After multiple days of inclement weather and cases of historic flooding across the Midwest to Kentucky, a cool air mass centered over the Great Lakes is forecast to bring much improved weather to the flood-stricken areas this weekend.
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As the cool air mass continues to advance eastward, showers and possibly severe thunderstorms ahead of a cold front will steadily progress across the central Appalachians and into the northern Mid-Atlantic through tonight before drier and cooler air filters further into the northeastern quadrant of the country on Saturday.
Meanwhile, the trailing portion of the front will remain nearly stationary across the southern Plains through Saturday as wave of low pressure is forecast to form and move eastward along the front.
This will keep the threat of heavy rain in place from the central High Plains eastward through the Tennessee Valley into Saturday, with the highest threat of heavy rain over the central High Plains into tonight.
By Sunday, the main energy associated with the frontal wave is forecast to shift eastward into the Tennessee Valley and then begin to lift northeastward into the Mid-Atlantic by Sunday evening.
The central Plains will have a chance to dry out a bit by then.
Meanwhile, monsoonal moisture is forecast to persist across Arizona into the Four-corners region this weekend.
Day-time heating will continue to trigger scattered thunderstorms across the region each day.
Some of the thunderstorms will likely contain heavy downpours that could lead to flash flooding concerns especially over burn scars.
The chance of heavy rain appears to decrease slightly across the region later on Sunday as the upper ridge over the Pacific Northwest is forecast to shift east toward the northern Plains.
This will bring increasing heat into the northern High Plains by the weekend.
Ahead of the upper ridge, a developing low pressure wave is expected to spread showers and thunderstorms eastward across the northern Plains during the weekend, reaching into the upper Midwest on Sunday.
The heat wave across the Pacific Northwest will continue through the weekend with only slight improvement on Sunday.
High temperatures are forecast to approach 110 degrees at the hottest interior locations of the Pacific Northwest while the streak of 90s continues closer to shore in Seattle.
The southern tier will remain hot but not quite as intense as earlier this week.
Meanwhile, cool air over the central Plains associated with the heavy rain is forecast to expand eastward.
The Desert Southwest will be slightly cooler than normal through the weekend. ■
A clipper system will move quickly across the northern Plains into the Midwest Friday and the Northeast by Saturday, bringing a wintry mix of rain and snow showers ahead of a sweeping cold front.