December 15

Near-Blizzard Conditions Possible Mid Atlantic and Northeastern USA

Twin Cities National Weather Service

GFS Forecast Pressure and Precipitation
Tropical Tidbits

Southern Detour to the Storm Track. The 12 NOAA GFS model run sweeps the most significant moisture well south of Minnesota, a trend we’ve witnessed in recent weeks. I see no major deviation from this (dry, relatively mild) pattern until possibly the last few days of December.

Then Again… I’ve seen this numerous times in the last few weeks: GFS suggesting a cold snap, only to have a persistent Pacific signal erase any bitter cold by the next model run. Let’s see if there is any consistency to the models before get too excited about a true shift in the pattern. If the GFS solution above verifies a mild signal would continue into early January. Stay tuned.

Dr. Judah Cohen, Twitter

Gary Szatkowski, Twitter

12KM NAM Accumulated Snowfall (00z Tuesday run)

Briefing: Issued Monday, December 14th, 2020:


Mid-Week Winter Storm Watches. While rain and snow are impacting portions of the Mid-Atlantic and Northeast today, a stronger, major winter storm is expected to impact the region as we head into Wednesday and Thursday. This will be due to a nor’easter that develops and moves up the Mid-Atlantic coast. Ahead of the storm, Winter Storm Watches have already been issued from western Virginia to just outside of New York City. However, I would expect Winter Storm Watches to expand across portions of New England later today. Some of the locations already under Winter Storm Watches include:

  • Charleston, WV: Wednesday morning through late Wednesday night for 2-5” of snow and up to 0.10” of ice.
  • Baltimore, MD: Wednesday morning through late Wednesday night for 7”+ of snow.
  • Harrisburg, PA: Wednesday morning through Thursday morning for 12”+ of snow.
  • Philadelphia, PA: Wednesday morning through Thursday morning for 5”+ of snow.
  • Scranton, PA: Wednesday afternoon through Thursday morning for 6”+ of snow.

American Model. Already as we head toward Wednesday morning snow is expected to be falling across portions of the Ohio River Valley, with ice across portions of the Mid-Atlantic. By the midday and afternoon hours, heavy snow will start to fall across the northern Mid-Atlantic and southern Northeastern states. Snow is expected to start around the evening commute Wednesday in the New York City area, lasting through the Thursday morning hours. The heaviest would fall Wednesday Night, when 8-12” could fall. Snow will spread northward to the Boston area Wednesday Night. The American GFS keeps the low a touch farther south, keeping heavier snow out of Boston, but the European brings heavy snow to eastern Massachusetts due to a more northern track.

Modeled Snow Amounts. A big difference in the American GFS and European models is that northern cut-off of heavy snow, with the farther south American model showing considerably less snow for Boston than the European model. The heaviest snow is expected to fall across interior portions of the Mid-Atlantic and southern New England, but heavy snow of at least 6-12” can currently be expected along I-95 from D.C. to Philadelphia, New York City, and (potentially) Boston. This snow would cause major travel disruptions and potentially power outages across the region. We will be ironing out the details of the overall track of this system over the next day or so, and should also get a clearer idea where the snow/wintry mix/rain line sets up. This will help determine how close to the I-95 corridor that 6”+ snow totals will get, as well as overall impacts farther north.

24 Hour 6”+ Snow Probability. As we look at snow probabilities, the greatest potential of seeing at least 6” of snow from Wednesday morning through Thursday morning will be inland toward areas like Cumberland (MD), Harrisburg, Williamsport, and Scranton (PA), and Middletown (NY). However, from Philadelphia to New York to Boston there is at least a 50-70% of that much snow falling during the 24-hour period.

Ice Potential. Farther south, icing will be a problem across eastern North Carolina into Virginia, where odds are above 50% that at least a tenth of an inch of ice could fall on Wednesday. Some models are outputting a quarter to a half an inch of ice across the region, which would cause power outages.

D.J. Kayser, Meteorologist.

NOAA NDFD Snowfall Forecast

Eric Fisher, Twitter


November 2020 Among Warmest Novembers on Record: NOAA and NASA. Yale Climate Connections reports: “November 2020 was the second warmest November since global record keeping began in 1880, behind the record set in 2015, NOAA’s National Centers for Environmental Information, NCEI, reported December 14. NASA rated the month as the warmest November on record, as did the European Copernicus Climate Change Service. The Japan Meteorological Agency rated it as the second-warmest. Minor differences in rankings often occur among various research groups, the result of different ways they handle data-sparse regions such as the Arctic. For the period September-October-November, the Northern Hemisphere had its second warmest autumn, only 0.01°C (0.02°F) behind the record set in 2015, NCEI reported. The Southern Hemisphere had its ninth warmest spring on record…”

Gritter Tracker 2020

Should We Give Snowplows Names? I think Scotland has the right idea (grandpa: what’s a snow plow?) If you need a smile check out the Gritter Tracker 2020: “One of Scotland’s great winter traditions has returned with the country’s hilariously named gritters hitting the roads. Every year the combination of frigid temperatures, festive cheer and unique Scottish humour sees the country’s gritter drivers nickname their vehicles, from Yes Sir Ice Can Boogie to License to Chill.Best of all, Scots concerned about the road conditions, or simply keen to track their favourite gritter can do so at the Traffic Scotland website…”

Map credit: Trunk Road Gritter Tracker, Traffic Scotland.

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