The heat wave will refocus east of the Rockies Thursday and Friday, allowing the Pacific Northwest to eventually cool back to more typical mid-August temperatures.
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The recent hot weather has exacerbated the dry conditions, and an increase in wind on Thursday supports a critical fire area over the Columbia Basin and northern Montana.
To the east, widespread 90s to 100s will encompass much of the Plains into Texas and the Lower Mississippi Valley as high pressure remains in control.
Rainfall will be limited to areas around the heat dome; namely, the Great Lakes into the Northeast, the Southeast, and the interior West (Great Basin/Four Corners region).
Many areas over Texas will see record-tying or breaking high temperatures 100-110F with heat indices over 110F.
Overnight lows will remain warm and at similarly high record-tying/breaking levels.
The duration and intensity of the heat is leading to a more significant health risk to the region than typical summer heat, particularly for those without adequate air conditioning.
Please see WPC's Heat Key Messages for more information on the heat wave.
A frontal system moving through the western Great Lakes will bring a chance of scattered showers and storms to the region this evening and across the rest of the Great Lakes and Midwest on Thursday.
By Friday, the system will push through the Northeast, with a focus on northern New York and New England with the front expected to clear the region Friday evening.
Cooler temperatures will follow behind the front, with temperatures into the 70s and 80s over much of the region.
This will be the coolest spot relative to normal over the Lower 48 during the next few days.
Over the Southeast, a lingering frontal boundary will provide a focus for mainly afternoon showers and storms.
High temperatures will be near or even a bit below normal on Thursday with a slight uptick in readings by Friday as the front starts to decay.
Anomalously high moisture in place over the Four Corners region and Great Basin will continue to lead to daily, scattered thunderstorm chances.
Some locally heavy downpours are possible with an isolated risk of flash flooding, particularly for more sensitive locations such as urban areas, burn scars, dry washes, and slot canyons.
High temperatures broadly across the southern tier of the West will range from the 70s along coastal California, the mid-80s in the precipitation-cooled Four Corners region, and low to mid-90s for the Central/Southern Rockies and Great Basin.
The CA Central Valley will see another day of hot temperatures into the low 100s on Thursday before a cooldown back into the 90s for Friday. ■
Modified arctic air combined with a moisture-laden area of low pressure along the Gulf Coast will continue to allow for a broad area of winter weather impacts from the Lower Mississippi Valley to the Southeast today into early Saturday morning.