December has been a chilly month in the D.C. area, with the balance of days colder than average. But, due to an impressive shot of warmth coming this weekend, the average temperature for December may vault into positive territory. Yes, there’s a realistic chance of hitting 70 degrees or higher by Sunday.

Let’s take a look a how warm the models are predicting it could get, day by day.

We first feel the above normal warmth Friday, when highs reach 55-60. Remember that normal highs are now in the mid-40s.

European model forecasts highs in the mid-50s Friday (

By Saturday, highs of 60-65 are a good bet – maybe a little  warmer if it’s sunny and rain showers stay away. The GFS model predicts we’ll have highs near 60, whereas the European model simulation predicts toastier mid-60s; both models are shown below.

GFS model forecast highs for Saturday (

European model forecast highs for Saturday (

It’s Sunday when the models really bring on the heat.  Both the GFS and European models, seen below, predict 70-degree highs. We show you the Canadian model as well, which tells the same story.

GFS model forecast highs for Sunday (

European model forecast highs for Sunday (

Canadian model forecast highs for Sunday (

Redskins fans may be able to wear short sleeves for the rivalry match-up against the Cowboys at FedEx field Sunday afternoon.

The record highs Sunday of 72 (from 1889) at Reagan National Airport, 69 at Dulles (from 1984), and 70 at BWI (from 1889) are all potentially in play.

The GFS Model Output Statistics (MOS) – which essentially adjusts the raw output shown above to account for local conditions  – forecasts an astonishing 76-degree high Sunday – which would be close to the all-time December record high of 79 (set on December 7, 1998).  It would be the warmest day on record in D.C. so late into December.

GFS Model Output Statistics temperature forecasts for D.C.

Behind the warmth

As a cold front, which may produce hefty snows in Chicago this weekend, pushes east, very warm air will be drawn northward out ahead of it.   A large area of high pressure off the Florida coast – known as the Southeast ridge – will be favorably positioned to pump this warm air all the way up into New England.

European model shows big ridge of high pressure off Southeast Coast, helping to pump warm air northward ahead of the cold front in the central U.S. (

Temperatures may be as much as 30 degrees above normal in the Mid-Atlantic and Northeast.

Temperature difference from normal predicted for Sunday afternoon by the GFS model (

What could go wrong with the forecast?

70-degree highs are not a guarantee Sunday, especially if the cold front speeds up a little bringing clouds and rain showers into the region during the afternoon.  Of the ensemble of simulations run by the GFS model, quite a few hold highs in the 60s, as shown below.


The rectangular bar outlined in green Sunday afternoon shows that a number of the members of the GFS ensemble have highs in the 60s rather than 70s, illustrating the uncertainty in the forecast  (

But if the front takes it time and clouds and rain hold off until around dark, 70+ temps are a good possibility.