Tomer’s Take: A panhandle hooker storm system continues to slide through CO/NM then it becomes a Northeast storm system. The Western pattern then shifts. The jet moves north and higher pressures build across the Pacific and West Coast. Two additional storm systems might deliver big totals to the Northeast on 1/22-1/23 and 1/24-1/25.

Wolf Creek, CO is reporting another 16 inches in 24 hours and 52 inches in 4 days.

A note on Mammoth Mountain. Their season total measured at the Main Lodge is 378″ with of course more at the summit.

My forecast video 1/18:

Current Setup

Forecast Pattern

Forecast jet stream valid 1/27. Notice the high pressure ridge over CA and parts of the Pacific. The storm track runs into the PNW, BC, MT, WY, CO.

Early February Pattern

Below is the EPS forecast atmospheric pressure anomalies (mid atmosphere) valid 2/1/2023.

The pattern continues to favor the West/PNW/Northern tier for snow and cold.

Forecast Timing

Forecast radar/satellite valid 1/18-1/23.

Forecast Totals

Forecast snow totals (inches) valid 1/18-1/20.

Forecast snow totals (inches) valid 1/21-1/27.

Forecast snow totals (inches) valid 1/18-1/27. Three total storm systems possible. 1) 1/19-1/20, 2) 1/22-1/23, 3) 1/24-1/25.

Tomer’s Take: A major low pressure (last of the atmospheric river) slides through UT/AZ/CO/NM next 24 hours with big totals. Then, the pattern shifts north with high pressure ridging over the Pacific Ocean and West Coast. The jet takes a NW orientation favoring PNW/BC/ID/MT/UT/WY/CO. By February 1, a trough might establish itself across the entire West with snow and cold.

Alta, UT is reporting 20 inches in the last 24 hours. That’s a 4-day total of 49 inches = about a foot a day. 423 inches for the season so far where they’re “Rolling in the Deep”.

Mammoth Mountain is reporting 11 inches in the last 24 hours. 378 inches for the season so far.

Season Totals So Far:

My forecast video 1/17:

Current Setup

Visible satellite shows a split jet with leftover AR moisture and a southern track low. It becomes a Panhandle Hooker storm system for CO/NM.

Forecast Pattern

Forecast jet stream valid 1/25. Notice the high pressure ridging off the West Coast and PNW. This flow favors Banff, MT, WY, northern UT, and the Central and Northern Mountains of CO.

February 1

Below is the EPS forecast atmospheric pressure anomalies (middle atmosphere) for late 1/31.

The high pressure ridge drifts West and a trough develops across the West. This type of pattern supports snow across the West.

Forecast Timing

Forecast radar/satellite valid 1/17-1/22.

Forecast Totals

Forecast snow totals (inches) valid 1/17-1/19.

Forecast snow totals (inches) valid 1/20-1/26. Notice the NW orientation of the snowfall/storm track.

Forecast snow totals (inches) valid 1/17-1/26. Central and Northern Mountains of Colorado:

Forecast snow totals (inches) valid 1/17-1/26. Most of this snow falls 1/19-1/20 and 1/22-1/23.

Tomer’s Take: The final storm system loaded with atmospheric river (AR) moisture is moving through CA. It’s a southern track low headed for AZ, NM, UT, and CO with moderate to heavy snow accumulation. What happens after this? Higher atmospheric pressures build across the Pacific/West Coast pushing the jet stream north where it favors the PNW, BC, ID, MT, Banff, WY, UT, and CO via a northwest flow type orientation.

Alta, UT is reporting another 15 inches in the last 24 hours. That’s 399 inches for the season so far. I’m forecasting another 11″ in the next 48 hours.

My forecast video 1/16:

Current Setup

Water vapor satellite shows the final area of low pressure and Pineapple Express.

Forecast Pattern

Forecast jet stream valid 1/25. Notice the high pressure ridging over the Pacific and NW orientation to the flow out of the PNW.

Late January/Early February

The EPS forecast atmospheric pressure anomalies (in the middle of the atmosphere) by late January 30 show the high pressure ridging gone and lower anomalies across the West. This would translate into a stormy pattern for the West by early February.

Forecast Timing

Forecast radar/satellite valid 1/16-1/21.

