Nine days after the Four Corners flood, the National Weather Service is telling southwest Colorado to get ready for another one. An atmospheric river carrying moisture the Weather Prediction Center calls "extremely anomalous" arrives before sunrise Sunday, November 1, and is expected to drop 2 to 4 inches of rain on the San Juan Mountains through Monday morning before a cold front turns it to a foot or more of heavy, wet snow. Flood watches cover both sides of the Continental Divide, from Cortez and Durango to Pagosa Springs, Creede, South Fork and the western San Luis Valley. The watch for the valley runs through Tuesday night, because the rivers will take that long to carry the water down.

"Folks, the window for flood preparations is closing," the Pueblo forecast office wrote in its discussion early Saturday. "Preparations should be ongoing and finished by this afternoon. Do not wait until it starts to rain and do not wait until the waters start to rise. By then it is too late."

What is coming

The Weather Prediction Center's excessive rainfall outlook for Sunday puts the San Juans under a Moderate Risk, its second highest category. The moisture in the air over the Four Corners on Sunday, the center wrote, will be four to six standard deviations above normal and will threaten daily records. "The San Juans have recently seen a high-impact flash flooding event from a similar feature about a week ago, and soils have not had a chance to dry out due to a series of smaller rainfall events in the meantime. Now this event will threaten to rival the first."

The Grand Junction office, which covers the west side of the mountains, expects rain to reach the Four Corners before dawn Sunday and spread northeast through the morning. Its guidance gives the U.S. 160 corridor east of Cortez a 50 to 70 percent chance of 2 inches or more, with more than 3 inches in the high San Juans. The Pueblo office, which covers the east side and the San Luis Valley, puts totals at 2 to 4 inches of liquid, most of it falling as rain on Sunday because the air ahead of the storm is warm, with snow levels near 11,000 to 12,000 feet. "This amount of liquid on top of already highly saturated soils, water laden snow, and running into rivers that are already elevated from last week's rain event, will likely lead to another highly impactful flood event across the southwestern mountains and into the San Luis Valley," the office wrote. Confidence in the pattern, it said, is above 80 percent.

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The cold air comes Sunday night. Snow levels fall to about 9,000 feet on the east side by Monday morning and to 7,500 to 8,000 feet on the west side as the storm departs. Winter storm watches call for 8 to 14 inches above 10,000 feet in the eastern San Juans with gusts to 55 mph, and 10 to 15 inches in the southwest and northwest San Juans. Grand Junction's discussion says 14 to 20 inches is the likeliest range above 11,000 feet. Snow ratios will be low, so what falls will be heavy and slushy, and the Weather Prediction Center gives the San Juans a 70 to 90 percent chance of at least moderate snow-load impacts, including tree damage near timberline. The Flat Tops, Grand Mesa and the central mountains are under a winter weather advisory for 5 to 10 inches from noon Sunday to Monday evening.

The rivers

The rivers that set records on October 23 have fallen but not recovered. Saturday morning the Animas at Durango was running about 1,800 cubic feet per second, the San Juan at Pagosa Springs 1,400, and the San Juan at Farmington 3,200, all still well above where they ran before the October flood. Snow survey stations above them hold water too: Red Mountain Pass reported 14 inches of snow on the ground Friday and Wolf Creek Summit 11 inches, with more than 4 inches of water in each, and Wolf Creek Summit has recorded 15.4 inches of precipitation in the 30 days since the water year began.

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The weather service's river forecasts, issued Friday afternoon, already show flooding on the east side. The Conejos River near Mogote is forecast to crest near 8.1 feet early Monday, above its 7-foot major flood stage. The San Juan at Pagosa Springs is forecast to reach 10.6 feet Monday morning, just over its 10.5-foot flood stage. The Rio Grande at Alamosa is forecast to reach flood stage by Wednesday evening as the water moves down the valley. The Animas at Durango and the Dolores at Dolores are forecast to rise but stay below flood stage, and the San Juan at Shiprock to crest near 14 feet early Tuesday, below its 15.5-foot flood stage. Pueblo's discussion warned that rivers in the southwest mountains could rise "into moderate to major flood stages heading through Monday, with some rivers nearing record crest levels," and the forecasts will be updated as the rain begins. The Pueblo flood watch says U.S. 160 and Colorado 17 "will likely be significantly impacted by this storm," names Del Norte and Mogote as the greatest flood risk, and warns of rockslides.

The roads and the recovery

The storm arrives with last week's repairs barely started. The Federal Highway Administration approved 6.5 million dollars in quick-release emergency relief on Friday, the first installment of the Colorado Department of Transportation's 65 million dollar request, for immediate work on U.S. 160, U.S. 550 and Colorado 151. U.S. 160 over Wolf Creek Pass reopened Tuesday with one-lane alternating traffic west of Pagosa Springs. U.S. 550 over Red Mountain Pass is one lane while a washed-out embankment is stabilized. Colorado 151 at Chimney Rock was still washed out in two places as of Wednesday. Farther north, the department closed Colorado 82 over Independence Pass between Aspen and Twin Lakes at 8 a.m. Saturday for the snow and wind, and will decide after the storm whether it reopens or stays shut for the winter.

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The state emergency operations center remains activated at Level 1 for both response and recovery, according to the Division of Homeland Security and Emergency Management, which on October 26 activated a temporary housing partnership with 211 Colorado and Airbnb.org for residents under mandatory evacuation orders from the October flood. Colorado 211 is the number for evacuation, shelter and housing help. Road conditions are at cotrip.org.

Elsewhere in Colorado

The same storm reaches the rest of the state in weaker form. On the eastern plains the first sign is fog: dense fog advisories covered Kiowa, Prowers, Bent, Otero, Crowley and Pueblo counties Friday morning and Cheyenne County into Friday afternoon, and Denver, Boulder, Fort Collins and Greeley were under one Saturday morning. The Goodland office expects fog each morning through Tuesday.

Wind is the plains' share of the storm. Pueblo expects southwest gusts of 30 to 50 mph Sunday ahead of the system and northwest gusts of 30 to 50 mph behind the cold front Monday, with a 30 percent chance of something stronger Monday night. The forecast for Eads has southeast gusts to 40 mph Sunday, showers and thunderstorms likely Monday with northwest gusts to 55 mph, winds of 35 to 40 mph Monday night, and gusts to 50 mph still on Tuesday. Goodland's forecast for the Tri-State area says Monday "could bring some strong winds with gusts around 30 to 60 mph." Rain on the plains will be light, generally less than a tenth of an inch at Eads, and Tuesday turns sunny and cooler behind the front, with a low in the mid 30s.

Along the Front Range, the Denver office gives the mountains above 8,500 feet a better than 70 percent chance of snow Sunday night and Monday and calls the foothills and plains highly uncertain, with a cold front crossing northeast Colorado Monday morning. Pueblo expects 4 to 10 inches of wet snow on the Sangre de Cristos and the rest of the high terrain outside the San Juans.

After Monday

The storm moves out Monday night, but the pattern does not. Pueblo gives 60 to 70 percent confidence that more waves follow through the end of the week, with precipitation chances mainly in the mountains. Reclamation's reservoirs below the San Juans, which have been gaining since the first flood, will take another share of whatever runs off. The drought map released Thursday showed southwest Colorado out of drought for the first time since January. The ground has had its fill.