Tomer’s Take: Snow is sneaking through the Western Ridge 11/23-11/24 with a larger pattern change after 11/25.

• In the Northeast, a minor storm system slides through 11/25 with light snow accumulation. 2nd warmer storm system 11/27-11/28 is initially rain then changes over to snow. 3rd storm system 11/30-12/1 also starts as rain then changes over to snow.
• Out West, widespread heavy snow likely 11/27-12/1.

Current Setup

Two inches of new snow is reported at Jackson Hole this morning from the “sneaker low pressure”. This snow is headed for the Central and Northern Mountains of Colorado next.

Infrared satellite shows the low pressure sneaking through the Western Ridge. Large 2nd storm system helps usher in a pattern change later in the month.

Northeast Pattern

What was once a snowy outlook has flipped 180 degrees. A minor low slides through 11/25. Then two larger but warmer storm systems race on 11/27-11/28 and 11/30-12/1. Both start as rain.

Forecast jet stream valid 11/26.

Forecast total snowfall (inches) valid 11/23-11/29.

Western Pattern

Forecast jet stream valid 11/28 shows a large trough replacing the high pressure ridge. This pattern would support widespread snow and colder temps.

Forecast jet stream valid 12/1 continues to show an active pattern for the West.

Forecast Timing

Forecast radar/satellite valid 11/23-11/28.

Forecast Snowfall

Forecast snow totals (inches) valid 11/23-11/25.

Forecast snow totals (inches) valid 11/26-12/1.

My forecast video 11/23:

Tomer’s Take: Northeast storm system 11/25-11/26 trending much weaker with possible 2nd storm system 11/27-11/28.

• Northeast snow amounts continue trending lighter 11/25-11/26. Low pressure appears to be an open wave.
• Additional accumulation with 2nd storm system 11/27-11/28. This could be the stronger of the two storm systems.
• Larger pattern change for the West 11/25-12/1. Widespread snow and colder temps appear likely.

Current Setup

Infrared satellite shows two storm systems that degrade the high pressure ridge. The first low sneaks through 11/22-11/24. The 2nd low has a more a more profound effect across the West on/after 11/25.

Northeast Storm System

What a wild ride this forecast has been. The potential for a large storm system 11/25-11/26 is diminishing.

Forecast jet stream on 11/26. Note the initial storm system 11/25-11/26 is now merely an open wave. A second storm system might be more promising.

Forecast total snowfall (inches) valid 11/22-11/28.

Western Ridge Breaks Down

Forecast jet stream valid 11/29. Western ridge is replaced by a large trough with low pressure systems moving through. This would translate into widespread snow and colder temps.

Forecast Timing

Forecast radar/satellite valid 11/22-11/27.

Forecast Snowfall

Forecast snow totals (inches) valid 11/22-11/24.

Forecast snow totals (inches) valid 11/25-11/30.

My forecast video 11/22:

Tomer’s Take: Northeast storm system remains in question. Western ridge starts to weaken with moisture sneaking through on 11/22.

• Intensity and track of potential Northeast storm system remains uncertain with inconsistent data.
• Moisture breaks through Western ridge on 11/22.
• Larger pattern change 11/24-12/1 with trough replacing ridge and higher chances for snow.

Current Setup

Infrared satellite shows the Western ridge and next low pressure that will push moisture through the ridge into the PNW/BC.

Northeast Storm System?

Forecast jet stream valid 11/25 continues to show a large dip in the jet stream. What happens after this is still in question.

Snowfall forecast contrast: Yesterday (11/20) afternoon versus today (11/21). Talk about inconsistent data. Pull the slider back and forth:

Western Ridge Breaks Down

Forecast jet stream valid 11/29. The high pressure ridge is gone and replaced by a large trough. This would support colder air and widespread snow across CA, UT, CO, WY, ID MT, PNW, BC.

Forecast Timing

Forecast radar/satellite valid 11/21-11/26.

Forecast Snowfall

Forecast snow totals (inches) valid 11/21-11/23.

Forecast snow totals (inches) valid 11/24-11/29.

Tomer’s Take:

• A see-saw jet stream setting up East versus West through Thanksgiving (ridge West, trough East).
• Robust high pressure ridge over AK/BC/PNW is problematic through Thanksgiving keeping most of the West drier than normal.
• Out East, a strong storm system possible for Thanksgiving Weekend.
• When will the pattern flip? Possibly on/after 11/27. See below.

Current Setup

Infrared satellite shows the robust ridge over the PNW/BC/AK and ridge amplifiers to its West over the NPAC.

This also creates the see-saw jet pattern with large trough over the East.

Thanksgiving Pattern

High pressure remains strong through 11/24 with jet axis bending far north into Canada. This leaves most of the Rockies drier than normal.

Forecast jet flow valid 11/27. Now this is a different story with a breakdown of the ridge and lower atmospheric pressures plus a strong jet buckling south. This pattern would feed moisture into the PNW and interior Rockies.

East Coast Storm System?

Forecast jet stream valid 11/26 shows a large dip in the jet stream over the East/Northeast and powerful jet streak. Best snow with this setup occurs interior-north through NH, VT, ME. But, this is not set in stone and my feeling is the track and intensity are still a question mark.

Forecast Timing

Forecast radar/satellite valid 11/19-11/24.

Forecast Snowfall

Forecast snow totals (inches) valid 11/19-11/21.

Forecast snow totals (inches) valid 11/22-11/27.

Forecast snow totals (inches) valid 11/19-11/27.

