Avalanche Forecast

A deep low pressure system should move over about Cape Flattery and across south Vancouver Island Sunday morning and afternoon. This should bring stormy weather to the Cascades Sunday. This is a little faster than previously expected. A vigorous, strong front should rapidly cross the area and cause rapidly shifting winds Sunday.

The main avalanche problem along the east slopes on Sunday should be increasing strong winds and increasing snow transporting recent or new snow and building new wind slab on lee slopes. This is very likely to be northwest to southeast slopes. New storm slab should also be likely where there is rapidly accumulating new snowfall.

The pattern makes for a tricky forecast Sunday. Dangerous avalanche conditions are expected to develop Sunday afternoon. Careful snow evaluation will be needed before the end of the day along the east slopes.

Weather and Snowpack

During a period of fair weather in late February, widespread surface hoar formed in the northeast zone mainly surviving outside of steeper solar aspects and wind affected terrain. A weak front buried the surface hoar layer in the Washington Pass area about 2/27 and to a lesser extent the central-east zone.  

The nonstop active weather pattern continues to push a storm system through the PNW almost every day or two with fluctuating but generally moderate snow levels.

The last storm impacted the area Wednesday through Thursday with a warming trend that peaked Wednesday night and very strong winds seen throughout the Cascade range. Generally 1 to 1.5 inches of water accumulated along the east slopes in the 24 hours ending 4 am Thursday. Snow levels rose above 5000 feet in the Mission Ridge area Wednesday night but stayed lower closer to the Cascade crest and in the northeast Cascades. About 6-16 inches of snow accumulated through Thursday morning with the higher tallies of over a 1 foot seen at Holden, the NWAC station at Washington Pass and the NRCS sitess at Lyman Lake and Hart's Pass.

A front on Saturday is causing west-southwest winds and there should be a couple inches of new snow at most sites by Sunday morning.  

We are no longer tracking any layers of concern formed earlier this winter in the mid or lower snowpack due to lack of recent activity at these interfaces and confirming field observations. 

Recent Observations

Strong winds on March 3rd caused widespread natural wind slab avalanches in the NE zone. While many were contained to the recent storm snow, one larger slide on a N-NE aspect at Windy Pass likely released down to the 2/27 PWL. The last known human triggered avalanche on this layer was also in the Washington Pass area on March 2nd. 

Mission Ridge pro-patrol reported a very active day of control on Thursday, March 10th with 1-4 foot slides produced during control work on lee slopes below ridges. Wind slabs were sensitive and ran far.  Widespread cornice growth was also noted along ridge lines.

The North Cascade Guides report for the Washington Pass area on Friday indicates 20-50 cm of HST on lee slopes. Several pits had a mix of homogeneous snow or crust in the top meter of snow. Tests gave no results or RP results including on the 2/27 interface. Crowns or debris with sizes to 2.5 was noted from an avalanche cycle on Wednesday to Thursday.