Thanksgiving weekend looks to conclude with a storm that will likely produce some snowflakes at all elevations in northern Utah. It's not a big storm, but being the first that might bring winter driving conditions to some areas so far this season, at the end of Thanksgiving weekend, it's worth monitoring if you will be traveling.
The storm will be produced by an upper-level trough and cold front that will drop into Utah on Sunday from the northwest. Below is the GFS forecast valid 1800 UTC 30 November (11 AM Sunday) showing the trough extending across northern Utah and Nevada.
Below is the HRRR forecast sounding for the Salt Lake City International Airport valid 1800 UTC 30 November (11 AM Sunday). It shows saturated conditions down to the valley floor with temperatures just above 0°C.
Below is our HRRR-derived snowfall guidance which suggests 1.6" at the airport, 2.6" at Cottonwood Heights, and 8.4" at Alta-Collins. This product does not, however, consider on-the-ground melt, which could be an issue on the valley floor and might limit actual accumulations there. A lot will depend on the snowfall rate during the passage of the system.
We can also have a look at the 6-member RRFS ensemble. It appears to be a smidge warmer than the HRRR as most members are producing 0.2" of water or more at the airport, but snowfall is scant with one member getting up to a bit under an inch.
For Alta-Collins, five of the six members are coming in between about 3.5 and 8", but there is one very optimistic member going for close to 18. There is always hope.
So to summarize, a trough and frontal passage will be bringing precipitation to northern Utah on Sunday. Snow is expected and bench and mountain locations. At the lowest elevations, temperatures are such that we could see wet snow or a rain/snow mix. It's worth monitoring the weather and road conditions if you need to travel on Sunday.
Any hope for real winter mid week?nws looking faborable on paper...
ReplyDeleteJim, been seeing signals recently of PDO finally switching to positive potentially in 2026. Would be curious to see your thoughts on how that could affect the pattern here if that happens. On the surface, seems like maybe a more active storm pattern out of tropical Pacific would mean more valley rain/mountain snow type events, but would be curious your thoughts as I know it’s rarely that simple
ReplyDeleteYou got my hopes up w PDO, asked Gemini, here's the answer, curious if Jim sees it differently than Gemini
DeleteCurrent Status: The PDO has been in a Negative (Cool) Phase since late 2019 and has remained persistently negative, with no positive monthly values recorded in the 2020s (as of the search results). The current pattern is even one of the strongest negative PDO regimes in the last several decades.
Forecast: There is no strong indication from the latest long-range climate models that the PDO will flip to a Positive (Warm) Phase during the 2025-2026 winter season. The general consensus suggests the Negative PDO will likely continue for the remainder of 2025 into 2026.The current pattern, therefore, is a combination of a Negative PDO and a Weak La Niña—a classic pairing that favors the northern storm track (Canada and the Pacific Northwest) and reinforces the drier, "hole" effect over Northern Utah.
Would a Positive PDO Benefit Alta?
This is where the climate mechanics get complicated, as a positive PDO doesn't automatically mean more snow for Alta.
The Theory of PDO and Alta Snow
PDO Phase Associated ENSO Phase General Impact on Northern Utah
Negative (Cool)Tends to reinforce La NiñaDrier overall, as the storm track is pushed North (bad for Alta).
Positive (Warm)Tends to reinforce El Niño Often associated with a more southerly storm track, which can be Wetter for the Southwest/Southern Utah.
Gemini also reported Jackson WY is in the same boat as Alta but Revelstoke had 57 in in Nov, 160% of avg 35 in because storm track has shifted north benefitting interior Canada
DeleteI don't consider such multi-week forecasts to be reliable, meaning that on average they don't do any better than climatology for Utah (although there may be a bit of a signal in other regions like the Pacific coast).
Delete