The Forecasting Funnel: Cool and Active

Some ominous stratocumulus clouds are streaming rapidly from the WSW to ENE across the Wasatch Front this morning, with breezy winds at the surface. A few dusty raindrops out there earlier as well. It feels like something weatherwise will be happening today...

GOES-19 East True Color imagery - Focused over northern Utah ~1400-1500 MDT 4/22/2026

Overnight, conditions were a bit turbulent, with periods of gusty winds and some light blowing dust observed at air monitoring stations. Winds had been southerly through part of the night but shifted out of the WNW over the northern SL Valley during the pre-dawn hours, indicating a potential boundary or front moved over. Coincidentally, temperatures  dropped from the mid 60s to mid 50s at KSLC with the WNW wind shift (~0330 MDT).

KSLC surface observations ~0300-0400 MDT 4/22/2026. Wind shift from WSW to WNW near 0330 MDT, with a 7 degree F drop in temperature.

So... it looks like we had a cold front move into the SL Valley this morning. Currently, the surface frontal boundary looks to be draped halfway south down the valley (figure below), but often affects from terrain can make identifying the precise location of a surface front difficult. The actual front may be somewhere further east than indicated here.

Surface observations across the SL Valley 4/22/2026. Blue dashed line represents the approximate location of the cold frontal boundary.

The Forecast Funnel

Now zooming out and looking at all available information, let's determine what's going on. We will start by taking a quick look at what the upper-level pattern looks like on a hemispheric scale. The chart below shows a number of squiggles (troughs and ridges) in the 300 mb pattern. These squiggles are called Rossby Waves and provide information on the large scale atmospheric pattern and how it can potentially evolve. The more large scale squiggles (> ~3000 km in wavelength) the faster the progression of the 300 mb pattern. From the chart below, the current number of Rossby Waves (wave number) looks to be around 3-4, which is a low wavenumber and means the atmospheric waves likely will move more slowly. The next piece of information we can gather is that there is a large scale closed trough located along the western seaboard of the U.S. 

Next we move down the level of non-divergence (500 mb). The 500 mb analysis (heights, winds, and temperature) and satellite imagery below reveals a broad longwave trough slowly progressing east across the western U.S. The 500 mb analysis indicates a cold pocket of air and jet streak - area of increased wind speed (blues) - working its way over Utah. Both of these features are important for creating active weather, with the colder upper-level temperatures creating steep lapse rates/unstable conditions and the jet streak aiding in dynamic lift.

SPC 1500 Z 500 mb heights, temperature, and wind analysis 4/22/2026 

GOES-19 East True Color imagery, with 500 mb heights, winds, and vorticity overlaid 4/22/2026

Progressing down the atmospheric column and zooming into Utah a bit, we next check out the 700 mb analysis (heights, winds, temps, and RH). The 700 mb analysis is considered in the mid-levels of the atmosphere and can provide a lot of information on what the winds, temperatures, and precipitation will do at the surface. In the 700 mb analysis chart below, a trough (axis-thick dashed blue) associated with cooler air (thin-dashed blue lines) and moisture (green fill) is moving into northern Utah. Winds are also identified as out of the W at 15-30 kts. 

SPC 1500 Z 700 mb heights, temperature, wind, and RH analysis 4/22/2026 

Finally, moving down to the surface once again, we look at the surface analysis (MSLP, temp, and wind). I zoom out a bit more from Utah to reveal the complete picture of the surface pressure pattern. In the figure below, the surface low and surface high are identified. Utah sits somewhere right in the middle of these two features, with a westerly surface winds and relatively tight pressure gradient noted over the state. Regions of tight pressure gradients can indicate areas of increased wind speeds.

SPC 1500 Z surface MSLP and wind analysis 4/22/2026 

Now that we have developed an understanding of the current state of the atmosphere over Utah, we can move on to determining how the current conditions will evolve through the day and beyond. This is where numerical weather models come into play.  The below figure shows the ECMWF 00Z model products across the western U.S. today through tomorrow (4/22-4/23/2026).  

ECMWF 00Z 4/22/2026 four-panel forecast 4/22-4/23/2026: (Top left to bottom right) MSLP, 1000-500 mb thickness, and precipitation type; 300 mb gph and winds; 700 mb gph, RH, temp, and winds 

In short, the progression of the model shows the trough moving over Utah today through tomorrow, with a few embedded shortwave troughs (pieces of energy) impacting the state with cooler and wet weather. The first shortwave trough will bring cooler air and periods of scattered valley rain and high mountain snow showers and maybe a thunderstorm today (4/22/2026). By early Thursday, a trailing shortwave trough will move through, bringing an additional shot of colder air and a period of light valley rain/snow and mountain snow showers. Conditions look to dry out by late Thursday, but it doesn't look like either today or tomorrow to be a washout.

