| Day | Date | High/Low | Forecast |
| Tue | 17th | 59/45 | Update…Mostly cloudy through the evening and breezy at times. Chance of brief showers during day. Rain, heavy at times developing in evening. |
| Wed | 18th | 58/44 | Amended high temperature…Overnight rain tapering to a slight chance of early morning showers. Becoming mostly sunny and breezy at times. Partly cloudy evening. |
| Thu | 19th | 55/43 | Rain likely during day; Possibly breezy at times. Partly cloudy evening. |
| Fri | 20th | 59/45 | Amended high temperature…Mostly sunny day with variable high clouds. Scattered evening high clouds. |
| Sat | 21st | 63/47 | Mostly sunny day with scattered high clouds. Scattered evening high clouds. |
Synopsis
The first storm (yesterday), generally speaking, came about as planned (a bit faster in arrival and a little less windy in places). Today, while partly sunny at times, got a little warmer than I expected. Hence, I postcast today’s high temperature and amended the forecast high for Wednesday and Friday (upward slightly from preliminary forecast). This second storm is a colder system than storm #1. Good storm dynamics and fair atmospheric instability are forecast as the storm moves through the Southland tonight-early tomorrow. However, it will possess noticeably less, available water vapor (no tap into any sub-tropical moisture). So, despite an expected period of heavy intensity rain in most areas (west of the mountains), storm totals should come in quite a bit less than with storm #1 (that was largely 1.5 – 2.5 inches in the lowlands away from the mountains).
Expected totals tonight through early Wednesday in the L.A. Basin should be in the 0.30 – .80 inch range although any strong thunderstorm activity may add as much another third inch. Several more inches of snow should be common at the local resorts (as much as a foot in places). Snow levels should fall to about 3000 feet or slightly lower early tomorrow. Up to a couple inches of snow could fall at those lower elevations.
Like storm #1, it should be breezy in most areas during the height of the storm and even afterwards (blustery afternoon). However, most of the time, wind directions should be more westerly (blowing from the west) rather than southerly. That may also favor west facing coastal, mountain slopes for heavier precipitation. At least it should be more generally sunny in the coastal plain by tomorrow afternoon.
Storm #3 is slated to arrive sometime Thursday. Computer model forecasts have varied as to when steady rain would begin in L.A. County. As it stands today, I’m expecting steady rain on the Westside by late morning (10 AM, plus or minus a couple hours). The predicted, upper level structure of the storm looks more like a marginal, “inside slider” type (more wind storm than rain storm). However, sufficient, available water vapor and decent, low level dynamics should still support widespread precipitation. Storm totals should be mostly a third inch or less (no widespread moderate or heavy intensity precipitation expected). At this point, I’m not expecting any relevant chance for thunderstorms. Snow levels should be above 4000 feet (a few inches at resort level).
Dry weather is anticipated Friday through the weekend. Despite some variable high clouds, a possible, marginal, surface off-shore flow could favor a return to seasonable temperatures by Sunday. After that time, things become more uncertain next week. Some model solutions show a chance of showers returning to the Southland on Monday (better chances of widespread, wet weather in northern California). Greater chances of wet weather may occur sometime in the Tuesday-Wednesday period (24th-25th), but it would be a warmer storm (snow levels mostly above 6500 feet). The storm, if it comes about, should be a modestly wet system (rainfall mostly under a half inch). Looking farther out in time (speculation zone), the model consensus is leaning (slightly) toward a retreating (northward) storm track. A return to dry, warmer than normal weather may happen in early March.
Next issued forecast/synopsis may follow on Thursday, 19 February…time permitting.