492 FXUS62 KRAH 061509 AFDRAH AREA FORECAST DISCUSSION National Weather Service Raleigh NC 1109 AM EDT Wed Oct 6 2021 .SYNOPSIS... Between a sub-tropical ridge over the southwestern Atlantic and a strong mid and upper level low that will drift very slowly north across the MS Valley, weak disturbances will track northeast across the southern Appalachians and Carolinas throughout the week. && .NEAR TERM /THROUGH TONIGHT/... As of 1100 AM Wednesday... Water vapor imagery shows a large and strong mid/upper low centered over Arkansas, which will slowly lift north into Missouri today and tonight. While moist southerly flow around this low is helping generate areas of showers from the FL panhandle into the TN Valley, our region is also feeling the influence of a mid/upper ridge over the western Atlantic, which is nosing north into eastern NC. At the surface, 1030 mb high pressure over SE Canada and New England will extend down into the mid-Atlantic. While the high is too far east for a classic CAD setup, east/northeast flow around this high will still keep broken cloud cover and limit potential for instability this afternoon, with SBCAPE of only 500-750 J/kg possible in the west. Overall, drying from the ridge to the east, along with low instability and forcing for ascent, mean only some isolated showers are expected today, and thunder potential is limited. CAMS are similarly unimpressed. The best chance for any showers will be farthest from the ridge over the western Piedmont, and in the far NE Piedmont/northern Coastal Plain near a backdoor front stalled over southern VA. Lowered forecast highs a bit today with all the cloud cover and NE flow, but with the backdoor front to our north, they will still be about 5-10 degrees above normal (upper-70s north to mid-80s southeast). A shortwave trough will rotate around the periphery of the aforementioned closed mid/upper low and reach the Carolinas late tonight, while the ridge gets shunted a bit south. This will result in some weak height falls and forcing for ascent across the area. However, considering this will be at night when instability is at its minimum, and forecast soundings actually show an inversion developing, only patchy light rain/drizzle is expected (again best chance in the west). Widespread low clouds and areas of fog are also expected, thanks to the moist NE surface flow. This will also help keep low temperatures similar to last night in the mid-to-upper-60s, which is around 15 degrees above normal. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 415 AM Wednesday... The mid/upper-level low initially over MO will continue to lift nwd across IL through 12Z Fri, while the sub-tropical ridge initially off the South Atlantic coast weakens and drifts swwd into the Gulf of Mexico. Weakly perturbed swly flow aloft between the two will result over cntl NC. At the surface, nely flow will remain, though it remains unclear to what degree, if any, cooler air from the nrn middle Atlantic and Northeast can infiltrate cntl NC. Instead, it is more likely that the warm airmass of recent days will remain, but simply not reach full heating potential owing to widespread early day low overcast that may linger into the afternoon over the nrn and nwrn NC Piedmont, with high temperatures likely to range from mid 70s to lwr 80s. Shower/storm coverage should again remain somewhat limited given only nebulous forcing for ascent in the aforementioned swly flow aloft, along with continued only weak instability. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 350 AM Wednesday... Friday through Sunday: As the upper low lifting northward through the western Great Lakes and into Canada opens into a trough Friday and Saturday, that trough will extend southeastward through the OH Valley, mid-Atlantic and Southeast US. While the remaining shortwave energy gets absorbed into the larger scale northern stream trough (moving through the western US), the trough will linger along the East Coast into Sunday despite a ridge briefly building from the western Gulf into the OH Valley. At the surface, high pressure drifting southward through eastern Canada will strengthen through Saturday, ridging southwestward through the mid-Atlantic and into the Deep South by Sunday. Meanwhile, an area of low pressure will sit off the Southeast US coast, slowly drifting northward to off or along the NC coast by Sunday. Generally expect northerly flow across the area at the surface in conjunction with the ridge and offshore low. As for precipitation, expect a chance for showers each day, with the best chances/coverage/intensity on Saturday aft/eve as the upper trough lifts through the area, taking on a negative tilt as it lifts through the mid-Atlantic. However, there is still some uncertainty given the continued model differences with respect to both the coastal low and the upper trough. As a result, forecast confidence remains below average. As for temperatures, still expect highs ranging from low 70s NW to around 80 degrees southeast and lows generally in the low to mid 60s. Sunday night through Tuesday: Significant model differences result in below average forecast confidence for early next week. As multiple upper level waves lift through the Plains ahead of an amplifying trough over the west, the sub-tropical ridge will try to build into the mid-Atlantic. At the surface, A pair of surface lows coincident with the waves aloft will also lift through the Plains. A cold front will strengthen over the Plains associated with the southern-most low. The surface high is largely expected to remain over the mid-Atlantic with the front and associated series of lows remaining to the west. && .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... As of 645 AM Wednesday... While humid air near the surface will favor at least patchy and short-lived LIFR-IFR stratus and LIFR to MVFR visibility restrictions over cntl NC around 12Z, the models and observational trends suggest those conditions will be relatively widespread from srn and cntl VA swwd across the nrn and nwrn NC Piedmont (INT/GSO). As such, near surface saturation/clouds may only slowly lift through MVFR range at INT/GSO through midday-early afternoon. While passing showers and afternoon storms will be possible throughout the forecast period, primarily at INT/GSO, overall coverage and the probability of occurrence should be low and insufficient to include more than a vicinity mention in the TAFs owing to a lack of strong and/or discernible forcing mechanisms. Widespread stratus and fog are likely to redevelop throughout cntl NC late tonight-Thu morning. Outlook: Persistent moist nely flow will be in place Thursday through Sunday, continuing to favor early morning fog/stratus and a chance of showers/rain. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...Danco SHORT TERM...MWS LONG TERM...KC AVIATION...MWS/Kren