00:00It's been a hot time earlier this fall across Southern California. We're coming off of another heat wave that was,
00:06again, kind of a nuisance level heat wave, moderate heat wave.
00:10But you go back to the beginning of the month and we had a severe heat wave, an extreme heat
00:14wave, in fact, across much of the Los Angeles metro.
00:18So we're looking forward to change and not just the cooler air, but also the benefits of the rain, the
00:23beneficial rain that will be returning soon.
00:26So here's the big picture across the West. We have moisture streaming in from two separate angles.
00:31We've got tropical moisture. There's been a lot of traffic in the East Pacific, but also this new zone of
00:37low pressure that's really spinning its wheels due west of the mouth of the Columbia River, west of Oregon and
00:43Washington.
00:43That's diving south and eventually it's going to redirect a feed of moisture that's currently oriented into the southeastern part
00:51of the storm.
00:51That's going to be directed right into L.A. And we're going to see some decent rain there later this
00:55week on Wednesday.
00:56We're not expecting flooding in L.A., but we are expecting some rain.
00:59And the East Pacific is still very active right now. I'm just going to briefly touch on that.
01:04As tropical storm, Trudy is still out there.
01:07And you can see there's not like a direct line of moisture from any individual storm into the southwest.
01:12But you can see this vector, a lot of this moisture entering the Four Corners region has been coming from
01:19the southwest in recent days.
01:22And that's been the case here as Simon is no longer a tropical entity, but that helped to plant some
01:28moisture in that direction.
01:29And we've got more coming.
01:30We're going to see more development here off to the south of Mexico.
01:33Small chance of development out into the central Pacific west southwest of Hawaii as well.
01:38But let's look at the bottling here, and I wanted to take you into a look at how this will
01:41play out.
01:42And what a change.
01:43In southern California, if the wind is offshore, you've got fire danger, and you've got heat.
01:48And that's what we faced last week.
01:50It was a stressful week.
01:52There were a few fires of significance out there.
01:56One burnt seven homes.
01:58We've had several hundred acres burnt and even a few thousand acres burnt in another case.
02:02But while they have been geographically a little smaller than others that have been newsworthy in the past, they've been
02:08in neighborhoods and in populated areas.
02:10And that makes a huge difference.
02:11Well, look at this.
02:12This pattern is totally different here.
02:14As we get into Wednesday, this is an onshore wind.
02:17So it's the opposite of that dry offshore wind.
02:19This is going to send moisture in.
02:20It's going to be a high humidity wind that cools you down as well, transporting moisture and cooler air from
02:28the Pacific right into the southwest.
02:30And at the same time, it also helps to kind of draw more moisture northward from the East Pacific into
02:37the interior around a zone of high pressure that's centered over Texas and over eastern parts of Mexico.
02:43So these two things are working in tandem with one another to pump all this moisture in from multiple angles,
02:49whether it's coming in from west to east into California or from south to north over western Mexico from the
02:54tropics.
02:55And this is going to cool us down.
02:57And then look at this.
02:58This runs the whole full latitude trough across the west from Arizona to the Dakotas and across Montana by Friday
03:05and Saturday.
03:06And it'll be a big player in delivering widespread rain and mountain snow later this week.
03:12So let's take a look at this here.
03:14When we look at the precipitation, don't expect any changes in L.A. Tuesday.
03:18You're still going to be dry Tuesday.
03:20It'll be a little less hot, highs in the low 80s, with that onshore breeze just beginning to show its
03:26hand.
03:26But there won't be much of a change yet.
03:28It's Wednesday when we expect Wednesday night to see some showers roll in.
03:32Wednesday evening and Wednesday night, here they come into the Los Angeles metro.
03:37It's not going to be a flood situation, we don't think, but there will be some rain out there.
03:41It's going to slow some of you down.
03:42And then you can also see the modeling hinting at some blue in the map, on the map here into
03:46the high elevations of the Sierra.
03:47So there will be some high elevation snow, not a ton of it, but some, Wednesday night and into Thursday.
03:54And then watch as this system overtakes Thursday night, Friday, across most of the west and the states of Wyoming
04:00and Montana.
04:00We're going to see a much colder pattern here.
04:04Strong cold front associated with this here plowing into the plains.
04:07And behind that, we do get into some colder air.
04:10And it'll be a snowmaker into parts of Montana.
04:14So as we go back to kind of summarize the southwestern impacts, Tuesday night, Wednesday into Thursday, rain, some drought
04:21relief.
04:21It'll mitigate fire danger through two means.
04:24One, the humidity rises so the fuels won't burn as well.
04:28And number two, you just dump some rain on top.
04:29And that certainly helps as well, moistening the soil.
04:32And as the core of this upper level low pressure system moves across the interior west, we're going to see
04:36a situation where the temperatures aloft, chill.
04:40And if you have a stronger contrast between relatively warm near the ground and colder air aloft, you're going to
04:45get some stronger updrafts going.
04:47There's some wind energy out there as well.
04:49So we will see some strong and potentially severe thunderstorms in Phoenix and Tucson.
04:53There could be some dust storms around the periphery of these storms as well.
04:56So that's a concern.
04:58And there will be the risk of some flash flooding into the Four Corners region Wednesday and Thursday after spottier
05:04activity Monday night, Tuesday.
05:07So those are some things to keep an eye on.
05:09And regarding that snow, let's take a look at this freezing, the freezing levels.
05:13Through Wednesday night and Thursday into central California, when you see the brighter red, these hints of brighter red here,
05:21that's where you're getting into some elevations, maybe around 7,000 feet, where it's barely cold enough for some wet
05:29snow.
05:30And above 8,000 feet, certainly cold enough for some snow out there Thursday night.
05:35And when we look at accumulating snow here in the Sierra, it's going to be just the high ground.
05:40The best chance for plowable snow is going to be above 10,000 feet.
05:44And here you can see a little 0.7 there.
05:46Most of these areas are not all that populated, so we don't plot that.
05:50But you can see some hints of 4 or 5 inches.
05:52Let's go to the northwest, though.
05:53At the end of the week, the snow levels really come down behind this Friday night front.
05:58Look at this.
05:58Saturday, I'm going to go farther out.
06:00And here the snow levels in northern Idaho drop to like 3,000 feet.
06:04And for broad areas here, we're in the orange.
06:07So here we're getting down to areas where if you're above 4 or 5,000 feet, you're going to be
06:10into the snow zone in many areas here.
06:14Now, down in the valley floor near Boise, it's a little bit higher than that.
06:18But when it comes to the snowfall forecast here, here's the GFS hinting at 3.7 inches into parts of
06:25Yellowstone National Park.
06:26West Yellowstone about 2.9.
06:28Here's another depiction.
06:29And you can see the high ground of the Tetons in that deeper purple foot and a half of snow
06:35up there in the highest elevations of the Tetons through the weekend.
06:38So it's getting to be that time of the year where at least the high ground is beginning to sneak
06:42into some snow, even a little bit in parts of Washington state.
06:45So it's getting to be that time of the Tetons in the valley.
Comments