J.Spin

The Northern Greens certainly seem to excel in the ability to put at least some flakes in the air throughout the winter. I haven’t really looked at that stat for other sites in the region or in the country, so I don’t know what’s typical, but 100+ days with snowfall certainly feels snowy. There are presumably sites in closer proximity to the lakes that get even more days with snow. I’d argue that many days with snow is a solid benefit when it comes to areas where winter tourism is important, since it at least improves the winter aesthetics for the visitors as you’ve noted. Thankfully, the flakes can be more than just window dressing and produce accumulations substantial enough to improve the surfaces on the slopes as well. If I check my data from last season for days with ≥½” of snow, which typically correlates with ≥1” of snow at the local resorts, that’s still 64 days. I should be able to do the monthly breakdown on days with snowfall, so we can look at that as well and see how last season stacked up. With 117 days of snow, it’s already up there at the top of the charts for the data set here, and I seem to recall we had a month this past season with just a couple of days where it didn’t snow.

That’s actually great timing on the inquiry LaGrange, days with snow was the next category I was planning to cover. Phin’s recollection is correct, based on the data I’ve collected so far, the average days with snowfall per season at our site is around 100. I didn’t track days with snowfall before joining CoCoRaHS, so I only have data from 2010 onward, but the plot is below. This past season didn’t have much to lay claim to since it was kind of lackluster in general snow stats, but days with snowfall was a category in which it edges out all the other seasons in the data set. Therefore, at least in our area, we had plenty of days with snow this past season, even if it was only average in terms of total snowfall.

Thinking about ways to get at which winter seasons had a tendency to deliver “larger snowstorms” vs. those that didn’t, I’ve made a couple of additional comparisons. Presenting the single largest storm as done in my initial plot above is certainly useful, but the single largest storm could easily be an outlier and not quite portray the tenor the season. Bringing a few more large storms from each season into the picture would temper the effect of those “one hit wonder” types of seasons. There are still plenty of options to consider with respect to how many storms to select, and whether to use mean and or median values from those storms, but here are two plots I made for now: 1) A clustered column plot that simply contains the snowfall for the five largest snowstorms from each season 2) A column plot that presents the sum of the snowfall from the five largest snowstorms from each season The first plot below is nice in that it lets one view the totals for the five largest storms of the season. It’s helpful for quickly identifying instances such as you mentioned above, where seasons had >1 storm of 20”+. I don’t think it works all that well for quickly getting at whether or not a season was one that tended to deliver large storms though. There’s enough data there in each set that they all just look like stair steps of data points unless you dive in and examine them closely. I think the second plot may do a better job of quickly highlighting those “big storm” seasons. Since each point is the sum of the top five storms, a season that consistently brings larger events is likely going to poke its head above the rest of the crowd. The 2016-2017 season is of course bolstered by the big 41” storm, but it’s still up there even when tempered by incorporating the next four storms. In this analysis, 2010-2011 and 2006-2007 also seem to pop up as potential “big storm” seasons. I like that 2006-2007 popped up on that plot, because it did have that “consistent, big storm feel” once it got going with what seemed like a notable storm on each holiday in the spring. Note that one could also plot the averages for the top five storms for each of these seasons and produce the same relative plot, but I think providing the number for total snow from the five storms gives a more immediate sense for the contribution that those top storms made to the season’s snowfall. While my initial plot of largest storm of the season certainly suggested that this past season was relatively weak with respect to large snowstorms, I think the plot summing the top five storms from each season solidifies that feel. This past season again came in as the second lowest in the data set next to the horrendous 2015-2016, suggesting that it was quite weak in the “big storm” department.

