During the summer the Washington Cascades can have thunderstorms at times, which is certainly something to avoid while hiking in the higher terrain. When are thunderstorms most likely to form? They are likely in the summer when there is a trough of low pressure to the south of Washington. The map below is a 500 mb chart of what the atmospheric conditions are at the 18,000 foot level.
When this low is in place, the Cascades usually get a moist and warm southeast wind pattern and can bring an unstable air mass, which is a very good recipe for thunderstorms.
How to avoid thunderstorms? If you don’t want to analyze weather charts just check weather forecasts from the National Weather Service Seattle office. Another option is to sign up for my mountain weather forecast (contact information at end of the article).
Here’s a forecast tip to use while you are in the field: Monitor the sky and if you see this fair weather cumulous cloud and if this does not get bigger during the day then there is probably a low likelihood of thunderstorms forming.
However if several hours later the cloud grows to this size, then it is time to quickly head to lower terrain.
Now with the weather pattern figured out we are ready to head for the hills to hike. Many great summer hiking and backpacking trips are just outside of Leavenworth, Washington. Some of these hikes are warm south-facing slopes so make sure you leave early and have lots of fluids. Here are two of my favorites: Fourth of July Creek and Colchuck Lake. Of course part of these hikes is enjoying the great views!
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