Rogue Shower, October Storm

Yesterday (Tuesday) morning, the Salt Lake City International Airport observing site, which is located at the south boundary of the airport just north of I-80, observed as rogue of a rogue shower as you will ever see.  The storm produced rain at the observing site from about 0725–0755 MDT, generating 0.16" according to the rain gauge.  

KSLC Time Series 0725–0755 MDT 6 Oct 2026. Source: NWS.

The radar at 1317 UTC (0717 MDT) showed the rogue cell moving over the airport as it intensified.  The cell was perhaps 5 km across and developed pretty much over or just upstream of the southeast corner of the airport.    

The weather cam image at the top of this post, taken looking west from the University of Utah, shows just the narrow area of falling precipitation associated with the cell.  What conspired to make such an isolated precipitation shaft is known only to Mother Nature.  

Radar-estimated precipitation from the National Severe Storms Laboratory Multi-Radar Multi-Sensor (MRMS) system for the 6-hour period from 0900–1500 UTC (0300-0900 MDT) showed this to be the sole area of precipitation in the Salt Lake Valley and immediate surrounding area.  

Additionally, it was a direct hit on the southeast corner of the airport.  

Someday someone (or some AI bot) will be looking at the airport observations and wondering what the hell happened.  If they don't look at all the available evidence, they will probably consider the rain report to be questionable.  

Speaking of rogue, the jet stream is about to go rogue due to the influence of two powerful cyclones from the tropics and midlatitudes that are about to merge into a potent beast over the Bering Sea.  The resulting storm will peturb the jet stream and cause a trough to dig down the west coast of the US this weekend (see How to Break the Jet Stream for more info).  The pattern is giving me an ulcer because my son is getting married on Saturday and they would like to have the ceremony outside.  These are the joys of being a meteorological parent. 

It's a mess of a forecast.  For 0000 UTC 11 October (1800 MDT Saturday) there's the digging trough over the Pacific Northwest.  That trough is forecast to pull the remnants of Hurricane Rachel northeastward (they are likely to make it to Utah on Sunday and Monday).  Ahead of Rachel's remnants is a surge of monsoon moisture that will increase convective chances over portions of Utah on Saturday.  Oh yeah, there's also a cold front ahead of the digging trough and, between all of these features, a slot of dry air most apparent over Nevada (although it extends into a part of northern Utah) that may stay precipitation free on Saturday.  

Time will tell how this all comes together and if the nuptials can be outside.  Regardless, our run of mainly clear, dry, and warm early October weather is coming to an end this weekend with storminess continuing into next week.  

It's been a while since we looked at the Utah Snow Ensemble.  It's worth a peek for Alta-Collins. In addition to all of the moving parts described above, the models have a lot of different ideas about how Rachel's remnants and the mid-latitude trough will move through the region next week, resulting in an enormous spread of possible outcomes.  Cold air may ultimately come in with the trough too, so snow is a possibility, although not all members are sold on this idea.  

The range of water equivalent by 0000 UTC 14 October (1800 MDT Tuesday) is 0.56–4.20" and by 0000 UTC 17 October (1800 MDT Friday) the range is 1.13–5.68", with a median of 2.76".  Much of that falls as rain, but some ensemble members bring in colder air and lowering snow levels, some starting late Sunday, others later next week.  There's little agreement on the timing of precipitation periods, amounts of precipitation, or temperatures.  The easiest way to summarize this is to say buckle upm, expect and active period, and we will see what happens.  If you want odds, through 0000 UTC 17 October (1800 MDT Friday), half the ensemble members produce more than 6" of snow at Alta-Collins and the snowiest 10% are at or above 18".  Enough to ski is a low probability outcome (except for the true lunatics out there), but not impossible. 

I'll add that the best outcome right now is probably no snow and no gully washers (this has the potential to be a high-impact event with threat of flash flooding).  Concerning snow, early snow on north aspects almost always turns to weak snow, creating long-term avalanche problems.  

I'll finish by recommending you monitor future forecasts from the National Weather Service.  Their weather story from this morning is below.

NWS Weather Story downloaded 0935 MDT 7 October 2026