NYC Weekend Weather – Dec 18, 2020

We could see the coldest overnight temperatures this season tonight following the big snowstorm earlier this week. High pressure builds in Saturday, though colder than normal temperatures remain in the low-30s. Temperatures start to rebound to the normal range in the low-40s next week. There’s a chance of stray showers Sun, otherwise a dry forecast. Possibility for more showers Tuesday, though uncertain at this time. Warming trend continues and and chances for precipitation increase later into next week.

Rest of today – partly cloudy with high temperatures in the low-30s. Overnight lows dropping to as low as around 20ºF with high pressure building leading to calm winds and good radiational cooling. This is only further enhanced by the presence of relatively fresh snowpack that helps insulate the ground from radiating heat upwards.

Weather Prediction Center’s surface forecast for 7AM Saturday, depicting high pressure sitting over much of the eastern US.

Saturday – with a cold start to the day, temperatures will only be climbing into the low-30s again, though high pressure should provide us with lots of sunshine. Overnight lows “warm” up to around 30ºF with return flow from the southwest as high pressure starts exiting east.

Sunday – a weak shortwave moves through, and could bring a couple of scattered showers. However, the associated frontal boundary will be weakening as it approaches, so precipitation isn’t all that likely, so we may instead just get a partly sunny day. Temperatures should rise to around 40ºF with warmer southwesterly flow ahead of this disturbance. Overnight lows in the low-30s.

GFS model 500 mb height and relative vorticity at 1PM Monday

Monday high temperatures rising to the low-40s, back into normal range for this time of year with partly sunny to partly cloudy skies. A stronger mid-level trough will be approaching at this time. This may portend some precipitation going into Tuesday. Overnight lows in the mid-30s.