Forecast Totals

Forecast snow totals (inches) valid 1/16-1/18. This is the final AR period.

Forecast snow totals (inches) valid 1/19-1/25.

Forecast snow totals (inches) valid 1/16-1/25.

Tomer’s Take: The final atmospheric river (AR) surge is underway with big totals across the West. What happens after? A transition occurs with a high pressure ridge building.

My forecast video 1/13:

Current Setup

Infrared satellite shows the Pineapple Express and remaining two areas of low pressure.

Forecast Pattern

Forecast jet stream valid 1/22. Notice the amplitude and high pressure ridging across the West Coast.

Late January

Below is the EPS forecast atmospheric pressure anomalies in the middle of the atmosphere valid late 1/27. This forecast pattern has remained consistent the last few days.

If this occurs, then a drier period is likely for parts of the West.

There is disagreement in this pattern. The GFS/GEFS forecast model(s) doesn’t develop this large ridge. It keeps the PNA negative throughout late January. If that occurs then the pattern remains active for the Intermountain West.

What happens after 1/28? I believe the pattern turns more active for the West in February.

ENSO

La Nina is fading. The next stop is Neutral then data points towards El Nino by Summer and Fall.

Forecast Timing

Forecast radar/satellite valid 1/13-1/18.

Forecast Totals

Forecast snow totals valid 1/13-1/15.

Forecast snow totals (inches) valid 1/16-1/22.

Forecast snow totals (inches) valid 1/13-1/22. Most of this occurs 1/19-1/20.

Tomer’s Take: One more large atmospheric river (AR) surge occurs through 1/17 then the pattern shifts through late January with high pressure ridging.

My forecast video 1/12:

Mammoth Mountain is crystal clear this morning after about 7.5 feet of snow in the last few days. I’m forecasting another 2-3 feet with the next AR surge. They’re reporting 330 inches for the season so far. That’s just behind Alta (370″), Brighton (355″), and Snowbird (351″).

Current Setup

Infrared satellite shows two low pressure systems remaining with Pineapple Express moisture.

Forecast Pattern

Forecast jet stream valid 1/21. The 15-day AR pattern is gone. It’s replaced by an amplified jet stream and building high pressure ridge.

Late January Pattern

Below is the EPS forecast atmospheric pressure anomalies for the middle of the atmosphere valid late 1/26. It shows a high likelihood of high pressure ridging off the West Coast – especially the Gulf of Alaska/British Columbia Coast.

Forecast Timing

Forecast radar/satellite valid 1/12-1/17.

Forecast Totals

Forecast snow totals (inches) valid 1/12-1/14.

Forecast snow totals (inches) valid 1/15-1/21.

Forecast snow totals (inches) valid 1/12-1/21. 90% of this falls on 1/19-1/20.

Tomer’s Take: 1-2 additional atmospheric river surges are likely through 1/17 then it fades. A high pressure ridge is possible across the West on/after 1/22, but some places might actually be favored for snowfall.

Snowbird, UT is reporting 36 inches in 48 hours.

Mammoth Mountain, CA is reporting 72 inches in 72 hours.

My afternoon update forecast video:

Season To Date

Current Setup

Infrared satellite shows the Pineapple Express and two additional areas of low pressure over the Pacific. They represent the final pieces of this incredible 15 day atmospheric river.

Forecast Pattern

Forecast jet stream valid 1/20. A West Coast ridge is starting to develop. But, that could deliver snow to MT, WY, UT, CO.

Late January

Below is a look at EPS atmospheric pressure anomalies in the middle of the atmosphere. Notice the West Coast Ridge.

Forecast Timing

Forecast radar/satellite valid 1/11-1/16.

Forecast Totals

Forecast snow totals (inches) valid 1/11-1/13.

Forecast snow totals (inches) valid 1/14-1/20.

Forecast snow totals (inches) valid 1/12-1/20. Snow to rain is likely 1/13-1/14. A colder, more potent storm systems is possible 1/19-1/20. That’s when 90% of this accumulation occurs.

Tomer’s Take: Feet of snow accumulation continues in CA with a moderate to strong intensity atmospheric river (AR) surge through 1/10. The next surge occurs 1/14-1/17. Snow from both AR’s hit UT, WY, ID, CO.

