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Afternoon Update: Countdown to Substantial Snow

A. Camden Walker @ 3:45 PM

Estimated Next update: 7:00pm

  • Probability of accumulating snowfall: 85% [+5%]
  • The greater DC metropolitan area will receive 4"-7" mainly after sunset Saturday before ending Sunday morning. [unchanged]
  • Temperatures will dive near sunset Saturday, quickly facilitating accumulation. [unchanged]
  • Forecast confidence remains high. [Slightly higher than this morning]
  • No major changes have been made to the official team forecast, except time-frame.
  • Wind and Cold behind this storm will be felt for a couple days after storm departs. [unchanged]
  • Points far south (Fredericksburg) and east (Annapolis) should remain all-snow. [unchanged]
Winter Storm Forecast: Saturday midday, Feb. 11 -- Sunday A.M., Feb. 12
10am SAT to 2pm: Snow showers begin far S&W, then spread toward DC and points N&E
2pm to 5pm: Light snow slowly takes hold. 1" probable--limited to grass in urban areas.
5pm to 8pm:
Moderate to Heavy snow. 2" possible in metro area.
8pm to 3am SUN:
Light snow & wind. 2" possible in metro area.
3am to 11am:
Snow tapers w/periodic bursts early- 1" possible. Wind & clouds remain.
Storm Impact: Travelcast:Schoolcast (Mon.):

What factors may raise the accumulation forecast?
  • Storm hugs the coast
  • Snow falls mainly after sunset
  • Storm moves more slowly
  • Storm remains weak, but laden with moisture, not disturbing our cold air
What factors might lower the expected accumulation amounts?
  • Storm goes more out to sea, after passing Norfolk--and doesn't head up DelMarVa
  • Storm deepens "bombs" in close proximity to us-- throwing warm air over the region
  • A warm pocket in the atmosphere would changeover snow to sleet or rain (briefly well S&E of Washington) reducing moisture available to fall as snow crystals.
NOTE: Surface temperatures will not allow for immediate accumulation at the onset of snow. Travel will be most difficult after 5pm on Saturday evening.

ACCUMULATION amounts: could still approach 8" in spots, especially S&E of Washington. N&W suburbs have decreasing chances of bullseye (7"+) snow. More likely it will be closer to 5". The team will continue to make very deliberate and measured forecast updates throughout the night tonight.

MAP: We will tweak the accumulation map on the next post. Amounts will only be slightly raised S&E of town, and lowered N&W. You can still trust the contour lines as general guide to the striation of precipitation accumulation through the region.

TIMING: More to fall overnight. The storm is slowing based on weather model output, and efficient overnight snowfall will easily accumulate. I forecast delays regarding the snow's initial onset. Wherein the afternoon will likely feature more spotty light snow... until approaching sunset.
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The Washington Post company's storm article and Express(.pdf) "blog log" have commented on this upcoming storm. is a new, local venture also covering this storm's community impact!

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