Weather Underground Forecast for Tuesday, August 13, 2013.
The nearly stationary weather pattern over the East and Central U.S. will become more progressive over the East on Tuesday. The long frontal boundary extending from the Mid-Atlantic States into the Plains will become reinforced by a frontal system to the north early Tuesday morning. Low pressure associated with this redefined disturbance will lift northeastward from Lake Erie to Lake Ontario with rain and chances of thunderstorms. Meanwhile, an associated warm front will lift northward from the Mid-Atlantic through the Northeast, while an associated cold front treks eastward across the Eastern Valleys into the Mid-Atlantic and Northeast and southward through the Southern Plains and Southeast. Ample moisture and energy along and to the south of this system will maintain showers, areas of heavy rain and thunderstorms through the day. Clusters of strong storms from areas of eastern North Carolina northward through coastal areas of the Mid-Atlantic into Lower New England may turn severe with isolated damaging wind gusts.
Behind this system, another cold front will drop across the Midwest on Tuesday with an unseasonably cooler airmass. Well below normal temperatures for this time of year are anticipated with the passing of this cold front. Daytime highs may run 10-15 degrees below normal through the midweek, while overnight lows are expected to drop into the 30s. This disturbance will catch up with the aforementioned system by Tuesday night as it reaches through the Eastern Seaboard into the Southern Plains.
Out West, monsoonal moisture will continue across areas of the Four Corners with more afternoon and evening showers and thunderstorms.
Temperatures in the Lower 48 states Monday have ranged from a morning low of 33 degrees at Truckee-Tahoe, Calif. to a high of 108 degrees at Thermal, Calif.