Quiet plus haze

Tropics

Nothing much going out there in the skies over Utah today. Quite the opposite for the areas in the Caribbean. Hurricane Melissa is currently impacting eastern Cuba as a weakened but still strong hurricane. Damage across Jamaica probably won't be totally assessed until later this week/weekend as power and internet comes back online. Satellite imagery from Melissa yesterday - 10/28/2025 - showed a textbook example of an annular (donut-like) hurricane.

The symmetrical nature of the storm was quite mesmerizing and revealing of it's strength. Top winds just before landfall reached 185 mph, which ranks the storm as the second highest wind speed ever recorded from an Atlantic hurricane and ties Melissa for the strongest Atlantic hurricane to ever make landfall. Melissa's lowest central pressure of 892 mb ties for third most intense Atlantic hurricane on record. 

Utah

Another cold crisp morning in Salt Lake City. Not a cloud in sight over Utah. KSLC didn't break freezing this morning - low only got to 34 F - but they break freezing yesterday morning, with a low of 30 F. First frost/dip below freezing for the season for the Salt Lake Valley. The average date the SLV sees low temperatures reach freezing or below is Oct. 20, so a bit later than average but pretty close to on track. 

KSLC Min, Max and Average first and last freeze days (<= 32 F)

Minimum	Mar-07 (2017)	Sep-13 (1928)
Mean	Apr-22	Oct-20
Maximum	Jun-06 (1914)	Nov-17 (2021)

Not surprisingly, the state of Utah cold spot yesterday - 10/28/2025 - was Peter Sinks, with a low of -10 F. Peter sinks is a small crater like area in the far northern Wasatch/Bear River mountains that pools cold air easily and commonly can be the coldest spot in Utah and even the CONUS. 

Observed temp (F) at Peter Sinks on 10/28/2025

Ridging has quickly established itself  after our mild AR event this past weekend.  Warming mid-level temps associated with the ridge has already created inverted conditions across the Wasatch Front. The sounding from KSLC this morning reveals an inversion and stable conditions up to and above 700 mb, where there is a fairly obvious warm-nose (area of high temps). The consequence? Air quality will gradually degrade over as pollutants build up below the inversion and a haze will begin to blanket the SLV.

1800Z 10/29/2025 - Observed 500mb ghp, temp (C), and winds

KSLC 12Z 10/29/2025 sounding - temp (red) and dewpt (green)

Besides a grazing dry cool front overnight Wednesday into Thursday, there is nothing on the horizon weatherwise for Utah through the upcoming weekend. The cool front won't change things much, with haze likely continuing to build. Warming temperatures and dry conditions are expected through at least the next 5 days. There are hints of a trough and cold front moving through Utah sometime around 11/6/2025, but too far out to say with any confidence. Personally, I will be enjoying the abnormally warm start to November with temps in the 60s and sunshine before winter decides to set in... 

*I want to add a quick correction to a previous post about the ranked top five monthly total precipitation for KSLC. Here are the correct top five wettest months on record:

Melissa

Weather history is currently unfolding in the central Caribbean. Hurricane Melissa is beginning to make landfall on the southwestern coast of Jamaica as a CAT 5 hurricane (winds  > 157 mph). It's central pressure is 892 mb - a drop of about 10-12 mb since yesterday morning - and has maximum surface winds of 160 kts (~ 180 mph). IR and visible satellite imagery from this morning (10/28/2025) reveals an extremely intense hurricane. The symmetry and clarity of the eye in the both the IR and visible are obvious, which is one indicative sign of a very strong storm.

GOES East True Color imagery 10/28/2025

GOES East IR imagery 10/28/2025

Up until the past 12-24 hrs, Melissa's movement had been nearly stagnant as it spun off the coast of Jamaica for more than two days. The slow moving nature of Melissa - in close proximity to Jamaica up until this point - has inundated the island with relentless rainfall, and with more rain on the way catastrophic flooding is very possible. Total precipitation amounts could top out around 30".

