Update - Another messy storm hits the region

A very complicated weather picture with rain, sleet, ice, and snow for parts of the area. Be very careful on the roads indicated below.

Updates Below (most recent - 10:00am)

Merry Christmas!

I'll be back in tomorrow, but the blog doesn't stop... Another big headline-making storm cutting across the Ohio Valley headed for New England. This one is going to get a little messy for our area, so I'll try to make this post as least complicated as possible (I know, "good luck", right?)

1. This system is not a big snow-maker for us - The dynamics with this storm are calling for a large influx of warm air aloft, despite temperatures closer to freezing at the surface. This is going to cause problems in its own right, but it will be cutting down on anticipated snowfall.

2. Icing is the biggest threat - This is more for travelers heading north toward US-50 and farther northward (as well as US-219). Icing is almost guaranteed to occur for at least some of the time, and no one likes this.

3. It's best to be in the annoying chilly rain category, and most of us will get this - A silver lining that the snow-lovers may not appreciate a whole lot. The I-64 corridor will be too warm at all levels for anything besides rain. Road conditions ironically may be the best where the moisture is falling the hardest. (the least of all the evils anyway).

So let's get to the goods...

First up is the larger weather picture.

HPC - Surface Map - Wednesday Morning

Yes, what a mess...but it's a GREAT example of a jack-of-all-threats storm system for the tri-state, even if not all of us will see every part. I've drawn in a few arrows to help sort this out: The green arrow represents the moisture influx of warm, moist air that will be riding up and over the warm front into our region direct from the Atlantic and Gulf of Mexico; the dark blue arrow represents the cold air return behind the low-pressure system that wraps around the back end and transitions everyone to snow... This won't be coming to our area until the last stage; the light blue arrow is the key-- it represents a slow seepage of cold air that sticks to the valley floors and will become very difficult to scour out. Remaining there when the storm arrives, it will be the reason for an actual ICE STORM. Let's talk about this for a second (skip over it if you're uninterested).

-----<Tangent> ingredients for an ice storm, "Cold-Air-Damming" style-----

As we all know, temperature is not the same over the same spot on the ground as you go up in altitude. Most of the time, temperature decreases with height as any hiker (or mountaineer) will tell you. Identifying precipitation type, therefore, can usually be a simple thing. If it's below 32°F, we're talking snow, above that it's rain.

The fun thing for meteorologists (and probably only meteorologists) is that it can get a lot more complicated than that.

What if we had temperatures at the surface that were below freezing, but aloft instead of cooling with altitude we get a shot of much warmer air nosing in. Kind of like this:

If we've got a good shot of warm air coming in, it can interrupt the normal way of things. Falling snow would melt in this warm layer, and then re-freeze once it hits the surface. It looks like rain when it you are out in it, as the there's not enough cold air to refreeze the raindrops into an ice pellet. However, just like when you lick the spoon that contains some cold yummy ice cream any water droplets (or saliva) that are around will freeze instantly, and stick to whatever surface it hits, be it a spoon or a power-line.

The over-running air of a warm front is sufficient to cause this sort of scenario, but usually that is a more temporary deal as the fronts always progress forward. What we need is a persistent scenario in order to get a real storm of ice. The temperature profile is similar to the above, but it's called "Cold Air Damming". I'll try to draw this out too :-)

...So the warm air will be flying in, keeping everything rain on the western side of the slopes (and the peaks too), but in the valleys on the opposite side the cold air will still be 'dammed' in, with no real good way of scouring it out. This puts us in that precarious situation where freezing rain will come with temperatures in the 20s at the surface, despite temperatures closer to the 40s aloft. The biggest hazard spots for this will be Canaan Valley through to the Tygart River valley and on down into the Greenbrier valley. A good marker will be if your car thermometer dips below 30, it will be very dangerous driving, especially on the bridges and overpasses.

-----</end Tangent>-----

The good news for most of us is that we'll just be seeing a cold rain-- and trust me, this is way better than seeing any icing. At first, however, some folks may get some light snow or freezing drizzle as the initial push of moisture and warmth interacts with departing cold air in sections of interior Ohio and West Virginia.

Hi-Res NAM - Wednesday Morning

The boundary line will most likely be set up around US-Route-50. This area will have cold enough temperatures to start off as a little light snow and/or freezing drizzle before warmer air overwhelms. However, unfortunately this is timed with the AM Commute so be very careful in these areas. Anyone traveling farther north than this line, expect to encounter snow for a longer period of time, and a half-foot of snow can easily fall from Columbus to Canton to Pittsburgh. Notice the valleys east of the mountains are going to be in this nasty icy scenario, perhaps even starting off as a little bit of snow. As the deeper moisture moves in, that's where the danger gets elevated there.

Hi-Res NAM - Wednesday Afternoon

The temperature profile doesn't change much, except to just about push everyone locally into the rain category. Travelers should still beware north of US-50, and along I-68 and US-219. Cold air will still be trapped, so ice will be the order of the day given the warmer air aloft.

