... Warming continues on Sunday with scattered showers and isolated thunderstorms, mainly across the mountains. Dry and mild high pressure returns Monday. Cool Canadian high pressure drops south across the Great Lakes through midweek creating progressively cooler weather each day. Tropical cyclone Ian moves north from the Caribbean and may affect our weather by Friday.
NEAR TERM /THROUGH TONIGHT/... As of 1215 pm EDT: The current forecast appears in good shape, with a broken altocumulus deck moving across the northern half of the forecast area on WNW flow aloft. This will reduce insolation over the northern tier this afternoon, and maximum temperatures in these area have already been reduced accordingly. Cloud bases around 10 kft are generally high enough to yield mainly virga across the forecast area, but slightly higher precipitation rates arriving from the WNW could yield some very spotty showers at times along the spine of the southern Appalachians. Some slight chance PoPs for light showers at high elevations and near the TN border are now included this afternoon.
Otherwise, quiet wx will continue today through tonight, as high pressure slowly migrates from the central Appalachians to the Carolina coastal waters. As high pressure shifts to our east, winds will turn out of the SW and temps are expected to warm a category or so from yesterday's readings in most places - still a degree or two below normal. Increasing westerly low-level flow and WAA will keep tonight's temps a few deg warmer than this morning's readings.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 1230 PM EDT Saturday: By late Sunday evening, a weakening frontal zone looks to be situated across the SC Upstate beneath a robust 500mb trough. Models are in decently good agreement on the residual frontogenesis and associated low-level forcing rapidly shifting east out of the CWA through the overnight, such that winds will be squarely out of the NW across the region by daybreak Monday. Dry air impinges on the area quickly as the boundary passes, and by the late evening instability should be virtually nonexistent, so precipitation should quickly let up giving way to drying and clearing.
Upper trough struggles to move much through Monday night as models alternately depict a shortwave or two rotating about its periphery. Despite the modicum of synoptic forcing this will provide, profiles will be far too dry and stable to warrant any PoPs or cloudiness. This pattern should generally persist through Tuesday, with increasingly NNWly flow holding temperatures 2-3 categories below normal.
LONG TERM /TUESDAY THROUGH FRIDAY/... As of 305 AM EDT Saturday: The upper trough remains over the eastern CONUS through Wednesday. The trough then moves east Thursday leaving a weakness in the flow for Friday. This will have a significant effect on the weather for our CWFA. A dry cold front crosses the area Tuesday with broad high pressure centered over the Great Lakes moving in for Wednesday and Thursday. Model guidance agrees that the trough moving east now doesn't pick up Ian. This allows Ian to move north out of the Gulf of Mexico into or near our area by Friday. Of course, the guidance still differs on the speed and exact track of Ian, which could have a significant impact on our weather. That said, it's still too early to know how significant. Given the uncertainty, have gone with WPC's depiction and the model blend for the forecast. This means a dry forecast through Thursday with highs falling to around 10 degrees below normal. Lows will be nearly steady 5 to 10 degrees below normal. PoP increases into the chance range on Friday. Highs drop a couple of degrees from Thursday.