Tomer’s Take: We’re heading into a much quieter period for the Intermountain West with one exception. An area of low pressure develops in Southern Colorado and Northern New Mexico 12/13-12/14 with moderate to heavy accumulation.

New snow at Steamboat, CO in the last 48 hours. Steamboat is benefiting from a dirty NNW flow out of WY.

Current Setup

Infrared satellite shows the storm track and fast moving areas of low pressure.

Forecast Jet Stream

Valid 12/13. An area of low pressure develops in Southern CO and Northern NM. Southern jet provides a little support. Polar jet runs north into Canada.

Valid 12/13 at 11pm. Storm system matures in Southern CO/Northern NM.

Valid 12/20. A trough of low pressure approaches California. CA stays totally dry until 12/18.

Forecast Radar & Satellite

Forecast Totals

Southern CO Snow: 12/13-12/14.

Northern NM Snow: 12/13-12/14.

100% of this snow falls on 12/11.

Tomer’s Take: A shifting Western pattern delivers 3-6 inches of new snow to the Tetons today (12/10), generates 30-70mph wind gusts across CO’s Continental Divide and light snow, and eventually might force the development of a storm system in Southern CO/Northern NM by 12/13-12/14. Pattern remains mostly dry for CA through 12/18, and minimal snow for UT’s Wasatch.

A windy storm system is moving into the Northeast with rain initially at the ski resorts of VT/NH/ME changing over to snow late tonight into 12/11.

My forecast video:

It’s a brutal day across Colorado’s Continental Divide including Front Range high peaks, Indian Peaks, Longs Peak, and Cameron Pass zones. 30-70mph gusts, single digit air temps above 12k, and snow shrouding with low visibility.

Below, the view from Loveland Ski Area at 12,700ft paints the picture:

Current Setup

Forecast Totals

WY Snow: PM 12/10.

UT Snow: PM 12/12.

CO Snow: 12/10-12/11.

ID Snow: 12/10 – AM 12/11.

Area of low pressure might develop in Southern CO/Northern NM 12/13-12/14 with moderate snow accumulation.

Bulk of snow occurs late 12/10 into 12/11.

Tomer’s Take: Two shots of accumulating snow hit WY on 12/10 and 12/11. 30-60mph wind gusts hit Colorado’s Continental Divide on 12/10. Shifting flow pattern favors ID, WY, MT, PNW, BC through 12/18. Unfortunately, UT and CA look mostly dry through 12/18.

My forecast video:

Windy CO Continental Divide 12/10

Valid 7am 12/10. Expect 30-60mph gusts on the Front Range high peaks, Indian Peaks, Longs Peak, and Cameron Pass.

Forecast Totals

Windy East Coast Storm System

Valid late 12/10. Powerful jet but bad track for heavy snow in VT/NH/ME with rain initially then changing over to snow late 12/10 into 12/11.

Valid late 12/10. Forecast radar shows rain initially then changing over to snow.

Tomer’s Take: Snow continues today in WY, UT, and CO. Saturday is dry. Additional snow hits the Tetons and Colorado on Sunday and Monday.

In the Northeast, a windy storm system hits 12/10-12/11 with rain initially then changing over to snow on 12/11.

About 7 inches in 24 hours at Winter Park, CO with a 2nd wave of snow this afternoon. Additional light snow hits PM 12/10.

7 inches in 24 hours at Aspen & Snowmass with a 2nd wave this afternoon.

13 inches in the last 24 hours at Alta, UT and still snowing.

Current Setup

Water vapor satellite shows the storm system moving through UT, WY, CO. It’s next stop is the Northeast.

Additional areas of low pressure across the Pacific will deliver snow to the Northern Tier of states.

Forecast Jet Stream

Valid 12/8. Trough over WY/UT/CO delivering snow. This storm system becomes the large East Coast storm system 12/10-12/11.

Valid 12/10. Fast, progressive jet flow favoring Northern Tier for additional snow accumulation.

Valid 12/17. Slight dip over West Coast might bring snow back to CA.

Forecast Radar & Satellite

Eastern Storm System

Valid 12/10. Powerful jet generating a storm system and strong wind. Pushes warm air and rain initially into VT/NH/ME.

Valid 12/10 9pm. Forecast radar & satellite.

Forecast Totals

*Updated 2pm 12/8.

