Severe winter storm expected; worst in mid-Atlantic

Good afternoon.

It is basically the calm before the storm in the eastern US. Models have largely honed in on a small number of possibilities, but they do have some differences. That said, we are pretty much in agreement that it should be a non-event for northern New England and a crippling winter event for parts of the mid-Atlantic, particularly in the DC/Baltimore area. Areas north and south of there, however, have regional uncertainty that can make a great difference in the exact impact of the storm.

In addition to the potential for severe snow (some of the models are showing “outrageous” amounts – which we will highlight later today when we make our first call on amounts), significant storm surge and coastal flooding is another threat for coastal areas, particularly in the upper mid-Atlantic coast (such as the Jersey Shore) where the impact could even locally approach that from Hurricane Sandy in 2012. A track slightly farther north would result in significant storm surge for New York City at high tide. The ESTOFS run shows a surge of 5 to 6 feet in the NYC area, which combined with tides would be approximately 10 to 11 feet, which would be a top-5 event. High winds are another threat, which could lead to power outages and whiteout conditions. We have largely narrowed down the situation to three main scenarios (from south to north), of which one is clearly the most likely.

Worth noting that the NWS office in Sterling, VA has already issued a Blizzard Watch for their region (including Washington DC and Baltimore).

Scenario 1: Low exits south of Hatteras, main focus on southern Mid-Atlantic (10% chance)

This scenario has the low center tracking a bit farther south, emerging into the Atlantic somewhere along the lower North Carolina coast and remaining well south of Cape Hatteras. This scenario has no model backing anymore with virtually all models showing the low remaining onshore through eastern North Carolina or southeastern Virginia, except for a couple lifting it farther north. In this scenario, the heaviest snow would likely be concentrated in central Virginia through southern Maryland and the Delmarva, where the best moisture would be concentrated, although snow would likely be heavy into northern North Carolina and southeastern Virginia as well. It would largely be a non-event for New England. This had some model support yesterday but not anymore.

Scenario 2: Low exits Hatteras to Chincoteague, main focus on central Mid-Atlantic (70% chance)
12Z GFS (January 20) forecast for Saturday morning. Notice heavy snow continuing in the DC-Philadelphia corridor and expanding northeastward.

12Z GFS (January 20) forecast for Saturday morning. Notice heavy snow continuing in the DC-Philadelphia corridor and expanding northeastward. Other models mostly agree as well.

This is our preferred solution, and also the most severe (by far) for the mid-Atlantic. Reliable models are close to unanimous in that the low center will emerge off the coast either in eastern North Carolina or southeastern Virginia on an east-northeast trajectory. The rapidly intensifying low would remain south of the New England coast, likely tracking just south of the 40/70 benchmark with a pressure around 980 mb and a strong gradient to the north. Combined with very deep moisture, it would result in potentially phenomenal snow totals for parts of the mid-Atlantic, particularly from central Virginia through DC into Maryland and southern Pennsylvania and New Jersey.

Some models have shown absolutely outrageous snow forecasts, which may be overdone but they clearly show the potential this storm has. In addition, strong winds would likely lead to near-blizzard, if not blizzard, conditions making transportation impossible (with airports closed, highways blocked and public transit suspended) and shutting down commerce for at least several days. Don’t be surprised if the region is still largely shut down come Monday. Power outages are also quite likely for some areas that receive both heavy snow and high winds.

Areas south and east would likely mix with rain (or freezing rain) as warmer air attempts to push northward during the storm. In addition, amounts would drop northward towards New York City and particularly New England as the precipitation shield and moisture is less pronounced for them, although it could still be a significant event for snow especially south of I-90. Nonetheless, for those areas, coastal impacts and winds would still be a major issue even if moisture is reduced, with coastal flooding possible along with whiteout conditions.