NHC Probabilities of the hurricane-force wind speeds

One silver lining of this hurricane is that is compact and the strongest of the hurricane force winds lie within a focused area around the eyewall. In other words, not all of Jamaica will be impacted by 180+ mph winds. Nevertheless, this is an extremely dangerous situation for the island nation. This could be the most powerful hurricane to ever make landfall in Jamaica.

ECMWF 00Z 10/28/2025 four-panel forecast for 10/28-11/1/2025: (Top left to bottom right) MSLP/precip and 1000-500 mb thickness;700 mb gph, RH, temp, and winds; 300 mb gph and winds; 500 mb gph, vorticity, and winds

Melissa will progress over Jamaica on Tuesday before briefly crossing open water and making landfall across far eastern Cuba sometime Wednesday. At that point, Melissa will likely be weakened due to interactions with land but still could be a strong hurricane. The storm track will accelerate rapidly to the NE after Wednesday as the hurricane begins to interact with a deep trough across the SE CONUS. Strong upper-level wind shear - associated with the upper-level trough and corresponding jet streak - and cooler ocean water temperatures will also aid in weakening the hurricane. There could be some interaction between the trough and hurricane remnants along the NE U.S. seaboard come late week into the weekend, but that is tbd...

ECMWF 00Z 10/28/25 Ensemble tracks for Hurricane Melissa

Last one for a bit

Low hanging cumulostratus and light rain out there across the Salt Lake Valley this morning. Compliments of the last bit of AR energy and moisture that's grazing Utah. I'm wondering if the sun will make an appearance and things will clear up later. 

KSLC top 5 monthly total precipitation (in)

Even with the meager precipitation from this AR event - 0.17" at KSLC for the event -, Salt Lake City has broken 5" total precipitation for the month of October (5.12" as of 1600 UTC 10/27). This puts October 2025 within the top five wettest months on record. Kind of impressive.

10/27/2025 @ 1500 UTC: Observed 700 mb gph, temp (C), and winds

The coldest air - associated with a short-wave trough - is passing over the northern part of the state this morning. 700 mb temps range from -5C to -8C across the Wasatch Front, with some snow flakes mixing down as low as 6000-6500' for the central Wasatch and 5000-5500' for the northern Wasatch by late morning. However, any snow will likely focus a bit higher for each area as the bulk of the moisture will be exiting the state as the coldest temps arrive, and any accumulations at elevations below 7000' will be light or nonexistent with at least a few inches possible for the higher elevations.

GOES East True Color imagery 10/27/2025

I think the cloudiness and precipitation will largely be a morning issue as ridging and accompanying subsidence is forecasted to build in quickly behind this morning's trough. Satellite imagery showcases how sinking air (subsidence) behind the main trough axis and baroclinic zone - extending NE from northern Nevada into Utah - is creating clear conditions. In general, things look to improve and gradually clear through this afternoon. 

CPC 6-10 day temp outlook Nov. 1-5

Not much on the horizon weatherwise after Monday through the remainder of the workweek. As of now, a hardy ridge is forecasted to build across the western half of the CONUS, bringing dry and warming conditions across Utah. Temperatures look to moderate and warm a bit each day through the Halloween weekend. By Nov. 1st, temps are forecasted to be well above normal for the northern Utah valleys, with near 70 F possible for the Salt Lake Valley. Looks like cold temperatures for costumes and trick or treating won't have to be factored in this year.

Forecasted surface temperature for KSLC 10/27-11/2/2025

 

Hurricane Melissa

Pivoting quickly southeastward from the West and Utah, let's take a look at the tropics. A powerful Atlantic hurricane named Melissa swirls just south of Jamaica this morning. Hurricane Melissa has gone under rapid intensification over the weekend and now sits as a CAT 5 hurricane (Saffir-Simpson Scale), with maximum winds at 145 kts (165 mph) within the eyewall. 

