The Hiker’s Handbook: Weather

In the last blog, I did a quick and tidy breakdown of climate and how it factors into general planning. I compared climate to “personality” by pointing out how it’s a collection of traits, tendencies, temperaments, and characteristics that remains stable over time. I then compared weather to “moods,” which are day-to-day, or even moment-to-moment fluctuations present in the atmosphere.

Just like human moods, weather fluctuates constantly. Even in California, the conditions are rarely the same two days in a row. Because the weather is in flux, and because climate conditions can create a wide array of potential conditions producing a variety of potential hazards, weather is one of the primary factors that hikers must account for.

Forecasting

Modern humans rely on forecasting provided by a number of outlets to get a picture of weather. Although most people view forecasts as numbers that show up on smart phone applications, there’s actually quite a bit that goes into predicting the weather. Furthermore, forecasting is an extremely imprecise science, and understanding this lack of precision can also aid in your planning.

Long- and Medium-Term Forecasting

We derive nearly all of our weather information from meteorologists interpreting data gathered by sophisticated, multi-billion dollar computer forecasting systems. Those forecasting systems collect conditions from weather stations across the world, and then they crunch that data to paint a picture of how current conditions will evolve over time. Meteorologists then interpret this picture to glean patterns and trends in conditions.

Some of these computer-based data systems create forecasts spanning several months or even entire seasons. As you might expect, these forecasts are imprecise, as they only paint a picture of what kind of trends meteorologists might expect to emerge during a large period of time.

Another set of computer models, which includes the American Global Forecast System (GFS) and the European Center for Medium-Range Weather Forecasts (ECMWF or the Euro), collects data and portrays potential weather trends over a two-week period. The further out the forecast, the less precise it tends to be. Accordingly, most forecast data presented by models like the GFS and ECMWF are only reliable within a five day window.

Short-Term Forecasting

The National Weather Service incorporates a short-range, high-resolution weather model known as the North American Mesoscale Model, that provides high-detail predictions up to 84 hours out – that’s 3.5 days for all you math haters. This model, when paired with an ensemble of the GFS, ECMWF, and even other models like the Canadian, Japanese, or English weather models, creates the clearest possible picture of weather conditions for specific dates. Meteorologists can then analyze that data and create a forecast for the National Weather Service, which meteorologists present in their Area Forecast Discussions (AFD).

Commercial meteorological agencies like the Weather Channel, Wunderground, local news, etc. rely on the National Weather Service interpretations for their own forecasts; this is an important consideration to keep in mind as you try to figure out the best way to prepare for weather conditions.

What Does This Mean For Planning?

With all of that explanation out of the way, you can begin applying what you know about weather forecasting to hike preparation. Let’s assume for a second that you are considering a hike in three weeks time. At that point, you won’t have much information on weather. But two weeks out, you can begin checking weather data to see what might happen on the day of your hike.

Because you know that the medium-range forecast is very inaccurate, you can continue to check on the forecast to see how it evolves. Weather events frequently show up in the medium-term only to disappear in the short-term. Occasionally, those weather events “reappear” as the models get a better handle on what’s going to happen. As you follow the evolution, you can consider what conditions you need to plan for, and you adjust your corresponding preparation for your hike. The factors influenced by weather include where you hike, what you pack, what you wear, what time you start, and what time you need to finish – you know, pretty much everything.

You also know that no forecast is all that reliable until you start to reach the 84 hour window. The short-term models begin to pick up with fairly remarkable clarity what kind of conditions you can expect. As with all models, the accuracy improves all the way up to the morning of your hike. Of course, no forecast is full-proof, and despite the remarkable amount of skill, research, data, and money that goes into forecasting, meteorologists occasionally get it wrong. Now, does this mean that forecasts are useless? Not at all. Many times, the forecasts are dead on, and without them we would have absolutely no idea what’s going to happen until it happens.

Where Can I Get the Best Weather Data?

As I indicated earlier, most American forecast data comes straight from the National Weather Service. Their computers collect the data, and their scientists interpret the data into forecasting. Commercial weather platforms often regurgitate the information provided by the NWS, and therefore it’s best to go straight to the source.

1. Models

You can actually follow model data from both the GFS and the NAM. It takes some work to understand what you’re looking at, but the color coded system (Red for high pressure/fair weather; blue for low pressure/unstable weather) coupled with green for moderate rain and blue for heavy rain can help you follow potential storm patterns.

2. Area Forecast Discussions

You can go straight to your regional National Weather Service website to review their area forecast discussions. The AFD’s contain a synopsis on overall trends, specific conditions across the region, aviation and marine conditions, fire conditions, and specific watches and warnings. Yes, they often type in all caps. No, they are not shouting at you.

3. The California Nevada River Forecast Center

This remarkable website contains an astonishing amount of weather information, ranging from predicted and observed temperatures, predicted and observed precipitation, historical data, snow pack depth, river flow levels, drought information, and a wealth of minutiae certain to satisfy weather nerds everywhere. This is my preferred tool for trip planning, as it gives an idea of temperatures and how much rain will fall over any given period up to seven days out. It also allows me to see how much rain falls at a number of specific locations across the entirety of California across the year.

4. Mountain Forecast

This website provides weather forecasts for specific high points across the planet. The really useful feature with this website, aside from the specificity of rainfall, temperature, and wind speed forecasts for a massive number of peaks, is that it provides temperature information across a number of different elevations. So, if you want to hike Mt. Whitney, and you want to know the temps at the summit, Trail Camp, Lone Pine Lake, and Whitney Portal, the forecast information on this site can help you determine what those temperature ranges will encompass.

5. Commercial Weather Forecasts

Apps, television, radio, and even amateur weather persons can provide information that’s consistent (mostly) with what the NWS provides. Of course, this is often second-hand information, and commercial entities often bundle their forecasts with news stories, ads, and the occasional sensationalist slant. It’s not as reliable or straightforward as NWS forecasts, but there are certain user-friendly features on apps like Wunderground and Weather.com that allow you to follow hour-to-hour conditions or to check satellite images showing the progression of weather systems.

6. Weather West

This isn’t a forecast site, but Daniel Swain’s popular blog provides monthly/bi-monthly summaries of overall weather patterns. In addition, the comment section is heavy on speculation and analysis of ongoing weather patterns, and the comments provide information that’s often just as useful as official forecast data – a remarkable feat for the internet age.

The hour-to-hour features can help you identify when you need to start hiking to avoid heat or rain. Satellite functions can show you the progression of rain so that you can time your hikes around possible storm front arrival – provided of course that you have reception.

In Summary

There are a host of information sources available to hikers that enable them to prepare for weather conditions. Those weather conditions are often a primary source of hazards for hikers, with cold, rain, heat, snow, and thunderstorms causing a variety of injuries, safety concerns, and deaths every year. Incorporate this arsenal of information into your preparation, and you will be able to avoid the vast majority of those hazards.