Pattern change remains possible on/after 10/23 across the West.
Beneficiaries: CO, UT, WY, ID, MT, PNW, Banff.
Lower atmospheric pressures replace high pressure ridge.
Snow and colder temps = net result.
If this verifies it would be the first significant snowfall of the season for much of the Intermountain West.
Current Setup
Infrared satellite shows the dominant high pressure ridge across the West. Notice the train of low pressure systems further West including the larger low rotating through Alaska. That is the start of what will gradually break down/dislodge the big high.
Infrared satellite 8:20am 10/15/2022.
Pattern Flip
Forecast mid-atmospheric pressure data suggests a complete pattern change on/after 10/23 through 10/27.
Forecast mid-atmospheric pressure anomalies valid 10/23/2022, Euro interpretation.
Some additional variety looking down the road. The Pacific North American Pattern (PNA) turns negative on/after 10/23 suggesting a pressure change across the West. The signal has been inconsistent on the Global Forecast System but is now back to negative.
Forecast PNA, GEFS interpretation.
Forecast
The Global Forecast System has been inconsistent the last few days but has now flipped back to optimistic for snowfall on/after 10/23. Questions remain – such as how deep will the trough go? Where is the axis? How much cold air? How strong of a jet stream? And of course, duration.
Forecast total snowfall by 10/25/2022, GFS interpretation.
Another perspective with different guidance. Snow possible on/after 10/23 through 10/27. Again, if this verifies it would be first significant snowfall for much of the Intermountain West.
Forecast total snowfall between 10/23-10/27, EPS interpretation.
A large Western ridge of high pressure remains in control through 10/22.
A pattern change is possible on/after 10/23.
A large dip in the jet stream and lower atmospheric pressures might replace the large Western high pressure ridge.
This pattern change might run 10/23-10/27.
Net result: snow and colder temps for UT, CO, WY, MT, ID, Banff, and the PNW.
The strongest La Nina since 2010 remains in control.
Current Setup
You’re looking at the key to the potential pattern change on 10/23. Notice the trio of low pressure systems. They will set the stage for the weakening/dislodging of the big Western high. They will not act alone.
Water vapor satellite 10am 10/12/2022.
Current mid-atmosphere pressure pattern:
Current mid-atmospheric pressure pattern 10/12/2022.
Loveland Ski Area started making snow Wednesday morning 10/12/2022.
Parker the Snow Dog was there supervising:
Parker the Snow Dog, Loveland Ski Area, Photo Dustin Schaefer.
Arapahoe Basin also started making snow. See their update here.
Alta, Utah October 2021
October generated 67″ of total snow.
Average October snowfall is 28.5″.
Snow started falling after October 7, 2021.
The view at Alta on October 13, 2021 with 14″ storm totals:
Alta, UT, 10/13/2021.
La Nina Holding Strong
The latest (10/6/2022) Multivariate ENSO Index continues to indicate the strongest La Nina since 2010 at -1.8. This is a triple-dip La Nina.
This has created three straight Fall Seasons with abnormally warm and dry conditions across the West.
Significant snow in Colorado appeared likely based on data a few days ago. Now, that possibility has vanished.
Why? It goes to what I talked about in my Winter Forecast: The North Pacific Heat Wave.
This warmer than normal ocean water tends to anchor a large dome of high pressure over the PNW/West Coast. This in turn affects the jet stream and eventually Colorado’s snow chances.
Current Setup
The West Coast high pressure ridge is significant running 2-3 standard deviations above the 20-year average. Water vapor satellite shows the pattern. Orange/red = drier air aloft.
Water vapor satellite 10/7/2022 5:45am.
Taos had some nice early season snow at higher elevations on 10/5-10/6. Taos could see additional light snow late 10/7 into early 10/8.
Photographer Larry Pierce snapped this photo in the Flat Tops on 10/4.
Flat Tops, CO, Larry Pierce, 10/4/2022.
Silverton Mountain in Colorado continued a year tradition with early season skiing at high elevations on 10/2.
Silverton Mountain, CO, 10/2/2022.
Forecast
The mid-atmosphere pressure pattern through 10/16 suggests the West Coast high pressure ridge maintains its dominance. This effectively limits snowfall in Colorado’s mountains to the light accumulation category. The Front Range of Colorado would stand a better chance at getting hit with fast moving cold fronts.
500mb pressure anomalies valid 10/16/2022, Euro interpretation.
Forecast total snowfall through 10/16. Only light snow accumulation in Colorado’s mountains.
