Category Archives: Uncategorized

Latest first snow, Chinook winds

5:45 AM MST, Saturday, November 13, 2021

I’m getting questions about the lateness of this season’s first measurable snow (measurable is 0.1 inch). Most parts of the Front Range foothills and plains had a trace of snow on November 1-2. In Cheyenne and around the Fort Collins/Loveland area, there was measurable snow at that time. But for official recording locations in Denver, Boulder and Colorado Springs, there has not been measurable snow yet.

November 21, 1934 is the latest Denver has gone without its first measurable snow. November 19, 1900 is the latest in Boulder (the records show November 26, 1978, but the observer missed several snowfalls in October that year). We will get a cold front through the region Tuesday night/Wednesday, but the chances for measurable snow are slim. So we are still in the running for the record. This is especially noteworthy since only a year ago we saw record early snow on September 8, 2020.

For the immediate future, the word is windy. Between today and Tuesday there will be warm weather, but with occasional periods of very gusty Chinook winds out of the west in and near the foothills.

Dry, mild weather returns

6 AM MDT, Wednesday, November 3, 2021

The cool, damp weather of the last few days will begin to release its grip after some dense morning fog in some parts of eastern Colorado. Afternoon temperatures today will be milder than we have seen in a few days. Thursday through Monday should bring dry weather with unseasonably mild temperatures. Windy conditions are likely to develop on Friday for some areas in and near the foothills.

Looking farther away, a significant solar flare took place (second on in a week), and a solar storm is heading toward Earth. This should trigger aurora borealis (northern lights). Like the one a fews days ago, it probably won’t be visible as far south as Colorado. But forecasting solar storm impacts is quite challenging, so if you in a dark area tonight (or very early tomorrow), take a look to the north in case the sky is glowing this far south.

Colder week starting Sunday

5:45 AM MDT, Friday, October 29, 2021

We have not had any prolonged cold spells yet this season, but that is about to change. The good news is that we are not likely to experience record cold. But a period of below average temperatures is likely by Sunday and expected to continue through most or all of next week. Lower elevation temperatures will probably remain below 50 the whole time, and the coldest day or two next week may stay in the 30s. The initial cold front will probably be Saturday afternoon or early evening.

Will the lower foothills and eastern plain get their first snow? Possibly, but it’s not looking very likely at this point. There is no organized storm system coming through, just some very subtle and weak disturbances. So we may see a few periods with low clouds and light amounts of snow or drizzle next week.

So in summary, plan for Saturday to be the milder day this weekend, and the colder weather moves in.

Little precipitation east of mountains; wind instead

5:45 AM MDT, Tuesday, October 12, 2021

Significant snow is likely in the high elevations over the next 24-36 hours. Some areas are likely to get over 12″, but mainly in unpopulated areas above treeline. Watch out for winter travel at the high passes. Some snow will likely occur east of the continental divide, but mainly west of Peak to Peak highway and within a few miles of Eisenhower Tunnel.

For the eastern foothills and plains there may be a brief period with showery rain or graupel today, but little or no overall accumulation (except up toward Cheyenne where light amounts are more likely). A major snowstorm is expected to take shape later today and tonight a short distance north of Cheyenne in east-central and northeastern Wyoming.

As the storm pulls away from the Front Range region this evening, we are likely to see strong west and northwest winds across the eastern foothills and plains this evening through Wednesday morning. With trees still leafed out, there could be some scattered tree and power line damage.

A weaker storm on Thursday should bring some light snow to the mountains and maybe a little rain changing to snow for the eastern foothills and plains. Although the chance for snow in the urban corridor is better with that one, the chance for anything measurable is less than 50-50. However, the chance for widespread freezes by Friday morning is quite good.

Snow for mountains, unsettled eastern plains

6:30 AM MDT, Monday, October 11, 2021

A strong storm system is expected to move across Colorado and into western Nebraska on Tuesday and Tuesday night. It should bring the first significant snow to the mountains (especially west-facing slopes) where 6-12″ is likely. Lesser amounts are expected in western valleys.

The track of the storm won’t result in easterly upslope for the eastern foothills and plains, so much less precipitation is expected there. Some snow may spill over from the west a result in some light accumulation, mainly west of Peak to Peak highway. We may have some brief squally showers (mainly rain) in the urban corridor, but precipitation totals are likely to be scattered and generally light. There is only a very small chance for widespread measurable snow. There is a better chance for some measurable snow in Cheyenne, but the more significant snow and wind is likely to be north of there.

We get another shot for snow on Thursday and Thursday night. The next storm is weaker and will likely bring some light snow amounts to the mountains. The Thursday afternoon/evening storm will bring a better chance for widespread light precipitation (rain changing to snow) for the eastern foothills and plains.

Temperatures through the period (except Tuesday morning) may result in localized frost. By Friday and Saturday mornings, widespread freezes are increasingly likely.

