Monsoonal moisture makes its 2020 debut


SALT LAKE CITY, Utah (ABC4 News) – Utah is closing in on the Independence Day holiday and weekend, and ironically, on par with 2020, as many of us head to the outdoors, a subtle monsoon push will move into the state.

This monsoonal moisture arrives most clearly on Friday and Saturday and will impact eastern, central and southern Utah. Weather models bring in the threat of thunderstorms south of Provo and Evanston, Wyoming for the weekend.

This initial push will increase mid level moisture, but what does that even mean? Well, the translation means we could see dry thunderstorms pop up with a lack of rain, but plenty of lightning and gusty winds. An elevated risk for fire danger will be around for the Fourth of July, and it’s noteworthy for any of us packing up the family for a camping trip to the Uintas or any mountainous area in central, eastern and southern Utah.

Keeping those eyes to the skies is critical over the holiday weekend, but it’s a great habit to get into because the start of the monsoon season in Utah indicates the start of several Utah weather phenomena. To understand what that means, we back it up a little and breakdown exactly how the monsoon season happens in the Beehive State.

The word “monsoon” actually means the seasonal reversal of winds. The seasonal change occurs in upper level winds from the polar westerlies to tropical easterlies and includes a switch from dry west winds high up in the atmosphere to moist winds from the east or southeast. Rain actually starts to the south of us over southern Mexico, when heavy rainfall starts in May and June. Rain quickly spreads north along the western slopes of the Sierra Madre Occidental mountain range, and starts to move north. Typically, the monsoon season begins in the Southwestern United States in early July and can hold on until mid to late September.

For Utah, we have a couple of key players when it comes to the monsoon, that includes the “Four Corners High” and our sources of tropical moisture. We have two different sources of tropical moisture with the Gulf of Mexico and the Gulf of California. The Four Corners High sets up near southeastern Utah and has a clockwise flow, which helps draw moist, humid air into Utah. We get thunderstorm development when hot, unstable air rises and with plenty of mid and low level moisture present during monsoon season, we can tap into heavy rain, numerous thunderstorms and frequently trigger severe storms and flash flooding. Utah has plenty of steep terrain and slick rock, and flash flooding can tear through slot canyons and popular landscapes throughout the state. For a visual of how this happens, you can watch the video.

It’s the time of year when Utahns flock to the outdoors, so you always want to know when we get a surge of monsoonal moisture. This weekend from Thursday through Saturday, we get some mid-level moisture and not so much low level moisture, so we can often see dry thunderstorms as a result. Be careful in the outdoors and stay with Pinpoint Weather Team for changing conditions and Utah’s Most Accurate Forecast.

Alana Brophy
Alana is an award winning journalist who before joining ABC4 Utah, spent the last five years anchoring, reporting and forecasting in Boise, Idaho.

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