Next Winter Storm Blasts First Arctic Air of the Season Into West, Plains This Week

Linda Lam
Published: November 23,2015

An impressive arctic blast will engulf the West and Plains this week, setting the stage for a significant winter storm.
A cold front will move into the Pacific Northwest early this week bringing rain and mountain snow to the region. This low-pressure system will then spread snow across the northern and central Rockies midweek. Snow may even accumulate on the valley floors.

Western Storm Setup

This system will then move through the Rockies and into the Plains later this week into this weekend, potentially bringing moderate to heavy snowfall along with icy precipitation.
(MORE: Thanksgiving Travel Forecast)
A strong arctic high-pressure system will then move in behind this system allowing the first real blast of arctic air to surge into the U.S. The coldest air mass of the season to date is expected for the West and the Plains beginning Wednesday and lasting into the start of the weekend.

Another Winter Storm

Rain and mountain snow began developing in the Pacific Northwest on Monday as this low-pressure system pushes into the region. This area of low pressure will continue sliding south and east through much of the West early-to-midweek.
Seattle and Portland will see rain into Tuesday while accumulating snow will fall in the Cascades, with snow levels dropping to around 1,000 feet above sea level.
Freezing rain and icy roads are also a concern in portions of southeastern Washington and northern Oregon, including Yakima and Pendleton, where a freezing rain advisory has been issued for ice accumulations up to one tenth of an inch.
(FORECAST: Seattle | Portland)
Showers are then expected to expand along the West Coast, including much of central and southern California Tuesday and possibly lingering into Wednesday. Snow will fall through the Sierra Nevada as well as the Intermountain West. Snow levels in the Sierra are expected to drop to 2,000 feet, with up to 18 inches of snow possible in the higher elevations.
Snow levels will remain low through the West, with accumulating snow expected in more populated areas compared to the last few winter storms.

Snowfall Forecast

Winter storm warning and winter weather advisories have been issued for much of central and western Montana, northern Idaho, eastern Washington and much of central and southern Oregon. This includes Spokane, where more than 30,000 customers were still without power Monday morning six days after a destructive windstorm swept the Northwest.
Winds will be gusty at times again with the upcoming winter storm. Though not as strong as last week's winds, they could create near-blizzard conditions on Tuesday over parts of the northern Rockies.
Winter storm watches and warnings and winter weather advisories are also in effect for the Sierra Nevada in California and northern Nevada.
For those traveling midweek for Thanksgiving, delays are anticipated across much of the West, including Interstate 15 in Utah, Idaho, and Montana; Interstate 80 in parts of California, Nevada, Utah and Wyoming; Interstate 90 in Montana; and possibly sections of Interstate 70 in Colorado.
(FORECAST: Boise | Missoula | Salt Lake City)
Upslope winds may also develop on the eastern side of the northern and central Rockies which would enhance the snowfall along the Front Range.

Arctic Blast

The upper-level trough, or southward dip in the jet stream, will dive across the West midweek and combined with a strong area of high pressure from Canada, the result will be the first blast of arctic air arriving in the West and Plains.
Low temperatures will be up to 25 degrees below average in interior portions of the Pacific Northwest and Rockies Thursday and Friday mornings.

Morning Forecast Lows

Overnight lows will range from single digits to well below zero in the northern and central Rockies beginning Thursday morning and lasting until Saturday morning.
This will lead to the coldest temperatures so far this season for many areas. A couple of examples include Helena, Montana, where the lowest temperature recorded so far this season is 14 degrees on Nov. 21; lows there are expected to drop to around zero this week. Reno, Nevada has seen the mercury drop as low as 21 degrees on Nov. 11; lows in the upper teens are in the forecast late this week or this weekend.
Temperatures are expected to drop into the upper 30s at the San Francisco International Airport late this week, and a new daily record low may be threatened on Friday morning (current record is 37 degrees).
(FORECAST: Great Falls, Montana | Casper, Wyoming | Denver)
Wind chills may plummet between 20 to 25 degrees below zero in parts of western Wyoming Thursday night.

Forecast Highs

High temperatures will remain very cold as well. Highs will be 10 to 30 degrees colder than what is normally expected for the end of November over parts of the West Wednesday through Friday. Highs will only reach the teens and 20s in the Rockies, with 30s and 40s for the Pacific Northwest and Great Basin.

Snow and Chilly Conditions Move Into the Plains

Late Week Setup in the Plains

The arctic chill will push south and east late this week and into the weekend. High temperatures in the Plains will be up to 30 degrees colder than average beginning Thanksgiving and persisting into the holiday weekend.
(FORECAST: Rapid City, South Dakota | Oklahoma City)
High temperatures in the central and southern Plains will only climb into the 20s and 30s, with 40s for highs as far south as Dallas.
These cold temperatures will allow snow and/or icy precipitation to fall in parts of the Plains late this week. Ahead of the cold front, rain and thunderstorms are expected and locally heavy rainfall may bring the threat of flash flooding from Texas to the Midwest, especially Thursday into Friday.
(FORECAST: Amarillo, Texas | Dallas)
Behind the cold front, snow will begin to develop in South Dakota and Nebraska Wednesday night and into Thursday. Snow, sleet and freezing rain will stretch from the Upper Peninsula of Michigan through northern Wisconsin, southern and central Minnesota, northwestern Iowa and into South Dakota, Nebraska and Kansas on Thanksgiving.
By Thursday night, snow, sleet and ice may be concerns in portions of the southern Plains including Kansas, western Oklahoma, and the Texas Panhandle.
(MAPS: Weekly Planner)
An upper-level low is expected to become cut off over the Great Basin with moisture continuing to flow into the southern Plains. Some of this moisture will be from the tropics, including moisture from Tropical Depression Twenty-Two-E in the eastern Pacific.
This moist air will be lifted over the cold shallow airmass over the region allowing freezing rain, sleet and snow to continue at times, especially in western Texas Friday and Saturday. These conditions may create slick and dangerous travel conditions. There is the potential for a significant accumulation of ice over a prolonged period of time which could create a serious situation, especially across the Texas Panhandle and western Oklahoma Thursday night through Saturday night.
Check back for updates and the latest information on this developing winter storm.
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