Bit of a Break…And One Explanation For This Record Setting Winter

While we still could see some scattered snow showers on Thursday, we do have a bit of a break in the action that should allow us to recover a bit while we prepare for another couple winter storms over the weekend. Temperatures will remain quite chilly throughout as the flow swings around out of the northwest. Imbedded in the flow are a few weak impulses that could spring a few snow showers Thursday, but it’s not likely it will result in more that small localized accumulations. Late on Saturday, the first of a couple chilly winter storms moves back into the area, with snow showers in the valley (and heavier amounts in the mountains) once again causing some travel challenges.

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So just what might be causing all this record setting precipitation this winter? Well, it’s never a simple cut and dry answer, but there are a few things going on that almost always accompany record rainfall around here, especially during atmospheric rivers (aka Pineapple Expresses). There’s a phenomenon called a Madden-Jullian Oscillation that occurs out in the Pacific Ocean. It’s a travelling wave pattern that goes from west-to east across the tropical Pacific. Tomorrow, I’ll tell you how that helps get the Pineapple rolling.

 

 

A Bit of a Break…And What’s (Not) The Reason For This Wild Weather?

After scattered snow Tuesday night, we are probably going to get a bit of a break over the next few days. Scattered to isolated snow showers Wednesday will probably break up to partly cloudy conditions Thursday and Friday, before another series of storms move through the region over the weekend, likely bringing another round of snow, and likely to all elevations. Temperatures will likely stay near the upper 30s throughout the rest of the week, with overnight lows dropping to the low 20s and possibly the upper teens.

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We’ve been talking about how extraordinary this winter has been. At last check, after January clocked in as the wettest in Reno since they began taking records at the airport (1942), February has already accumulated enough precipitation to rank 3rd using the same criteria. What’s the reason? Let’s first talk about what isn’t the reason: El Niño. I’ve had a lot of people writing to ask me why we haven’t been talking about El Niño. There’s a good reason for that: There isn’t an El Niño right now, and there hasn’t been one out there for about a year. We’ve been anywhere from a weak La Niña to neutral conditions since. Tomorrow, I’ll talk about what is happening.

 

Rain Turning To Snow…And What’s The Reason For This Wild Winter?

Our insane winter continues. A Flood Watch continues through Tuesday mid-morning with cooling temperatures that will bring the snow levels down close to the valley floors by Tuesday afternoon. Expect fairly heavy rain to gradually switch over to snow showers. The mountains will continue to pile up snow with a Winter Storm Warning in effect until 4 pm Thursday. As the precipitation begins to wane through the rest of the week, the flow turns to come out of the northwest, and temperatures will cool down into the 30s with a chance of snow showers off and on through the rest of the week.

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As is usually the case when we get weather that is out of the ordinary (and by pretty much any metric, this has been an extraordinary winter), I will get people asking me what’s causing it. The overly simplified answer (with a dash of facetiousness) is the unusual winter is caused by a whole lot of rain and snow. But is there a single meteorological answer to it? Not really, although there are a lot of factors involved in what’s going on. Tomorrow, I’ll start with what’s not causing it.

 

 

Flood Watch Returns…And Contrails Predict Weather? (Conclusion)

As we head into the weekend, we can still expect to see some shower activity here and there, but in the large scheme of things, it’s going to be relatively benign through Sunday afternoon. Temperatures will reach near 50 degrees through the weekend, after which another moderate to strong atmospheric river hits the coast late Sunday into Monday. Very heavy rain up to about 7,-8,000’ will once again cause some flooding concerns, especially in the small creeks and drainages, but could also strongly impact the rivers north of Reno (Feather and Susan Rivers, for instance), as well as the lowland areas in the Carson River region. An Areal Flood Watch has been posted for the Reno-Tahoe areas from Monday morning through Tuesday morning.

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More on contrails: If you have high humidity aloft, the contrails that form behind commercial air traffic won’t evaporate very quickly, and with all the jets crisscrossing our skies, a spider-web of contrails can pretty quickly cover the skies. High-altitude moisture is also a possible sign that a storm is incoming. So in this respect, contrails can be a sign of future showers.

But it is tough to rely too heavily on those kinds of signs in this neck of the woods. Forecasting by cloud patterns works better in other parts of the country than it does here in the Silver State. Part of the reason for that is our location on the lee side of the mountains. Being located in a rain shadow tends to mess with a lot of “weather rules” that apply elsewhere. But that’s not the only reason.

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Cloud Chart produced by the National Weather Service.

We have another aspect of our weather that you have to take into account. We are located in the transition zone between two dominant airmasses. The marine airmass which dominates the weather over the Pacific Ocean transitions to a continental airmass once it gets to the Rocky Mountains. We’re in that zone where the change occurs, which changes a lot of “rules” about what works forecast-wise. Sometimes our weather plays by ocean rules, and other times by continental rules, which can get very confusing.

Most of the cloud-forecasting charts you see were developed in the central and eastern part of the country, and tend not to work as well in our neighborhood.

Really? More Floods?…And Can Contrails Predict Weather? (Cont.)

The second of a series of storms will come though the region Friday with showery conditions off and on through the weekend, before another potentially scary wet storm hits our area Monday. Friday’s storm is fairly cool, with snow levels reaching close to the valley floors, but I don’t expect significant accumulation until you get above 5,500’. High temperatures will only reach the mid-40s before rebounding to the 50s Saturday and Sunday.

