Sugar Mountain

Forecast Discussion

Summary

SYNOPSIS

... A cool wedge of high pressure will linger across the region into Monday. Warmer air and increased shower chances are on tap ahead of an approaching cold front Tuesday and Wednesday. Drier weather is possible behind the front to end the work week.

NEAR TERM /THROUGH TONIGHT/... As of 645 AM: The parent high of our ongoing CAD event is centered near the east end of the US-Canada border. The wedge boundary looks to have pushed as far south as I-20 in SC, curving up into north central GA. Stratus remain over large swaths of the CWFA, but some lifting and even scattering has occurred in the NW NC Piedmont. Isentropic lift above the wedge is minimal--winds are northerly aloft--which is likely responsible for the loss of the low cloud in the deeper part of the wedge. Most areas are expected to stay dry thru tonight to boot. Near the Escarpment, easterly sfc flow will give an upslope boost and a small PoP continues to be warranted today, and the SW NC mountains have a small chance of sfc-based convection this aftn, with heavy rainfall being the main threat from those. The upglide o, and the midlevels subsequently dry. This leads model guidance to depict lifting cigs and perhaps breaks in the clouds that will permit max temps mainly in the 70s for the Piedmont; temps overall will be much more uniform than yesterday, when the immature wedge brought a remarkable temp gradient across the area.

Low-level flow veers to a more typical southeasterly direction tonight, with moist upglide reinforcing cloud cover but still not looking likely to produce much PoP on its own. The approach of a shortwave from the lower Mississippi Valley warrants a gradual uptick in PoPs over the western zones overnight. Piedmont mins will be mainly in the mid to upper 60s, with lower 60s in the mountain valleys and northern foothills.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 308 AM EDT Sunday: The early part of the week still looks complicated with all the interaction between an upper level block over northeastern North America, a potential tropical or sub-tropical low pressure off the Carolina coast, and a short wave lifting northeast across the TN/OH valleys. The upper block to our northeast will continue to support parent sfc high pressure wedging down the east side of the Appalachian mountain chain through Monday and Monday night. The high will conspire with the low pressure system off the NC coast to keep conditions relatively inhospitable to convection east of the mtns as the short wave lifts past to our NW. Thus, we keep the more meaningful precip chances over the mtns into Monday evening. Eventually, this arrangement will facilitate the draining of the old wedge on Tuesday as we lose the strength of the parent high. Instability will creep back from the S/SW by afternoon, allowing a better chance for convection, at least over the srn half of the fcst area. The fcst follows closer to the NAM with its better coverage of precip by afternoon, but this could easily be overdone. High temps will remain on the cool side of normal...by about ten degrees.

LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 326 am EDT Sunday: Not much change to earlier thinking that by Wednesday, any lingering affect from the remnant wedge will have ended as a sfc front approaches from the west. Temps ought to rebound close to normal, which means a return to the usual summertime instability that will fuel scattered thunderstorms Wednesday afternoon and evening. The front should cross the region Wednesday night as it is driven east by an advancing upper trof. The latest guidance has more of a drying trend behind the front for the latter half of the week as sprawling high pressure builds in from the west. So, precip chances were cut back to give us a few dry days. Temps should be close to normal.