Upcoming Weather System Brings Heavy Rain Threat and Possible Light Icing to Northern Foothills on Tuesday

Good afternoon, everyone in the foothills! It had been a wet morning, but any ice accumulation had been limited to sheltered valleys. Precipitation started around 1:00 AM in Hickory as rain. Still, it mixed with sleet and snow west of Morganton and continued as rain south of I-40. The high-pressure system moved out of the area, and as soon as the cloud cover rolled in last night, temperatures increased by two to three degrees. I’m okay with missing the ice on the low side. Less ice is excellent news, and impacts were limited. There were icy roads for roadways up the mountains early this morning, such as 181, 183, 221, 226, 321, and I-40, but there were no issues outside of that. Overall, this was a benign event.

We are preparing for an upcoming weather system forecast to impact our region on Tuesday. A powerful low-pressure system will move from the Southern Plains towards the Arklatex Region. In contrast, high pressure will move over the Mid-Atlantic states. The high and its position will result in cold and dry air being funneled down the Blue Ridge’s eastern side, starting Monday night until Tuesday. A cold front will move towards our region as the aforementioned low-pressure system moves northeast towards the Tennessee and Ohio Valley. On Monday night, precipitation will filter in from the southwest again. There is a possibility of sleet and freezing rain briefly along and north of I-40. However, the more significant issue will be the amount of moisture funneled into the region by a low-level jet, which will set the stage for a complex forecast.

I’ll start with the temperatures for Monday Night into Tuesday. The areas located along and north of I-40 and along the Blue Ridge Escarpment should experience low temperatures dropping into the low 30s on Tuesday morning. It may take some time for these areas to warm up throughout the day on Tuesday. However, south and east of the wedge boundary temperatures will rise to the mid-60s. That means we could see up to a 30-degree temperature difference within only 25 miles on Tuesday afternoon. Locations such as Lincolnton, Dallas, Lake Norman, Town of Catawba, Gastonia, Shelby, Kings Mountain, Vale, Caser, Ellenboro, and Lawndale can expect high temperatures around 65 degrees ahead of the front. On the other hand, areas such as Morganton, Marion, Lenoir, Taylorsville, Hickory, Bethlehem, Kings Creek, Nebo, Old Fort, Crooked Creek, Ashford, North Cove, Jonas Ridge, Little Switzerland, Globe, Blowing Rock, and The Blue Ridge Parkway will likely only see high temperatures around 39 degrees.

Above: Model projected high temperatures Tuesday.

The next factor to consider will be the winds. In areas where the temperature rises and breaks out of the CAD (Cold Air Damming) boundary, winds may become gusty, reaching as high as 50 mph, even without thunderstorms. If Tuesday afternoon brings enough instability, severe thunderstorms could develop south of the residual CAD boundary. Although instability looks weak, it wouldn’t take much to trigger severe weather as wind shear will be significant due to the low-level jet. In the areas that remain locked into the CAD boundary, winds are projected to stay much lighter, and severe weather is not likely north of I-40.

Above: Peak wind gusts Tuesday as modeled by GFS

The next issue is the heavy rain that is coming with this system. Warm air moves northeast ahead of that approaching frontal boundary Tuesday. Precipitable water values at this time of year are often limited to .50 to .75 of an inch. With this system, precipitable water values will be 2 – 2.5 inches. Southern-facing slopes will see the highest rainfall totals, but 2 – 3 inches area-wide is a good bet. Those favored areas in McDowell, Polk, and Rutherford Counties must be watched for flash flooding as antecedent soil conditions will be wet. I anticipate some issues from flooding on Tuesday morning. 

Above: Model projected rainfall totals Monday Night and Tuesday

Summarizing;

• Heavy rain moves in Monday Night and lasts through Tuesday.
• Briefly freezing rain and sleet are possible in the northwest foothills and the escarpment. Freezing rain changes to rain, though, with limited impacts.
• A dynamic temperature gradient is forecasted for the area, with Morganton in the 30s and Lincolnton in the 60s.
• Damaging non-thunderstorm winds are possible on Tuesday in areas with temperatures above 45 degrees.
• Flash flooding is possible along the eastern slopes and the western foothills Tuesday Morning through Tuesday Evening. 
• Severe weather is possible outside of the wedge boundary on Tuesday afternoon. Still, it appears to be a limited threat.