Carvers Gap

From MRX and a stellar write-up over night w/ mountain wave discussion to boot....Never know, this might have been written by a contributor here. National Weather Service Morristown TN 620 AM EST Thu Jan 22 2026 ...New AVIATION... .KEY MESSAGES... Updated at 619 AM EST Thu Jan 22 2026 - One last day of warmer temperatures today with light precipitation exiting to the southeast. - Confidence in a significant winter storm affecting the southern Appalachian region Saturday into Monday is increasing. However, it must be stressed that details on where the axis of heaviest precipitation and resulting wintry precip totals remain unclear. There is also the possibility that some will see only rain or a combination of rain and freezing rain. This weekend`s system will need monitored closely. - Cold air behind this weekend`s storm will keep temperatures at/below freezing during the day with some very cold mornings. This will prolong the effects of any winter weather, with power outages possible as well. && .DISCUSSION... Issued at 1100 PM EST Wed Jan 21 2026 Discussion on the weekend system starts with the third paragraph. A cold front lays to our west with light precipitation mostly along the mountains now. Only a few hundredths of an inch, at best, have been recorded across the forecast area last night. This weaker system will exit the region around mid-morning today. Today will also be the last day of 50s for highs across much of the forecast area through possibly the rest of the month. For tomorrow, northern parts of the forecast area will most likely remain dry up until the strong weekend storm arrives. High pressure tries to punch in on the backside with nearly zonal flow aloft following the shortwave responsible for the Wednesday system. It`s possible that whatever precipitation reaches into the forecast area Friday, will mix with other forms of precipitation type, especially across higher elevations. Surface temperatures will be colder Friday. However, this is a window of warmer air aloft trying to be replaced by colder air to the north. Like it has been stressed for almost every new forecast run, we just want to re-iterate that this forecast is very difficult and has changed from run to run. Consensus still trends warmer, but will get into that in a bit. On-set could be early or mid Saturday, depending on many factors; models still vary on this. A later arrival and peak of the event have trended out in time. Sometime overnight Sunday or Monday morning is when the core of the precip shield should be mostly to our east with some wrap around possible on the back-side. So, what is the set-up for this? Surface high pressure is expected to dive down from western/central Canada. Compared to 24 hours ago, it is close to 10 mb weaker from the strongest reading it had in previous runs. Longwave troughing sinks south across the country, meanwhile, a Baja upper low/closed low will eventually eject eastward once it phases with the mean flow. Headed later into Friday, a low center over the Four Corners region forms with a couple of other low centers over northern Mexico region. A front also arcs along the Gulf coast. Later Saturday an additional low center forms near the FL Panhandle, as well as another off of the Carolina coast. How the high pressure to our north and the Gulf and Carolina lows interact, is pretty much the end all be all of just what impacts we will see in regards to precipitation type. The high and troughing will send in the colder air, however a strengthening low to our south will send overrunning air out of the southerly direction, or simply, much warmer air. Although confidence has been severely low up until this point, the confidence in higher snowfall amounts is surely lessening with what seems to be a weaker surface high, therefore much warmer temperatures at the surface, and signals for fairly strong southerly low level winds. High wind potential or mountain wave enhancement will need monitored especially during the Saturday night time-frame. The NAM and RRFS runs show near 70 kts of southerly low level flow. That would bring strong winds and gusts to the mountains and foothills. Overall, things could still change, BUT surface temperatures have increased each forecast run for Saturday and Sunday highs, to be precise. We just haven`t gotten into ranges or specifics on snowfall totals, for example, because of just how much this forecast has changed. Amounts were essentially slashed from yesterday afternoon`s totals. I believe the increasing unknown or challenge will be the question of freezing rain or rain and how much. Storm total QPF range in the area of nearly 2 inches to over 3 inches. In conclusion, the rain/snow line has shifted north, therefore, snowfall amounts are decreasing from south to north, with increasing chances of freezing rain and rain with each new forecast run so far. Counties bordering Kentucky and West Virginia are trending towards mostly snow with the greatest amounts of the forecast area.

0z GEM and GFS maps....

.3-.4" of ice accretion(using Jeff's 1/3 rule) for Knox on most modeling if not more. Let's hope the lights stay on w/ that type of cold coming in. Roads could be a mess. Not having power is what we need to avoid. We need it to trend to liquid.

I should add that I pretty much gave up on snow for MBY at lunch. I am fully aware I am tracking sleet and ice w/ a possible front end thump. Hopefully ice amounts moderate.

Yes, especially when a feature in the STJ makes landfall or a northern vortex finale gets sampled well. For now, it looks like the STJ is going to slam into a very cold area of hp. Looks very icy. Classic over-running setup w/ snow and sleet to lead out...and then another wave to follow.

0z GEM might have ticked one county north... pretty much the same look as it had at 12z. Steady. Icy.

Knoxville has 24 hours of frozen precip according to the WxBell algorithm. Hour 69-83. Hour 78-93 is ice. Debatable whether that run would actually flip Knoxville rain just knowing how ZR behaves there from experience. Having done the ice deal in Knoxville during the eary 90s(surprise ice storm that hit right as school started on maybe a Friday)....Knoxville can get stuck at freezing sometimes. Either way...quick thump of snow, sleet, zr, and then rain for Knox. Right around an inch of ZR for TYS and .60-.70 for TRI w/ TRI managing 2" on the front end, then zr, then wrap around snow to end w 6"...doubt that snow total holds. North Georgia gets 2.44" of ZR. SW TN gets the sleet hammer. Chattanooga 1.11" of ice.

Nope. It could end up that way in reality, but not that run.

Interestingly, the 0z GFS runs a weak surface low from south Alabama into south/central Georgia and into the Carolina Piedmont to end the storm. Just something to watch w/ future runs. Pretty heavy icing over the eastern 2/3 of the forum. Hammers Atlanta metro. The rain snow axis didn't jump as much as I thought it would. Ice is the story as it was at 12z for all other models. GFS is on board.

That was a really odd phase out West w/ the northern stream losing symmetry for lack of a better word. Didn't have that parabolic look. Looked like you bent a straw and held it on its side.

Definitely more amped by the GFS. Looks like a lot of ice.

By 78, the GFS is doing something wonky w/ the polar jet(squashes the bend like bending a straw a bit to much).

Maybe and hour or two slower at 63...track looks similar for wave one.

Out to 60...minute differences to this point when compared to 18z.

Early in the run, the position of the Baja low(and it may not matter) has been maybe 25-50miles southwest of 18z just based on quick glances at each 500 vort map tonight.