After the record heat in Western Washington on Monday, attention will turn to central and eastern Washington on Tuesday as strong winds, low humidity, and continued heat will create conditions ripe for swift spread of wildfire.
A Red Flag Warning has been issued for most locations east of the Cascades Tuesday, and NOAA’s Storm Prediction Center (which also issued fire danger outlooks) has circled much of the same area in a “critical” risk for low humidity and high wind on Tuesday.
Large fires are already ongoing in a few locations, and winds will be turning from northeasterly to northwesterly to west on Tuesday east of the Cascade range, which will potentially move fire lines in new directions.
The reason for the critical fire danger is the same weather pattern that will bring cooler (but still warm) daytime temperatures to Western Washington — the westerly wind off the Pacific Ocean. While this wind is “nature’s air conditioning” for locations west of the Cascades, the wind currents will get squeezed through the mountain passes and then accelerate, warm, and dry on the eastern slopes Tuesday.
The ground cover on the lower elevations of central and eastern Washington consists largely of grasses and other fine fuels which have already dried out. This means that any source of flame will cause ignition, and with low relative humidity and strong winds, fires can spread rapidly.
Winds will calm down east of the Cascades as we go into the second half of the work week, but it will still stay critically dry there.
West of the Cascades in the lowlands, Tuesday will be breezy but cooler with highs in the 70s in most locations around the Sound with 60s at the coast. There will be a bit of warming with more areas seeing the 80s by the end of the work week and the upcoming weekend, but I don’t see another heat wave coming over the next week to ten days.