My afternoon mountain weather update video with new numbers:

Mammoth Mountain is reporting 31-46 inches of new snow. Additional snow accumulation likely today.

Current Setup

Infrared satellite shows the current storm system hitting CA and the final storm system lined-up in the Pacific for 1/14-1/17.

Forecast Pattern

Forecast jet stream valid 1/19. In the wake of the 10-15 day AR pattern we’re left with a split jet, which redirects storm systems to the PNW.

Atmospheric River

Below is the ECMWF IVT 15-day forecast by latitude. IVT continues until 1/17 then the flow dries up.

Forecast Timing

Forecast radar/satellite valid 1/10-1/15.

Forecast Totals

Forecast snow totals (inches) valid 1/10-1/12.

Forecast snow totals (inches) valid 1/13-1/19. The final AR surge delivers nice snow totals to the interior Rockies.

Forecast snow totals (inches) valid 1/10-1/19.

Tomer’s Take: The atmospheric river (AR) continues through 1/16 then fades. The next two AR surges deliver feet of snow to the West.

Heavy snow continues in the Sierra through 1/10 with a moderate to strong AR surge. Snow levels run abnormally high on 1/9 then gradually fall. Mammoth Mountain is reporting 14-18 inches of new snow.

Kirkwood is reporting 11″ in the last 24 hours and 55 inches in the last 7 days.

Mount Rose is reporting 14-18″ storm total so far.

Current Setup

Infrared satellite shows a busy Pacific with 3 different storm systems lined-up and Pineapple Express.

Forecast Pattern

Forecast jet stream valid 1/18. The pattern shifts to a split jet. This is a very different pattern than during the heart of the AR.

Atmospheric River

Below is the ECMWF IVT 15-day forecast by latitude. Moisture transport fades after 1/16.

Forecast Timing

Forecast radar/satellite valid 1/9-1/14.

Forecast Totals

Forecast snow totals (inches) valid 1/9-1/11.

Forecast snow totals (inches) valid 1/12-1/18.

Forecast Grand Totals:

Mount Shasta: 80″

Heavenly: 70″

Mammoth: 84″

Alta, UT: 50″

Wolf Creek, CO: 27″

Steamboat, CO: 25″

Jackson Hole: 26″

Snow timeline for the Wasatch:

1/9: 6″

1/10: 12″

1/11: 6″

1/12: 0″

1/13: 0″

1/14: 1″

1/15: 10″

1/16: 6″

1/17: 6″

1/18: 4″

Forecast snow totals (inches) valid 1/9-1/18. Most of this snow occurs 1/12-1/15. Precipitation changes to rain on 1/13 then back to snow.

Tomer’s Take: The atmospheric river (AR) runs through 1/16 then fades to zero. I’m forecasting big snow totals in CA, PNW, BC, parts of ID, parts of MT, WY, UT, and the Western Slope of CO.

My forecast video 1/8:

Current Setup

Water vapor satellite shows the Pineapple Express flow and remaining areas of low pressure.

Atmospheric River

Below is the ECMWF IVT forecast by latitude. Another two surges are lined-up through 1/16. Then the moisture fades and the jet configuration changes.

Forecast Pattern

Forecast jet stream valid 1/17. It’s a different jet configuration versus the last 10-15 days. The jet is split.

Forecast Timing

Forecast radar/satellite valid 1/8-1/13.

Forecast Totals

Forecast snow totals (inches) valid 1/8-1/10.

Forecast snow totals (inches) valid 1/11-1/17.

Forecast snow totals (inches) valid 1/8-1/17.

Tomer’s Take: I’m forecasting 3-4 additional atmospheric river (AR) surges through 1/16. Sierra snow levels will run abnormally high with the biggest accumulation above 7,000ft.

My forecast video 1/7:

Current Setup

Water vapor satellite shows the Pineapple Express and low pressure systems lined-up through 1/16.

Forecast Pattern

Forecast jet stream valid 1/9. This is a moderate to strong intensity AR surge plus deep trough.

Forecast jet stream valid 1/16. Any additional AR contribution is weak and fading.

Forecast Timing

Forecast radar/satellite valid 1/7-1/12.

Forecast Totals

Forecast snow totals valid 1/7-1/9.

Forecast snow totals valid 1/10-1/16.

Forecast snow totals valid 1/7-1/16.