1:00 PM, Wednesday, August 26, 2015
The risk of showers and thunderstorms returned to Colorado (mainly west of the continental divide), but there is at least a small chance for some showers or a thunderstorm in parts of eastern Colorado and Wyoming tonight.
A weak storm system and its associated sub-tropical moisture is moving north into western Colorado as of midday Wednesday and it’s likely to move eastward across eastern Colorado and Wyoming tonight. For the Front Range region, the risk of heavy rain at any given point is low, but it’s higher than we seen in a while. In addition, the small chance for rain may extend through the night and into the Thursday. Temperatures Thursday should be a little cooler, but above average temperatures and mainly dry weather is likely to return for the weekend.
Firefighters in hard-hit Washington, Oregon, and Idaho may get a little help form nature this weekend with cooler weather and a small chance for some showers. Unfortunately, widespread precipitation is not expected.
On the other end of the country, tropical storm Erika is being closely watched as it moves to the west from its location east of the Virgin Islands. The storm is weak and in an area unfavorable for hurricane development which may cause it to dissipate in the next 48 hours. However, if it hangs on it will likely reach an area with favorable conditions for hurricane development near the Bahamas and become a threat to the Southeast U.S. early next week.
11:55 AM, Friday, August 21, 2015
A cold front on Saturday is not expected to be either as cool or as moist as the one this past Tuesday. In Wyoming temperatures should be a little cooler by Saturday. In Colorado, temperatures may warm rapidly in Saturday morning before leveling out or cooling off, first in the northern Front Range, and later to the south. It is likely that it will still reach around 80 in many low-elevation areas of eastern Colorado on Sunday.
Little or no shower or thunderstorm activity is expected with the cold front, and a dry, warm pattern is expected to continue into next week. Many parts of Colorado north of I-70 have been quite dry since mid July and the risk of wildfires is starting to increase. The smoky skies around now are due to fires to the west and northwest of Colorado. Although the cold front tomorrow may sweep in some cleaner air, the general flow is still from the west and northwest, so we can’t assume that smoky spells won’t reoccur in the coming week.
12:45 PM MDT, Monday, August 17, 2015
Enjoy some below average temperatures through Wednesday, especially east of the mountains. But watch out for some localized strong thunderstorms late today.
Cooler weather is already here, but another cold front Monday night into Tuesday morning will keep temperatures below average through Wednesday. Thunderstorms today may become severe, but the greatest risk of that is east of I-25. There may be some low clouds and localized drizzle or fog with the cold front tonight and possibly again early Wednesday morning. Heavy rainfall should be limited to local areas that experience thunderstorms this afternoon and evening, and again late Tuesday.
Wednesday afternoon through Friday should be warmer and drier ahead of another cool front this weekend.
2:20 PM, Thursday, August 13, 2015
We will remain in a pattern of average to above average temperatures into this weekend. Lower elevations areas should see highs ranging from upper 80s in Cheyenne to 90s in most parts of eastern Colorado and the western valleys. Friday and Saturday are likely to be a little hotter than Sunday.
There will be a scattering of afternoon thunderstorms each day, but only a small percentage of the area is likely to see anything of significance. If you get a good soaking for your garden, consider yourself lucky.
There has been a high frequency of hurricanes in the Pacific Ocean (called typhoons on the Asian side) and some of these have been drawn up into polar regions which has an impact on the position of the polar jet stream over North America. One of the impacts being forecast by the long range models is for a cooler pattern in the western United States in the second half of next week.
12:15 PM MDT, Tuesday, August 11, 2015
The Perseid meteor shower is one of the two best meteor showers of the year for the United States, the other being the Geminids in December. The Perseids have the great advantage of occurring in the summer, and, they have a reputation of producing some real bright ones complete with vapor trails.
Because of the geometry of the Earth’s encounter with the comet debris that causes the Perseids, they don’t really ramp up until after midnight, with the peak time in the darkness before dawn. Look overhead and to the northeast for the best chance of seeing them. Wednesday and Thursday mornings should be the peak (it seems most astronomy pros are favoring Thursday morning). There will be a nearly new moon, so we shouldn’t have interference from moonlight.
What’s going to crash this party? The leftover clouds from afternoon and evening thunderstorms often mess up perfect viewing. Monsoon moisture has been triggering a scattering of thunderstorms, especially in areas south of I-70. Today will see more of those thunderstorms throughout Colorado. Forecasting cloud formation and dissipation in the Rocky mountain region is a challenge, but there should be at least some areas of nighttime clearing, especially Wednesday night into Thursday morning.
11:15 AM, Friday, August 7, 2015
Expect slightly cooler temperatures, but still warm, with some thunderstorms around this weekend.
There is lots of monsoon moisture south of Colorado, and that moisture extends over Colorado in the middle and upper parts of the atmosphere. As a result there are more clouds around and the chance for thunderstorms is back in the forecast. But because the lower atmosphere is rather dry along the Front Range, the chance of hearing thunder is greater than the small chance of getting rain. There may be some brief gusty winds too. The best chance for strong thunderstorms today and through the weekend appears to be on the plains east of the urban corridor, and in the southern mountains.
Here at the Boulder climate station the warmest temperature so far this summer has been 94 on August 6th. Although this summer has not been nearly as cool as recent cool summers in 2004 and 2009, the lack of 95-degree days is unusual. The weather pattern this coming week may result in some 95-degree days, but with the monsoon moisture so close, we can’t yet rule out increased clouds limiting the afternoon temperatures. It’s not typical, but not terribly unusual either, for August to score the hottest temperature of the year. In the last 66 years in Boulder the hottest temperature occurred 61% of the time in July, with the remaining 39% split nearly evenly between August and June, and one year (1983) had it’s hottest temperature in September.