What a month this has been. We continue to experience a very active weather pattern that favors storm development off the Atlantic coast. Our fourth March nor’easter is a complicated setup that will arrive in two parts, beginning tomorrow and ending early Thursday morning. This post will separately review both stages of the storm and their impacts on our region.

March Nor’easter #4 Round One

The first piece of the storm will arrive midday tomorrow with mixed precipitation in the form of snow, sleet, and rain. There will be minor accumulations on grassy surfaces, but the roads should remain mainly wet.

By Tuesday night, some models have indicated a prolonged period of freezing rain, which could make road conditions slippery by Wednesday morning. Regardless of precipitation type, impacts from round one will be manageable. Even with a period of freezing rain, roads will be mainly wet.

Round One Timing

10 AM-12 PM: Precipitation starting as a snow/sleet mix from south to north

12 PM – 7 PM: Mixed precipitation continues, heavy at times. Minor accumulations expected on grassy surfaces

7 PM – 3 AM: Mixed sleet/rain/snow possibly changing over to freezing rain. Precipitation will slow down by 2-4 AM before transitioning to light snow.

March Nor’easter #4 Round Two

As the first system moves east, it will phase with a secondary low off the coast and begin to strengthen. The storm will begin to display the hallmark features of a nor’easter as it begins to move northeast. A resulting area of widespread snow will overtake the I-95 corridor from DC to Boston.

While a prolonged period of snowfall is expected, accumulations will be diminished because of the storm’s timing during the daytime hours. Since it’s late March, the angle of the sun is relatively high (equivalent to early October), which means any snow that falls will have issues sticking on paved surfaces. Even with these opposing factors, roads will still be very slick by Wednesday afternoon, and I would recommend against unnecessary travel after 12 PM.

Round Two Timing

7 AM – 11 AM: Light sleet/freezing rain changing to snow during the morning hours

11 AM – 5 PM: Moderate to heavy snow, plowable accumulations expected. Roads will be slush covered and slick. Widespread power outages from fallen trees and power lines.

5 PM -12 AM Thursday: Snow moving out south to north. Watch for re-freeze overnight.

Round Two Totals and Impacts

Forecasting March snow totals are particularly challenging because of the previously mentioned high sun angle and warmer surface temperatures. Based on model guidance and knowledge of the surface conditions, a general 6-10 inches of wet, heavy snow is likely throughout the Delaware Valley. Widespread power outages are possible from trees and power lines weighed down by the dense snow. Travel will be arduous Wednesday afternoon; please take precautions if you need to drive.

This will be a very entertaining event with all types of precipitation and significant accumulating snowfall. I will provide any updates at the top of this post. Enjoy and stay safe!