National Weather Service United States Department of Commerce

Prolonged Atmospheric River Will Impact the Northwest Early this Week

A weather system in the Pacific Northwest will produce rain throughout the day, before a potent atmospheric river produces a prolonged round of heavy rainfall, widespread urban and river flooding, and high elevation snow to the region Monday through Wednesday. Showers and thunderstorms may produce isolated damaging winds, a brief tornado, and locally heavy rainfall across parts of Florida today. Read More >

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Last Map Update: Sun, Dec 7, 2025 at 12:56:45 pm MST

⚠️❄️ Difficult Travel Over Mountain Passes this Afternoon & Evening: Another surge of moisture arrives this afternoon and evening, leading to difficult travel over Lookout, Marias, Lost Trail, or Lolo Passes. Be prepared for winter driving conditions, especially after sunset. What to expect: Periods of moderate and heavy snow 🌨️ Slushy or snow-covered roadways ⚠️ Lower visibility at times 🌫️ Check 511 for the latest road status before you head out!
🚨 Significant Atmospheric River this Week🚨 Multiple rounds of Pacific moisture from Atmospheric Rivers will target the Northern Rockies from Monday afternoon into Thursday (Dec 8-11). This long-duration event could bring moisture totals rivaling historic amounts for this time of year. ⚠️ Key Impacts & Concerns: 💧 Potential for roadway ponding & urban flooding. 📈 Sharp rises on creeks and streams. 🪨 Risk for rock and mudslides in steep terrain. 📍 Flood Watch Area: The greatest flood risk is across Idaho, Clearwater, and Mineral Counties, where a Flood Watch is in effect. ❄️Heavy, wet mountain snow above 7,000 ft bringing changeable avalanche conditions! Check www.avalanche.org for the latest forecasts.
Southwest to west winds will be strong late Monday afternoon through Tuesday morning. There is a concern for localized tree damage and power outages. Also, trees may fall into roadways given the saturated grounds in some valleys. The strongest winds will be in Northwest Montana.

 

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