... Dry fall-like weather is expected through Thursday as high pressure builds into the region. Rain and wind associated with the remnants of Ian may reach our area by late Friday or Saturday, and continue into early next week.
NEAR TERM /THROUGH TONIGHT/... As of 934 AM EDT Wednesday...
Dew point values lowered today...
The 12Z RNK sounding revealed an abnormally dry airmass in place with PWAT values at 0.25" which is historically low for 12Z/Sept. 28th. An upper level trof digging southeast across IN/OH will enter the forecast area this evening, but any showers associated with this feature and its associated cold front will stay north of our area considering the amount of dry air in place.
Otherwise, lowered dew point values based on the large area of dry air between 850-350mb. Also bumped up temps a degree or two east of the Blue Ridge with some downsloping winds.
With high clouds continuing to increase late today and tonight...lows tonight will be warmer ranging from the mid 40s for most of the area. Some upper 30s are possible in the sheltered mountain valleys and higher elevations.
Forecast confidence is high.
SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... As of 215 AM EDT Tuesday...
Remnants of Hurricane Ian to Have Major Impact on Forecast Area Beginning This Period...
Deep trough will be centered over the eastern CONUS as strong Canadian high pressure begins the build eastward. Meanwhile, Hurricane Ian will be making landfall along the western coast of Florida. With the expansive cloud shield spread north from Ian as it starts to head NNW through SC, would expect extensive high cloud cover especially by afternoon. Cool, dry, northeast flow will become enhanced throughout the day as the gradient strengthens between Ian approaching from the south and cold high pressure to the north.
Models have come into good agreement on the general track of Ian after the northeast U.S. upper trough passes by leaving the future track of Ian subject to an upper high to its north and an upper low moving southeast from Ohio. Thus, from this point, good consensus among the longer range models of the remnants of Ian tracking NNW toward the southern/central Appalachians. By Sunday, it appears that the remnant low will gradually become absorbed within the upper low moving southeast from the Ohio Valley and could potentially linger in the general TN/VA/NC area into early next week. Clearly this could evolve into a significant rainfall situation which will becoming an increasing concern after successive days of moderate to potentially heavy rainfall. The limiting factor or saving grace, as it may be, would be the persistent northeast flow which may tend to lower the dewpoints and PWATS and hopefully the rainfall amounts as well. See hydrology section below for further information.
With this forecast, have decided not to mention thunder as the air mass across the region with northeast flow and a strengthening wedge thanks to the persistent northeast flow and tightening gradient will keep temperatures way down, perhaps only in the 50s Saturday and Sunday. This should also greatly reduce the tornado threat and with our area being closer to the core of the remnants of Ian as opposed to the eastern outer feeder bands, the tornado threat, such as it will be, will be removed to areas east of the RNK CWA.
Temperatures will trend well below normal during this time frame, mainly for high temperatures however. Low temperatures will actually trend above normal with dewpoints creeping back into the 50s and persistent clouds, rain, and wind. This will be a very chilly, cold, persistent rain beginning Friday night and continuing through the day Saturday for sure, becoming a bit more showery Sunday. High temperatures Saturday and Sunday will only be in the 50s for much of the CWA and I would not even be surprised to see a couple of upper 40s in the western mountains.
Finally, beginning late Friday, the southwest portion of the RNK CWA is now within the GTCM wind field of NHC. After collaboration with our neighbors to the south, we went with a background wind of NBM/NBM90 and then ran the GTCM wind tool. Capped winds at 34kts in the southwest part of the CWA for now.
/Confidence Levels in Forecast Parameters/ - Moderate to High Confidence in Temperatures, - High Confidence in 100% Pops, - Moderate to High Confidence in Wind Speed and Direction.
LONG TERM /SUNDAY THROUGH TUESDAY/... As of 245 AM EDT Tuesday...
Remnants of Hurricane Ian Will Continue to Impact the CWA Through the First Half of Next Week...
Sunday, based on current model trends, the remnants of Hurricane Ian will be meandering about the tri state area of eastern TN/western VA/northwestern NC trapped within a slow moving upper low. Outer spiral remnant feeder bands will be located further east potentially across the Piedmont and toward the coast. Core rainfall associated with Ian will remain in the tri-state area and with successive days of such, WPC has now included this area in a Moderate Risk for Excessive Rainfall on Saturday and Sunday. Additional showers and localized flooding could continue even into Monday and Tuesday. It will take until midweek when an upper trough and associated frontal system finally sweeps the remnants of Ian and the pesky upper low out of the CWA.
Temperatures will slowly creep closer to seasonal normals for high temperatures and remain above normal for low temperatures with clouds, precipitation, and northeast flow slowly diminishing as the remnants of Ian spin down after successive days inland. High temperatures will slowly rise back into the 60s and perhaps even a few 70s Piedmont by the middle of next week with lows mainly in the 50s.
Confidence in the forecast during this period is Moderate.