GOES East IR imagery 10/27/2025

GOES East True Color imagery 10/27/2025

Melissa's progress, at the moment, is slow to the W but is forecasted to recurve to the N-NE as it begins to interact with a mid latitude trough currently located across the eastern half of the CONUS. IR and visible satellite imagery reveals the distinct, symmetrical, and clear eye of the hurricane. Specifically, the darker colors in the IR imagery identify the intense convection surrounding the eye - colder temperatures associated with high clouds and deep convection - which correlates to the significant strength of the hurricane.

NHC Hurricane Melissa forecast cone

Melissa will likely undergo some changes in the next 24hrs, but is forecasted to remain a major hurricane as it makes landfall with Jamaica and Cuba over the next two days. Significant impacts for those areas. The storm intensity will weaken as it makes landfall, with some slight restrengthening once the hurricane passes back over water near the Bahamas later this week. Once Melissa makes it's way north of the Bahamas, it's progress will accelerate to the NE and be taken out to sea. It will likely weaken further as it passes over cooler sea surface temps and encounters some upper-level wind shear. 

AR Tease

The mornings as of late have finally gotten that touch of chill characteristic of mid fall. This morning was no different. Not much going on out there, with clear skies and calm winds. Seems to be the precursor to a typical fall day. The light haze we had Wednesday and Thursday has finally dispersed. We can thank some northerly near surface winds yesterday afternoon for sweeping the pollution out of the Salt Lake Valley. Ceilometer data from a site in the northern SLV near the airport reveals how the pollution cleared out of the area once winds shifted N-NW and picked up in the afternoon. 

Top: Observed KSLC wind speed/direction 10/23-10/24/2025; Bottom: Ceilometer reflectivity 10/23-10/24 from the Utah Tech Center (norther SLV).

Friday-Saturday

The closed upper-level low that impacted the state yesterday has exited to the east, with a short-wave ridge following in it's wake and building across Utah today (Friday). Conditions are expected to be clear, calm, and relatively warm Friday, with temps topping out in the mid-60s for the northern Utah valley areas, which is near normal for this time of year. Ridging remains through the first half of Saturday before the upper-level pattern will begin to transition into a more active pattern. Temps will be a few degrees above normal Saturday along the Wasatch Front and winds will become a bit breezy in the afternoon as warm air advection precedes the weekend storm.

Observed 500 mb gph and temperatures (C)

A broad Pacific trough and stream of moisture (atmospheric river (AR)) is currently making landfall along the PNW coast. A short-wave trough and surface low embedded in the larger scale trough will move inland today through Saturday. Models have been tracking the center of this trough across the interior northwest into Idaho and Montana by late Saturday. 

Saturday - Monday

There is still some uncertainty about how shallow or deep the trough digs into the Great Basin and Intermountain West region. Currently, models are taking the system on a more northerly track, with only grazing impacts across Utah. This means the bulk of the moisture and colder air are forecasted to miss Utah late Saturday into Sunday. However, a strong 140 kt jet and stronger area of baroclinicity is forecasted to progress into the far reaches of the state near the Idaho border, which could provide better dynamical forcing for precipitation for Bear River mountains and Cache Valley.

ECMWF 00Z 10/24/2025 four-panel forecast for 10/24-10/28/2025: (Top left to bottom right) MSLP/precip and 1000-500 mb thickness;700 mb gph, RH, temp, and winds; 300 mb gph and winds; 500 mb gph, vorticity, and winds

The northern third of the state looks to have the best opportunity for some rain/snow showers Saturday evening through Sunday, with a cold front moving across the area at the same time. Guidance has trended warmer with the air that moves in behind the cold front, so not looking lower elevations to get in on the snow action. Snow levels look to remain above mid elevation areas ( >6500-7000'), but could come down a bit lower across the far northern portions of the state. In general, Utah forecasted to only get a kiss from this AR event, with the Utah/Idaho border area getting the most precipitation. Central Wasatch areas - Cottonwoods - currently look to get meager pickings in terms of liquid/snow. 