Most likely, the first snow will arrive in the region early Friday, spreading on Friday across the mid-Atlantic and remaining in place for at least 36 to possibly 48 hours. It is difficult to determine who will get the absolute maximum snow as mesoscale banding would be a prime factor in increasing amounts (along with embedded thunderstorms) which cannot be predicted this far out. It should spread eastward on Saturday, although the heaviest snow may remain offshore of Long Island and southern New England – it will be a close call especially for the southern coast. The storm should depart the region Sunday as it moves out to sea south of Nova Scotia and slowly weakens, however, it will likely take days to clean up and get everything running again in the hardest hit areas.

Scenario 3: Low exits Chincoteague to southern New Jersey or northward, main focus on northern Mid-Atlantic (20% chance)
12Z NAM (January 20) model run for Saturday afternoon. Notice the snow somewhat farther north and mixing in the Delmarva.

12Z NAM (January 20) model run for Saturday afternoon. Notice the snow somewhat farther north and mixing in the Delmarva.

The NAM, which is not a particularly reliable model, surprised us all last night and continues to do so by predicting a more northerly and slower track. In this scenario, the low would actually remain farther inland and then continue northward towards the Delmarva, emerging offshore somewhere near Ocean City, MD and tracking east-northeast near or over the 40/70 benchmark with a pressure between 985 and 990 mb (slightly weaker). This is a much more severe scenario for the northern mid-Atlantic and southern New England, but is not particularly likely.
This scenario would likely result in most of the precipitation falling as rain across eastern Virginia, with mixing with sleet, freezing rain or even pure rain likely a major factor in the Delmarva, southern New Jersey and parts of the lower Chesapeake and Potomac regions. The heaviest snow would likely fall in a swath from northwestern Virginia through central Maryland (north and west of DC) and interior eastern Pennsylvania into central New Jersey, possibly into the New York City region, Long Island and coastal southern New England as well. Significant snow would extend well north and west of that area as well.

This would likely be the worst case scenario for the New York City region, with a combination of heavy snow, high winds and coastal flooding all occurring with the potential for crippling impacts depending on the exact evolution of the storm. It would not be as severe farther south, but significant impacts would certainly still occur in the urban mid-Atlantic region and crippling snows would be possible inland. The time frame would likely be a few hours slower than Scenario 2 for both the arrival and departure of the storm system.

Conclusion

Confidence is much higher today that a very severe winter storm will impact at least parts of the US east coast, with blizzard conditions certainly possible. We are most confident in crippling impacts in the mid-Atlantic, with at least some potential up as far north as southern New England (although far less likely). As this storm is only about 48 hours away, it is definitely time to start thinking about preparations. That is especially true in the areas likely to experience the maximum impact.

Normally having 72 hours worth of supplies is recommended, but given the potential impact, for those in the greatest risk areas I’d recommend having 5 days worth of supplies in urban and suburban areas and 7 days in rural areas to be on the safe side. A storm this large will take time to clean up from. Power outages are certainly possible as well so be sure to have a hand-operated or battery radio and flashlight and a way to stay warm if the power goes out. If you have travel plans, consider changing them now since there are multiple hubs that are likely to be affected. Certainly if your flight or travels go through the Washington DC area airports, change the route or cancel the trip since closures are likely. This is an excellent guide written by Mike Smith in 2011 on airline issues due to weather and what to do.

There remains some uncertainty in the exact placement of the worst of the storm, which may change things at the edges of the track. However, we should all be preparing for the worst and hoping for the best. This is a long duration storm that will likely have great impacts that extend well into next week too in the aftermath. The sooner we are prepared, and the better we are prepared, the quicker we will recover. Most importantly, stay off the roads. A good number of fatalities happen from traffic accidents during dangerous weather which are totally preventable.

So stay home, and stay safe.

Forecaster Craig Ceecee – @Ceecee_Wx

P.S. if you have kids who have never been through or never remember blizzards, I suggest today or tomorrow purchasing or borrowing the 2014 book Freddy the Frogcaster and the Big Blizzard from Janice Dean (Fox News national meteorologist). You will likely be able to find it at your local library, at major book stores or on Amazon.com (if you have an e-reader, since purchasing online will not get it delivered before the storm). Your best bet is probably your local library, I know it is available at many libraries in my area. Your kids will certainly love reading safety and awareness tips in a language and theme they can understand.

Leave a Reply