National Weather Service Forecast Discussion For Weekend
Sep 26, 2022, 8:59 AM
For those interested, or weather geeks like Rev and me, here's the AFD from NWS at GSP this morning for this weekend. Translation, the system has slowed a tad (not good for Saturday). Very windy and raw Friday with temps around 60 throughout the day and heavy rain. Saturday will be in the mid 60's with stiff wind and heavy rain. Timing still to be fine tuned. Hoping for a faster and more easterly track.
As of 230 AM Monday: Our medium range forecast will completely depend on the fate of Ian, as the consensus forecast still brings Ian (or it`s remnants) right up into our forecast area. The models agree that Ian will miss the deep trough as it exits off the East Coast. This will allow Ian to drift north across the eastern Gulf. The EC and ECENS continue to be on the east side of the forecast envelope, while the GFS and the GEFS are on the western side. But they do seem to be in better agreement than the last couple days. The onset of deep tropical moisture streaming in on the north side of the circulation has been delayed a tad, with PoPs ramping up Thursday night into Friday. In fact, the 00z GFS is even slower, with mentionable PoPs starting after 12z Friday. Whenever the precip starts, a 1030+ mb high will be over Upstate NY, so hybrid CAD should set up quickly. This will strengthen a wedge front near the SC coast, as Ian near landfall somewhere along the northern FL Gulf coast. This set up could focus the heaviest rain to our SE, with cool, wedgy air mass atop the forecast area. Highs will be about 5-8 deg below normal Thursday, and 10-15 deg below normal Friday. Breezy NE winds expected both days.
The latest forecast has Ian slowly drifting north across GA Saturday, weakening to a tropical storm and transitioning into an extratropical cyclone. Heavy rain looks like the main threat as Ian approaches, with widespread 2-4" of QPF possible Thursday night thru Saturday. It will be breezy due to the tightening pres grad between Ian and the high to the north, but confidence is low on tropical-storm-force winds making it all the way into the forecast area. But with the heavy rain and gusty winds, still may see some trees and power lines come down. Also, any tropical tornado threat looks to remain to our SE near the wedge front. The 00z ECMWF has Ian take a sharper NWWD jog across GA, and suggests a tropical/warm sector air mass might get into the lower Piedmont Saturday aftn. But that is an outlier solution.
PoPs linger into Sunday, as the remnants of Ian wobbles across the region. Temps rebound from the chilly Friday highs, but still below normal thru Sunday.