WASHINGTON - It has been a mild fall season, but winter is just around the corner! The FOX 5 Weather Team has five things you need to know about their 2015-2016 Winter Weather Outlook.
1. We favor a “warm” winter
As of November 19th, the average temperature in Washington D.C. during the month of November is 56.8 degrees Fahrenheit, which would be D.C.’s warmest November ever on record if it holds. This number should fall however as we are expecting the majority of the last ten days of the month to come in below normal, but the overall message is that the general autumn pattern to date has been a pretty warm one.
We expect the warm pattern to continue as we through the winter months, especially during December and January. However, it’s important to stress that a warm winter does not mean you should keep the beachwear out and the A/C at the ready. D.C.’s average high temperature through the first half of January is 43 degrees Fahrenheit, so a couple degrees above that is still a cold winter day. Even in the warmest of winters, cold air always makes the occasional appearance.
We believe that it will this winter as well. We just favor the colder outbreaks to not be as longed lived or as intense as they were during the previous two winters.
2. One of the strongest El Niños
Prepare to hear this word a lot this winter because of all the factors that drive our winter pattern -- this is by far the biggest. El Niño is simply abnormally warm sea surface temperatures along the equator in the Pacific Ocean. The abnormally warm waters help increase upper level winds in the tropics, which help bring more moisture into the United States and can heavily influence the track of storms across the United States.
El Niño’s comes in four categories: weak, moderate, strong, and very strong all depending on just how far above average the water temperatures are. This year’s El Niño is one of the strongest, if not the strongest on record.
For Washington D.C., we tend to see some of our biggest snowfalls when El Niño strength is weak to moderate. Strong and particularly very strong El Niño strength can overwhelm the atmospheric pattern, and tend to give us less of an opportunity for snow due to more warm air being present.
3. No two El Niño winters are the same
While El Niño can be one of the best indicators for the coming winter, it is far from a perfect indicator, and similar years to this one have thrown us a couple of curveballs.
As far back as accurate global ocean temperature rankings go (only to the late 1940s), there have only ever been two other El Niño years that have been as intense as the current one.
The most recent one was the winter of 1997-1998. In that winter, D.C. saw one of its lowest snowfall winters on record, only picking up a measly 0.1” of snowfall. Before that, there was the very strong El Niño winter of 1982-1983. This winter featured one of D.C.’s worst snowstorms -- the Presidents Day storm of February 1983 -- which dumped more than two feet of snow just northwest of the city.
This year’s very strong El Niño features some differences from both of those years that could make the winter to come very interesting, but in all honesty, we will just have to wait and see what those surprises are.
4. Snowfall forecasts are a shot in the dark
It is tough enough forecasting snowfall totals a day before a big storm. So forecasting accurately an entire season ahead? Forget about it. There is no crystal ball to look into and every year is different.
However, we can take an “educated guess” based on other factors that we can forecast with reasonable accuracy given the range, and those are moisture and temperatures relative to normal.
Looking at a number of factors, we are forecasting above normal temperatures and above normal moisture for the D.C. region, but also below normal snowfall. The reason why is simple -- we feel that more often than not, the cold air will not be in the right place at the right time for a number of big snow events.
Take both the very strong El Niño winters of 1997-1998 and 1982-1983 for example. While one featured major snow and the other did not, both featured less than half the typical number of days of measureable snowfall from a normal year (eight days at DCA) with one day and four days in each season, respectively. This means that getting the right ingredients together for snow happen less in these strong El Niño years compared to others, and with that being the case, we are playing the odds and going with below normal snowfall in D.C.
However, as 1982-1983 shows, cold air in the right place in the right time can completely blow our snowfall forecast out of the water. So take them with a grain of salt snow lovers as the big snow could still be lurking this year!
5. Late winter has the best chance for big snow
December may start off on a little bit of a chilly note, but we have reasonable confidence that the pattern will return warmer for the second half of the month and through the majority of January as well. For all those hoping for a white Christmas, sorry to say that your odds this year look significantly less than a typical December (but never say never in weather!).
By the time we get to February however, more question marks begin to appear. A significant factor in this is once again El Niño, which while very strong now, is expected to weaken through the winter months. If the weakening can occur fast enough, this may just open the door for enough late winter cold air to arrive, which would increase our odds for a late season snowstorm.
This is yet another year where some of winter’s strongest cold may come in late February and even extend into early March. If D.C. is able to get a big storm during this time period and end up with above normal snowfall (more than 15.6”), this would end up being the third consecutive winter with above normal snowfall. This is something D.C. has not done in 35 years!