Update (10:30am) - The changeover has made it all the way up toward the I-64 Corridor, but it was impressive that the hair-line between this ice and accumulating snow held on so long this morning. An adjustment of even lingering an extra hour meant an extra inch of snow in this environment. In total, it looks like the Huntington area came out with about 3" of snow before the change. Even though a lot of this will slush out in the rain to follow, the roads remain extremely dangerous with the compacted slush not giving traction. The narrow band of good snows ended up 10-20 miles farther south than I had anticipated yesterday-- in fact it would appear the Huntington area got one of the better accumulations it's seen in the last 2 winters (which isn't saying much for the past couple of snow seasons, but still...)
Until you can actually see bare road, you will have to exercise caution and expect the road to be unforgiving to your tires. Give lots of stopping distance.
Flood Watches, Winter Weather Advisories, and Winter Storm Warnings appear once again across much of our area. Check below on the watch/warnings map to see how things have been updated.
HPC - Surface Map - Sunday Morning
The actual synoptics of this next storm don't look too impressive-- except to say that the high pressure systems at work are pretty good. But, a 1020mb "low" isn't that low. In fact, most other cases that sort of pressure reading would be a center of high pressure. You certainly can still get an impactful system out of this, but it would be unusual. So then, we've got the moist inflow still coming right up the Appalachian Trail, and the warm air with it. When it gets here, there's a lot of cold air already waiting. Cold air is more dense than warm air, so it sticks around at the lower levels of the atmosphere, allowing the warm air to rush right up and over it. Precipitation would then initially start as snow, melt in the warm air as it falls toward the surface, then once more ice up as it hits the sub-freezing ground. At least, that's the textbook profile for an ice storm.
Here's the thermal profile for the atmosphere (from the GFS) Sunday morning:
In this particular example, the cloud heights are a little above 15,000 feet, and it is well below freezing there. Snow develops and begins to precipitate. At the 5,000ft mark it is about +3 Celsius, and it would then be raining. However, closer to the surface there's an inversion covering the bottom 2,000 feet of the atmosphere. This wouldn't be thick enough to freeze the raindrops as they are falling pretty fast. But, it would be cooling all the objects on the ground such that when these rain drops hit those objects, they freeze on contact. This is essentially how "freezing rain" exists, and why it can keep accumulating as ice on the ground. Now, the question becomes, "how much are we talking..?", as that's the difference between a hardly noticeable annoyance and an power-outage type ice storm.
There is a pretty good agreement that we'll first see some snow, followed by a measure of ice, before going to straight rain. The warn air will have less trouble penetrating up through Corridor-G and I-79, so there will be the lesser threat for ice/snow (but more for continuing the high water problems). It takes about 0.1" of ice coating to cause slick travel roads and all that, and at 0.25"+ there's a serious threat for power outages and breaking limbs. Winter Storm Warnings are up for the eastern mountain valleys of WV east of Charleston for that very possibility. Back toward the River Cities area this looks like less of a threat. Notice the holes in the precipitation showing up on the left-hand map above off the NAM. This reflects a downsloping wind-flow that can dry the air out. The GFS is coming in wetter than the NAM, but I'm edging toward the NAM (as is the National Weather Service on the right-hand map).
Be very careful traveling early Sunday morning because of the ice, no matter how much you see. Most places along and north of I-64 will see a coating or so of snow before the sleet/ice arrives. Farther to the north and west the cold air hangs around longer as you are on the outer stretch of the storm. Folks in Ohio that got 2"+ of snow in Friday's event can look for another 1-2" this time as well, but still watch for icing ontop of that. You might want to shelve the travel idea entirely if you are heading through the eastern WV mountain valleys, as they can approach those power-outage type ice accumulation amounts.
Outside of the WV mountains to the east, and the colder air locations to the far north and west, most of us will end up transitioning to rain. It's going to stay rainy until finishing (again) as some snow on early Tuesday. The total amount of rain isn't as crazy as the last event, but since water is already high everywhere we can expect those kinds of problems to just continue unfortunately (hence the Flood Watches again).
HPC - Total Precipitation - Through Tuesday
It could be worse... but it's already bad enough... Rivers will be running high for several days after this series of storms.
Have a great day everyone!