Don’t let anything get in the way if you have a chance to live out there – we certainly wouldn’t trade our time living in the Rockies; it was simply fantastic. My comments are of course just noting preferences from a weather/climate perspective, and while people certainly factor that into where they decide to live, it’s typically way down the list relative to factors that actually matter when it comes to making a living. Based on my years of roaming around and checking out much of Western Montana, I think my preference leans toward the northwestern part of the state if it was solely based on climate. Where we lived in the Bitterroot Valley is farther south, and when we’d visit equivalent valley areas in the northwestern part of the state, there always seemed to bit more moisture, more clouds, cooler temperatures, more snow, etc. Those areas are on the windward side of the Glacier National Park area along the continental divide, and like here in NVT, they’re not far from the Canadian border. I’m sure the bit of extra latitude helps too. I didn’t know it before we lived out there, but the Canada-U.S. border out in that part of the country is substantially farther north than it is out here. While the border here in Vermont is at the 45th parallel, the border out in Montana is notably farther north at the 49th parallel. From our numerous visits, I always had the perception that those valleys in the northwest part of the state had more clouds, precipitation, snow, etc., and if I look up the actual numbers, they support that. You can see the climate difference between where we lived in Hamilton and farther to the northwest in Whitefish: Hamilton, MT Elevation: 3,570’ Annual Precipitation: 13.1” Annual Snowfall: 32.1” Days with Precipitation: 106.4 Whitefish, MT Elevation: 3,028’ Annual Precipitation: 18.4” Annual Snowfall: 72.7” Days with Precipitation: 119.7 Of course, even the higher Whitefish values for precipitation and snowfall are quite paltry compared to the ~55” of precipitation and ~160” of snowfall we get out here; the precipitation isn’t even in the same ballpark, and the snowfall is only on par with BTV, which is generally chided for how snowless it is for this area. However, from a comparative perspective, the numbers do speak to my causal observations, and the differences are quite notable. In Whitefish you’re looking at a ~40% increase in precipitation, and a ~125% increase in snowfall. In addition, that’s with Whitefish being at ~500’ lower elevation. It’s funny, because in the grand scheme of Montana geography, even Hamilton is typically considered part of “Northwest Montana” because of the shape of the state, how big the state is, and the way the mountain ranges build natural climate areas (see maps below). The northwestern region is generally considered the wettest part of the state, but the greater northwestern or “Glacier Country” area extends well to south, and of course, there are many microclimates. The Bitterroot Valley is in the rain shadow of the 10,000’+ Bitterroot Range, which presumably cuts down on the precipitation and snow there relative to some of the other parts of the region. If you keep with the ski industry, I’m sure you’d be in a mountainous locale wherever you end up, but just watch out for the potential lack of “weather” and hot temperatures in the lower mountain valleys if that’s of interest. It’s probably great for the average person who would just as soon have little to no rain or snow where they live, but it’s very benign relative to what we’re used to around here.

I’m not sure if you’re actually allowed to say that last part aloud, because the subforum sunshine police will probably lump you in with the standard list of summer pariahs they pull out any time the forecast suggests it might get a bit cool and showery. Unless you really want/need a consistent San Diego-style climate for your work, exercise, recreation, or daily activities, the summer climate in NNE, especially the mountainous areas of NNE, is pretty sweet. We don’t have to deal with the constant heat and humidity of the Midwest or Southeast, or even what they seem to experience in parts of SNE. We still typically get a hot stretch or two each summer, sometimes more, sometimes less, that will warm up the swimming holes and make for great river tubing etc. As much as it can be a nuisance having to deal with a few sticky nights, it’s a nice change of pace and lets you comfortably get out on the water for some high summer activities. Even in July though, our temperature averages around here are lows in the 50s F and highs in the 70s F. Right from those numbers you can get a sense of what the typical, climatological dew points are up here in the summer, even if some warm season agendas in the subforum leave people trying to convince themselves that summer in New England somehow means dew points of 70 F. I certainly love it when our local trails are dry and the riding is great. Like PF, I enjoy that Rockies-style climate with the lower humidity, warm sunny days, cool nights, and generally dry conditions for recreation. However, having lived in the Rockies for several years, I can say that for me, the constant dry, sunny, cloudless days throughout the summer can get quite monotonous. The generally drier air is great in that it would cool down into the 40s and 50s F each night for consistently great sleeping, but that same dry air and lack of clouds meant that it would easily heat up into the 90s F every day. You certainly do get that big diurnal temperature range that PF loves. I just found that the constant sunny, dry, and hot weather, day after day after day all summer took its toll. Rain was infrequent enough that it was notable when it rained during the summer. I can distinctly remember the relief of actually having a night of getting to listen to the sound of the rain falling and thinking, “Wow, that is really cool, I wish that would happen more than once in a blue moon.” Now this was in Montana mind you, so it was nothing in the realm of what spots farther south like Salt Lake City or Arizona deal with, but the summers can still feel unnecessarily hot when it’s day after day of cloudless skies. If I was to live in the Rockies again, I think I’d pick a spot with more elevation that would provide more opportunities for orographic clouds, precipitation, and lower daytime temperatures. Here in Waterbury, we get four times the annual precipitation, and five times the annual snowfall compared to where we lived in Montana. There’s just so much additional potential for weather variety that comes with those numbers. I can remember a specific day soon after we’d moved back to Vermont where I really noticed a dramatic climate difference. We were out on the Stowe Recreation Path with the boys, and it was a typical summer day where perhaps a third of the sky happened to be covered with fair weather cumulus clouds. Every so often, a cloud would pass in front of the sun and bring on some shade. I’d rather forgotten that one could even have midsummer days like that with cool, refreshing interludes, and it was spectacular. I love the variety of weather we get here in the mountains of NNE; it’s likely akin to the typical mix of weather that a lot of the Eastern U.S. gets, but biased on the cooler (and in winter, snowier) side due to our latitude and orographics. I wouldn’t want every summer day to be socked in with clouds, fog, and rain, but I definitely enjoy those days as part of the mix. Yesterday after work, I was going to go for a ride, but it was a bit misty and gray, and it seemed like the trails might be a bit wet. So, I decided to go for a trail run instead, and the cool conditions were perfect for that. In my years up here, I’ve learned that it’s best to have many potential activities in your bag of tricks so that you can easily roll with whatever Mother Nature decides her mood of the day is going to be. Obviously, some activities have to be planned/scheduled and you have to hope for a certain type of weather, but it pays to have some alternatives available. If one really needs consistency, I guess there’s always San Diego.

