DUST, CHANGING TEMPS, AND A CHANCE FOR RAIN?

Springtime is in full swing here in the desert. Typically, that means we are in store for wildly fluctuating temperatures and a lot of wind, and this spring has been no different. However, this spring has been particularly dusty, with even modestly windy days creating reduced visibility.

FREQUENT DUSTSTORMS THIS SPRING

Each time the winds gust above about 25 mph, the skies along the I-10 corridor have been clouding up with dust this spring. If the winds increase over 35 mph, excessive sand begins blowing across roads. There have been several stories in local media recently discussing the challenges with frequent road closures due to blowing sand (and water during severe storms) along Indian Canyon Dr, as well as less frequent closures on Gene Autry Trail and Vista Chino. There has been a lot of chatter about what the city could do. Building a bridge, which recent estimates place OVER $200 MILLION, is clearly not an affordable option.

As the various leaders attempt to come up with viable engineering solutions, it is a good moment to understand what scientific processes are at work to create these problems in the first place.

Let’s take a look from the air first. Here is the satellite view of the Whitewater River wash as it crosses Indian Canyon Dr, south of the I-10 interchange (courtesy of Google Satellite).

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Indian Canyon Drive is located on the right side (above), and the area of most concern is highlighted by the red rectangle. The dotted red lines indicate the approximate boundaries of where the water flows during extreme rainfall events, like those we experienced several times this past winter. The normally dry wash fills with water and soil during those events. On the left side of the photo, the blue arrows represent the Whitewater River flowing southeast. The greenish colored rectangular shapes in the center of the image are the water retention basins, where the normal Whitewater River flows are diverted, to allow ground water to sit in these basins, and slowly seep down into our underground aquifers. Only during periods of high runoff does the river flow past the retention basins, and southeast across Indian Canyon Dr. down valley toward Indio and the Salton Sea.

IT’S AN UPHILL BATTLE - LITERALLY!

To fully grasp the magnitude of what engineers are up against, it is important to look upstream from Indian Canyon Dr…. to see where the source regions are for the sand, silt and water that flows downstream. Here’s another expanded Google Satellite view, below.

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As you can see, there are several creeks and rivers that flow out of the nearby mountains. The areas outlined in the red dotted lines indicate the larger creeks and riverbeds. While our average annual rainfall in Palm Springs is typically less than 6 inches, the nearby mountains receive more than 35-40 inches. This past winter, even more than that has fallen on the middle slopes (with an extensive snowpack at higher elevations). The areas outlined in the solid yellow lines are sand dunes. It’s easy to miss these while driving along highway 111, but these areas capture an enormous volume of sand as the strong prevailing winds blow from the west, through the San Gorgonio Pass. Recent high water flows supplied these areas with a fresh inventory of silt, sand and dirt.

EXTREME RUNOFF AND DEBRIS FLOWS: MORE DUST!

As mentioned above, the high rainfall and runoff this past winter has led to a fresh supply of dirt, sand and silt into all the river systems to our west. While local officials can use bulldozers to clear the roads after a specific high wind event, they are up against at least 15 miles of dirt, sand and silt that will slowly track to the southeast over time. In the spring and early summer, it is quite common to have very strong west and northwest winds blowing through the San Gorgonio Pass. Nature will continue to push sand and silt our way.

Because of the high supplies of dirt and sand, visibility has been reduced many days this spring thus far due to airborne dust and sand. In years past, typically it would require winds over 35 mph to begin causing areas of blowing sand and dust. However, this year, even winds under 30 mph have been able to generate dusty condition. Even those areas outside the normal wind belts feel the effects of this. Most of us have noticed a fine layer of dust on our cars left outside, even if the winds in our particular neighborhood have remained calm. Being downwind, the normally calm areas have experienced higher levels of dust settling as the fine dust particles that blow high into the air near the I-10 corridor eventually come settling back down to the earth further to the south and east.

Sorry for the bad news, but dusty and sandy conditions are likely to continue into early summer!

UPCOMING WEATHER CHANGES: COOLER, WINDY AND POSSIBLY WET?

Getting back to our upcoming expected weather - we have a few interesting weather changes to keep an eye on the next 7 days.

Heat will continue through Saturday, with high temperatures in the low 100’s (90-94 in the Joshua Tree area). This is close to record breaking heat for many communities.

By Sunday, an approaching system will bring slight cooling, down into the 90’s (low 80’s Joshua Tree).

Monday will see partly cloudy skies, and even a chance of scattered showers and thunderstorms, as well as increasing winds Monday and into Tuesday. Temperatures will likely cool into the 80’s for Monday - Wednesday (low 70’s Joshua Tree). A low pressure system will pass through our area, creating an unstable airmass and the possibility of storms. Storms are likely to be scattered, meaning many locations will likely remain dry. Low pressure systems this time of year are erratic and difficult to pinpoint this far ahead.

The extended weather pattern suggests the remainder of next week we will be susceptible to small disturbances from the northwest, as well as periods of wind, most likely on the north end along the I-10 corridor, and in the high deserts from Morongo to Joshua Tree. Highs will likely juggle between the 80’s and 90s (with 70s and 80s in the Joshua Tree area).