The nation's weather

AP News
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Posted: Apr 14, 2011 4:50 AM
The nation's weather

An active weather day is expected across the Central U.S. on Thursday, when a trough of low pressure strengthens by moving off the Rocky Mountains and into the Plains.

The system creates interesting weather across the Plains due to its strong counter-clockwise rotation. The leading edge of the system pulls warm and moist air in from the Gulf of Mexico, creating favorable conditions for thunderstorm activity across the Central and Southern Plains. The strongest chance for severe storm development will be confined to Oklahoma and Kansas. At the same time, the northern side of this system will see drastically cooler temperatures as it pulls cold air in from Canada, thus creating widespread scattered rain and snow showers. Daytime highs will return to the lower 40s across Nebraska and the Dakotas, but overnight lows dipping into the 30s will allow for some overnight snow showers to develop. Snow showers will also persist across the High Plains as well as the Northern and Central Rockies, with total snowfall accumulation between 2 to 4 inches.

Farther West, another low pressure system and associated cold front move into the Pacific Northwest. This brings more rain showers with high elevation snow showers to Washington, Oregon, and northern California. In the Southwest, however, a ridge of high pressure dominates, allowing for warm, sunny and dry conditions across southern California and Arizona.

Temperatures in the Lower 48 states Wednesday ranged from a morning low of 12 degrees at Yellowstone, Wyo., to a high of 90 degrees at Laredo, Texas.