Urban Avalanche Advisory

Current Advisory as of

January 18, 2020

Expires 7:00 AM the following morning.

Issued By Tom Mattice

Danger Level: 2 - Moderate
View Danger Definitions

Today's Discussion

Good morning and welcome back to the Juneau Urban Avalanche Advisory. This is Tom Mattice- CBJ Emergency Programs Manager and Avalanche Forecaster.

Please remember this advisory is intended for the Urban areas of the City and Borough of Juneau and is Not a Backcountry Forecast.

If you are recreating in the backcountry please take avalanche educational courses and learn to make the educated decisions you need to make to increase your personal safety.

The National Weather Service Forecasts-

Today- Partly cloudy early in the morning then becoming mostly cloudy. Slight chance of snow in the afternoon. Highs 16 to 22. East winds 15 to 25 mph. Gusts to around 60 mph near downtown juneau and douglas.

Tonigh- Cloudy. Chance of snow in the evening, then snow likely late. Snow accumulation of 1 to 3 inches. Lows 15 to 21. East winds 10 to 15 mph. Gusts up to 60 mph in the evening near downtown juneau and douglas.

Sunday- Snow likely in the morning, then chance of snow in the afternoon. Snow accumulation of 2 to 4 inches. Highs in the mid 20s. East winds 10 to 15 mph.

HIGH WIND WARNING REMAINS IN EFFECT UNTIL MIDNIGHT AKST TONIGHT...

* WHAT...Northeast Taku winds 25 to 40 mph with gusts to around 75 mph.

These outflow winds will gradually diminish this afternoon into Sun as southerly flow slowly pushes the cold air out of the area. 

Now focus shifts from the outflow winds and cold temperatures to warmer weather and snow.  Snow has already started from Sumner Strait southward with maybe an inch or two of accumulation in Ketchikan based on webcam images. This is a little earlier then what was originally thought.

The precip will gradually spread northward as the outflow starts to weaken. The northern panhandle will likely start to see some precip by late tonight at the latest. Not expecting as much accumulation as the southern panhandle, but a few additional inches of snow is not out of the question Sat night into Sunday night. The rest of the short range features a gradual warm up with continued chance to likely precip. Areas across the south will likely warm up enough for a switch over to rain by sun afternoon.

Currently this morning its 4f at the Eaglecrest summit, 7f at Powder Patch and 10f at the Base.  The Mt Roberts Tram is showing 7f.

Winds have slowed a bit over Douglas Island with Eaglecrest showing 6-12 from the NNE.  The tram winds are a bit higher at 30-38mph and Sheep mountain is still blowing 70+.

We have not seen snows in over a week now and during that time we have had many days of 70+ winds including peaks up as high as 152mph on Sheep Mountain and 102mph at Eaglecrest.  We even logged 96mph winds in downtown Juneau.  Much of the snows have been stripped away completely.  Yet most of this wind event has been out of the N-NNE allowing for some windslab buildups on lee slopes.

We are still seeing small slides occurring all around town from Mt McGinnis to Sheep Mountain on any faces where snow has been able to accumulate.  Recognizing that small natural avalanches are possible and human triggered avalanches remain possible avalanche danger remains MODERATE.

Any slides occurring will be small in nature for the Urban environment and with little to no snow in the runouts we do not expect to see any larger activity.

Primary Avalanche Problem

Wind Slab

Problem Type:Wind Slab
Avalanche Size:Small
Avalanche Likelihood = Possible
Avalanche Trend = Steady Danger

Description

We continue to see small windslabs releasing around the region.  Shallow for the most part.  Winds have been very strong.

When the last storm came in it had a weak bed surface.  This week of long strong winds has added load to that weak layer in isolated locations that remain of concern.

As new snows begin dangers will increase but loading rates look to be small.  It appears the vast majority of 2-4" would come in late Sunday.

Learn more about Wind Slab.

Secondary Avalanche Problem

Storm Slab

Problem Type:Storm Slab
Avalanche Size:Small
Avalanche Likelihood = Unlikely
Avalanche Trend = Decreasing Danger

Description

The storm slab came to rest on a weak bed surface.

It was reactive the first day after the storm but quickly settled and bonded.  It never quite loaded enough to become reactive regionwide.  For the most part it was a shallow slab.

Most of this has been stripped away in any areas seeing wind now and danger will be low in these areas.  The concern once again is the windloaded areas over this storm slab weak layer from last weeks event.

Learn more about Storm Slab.

Today’s Avalanche Tip

A quick video from Backcountry Access to remind you how to conduct trailhead beacon tests-

https://backcountryaccess.com/beacons-check-videos-how-perform-trailhead-transceiver-test/