| Day | Date | High/Low | Forecast |
| Tue | 18th | 66/52 | Mostly sunny remainder of day with variable high clouds. Scattered evening high clouds. |
| Wed | 19th | 70/54 | Mostly sunny day with scattered high clouds. Mostly clear evening. |
| Thu | 20th | 75/56 | Sunny day; Possibly. breezy at times early. Clear evening. |
| Fri | 21st | 78/58 | Sunny day. Clear evening. |
| Sat | 22nd | 79/59 | Mostly sunny day with some high clouds possible. Mostly clear evening. |
Synopsis
High pressure aloft is building into the state in the wake of a passing, weak, trough aloft (“inside slider” type). It’s already producing some breezy weather in the higher mountains (isolated gust speeds into the low 30s). However, so far, it’s too weak to reach down to low elevations. The usual sea breeze in the coastal plain kept temperatures in most areas a little lower than it got yesterday (noticeably lower than Sunday temperatures when weak, off-shore peaked).
Most of the rest of the week should include at least a marginal, off-shore flow pattern (more full fledged by late in the week). Some occasionally breezy weather can be expected in Santa Ana wind prone areas, but peak gusts should mostly stay under 50 mph (higher elevations…wind prone areas in the lowlands should be mostly under 30 mph). If some computer model forecasts are right, the passage of an “inside slider” early Thursday may produce some slightly higher wind gusts (enough upper air support to bring some breezy conditions to the campus area…short duration though).
The main consequence of the off-shore flow this week and weekend should be warmer than normal weather west of the mountains. Except for a chance of marine layer clouds early Thursday (should be only Orange/San Diego Counties), the air mass should get too dry to support coastal low clouds (not “bone dry” though as some off-shore flows can be). The predicted, sub-tropical nature of the high pressure aloft should help warm the lower atmosphere by Friday into the 80s in places (lasting through the weekend). It’s not common for late winter in southern California, but it’s also not that unusual of an occurrence by this time of year (spring is about a month away, astronomically speaking).
Last week, some of the longer range models were showing a couple of storms reaching southern California by the end of the month. While this is still possible, fewer model solutions favor it compared with runs made last week. At best, a couple of minor precipitation events could occur. Cooler weather is currently anticipated regardless of whether wet weather returns to the Southland (minor cooling trend early next week; then perhaps, more pronounced late next week). Since we’re nearing that transition period when the jet stream tends to undulate more frequently (compared mid-winter), longer range model forecasts can be subject to poor day to day agreement (i.e. predicting a high pressure one day; low pressure for same period a few runs later).
Next issued forecast/synopsis may occur on Friday, 21 February.