Fairly typical weather looks to remain on tap for the foreseeable future. Warm with brief cooldowns as we transition to a more Fall-like weather pattern. Smoky skies should linger from time to time as hundreds of wildfires burn in the Western U.S.
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Short Term Forecast
There's not too much going on in the Utah weather world as of today (Sept 16). We have generally remained warm, with the exception of two noticeable cooldowns earlier this month. However, each cool off, while profound, was brief. We are now back above normal thru the rest of this workweek. This weekend, we will see a system brush mainly northern Utah. This will bring cooler temperatures for Saturday and Sunday along with the threat of a few light showers (mainly farther north). We then should rebound back to above average next week as high pressure regains control.
The other variable is smoke. There are literally thousands of wildfires burning in the western US right now, and with that comes plenty of smoke.
Here is the latest smoke coverage from our OpenSummit product:
Fairly extensive coverage. While we have seen plenty of smoke and haze in Utah, we've actually been quite lucky compared to many surrounding states. Hopefully, it stays that way.
You can view the above HRRR smoke forecast for the next 18 hours over on our OpenSummit app as well. It's awesome to have this smoke forecast data in an easy-to-view map on your phone.
Looking out into fantasy land (beyond 10 days) in the models, we see chances for some additional troughs cooling us off at the end of September. This is most pronounced in the operation GFS model, but doesn't have much support yet from the ensembles or the ECMWF (Euro)... so for right now, it's just something to watch. We really could use a good soaking rain in Utah to mitigate our own fire danger (which is very high!).
La Niña Outlook:
Some of you may have seen that La Niña has developed in the Pacific and is expected to continue thru the winter season. This is so far just a weak to moderate La Niña event, but could certainly strengthen over the coming months. What does that mean for us? If you've been reading my forecasts for years, then you probably already know what's coming... ENSO (El Niño/La Niña) doesn't correlate strongly to precip in Utah. Put simply, we can have both good and bad winters in either ENSO state.
However, let's take a look at the data just for kicks. First, Brian Brettshneider, a climatologist in Alaska, made a great set of maps the other day that looks at La Niña effects over the past >100 years. This first map looks at temperatures compared to normal in moderate La Niña winters:
You can see that while cooler along the immediate west coast and northeast, the intermountain west tends to be warmer than average.
And here is precipitation:
This one is a bit more straightforward than temperatures. Essentially, the farther north you go, the more likely you are to have above-average precip. The same applies to Utah. Southern Utah tends to be a bit drier than normal, while Northern Utah is a bit wetter.
I went back and looked at all La Niña winters since 1950 in which we had at least a moderate or strengthening La Niña in the fall that persisted into winter. I identified 22 such analog winter seasons, then used Alta-Guard snowfall data on the UAC website to see how those seasons fared.
11 seasons were below the 70-year seasonal average of 497" of snowfall at Alta-Guard.
11 seasons were above the average.
While this list included some truly epic winters like '83-84 and '10-11, it also included some huge, recent duds such as 2011-12 and 2017-18.
The mean of all 22 of these seasons was 517", which is 20" higher than the average. That seems to correspond fairly closely with the map above showing above-average precip in Northern Utah.
Unfortunately, the even split of 11 to 11 emphasizes what I've always said, ENSO is really not a good indicator here in Utah. Still, perhaps we have a few encouraging signs. If you're waiting for an official winter forecast, you won't find it from me. I never give seasonal predictions because I'm honest about the fact that I have no idea. Nobody has any idea. We can make a few speculations, but that's about it. Let's just see what happens and then ride it when it does (and let's hope we get this stinking virus under control).
Evan | OpenSnow
P.S. I may be posting less frequently this fall as my wife and I are celebrating the birth of our son, Zephyr, this past weekend. If you've ever raised a newborn, you'll understand how it may be tough to post as frequently. Still, I will make sure to keep you informed of any major changes to our weather in the coming month or two.
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