Additional snow accumulation 12/8-12/9.

*Updated 2pm 12/8.
CO Snow: 12/10 (light), 12/10-12/11 (light), 12/12-12/13 (light).

WY Snow: 12/10-12/11 (moderate).

*Updated 2pm 12/8.

*Updated 2pm 12/8.
Rain 12/10 changing to snow 12/11.

Tomer’s Take: The next storm system departs the PNW and hits ID, MT, WY, UT, and CO 12/7-12/9. This same storm system develops into a strong, windy East Coast storm system with rain on 12/10 and then snow 12/11.

7″ in 24 hours at Big Sky and snow continues to fall plus 30-50mph wind gusts. Additional snow is likely on 12/8, 12/10-12/11.

It’s snowing hard at Alta, UT with a break tonight then snow returns on 12/8.

Current Setup

Water vapor satellite shows two storm systems over the Pacific. Both hit the PNW and then Intermountain West. The 1st storm system is major, and the 2nd is minor.

Orange/red = drier air aloft.

Forecast Jet Stream

Valid 12/8. Notice the trough over WY, CO supporting an area of low pressure and snow accumulation.

Valid 12/16. Possible area of low pressure pulling out of Southern CO and Northern NM.

East Coast Storm System

Valid 12/10. Powerful jet stream and lots of wind. This setup puts the ski resorts of VT/NH/ME in the warm sector and mostly rain on 12/10 then changing to snow early 12/11.

Valid 12/10. Forecast radar shows all wind and rain for VT/NH/ME. Changes to snow on 12/11.

Forecast Radar & Satellite

Forecast Totals

WY Snow: 12/7-12/8 (Heavy), 12/10-12/11 (Light).

CO Snow: Late 12/7-12/8 (Moderate), 12/14-12/15 (Light).

UT Snow: 12/7-12/8 (Moderate to Heavy).

Rain changes to snow around 5am on 12/11 in VT.

El Nino Update

Latest forecast guidance suggest a rapid and sharp transition from a strong El Nino to La Nina during Spring 2024 into Summer 2024.

Below is the ECMWF ensemble for ENSO region 3.4 next 10 months.

It’s a sharp turn after JAN/FEB 2024. This is one reason why an El Nino Modoki is possible JAN/FEB/MAR during the transition.

Tomer’s Take: Moderate to heavy snow accumulation hits ID, MT, WY, UT, and CO 12/7-12/8 with light accumulation 12/10. Out East, a large, windy storm system pushes most ski areas into the warm sector with primarily rain on PM 12/10 changing to snow on 12/11.

My PM forecast video:

Current Setup

Water vapor satellite shows an active PNW flow with two areas of low pressure en route.

Orange/red = drier air aloft.

Forecast Jet Stream

Valid 12/8. This is the best shot of snow for the Interior Rockies. Notice the large trough over WY, CO. The 2nd storm system on 12/10 is much smaller.

Valid 12/10. Progressive, fast flow with light snow accumulation across the Interior Rockies.

Valid 12/15. Potential storm system development in SE CO/N NM. Confidence is low.

Eastern Storm System

Valid 12/10. Most big ski areas are on the warm side of the jet with rain initially then changing to snow on 12/11. This is a windy storm system.

Valid 12/10. Forecast radar/satellite shows mainly rain for the big ski resorts with snow on the colder, western side. Rain changes to snow at the ski areas on 12/11.

Forecast Radar & Satellite

Forecast Totals

*Updated 4pm 12/6.

UT Snow: 12/7-12/8.

CO Snow: Late 12/7-12/8.

WY Snow: 12/7-12/8, 12/10.

MT Snow: 12/7-12/8, 12/10.

*Updated 4pm 12/6.
Second storm system is lighter and faster but a few places squeeze out 4-5 inches.

*Updated 4pm 12/6.
Most of this accumulation in VT/NH/ME occurs on 12/11 after rainfall initially (on PM 12/10).

Tomer’s Take: Atmospheric river continues in the PNW next 24 hours with high rain/snow levels. This storm system then breaks loose and races through the Intermountain West 12/7-12/8. A second minor, fast-moving storm system rides its coattails 12/9-12/10. A third feature is possible 12/12-12/13; A cold front dives south through CO and NM and might develop into a stronger area of low pressure.

