Mid-week Low

No, I'm not talking about that feeling you get Wednesday afternoon after eating a greasy cheeseburger at your desk. A low pressure system looks to track across Utah by the middle of this week. 

I woke up this morning and saw some cumulostratus clouds streaming south to north quite quickly across the sky. Pretty intuitively, I gathered that means the winds at cloud level were moving fairly fast out of the south. Temps were also hovering near 50F, which was quite warm for an overnight low, considering the high yesterday didn't make it out of the 50s. After a clear, calm, and dry day yesterday, where winds were W-NW and temps were cool, the observations this morning make me think changes are coming.

Currently

GOES West water vapor imagery 10/13/2025

The satellite water vapor channel uses electromagnetic radiation absorbed and emitted by water vapor to detect varying amounts of moisture in the atmosphere. The water vapor channel is useful when trying to identify circulations in the atmosphere, due to the way water vapor acts as a tracer for atmospheric motion. Imagery from this morning (10/13/2025) reveals a broad upper-level low sliding south down the U.S. Pacific coast. Some moisture is also noted, by the cloud field and brighter colors, moving SW to NE across Arizona into southern Utah. 

500mb gph, wind obs, and absolute vorticity (shear+curvature+earth)

If we look at this morning's current upper-level 500mb analysis chart, we can see the broad spinning low/trough along the U.S. Pacific coast noted by the higher values of vorticity (warm colors) and the cyclonic curvature (counter clockwise) in the height and wind field. 

Monday

Today - Monday - Utah sits downstream of the Pacific trough, putting the state under southerly to southwesterly flow, hence the cloud movement this morning. The deep layer southerly flow is clearly evident in this morning's sounding from KSLC as is the warmed mid-level temperatures - from about -2C at 700mb yesterday to about +2C at 700mb this morning.

KSLC 12Z 10/13/2025 sounding skew-t: temp (red), dew pt (green), and winds

A slug of moisture and associated energy (short-waves) will move south to north into southern Utah going forward through the day, bringing the potential for scattered showers and thunderstorms. There's the possibility of a few stronger thunderstorms across SE Utah Monday afternoon due to a combination of deep layer wind shear, low-level moisture advection, and daytime heating. 

Left: CONUS 700 mb gph, winds, RH, and temp; Right: Intermountain West 700 mb gph, winds, temp, and RH - blue dashed lines note short-waves, red arrows note direction of moisture transport

Winds will become breezy out of the south for areas by Monday afternoon, but temps should warm 10-15 degrees compared to yesterday's highs. Northern Utah and the Wasatch Front will likely remain dry, with mostly sunny conditions in the morning and increasing clouds come the afternoon. Highs in the upper 60s for the SLV. By later afternoon/evening this is an increased opportunity for a shower or storm as moisture from down south rotates northward. 

Tuesday

The Pacific trough is forecasted to dig south and become a closed low by Tuesday. This means Utah will continue to to be on the down stream side of the trough with southerly to southwesterly winds from the surface to the upper-levels. Bouts energy and moisture will continue to rotate northward through the state on Tuesday, creating periods of scattered showers/storms. Most shower activity looks to focus Tuesday morning. So Tuesday is looking like a close repeat of Monday for most areas of the state, with some minor variations. Likely another mild-ish day across the Wasatch Front, with breezy southerly winds, a few showers possible Tuesday morning then a mix of clouds and sun. 

ECMWF 00Z 10/13 four-panel forecast for 10/15/2025 @ 00Z: (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 

Wednesday-Thursday

Tuesday evening into Wednesday things look to get a bit more interesting. The trough finally begins to make eastward progress and pushes into Utah, bringing a cold front and spreading precipitation over most of the state. Currently, it looks like a cold frontal boundary will slowly make it's way across Utah over the course of Wednesday. How this boundary progresses along with the movement of the upper-level low will determine precip location, amounts, and timing. But as of now, the most consistent precip for northern valley areas looks to be Wednesday morning into the afternoon. 

The air associated with the cold front has maritime polar origins, but by the time it gets to the state it will be highly modified - not as cold. Nonetheless, the colder mid to upper level temps will drop temperatures in the 40s and 50s in the valleys and drop snow levels down around 7500-8000' by Wednesday afternoon/evening in the mountains. Another few inches of snow accumulations possible for the high elevations by Thursday morning.

The trough exits the state by late Thursday, but not before delivering some wrap around precip, focused over northern Utah, Thursday morning and potentially in the afternoon.  

ECMWF 00Z 10/13 four-panel forecast for 10/15/2025 @ 18Z: (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 

ECMWF 00Z 10/13 forecast loop: 6-hr precipitation accumulation 10/15 00Z - 10/17 00Z

Beyond

As of now a ridge builds over the Intermountain West Friday through the weekend, bringing another period of dry and warmish weather. Should be a fairly nice weekend across Utah. Happy to break the weekend storm cycle before it got too strong of a hold. Hints of the next noteworthy system early next workweek.