Seasonal Outlook: Winter 2012/2013
(Released: December 10, 2012)
As mentioned in my "teaser" put out on the bottom of my forecast text page, I have seen enough changes in things in the past 60 days or so that I feel there is a need to make an update to my outlook.
Please keep in mind that just because I am updating this forecast, it does not mean that my feelings are any stronger than they typically are for ANY seasonal outlook. I still feel that there is a lot more guesswork than science.
As I mentioned in my first outlook put out in early October, there was an El Nino appearing to be getting under way, there were some signs that the pending El Nino might actually just be a head fake. It is looking quite likely that it was actually a head fake that was going on and not the actual development of a bonified El Nino. Most of the things we look at to measure if an El Nino or La Nina or neither (neutral) is going on, point to things being in the neutral phase. So that is item number one that brought about this update.
So what does no El Nino mean? In general, it means good news for snow lovers in the central US. El Nino's historically lead to winters in the northern 1/2 of the central US that are warmer and have less snow to them. So in a nutshell, we have just lowered the chances that this winter will be one that brings the Midwest above average temps and below average snowfall. With that said, it does not guarantee that this winter will be any snowier or colder than average either. One change does not automatically lead to the other. We could very well end up with a winter that is close to average for both temps and snow.
The other item is a little closer to home and also might lend itself to being a little more specific about this winter. That is the jetstream position over North America and in areas of the Pacific and Atlantic Oceans near (500-1000 miles or so) North America. Figure 1 shows the relative jetstream configuration for both the week of Thanksgiving and also the period from December 1-7. The thing I want to point out in that map is the large dip in the jetstream in the eastern Pacific, off the west coasts of Canada and the US. This dip or trough captured much of the jetstream energy going into it and thus caused a lot of storminess to occur in the Pacific NW US and into western British Columbia. In some cases, historical precipitation amounts resulted from those fairly long lived upper air troughs. Further downstream from that trough and across the hear of North America, the jetstream was displaced further north and that caused record or near record breaking warmth to occur in the central US, along with a pronounced absence of any storms.
Towards the end of November, the longer range computer models started picking up on a large scale change in the jetstream configuration over and near North America and that change was verified as we closed out last week and headed through the weekend. Figure 2 shows what the new pattern looks like. The models are in relatively good agreement that this new pattern will be the one that dominates things across North America through the days leading up to Christmas Day. So if those ideas from the models come true then the next 2 weeks should see much of the Pacific NW in a fairly quiet period, with most of the unsettled weather occurring in the eastern 2/3rds of the US. Please note, this does not necessarily mean that big storms like the one that occurred in SD, MN and parts of WI Dec 8-9 will be in the offing in the next 2 weeks, but rather the pattern will hold better opportunities for storminess in the nations midsection and since we are getting more and more into the snow season, that means better chances that the precip will fall as snow in the northern 1/3rd to 1/2 of the region.
I also believe the key to what the rest of the winter may bring lies in what happens in the eastern Pacific, off the coasts of Canada and the US. If that region can remain free of an unusually large upper air trough that persists for more than a few days, then most of the jetstream energy will become concentrated across the central parts of North America and up the odds for snows and some cold across the central US (including the Midwest). Combine that with some blocking in the northern Atlantic (negative North Atlantic Oscillation) and a big storm(s) could spin up in the nations midsection or east coast. On the other hand If the jetstream decides it liked that trough in the eastern Pacific and goes back to it, then we could be in store for a lot more days with mild and quiet weather in the Midwest. As to what I think will happen? Right now I think we are at 50/50. The new pattern has just become established and while the forecasts all call for it to continue, they are just that- forecasts. I can say that if the pattern we just got into is the predominate one (does not have to occur non-stop, just most of the time) for the next 2-3 weeks, then there are very good chances that this winter will end up being one that many snow lovers in the north central US like.
So with all of that in mind, here is my updated regional forecasts and below is the general map, with the outlook I did in October below that.
REGION 1 The Northwest Midwest - UPDATED Dec 10, 2012: This is one of the areas that was most dramatically changed from my thinking back in October. Gone are the ideas of El Nino doing it's nasty thing and a fairly active pattern is likely to bring these areas above average snowfall. The exceptions possibly being far northern MN, extreme northern WI and the western 1/2 of the UP, where I am going on an average winter to occur. However, one of the big reasons is because such a slow start so far. Snows in Jan and Feb could actually end up being above average in these areas if the jetstream energy flows into central North America, rather than the eastern Pacific.
REGION 2 The Southeast Midwest- UPDATED Dec 10, 2012: Overall, I think these areas are in for an average to slightly warmer than average winter, with below average snowfall. Areas of the southern Midwest could actually see above average precip occur, but a larger than average percentage of it could fall as rain, rather than snow.
REGION 3 The Northeast US- UPDATED Dec 10, 2012: This is an area that I believe could go either way. So far there has not been a lot to write home about. Sure Sandy brought some big snows to spots, but that was a hiccup (a big one!) in the weather and not a trend. I do think that the region will be wetter than average, so the main factor will be temps. The further north you go, the colder it gets on average and thus I have painted northern areas in above average snowfall. The opposite is true for southern areas. The bottom line is, I don't have any real strong ideas one way or another for this area and nothing would surprise me.
REGION 4 The Northern Rockies- UPDATED Dec 10, 2012: After a pretty slow start, many of these areas are now off to the races. Some areas were able to partake in the fire hose pattern that lambasted the Pac NW and since then have been able to grab snows from disturbances diving in out of the northwest. So my ideas have changed rather dramatically for this region and it could be the place to go for powder this season.
REGION 5 The Central Rockies- UPDATED Dec 10, 2012: As with the northern Rockies, a pretty large shift in my thinking has occurred. It's no secret that CO and to a lesser degree, UT are hurting for snow. Not so much cold, but moisture to make the snow. Unfortunately, the two possible scenarios I see as most likely for the rest of this snow season do not provide very good chances for snows. It will snow, it always does, there might even be a few big storms, but as far as regular snows leading to above average snowfall, things do not look too good.
REGION 6 The Pacific NW and Sierra Range- UPDATED Dec 10, 2012: The predominate jetstream position in the eastern Pacific will determine of these areas seen an above or below average winter of snowfall. Right now I am a bit on the fence, but do believe that even with the absence of the pattern seen the week of Thanksgiving and the first week of December, the far northern sections of the NW US as well as those into BC will see a pretty good winter snow wise.
REGION 7 Eastern Canada- UPDATED Dec 10, 2012: The story for most of Ontario, Quebec and the Maritime Provinces remains the same and is pretty similar to the Northeast US. Meaning that I believe there are equal chances of above, below or average winter snowfall and temps, but overall, I think it should be a pretty decent winter for these areas.