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Update - Frankenstorm's Dangerous Local Impacts

Hurricane Sandy combines with an arctic cold front resulting in heavy rains, snows, and winds, producing multiple threats. First call accumulation maps presented.

Updated! (see below)

Welcome to your Sunday morning, and we're still doing fine.

Some of you, however, need to start preparing today for storm arrival soon...

This blog post is an update to the previous blog post on the so-named "Frankenstorm" and its impacts. Here, we're only going to talk about the tri-state area.

What I first want to do, is put out there where the models are indicating the storm will end up being at it's peak impact time locally, together with its forecast storm track. I did this in the last blog post, so feel free to go back and reference that one as well for track changes.

NAM - Tuesday AM GFS - Tuesday AM ECMWF - Tuesday AM

There are several points of relative consensus now:

  • Hurricane Sandy will continue to curl around the outer banks of North Carolina (staying well out to sea), but then take a hard left into southern New Jersey as the polar vortex to the west captures it. (This is closest to the NAM representation yesterday).
  • All three models now have the storm staying along/south of the Pennsylvania Turnpike, and halting its westward progression over the mountains of SW PA/Western MD (Similar to yesterday's Euro Model)
  • The peak intensity of our local impacts will be felt Tuesday, as the storm spends nearly the whole day in a tight loop-de-loop pattern before lifting northward Wednesday.

When it comes to a storm of this magnitude, the warm air and cold air wrap all the way around the low such that they are on opposite sides of where they typically reside. I showed this graphic a few days ago:

Normal Storm System Crazy Storm System

To take this a step further, with specific relevance to this system, I'd like to indicate where the best snow potential is, and what can happen with even a slight jog of the storm from one side to the other:

Precipitation Map

I want you to think of this map as if the land didn't exist, and it was just what was going on in the air. You should be able to tell that as this system moves around (and in our case wobbles), some folks could go from heavy snow to instead heavy rain, and then back again. Also, note that the heavy rain will be able to curl around the low pressure center itself, while the ribbon of snow will be offset to the south and west. The heaviest snow will show up where the winds transition (and twist) from the NW to the SW.

For our specific situation, however, the mountains will also play a role. Naturally, they will enhance snow (or rain) that falls by them, plus they will edge the precipitation type toward the snow category at elevation.

Now...if the models are to be believed, this will be a record-shattering storm for West Virginia as it comes to October. I believe this will be a record-breaking storm for October, but I disagree with some of the model's expectations.

In full disclosure, here's what the models are saying...

"Frankenstorm" - Projected Snowfall

This would be an absolutely CRIPPLING situation... With the leaves still on the trees all throughout the lowlands, anything over 5" or so will bring down trees and powerlines on a large scale-- just think of what a foot of snow would do. The mountains would be in equally deep trouble even with leaves coming off the trees. It would take a while for folks to dig out of that mess, and the snow will be weighty as well.

However, in my mind there are some things that the models do a poor job of, and in some respects just flat out don't account for...

  • Compaction - Snow does not just stay fluffed up nicely and gently on top of each other such that every flake projected to fall will add to the accumulation on the ground without disturbing the snowpack beneath it. In this situation, it is much more so with how wet the precipitation will be.
  • Melting - Everyone knows the Earth is full of geothermal energy, and basements can often be mild in the dead of winter. In our region, air temperatures have only once or twice even reached the freezing mark, with the 80s seen as recently as just a couple of days ago. The most recent reports of "soil temperatures" indicate readings near 60°(!) This has nothing to do with the physics of the atmosphere, so when the snow falls, it's got to deal with that warmth.
  • Precipitation Type Changes - These same models are projecting upwards of 2" (and more) of rainfall to accompany this snow, primarily on the book-ends of the best projected snowfall time-frame (Tuesday morning), but also at times mixed in with the snow itself. It's simply not going to happen that an inch of rain water is going to fit nicely ontop of (or beneath) a snowpack without any interaction between the two.

