12:15 PM (Wed) | *Snow pack at high levels across the US for early December and throughout North America…impressive cold air outbreaks into at least mid-month for the central and eastern US*
Paul Dorian
12Z GFS 850 mb temperature anomaly forecast map for the middle of next week indicates widespread colder-than-normal conditions across much of the central and eastern US; credit NOAA, tropicaltidbits.com
Overview
The snow pack across the nation is well above-normal for early December and it is actually at or near record high levels across all of North America. In addition, the first few days of December are colder-than-normal across the nation as a whole and this follows a colder-than-normal month of November for the eastern two-thirds of the nation. Looking ahead, multiple cold air outbreaks are destined to reach the central and eastern US from Canada right into at least the middle part of the month, but there will be some short-lived warmer-than-normal breaks as well.
Snow cover reached nearly half across the nation earlier in the week which is well above-normal for early December; credit NOAA
Snow info
While the immediate DC-to-PHL-to-NYC corridor was largely spared from the snowstorm a couple of days ago (“Trace” at Dulles Airport, “Trace” at Philly Airport, 1.6 inches in Central Park), significant snow fell in parts of the interior Mid-Atlantic and NE US. In fact, more than two feet of snow was recorded in some spots of New England and interior New York State during this most recent storm and Albany, NY had its biggest snowstorm (22.6 inches) since March 1993 and their 8th biggest on record. Just last week, a snowstorm in the Colorado Rockies brought some of the highest snow accumulation levels ever for a single storm (22 inches) to places like Boulder. In fact, snow cover extent across the US is well above normal for this early in the season at nearly half and multiple cold air outbreaks over the next couple of weeks ensure more accumulating snow for much of the northern half of the nation.
Snow cover extent across North America is quite high for this time of year (arrow); courtesy NOAA
As of a couple of days ago, North America was at or near record high levels for snow cover extent this early in the season and it wasn’t only the US playing a contributing role to those above-normal levels. Greenland, for example, has seen a big uptick in recent days with respect to its “surface mass balance (SMB)” - the difference between snow accumulation and ablation (sublimation and melting) – with as much as 8 gigatons of an increase on Sunday, 12/1 and another 6 gigatons amassed on Monday, 12/2.
There was a big uptick in snowfall across Greenland earlier this week; data courtesy Danish Meteorological Institute (DMI)
Cold air outbreaks
In terms of temperatures, today remains colder-than-normal in much of the Mid-Atlantic/NE US in the wake of the storm earlier this week and a reinforcing shot of cold air will arrive overnight following the passage of a weak cold front. This front could generate snow showers in the I-95 corridor during the afternoon and evening hours and perhaps a dusting in some spots. As a result of the influx of reinforcing cold air, temperatures on Thursday will remain at below-normal levels for the early part of December. A second and stronger cold front will cross the region late Friday and this frontal system will usher in an Arctic air mass for the start of the upcoming weekend with well below-normal temperatures, but this cold blast will be rather short-lived.
Colder-than-normal conditions for the eastern two-thirds of the nation during November 2019; credit weathermodels.com, NOAA, PRISM Climate Group
Looking ahead, Sunday will actually be somewhat of a transition day in terms of temperatures with still chilly conditions in the Mid-Atlantic/NE US, but as high pressure pushes off the east coast, it will turn somewhat milder to end the weekend and that warm up will intensify on Monday and Tuesday. In fact, temperatures should actually climb to above-normal levels on both Monday and Tuesday in the DC-to-Philly-to-NYC corridor with highs well up in the 50’s (normal highs now: DCA 51°F , PHL 49°F, Central Park 47°F). The warm up early next week will be accompanied by some rainfall and some of it can get rather heavy on Tuesday - just ahead of the next strong cold frontal system. That frontal system will usher in another very cold air mass for this time of year - perhaps the coldest air so far this season for the Mid-Atlantic/NE US - and temperatures could fall into the teens by early Thursday morning in much of the I-95 corridor.
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com