| Day | Date | High/Low | Forecast |
| Fri | 13th | 69/51 | Sunny day. Mostly clear evening. |
| Sat | 14th | 67/53 | Chance of morning low clouds; Otherwise, mostly sunny day with scattered high clouds. Partly cloudy evening. |
| Sun | 15th | 63/52 | Amended…Mostly cloudy through the evening. Slight chance of morning drizzle. Chance of rain late evening. |
| Mon | 16th | 59/49 | Rainy and breezy much of day; Rain heavy at times in the morning. Evening showers likely and possibly breezy at times. |
| Tue | 17th | 58/45 | Showers likely, possibly heavy at times; Breezy at times. Chance of evening showers and possibly breezy at times. |
Synopsis
Today’s mild (for February) weather comes via a weak, elongated, upper level trough. There was a marginal, surface off-shore flow early today, but with the upper air trough in place, little subsidence warming as present (just enough for seasonable to slightly warmer than. normal temperatures west of the mountains). Weak high pressure aloft will build into the Southland tonight, but its axis should be east of L.A. County by late tomorrow morning. The various, computer models predict a weak but full-fledged on-shore tomorrow. Well inland temperatures may rise slightly above today’s levels, but most areas west of the mountains should cool a bit (relative to today’s highs).
While tomorrow should still be a mostly sunny day (not like today though), Sunday is expected to be a mostly overcast day. This happens as a large, cold, upper level trough approaches from the west. I amended the forecast for Sunday to include a slight risk of morning drizzle/light rain (better chance west of L.A. County). The effects from the aforementioned trough may induce some marine layer induced wet weather, but any rainfall in L.A. County will be minor (trace amounts to a few hundredths of an inch). I decided to include a risk of showers for late Sunday evening as some model solutions suggest.
The main event of the storm, however, isn’t expected till Presidents’ Day (Monday). Predicted storm dynamics are expected to be ample, and above average, water vapor content is predicted when the storm enters southern California. Unlike the storm of 10-11 February, several hours of moderate to heavy intensity precipitation is likely. Snow levels should also be lower (5000 feet or lower by late Monday afternoon). In addition, breezy weather is expected across the Southland for a time (potential for wind caused damage). In short, expect a fairly potent storm for much of Monday (forgot to mention that brief-lived thunderstorms possible).
Steady precipitation should taper off to occasional showers late Monday, and that may continue through Tuesday. Any noticeable decrease in areal coverage and intensity of showers aren’t expected till sometime Wednesday (depending on which model scenario is right, it may last through Wednesday morning). Additionally, the Tuesday-Wednesday period should be the coldest period for many areas. Daytime temperatures should struggle to reach 60 degrees (coldest this winter).
Storm totals for the period Sunday night through Wednesday could be in the 2 – 3.5 inch range (just talking about lowland areas away from the mountains…more around some coastal facing foothills/mountains). A good chunk of the total should fall on Monday (least contribution on Wednesday). Snowfall above 5000 feet may run in the 9 – 18 inch range (covering the Monday-Wednesday period).
At present, the model consensus favors dry weather next Thursday(19th). Some model solutions predict a modest storm reaching the Southland late next Friday or the following day (20th-21st). Today’s model consensus leaves the “storm gate” open to the state through the final days of February, but none look to be major down in southern California. Mostly cooler than normal weather is also favored in the extended period.
Next issued forecast/synopsis should be on Tuesday, 17 February.