A weak low pressure system has formed off the Southern Californian coast as advertised a few days ago, and is beginning to pull in copious amounts of cloudiness and increasing moisture from the tropics off the Mexican coast. In addition, Hurricane Paine has developed west of Cabo San Lucas, and is further contributing to the gradual saturation in the local atmosphere. This hurricane was not forecast to develop into as intense of a storm as it has become, with wind gusts over 100mph today. This may help provide additional dynamics as the hurricane turns to the north toward northern Baja. This storm is expected to weaken dramatically the next few days, so extreme winds are not indicated for our area. However, the remnant circulation will head into Southern California, Arizona and New Mexico the next several days, contributing to the possibility of rainfall and breezy conditions at times. More on that in a moment.
As of 3:30pm Monday, most areas have not yet experienced much of any rainfall, with a few exceptions near the LA area, as well as along the Mexican border near Mexicali and Brawley.
DETAILS FOR MONDAY NIGHT
A large area of light rain is moving north late this afternoon, just passing over the Mexican border and into the southern Imperial Valley around 4pm (Monday). Southerly winds are advancing ahead of the rainfall, with gusts near 30mph contributing to blowing dust and increased humidity levels south of the Salton Sea. Visibility is currently between 2-5 miles in these areas. This area of dust and haze may possibly move north into the Coachella Valley late this afternoon or evening, possibly reaching Indio or Palm Springs around sunset or later. This will be dependent upon whether the southerly winds continue, so it isn't a sure bet at this point.
Behind the dust and breezy conditions, periods of mostly light rain may fall at times tonight. Rainfall amounts are not expected to be large, but this storm is a bit more dynamic than earlier predictions. At this point, amounts are still expected to be 0.15 inch or less tonight, with locally higher amounts a slight possibility.
DETAILS FOR TUESDAY AND TUESDAY NIGHT
Hurricane Paine will continue moving north Tuesday, producing a more humid airmass and a good chance of showers or thunderstorms across the area, especially during the morning hours. Southeast winds may blow at times, occasionally gusty. Temps may not escape the 80's on Tuesday if the cloud cover remains thick. Rainfall amounts are difficult to predict at this time, possibly from only a trace up to 0.50 if any heavier storms manage to develop. It will likely be muggy, with dewpoint temperatures in the 60's or 70's a good possibility.
DETAILS FOR WEDNESDAY - THURSDAY
The remnants of Hurricane Paine will move northeast into Arizona, and the moisture will combine with a new low pressure system moving in from the northwest. This low pressure is the first somewhat significant system of the fall season, with snowfall possible in the High Sierras to our north. Locally, it is still possible that the lingering moisture may combine with the cold front and trough moving through to create a few more scattered showers on Wednesday or Wednesday night. However, the wind and cooling temperatures are the most likely effects, with strong west winds expected to howl through the I-10 corridor, with areas of blowing sand and dust likely to accompany the fresh weather change Wednesday night or Thursday. Some of these gusts may blow south into the central and northern areas of Palm Springs, North Cathedral City, as well as northern areas of Palm Desert, Rancho Mirage and Indio. It is also possible that southerly winds may blow through some of the southern canyons for a period of time ahead of the cold front.
THURSDAY NIGHT AND BEYOND
The cold front will move to the east, bringing clear skies and a possible light-moderate Santa Ana Wind condition later this weekend. This means humidity will be bone dry, skies should be crystal clear, and temps will likely jump back up to near or above 100 degrees by Sunday.
All in all, this is a tough forecast the next several days, as systems combining from the northwest and the south are notoriously difficult to predict. Cloudiness is definitely going to continue, but rainfall will be tough to predict with certainty. It may be that we only see sprinkles or light rain the next few days. However, the possibility is certainly there for heavier rainfall at times. I'm curious to see how it all plays out.