Sugar Mountain

Forecast Discussion

Summary

SYNOPSIS

... Strong high pressure will set up and persist over the southeast the rest of the week. This will greatly limit the potential for daily showers and thunderstorms and keep temperatures well above normal. The ridge of high pressure will strengthen further over the weekend into early next week, leading to near-record high temperatures over the Memorial Day holiday weekend.

NEAR TERM /THROUGH TONIGHT/... As of 640 am: E/NE low level flow will continue to strengthen through the morning, as ~1025 mb surface high pressure settles into the Mid-Atlantic. Meanwhile, easterly flow just above the surface will continue to advect an area of low clouds as far west as the Blue Ridge this morning. Weak isentropic lift above the shallow layer of lower theta-E air associated with the surface ridge will likely render those clouds quite persistent through the day, and while clouds are eventually expected to scatter across the Piedmont, SE flow should maintain mostly cloudy conditions near the Blue Ridge through the afternoon, and this will be good enough to hold temps to below-normal levels (mid/upper 70s) across much of the NC foothills.

The strengthening ridge will establish a surface boundary across the forecast area today, which will most likely set up in the vicinity of the I-85 corridor. Short term guidance is in good agreement in establishing robust convergence and pooling low level moisture along this feature, resulting in substantial sbCAPE (~2000 J/kg, if not a little higher) across much of the Upstate, northeast GA, and extreme southwest NC this afternoon, and all CAMs sources initiate isolated to scattered convection in this regime by mid-afternoon. Pops are featured in the 20-40% range across much of the southern 2/3 of the forecast area by the end of the 1st period. With the upper ridge axis building into the area, shear will be quite weak, but given the degree of instability, a few pulse severe storms will be possible.

Surface ridge weakens and boundary effectively washes out tonight, with lingering SE upslope flow becoming the main impetus for lift by late evening. Chance pops will therefore become increasingly centered near the Blue Ridge. Min temps will again be a solid 5 degrees above climo in most areas.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 330 AM EDT Wednesday: Wedge of high pressure from the north will begin to retreat from the area throughout the day on Thursday as the center continues to move off the Mid-Atlantic coast. Meanwhile, latest guidance continues to prog that the upper ridge well in place will dampen slightly for the day as a piece of s/w energy from upper troughing well to the north moves overhead. This feature along with available moisture and little instability in place will allow for isolated showers and thunderstorms across much of the FA Thursday morning through the afternoon hours. Do expect any convection to wane into the evening hours, with dry conditions expected overnight. High temperatures on Thursday will be in the mid to upper 80s/near 90 degrees along and south of the I-85 corridor, slightly cooler across the mountains. Overnight low temperatures well remain nearly 10 degrees above normal.

On Friday, upper troughing to the north will amplify and move eastward through New England, while back to the west, upper trough over the western CONUS will push northeastward into the northern Plains. The projected paths of these two features will allow for upper ridging over the eastern CONUS to re-amplify on Friday, as the ridge slowly propagates eastward. As a result, despite the potential for isolated thunderstorms along the escarpment in the afternoon hours, the main story for Friday will be the heat, as temperatures are progged to climb well into the low to mid 90s across the Upstate and NW Piedmont, slightly cooler, yet still above normal, across the mountains.

LONG TERM /SATURDAY THROUGH TUESDAY/... As of 355 AM EDT Tuesday: The main story through the weekend and into early next week will be the near-record high temperatures across the area. For record max temperature information for Asheville, Charlotte, and Greenville, please see the Climate section below.

Ridge of high pressure will remain well in place through the weekend, with nearly zonal flow aloft on Sunday, only beginning to deamplify into early next week. Isolated showers and thunderstorms will be possible across portions of the northern foothills on Saturday, but expect dry conditions elsewhere, with currently no PoPs in the going fcst for Sunday attm. Temperatures over the weekend will climb into the low to mid 90s across the Upstate and NW Piedmont, slightly cooler across the mountains.

Into Monday, as alluded above, upper ridge will begin to deamplify as broad upper troughing well to the north swings through the Great Lakes region and New England, while back to the west, another upper low over the western CONUS is progged to push into the central plains into Tuesday morning. The parent sfc low and it's southward trailing cold front will remain well to the west through the extended, though it's eastward extending nearly stationary boundary is progged to settle just to the north on Tuesday. Despite this slight progression of the synoptic pattern, high temperatures will remain in the low to mid 90s through the end of the period, with overnight lows above normal. Isolated showers and thunderstorms will be possible both Monday and Tuesday, but per latest guidance, anticipate this activity to stay confined to the mountains.

With the expected heat and essentially the warmest temperatures thus far of 2019, people with outdoor plans for the Memorial Day holiday weekend should stay well hydrated and find shade when possible to avoid heat-related illnesses. Don't forget about persons with disabilities and the elderly, as well as outdoor pets/animals.