Tomer’s Take:

• A strong cold front remains on track for MT, WY, and CO between 5/19-5/20.
• Forecast atmospheric pressure anomalies run 2-3 standard deviations below the 30-year average.
• The bulk of snow falls in SW MT and on CO’s Continental Divide-East.
• Yellowstone could see 1″ of accumulation. Big Sky and Cooke City could see several inches of accumulation.
• Air temps in parts of Colorado drop 30-40 degrees.
• Snow levels could drop to the valley floor.
• Strong winds precede this cold front.

Infrared satellite shows the storm track and two large storm systems lined-up. The first storm system delivers the strong cold front while the 2nd storm system amplifies the high pressure ridge and jet stream.

Pressure Pattern

An abnormally large trough rotates through the Intermountain West 5/19-5/20. Again, forecast atmospheric pressure anomalies run 2-3 standard deviations below the 30-year average.

Snow Forecast

5/17-5/26:

Tomer’s Take:

• A strong late-season dip in the jet stream could deliver snow 5/19-5/20 to MT, WY, and CO.
• Snow levels fall significantly to the valley floor in some locations. Frost/Freeze is also possible.
• Forecast atmospheric pressure anomalies could run 2-3 standard deviations from the 30-year average.
• Strong wind 30-80mph ahead of this storm system.

I took the skis out on Saturday near Torreys Peak in Colorado. It was a beautiful day and snow was melting quickly.

Current Setup

Infrared satellite shows the storm track and strong low pressure system pulling out of the Gulf of Alaska.

Late Season Anomaly

Below, this is a robust storm system and important by May standards. Forecast atmospheric pressure anomalies run 2-3 standard deviations from the 30-year averages.

Forecast Wind Gusts

Snow Forecast

5/16-5/25:

Tomer’s Take:

• High pressure rebuilds across the West 5/13-5/18. The storm track shifts into the PNW/B.C.
• Then pressures might drop with a large trough and dip in the jet stream 5/19-5/25.
• Beyond 5/25? High pressure might rebuild.
• What are the possible effects of a large trough 5/19-5/25? Colder than normal temps, mountain snowfall, and strong wind by May standards.
• Dust continues be a significant problem across parts of the West including UT and CO. New dust is being transported in as I write this column. The dust decreases snowpack albedo and accelerates snowmelt. This is likely the most dust since 2009.

Wasatch Dust

Look at the dust layers lurking in the Wasatch as presented by Dr. McKenzie Skiles:

In Colorado, MODIS satellite with MAIAC Aerosol Optical Depth overlay really paints the smoky/dusty picture.

Current Setup

Infrared satellite shows the storm track and powerful jet stream running through the Intermountain West.

5/19-5/25

A large trough of low pressure is possible across the West. Below, notice the atmospheric pressure anomalies. After 5/25? High pressure might rebuild.

Wind Gust Forecast

Notice how winds relax as high pressure rebuilds 5/13 and after.

Snow Forecast

5/12-5/21:

Tomer’s Take:

• A powerful jet stream returns to the West through 5/15. It resembles April.
• The future storm track keeps the bulk of precipitation north of Colorado through 5/15. This leaves Colorado and much of the Intermountain West in a windy pattern.
• Blowing dust is again possible.
• The best chances for snow stays in northern UT, WY, ID, MT, and PNW.

Infrared satellite shows the storm track and storm systems lined-up. They’re riding a powerful jet stream.

Wind Gust Forecast

Jet Stream

A powerful jet stream returns to the West resembling April. It’s following La Nina architecture. The yellow/orange/red colors represent the strongest winds.

Snow Forecast

5/6-5/15:

Everest Weather

Enjoyed a conversation yesterday with Alan Arnette, Michael Fagin, and Marc DeKeyser. The focus is on Everest Weather. Michael and Marc are fellow cohorts who provide weather forecasts and guidance to teams climbing Everest (and other peaks).

You can watch our discussion by clicking here.

Tomer’s Take:

• The dust storm on 4/22 was one for the books. Dust was deposited on most of the high mountain snowpack – especially the Southern Mountains.
• This could be the most significant layer of dust since 2009. Here’s a look back at 2009 in a paper I co-authored.

Dr. McKenzie Skiles at the University of Utah snapped this photo looking into the Wilson Massif in the San Juan Mountains of Colorado.

Here’s a look back at the 4/22 dust storm with wind gusts of 50-90mph. Notice how much dust was entrained on the MODIS satellite image with dust/smoke overlay.

MODIS satellite also has a feature that can look at “Dust Radiative Forcing”. Dust increases radiative forcing and promotes faster melting of the snowpack. Below, is the current satellite image as of 5/2.

Obviously, the Southern Mountains have high amounts of dust. I suspect the Central and Northern Mountains have more dust than what’s being detected. Why? It continues to snow in the Central and Northern Mountains covering up the dust from 4/22. The Southern Mountains have been relatively dry since 4/22 with very little snow. Eventually those dust layers in the Central and Northern Mountains will be revealed as the snow melts.

Below is a look at the current dust radiative forcing versus history. It’s clearly outside of the normal range.

How does this process work? The snowpack melts faster sending water downstream earlier and faster than normal.

Tomer’s Take:

• A minor storm system is spinning through the Intermountain West this morning with rain and snow.
• A larger storm system and dip in the jet stream is waiting in the Gulf of Alaska. This will drive the pattern across the West between 5/8-5/15. Some places get snow while others get mainly wind.
• The bulk of snow 5/8-5/15 falls in CA, ID, MT, WY, and northern UT.

Infrared satellite shows the storm track and large low pressure in the Gulf of Alaska.

A large dip in the jet stream and atmospheric pressure anomalies occur across the West 5/8-5/15.

Wind Gust Forecast

Snow Forecast

5/4-5/13:

Tomer’s Take:

• La Nina continues to anchor the pattern across the West through mid-May. It’s the strongest April/May La Nina since 1999.
• I’m expecting above normal levels of wind, snow, and rain.
• Across the Intermountain West, a larger dip in the jet stream and trough of low pressure still possible 5/8-5/13.
• Conditions might ease the 2nd half of May.

Infrared satellite shows the active storm track and larger low pressure sitting in the Gulf of Alaska. This becomes the dominate force through 5/13.

5/8-5/13

Falling pressures are still possible with a dip in the jet stream between 5/8-5/13. Uncertainty remains high regarding precipitation placement. Of higher certainty is strong wind. A trough of this size would deliver abnormally strong wind across the Intermountain West.

Wind Gust Forecast 5/8-5/11

Snow Forecast

5/3-5/12: