A surface frontal boundary stretching from the the Southern Plains, eastward through the Lower to Middle Mississippi Valley, Ohio Valley and Mid-Atlantic will be the focus for active showers and thunderstorms over the next 12 to 36 hours.
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An area of showers and thunderstorms expected to push east southeastward from the lower Great Lakes, across the Ohio Valley and into the Mid-Atlantic Monday evening into early Tuesday, producing areas of locally heavy rains.
The best chance for isolated flash flooding and severe thunderstorms with this area of showers and thunderstorms will be from the Middle Mississippi Valley into the Ohio Valley Monday evening/night and then across the eastern Carolinas during Tuesday.
At the same time, an upper level system will rotate east northeastward from northern California into the Pacific Northwest/Northern Rockies region from this afternoon into Tuesday.
This system will also support widespread showers and thunderstorms over the northwestern U.S., although any rainfall amounts are not expected to produce any significant flooding threat.
To the south of this, a stronger area of upper level energy will push quickly inland across Southern California on Tuesday and through the Southwest on Wednesday.
This system will be moisture starved with little if any precip expected to California or the Southwest over the next two day.
More widespread scattered showers and thunderstorms possible ahead of this strong upper system across the Great Basin and Central to Northern Rockies Wednesday afternoon into evening.
The best chances for heavy rains over the next two days will be across portions of eastern and coastal Texas.
Several waves of upper level energy expected to push east northeastward from northeastern Mexico into Texas and support a heavy rainfall threat over the next two days across these region.
With the potential for more than one round of heavy rains to affect portions of eastern and coastal Texas, there will be the threat of isolated flash flooding.
The heavy rains are expected to fall, however, to the east of areas of central and western Texas that remain in severe to exceptional drought.
The continued dry conditions and increasingly gusty winds across the Southern High Plains, will support an increasing fire weather threat for this region over the next two days, especially across much of New Mexico, southeast Colorado, the Texas/Oklahoma Panhandle and Southwest Texas.
Temperatures expected to remain above average for the early part of the week across much of the Plains, Mississippi Valley and into the Southeast.
Below average temperatures expected along the west coast into the Great Basin, across eastern Texas where heavy rains will limit sunshine and across portions of the Northeast and Mid-Atlantic Tuesday where rains will also limit the amount of sunshine. ■