There will be daily chances for scattered thunderstorms across portions of the Central and Eastern U.S. through the weekend, with severe thunderstorms possible in the northern Plains and Upper Midwest. Potential severe storm hazards may include large hail, damaging winds, and a few tornadoes. Storms could also produce heavy rain that may lead to isolated instances of flash flooding. Read More >
PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE CHICAGO IL 155 PM CDT WED AUG 22 2007 ...MINOR SEICHE AFFECTS SOUTHERN LAKE MICHIGAN... A MINOR SEICHE WAS OBSERVED ON SOUTHERN LAKE MICHIGAN THIS MORNING. A SEICHE CAN BEST BE EXPLAINED AS A LARGE SLOSH ON A LAKE...WHERE WATER FROM ONE SIDE OF THE LAKE IS FORCED OR PUSHED TO THE OTHER SIDE OF THE LAKE THEN RETURNS TO THE OTHER SIDE OF THE LAKE RESULTING IN A RISE IN THE WATER LEVELS. THIS OSCILLATION OF LAKE WATER LEVELS WILL OFTEN CONTINUE WITH PEAKS AND LOWS IN WATER LEVELS FOR SOME TIME BEFORE THE LAKE STABILIZES AGAIN. MOST COMMONLY SEICHES ON LAKE MICHIGAN OCCUR AS A RESULT OF A FAST MOVING LINE OF HIGH WIND PRODUCING THUNDERSTORMS...AND THIS WAS THE CASE THIS MORNING. AS THE LINE OF THUNDERSTORMS RACED ACROSS SOUTHERN LAKE MICHIGAN THIS MORNING PRODUCING WINDS OF 40 TO 60 MPH IT CAUSED WATER TO PILE UP ON THE EAST SIDE OF THE LAKE...FOLLOWED BY THE SLOSH BACK TO THE WESTERN SHORES OF LAKE MICHIGAN. LAKE WATER LEVEL DATA OBTAINED FROM CALUMET HARBOR THIS MORNING INDICATE THAT THE AMPLITUDE OF THIS SEICHE WAS ABOUT A FOOT AND A HALF...WITH LAKE LEVELS PEAKING ABOUT SLIGHTLY LESS THAN A FOOT ABOVE NORMAL AND FALLING TO LESS JUST UNDER A FOOT BELOW NORMAL. HERE ARE THE OBSERVED MAXIMUM AND MINIMUM WATER LEVELS MEASURED SO FAR THIS MORNING AT CALUMET HARBOR DURING THE SEICHE. 536 AM CDT 9.6 INCHES ABOVE NORMAL 730 AM CDT 9.0 INCHES BELOW NORMAL 930 AM CDT 7.3 INCHES ABOVE NORMAL 1136 AM CDT 5.7 INCHES BELOW NORMAL 142 PM CDT 3.8 INCHES ABOVE NORMAL SOME VERY MINOR...LIKELY UNNOTICEABLE...FLUCTUATIONS IN LAKE LEVELS WILL CONTINUE THIS AFTERNOON AS THE LAKE STABILIZES AGAIN IN THE WAKE OF THIS MORNINGS SEICHE. $$ IZZI
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