By Meteorologist Chris Spears

DENVER (CBS4) – Denver hit an official high of 91 degrees on Saturday, topping the 90 degree mark for the first time this season. It was also the warmest day so far in 2021.

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We’ll be just a few degrees cooler today in many areas, including metro Denver, due to increased mid-level moisture which will make for more afternoon clouds. In fact we woke up with some areas of cloud cover on Sunday and it made for a gorgeous sunrise!

Scattered cloud made for a beautiful sunrise in Morrison on Sunday. (credit: William Schmidt)

On Saturday we had a 40% chance for scattered storms in the mountains and a 10% chance in Denver and along the Front Range. That forecast panned out pretty well for us. Just before sunset yesterday we saw a handful of storms pop up in Douglas County and along the lower foothills of Jefferson County and Boulder County.

Today’s storm chances are a bit higher for the lower elevations. In Denver and along the Front Range it’s about a 30% chance. The eastern plains will see a 20% chance and in the mountains about a 40% chance once again.

Unfortunately the western slope will remain dry and it will be windy at times. We have extreme fire danger in the far southwest corner of the state where a Red Flag Warning is in effect.

Today’s thunderstorms are what we call air mass thunderstorms, meaning they will be triggered from daytime heating and the moisture present in the air, not by some large-scale organized storm system connected to the jet stream.

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On a day like today there are a few very valuable tools to use in forecasting general air mass thunderstorms. The dew point map helps track surface moisture. In the mountains you want values at least in the mid 30s and higher. In Denver and on the plains you want mid 40s and higher, but 50s are even better. If the numbers are lower you can still get a storm, but it will probably have more wind than rainfall.

The water vapor loop also comes in handy. It helps you see if there is moisture higher up in the atmosphere. You can track the dew point and other weather variables on our hiking weather page by clicking here.

Air mass thunderstorms are typically short-lived, lasting anywhere from 15 to 30 minutes. They rarely reach severe limits but every so often once can pulse and briefly become severe. We saw that Saturday evening in the Castle Rock vicinity when a storm produced 1-inch diameter hail for a brief period of time. The image below shows what is necessary for a storm to be considered severe.

Taking a look ahead some drier air will work back into the state on Monday and that will lower our storm chances once again. It will also mean less cloud cover so temperatures will climb a few degrees over the next several days.

But as long the main jet stream stays far away we won’t see any significant changes to the weather from day to day. Just subtle differences with cloud cover and storm chances each afternoon. Temperatures will stay within a few degrees of 90 for the entire upcoming week in Denver.

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Meteorologist Chris Spears