Weather update 27th September 2019

[UPDATE 28th September: Palm Springs media outlets are reporting that the Palm Springs Aerial Tramway, currently closed for maintenance, will not now reopen until Monday 7th October. Many thanks to Florian Boyd for this breaking news.]

I spent Monday to Friday in the San Jacinto high country, hiking mostly off-trail. It was a week of dramatic and changeable autumn weather.

After weeks dominated by west and south-west winds, a shift to a northerly air flow in the early hours of Tuesday 24th caused a dramatic temperature drop, with an air temperature near freezing and a windchill of 19°F at San Jacinto Peak. I posted a short video from there that morning. Later that morning I recorded a wind gust of 49 mph near Marion Mountain.

The cool N-NE wind flow remained all week. Although Wednesday 25th was a little warmer, it was cloudy, and in the afternoon I watched as haboob conditions (a type of sandstorm) developed in the Coachella Valley and Anza-Borrego desert. The north-east winds drove sand all the way through the San Gorgonio Pass as far as Beaumont by dusk.

Thursday 26th was a day of spectacular cloud formations throughout Southern California. While much of the western lowlands and many peaks were shrouded in cloud, with its exceptional prominence San Jacinto Peak remained above it for most of the day. Thunderstorms originating near Joshua Tree spread south to Borrego, but stayed east of the San Jacinto mountains. I posted a short video of the surrounding cloud view at noon yesterday.

A high, deep marine cloud layer over the coastal lowlands led to a dramatic (even by San Jac standards) sunset last night, and a great visual effect at sunrise this morning.

San Jacinto Peak is unusually prominent over its surrounding lowlands. In addition to creating much of it’s own weather, it also casts it’s own distinctive, if short-lived, shadow. Conditions vary, but at sunrise this morning, the deep marine layer to the west provided a perfect canvas for the “San Jac shadow“. My time-lapse video, recorded this morning, shows the spectacular 30 minute rise and fall of the San Jac shadow in just under one minute.

Regarding trail conditions, the status of water sources and highway closures is basically unchanged since last week, as described here.

Despite occasional milder days, hikers should now be prepared for temperatures around freezing above about 10,000′ elevation, and potentially lower when considering windchill effects.

Sunset over an ocean of cloud, as seen from San Jacinto Peak, 26th September 2019 (above looking west, below with the San Bernadino mountains “floating” on the right).

WEATHER After wintry temperatures for the next few days, milder weather will return on about 2nd October. Autumnal temperatures dominate, accompanied by periodic strong winds and extremely variable humidity at the highest peaks. Air temperatures, and certainly windchill values, at or below freezing overnight are now typical. There is no precipitation forecast for elevations above about 5000′ for the foreseeable future.

At San Jacinto Peak (10,810’/3295m) today, Friday 27th September 2019 at 0630 the air temperature was 47.0°F (8°C), with a windchill temperature of 40.1°F (5°C), 51% relative humidity, and a cool N wind sustained at 7 mph gusting to 13.9 mph.

At the Peak on Thursday 26th September 2019 at 0625, the air temperature was 37.2°F (3°C), with a windchill temperature of 31.5°F (0°C), 98% relative humidity, and a light NNE wind at 2 mph gusting to 6.2 mph, accompanied by cloud and brief drizzle.

At the Peak on Tuesday 24th September 2019 at 0625, the air temperature was 34.5°F (1°C), with a windchill temperature of 19.3°F (-8°C), 85% relative humidity, and a sevare NNE wind at 17 mph gusting to 29.9 mph.

Sunset on 25th September 2019, looking NW from San Jacinto Peak.

TRAIL CONDITIONS

All trails, including the entire Pacific Crest Trail throughout the San Jacinto mountains, have been free of snow since the end of June.

Hikers planning ascents of Skyline Trail are reminded that the Palm Springs Aerial Tramway is closed for maintenance until 7th October.

The Pacific Crest Trail remains open at the rockslide near Antsell Rock (Mile 172.5). The video report from late May (available here) can be useful for deciding whether to try to hike around the rockslide.

Forest Service closures to the Boulder Basin and Black Mountain Group campgrounds (both accessed from Black Mountain Road), and Dark Canyon Road, will remain in place all year. Consequently, Dark Canyon campground is also closed, and there is no vehicular access to Seven Pines trailhead.

Seven Pines Trail has at least 35 trees down, almost all above 7500′ elevation. This trail has been very lightly traveled since 2018, and is indistinct in places. Hikers without considerable prior experience of this trail should take great care with routefinding.

The Caramba Trail from near Reeds Meadow through Laws Camp to Caramba, and the Cedar Trail from Willow Creek Trail to Laws, are not maintained. Temporary signage to this effect has been in place since the end of June. Both trails are very indistinct and heavily overgrown in places, and hikers without considerable prior experience of this area should exercise extremely cautious navigation.

The Cranston Fire closure order expired at the beginning of August. Although this does not impact the wilderness trail situation, it does mean that the popular dirt roads and mountain bike trails of the May Valley and Bonita Vista roads area are now open.

Usually due to lighting conditions the shadow cast by San Jacinto Peak is less obvious at sunset than at sunrise. The evening of 25th September 2019 was an exception, with the dust of haboob conditions creating a perfect canvas east of the Peak.

One thought on “Weather update 27th September 2019

  1. The San Jac Shadow. While I have lived in and around Idyllwild for many, many years… I’ve never been able to hike the mountain. And I’d never seen nor heard of “the shadow”. How cool to observe it through your video! Thank you for posting this… it brought a smile to my face for sure.

    Blessings,

    Nanette Scott ~ Jeremiah 29:11 ~ For I know the plans I have for you,” declares the LORD, “plans to prosper you and not to harm you, plans to give you hope and a future.

    🌺 Life hands you… Life. 🌻Treat it with love, respect and joy. 🖼 Make memories. 🗺 Enjoy the view. ☄ Be you.

    >

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