The much-above-normal temperatures that the East Tennessee region is currently experiencing will come to an abrupt halt — at least temporarily — this weekend, with the arrival of a strong cold front that will deliver seasonably cool air, and even below-normal temps for a couple of days.
The front will arrive late Friday or Saturday, and it will bring some rain with it — though how much, what time, and whether we see thunderstorms all depends on several factors that aren’t clear yet.
Currently, it looks as though scattered showers could develop by Friday evening, just in time for high school football, though not everyone will see rain by any means. The more organized convection should remain back to our west during the evening hours on Friday, and it currently looks like it might arrive along the Cumberland Plateau by midnight or a little later Friday night.
There are some significant timing differences between the two major weather models at this range, the domestic GFS model and the ECMWF model from Europe. For example, the GFS has the main line of convection knocking on our door by midnight Friday night. At the same hour, the ECMWF — which has a more organized low pressure system over the Midwest and stronger convection ahead of the cold front further south — has the main line of convection just crossing the Mississippi River.
These timing differences have been present on the two models for the past several days, with each model sticking stubbornly to its own solution. By 1 p.m. Saturday afternoon, the ECMWF has moderate rainfall across most of the East Tennessee valley, while the GFS has already moved all rain well east of the Appalachians.
Either way, it looks like our primary rain threat here on the Cumberland Plateau will come during the overnight hours Friday into Saturday, and Saturday morning.
For folks heading to the Tennessee-Ole Miss game in Knoxville Saturday night, both the GFS and the ECMWF models clear the rain out before kickoff, though the ECMWF would keep wet weather around long enough to hamper some of the pregame festivities earlier in the afternoon.
Behind the cold front, cooler-than-normal temperatures will spill in from the northwest, and that’s going to be the biggest weather story of the weekend: Much cooler weather!
How quickly those cooler temperatures spill in will depend on how quickly the cold front clears the area. Again, the GFS is much faster than the ECMWF. If the GFS is correct, we’ll be in the low 50s, maybe even dipping into the upper 40s, by around sunset Saturday evening here on the plateau. That’s going to be quite a shock to the system after we’ve been in the 80s for almost two weeks! The ECMWF, on the other hand, keeps us 8-to-10 degrees warmer, with the colder air slower to arrive. We’ll still be in the upper 50s by sunset Saturday if the ECMWF is correct.
Eventually, though, the colder air will arrive. Just about everyone in Tennessee, regardless of location, will be in the 40s by daybreak Sunday morning. We may drop down into the mid 40s here on the northern plateau. The GFS has us dropping into the lower 40s but it’s probably undercutting the actual temperatures by a few degrees.
After a high temperature that stays in the 60s Sunday afternoon, we’ll be back down in the 40s on Monday morning as well.
This weekend could bring the first frost of the season for the highest peaks of the mountains, though all of us west of the mountains — even here on the higher elevations of the plateau — will have no threat of frost.
A warming trend begins fairly quickly, and we may stay well into the 50s Monday night into Tuesday morning, although the ECMWF is a bit more stubborn than the GFS with the cooler air sticking around longer. By Tuesday afternoon, pretty much everyone will be in the 70s.
Our average high temperature in Oneida for this time of year is around 70°, while the average low is around 42°. Obviously we’ve been significantly warmer than that so far in October, and will remain that way for the rest of this work week. Even this weekend, our low temperatures will be around seasonal norms before we rebound to above-normal temperatures early next week.
In other words, our overall theme of put-up-the-pumpkin-spice/break-out-the-flipflops will continue to apply. Officially, we’ve only hit 80° twice through the first 11 days of October, reaching 83° on Oct. 1 and hitting 82° today. But we’ve been close to 80° most other days this month; eight of 11 days have featured high temps of 78° or warmer, and a ninth day featured a high of 77°. We’ve only been in the 60s for a high temp one day out of 11 so far this month. And we’ve yet to have a night where temps dropped into the 40s; our coolest night so far was 53°. As a result, our average temperature for October is running a whopping 7.6° above normal so far.
That theme isn’t going to change. We’ll likely hit 80° at least a couple more times this week, and we’ll rebound quickly through next week. The latest outlook from the Climate Prediction Center shows a return to warmer, dry pattern for the Oct. 19-25 period.