Forecast total snowfall through 10/16, GFS interpretation.
A series of cold fronts deliver colder air and snow accumulation above treeline Friday, Saturday, and Sunday in Colorado.
Below treeline precipitation stays rain.
Snow accumulation is possible in all mountain zones above treeline.
Some of the biggest totals might occur in the San Juan Mountains.
Air temps in the mountains will gradually drop each day.
Monday-Tuesday (10/3-10/4) look even colder with continuing snow chances.
10/1 Update: October snow! Loveland Pass–>
October 1, 2022 snow on Loveland Pass.
Current Setup
Water vapor satellite shows a low pressure system and cold front sliding through Utah, Wyoming and into Colorado. Red/orange = drier air aloft.
Water vapor satellite 9/30/2022 11:15am.
Mountain Forecast
Atmospheric moisture this weekend will be running high. Rain is likely at lower elevations with snow above treeline. Here’s humidity mid-troposphere valid 10/1-10/2.
Humidity mid troposphere, Euro interpretation valid 10/1-10/2.
Monarch Pass and Above
Snow Chance
AM
PM
9/30
Dry
50%
10/1
30%
80%
10/2
20%
80%
10/3
Dry
70%
Snow chances on Monarch Pass and Above.
How much accumulation? Possibly 1-2″ each afternoon/night above treeline.
Mount Sneffels and Above
Snow Chance
AM
PM
9/30
Dry
20%
10/1
60%
100%
10/2
100%
100%
10/3
10%
100%
Snow chances on Mount Sneffels and Above.
How much accumulation? Possibly 2-4 inches each day above treeline.
Total weekend snowfall is shown below according to the NAM model. It’s optimistic with accumulation and believes almost 18 inches is possible on the 13ers/14ers.
Total snowfall 9/30-10/2, NAM model interpretation.
The mid-atmosphere pressure pattern favors the Pacific Northwest/West Coast for above normal precipitation. In Colorado, we’ll get leftovers with high pressure regulating most days.
October middle atmosphere pressure pattern.
Snow Forecast
Forecast October grand totals are below. Best accumulation is at higher elevations in these locations. Normally, this snow falls then melts except on the higher peaks. Also, strong wind starts kicking-in with these stormy periods.
Forecast
Inches
Loveland
12
Wolf Creek
12
Steamboat/Werner
12
Collegiate Peaks
10
Aspen/Snowmass
13
Winter Park
12
Mount Elbert
13
Monarch Pass
6
Telluride
8
Fall Color Update
Peak Fall Color is running behind schedule in Colorado. Parts of the mountains saw a robust Monsoon season.
Jennifer Broome snapped this photo on 9/22 in Vail:
Vail 9/22/2022, Jennifer Broome.
Some zones like Grand Lake, Berthoud Pass, RMNP, and the Northern Mountains are further along.
John Williams snapped these photos between 9/21-9/22:
Grand Lake 9/21/2022, John Williams. Berthoud Pass 9/22/2022, John Williams.
Abnormally warm and dry Fall season across the West.
Late start to Winter.
Large Western ridge of high pressure September 2022 – March 2023.
Overall, target PNW, British Columbia, Banff Area, Wyoming, Idaho, and Montana for most consistent winter snowfall.
Two big unknowns: Warm SST’s North Pacific and underestimation of La Nina strength this Fall and early Winter. Both could complicate the Winter storm track and snowfall pattern(s).
Winter Forecast Video
Video contains my entire forecast.
Triple-dip La Nina
What is La Nina? Colder than normal (-0.5C or colder) sea surface temperatures in the Equatorial South Pacific (see graphic below). El Nino is the opposite (+0.5C or warmer). Both anomalies have global implications on weather and climate.
Currently, sea surface temperatures near the equator are running colder than normal for the third straight year. Triple-dip La Nina’s are rare only occurring three times in the last 73 years.
Sea surface temperature 28-day anomalies.
Here’s the global sea surface temperature anomalies valid 8/29/2022. Red/orange = above normal. Blue = below normal.
Notice the sea surface heat wave in the North Pacific and North Atlantic.
Global sea surface temperature anomalies valid 8/29/2022.
The Multivariate ENSO Index (MEI) factors in five different variables and assigns a value. It’s currently the strongest (coldest, negative) value since 2010. It says this dip is the strongest of the three dips so far.
