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.
Tropical Depression Two has formed in the Atlantic and could become the next tropical storm of the season by midweek.
Warm and humid air in place over much of the Midwest and Northeast at midweek will contribute to the risk of drenching, gusty and locally severe thunderstorms on Wednesday.
After temperatures briefly climb to typical midsummer levels, another cooldown will roll into the Midwest and expand to the East for the last part of July.
Severe storms will fire up Tuesday afternoon and evening, threatening outdoor activities and travel for many.
Powerful winds, heavy rainfall and dangerous mudslides will threaten Taiwan on Wednesday as Matmo moves across the island.
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Atlantic Ocean (1498)
Christopher Columbus' third voyage. After leaving the Cape Verde Islands, the 4 ships drifted WSW in the equatorial current. "The wind stopped so suddenly and unexpectedly and the supervening heat was so excessive and immoderate that there was no one who dared go below after the casks of wine and water which burst, snapping the hoops of the pipes; the wheat burned like fire; the bacon and salted meat roasted and petrified."
Wasatch National Park, UT (1918)
504 sheep were killed by one lightning bolt.
Waterbury, CT (1926)
105 degrees -- record high for state.