... A quasi-stationary front south of the forecast area will keep intermittent rainfall in the forecast through the end of the week. Cool high pressure will nose in from the north and keep temperatures below normal until warming up for the weekend. Moisture will increase as low pressure swings out of the northwest over the weekend, and an attendant cold front will arrive early next week, further boosting rain and thunder chances.
NEAR TERM /THROUGH THURSDAY/... As of 545 PM EDT Wednesday: We're still seeing patches of sct showers make their way SE over the NC Mtns and Foothills early this evening. We've yet to see any lightning from the shower activity with the overall potential for thunderstorms still looking minimal thru the evening. Showers will likely linger through late this evening, with the potential to redevelop overnight into early Thursday morning. Thus, some chance PoPs are maintained tonight into Thurs morning. However, confidence on PoPs this evening into Thurs morning remains low as CAMs are not in good agreement regarding coverage or timing of showers overnight into Thurs morning. Lows tonight will be near to a few degrees below climo.
Otherwise, a large upper-level low will meander over New England into tonight, before gradually lifting northeast into SE Canada throughout Thurs. This will allow for upper-lvl trofing to remain in place over the Southeast throughout the near term fcst period. This synoptic pattern will lead to partly to mostly cloudy skies, below climo temps, and continued rain chances. Expecting another round of sct showers and perhaps thunderstorms to develop Thurs afternoon into early Thursday evening. With winds becoming to SELY we will likely see better destabilization compared to previous days. However, Sfc-based CAPE values still only look to reach about 500 J/kg across the CWA. So, confidence on thunderstorms developing is low. Despite the expected SELY flow, high temps look to remain about 5-7 degrees below climo Thurs afternoon.
SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 200 pm EDT Wednesday: A closed low pressure system over the northern Plains and Upper Midwest Thursday night will settle southward into the Midwest Friday through Friday night. A weak shortwave ahead of the main low center will lift from the mid/lower Mississippi River Valley to the southern Appalachians during this period. DPVA with the upper wave, along with improving upper jetlet entrance region divergence, will increase omega atop the area Friday. In addition, low-level flow will be primarily from the southeast and the associated upslope and persistent moisture will generate numerous showers and embedded thunderstorms. The combination of abundant sky cover and good precipitation coverage will keep max temps some 10 degrees below climo.
The passing shortwave will lift northeast of the area on Saturday, with flattening mid-level flow developing. Deep-layer southwesterly winds will remain in place ahead of the next upstream closed system. Precipitation will be a bit more scattered and diurnally focused on Saturday, with the greatest PoPs over the higher terrain. Temperatures will rebound slightly in the warm advection southwesterly flow and improved insolation, with maxes rising to within about a category of climatology.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 230 PM EDT Wednesday: An upper level low from Canada descends south and reaches the midwest by Saturday and slowly moves across the Great Lakes region through mid next week. The location of the low will enhance a series of upper shortwaves to sweep across the Appalachians. Exact timing and location will likely change as model runs update through the week. For this weekend, closer to climo temperatures return, with a gradual increase of chances for typical summertime thunderstorms and showers, especially concentrated over the Appalachians.
As the low over the Great Lakes region progresses northeastward, a weak cold front will sag into the CWA on Tuesday. Expect an increase in thunderstorm and shower activity through mid next week as elevated low- level moisture ahead of the weak cold front will aid in the development in normal summertime storms.