The ingredients have come together for major late-season snowstorm — we are calling it Snowquester — that may prove crippling for western sections of the Washington metro region.

Accumulations of heavy, wet snow that could measure in the double digits in some areas, combined with windy conditions, could produce dangerous travel conditions and pose a power outage risk from Manassas to Fairfax to Rockville, and — especially — to the west and north of those cities. Even inside the Beltway, where snow accumulations of 3-8 inches are most likely, travel will be impaired at times on Wednesday.

Snowfall rates of at least an inch per hour are possible at times Wednesday, reducing visibility to less than half of a mile. “Thundersnow” is possible.

Links: March snow in Washington, D.C.: Precedent exists for ending winter with a bang | History as a helper: past suggests Snowquester storm will pack a punch

This storm will most likely end Washington’s longest streak on record without a snowstorm of at least two inches, which has lasted for the last 769 days. It should be the biggest snowstorm since Commutageddon, on January 26, 2011. Total accumulation may exceed totals from that storm in many areas.

Key points

* Snowfall amounts around the city are likely to range from 3-8 inches, but there will be significant variability over small areas. For example, upper Northwest Washington is likely to receive several more inches than Capitol Hill and Washington Reagan National Airport.

* Snowfall amounts will be dramatically higher west of the Beltway, with double-digit inch totals possible in places like Oakton, Gaithersburg, Sterling, Ashburn, Germantown, Leesburg, Warrenton, Frederick, etc. Out towards Winchester, a foot or more of snow is very likely.

* Precipitation may start as rain or a rain/snow mix late this afternoon and this evening, before changing to snow. Conditions will not deteriorate significantly until after midnight in most areas. This evening’s commute should be fine.

* Inside the Beltway and to the east, rain and sleet may mix with snow at times — especially when the intensity of precipitation wanes. The mixing will reduce snowfall totals, as will temperatures that are expected to remain above freezing during most of the storm.

* Because temperatures will be near or a little above freezing in many locations, the snow will be very heavy. Power outages are possible in locations that receive at least six inches of snow, and could even become widespread. Charge your portable devices, and make other necessary preparation. Also, this snow will be challenging to shovel. Older adults and those with heart conditions should use caution.

* While we have high confidence that the area will receive substantial amounts of precipitation, slight changes in the storm track could impact totals across the region. The areas most sensitive to forecast changes are those inside the Beltway and to the east, where temperatures are most marginal for snow. If the storm is a little warmer than forecast, snowfall totals could be greatly reduced. On the other hand, if the storm is a little colder, double-digit inch totals are possible even inside the Beltway.

* With wind gusts of 50 to 60 miles per hour expected, this powerful storm could cause large waves, significant beach erosion and minor to moderate coastal flooding at Maryland, Delaware, and Virginia beaches. For more information, see this briefing covering from the National Weather Service: Late Winter Coastal Storm

Impact forecasts, Wednesday







4-10 p.m. Tuesday: A light mix of precipitation develops from southwest to northeast, especially after 7 p.m. Temperatures 35-40 degrees (coldest temperatures in the western part of the region). No travel issues or accumulation expected.

10 p.m. Tuesday to 4 a.m. Wednesday: Widespread mix of precipitation developing; mostly snow in far western suburbs; rain/sleet changing to sleet/snow immediate D.C. area; a mix east of I-95. Temperatures 31-36 (coldest to the west).

4 a.m. to 10 a.m. Wednesday: Snow, heavy at times, in western suburbs. Mix to mostly snow immediate D.C. area; a mix east of I-95. Temperatures 30-35 (coldest west).

10 a.m. to 4 p.m. Wednesday: Snow, heavy at times. Snow may mix with sleet and rain east of I-95. Temperatures 31-35 (coldest west)

4 p.m. to 10 p.m. Wednesday: Snow, possibly heavy northeast of the District, starts to taper off west and southwest of the District. Temperatures 31 to 34 (coldest west)

10 p.m. Wednesday to 4 a.m. Thursday: Snow tapers off everywhere, with little additional accumulation. Temperatures 29-33 (coldest west).

Frequent questions

Will my flight be canceled or delay? Expect widespread flight delays and cancellations at all three major airports (National, Dulles and BWI) Wednesday. Dulles airport will likely be hardest hit. By Thursday morning, the snow is over, so travel will be possible, but there may be some backlash delays.

Can I take my road trip Wednesday? Snowfall will lead to low visibility and difficult travel conditions, especially west and northwest of the Beltway. Unless you are comfortable and experienced driving in the snow, you should wait to travel until Thursday.

When will conditions improve and travel be possible? By Thursday morning, the snow will have ended, although some re-freezing may occur overnight, leading to slick roads in the morning. Most air and road travel should be possible by Thursday afternoon.

Assuming that many schools do close on Wednesday, are they likely to stay closed Thursday and Friday? On Thursday morning, while major roads should be in fine shape, crews will probably not have had the opportunity to plow/treat many secondary and side roads. So expect some school closures and delays Thursday, and possibly Friday as well in the hardest-hit areas.

Who will see the heaviest snow? Northwest Virginia appears to be the most likely sweet spot, with totals over 12 inches a decent bet in Winchester, about 70 miles west of Washington.

When will the heaviest snow fall? Right now, it appears the window with heaviest snowfall would be between 5 a.m. and early-to-mid afternoon Wednesday.

Could the storm turn out to be a bust and we get little or no snow? The bust potential is highest in the immediate D.C. area, due to temperatures that are only marginally cold enough for snow. There’s about a 20 percent change it becomes too warm and precipitation is not sufficiently heavy for more than a couple of sloppy inches of snow. In the western suburbs, at least moderate amounts of accumulating snow is a pretty safe bet.

When will the snow melt? Temperatures will rise to near 50 degrees by the weekend, and with the help of the March sun, snow will fairly rapidly melt by then or early next week.

What are other forecasters predicting? Follow these links:

National Weather Service: 6-8 inches around town, 8-14 inches north and west

AccuWeather: 3-6 inches around the District, 6-12 inches north and west.

WUSA9: 6-9 inches around the District, 9-12 inches western suburbs

WJLA-ABC7: 3-7 inches around the District, 5-10 inches north and west

NBC4: 4-8 inches around the District, 8-12 inches west of town