How Much Snow? How Low Will Temps Go?

Winter likely to be similar to last year

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    NEWSLETTERS

    We had Snowmaggedon in 2010 and Carmageddon last winter, so what are we getting this winter?

    I have been doing winter forecasts for this region for a long time. I love doing the research behind them and I love to watch what happens all winter long after that forecast is made.

    Many people ask if we can really forecast what a winter is going to be like. The answer to that question is YES. We can forecast how much snow we may see and we can forecast what temperatures may be like overall, but what we cannot do is tell you what day the snow will fall or what it will be like on Jan. 18, for example. We are able to give an overview of the winter and we normally do a pretty good job of it.

    Last winter, we predicted between 8 and 14 inches of snow and we received 10.1 inches for the season, so we nailed it. Temperatures, though, were a bit tougher, and we were wrong for December and January as both months were cooler than predicted. We did well with February and March though.

    So how about this year?

    There really is a lot of research that goes into making our winter forecast. We look at a number of factors around the world, some have more of an impact on our weather than others, but they are all very important. We look at things like the El Nino Southern Oscillation in the Pacific, the North Atlantic Oscillation in the Atlantic, the Artic Oscillation, the Pacific Decadel Oscillation and the Pacific North American Pattern. You can learn more about each by clicking here and looking under Climate & Weather. We also look at things like snow cover in Siberia in late October as well as sea surface temperatures in the western Atlantic and the Pacific.

    The biggest factor most years is the El Nino Southern Oscillation, or ENSO. It consists of warmer than average sea surface temperatures in the equatorial Pacific, which is El Nino, or below average sea surface temperatures, known as La Nina. Even though that area is thousands of miles away from us, it still has a huge impact on our weather all year long. Right now we are in a La Nina phase, and currently, it is a weak to moderate La Nina and it is forecast to last through the winter.

    During a La Nina, our region is normally dryer than average and slightly warmer than average with below average snowfall. The La Nina this year is predicted to be of moderate strength. If that is correct, then our forecasted snow goes way down. We have never had a snowstorm in Washington of more than 8 inches during a moderate or strong La Nina. That is why we are forecasting much less snow this year than average.

    Here is the forecast from NOAA, or the National Oceanic and Atmospheric Administration, mostly based on La Nina:

    Northeast and Mid-Atlantic: equal chances for above-, near-, or below-normal temperatures and precipitation. Winter weather for these regions is often driven not by La Niña but by weather patterns over the northern Atlantic Ocean and Arctic. These are often more short-term, and are generally predictable only a week or so in advance. If enough cold air and moisture are in place, areas north of the Ohio Valley and into the Northeast could see above-average snow;

    I am in agreement with NOAA on their winter forecast, but they are very vague in our region, and we are able to take it much further.

    There are a few other factors out there that are slightly more important than others in predicting snowfall and temperatures during our winters. Those factors would be the North Atlantic Oscillation and the Arctic Oscillation. These two factors, however, are extremely hard to forecast and cannot be forecasted more than a week or two in advance. These are the two factors responsible for bringing very cold air into the region and increasing our chances for snow. In their negative phase, the NAO and AO allow for cold air to move south from Canada.

    This is what happened last December and why it was so cold. It was still dry, however, as the effects of La Nina did not allow moisture to move into the colder air.

    So what are we thinking for this year? Well, we think it could be very similar to last winter with below average snowfall and similar temperatures.

    The average snowfall for the D.C. metro region is about 15 inches. We see a good chance of below average snowfall with a total between 7 inches and 13 inches. I would actually like to lean toward the 7 inches number, but Carmaggedon and a few other storms recently have me a little scared to go so low. Why? Because we are seeing stronger and stronger storms every year across the country and across the world. The storm that brought us Carmaggedon last year was one of these exceptionally strong storms. We saw things in that storm that we very rarely see, like thundersnow. Sure, we have seen that before, but it is rare to see it all across the region, and our snowfall rates were 1-2 inches per hour, which is even more rare. What made that storm even more dangerous was the fact that we saw most of that snow at the beginning of our rush hour. We only saw 5 inches at the airport, yet it came down so fast that there was little we could do to avoid getting caught.

    Could we see another storm like that this year? My answer is yes, although the timing would most likely not occur during the peak of Washington rush hour. These storms are becoming more and more common, and they could become the norm. Now, put a similar storm in an El Nino year, where moisture is plentiful, and you get the Blizzard of 2010 -- Snowmaggedon!

    I do not think we will see a storm that produces more than 6 inches of snow in Washington, but we could still see a few strong storms this winter.

    As for temperatures, I think we will see below average temperatures once again this year in December and January and then above average temperatures in February and March.

    So there you have it, our official forecast. One other thing to remember is that areas to the north and west of Washington will see higher totals, as usual, and areas to the south and east will see lower totals.

    For those of you that love snow, this may not be your year, but I would not hang up that snow shovel just yet.

    Have a great Winter everyone!


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