[UPDATE]

1/20, 3:08 PM:

Our entire readership is currently under a blizzard watch for the storm. Expect these watches to upgrade in the next few days. The Models continue in almost full agreement: The DC area will get covered in crippling, heavy snow that will bring the area to a halt beginning Friday afternoon and lasting almost 36 hours into Sunday Morning. The timing could still shift, and the track could shift to favor one area or another. But we know a severe winter storm WILL be impacting our region Friday into this weekend.

The sweet spot spans a portion of Northern Virginia into DC. This zone can very well shift, and we will reflect any shifts in our final call and forecast discussion tomorrow. For now, we expect the heaviest band of snow to set up where he have it drawn and potentially drop over 2 feet of snow on some places. It is also not out of the question that an isolated 3′ of snow falls somewhere. While we pin down the details of this forecast, here’s our first look and guess at how much snow everyone can expect: **Start preparations now – make sure you have shovels ready, as well as food and shelter for the storm. This amount of heavy snow is a threat to life and property if not taken seriously.

[Original Post]

1/16, 8:00 PM:

After a review of the model data this afternoon, our thinking remains essentially unchanged. Models are unanimous in taking an energetic upper level disturbance just to our south and popping a surface low pressure off of Cape Hatteras. Expect snow to overspread the area Friday morning and last until late Saturday. Accumulations of at least a foot and possibly much higher seem very likely. Due to the rare agreement among models as well as the perfect track and Miller A type cyclogenesis, confidence in a major snowstorm is ABOVE normal.

It is a good idea to start preparing for what could become a prolific winter storm. Expect widespread cancellations Friday, Saturday, and even Sunday. Due to the long-duration nature of this snowstorm, non-crucial roads could take days to be plowed, so be ready to be stuck all weekend. Strong, possibly damaging winds could lead to blowing and drifting of snow as well as scattered power outages Saturday, especially east of DC. There will also be major coastal flooding due to the strong onshore winds.

The two primary ways this storm could still fall short of predictions are the out-to-sea scenario we detailed in our earlier post and the over-amplified scenario that would cause much of the area to flip to sleet or even rain at the height of the storm. The odds of each scenario are around 10% at this point, meaning there is an 80% chance of the high-impact snowstorm scenario.

All major models including the GFS, Euro, Ukmet, GGEM, JMA, and the GEFS, EPS, and GEPS ensembles depict at least a foot of snow over the area. This is one reason why we have such high confidence in heavy accumulations. Comparisons to the New York City bust last winter or the Snowquester debacle way back in 2013 are misguided because both of those storms were Miller B’s, which tend to be much more finicky and unpredictable than Miller A’s such as the one predicted for late this week. (Miller A’s involve a single storm moving up the coast from the gulf of mexico while Miller B’s have a primary storm transferring their energy to a coastal storm.)

We will continue to update you as this storm approaches! Expect a first look at accumulations tomorrow afternoon.