Will Winter Ever Return? If So, When? Or, Why Has it Been So Warm Recently?

With two thirds of January already having passed, we're +8.3 degrees above normal in temperatures so far this month in Denver; that may not sound like a huge deal, but it is several standard deviations away from "normal." It gets even more pronounced if you look at just the past 5 days, when our temperatures have averaged a staggering 18 degrees above normal. (To put this in perspective, if the same mild weather that we've seen over the first 2/3 of the month were to continue over the next 10 days, this month would end up as one of the warmest Januarys ever on record for our region.)

...Meanwhile, many areas along the eastern seaboard back through the Great Lakes have seen the coldest temperatures in over a decade over the past week. What gives?

I tell people that about 2/3 of the time when it's colder than normal in Colorado, it's warmer than normal over the eastern US and vice versa. That's because the jet stream consists of ridges and troughs. The former, in general, fosters warm, dry conditions while the latter usually fosters cooler and wetter conditions. Several factors of climate variability (which I won't get into here, but would be happy to explain if you leave a comment or email me) have basically kept a trough more or less locked in over the eastern US for much of the month so far, with a ridge over our area for this time.

So, will winter ever return for our area? The answer is yes, and perhaps sooner than some of you might like. Though we'll see 20+ degree above normal temperatures again Wednesday and Thursday -- in the mid 60s -- a strong cold front will push through the area by Friday into the weekend, finally establishing a trough over the western US; atmospheric indicators signal that below average temperatures will probably begin early this weekend and persist trough at least February 1st -- and perhaps laterl; more or less, 7-10+ days of below normal temperatures developing shortly. In fact, the latest run of one of the major computer models suggests that by late this month we may again see sub-zero temperatures in our area.

And some snow -- though how much remains to be seen at the moment -- is definitely likely accompany this developing much colder weather pattern. In fact, the first half of next week may be appreciably snowy; it's a bit too early to pin down the details, but a slow-moving area of low pressure probably will try to develop during the Monday-Wednesday time period. (See image at right.) In fact, I think it's likely (70% chance) that we'll see as much, if not more, snow in the greater Denver metro area during the last week of the month than we've seen up until then -- generally 3-6" depending on where you live.

Even with a dramatic switch to colder temperatures and snowier weather in the last week of January, it is still highly likely we'll finish the month with significantly above normal temperatures -- though perhaps near normal snowfall. But I have a feeling we may (more than?) make up for these amomalies in February -- a month which I have a gut feeling may very may well turn out colder and snowier than usual.

...And don't forget, our snowiest month is not until March!