Big Changes Possible Late Week as Powerful Nor’easter May Threaten Mid-Atlantic Coast

Last week I warned that the upper-level pattern was showing signs of becoming blocked and a pattern change to below- average temperatures is likely the second half of April across much of the eastern United States.

Potent Nor’easter May Impact Mid-Atlantic and New England Friday and Saturday

A very potent upper-level low pressure system depicted in the forecast model above (courtesy pivotal weather) will slide across the northern Mid-Atlantic states on Thursday, likely spawning the development of a coastal storm (Nor’easter) on Friday.

Depending upon the exact track of this system wet snow may accumulate in spots from the Alleghenies to the Poconos with a cold rain, gusty winds, and temperatures running twenty degrees below average (or more) for the lower elevations.

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Snow & Sleet Map Posted for Major Winter Storm

Snow will develop across the Washington Region during the morning hours on Sunday continuing through the late afternoon with a widespread 3 to 5″ of accumulation expected.

Snow may mix with Sleet during the evening hours and then potentially taper off to Freezing Drizzle during the overnight hours.

A glaze of ice from freezing rain is expected for locations east of interstate 81 and south of interstate 70.

On Monday a secondary storm will deepen off of the Del-Mar-Va coast line and slowly move northeast allowing for any Sleet and or Freezing Rain to change back to Snow. 

The Snow will likely pick up in intensity on Monday afternoon through the evening with low visibility and treacherous travel conditions. Snow will taper off to flurries on Tuesday morning before ending around noon. This will be a major winter storm with widespread travel disruptions.

The latest forecast models continue to show some differences in how far north the wintry mix makes it on Sunday evening, and how far south the wrap-around heavy snow falls on Monday afternoon through Monday night. My snow map took the middle ground (a blend of the GFS and European models).

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Map Posted for Snow Accumulation through Sunday Evening

I have a medium-high confidence that the snowfall totals below will materialize by Sunday Evening by 8PM.  I have looked at all of the deterministic forecast models from the American (GFS, Navy) to the European to the Canadian and the all important ensembles.

The million dollar question remains: How close to the coast does the secondary storm form and how strong will it be?

The heaviest snow on Sunday will occur across our southwestern zones from Charlottesville to Fredericksburg and across the Potomac river into southern Maryland where 4 to as much as 8″ of snow is likely before a lull in the precipitation develops across these areas on Sunday night.

Most models show snow redeveloping across northern Virginia, DC, points north during the pre-dawn hours on Monday and continuing through the day on Monday before tapering to flurries on Tuesday.

Monday is still three days out — I’d like to see another run of the European and GFS models tonight before I put up a total snowfall accumulation map for the entirety of this winter storm.

Yes there is the potential that someone in our region will wind up with 8 to 12″+ of snow… (best chance right now being from northeast Maryland to the Jersey Shore) but that will be highly dependent on the evolution of Monday’s storm system.  Some models have trended with heavy snow continuing through the immediate Washington Area all day on Monday so even in DC… there could be up to a foot. Too soon to make any promises…I’ll update tomorrow morning.