Brief Cooldown, Dangerous Fire Weather Conditions in Eastern WA

 FastCast--Sunday, June 23 to Thursday, June 27:

A significant, but brief, cooldown is expected across the region on Sunday, with overcast skies, a chance of light showers (especially Seattle northward and on the coast), and highs dropping to the low to mid 60s. This is caused by a weak cold front moving through, which will bring dangerous fire weather (low humidity and strong winds) to Eastern Washington. Conditions will rebound on Monday, with partly sunny skies and highs returning to the upper 60s to low 70s. Tuesday will be mostly sunny and warmer, with highs in the mid to upper 70s (and possibly the low 80s). However, a significant change is store for Wednesday and Thursday, with troughing bringing highs back down to the mid 60s, with a chance of showers (up to 0.3" for the lowlands). Through Thursday, expect overnight lows to be in the low to mid 50s.

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A relatively weak system moving through the Northwest on Sunday will bring a brief cooldown and dangerous fire weather to Eastern Washington. Let's take a look at the forecast!

We'll start with the NAM high-resolution forecast for 24-hour temperature change across Western Washington on Sunday afternoon.

Notice that most of the region will be 10-20° cooler than Saturday, especially in and east of the Cascades and in the Convergence Zone (between Seattle and Everett).

These significant temperature declines will be fueled by strong onshore flow moving into the area. Below is the European model forecast for peak winds on Sunday.

This forecast shows 20-30 mph gusts for Western Washington and 30-45 mph gusts in Eastern Washington. Those winds are of note, as they will fuel high fire danger.

Next, let's take a look at the forecast for relative humidity on Sunday afternoon, also from the European model.

This forecast shows relative humidity dropping to 10-20% for most of Eastern Washington, with some areas reaching values of 5-10%. These humidity values will make it very easy for fires to spread rapidly. This especially applies to any grass fires that start, which will have explosive rates of spread due to the combination of gusty winds and low humidity.

This combination of fire weather conditions has caused the NOAA Storm Prediction Center to put Eastern WA under a "critical" fire weather risk area.

In addition to this risk area, NWS offices in Spokane and Pendleton have issued Red Flag Warnings due to the fire danger.

This system will also bring a chance of light showers to Western Washington, as seen in the NWS NBM forecast below.

The best chance of showers will be on the coast (0.1-0.2"), in the Cascades (0.15-0.4") and from Seattle northward. Showers will be most likely on Sunday, tapering by Monday.

Finally, let's take a look at temperatures, from the NWS NBM high-resolution model. First, the forecast for Sunday.

This forecast shows Sunday's highs in the lowlands reaching the mid 60s, which is likely too high, as this forecast underestimates the impact of thick cloud cover. I'd expect highs in the low to mid 60s (same on the coast), and in the upper 60s to mid 70s for the Willamette Valley. Eastern Washington will reach the upper 70s to upper 80s, except only the mid 70s in the Kittitas Valley, due to strong west winds.

Temperatures begin to rebound a bit on Monday for Western WA, as seen below.

Expect the lowlands to reach the upper 60s to low 70s, the coast to reach the low to mid 60s, and the Willamette Valley to reach the upper 70s. Eastern Washington will cool to the mid 70s to mid 80s.

Finally, here's a look at the forecast for Tuesday, likely the warmest day of the week.

On Tuesday, expect lowland highs in the mid to upper 70s (isolated low 80s in the South Sound), with the coast reaching the mid 60s to low 70s, and the Willamette Valley reaching the mid to upper 80s. Eastern Washington will reach the mid 80s to mid 90s.

Stay tuned for more details about the forecast for next week, and the impending midweek cooldown.

Hot Through Saturday, Cooler Sunday with Fire Danger

 FastCast--Friday, June 21 to Tuesday, June 25:

One of the hottest days of the year (so far) is ahead on Friday for the lowlands, with highs likely reaching the mid 80s across the region. Areas north of Everett and closer to the water will likely remain in the upper 70s to low 80s, with areas south of Tacoma and in valleys potentially reaching the upper 80s. Conditions will get cloudier and temperatures will cool somewhat on Saturday, with highs back in the upper 70s to low 80s. Further cooling and a region-wide chance of showers is ahead on Sunday, with highs dropping to the mid to upper 60s. Highs will return to the low to mid 70s on Monday and Tuesday, with partly cloudy to mostly sunny skies and a lingering chance of showers on Monday. Overnight lows through Monday will be in the low to mid 50s. There is significant fire danger in Eastern Washington on Sunday. Keep reading for more information.

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A hot few days are expected across Washington state, with cooling later in the weekend and potentially significant fire danger in Eastern Washington on Sunday. Let's take a look at the forecast!

We'll start with the high-resolution NWS NBM model forecast for highs on Friday, seen below.

On Friday, expect highs from Seattle northward in the upper 70s to mid 80s (warmest away from the water). From Seattle southward, highs will reach the mid to upper 80s, warmest in river valleys. The coast will be cooling down a bit, with highs in the mid 60s to low 70s. The Willamette Valley will likely reach the upper 80s to low 90s, with Eastern Washington in the mid 80s to mid 90s.

