‘Bomb Cyclone’ Will Add To High Water

An already-soaked middle and southern U.S. will soon be getting another surge of water from snowmelt from the “bomb cyclone” that pummeled part of the Upper Plains with “historic” levels of wind and snow beginning March 13.

A “bomb cyclone,” a very rare occurrence, happens when air pressure in a particular area drops 24 millibars or more in a 24-hour period. The low pressure causes an inrush of surrounding moisture-bearing air, causing intense storms and high winds. This one, which the National Weather Service called “historic,” was centered on the Rocky Mountains and upper plains states and brought winds of up to 100 mph. in some areas, along with snow and rain. It resulted in thousands of Denver flights being canceled.

Meanwhile, the Ohio River valley got a slight break from additional rainfall. Smithland Lock opened March 9 after being closed for more than two weeks. National Weather Service charts showed a high of 54.6 feet on March 7. Flood levels fell slightly, then rose again at Smithland to 46 feet on March 17; NWS charts forecast a further fall to about 39 feet by March 27.

On the Cumberland River, Cheatham Lock has been mostly closed since February 26, with current predictions having it closed for at least 30 days from that date. Water has overtopped the lock walls, damaging equipment. While a few test tows were allowed through, no further tows were allowed until after a new weather event was assessed March 15.

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The Tennessee River remains closed due to flood conditions, with the gorge around Miles 440-450 expected to reopen sometime during the week of March 25. On March 12, a seven-barge tow wedged against a pier of the Tennessee River Bridge, temporarily closing Highway 70 across the bridge. The bridge reopened two hours later after inspection.

Big Melts

On the Upper Mississippi and Missouri rivers, significant ice and snow melts were moving downriver, closing locks.

The following Upper Mississippi River locks were expected to close: Lock 16 at Mile 457 and Lock 17 at Mile 437 on March 17; Lock 20 at Mile 343 on March 18; Lock 18 at Mile 410 on March 19; Lock 21 at Mile 325 and Lock 22 at Mile 301 on March 20.

From St. Louis to Cairo, tow sizes have been reduced to one string of five barges due to high water. There is daylight-only transit through St. Louis harbor and under the Thebes bridge at Mile 50, conditions that could last through the middle of April.