A Historic Cold March Day In Some Parts of the Pacific Northwest

March 3, 2019

7pm Sunday…

Whew…it’s C-O-L-D outside!  It’s early March, the sun set less than an hour ago, and we’re already down to 32 here at KPTV on the west side of Portland.  Add in a gusty east wind and it feels like about 20 degrees outside.  I think it felt warmer all of December and January!

We are currently feeling the effects of a modified arctic airmass that surged over the Rockies and down into the Pacific Northwest.  The most obvious result from a meteorological standpoint is the dropping dewpoints.  We’re down to around 10 in the metro area, headed for single digits overnight.  This is the driest airmass of the season folks; nosebleed and skin-cracking territory.  Think even drier than Central Oregon dry.  Of course this has come in on a gusty easterly wind, peak gust so far today has been 40 at PDX.

Today was the coldest day (maximum temperature) in the month of March at PDX since the late season snow in March 2012.  Keep in mind those cold days involved clouds and snow showers (or even a steady cold rain).  That makes it even MORE amazing that we only reached 42 with 11 hours of solid sunshine.

Mark Portland Record Cold Night

Take a look at regional high temps.  You can see the effect of cold easterly flow coming through the Gorge; Portland is colder than all other locations except Roseburg.  They still have some snow on the ground which led to low clouds much of the day.

Todays Observed Highs OrWa 2017

Then notice the REALLY cold stuff east of the Cascades.  All these areas have a thick blanket of snow, even down to the Columbia River

Todays Observed Highs OrWa 20172

At first glance it doesn’t seem too unusual right?  Except for the date…it’s early March.  After checking through the records it’s obvious that in many parts of Central/Eastern Oregon this was the coldest March day in decades.

Cold Temps Record Eastern Oregon March

The Redmond airport observations go back to 1949 and the 20/21 there appears to be the coldest March day on record.  This is due to thick snow cover, a cold arctic airmass, and low clouds overhead the entire day.

By the way, the low of 26 in Portland Saturday morning was the coldest March temperature (30 years!)  since that early March 1989 cold spell.

March Coldest Temp

What’s ahead?  As long as we keep the easterly/offshore wind going in the region and snow cover remains on the ground eastside it’ll be slow to warm up here in Portland and east of the Cascades.  We’re seeing a rare convergence of several weather factors that don’t usually line up in March:

  1. Thick snow cover east of the Cascades
  2. Weak/splitty systems moving through the region for the next 7 days
  3. No widespread warm or southerly wind flow to quickly melt that snow eastside or warm us into 50s in metro area.

This tells me we’ll be slow to warm up through at least next weekend.

Models disagree on how much moisture makes it north Wednesday/Thursday.  The ECMWF is insistent on bringing light snow or a rain/snow mix to the Portland area Wednesday morning.  Since we’ll have such dry air, evaporative cooling could be a big deal = we COULD actually get sticking snow with that setup.  OR, if light/spotty showers wait until midday to show up = no big deal and we get some “conversational snow” that doesn’t affect our lives much.

I’ll take a closer look at that setup tomorrow.  For now…stay warm!  With such low dewpoints any part of the region west of the Cascades that goes completely calm could drop to 20 or even a bit lower.  Brrr!

Chief Meteorologist Mark Nelsen