Autumn arrives early Thursday; autumn weather arrives late Friday

The autumn equinox is tomorrow (Thursday) at 8:21 AM MDT. Expect this coming weekend to be much cooler than last weekend, with a scattering of showers possible in the mountains.

 

A Pacific cold front should be moving east through western Colorado early Friday, and probably through the Front Range region late Friday. A brief burst of rain and squally winds may accompany the cold front, but a widespread significant rain is not expected. Above treeline a light accumulation of snow may whiten some mountaintops.

 

Saturday and Sunday are likely to be mainly dry, but because of cold air in the upper atmosphere I can’t rule out a brief shower in the afternoon, especially in high elevations where it could be snow or graupel. And for those who don’t know, graupel is small snow pellets that form in convective clouds, fairly common in the mountains in summer and early autumn.

 

Happy Autumn!

Somewhat benign weather pattern to continue through the weekend

12:15 PM, Thursday, September 8, 2016

It has been a while since I blogged due in part to the lack of major weather locally. Dry weather is likely to continue statewide through the weekend. The only spice in the forecast will be some moderate swings in temperature. A cold front Friday will likely send temperatures to slightly below average Friday through Saturday morning. (The average high temperature this time of year for Denver and Boulder is mid to upper 70s.) By Sunday temperatures should be above average again ahead of another cold front on Monday. We can hold out hope that the change on Monday will bring some rain, but at this point the chance for widespread measurable rain on Monday is looking very small.

 

Meteorological summer (June-July-August) was drier than average for almost all of the Denver-Boulder-Fort Collins corridor (Colorado Springs was wetter). So if you are enjoying the outdoors this weekend, remember to be very careful with fire!

 

 

Cooler for second half of the week

10:35 AM, Tuesday, August 23, 2016

Once again we have a cool air mass moving in from the north that is expected to bring cooler than average weather Wednesday through Friday. Daytime highs in the Denver-Boulder-Fort Collins area will probably stay below 80 Wednesday and Thursday, and maybe Friday too.

 

The last cool air mass on Friday and Saturday last week didn’t stay around long, but it did result in a record low of 43 in Boulder on Saturday morning (Aug 20), and Denver’s low of 47 missed their record by 1 degree.

 

An increase in atmospheric moisture across southern and western Colorado should result in numerous showers and a few thundershowers there this afternoon and tonight. The best chance for significant rain is south and west of Denver, but some parts of the Denver-Boulder area will probably see a shower or thundershower this afternoon and again Wednesday. There could even be some patches of low clouds during the night and early morning.

 

Enjoy the late summer cooler weather!

Strong cold front and rain, then nice weekend

12:35 PM, Friday, August 19, 2016

 

A strong cold front was just about to Cheyenne at noon, and should surge south through the Front Range this afternoon. It’s only 48 degrees with cloudy skies in Casper, WY at noon!

 

Expect the mid-late afternoon to turn much cooler with clouds and some showers and thunderstorms. The primary chance for rain should be over by late night, but low clouds and some areas of fog or drizzle may persist into early Saturday morning. The weekend should be nice after a chilly start on Saturday, with relatively cool temperatures Saturday afternoon and closer to average temperatures Sunday afternoon.

Strong cold front to end the week

12:30 PM, Wednesday, August 17, 2016

A strong cold front on Friday is expected to bring cooler weather late Friday through Sunday. There is also a good chance  for clouds and areas of rain and thunderstorms late Friday into early Saturday.

 

There may end up being more than one push of cool air from north to south on Friday, so it’s possible that the real cool down may not occur until late Friday. With northeasterly winds accompanying the arrival of the cooler air, some moisture may be pushed upslope into the Front Range increasing the chance for showers and thundershowers. There may even be a multi-hour period of overcast with some steady drizzle or rain late Friday into early Saturday.

 

Denver, Boulder, and Fort Collins have all been running drier than average for June-July-August (Colorado Springs has not been as dry). So if this push of cool air late Friday manages to trigger some widespread rain, that moisture would be welcome.

Cooler, showery through Saturday

1:15 PM, Thursday, August 4, 2016

A batch of mid and high level moisture has moved up from the south as forecast a few days ago, and the moister atmosphere should be with us through Saturday. For eastern Colorado, low levels of the atmosphere are still a bit dry, so there may be a lot of evaporation beneath the clouds when the first showers form today.

 

Numerous showers/thunderstorms should develop late today (Thursday). Almost everyone will probably see at least a little rain, and a few pockets may see locally heavy rain. The chance for heavy rain is a little greater in the mountains than it is on the plains. There is even indication that areas of showers may continue through the night. So don’t be too surprised if you hear some rain falling during the late night.

 

Friday and Saturday will likely see showers and thunderstorms mainly in the afternoons and evenings. If you have outdoor plans, you may very well be fine and it won’t be hot. But you should have a plan B in case of rain. Beginning Sunday we are likely to trend toward fewer showers and warmer temperatures.

Hot Wednesday; then a bit cooler and moister

4:05 PM, Tuesday, August 2, 2016

The Southwest monsoon of 2016 has been reluctant to leave its origins in Mexico even though this is the time of year when it sometimes surges into the southern or central Rockies. It now appears that may change, at least for a couple days, beginning late Thursday. The weather pattern should allow some tropical moisture from the south  associated with the monsoon and a cool front from the north to team up and give us a break from the heat and and dryness late Thursday, Friday, and maybe Saturday.

 

It’s too early to have a good handle on the magnitude of the rain chances. But during the period late Thursday through Saturday it appears there is a good chance for more widespread afternoon and evening showers and thundershowers, and some localized areas of heavy rain.  At this point it doesn’t appear to be a long-lasting change to the pattern.

 

For my colleagues at UCAR/NCAR planning their summer party and road race Friday afternoon…  the good news is that it won’t be as hot. The not-so-good news is that there is a better chance for rain than we have seen in recent days. As usual, there should be areas with no rainfall, but it appears likely that most areas will get some measurable rain.