ECMWF 06Z 10/24/2025 Ensemble Total Snow Accumulation at Alta, UT

It's very likely that details of this forecast will continue to shift, so it is difficult to put numbers on precip and snow amounts this weekend. But for the sake of curiosity, let's look at the ensembles - collection of multiple model runs with slightly varying input conditions - for Alta, UT. Essentially, the ensembles spell out a bit of a bleak future in terms of snow for the upper central Wasatch, with a few inches of snow late Saturday into Sunday/Monday the most likely solution at the moment. 

Beyond

While Utah will likely miss out on the AR party this weekend, the flood gates will open for the PNW with a wave train of multiple systems moving into the region through the middle of next workweek. Utah may get a bit more energy and moisture from one of these systems late Sunday into Monday, but not expecting anything super significant. I think the more interesting thing is if this storm squeezes out enough liquid to help SLC break 5" total precipitation for the month of October. As of now, KSLC sits at 4.95" which already smashes the old monthly record. Just need a little more...

ECMWF Extended Ensemble 00Z 10/23/2025: 7-Day Precipitation anomalies Oct. 23-Nov. 1

It's difficult to say what will happen beyond early next week, but there are hints that a decent period of ridging accompanied by dry and relatively warm weather will settle in across the Great Basin and Utah the middle of next week through the first week of November. So looking like warmvember to start... 

ECMWF Extended Ensemble 00Z 10/23/2025: 7-Day 500 mb gph anomalies Oct. 31-Nov. 7

AR Flavor

KSLC 12Z 10/22/2025 sounding skew-t: temp (red), dew pt. (green), and winds

Not a cloud in sight out there earlier this morning, but a very light haze does seem to have developed over the Salt Lake Valley. If one is thinking it will be repeat of yesterday's conditions for the northern Utah valleys - sunny with a high in the low 60s - then they would be mostly correct. The light haze can be blamed on the marginal cold air pooling and ridging over Utah. 

At this time of year, strong radiational cooling overnight really takes off on clear calm nights. This creates a near surface nocturnal temperature inversion that is difficult to erode with weaker solar heating due to the lower sun angle. When you add a subsidence inversion due to ridging/high pressure on top of that, it easily creates stagnate conditions where pollutants can build up. A quick look at the sounding obs from KSLC this morning (10/22/2025) reveals an inversion over the SLV from the surface to about 775 mb (~1000 m deep). The weather today will be close to yesterday's, with a slight variation due to a weak system progressing into the region. 

GOES East True Color 10/22/2025 with 500 mb Rap analysis overlaid

Satellite imagery this morning shows a closed upper-level low rotates just off the So Cal coast, with Utah lying downstream of the upper-level trough axis. Not much cold air or moisture is associated with this system, but the low will shift onshore through the day, spreading clouds northward into Utah. Clouds will increase over the course of the day for northern portions of the state. As the system translates inland across the Mojave Desert a few scattered elevated showers/thunderstorms are possible for the southern 2/3rd's of the state going into the afternoon. Weak upper-level forcing and limited moisture will largely hamper any organized shower or storm development, however, some instability due to surface heating this afternoon will aid in forming some disorganized precipitation. Shower activity will focus across the higher terrain. 

ECMWF 00Z 10/22/2025 forecasted precipitation for 00Z 10/23/2025 (1800 MDT)

The closed low continues to translate across the southern tier of the state tonight through Thursday, spreading more low to mid-level moisture into the state. A few isolated showers may make their way as far north as the Wasatch Front by Wednesday night into early Thursday morning. However, the focus of shower/storm activity will remain over the southern half of the state. The northern valley areas will likely just remain dry. Isolated showers/storms, focused over the higher terrain and SE Utah, continue Thursday before the low exits the state by Friday morning. 

The Weekend

Going into the weekend it looks like the weather gets a bit more interesting. After the passage of the closed low, a short-wave ridge quickly migrates over Utah, bringing southerly flow and warm air advection Friday through Saturday. In effect, this will create for some nice sunny and relatively warm fall days, with some breezy southerly winds come Saturday. 

