Summer Rain Making Brief Comeback

With an average total precipitation accumulation of 1.05 inches, the month of August is the second driest month of the year at Paine Field. At the time of writing this, the monthly total at KPAE is 0.51 inches, slightly behind the normal 0.56 inches. However, over the next few days, we could double our monthly total as the first atmospheric river of the season heads our way.

Figure 1: Integrated Water Vapor Transport forecast; darker colors show areas of more moisture

Figure 1 shows the setup of the atmospheric river, with the moisture aiming right at Washington. To read more about atmospheric rivers, click here.

Through the above visible satellite animation courtesy of NWS Seattle, you can see clouds associated with the incoming system poised to take aim at us.

For August, some of the rainfall totals across Western Washington look to be quite impressive.

Figure 2: Euro model for accumulated precipitation through Saturday evening

Areas especially near the Olympics look like they’ll get a good soaking, with some places approaching 2 inches!

Closer to home, the Euro model shows Everett to having just over a quarter inch. But when you look at the Euro ensemble (shown in Figure 3 below), the average (which is generally more skillful than individual members) is approaching a half inch.

Figure 3: Euro ensemble for total accumulated precipitation for KPAE

For the rain lovers out there (🙋‍♀️), enjoy it while it’s here because we are still in one of the driest times of the year, and the dry comes back full swing afterwards with not much more rain expected in the next couple weeks (at least at this time–it can change still).

Figure 4: 24 Hour Precipitation accumulation for KPAE (Euro ensemble)

It’s like a little taste of fall and winter weather in the midst of summer…but it makes me really excited for the cooler and wetter days ahead of us! Fall is coming… just gotta wait a little while longer!

Are you excited for Fall? Let me know in the comments below!

Abnormally Dry April About to Turn Wet

water droplets on clear glass

Much of this month has been the taste of Spring that many of us has needed as a sort of mood-booster during these uncertain times. There has been plenty of dry weather and sun to go around.

In fact, this mostly dry start is abnormal. Take a look at these charts showing the minimum 20 day precipitation total at both KSEA and KPAE:

Table 1
Table 2

These tables show the driest starts to the month of April on record for both Sea-Tac and Paine Field, respectively. Since records began in 1948, this has been the second driest start to the month of April at Sea-Tac…the driest since 1951! Paine Field isn’t quite as impressive, but it still sits at number 7 (although most of that total fell on April 18th).

This has been great to go outside for some walks or bike rides as we all continue to do social distancing. I know I’ve taken advantage of it by going on many bike rides!

Unfortunately (or fortunately, depending on who you are), our weather pattern is about to shift.

The first system is on deck by tomorrow, packing quite a punch for this April’s standards. You can see it on visible satellite imagery, lurking in the eastern Pacific.

Figure 1: Satellite image taken around 3:30 PM on 4.21.20

Take a look at the following GIFs, showing the 3-hour precipitation totals as the system moves into the area:

Figure 2: 12z Euro run of 3 hour precipitation for 4.22.20
Figure 3: 12z GFS run of 3 hour precipitation for 4.22.20

Much of the state looks to take a hit, with even Eastern Washington getting in on the action.

Figure 4: Euro Ensemble showing 24 hour QPF (accumulated rainfall) for KPAE

Figure 4 above suggests that this system could be one of the wetter ones on tap for the area in the next week or so. But it also shows that it’s not the only system on its way.

Showers decrease gradually throughout the day Thursday, with a mini ridge of high pressure taking shape. This should help keep Friday mostly dry, with the exception of some scattered showers. Yet, another system arrives late Friday into Saturday, with potentially a third following it (things could certainly change a week out from now). You can see the three spikes in the 24-hour QPF in Figure 4 corresponding to each system. The GFS shows similar spikes, as shown below.

Figure 5: GFS Ensemble showing 24 hour QPF for KPAE

By next week, both models are suggesting we could add an additional 2 inches of rainfall to our April total at Paine Field. The Euro and the GFS don’t agree as much at Sea-Tac, with the GFS showing just over an inch while the Euro is near the 2 inch mark.

If those totals came into fruition, our April rainfall deficit could be completely erased. To give some perspective, the normal rainfall for the month of April is 2.58 inches at Paine Field and 2.71 inches at Sea-Tac.

During this time, high temperatures should be close to normal.

This month has given all the sun-lovers something to rejoice over…but now it’s the rain-lovers’ turn!