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I'll open this one up with a MRX discussion: Upper low over the Ohio river valley today will dig southeast as shortwave dives southwest from the central plains into the deep south and helps establish longwave trough over the Appalachian chain by late tonight. This trough shifts to eastern seaboard by Monday afternoon but does not pull away from the east coast until Canadian shortwave drops into upstream side of trough and helps kick it off to the east Wed night. This will set the stage for a prolonged period of northwest flow over the forecast area, and subsequent significant snowfall event over the east TN mountains. Light snow will be ongoing over the mountains by Monday morning but inbound vort lobe associated with upper low will kick off a 12 to 18hr period of moderate to heavy snow, at times, across the area. Temps at H85 drop to -8C to -10C during this time and should help to boost snowfall ratios into the mid teens most likely. This is especially true given that saturation will extend well into/above the DGZ, which is not typical of your average NW flow snowfall event. Successive periods of 0.15 to 0.25" should therefore yield some 7-10" snowfall amounts in the Smokies and adjacent TN mountain zones Monday through Monday evening. Snowfall rates will taper off tomorrow night into Tuesday morning, but an additional 2-4" would certainly not be out of the question during that time. Moisture thins out during the day Tuesday but one last vort lobe moving through Tuesday evening may help snow showers continue, especially in southwest VA and the far northeastern TN mountains, through Tuesday night and early Wed morning. Storm total amounts of 10-12" in the Smokies seem very reasonable, and may even be a bit underdone, with 7-9" possible south of there into Monroe county and also north of the Smokies into Unicoi county. It should be noted here that these values will be for areas above 2,500 ft in elevation. Below that, totals will likely be 40-50 percent lower. Elsewhere, uncertainty in snowfall totals is a little higher. The northern plateau, higher terrain of southwest Virginia, and the far northeast TN mountains will all see accumulating snowfall. How much is less certain than the mountains. At this point the forecast calls for 1-3" in the plateau and southwest Virginia, and mountains of Carter and Johnson counties in TN. In general this seems reasonable for now. Accumulating snowfall in the TN valley is certainly possible, north of the Knoxville metro area, but will be largely dependent on precipitation rates I believe. In other words, suspect there will be plenty of snow in the air, but unless there are bursts of heavier precip rates I`m not sure there will be much chance for it to stick during the day Monday. And as moisture thins out Monday night into Tuesday, more typical NW flow snow shower activity will limit how much QPF and thus the amount of snowfall, there is to be had in the valley.- 195 replies
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