Updated forecast: Dangerous storm still in store for many

Good evening.

If you aren’t already prepared for what will likely be a long-duration winter storm and aftermath, I recommend you do so tonight. In the mid-Atlantic, I would strongly recommend having enough supplies to get you well into next week, perhaps the whole week for rural areas.

The general trend has been southward for the storm and its impact. That will likely hold down the impact in areas such as northern Pennsylvania, upstate New York and most of New England. However, Mother Nature is not showing any mercy in the mid-Atlantic, where a paralyzing storm is imminent. Note that the amounts in some areas may be conservative, as some models are showing outrageous amounts as high as 35-40 inches or more in a few spots – these are general amounts.

Second call for the snow forecast for the Northeast. This may be conservative for some areas, particularly from southeastern Pennsylvania through Maryland and Virginia.

Regional synopsis:

Note that these are general amounts for each region. More specific city-based forecasts cannot be made at this time.

  • Northern New England and northern New York: No impact. Confidence: High
  • Coastal southern New England: Little or no impact near Boston; 1 to 4 inches most other areas with locally up to 8 inches in SW Connecticut. Confidence: Low to Moderate
  • Interior southern New England and Catskills: Little or no impact. Confidence: Moderate
  • Central valleys (Mohawk, lower Hudson, Susquehanna, Lake Ontario shore, etc.): Little or no impact. Confidence: Moderate to High
  • New York City region: 4 to 8 inches north, 7 to 14 inches south. Confidence: Low
  • Northern Mid-Atlantic coast (NJ, DE, Philadelphia area): 5 to 10 inches on the coast with significant mixing, rain or ice especially on immediate coast, 10 to 20 inches inland. Confidence: Moderate
  • Central New York and northern Pennsylvania highlands: Little or no impact north, 1 to 4 inches south. Confidence: Low to Moderate
  • Interior Southern Pennsylvania: 4 to 12 inches north, 10 to 20 inches south; locally to 30 inches possible along Blue Ridge front near Maryland border. Confidence: Low to Moderate
  • Chesapeake and Potomac region (DC, Baltimore): 18 to 28 inches (somewhat less just east of Chesapeake Bay); locally to 40 inches possible just west of DC. Confidence: Moderate to High
  • Central Appalachians/Blue Ridge: 14 to 22 inches; locally to 30 inches possible along Blue Ridge. Confidence: Moderate
  • Southern Piedmont/valleys (Shenandoah, James, New River Valley, etc.): 14 to 22 inches in west, 10 to 16 inches in east. Confidence: Moderate
  • Southern Mid-Atlantic coast (MD, VA): 1 to 4 inches south (most falling as rain, sleet or ice), 4 to 10 inches north plus some mixing or ice. Confidence: Low to Moderate

Additional threats

  • Storm surge/coastal flooding: This is another significant threat especially from the Maryland coast northward to southern New England. In fact, for some areas (especially on the Jersey Shore) the impacts at the coast may rival that from Hurricane Sandy in 2012, and according to WPVI meteorologist Cecily Tynan, the beaches could face their biggest test. In terms of surge amounts, I believe 2 to 4 feet is a reasonable guess south of Delaware Bay, with 4 to 6 feet possible along the Jersey Shore and around New York City and in Long Island Sound, decreasing northward from there. Given the high tides, at least 3 to 4 feet of tidal range can be added to those numbers, resulting in a peak water rise of 6 to 10 feet. For most areas that is not at the levels of Sandy, but still very dangerous. South of Atlantic City, this storm could rival or exceed Sandy though. Regardless it is a dangerous threat that must be prepared for as well.
  • High winds: In general, many areas can expect sustained winds of 25 to 35 mph inland and 30 to 45 mph near the coast. Gusts will likely be higher – up to 50 mph inland and up to 65 mph near the beaches (locally higher). The strongest winds especially will likely lead to significant power outages and tree damage. Areas that experience those winds along with heavy, wet snow or ice (the wettest snow will be on the southern envelope of the snow region) will be at even greater risk for such, and may also combine for structural damage as well. It is likely that hundreds of thousands, or even millions, of customers will lose power and possibly for an extended period. Regardless of power issues, the wind and snow will likely combine for blizzard or near-blizzard conditions and zero visibilities, making driving extremely dangerous if not impossible.
  • Freezing rain: This is not a major threat in our region, but a significant threat in parts of the Carolinas, particularly from central North Carolina into upstate South Carolina. Those areas may experience widespread ice amounts of 1/4 inch or greater with the heaviest amounts of 3/4 inch to 1 inch possible. Combined with strong winds, that will likely lead to widespread power outage problems and given the larger area to be affected, slow down recovery as power crews will need to spread out more or will be stressed.

Confidence: High on the general synoptic setup, variable (see above) on the amounts and their locations. I have previously mentioned advice on how to prepare – for western areas, time is running out. You should be fully prepared and in place (possibly for many days) starting tomorrow afternoon in the inland mid-Atlantic and by tomorrow evening on the coast. It is a very tough forecast on the northern flank, and the numbers could rise or fall greatly, so it is good to be prepared for much more than forecast there as well.

Stay safe and stay off the roads!

Forecaster Craig Ceecee – @Ceecee_Wx

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