- The Southeast and northern to western Midwest remain the most challenged viewing locations.
- Pacific Northwest viewing prospects have improved some.
- Interior West and East Coast cities should see mostly clear skies.
Forecast confidence: Medium to high
- Corvallis, Ore.: Morning fog likely to burn off in time for good view
- Madras, Ore.: Mostly clear but light smoke haze possible
- Rexburg, Idaho: Scattered clouds, light haze
- Casper, Wyo.: Scattered clouds, little interference
Forecast confidence: Medium
- Grand Island, Neb.: Greatest risk area for mostly cloudy conditions
- St. Joseph, Mo.: Partly cloudy, frequent interference possible
- St. Louis: Partly cloudy, occasional interference possible
- Carbondale, Ill.: Scattered clouds, limited interference
- Hopkinsville, Ky.: Scattered clouds, limited interference
- Nashville: Scattered clouds, limited interference
Forecast confidence: Low to medium
- Greenville, S.C.: Partly cloudy, occasional interference possible
- Columbia, S.C.: Partly cloudy, occasional interference possible
- Charleston: Partly to mostly cloudy, frequent interference possible
We are well-within range of the best global forecast models, including the American Global Forecast System and European models. Below are illustrations of the cloud cover that these models are predicting as of Saturday.
In the graphic below, showing the GFS model, clouds are displayed in blue. It doesn’t exactly match what we’ve illustrated in our forecast map at the top of this article. That’s because it is just a single prediction from a single model.
For another point of view, below is the cloud cover forecast from the European model. Shades of gray illustrate where clouds are forecast. The darker the shades, the more cloud cover predicted.
For the Capital Weather Gang cloud cover forecast, we take into account all the models’ predictions as well as what we know about typical August conditions.
Finally, note that the above maps display the model forecasts for total cloud cover, which take into account both high and low clouds. In some areas, their illustration is probably overly pessimistic because the eclipse may still be viewable through high, thin clouds.
Average weather 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 often occurs there.
The intermountain areas sometimes 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, before most of the storms develop, so the storm risk should be low there.
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.
NASA created the map below, which shows how, on average, the best chance of clear skies Aug. 21 is focused in western areas, and the chance of cloud cover increases as you head east.
Additional cloud cover resources:
Jason Samenow contributed to this post.