High Sierra Topix

hey mav, does your reading of long range sierra weather come from the nws 'forecast discussion'? or elsewhere?

The NWS is more conservative (scientific) in their forecasts more than 5 days out than some other commercial forecasts, such as Weather Underground, which will forecast in detail out 10 days. There is actually a mathematical reason why forecasts fall apart after about 5 days, regardless of the sophistication of your weather models, due to too many variables. The exact timing and location of specific storms cannot be forecast far in advance, even if the general weather (such as "monsoonal") can be speculated. The NWS has a section on "climate" that presents probabilities of warmer/colder and dryer/wetter than normal months out.

I take all forecasts more than 5 days out with a grain of salt. If you are carrying an In-Reach, you can get forecasts while you are out.

Wandering Daisy wrote: ↑Tue Jul 20, 2021 2:05 pm I take all forecasts more than 5 days out with a grain of salt.

Solid advice.

Plus thunderstorms don't mean you can't go, just mitigate the hazard. Get out of those high places by noon, camp lower in wind sheltered areas, bring good rain gear, and don't forget the guy lines for your rain fly. Choosing a less remote trailhead helps too. It'd suck to have mud or down trees block your exit road.

yeah i agree. i was just curious where mav was looking.

hey mav, does your reading of long range sierra weather come from the nws 'forecast discussion'? or elsewhere?

Frozenintime,

I use a few sites like Windy, NWS, and local weather sites, and if two or more agree with one forecast, it might turn out right; the keyword is "might," and as others have mentioned, anything five days and beyond is iffy at best.

maverick wrote: ↑Tue Jul 20, 2021 3:45 pm

hey mav, does your reading of long range sierra weather come from the nws 'forecast discussion'? or elsewhere?

Frozenintime,

I use a few sites like Windy, NWS, and local weather sites, and if two or more agree with one forecast, it might turn out right; the keyword is "might," and as others have mentioned, anything five days and beyond is iffy at best.

Yeah, I've found Windy to be especially iffy. Their forecasts deviate from the NWS regularly, and at least anecdotally they're often wrong. Their interface is slick, but the NWS still is king for accuracy in my opinion. Sites like OpenSnow are pretty good in the winter though.

Is it possible that the Sierras won’t even get a monsoon? I remember being nailed by the monsoon weather pattern the multiple times I hiked the JMT. But this year it seems to be absent.

Next monsoonal flow could bring heavy rainfall with flash flooding possible.

NWS:

Light zephyr breezes will prevail over the weekend with gusts mostly around 20-25 mph. After a few days of drier weather, another push of monsoon moisture looks to work its way back across the Sierra and western Nevada. This moisture could trigger isolated showers and thunderstorms across southern Mono and Mineral counties by Sunday afternoon with chances spreading northward through early next week as the bulk of the moisture
arrives. Ensemble guidance introduces PWATs around 0.75-1.0" Monday into Tuesday which could develop more widespread shower an thunderstorm coverage roughly south of I-80 each day. With higher moisture and moderate storm motions, localized heavy rainfall could lead to flash flooding potential early next week.

Thanks! I'm planning on the Rae Lakes Loop and it looks like things seem forecast for further north - hoping that holds. I've been keeping an eye on the cedar grove NWS forecast - I'd assume that's probably a good one to check for Rae Lakes.

My wife and I did a section of the JMT from Tuolumne Meadows to Kearsarge pass 6/24-7/12. We had 6 days of no rain. We had about 5 days of really bad weather lasting for five hours or more with heavy rain, lighting, thunder and hail. Worst day was on 7/10 coming over Glen Pass I think it was the worst storm either of us has seen in the Sierra.