Updates Below (most recent 5:00pm)
Sunday SUNDAY Sunday!
We've been talking about the storm possibilities regarding this event for a while now, and now the time has come. Though the entire area will be seeing temperatures that are well below normal, particularly in the afternoon, the good news is that the storm will primarily be most threatening for areas to our east. Here's the lates breakdown of the storm's development and evolution from HPC (a division of the National Weather Service):
|HPC - Weather Depiction - Sunday AM through Monday AM|
One thing you should be doing when following along with a forecast projection like this, is to verify it against the radar maps and observations that will be coming in (the storm tracking maps below are a good place to start). Our main storm system will be strengthening across the Carolinas and then curl around the Delmarva peninsula and back inland over New Jersey, eventually settling for several hours over Pennsylvania before getting launched northward again into Canada. Its rapid development will be able to pack a punch in several different dimensions, including flooding in New England (where they too haven't had any appreciable rain in weeks), gusty winds across the whole area, and yes snow in late April for the corridor east of I-79-- about 30 miles or so east especially. However, for spots closer and west of the Big Sandy river, not much more than a few chilly sprinkles will be seen. 'Tis a good thing to avoid this storm if you ask me.
But since so much of the region won't, let's talk about it some more. First off, here are the anticipated precipitation forecasts (liquid-equivalent as well, including melted down snow):
|HAS Precipitation Forecast||HPC Precipitation Forecast|
Note the sharp cut-off in precipitation west of I-79. If you live in the river-cities area and were hoping for snow, this isn't going to be anything for you. Another bit of good news: We won't be threatened by any freeze conditions either. With skies breezy and cloudy overnight low temperatures will continue to be stirred up. Expect lows in the mid/upper 30s and highs struggling to get back to 50 (much more below normal maximum temperatures than the morning lows). The real danger comes in for those mountain counties, particularly up by Canaan Valley where, because of the deep moisture and expected heavy wet snow, temperatures will not much above Freezing from later tonight through Monday. Now, in those locations a killing freeze for the plants still may not happen because any fallen snow will insulate the plants from the real chill.
A Dangerous Heavy Wet Snow For The Mountains!
Travel is NOT recommended above 2000-feet in the mountains east of I-79 when it comes to early Monday-- possibly including the morning commute. The computer models are having a real difficult time handling the consistency of the snow that will fall-- but so far aren't having difficulty with the idea that this is going to be a big event considering the time of year it will be happening. Check out the progression of modeled snowfall from one model run to the next:
|NAM - Snowfall Forecast Creep|
The last image is the rendition of snowfall from the most recent model run. So you can see from the first iteration until now the successive model runs have only confirmed greater and greater snowfall totals for the mountains, and the trend has always gone in the same direction. Usually in a situation like this, any inconsistency or deviation is a red flag worth jumping on (because frankly, huge snow events are the exception, no matter how much snowbirds out there wish it were otherwise).
Now, when I make snowfall forecasts, I typically examine a bunch of different parameters at different levels of the atmosphere, viewed through a few different models, etc. etc. One of the things I'm utterly struck by is how much snow my usual ways of analyzing the weather are trying to spit back out at me.
Here's a table of what I'm seeing from the recent model runs:
|City||NAM - Snowfall||GFS - Snowfall|
It looks like the NAM model (normally one of my favorites this close to game-time) has gone on TILT. Personally, I would throw in some caveats into this equation that help adjust the snowfall totals. First I'm saying that the snow does not stick anywhere under around 2000-feet (sorry Charleston). Next, I'd say that the ground temperatures are uber-warm owing to the unseasonable warmth from the past several weeks. This will add a component of melting that will work against the sticking even as the snow falls. Think about it like pouring water into a leaky bucket. This can significantly knock down snowfall totals (though can still be dicey on elevated surfaces like leafy tree branches and highway overpasses). Another thing I can do is simply take the lowest value of the various data points I get of the cities for which I forecast. Anyway, after a bunch of tinkering, here's what I've got for a snowfall forecast:
|Snowfall Forecast - Sunday Night - Monday Night|
The snowfall that will be happening tonight and Monday along US-219 is going to be a big deal I fear. Even 6-12" can cause extensive issues with power outages, fallen trees, and the like (as folks in southeastern Kentucky can attest from a storm of a much smaller magnitude earlier this year). The peak of the storm for the WV mountains will be early in the day on Monday, so be very careful on the roadways-- or simply stay put. On the one hand, I would not be surprised at all to see even greater snowfall totals in places like Canaan Valley-- after all, the models are trying to call for it, and if this were the actual winter I may be going 12"-24"+ with this system up there. But, on the other hand this snow event is going to be fighting the constant melting influence at the ground from the warm soil temperatures. At times you may see the snow melting on the ground even as it continues to snow because it may not be snowing fast enough to make a difference.
