A batch of heavy rain and thunderstorms will bring the risk of urban and flash flooding, as well as travel delays into Tuesday night along much of the Atlantic Seaboard.
The downpours can be heavy enough to not only bring street and catch basin flooding, but may also greatly lower the visibility.
Poor visibility and locally severe thunderstorms in the heavily-concentrated airport zone of the Atlantic Seaboard could lead to widespread flight delays within the region and possibly ripple-effect implications elsewhere in the nation.
The storm system dumped up to 6 inches of rain and has a history of flash flooding in Tennessee to start the week.
Cities that will be impacted by the heavy rain and related issues into Tuesday night include Raleigh, N.C.; Richmond, Va.; Hagerstown, Md.; Philadelphia and Harrisburg, Pa., Washington, D.C.; Baltimore; Wilmington, Del.; New York City and Albany, N.Y.; Hartford, Conn., and Boston.
Enough rain can fall at a fast enough pace to cause rapid rises on small streams in hilly terrain areas anywhere along the Atlantic Seaboard.
The system is forecast to bring a general 1.00 to 2.00 inches of rain with the potential for 4.00 inches or more in a few locations. Much of the rainfall will occur over an 8- to 12-hour period. A few locations along the East Coast can receive an inch of rain in an hour's time.
A system responsible for heavy rain in the South Central states over the weekend will join forces with a front approaching from the Upper Midwest and moisture from the Gulf of Mexico and the Atlantic Ocean.
During the second half of the week, high pressure will return to the region with sunshine.
**However, locally dense morning and midday fog could become a travel problem Thursday and Friday, after cool winds subside.**
This story was originally published at 10:00 a.m. EDT, Monday, Sept 18, 2012 and has been updated.
The late-season swelter will continue along much of the Atlantic Seaboard through the week as tens of millions head back to school and work.
The next Atlantic tropical depression or storm may take shape in the southwestern Gulf of Mexico's Bay of Campeche during the next couple of days.
A second volcanic eruption occurred on Sunday morning in Iceland in the same area that had one on Friday.
Severe thunderstorms will threaten holiday festivities across parts of the Midwest to close out the extended Labor Day weekend.
While flooding is a threat, monsoonal rains will be beneficial for most areas across northwest India this week.
Gusty winds, large hail and power outages occurred Sunday into Monday morning in the north-central United States.
Los Angeles, CA (1955)
110 degrees, hottest day ever in September. This mark was tied September 4, 1988.
Milwaukee, WI (1988)
Hottest summer on record. Six days of 100 degrees or greater and 36 days of 90 or above. Average temperature of 73.8 beat the old record of 72.8 set in 1921 and 1955. The normal average tempera- ture for a summer in Milwaukee is 68.3 degrees.
Washington Co., IA (1897)
Hail fell and drifted in piles 6 feet deep in Washington County.