A strong jet stream will develop over the south-central portion of the U.S. this weekend and into next week, as cold Canadian air moves southward into the Northern Rockies. This weather pattern will bring abundant Pacific moisture as Southwest to West winds increase over Western Colorado. Periods of moderate to heavy snowfall are expected beginning late Saturday and continuing through Wednesday. Heavy snow will first fall over the Southwest Mountains, particularly the San Juans, and will continue through Monday. Blizzard conditions, with near zero visibility in blowing snow, are expected over the Eastern San Juans Sunday night and Monday morning. By Tuesday, the heavier snow will shift to the northern ranges including the Sawatch and Elks. Snow totals over the Passes, including Monarch and Wolf Creek, will probably exceed one foot by early next week, and along with windy conditions this is likely to create difficult travel over the passes through Thanksgiving. As a storm system moves out of the Pacific Northwest and into the Rockies, snow may shift to areas east of the mountains on Wednesday, and while significant snow accumulations are not currently anticipated with this system, travelers should be prepared for at least the possibility of hazardous conditions before Thanksgiving. People with travel plans should continue to monitor the latest forecasts and statements issued by the National Weather Service, and consider alternate travel plans if this becomes necessary.