I think on average, folks wouldn’t call this past winter season in CNE/NNE one that was notable for larger storms, and in the case of our site, the data for largest storm of the season speak to that. I don’t think the downward trend of the past few seasons it’s too much more than normal variance in our neck of the woods though, simply because I wouldn’t have thought twice about even the 17.0” top storm from 2019-2020 – that seems very typical off of a 21.4” average. The S.D. on that mean is 7.5”, so the 17.0” is well within that. That record you note from your past three seasons does seem rather anomalous though. Using just the single largest storm could be a bit misleading for some seasons due to the potential for those “fluke” types of storms that hit every so often. For example, some areas in central/southern NH and VT were hit with that intense banding storm this past season, so some of those sites may have a big 30-50” total for that largest storm, even though it may not reflect the tenor of the season. I can’t recall, did those areas have any other notable storms this past season, or was that a “one-off” sort of thing? For the 2016-2017 season when we had that notable 41.0” storm (Winter Storm Stella), we did at least have three other double-digit storms, topping out at 18.2”, so it wasn’t an entirely anomalous event among a sea of nothing. A better approach to get the feel for the occurrence of larger storms in a season and reduce the effects of anomalies might be to take the top five, or maybe top three storms, and then take the mean of that group (or maybe median would be even better to remove anomalies).

Continuing with the storm-related analysis, the next plot lets us look at the largest snowstorm for each season in the data set. The 2020-2021 season really wasn’t one for large storms in our immediate area, and that’s definitely borne out in this plot. This past season’s largest storm was just over a foot, it was well below the average, and second lowest in the entire data set. The trend since that 41-inch storm in 2016-2017 has shown quite the consistent decline in storm size, so we’ll see if this past season marks the nadir of that decrease.

