Carvers Gap

Understandable but still wild....some big swings in the d+10 range. The left is the new GFS run. IF Alaska has a block like that, that trough likely corrects eastward. In that trough is very cold air. At 0z, the pattern was less amplified and blocky. The left has an east based NAO and a full fledged Alaskan block. As a result, the 12z GFS finds a cold front on Christmas Eve. It isn't huge, but interesting to see it parked right in the middle of the warm-up.

The CMC and GFS at 12z are a great example of the conundrum. The CMC has the December 20th cold front. The GFS does as well, but it is more seasonal. If that Canadian Yukon air can find a mechanism southward, those d10+ forecasts could change rapidly.

At 195 on the CMC, the air over the Canadian Yukon is -79F. The GFS isn't quite that cold, but it is impressive as well. With that type of cold air sitting upstream, that is why we have to keep our eyes open.

This is the Chinook mentioned above...It will race eastward.

On the GFS at 246, you can really see the Chinook blowing over the peaks of Colorado's Rockies. That "should" be followed by a cold air mass diving down the Plains behind it. Let's see if it can make it SE. About half the model runs shunt it across the northern border. About half, it's a jailbreak.

The 12z Canadian(even for the cold bias CMC) has a very cold air mass for early next week. Wind chills in many places are below zero w/ temps in the single digits. Portions of TRI are in the low single digits (or slightly bz) by Monday morning.

It is gonna take me forever to remember this PowellVolz. LOL. I have said it before, but glad to see you back posting here.

I am watching the 12z GFS roll in right now. Through 174, it is much colder across the NA continent. Let's see if that trend continues to hold for the rest of the run. This fits the trend of modifying warmer air masses. Looks like it has the post Dec 20 cold front rolling down the Canadia Prairies. Let's see if it can push all the way SE - I am still 50/50 on whether it can make it. Nice push SE on this run.

Thanks for posting that. I could see that get expanded into W NC overnight. They almost meet the criteria.

For kicks and giggles, take a look at the blizzard warning posted for West VA.

Just looking at yesterday’s Euro weeklies which have been the source of much gnashing of teeth and have the worst possible of all the outcomes. Warms up Christmas and is back to this current colder pattern by mid Jan. Wash, rinse, repeat. Actually, temps return to seasonal abruptly during the second week of Jan. Seasonal during that time frame will get the job done.

From what I can tell on the 6z GFS, the warmth rolls in and the warmth rolls out w/ each cold front. The warmth in the medium/LR is originating from a chinook. Whether that is MJO related, feel free to debate. However, as we have seen with other warmups, the warmth on deterministic models is being eroded into shorter timeframes as it gets closer. At one point, medium range modeling had the Dec 14th system moderated to a minor cold front passage. As is, we likely see very cold wind chills with this and temps in the lower teens and upper single digits in portions of NE TN. The mountains will be below zero. Just using the 6z GFS which looks reasonable. Temps warm on Dec18th and 19th before another cool front arrives. Then temps warm from Dec 21-24, before the GFS slams the door on it. The danger w/ this Dec 20th front is that modeling could be too weak. The 0z CMC has what looks to be an anafront line up in the Plains during that time. A trend I have noticed w/ modeling is that cold fronts are modeled as pretty vigorous at range. Then, they are moderated...then w/ about 7-10 days to go...the are much colder yet again. Just combing through ensembles this AM...the 0z GEFS erases the aforementioned chinook warmth by Dec 26. The 6z GEFS is still rolling. The 0z CFSv2 basically repeated the current pattern through the entire run. It has a strong cold shot to end December and begin January. More on that later if 6z and 12z support that run. The trend we have been seeing for weeks is modeling which moderates warm air masses which roll through. TRI is -5.4F for the month so far.

This is the GFES ext from last night....this is its 35d map.

National Weather Service Morristown TN 611 AM EST Wed Dec 10 2025 ...New AVIATION... .KEY MESSAGES... Updated at 609 AM EST Wed Dec 10 2025 - Dry and warmer to start today, before a cold front arrival later tonight. Gusty winds ahead of the front for the forecast area. Wind Advisory in effect for all except the southern part of the forecast area. - NW flow snow event expected later today through early Thursday with accumulating snow over parts of the Southern Appalachians and higher terrain of southwest Virgina. A Winter Weather Advisory has been issued. - We will warm up again late week with low chances of precipitation across the north. - Stronger cold front Sunday into Monday will considerably drop temperatures. Lows in the teens with some single digits Monday morning. Cold wind chills also possible. && .DISCUSSION... Issued at 1138 PM EST Tue Dec 9 2025 The forecast for today has come into better agreement over Wind Advisory level winds for everywhere north of the southern valley and southern plateau later today. As well as an accumulating snow event for northwest flow prone locations of the forecast area; Southern Appalachians and parts of southwest Virginia. Temperatures will be warmer today, however, cloud cover will be on the rise. Almost advisory level winds are being observed at Cove Mountain with gusts in the upper 30s at the time of this discussion. A WSW LLJ will increase into the overnight hours, bringing increasing winds to the higher terrain. Later in the day as mixing occurs, the gusty conditions will translate to the surface for the lower elevations, hence the advisory covering the day-time. A heavier weighted blend of the HREF/RRFS was used to capture the usually overperforming SWly winds for the valley. Gusty winds will continue into Thursday morning for the higher terrain, slowly decreasing behind the FROPA. A Wind Advisory is in effect later this morning first beginning in the mountains, expanding to the lower elevations, later finishing for the mountains early tomorrow. Confidence has also increased on higher snowfall amounts for the higher terrain with the latest guidance. The day will start warm, but temperatures will fall coinciding with the cold front later this evening. Rain will transition to a rain/snow mix, and then eventually all snow for elevations primarily above 2500 feet. Low-level moisture, NW winds, and temperatures below freezing are evident on forecast soundings, all supporting northwest flow snow. Snow will end early to mid Thursday when low-level winds drop off and lose the NWly component. Total snowfall accumulations will generally be 1 to 3 inches with higher mountain tops possibly seeing above that, for example, LeConte may see up to 5 inches. It`s possible some light snowfall may be seen across lower elevations of the northern valley and plateau, but is generally not favorable with NWly flow due to more downsloping on the valley side, which means drier. A Winter Weather Advisory has been issued and will begin mid-day, running 24 hours highlighting the potential for the aforementioned areas. Following the snow`s exit Thursday, a short cool-down can be expected with drier conditions throughout the day and decreasing cloud cover. However, precipitation from a weak system will bring increased chances to northern parts of the CWA Friday. Meanwhile, upper heights will be rising which will bring the warmer temperatures back for Friday and Saturday. Later this weekend becomes a bit complicated in regards to more precipitation due to potential interaction of southern and northern stream systems, but the one thing models agree on, is a substantial drop in temperatures Sunday into early Monday. Strong high pressure is expected to barrel its way through, originating from Alaska and Western Canada, where temperatures there have been in the 50s below at night, but we will not see that here. Monday morning lows are currently forecast to be in the teens with some single digits for the highest elevations and parts of southwest Virginia. Wind appears will be on the decline once we get later in the night Sunday into Monday, which is good news and may suppress what could be much worse wind chills. High pressure will eventually shift eastward but will keep us dry through at least early Tuesday.

Sometimes when we look at weather in the d10-15, we miss the stuff right in front of us. Light snow is possible tonight across NE TN and SW VA(assuming that also means SE KY). Then, again on Friday w/ a slightly more "vigorous" system. WWAs have been hoisted for portions of those areas for tonight - mainly higher elevations.