Colorado Weather

Forecast Summary

Forecast Posted at 12/07/23 8:00 pm by Seth Linden

 
Well 24 hours has passed since my last forecast and not much has changed in terms of model chaos for the approaching storm system. Still so much disagreement between the models at this hour.
 
They seem to be really struggling with the second wave (the western split in the trough) that is expected to drop into southern CO tomorrow evening….some of the models are further north (like GFS) and show a more progressive wave with more northwesterly downslope flow on the front-range. Other models like (ECMWF) are further south / deeper, a bit slower and show a good shot of northeasterly upslope along the front-range (and hence a good shot of snow for Den/Bou).
 
The forecast remains on track for most of the mountains but I did make some changes to my snowfall forecast map below. Lowered numbers for southern CO (all the lift is north of the jet-stream). I raised the numbers near Aspen/CB (looks like Elks will be favored with this event). I left the much of the north-central mountains / local ski areas unchanged.
 
The good thing is it is already snowing across western CO, near Vail, BC and Steamboat. Most of the more meaningful snow will be from 2am Fri to 2pm Sat. Still looking at generally 3-10″ of new snow with highest amounts west of Vail Pass.
 
For Den/Bou foothills and northern front-range initially just a few snow showers near the Palmer Divide tomorrow morning. Then best chance for snow will be from 8pm Friday to 5am Saturday (Trace-4″ in spots).
 
Best chances for >2″ will be from Denver south and east. With heaviest snowfall looks to be along the Palmer Divide (Castle Rock, Monument) and east towards Limon a good 4-8″ in those areas.
 
For the foothills its going to be very hit or miss. Some models show more snow in Denver than Evergreen (due to some northwesterly downslope flow). Generally best chances for more meaningful snowfall will be from Nederland south: 2-6″ in spots.
 
Looks like heaviest snowfall for the front-range may be near Woodland Park to Pikes Peak and northern parts of Colorado Springs possible >5″ in those areas as well.
 
Bottom line uncertainty remains high especially for the front-range (and you can clearly see that below between the different models).
 
Below I show my final snowfall forecast map along with total snowfall forecast through 5pm Sat from latest NAM (00z), HRRR (00z) and ECMWF (18z)

Latest Observations (Rain or Snow Reports)

Observations Posted at 12/04/23 8:00am by Seth Linden

 
 
Morning. It’s Monday. I put together some final 4-day snow totals below (pretty close to what we estimated yesterday with a bit more snow in spots, especially near Steamboat) So good to see generally 15-30″ across the north-central mountains, that is a great base! And there are unconfirmed reports that parts of the Park Range near Buff Pass and north picked up 50-60″ total in the last 4 days.
 
Second image shows 24-hour snow reports for the front-range and foothills. Third image shows 72-hour snowfall from NOHRSC (interpolated so can be off in spots, like near Vail). Fourth image shows current snow-depth across the mountains.
 
Anyway, with the northwest flow oriented jet-stream still over northern CO expecting strong wind today, especially over the Front Range mountains and foothills. Already wind-gusts of 40-60 mph in the foothills and adjacent mountains this morning. High-res models show strong wind continuing near the Cont. Divide with wind-gusts of 50-70 mph today (for areas near Berthoud Pass, IPW, RMNP, and towards Hoosier Pass, less wind west of Vail Pass).
 
For Den/Bou and the front-range urban corridor warm and windy today: westerly wind-gusts of 20-40 mph but temps getting towards 60 degs this afternoon…even warmer Tue-Thu
For this week ahead models show a big ridge of high pressure with dry and seasonably warm conditions across CO.
 
Looking ahead, next storm system arrives on Friday into Saturday. Snow returns to the north-central mountains by 5am Friday with snow likely from 5am Friday to 5am Saturday. Could be another 6-12″ by Sat morning (pow day maybe).
 
Also looks like a pretty good chance for Den/Bou and the front-range to get some snow from 11am-11pm Friday, could be several inches of snow in spots, details need to be worked out.

Additional Forecast Info (Longer Range)

Forecast Posted at 09/23/23 8:00pm by Seth Linden

 
Y’all ready for the 2023-2024 Seasonal Snowfall Forecast! Like all seasonal forecasts take it with a grain of salt because it can be ripe with error but I’ve been looking at the data and here is my best guess based on some analogs and current ENSO conditions (El Nino).
 
We are currently in El Nino conditions with a current Oceanic Nino Index (ONI) index of +1.1. Models show a moderate to strong El Nino peaking in Jan/Feb with an expected ONI of + 1.5 to 2.0.
 