I think there may be recency, availability, and repetition bias in some of these perspectives though. When it comes to this forum, whatever happens in the populated areas of SNE is heavily announced, discussed, echoed, rehashed, and dissected to the nth degree. That’s 95%+ of the discussion, so it largely sets the appearance of what people in the subforum think is happening. As the actual data show, there’s little doubt that large areas of SNE get more annual precipitation than the typical valleys in NNE on average, but when it comes to the mountains in NNE (such as Phin’s NH place), there’s just more overall liquid up north. On the map, there’s really nowhere in SNE that has annual precipitation beyond that light green 49-55” range; the next tiers of darker green are all up in the mountains of CNE and NNE. Phin wasn’t around when his NH site saw over 70” of precipitation a few years back, but you can bet that there weren’t 10 pages of discussion about it in the forum. This has been a drier than average year up here in NNE, so it’s definitely not the norm. The numbers don’t lie: Mt. Mansfield averages ~80” of liquid a year, and Mt. Washington averages ~100” of liquid a year. Sure, those numbers fall off somewhat as you head down in elevation, but the larger, orographically influenced annual precipitation totals still extend a good distance out from the summits as the map shows. The higher annual precipitation numbers up here in the mountains must come from somewhere, and it has to be from some combination of more rain events, and/or larger rain events. As for the “socked-in clouds and drizzle for days”, it’s tough to say exactly where Phin’s NH place falls. It’s becoming clear that the climate there is somewhat different than what PF and I experience here along the spine of the Northern Greens (it actually seems that Alex’s area might be more similar to what we experience), but this past year being drier than normal is not going to be a solid representative sample. I can tell you that typically at our site, I’m looking for windows in the precipitation regime to be able to mow the lawn, but I haven’t had to worry about it as much from last summer into this early summer thus far. Even in this relatively “dry” winter we just went through, we still had new snow recorded on 29 out of 31 days in January, and 23 out of 28 days in February. There are a few days per winter where we might get diamond dust from clear skies, but the vast majority of that snow comes from clouds. That’s many cloudy days. I’d say our route to higher annual precipitation totals along the spine of the Northern Greens tips toward more episodes of precipitation vs. larger episodes, but the distribution could be a bit different at Phin’s NH site. Whatever the case, something is pushing the annual precipitation there into that 55”+ range, and the data say that’s what happens when it all shakes out, even if it doesn’t feel like it.

At least in terms of average numbers at our site, snowfall occurrence with respect to size really drops off below the “once a season” level when the 20” threshold is reached. The list of snowfall sizes that I track in my data set are shown below, where the average number of occurrences per season is plotted. I have snowfalls up to the 48” threshold counted, although as the data indicate, I haven’t yet recorded a 48” snowfall at our site. Snowfalls above the 30” threshold seem to be relatively infrequent at our site in the valley, but the numbers change notably by simply going up in elevation in the Northern Greens. Based on my years of observation, a good way to obtain a rough estimate for snowfall occurrence in the higher elevations of the Northern Greens can be obtained by just doubling the snowfall sizes shown in my data set. Therefore, if our site averages one 18”+ snowfall a season as shown in the plot, then the higher elevations of the Northern Greens should average approximately one 36”+ snowfall a season.

As the snowfall size increases, eventually it becomes impractical to monitor first occurrence dates because they’re just too infrequent, so the 12” threshold is as high as I go in my data. Mean and median occurrence for first 12” snowfall in the data set here are right around the end of December/beginning of January, so this past season was certainly on the slow side for first 12” snowfall, but still ahead of a number of seasons where it didn’t occur until February.

As we move on to the 10” snowfall data, I referenced Tamarack’s earlier post, since he’d included 10” snowfall data there. Mean and median dates for first 10” snowfall in our data set are Dec 17th, and Dec 13th, respectively. Last season was near the back of the pack, which is consistent with the way larger storms were simply hard to come by around here during the 2020-2021 season. One thing that is quickly obvious in the lower right of the plot is that both of the past couple of seasons have been slow to reach that 10” snowfall threshold.

As we move on to looking at the data for first 8” snowfall of the season, we shift from November into December, with the mean and median dates of December 13th and 6th, respectively. The visual of the plot speaks to that difference between the median and mean nicely, with an obvious skew of the distribution of dates toward the end of November/beginning of December, but a few outliers later in the season. Getting into these larger snowfalls is where the 2020-2021 season moved from being at the very front of the pack due to the early November storms we had, to nearly the tail end of the pack. Indeed, it took until January 17th to get an 8” snowfall this past season, which is more than a month later than average. With the relatively weak December that we experienced, it’s not too surprising that the first 8” snowfall was delayed until things started to pick back up in mid-January.

I see that Tamarack has up his 10” snowfall data, but I still have 6” and 8” snowfall data before I get there, so I’ll keep working through the series. Even up at the 6” level, we still see last season holding onto that earliest spot, and indeed the last three Novembers continuing with that strong showing. These seasons are all well ahead of the mean and median date of November 27th for first 6” snowfall. The 2015-2016 season is still out there at the back of the pack, but it’s not sticking out quite as anomalously now as we head into these larger snowfalls.

