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Strong Thunderstorms Possible on Wednesday


Moisture and instability will be on the increase Wed in response to a low pressure system located to our west. Storms will be possible by midday Wed with multiple rounds possible thru the PM hours. Stronger storms could produce frequent lightning, hail, and heavy rain. On Thu we will see more cloud cover & cooler temps which may limit t-storm potential, but light showers will be possible at least.

Short Term Forecast

Forecast for Wednesday:

A large area of low pressure is moving slightly northward along the California/Nevada border. South/southeast winds around this low will transport abundant subtropical moisture into Wyoming, and a couple of shortwaves embedded in the flow will support a high likelihood of thunderstorms and showers during the afternoon hours.

Skies are starting out mostly sunny on Wednesday morning so we have a nice weather window over the next few hours. However, thunderstorm development is expected to occur earlier today. I wouldn't rule out storms as early as 11am-noon, with a higher likelihood of storms from 1pm and beyond.

In addition, multiple rounds of thunderstorms will be possible this afternoon and heading into the early evening hours. Storm motions will be from SSE to NNW and will be fairly slow-moving.

Instability is expected to be significant on Wednesday afternoon and wind shear (change in wind speed/direction with altitude) will also be stronger compared to prior days. This will support a threat of stronger thunderstorms, which will be capable of frequent cloud-to-ground lightning and medium-size hail.

Locally heavy rain will also be possible with stronger storms given the uptick in moisture we are seeing, along with the fact that storms will be relatively slow-moving. Storm cloud bases will generally range from 10,000-11,000 feet during the afternoon with further lowering of cloud bases in the evening.

Snow levels will also be high, ranging from 12,000-13,000 feet.

Lighter showers will also remain possible through the overnight hours and an overnight thunderstorm also couldn't be ruled out.

Forecast for Thursday:

Significant moisture will be in place throughout the day on Thursday, and this will likely result in widespread thick cloud cover with a good chance of showers during the morning hours. 

The cloud cover could very well end up suppressing afternoon thunderstorm development due to a lack of solar heating. If we do manage to see any breaks in the clouds then stronger thunderstorms and locally heavy rain will be possible, but it's very much a conditional threat. 

Extended Forecast

Outlook for Friday to Saturday:

We will be in-between low pressure systems on Friday and Saturday with more abundant sunshine expected during the morning to midday hours. However, lingering moisture and instability (aided by more solar heating) will result in scattered thunderstorms on both afternoons.

Outlook for Sunday through Mid-Next Week:

Another low pressure system will move into the Southwest U.S. on Sunday and Monday with southerly winds transporting moisture from the South Pacific back into Wyoming, leading to another uptick in thunderstorm chances.

By the middle of next week, we may see a trough of low pressure drop in from the northwest, which would be a different look from recent weeks in which we've seen south/southwest flow. However, it still looks like we could see a continuation of daily shower/thunderstorm chances.

Thanks so much for reading! Next update on Thursday (June 8).

Alan Smith