Cliff Mass Weather Blog

I will define a Super Inversion when temperature increases by more than 20F in the lower atmosphere (from the surface to roughly 3000 ft).
As noted many times in this blog, temperatures normally decrease with height, but in inversion situations that opposite occurs....

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...

This winter, persistent high pressure has frequently developed over the western U.S.
High pressure that has often brought dry conditions and afternoon sun.  But such high pressure also results in extensive fog, particularly in valleys and basins.
Fog is a serious threat with such high-pressure conditions, often resulting in multi-vehicle collisions, injuries, and loss of life....

We are now solidly into mid-winter--a good time to check on the status of precipitation over the region.
Let's start with the total cool-season precipitation since October 1, the beginning of the "water year" (see below).
The majority of the western U.S. has received above-normal precipitation, with the North Cascades and the Los Angeles area being substantially wetter than normal....