The data for first 4” snowfall by season are very similar to the first 3” snowfall data, with 2020-2021 showing the effect of those early storms we had this past November. 2015-2016 set the other extreme, and waiting until essentially the start of the new year to get a simple 4” snowfall seems quite anomalous. While it’s not quite as crazy as the fact that we also had to wait that long for even a 3” snowfall, but both occurrences are quite remarkable in the context of the snowfall climatology at our site.

I do track first 3” snowfall by season, so that’s the next plot in the series. There’s not a huge disparity from the first 2” snowfall mean, but it does shift a couple of days later to November 25th. Again, we see the past three seasons with strong showings, and the 2020-2021 season making its mark at the front of the pack. The 2015-2016 shows itself as a massive outlier, not hiding anything in its effort to incite mreaves’ PTSD.

For the data on first 2” snowfall by season, what really jumped out when I made the plot was the stretch that has occurred over the past three seasons. After recording weather data, I don’t really pour through it much until I’m doing an analysis or putting together plots like these, so I hadn’t noticed that the past three seasons have delivered the earliest 2” snowfall occurrences in my entire data set. The mean date for first 2” snowfall here is November 23rd, so these past three seasons have been well ahead of that, and in fact, the past five seasons have all come in ahead of average. For a somewhat unremarkable season overall, this is a category where the 2020-2021 season actually gets to make its mark in the records by coming in well ahead of the pack. This past November had a 7.1” storm right at the beginning of the month, so the season is going to make its presence known in a couple more upcoming plots as well.

Actually, I was just out in BTV catching a bus, and it did have that feel. The strong wind was definitely notable. It’s neat when it’s warm and windy like that, since that’s not our classic summer climate. It certainly beats hot and humid with dead calm, although thankfully that’s not quite our classic summer climate up here either.

Seeing your comment, I checked my data, and it appears that there has been one occurrence of hitting all three of those thresholds at once at our site – I see that in October 2006 I recorded first trace, first measurable, and first 1”+ all on October 20th. The reality here of course is that the “trace” occurrences can easily be missed. If I don’t observe that frozen precipitation fell, I can’t record it, and I’m sure there are instances where I’ve missed first frozen trace because I just didn’t happen to see it. As far as I know though, there wasn’t an earlier trace of frozen at our site that season. For the second part of your comment, I looked at October 2011, and indeed that is close to simultaneous occurrence as you noted. I see first trace and first measurable at our site are on October 29th that year, and then first 1”+ was the next day on October 30th. I was thinking that your dates would thus be the same as mine that year, but I’m wondering if there’s a typo in the data table you presented? Your 2011 data show first 1”+ on November 30th, which wouldn’t fit with the idea of the dates for 1st trace, 1st measurable, and 1st 1”+ being close. Also, if the note about the big October snowstorm bringing 4.5” is correct, that would suggest that the 1”+ threshold was achieved before the end of October? I guess getting a larger storm might not meet a smaller snowfall threshold if specific time intervals are imposed on the accumulations, but it’s hard to imagine the 4.5” from that storm being spread out enough to not hit at least 1” in a reasonable amount of time.

After first accumulating snow, the next snowfall threshold I monitor for our site is first 1” snowfall. On average, this occurs at our site by November 8th, so this past season was almost a week ahead of that. While 2020-2021 was a bit ahead of the curve in the 1” snowfall category, this past season had some notable early November snows, so it really made its mark in some of the higher early snow categories. I’ll present those data as I continue with the analysis.

In the hierarchy of early snow occurrence, the next parameter I record for our site is the first accumulating snowfall. I’ve quoted the previous post with the data plot on first frozen precipitation for comparative purposes, since the two occurrences are often from the same event, but sometimes they differ. As noted earlier, this past season’s first accumulating snow was October 26th, and that was also the first frozen precipitation for the season. In terms of first accumulating snow, this season was very typical, with the mean occurrence date being October 27th. One thing that jumped out at me immediately once I saw the plot was how late the first accumulating snow was for the 2007-2008 season. We’d already had at least a trace of frozen precipitation that October, but it’s interesting that such a strong season with over 200” of total snowfall had a relatively slow start for snow accumulation.

