11:30 am Update 2/2/19
The cold front is moving east into the Los Angeles area currently. A squall line has set up, with a band of extremely heavy rain and wind gusts approaching 50 mph. Ahead of this line of stormy weather, the wind is blowing from the southeast. Rainfall rates within the narrow squall line have been as high as 0.50 inch in 10 minutes time, indicating blinding rainfall. Fortunately, the squall line is rather narrow, and rainfall rates quickly are diminishing to heavy, but not torrential levels, once the band moves east. The winds quickly switch to the southwest behind the squall line.
A closer look at the wind observations shows this squall line is the intersection of the wind shift from the southeast to the southwest.
This cold front is moving east into LA, San Diego, the Inland Empire, and the San Diego areas. Those areas will experience increasingly heavy rainfall and increasing winds. As the squall line passes through, it will provide a short period of perhaps 10-20 minutes where rainfall rates will become extreme, with low visibility and suddenly increasing winds to over 40-50 mph. As the squall moves east, rainfall rates will likely diminish somewhat, and winds will shift and slowly diminish about a half hour later.
Based on the current forward speed, this wind shift should hit the deserts somewhere close to 3:00 - 4:00pm this afternoon.
Due to the terrain, it will not likely be as dramatic as what is being experienced in the coastal areas. Flash flooding has been reported in many areas of Santa Barbara, Ventura and LA Counties.
However, it is likely that rainfall rates will increase in the deserts between 2:30-4:30pm. Also, when winds shift to the southwest, it is possible that some sections of the Coachella Valley will become very windy for a few hours.
Thus far, the Coachella Valley has had winds mostly under 10 mph. Some southeast winds approaching 25 mph have been blowing in the far east valley near the Thermal and Coachella area.
In the Yucca Valley, Landers and Joshua Tree area, winds have been stronger, as was expected. As of just before 12 noon, here’s a map of the wind gusts (in red, below) for those areas. Notice that the Burns Canyon site on the north slopes of the San Bernardino Mountains has a current gust to 63 mph. Gusts there have been between 60-80 mph most of the morning. A bit lower in elevation, the Landers and Yucca Valley area have begun to see winds increase into the 40-50 mph, as have higher peaks within Joshua Tree National Park. As the cold front approaches, it is likely these areas will continue to see widespread high winds the remainder of the afternoon as well.
EXPECTED IMPACTS TO THE COACHELLA VALLEY
As the cold front moves into our area, it is largely expected that nuisance flooding of roads and intersections is likely. As the rains continue into the night, most of the area washes are expected to begin swelling with water, with many of the usual wash crossings running the risk of closure due to high water flows. POSSIBLE ROAD CLOSURES for tonight and Sunday are noted in RED below, including Indian Canyon south of I-10, Gene Autry Trail south of I-10, and Vista Chino east of Gene Autry Trail, as they cross the Whitewater Wash.
In addition, Golf Club Drive north of highway 111 and Cathedral Canyon Rd north of Perez Road can sometimes experience water across the roadway in the Cathedral City area where the roads cross the Whitewater River. Also, Dinah Shore can experience some short term flooding west of Cathedral Canyon Rd during a heavy rain event. The areas outlined in RED (below) indicate the areas to be on the lookout for water and potential flooding or road closures the next few days.
MORE STORMS LINED UP
Additional rainfall is likely Sunday through Tuesday, although rainfall amounts in the deserts are not anticipated to be as significant. Mountain areas will see snowfall pile up the next several days, especially in the Big Bear area, as indicated in the previous reports. Anyone traveling to the High Sierra should consider postponing their travels as well. Mammoth is expected to receive 5 feet of snow in town the next few days, with 10 feet up on the ski summits. Lake Tahoe is also expected to receive 2-4 feet in town and 5-8 feet up on the slopes. This will make travel impossible at times along I-80 and US-395 in various locations the next several days.
Enjoy the rains, and watch for any weather warnings via the National Weather Service the next several days.