Tomer’s Take: The Christmas Eve storm system looks about the same as yesterday. A weak merger (of two areas of low pressure) generates light snow accumulation in the Wasatch and Tetons. Moderate to heavy accumulation in Southern Wyoming and parts of Colorado.

A couple different storm systems and rich flow impact the Sierra 12/27-12/30.

That storm system exits CA and moves through UT/MT/ID/WY/CO on/around New Year’s Eve.

My afternoon forecast video:

Current Setup

Water vapor satellite shows the two areas of low pressure that eventually merge over WY/CO. The third low hits the PNW/BC with heavy precip.

Orange/red = drier air aloft.

Forecast Jet Stream

Trough quickly exiting WY/CO.

Trough and strong jet ushering moisture into the West Coast/PNW/CA.

Forecast Radar & Satellite

New Years Eve Forecast

A storm system slides through the Intermountain West with light snow accumulation.

Forecast Totals

*Updated 2:30pm 12/22.
UT Snow: 12/23.

Teton Snow: 12/23.

CO Snow: 12/23-12/24.

*Updated 2:30pm 12/22.
CA Snow: 12/27, 12/29-12/30.

*Updated 2:30pm 12/22.
NY/VT/NH/ME Precip: 12/27-12/29.

Tomer’s Take: Calendar Winter (Winter Solstice) officially arrives today. Two pieces of energy merge over WY/CO 12/23-12/24. The merger timing is slower and final low not as deep resulting in lower totals for the Wasatch and Tetons. Heavier totals in southern WY and parts of CO.

Looking down the road, a rich flow and strong jet stream hits California 12/27-12/30 with heavy snow potential.

My afternoon forecast video update:

Current Setup

Water vapor satellite shows both areas of energy and ultimate merger zone over WY/CO.

Orange/red = drier air aloft.

Forecast Jet Stream

Notice the trough over WY/CO. It’s not as deep as previous forecasts.

Active, powerful jet pattern ushering rich moisture into CA/West Coast.

Forecast Radar & Satellite

Forecast Totals

*Updated 2:15pm 12/21.
CO Snow: 12/23-12/24.

WY Snow: 12/23-12/24.

UT Snow: 12/23.

*Updated 2:15pm 12/21.
CA Snow: 12/27-12/30.

*Updated 2:15pm 12/21.
NY/VT/NH/ME Precip: 12/27-12/30. Rain initially then changing to snow.

Tomer’s Take: Two pieces of energy will merge somewhere over UT/WY/CO 12/23-12/24. The timing and placement of the merger determines total snowfall for UT, WY, CO, NM.

My video forecast update:

Current Setup

Water vapor satellite shows both pieces of energy and eventual merger zone.

Orange/red = drier air aloft.

Forecast Jet Stream

Notice the trough over WY/UT/CO.

Powerful Pacific flow and jet power. Active New Years pattern into January 2024.

Forecast Radar & Satellite

Forecast Totals

*Updated 2:30pm 12/20.

WY Snow: 12/23-12/24.
UT Snow: 12/23-12/24.

CO Snow: 12/23-12/24.

*Update 2:30pm 12/20.

CA Snow: 12/27-12/29.

*Updated 2:30pm 12/20.
Storm system 12/26-12/28 appears warmer with mostly rain.

Tomer’s Take: A more active Western storm track develops after 12/20 and runs through Christmas and especially New Years. In California, the rain/snow line today drops to 8,000′-8,500′ with heavy snow accumulation above that level. On 12/23-12/24, two pieces of energy merge over Colorado/Wyoming to deliver moderate to heavy snow accumulation. There is a trend now for a weaker energy merger.

My afternoon/evening forecast video:

Current Setup

Water vapor satellite shows two areas of low pressure over the Pacific. The first low drops south and takes a southern track. The 2nd low hits the PNW then moves through WY/UT/WY. Both pieces of energy merge over WY/CO/NM 12/23-12/24.

Orange/red = drier air aloft.

Forecast Jet Stream

Valid 12/24. Trough over WY/UT/CO escorts a storm system with moderate to heavy snow accumulation.

Valid 12/28. Powerful jet stream and large trough translating over the Pacific. This could represent more active and colder pattern around New Years into January 2024.

Forecast Radar & Satellite

Christmas Forecast

Valid 1pm 12/24. Low strengthens and slides from UT through WY & CO.

Valid 4:30am 12/24. Low exits WY/CO and snow decreases.

Forecast Totals

*Updated 2pm 12/19.

*Updated 2pm 12/19.

UT Snow: Late 12/22-12/24.

WY Snow: Late 12/23-12/24.

CO Snow: 12/23-12/24

NM Snow: 12/23-12/24.

*Updated 2pm 12/19.

99% of accumulation: 12/26-12/28.

Tomer’s Take: Rain/snow hits California 12/18-12/20 with a rain/snow line 9k-10k (heavy snow above that level). Then two pieces of energy might merge over CO/NM for moderate to heavy snow accumulation 12/23-12/24. This setup leaves UT and WY with lighter snow accumulation.

Looking down the road, a more active storm track is possible for New Year’s into January 2024.

My afternoon forecast video:

Current Setup

Water vapor satellite shows the trough hitting CA and blasting the West with abnormally warm air. The two areas of low pressure in the North Pacific are important players 12/23-12/24 across the Interior Rockies.