My video forecast 11/19:

Tomer’s Take:

• Current fast N-S jet flow through MT, WY, CO gradually ends.
• Much drier pattern for West continues.
• Pattern shift for PNW/BC, MT, ID, WY on/after 11/21 but it’s not optimal.
• Jet axis bends even further north keeping most of the Rockies drier than normal.
• Eastern/Northeast: A larger Thanksgiving weekend storm system possible 11/25-11/27.

Current Setup

Infrared satellite shows the storm track, fast N-S jet flow with cold front, and robust PNW high pressure ridge.

Thanksgiving Pattern

Forecast jet stream flow on Thanksgiving 11/24 shows the shifting pattern with the jet axis bending far to the north. Some moisture feeds into the PNW/BC/Banff. The trend is for this bend to bend even further north keeping CA, UT, CO, NM drier.

Forecast jet stream flow on 11/26. The axis stays put with CA, UT, CO, NM staying dry.

Northeast Storm System?

Forecast jet stream flow valid 11/25 suggests a large dip supporting a developing area of low pressure. This is something to watch.

Forecast Timing

Forecast radar/satellite valid 11/18-11/23.

Forecast Snowfall

Forecast total snowfall (inches) valid 11/18-11/20.

Talk about an incredibly dry period with robust ridging over the PNW/BC.

Forecast total snowfall (inches) valid 11/21-11/26.

Even after a pattern shift on/after 11/21 the jet axis bends far to the north leaving most of the Rockies dry.

My forecast video 11/18:

Tomer’s Take:

• Fast N-S jet flow 11/17-11/18 delivers light snow accumulation to WY and CO and much colder air temps.
• In Colorado, moderate snow accumulation likely in the Foothills of Boulder and Larimer Counties with 5-10 inches of total accumulation.
• PNW/BC stay dry through 11/20 then pattern shifts on/after 11/21.
• Best snow on/after 11/21 favors PNW/BC/Banff and northern tier of the Rockies.
• Pattern does not immediately favor UT, CO, NM, CA but might in the longer term.
• Watching Thanksgiving weekend for possible East/Northeast coastal low.

Current Setup

Infrared satellite shows the storm track, robust Eastern Pacific high pressure ridge, and strong cold front racing through MT, WY, CO on a fast N-S jet.

Thanksgiving Pattern Shift

Forecast jet flow valid 11/18 shows the robust PNW high pressure ridge and fast N-S jet flow through MT, WY, CO.

Forecast jet flow valid 11/25 shows a complete pattern shift. A powerful jet stream has replaced the PNW high pressure ridge. The axis is so far north that the best snow favors PNW/BC and northern tier of the rockies.

Forecast Timing

Forecast radar/satellite valid 11/17-11/22.

Forecast Snowfall

Forecast snowfall totals (inches) valid 11/17-11/19.

In Colorado, moderate snow accumulation likely in the Foothills of Boulder and Larimer Counties with 5-10 inches of total accumulation. Eldora, Longs Peak, Cameron Pass, and the Indian Peaks all included.

Overnight lows into Friday morning reach -10 to -20F on the CO 13ers/14ers.

Forecast snowfall totals (inches) valid 11/20-11/25.

Tomer’s Take:

• No big storm cycles for the West until on/after 11/21.
• Current pattern includes high pressure ridge over PNW/BC/CA through 11/20. This is an anomalously strong Eastern Pacific high pressure ridge.
• Fast N-S jet flow favors Banff, MT, WY, CO, NM for light snow accumulation with cold fronts. Next front races north to south 11/16-11/18.
• On/after 11/21 the pattern shifts and precipitation returns to the PNW/BC, ID, MT, WY, UT, CO. Uncertain whether snow makes it further south into CA.

Current Setup

Infrared satellite shows the storm track and big players in the forecast. This pattern stays in place until 11/20 then changes on/after 11/21.

Of note is the strength of the high pressure ridge over the Eastern Pacific. It’s currently 3+ standard deviations above the norm.

Pattern Shift

Forecast jet stream flow valid 11/23 shows the high pressure ridge replaced by a powerful NW-SE jet stream.

Notice downstream effects in ID, WY, UT, and CO with WNW flow on/after 11/21.

Forecast Timing

Forecast radar/satellite 11/15-11/20.

Forecast Snowfall

Forecast snow totals (inches) valid 11/15-11/17.

Forecast snow totals (inches) valid 11/18-11/23.

My forecast video 11/15:

Tomer’s Take:

• PNW/Western BC/CA stay mostly dry through 11/20 with high pressure ridge.
• Then the pattern shifts on/after 11/21 as the high gets dislodged and lower pressures move into the PNW/BC with a powerful jet.
• Between 11/14-11/21 the Intermountain West stays active with fast-moving north to south cold fronts but only light snow accumulations. This favors Banff, MT, WY, CO, NM.

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My forecast video 11/14:

Current Setup

Infrared satellite shows the storm track, high pressure building into the PNW, and powerful low tracking into AK. This low will reinforce the high pressure ridge across the PNW/BC/CA through 11/20 before the pattern changes.

Pattern Change On/After 11-21

Forecast jet stream flow valid 11/16. Notice the high pressure ridge draped across CA/PNW/BC and fast N-S flow from Banff to MT to WY to CO.

Forecast jet stream valid 11/22. Notice the high pressure ridge is gone from the PNW/BC and is replaced with a powerful jet stream/streak. This would translate into precipitation for the PNW/Banff/BC.

Forecast Timing

Forecast radar/satellite valid 11/14-11/19.

Forecast Snowfall

Forecast snow totals (inches) valid 11/14-11/16.

Forecast snow totals (inches) valid 11/17-11/22. The PNW/BC/CA snow occurs on/after 11/21.