Last year, winter briefly showed up in November before taking the rest of the season off. Records were set all around the country, including here in Pennsylvania, for the least snowy season in recorded history. Philadelphia failed to reach an inch of snow, and Harrisburg saw about a half foot.
Is that the new normal? Certainly not. For this upcoming winter season, we expect to see frequent pattern changes. There will be times of harsh cold, and other periods of pleasant warmth. That is what La Niña typically brings us and what we have already experienced in the past three weeks.
This winter is expected to get off to unusually early start in November. A few frigid cold snaps are expected, but don’t be surprised to still see a few very warm days. Why? The month will likely start with storm systems cutting to our northwest, bringing a warm day as they move overhead followed by several very chilly days. As we progress into mid to late November, a wintry mix or two will be possible given the expected favorable pattern.
In December, we anticipate a pattern similar to November. Several mixed winter storms will likely occur and perhaps a few all snow events especially in northern PA. Our analog winters of 95-96, 10-11, 11-12, and 17-18 suggest December may bring the most favorable pattern we see all winter.
As the calendar flips into 2021, our pattern may also flip soon after. Analogs suggest coldest air will retreat to the northern Rockies, and the infamous southeast ridge will become pronounced. It is very difficult in a La Niña winter to not see the southeast ridge present itself, and this winter likely won’t be any different. What does this mean? We could see many plain rain storms in January, perhaps starting as a mix in the Appalachians. There is the possibility this unfavorable pattern may not come until late January, so don’t write off January entirely.
Remember that no two winters are alike, but if seasons that were setup very similar to this one performed a certain way, we are not going to go against that.
In February, the southeast ridge is known to take over the pattern during La Niña winters. To put things lightly, February is not looking favorable whatsoever for snow-lovers. We anticipate well above average temperatures, and it will likely be difficult to come across much of any snow. Thread the needle events may be possible, but overall well below average snowfall is expected in February.
Finally, March will be our wild-card month. Partly because it’s still a while away and partly because analogs suggest it will either be a continuation of the February pattern, or a flip back to a more favorable pattern for at least mixed winter storms. We are leaning towards a southeast ridge pattern.
We will have a more detailed breakdown of the science behind our outlook in our official winter outlook in November. But does this overall outlook of below average snowfall and above average temperatures make sense? Based on what La Niña has produced in the past in our region, yes. Below is a graphic showing snowfall during various La Niña winters in Harrisburg. Departures from normal are on the right, and it’s easy to tell La Niña typically produces below average snowfall in our area. Note that most other parts of the state have similar departures during La Niña.
WINTER 2020-2021 FORECAST GRAPHICS
If you did not read the monthly breakdown, I highly recommend you do because we expect much a much different pattern during the holidays versus February. These maps represent forecast departures from normal during a four month period.
WINTER 2020-2021 TEMPERATURE OUTLOOK
WINTER 2020-2021 PRECIPITATION OUTLOOK
WINTER 2020-2021 SNOWFALL OUTLOOK
If you are one to like wintry weather around the holidays and then get tired of it afterwards, this season may be for you. But for the snow-lovers out there, look on the bright side. This winter will likely be much snowier than last season, even though that’s not saying a lot!
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