Here’s the Mt. Mansfield analysis I referred to in my post above – I just copied the text from the initial post below. The return rate on August snow seems to be 50+ years, but for September snow it’s about once every 6 years, and for October it’s almost a lock. “A comment in the main discussion thread had me pull up some of the first snowfall of the season data for Mansfield, but I’m putting it here for archival/discussion purposes as well. In a few more weeks and we’ll definitely be watching for those first dustings in the peaks around here in NNE. The earliest recorded accumulations on Mt. Mansfield are actually only a week from today (see inset in the graph below), and of course on Mt. Washington it can happen at almost any time. I ran the early snowfall numbers for Mt. Mansfield a few years back and found that first snows occurred in September at an average rate of about twice a decade, and only about once a decade do we not have that first snow by October. I recently assembled the actual numbers though, and I’ve plotted those below. The occurrence of first snow by October is actually a bit higher than 90% though, so the absence of snow by October is closer to once every 15 years vs. once a decade. First snows are potentially a bit more frequent than the numbers indicate too, since there are some seasons with chunks of autumn data missing, and with the ephemeral nature of early season snow and the variability in personnel making those observations, some occurrences of snow could have easily been missed.”

That’s really cool Tamarack; those observations certainly demonstrate the effect of that extra latitude up there.

I’d actually been thinking about putting together plots of earliest snowfall dates (First Frozen, First Accumulating Snow, First 1” Storm, First 2” Storm, etc.) because I have all those data, but figuring out a presentation format that I felt was effective has been tough. This inquiry got me working on it some more though. I wanted the dates to be on the horizontal axis in a plot because I like that format for chronological data. In addition, what I really wanted to do was have each season as a row in the plot, and stack all the first occurrence dates for each threshold of snow in the row as different colored dots/points for each category. Excel hasn’t quite been able to hit what I want, and I really haven’t felt like dealing with export to another graphing application just to achieve that result, but I think I’ve settled on a format I like. I’m putting just one category on a plot at a time, and it’s much less busy, so I can actually display the data points as the dates themselves. The date text markers aren’t placed perfectly with respect to the date axis (they’re on the left side of the desired position) because I’m sort of adapting a horizontal bar graph to get my result, but I still think effectively shows the distribution of dates by season. So to get to DS’s question about September snow, I’ve never seen it at our site, consistent with what backedge suspected. Below I’ve added the plot of earliest frozen precipitation at our site, which is the lowest threshold I record for early season occurrences of frozen precipitation. This first frozen precipitation observation doesn’t need to be specifically snow (although it often is), so it can be graupel or sleet, etc., as long as it’s frozen. It also doesn’t need to accumulate, just be observed as falling frozen precipitation. I record first accumulating snow as its own category, so I’ll do a separate plot for that. Anyway, as the plot below indicates, the earliest frozen precipitation in the records we have for out site is October 11th. That really doesn’t seem all that far from September, but it’s probably an eternity at that time of year. Even Mt. Mansfield struggles to get snow in September as PF noted, but I’ve got a plot of those data that I made for a post a couple of seasons back, so I’ll grab that for a separate post. So in terms of this past season, first frozen precipitation came on October 26th, which is a little on the late side (mean occurrence date is October 21st), but certainly right in that typical period where we see it. In this case, that was also the date for the higher threshold of first accumulating snow, which is very typical for that parameter with a mean occurrence date of October 27th.

I’ve never recorded snow in June at our site, so I consider May the final month of our snow season. The variability in the plot of snowfall by season speaks for itself, with accumulating May snowfall being quite inconsistent and only happening every few seasons or so. Similar to November and April, I consider October the counterpart to May on the front end of the season. Although there can be a lot of variability in both months with respect to whether or not we get any accumulating snow at all in a given season, I think a comparison of the plots for the two months is informative in the context of PF’s recent comments. Although both months have surprisingly similar mean snowfall values, the October snowfall mean comes from a much more consistent distribution of snowfall among the seasons. Those October snows often come as autumnal cold fronts push through and the mountains help wring out some moisture as the cold air arrives, which is certainly in line with PF’s idea about the types of setups that work well to produce snow here.

Great inferences PF; that makes a lot of sense. In addition, when I think about it, it fits the typical weather experiences for many of us who live along the spine of the Northern Greens. As with the November/April dyad, I’d say the trend is there even for the October/May dyad despite the fact that those months are the very fringe of the snow season and exhibit high snowfall variability. I’ll have the May snowfall plot next as the final in that series of analyses.