Turnagain Pass

There were no new avalanches reported in the forecast zone yesterday. The last known avalanches were two and three days ago when several wind slabs released durning the strong NW outflow winds. To the south of the forecast area, at 6pm yesterday, a motorist saw an avalanche near Summit Lake at the Sterling Wye intersection with the Seward Highway. This was likely a natural wind slab as strong winds were impacting this area.

After four days of strong NW outflow winds impacting the region, it appears the wind is finally on the decline. The one exception is along Turnagain Arm in Portage and Whittier where westerly gap winds are still being seen. These winds have affected a significant amount of snow regionally, yet lucky for Turnagain Pass there are still some areas that escaped the brunt. That all said, lingering wind slabs will be the main avalanche concern today. The next concern will be warming temperatures – an impressive inversion is in place this morning as high elevations have warmed into the mid 20’sF overnight while valley bottoms sit in the single digits. More on this in Problem 2 below.

Triggering a lingering wind slab is possible on the steeper slopes. Although we found wind slabs to be on the stubborn side yesterday, we can pretty much bet there are still some ready to pop in steep complex terrain. They may also become more reactive with daytime warming this afternoon. Slabs should be in the 1-2′ deep range and fairly easy to see by looking at the surface texture and smooth rounded pillows. Also, feeling for stiffer snow over softer snow and looking for cracks that shoot out from us are definitely clues we’ve found a wind slab. Look for them just off ridgelines, in cross-loaded gullies, and on the steep sides of rollovers.

Cornice Falls:  With easy travel along ridgelines, be sure to give cornices an extra wide berth. They can pull back further than expected, especially the larger ones. Also, the warming temperatures can make cornices a bit easier to break off if they are close to failure.

Loose Snow Avalanches:  Sluffs on steep slopes should be expected where loose snow exists on the surface. These looked to be on the smaller side yesterday, but areas with more loose snow, they could be large enough to possibly cause some grief.

A natural cornice fall from several days ago that we saw yesterday in the upper cirque of Spokane Creek (between Lipps and Pete’s N). The cornice looked to have pulled out a couple smaller wind slabs below. 3.4.23.

Sunshine and warming temperatures. It’s that time of year where we need to remember about those afternoon solar effects. Not only is the sun expected to be strong today, there is also a ‘subsidence inversion‘ taking place that is warming the air mass in the upper elevations without the sun. Sunburst weather station has climbed to 26F overnight, believe it or not. Couple this with daytime warming and we could see some moist/wet loose avalanches this afternoon. This upper elevation warming is expected to continue into Tuesday when we could see overnight temperatures near 32F. Hence, wet loose avalanches, cornice falls, and even some weakening wind slabs or other funny business could begin to occur in the days ahead. Stay tuned and heads up!

There are a few questionable weak layers in the upper 2-3′ of the snowpack that may be capable of producing a surprise avalanche in isolated pockets. The most problematic terrain will be in areas with a thinner snowpack. This includes the Crow Ck area in Girdwood Valley, the southern end of Turnagain Pass (See this observation from Pete’s North on Wednesday) and down towards Summit Lake. Luckily, for most of our core advisory area it is looking like these layers are unreactive and unlikely to trigger. It has been several weeks since we’ve seen any avalanches failing deeper in the snowpack, yet it is worth keeping these layers in mind and adjusting your terrain use accordingly if you are traveling in a zone with a thinner snowpack.