Many areas from the Great Lakes to the mid-Atlantic and the Southeast will continue to be hit with torrential downpours and locally severe thunderstorms this week.
There is the potential for some communities to be hit with 1 to 3 inches of rain in a hour or two through Wednesday, where storms repeat. Such rainfall rates can lead to flash and urban flooding.
Repeating, slow moving storms caused flash flooding in parts of Queens, N.Y. during the midday Wednesday, August 1, 2012.
Two people were struck by lightning and injured on the beach at Wildwood, N.J. Wednesday, August 1, 2012.
The best chance of getting drenched is between 3:00 p.m. and 9:00 p.m. This is when the greatest aerial coverage of the storms will occur. However, a small number storms will erupt prior to this time, while others can survive well after dark.
A very small percentage of the area can also be hit with powerful wind gusts that knock down trees and power lines.
A dry wedge of air that toned down storms in the Northeast Sunday will retreat over the next few days, opening the door for greater coverage of drenching storms into the middle of the week.
Most of the blame on the overall wet and stormy pattern can be placed on a southward dip in steering winds (jet stream) high in the atmosphere. The dip in the jet is centered over the eastern third of the nation.
At the same time the lower layers of the atmosphere in the East are plenty moist in many areas.
Throw in strong sunshine and the warm, moist air explodes upward into the cooler air aloft, leading to towering clouds and drenching and locally gusty thunderstorms.
The higher up into the atmosphere the storms poke, the greater the chance of there being damaging wind gusts near the ground.
Any disturbance that comes along in this moist pattern can help entice such activity, by giving the storms an extra upward boost.
The wet pattern began to evolve over the past couple of weeks, but is really coming into its own this week.
The pattern will continue to chip away at abnormally dry and drought areas in the upper part of the Midwest, the Ohio Valley, East and South. At the same time rain will continue to be stingy to non-existent, moving from the central Plains to the southern Plains and interior Texas.
A gap in the downpours will work from the Midwest Wednesday to the East Thursday. A new round of drenching and locally severe storms is likely to spread slowly from west to east late in the week into the weekend.
Senior Meteorologist Dave Samhuel contributed content to this story.
A prolonged heat wave across northern Argentina has led to blackouts in and around Buenos Aires.
The heat that griped Perth the past week will shift east to Adelaide, Melbourne and Sydney this week.
Dry and sunny conditions will continue in San Francisco for the official start to winter and the Christmas holiday.
Sunshine will return in full force for the weekend, the official start to winter, and Christmas in Los Angeles.
Big changes are on the way for parts of the Western and Central states late this week and into this weekend.
Similar to the days prior to Thanksgiving, the worst weather will focus on the days prior to Christmas as millions of travelers take to the roads and skies in the U.S. and southern Canada.
A cold outbreak sent the temperature plummeting to 3 degrees below zero at Nantucket, MA and to 11 degrees below zero at Boston, MA
Black Hills, SD (1964)
Chinook: temp. rise 0 degrees to 50 degrees.
Lander, WY (1924)
Bar. pressure 31.29" 1060 mb.