Heavy snowfall in northwestern US heading into holiday weekend (with forecast video)

Plow clearing snowy highway in Montana.

Snow and rain showers are popping up across the northwestern states, and they could get heavier over the next few days as additional rounds develop heading into the Memorial Day weekend.

SONAR Critical Events and radar: Thursday, May 21, 2020, 9 a.m. EDT; Heavy snowfall

Late season snowfall isn’t unusual in this region of the country, but it could still cause minor freight flow delays for drivers who have to go over mountain passes in parts of the Cascades and northern Rockies.

Some of the heaviest snowfall will occur tonight and Friday morning in southwestern Montana. The National Weather Service (NWS) has issued a winter weather advisory for elevations above 6,500 feet, including West Yellowstone, Raynolds Pass (MT-87) and Targhee Pass (US-20). Five inches or more of accumulation is possible in these areas.

Further periods of moderate to heavy snowfall will hit the high elevations of Washington state, Oregon, Idaho, Montana and Wyoming Friday and Saturday, possibly impacting portions of Interstates 15, 84 and 90. Totals could exceed 12 inches in some places, based on the latest computer models. Lookout Pass will see a mix of snow and rain, leading to slushy conditions. Meanwhile, Snoqualmie Pass will mainly be wet with no snowfall in the forecast at this time.

However, rainfall may be heavy at times in some of the lower elevations and valleys of the Northwest as the snow falls in the tallest peaks. Some rivers are already swollen from recent rainfall, especially where it’s been falling onto snowpack.

The NWS has issued flood warnings in southeastern Washington, including Walla Walla, as well as northeastern Oregon and parts of western Montana. A dam floodgate release is scheduled to continue until this evening in the Pendleton, Oregon area. Minor flooding may last through the weekend in some spots as additional rain showers pop up.

Other potential flooding

The threat of more flash flooding continues for one more day across the Southeast, from the Carolinas to the Ohio River Valley. Flash flood watches remain in place from Florence, South Carolina to Wilmington, Charlotte, Raleigh-Durham and Winston-Salem, North Carolina; Danville, Roanoke and Harrisonburg, Virginia; as well as Charleston and Parkersburg, West Virginia.

SONAR Critical Events and radar: Thursday, May 21, 2020, 9 a.m. EDT; Flash flooding risk

Daily rainfall records were set on Wednesday in Blacksburg and Roanoke, Virginia, as well as Charleston, Huntington, Bluefield and Parkersburg, West Virginia, where totals ranged from 1.78 to 2.76 inches. An additional 1 to 3 inches could fall today before the flash flooding threat fades.

Storms ahead

Severe thunderstorms could pop up in the Plains today, from western Kansas to the Oklahoma and Texas panhandles. Drivers may run into areas of damaging winds, increasing the chance of rollovers. Large hail and isolated tornadoes are also possible.

SONAR Critical Events and radar: Thursday, May 21, 2020, 9 a.m. EDT; Severe thunderstorm risk

The risk of severe storms subsides a bit Friday before increasing Saturday, mainly between I-80 and I-90 from Nebraska into South Dakota.

Have a great day! Please stay healthy and be careful out there!