... Abundant moisture across the region will lead to solid daily chances of mainly afternoon showers and thunderstorms, especially in and near the mountains, each day through the middle of the upcoming week. A strong cold front will arrive from the northwest by late Wednesday or early Thursday, and bring cooler and drier air for the last half of the week.
NEAR TERM /THROUGH SUNDAY/... As of 1015 pm: Convection has all but dissipated across the forecast area this evening. However, scattered showers may redevelop later tonight along the eastern escarpment/upslope areas of the southern mountains as flow above the surface becomes more SE and increases a bit. Mild minimum temperatures will continue and another round of valley, lake, and river fog is likely - although lingering convective debris/mid and upper clouds could limit this a bit more in southwest sections.
On Sunday, 850 mb southeasterly flow will experience a slight uptick as the gradient increases between lower MS River valley troughing and ridging over the eastern Carolinas improves. This should permit shower and thunderstorm coverage to start a bit earlier Sunday and perhaps yield slightly better coverage overall for the afternoon hours. Surface-based instability will remain limited by cloudiness at times, but mainly by unimpressive lapse rates aloft - generally less than 6 deg C/km at mid-levels. Heavy rainfall should again be the primary threat with slow-movers and training cells.
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... As of 100 PM EDT Saturday: Weak upper ridging will slowly lift offshore Sunday night into Monday as very gradual height falls begin to enter into the CFWA from the west. This is due to to an open upper low over the southern half of the MS Valley that will send an axis of upper divergence across the western Carolinas and northeast Georgia. Broad surface high over New England will gradually move offshore with the upper ridge and influence the low-level flow which will come out of the E/SE and provide a continuous Atlantic fetch through much of the period. All of this combined will help promote daily diurnal convection with modest instability available and PWAT values between 1.50"-2". Thus, localized hydro issues could prevail in locations that receive multiple days of heavy rainfall and/or receive a good amount of QPF in a short time period. Deep layer shear parameters of 15-25 kts indicate that some organized convection could get going, especially in storms that develop along outflow boundaries and cold pools, mainly during the day on Monday. Models are not impressed with available instability for Tuesday compared to Monday due to a tricky, but weak hybrid CAD from the surface high off the New England coast that seems to filter in more stable air. The southern half of the CFWA would have the best chance for thunderstorm development with a low-end severe threat due to slightly higher shear parameters and better instability overall per model guidance. The severe threat is nonzero during the short term, but the thermodynamics don't support much cause for concern as of now. High temperatures will be at or slightly below normal for the early part of next week due to the extensive cloud cover and decent precip coverage that is expected, which will also produce well-above normal low temperatures.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 215 PM EDT Saturday: The unsettled weather pattern will continue to unfold during the beginning portions of the extended period. Deep upper longwave trough will dig from the north-central CONUS and approach the CFWA with an attendant cold front riding underneath on the leading edge of the upper trough by the middle part of the week. Deterministic models have slowed the frontal boundary's progression and has the main brunt of the front pushing through during a more favorable time of the day on Wednesday. This would line up with better instability and shear parameters (0-6 km bulk shear: 25-35 kts) with an organized line of convection, but not confident this far out to consider this a potential QLCS setup. The ECMWF still produces a negatively tilted trough and evolves into a closed low over the OH Valley Wednesday into Thursday in the latest run. This would bring even higher shear parameters and a more worrisome severe threat in this case. Severe weather concerns would prevail in either scenario given the thermodynamics and strong lifting mechanism. Once the boundary enters the CFWA, a true fall season fropa late Wednesday into Thursday will prevail with CAA filtering in behind the front as deep layer northwesterly flow settles in. Tight pressure gradient behind the front would suggest breezy conditions will be in store Thursday, while remaining dry. The post-frontal regime will likely last through the weekend as surface high builds over the region. Temperatures will be way below-normal Thursday through Saturday with 50s & 60s in the higher terrain for highs, while 70s exist elsewhere. Lows will be in the 30s on the ridgetops, 40s over the rest of the mountains/foothills, and low 50s east of the mountains/foothills with some locations flirting with upper 40 degree values.