July 20, 2012: The nation's weather

Weather Underground Forecast for Friday, July 20, 2012.

Hot temperatures continue for the Central US, while showers and thunderstorms move into the East Coast on Friday. A strong ridge of high pressure will remain the dominant weather feature over the Central US. This will keep the region hot with high temperatures reaching into the lower 100s again. Humid conditions will allow for heat index values to reach above 110 degrees for some areas. Thus, excessive heat warnings will remain in effect from the Plains through the Mid-Mississippi River Valley and into the Ohio River Valley. Ahead of this system, a trough of low pressure extends over the Northeast and Mid-Atlantic States, kicking up scattered showers and thunderstorms. Moisture feeding this system from the Gulf of Mexico will allow for storms to turn severe from the Lower Mississippi River Valley through the Ohio River Valley.

Meanwhile, out West, a trough of low pressure over the Pacific Northwest produces more rain showers as it moves over the Intermountain West and into the Northern Rockies. As this system moves over higher elevations, there is a slight chance that severe thunderstorms will develop across northern Idaho and western Montana. Main threats will be strong wind gusts and large hail. In the Southwest, monsoonal moisture will bring more showers and thunderstorms to the Four Corners. Temperatures in the Lower 48 states Thursday have ranged from a morning low of 35 degrees at West Yellowstone, Mont. to a high of 108 degrees at Philip, S.D.