These are SERIOUS issues that must be unaccounted for when it comes to snowfall accumulations.

As far as the snow goes, it's going to come down to just two things:

  1. Storm Placement - As the earlier image describes, you're going to be looking a huge storm with an expansive moisture and wind field, but only in precise areas will the heaviest snows fall, and not far from regions of heavy rain mind you. Any jog to the south/west puts us out of the best cold air advection and back into the rain; any jogs to the north/west takes the best moisture away even if it does leave us in the cold air.
  2. Intensity (vertical velocity) - To get snow to fall down, air must go up. Wind travels in 3-dimensions, and the component that is lifted (however forced) is what will be contributing to stuffing moisture into the clouds and creating precipitation that the clouds can no longer hold. It's kind of like a factory. The reason why the intensity is so critical, is that the air temperatures may not go below freezing during the entire event for cities and towns that are not at elevation. Normally, this is certainly not very good for snowfall. But, when flakes fall fast enough, hard enough, you can get them to bring cold-enough air with them, and to keep each other cool as they stack up. [Think of it like tossing a cooler full of ice cubes onto the grass on a hot summer day-- they do not melt instantly]. The intensity must stay up, or else the flakes will succumb to above freezing temperatures and/or ground melting. In these situations it's possible to observe the snowpack on the ground melting even while it never stops snowing-- it's just that it stopped being intense enough to make the difference.

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So with that... here's my own assessment of where we stand on snowfall accumulations: Snow flakes will first start to fly in the highest elevations of the WV mountains overnight tonight. The sticking will begin early Monday out that way, particularly in the southern half of the mountains, at least until the cold air advection can wrap around northward far enough. Cold air will continue to feed into the area as the storm approaches, gradually able to mix in snowflakes, and where the intensity is strong enough, accumulate. The best opportunity for this to occur in the lowlands is Tuesday morning into Tuesday afternoon. This will be a dangerous time to be out on the roads where snow sticks. It will be heavy, or not at all. The good news is that this kind of snow is easy to plow if it comes to that. The bad news is that it's not something that sand can quickly handle. This is more like a slush-cake than a snow, occupying twice the normal water content of a normal snow (which could be thought further as 3-4 standard deviations beyond average). It's an open question as to whether or not there are enough plows to handle it.

BUT, the mitigating factors I described above will be strong... So if I'm to offer an accumulation map, this is what I'm thinking about:

Brandon's Forecast - "Frankenstorm" - Projected Snowfall

Please understand this is a very volatile situation, and for folks in the lower elevations of I-64, the first snowflakes may not even appear until almost 48 hours from now. It's still a very fluid thing, in which you should probably expect adjustments-- possibly to either direction. However, it is my estimation that there will be just too much to overcome, even for this incredible storm, to put down a considerable snowpack in our western areas, and I would not be surprised at all to see what falls melt very quickly as soon as this thing departs. Of course, it's also possible that we could end up with even more, but I would like to see some movement in the models on a few variables before I'd feel good about making that call. Also, even a 2" snowfall is going to be nasty for traffic. It's more like 2" of slush. The grassy surfaces, overpasses, and bridges will be vulnerable for more snow because the cold air flow underneath each surface provides insulation from an otherwise warm ground.

Dangerous impacts are possible closer to the Kanawha Valley, up I-79, and down through Corridor G (and points east)... Anything over about 5" or so of snow (especially this slop) will greatly stress leafy trees. I would be preparing for the possibility of power outages if your foliage is still thick and your in that 5"+ range.

Impacts will be felt worse at elevation-- the valleys dips and hollows in between the hills, even in the higher color contours, will not see as great of snow prospects (and therefore less severe threats).

