This Saturday is the Winter Solstice and the official start to the winter season, according the calendar at least. Next week is Christmas and then it’s a whole New Year!

To help you plan you your travels, or your ski destination, or to just to get a sense of how white your Christmas is going to be this year, I have compiled the best short and longer-term snowfall forecasts for you to consult. Looks like some places do better than others, by a large measure.

The Short Story

Current weather situation shows Low-pressure systems in the Pacific that weaken and/or split as they move inland this week and Christmas week. Jet stream not continuous or too strong coming out of the Pacific right now.

Solstice Snowfall Forecasts

From today, Wednesday Dec. 18, into Saturday Dec. 21, here are two short-term forecasts that tell a similar tale for new snow accumulation:

Snowfall Through Christmas Week

Smaller weather disturbances follow after Christmas and into New Year’s Day. Best bet for big snowfall accumulations this week and next are the Washington Cascades (Mt. Baker) and Southwestern British Columbia’s mountains (Whistler).

Caution: Differences in snow accumulation between the two models below due to the Euro model going out 10 days and the GFS out 14 days. Biggest difference between models is seen over Northwest Wyoming and the Colorado Rockies, due in part to more snowfall after Dec. 28th.

I’ll update this post again in a few days to see if there is any significant change to the snowfall outlook for the Holidays.

Post by meteorologist Jim Woodmencey

A West to Northwesterly flow aloft over the Western U.S. will yield additional snowfall through this coming weekend. A large area of Low pressure in the Gulf of Alaska, combining with a smaller Low-pressure center currently further out in the Pacific will rotate Pacific moisture across the Cascades, Sierra Nevada, and the northern & Central Rockies.

An area of High pressure also sits off the southern California coast, with a strong jet stream between this High and the Low’s to the north. (Jet Stream is yellow line).

These two Low pressure centers hang around out in the Pacific into the weekend and the jet stream relaxes a bit & winds decrease. Pacific moisture will continue to pulse inland through this weekend. Best periods of snowfall in the mountains appears to be Thursday night and again overnight Friday into Saturday. Best break in precip is during the day Friday.

As time goes on , a Ridge of High pressure builds along the West Coast and more Northwesterly flow aloft brings cooler temperatures over the Rockies this weekend. Extending light snow over the northern & central Rockies through Sunday into Monday.

700mb Maps with Forecast Clouds (gray) & Precipitation (blue-green). Maps from Windy.com

Snowfall Forecasts

Models differ slightly about how much snow will accumulate, but it looks like some mountain areas are favored by this West-NW flow. A few of these models predicted snowfall amounts are shown below.

The first is the high resolution WRF from the Colorado Avalanche Information Center, which shows the greatest amounts in the mountains. Their regular WRF model follows, both examples show snowfall totals from Thursday afternoon to Sunday morning.

The NAM (North American Model) below with total snow accumulations from Thursday afternoon through Sunday afternoon.

Post by MountainWeather meteorologist Jim Woodmencey

Back in early September I did my first outlook for the winter season in this blog. That was just after the Farmer’s Almanacs came out with their predictions. Two of those Almanac forecasts had most of the Mountain West painted under cooler and snowier conditions, overall. Those forecasts don’t change, once they are published in late August. (See their maps below).

The Climate Prediction Center (CPC) forecast that I reviewed from NOAA, that was issued in mid-August, revealed that the western U.S. would be warmer than normal, but was undecided about precipitation. That outlook was non-committal about it being above, below, or normal for precipitation for the three-month period, they gave it “equal chances” for each. No help there. However, the latest update looks a little different.

Latest Look

The newest three-month long-range outlook from the Climate Prediction Center, issued on November 21, 2020, still has western Wyoming under warmer than normal conditions for December, January and February. This is still in direct contrast to both Farmer’s Almanac temperature forecasts.

The precipitation forecast from the CPC has now shifted to placing Northwest Wyoming & western Montana under about a 55-percent chance of having above normal precipitation. That’s somewhat more encouraging.

Most of the Pacific Northwest, northern Utah & northern Colorado are riding the 50-percent chance of above normal precip line.

El Nino Situation

The El Niño Southern Oscillation, or ENSO, is one of many indicators long-range forecasters use to decide what the general conditions for the winter season might be across the Northern Hemisphere.

The ENSO actually has three different phases: El Niño, La Niña and Neutral. Sea surface temperatures in the Equatorial Pacific determine the current phase of the ENSO.

An El Niño is occurring when sea surface temperatures are warmer than normal. A La Niña is occurring when temperatures are colder than normal. Neutral ENSO conditions (No Niño) occur when temperatures are near normal, usually when transitioning between the El and La phases.

In general, during an El Niño Winter the northern tier of the United States experiences warmer than normal temperatures and below normal precipitation. At the same time, the southern tier of the United States is usually cooler with above normal precipitation.

During a La Niña Winter the opposite is true, the northern tier of the United States usually experiences a cooler and snowier winter, while the southern tier is usually warmer and drier.

Neutral or No Niño Winters, could go either way. And the ENSO forecast for this winter is for Neutral conditions in the Equatorial Pacific.

ENSO Current status: “Surface temperatures in the east-central tropical Pacific were near to above average in October 2019, but the atmosphere did not react to the warmth. Sub-surface heat that spread across the basin in mid-September was dispersing. Thus, of the three possible outcomes—return of El Niño, La Niña, or neutral—forecasters give neutral the highest odds (70% chance) of continuing through winter.”

What’s it all Mean for JH?

Last winter was a weak El Niño, and pretty much the entire western U.S had a cooler and wetter winter. Jackson Hole was above normal for snowfall, after a record February. That wasn’t supposed to happen.

Historically, from snowfall data for the past 44 winters at the Jackson Hole Mountain Resort, El Niño’s have produced more below normal snowfall winters here than above normal (10 below and 4 above). La Nina’s have produced more above normal snowfall winters than below normal (10 above and 4 below).

Neutral or No Niño’s have also produced more below normal snowfall winters than above normal snowfall winters, but by a smaller margin (9 below and 6 above).

What’s really interesting is, two of those six above normal No Niño winters were the two snowiest winters on record at the Jackson Hole Mountain Resort, the winter of 1996-97 and the winter of 2016-17.

Based on those stats, an optimist would be rooting for another one of those record-breakers during this winter’s No Niño. The pessimist would say chances are less than 50/50 for an above normal snowfall winter.

I already know how many optimists there are in Jackson, just count how many season ski passes have been sold so far.

Post by: Meteorologist Jim Woodmencey