Orange/red = drier air aloft.

Forecast Jet Stream

Valid 12/24 11pm. A trough is forecast over the Intermountain West including WY/UT/CO/NM supporting an area of low pressure and colder air.

Christmas Forecast

Valid 12/24 12pm. Snow is possible in CO down to 5280′.

Christmas Morning. Storm system departs CO/NM.

Early to Mid January Storm Track

The NCEP Climate Forecast System hints at a more active storm track for the West.

Forecast Totals

*Updated 2:45pm 12/18.

CA bulk of snow above 9-10k.

*Updated 2:45pm 12/18.

UT Snow: 12/20, 12/22-12/23.

WY Snow: 12/23.

CO/NM Snow: 12/23-12/24.

Tomer’s Take: It’s a waiting game out West where the mountains continue to get blasted with abnormally warm Pacific air. Precipitation hits CA 12/18-12/20, but the rain/snow line starts at 9,000-10,000ft. I’m only forecasting light snow accumulation for the Wasatch, Tetons, MT, and ID on/after 12/20. The exception will be CO, NM, and Southern UT where a stronger area of low pressure might develop 12/24-12/25.

My forecast video:

Christmas Day Forecast

Potential stronger area of low pressure develops in Southern CO and Northern NM. This is a long shot.

Valid 10am 12/25, Forecast Radar & Satellite:

Forecast Radar & Satellite

Forecast Totals

Sierra rain/snow line starts at 9,000-10,000ft 12/17-12/19 then gradually falls to 8,000ft.

This assumes best/worst case scenario with stronger low development in Southern CO/Northern NM 12/24-12/25.

Tomer’s Take: Snow continues on 12/14 across Southern Colorado and Northern New Mexico. Then this storm system departs and develops into a strong East Coast storm system 12/17-12/20 with wind, rain, and snow.

Looking down the road, light to moderate snow hits the Sierra late 12/17-12/18 with high rain/snow levels. Light snow hits the Wasatch 12/19-12/21. A more active pattern might develop after 12/23.

Current Setup

Water vapor satellite shows the storm system in Southern CO/Northern NM. It also shows a large Pacific trough that will slowly work its way towards CA.

Forecast Jet Stream

Valid 12/17. Trough and moisture approaches CA coast, slowly. Warm air floods the West generating high rain/snow line.

Valid 12/23. A transition point as Pacific delivers energy. Pattern turns more active.

East Coast Storm System

Valid 12/17. Jet supports a strong area of low pressure, but it lacks cold air. Rain and wind dominate through 12/18. Then colder air turns rain to snow in NY/VT/NH/ME.

Valid 11:15pm 12/17.

Forecast Radar & Satellite

Forecast Totals

*Updated 2pm 12/14.

*Updated 2pm 12/14.
CA Snow: Late 12/17-12/18 (Light to moderate).

UT Snow: Late 12/19-12/21 (Light).

CO Snow: Late 12/20-12/21 (Light).

*Updated 2pm 12/14.
NY/VT/NH/ME —>

Late 12/17-12/18: Rain

12/19-12/20: Snow possible.

Tomer’s Take: A storm system is spinning up in Southern CO and Northern NM through 12/14 with moderate to heavy snow accumulation. This area of low pressure then turns into a coastal storm system for the East/NE with mainly rain on 12/18. California stays dry until late 12/17 into 12/18 when a wave of rain/snow arrives.

My forecast update:

East Coast Storm System

Valid late 12/17. A strong area of low pressure departs Florida on 12/17 and up the East Coast on 12/18 with mainly rain.

Valid 12/18 5:45am. Forecast radar shows mainly rain.

Forecast Radar & Satellite

Forecast Totals

CO & NM Snow: 12/13-12/14.

CA Snow: Late 12/17-12/18 and 12/19-12/20 with a high rain/snow line.

Tomer’s Take: The Western pattern turns tranquil with one exception. An area of low pressure develops 12/13-12/14 in Southern CO and Northern NM with moderate to heavy snow accumulation. Otherwise, the storm track stays quiet through 12/20.

In the Northeast, a Nor’ Easter might occur on/about 12/18 but it looks warm.

Season Totals so far:

Skies have cleared at Steamboat Ski Area. The view from Thunderhead and uphill traffic:

Current Setup

Water vapor satellite shows an area of low pressure cut-off from the northern branch sliding through the Intermountain West. This energy develops into a stronger area of low pressure in Southern Colorado and Northern New Mexico 12/13-12/14.

Forecast Jet Stream

Valid 12/13. Northern branch runs north into Canada leaving most of the West warmer than normal. Developing area of low pressure with southern branch support in Southern CO and Northern NM.

Valid 12/21. Northern branch runs north into Canada leaving most of the West warmer than normal. A trough stays offshore of CA.

Possible Nor Easter

Valid 11pm 12/17. Developing area of low pressure in the Carolinas.

Valid 11:45am 12/18. Lack of cold air is a problem with mainly rain.

Forecast Radar & Satellite

Forecast Totals

CO & NM Snow: 12/13-12/14

Quiet period continues.

Nor Easter possible 12/18. A lack of cold air generates mainly rain initially then changing to snow in VT/NH/ME.