Going Forward

Conditions moderate some going into the weekend, with the warmest day slated on Saturday (highs near 60 F for the northern Utah Valleys). The second half of the weekend into early next workweek looks to turn cooler and wetter once again as multiple troughs merge and slowly spin across the western and central U.S. Best opportunity for precipitation is currently forecasted for Sunday into Monday. As seen from the ensemble ECMWF output below (positive precip anomaly in green and cooler temperature anomaly in blues), prepare for a slightly cooler and wetter than normal period over the next 5-7 days. Not expecting significant precipitation of deluges, but there looks to be plenty of opportunities for intervals of showers across the state. 

ECMWF Ens 00 Z 4/22/2026 - Left: 7-day precipitation anomaly (in); Right: temperature anomaly (F)

Rubbing the crystal ball a little more, we can peer into the long-range forecast, which alludes to additional active cool and wet periods going into early May. This loose forecast has the high likelihood of changing, but it is the pattern the ensemble models have been hinting at for the past few days. We will see...

ECMWF Ens 00Z 4/22/2026 - Total Precipitation Plume (in) for KSLC 4/22-5/06/2026

The Quick and Dirty: Forecasting Surface Temperatures

Lows bottomed out in the mid 50s across the Salt Lake Valley earlier this morning, but they have already climbed into the low 60s as of 0900 MDT. Skies are mostly clear, with only a few high stratocumulus, and winds are light out of the south. These are all cues - but not guarantees - that it will be a warm one out there today. Based on conditions this morning, let's attempt to determine how warm it will get today (4/20/2026). 

If we look at the mid-levels (~ 700 mb), 700 mb temps are near 5 C at 3100 m ASL according to the SPC mesoanalysis (figure below), which is fairly mild air and points to a warm day ahead. But why are we looking at the 700 mb level? How does 700 mb temperatures - more than 1800 m above the surface - predict temperatures at the surface? 

SPC 1500Z 700 mb Analysis: heights (m), winds, temperature, and RH (> 70%)

Over the higher elevations across the Western U.S., 700 mb air has a lot of influence on conditions at the surface. A quick overview of how this is the case: diurnal heating of the Earth's surface creates buoyant eddies (thermals - bubbles of rising air) that help mix heat, moisture, and momentum in the lower parts of the atmosphere. The layer in which this mixing due to buoyant eddies occurs is called the Planetary Boundary Layer or more precisely the Convective Boundary Layer (CBL). Similar to how a fan mixes air within a room in your home, these eddies mix air through a layer of the atmosphere. Rising and sinking motions created by mixing allow for air from different levels to be transported in the vertical, hence the 700 mb air (on days like today) can be mixed down to the surface. 

Schematic of the evolution of the CBL adapted from Stull, R.B. (1988)

Although this exchange of air is an adiabatic process (no heat is transferred into or out of the system), this is not an isothermal process - temperature of air does not remain constant. Therefore, the 5 C air from 700 mb will no longer be 5 C by the time it descends to the surface. This is due to a thermodynamic process involving the relationship between temperature, pressure, and volume , which you may remember from freshman level chemistry or physics - PV = nRT. Through some differential calculus - that will not go through here - this relationship/equation PV = nRT is derived and combined with the first law of thermodynamics to formulate the dry adiabatic lapse rate (DALR) of the atmosphere. Interestingly, the DALR comes out to be 9.8 C/km (the same number as the acceleration due to gravity). In plain language, this means that as air sinks it warms by 9.81 degrees (C or Kelvin) and as it rises it cools by the same rate. For convenience and quick calculations, a DALR of 10 C/km is commonly used.

So let's put this information all together to forecast surface temperature from the 700 mb temperature. Below, I will give a short and dirty tutorial on how to forecast surface high temperatures. The questions we want to answer and the pieces of information we know:

But wait, let's make a few corrections to refine this forecast...

There are many assumptions that are made using this method for quickly calculating surface temperatures. One major assumption is that 700 mb temperatures will remain constant through the day. This is likely not going to always be the case, and it is necessary to investigate how the 700 mb temperature may change through the day. Today, there's a good chance that the 700 mb temperature will warm 1-2 degrees C by this afternoon (some marginal warm air advection). 

So if we redo the above calculations with a 700 mb temp equal to 6 C: 

76.6-78.6 + (1 C = 1.8 F) = 78.4-80.2 F

We get a forecasted surface high temperature of 78.4-80.2 F!

