The chance of some winter storminess Saturday afternoon and evening has increased in the D.C. area, but the details are still fuzzy.
Snow lovers, we still can’t say with confidence whether the storm will deliver snow, slop or a cruel, cold rain. The models are converging toward the idea that a storm will track along a front to our south and deliver some wintry weather, but how much, if any, of the precipitation will be snow — and how much snow would stick — differs.
There is some potential for a thump of accumulating wet snow between about 3 p.m. Saturday and 2 a.m. Sunday, which could disrupt Saturday evening and, perhaps, some Sunday morning activities. The impact of any snow will be limited because of its occurrence on the evening of a holiday weekend, when schools are out, and it being sandwiched between two unseasonably warm days: It could hit 70 on Thursday and again Tuesday.
This is another complicated forecast, because temperatures are expected to be marginal for snowfall. The high-pressure system to the north feeding in the cold air is predicted to slide off the coast, and there still is uncertainty about the storm track.
Track a stronger storm to our south along the coast and delay the eastward shift of the high-pressure system, and we’d likely end up with more snow than rain.
Speed up how quickly the high-pressure zone exits the coast and delay how quickly the storm reforms along the Carolinas’ coast, and the storm becomes primarily a rain event.
As usual, our typical colder locations north and west of the District have the highest likelihood of seeing accumulating snow, while locations south and east of the city have the lowest.
The models, including their ensemble members (different simulations of the models with initial conditions tweaked), suggest four possible scenarios:
1. Sloppy mess (40 percent chance)
Temperatures aloft and near the ground are just a little too warm for a snowstorm, resulting in a messy mix of conditions that vary across the area.
In this scenario, locations south and east of the city might start with a brief period of snow or sleet but would quickly change to rain. Locations west of the city would start as snow that could accumulate an inch or two before transitioning to sleet and then freezing rain and possibly rain.
In this scenario, freezing rain west of the city would be the biggest threat, as surface temperatures during the night could fall into the upper 20s if some of the colder models are correct. East of the city, the storm would primarily bring a cold rain.
This morning’s GFS, NAM and Canadian models support this scenario.
2. Moderate snow (30 percent chance)
A low-pressure system tracks to our south and develops off the North Carolina coast quickly enough to keep cold air in place through most of the storm. Snow spreads across the region late Saturday afternoon, and temperatures drop from the upper 30s to around or just below freezing.
Such a scenario would offer a thump of accumulating snow north and west of the city and would offer many the heaviest snow of the season. The snow would fall hard enough to build up some, especially on untreated roads.
South and east of the city, temperatures might stay just warm enough to keep any accumulations limited to grassy surfaces unless a band of heavy snow were to develop. South and east of the city, the precipitation would likely end as rain. Even west of the city the snow could end as freezing rain or drizzle in the middle of Saturday night.
The European model supports this scenario.
3. Light snow scenario, little accumulation (20 percent chance)
A weak low tracks to our south and remains poor enough as it exits off the coast to bring only light precipitation to the area.
Such a scenario might offer snow to the north and west of the city, but temperatures might struggle to fall below freezing. Accumulation might range from a dusting to a couple of inches like many of the snow events this winter.
Unfortunately for snow lovers, the heaviest precipitation would probably fall to our south.
4. Storm misses (10 percent chance)
The front and weak low remain too far south to give us any precipitation. This is the least likely of the four scenarios, but it is shown as a small possibility in the various modeling systems.
The bottom line is it’s looking increasingly likely we’ll see a storm on late Saturday afternoon and night. As we get closer to the event, a more solid picture of how the event will unfold will emerge.