|Picture of the December 2011 lunar eclipse over the slopes of Peavine, taken from NWS Reno|
- Partial eclipse start - 3:16 AM PDT (roughly mid-way up the southwest sky)
- Total eclipse start - 4:58 AM PDT
- Total eclipse ending - 5:03 AM PDT (that's only five minutes long!)
- Partial eclipse ending - 6:45 AM PDT (moon setting in the west about this time; also note that it will start getting light out between 5:55 and 6:11 AM, and sunrise is at 6:38 AM)
So, we've been in a drought all winter with (too) many clear sky days. Is that going to be the case for Saturday morning? The GFS (American forecast model) simulation is has been indicating that the storm track will remain to our north Friday-Saturday. In the map below, the green and blue color shadings show light precipitation over the Pacific Northwest. The other simulations, including the European forecast model, show something similar with dry weather over our region.
A more likely scenario are high-altitude clouds rolling through, and we don't necessarily need a storm to create those. Forecasting the extent of these clouds especially five days in advance is tricky. This is readily seen in the big differences in cloud forecasts from the two most recent GFS simulations. We run the simulation four times each day.
This map shows the most recent GFS simulation of humidity at about 25,000-30,000 feet for Saturday morning. Based on this one simulation, anywhere in the blue shading has a good chance of seeing thick high altitude clouds, perhaps enough to obscure portions of the eclipse. The green and black areas are drier and have less of a risk of clouds. Note the Reno and Tahoe areas are right on the gradient, and given that the eclipse is taking place in the western sky, there may be some clouds around.
Here's the previous GFS simulation - a bit different, huh? The blues are not as widespread over northern California and Oregon, but there's a few more spots over Nevada.
Bottom line -- there's potential for seeing some of these high-altitude clouds around Saturday morning, but whether or not they'll impede viewing of the eclipse is too soon to call right now. Hopefully by Wednesday or so our simulations will come into better agreement so we can answer that question with more confidence.