Record-Breaking Cold in Eastern Washington

The cold that has been experienced in eastern WA  since early February has been totally amazing.  And unlike western WA they have had little relief the past week.

You will not believe the minimum temperatures this morning (see below).  Yakima got down to 7°F, with a number of locations around Ellensburg dropped to 2-3F. 

Such temperatures are unusual this late in the season, as shown below at several sites in northeast Oregon and southeast WA.  Some of the daily low temperature records were smashed by 5-8F.  That is significant.

Want to be really impressed?  Yakima set a new record for coldest temperature so late in the season with 7 F today.  Prior to 2019 the temperature had never dropped lower than 13 F this late in the season.

Today marks the 4th consecutive single-digit minimum temperature at Yakima with 7, 7, 4, and 7 F.  Over the past month, Yakima's highs have been hanging around the normal lows, with temperatures dropping below 10F on roughly 1/3 of the days.

Even worse was Pasco, where the highs on several days did not get even near the normal lows.

Over the last week, the departure of the daily average temperature from normal has been stunning east of the Cascades crest, with much of eastern WA more than 16F below normal.

An interesting aspect of the cold air is how shallow it was.  As suggested by the minimum temperature map, the coldest temperatures were at low elevations, with warmer air above. This structure is suggested by the radiosonde (balloon-launched weather station) observation at Spokane for 5 AM Monday, which shows cool air near the surface topped by a strong inversion (temperature warming with height).  So a modest hike to higher elevation would bring much warmer tempeatures.

In this plot, temperature is the right line and dew point temperature is the left line.  

Heights are in pressure (850 is roughly 5000 ft).

Why do cold?  We start with unusually extensive snow cover for this time of the year, with snow producing cooling by reflecting solar radiation back to space and through emission of infrared energy away from the surface.

A satellite picture shows the total snow cover over eastern WA today.

With virtually no cover over the Columbia Basin a year ago.

And the general weather circulation pattern has been highly anomalous, with ridging offshore and a trough of low pressure and cold air over us for most of the past 30 days (see the upper level height anomaly below, with the purple being more lower heights/pressures).

The extreme low  temperatures in eastern Washington have already killed thousands of cattle and winter wheat emergence has been slowed.   Fortunately, major warming is in store during the next few days, with highs moving into the 40s and low temperatures rising into the 20s or more.