It sure felt like spring for a few days around Washington, and indeed, it may be meteorological spring (more on that later), but Wednesday’s cold, blustery winds and scattered flurries are a reminder that it’s actually still winter.
The pieces of energy will form an area of low pressure at the surface that will scoot to our south, as opposed to Wednesday’s low pressure system, which passed up toward our northwest — keeping us in the “warm sector” until the cold front went through and drying us out before we got too cold. This low will intensify as it heads towards the Mid-Atlantic coast, and bands of precipitation will move over the area starting Thursday evening through Friday morning.
Both processes take heat out of the air and moisten it, allowing more snowflakes to get closer to the ground. Eventually they do. In the dead of winter, they would start accumulating immediately on all surfaces, but not in this case. Here, the most likely areas for sticking will be grassy areas and then pavement and sidewalks.
As Storm Team 4 looks at all the ingredients, factors and qualifications, and how they all work together, there’s a belief that many folks could wake up to one to three inches of a slushy, wet, half melted snow Friday, but mostly on the grassy areas. That means the plows may not really be needed for shoveling — only road treatments. And then as the snow ends Friday morning and some sun comes out in the afternoon and temperatures get close to 40 again, even more of the snow will melt away.
In a typical winter storm, the ratio of snow to rainfall equivalent is 10:1; in other words, the moisture that would make for one inch of rain would produce 10 inches of snow in a highly idealized environment. This storm will likely have less than that — probably 5:1. That’s another reason it will be very wet and slushy, as opposed to dry and fluffy (the higher those ratios, the higher the fluff).
But then high pressure will build in for the second half of the weekend and flatten out the jet stream, keeping the cold air from flowing down from Canada. More sunshine, too, will mean moderating temperatures back closer to our average for Sunday. The arctic air will be trapped in the Arctic.
But every day we go through March because of the higher sun angles, it gets harder and harder to get snow and ice. It’s not impossible (as we know from blizzards like 1993), but it’s unlikely. So short of a fluke, Friday’s snow may be the last we see this season.