Model forecasted surface temperature (F) for the SLC

The short-wave ridge is 'short' lived though, with a broad Pacific trough proceeding closely behind it. The trough looks to be associated with an Atmospheric River (AR), which is defined as a concentrated or focused region of atmospheric moisture transport from the lower to higher latitudes. AR events are difficult to forecast due to their complex nature and lack of observations over the oceans - where AR's originate. 

ECMWF 00Z 10/22/2025 four-panel forecast for 10/24-10/28/2025: (Top left to bottom right) MSLP/precip and 1000-500 mb thickness;700 mb gph, RH, temp, and winds; 300 mb gph and winds; 500 mb gph, vorticity, and winds

I think going into detail about how this AR is forecasted to impact Utah this weekend would be unwise at this point. But I will attempt to outline the potential timing and impacts from this system. Models have been trending on a solution that brings moisture and energy from the AR/trough across northern Utah sometime Saturday night into Sunday morning. This means a cold front along with precipitation will likely pass over the SLV the second half of this weekend. 

How much moisture makes it into the state is highly suspect and will change with each new forecast model run, so I would not get hung up on amounts at this point. The bulk of the moisture looks to miss Utah as of now. Like I mentioned, forecasting AR events are difficult. It's analogous to determining the movement of an unattended fire hose spraying water. Modeled integrated vapor transport shows the main region of moisture transport associated with the AR. It seems that due to terrain and trough characteristics the moisture field breaks up some upon landfall, with a more dispersed and weakened moisture field making it's way into Utah late Saturday into Sunday. 

ECMWF 00Z 10/22/2025 forecasted integrated vapor transport (IVT) through this weekend

Some rain likely for the valleys and snow for the mountains. Snow levels could potentially be pretty low (~5500-6000'), depending how how the trough tracks across the state. Temperatures will take a quick dip Sunday, with highs in the SLV 20-25 degrees cooler than Saturday only maxing out near 50F. A few additional bouts of energy and moisture associated with the AR are possible through early next week, keeping cooler air in place and bringing periods of showers into the state. However, there is a high probability of details changing during this period so there will likely be updates to this. Anyway, a period of unsettled and cooler weather is possible the second half of this weekend into early next week. Keep the liquid coming. Utah needs it...

Quick cool down

Clear day to start the second half of the weekend. An upper-level ridge still remains over Utah, aiding in another dry and relatively warm day across the state. May be the last day that is this warm this year. Typically, temps really start ratcheting down m as daylight hours shorten quickly.

A trough and cold front are currently progressing from PNW into the interior, which will flatten the ridge through Sunday but increase mild southerly flow across Utah. Temps will top out in the 60s and 70s in valley areas across the state, with breezy winds out of the south this afternoon. 

The trough is forecasted to move eastward Sunday into Monday morning, but will largely skirt north of Utah. The cold front and a bit of moisture will graze the northern third of the state overnight, bringing cooler air and the opportunity for a few showers across the northern valleys and mountains in the early morning hours. Snow levels look to be around 7500-8000’, but most of the moisture will have moved on before the coolest temps arrive. Potential for 1-3” in the higher elevations of the Wasatch. This is a quick moving system, so not expecting much in terms of liquid or impacts.

A ridge quickly reestablishes itself late Monday into Tuesday. Temps rebound some and conditions look to be dry. Not much excitement through the remainder of the workweek. Just keeping an eye on a mid week disturbance across the southern half of the state, but not too much expected out of that. Hints of a more significant storm for this next weekend. However, still out too far out to talk about with any sort of confidence…

Setting Records

I woke up this morning to signs of rain overnight. Windows had droplets, smell of wet ground, and also the subtle smell of the GSL gases. When I checked yesterday morning, the October 2025 monthly total precipitation was already within the top five wettest Octobers on record, so obviously I wanted to check on where SLC ranked this morning after potentially more rain overnight. As of yesterday's and last night's rainfall (0.83"), Salt Lake City has broken the October monthly record for total precipitation (4.31"). This is a fairly large number for only being halfway through the month. With more liquid on the way today through tomorrow and whatever the remainder of the month bring, I am interested in where SLC will end the month at. 

