The Salt Lake Valley woke up this morning to an already decent - by Utah standards - rainfall. Most areas accumulated .2-.3" of liquid as a wave of showers passed over the valley in the predawn hours Friday
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| Precip Totals SL Valley 10/10/2025 @ 0900 MDT |
Current Conditions
As seen by the water vapor satellite imagery below, Utah is sandwiched between a large scale upper-level ridge over the central U.S. and a large scale trough edging onto the NW U.S. Pacific coast. This setup has created a corridor of southerly to southwesterly winds from the surface to the top of the troposphere, facilitating the transport of tropical moisture from the remnants of the tropical depression Priscilla north through the Desert SW up into the Intermountain West. The broad swath of moisture surging north from the Mexican Baja/Priscilla and the broad spinning upper-level low/trough off the NW U.S. Pacific coast is evident in the water vapor satellite imagery below.
A short-wave trough - a ripple embedded within large scale pattern - moved across Utah and Colorado overnight through this morning, bringing showers and storms. Short-wave troughs are associated with vorticity maxima (areas of cyclonic spin), cooler air aloft, and the energy responsible for creating clouds and precipitation. The the short-wave trough axis is noted by the dashed blue line in the figures below. The upper level ridge axis over the central U.S. is noted by the dashed red lines.
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| Left: 500 mb gph, winds, and temp; Right: 700 mb gph, winds, temp, and RH |
Friday into Saturday morning
Going forward into Saturday afternoon, multiple ripples or pieces of energy (short-waves) will progress approximately SW to NE across Utah. Combined with access to the deep moisture field - thanks to Priscilla - and support from some jet-streak dynamics, these pockets of energy with bring waves of rain showers and storms. Precipitable water across the region is forecasted to be near all time record levels for this time of year, with > 1" for portions of the state, particularly SE Utah.
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| ECMWF 00Z 10/10/2025 forecast for 10/10 @ 18Z: Left: precipitable water (in); Right: precipitable water % anomaly |
Northern Utah
Northern Utah will likely get a bit of a break from the consistent precip after Friday morning, with a mix of clouds and sun through most of the day. Temps will remain mild for early October. A spotty shower or thunderstorm is not out the question for the SL Valley, particularly later this afternoon, but as noted by the warm colors in the water vapor imagery below drier air will intrude into the area before additional moisture resurges north later Friday into Saturday.
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| GOES West Water Vapor Imagery 10/10/2025 |
Southern Utah
Southern Utah looks to get periods of showers and storms through Friday afternoon before the most consistent precipitation arrives late Friday into Saturday. Flooding and flash flooding will be a major threat for areas across southern Utah. Mountainous areas will also potentially see enhanced precipitation. By Sunday, 1-3" of liquid is forecasted, particularly for SE Utah, the Book Cliffs/Tavaputs, and Pine Valley mountains.
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| Left: ECMWF 00Z 10/10/2025 forecasted Total precipitation (in) for 10/12 @ 12Z; Right: WPC Flash Flood Risk |
Saturday Morning-Night
Last Major Tropical Moisture Impacts
The figure below shows multiple forecasted fields on Saturday 10/11 @ 12Z for four different levels in the atmosphere (top left to bottom right: surface, 300-200mb, 500mb, and 700mb). Areas are marked to indicate regions of heaviest precip, enhanced lift due to upper-level dynamics, trough axes, and cold front boundary, respectively.
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| ECMWF 00Z 10/10 four-panel forecast for 10/11/2025 @ 12Z: (Top left to bottom right) MSLP/precip and 1000-500 mb thickness; 300 mb gph and winds; 500 mb gph, vorticity, and winds; 700 mb gph, RH, temp, and winds |
Upper-level Trough and Cold Front
By late Saturday afternoon/early evening, the attention pivots to the upper-level trough and associated cold front moving into northern Utah. There's a decent amount of baroclinicity with this trough, indicated by the sharp temperature gradient/cold front in the forecasted 700mb chart below, and the strong jet-streak noted in the 300-200mb chart oriented roughly parallel to the frontal boundary. A combination of frontogenesis and upper-level lift coinciding with the left front exit region of the jet streak could create for some interesting conditions across the Northern Wasatch Front Saturday evening/night.
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| ECMWF 00Z 10/10 four-panel forecast for 10/11/2025 @ 12Z: (Top left to bottom right) MSLP/precip and 1000-500 mb thickness; 300 mb gph and winds; 500 mb gph, vorticity, and winds; 700 mb gph, RH, temp, and winds |
Without trying to add every available plot and piece of information to this post, I will try and summarize. Storms and shower activity will fill into northern Utah late Saturday afternoon into the evening. The front is forecasted to move through sometime between 1700-2000 MDT. Precipitation will be most consistent and heaviest during this period before decreasing through the first half of Saturday night. From the met variables in play that I mentioned previously, there's a good opportunity the Wasatch Front gets in on some thunder and lightning activity with a possible stronger storm. Maybe even some thunder-snow and graupel for the higher elevations in the mountains.
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| UoU LCC guidance: Alta total snow accumulation (in) |
Snow levels will drop down to 6500-7000' by Saturday night as colder air filters in and heavier showers lower the wet-bulb freezing level. With the wind shifting NW for a short period overnight Saturday, the Cottonwoods look to pick up a few inches of the white stuff by Sunday morning. So for all the addicts that will be shaking in their beds Sunday morning, get out into the mountains on Sunday and get a good snort in.
Sunday into the Beyond
Unfortunately (or fortunately), the pattern shifts quickly, reverting winds back westerly and then to southwesterly in a 24-36hr period. Unfavorable flow, dissipating moisture, and warm air advection will shut down the upslope flow in the Cottonwoods. However, next workweek looks to provide a few more opportunities for liquid and mountain snow. Is all this active weather just an early season tease or will it continue into the late fall and winter? May be time to rub the forecasting magic eight ball...
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