When it comes to snow, sometimes the most difficult forecasts are for light accumulations.
The 1300 UTC initialized HRRR simulated reflectivity forecast below shows the challenges for today. A relatively weak weather system over Oregon and Idaho is forecast to strengthen some as it moves into the Wasatch Front later today.
For Salt Lake City, most ensemble members produce less than 0.1" of water equivalent through 0200 UTC (7 PM MST), although there are a couple that to for around 0.15".
|NCAR Ensemble forecast for the Salt Lake City International Airport|
Thus, this could be everything from a few snow showers to an inch or two of snow. On a meteorological scale of 0 to 10, that's about a 1, but it's coming in around rush hour. If precipitation is light and intermittent, it probably won't be a big deal, but a brief burst of heavier precipitation, while a lower probability possibility, could cause some snafus. Best to keep an eye on this as the day evolves.
A couple of members go for some significant snow overnight due to lake effect. As usual, that's a tough forecast, so consider yourself fortunate if you get some.
Best guess is perhaps 2-4" of cold smoke in the Cottonwoods later this afternoon and tonight. Emphasis on guess as the models have been erratic and the lake is always a dicey proposition. These amounts are a little lower than one might infer from the NCAR ensemble or overnight NCEP model runs (not shown), but reflect the fact that the system seems pretty weak right now. Thus, hope we do better.
We've already discussed the big cool down for tomorrow (Wednesday) and how it will be short lived. The models bring in a pretty juicy pattern beginning late Thursday through Saturday night. The NAEFS plume for Alta shows the weak system passing through later today (~0000 UTC 7 December), a break for tomorrow and early Thursday, and then the action picking up. By 1200 UTC 11 December (5 am MST Sunday), our downscaled accumulation estimates fringe from about in inch of water equivalent to just over 4 inches of water equivalent. You can further excite yourself by looking at the snowfall plume.
|NAEFS forecast for Alta|
Personally, I think it's too early to be talking about accumulations, but the pattern does suggest we will be adding to our base at upper elevations. There will, however, be some yo-yoing of the snow levels, which could reach or even exceed 7000 feet Friday night.
Most ensemble members suggest an active, stormy pattern through next week. The Utah Avalanche Center and snow-safety teams at the resorts and along the highways will have their work cut out for him if the advertised pattern verifies. I've already said more than I should as I put little faith in 5-10 day forecasts, but lets keep our fingers crossed.