Thursday's Synopsis

NOTE: CURRENT WEATHER STATION IS NONFUNCTIONAL. REPLACEMENT PLANNED BUT DATE STILL UNKNOWN.

The latest storm has essentially left the state, but a moist, northwesterly, wind flow pattern remains today. Some showers continued in places this morning (mainly south and east of L.A. County). However, the showers posed no real threat of heavy precipitation, let alone producing brief tornadoes (FYI--Yesterday's Montebello tornado may have been the most destructive since March 1st, 1983. Back then, a tornado did roof damage to the L.A. Convention Center.). Isolated, mountain showers could continue into the evening, but things should finally dry out overnight.

The northwest wind flow pattern should continue through the weekend, but weak high pressure aloft is also expected to nose into the state (from the Pacific). The northwest, wind flow pattern will promote rather cool (for late March), overnight low temperatures (low/mid-40s in many lowland areas). A minor warming trend in daytime temperatures is likely for most areas west of the mountains (warming limited by the weakness in the high pressure, as well as a lack of a full fledged, off-shore flow).

Some earlier, computer model forecasts showed a minor shower threat for some mountain locales on Saturday. That would be due to a passing, "inside slider" type trough. Based on today's model consensus, mountain showers appear unlikely, but it can't be completely ruled out. In any case, sunny weather should prevail over the weekend for most of the Southland.

Things become more uncertain, weather-wise early next week. All the models show a trough capable of showers in the state. A few model solutions show the northwest portion of southern California getting wet as early as late Monday. In L.A. County, it could happen on Tuesday. However, solutions vary on timing (could be morning or as late as evening). Showery weather would continue through Wednesday. Some model solutions show lingering showers Thursday morning (mostly to the east and south of L.A. County). Dry weather would follow for the remainder of the week.

The model consensus doesn't favor a major storm (no tap into an atmospheric river). A cold storm is probable (snow levels possibly down to 3000 feet for a time). For now, I'm expecting an average, early spring storm (lowland rainfall less than half an inch most areas away from the mountains). Depending on which model solution is right, sufficient atmospheric instability may occur with the storm for scattered thunderstorms. Like the most recent storm,the predicted, winds aloft may support brief-lived, tornadoes or a good amount of small hail with the thunderstorms.

Looking farther out in time, another storm or two could affect the state sometime after the 4th of April. These projected storms look like "ordinary" storms. A fair number of model solutions, however, keep wet weather up in northern California only. April is still capable of producing decent, wet weather in the state, but it typically marks the end of relevant precipitation.

Next issued forecast/synopsis may be on Wednesday, 29 March.

UCLA Forecasts and analyses are written by James Murakami

– posted: 2023-03-23