Noon, Thursday, May 24, 2018
For the long holiday weekend it looks warm and dry for Colorado and southern Wyoming. The chance for clouds and an afternoon thunderstorm may be on the increase by Monday, and temperatures may be just a little less warm. Daytime maximum temperatures Friday-Sunday in the Front Range urban urban corridor are likely to range from the mid 80s to around 90 (a little cooler in Cheyenne) with Saturday bringing the best chance for topping 90. Unlike northeastern Colorado, other parts of the state have been somewhat dry in May and those areas may see elevated wildfire risk this weekend.
We should get close to some of these records, and it’s not out of the question that there may be a few locations around the region that set a record high. Record high temperatures in Denver are:
Friday 91 (1964), Saturday 95 (1942), Sunday 93 (2006),
and for Boulder:
Friday 87 (2013), Saturday 91 (1969), Sunday 92 (2006).
7:00 AM, Saturday, May 19, 2018
The potential for additional heavy soaking rain today along the Front Range is low. Heavy rain is occurring out on the northeastern plains and the western edge is moving toward the northern Front Range but the heaviest rainfall is likely to stay north and east of Fort Collins and Greeley (Cheyenne will probably get a period of moderate or heavy rain). For the Denver-Boulder area the day will be mainly cloudy with some intermittent rain, but total amounts are not likely to cause problems.
Sunday should be milder and drier, but still with the chance for a few afternoon showers and thunderstorms.
1:15 PM, Friday, May 18, 2018
Parts of the Front Range region are in for a lot of rain today and Saturday, with wet snow above treeline. There are two phases of rainfall expected. Phase one will be in the form of showers and thunderstorms this afternoon and evening, some producing intense rain and hail.
Phase 2 (after a possible lull during the night) will come later tonight and Saturday with a soaking rain. It’s possible that not all areas will get a heavy soaking rain. The chances are greater north of Denver than they are south of Denver. I’d say the additional heavy rain is likely over Weld and eastern Larimer counties into southeastern Wyoming. But the risk of additional heavy rain exists throughout the Denver-Boulder area later tonight and tomorrow. Where the heavy rain hits there could be more than a month’s worth by Saturday evening (an average May brings about 3 inches total in Boulder and 2-3 inches in Denver).
Watch out for localized street flooding and the potential for creeks to spread out of their channels in some places. The Saturday morning Farmers Markets may be in for the second wet Saturday in a row.
For those interested, the GFS is a good, reliable model but not always the best at resolving the terrain influences. That one brings heavy rain to the entire Front Range region from the Denver area to Cheyenne. Many of the models that have better terrain representation (the NAM and different versions of the WRF) keep the most intense rainfall amounts just to the north an east of the Denver-Boulder area (but watch out Fort Collins and Greeley). I wouldn’t dismiss the GFS solution even though I’m a little suspicious. Stay alert.
12:10 PM, Thursday, May 17, 2018
Thunderstorms, some severe, may return to the northeastern plains of Colorado this afternoon, but the threat is mainly east of the Front Range urban corridor. On Friday a storm system developing to our west should draw moisture westward into the Front Range. The result is likely to be showers and thunderstorms Friday and Friday night for the Front Range and plains. Some areas may experience heavy rain and hail.
The location of the heavier precipitation on Saturday is uncertain. The surface storm system is likely to be in Kansas, but the mid & upper level storm should be near or over the Front Range. If it is a little west/southwest of the Front Range we could see steady rain early and then thunderstorms. But if the upper storm is over or a little east of the Front Range the tendency will be for the heavier precipitation to shift to the east on Saturday. The current modeled data favor the more eastern location of heavy rain on Saturday, but that is not a high confidence forecast. I will update tomorrow.
12:00 Noon, Monday, May 14, 2018
At noon the first heavy thunderstorm of the day is developing in Denver, and the afternoon and evening will likely bring numerous showers and thunderstorms across the Front Range and high plains. Most of us will experience at least a brief shower or thunderstorm, and a few localities are likely to experience a strong thunderstorm with heavy rain and hail.
On Tuesday afternoon thunderstorms will likely re-develop, but overall the atmosphere may be a little drier so that the coverage and duration may be a little less than today. By Wednesday and Thursday the chance for thunderstorms gets pretty small, and the sunshine more abundant.
The mid spring wet pattern will ease off, but probably not go away. It’s looking like another period of cool, wet weather may move into the Front Range region on Friday or early Saturday, but more on that later in the week.
11:45 AM, Friday, May 11, 2018
A large (but not very strong) storm system to the west of Colorado and a cool air mass to the northeast of the Front Range will make for a cooler weekend and maybe wet at times. The storm will probably never move through the Front Range region, but will instead weaken in place over the next few days. The circulation around it will draw low level moisture to the Front Range from the Great Plains.
The most likely result for the Front Range region is for a few periods of clouds and some showers and thunderstorms mainly in the afternoon and evenings. The chance for rain is small today but will increase a little Saturday afternoon through Monday. Up in Cheyenne the chance for rain and thunder is greater today than for most of the Front Range.
There is a small chance that a low level surge of moisture from the east will result in solidly overcast a damp conditions for a 1/2 day to a day this weekend for the eastern foothills and high plains.
West slope areas should be drier despite being closer to the storm system.
6:00 AM, Wednesday, May 2, 2017
Expected periods of rain to develop today and continue into tonight, perhaps punctuated by some brief heavier showers or thundershowers. Accumulating wet snow is likely in the mountains with the heavier accumulations (6 or more inches) mainly above 9000 feet and, and light accumulations above 7500 feet. The snow level may work it’s way into parts of the lower elevations later tonight, but little or no accumulation is expected in the lower foothills and plains.
As the storm moves east late tonight and Thursday morning the precipitation will likely become more intermittent. Prepare for a possible frosty morning on Friday in the low elevations followed by a nice warmup Friday afternoon.