11:00 p.m. — Upping our snowfall forecast from 1 to 3 to 2 to 4 inches
After reviewing the afternoon and evening models, the general forecast ideas expressed below generally hold but we have a few fresh thoughts and developments to share:
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Enough of the models show the potential for a heavy overnight burst of snow (Thursday night into Friday morning) that we’re increasing our projected totals from 1 to 3 to 2 to 4 inches. The onset time for the snow Thursday has shifted slightly later with snow probably moving in between 11 p.m. and a little after midnight. The likely window for heavy snow along with very difficult travel and low visibility is between about 1 a.m. and 3 a.m. Friday. The snow should end by around 4 a.m. in the immediate area and 5 a.m. in our eastern suburbs.
Here is what the latest models are projecting for the District:
American (GFS): 5.5 to 6 inches High-resolution NAM: 4 inches HRRR: 3-4 inches European: 2.5 inches Canadian: 2.5 inches NAM: 2-2.5 inches High-resolution Canadian: 2-2.5 inches
2:55 p.m. — Winter weather advisory issued for Thursday night into early Friday
Anticipating Thursday night’s snowfall, the National Weather Service has issued a winter weather advisory for the entire region. The advisory takes effect at 9 p.m. Thursday and continues until 5 a.m. Friday.
The Weather Service is calling for two to four inches of snow with isolated totals up to five inches. (As noted below, Capital Weather Gang is forecasting a hair less, one to three inches generally — but agree that locally higher amounts are possible.)
“Plan on slippery road conditions,” the Weather Service writes. “The hazardous conditions could impact the Friday morning commute. The heaviest snow is expected between 10 p.m. and 2 a.m. when snowfall rates of 1 inch per hour are possible.”
A winter storm warning is in effect for parts of the Blue Ridge and Appalachian mountains, where up to five to nine inches is possible along with wind gusts to 35 mph.
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Original article from 12:45 p.m.
A fast-moving storm system will sweep through the Mid-Atlantic and Northeast on Thursday night, probably laying down about one to three inches of snow in the Washington and Baltimore areas.
It’s not out of the question that a few areas will see a little more or a little less, but this event will not be nearly as heavy as Monday’s severe snowstorm.
Here’s what made Monday’s snowstorm so severe
The snow should start between 8 p.m. Thursday and midnight, and end before sunrise Friday. Because temperatures will fall as it snows, roads are likely to become quite icy, causing delays and cancellations Friday morning.
Amounts
Computer models suggest this storm could produce as little as a dusting of snow and as much as six inches, but they generally show two or three inches falling in the region. The models vary as to what areas will see the most snow; some show the heaviest amounts north of the District, while others put them to the south.
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Our snowfall map, showing widespread amounts of one to three inches, represents a blend of the model projections, as it’s too early to know what areas will be hardest hit or just fringed by this system.
There is a chance of a locally heavy corridor of snowfall that produces up to three to six inches, but it will be Thursday before we have a better idea of where that might set up.
Freezing rain snarls Northeast as it awaits another plowable snowfall
The National Weather Service’s snowfall map, pictured below, shows the potential for widespread amounts of two to four inches, which is a little higher than we’re comfortable predicting at this point.
Snow timing and temperatures
One of the reasons our snowfall forecast is a bit conservative is because temperatures will be above freezing in some areas when the snow first arrives, probably in the mid-30s in the immediate area (although colder to the north and west) after highs in the low 40s Thursday afternoon. Thus, some accumulation may be lost to melting.
After midnight, however, temperatures should drop below freezing areawide, causing roads to ice over and become snow-covered.
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8 p.m. Thursday to midnight: Light snow develops west to east, possibly starting briefly as rain in southern Maryland. Temperatures: 31-37 (northwest to southeast).
Midnight to 3 a.m. Friday: Snow, moderate to possibly heavy at times. Peak rates of one inch per hour possible. Temperatures: 28-33 (northwest to southeast).
3 a.m. to 6 a.m. Friday: Snow tapers off. Temperatures: 24-29 (northwest to southeast).
Most areas will see only about four to six hours of snowfall, with the heaviest and steadiest coming around or just after midnight.
We don’t expect wind to be a big issue with this system Thursday night while snow is falling. However, as the system pulls away Friday morning, winds will become gusty, blowing the snow around a bit and creating bitter wind chills in the teens and 20s.
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The consistency of the snow may start off as a bit heavy and wet, but it should turn more powdery overnight. The risk of power outages is low.
Sen. Tim Kaine’s nightmarish 27-hour commute on I-95
Discussion
A high-altitude disturbance, sometimes known as a clipper, will dive far enough southeastward to induce the development of a low-pressure center along a front to our south. The system will be somewhat moisture-starved, as it won’t tap into the Gulf of Mexico.
These types of systems historically produce a zone of light to moderate snow accumulating between one to three and two to four inches, nothing like Monday’s storm. Still, the snow will be falling at night amid dropping temperatures, so roads are likely to become slick.
Wednesday morning’s NAM and high-resolution NAM models both suggest one to three inches of snow, with the heaviest amounts north and west of Washington.
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The latest European model is a little heavier, predicting two to four inches of snow areawide.
The American (GFS) model also projects two to four inches for most of the area but suggests a narrow stripe of four to six inches south and east of the city, in the same zone walloped by Monday’s storm.
The UKMet and Canadian models forecast a general two to three inches across the region.
Picture-perfect scenes from Monday’s storm in Washington
Both the European and American modeling systems, containing dozens of simulations, suggest that an inch of snow is almost a lock but that there is less than a 50 percent chance that the city and nearby suburbs exceed three inches. Therefore, at this juncture we are being conservative with our forecast.
Capital Weather Gang’s Jason Samenow talks about what caused Monday’s disruptive snowstorm across the D.C. region and provides a forecast for Thursday. (The Washington Post)