Updates are definitely happening today. Feel free to check back often to see how things are going, and if you or folks you know are in the WV mountains, feel free to give us all a heads-up as to how the storm is going for that area. The rest of us will be sitting back to the west and watching intently.
The week ahead gets a little easier, but not by much. Most of my brain-space (and blog space) is going to occupied by today's storm, so we'll have to get to that a little later, but suffice it to say that it appears our 'needing rain' thing may be much more satisfied by the end of next week.
---Wonky Weather-Geeky Storm Tangent---
(skip to the tracker maps and updates below if uninterested)
This storm has eerie similarities to another very powerful storm system that hit our area a long time back. Before I get to it, I wanted to discuss the reasons why this storm is going to be able to curl back inland as opposed to continuing with some eastward component of movement. It is only seen in the strongest of large-scale storm systems.
Typically what happens, because of the rotation of the Earth, most base-level influencers of storm system movement direct things from west to east. Even in a particularly stormy pattern, there's usually at least some component of movement in an eastward direction:
|Normal Flow||Stormy Flow||Unusual Flow|
Notice how in the "unusual flow" the steering currents (jet stream) actually goes a little westward for a bit. This is called a "retrograde" because it is going against the grain of the normal way of things. One of the things you can do to see if such a condition occurs is to pick out a line of longitude (oriented north-to-south on a map). If the jet stream crosses that line, and then drifts back across it again later on in its path, then you have yourselves what we meteorologists call a "negative tilt" scenario-- one that bears extra concern.
This is precisely what's going on here with our present storm as well. You might find yourself asking: "How does such a weird weather situation occur?" Well, the answer lies in the weather currently happening directly overhead the tri-state area (and not the Carolina coast).
It is the weather in the upper-levels of the atmosphere that drive the conditions at the surface for large-scale weather systems (called "mid-latitude cyclones" in meteorology). We've talked about this before in terms of the rotational spin in the atmosphere known as vorticity, but the movement of warm and cold air aloft also means a lot. Take a look at what is happening with our current storm evolution:
|GFS - Upper Air / Surface|
On the left you can see how the upper air development of this storm is taking shape, while the maps on the right depict what's going on at the surface. In meteorology and forecasting, a proper understanding of the weather dynamics at all altitude levels is critical, particularly in a situation like this. On the first image of the animation, there is a slight kink or wiggle in the solid black lines indicating air flow. Right along with it, there's a darker red bulls-eye riding along it. This is what is known as a 'short-wave'. It's a spike in vorticity, and it will help drive down colder air from the north directly into the mid-western and Ohio valley states. Notice how this red bulls-eye gets even stronger as it amplifies the dip in the black lines on the left-hand map. This is what's known as a feedback mechanism, where multiple things that occur simultaneously are actually helping to enhance one another. In fact, eventually the cold air plunge gets so deep and fast that it becomes 'cut off' from whence it came (notice the solid black circles on the last few images). When this happens, a storm system is no longer directly controlled by the overall jet stream, because it's carved out its own niche. Okay, over to the more familiar surface map on the right. The storm is certainly going to be developing and strengthening quickly because of the available storm energy of the open waters of the Gulf of Mexico and Atlantic Ocean, but will also benefit from the contrast generated by the colder air aloft that is rapidly diving in. This sets up an engine of sorts that enhances further strengthening. The other thing that happens though is that when the main lobe of vorticity on the left-hand map fully rotates around the base of the curve created by the solid black lines, it forces the low pressure center at the surface to be drawn westward and closer to all that action. In extreme cases, the storm system at the surface will actually do a loop-de-loop in place (or simply appear to stall), as the incredibly strong upper-air dynamics dominate and over-ride any influences at the surface. So when you look up in the sky today, just think it's part of our own weather overhead that is responsible for all that's happening to our east-- and we won't feel any of it at the surface.