Two changes coming in next four days

6:30 AM MDT, Friday, October 8, 2021

Two cold fronts and accompanying storm systems are forecast to move through Colorado in the next 4-5 days, one tonight, and a stronger one on Tuesday.

Friday night and Saturday

A storm system is likely to bring some intermittent rain (snow above treeline) to mountain areas tonight and Saturday. For the Front Range foothills and plains, a brief shower is possible, but it is likely to remain mostly (or completely dry) in most areas. There may be some gusty west-northwest winds by Saturday morning. Although it will be a bit cooler this weekend, we should still have relatively mild autumn temperatures.

Tuesday and Tuesday night

A stronger storm system and accompanying cold front is forecast to move through Colorado and Wyoming on Tuesday. That one has a greater potential to bring significant snow to the mountains and high valleys. For the eastern foothills and plains, the chance for significant rain changing to snow is more questionable. Right now the orientation and track of the storm would result in winds changing from mostly south to mostly north, with very little easterly “upslope” flow. That evolution could change, but right now it looks like the best chance for moderate or heavy snow on the east slope will be north of Cheyenne. Updates to come.

You might want to start planning for widespread freezing temperatures on Wednesday and/or Thursday morning.

Some rain, and cooler weather on the way

6:30 AM MDT, Tuesday, September 28, 2021

A cold front is coming our way on Wednesday. But the trend toward cooler will start today as a weak storm system to the south creates some clouds that limit the solar heating. There may even be a few showers around, mainly in the mountains. It should still be warm, just not the record and near-record levels of the last few days.

Wednesday may start out mild, but a cold front during the day should usher in a few cooler days with afternoon highs in the 60s for the lower elevations. There is a good chance for rain between tomorrow afternoon and Thursday morning. Snow levels will be high, mainly up in the tundra where a few inches are likely. By the end of the week drier weather will be back over the Front Range region, but it won’t be getting as warm as what we had the last few days.

Record high temperatures possible

6 AM MDT, Thursday, September 9, 2021

As if the smoky haze isn’t enough, the high temperatures Thursday and Friday are likely to be near or at record levels. The records for Denver and Boulder both 94 today, and for Friday they are 93 in Denver and 94 in Boulder. The next chance for showers does not get here until Saturday, and then it’s only a very small chance.

For some historical perspective, last year we were experiencing an unusually early occurrence of snow and freezing temperatures on the 8th and 9th of September!

Slightly better chance of rain for a couple days

6 AM MDT, Wednesday, September 1, 2021

Moisture from what was once Hurricane Nora in the Pacific has resulted in some locally heavy rain in the desert Southwest. Some more locally heavy rain and flash flooding is possible today in western Colorado, particularly in the San Juans. For the Front Range, the chance for significant rain is smaller. It should be cooler, with some showers or thunderstorms around, but many parts of the Front Range could get through the next couple days without any significant rain that really soaks into the soil.

The good news is that the prevailing southwesterly winds should help lower the smoke concentration in the air for a day or two. The bad news is that the prevailing wind should become more westerly again by Friday, and there is still a lot of smoke being pumped into the atmosphere to our west in California.

For August, the Boulder climate station had 0.68 inches of rain, which is only 40% of the 30-year average. It is the 13th August in a row that is drier than average. No other month has had such a consistent anomaly, either dry or wet. Although there were some local areas that got a heavy thunderstorm during August, the major climate stations in Cheyenne, Boulder, Denver, and Colorado Springs had a drier and hotter August than average.

Some smoke coming, then wetter in early September

6 AM MDT, Saturday, August 28, 2021

Have you heard of Hurricane Nora? The weather headlines this weekend will be dominated by Hurricane Ida heading for Louisiana. But the lesser-known Hurricane Nora, on the Pacific Coast of Mexico, may be the one to have some influence on the weather in Colorado. An envelope of tropical moisture associated with the remnants of Nora are forecast to move north into Arizona and New Mexico by September 1st, and possible into Colorado and Wyoming during the period of September 2nd to 4th. That would increase the chances for widespread rain, but more on that in a few days.

Smoke: When prevailing winds are from the southwest, our smoke levels decrease because there is very little wildfire in the Southwest. But today the wind is more from the west, and some of the worst wildfire is to our west in central California. Smoke is already on the increase from Salt Lake to Cheyenne this morning, and that trend is likely to overspread the Denver-Boulder area today. A cold front this evening may help diffuse that smoke a little tonight and tomorrow, but the risk of occasional smoky skies will be with us for a few days.

Cold front: A cold front this evening will make Sunday a cooler day, but hot weather (90 in the lower elevations) is likely to return Monday and Tuesday. There may be some areas of low clouds and maybe some localized showers or drizzle tonight or Sunday morning, but widespread significant rain is not expected. Many areas will probably remain dry.