The five variables MEI incorporates: (sea level pressure (SLP), sea surface temperature (SST), zonal and meridional components of the surface wind, and outgoing longwave radiation (OLR)) over the tropical Pacific basin (30°S-30°N and 100°E-70°W)
Strongest triple-dip La Nina since 2010:
Strongest triple-dip La Nina since 2010 (MEI value).
Warm Blob
Sea surface temperatures are abnormally warm in the North Pacific (off the PNW/B.C. coast and California coast). This directly affects the storm track and precipitation patterns. Will this continue all winter?
28-day sea surface temperature anomalies.
This is where important uncertainty remains in the forecast.
I believe the water off the PNW coast stays abnormally warm through November then cools-off in December. Some forecast data suggest this water does not cool-off and the PNW stays abnormally dry.
The result: warm and dry across most of the Intermountain West through November then snowier/colder weather settles in December-March.
I believe the water off the California coast stays abnormally warm the entire winter. The result: warmer and drier than normal winter.
Warm and Dry Fall Season
Most of the Intermountain West is in for an abnormally warm and dry September, October, and November. It will mirror the last few years with a large Western ridge of high pressure.
Said another way, it’ll be a late start to winter.
The most consistent snow and cold temps arrive in December as the jet stream finally dips south.
Forecast
I agree with the official NOAA ENSO forecast, which maintains high chances for La Nina through Fall (blue bars) then it fades in January 2023 to Neutral phase (gray bars).
Important note: It’s possible some forecast data is underestimating the strength of La Nina this Fall and early Winter.
NOAA ENSO probabilities.
The latest ensemble forecast spread from the Climate Forecast System shows a strong Fall La Nina that fades early 2023.
Remnants from Typhoon Merbok to bring 50ft seas and 70mph wind gusts to Alaska.
In Colorado, remnants from Kay and a jet streak keep rain/snow and gusty wind going in the Central and Northern Mountain zones 9/15-9/17.
Pikes Peak Ascent/Marathon and Run Rabbit Run events occur this weekend.
Current Setup
Water vapor satellite shows the remnant tropical moisture continuing to influence Colorado as winds turn counterclockwise around the low. Orange/red = drier air aloft.
Water vapor satellite 9/15 6:20am.
Merbok
The track Typhoon Merbok’s remnants is noteworthy. Talk about a recurvature.
Impacts: 50ft swells and 70mph wind gusts. Impressive forecast graphics from the GFS valid 9/16-9/17.
On Denali, it’s more of a glancing blow with outer bands from Merbok. I’m forecasting 90mph gusts and snow.
Remnant tropical moisture slides across Colorado 9/14-9/15. Flash flooding possible.
Light snow on the 14ers on 9/14, 1-3 inches.
Lingering moisture with a jet streak on 9/16 and 9/17 north of I-70.
Jet streak appears weaker today with only a glancing blow to Colorado.
Drier, sunny, and gusty on 9/18.
Pikes Peak Ascent and Marathon, and Run Rabbit Run take place this weekend.
Current Setup
Water vapor satellite shows the tropical remnants (of Kay) crossing Utah and rolling into Colorado. Orange/red colors = drier air aloft.
Water vapor satellite 9/14/2022 6am.
It’s a wet morning in Western/Southwest Colorado including Telluride. Light snow possible on the Wilson Group.
Telluride live cam 9/14/2022 6:30am.
Telluride Regional Airport:
Telluride Regional Airport.
Snow forecast next 24 hours (9/14-9/15). Light accumulations in blue.
Snow forecast 9/14-9/15.
Flash Flood Potential
Flash flooding is possible on 9/14 with this remnant tropical moisture.
Excessive rain potential valid 9/14/2022.
Forecast
Friday 9/16 holds the highest percentage chance for morning and afternoon rain showers. A notch drier on Saturday 9/17. Significantly drier on Sunday 9/18 but gusty.
Forecast mid atmosphere relative humidity valid 9/16, Euro intepretation.
Pikes Peak
PP
AM
PM
Gusts
9/16
Dry
30%
15-35
9/17
Dry
Dry
20-35
9/18
Dry
Dry
30-40
Run Rabbit Run
RRR
AM
PM
Gusts
9/16
20%
80%
10-30
9/17
20%
50%
10-30
9/18
Dry
Dry
10-30
Loveland Testing Snow Guns
Loveland Ski Area says snowmaking could start in 16 days. Last year, Loveland officially opened on October 30.
Mayor Parker the Snow Dog, Photo Dustin Schaefer.Testing the Snow Guns, Photo Dustin Schaefer.
