January outlook: Variable, but month leans milder and wetter than average for D.C.
Snow chances may improve toward the second half of the month.
It’s a new year but with the same weather pattern as the end of 2020, at least at the outset. This means January is likely to feature periods of cold at times, but warmer days with heavy rainstorms will predominate.
More frequent cold air outbreaks become more likely later in the month, which could open the door for snow opportunities, as well.
For January, we are predicting average temperatures about one to three degrees warmer than the 30-year average of 36 degrees. Rainfall should be one to three inches higher than the 2.81-inch average for the month. However, snow should be near to below the average of 5.6 inches.
Forecast background
A strong Pacific-based weather pattern is poised to send warm and wet conditions into the eastern United States for much of the next two weeks. Computer models are in fairly good agreement that temperatures in the Mid-Atlantic could average about five degrees above average for the first half of January. However, we think this may be overdone.
One reason these models may be overstating the warmth is the presence of a feature known as the Greenland block, which tends to deliver pulses of cool to cold air down the East Coast. Another reason our outlook is not as mild for the overall month is the evolution of an event known as a Sudden Stratospheric Warming (SSW), which is happening this weekend into early next week. It is likely to have influences persisting over the North Pole into the second week of January and probably beyond, though there is considerable uncertainty regarding its long-term evolution.>>>
https://www.washingtonpost.com/weather/2020/12/31/january-climate-outlook-washington/?