Sunday, December 21, 2014

Oooh Baby, Talk Dirty to Me!

As anticipated for the last few days, atmospheric river conditions have pushed into northern Utah and are bringing widespread precipitation (valley rain, mountain snow) to the northern half of the state.

The large scale pattern is illustrated nicely by the 12-hour GFS forecast valid at 1200 UTC (0600 MST) this morning (sorry to use a forecast, but I have a narrow window to write this).  An upper-level ridge is parked off the U.S. West Coast with strong water vapor transport (color scale) extending inland into Utah.

Source: NWS
If you want to get strong water vapor transport into northern Utah, this is one of two ideal scenarios, the other being an atmospheric river that extends across Baja California and over the lower Colorado River Valley.  In both instances, the atmospheric river avoids interaction with the high, broad Sierra Nevada.

Patterns like this are often called dirty ridges by meteorologists since clouds and precipitation extend well downstream of the ridge axis.  Well oooh baby, talk dirty to me as I like the precipitation numbers coming in from the central Wasatch in these early storm stages.

From 3 to 8 am this morning, Alta-Collins has picked up 6 inches of snow with 0.53 inches of water. Our "Top Cecret" observing site in Albion Basin is at 4 inches with .39 inches of water.  It's mild by climatological standards, but temperatures this morning are at or below freezing at the central Wasatch resorts, including those on the Park City side.  Thus, we're getting some snow at mid elevations so far and we'll take all we can get.

Source: MesoWest
However, temperatures and snow levels will rise today, the latter maxing out near 8000 feet, before falling overnight.  Bring the gore-tex or the trash bag if you are skiing or boarding today as even the upper-elevation snow is likely to be wet and heavy.  The higher you can get the better.  Forecasts are still on track for the 2-3 inch storm-water totals through Monday afternoon in the upper Cottonwoods, which should significantly improve ski conditions for the coming holiday.  Backcountry travelers be aware that the Utah Avalanche Center has issued an avalanche warning for all the mountains of northern Utah.  This is a lot of weight to add to a cranky snowpack, and they are even concerned about rain on snow in the lower elevations.  Get the latest advisory here.


  1. I've been watching to Snowbird Snowstake and this evening the snow picked up. Watching the 4 hour loop though showed the snow picking up but the total amount measured dropping on the stake. Would this be due to upside down snow conditions picking up during that loop timeframe?

    1. Another loop at Looks like at least some wind scouring and then some compaction due to warming.