In the Northeast, the Western storm system develops into a major area of low pressure on 12/10 that runs up the East coast with rain, thunderstorms, wind, and some snow. The NE ski resorts appear to be mainly rain.

Current Setup

Water vapor satellite shows an active Polar Jet and Atmospheric River (AR) component.

Orange/red = drier air aloft.

Forecast Jet Stream

Valid 12/6. Main energy remains in the PNW, but will break loose 12/7-12/8.

Forecast PNW rain/snow line ->

12/5: 7700′

12/6: 5000′

12/7: 4000′

12/8: 2500′

Valid 12/8. Notice the dip in the jet over WY, CO. An area of low pressure and cold front will drive south with snow.

Valid 12/14. An area of low pressure might develop in CO with snow to follow including NM.

Eastern Storm System

Valid 12/10. Forecast radar & satellite shows mainly rain for the NE ski areas with snow on the colder side of the storm system. Also plan on thunderstorms and wind.

Valid 12/10. A powerful jet supports the area of low pressure, but the NE ski resorts are in the warm sector.

Forecast Radar & Satellite

Forecast Totals

CO Snow: 12/8, 12/10, 12/12, 12/14.

UT Snow: 12/7-12/8, 12/10.

WY Snow: 12/7-12/8, PM 12/9-12/10.

Tomer’s Take: The powerful WNW Flow delivered 40-50 inch grand totals to parts of UT and CO. The next storm system is already hitting the PNW/BC with heavy precipitation. It’s part of a strong intensity atmospheric river. This storm system and one behind it move through ID, MT, WY, UT and CO 12/7-12/11.

Grand Totals:

Alta: 49″

Rabbit Ears Pass: 41.5″

Solitude: 35″

Steamboat: 30″

Vail: 23″

Berthoud Pass: 19.5″

*There is one outlier. The Tower snotel (Buffalo Pass) in Colorado is showing over 5 inches of snow-water-equivalent (SWE). A 15:1 ratio suggests 78 inches of grand total snow.

Current Setup

Water vapor satellite shows the strong intensity atmospheric river hitting the PNW/BC. This storm will ride the jet into the Intermountain West 12/7-12/11.

White/Blue = moisture aloft

Red/Orange = drier air aloft

Forecast Atmospheric River

Forecast Integrated Vapor Transport next 7 days valid WA/OR coast at 46.5N/124W.

Forecast Jet Stream

Valid 12/6. Strong intensity AR for PNW/BC.

Valid 12/8. Notice the dip over WY/CO with area of low pressure.

Valid 12/13. Quiet period for Intermountain West with ridge of high pressure.

Forecast Radar & Satellite

Forecast Totals

WY Snow: 12/7-12/8, 12/10-12/12.

UT Snow: 12/7-12/8, 12/10-12/11.

CO Snow: 12/8-12/11.

ID Snow: 12/5-12/7, 12/10.

MT Snow: 12/7-12/12.

Most of this occurs on 12/4.

Storm system 12/10-12/11 is warmer with more rain than snow.

Tomer’s Take: WNW Flow continues to deliver snow in UT and CO through early 12/4 then drier. Light to moderate additional accumulation in ID, MT, WY. Brutally cold and windy above treeline in Colorado with 30-70mph gusts and single digit air temps. Then next storm system hits the Intermountain West 12/7-12/9. A strong intensity atmospheric river surge hits the PNW/BC 12/4-12/7 with copious amounts of valley rain and feet of higher elevation snow. Rainier could see 5 feet.

My forecast video:

Forecast Radar & Satellite

Forecast Totals

Remaining snow today/tonight, 12/3.

A more active period with 1-2 storm systems.

Bulk of snow arrives afternoon 12/3 through early 12/4.

*230pm 12/2 Update: Lull period for CO & UT then next big push of moisture/snow arrives tonight through 12/3.

Tomer’s Take: Snow continues in waves across the PNW, BC, ID, WY, UT, CO. The next big moisture push for UT and the C+N Colorado mountain zones arrives Saturday afternoon (12/2) through Sunday (12/3).

Looking down the road, another storm system arrives 12/8-12/11.

In Colorado on 12/2 and 12/3 expect increasing wind (30-60mph gusts) at ridgetop level and temps near zero or colder.

My PM forecast video:

Forecast Radar & Satellite

Forecast Totals

*Update 230pm 12/2.

Additional snow accumulation 12/2-12/4: