When To Do This Run
Generally this is runnable from mid July through September. Depending on the year you may be able to run it earlier or later.
Realize that for the majority of this run you are totally exposed. Only a small section of the trail is in the trees. So, if the weather is severe you are going to be fully exposed to it. If there is any chance of rain then I'd recommend bringing along at least a garbage bag. It may get quite hot too. My running friend Stacey recommends bringing a white shirt to soak in stream crossing in for hot days.
General Route Information
This run center around one high danger spot - crossing the Big Muddy river after running down the Klickitat glacier. Cross this river can be quite dangerous. I would not recommend doing this run solo. You can either cross the river on the glacier just before the water drains out or work your way down river until you find a spot which it is possible to cross. I do not recommend crossing the Big Muddy high up on the glacier. This should only be done if you have ropes and are trained in cravasse rescue.
After crossing the Big Muddy, you also have the issue of climbing up the bank on the other side. Both of these are difficult. I would recommend walking 1/4 to 1/2 mile downstream from where the water exits the glacier and crossing there.
Maps and Reference Information
This is going to be a long day. Make sure you bring your 10 Essentials along.
As mentioned above you do need to bring a map for this run.
You probably want to check the weather before heading out. Trout lake Washington seems to be the closest town with any weather information. This NWS link may take you straight to weather info.
It's a good idea to check with the ranger before heading up to find out if there are any trail closures or other info.
Mileage Splits and Time Estimate