Today's surface high temperature is forecasted be near 80 F for the SL Valley

Let's cross check our forecasted surface temperature against the NWS forecast :

NWS Forecasted High Temperatures (F) for 4/20/2026

Looks like our rule of thumb for forecasting surface temperatures worked well. The NWS has a forecasted high of 80 F for SLC today, which matches closely with our forecast using 700 mb temps. 

Anyway, that is the quick way to forecast surface high temperatures when you have clear and relatively calm large scale conditions. On days with precipitation or more active conditions, this rule of thumb breaks down. Now go forth and forecast...

April Snow Showers

Fairly mild in the Salt Lake Valley this morning, with winds shifting to the north and temps in the low 50s. Orographically induced stratus clouds edge across the northern Utah valleys but seem to hang over the Wasatch mountains. Clouds are moving SW to NE, indicating upper level winds are out of the SW. Typically, when clouds features like this exist, you can deduce winds at mid to upper levels of the atmosphere are moving quickly and the weather may be shifting soon. This is indeed the case as shortwave trough and cold front will be moving over the Wasatch Front come late morning into the afternoon. 

GOES-18 West True Color Imagery 4/16/2026. Focused over northern Utah, showing orographic stratus clouds ahead of the next storm

Currently, the cold frontal boundary sits just north and west of the SL Valley over the GSL. As seen in the visible satellite imagery below, this front is associated with a shortwave trough that has stretched south over the Great Basin off of a larger and more pronounced system/circulation over Montana and southern Canada. The main front will progress across the northern Utah valleys by late morning, with a band of valley rain/snow and mountain snow showers filling in along and behind the front. A very sharp temperature gradient exists along the frontal boundary, giving the front strong baroclinic characteristics and producing a region of strong frontogenesis along the front - tightening of temperature and pressure gradients that strengthen a front, low pressure system, and precipitation formation.

GOES-19 East True Color Imagery with 500 mb winds, heights, and vorticity overlaid. A broad circulation and trough spins across the U.S. and Canadian border with some energy shearing south over the Great Basin.

Although the shortwave energy and upper-level jet dynamics are supportive of lift and precipitation formation, moisture with this system will be a limiting factor. The bulk of the moisture will remain with the main system/circulation well to the north, with most of the precipitation in Utah oriented along a SW to NE band as the front moves over this afternoon. The front/band will translated NW to SE across the state through Friday morning (4/17/2026), bringing valley rain/snow and mountain snow showers. There will likely be a few hours of rain/snow and snow showers over the valleys this afternoon before things taper off by early evening. Periods of moderate to heavy snow showers are possible, particularly along and just behind the main frontal boundary.

ECMWF 00Z 4/16/2026 four-panel forecast 34/16-3/17/2026: (Top left to bottom right) MSLP, 1000-500 mb thickness, and precipitation type; 300 mb gph and winds; 700 mb gph, RH, temp, and winds 

As the trough axis passes over northern Utah tonight into Friday morning, winds will shift NW and strong cold air advection will cool 700 mb temps as low as -13 to -14 C. The combination of NW winds and very cold air overlaying the relatively warm GSL will bring the potential for some lake enhanced/lake effect snow showers across locations from Tooele over to the west side of the SL Valley. 

ECMWF 00Z 4/16/2026 12-hr Snow Accumulation (in) for northern Utah Friday morning. Band of accumulations are associated with potential lake effect snow.

As far as snow totals go, I don't expect much if any accumulation in the valley areas. Maybe a dusting or brief slush up during the day Thursday if rates are heavy enough. However, once the snow slows or stops, anything on the ground will melt. Temperatures will drop considerably behind the front, but are only expected to bottom out in the mid to upper 30s. Overnight temperatures in the valleys could dip below freezing, with the possibility of a dusting or dusting+ for locations impacted by any lake effect showers (see above figure). Otherwise, impacts from the wintry weather will be minimal in the valleys, but you may want to bring in those early April flowers tonight and Friday night. Not a significant storm in terms of liquid. Most Utah areas will see anywhere from 0.1-0.5" of total liquid through the storm event. That's not a ton, but at this point every drop counts, so the April flowers and Utah will take it. 

ECMWF ENS 06Z 4/16/2026 Total Snow Accumulation (in) for Alta, UT 4/16-4/22/2026

The mountains could see 3-6" of snow through Friday morning, so nothing crazy. The Cottonwoods will likely win out (see above figure), but at this point I'm not sure how much it matters. There probably is still some pockets of decent skiing very high up if you go searching hard for it, but I think most people are already well into spring mode...