Southern California Faces Rare Wet Halloween as Possible Atmospheric River Threatens Los Angeles With Heavy Rain and Mountain Resorts With Snow by Sunday
LOS ANGELES, CALIFORNIA — Southern California could be in for something rare this year: a wet Halloween. A moisture-packed storm is expected to move into the region this weekend, with the potential to become a Pineapple Express or atmospheric river event that could bring heavy rain, possible flooding and snow to mountain resorts by Sunday, November 1.
Calm Before the Storm: Nice Weather Today With Increasing Clouds
For now, the weather remains pleasant, with clouds gradually increasing. That calm will not last long, as moisture begins to build across the region over the next several days.
Moisture Builds Wednesday Through Friday With a Few Showers West of the Mountains
From Wednesday through Friday, moisture is expected to slowly increase ahead of the main storm. A few scattered showers could develop west of the mountains before the weekend arrives.
Pineapple Express Moisture Pulled North From Hawaii by a Cold Alaskan Low
The moisture feeding this storm is expected to stream in from near Hawaii, a setup often called a Pineapple Express. A cold low pressure system from Alaska is forecast to swing that moisture into Southern California.
The big question is how far north the moisture plume will reach, and forecast models still disagree on that key detail.
Halloween Night Timeline: Light Rain Begins Saturday Evening
Forecast maps for 10 p.m. Saturday, October 31, show:
| Area | Forecast 6-Hour Rainfall |
|---|---|
| Santa Barbara, Los Angeles, Long Beach | Light, around 0.04 to 0.12 in |
| Sierra Nevada near Fresno | Around 0.12 to 0.4 in |
| Lake Havasu City area | Around 0.12 to 0.4 in |
| Northern Nevada near Elko | Around 0.12 to 0.4 in |
That means trick-or-treaters across Los Angeles and the coast could see light rain by Halloween night.
Sunday Morning: Heavier Rain Moves Toward Los Angeles and Long Beach
By 6 a.m. Sunday, November 1, one forecast shows heavier rain building just offshore of Los Angeles and Long Beach, with 6-hour totals of about 0.8 to 1.2 inches over the water.
On land, Los Angeles, Long Beach and inland areas toward Ridgecrest and Las Vegas show about 0.2 to 0.4 inches in that same six-hour window.
Sunday Midday: Heaviest Bursts Possible East of Los Angeles
Another forecast for noon Sunday shows the heaviest rain shifting inland, with 6-hour totals of about 1.2 to 1.6 inches east of Los Angeles. Long Beach sits around 0.8 inches, while heavier pockets also appear near Las Vegas and St. George, Utah.
Cold Air Arrives Sunday With Potential for Significant Mountain Snow
The storm is expected to start out mild, but colder air will filter in on Sunday. That could turn precipitation to snow at higher elevations, potentially bringing significant snow to Southern California’s mountain resorts.
Wide Range of Outcomes: Major Flooding or Less Than Half an Inch
Forecasters stress there is a lot of uncertainty. Depending on where the moisture sets up, Southern California could see:
- Several inches of rain with major flooding
- Or less than half an inch of rain
Forecasters hope the computer models will come into better agreement within the next day.
Why a Wet Halloween Is So Unusual in Southern California
Rain on Halloween is a very rare occurrence in Southern California, where late October is usually dry and warm. This year, a wet Halloween now looks very likely.
Safety Tips for Halloween Weekend
- Plan rain gear for trick-or-treaters and costume events
- Avoid flood-prone roads and low spots if heavy rain develops
- Check road conditions before heading into the mountains
- Watch for forecast updates as the storm approaches
Stay with Bchssreport.com for the latest updates on this story.
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