This one is a doozy.

A low-pressure system originating in the Southwest is moving across the country tonight and will travel east before combining with a northern stream of energy and amplifying off of the Atlantic coast tomorrow evening. The pattern has been set with strong blocking high pressures in Quebec and Ontario, literally “blocking” the storm and allowing it to intensify quickly while remaining almost stationary. The following two maps show the phase of upper atmospheric vorticities beginning early Friday morning and completing by Friday afternoon:

 

The meteorological effects of this setup are extreme: high winds, significant storm surge, and heavy precipitation for an extended period. To provide complete coverage of this upcoming nor’easter, the post will be split into sections beginning with track and timing, then discussing the wind, storm surge, and precipitation impacts.

Track

As I alluded to in the intro, the current atmospheric setup is prime for a massive, slow-moving coastal storm. As it moves off the coast, the storm will intensify and slowly travel northeast. The system will then slow down as it’s blocked by strong Canadian areas of high pressure to the north. This is where the forecast becomes difficult. Models are having a tough time tracking the storm and where the heaviest precipitation will fall. Precipitation type forecasting has been challenging as well, with warm surface temperatures during the onset of the storm, but dynamic cooling occurring as the storm strengthens. The maps below show the blocking, track, and strength of the nor’easter as it moves slowly eastward:

By Friday night, we have a full-fledged nor’easter on our hands:

Precipitation Type and Timing

Precipitation will start Thursday night initially as rain. Temperatures will be in the 50s, but will rapidly fall overnight Thursday into Friday morning. We will experience a short lull on Friday morning as the storm begins to gather strength. Round 2 will start by the afternoon as rain, then changing to snow reasonably quickly from north to south. By Friday evening, most of our region will experience accumulating snow accompanied by 50-60 mph wind gusts.

Precipitation should end early Saturday morning as the storm moves further off the coast. Based on forecast models and data, 2-4 inches of heavy snow could be on the ground by Saturday morning, with higher totals north of I-95, and lower ones closer to the coast. It is important to note that elevation could also play a key role in final snow totals, as surface temperatures could remain above freezing in areas near sea level.

The map below shows final snow predictions from the NAM model (note that these are overstated because of a 10:1 snow/rain ratio assumption; a 6:1 ratio is more likely with this storm):

Wind

The sheer strength of this storm will create powerful wind and wind gusts on Friday. Sustained winds will reach 30-35 mph with gusts of up to 60 mph in some places. Winds will be even higher along the Jersey shore. Damage will be significant, especially with wet soil and trees weighed down by heavy snow. Expect widespread power outages by Friday night, especially in rural areas.

Storm Surge

A combination of high tide and a coastal storm is never a good combination for coastal regions. Major storm surge will occur, especially in New England, with waters rising over 4 feet from normal high tide levels in Massachusetts. The NJ coastline will likely experience a storm surge of 2-3 feet, which will cause some coastal flooding during the height of the storm.

Concluding Thoughts

Regardless of the final forecast, we are looking at possibly a historically complex and prolonged event. Impacts from the storm will affect most of the Northeast, and damage from wind and storm surge will be significant. Areas in NY could receive 2-3 feet of snow, while Boston might experience a hurricane and blizzard on the same day! Philadelphia won’t be the hardest hit, but conditions will still be dangerous most of the day on Friday into Saturday. Enjoy the weather and stay safe out there, it’s going to be wild.