Every place from Beckley up to Davis, WV (2500' elevation) should be preparing for a possible shut down. The number of lines down out that way could rival that of the June 29th derecho event, though structure damage is not going to be as much of an issue. Gas up the generator, and have more handy. The bulls-eyes for this event are in the Canaan Valley, Pickens, and Snowshoe areas of West Virginia. Those higher peaks face the expected wind flow just like they always do for lake-effect snows, and given their elevation they will get below freezing and keep the slop more fluffy. The only question mark is how close the low gets to Canaan... Too close, and you're rain, even up there. Imagine though, 5" of total precipitation, distributed in the mountains as rain and snow. Hence, the flood watches in effect for Preston and Tucker counties. The Cheat River will be swift.

As far as what the maximum snowfall accumulation amount will be..? It could be just about anything with a storm like this. There's enough moisture to crank out 50" of snow in the mountains, but I don't think that's going to happen. As a comparison, the 1950 Thanksgiving Blizzard put down 57" in Pickens as its highest-- but that storm featured a fluffy snow with temperatures in the single digits. Areas that get half that amount will actually see worse snow than that blizzard because of how weighty it will be. And, oh yes, blizzard conditions will be seen in the higher elevations-- winds around 30knots will exist for several hours of the day Tuesday.

I will probably update this post where/when I can today, particularly when the models come out again with new numbers. Also, I may get a companion piece that will set out a more blow-by-blow timeline of the storm.

As with the past posts, please comment/question/contribute in the comments section below. I will also get to as many of those as I can.

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Update (3:30pm) - The latest suite of models has fully come in, and I've taken a look at them to see how things have progressed/changed. So far, all of the near-term stuff is still going just fine-- Sandy is still going to take the hard turn into Jersey, and still going to be captured by the trough over the Great Lakes.

All of the models have shifted ever-so-slightly their positioning of the closest approach of our "Frankenstorm" low pressure center, placing it just a hair farther to the southwest. Directly over Garrett County, MD Tuesday Morning. Here's how that affects selected area's snowfall prospects as depicted by the models (the first snowfall graphic above):

Charleston - The NAM has been slowly dropping your accumulations, and stuffing them into a tighter time-frame, changing back to rain on the ends. It is still within the projected range on the map though. The snow is slated to happen Tuesday AM, and be accompanied by a total of more than 3" of rain by the time we're done. The GFS has increased its projections, and ticked it up to the high end of the range on the map. Furthermore, by tweaking the model output a little, an incredible 18" pops out between Monday night and Wednesday night. This one shocked me a little bit, because I had expected things to go the other way (like the NAM). I still like my numbers for the Charleston area (2"- 5"), but those who are particularly concerned about the prospects of power outages and all that are certainly within their rights in taking precautions.

Huntington - The NAM has backed off in projected amounts, and is now below the numbers on the above map. In addition, most of the opportunities for straight snow is confined to the first-half of the morning. The GFS is also down as well, and presenting the same shift in snowfall such that it ends by the first-half of the morning. This snow is accompanied by almost 2" of rain.

Other Areas - Numbers in Parkersburg are also down, and have reached 0"- 2", due to the shift of the storm permitting more warm air to advect its way from the east. Numbers in Eastern Kentucky are still holding up, matching what Huntington is showing now, though they drop off pretty good toward Jackson, KY. The line between Beckley and Davis, WV is still "Ground Zero", with lower bound numbers at 12" and high bounds at 22". The NAM and GFS disagree with the highest elevations though, with the NAM trying to spit out 38" - 48" of devastating snowpack from Snowshoe to Davis, but the GFS is picking up the encroachment of the low pressure center and wants to cut Davis down to a very sloppy 13" now. Nevertheless, this remains an extremely dangerous situation for elevations > 2000' along that line.

How This Affects My Numbers - I'm still holding onto my forecast map for now, though I'm favoring upping the numbers in the Kanawha hills around Charleston (and down through the coal fields for any place at or above 2000' or NW facing ridgetop). For example, I believe Mingo Central High School is at 2000'-ish. They may be in line for more than 5" if this present scene verifies. However, I'm not going there officially just yet. We're still more than 24-hours out. But, like I said, anyone looking at 5"+ of snow would be looking at solid power outage possibilities.

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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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