Refreshingly little change in the data today since our update yesterday. Models continue to show a strong winter storm moving through Northern Colorado Monday evening through midday Tuesday, bringing with it areas of heavy snow and wind.
Timing also looks about the same as yesterday. The National Weather Service has issued a Winter Storm Watch for Northeast Colorado beginning Monday evening and continuing through early Tuesday afternoon. Should no significant changes occur in thinking this afternoon, expect that Watch to be upgraded to a Warning ahead of tomorrow's storm.
We see rain and snow chances increase across Northern Colorado midday Monday, with about a 50% chance of rain and snow in Fort Collins by noon. Those chances climb to greater than 90% Monday evening, with a good chance of snow continuing well into Tuesday morning:
For Denver, the best chance of precipitation comes a bit later, likely around the evening commute Monday or shortly after that. As we noted yesterday, the best chance of heavy snow in Denver looks to come between 7 pm Monday, and 11 am Tuesday morning as timing looks today:
This will be a high impact event for much of Northern Colorado. For Denver, the boom and bust potential remains high, despite quite a bit of support for high-end snowfall totals in the city. The European model continues to hint at a track that could end up just about 50 miles or so too far north for Denver to see the heavier snowfall forecast by other models such as the GFS. It came south just a touch today, so we'll hedge our forecast a bit higher for the city than we were previously inclined to do.
For Denver, we'll start with 6 - 12" today and adjust tomorrow if needed. Depending on the eventual track of the low as it moves through Monday night, we could see forecast totals upwards of 1 foot in the city OR, have a hard time even hitting our 6" low end. There's not a lot of wiggle room here, only about 50 miles difference in the track. A shift farther south means more snow, a bit farther north less snow.
North of Denver, confidence is higher. The Front Range foothills and mountains west of Boulder/Loveland/Fort Collins could easily pick up a couple of feet of snow by Tuesday afternoon. The cities along the urban corridor and points east should manage 8 - 14" in most locations.
Finally, south of the Palmer, this storm looks less likely to have significant impacts. WIND will be a factor, and likely some snow, but the heaviest snow is expected to stay north.
Here is our forecast:
The Euro has been the holdout on heavier snow for Denver, especially its ensemble. This morning we saw its operational come a bit further south, again, it won't take much. Look at the 700mb forecast from yesterday (look for the circle over northeast Colorado) in the top map, then compare that to today's run in the bottom map. It's a touch further south, and more tightly wrapped –– and with that, we see more snow from this model in today's run:
If we look at its ensemble probabilities, we also see a shift south today (you'll recall they were pretty far north yesterday), but STILL, greatest odds are just north of Denver which is a big reason for our word of caution for those hoping for a BOOM in the city.
Here are the probabilities for 3" or more from the Euro:
And for 6" or more... telling that the Euro isn't totally convinced on this one yet, and why we reserve some caution:
And finally, here are our gamblers, full onboard with a heavy snow event for the northern urban corridor:
We stress impacts here on 5280, and with this system it'll be no different. Whether Denver ends up with 5" or 15", this will be an impactful storm. With lots of folks traveling this week for Thanksgiving, there are a few things you need to do.
1. If you are flying, you have to check your flight status with your airline. With a Winter Storm Watch in place and a likely upgrade to a Warning, airlines will likely be canceling flights. Don't be caught by surprise if your flight changes due to the storm.
2. If you are driving, you need to stay current with road conditions and possible closures. Also, if you are driving late Monday night or Tuesday, you need to have a plan B. That means altering the time that you are driving to avoid the worst weather, or taking an alternate route. Areas south of I-70 will likely not see as much snow with the storm. Thus, a likely better place to drive, versus along and north of I-70. If that is an option for you, then it is something to consider. Also, if you travel I-25 between Denver and Colorado Springs, it is possible that "The Gap" could be proactively closed before the storm gets too bad. CDOT has talked about doing this during prior storms, and while it is not a certainty that they will, you need to be prepared in case they do.
The worst combo of wind and snow will occur late Monday night through Tuesday and will be along and north of I-70. If you live in or have interests in that area, you will need to make sure your animals have food, water, and shelter.
Streets divisions and snow removal
This will be a busy storm for you all, particularly from Denver north to the state line. Snow removal crews, you’ll be in the thick of it for 12 to 16 hours, with potential to clear locations early Tuesday and again mid-Tuesday, with cleanup likely into Tuesday even for many locations as temperatures drop into the teens and single digits Tuesday night.