ShawnEastTN

MRX Afternoon Disco: Discussion: Strong northerly shortwave will continue to dive southeast tonight amplifying the longwave trough across our region. Lapse rates steepen this evening and early tonight as the trough axis pivots across the Tennessee Valley and Southern Appalachians. Hi-res guidance and current surface obs show a weak surface low associated with this shortwave diving southeastward from southern Indiana and western Kentucky toward the Cumberland Plateau and the Southern Appalachians this evening between 0z and 06z tonight. This weak surface low, combined with steep mid-level lapse rates, should result in most widespread scattered snow showers around 02z to 05z across the area. This is the most likely time period for some of these northwest flow snow bands along the plateau to extend into the valley with light localized accumulation possible. Even though accumulation across the valley will be localized and light, any minor accumulation may result in snow and ice covered roads as temperatures drop into the 20s. Significant snowfall is expected across the mountains. Snow has already began accumulating this afternoon across the higher terrain with this synoptic band of light precipitation associated with the mid-level front and widespread upper divergence across the Southern and Central Appalachians. As northwest flow of 20 to 35 kt and 850mb increases this evening and continues tonight, it will result in strong orographic lift parallel to the mountains. DGZ saturation continues through tonight and into Saturday morning, so this is expected to be an efficient and high impact northwest flow snow event for the mountains. High snow to liquid ratios will result in higher totals, and strong winds across the higher terrain will lead to low visibilities and blowing and drifting snow in some location. In addition, the strong winds will result in life-threatening cold wind chills across the higher elevations with values as low as -20F. The DGZ begins to dry out on Saturday morning with drier air and a clearer sky building across the area. With the arctic high pressure building across the region, temperatures will be nearly 20 degrees below normal. Winds remain strong across the higher elevations with breezy conditions across the area as northwest winds gust up to about 30 mph at times. Sent from my SM-G965U using Tapatalk

Yeah it's definitely more juicy than most NW flow events. I noticed new WWA issued southern Indiana think it has over performed in areas where they don't have the benefit of terrain enhancement. Sent from my SM-G965U using Tapatalk

That's one of the good and bad things about these events radar doesn't pick it up well. Nice little flurry here too but nothing on radar. Sent from my SM-G965U using Tapatalk

It makes sense, something we don't tend to think about with something as minor as an event like this, with it having been so cold previously with ground temps being right at or even below freezing even a minor amount of snow even less than an inch can make for treacherous roads where snow gets packed down onto the pavement by cars and refuses to go. Tonight and tomorrow will be even worse anything that sticks will be next to impossible to get rid of, salt doesn't work well once temps fall into the 20's let alone teens. Going to be some bad roads for sure later at least secondary roads. Sent from my SM-G965U using Tapatalk

Yeah I understand that, but I wonder since we had that initial moisture as the leading edge of the disturbance passes that fell as virga for most, it might be helping to saturating us for the better deeper moisture to come this evening. Sent from my SM-G965U using Tapatalk

Radars look pretty impressive in Illinois and Indiana rotating down this way for the evening. This might be quite a NW flow event, one strong enough to give a inch or so to valley locations. I can remember occasionally that occurring at my low valley elevation on the Tennessee River over the years. Sent from my SM-G965U using Tapatalk

3k Nam has had similar looks off and on over the last 24 hours. Hoping for that type of setup like a frontal passage that gets enough lift to drop decent snow rates while passing. Definitely can make for a quick surprise. Sent from my SM-G965U using Tapatalk

That could be interesting. That sort of look from previous arctic fronts while moisture starved have great rates and heavy thumping for short duration, a snow squall type event. While it may only snow for an hour or so that arctic front type event can put down 2" in spots in that hour. Sent from my SM-G965U using Tapatalk

Yep some dry flurries my way here and there in the wind. Trapped low level moisture falling temp squeezing it out. Sent from my SM-G965U using Tapatalk

Same here, technically got 4 times the amount modeled IMBY. I think it's a great concept for modeling but I think bias and climatology at least in some instances are possibly over emphasized in it's calculations, and maybe not emphasized enough in other situations. Sent from my SM-G965U using Tapatalk

Could if the energy is stout enough valley locations could get involved and under banding. Yesterday there were advisories issued in Iowa and Minnesota as it was diving south they have since ended but up that way it was moisture starved so that was impressive for a moisture starved disturbance in an area that doesn't have elevation to aid in lift. As we know our mountains are great a 1 thing, that being trapping low level moisture. If enough lingers it could be a nice surprise event for even the central valley. Sent from my SM-G965U using Tapatalk

Something im curious about is the clipper tonight/early morning. In similar situations like this with departing storm with clipper/energy on its heels there is often left over low level moisture from the storm for the clipper/energy to interact with and can make for an over producing event. Sent from my SM-G965U using Tapatalk

@PowellVolz Not sure if it's energy transfer or if it's ptype changing from higher reflective ptypes to lesser reflective like sleet changing to snow. Active reports of snow falling still as far west as Oxford MS and near Jackson TN. Sent from my SM-G965U using Tapatalk

Full mix snow, sleet, rain Meigs/Roane line. Sent from my SM-G965U using Tapatalk

Ha ha Sent from my SM-G965U using Tapatalk

Wish I had your numbers... 38.7/36.1 Sent from my SM-G965U using Tapatalk

We need a lot of different things, track being probably primary issue to strength, don't want the surface low tracking too close. We want dynamic cooling to be stronger than any effects of warm nose and/or downsloping (if you are in the Eastern valley). We want the cold to filter in fastest possible. Sent from my SM-G965U using Tapatalk

38 here and rain with what seems like partly melted flakes mixed in just started here. Sent from my SM-G965U using Tapatalk

0z NAM non kuchera: Sent from my SM-G965U using Tapatalk

0z NAM is running looks pretty good Knox county west and south. Looks like downsloping delays precip east of Knox for a time. Out to 25. Sent from my SM-G965U using Tapatalk

My PWS recorded the shockwave, Tellico and Blunder report theirs did too. Pretty awesome! Sent from my SM-G965U using Tapatalk

It's pretty fascinating areas in southern Illinois are still above freezing while western central Mississippi is below freezing. It's colder 100 miles south of Memphis than it is 100 miles north of Memphis. Here is roughly the freezing line. Sent from my SM-G965U using Tapatalk

They had to convert a lot of winter weather advisories to winter storm warnings in Arkansas the storm way over performed for a lot of areas that were not expected to see anything at all or very little. Sent from my SM-G965U using Tapatalk

Not something I see very often Chattanooga local TV WTVC News Channel 9 is not aligning with the NWS and channel 9 tends to be pretty conservative with snow but they are saying 1"-3" valley and 3"-6" or higher mountains. I think that is more reasonable than MRX forecast. Haven't checked Knoxville local stations, I live in an area where both cities TV stations are available. https://fb.watch/az7tq0RViK/ Sent from my SM-G965U using Tapatalk

All kind of confused my MRX forecast snow according to their map is 1-2" and Knoxville .5-1" Knox under advisory Roane/Meigs not, this really is bizarre even for normal MRX snow storms. Sent from my SM-G965U using Tapatalk