This particular storm actually has many parallels of another, even more powerful storm system that impacted the region more than 60 years ago. Ironically enough, it also occurred well out of season-- but in the other direction. I encourage you to look at the Great Thanksgiving Blizzard of 1950 and how that storm developed, because you will see many similarities. The Thanksgiving storm was oriented farther west and basically slammed us directly with 2 - 4 FEET of snow and temperatures as low as the single digits! This one won't be as bad, but is another reason why I won't be surprised at all to see any of a whole range of headlines that come from this one. Oh, and by the way, back in 1950, they still had the OSU - Michigan game despite the blizzard. Check it out.
By the way, I realize this is Earth Day today as well...and I had a post ready to go about it. Unfortunately, that content will have to wait until things quiet down a bit. I'm in storm mode for the time being.
Update 9:00am - New model runs are out, and they depict a little saner snowfall outlook for the higher elevations, getting closer to my own snowfall forecast. For example, this is the same table as earlier in the blog, but updated for the new model runs:
|City||NAM - Snowfall||GFS - Snowfall|
That's a good chunk off the top for Elkins and Davis, so that's good to see. I also noticed the GFS model is going the wrong way for Charleston, actually trying to give it a little more snow than the last run... I'm still thinking Charleston won't get any, or if there are flakes in the air, they won't last long on the ground because of the soil temperatures that the models do not take into account when assessing snowfall accumulations.
Update 3:00pm - The National Weather Service office in Charleston, in coordination with the other regional offices up and down the line, have upgraded the mountain counties to Winter Storm WARNINGs in anticipation of the overnight through Monday snows. You can see the local warnings below (note: Nicholas county in our viewing area is under a Winter Weather Advisory). Here's what it looks like in a regional sense for those who are traveling or have interests to the northeast:
|NWS - Watches/Warnings (as of 3:00pm)|
Folks who are living or traveling above 2000-feet along and east of US-19 and I-79, particularly along US-219-- be careful. The storm may be pretty fierce Monday morning. Give yourself plenty of time for that AM commute, or perhaps consider staying home if you can.
Update 5:00pm - Another set of model runs. In tinkering with the data, this is what I see them spitting out as their anticipated snowfall totals:
|City||NAM - Snowfall||GFS - Snowfall|
A couple things I see here: (1) I'm pleased with the way the numbers are coming down now in Charleston, though I suspect them to eventually be at zero by the time we're done with it. As stated before, the models are not taking into account any melting factors that are non-atmospheric (like a warm wet ground); (2) I'm a little concerned that the NAM model is actually bumping up numbers in Elkins and Davis, because that's the model that has the best ground resolution that can get at more nuances in topography that make for a better solution. Either it's missing something, or I'm missing something, you know? The GFS is typically not as great at snowfall prediction this close to game-time and in varied terrain (because it's resolution of the topography is not as fine, tending to smooth out peaks and valleys a little bit). However, like I said before, a little hint/trick I often use is tilting toward either model that produces the lowest output of snowfall anyway-- because there are always factors like compaction, melting, and sublimation that the models don't/can't resolve. I guess we'll see how it goes. My forecast from earlier on still looks good so far.
Here are your maps:
|Regional Radar/Satellite with Warnings Tracking||
|Temperatures||HD Doppler Radar||Estimated Rainfall||Active Warnings|
|Click For Larger||Click For Interactive Radar||Click For Larger||Click For Larger|
Have a great day everyone!
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