So how much more precip are we going to get with unsettled weather forecasted the next couple of days? 

Wednesday 10/15/2025

An occluded Pacific system/low located over Nevada will translate north and east through Utah today (Wednesday). Utah sits downstream of the low, with deep and relatively moist southwesterly flow across the state. 

GOES East True Color imagery on 10/15/2025 with 500mb analysis overlaid

The Pacific air mass associated with the system has been highly modified and the stronger baroclinic characteristics of the storm have been somewhat muted. However, a cooler air mass still remains under the center of the low, with an attendant cold front now located over central and southwestern Utah. As the low progresses E-NE through Utah on Wednesday, this cold front will move across the Wasatch front late morning into the afternoon. Cooler air along with precipitation will fill into the state as the cold front moves over. Rainfall will generally be light to moderate for areas, with a few opportunities for heavier showers if clouds part and the sun is able to destabilize things a bit. 

Thursday 

The trough axis (center of the trough) looks to pass over northern Utah sometime overnight Wednesday into Thursday morning. By this point, the main moisture field with be exiting the state but trailing wrap-around moisture and energy will filter in from the W-NW. Cooler mid to upper-level temperatures combined with surface heating will aid in some cold-core shower/thunderstorm development through the day. Most precipitation will be light and scattered. 

ECMWF 00Z 10/15 four-panel forecast for 10/16/2025 @ 12Z: (Top left to bottom right) MSLP/precip and 1000-500 mb thickness;700 mb gph, RH, temp, and winds; 300 mb gph and winds; 500 mb gph, vorticity, and winds

Mid to upper-level winds look to shift NW on Thursday, bringing more favorable conditions for some scattered upslope showers in the mountains. However,  Thursday morning 700 mb temperature drop to -4 to -5C under the core of the low, so the snow line will likely be somewhere near 6500-7000' early Thursday morning before rising to around 7000-7500' by the afternoon. 

ECWMF 00Z 10/15/2025 forecasted 10/16 12Z 700mb temperature

Another few inches of snow for the higher elevations across most of the state. Hard to say exactly how much the Cottonwoods will get due to the fairly disorganized nature and unfavorable conditions for much of the storm. However, most guidance puts down about 3-6" of snow for locations > 8000'.

ECMWF 00Z 10/15/2025 forecasted total precipitation (in) 10/15-10/17/2025 00Z

All said and done SLC is forecasted to get anywhere between 0.5-1" of additional rainfall between Wednesday and Thursday, with the highest accumulations expected along an arc spanning the west to north to east perimeter of the SLV. Much of the central SLV may get shadowed due to the flow direction associated with the storm.  

Beyond 

ECMWF 00Z 10/15 four-panel forecast for 10/19/2025 @ 06Z: (Top left to bottom right) MSLP/precip and 1000-500 mb thickness;700 mb gph, RH, temp, and winds; 300 mb gph and winds; 500 mb gph, vorticity, and winds

Conditions dry out by Friday, but cooler air remains in place across the state, with highs in the upper 50s for the northern valleys. Temperatures moderate each day going into the weekend as a ridge builds over the Great Basin. Next storm looks to impact the state early next week. However, there's plenty of uncertainty about the track and strength, and models have been trending drier and warmer with this storm. So far, I have been enjoying the relative storminess intermixed with periods of nice fall weather. Still hasn't got too cold yet..

KSLC observed and forecasted temperature (F) 10/15-10/22/2025

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.

Wet'n Wild

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

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. 

GOES West Water Vapor Imagery 10/10/2025

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. 

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.

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.

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.

 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. 

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. 

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. 

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...