No FastCast tonight…continue reading the full blog below!
Special Note: The 2620 Road/Jupiter Fire is burning on the slopes of Mt. Jupiter, west of Brinnon (on Hood Canal), and near the Duckabush valley and Dosewallips State Park. As of 10:00 PM Thursday, the fire has burned 350 acres and is 0% contained. This fire has been visible from the Seattle metro area, and will likely continue to be active on Friday. Stay tuned to local authorities (WA DNR & the Brinnon Fire Department) for updated information.
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A potentially significant thunderstorm event is looking likely this weekend across Washington. We’ll take a look at the forecast and approximate timing of this event in tonight’s blog post, and will nail down more exact details in an update either Friday night or Saturday morning, so stay tuned.
We’ll start with the forecast for the upper-air pattern (at 10,000 feet) early Sunday morning, from the European model. This is very important to understanding this thunderstorm event.
Notice how the lines over the lowlands go from SE to NW, indicating SE flow aloft. This is what will allow for thunderstorms to move through the region.
Now, let’s get to the thunderstorm forecast. We’ll start with the forecast for where thunderstorms will be on Saturday afternoon. This is from the European model.
On Saturday afternoon, the best chance for thunderstorms will be over the Willamette Valley, Oregon Cascades, and off the WA/OR coast. The thunderstorm threat is moving into the lowlands, with higher chances over the Olympics & Cascades.
Next, let’s take a look at the thunderstorm potential for Saturday night.
Now this is something…this shows a significant thunderstorm event, with heavy rain and frequent lightning, across the Puget Sound lowlands, Washington Cascades, and most of northern Oregon. This would be a memorable thunderstorm event if this verified.
Finally, here’s a look at early Sunday morning, as the thunderstorm activity begins diminishing and moving north out of the region.
Early Sunday morning, activity gets confined to parts of the lowlands and the east slopes of the Cascades. The European model likely underestimates the potential for thunderstorms over areas from Everett northward. We’ll take a more in-depth look at this in my next blog.
This is a very interesting forecast, with a very high thunderstorm potential across the region. The thunderstorm events of the past few weeks (mainly confined to the mountains and Eastern WA) have been notable for their lack of rainfall, and therefore, a high chance of starting fires. However, this is not the case with the weekend event.
Below is the European model forecast for total rain through Sunday.
This forecast shows most of the region from Portland to Everett getting 0.3-0.7” of rain, more than the past 2 months for much of the area.
Let’s compare this to the NWS NBM high-resolution forecast, which has a somewhat different solution (also showing rain through Sunday).
This forecast implies that thunderstorms will move northward across the region in a more uniform fashion than the European model shows. In this forecast, all areas west of the Cascades receive 0.3-0.7” of rain, with isolated higher totals in the WA Cascades and Olympics.
This rain would be beneficial, and would help to significantly decrease the threat for new fires started by lightning. However, with a lack of rain predicted for most of Eastern Washington (generally under 0.1”), any thunderstorms east of the Cascades may have a chance to spark new fires.
A very important thing to note is that as usual with our thunderstorm events, everything is still quite uncertain. The most uncertain aspect is how the storms will move through (either multiple rounds or one big area of thunderstorms), how much rain will fall, and how strong any thunderstorm-related winds will be.
One prediction is found below, on the NAM high-resolution model. This is basically showing predicted weather radar on Saturday night.
The NAM shows a huge area of thunderstorms, stretching roughly from Lake Quinault to Moses Lake, moving northward across Washington on Saturday night. Other forecasts (like the European) show a feature like this, preceded by scattered storms.
More high-resolution models will be in range over the next 24-36 hours, and I’ll use those in my next blog, either Friday night or Saturday morning.
In the meantime, you can follow along on my Twitter/X page, the Pacific Northwest Weather Watch YouTube channel (both on the right side of the blog under “Helpful Weather Websites”), or my brand-new Facebook group for Western Washington Weather! Click the large Facebook logo on the top right of the blog page to access the group. If you have a Facebook account, please join the group so you can follow along with even more updates and share what weather is happening at your location!
The dried up grass will be happy for the rain.
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