4:20 PM, MDT, December 12, 2017
A cold front and upper level disturbance on Wednesday evening will likely have a bigger impact along the Front Range than what we were thinking as recently as yesterday. Accumulating snow (probably minor) is appearing likely in and along the mountains with less chance farther east. The timing is Wednesday evening through early Thursday. So, nothing big appears on the way, but it may very well be something different than what we have had lately. I will update tomorrow.
Friday, December 1, 2017, 11:15 AM
Expect a mild, dry weekend with above average temperatures and possibly a bit breezy at times. A cold front overnight Sunday into early Monday will make the early part of next week more like December. Over the last few days it was appearing that the cold front would bring a snowfall with it on Monday. Although that still looks like a possibility, the magnitude is looking rather minor. I will update Sunday if there are major changes.
La Nina this winter
The Pacific Ocean is in a La Nina pattern this winter, with below average sea surface temperatures in the eastern Tropical Pacific. Although there is always a lot of talk about what it means for our winter season, the truth is that the El Nino-La Nina phases are important influences but they don’t act alone. For that reason there can be a lot of variability from one season to the next. The general expectation is for wetter/snowier in the Pacific Northwest and northern Rockies, and drier for the Southwest and southern Rockies. Colorado is often in between these two tendencies. But more often than not the Front Range east slope region and eastern Colorado run on the dry side during La Nina. The West Slope is more uncertain with the best chances for a snowy winter in the northwestern and north central part of Colorado.
Although the snow pattern is somewhat uncertain, there appears to be a much stronger correlation between La Nina and downslope windstorms. So be prepared for frequent visits from Chinook winds.
6:00 AM, Monday, November 27, 2017
Expect one more day with record or near record warm today, then more seasonable weather Monday night and Tuesday. Light snow is likely Monday night in the mountains and Palmer Divide region.
On Sunday record warm temperatures included 74 in Denver, 73 in Boulder, and 71 in both Colorado Springs and Cheyenne. Monday’s records are 74 in Denver (1950), 75 in Boulder (1903), 72 in Colorado Springs (1998), and 68 in Cheyenne (1950).
The cold front should sweep north to south this evening, maybe late afternoon in Cheyenne. Some light snow (generally less than 3 inches) is likely in the mountains and Palmer Divide Region tonight and early Tuesday. There is only a small chance for accumulating snow along foothills and plains of the Front Range region, and many areas will likely stay dry. It appears that the chance for snow is a little greater south of Denver. By Tuesday afternoon the sun should be showing again and temperatures are expected to be 25 degrees colder than Monday afternoon. It should be a little milder again on Wednesday, but not a return to the warmth we have seen.
There are indications that a more substantial cold spell may hit in about a week’s time.
11:30 AM, Tuesday, November 21, 2017
The whole Rocky Mountain region and adjacent high plains are in for a dry and unseasonably warm Thanksgiving weekend. There may be a slight and temporary cool-down late Friday and Saturday, but the cold and snow that sometimes occur this time of year are not expected.
A small chance for record highs
There is only a small chance for reaching record highs, but we should at least get close. The record highs for Wednesday, Thursday, and Friday in Denver are 74 (1998), 73 (1915), and 74 (1990). For Boulder the Wed-Fri records are 73 (2006), 72 (1901), and 71 (1990). On Saturday we might be a bit cooler and the record is an impressive 77 (1990) in both places, so that one seems very out of reach. Right now it appears Sunday could be approaching record warmth again (72 in both locations).
Given that this time of year does sometimes bring major storm systems, this year appears rather quiet by comparison. Clouds and precipitation are likely to effect parts of the Pacific Northwest on Wednesday and Thursday and again at the end of the weekend. It may be showery in Florida on Thanksgiving day.
2:00 PM, Thursday, November 16, 2017
A cold front will make itself known late Friday and may be accompanied by some precipitation, mainly in the elevations above treeline and the West Slope region.
For the Front Range expect cool winds to move in on Friday with some areas of rain or snow showers late Friday or Friday night. This is probably going to be a fairly minor precipitation event for the foothills and plains, and some areas might not get any. Above treeline and closer to the continental divide there may be 6 or more inches of snow and blowing snow. Cool, dry weather Saturday should give way to milder weather Sunday.
7:30 AM MST, Tuesday, November 7, 2017
If you live in Denver (or south of Denver) you are probably wondering where the snow is. Roughly 1-5 inches accumulated through early Tuesday morning from around Broomfield north to Cheyenne (more in the mountains). Little or nothing accumulated from Denver southward.
After a lull today it appears that some areas of light snow may redevelop late this afternoon or evening from the Denver-Boulder area southward. Around an inch may occur, so it’s possible that Denver will whiten up a bit.
Dry weather is expected the rest of the week.
6:20 AM, Monday, November 6, 2017
Colder weather and intermittent snow (maybe starting briefly as rain) is expected this evening into at least Tuesday morning. Most areas should have light accumulation. A return to more seasonable temperatures is expected by Thursday.
The front and initial precipitation is expected this evening, possibly late afternoon in southeastern Wyoming. Most of what we get will probably occur overnight and Tuesday morning, but there is a good chance for clouds and maybe flurries to linger into late Tuesday.
1-3 inches should be the most common amount below 7000 feet
3-5 inches will probably be common above 7000 feet (maybe 5-10 in local areas above treeline, especially the northern Front Range)
Chance for enhanced snowband: This is the kind of storm where a long-narrow, west-east band can develop and enhance snowfall rates in the lower elevations, but only for about 10% of the area. That could cause local amounts in the 3-6 inch range. Right now (as of this 6 AM writing) it appears the best chance for that would be in northern Larimer County or in the Cheyenne area. The chance for a heavy snowband over the Denver or Boulder area is much smaller, but it’s not a zero chance.