Month: April 2020

Showery Saturday On Tap For Western Washington

On By Kelsie NelsonLeave a comment

After a wet Wednesday and some showers on Thursday, today has been a break in the rain. We are currently in between systems–but the break won’t last long.

First, here’s an update on the monthly precipitation after this first system in a train of them expected to hit the area:

Figure 1: Monthly precipitation for KPAE (blue) and KSEA (black)
Figure 2: Monthly departure from average precipitation for KPAE (green) and KSEA (orange)

Paine Field is only slightly below average at this point. Sea-Tac is still around 1.3 inches below average, but the next series of systems should help chip away at the deficit.

The first system arrives early Saturday morning, as another front rams into us:

Figure 3

It will be quite the soggy start to our Saturday morning, but thankfully, there shouldn’t be a lot of people out and about at that time (because, let’s face it, people STILL can’t drive in the rain).

The main front is out of here by the afternoon, but some scattered post-frontal showers should remain for the much of the day. Some of these could be locally heavy and could even contain a stray bolt of lightning or some hail. There is a little bit of instability to work with, as shown below in the CAPE values.

Figure 4: CAPE (Convective Available Potential Energy) values for KPAE

CAPE indicates the amount of fuel available for a thunderstorm to form and is a measure of the instability in the atmosphere. The “large” spike is for Saturday afternoon. The values here are generally minuscule compared to other areas of the country, especially the mid-west (to compare, values for tomorrow in South Texas could exceed 1000), but it still might be enough to get an isolated thunderstorm.

Besides the isolated chance of a thunderstorm, westerly (west to east) winds could trigger a PSCZ or Puget Sound Convergence Zone (click here to read up on this common PNW phenomenon). This, too, has the potential to spark (no pun intended) a stray bolt or two. I know many lightning lovers (including myself) are crossing their fingers.

Sunday will be another short break in the action, with partly to mostly cloudy skies at Paine Field. Emphasis on short. Because by Sunday night into Monday, another front is due over the area, again bringing rain. This “system-then-short-break” pattern could continue into next week. Updates to come on this.

Now that our “normal” April showers seem to be back on track, maybe our May flowers will be that much better. 🙂

Abnormally Dry April About to Turn Wet

On By Kelsie Nelson1 Comment
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!

They Say “April Showers Bring May Flowers”… So Where Are The Showers?

On By Kelsie NelsonLeave a comment

The majority of this month has been quite pleasant weather-wise. The sun and dry weather has served as a mood-booster for so many people in the midst of the COVID-19 pandemic. But it still begs the question…where is the rain?

Here is the Paine Field precipitation accumulation graph so far for the month of April.

Figure 1: Accumulated precipitation for KPAE, via NOAA

With the exception of some trace rainfall on April 11, all the rainfall has occurred in the first few days of the month, amounting to just 0.35 inches. The normal amount for this period is 1.48 inches.

When looking at the same graphic for Sea-Tac, we get a similar story.

Figure 2: Accumulated precipitation for KSEA, via NOAA

Except here, there has only been 0.01 inches of accumulated rainfall. You can hardly even see the green line on the graphic.

To put this into perspective, take a look at this tweet.

Much of California has been getting hammered by storms and rainfall and has significantly more than us here in western Washington. Even areas of Arizona have more than Sea-Tac! Wow.

So why has our weather been so nice recently? It has been the result of a ridge of high pressure that has been acting as a block, preventing storms from making it to our region. (You can read more about this in Cliff Mass’ blog, found here.)

And, spoiler alert, this nice weather is likely to continue through the rest of the week.

Highs today should be in the mid-to-upper 60s for most of us.

Overnight tonight, clouds begin to increase as onshore flow (i.e. from west to east) develops. As a result, Wednesday morning has a chance to start cloudy. But as the figure shows below, clouds should burn off by the afternoon. Because of the cloudy start, Wednesday’s highs could be slightly lower than today’s.

Figure 3: Cloud cover percentage (darks = less clouds, lights = more clouds)

Thursday and Friday look to be the warmest and nicest days of the week, with highs in the low 70s possible!

Figure 4: GFS high/low temperatures for KPAE
Figure 5: GFS high/low temperatures for KSEA

It should be perfect to go outside and go on bike rides, walks, and the like… of course maintaining social distancing 🙂

Some models/ensemble members of models show a chance for light showers on Saturday, but if anything falls, it likely won’t amount to much. Models are also suggesting the chance of some rainier weather next week, but it’s too far in advance to know for sure.

In the meantime, enjoy the sunny weather!

Sunny and Dry This Week… But Please Stay Home

On By Kelsie Nelson3 Comments

This week, for the first time in forever (or so it seems), it should be dry and the sun should be out at times for much of Western Washington. But that doesn’t mean you should be going out to public parks and beaches to enjoy it.

The last time it got super nice, people flocked to parks and beaches, hardly taking any consideration for social distancing. Exhibit A:

Figure 1: Tweet originally found here

Please, for the sake of those around you (especially the most vulnerable), don’t do this. If you go outdoors, do not congregate in places with a lot of people (yes, that includes certain hiking trails). Try to stick with walks and bike rides around the neighborhood, always maintaining distance from others.

Okay, rant over (sorry about that).

It will be tempting at times to want to go out to these public places, though. Take a look at the daily temperatures at Paine Field in Everett according to the GFS (i.e. American) ensemble.

Figure 2: Temperature GFS Ensemble for KPAE

Much of the week will see highs in the mid-to-upper 50s, while the low 60s are possible by the end of the week. For native Washingtonians like me, that is almost t-shirt weather. The European model doesn’t show temperatures quite as warm, but are still in the mid-to-upper 50s. Temperatures closer to Seattle and Sea-Tac look to be a touch warmer than Everett, as shown below.

Figure 3: Temperature GFS Ensemble for KSEA

Not only is it supposed to be warmer, but it’s also supposed to be dry. Take a look at this:

Figure 4: 24-Hour Precipitation GFS Ensemble for KPAE
Figure 5: 24-Hour Precipitation GFS Ensemble for KSEA

All of the above GFS ensemble members are not showing the chance of rain until Saturday… BUT, there’s still plenty of time for that to change in the coming days.

Even though it’ll be warmer and dry, it won’t be 100% sunny the whole week. Expect to see some cloudy to partly cloudy skies at times; but don’t worry–we should definitely see our fair share of sun. There will be plenty of opportunities to go outside for a walk or bike ride–again, keeping your distance from others!

This week, it’ll finally start to feel more like Spring after a stretch of below-normal temperatures. In this time of uncertainty, I know it will lift the moods of many people. Just like the sun always eventually comes out, even after the darkest of days, we will eventually get through this.

In the meantime, I hope you stay safe and healthy.

#WeGotThisSeattle

#WeGotThisWashington