After scattered showers Saturday and Sunday, another very wet atmospheric river moves back onshore Monday, with localized flooding once again a possibility, especially in NE California. Heavy rain with snow above 6,500-7,500’ will once again cause many of the local rivers (such as the Feather) to flood, and although the Truckee River will rise to fairly high levels, it is not expected to exceed flood stage.

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More on contrails: The ability to see contrails on any given day depends on how close to saturation the atmosphere is up at 30-40,000’ of elevation. When the air up there is very dry, contrails won’t form… or else they evaporate almost immediately.

But just because the skies are blue, that doesn’t mean that the air is especially dry up there. It just means it isn’t saturated. Tomorrow, what persistent contrails mean.

 

 

More Storms…And Can Contrails Predict Weather?

We are falling back into an active weather pattern for the next week. A series of moderate strength storms is lined up to move through starting Thursday. Strong winds will accompany Thursday’s storm (a valley Wind Advisory has been posted), and while there will be significant shadowing in Reno, the west side of the valley should receive some spillover precipitation. The mountains will see snow levels drop to about lake level by the middle of the day, and a Winter Weather advisory has been posted in the mountains. After a brief break Thursday night, the next storm system will move through Friday afternoon, striking the coast farther south, but is large enough to bring rain and snow to our region as well. Scattered showers continue through the weekend, and then another stronger storm moves through Monday and Tuesday.

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So can contrails be used to forecast the weather? Like most efforts to forecast the weather just by looking at the clouds, your success can vary greatly depending on what the clouds are, and where you are in the country. But as strange as it sounds, there is some meteorological logic to contrails hinting at upcoming weather. I’ll tell you why tomorrow.

 

Here Come More Storms…And Can Contrails Be Used in Forecasting?

We have one more day to dry out before a series of moderate storms return to the region. Clouds will increase Wednesday with temperatures warming to near 60 degrees in the valleys. The next storm system, a weak to moderate atmospheric river will follow on Thursday bringing valley rain and mountain snow and rain (snow levels will start near pass level in the morning and then lower to near lake level by the late afternoon.)

A second colder system comes through Friday. Although the brunt of that storm will likely focus south of the Lake Tahoe area, it will probably be strong enough to bring valley rain and mountain snow to our latitude. Scattered showers continue through the weekend, and another strong to moderate storm arrives for the start of next week.

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Margaret Fish of Reno (whose uncle, Henry T. Harrison, was the meteorologist on Admiral Byrd’s first expedition to the South Pole back in 1928-30) wrote me some time ago and included a quote from a meteorologist in Maine who says that the appearance of jet contrails could be a signal of an oncoming storm. She wondered if that was something that only worked back east, or did it work here too? I’ll continue this tomorrow.

 

 

Here We Go Again…And Ways To Help You Forecast (Pt. 1)

After a couple more dry days, it looks like we are going right back into a wet and stormy pattern. Tuesday should bring mostly sunny skies across western Nevada with mild valley temperatures in the 50s. Another atmospheric river type of pattern will send some mid to high level clouds on Wednesday, pumping high temperatures up to around 60 degrees. By Thursday, the river makes its way into our region, bringing valley rain and snow and rain to the mountains. A series of storm systems make their way through the region off and on through most of the President’s Day weekend, bringing scattered valley rain and mountain snow, with snow levels lowering to lake level by the weekend.

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“Many are called… but few are chosen.”

I like to playfully use the above quote when people tell me that they like to try and forecast the weather on their own. But I think it’s great when folks investigate all the different hints we get when we just observe the world around us.

Tomorrow, I’ll talk about one thing that we see around here frequently that can tell us a lot about what is going on in the atmosphere.

 

Finally, A Dry Weekend…And More Perspective on This Wet Winter

While we still have a lot of time to add to this historic winter’s rain and snowfall totals, we are going to get in a break. After a slight chance of an isolated early Saturday morning snow shower, our skies should start clearing off for the weekend.  Temperatures will drop to below freezing levels to start the next several days (it’s been a while since that has happened.) High temperatures on Saturday will drop to the mid-40s, stay in the upper-40s on Sunday before rising back into the 50s and low 60s by mid-week.

After our five day chance to catch our breath, it looks like we will get back into an active pattern again late next week with rain and snow returning to the region.

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It’s pretty difficult to try to put into perspective just how amazing this winter has been…and we still have more than a month and a half left in what we consider the “snow season.” As of this date, each of our four water basins (Tahoe, Truckee, Carson and Walker) is at record levels for this date. And it’s not out of the realm of possibility that some or all of them could finish the year that way.

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The (Temporary) End is in Sight…And Could This Be the Wettest Winter Ever?

We will finally move into a drier and calmer pattern after rain and snow Thursday night. Colder air will move into the region, dropping snow levels to near Lake Tahoe level, and scattered showers of rain will remain for the valleys. High temperatures will fall to the lower 50s Friday, and will drop further into the 40s over the weekend as the skies clear out.

In the meantime, a Winter Storm Warning remains for the mountains through Friday with an additional foot or more of snowfall in the upper elevations.

The high winds will ease as we head into the weekend, still breezy on Friday (gusts to 30 mph) and dropping to about 10 mph on Saturday.

After a slight chance of an early Saturday morning snow shower, the weather clears out and remains dry through the middle of next week, after which another storm appears ready to move on shore.

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Comparison of average winter (left bar graph) with the last four winters (this winter is second from left)

If you were wondering how all this is contributing to the snowpack, the numbers are pretty impressive. In the area snow basins, even if we didn’t get another drop of rain or flak of snow (not likely), we would still finish the snow year at 145-155% of average. We have a real shot at the highest ever.