| Day | Date | High/Low | Forecast |
| Mon | 6th | 73/60 | Mostly sunny remainder of day with some high clouds. Chance of evening low clouds. |
| Tue | 7th | 71/59 | Good chance of morning low clouds; Otherwise, mostly sunny day with some high clouds. Chance of late evening low clouds. |
| Wed | 8th | 73/60 | Mostly sunny day with scattered high clouds. Becoming partly cloudy in the evening. |
| Thu | 9th | 71/59 | Partly cloudy with high clouds through the evening. |
| Fri | 10th | 68/58 | Mostly cloudy through the evening. Slight chance of daytime light showers. Chance of evening light showers. |
Synopsis
A weak, upper level trough passed through southern California this morning (reason for considerable mid/high clouds earlier today). High pressure aloft will build into the state tomorrow (peaking in strength Wednesday morning). The high pressure ridge should weaken and move east by Wednesday evening. A “cut-off” low pressure, which currently is over a thousand miles west of northern California, will bring wet weather to most of the state by this weekend.
Despite a coastal eddy and developing, strong on-shore flow, temperatures today in some areas (like the Westside) wound up warmer than I expected. The eddy circulation appears to have delayed on the onset of the daily sea breeze on the Westside. That in turn, allowed for better than anticipated (by me) warming. Since the computer models are predicting minor deepening of the marine layer tonight (lasting into the Tuesday morning), I decided to keep my preliminary forecast unchanged. Tomorrow should be a little cooler than it got today. Wednesday should be a little warmer than it gets tomorrow unless the marine layer remains well defined (more than what model forecasts show). In that case, Wednesday temperatures should essentially mirror Tuesday (applicable to the coastal plain…some modest warming likely for valley locales).
A cooling trend will increasing clouds (high altitude one at first) should begin on Thursday. There is even some chance at light showers as far south as San Luis Obispo County (evening hours). A chance for showers should spread into Santa Barbara County by Friday morning. A relevant chance for light showers in L.A. County should occur by late Friday evening (unless “cut-off” low pressure moves toward the state more slowly than model predictions). If all goes according to plan (?), Saturday morning should be a wet one in the L.A. Basin. While cold air instability should be limited (temperatures that day shouldn’t exceed mid-60s), there is a chance at isolated thunderstorms that day. An overall decrease in shower activity in L.A. County is anticipated Saturday evening.
As spring storms go, this one should be a decent one for early April. Ample, available water vapor is predicted, and some fair storm dynamics are expected to reach L.A. County. Storm totals (Friday-Saturday) in the lowlands away from the mountains should be in the 0.25 – 0.75 inch range. If thunderstorms do develop, totals may exceed an inch. As common with many storms, areas around coastal facing mountains may receive up to twice as much rainfall. Snow levels should stay above 7500 feet for much of the storm period (not lowering to 6500 till Saturday evening). Even so, most of the snow should be on the slushy side.
On Sunday a secondary trough is forecast to pass through the state. One model (GFS) brings significant storm dynamics into the Southland (almost a repeat to Saturday weather on Sunday). Most model solutions, however, keep the better storm dynamics and instability farther north. Some showers may occur on Sunday, but most should favor areas over/adjacent to the higher mountains (best chance of showers west of the mountains may be Inland Empire southward into coastal San Diego County. At this point, I’m not expecting much chance at wet weather in the L.A. Basin on Sunday (continued cool weather though).
Next Monday should be the clear out day in southern California. A minor trough is forecast to pass through the state on Tuesday next week (limiting warming but dry weather likely). Sunny weather and slightly warmer than normal weather is possible for the middle of next week. After that, model solutions get rather varied. Mostly sunny with near seasonable temperatures may occur. However, some model solutions show a chance for some minor wet weather late next week or over the subsequent weekend. For now, I’m leaning toward today’s model consensus (dry in Southland).
Next issued forecast/synopsis should be on Thursday, 9 April.