A Wet October Comes to an End -- and Now, Your Halloween Forecast

Update, 4 p.m. Sunday, Oct. 30: A little behind schedule, most of the Bay Area got a pretty good dousing Sunday morning from a fast-moving storm that's now moved across the Central Valley and into the Sierra Nevada.

The highest storm totals for our nine-county region: 1.52 inches at Venado in northern Sonoma County and 1.50 on Mount Umunhum, high above the Santa Clara Valley in the Santa Cruz Mountains.

Totals for places where people actually live include .57 of an inch at Charles M. Schulz/Sonoma County Airport in Santa Rosa, .68 in San Rafael, .73 at the Oakland Museum, .37 in downtown San Francisco and .17 at Mineta San Jose International Airport.

And now for a look at the all-important Halloween forecast for Bay Area trick-or-treaters. Another storm -- this one rather anemic compared to what we've seen the last few days -- is forecast to blow through the area late Monday afternoon and into the evening.

Rain should begin first in Sonoma County, then sweep south through the course of the evening. The National Weather Service is forecasting precipitation totals ranging from .39 of an inch in Santa Rosa to .05 in San Jose.

Halloween bottom line: It will be damp, not a deluge.

After the storm passes, forecasters say, most of the Bay Area should see a prolonged stretch -- at least a week -- of dry weather.

Original post, Friday, Oct. 28: It's officially a really wet October in the Bay Area.

The warm storm that arrived early Thursday morning gave an unusually even distribution of rain across the region through midday Friday, ranging from nearly an inch at most sea-level locations around San Francisco Bay up to 2 and 3 inches in the Sonoma County hills and Santa Cruz Mountains. (See table.)

More remarkably, the latest rains added to already remarkable precipitation totals from our mid-October storms.

The Santa Cruz County hamlet of Ben Lomond, on Highway 9 in the Santa Cruz Mountains, has topped 12 inches of rain this month. That compares to an October average, going back to 1937, of 2.76 inches.

Venado -- little more than a soggy hillside in the Russian River watershed west of Healdsburg, has picked up more than 15 inches for the month. And that compares to a normal of. ... Well, I can't find a good data source for that, though the California-Nevada River Forecast Center publishes a data table that purports to show that Venado, hands down the wettest location in the greater Bay Area, averages 2.01 inches in October. Not buying that, but I'll have to figure out a better number.

(And if you want to talk about someplace that's really moist, let's talk about the Gasquet Ranger Station, on the Smith River in Del Norte County, up in the northwest corner of the state. Gasquet has gotten a dumping of 24.52 inches this month. It's normal rainfall for October is 5.60 inches.)

Less dramatically, San Francisco International Airport has seen 1.93 inches since the first of the month, almost exactly double the 30-year normal of .97 inches. Downtown San Francisco has gotten 2.31 inches, compared to a normal of 1.12 inches for October. The rain gauge at the Oakland Museum has recorded 2.70 inches, against the norm of 1.37 inches.

We're likely to see those totals grow significantly over the final three days of the month. The National Weather Service says a pair of storms are due to arrive over the next several days.

The first is expected to move into northern Sonoma County by late Saturday afternoon and bring rain to the entire region by Sunday morning. Rainfall totals are expected to range from a quarter-inch to half-inch in most of the central Bay Area and up to 2 inches in the hills north and south of the bay.

Forecasters say the Saturday night-Sunday storm will be a snow maker, too, dumping about a foot of snow on Donner Pass (Interstate 80) and Echo Summit (U.S. 50), both about 7,200 feet above sea level. Several feet of snow are possible at higher elevations throughout the northern Sierra.

After the weekend rain, a fast-moving storm is expected to bring more rain Monday evening.

A quick rundown of 48-hour precipitation totals through midday Friday, Oct. 28:

Source: NOAA/California-Nevada River Forecast Center