ForecastHistoric Arctic Outbreak Moves Out of Colorado; Patterns Turns Mild, But SnowyA powerful Arctic outbreak brought frigid temperatures, high winds, and snow to Colorado, but milder conditions are on tap by next week, with decent snow chances to end December.
- One of the most intense temperature drops on record for the area.
- Last night's snow generally underperformed in the mountains, but the Front Range urban corridor did well.
- Today, gusts of 70-100mph on the higher terrain, with wind chills well into the negatives.
- Warming into next week.
- Some chances for snow in the northern mountains and parts of the central mountains into Monday.
- The jet stream setup next week will advect warm, moist air into Colorado, which will set the stage for ongoing snow chances from mid next week and into the following week, favoring the western mountains.
- Otherwise, mild in the Front Range.
Temperatures and Winds
Denver's 75° change in temperature, from 51° to -24°, was its second largest on record and its one hour temperature drop of 37° was its largest recorded at the airport weather station.
The airport briefly hit -24° degrees this morning which was one degree shy of the December record. Other notable lows include -21° in Estes Park, -21° near Evergeen, -26° on the Laramie River, -21° in northern Colorado Springs, and -30° west of Cheyenne.
Right now, it's looking pretty miserable in the mountains. Many ski resorts and mountain passes are recording gusts of 70 to 95mph and a couple ski areas have declined to open today due to the negative temperatures + high winds amounting to dangerous wind chills.
Some people are having fun in some protected spots though :)
Conditions earlier this morning in much of the central and northern mountains were actually warmer than later this morning and as we get into the afternoon. Cold air is continuing to work its way into the mountains, and the temperature is dropping steadily while the winds remain fierce up high. Here are forecasted wind chills:
In previous forecasts we discussed the consistent downward tend in the weather models, but begrudgingly held onto a 5-10" forecast for many ski areas along and north of I-70.
Well, that was a mistake, as some of the latest snow forecast maps we had shared yesterday ended up verifying quite nicely. Many areas just didn't get the heavy banding of snowfall until later than expected (closer to midnight) and then only had a couple hours before the best moisture and dynamics pushed south.
Near Steamboat, lots of dry air entrainment as we had feared, but luckily we dropped the forecast to 3-8" to get ahead of it. In hindsight, 2-6" was the right call for most of those further north mountain ranges.
Along I-70, a decent showing near Winter Park but otherwise mainly 3-4", most of that falling near midnight and a couple hours after.
Further south, not much snow -- as expected -- but still only low end totals.
For the Front Range, forecast seemed pretty decent with generally 2-4" along I-25 and 6-7" for areas that got better banding. Boulder overperformed with a really nice band, this also brought heavy snow to Eldora so many reports of 8-10" along that corridor. Eldora had 14"+ on their snow stake cam!
Today to Monday
Another cold day today with highs not getting out of the negatives for some places.
Temperatures should be pretty steady, as night falls the coldest air will also be departing so the temperature wont really drop that much on the Front Range if at all.
As this system moves east, it will bring freezing temperatures are far south as New Orleans...
...and undergo explosive cyclogenesis over the northeast, creating blizzard-like conditions.
Right now it looks like the storm will just barely miss Chicago, DC, and other areas south of Michigan and New York, which is likely a relief for many people and a change from forecasts over the past few days that had the storm further south.
For Colorado, seeing a weak shortwave on the backside of this system tomorrow. Since the atmosphere is way too dry over northern Colorado this will probably only drive snow over the western San Juans, and not much of it. Expecting areas like Telluride, Durango, Cortez, and Farmington to see some snow from midnight to 10am tomorrow, but looking like only a couple inches at best tomorrow. This snow could end up as far north as Grand Junction and Powderhorn.
Moisture starts to advect into the state more consistently tomorrow. When we get another shortwave on Saturday, it should be able to drive more snowfall. Expecting another round of snow for the northern mountains (and parts of the central mountains) from 10pm Friday to Saturday noonish, up to 4-6" in spots but generally light (3" or less).
Then, another round Sunday evening. Best dynamics move in after 12am on Monday, and should wrap up Monday morning. Thinking by Monday morning, Friday night to Monday morning's accumulations will be something like 3-8" near Steamboat, 3-8" near Cameron Pass, 2-6" near Winter Park, and 1-5" for Summit and Eagle counties, very little elsewhere.
Something remarkable happens over the Pacific Ocean next week: flow aloft becomes almost completely zonal. This will act as a firehose blasting warm, moist air into the western United States.
No surprise then that next week's temperatures should be above average for much of the west, with mid 50s expected in Denver by mid next week.
Starting Wednesday we'll have lots of moisture in place, and the mountains should get some regular rounds of snowfall through the following weekend and into the next week.
Due to the westerly flow this snowfall favors the western mountain ranges, with some southwesterly moisture advection as well favoring the San Juans. Looking for the Park Range, Vail/BC, Aspen, Crested Butte, Silverton, and Wolf Creek to have some very nice totals by the end of next week.
Perhaps not as great for eastern Summit County and the Front Range mountains, but hard to say for sure at this point. Also, the overall flow regime wouldn't suggest much, if any snow, for the Front Range urban corridor and high plains -- mild conditions instead.
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