5:30 AM MDT, Friday, May 17, 2019
The 80 degree days are over for at least 5-7 days. Two major storm systems will move through the Colorado/Wyoming region, one later today and tonight, and another early next week.
Today and tonight
It will still be near or a little above average in temperature today, but with a better chance for thunderstorms this afternoon and evening. The best chance for strong or severe thunderstorms will be on the far northeastern plains of Colorado, southeastern Wyoming, and in Nebraska. The lowest chance for thunderstorms is south of Denver.
Saturday and Sunday
Cooler weather with some showery periods possible, but for the foothills and plains it should be dry most of the time. In the mountains, the chance for showery periods is a little greater, and there may be some snow above treeline. The potential for clouds and precipitation increases a little late Sunday as the next storm approaches.
This could end up being a very cool and occasionally wet period, with substantial snow above 8000 feet and cold rain in the lower elevations. I’ll have to update on this later in the weekend. There is a small chance for damaging nighttime temperatures for tender plants, but it’s too early to tell yet.
6:00 AM MDT, Tuesday, May 7, 2019
We are in for several days of generally cloudy, damp weather with some freezing temperatures in the lower elevations possible Thursday and Friday mornings.
The clouds may thin a bit at times today, but even if that happens, expect some more showers or even some thunderstorms this afternoon, and cool temperatures. The coldest stretch of this pattern will move in on Wednesday. Several intervals of steady rain (snow in the higher elevations) are likely Wednesday afternoon into Thursday, It is now looking more likely the rain will mix with or change to snow in parts of the urban corridor Wednesday night or Thursday morning. I would not be surprised to see a couple inches, mainly in grassy areas. The amount of snow will be greater as you go up in elevation, with 5-12″ above 7500 feet.
Temperatures are likely to be within a few degrees of freezing on Thursday and Friday mornings, so prepare to protect tender annuals that are outside.
11:30 AM MDT, Sunday, May 5, 2019
This coming week is likely to bring a multi-day stretch of below-average temperatures and a good chance of rain (snow in the mountains).
Although Monday may be a little cooler than today, it will likely still be a mild day with only a slight chance of afternoon showers or a thunderstorm. Tuesday might be a bit cooler with another chance for afternoon showers or a thunderstorm.
The peak of the cold snap appears to be on track for Wednesday and Thursday. During that time there may be long cloudy stretches and a period or two of steady rain (snow in the mountains). Although this spell is not likely to be quite as cold as last week’s cold snap, I can’t completely rule out the chance for some wet snow in the lower elevations, but the chance appears to be small. Gardeners even in the low elevations should prepare for the risk of damaging frosts (for tender annuals) on one or more mornings from Wednesday to Friday.
11 AM MDT, Sunday, April 28, 2019
At 11 AM Sunday a cold front resulted in a 15-20 degree drop in temperature at Casper, WY. That cold front should move through Cheyenne in the midday hours and then through the Colorado Front Range urban corridor by late afternoon.
Rain and snow is likely to come in several intervals. The first this evening. After a lull, the period with the best chance for snow at all elevations will probably be late Monday afternoon and night. There may be one more round of precipitation Tuesday evening too.
Some showers and thunderstorms are likely to develop behind the front this afternoon/evening followed by some areas of drizzle during the night. Snow above 9000 feet is likely to move to lower elevations by late night, but accumulation, if any, should be mainly above 7500 feet and mainly in the 1-5 inch range (highest above 9000 feet).
Monday and Monday night
The second round of precipitation likely from about midday Monday until late Monday night will occur with the highest amount of atmospheric moisture during the next few days, and the lowest temperatures. Therefore, this period may bring the best chance for heavy snow in the mountains and rain changing to wet snow with some accumulations in the lower elevations. During the period 5-9 inches could occur above 7500 feet, with 3-6″ in the 6500-7500 elevation range, and 1-4″ below 6500 feet.
Tuesday night and Wednesday morning
There may be one more round of rain and snow Tuesday evening through Wednesday morning. It looks like the atmosphere may be a little warmer for this period (than on Monday night) so the chance for additional snow in the lower elevations is small.
With this kind of wet period over several days, the total amount of snow accumulated will probably be higher than the maximum on the ground at any one time due to melting during lull periods.
9 AM MDT, Friday, April 26, 2019
Many parts of the Front Range urban corridor have had 10-11 days without a frost or freeze and gardens are coming to life. But don’t be fooled. Not only does climatology suggest that the last freeze in Denver-Boulder-Fort Collins is typically in early May, but today’s weather maps strongly suggest a cold period beginning Sunday evening and continuing until midweek. We will probably see widespread freezing temperatures during at least one morning in that stretch. There is also a chance for one of more periods of cold rain giving way to wet snow even in the lower elevations (possible heavy amounts in the mountains) in the Sunday night through Tuesday time period.
Until then the weekend should be relatively mild and dry. But be prepared for some afternoon/evening showers or thundershowers scattered around today and again on Saturday.
Noon, Saturday, April 20, 2019
Showers and thunderstorms are likely to develop in the Front Range region on Easter Sunday, but probably not until mid afternoon or later. So odds are that morning Easter egg hunts will be okay.
After some showers and thunderstorms late Sunday, there may be a period of steady rain or drizzle in the evening or overnight. The snow level will start to lower, but probably not enough to result in accumulating snow below 6500 feet. Even higher up snow accumulation will likely be minor. Cooler weather arriving late Sunday will continue into Tuesday.
12:25 PM MDT, Wednesday, April 10, 2019
The changeover to snow is occurring a couple hours ahead of schedule compared to yesterday’s forecast. For the urban corridor (north of Colorado Springs) we are still looking at 2-5 inches widespread. But, it is likely that a band of intense snow, roughly in a north-south direction, will develop on and off between now and early evening. This could make some heavy snowfall rates of 1-2 inches per hour and maybe thundersnow. In areas that end up under the band for a couple hours there may be some local reports of 5-8″, but that is likely to be a subset or the region between Denver and Cheyenne. Be prepared for rapidly changing conditions over distances less than 10 miles.
Thursday morning’s commute should be fine.