Friday December 18 2020

This is like deja vous, right? Last week  I wrote about the recent winter storm and wondering if it was OK to get excited for snow.  This time there is more confidence and there is a very simple reason: The Arctic Front!

Arctic Cold Fronts are often easier to forecast than solo storms and ‘phasing’ events.  This a large, dense air mass which can be handled better by computer modeling even 7 days away.  The real questions will be the timing of the arrival and what amount of moisture will be left behind the front.

The quick version of the outlook:

  • Christmas Eve: Mild, with rain.
  • At Night: There could be thunderstorms, winds with the front to 50 mph, then a change to snow.
  • Christmas Day: Flash Freeze! Some flurries or snow showers and brutally cold air likely falling through the teens.


Let’s take a quick look at all the buzz, then explain a little more about why this is expected to happen.


GFS Animation

This reminds me of the Christmas 2002 snow. A warm rain on Christmas Eve  was followed by a burst of  to 6 inches of wet snow for much of Maryland and southern PA on Christmas morning.  I remember because I was working EVERY HOLIDAY SHIFT on WBAL!  The night shows, and the morning shows.

December 18 Christmas snow



Transition From Rain To Ice And Snow

The timing is what is not agreed upon at this time.  The GFS is faster, on Christmas Eve Night.  But the European Model is slower, arriving early on Christmas morning.

Note: While this is one week away, this type of set up can bring:

Thunderstorms, damaging winds, then a quick drop in temps with sleet and snow. This may all result in a Flash Freeze!

We can see why below…

GFS Model Snapshot

December 18 storm ice snow Christmas Eve GFS


European Model

Later time, but still passed through by morning…

December 18 storm ice snow Christmas Day ECMWF 1 AM



December 18 storm ice snow Christmas Day ECMWF 7 AM



Jet Stream Maps

This is a look at the 500mb level, which is about 18,000 Ft above the ground.

Christmas Eve Day

An extremely deep trough will be digging into the Gulf Coast Region. This will open up air from the arctic to drop all the way south into the US.

We will have warming just ahead of its arrival.

December 18 storm jet stream Christmas eve USA


Closer Look

At this time, the  cold air will be pushing the warm air out.  The contrast may spark strong storms, very strong winds, and a sharp transition from rain to ice and snow.

December 18 storm jet stream Christmas eve


Christmas Day

The core of the cold air will reach us in the afternoon.  Rapidly falling temperatures will resemble the heart of winter.

December 18 storm jet stream Christmas Day



Thickness between 1000 mb and 500mb

This measurement is a good reflection of how cold the air will be.  Note: The 540 (dm) line is where we spot the freezing point at cloud level between rain and snow. Here we see 509 (dm) that represents roughly 30 degrees colder.  Yes, it should be near or below ZERO aloft in the afternoon.

December 18 storm jet stream thickness Christmas Day


Afternoon Surface Temperatures 

Temperatures should be falling all through Christmas Day.

These numbers are for 4 PM in the afternoon!

It will be windy as well, which should take chills down to near or below Zero!

December 18 weather temperatures Christmas afternoon


More Support

The long range global patterns support a cold period ahead.

The Arctic Oscillation remains with a negative signal. It will reach near neutral on Christmas, then drop further than it has been in the days that follow.

December 18 arctic oscillation Christmas


The North Atlantic Oscillation is a prominent signal when negative to support east coast snow.  But I have seen many occurrences when it is negative, and while it rises to neutral, we can get a winter event on the east coast of the US.

That’s what we see here on Christmas, then falling deep negative a few days later.

December 18 north atlantic oscillation Christmas


Temperature Outlook

This is an abrupt change. This is also EXTREME!  I expect this will adjust and may modify a little as we get closer. But WOW! What an impressive perspective now for Baltimore:

Christmas Eve: 50s

Christmas Day: Falling! That 35ºF would be at midnight, as we’ve seen the afternoon in the lower 20s.

December 26: Highs in the lower 20s!

Notice the temps recover to the upper 30s, still well below average to end the month.


December 18 weather temperature outlook Christmas cold


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December 5 Snowfall History Start Of Faith in the Flakes


14 Local Maryland Pages (and York PA)

We have made a page for Maryland Weather which gives you the current conditions for 14 present area locations.

Local Hourly Forecasts and Local Radar
Central Maryland



Bel Air

Carroll County/Westminster




Ocean City

Dover DE

Southern Maryland

Patuxent River 

Washington DC





National Weather Service Adds Maryland Cecil And Garrett Counties




Also see:


Winter Outlook Series

Winter Outlook 2021 Tropical Hints

Winter Outlook Polar Vortex Arctic Oscillation

Winter Outlook Solar Minimum

Early Winter October

Winter Outlook Series Weather Folklore


Winter Outlook 2021 La Nina Advisory

Winter Outlooks Farmers Almanacs




14 Local Maryland Pages (and York PA)

We have made a page for Maryland Weather which gives you the current conditions for 14 present area locations.

Local Hourly Forecasts and Local Radar
Central Maryland
Southern Maryland




National Weather Service Adds Maryland Cecil And Garrett Counties



Maryland Weather Page

Maryland Weather 

I wanted to keep it simple. Just the basics for a quick view at any time.

Maryland Weather Just In Weather




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