I’ve been looking for some analog years, coming off a double to triple dip La Nina followed by a moderate to strong El Nino. Some of the years I have been looking at are: 1986-1987, 2009-2010, 2015-2016, 2002-2003, etc.
 
El Nino typically drives a more southern storm track over the U.S. during late fall, winter and spring. But impacts to CO in terms of above/below average precip and temperatures can vary widely from event to event and there is only a limited, statistical correlation with ENSO over much of CO…but still some signals that can be deduced.
 
In the 17 years of measuring snowfall at my house in Westminster a majority of the biggest snowfall events >15″ have occured during El Nino years and most of my biggest snowfall seasons have been during moderate to strong El Nino events. Think big upper-level lows that track across southern CO and produce upslope on the front-range (especially during the fall and spring). On the flip-side parts of the northern mountains / northwest CO typically get less snowfall (they need northwest flow), but it can vary from episode to episode.
 
Here is what I’m thinking in terms of above/below average snowfall and temps from October through April (so part of fall, winter and part of spring):
 
  • Northern Front Range (Den, Bou, Ft. Collins, foothills): Above average snowfall. Near to below average temps.
  • Southern Front Range (C. Springs, Pueblo, etc): Above average snowfall. Near to below average temps.
  • Front Range Mountains (Cameron Pass, RMNP, IPW, Winter Park, Loveland, Grays/Torreys/Evans): Near to above average snowfall. Near average temps
  • North-Central mountains near Summit Co (A-Basin, Keystone, Copper, Breck, Hoosier Pass): Average snowfall. Near to above average temps.
  • Central mountains, Gore, Elks, Sawatch (Vail, BC, Aspen, CB, Grand Mesa, etc): Near to below average snowfall. Near to above average temps.
  • Northwest mountains (Steamboat, Park Range, Rabbit Ears, Flat Tops): Below average snowfall. Near to above average temps.
  • Southwest mountains, western and eastern San Juans (Telluride, Silverton, Wolf Creek): Near to above average snowfall. Above average temps.
  • San Luis Valley / Sangre De Cristos: Near to above average snowfall. Above average temps.
  • Western Slope (Grand Junction, Fruita): Near average snowfall. Near to above average temps
  • Northeastern Plains (Sterling, Ft. Morgan, Limon etc): Near to above average snowfall. Near to below average temps.
  • Southeast Plains (Lamar, La Junta, Springfield, etc): Near to above average snowfall. Near to below average temps.
 
The precip anomaly slides in image 4 are from a great web site that Meteorologist Jan Null (of Golden Gate Weather Services) put together. He is somewhat of an ENSO expert and has some great info (I’ll link to it in comments).
 
I’ll leave you with this from Jan Null: “It is extremely important to note that ENSO is not the only large scale climatological phenomena that impacts the world’s weather. ENSO’s impact in any given year is dependent on not only its strength but also on the location and extent of the event along the Equator in the Eastern Pacific Ocean. It’s also a function of ENSO’s interaction with the whole “alphabet-soup” of other Indices and Oscillations; such as the PDO (Pacific Decadel Oscillation), NAO (North Atlantic Oscillation), (AO) Arctic Oscilation (AO), (MJO) Madden-Julian Oscillation and others.”
 
First image is my seasonal snowfall forecast (subject to change some). The second image is from Brian Brettschneider and shows percent of average snowfall during moderate to strong El Nino events. Third image is also from Brian Brettschneider and shows the number of El Nino years with above average temps by county (yellow is warm and blue is cold). Fourth image shows winter (Dec-Feb) precip anomalies during some moderate to strong El Nino events just to show example of how much it can vary from episode to episode.

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Colorado High Wind Warning

High Wind Warning
...high Wind Warning Remains In Effect From 5 Am To 5 Pm Mst Sunday... * What...west Winds 35 To 45 Mph With Gusts Up To 80 Mph Expected. * Where...rocky Mountain National Park And The Medicine Bow Range, The Mountains Of Summit County, The Mosquito Range, And The Indian Peaks, The Northern Front Range Foothills, And The Southern Front ...Read More.
Effective: December 10, 2023 at 5:00amExpires: December 10, 2023 at 5:00pmTarget Area: Jefferson and West Douglas Counties Above 6000 Feet, Gilpin, Clear Creek, Northeast Park Counties Below 9000 Feet; Larimer and Boulder Counties Between 6000 and 9000 Feet; South and East Jackson, Larimer, North and Northeast Grand, Northwest Boulder Counties Above 9000 Feet; South and Southeast Grand, West Central and Southwest Boulder, Gilpin, Clear Creek, Summit, North and West Park Counties Above 9000 Feet

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3 thoughts on “Colorado Weather”

  2. Love this option. Especially when traveling across the state(s). Thanks, Seth!

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