Southern California Weather Force
has issued a Special Weather Statement for the entire state starting the end of this week and going into the weekend. Latest estimations is that a cutoff low will drop through Southern California on Thursday and into just south of San Diego by Friday. As it does so, southerly flow will ensure out of Mexico and this will bring the ‘monsoon’ moisture back into Arizona then and finally westward to the southland.
As stated in my Fall forecast, this pattern this year is that of 2019, which saw severe thunderstorms and even tornadoes across Arizona, but some of it leaked toward our region as well. These are becoming more frequent due to the blocking ridge west of Oregon, sending these dynamic systems southward into the region. This event, from end week well into the weekend will be monitored for severe thunderstorms being this is a dynamics system. It could be just the mountain/desert regions, but the pattern does support an upper-level low dropping in. It is a cutoff system so it will change slightly on the details and track. Latest models (not from this office) shows it missing to the east, but if the trend is your friend, the last 12 runs have shown the cutoff directly overhead and not too far east.
The date says around September 24th, but it could mean around the 23rd as well so keep both days in mind.
This also is not a Santa Ana Wind Pattern nor am I monitoring it to change to be such.
So, you have your heads up and statement. As it gets closer, micro-climate alerts will get zoned in.