On Saturday, temperatures will cool some west of the Cascades, while remaining hot on the east side. Below is the NWS NBM forecast.

On Saturday, expect lowland highs to reach the upper 70s to low 80s (cooler near the water and in the NW Interior). The coast will cool to the mid 60s, and the Willamette Valley will drop slightly to the mid to upper 80s. Eastern Washington will warm up, with highs in the upper 80s to upper 90s, hottest in the Tri-Cities area.

Sunday will see more dramatic cooling for Western WA, with some cooling in Eastern WA as well.

On Sunday, the lowlands will only reach the mid to upper 60s, with the coast remaining in the low 60s. The Willamette Valley will cool to the mid 70s, and Eastern Washington will cool to the upper 70s to upper 80s (hottest in the Columbia Basin).

However, this cooling will come at a price, especially for Eastern Washington. Below is the forecast for winds on Sunday, from the European model.

This forecast shows a breezy day west of the Cascades (20-25 mph gusts, except 30-35 mph along the Strait). However, Eastern WA is quite windy, especially in the lee of gaps in the Cascades. Gusts of 30-45 mph are expected, strongest east of the Gorge and around the Kittitas Valley.

With these winds will come very dry conditions. Below is the European model forecast for relative humidity on Sunday afternoon.

Notice the extremely low values of 10-20% across Eastern Washington. This will pave the way for rapid fire spread. Any fires that start on Sunday will have the chance of becoming out-of-control very quickly, due to strong winds, very low humidity, and overall dry conditions.

Finally, let's take a look at what will be happening on the western side of the state on Sunday and Monday. The weak weather systems ushering in cooler conditions will have some light showers and a potential Convergence Zone, as seen in the European model rain forecast below, showing rain through Monday night.

This forecast shows light rain across Western Washington, with 0-0.15" in the lowlands, up to 0.25" on the North Coast, and 0.2-0.5" in the Cascades and Olympics.

Stay tuned over the next few days for more information on the Eastern WA fire weather situation and the overall patterns we'll have to wrap up June.

Warmup Ahead as Solstice Approaches

 FastCast--Tuesday, June 18 to Sunday, June 23:

After an active couple days with showers and thunderstorms around the region, conditions will calm down, clear out, and warm up as we approach the "official" start of summer and the longest day of the year. Tuesday will begin mostly cloudy, gradually becoming mostly sunny, with highs in the upper 60s to low 70s. Mostly sunny conditions are expected from Wednesday to Friday, with highs in the mid 70s to mid 80s, warming as we get later in the week. Highs will remain in the low 80s on Saturday, with some high clouds moving through the region. A marine push is likely on Sunday, bringing breezy southwesterly winds, an influx of marine stratus clouds, and highs dropping to the mid 60s.

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After an active few days, with lots of showers around, conditions will get sunnier and drier as a ridge builds over the Northwest.

Below is the upper-air forecast for Tuesday, from the European model.

This forecast shows broad troughing across the Western US, including the Northwest, although the trough is starting to move east, giving us sunnier conditions.

Let's fast-forward to Friday, seen again on the European model.

Notice the significant change, with broad ridging across most of the US, including the Northwest. This will bring sunnier and warmer conditions to our area.

Now, let's take a look at what kind of temperatures are in store, especially with a big warmup throughout the week. These forecasts for high temperatures are from the high-resolution NWS NBM (which stands for National Weather Service National Blend of Models, a NWS-run forecast model combining the output of all major models).

First, the forecast for highs on Tuesday, seen below.

On Tuesday, expect lowland highs in the upper 60s to low 70s, coastal highs in the low 60s, Willamette Valley highs in the mid 70s, and Eastern Washington's highs in the upper 60s to upper 70s.

Wednesday will be noticeably warmer across the state, as seen below.

On Wednesday, expect lowland highs in the upper 70s (low 80s Olympia southward), coastal highs in the upper 60s to low 70s, Willamette Valley highs in the mid 80s, and Eastern Washington's highs in the mid 70s to mid 80s.

Thursday will be even warmer, as seen below.

On Thursday, expect lowland highs in the upper 70s to mid 80s, coastal highs in the upper 60s to mid 70s, and Willamette Valley highs in the mid to upper 80s (isolated low 90s possible). Eastern Washington will reach the mid 80s to low 90s, hottest in the Columbia Basin. 

Additionally, Thursday is the "official" start of summer, and the summer solstice. This means that we only have 1 hour and 58 minutes of "night", with partial twilight beginning around 2 AM and remaining until 12 AM the next morning. It will be quite a warm day that will also be the year's longest!

Finally, let's take a look at highs on Friday, seen below.

Notice that the coast has begun to cool ever so slightly as marine air starts to move back in. On Friday, the lowlands will reach the upper 70s (north of Everett) to the mid 80s (Seattle south and east). The coast will reach the upper 60s to low 70s. The Willamette Valley will be quite hot, in the upper 80s to low 90s. Eastern Washington will reach the mid 80s to mid 90s, hottest around the Tri-Cities.

Stay tuned this week as we get more accuracy in the forecast beyond this weekend, and whether we will remain warm and pleasant, or if conditions will turn cooler and potentially wetter.