Submitted by: Daniel Crawley (@SoApps1979)
Good Saturday morning to everyone, it has been a very active week across the Western Carolinas thanks in part to a slow-moving storm system in the upper levels that provided the fuel and a focus of heavy rainfall. Computer models helped supplied us, as forecasters, some advance notice that stormy weather was coming.
A shortwave coming from the Plains states dropped southeast and helped develop a positive tilt upper low and trough that centered itself along the Mississippi River. That along with Western Atlantic ridging meant the region was under divergent flow aloft (good indicator for lift) with deep tropical moisture of a Central American origin. The divergent flow at the upper levels combined with a surface boundary and low pressure was all that the region needed. Add some upslope flow to boot and the recipe was there for heavy and excessive rainfall. Click on the YouTube link below for a loop of moisture over the past 96 hours as it streamed up the east coast…
Showers and thunderstorms began Monday and continued up through last night. Several rounds followed the same general track. To sections of the eight-county coverage area received the highest rainfall amounts, the first being from Eastern Lincoln and Catawba Counties into all of Alexander County and northeast from there up into Southern Virginia. The second bullseye occurred along the eastern escarpment from near Lake Lure northeast to Jonas Ridge (Burke County) and Globe (Caldwell County). The locations with the heaviest totals were in the 4-8 inch range and some local higher amounts likely has occurred. Flood reports confirmed the threat across parts of Alexander, Burke, Caldwell and McDowell County, a couple isolated landslide reports came in as well along the escarpment.
You can see these areas depicted clearly on the doppler radar multi-day rainfall estimate. The areas that received the least rainfall still picked up amounts in the 1-3 range so for those locations flash flooding of small streams and rivers were not as common as it was in the hardest hit zones. This doppler estimate covered the timeframe from late Tuesday through Friday.
After researching through local data, here is a detailed storm total rainfall map for the coverage area, the amounts range from Monday afternoon until Friday afternoon. The data was pulled from various sources including local storm spotters, local CoCoRaHS members and data from local COOP stations. The highest 4-day total was over 8 inches in the Taylorsville area, several areas of 3-6 in totals. And even the lowest amounts were still in excess of 2 inches.
One thing we would like to note in this report is the lack of reliable data available this week in sections of Caldwell and Rutherford Counties. There is a real void in rainfall data in those two areas as you can see on the map, at least data that is consistently submitted. This is an issue that has a somewhat easy remedy and it’s crowd sourcing through programs like CoCoRaHS.
We have a lot of loyal followers who ask us often how can they could help contribute reports? Well, honestly joining a program like CoCoRaHS would go a long ways. And best part is that the process is easy. All you have to do is purchase a standard manual rain gauge certified by CoCoRaHS (a $25 investment) and committing to submitting daily rainfall data online…that’s all one has to do in order to join the CoCoRaHS family. The data gathered is for public use and can be very useful in helping verify rainfall amounts vs doppler radar estimates along with using data to help determine risk areas for flooding and/or flash flooding.
Additional info on CoCoRaHS is available for those who may have interest in being a part of the crowd-sourcing program…. https://www.cocorahs.org/