Colder Air Moving In While Windfires Burn East of the Cascade Crest

 During the past week or so, several fires were started in British Columbia and east of the Cascade crest.  Some were initiated by lightning, and strong westerly (from the west) aided growth in some locations.

But the meteorological situation is shifting, which has implications for fire initiation and spread--and in a generally positive direction

The high-resolution visible satellite image yesterday around noon shows the smoke from several fires in southeastern British Columbia, a fire in the northeast Cascades, two in the Okanagan area of northwest Washington, one near Wenatchee, and another in the Blue Mountains near Walla Walla.

Western Washington and northwestern Oregon were essentially smoke-free with the influx of clean marine air.  The latest air quality analysis is favorable (green) for the westside:

Interestingly, as some of the fires revved up during the heat of the day, they became clearly evident in weather radar imagery (see below, red circles indicate the features)

This morning, the low-elevation sun highlighted the smoke.  Pretty dense over northeast Oregon.  And a major influx of cloudy, cool, and clean (the three C's) over western WA and OR.

Many of the fires have burned in grass/rangeland or in grass/forest mixes, which is not surprising considering how dry the light fuels (grass, rangeland vegetation) are right now after a dry spring and the big heatwave.

The weather situation is now shifting to a far cooler configuration for the region and particularly west of the Cascade crest.  As illustrated by the upper-level forecast for 5 PM Friday, an upper-level trough (blue colors) will move towards our region, while high pressure (yellow/orange colors)  weakens and extends eastward.  A similar pattern will hold for most of next week. Not a hot pattern for the Northwest.

The predicted situation for the next several days is one with much cooler temperatures in the west (mid-70s), considerable low-level clouds, and even some drizzle--particularly Saturday morning. East of the Cascades, temperatures will drop into the 90s.

At this point, the models do not point to strong winds accompanying the transition, which is good since winds can stoke the fires.  Importantly, no lightning is being forecast during the next 4-5 days.

The bottom line is that as we move into the climatological driest time of the year, the meteorology is becoming more favorable for controlling preexisting fires and does not have several of the elements known to start fires (strong winds, lightning).   

But humans need to be careful not to start fires in the dry fuels present throughout the region. And, of course, we don't know our weather future with any confidence more than two weeks ahead.