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Snowfall_20210217.

Snow, Sleet, and Freezing Rain Likely on 18 February 2021

  POSTED ON: Wednesday, February 17, 2021 7:17 AM by METEOROLOGIST A.R. DAVIES

An area of Low pressure, that has resulted in significant winter impacts across the South-Central U.S. this week, will push into our area on Thursday morning, before redeveloping along the coast Thursday night. Precipitation will overspread Central Maryland between 0700 and 0900 on Thursday morning. Temperatures at the surface and throughout the atmospheric column will initially be below freezing with periods of moderate/steady snow likely through mid-morning. Warm air will infiltrate into the mid-levels of the atmosphere from south to north throughout the day. By mid-morning the snow will likely transition to a snow and sleet mix in Annapolis which will likely cut-down on overall snow totals. As warm air continues to push northward, a transition to a sleet and freezing rain mix will occur sometime around midday/early afternoon in the Annapolis area. The sleet and freezing rain mix will continue through the evening as the coastal storm develops and slowly moves offshore around midnight.

Plan for 2.0 to 3.0 inches of snow/sleet accumulation in Annapolis through midday. The initial burst of snow in the morning will likely be steady and quickly cover untreated roads and surfaces. Once sleet mixes, additional measurable accumulation will be limited but conditions will remain slushy and slick. The big concern in the afternoon and evening will be ice accretion as the snow/sleet mix will transition to a mix of sleet and freezing rain. Plan for around 0.25 inches of ice accretion in Annapolis in the afternoon, evening, and overnight. However, there is still some uncertainty surrounding the timing of precipitation type changes. There is a 20% chance that snow lingers longer in the morning and/or the snow/sleet mix does not transition quickly to freezing rain in the afternoon. This scenario would result in > 3.0 inches of snow/sleet accumulation and potentially lower ice accumulation. There is also a 25% chance the precipitation types transition faster which could result in lower snow/sleet totals but potentially ice accumulation > 0.25 inches. Surface temperatures in the Annapolis area are expected to remain near freezing throughout the event (between 29oF and 33oF). See the forecast map for additional information.

The forecast map reflects the anticipated gradual south to north transition in precipitation types. Snow and sleet are expected to last longer north of Annapolis (with less ice accumulation) and the transition is expected to happen quicker south of Annapolis with a greater potential for ice (although surface temperatures could be marginal). Well north and west of the metros might not transition to freezing rain at all and therefore higher snow/sleet totals (>5.0 inches) are likely.

ISSUED: 17 February 2021 at 0715
FORECASTER: Meteorologist A.R. Davies   


Category: Press Releases, General Interest

Press Contact

Alexander R. Davies
Meteorologist & Oceanographer
Ocean and Atmospheric Sciences Department, USNA
  adavies@usna.edu
  410-293-6565