| Day | Date | High/Low | Forecast |
| Mon | 17th | 63/52 | Chance of morning showers; Rain developing in the afternoon, possibly heavy at times. Rain tapering to a chance of showers by late evening. |
| Tue | 18th | 60/50 | Partly to mostly cloudy through the evening. Chance of daytime showers; Slight chance of evening showers. |
| Wed | 19th | 61/51 | Partly to mostly cloudy through the evening. |
| Thu | 20th | 59/51 | Mostly cloudy through the evening. Chance of showers by afternoon; Good chance of rain late afternoon or evening. |
| Fri | 21st | 60/51 | Partly to mostly cloudy through the evening. Overnight rain; Chance of some daytime showers decreasing to a slight chance in the evening. |
Synopsis
The first of three storms expected to affect southern California stuck around a little longer than I anticipated (into Sunday evening…some computer model forecasts showed that though). Storm totals in L.A. County, however, were pretty much in line with expectations (2.53 inches at UCLA, as 4 PM yesterday). There were some impressive totals occurred in Santa Barbara/Ventura Counties where double digit rainfall were recorded (not all over the mountains).
The second storm is slowly moving through the Southland today. While it is predicted to transform into another semi-“cut-off” low pressure, it doesn’t have a tap into tropical moisture. So, storm totals shouldn’t come close to the first storm in most areas. Still, brief bursts of heavy intensity rain (not all associated with thunderstorms) are expected in L.A. County (been the case in parts of Ventura County much of the daylight hours, so far). The steadier rain should taper off to scattered showers by late evening. The core of the “cut-off” low pressure should wander somewhere over area (could be Santa Monica Bay, could be closer to southern Tehachapi Mountains) through much of tomorrow. Cold air instability showers and isolated thunderstorms could form just about anywhere (“home grown” variety rather than moving in from a distant locale). By early Wednesday, the rain threat should exit southern California.
Storm totals in L.A. County should be in the one third to one inch range (valid for lowland areas away from coastal facing mountains). Twice as much rainfall may fall in the usually favored, coastal facing foothills/mountains. Since tropical moisture isn’t involved this time around, snow levels should fall to near 5000 feet by tomorrow morning. Snowfall could be a few to several inches down to 6000 feet.
Originally, Wednesday was expected to be cool but mostly sunny day across the Sourhland. This may still occur in some areas, but the latest model runs favor much lingering moisture. So, I show a “partly to mostly cloudy” day in the campus forecast. I don’t expect any shower threat in the lowlands. However, if this deep layered moisture does verify, I wouldn’t be surprised by isolated, light showers around or over the higher mountains.
The third and last storm of the series (forecast to develop into yet another “cut-off” low pressure) should reach southern California sometime on Thursday. If today’s model consensus, some showers may start in L.A. County by midday, but the bulk of the wet weather shouldn’t occur before late Thursday evening (maybe not till the predawn Friday). There are still a wide variety of solutions when it comes to storm totals. Some solutions favor a minor rain event while others favor totals similar to storm number two. Snow levels may stay slightly higher (no lower than 6000 feet).
While L.A. County should dry out by Saturday, there are some scenarios where the third “cut-off” low pressure lingers around well into Saturday. That would allow for some lingering showers at least through Saturday morning (rather than ending late Friday evening). For the time being, I’m going with the model majority solution (earlier dry out).
One way or another, a modest warming trend should begin over the weekend (minor day to day changes expected till then). Some model forecasts showed a weak, off-shore flow early next week, but that appears to be a minority solution (for the time being). At best, near seasonable temperatures early next week may occur (a little warmer than normal, perhaps). This may extend to the rest of Thanksgiving week though some model solutions show some cooling over the holiday weekend (nothing too cold though). Much could happen between now and next week. So, I wouldn’t place too much faith in any one scenario (for now).
Next issued forecast should be on Thursday, 20 November.