Half Dome via Cables

The big problem here is the weather pattern stacked against the Half Dome cables. Today's forecast is 90% chance of thunderstorms with a 46°F high — that's an active lightning environment on an exposed, steel-cable route at 8,800 ft with no retreat option once you're committed. Tonight drops to 34°F with rain and snow. Sunday's high of 39°F with light snow likely means the cables and the apron below them will be iced over, and wet or frozen granite on that final 400-foot friction section is a different climb than a dry summer day. Monday improves to 43°F with only a 25% chance of lingering snow, but that's not enough warmup to clear ice off north-facing rock at elevation in a single afternoon.

The snowpack data here is noisy — the SNOTEL stations in the raw feed don't correspond to the Yosemite Valley area and should be disregarded for route planning. What matters is the 37-inch snow depth reported at elevation for this location, combined with overnight lows in the upper 20s through Monday. That's a snowpack that is not moving fast, which keeps stream flows moderate (all five gauges are running 87–118% of median, well below the danger threshold), but it also means the upper Half Dome route will have consolidated snow and ice through your entire trip window. Expect full winter conditions above 7,000 ft.

Stream crossings on the approach — including the footbridges over the Merced and any early-season creek crossings on the JMT — are fine. Flows are normal and stable. That part of the trip is a non-issue.

If you're committed to going out this weekend, a lower-elevation backpacking loop in the valley corridor avoids the technical hazards entirely. The weather clears meaningfully Monday night into Tuesday. If you can shift the trip to midweek, the cables will be in far better shape — but check NPS conditions on cable installation status, as the cables are typically not raised until late May and may not be in place at all. Bottom line: don't start up the cables in active thunderstorm and icing conditions. The objective will be there when the weather cooperates.