One of the most severe bouts of winter weather the D.C. area has seen in years is poised to begin late Friday, as a punishing cold spell arrives and is punctuated by a disruptive snow and ice storm this weekend.
Temperatures will plunge to near 10 degrees early Saturday. Then, from Saturday night through Sunday night, a powerful winter storm is expected to unload heavy snow and ice, turning roads and sidewalks treacherous and disrupting businesses and schools, potentially for days.
The heaviest snow and ice is expected between predawn and midday Sunday when “travel is likely to be difficult or impossible,” according to the National Weather Service.
The storm may deliver 5 to 10 inches of snow in the Beltway area, topped by a thick layer of sleet and freezing rain. Snow totals could be trimmed by icing, but this system — sweeping thousands of miles from the Southwest to southern New England — is shaping up as a prolific frozen-precipitation producer.
The Weather Service has placed the area under a winter storm watch from 7 p.m. Saturday through 7 a.m. Monday while Virginia has officially declared a state of emergency and Maryland a “state of preparedness.”
The Weather Service also issued a cold weather advisory from 8 p.m. Friday to 10 a.m. Saturday as wind chills dive as low as minus-10 degrees ahead of the storm.
Once the storm ends, the mercury may not rise above freezing for a week or longer. At times you may mistake D.C. for Fairbanks, slogging through a cement-like mix of snow and ice amid bitter winds.
Storm timeline
Here’s an approximate timeline for the evolution of this storm (lowest temperatures in northwest areas, high temperatures in southeast areas):
7 to 11 p.m. Saturday: Chance of light snow, developing from southwest to northeast. A coating possible, especially southwest of D.C. Temperatures: 16 to 20.
11 p.m. Saturday to 4 a.m. Sunday: Snow increases in coverage and intensity from southwest to northeast. Accumulation begins immediately once snow is steady. Temperatures: 15 to 19.
4 to 10 a.m. Sunday: Snow, heavy at times. Rapid accumulation of up to 1 to 2 inches per hour. Snow may gradually mix with and change to sleet, especially south and east of the Beltway. Temperatures: 15 to 20.
10 a.m. to 4 p.m. Sunday: Snow north and west of the Beltway may mix with or change to sleet. Mostly sleet near the Beltway, mixing with snow at times. Mainly sleet south and east of the Beltway, with some freezing rain also possible. Temperatures: 18 to 25.
4 to 10 p.m. Sunday: Mix of sleet and freezing rain, except more snow far northwest. Temperatures: 20 to 27.
10 p.m. Sunday to 2 a.m. Monday: Lingering areas of mixed precipitation or freezing drizzle possible. Temperatures: 20 to 26.
What is the latest thinking on snow and ice amounts?
Computer model projections for snowfall have largely converged in the 5- to 10-inch range in the Beltway area. Models that switch snow to sleet more quickly produce the lowest totals while those that delay the changeover allow snowfall to climb closer to 10 inches.
The transition from snow to sleet is expected to occur first Sunday morning south and southeast of the Beltway, and last Sunday afternoon to the northwest. In far northwestern areas that see less sleet, double-digit snow totals are probable. It remains uncertain how far northwest the sleet zone will ultimately extend.
South of the Beltway, where snow is likely to change to sleet earliest, snowfall may be limited to less than 5 inches, but could be topped by 1 to 3 inches of sleet.
Then there is the question of freezing rain. As the storm progresses, sleet may mix with and change to freezing rain, especially in southern and eastern areas late Sunday. If freezing rain accumulates to more than 0.25 inches, impacts could become significant.
The weight of freezing rain can snap tree limbs and power lines, leading to power outages. Most projections for our area currently suggest 0.1 to 0.2 inches or less, but this bears close watching — particularly from around Fredericksburg into Southern Maryland. The highest risk for disruptive icing appears to be farther south, toward Richmond.
How severe will the storm effects be?
This storm ranks as a Category 4 out of 5, or “severe,” on Capital Weather Gang’s winter storm impact scale. Although snow totals will not rival the all-time greats, the perilous combination of snow, ice and bitter cold before, during and after the storm means it is likely to have serious and prolonged effects. It is highly unusual for temperatures in D.C. to remain in the teens and 20s throughout a winter storm and then stay that cold for several days afterward.
All of the snow and ice will accumulate as it falls and, with freezing temperatures lingering, it may not melt for a week or more. The resulting conglomeration of frozen precipitation will be difficult to remove, meaning it will take much longer than normal for the region to recover.
This may not be a storm remembered for generations, or a Category 5, but it is likely to take a meaningful toll.
How cold will it get?
The Arctic air mass settling into the region will be remarkable both for its strength and staying power. “Dangerously cold wind chills and near record-breaking temperatures are likely,” the Weather Service wrote.
Cold air will surge in Friday night, with temperatures tumbling into the low teens, and even single digits in colder areas north and west of the Beltway. Wind chills are expected to drop below zero.
High temperatures this weekend will struggle into the teens and 20s, and if readings remain in the teens, they could challenge daily records.
Any snow and ice that fall are likely to linger for an extended time. Highs next week are forecast to remain mostly in the 20s, with nighttime lows frequently dipping into the teens and single digits. At times, wind chills may again fall near or below zero.
How to prepare
With the storm two days away, it’s time to take action. If you have scheduled flights or appointments on Sunday, consider changing them. Most airlines will allow you to make changes at no cost.
Stock up on groceries as well as snow and ice clearing supplies like shovels and salt.
Take steps to protect your home and yard from snow and ice (make sure your gutters are clear) and extreme cold (protect your pipes).
“Have an emergency kit in the car including extra batteries, a flashlight, and blanket just in case you get stranded,” the Weather Service advises. “Make sure to refuel your car before the storm hits. Check on elderly friends/neighbors and don’t forget about your pets during this prolonged cold period.”
Read more about D.C.-area winter storms
Here’s how to measure snow like a pro
It is tough to predict when it will snow in Washington. Here’s why
Everything you ever wanted to know about snow in Washington, D.C.
Ice storms: Inside wintertime’s dreaded, frozen mess
Wes Junker, Ian Livingston, Jeff Halverson and Dan Stillman contributed to this report.
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