A warm upper-level ridge that has been dominating the weather pattern in the western to central U.S. is forecast to shift eastward as a cool upper trough reaches the Pacific Northwest.
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This change in the upper-level pattern will break the prolonged heat wave over the Pacific Northwest by Thursday as cool air will be ushered into the region behind a cold front.
Meanwhile, more triple-digit heat is expected across much of the central and southern Plains where the upper ridge will remain in place.
For the northern Plains, triple-digit heat today will be replaced by cooler air from southern Canada on Wednesday before the resumption of triple-digit heat on Thursday.
In the meantime, anomalous heat is forecast to reach the northern Mid-Atlantic into New England by Thursday with record high temperatures possible as afternoon readings reach into the 95-100 degree range behind a warm front.
In terms of rainfall prospects, moisture will continue to linger in place across much of the Intermountain West through the middle of the week and also the Desert Southwest, although the convective activity should be more scattered in nature compared to the widespread storms and flooding that has been observed over the past few days.
A corridor of heavy showers and possibly severe storms is expected to organize late Wednesday and into early Thursday across portions of the Midwest and the Great Lakes ahead of a cold front, with some potential of 1-2 inch rainfall totals.
Heavy rain threat currently across portions of the Midwest/Ohio Valley should gradually diminish by this evening.
Fire weather concerns will also continue to make headlines across much of the interior northwestern U.S. and extending eastward across Montana and western North Dakota.
A combination of gusty winds and low humidities will increase the potential for wildfires, and some high based thunderstorms with limited rainfall and cloud-to-ground lightning may also be cause for concern on Tuesday.
The fire weather risk is likely to persist going into Wednesday as well across portions of the interior Pacific Northwest and central Montana. ■
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.