One-Two Punch

A hurricane, a cold front, and a split jet stream walk into a bar... As far as Utah weather is concerned, this weekend looks quite interesting. The weather will be playing 3-D chess, and if conditions come together areas of the state will see another big rain maker, storms, strong winds, and mountain snow to top it off. 

The Next Few Days:

Before the excitement of this weekend, Wednesday will be another great fall day, with sun and mild temps. Thursday will bring the opportunity for scattered showers to edge up into southern and central Utah, focused across the higher terrain. The Wasatch Front valleys will likely eek out another nice dry and warm day, with a spotty shower possible in the Wasatch mountains. My suggestion is to get out and enjoy the weather before conditions go downhill Friday into the weekend. 

The atmosphere and earth is an interconnected system, with no one atmospheric or surface phenomena being independent from another. Hurricane Priscilla currently spins just to the south of the Baja Peninsula of Mexico. In the next few days it will slowly progress N-NE before decaying into a tropical depression and ultimately impacting Utah weather a thousand miles away.  

The Late Week to Weekend:

At the moment, an upper-level trough is digging south off the west coast of British Columbia and the PNW. The trough will continue to dive south over the next 24-36 hrs before closing off and stalling briefly off the N. California/Oregon coast by late Thursday into Friday. During the same period, an upper-level ridge will build over the southern Plains and central CONUS. The anticyclonic (clockwise) winds around the ridge and the cyclonic (counter clockwise) winds around the trough will create a corridor of southwesterly mid to upper-level winds across the Southwest and Intermountain West. Additionally, a split polar jet stream (southerly and northerly branch) will make for some enhanced upper-level dynamics/lift. It's these southwesterly winds and enhanced dynamics that will help tap into the tropical moisture and energy of Priscilla, bringing it north into the Desert SW and Utah, and creating an environment conducive for extended moderate to heavy rainfall over locations. 

ECMWF 00Z 10/08 two-panel forecast for 10/10/2025 @ 12Z: (left to right) 500 mb gph, vorticity, and winds; 700 mb gph, RH, temp, and winds 

There's a bit of uncertainty as to exact interplay between the upper-level trough, ridge, and Priscilla, with small changes in any one of these atmospheric players changing the forecast down the line. However, simplifying this complex situation, the most recent guidance does offer a general depiction of what will occur this weekend:

ECMWF 00Z 10/08 two-panel forecast for 10/08/2025 12Z - 10/13/2025 12Z: (left to right) MSLP, 1000-500 mb thickness, and precipitation; 700 mb gph, RH, temp, and winds 

Thursday

A combination of moisture transported around the upper-level ridge across the south-central CONUS and moisture tapped from Priscilla will be transported northward across the Desert SW and into Utah. Scattered showers and storms possible, mainly focused across the southern tier or the state in the afternoon. SL valley temps near 80F. 

Friday

1st act: Moisture from Priscilla is tapped further, bringing more widespread showers/storms into Utah, with the greatest coverage across the southern two thirds of the state. SE Utah looks to see the heaviest and most consistent precip, with the threat of flooding. Potential for some thunderstorms across the Wasatch Front. Winds strengthen out of the S-SW for SW and central Utah desert areas. SL valley temps upper 70s. 

Flash flood potential

Saturday morning/afternoon

The eastward progression of the Pacific trough speeds up and moves inland across the Great Basin region. Pacific moisture and a maritime polar airmass begin to combine with the tropical moisture from Priscilla. At this point, northern Utah has remained removed from the bulk of precipitation. Maybe a bit of a lull in shower and storm activity across the state, but still ongoing for areas. SL valley temps upper 70s. 

Saturday evening/night 

2nd act: A cold front and associated precipitation field moves across northern Utah, bringing the most consistent and heaviest precip to the Wasatch Front. As is typical, the most favorable period for precipitation in the valleys and particularly the mountains will occur when mid-level winds shift NW, which should occur sometime Saturday evening/night. This will also be the same period when colder air advects into the state, lowering the rain/snow line down to about 6500-7000'.

Sunday

Cooler drier air moves in as the trough exits the state to the east. Maybe a few lingering valley rain or mountain snow showers in the morning before drying out by the afternoon. SL valley highs in the 50s. 

ECMWF 12Z 10/8/2025: Total precipitation (in) 10/8 - 10/13

Beyond

May provide some updates on the storm event this weekend as we get closer. Otherwise, conditions beyond this weekend into next workweek also look intriguing, with active, wet, and cool conditions possible. For those already foaming at the mouth about snow in the Wasatch, you may start convulsing by mid to late next week. We'll see...