Forecast notes as of Aug. 7:
Forecast confidence: Low
- On the West Coast, the concern for early fog shifts farther south, giving totality path a better chance of clearing out
- Storm system in upper Midwest raises concern that midday t-storms could partly obscure viewing
- Plenty of moisture makes it quite likely that pop up afternoon t-storms lead to spotty interference with viewing in Southeast
Average weather conditions for Aug. 21
The timing of the eclipse is ideal, at least for the West. It begins just after 10 a.m. local time on the West Coast, which is usually enough time to burn off the fog that can often occur there.
The intermountain areas typically see thunderstorms bubble up in the afternoons during this time of year. These are associated with the Southwest monsoon, a period of increased thunderstorms and rain during the late summer and early fall. But the eclipse passes through this region around noon, so it should beat the worst of that threat.
Clouds often pop up along the rest of the path throughout the day simply because of warmth and moisture. Those two things combined lead to rising air, which creates clouds. So the cloud risk gets greater the farther east you go. On top of that, South Carolina will see totality the latest in the day — after 2:30 p.m.
Obviously the eclipse is still too far away to get a good forecast. But some of the forecast models we use to predict the weather go out several weeks, and at this point, they cover the day of the eclipse.