Winter Outlook for 2020-2021
HARRISONBURG, Va. (WHSV) - It is time for our annual winter forecast.
There’s no perfect recipe with a winter forecast and there are a lot of variables to look at. One thing to keep in mind is that a preceding season has absolutely nothing to do with the following. Meaning, a hot summer doesn’t mean a warm winter or vice versa. A wet summer doesn’t mean a snowy winter. It’s the same with every season. A mild winter doesn’t translate to a cold spring.
What does have more weight is seasonal patterns like an El Nino, or a La Nina. Arctic sea ice, Eurasian snow cover (growth in the fall), and a few other phases like the Atlantic Multidecadal Oscillation, and the North Atlantic Oscillation. It may sounds like a bunch of gibberish but they all have meaning.
Something else we look to is the polar vortex. Now despite the hype over the polar vortex in recent years, let’s talk about what it is and what it isn’t.
It is NOT: A storm. The polar vortex is not responsible for every cold outbreak in the winter.
It IS: Always there. It’s what we call a semi-permanent feature. Just like the Bermuda high in the Atlantic in the summer. It’s always there but it shifts in intensity or position.
So what does it mean? When the polar vortex is stronger, the extreme frigid air gets locked up at the poles. When there is a weakening in the polar vortex, that’s when the really cold air can spill down into the U.S.
For this winter, some of our long-range forecast models are indicating a stronger polar vortex especially early in the season, meaning less really cold air outbreaks, or even none at all.
Now this doesn’t mean we won’t see any cold air. The polar vortex is responsible for the coldest of the winter cold outbreaks.
Overall, with a La Nina and possibly a strong La Nina in place we expect a milder than average winter. In addition, less than average snow for the Shenandoah Valley and the Potomac Highlands. We also expect near or just slightly below average snowfall for the Allegheny mountains.
You can see what average snowfall is for the area here:
One other key factor is storm track. Sometimes a small shift in a storms track, 20-50 miles can make the difference between a cold rain and a heavy snow event.
With the patterns in place, this is just not expected to be a very cold or snowy winter. Looking at our past La Nina winters, we’ve never had more than 14″ of snow in the combination of a La nina and being in the positive phase of the Atlantic Multidecadal Oscillation.
We do expect the cold air outbreaks to be more brief instead of extended periods of cold.
There may be one catch and that could be the end of winter. La Nina is expected to weaken between the end of winter and very early spring. If we start to see more cold outbreaks at this time, it won’t take but one storm to give us a good dosing on snow. I would watch more the end of winter for the coldest air and even a better chance of some snow.
Bottom line, no matter what the winter brings, it’s important to always be prepared. We can still see some snow, and ice, and of course it will be cold at times.
In the winter sometimes storms can change quickly. A few degrees can make the difference between ice, snow or just a cold rain. Download the WHSV weather app. this is your best source for the local weather forecast. We input the forecast by hand, multiple times a day. We can update you when a storm changes.
Find out what this means for some local farmers:
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