| Day | Date | High/Low | Forecast |
| Mon | 21st | 80/62 | Mostly sunny remainder of day with variable high clouds. Mostly clear evening. |
| Tue | 22nd | 80/62 | Sunny day. Mostly clear evening. |
| Wed | 23rd | 81/61 | Sunny day. Mostly clear evening. |
| Thu | 24th | 78/59 | Chance of some early morning fog; Otherwise, mostly sunny day with some high clouds. Some evening high clouds. |
| Fri | 25th | 76/58 | Chance of early morning low clouds/fog; Otherwise, mostly sunny day with scattered high clouds. Scattered evening high clouds. |
Synopsis
The off-shore flow that began this past Friday produced more warming in most areas (west of the mountains) than I anticipated. I was too swayed by the numerical model, temperature forecasts. There was less of a polar air intrusion into southern California than what the models showed (not a total surprise though…models occasionally over predict strength of polar air). At least wind-wise, that part of the forecast fared reasonably (definitely helped scour away the local, marine layer).
The latest model forecasts show only minor day to day, weather changes through midweek. High pressure aloft is expected to strengthen some over the next couple of days. Slightly warmer days should occur for well inland areas. Little or no additional warming may occur near the coast, however. The surface, on-shore gradient toward the low desert is expected to increase some (promoting earlier sea breeze). On the other hand, a predicted increase in the off-shore gradient toward the north may off-set the gradient change toward the low desert. The weather outcome should minor nonetheless.
Some of the model forecasts show a shallow marine layer by Thursday. Areas of early morning low clouds/fog may return on that day. A chance for more widespread coverage in the coastal plain could occur late Thursday night/Friday morning (slight weakening of high pressure aloft and predicted increase in overall, on-shore flow). There could be less coverage of low clouds/fog by the coast over the weekend if on-shore flow weakens again as predicted (slight uptick in daytime temperatures too but mainly applicable for well inland areas).
Most of the longer range models predict a northwest wind flow pattern aloft along the West Coast early next week. This pattern would allow for multiple, “inside slider” type troughs to pass through the state. One such trough on Monday may promote a strong on-shore flow (deep marine layer favoring widespread, more persistent, low clouds west of the mountains). Breezy weather should prevail in the interior. A deep marine layer may also support patchy drizzle (mainly early morning). Other “inside sliders” could pass through the Southland later next week. Other than bouts of marine layer clouds (not necessarily as a solid overcast after early next week), there should be ample of sunshine by day. Most or all of next week should be at or slightly cooler than normal (including Halloween).
Next issued forecast/synopsis may be on Friday, 25 October.