Sharply colder air will pour over the western Plains and eastern Rockies on Monday as a cold front sweeps past the region. Indeed, temperatures will only peak in the 50s and 60s in many places. Clouds and a few showers will accompany the chill, while some snow coats the mountains of central Colorado. Showers and a few potent thunderstorms will erupt on the eastern Plains as the front encounters a warm and humid air mass. Some of the storms will have damaging winds, hail and possibly tornadoes. High pressure will promote sunshine and pleasantly warm weather in the Northeast, although dense fog patches will limit visibility in a few interior valleys at daybreak. Farther west, a corridor of clouds and showers will stretch from the Ohio Valley to the central Great Lakes. Elsewhere, the West Coast will be sunny and unusually hot for late September. FOCUS: TYPHOON CONNECTION Typhoon Choi-wan, once a potent storm with winds of 160 mph, weakened significantly on Sunday as it passed northeast of Japan. The storm will continue to lose its tropical characteristics on Monday as it connects with a front in the Pacific and heads into the Gulf of Alaska. The downstream effects of the former typhoon on North America's weather remains to be seen. However, in many prior cases, recurving western Pacific typhoons have been followed by a discharge of cool, dry air from Canada into eastern North America about a week hence. If this connection holds true this time, it will turn much cooler in the Northeast early next week. 