The nation's weather

AP News
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Posted: Sep 17, 2011 5:13 AM
The nation's weather

Weather Underground Forecast for Saturday, Sept. 17, 2011.

The Northeast is expected to see another chilly day on Saturday, while scattered storms persist across the Rocky Mountains and Southern Plains. A ridge of high pressure is expected to advance eastward from the Great Lakes to the East Coast. Flow around this ridge is expected to continue pushing cold air in from Canada, allowing for overnight frost and freeze advisories to remain in effect from upstate New York to Maine. Overnight lows will dip into the 20s, while daytime highs will remain in the 50s and 60s.

Behind this system, a trough of low pressure is expected to move through western Canada, and push a strong trough over the Rockies. Flow around this system is expected to push warmer air into the Plains, allowing for more seasonable temperatures to return. Highs across the Northern Plains and Upper Midwest will return to the mid-60s, while overnight lows will only dip into the 30s and 40s.

In the South, the trough is expected to pull in some moisture from the Gulf of Mexico, which will allow for scattered showers and thunderstorms to develop again across northern Texas and Oklahoma. Some of these storms are expected to turn severe with strong winds, large hail, and heavy downpours. However, not enough rainfall is anticipated to help the drought conditions across the region. Meanwhile, a few scattered thunderstorms are also expected to pop up across the northern and central Rockies throughout the day.

Further west, California is expected to start to warm up as a ridge builds in from the Pacific Ocean. This will help push clouds and moisture offshore, creating a warming trend for the weekend. However, in the north, another trough is expected to move in from the Gulf of Alaska and trigger scattered showers over the Pacific Northwest. Temperatures in the Lower 48 states Friday ranged from a morning low of 21 degrees at Hibbing, Minn. to a high of 97 degrees at Kingsville, Texas