October Snow Is Here

October is coming in like a lion with thunderstorms late yesterday and more action overnight.  Dawn broke this morning with a light coating of snow at Alta.  I'm surprised nobody has put a skinner in yet. 

Source: Alta Ski Area

Looks like trace amounts at the base, but perhaps 2-3" up high, which may include a bit of snow from Saturday night.  It's unclear if the Collins snow-depth sensor is working yet, but the gauge came in with 0.38" of water equivalent in the last 24 hours. 

I mentioned in the previous post the possibility of snow, but was leaning toward a few inches and was inclined to have low expectations for the event.  The models, however, have been trending toward a wetter event.  The GFS, for example, is putting a low moving precipitation band directly over the central Wasatch today.  

It then brings a cold, moist secondary trough trough Utah tomorrow.  

Telescoping down to Little Cottonwood, the GFS generates a remarkable 1.75" of water at Alta-Collins from midnight last night through this afternoon, followed by dribs and drabs tomorrow with the trough passage.  It's a warm event, with the wet-bulb zero between 8000 and 9000 feet, but that would still mean snow levels around 8000 feet.   

The HRRR is coming in with somewhat similar numbers, but has a bit less precipitation for today.  

Snow totals for the HRRR are around 12" and for the GFS around 20" for Alta-Collins, which is at 9700 feet.  I suspect the snow-to-liquid ratios being produced by our algorithm are going to be too high for this event since it's not really designed for early season events with a warm ground and frequent excursions during dry periods to temperatures above 32°F.  

I'm inclined to lean toward 4-8" of wet snow from 8 AM to 6 PM for today at and above Alta–Collins.  The GFS is putting out some big numbers, but I think it may be generating a bit too much precipitation based on what I'm seeing on the radar this morning.  Things should quiet down tonight and then we will have to see what happens with the trailing cold trough.