First Alert Weather Day: Heavy Rain, Damaging Winds, Small Hail Possible

GREENVILLE, N.C. (WITN) - A frontal boundary is forecast to develop over the Southeast US overnight and into Sunday morning. The frontal boundary will progress eastward across the Carolinas, increasing the risk for severe storms.

Possibility for a few storms to contain damaging winds and small hail(Russell James)

There are four ingredients that are needed for severe weather on Sunday

1. Lift - With a frontal boundary developing over the area, it will serve as a lifting mechanism for warm, moist air to quickly rise into the atmosphere. Depending on the strength of the frontal boundary, scattered to widespread showers are likely to develop Sunday afternoon from 2-6 pm, especially along the coast.

2. Moisture - A ridge of high pressure, responsible for the record breaking temperatures across Eastern NC the past couple of days continues to move offshore. Because high pressure systems rotate clockwise with the ridge to the east; warm moist air continues to flow in from the southwest. This allows the atmosphere to be primed for any potential thunderstorms and this will be the primary airmass over Eastern NC for the next day.

3. Instability - With warm moist air being lifted into the atmosphere by a frontal boundary, how quickly the warm air can rise, and become displaced into a colder airmass, will determine how unstable the atmosphere could get before storms develop. When warm moist air moves into a colder environment, the air condenses into water vapor, leading to cloud formations and storm growth. We have enough moisture and lift in place, but temperatures will be a bit cooler on Sunday compared to today. This means that we will have a slightly unstable atmosphere.

4. Shear - With a cold front recently passing over the area, Eastern NC is still not far from the jet stream. The jet stream is a strong river of air in the upper levels of our atmosphere that separates cold air to the north from warm air to south. These strong winds can vary at different levels and directions in the atmosphere. Shear is used as a great indicator for tornadoes and damaging winds. Eastern NC will be in an area where the stronger winds in the upper-level atmosphere is blowing in one direction. In this case, speed shear will be a concern which means damaging winds are a greater risk. There is little to no risk for tornadoes tomorrow.

Despite the threat of severe storms, locally heavy rainfall is also possible. 0.5″ to 1″ inch of rain is expected to fall throughout-Sunday time period. We could use the rain since some parts of the viewing area is under abnormally dry to moderate drought conditions. Watch for standing water in areas with poor drainage. Roadways could have ponding Sunday morning too. Be sure to download the WITN First Alert Weather APP, stay tuned to WITN-TV, and witn.com for latest information.