Sunday night...

Another storm is on the doorstep.

******I wanted to look back at the last few days to put together a MODEL of the current situation********.

Last Tuesday/Wednesday's storm brought storm totals of 16.5"/2.21 SWE (snow water equivalent) in upper LCC. The initial precipitation came in wet and warm (rain/snow lines to 8000' or so) but Wednesday's cold front mercifully provided a few inches of low density snow to cap the Sierra cement.

As they say, idle weather does the devil's work. Thursday, Friday, Saturday's clear and cold weakened the snow surfaces on all aspects and nearly all elevations through both diurnal and radiation recrystallization (read: facets). These are bona-fide weak layers ahead of the next storm. Photos below.

At this point, we have a good bed surface of crusts on east to south to west facing slopes...and a nice thin weak layer on all aspects. Now we just need a slab. This is Avalanche 101.

Here's where it gets tricky.

Wind

Saturday and Sunday's moderate to strong south to southwest winds eroded the facets from many starting zones in exposed locations...but not necessarily in wind protected terrain. This erosion/drifting produced wind damage and wind slabs in the high northerly terrain.

My read on this is that - with a slab - the tricky avalanche conditions might be found well off the ridgelines on mid-slope break-overs and particularly sensitive on these protected solar aspects.

Tonight's Storm

The question with tonight and tomorrow's storm: Will it deliver a slab?

The answer is Yes in wind drifted areas and during periods of high snowfall rates...or with too much snow.

Otherwise, sluffing will be widespread on all steep terrain.

******How to Test the MODEL?******

It would be perhaps reckless to take the model on a cross-country flight. Choose test slopes for ski cuts to gauge the reactivity. Cracking, collapsing will be signs of slab development. Dig down to perform some snow tests with the shovel. Remember that spatial variability will exist: do not make assumptions that because THIS slope did not avalanche that THAT one will not.

DISCLAIMER (8pm Sunday night) - Some weather forecasts show heavy snowfall tonight and tomorrow. Guidance doesn't offer much wind, but we'll see. It may just be a day to choose low angle terrain.