12:35 PM MST, Thursday, February 28, 2019
Cold front #1 late Friday will start the colder trend. Cold front #2 on Saturday afternoon and early evening will bring in a bitterly cold arctic air mass. Snow in the eastern foothills and plains could occur at any time from Friday evening through Sunday morning, but it appears that late Saturday may bring the best chance for significant accumulations.
Eastern foothills and plains, including the urban corridor:
Friday evening and overnight will bring the first chance, but this is looking fairly minor and spotty. There may be an east-west band that can produce a couple of inches, but if that happens it will most likely be north of the Denver-Boulder area.
Saturday into early Sunday is forecast to bring a better chance of significant snow, with 4-8 inches from the Palmer Divide northward (probably a little less in Colorado Springs). Snow will likely be underway in southeastern Wyoming during the morning Saturday, and then spread north to south along the Colorado Front Range Saturday afternoon. Some east-west bands (aligned with the jet stream) may propagate north-to-south resulting in occasional heavy snowfall rates. Although the heaviest snow may end up near the foothills, the chance for blowing & drifting snow increases as you go east.
The Pacific moisture helping to feed the Front Range snow will bring some heavy snow to the mountains and west-facing slopes first, especially on Friday. Over a foot is likely in parts of Colorado’s northern and central mountains, and Wyoming’s Medicine Bow range.
Friday should start mild but colder air should be working it’s way in from the northeast during the afternoon. Saturday may still reach the 30s along the Colorado Front Range urban corridor but fall during the afternoon with the arctic front. Then, temperatures are likely to tumble into the singles digits Saturday night, only get to the teens Sunday, and if skies clear, there may be widespread readings near or a little below zero on Monday morning.
The record low maximum temperature for Sunday is 15 in Boulder and 14 in Denver.
The record low for Monday morning is -1 in Boulder and -3 in Denver.
All of the above records were set in 1978 and could be within reach.
6:20 AM MST, Wednesday, February 27, 2019
An arctic air mass is expected to arrive Friday evening and be with us through the weekend. Daytime temperatures within the Front Range urban corridor may struggle to reach 20, and there will likely be at least one night with widespread readings slipping below zero.
Snow is likely, perhaps a couple periods of snow, from Friday evening until Sunday morning. The details of that are still uncertain but the potential does exist for a widespread 3-6″ snowfall over a 2-day period. More details will follow on that.
The main point of this blog is to inform you that after mild weather Thursday (and maybe Friday morning), you should be prepared for a cold weekend with wintry travel conditions.
1PM MST, Friday, February 22, 2019
In yesterday’s forecast blog I mentioned that the wildcard in the forecast was the chance for southwest-to-northeast oriented bands of heavier snow this evening in the overall light snow event. I don’t think that is wildcard anymore. It appears likely that there will be bands of snow causing several hours of moderate or heavy snowfall rates starting around the evening commute.
Accumulations may be on the order of 5-8″ under those bands while at the same time there may only be an inch or less a short distance away. Current mesoscale models suggest that the Denver area may get under one of those bands, mainly the south and east sides. But the position may change and there may be more than one band. Prepare for fast changing conditions over short distance. And remember that this is not a typical upslope, so the heavier snow could be away from the foothills.
2PM MST, Thursday, February 21, 2019
A large storm system to the southwest of Colorado will pass well south of the Front Range region, but close enough to have some impacts. Over an extended period from this evening through Friday evening the may be one or two periods of mainly light snow or fog, along with lull periods when the clouds might thin a bit.
Accumulations from the foothills eastward will generally be on the minor side, a dusting to 2 inches through Friday night. The one wildcard is that a band of more moderate snow may develop (southwest to northeast oriented) that could produce 2-4 inches over a small area (about 10 miles wide) in a few hours. If that happens it appears most likely late Friday. But for most of the Front Range region the accumulations will probably be less than 2 inches.
The weekend should be dry and cool. If you are traveling east the will likely be snow and blowing snow Saturday in western Kansas and western Nebraska.
9 AM MST, Sunday, February 17, 2019
Very cold temperatures are into southeastern Wyoming and western Nebraska now and will work their way into eastern Colorado and the Front Range region this afternoon. Temperatures this evening are expected to fall into the single digits along the urban corridor and probably only reach the 15-20 degree range Monday and Tuesday.
A big snowstorm is not expected, but rather and extended period (this evening through Tuesday) of mostly cloudy skies and periods of mainly light snow. There is not much moisture with this storm, but what moisture there is may convert into rather fluffy snow.
There will probably be some local accumulations around 6 inches by Tuesday in and near the foothills from Boulder County southward. Most areas will probably be under 6 inches. The chance for greater than 4 inches is about 20%. The most likely accumulations are:
2-4″ Boulder, Broomfield, Colorado Springs and metro Denver west of I-25 and south of I-70.
1-2″ northeast Denver, Longmont, Fort Collins, Cheyenne
Although the temperatures should be less cold Wednesday, it will likely be a cold week overall, with another chance for clouds and light snow late Thursday or Friday.
7:30 AM MST, Saturday, February 16, 2019
Each day during this 3-day weekend will be colder than the one before so that by Monday the entire region should experience very cold temperatures. Some snow is possible throughout, but for the Front Range foothills and urban corridor the best chance for accumulation is Sunday evening through Monday.
Snow will be mainly near the continental divide today where there may be some wintry travel at the high passes. Some flurries or sprinkles may break off and move over the foothills and urban corridor, but little or no accumulation is expected. Although temperatures are likely to get no better than the 30s, today will be the “warm” day of the weekend.
Temperatures will likely climb to the 30s in the low elevations Sunday before an arctic front late in the day plunges temperatures into the single digits Sunday evening. Monday and Tuesday are likely to be mainly cloudy with temperatures reaching the teens to near 20 and falling to within a few degrees of zero at night.
Snow: For the foothills and urban corridor accumulating snow is likely to accompany the very cold temperatures Sunday evening and Monday and possibly extending intermittently into Tuesday. The most (3-6″) will probably occur in and near the mountains and foothills of Boulder, Broomfield, Jefferson, Gilpin, and Douglas counties (including Boulder, Nederland, Castle Rock, and the west/south side of Denver). As you go northeast there may only be a dusting to an inch in Weld County, eastern Larimer County, DIA, and around Cheyenne.
Noon MST, Thursday, February 14, 2019
At noon it was in the upper 50s in metro Denver and the low 30s in far northeastern Colorado. The cold front is right about at DIA and marching west, so the afternoon will be turning colder with some areas of low clouds developing. As moist Pacific air streams across the region from the west, there will continue to be snow near the continental divide. That moisture will probably result in a few areas of light snow (or a bit a rain at first) this evening in eastern Colorado, including the urban corridor. Accumulations, where they occur, are likely to be minor.
The cold air will probably get pushed back to the east during the day on Friday by milder westerly flow, but the chinook winds with it are likely to be more localized than the intense gusts last night. On Saturday the next cold front is likely to arrive by afternoon perhaps accompanied by some gusty north or northwest winds. Little or no precipitation is expected with it.
The remainder of the holiday weekend and the start of the workweek is looking colder than average, perhaps staying below freezing all day even in the lower elevations by Monday. There is a chance for light snow amounts. I’ll update over the weekend if the snow chances start looking more certain for Sunday or Monday.