Avalanche Forecast
Jan 9th, 2019–Jan 10th, 2019
Alpine
3:
Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2:
Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2:
Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2:
Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2:
Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2:
Moderate
The avalanche danger rating below treeline will be moderate
Regions: Mt Hood.
The bottom line: You can trigger a fresh wind slab near and above treeline that might be large and reactive, sitting on a thin crust interface. Increasing winds and snow at gradually lowering snow levels will move the Wind Slab problem to lower elevations relative to Wednesday. Below treeline, reduce exposure to small wet loose avalanches that you can trigger on steeper slopes.
Regional Synopsis
January 7, 2019
This latest round of storms in early January continues to highlight some of this season’s region-wide themes in our snowpack. I’d describe them as Bottom to Top, North to South, and East to West. Let’s take a look at each of these.
Bottom to Top:
In general, this winter has been on the warm side in the Cascades. Nowhere is that more evident than in the lack of low elevation snow. Heavy rain events continue to wash-away and thoroughly wet the lower elevation snowpack. In most regions, you will see a substantial increase in the height of snow from low elevations (3000 ft), to mid elevations (4500 ft), and again at upper elevations (5500/6000 ft). Above the typical rain lines (5000-6000 ft) a deep and cold mid-winter snowpack exists.
North to South:
With few exceptions, this season’s storm tracks have favored the North Cascades. Sunday, Mt Baker’s Heather Meadows weather station passed 100 inches of snow on the ground. A quick look around the state’s weather stations demonstrates just how deep this snowpack is. Most other locations are reporting between 50 and 75 inches. The massive amounts of snow for the northern forecast zones are reflected in several impressive avalanche cycles spread out over the last month.
East to West:
Several stacked persistent weak layers have been buried in the eastern forecast zones. This isn’t unusual, but it is noteworthy. The thickness of the slabs over these weak layers can vary greatly. Closer to the Cascade Crest, the deep snowpack may more closely resemble Stevens or Snoqualmie Passes. Further east, shallower snowpacks and significant variability are keeping snowpack assessment tricky.
So what now? Well, on January 3 and 4 a high elevation rain event impacted areas from Mt Baker to Mt Hood. In many locations, this has created a firm and thickening crust. In these locations, this new crust is limiting the impacts of any deeper weak layers. In locations that didn’t receive as much rain like WA Pass, Mission Ridge, Crystal Mt, and White Pass, how the small amount of rain impacted the mid and lower snowpacks remain to be seen.
One thing is for sure, we’re not even a month into the winter season, there’s a lot more winter to come.
This latest round of storms in early January continues to highlight some of this season’s region-wide themes in our snowpack. I’d describe them as Bottom to Top, North to South, and East to West. Let’s take a look at each of these.
Bottom to Top:
In general, this winter has been on the warm side in the Cascades. Nowhere is that more evident than in the lack of low elevation snow. Heavy rain events continue to wash-away and thoroughly wet the lower elevation snowpack. In most regions, you will see a substantial increase in the height of snow from low elevations (3000 ft), to mid elevations (4500 ft), and again at upper elevations (5500/6000 ft). Above the typical rain lines (5000-6000 ft) a deep and cold mid-winter snowpack exists.
North to South:
With few exceptions, this season’s storm tracks have favored the North Cascades. Sunday, Mt Baker’s Heather Meadows weather station passed 100 inches of snow on the ground. A quick look around the state’s weather stations demonstrates just how deep this snowpack is. Most other locations are reporting between 50 and 75 inches. The massive amounts of snow for the northern forecast zones are reflected in several impressive avalanche cycles spread out over the last month.
East to West:
Several stacked persistent weak layers have been buried in the eastern forecast zones. This isn’t unusual, but it is noteworthy. The thickness of the slabs over these weak layers can vary greatly. Closer to the Cascade Crest, the deep snowpack may more closely resemble Stevens or Snoqualmie Passes. Further east, shallower snowpacks and significant variability are keeping snowpack assessment tricky.
So what now? Well, on January 3 and 4 a high elevation rain event impacted areas from Mt Baker to Mt Hood. In many locations, this has created a firm and thickening crust. In these locations, this new crust is limiting the impacts of any deeper weak layers. In locations that didn’t receive as much rain like WA Pass, Mission Ridge, Crystal Mt, and White Pass, how the small amount of rain impacted the mid and lower snowpacks remain to be seen.
One thing is for sure, we’re not even a month into the winter season, there’s a lot more winter to come.
Weather Forecast
Weather Synopsis for Thursday night through Saturday
The Pacific Northwest will be quite mild at the end of this prolonged period of warm generally southerly flow which has scoured out the cold air pool east of the Cascade Crest. Meanwhile, a ridge is amplifying across the Inter-mountain West, pushing out the last moisture from the moist southerly flow during the early evening hours. The ridge diverts storms to the north and south of our region. It will also re-amplify the pressure gradient across the Cascades, setting up a prolonged pattern of moderate easterly flow. Inversion conditions will also develop, leaving a shallow pool of cold air in the deeper valleys east of the Cascade Crest. This low cloud will likely stream through the lower Cascade passes.
The Freezing level will climb to 7000 ft or higher in many locations west of the Cascade Crest Friday through Saturday. Expect cooler temperature through the pass and on the east slopes with the inversion conditions in place.
Avalanche Problems
Wind Slabs
Fresh wind slabs are expected to be touchy to reactive in widespread areas at higher elevations due to moderate and gusty winds peaking Wednesday night and gradually decreasing on Thursday. The new slab may sit on a thin melt-freeze crust as temperatures reached the freezing mark up to 6500-7000 ft on Wednesday. Bonding to this interface is expected to be poor as surface refroze before precipitation started Wednesday evening.
The size and distribution of older wind slabs may vary more than usual in the Mt. Hood area. The Mt. Hood Meadows area saw light winds and only a few inches of snow, while Timberline and Skibowl received a bit more snowfall and stronger east winds Tuesday.
Look for uneven snow surfaces, snow drifts, and fresh cornices to identify where fresh wind slabs may have formed. Feeling for firm or hollow sounding snow provides clues that you may trigger a wind slab avalanche on nearby steep slopes.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 2 - 2
Loose Wet
The Wet Loose avalanche concern will be decreasing on Thursday without significant new water inputs. Natural rollerball or pinwheels are a sign of loose wet hazard. Avoid very steep slopes where even a small avalanche could cause injury.
Aspects: All aspects.
Elevations: Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1