Storm taking shape over the Desert Southwest and Intermountain West
The storm is developing over the Desert Southwest, energized by the same dip in the jet stream that spawned the Pacific “bomb cyclone” earlier this week. A rare line of severe storms barreled across the California-Arizona state line Thursday night, unleashing a 73 mph wind near Golden Valley, Ariz. The storms also brought heavy rainfall, prompting flash flood warnings near Phoenix.
At higher elevations, precipitation is falling as heavy snow. At elevations as low as 2,000 to 2,500 feet, heavy snow fell in the high terrain of the Southern California desert Thursday:
In Arizona, Flagstaff is forecast to pick up to 15 inches by Friday night, while some mountain passes to the south could flirt with the two-foot mark.
As the storm slips north of the Four Corners on Friday evening and emerges over the Sand Hills of Nebraska by early Saturday, several communities in high elevations throughout the Rockies could see more than a foot of snow. Heavy snows are expected Friday night in sections of Utah, Colorado, Wyoming and southeast Montana.
High Plains and Plains
The action gets underway across the High Plains on Friday, evolving as an icy mix of precipitation that eventually changes to blinding snow.
Light freezing rain and freezing drizzle ongoing Friday morning over much of northeast Colorado and Nebraska will sneak north into South Dakota later in the day before spilling into northwest Iowa and southwestern Minnesota. A thin glaze is possible, icing over untreated roadways before the snow even starts to fall.
The snow will break out by 7 or 8 p.m. Friday, perhaps first in South Dakota, before expanding to include northern Nebraska, North Dakota and western Minnesota by midnight Friday night. Snowfall rates topping an inch per hour will be possible at times very late Friday night until well into Saturday.
Accompanying the snow are strong winds, likely to exceed 50 or 60 mph in some areas. Blizzard warnings are up in eastern Wyoming, western Nebraska north of Highway 2 and western South Dakota including the Badlands through Saturday night. The visibility may drop to a quarter-mile at times as blowing snow brings near whiteout conditions. This is unlikely to affect Interstate 80 but could impact Highway 26 in Wyoming and Nebraska, as well as Intestate 90 through South Dakota.
Upper Midwest and Great Lakes
Minneapolis will be right along the southern edge of where substantial snow is possible. Just a county or two north of Minneapolis, accumulations will reach warning levels, closing in on six inches or more. But in the Twin Cities, the current forecast calls for 3 to 5 inches. A winter storm watch is in effect.
Uncertainty lies within the temperatures; Minneapolis is predicted to be on the edge of the snow/mixed precipitation line with marginal temperatures, so any fluctuations could have a bearing on how much snow is realized.
In Wisconsin, most of the snow looks to fall north of Appleton and Green Bay. Milwaukee is anticipated to begin as mixed precipitation or sleet Saturday, quickly transitioning to a cold rain that will last off and on through Sunday night. Madison is expected to see a wintry mix late Friday turn to rain on Saturday before perhaps ending as snow on Sunday.
In Chicago, it’s all rain. One wave of rain will make for a gray morning Saturday, but a steadier period of shower activity will come Saturday night into the early morning hours Sunday. There may also be another round of moderate rain during Sunday evening.
As the snow clips northern Michigan, 6 to 12 inches is possible Saturday evening through Sunday afternoon.
This time around, the Upper Midwest will not be prone to particularly strong winds with this system. In fact, winds from over the Great Lakes and the Ohio Valley are looking at gusts predominantly below 25 or 30 mph. That’s because the system will be in a slightly weakened state then, reorganizing and reshuffling.
That restructuring will transfer the storm’s energy off the coast of Delmarva late Sunday night, spawning a new storm center as a nor’easter brews off the New Jersey coastline. It will intensify as it rushes northeastward, passing southeast of Nantucket as it throws precipitation and wind back toward New England.
A New England nor’easter
Bands of snow are possible from the Tug Hull Plateau in New York State to the Hudson Valley by late Sunday, with some six inch-plus totals possible when all is said and done on Monday.
But the real action will be focused in Southern New England, where precipitation moves in Sunday evening. Sunday night and much of Monday will then feature moderate to at times heavy snow.
Two zones of locally heavy snow are possible. One will stretch from east of the Berkshires from northern Massachusetts down to west central Connecticut.
The other zone of heavy snow depends on where the storm’s coastal front sets up, which will determine the whereabouts of the rain/snow line. A strip of heavier snow is typical west of that boundary.
The Boston-to-Providence corridor may end up along this dividing line, with 5 to 8 inches possible west of there and localized 10-inch amounts. That may end up being in the Blackstone Valley.
To the east, where rain and sleet may mix with snow, 3 to 5 inches are possible, except one to four in eastern Bristol and Plymouth counties. The Cape and Islands may not see much more than a few flakes.
These snowfall projections may change some as this forecast comes into better focus over the weekend.
Mid-Atlantic to New York City
Farther south, the forecast is even tougher. New York City may see a snow sandwich — a touch of snow at the start of Sunday night and finish Monday night, with rain in between. A few inches are possible farther east on Long Island.
In Philadelphia it’s looking like mostly rain, although snow showers could develop on the storm’s backside Sunday night and Monday, especially in its colder areas to the north and west.
And in Washington and Baltimore, rain will span from late Saturday afternoon through Sunday, with perhaps some rain and/or snow showers on the storm’s backside on Monday.