Matt Makens

A more active weather pattern will return this weekend to close out 2020 with
chances of snow.

We discussed last week that if December was to end wetter than average for the
metro areas, and much of the state for that matter, we will be reliant upon a
pattern shift for the last few days of the month.

It's too early to say if the snowfall amount to come will do the trick, but at
least the flow will again turn more active.

A ridge in place for Christmas
[https://www.weather5280.com/2020/12/21/the-state-of-the-atmosphere-monday-december-21st-2020/] 
will begin to flatten by Sunday and that will allow some activity to flow
through the area for several days thereafter.

Sunday's 500H, note the dip in the flow over Colorado: 

Tuesday's 500H, a bit more of a pronounced trough overhead, with a larger ridge
in place east: 

Let's look at potential snowfall totals from this "troughier" pattern to close
out 2020.

EuroEns:

GFS Ens:

In both cases we don't see a huge amount of snow for the Front Range/metro areas
but at least it is something. Regionally, we do see an uptick in snowfall
potential, however, with our mountains lined up to see some much needed snow,
and the potential for some heavy snowfall totals across the Plains and Upper
Midwest as well. 

Is there potential for a deeper trough and thus more snow across Eastern
Colorado? I suppose, but teleconnections still aren't all that supportive of
that scenario. The PNA and MJO do not give indication of a significant system in
the next two weeks for the eastern half of the state. 

With that said, however, we have seen an uptick – albeit subtle – in
precipitation totals depicted in the past 24 to 48 hours of model and gamblers
data [https://www.weather5280.com/insider/probabilities/precipitation].

https://www.weather5280.com/insider/probabilities/precipitationSo, will the
currently depicted snowfall totals be enough to end December snowier than
average?

Look at the month-to-date snowfall departure from 'normal.' For the metro areas,
a 2.5 to 5 inch, and more, deficit will need to be erased for some spots. 

Based on projected snowfall totals, the December deficit may very well be
normalized with a 2 to 3 inch snowfall in many areas. 

The higher deficits between Colorado Springs and Pueblo, and that of the
Northern Front Range Mountains and Foothills may not be totally wiped
out...again, based on the current projections.

In any case, we will see a more active end to the month but still not quite what
a snow lover waits for unless we start to see a trend toward a slower, stronger
solution early next week. So far, that isn't there.

A more active pattern returns to end 2020, what that may mean for snow across Colorado and the region