Smoke Relief & Potential Rain, Uncertainty Remains

No FastCast tonight…continue reading the full blog below.

Air quality across Washington state on Sunday was quite horrible. The PurpleAir map below shows air quality at 10 PM Sunday.

Some improvement has begun, with air quality improving for areas from Everett northward and on the coast. The lowlands, from Everett to Olympia, remain in the “unhealthy” to “very unhealthy” categories (150-220 observed). In Eastern Washington, most areas are in the “very unhealthy” to “hazardous” categories (200-400), except the Spokane and Pullman areas, where air quality has decreased to “unhealthy”, at 150-175, as winds begin to move smoke away.

So, how does this compare with the forecast? Let’s take a look below at the HRRR smoke forecast for 10 PM Sunday.

The forecast is largely on track, except improvement has happened faster than forecasted from Everett northward and around Spokane and Pullman.

A word of caution: In recent smoke events, this forecast has cleared smoke out of the lowlands far before it actually happened. The smoke will likely move out of the region in the manner the forecast shows, but the times could be many hours later than what is posted here. (For example, the situation at 5 AM Monday might not happen until later in the day).

Next, let’s look at the forecast for 5 AM Monday.

By 5 AM, this forecast shows smoke beginning to clear for most of Western Washington, except the foothills, with most of Eastern Washington still stuck under heavy smoke. Notice moderate to heavy smoke still present from Olympia to Seattle.

Next, the forecast at 12 PM Monday.

By 12 PM, smoke in Western Washington is moving, but being sloshed around by onshore winds. It remains between Tacoma and Kelso. The Cascade foothills, mountains, and western half of Eastern WA remain very smoky, with substantial improvement for the eastern half of Eastern WA due to the remnants of Tropical Storm Hilary bringing fresh air.

Next, the forecast for 5 PM Monday.

Improvement will continue in Eastern Washington on Monday evening, but easterly winds from the remnants of Hilary could have an adverse effect on the Gray and Oregon Road Fires. Surface smoke will be pushed back into the Seattle-Tacoma metro area after clearing Olympia and Everett. The foothills and a large part of Central Washington remain very smoky.

By 7 AM Tuesday, the marine air’s influence is clear.

By Tuesday morning, this forecast shows Western Washington entirely clear of smoke, with marine air pushing the remaining smoke east across Eastern Washington and out of the state. As marine westerlies continue, smoke plumes off fires in the Cascades will grow, bringing more degraded air quality to Eastern Washington, mainly from I-90 northward.

Remember, the timing of this could be radically different if this forecast is too aggressive clearing out smoke. It is reasonable to think that smoky conditions will last until sometime on Tuesday, instead of clearing out before Tuesday. Additionally, this is unlikely to be our only statewide smoke event. More are likely and could come soon, so stay tuned.

Switching gears, the remnants of Tropical Storm Hilary, which are currently and will cause devastating and potentially catastrophic flooding across parts of California and the Intermountain West, will also clip Eastern Washington, potentially bringing showers to the Gray and Oregon Road Fires. Let’s look at the forecasts below.

First, the European model forecast for rain through late Wednesday night.

The European model shows 0.2-0.8” of rain around the fires, with 0.5-1.5” of rain possible in far SE Washington due to the remnants of Hilary. This rain will fall from midday Monday through early Tuesday afternoon. The European model also shows a system bringing 0.2-0.5” of rain to Western Washington (most north of Everett and south of Tacoma, and on the coast) from Tuesday evening through Wednesday.

The GFS forecast has some significant differences. Below is the GFS forecast through Wednesday night.

The GFS shows 0.1-0.3” of rain over the fires near Spokane, and 0.5-1.5” of rain in SE Washington from the remnants of Hilary. This forecast also shows an area of heavy rain (0.75-1.5”) over North Central WA and into areas of BC with major wildfires. Additionally, there is little to no rain for Western Washington in the GFS forecast. This forecast shows most rain in Eastern WA falling from midday Monday through Tuesday afternoon, with the heavy rain in North Central WA falling from Tuesday afternoon through Wednesday afternoon.

Finally, we will look at the UW WRF high-resolution forecast, through early Thursday morning.

The UW forecast shows 0.2-0.5” of rain over the fires near Spokane, with most of far Eastern Washington getting 0.2-1.25” of rain from the remnants of Hilary. This forecast also shows Western Washington getting 0.1-0.75” of rain, with amounts varying due to heavier showers. This forecast shows most rain in Eastern Washington falling from Monday afternoon through Tuesday afternoon, and most rain in Western Washington from Tuesday afternoon through Wednesday morning.

Each of the forecast scenarios shown are possible. Stay tuned for Monday night’s update on the progress of smoke moving out of the region and the potential for rain across the state!