Pacific storm to bring drenching rain and flooding to Southern California

AccuWeather

AccuWeather's Ken Clark says a powerful storm system from the Pacific will bring drenching rainfall and an increased risk of flash flooding and mudslides to Southern California this weekend.

Transcript

00:00Ken, before we go through the setup that we're looking for in California over the next couple

00:06of days, from a resident of California, explain to everybody that doesn't understand this

00:13to a certain extent how important this time frame is for rainfall across California.

00:21Sure, Bernie. The vast, vast majority of the rain in California, and especially in the

00:26southern half of California, only falls in a four to five month period, late October,

00:31November, and especially in December, January, and February into March. As you can see by this

00:36graphic, look at the lack of rain the rest of the month. So we rely on these winter months and these

00:43winter storms for the rain and to fill up the reservoirs in California. You know, speaking of

00:49the reservoirs, Ken, I mean, your thoughts when you look at the reservoirs, the two biggest reservoirs

00:55in California are Shasta and Oroville. But overall, while I know there is some drought being shown on

01:01the drop monitor in southern California, there's not a shortage, let's say, of water right now.

01:08There is not a shortage of water in the reservoirs. All reservoirs across California are chock full

01:13right now to historical averages. And that's all we want to see. Now, as for groundwater, that's a

01:19little bit different of a story. And there has been a historical lack of rainfall in the last,

01:25you know, 10, 12 months across southeastern California. But in general, water is not a

01:32problem right now in California. All right, let's go over this, Ken, as we move forward. Now,

01:37this is coming in two waves. We're going to actually concentrate on the upper low and the rain that's

01:43coming in the southern California, at least for now. I have everything on the satellite picture here,

01:48Ken, and all the ingredients are there for a heavy rain in southern California. What do you see

01:53when you look at this? This is the typical setup that brings a lot of rain to southern California,

02:00especially in the south-facing and west-facing mountains and foothills. This low, as it progresses

02:05slowly eastward, the upper-level winds will turn from southwesterly into southerly. And this will jam

02:12all this moisture coming up from way down into the tropics, right on up into southern California.

02:17And those strong southerly winds will force that air to go over top of the mountains. And that's why

02:23we just wring out that water like a sponge across the higher elevations of southern California and even

02:30the lower elevations. This is a perfect scenario. This is more like a January, February type of storm

02:36for southern California when we get large amounts of rain. Yeah, so southwest and facing mountains. And

02:42it appears to me, Ken, the sweet spot, or maybe not sweet's not the best, the heavy spot's going to be,

02:48you know, Ventura, Los Angeles counties, maybe Santa Barbara, because they come in out of those

02:54mountains face to the southwest. And you get that upslope flow. And explain just how extreme that upslope flow

03:02is. Well, rainfall amounts can double, triple from coastal areas to those mountainous areas, the

03:09southwestern facing mountains. It's not unusual to see rainfall amounts an inch or two in Los Angeles,

03:16but in those hills, you know, five, six, seven inches of rain out of the same storm. This storm is going

03:21to have even more than that. This storm is going to have probably two to four inches of rain generally. In

03:27those south facing mountains and foothills, we're looking at least three to six inches. And I think there's a

03:32slight chance that some places could pick up between six and 10 inches of rain. And the sweet

03:38spot where the worst area to be in is probably Santa Barbara County mountains over into Ventura and the

03:44western half of the L.A. County mountains. That's where I'm concentrating the worst case scenario for

03:50those eight, maybe nine, 10 inches of rainfall. We're always tracking some rain here this morning,

03:56not so much in Southern California, Ken. But, you know, we've been looking at the rain here

04:00in Central and Northern California continues to come on down and the winds. But what really

04:06impresses me, Ken, now we are going to get a little bit of rain late tonight into tomorrow

04:12in Southern California. It doesn't look like a huge problem, but it is some rain that will fall before

04:17the main event. Yeah, there's going to be lighter amounts of rain that fall and that causes problems

04:22in itself just because rain isn't an unusual event in Southern California. The roadways get messy,

04:28traffic gets messier than normal. But the main event, the biggest part of this storm is going

04:34to come for Southern California from later Friday night through the day on Saturday. That's when the

04:39greatest amount of rain will fall. That's probably when 80, 90 percent of the rain that accumulates

04:46will actually occur. Ken, by the end of this event, we could get five to six inches of rain

04:52through early next week. That could be 40 percent of the winter rainfall

04:56for Southern California. That's right. That's a lot of rain. It is a lot of rain. All right.

05:01Meteorologist Ken Clark.

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