Written by: Robert Sandberg/Carson City Weather – 09/10/2020
As we all know, the fires in the western US continue to produce prolific amounts of smoke into the atmosphere especially over California and Oregon. More interestingly the smoke plume that has retrograded west over the northeast Pacific continues to be rather defined. A look at the latest GOES West satellite image continues to show a dense smoke layer over California progressing very slowly east southeast due to a persistent closed low over the intermountain region that has brought snow to some areas.
A look at the big picture (18Z GFS) shows a pseudo omega block like of pattern a slightly atypical of early September with a closed low well off the west coast and the aforementioned closed low centered over western Colorado. High pressure is located just off the west coast, with some weak undercutting of what is left of the westerlies rounding the base of a flabby trough located just of the SoCal/Baja coast.
Looking at the same 500mb anomalies also show the very defined closed lows in the same locations with above normal heights along the west coast, with stronger positive height anomalies from Alaska to western Canada. This is also reflected closer to the surface too, with an elongated area of low pressure just off the west coast.
So now that we have the analysis out of the way, it looks like a prolonged period of continued smoke will continue over much of CA/OR progressing very slowly east over the next few days especially if fire activity continues flare up as we have seen over the last few days. What is interesting is the areas of smoke look similar of a storm moving southeast toward SoCal into the southern tier of states like we commonly see in the cold season. Without all the smoke in the various levels of the atmosphere, it would hardly be noticeable.
As for precipitation, most forecast models continue to suggest that dry conditions will persist over much of the region through the period. Any showers that develop will likely be well north of Reno/Carson City and will be mostly focused over northern California for now. Smoke may temporarily move out of the area once again but is likely to persist off and on for the new couple of weeks at least.