Showers and Storms Return: Derecho for Western NC Saturday?

SUMMARY

Showers and thunderstorms will make a comeback for the foothills starting Friday afternoon and off‑and‑on through the weekend, with a few storms Saturday potentially strong, followed by a hot, increasingly muggy stretch next week with heat indices near or above 100 degrees in our lower elevations.

The big picture for our area

We’re shifting from a relatively dry, “tame” early‑summer pattern into a more typical late‑June setup: daily storm chances and building heat. For the foothills of western North Carolina, more moisture and instability will move in from the south and southwest, and that’s the fuel that helps our afternoon showers and storms develop.

Friday: STORMS RETURN

Late tonight into Friday, winds near the surface turn more from the south and southwest, pulling in more moisture from the Gulf and Atlantic.

What does that mean for us? No really? Someone ask? Please?

• Friday morning: Patchy fog or low clouds may develop in the typical mountain valleys and near rivers, but most our foothill locations will just see a bit of early haze that burns off quickly.

• Friday afternoon: With more humidity and June sunshine, we’ll get just enough warm, moist air for scattered showers and thunderstorms to form. Coverage looks like the classic “hit‑and‑miss” pattern and not everyone gets a storm, but many of us will hear some thunder in the vicinity.

Temperatures Friday will run close to average for late June, generally mid‑80s to upper‑80s in our area, with humidity starting to creep up.

Saturday: Weather Ready Action Day!!!!

Saturday is the day to watch for more widespread storms, including a few that might become strong to isolated severe in and near the foothills. A weak disturbance in the upper atmosphere and a subtle boundary near the surface will give storms a focus to form and organize along. Think of this boundary as a weak front or a line where winds shift; storms like to follow these features. The atmosphere upstream of the mountains could support a significant line of storms, that could develop.a derecho that sweeps across the area late day into the early night time hours.

For our area on Saturday:

• Rain chances: This looks like the highest‑coverage storm day of the period. Many communities should expect at least one shower or thunderstorm sometime Saturday afternoon or evening.

• Temperatures: Highs will run a couple degrees above normal, reaching the upper‑80s to near 90 in the lower foothills before storms briefly cool things down.

• Storm strength: With strong heating and higher moisture, we will have “moderate instability,” meaning storms can grow tall and become capable of heavier rain, gusty winds, and frequent lightning. Winds higher up in the atmosphere aren’t particularly strong, but there will be just enough change in wind near the surface (what we call “low‑level shear”) to help storms cluster together along their own cool outflows.

When storms send out a rush of cooler air, that air spreads out along the ground as an outflow boundary, new storms often develop. Because of this setup, a few storms Saturday could reach isolated severe levels, mainly with damaging wind gusts, even without a upstream derecho developing. Outdoor plans should include a shelter option, multiple ways to receive warnings, and a way to check radar.

Sunday: fewer storms, more heat

By Sunday, we fall more under the influence of high pressure aloft (anticyclonic flow), meaning we’re under a big dome of sinking air. Sinking air tends to limit widespread storms but encourages warmer temperatures.

Key points for Sunday in our area:

• Storm coverage: The atmosphere still supports taller thunderstorms (we call this “deep convection”), near the Blue Ridge but coverage looks lower than Saturday. Expect widely scattered storms rather than the broader coverage we will likely see Saturday.

• Temperatures: Highs run about 5 degrees above normal. Many foothill towns will push into the low‑90s.

• Heat index: With the humidity, it will feel hotter than the thermometer reads. The heat index is a “feels‑like” number that combines temperature and humidity to show the actual stress on the body. On Sunday, those values could reach or slightly exceed 100 degrees in the warmer, lower elevations of our area.

Early to mid‑week: HERE COMES THE HEAT

As we move into the new work week, a strong anticyclone — essentially a big, strong area of high pressure — becomes the dominant feature over the Southeast and Mid‑Atlantic. That usually means hotter, more stagnant conditions and fewer organized storm systems. That doesn’t mean no storms, just very few.

For the foothills Monday through Thursday:

• Temperatures:

• Monday: Highs start out around 5 degrees above normal, solid upper‑80s to low‑90s.

• By Thursday: We’re talking nearly 10 degrees above average, with some locations close to, if not above,100 degrees for actual air temperature.

• Humidity and heat index:

• The air above us stays relatively dry and is sinking (a subsident regime). That sinking motion can mix down slightly lower humidity each afternoon, so we may see dewpoints drop a bit during peak heating.

• Even with some mixing, the combination of heat and humidity will push heat indices near or around 100 degrees by mid‑week.

• Thursday looks like the peak heat day. Areas east and southeast of us may be more likely to meet official heat advisory criteria, but our area should still treat the heat as dangerous, especially for those working or exercising outdoors.

In this kind of pattern, the large high pressure dome tends to suppress widespread thunderstorm activity. However, it’s June in the southern Appalachians — it’s hard to completely shut off mountain‑driven showers.

So for our area:

• Storm chances: Most days Monday through Thursday, the better chances for afternoon showers and storms will be over the higher elevations. Foothill coverage will be lower, roughly “isolated to scattered” at best.

• Impacts: Where storms do form, brief heavy downpours and gusty winds are possible, but the bigger day‑to‑day story will be the heat and humidity rather than severe storms.