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Wednesday snow event probably minor, but can’t rule out some disruption

2:58 p.m. update: The National Weather Service has issued a winter weather advisory from 6 a.m. to 6 p.m. Wednesday for the immediate D.C. metro area and points north. The advisory excludes areas to the south, including Prince William, Fauquier and Stafford counties in Virginia, and southern Maryland (Calvert, Charles, and St. Mary’s counties).

The advisory indicates the potential for 1 to 3 inches in the immediate metro area with locally higher amounts. We think this is overdone as a most-likely scenario, but it’s possible in a boom scenario should a heavy snow band develop over the region.

Original post, published at 2:52 p.m.

A little weather disturbance known as an Alberta Clipper zips through the D.C. and Baltimore metro regions Wednesday, likely putting down some snow. Amounts should generally be light, but this is one of those storms where a small area of heavier snow could develop, so don’t let it surprise you!

With the exception of those areas where a localized snow burst materializes, this storm should be a relatively low-impact event. Temperatures are the big difference between this event and the one that wreaked havoc Jan. 6.  We expect this storm will result in fewer traffic and school disruptions because temperatures will be around freezing or a little above, so snow will have a harder time sticking. On Jan. 6, temperatures were in the low 20s, which allowed every flake to accumulate.

Key points:

  • Snow should start between 7 and 10 a.m. from west to east. Confidence: Medium-High
  • Snow should taper off between 1 and 4 p.m. from west to east, though patchy flurries or drizzle could linger into the evening. Confidence: Medium
  • For most of the metro area, a coating to 1 inch of snow is favored, with most accumulation on grassy areas. However, if a heavier snow band develops, 1-4 inches of snow could fall with some accumulation on roads (boom scenario). Especially into the afternoon and south of the District, snow could mix with or change to light rain. There’s also the (bust) scenario, where most of the snow passes by to the north resulting in bare ground in metro D.C.
  • From roughly Winchester to the north side of Baltimore, 1-3 inches is most likely with locally heavier (boom) and lighter (bust) amounts possible.
  • South and east of a line from roughly Charlottesville to Fredericksburg to Salisbury, mostly rain is expected.

Some of the modeling shows the best chance of a burst of heavier snow (or snow-rain mix) east of I-95 through Anne Arundel County and into the northern half of the Delmarva Peninsula. Snow or a nasty mix of snow and rain could fall during the inauguration ceremony for Maryland Gov.-elect Larry Hogan (R) in Annapolis, set for noon.

SchoolCast:

The forecast poses another challenging decision Wednesday morning, but we expect fewer delays and cancellations compared with previous events primarily due to two factors: 1. The later onset of the snow (after 7 a.m. in most locations and perhaps holding off until 9 or 10 a.m.) 2. The milder temperatures that will make snow accumulation challenging.

The worst-case scenario for schools would be a localized heavy snow band developing in the 7-9 a.m. time frame. The chances of this are low, but decisionmakers might consult meteorologists who could advise on this possibility early in the morning before making a call.

The steadiest precipitation should be moving out in the early- to mid-afternoon with temperatures easing above freezing, so the ride home poses fewer risks. However, conditions should be monitored in case the snow lingers longer than expected.

Here’s our take on the SchoolCast…

  • Frederick County: schoolcast-2-apples(2 apples: 50-50 chance of no school, good chance of a delay or early closing, at least)
  • Loudoun, Montgomery, Howard, Anne Arundel, Fairfax, Arlington, Alexandria, Prince George’s, Prince William, Fauquier counties:schoolcast-1.5-apples(1.5 apples: Slight chance of a delay or early closing)
  • The District, Stafford, Charles, Calvert, and St. Mary’s counties:1_apple (1 apple: Schools likely open and close on time)

FedCast:

  •  fedcast-1.5-domes(Chance of an unscheduled leave or telework option)

Next update: See our PM Update around 4:45 p.m.

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