We continue to be very impressed with the cold pattern that’s looming. Even before the warm up and thaw last week, we made mention that the seeds were being planted for a very cold close to December and open to 2014. Latest data continues to back this idea up. Additionally, in the longer term, there are some goings on that would suggest we better hunker down for a colder than average January. While December will finished colder than average, a colder than average January can really hurt the pocket book as “average” temperatures are obviously even colder than December.
Today’s 12z ensembles are locking in on the pattern than can deliver one shot after the other of arctic air in the 8-10 day range.
As for the snow, we still think we need to watch the models around the New Year for the threat of some southern stream energy interacting with the available cold air. That said, even without the southern stream, one must remain abreast of the challenge that a northwest flow pattern can produce.
Forecast models have a difficult time handling clipper systems in these type of patterns until within 24-48 hours within an event. Many times what appears to be a rather “harmless” clipper 4-7 days out can suddenly turn much more robust once the model catches onto the track and ability to literally squeeze out any and all available moisture from a cold air mass. Furthermore, the “normal” 10:1 snow ratio, many like to use, doesn’t apply in the least to these type systems. In cold environments you can easily get what’s called the “fluff effect” and snow ratios are more in the 20-30:1 range. Needless to say, it’s a challenging pattern that will keep us on our toes over the coming couple of weeks.
To summarize, we’re extremely confident on a colder than average close to December and open to January. We’ll have to monitor fast moving clipper systems that modeling will struggle with until right up to the event. Finally, we’ll keep a close eye on the potential interaction of the southern stream and cold air around the New Year time period for the possibility of a storm of “more significance.” Stay tuned!