During this same time, a transition of storm energy to the coast will be taking shape. This is a common sight with northeastward moving systems once they hit the Appalachian mountains, but it will be more magnified this year due to the above-normal water temperatures in the Altantic (something we discussed in our winter weather preview). This will do two things: (1) It will speed in the arrival of cold air, but (2) speed the removal of moisture from overhead.

Hi-Res NAM - Thursday Morning

The cold air arrives, but the moisture is leaving (seen that movie before). We'll be left with just the up-slope snow event, the kind mainly for the WV mountains. The wind-flow will be off Lake Erie, with not much of a contribution from Lake Michigan. Temperatures won't get out of the middle 30s at best, and generally everyone will be in for a blustery day. The new storm track of this transitioned low will take it along the southern New England coast, making for an inland snowstorm for ski country and rain for the populated areas along I-95.

Overall Danger Zones - The places to worry about the most would be US-219 in the WV mountains, as they will see an ice storm. I actually like the GFS representation of the ice-event a little more as it keeps the moisture intact longer, but the Hi-Res NAM has a better surface resolution of the temperature spread. Simply color in more precipitation intensity on the Wednesday and that should cover it. Secondary worries will be the morning commute weather in places where freezing rain and light snow can fall. This would be Ohio and sections of WV north of I-64. This is especially true along US-50 and points north. The next worry will be the transition to the upslope snowfall event early Thursday. This should be a manageable thing for the River-Cities area, as most of the moisture will be farther east. The WV mountains from Beckley to Summersville and up through to Canaan Valley will again be under the gun for some fresh powder. This makes I-64 at Beckley and I-68 again a trouble spot Thursday.

Expected Snowfall - Since our area for the most part will be seeing rain, I'll just put up the model rendered snowfall forecasts and then comment on them.

GFS - Projected Snowfall NAM - Projected Snowfall

A blend of the two would be good, but remember that a projected snowfall map completely masks all the threats with the icing. In parts of Randolph, Tucker, Preston, Garrett, Pocahontas, and Greenbrier counties we could see ice come in greater than 0.25" thick. It may not sound like a lot, but that's the threshold for power outages.

Note the sharp gradient in snowfall amounts in interior Ohio and PA. According to the NAM, Chillicothe, OH will be barely scraping 1", but by Columbus nearly a foot of snow will fall. I do like the gradient idea, but perhaps not to that extreme. Regardless, expect some drastically worstening conditions north of Jackson, OH tomorrow as the cold air will be more persistent there (the storm track passes well southeast of that area). We still have that time-honored notorious "donut hole" of little to no snow in the River-Cities area, and whatever we do see there will be on the back-side of this storm Wednesday night into Thursday morning. Once again the Beckley-to-Canaan corridor will shovel the most snow on Thursday after dealing with that cold rain / ice scenario the day before. Overall, it won't be as snowy as the last event, but expect to have to plow/shovel.

Updates will be posted below as needed. Please feel free to ask questions and post storm reports in the discussion space below. The tracking maps will be updating as well, featuring NWS warnings and advisories, as well as an interactive radar. If you are having problems interacting with the content of this blog, either post about it in the discussion below, or email me at brandon.butcher@wsaz.com .

Be Safe! :-)

Update (7:30am) - The snow is flying from Columbus toward Pittsburgh, primarily along a line north of I-70. Just to the south of there, icing is creeping in. In the tracking maps below, there's a discussion about this from the Storm Prediction Center. Even if you started out with a chilly rain, icing is still possible. The radars below are also indicating the transition to secondary development on the other side of the Appalachian Mountains. There's a break between the two, right along and east of I-75 in Kentucky. Despite spending the day primarily in the rain category, sections of Kentucky should be on their toes later in the day as the colder air swings in from the west. Rain will change back to snow, and can make for quickly slickening roads later today. This same threat exists for sections of Ohio and WV at night.

Overall accumulations are not looking significant, still tracking at a coating to an inch or so in KY and the River-Cities area, with a little more than that on any ridgetop (starting this evening). Elevated areas along Corridor-G and I-79 can see 1-3", and the WV mountains 2-4"+. As is typical with these systems, you'll have to be on a ridge that can take advantage of upslope conditions from Lake Erie to get the higher accumulations.
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Update (10:00am) - Just as that dry slot has worked its way through the Huntington area, a few breaks in the clouds can be seen. Some of you may have been able to catch a peek of blue sky. It's only temporary. More moisture will be filling back in soon enough as the parent low works eastward. Even though the coastal redevelopment ramps up this afternoon, the remnant low that started it all still has some upper-level support and will continue to spin up rain and snow beneath it as it works eastward. You can follow this on the radars below.
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Regional Radar/Satellite with Warnings Tracking

Accuweather Radar

From the Storm Prediction Center (below): Click For a Larger Image

Activity Overview Storm Outlook Watches Potential Watches Storm Reports
Temperatures HD Doppler Radar Estimated Rainfall Active Warnings
Current Temperatures HD Doppler Radar Estimated Rainfall Active NWS Warnings
Click For Larger Click For Interactive Radar Click For Larger Click For Larger

Have a great day everyone!

-B

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