Late summer is hanging on across the mountains, foothills and northwest Piedmont, and we are going to keep this warm, humid and somewhat unsettled pattern around through the weekend and into Monday. Thunderstorms will not affect everyone each day, but the atmosphere will remain favorable for scattered afternoon and evening development. A few of the stronger storms could produce damaging wind gusts, along with torrential rainfall and frequent lightning.

Today will be one of the warmer days of this stretch. Temperatures across much of the foothills and Piedmont will climb well into the 80s and lower to middle 90s, while even some of our normally warmer mountain valleys make a run toward 90 degrees. Humidity will also increase as moisture continues to pool across the region.

That combination of heat and moisture will build a moderately unstable atmosphere by afternoon. We expect roughly 1,500 to 2,500 J/kg of surface-based CAPE across portions of the region. Wind shear remains fairly modest, generally around 20 knots, so this is not an environment that favors widespread organized severe thunderstorms. However, there is enough instability for individual storms and small clusters to become fairly strong.

There is also some energy moving southeast out of Kentucky and West Virginia this morning. Thunderstorms associated with that feature will continue moving generally southward, and the leftover disturbance and outflow could eventually help initiate additional thunderstorms closer to the Virginia/North Carolina border. At the same time, daytime heating should allow additional scattered storms to develop farther south across western North Carolina and northern Georgia.

The main concern with the strongest thunderstorms this afternoon will be localized damaging wind gusts. A stronger storm core could produce winds in the 50 to 60 mph range as heavy precipitation develops and accelerates toward the ground. That does not mean everyone is going to see severe weather. In fact, many communities may get through the afternoon without a thunderstorm at all. But where the stronger cores develop, a quick burst of damaging wind will be possible.

Heavy rainfall will be another concern. There is plenty of moisture available through the atmosphere, and steering winds remain relatively weak. That means thunderstorms may not move particularly fast. Any storm that sits over the same community for an extended period could dump a tremendous amount of rain in a short period of time. Localized street flooding and rapid rises in poor-drainage areas will be possible, especially where storms repeatedly develop or move across the same location.

The front responsible for helping focus some of this activity will gradually settle southward tonight and into Saturday. By Saturday, slightly cooler air should begin filtering into portions of western North Carolina on an easterly wind. This is not a particularly strong push of cool air, so temperatures will still run above normal, but most locations should shave a few degrees off today’s highs.

The location of the front will become important Saturday. Somewhat drier and more stable air may work into our northeastern counties, potentially limiting thunderstorm coverage there. Farther west and southwest, particularly along the eastern escarpment and toward northeast Georgia and the western Upstate, deeper moisture and instability should remain in place.

There is an interesting difference in Saturday’s atmosphere as well. While moisture remains available, somewhat drier air aloft could make thunderstorms more efficient at producing strong downdrafts. With plenty of instability still present, an isolated microburst capable of producing damaging winds cannot be ruled out. Once again, this should be a localized threat rather than something affecting the entire region.

By Sunday, the front begins moving back north as a warm front while low-level winds become southerly again. That will bring the deeper moisture right back into western North Carolina. Sunday should therefore feel very similar to what we normally experience during the heart of summer: warm, humid and unstable with scattered afternoon thunderstorms.

The eastern escarpment will probably remain one of the favored areas for thunderstorm development because southerly flow interacting with the terrain provides an additional source of lift. The same basic pattern hangs around Monday, with another warm and humid afternoon and scattered showers and thunderstorms developing across portions of the mountains and foothills.

A more noticeable pattern change begins taking shape Tuesday and Wednesday.

A strong area of high pressure moving across eastern Canada should eventually establish a northeasterly flow down the eastern side of the Appalachians. At the same time, the upper-air pattern becomes increasingly complicated as an upper low becomes cut off around the Great Lakes.

By Tuesday, we should begin seeing temperatures trend downward as northeast winds, increasing cloud cover and continued moisture start taking some of the edge off the late-summer warmth.

Wednesday could bring a much more noticeable change. Cooler air may become wedged southward against the eastern side of the mountains, which is the classic cold-air damming setup we watch across the Carolinas. Exactly how strong that wedge becomes remains uncertain, but the overall signal supports cooler temperatures, considerable cloud cover and continued opportunities for rain.

If the cooler air becomes firmly established, afternoon temperatures Wednesday could struggle to reach normal levels across portions of the foothills and northwest Piedmont. How cool we ultimately become will depend heavily on the strength of the northeast flow, cloud cover and how much rain develops.

Another system approaching from the west should eventually push a cold front across the Appalachians around Thursday. That would reinforce the cooler pattern before helping sweep deeper moisture out of the region and bringing a better opportunity for drier weather later in the week.

So, for the next several days, summer isn’t quite ready to leave us. Expect warm and humid conditions through Monday with scattered thunderstorms primarily during the afternoon and evening. Storms will not affect everyone, but any stronger thunderstorm will be capable of producing torrential rainfall, frequent lightning and a localized burst of damaging wind.

Then we should finally begin turning the corner toward a cooler pattern Tuesday and especially Wednesday, when temperatures may fall below normal across parts of western North Carolina.