a real cold wind, but it’ll feel much cooler than 60-70 degrees.  Peak gusts will likely be in the 30-50 mph range in the Gorge and 20-35 mph range in the east metro area (east of I-205).  This happens during March warm spells, just like in mid-late October when that wind turns a bit cooler.

How many of you remember this early March “heat wave” in 2005?

I’ve never seen anything like it in the first half of March during my entire career.  Day after day with solid sunshine and highs in the low-mid 70s.  Note the 5 consecutive record highs that still stand 13 years later.  This is the ONLY such occurrence in Portland’s daily weather records anytime in the year.

Chief Meteorologist Mark Nelsen