Monthly Archives: July 2015

Typical Summer weather continues, El Niño this Winter

2:00 PM, Thursday, July 30, 2015.

It has been a while since I blogged, partly because the weather for several weeks has not presented any unusual temperature or precipitation extremes. Fairly typical summer weather is likely through the weekend, with only small chances for afternoon thunderstorms and daytime temperatures near or slightly above average.

I say “fairly typical” because this is normally the peak monsoon season with numerous showers and thunderstorms. The monsoon pattern is active, but mainly south of Colorado. A very slight shift in the pattern can allow the moisture to surge back up into Colorado, but that appears unlikely for at least the next few days.

The tropical Pacific Ocean is now seeing the strongest El Niño conditions since 1998. Whether that will persist into the winter is uncertain, but the odds slightly favor a strong El Niño into early 2016. El Niño is certainly a major climate influence, but it acts in concert with other periodic patterns in the Atlantic, Pacific, and Arctic regions which makes it’s specific impacts in Colorado variable. Here are the Colorado weather impacts that are typically associated with El Niño.

1. Less frequent chinook windstorms (and maybe more winter days with air stagnation).

2. Below average midwinter snowfall is favored along and north of I-70 and up into Wyoming.

3. Above average midwinter snowfall is favored in New Mexico and southern Colorado.

4. Early and late season snowfall may be concentrated into a high-impact storm. At the Boulder climate station the chance for a storm with over 12″ in one day during the early and late season doubles during El Niño compared to non-El Niño years. The last two strong El Niños were in 1982-83 and 1997-98. Both March 1983 and March 1998 were stormy along the Front Range. 1982 also brought the infamous Christmas Eve blizzard while 1997 brought the paralyzing and deadly blizzard of October 24-26th. Even some weaker El Niño years in the recent past produced memorable snowstorms in March 2003 and December 2006.

Wet period continues for a couple more days

1:50 PM, Tuesday, July 7, 2015

The moist, cooler-than-average pattern that began Sunday night is likely to remain across the region through Wednesday. Although Thursday and Friday are likely to be a little sunnier and warmer, it may be the weekend before we return to average July temperatures.

As of early afternoon Tuesday there are breaks in the overcast, especially west of the divide and out on the plains. But just small amounts or solar heating are triggering showers and thunderstorms. Almost everyone is likely to see at least some light amounts, and a few spots may see locally heavy rain this afternoon and evening.

Wednesday is likely to be similar with some breaks in the overcast, but considerable amount of clouds and some showers around throughout the day. Locally heavy rain in afternoon thunderstorms may trigger some local flooding.

Significant cold front this evening

2:40 PM, Sunday, July 5, 2015

A cool front will bring much cooler and cloudier weather Sunday night and Monday, and it may be the second half of the week before we return to average temperatures for July.

On Sunday afternoon a cold front was moving south through eastern Wyoming and is likely to move through the Colorado Front Range this evening. A scattering of thunderstorms are developing up and down the Front Range. It’s possible they will get a little boost with the cold front, so watch for some localized heavy rain and small hail.

Monday will be cooler with high temperatures mainly in the 60s and 70s depending on elevation. We may even have some areas of low clouds and drizzle by morning along with the usual chance for afternoon thunderstorms. Cooler than average weather is likely through midweek, but with a gradual warming each day.

Holiday Weekend Forecast

2:15 PM, Thursday, July 2, 2015

Expect a typical early July weekend with warm temperatures and some chance for thunderstorms.

For the Front Range region, eastern Colorado, and southeastern Wyoming, temperatures are likely to be near to slightly below average (average is for highs in the mid to upper 80s in the Denver-Boulder area). There is a chance for late day thunderstorms each day. At this time it appears that the chance for thunderstorms on the 4th is lower than it is today and tomorrow. There may be a significant cool front Sunday evening or early Monday, but that’s still too far off to have high confidence in the specific details.

For western Colorado and Utah, temperatures are likely to continue above average through the weekend with only a small chance for thunderstorms in the mountains.