A dangerous heat wave will continue in the Pacific Northwest/Northern Rockies as a strong ridge of high pressure remains in place aloft, with most of the region under heat-related advisories and warnings.
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High temperatures will be in the low to mid-100s for most interior locations, with 90s around Puget Sound.
Numerous near record-tying/breaking highs are possible.
Overnight lows will be near record-tying/breaking warm levels as well, providing little relief form the heat overnight.
These temperatures combined with the duration of heat, expected to continue through this week, will increasingly pose a heightened health risk, especially for those without adequate air conditioning.
Meanwhile, some relief from the oppressive heat has finally come to northern portions of the South and will continue through midweek as a cold front pushes through the region.
Highs on Tuesday from northern Georgia west through north Texas will drop below seasonable averages in the mid-80s to low 90s.
Oppressive heat will remain in place to the south of the front along portions of the coastal Carolinas southwestward to Texas along the Gulf Coast.
Highs will be in the mid-90s in the coastal Carolinas, Southeast, and Florida, with upper 90s to low 100s possible for central and western portions of the Gulf Coast.
These temperatures when combined with high humidity will allow for sultry heat indices as high as 110 to 120F for many locations.
Numerous record-tying/breaking highs are forecast.
However, the cold front will continue southward on Wednesday, bringing a brief reprieve from the central Gulf Coast eastward to the Carolinas as well.
Highs will remain summer-time hot but be closer to seasonable averages.
Unfortunately, portions of the western Gulf Coast and far south Texas will remain south of the cold front and not see any relief.
The relief looks to be brief as well, particularly for portions of Texas, where 100s are forecast to return to most locations by Thursday.
To the north, additional showers and thunderstorms are expected Tuesday along coastal portions of the Mid-Atlantic and Carolinas which remain ahead of the slowly moving frontal boundary.
Seasonably high moisture in place will help lead to the risk for some locally heavy downpours, with a Slight Risk of Excessive Rainfall (level 2/4) in place for the risk of a few scattered instances of flash flooding.
In addition, the Storm Prediction Center has also outlined a Slight Risk for severe weather (level 2/5) as moderately strong flow aloft associated with an upper-level wave passing overhead will provide enough deep shear for a few more robust, organized storms capable of producing some damaging winds.
Additional storms with a more isolated risk of flash flooding and severe weather will be possible north into coastal New England and southwestward to portions of the central Gulf Coast east through the Florida Big Bend.
The front will become nearly stationary by Wednesday, allowing for additional storm chances from the coastal Carolinas southwestward to Florida with a continued risk of isolated flash flooding.
Another frontal system will consolidate/organize over south-central Canada and the Northern Plains/Upper Midwest through the day Tuesday and overnight Wednesday and bring a chance for some thunderstorms to the Upper Midwest Wednesday.
A Slight Risk of severe weather is in place as moist return flow ahead of a cold front will provide enough buoyancy ahead of the front for some potent storms, with the main threat damaging winds and perhaps some large hail as storms will likely organize into a line along the front.
Highs behind the cold front will remain much below average Tuesday for many locations in the Midwest and Northeast/New England, with mainly 70s expected.
Temperatures will rebound into the low 80s outside of New England on Wednesday.
Highs will be much warmer following more moderation further west, with upper 80s to low 90s for the Northern/Central Plains.
Some locations from the Central High Plains northeastward to the Middle/Upper Missouri Valley will jump into the upper 90s Wednesday.
Daily rounds of Monsoonal showers and thunderstorms are forecast across the Four Corners region northwestward into the Great Basin and for portions of the Sierra, with locally heavy downpours possible and an isolated threat for flash flooding.
Daily highs will be a bit below seasonable averages around the Four Corners due in part to precipitation chances, with upper 70s to mid-80s.
Otherwise, highs will be near to a bit above seasonal averages more broadly in the region with 70s along the California Coast, low to mid-90s for the Great Basin and Central/Southern Rockies, and 100s to low 110s for the Desert Southwest.
Highs in the interior California valleys will trend a bit hotter with mid-100s expected and Heat Advisories in place. ■