1:30 PM MDT, Wednesday, September 18, 2019
I haven’t written much because we have been in a rather uneventful pattern for a while. With a few local exceptions, the Front Range region has generally been warmer and drier than average since mid July. Average afternoon temperatures in the lower elevations have now fallen to the mid 70s, and we are likely to be around that (or a little warmer) through the Monday (and the autumnal equinox is Monday at 1:30 AM MDT). There is a small chance for afternoon showers or thunderstorms (and maybe a light coating of wet snow in the highest elevations), mainly Thursday or Friday, but many areas are likely to come through with no significant precipitation. The weekend is looking dry.
The next chance for significant widespread precipitation is late Monday or Tuesday, but even that is iffy. The path and development of that particular storm is too uncertain at this time for me to be confident of some good precipitation, but it’s worth watching.
The average time for the first measurable snow in places like Denver, Boulder, and Fort Collins is mid October. In the last 70 years the odds are about 1-in-4 for the first snow to occur in September. In the last 18 years measurable snow only occurred once in September (in 2014) along the urban corridor. So you can say we are due, but there are no obvious signs yet that this will be a year for September snow.
5:50 AM MDT, Friday, September 6, 2019
The 90-degree days are gone for at least the weekend, and you should expect more late-day cloud cover along with a scattering of afternoon showers and thunderstorms for the next three days. Today may be the first time in a while when measurable rain occurs at more than just a few isolated locations, and there may even be some locally intense thunderstorms. Although thunderstorms may be around both afternoons of the weekend, it appears that the chance for thunderstorms is greater on Sunday than it is on Saturday.
Drier and warmer weather will likely return early next week, but we don’t expect the same levels of record heat to return.
7:30 AM MDT, Friday August 30, 2019
Today and Saturday should be a little less hot that yesterday, but still warm during the afternoon. The average high temperature for this time of year in the lower elevations is low to mid 80s, and we will likely warm to at least that today and Saturday. There is a little more moisture in the atmosphere, so a scattering of thunderstorms is also likely this afternoon.
By Sunday and Monday there should be little or no thunderstorm activity and lower elevation temperatures are likely to reach the 90s. With a few local exceptions, August has been dry for much of the Front Range. Fire danger may be high this weekend, especially where it doesn’t rain this afternoon and evening. The national drought monitor (produced by the University of Nebraska-Lincoln) put parts of central Colorado and the Front Range in the “abnormally dry” category; not quite drought, but moving in that direction.
The real weather news this weekend will likely be with respect to Hurricane Dorian in Florida.
1:30 PM MDT, Friday August 16, 2019
The atmosphere over Colorado should continue to be dry with little or no monsoon influence through Monday. The only exception is that a surge of slightly moister and less hot air moved into eastern Colorado from the Great Plains this morning. That should enhance the chances of thunderstorms a little, mainly east of I-25. The chance for thunderstorms Saturday and Sunday will be very small, and afternoon temperatures in the low elevations are likely to climb to the 90s. Vegetation has become dry so be especially careful with fire.
There is indication that a surge of monsoon moisture from the Pacific Coast of Mexico might arrive in the middle of next week. It’s not looking like a very impressive surge of moisture, but it may be enough to increase the chances for widespread showers.
3:20 PM MDT, Friday, August 9, 2019
For those who like to get some high country hikes in this time of year, you may be familiar with the tendency for afternoon lightning associated with monsoon-pattern thunderstorms. Those will be around this Saturday and Sunday for both the mountains and plains. So keep an eye to the sky. But for several days now the indications have been for a dry period with the monsoon moisture pushed to the south of Colorado beginning on Monday and possibly lasting all week. That would mean warm conditions with lower than average chances for late day thunderstorms.
6:15 AM, Thursday, August 1, 2019
An area of high atmospheric moisture is moving across Colorado today. This will increase the amount of afternoon clouds and thunderstorms and keep the afternoon temperatures cooler than what we have seen lately. A few areas in the Front Range and eastern plains regions will probably see some heavy rain in the thunderstorms, so it is good to keep an eye out for localized flash flooding this afternoon and tonight.
The high moisture content of the atmosphere will decrease as we go into the weekend, so although the chance for thunderstorms will remain, the coverage of thunderstorms should decrease after today.
The Southwest monsoon
Moisture in the mid and upper levels today is connected with the tropical Pacific off the West Coast of Mexico. This pattern is relatively common in to mid to late summer and is referred to as the Southwest Monsoon or the Mexican Monsoon. Although it has been around intermittently for a couple weeks, today it is being combined with low level moisture from the Great Plains. That’s why we are in an somewhat enhanced risk that some thunderstorms may produce high rainfall rates.
8 AM MDT, Saturday, July 19, 2019
When I blogged a couple days ago I said that Saturday may or may not see the continuation of the heat wave. Now it looks like Saturday will see a cold front pass through, probably by morning in Cheyenne and then morning to afternoon as you move south down the Front Range. So today will likely be the last in this stretch of days near 100, and then it will be 15-20 degrees cooler for high temperatures by Sunday.
There should be an increase in moisture behind the front, so expect some areas of clouds and thunderstorms Saturday and Sunday, especially afternoon and evening.