01:03 ‘Total Disbelief’: Families Isolated as Isaias Washes Away Only Road to Their Homes Heavy rain and rising waters washed away a private road in Huntingtown, Maryland, stranding 7 families on the wrong side of the break.

At a Glance Clusters of thunderstorms will wring out heavy rain from the southern Plains to the Ohio Valley and mid-Atlantic this week.

The downpours will likely trigger flash flooding in some areas.

This includes parts of the Arkansas and Mississippi River valleys where significant flooding has already occurred this spring.

A few severe storms are possible each day, as well. Heavy rain could cause localized flash flooding across an expansive area this week, from the southern and central Plains to the Ohio Valley and mid-Atlantic. A few severe storms are possible each day as well, posing mainly a risk of damaging wind gusts and large hail.

Happening Now

Rain and thunderstorms are ongoing this morning from the southern Plains into the Ohio Valley.

Flash flooding hit parts of the Cincinnati, Ohio, metro area early Sunday morning. A portion of Interstate 75 had to be closed because of high water near the border between Kentucky and Ohio. A water rescue was also reported several miles west of downtown Cincinnati.

Stormy Forecast

A frontal system will stall from the Plains eastward into the mid-Mississippi Valley, Ohio Valley and mid-Atlantic this week, and it might be there for a while.

Warmer, more humid air will be pulled northward into this stalled frontal boundary providing ample moisture. The jet stream will send disturbances into this same general region, igniting clusters of thunderstorms , common in the summer months. This will lead to areas of locally heavy rain near that stalled front.

This is a prime recipe for summer flash flooding, and it will likely last into late week.

The exact track of thunderstorm clusters on each given day is somewhat uncertain, but the general area with a risk of at least locally heavy rain stretches from parts of Oklahoma, Kansas and northeast Texas into the Ohio Valley and the mid-Atlantic.

Local flash flooding is possible with any of these thunderstorm clusters since the ground is so saturated in this zone. According to National Weather Service flash flood guidance, it may take less than 3 inches of rain in a three-hour period to trigger flash flooding in parts of the Arkansas , Mississippi , Missouri and Ohio valleys.

If these thunderstorm clusters repeatedly form and track over the same areas on multiple days, flash flooding could become much more severe.

The National Weather Service has issued flash flood watches from central Illinois into northwestern Pennsylvania, where rounds of heavy rainfall over already wet ground may result in flash flooding. Flood watches are also in effect from southeast Kansas into southwest Missouri.

A few severe storms are possible each day across the same general corridor at risk for heavy rain this week. Any storms that turn severe will pose mainly a threat of damaging wind gusts and large hail, though an isolated tornado cannot be rule out.

The greatest chance of a few severe storms on Sunday is in parts of north Texas as well as the mid-Atlantic.

Rain May Prolong River Flooding

The rounds of heavy rain may also slow the rate of fall of mainstem rivers this week, rather than produce another crest, as illustrated nicely by the NWS office in St. Louis on Tuesday.

The Mississippi River crested last weekend in St. Louis at a level exceeded only by the Great Flood of 1993. That crest is now working its way downstream.

Water levels in the Arkansas River continue to fall after hitting record highs in six different locations from northern Oklahoma to southeastern Arkansas.

(IMAGES: Before/After the Record-Setting Arkansas River Flood)

In addition, the Mississippi River has already set records for flood longevity . In some areas, the river has been above flood stage since around the first of the year.