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Seasonal Outlook: Winter 07/08 Well, first things first. If there is one item that you take with you after reading this outlook it should be: There is no way to reliably predict the weather on a seasonal scale! Those of you who have been following my site know that I have always been pretty low key and skeptical of any seasonal forecast- even my own. In fact I like to use the work "outlook" as I feel "forecast" should be reserved for something that has a little more proven science behind it. For those of you that are relatively new to the site, you might want to click here and read my "Soap Box Speech on Seasonal Forecasting". For those of you that have read it before, no need to again- it is the same as in years past. Now with that said, lots of folks still want me to produce a winter forecast, so here it is:
Unlike last year when the sources of good news for snow lovers were scarce, I believe there is reason for optimism this snow season. Not that I am guaranteeing all of the Midwest will see above average snowfall and a colder than average winter, but I think there are several factors occurring that all point to enhanced chances that at least a good portion of the Midwest will see average to below average temps and that will lead to average to above average snowfall. The three factors that I see contributing to chances for a decent winter in the Midwest are: 1) The existence of a weak La Nina that should persist through the winter months and perhaps even grow to a moderate one. 2) The fact that below average temps and above average snowfall have not been seen for large areas of the Midwest in many years. 3) The presence of above average temps across the Midwest so far this Autumn. Of these three, the presence of a La Nina is the strongest argument, with the other two factors lending some hope, but do not have strong scientific support. To expound on these three items a bit more, the existence of a La Nina does not guarantee a cold and snowy winter across the Midwest, but it does increase the chances for it to occur. Much like the El Nino last winter produced a mild and rather scant snow season last winter and in many of the previous El Nino winters (Figure 1), the opposite tends to occur when a La Nina is occurring. An area of below average temps establishes across the Canadian Prairies and extends down into the northern ½ of the Midwest (Figure 2). It should be noted that a weak La Nina tends to produce a better chance for below average temps in the Canadian Prairies and north central US than a strong one, although each La Nina has its own personality and there are no strict rules to follow here. It should also be pointed out that La Nina typically does not cause precipitation to be any more or less than average across the Midwest (Figure 3), but if temps are below average, then it is likely that more of the precip that falls across the Midwest will fall as snow rather than something else and the snow that falls will stick around longer as the occurrence of thaws would be less common. It has always been my battle cry to get people to hope for a cold winter more than anything else as it would produce the kind of conditions that snow lovers like more than a winter that sees above average snow, but also pronounced thaws that eat into that snowpack and make for poor snow-play conditions. The second point (lack of a cold and snowy winter in a large portion of the Midwest in the past several years) is one that I have been using for a few years now and is not one that can be a great indicator of the upcoming winter, but the bottom line is mother nature can only produce so many winters with above average temps and below average snowfall before she has to swing things the other direction. It is possible that we have entered into a period of 10-20 years in which wintertime temps will tend to be above average and snowfall will tend to be below average across the Midwest, but even in these multi decade temperature trends, there are years that will buck the trend. Since the mid 80’s the trend towards warmer than average winters and average to below average snowfall seems to be occurring, yet there have been standouts like in 1995 and 2001. With the La Nina looking to be in place, perhaps this is one of those years will buck the long term trend we seem to be in right now. The third point bears a resemblance to the second in its thinking and mechanics, only on a smaller time scale. So far this meteorological autumn (since September 1) has produced above average temps across a good portion of the Midwest. It is my opinion, based on some evidence in the past, that a warm autumn can lead to a colder and snowier than average winter. The data to support this is not overwhelming, but I see lots of snowlovers get excited when October turns cold and snowy across the upper Midwest (like last year), only to be followed by a winter that turns out to be a bust (like last year). There have also been years in which autumn temps were milder than average (78,79, 94, 01) and then as we worked through the middle of November a shift in the overall jet stream configuration occurred and that led to below average temps and above average snowfall across the Midwest. It can be a little nerve wracking to have to endure, but I have noted that the longer the warm anomaly can persist into October or even early November, the better the flip seems to turn out. I would not even be overly concerned if we get to very early December and the flip has not occurred. Although if the flip does not occur through the middle to end of December, then all bets are off! Also, if the flip occurs at the middle to end of October, that is not as good as early to middle November, but there is still no reason to hit the panic button. It may just be a case where the flip has occurred earlier and could then persist through the winter. So in a nutshell, there are several reasons to be optimistic about this winter. Obviously there are no guarantees and even with in a colder and snowier than average winter, there are the occasional thaws- especially in areas south of the Northwoods. So folks in places like southern MN, WI and lower MI as well as IA and northern sections of IL, IN and OH should not get your hopes up that temps will fall to below freezing in December and stay there until March. It just does not happen that way, even in the coldest of winters. Below are the details to the forecast for the different regions of the northern US: REGION 1 – The Northwest Midwest: Most of this region stands a good
chance to see below average temps occur during the winter of 07-08. The
existence of a La Nina is the main driving force for this idea. The further
north you go the stronger the chances for below average temps you will see. So
that means that areas like NE and IA have a small chance for below average
temps, whereas areas like ND and northern MN have the best. As for snowfall, I
see better than average chances to occur, but mainly because I believe the
colder than average temps will cause more of the precip to end up falling as
snow rather than something else. The other thing that the colder than average
temps would do is to allow the snow that falls to stick around. This would lead
to deeper snowpacks as the season progresses and a longer window of opportunity
for snow play in these areas as well. REGION 2 – The Southeast Midwest: The news for this region is not
as rosy as it is for the NW Midwest, but I do not see anything to be too
concerned about. As mentioned in the region 1 write up, La Nina can actually
cause the far southern Midwest to see above average temps, but we are talking
about areas more down along the OH River and not in the true snow belts of the
Midwest. It is possible that this type of warm anomaly could extend further
north and impact areas like northern IL, IN and OH, maybe even into far southern
WI and lower MI, but the rule of thumb is that the further north you go in the
Midwest, the less chance of above average temps you will have. REGION 3 – The Northeast US: I do not see any strong signals to go
one way or the other for this region. The La Nina should not have a direct
impact on this region and I do not see any other factors pointing towards one
thing or another. I can say that is has been a few years since they saw a
whopper of a winter in these parts, so there may be a slight trend towards a
colder and snowier than average winter, but the signals to me are just not as
strong as they are for the north central US. REGION 4 – The Northern Rockies: Many of these areas saw a
fairly poor season last year. There were a few bright spots in Jan and early
Feb, but overall, most snowlovers in these areas would just as soon forget about
last winter. REGION 5 – The Central Rockies: This region saw an OK winter in some spots and a below average winter in others. My feelings for this winter are that this winter will be pretty much the same. Some spots will do OK, while others will not do as well as they would like. I believe that the further north you go the better the chances for average to above average snowfall and below average temps you will have. REGION 6 – The Pacific NW and Sierra Range: Much like last winter, I expect this area to see above average temps and average to above average precip. Thus it will be a case where elevation will play a huge role in how much snow falls. The higher the elevation the more snow. I know this is the case everywhere out west, but I guess what I am trying to say is that some places that are usually high enough to see mainly snow fall with a storm may see rains occur more than average this winter. So you will have to go even higher than you might normally have to go to hit the snow line with many of the storms this winter. REGION 7 – Eastern Canada: I should really break this region into two separate regions as it is big enough. In any case, I expect the western sections of this region (Ontario mainly) to see average to above average snowfall, with close to average snowfall in Quebec and the maritime provinces. Temps across Ontario will be average to below, with the best chances for below average temps occurring the further east you go. Temps across Quebec and the Maritimes will be close to average overall.
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