By now, everyone has their places ready and arrangements made for the solar eclipse that is to occur Monday, August 21st, 2017. As a note of extreme caution, when viewing the eclipse, make certain that you have the proper, certified visual gear to watch the eclipse in safety. For more info on viewing safety, visit: https://eclipse2017.nasa.gov/safety.
Two of the biggest questions that have been asked to this point, and naturally so is “will it rain and how will clouds impact my viewing chances of the eclipse?” Both really good questions, yet tough to answer with great certainty beyond a handful of days. The main time window we are looking at for the “start to finish” of the event is from around 9:00 AM (Noon ET) to around 4:00 PM ET. Those in the path of totality will have a much shorter window to view the eclipse in totality, along the order of a few minutes. Here are a few cities that fall in the path of totality. Note that the beginning and end of the eclipse are a much broader widow than the window of totality (a little over two minutes, on average).
Here is a look at rain precipitation chances by the two premier global models, the GFS (American) and the ECMWF (European) outputs.
This GFS output is valid at high noon ET, the commencement of the eclipse for the Pacific Northwest. We can note that as of now (and this will likely change), folks across the Pacific Northwest may run into some hard times viewing the eclipse. We also still have continued showers across parts of the eastern US by noon.
This ECMWF output is valid at high noon ET. We note on this rendering that scattered showers may develop across southern Appalachia but an a clear viewing for the solar eclipse across the Pacific Northwest as the event commences.
And finally, a quick peek at the cloud cover as modeled by both the GFS and ECMWF suggests that cloud cover may play a role in viewing the eclipse for parts of the Pacific Northwest, desert Southwest, Midwest and Appalachia. I suspect that as new data comes out, we will be able to assess locations of high pressure features, lending to a cloud-free environment.
Overall, two regions to watch for are the Pacific Northwest and Appalachia as precipitation and cloud cover chances are heightened at this stage. As noted, these parameters are likely to adjust over the coming week. This discussion was to give you an idea of what we are looking at in the short-term for the solar eclipse. I will have a follow-up forecast discussion a week from this evening (Sunday, August 20th). That discussion will have more detail as we will be within a 24-hour window of the event.