U.S. Extremes: Big Warm Ridge over the West and Deep, Cold Trough over the East

There is a lot of talk about extreme regional differences in politics these days, but during the next week, we will see amazing differences between the western and central U.S. in temperature:  

A very strong ridge of high pressure will prevail over the West, with very warm temperatures aloft, while the east will be dominated by a deep trough of low pressure, that will bring extreme cold down to the surface.

Let me start by showing you some very colorful maps created by Alicia Bentley (a NOAA/NWS employee!)  These show the upper level maps (500 hPa pressure level, about 18,000 ft ASL), with the heights of the pressure level shown in black, and a measure of the differences (or anomalies) from normal shown in colors (orange/red are above normal, blue/purple below) normal.

Today at 10 AM (1800 UTC) there is a big ridge of higher heights (think high pressure) over the West Coast and a trough (lower heights/pressures) over the east.   Major anomalies, with the purple colors indicating very usual low heights.

Ridges tend to be associated with sinking air and warm temperatures in the lower atmosphere, while troughs are connected with cold air.   So let me show you the anomalies for temperature around 5000 ft (850 hPa) at the same time as above (10 AM today).  Warm air along the West Coast, but cooler air in the east, with a slug of very cold air moving into Minnesota and environs (see below).

In fact, we do have very warm air above us right now.  The balloon-launched weather reports at Quillayute, on the WA coast, are shown below (the two lines are temperature--the warmer one--and the other is dew point).  Winds to the right and heights are in pressure (700 is roughly 10,000 ft). Very warm air aloft, with a freezing level (when temperature falls to 32F) ABOVE 10,000 ft.  Toasty.

There is some cooler air near the surface, with an inversion (temperature warming with height) in the lower atmosphere.  The mountains will be toasty today.  In fact, at 9 AM Stampede Pass at 4000 ft it is warmer (40F) than Seattle (38F and fog).

The latest satellite pictures shows the low-level fog over the lowlands of western WA/Oregon and parts of eastern WA.

That is the great irony of high pressure over the Northwest in winter.  When we have high pressure over us during mid-winter, with warm temperatures aloft, we can't mix the warm air down and we tend to develop low-level inversions and near-surface fog.    But all you have to do is gain elevation and you can escape the cool stuff. Offshore (easterly flow) can destroy the cold air layer and later in the season, when the sun is stronger, solar radiation can do the job.

But then we get to the story that the media is already starting to pick up on-- the  deepening of the East Coast trough accompanied by a slug of MEGA-COLD air.   Here is the 500 hPa upper level map for 4 AM on Wednesday (January 30th).   Extraordinary low heights over the upper Mid-west (the light purple colors--the anomaly from normal in standard deviations--are amazing).  Ridge of high pressure off our coast (dry for the NW).

The 850 hPa (5000 ft) temperature anomalies (again differences from normal) coming into the Upper Plains state will be amazing and some locations will probably break record lows for the date.

I suspect a certain President will tweet about this event, suggesting it contradicts global warming, and some activist/media types will claim it is the result of global warming.  Neither will be correct.  Perhaps something I will talk about in a future blog.



from Cliff Mass Weather and Climate Blog http://bit.ly/2G2NQmP