Washington DC (LWX) — the National Weather Service forecast in plain English · Plaincast

What has changed

No substantial changes were made to the snowfall forecast for the mountains over the next couple of days.

Made substantial edits to the Marine Discussions, including the extension of ongoing Small Craft Advisories.

Added a short fire weather discussion to touch on breezy conditions and lower RHs in the coming days. See below for details.

Messages

1) First snowfall for parts of the Alleghenies with spotty showers & brisk conditions elsewhere through Saturday.

2) Below normal temperatures and dry condtions are expected Monday and Tuesday before a warm up occurs.

Discussion

KEY MESSAGE 1. First snowfall for parts of the Alleghenies with spotty showers & brisk conditions elsewhere through Saturday.

Latest surface analyses and satellite data depict low pressure moving well off to our northeast and occluding off the NJ/NY coast. Mosaic radar imagery depicts some showers moving out of southeastern PA into NJ at this time, which is pretty in line with most model guidance at the moment. A broad upper low sits to our north, with numerous pieces of upper-level energy rotating about it's axis. There is also some lingering moisture impacting western Highland and Pendleton counties in the form of some light snow showers, where and SPS is in effect through daybreak. This activity will come to an end by mid-morning as the moisture source for this gets cut off.

One of these pieces of energy moves through later this morning, and interacts with the aforementioned occluding boundary offshore. This may be enough to throw some showers back into northeast MD on the back side of the departing low. Otherwise, most areas likely stay mostly dry for much of the day. As flow turns more northwesterly aloft throughout the day, we start to get a bit more of a connection to the moisture source off the Great Lakes moving towards the Allegheny Front. This will lead to another round of upslope snow shower activity by tonight into early Saturday. These will of course be maximized at elevations above 2000 feet and in particular the upslope favored zones of western Garrett, western Pendleton, and western Grant counties. If travel disruptions were to materializes, expect impacts to US-219 from the MD/PA line to WV line, US-48 from Mount Storm, WV west to Davis, WV, and US-33 west of Franklin, WV. Snow accumulations will remain on the order of a coating to 2" with the greater probabilities of 1-2" with localized 3" amounts above 3000 feet pending any squalls/streamers (mainly late Friday night through Saturday midday).

KEY MESSAGE 2. Below normal temperatures and dry condtions are expected Monday and Tuesday before a warm up occurs.

Heights will start rising Monday as the amplified upper level patterns slowly progresses eastward. Winds should be much less noticeable by Monday and Tuesday as the surface high finally reaches the Mid Atlantic, although temperatures remain below normal. Given the lighter winds, the subsequent nights could turn out colder in many areas, with widespread near or below freezing temperatures outside of the urban centers and tidal shoreline. Since this will be more than two weeks after the average first freeze, no frost/freeze headlines will be issued.

Further upper level amplification will likely happen toward mid week. While a trough or low could develop toward the southeast coast, it appears that ridging will dominate the Mid Atlantic, maintaining dry conditions through next week. The ridging will also lead to a warming trend, with high temperatures rising back into the 60s for many areas Wednesday and especially Thursday.