The National Weather Service drastically beefed up its snow accumulation forecast overnight, and is now calling for up to 4 to 6 inches of snow for Scott County and the northern Cumberland Plateau region tonight, as another winter storm impacts the region.
A Winter Storm Warning will take effect at 7 p.m. tonight for Scott, Campbell and Morgan counties, and continue until 7 p.m. Thursday evening. The text of the storm warning calls for 3 to 5 inches of snow for the region; the NWS’s point forecast calls for 4 to 6 inches of snow in and around Oneida.
Let’s break it down:
Timing: Wintry precipitation is expected to begin around 8 p.m. or a little later this evening.
Precipitation Types: There is a 100% chance of a “wintry mix” tonight and a 70% chance of a “wintry mix” tomorrow. Precipitation may initially start with a little rain and sleet mixed in with the snow, but is expected to be primarily snow early. Towards daybreak, precipitation is expected to change to sleep, and then will eventually change to rain during the day on Thursday, before changing back to snow Thursday night.
Hazards: Widespread power outages aren’t expected to be an issue, but isolated power outages certainly can’t be ruled out. The snow isn’t expected to have quite as high moisture content as the last heavy snow we had, 10 days ago. While some freezing rain is also anticipated, amount should be on the light side — generally less than a tenth of an inch. The biggest issue will be road conditions. Roads will be expected to become hazardous overnight before beginning to improve during the day on Thursday.
Temperatures: It’ll be interesting to watch temperature trends today. We originally expected to get to 40 degrees; the NWS forecast now calls for a high of 35. The return of some off-and-on sunshine will help bump up temperatures, but it’s still going to be a chilly day, and ground temperatures will be sufficiently cold for accumulation of wintry precipitation tonight. Our temperature tonight will be below freezing; the forecast calls for a low of 29. We’ll gradually climb to above freezing, helping to promote a changeover to all rain, with a high of 36 on Thursday. Exactly how much melting we see on Thursday will depend on how much rain we see fall.
Probabilities: The short-range HRRR model is showing 5 to 7 inches of snow accumulation for most of Scott County through daybreak tomorrow. It should be noted that this is the only major model that is showing such heavy accumulations; most others show lighter accumulations, generally in the range of 2 to 3 inches. But the NWS feels confident that we’ll see heavier snow amounts verify. Temperatures are going to be extremely borderline throughout the atmosphere. It’s not an impossibility that we could go to bed expecting heavy snow and wake up to a whole lot of rain. But, for now at least, it appears that temperatures will be cold enough to support snow through much of the night. With that said, 4 to 6 inches of snow seems a little pessimistic (or optimistic, if you’re actually still wanting snow at this point) — but it’s not outside the realm of possibility, either.
Progression: The cold air mass that is in place is still expected to erode from the top down. That’s why we’ll likely see precipitation begin as snow, then change to sleet before finally changing to rain. At some point, perhaps towards or just after daybreak Thursday morning, it’s a possibility that folks in the Robbins-Elgin area are watching it rain while folks in the Oneida-Winfield area are still being pummeled by snow. The HRRR model currently has all of Scott County but the northern extremes above freezing by 7 a.m. tomorrow. At some point during the morning hours, snow and sleet will give way to rain. There may initially be some freezing rain if temperatures are below freezing at the surface, but a change to just plain rain will follow relatively quickly. Rain will then be the primary precipitation form through much of the day on Thursday, before changing back to snow as colder temperatures return Thursday night.
What about additional accumulation? Some light accumulations of snow are possible Thursday night, but precipitation amounts are expected to be light.
Aftermath: Very cold temperatures return in the immediate aftermath of the storm, similar to what we saw with the winter storm just past. Our high on Friday likely will not reach the freezing mark, and we should be in the teens both Friday morning and especially Saturday morning. We’ll return to the 40s on Sunday.
Need reason to keep hope alive? Temperatures look very warm the last few days of February. That’s still a little ways away, but we could see widespread temperatures in the upper 50s or even into the 60s the last few days of the month. Hold on to hope; spring is coming (eventually).
The bottom line: This is a very complex winter storm that is going to be problematic for weather forecasters, simply because the northern Cumberland Plateau region is right in the middle of the battle between the arctic air mass to our west and the subtropical ridge to our east. Temperatures are borderline, and multiple precipitation types are expected. That makes it difficult to accurately forecast accumulations, and if we’re being completely honest there is high bust potential with this storm — for better or worse. But expect road conditions to be in rough shape overnight tonight, before beginning to improve on Thursday. The forecast and expectations should become more finely tuned through the day today.