... Air quality should continue improving throughout today. Scattered showers and thunderstorms remain possible again late this afternoon into this evening. A weak cold front brings active weather into the forecast tomorrow and Wednesday, before we return to a typical summertime pattern toward the weekend.
NEAR TERM /THROUGH TODAY/... As of 100 am: Other than a couple of stray light showers, convective activity has dissipated across the forecast area early this morning. Still wouldn't completely rule out a cell or two initiating near the TN border in weak low level westerly flow, so a token small PoP will be carried there through daybreak. Otherwise the morning will be warm and muggy, with gradually expanding mountain valley fog and stratus.
Synoptic and CAM guidance show a better chance of convection overall for later today. A weak short wave crosses the area in the WNW flow which may help push a weak boundary into the area. The right entrance region of an upper jet moves overhead as well increasing upper divergence. PW values will be back on the increase with at least moderate instability developing. DCAPE values may not be quite as high but bulk shear looks to be higher with the short wave moving through. Isolated severe storms will be possible. Isolated flooding remains possible as well even though storms will have decent movement due to higher PW values and more storms in general. Still show highest PoP across the mountains and foothills where convection initiates, but there's a better chance of convection moving south and east into the Piedmont during the afternoon. Highs will be near to slightly above normal.
SHORT TERM /TONIGHT THROUGH WEDNESDAY/... As of 145 PM EDT Sunday: Broad ridging will be in place over the western part of the country, with the main ridge axis centered over the Pacific Northwest. This pattern appears to slightly amplify over the course of Tuesday and Wednesday as a trough digs down over New England and the Mid-Atlantic. A band of weak upper forcing for descent may somewhat suppress precipitation on Tuesday, but shouldn't be nearly enough to overcome the much more robust surface circulation brought on by a stalling cold front over the CWA. Guidance depicts a band of low-level convergence draped across the SC Upstate on Monday night; this feature gradually slides south and east over the course of Tuesday, weakening significantly as it does so. Model wind fields are in line with this, indicating that the front lingers over the far southern tier of our CWA through Tuesday evening. This will result in widespread showers throughout the day on Tuesday, with some embedded thunder during the afternoon hours. Despite fairly high LFCs in most areas, robust lifting along the boundary, which is discernible even above 850mb, should be enough to get some parcels to convect in the presence of good instability across the board.
As the boundary weakens further Tuesday night, it will pull back northward and any northerly flow that had crept into our CWA will be replaced by renewed southerly flow and continued influx of moisture driven by the persistent Bermuda High off the coast. As the frontal circulation abates, and continued synoptic suppression limits lift, stratiform precipitation should ramp down by Wednesday morning. We'll perhaps see a lull in precip late Wednesday morning, before the usual diurnally-driven showers pick up that afternoon. PoPs climb into the chance range across the SC Upstate and perhaps into the eastern NC Piedmont, as model guidance suggests good instability here. Farther north and west, lesser instability combined with capped profiles on the cool side of the remnant frontal boundary should inhibit widespread convection.
Expect highs on Tuesday to be a degree or two cooler than this weekend, with the continued wet pattern and weak northerly flow on the cool side of the boundary dropping our temps a bit. By Wednesday, renewed southerly flow and WAA will boost temps several degrees, and they should climb to at least a couple degrees above climatology.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 200 PM EDT Sunday: Ridging over the western CONUS will remain in place as the overall upper pattern continues to amplify. Heights over the Four Corners and Southern Plains should bump up a bit even as the trough anchored over the east coast deepens. Remnants of the boundary over the Southeast should fall apart entirely by Thursday morning, and heights rise a bit as the western-U.S. ridge nudges eastward. After a bit of dry weather on Thursday, the weekend will see at least one shortwave skirt along this broader trough and produce another wave of precipitation on Friday or Saturday, perhaps even into Sunday. Confidence at this point is low, as model guidance has not come into good agreement on the general synoptic pattern, let alone local details. Sticking with chance PoPs late Friday and into the weekend for now, but these details will likely change a bit closer to the weekend.
Temps should stay a few degrees above normal on Thursday and Friday, as WAA and decent surface heating allow for afternoon temps well into the mid-90s. They back off again into the weekend with increased moisture and renewed rainfall, returning to near-normal by Saturday.