Frost in July Hits the Pacific Northwest

Seems a little chilly for mid-July?    Amazingly, a number of locations east of the Cascade crest have experienced FROST during the last few days, stretching from Washington into northern California.  Here is the proof, a plot showing the low temperatures of 36F or below last night.  A few locations got down to 25F!

A number of the upper air locations around the region experienced record, or near record, cold temperatures in the lower atmosphere last night.  Here is an example of the temperature at 925 hPa (about 3000 ft) at Spokane, WA.  The silver dot is the observed temperature and the blue line is the daily records low....pretty much the same!

Particularly cold temperatures (down to 25F) were found east of Crater Lake, at locations such as Kirk, Oregon (4500 ft).   This map shows last night's temperatures in that region.

And here is the temperature plot at Kirk, Oregon.

Why so cold there?  The station is in a high valley, so cold air drains down from higher elevations.  The air was unusually cold aloft and skies were clear (thus, good radiational cooling to space).

And for snow lovers, good news!  Parts of the Rockies picked up snow during the last few days.  Here are the snow analysis for July 1st and today.  You will notice some new light snow over northeast Oregon, central Idaho and western Montana.