| Day | Date | High/Low | Forecast |
| Tue | 12th | 71/52 | Mostly sunny with some high clouds; Breezy at times, mainly in the morning. Mostly clear evening. |
| Wed | 13th | 75/54 | Sunny day. Clear evening. |
| Thu | 14th | 70/51 | Sunny day. Chance of evening low clouds. |
| Fri | 15th | 60/48 | Mostly cloudy day with a chance of showers, mainly morning. Partly cloudy evening with a slight chance of showers. |
| Sat | 16th | 61/46 | Partly cloudy day with a slight chance of showers; Possibly breezy at times in the afternoon. Mostly clear evening. |
Synopsis
With the passage of an “inside slider” type, upper level trough, a new off-shore flow episode is developing. Moderately strong, northerly winds started late last night (mainly Santa Ana wind prone areas), but that was due to the passing “inside slider”. Wind speeds, which peaked in the 30s to low 40s in lowland areas (as high as the mid-60s in the higher mountains), have decreased some this afternoon. The surface, off-shore flow strength is expected to peak tomorrow morning, but without upper level support (rapidly waning as the “inside slider” slips away), peak wind gusts tonight through tomorrow should stay under 45 mph (mainly higher elevations). Areal coverage should also be less than it was this morning (not expecting return of significant wind in the campus area…peak 30 mph around 9 AM today). The off-shore flow should transition back to on-shore flow Thursday afternoon (weak at first).
The off-shore flow should promote more warming tomorrow than it’s gotten today (most areas west of the mountains). Some readings into the low 80s are possible for some coastal valleys (a little cooler than it got over the past weekend). As with most, other autumn off-shore flows, the dry air and long night hours should promote good cooling at night (especially wind sheltered locales). Although the computer models show noticeable, daytime cooling on Thursday (approaching Pacific storm), I’ve leaned today’s forecast toward more modest cooling for that day (should happen by Friday though). The models killed off this past weekend’s off-shore flow too quickly (reason it stayed warmer than I expected). The models may be collapsing the off-shore flow too quickly on Thursday as well (I think).
There is unanimous agreement on a larger, upper level trough entering the state from the west on Friday. Wet weather over portions of northern California may begin as early as Thursday evening. The storm is predicted to be a modest precipitation producer (somewhat limited available, water vapor content). When its southern end reaches the Southland, cold air instability should promote numerous showers around the mountains (snow level rapidly falling to around 5000 feet…4000 feet possible early Saturday). The predicted, low level northwest winds, however, aren’t typically associated with widespread rain west of the mountains (would be different story if low level winds turned out westerly or better yet, southwesterly). Since storm dynamics look to be marginally favorable (for wet weather), I wrote shower odds at “chance” instead of “slight chance” (better odds of showers occurring in campus areas). If, however, low level winds end up more northerly than predicted, or the storm winds up weaker than currently forecast, nothing should fall at UCLA on Friday.
None of the “wet” weather scenarios are supporting a heavy precipitation event. Most scenarios show storm totals under a quarter inch for lowland areas away from the mountains. Snowfall shouldn’t be more than a few inches with most, probable scenarios. There is a predicted, secondary system slated for early Saturday, but that one looks moisture starved. Rainfall, where it occurs, should be less than a tenth inch away from the mountains. A couple inches of snow at resort level are possible, but widespread coverage may not occur (snowfall down to 4000 feet early Saturday should be just a dusting except perhaps, Tehachapi Mountains… an inch is possible in spots).
A return to mostly sunny weather is expected on Sunday, but temperatures should rebound only slightly (remaining well below normal levels). Another storm is possible for early next week. At present, the model consensus favors a regular, “inside slider” trough (more wind storm than wet storm). So, at this time, I’m expecting most of the L.A. County will remain dry early next week. A number of the longer range models show a moderate strength high pressure by the middle of next week. That favors widespread, warmer than normal weather (some chance of 80 degree weather for the campus area). Things look less clear again (pun intended) at the end of next week. Some model solutions show a new storm rolling into the state (another modest strength system). At the least, a cooling trend would occur late next week (back toward seasonable temperatures).
Next issued forecast/synopsis may be on Friday, 15 November.