Minor Tweaks; Regionwide Snow Expected
Good morning folks! Today is the day and for some of us snow will begin to fall as soon as the early afternoon hours, however most of the region will see flakes beginning to fall between the late afternoon - mid evening hours. The forecast is still on track and I'll keep the SNOWCAST map the same, however I will bump the Plateau and northern Transylvania totals up a few inches as this now looks to be a new sweet spot for 12" or more through Sunday afternoon. Black Balsam Knob and the surrounding portion of the southern Great Balsams continues to be the number one spot for totals regionwide, with storm total north of 18"; an easy forecast with no one up there to measure and verify. The NWS has changed their maps several times with each new set of models and will likely do one or two more tweaks to their call maps as we enter the last few model runs of the event. Their maps are running anywhere from 3 - 6" higher than the SNOWCAST map above, which very well may be the right call but the deeper valleys still give me pause, especially Bryson City with possible downsloping from the Cowee and Alarka mountains.
That being said, this excerpt from GSP's morning discussion is certainly interesting and something to cling onto if you want higher totals; "The mountains, meanwhile are on track for a mostly-snow forecast. The warm nose should not penetrate into the Appalachians. Profiles here appear to remain well-saturated and sub-freezing through most of the event, allowing for an easy transition from a rain-snow mix to all snow from Saturday night onward."
I for one would love higher totals so am rooting that the above SNOWCAST map is on the low end. Team choosing aside, lets dive into the timeline as this is all we can really discuss at this point, with the event less than 12 hours away. A round of light snow and flurries is possible around midday, however the bulk of the action will be to our north and whatever falls across the area will not amount to much at all. Clouds thicken as the day moves along, indicating the warm and moist layer above the pool of cold air is increasing. Temps will reach the low 30's - mid 40's depending upon elevation and don't worry too much about surface temps, as the dry air will be our friend with this setup.
Science Lesson: The dry air in place evaporates the initial precip as the event unfolds and this cools the column of air as precip moistens the air (heat used to evaporate the precip is lost and the air parcel cools), eventually reaching the ground as snow and bringing with it cooler temps. For those who see the initial round of precip while outside this afternoon, you may notice it not reaching the ground. This is called virga and the process described above is doing its magic to bring precip and cooler temps to the ground. Science!
Snow coverage should expand from the south along the SC state line to the rest of the region by the late evening hours, with maximum coverage occurring during the pre dawn hours, slowly scaling back around the mid morning hours on Sunday. The track of the low pressure system is along the Upstate so we are likely to experience a dry slot sometime Sunday morning before switching over to the backend round, which will morph into a WNW flow event for the TN line Sunday night into Monday. An hour or three of sleet and light freezing rain is possible closer to midday on Sunday, however this should not be a major issue, with snow making up 80 - 90% of the precip type throughout the event. Snow ends for most of the region Sunday afternoon, scaling back to the TN line as we transition to a WNW flow event that will keep light - moderate snow going along the TN line into the mid afternoon hours on Monday; couldn't ask for a better setup for the slopes. Flurries and clearing skies make up the forecast for the rest of SW NC on Monday, but WNW winds around 15 - 30mph will keep wind chills in the single digits.
If you want to cash in with high end snow totals, head to the Plateau or southern Jackson County - northern Transylvania County; 10 - 14" expected. Southern Haywood County will also do quite well, especially above 3000', but the upslope areas along the escarpment above 4000' will tap into the highest moisture levels, while at the same time remain all snow.
If you want to experience low end totals find elevations below 2500', along the riverside, and just below larger mountain ranges that sit south of your location. I dog on Bryson City often because their setup typically meets all three of the criteria and in this setup its likely to occur again, same for many locations in southern Macon County along the valley floor, just below the Plateau; I'm also thinking about you Cullowhee, Sylva, and Dillsboro. Downsloping will be an issue around sunrise, limiting moisture amounts to the valleys towns that sit just north of a large mountain range; Cowee Mountains; Plateau/Big Ridge, Alarka Mountains, etc.
Temps Sunday and Monday will be frigid with most of SW NC sub freezing over the 48 hour period. High temps reach the low - mid 30's each afternoon along the valley floor, while the higher elevations above 3500' sit in the 20's. Overnight lows dip to the low - upper teens regionwide each night.
We have another chance for snow Thursday into next weekend, but we'll stop here and circle back tomorrow afternoon with an update on the event and a better look at the week ahead. ENJOY!