The End of Northwest Cold for The Winter and A Short Heat Wave

There comes a point each winter when it is simply not possible to get really cold anymore.

Here in the Pacific Northwest, we are now crossing that line.

The figure below shows observed temperatures at SeaTac Airport so far this year as well as the daily record highs (red lines) and lows (blue lines) for the entire year.  The brown band shows the average daily range throughout the year

Our temperatures so far this year have been quite normal, with warmer and cooler days.  

But now look at the cold records.  In January, record temperatures have dropped below ten degrees on many occasions.  But past the first few days in February, there is an abrupt jump to warmer temperature records, with record lows never getting below 15F.

By early March, we never get below roughly 25F.  

East of the Cascades at Yakima Airport, the situation is similar, except that the temperatures are much colder.  After early February, sub-zero temperatures are history!

The key driver of the transition to warmer temperatures is that the sun is getting stronger and days are getting longer.  You can see this in the plot of solar radiation reaching the top of the atmosphere over the year (below).  

The sun now is about the same as it was in early to mid-November.

 Talking about warmth, according to the highly accurate weather.com prediction, tomorrow through Friday should rise to near 60F at SeaTac.

But if you are willing to take a short drive, you may be able to experience 70F!

Where? In the western foothills of the Cascade!

High pressure has built over our region and will be in place overnight (see the upper level map--at 500 hPa pressure..about 18,000 ft for tomorrow morning).    High pressure results in warm temperatures aloft.

Tomorrow, low-level easterly (from the east) winds will develop that produce sinking on the western slopes of the Cascades, producing additional warming by compression.

As a result, there will be a band of uber-warm temperatures on the slopes in areas such as North Bend.  A UW model temperature prediction at 1 PM shows the warm zone.

A similar, if not stronger, warm zone will be apparent on Thursday (see below), with powerful warming on the western side of the Olympics tomorrow.

There are a lot of weather enthusiasts/weather chasers in our area.  Will one of you take a hike up Tiger Mountain or Mount Si tomorrow, making temperature measurements every few hundred feet?

I will add it to this blog if you give me the information!