Newbie weather question

[inside]

Hi Guys, a few of my coworkers and I are planning a trip to south Colorado (San Juan Nat'l Forest) next weekend. We've never hiked in Colorado before (we're from Texas) and I'm trying to figure out if these rain forecasts are normal. Is it just basically expected that there's better than a 50% chance of rain most days?

[Pops921]

Most of the rain is in the form of afternoon thunderstorms, mornings typically clear.

[colokeith]

First weather forecasts for next weekend are pretty much worthless. I would only begin to value a forecast about 48hours out.

Second a 50% chance of thunderstorms is pretty common any particular day. What is far more important is the timing of the big uptick in precipitation potential. In the weather forecast linked from any particular page drill down to the weather hour graph. View the graph for lightning and precipitation potential and note where the jump in potential. Then watch the sky and correlate what you are seeing to this expectation

[JROSKA]

50% chance of thunderstorms is pretty common any particular day. What is far more important is the timing of the big uptick in precipitation potential. In the weather forecast linked from any particular page drill down to the weather hour graph. View the graph for lightning and precipitation potential and note where the jump in potential.

I second this, and have learned that "50% chance of storms, mainly after noon", is basically reality in Colorado mountains in summer. With that type of forecast, it's worth showing up, starting early, and keeping an eye on the sky. But yes, especially in monsoon season, 50% is normal. It's when you get within a few days of the climb, and you see afternoon numbers like 70% or 80%, with "chance of showers before 10 am", (i.e., uptick in precipitation potential even in the morning hours) that's when things are getting into the "abnormal" territory and it might not be a great day to summit. It's taken me awhile, but I've learned not to be too intimidated with 50%.

[MitchellS]

Predicting thunderstorms in the mountains is incredibly difficult so your best bet is to show up and keep your eye on the sky. The usual rule is "be heading down the mountain by noon" but sometimes this is faulty in either direction. You can have thunderheads roll in at 10:30am or you can have blue skies until 2pm. Just keep your eyes open and be wary of cloud formations.

[Daniel Joder]

BTW, an "early start" doesn't mean 9a.m., or really even 7a.m. It means first light at a minimum...4a.m. even better (it'll depend on how easy the initial part of the trail is to follow with headlamps until you get first light). Note that many hikers on Longs Peak start at 1 or 2a.m. I came down off of Quandary once after my typical very early start (sunrise on top) and found, at 9a.m., folks strapping on their packs for the hike up--setting themselves up perfectly to meet a big storm somewhere between treeline and summit. You may already know all this, but just in case...Have a great Colorado vacation!

[peter303]

BTW, an "early start" doesn't mean 9a.m., or really even 7a.m. It means first light at a minimum...4a.m. even better (it'll depend on how easy the initial part of the trail is to follow with headlamps until you get first light).

You need to know you own pace and skills. I'm a strong walker and get up Quandry in two hours, more for longer mountains. So dawn is OK for me. If it takes you six hours, start at 4AM. Know yourself.

The rule is to be below the treeline by noon if possible. That means starting at first light and summiting before 11AM.

But even this rule doesnt work on particularly stormy weather. Eight people were hit by lightning at 11:30AM on Bierstadt a few weeks ago. All lived, but three spent days in hopsital.

[inside]

BTW, an "early start" doesn't mean 9a.m., or really even 7a.m. It means first light at a minimum...4a.m. even better (it'll depend on how easy the initial part of the trail is to follow with headlamps until you get first light). Note that many hikers on Longs Peak start at 1 or 2a.m. I came down off of Quandary once after my typical very early start (sunrise on top) and found, at 9a.m., folks strapping on their packs for the hike up--setting themselves up perfectly to meet a big storm somewhere between treeline and summit. You may already know all this, but just in case...Have a great Colorado vacation!

Thanks for the advice! I was planning on doing some very easy hikes - Engineer's Mountain (near Silverton) and then Handies Peak so they should be reasonably done in ~4 hours ea.