Isaias Briefing #4: Rainfall/flooding potential increasing along Blue Ridge

By: Lead Forecaster Daniel Crawley

Good Friday afternoon,

Isaias is now a major hurricane just a couple hundred miles off the coast of the Florida Panhandle as of 11 am Friday, the first major hurricane of the 2026 Atlantic season.

The combination of Isaias and southeast flow off the Atlantic overriding a wedge boundary is going to make for a near-washout of a Saturday for the Western Carolinas. Short range computer model guidance has made two notable trends since late Thursday.

1. Timing of impacts (Saturday AM – Sunday AM)
2. Increasing precipitation amounts especially in Burke, Caldwell, McDowell, Polk and Rutherford Counties.

First, we continue to deal with a faster start time on precipitation. Overcast skies today will thicken and as southeast winds increase tonight, precipitation will blossom over Georgia and South Carolina and will eventually move into western North Carolina after midnight.

All of Saturday looks like a real mess right now with steady rain along the Blue Ridge by daybreak and for Piedmont areas, closer to mid-morning. We have noticed that some outdoor events have been cancelled today with the accelerated timeline. Local sporting and recreation events are significantly impacted. Even simple things like camping and hiking are discouraged especially once we get into Saturday night and rainfall amounts begin to elevate local streams. The heaviest of the rain is anticipated late in the evening and overnight which will make for unpleasant travel.

From a weather hazards standpoint, the risk of flooding is the highest and for some locations the risk is increasing. The eastern and southeastern slopes of the Blue Ridge always fare the worst in these setups. With guidance coming in higher on rainfall amounts we have introduced a medium risk for flooding for late Saturday night through early Sunday morning when rainfall rates will be heaviest.

With Isaias now expected to make landfall as a major hurricane, its also going to produce an increased pressure gradient that will elevate winds for a period Saturday. Right now we anticipate wind gusts would reach the 35-40 mph range as Isaias tracks to our west. Ridge tops could have slightly higher amounts that are exposed to the east and southeast. The combination of rain and some wind could result in a few power outages.

Lastly, with any tropical feature, you have a ton of wind shear that can be utilized to produce isolated cells that can spin-up a tornado with little notice. Again, the overnight hours and early Sunday morning would be the timeframe on that.

As we mentioned earlier, rainfall amounts are trending up across the region to where 3-6 inches along the Blue Ridge is quite attainable and 1-3 in the Piedmont. Thankfully we are coming off a dry spell of about a week so stream and lake levels are not vulnerable right now. However, we are probably pushing the upper limits on that with this latest boost in rainfall totals from Saluda and Tryon northeast to Old Fort and Jonas Ridge.

Rainfall amounts of near six inches also begins to introduce the threat of landslides in the steep terrain. We know many people deal with PTSD from two years ago and we again want to re-assure that this weather event is a totally different setup. At the same time we acknowledge the post-Helene landscape has changed the topography along the Blue Ridge. Isaias will be our first true test study on how stream flows and vulnerability of slopes behave compared to past experiences.

For an overall risk assessment Isaias will end up being a beneficial rain event for Piedmont areas as drought still exists off the mountains. We just have to keep an eye on the higher terrain to see how it handles our first tropical system in two years.

Summary…