Dry and high-pressure weather conditions will continue until Friday. It will then move off the coast by Saturday. Expect warmer temperatures over the weekend before an approaching cold front brings rain and some thunderstorms on Saturday night and Sunday. As the rain ends on Sunday night, colder air will move in behind the front. Light snow is expected in the North Carolina Mountains, but the cold air will chase the precipitation out of the area before it can turn to anything frozen across the foothills.
Temperatures are expected to increase across the area due to a short-wave ridge moving across the region. Meanwhile, a trough deepens across the West, creating a return flow from the south locally. Surface high pressure will settle off the southeast coast. Cirrus clouds will increase from the southwest this evening. Low temperatures tonight will likely be all over the place. Higher elevations will likely remain warmer than the sheltered valleys and lower elevations. Even that will vary significantly, however. Overall, the average low temperature should end up in the mid-30s across the I-40 corridor, upper-30s to around 40° along mountainous areas, and upper-30s along Highway 74.
On Saturday, the upper-level weather pattern will shift from a ridge axis to an increased diffluent flow. As a result, a surface high-pressure system off the Atlantic coast will move away, allowing for moist air from the Atlantic and the Gulf of Mexico to move in during the afternoon. Between the moisture arriving and mechanical lift, ringing that moisture out, we will have to add showers to the forecast for the bulk of the day on Saturday. While it shouldn’t be an all-day washout, do expect periods of light rain throughout the day. High temperatures on Saturday should reach into the low 60s.
The atmosphere will become very dynamic on Saturday night as a surface front develops over Central Tennessee. The weather on Sunday will be wet, and it could be quite stormy in the afternoon and evening. Due to the northern and southern jet stream coupling over Western North Carolina, high shear with increasing upper-level divergence will be present. We expect the dynamics on Sunday afternoon will be paramount enough to allow a line of showers and thunderstorms (QLCS) to develop and race east. This event will be one of those low CAPE (Convective Available Potential Energy) / high shear events, and severe thunderstorms along the line are likely. Damaging winds and a few brief tornadoes appear possible.
The details of the dynamics are between 150 and 300 J/kg of surface-based CAPE with 35 – 50 knots of 0-1 km shear ahead of the line of thunderstorms. It is advisable to watch this line segment closely because where the line breaks, those little tail-end charlies (southernmost storm along the line) could spin up a few tornadoes. However, damaging winds should be the most significant concern to emergency managers and those planning outdoor events. Winds could gust as high as 30-45mph ahead of the front without any thunderstorms present. High temperatures on Sunday across the foothills should be similar to those in the low 60s on Saturday.
We have been dry and are still in quite a drought, but vibrant moisture flow could create heavy rains that will saturate the ground. Expect the possibility of a few power outages on Sunday afternoon as well, even if your area doesn’t experience severe weather. Tomorrow’s day 3 SPC Risk will likely be introduced as marginal, and if the dynamics continue to look as pronounced as they look right now, expect that risk to be upgraded as we go through the weekend. Preliminary forecasted rainfall totals from this event are 2-4 inches, with locally higher amounts, especially along southern-facing slopes. With that amount of rainfall falling in a short amount of time, a few isolated flash flood instances are possible.
Sunday Night, wrap-around moisture will continue as a colder Canadian polar air mass mixes in from the northwest. This air mass will cause the development of northwest flow snow showers across the western North Carolina mountains, continuing towards daybreak on Monday, producing a couple of inches of accumulation across the higher elevations. Across the foothills, we will dry out.
High pressure will continue to build into the area on Monday. Any remaining snow showers across the North Carolina mountains will quickly end. The weather pattern will be quiet for the first half of the week. Surface high pressure will be reinforced on Monday. We can expect good insolation each day, but with this colder airmass unlikely to moderate quickly, maximum temperatures will generally remain in the 50s. In comparison, lows will fall into the 20s and 30s each night.
Winter Storm Outlook:
Mountains: Sunday Night snow is possible
Foothills: None
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Great summary; thank you!!
Thank you for following!