Sierra Thunderstorm Outlook

[mt.eo]

Does anyone have any experience using windy.com in the Sierra? It seems like their models are predicting this upcoming weekend will be quite active for thunderstorms. It makes me slightly nervous as I've never had to deal with a thunderstorm in the backcountry. Maybe I'm just looking for a bit of reassurance . I enter the Bishop Pass trail on Thursday. What are your experiences with thunderstorms in the high Sierra?

[giantbrookie]

I do not have experience with windy.com. Like many, I use the NOA site (National Weather Service) and then use their map to do smaller area forecasts. When I do this for the Bishop Pass area, the one-week forecast (accessed as of 1520hr PDT Tuesday July 9), gives a forecast of thundershowers, only for Saturday July 13 for their one-week forecast that spans from tonight (ie night of July 9) to Tuesday July 16. For Sat. July 13, the forecast reads "A slight chance of showers and thunderstorms after 11 am. Partly sunny with a high of 63. Forecast square is at an averaged elevation of 11600' E of Bishop Pass.

For summer backpacking in the Sierra the odds are reasonably high that you will encounter thunderstorms. This enters into planning of routes and timing of various segments of routes. For example, in most cases thunderstorms are in the afternoon and evening, so if you have to cross a high point you try to get that done early in the day. There are days in which it storms all day and night. On such days I have to revise plans so as not to cross high ridges and the like.

There are other threads on this board regarding maximizing safety during thunderstorms. You should be comforted by the fact that the number of people seriously injured or worse by lightning in the Sierra is very small compared to other sources of harm (such as slip and fall and stream crossings, for example). This is not to say that thunderstorms aren't scary at times, like when the time delay between the flash and boom falls below one second, for example.

[mt.eo]

There are other threads on this board regarding maximizing safety during thunderstorms. You should be comforted by the fact that the number of people seriously injured or worse by lightning in the Sierra is very small compared to other sources of harm (such as slip and fall and stream crossings, for example). This is not to say that thunderstorms aren't scary at times, like when the time delay between the flash and boom falls below one second, for example.

Thank you for this response. I also often rely on the weather.gov forecasts. I plan on crossing Bishop Pass with my hiking partner in the AM (the goal is before 9) on both July 12th and 13th for this very reason. I'm hoping that I can find a depression or small valley in Dusy to offer some slight protection in the event we have to post up in the tent for a few hours while a storm passes. I appreciate the insight, and I'll go through the other thunderstorm threads on here. Thanks again!

[maverick]

viewtopic.php?t=8001&hilit=lightning+lightning+safety

[c9h13no3]

Does anyone have any experience using windy.com in the Sierra?

A little bit. Windy is neat in that it allows you to see each individual weather model. Sometimes I'll look at it if I know the NOAA forecast is lacking in some way (for example, the NOAA forecast tends to over-estimate snow). The MeteoBlue model is also supposed to do well in alpine areas, so sometimes I'll give that a little more weight. But yeah, the NOAA forecast tends to be hard to beat in terms of convenience.

[wildhiker]

Always be prepared for thunderstorms, even if the forecast is sun, sun, sun. Last September I was planning a 5 day trip doing some cross-country around Mount Hoffman in Yosemite. The NOAA forecast that I saw the day before I left was for nothing but sun. First day, sun. First night, thunderstorm at 1 am. Rest of the trip - thunderstorms every day starting by noon.
-Phil

[John Harper]

I was up at Horseshoe Meadows a couple weeks ago. NWS forecast was for clear skies. Well, it was, except for about 2 hours each day in the afternoon when we had thunder, rain, hail, and wind. So, don't always trust the forecasts.

John

[c9h13no3]

Always be prepared for thunderstorms, even if the forecast is sun, sun, sun. Last September I was planning a 5 day trip doing some cross-country around Mount Hoffman in Yosemite. The NOAA forecast that I saw the day before I left was for nothing but sun. First day, sun. First night, thunderstorm at 1 am. Rest of the trip - thunderstorms every day starting by noon.

While this is good advice, I can't help thinking there's some user error. I've never had the forecast show 0% chance of precip and then it rains. I have had chances of rain grow from very slight to significant from 5 days out to the morning of, or the timing or size of a storm can certainly shift within three days. But a 10% chance of rain, and then it raining doesn't count as the forecast being wrong.

[wildhiker]

Always be prepared for thunderstorms, even if the forecast is sun, sun, sun. Last September I was planning a 5 day trip doing some cross-country around Mount Hoffman in Yosemite. The NOAA forecast that I saw the day before I left was for nothing but sun. First day, sun. First night, thunderstorm at 1 am. Rest of the trip - thunderstorms every day starting by noon.

While this is good advice, I can't help thinking there's some user error. I've never had the forecast show 0% chance of precip and then it rains. I have had chances of rain grow from very slight to significant from 5 days out to the morning of, or the timing or size of a storm can certainly shift within three days. But a 10% chance of rain, and then it raining doesn't count as the forecast being wrong.

Well, perhaps "user optimism". I do remember seeing forecasts that implied clear weather, although I don't remember the exact forecast. I poked around with Google searches to try to find historical forecasts. I did find an archive of the point (city) and area forecasts at https://mtarchive.geol.iastate.edu/. I left to drive to the mountains in the evening of September 7. The last forecast I checked would have been during the day on September 7. At that website, I found this file with forecasts from Sept 7 at 8 am: https://mtarchive.geol.iastate.edu/2023 ... 15_mod.txt . Search this very long file for "Yosemite NP outside of the valley" to find the forecast applicable to my trip to May Lake and around Mount Hoffman. This forecast predicted clear weather with 0% chance of rain through Friday Sep 8 (which matches what happened) and then few to scattered clouds with 5% change of rain for Saturday to Tuesday - which did not happen. Instead, there was full cloud coverage, rain and thunderstorms each of those days.

-Phil

[Wandering Daisy]

There are several sources of forecasts and they can be significantly different. I use the NWS forecasts. My husband prefers Weather Underground. The "basic" forecasts on Garmin In-Reach miss a lot of storms. I find the temperatures are pretty accurate but precipitation not so.

Thunderstorms can have heavy short-term rain that easily flood low spots, so be sure you set up in a location with good drainage. Sadly, there have been cases where people camped in a large meadowy flat area that got flooded and then lightning struck and carried through the water and they were killed. So it is not only high passes that can be dangerous.

Having backpacked extensively in the Rockies, where multiple afternoon storms are so common, I find that working around these storms is just normal, never anything to keep me from backpacking. In fact I have many times set up my tent to wait out a storm, then packed up and gone further. That said, some of the more severe storms I sat out have been in the Sierra. Sierra storms can be severe, they just are not as frequent.

High winds also come with lighting- be sure to tie down your tent solidly and preferably locate with wind shelter. Stop early enough to get set up before the storm hits.