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Central PA/fringes of MD - December 2013 continued


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Things could get pretty interesting later this afternoon into the evening as the nose of a 250 mb jest streak approaches southern PA, putting much of the region in the left exit region. This could place areas in central PA in the rising branch of a frontogenetic circulation. The 850 mb low and 700 mb trough over Ohio may bring in some relative unstable, moist air into the region at the same time. This may increase the potential for some banding and possible some CSI. The 12z NAM actually has an unstable layer near 650 mb at this time so straight up elevated convection is a possibility.

 

post-869-0-38499300-1387035655_thumb.png

 

You can see that the 06z GFS brings in a tongue of moist, lower stability air, which poleward of a westerly jet would favor mid-level -EPV values. The question is where exactly does this area of -EPV and frontogenesis set up. Right now it seems to be along a track to the southeast of UNV based on the 06z GFS. The 12z NAM brings it a bit further north.

 

post-869-0-03750900-1387036070_thumb.png

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Given how light the echoes are on radar, I'm pleasantly surprised that this snow is accumulating. Seems we've got about 1/2" here over the past two hours.

Yeah it's pretty nice snow given the radar. Less than one mile vis. For people worrying about how things look now, I don't believe this period was ever suppose to be that impressive. If you're getting 8", you might get 2-3" in these first 6 hours and the rest in a couple of hours near the end.

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Yeah it's pretty nice snow given the radar. Less than one mile vis. For people worrying about how things look now, I don't believe this period was ever suppose to be that impressive. If you're getting 8", you might get 2-3" in these first 6 hours and the rest in a couple of hours near the end.

 

Exactly. It's all about the stuff that's over southern Indiana, southwest Ohio, and northern Kentucky right now.

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I have yet to see thundersnow. I was asleep the only time it ever happened where I lived (in Seattle during a Puget Sound Convergence Zone snow squall)

 

I distinctly remember hearing it in March '09 and I think one other time, back in N. GA. It's neat, and really freaks out people (and dogs!).

 

Snow might have lightened a bit here, but still gradually accumulating. 

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In Greencastle? I can tell you that temps and rates just east of you in Waynesboro are not good. Nothing is sticking, and temps at my house are at 33.4F. That would be odd considering weather usually isn't much different between those two locations.

 

Is there a heater on there or something? lol Just about 2" here. 

 

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I'm not that confident we'll have thundersnow. The dynamics for this event are pretty good but they are not extreme like those you would see with strong cyclogenesis. I guess it's a possiblity. Keep an eye out for graupel though, which indicates the potential for charge separation within the cloud.

 

It's definitely a cool thing to experience; I've seen it several times with lake-effect.

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I'm not that confident we'll have thundersnow. The dynamics for this event are pretty good but they are not extreme like those you would see with strong cyclogenesis. I guess it's a possiblity. Keep an eye out for graupel though, which indicates the potential for charge separation within the cloud.

 

It's definitely a cool thing to experience; I've seen it several times with lake-effect.

March 2011 was amazing - that storm went rain to sleet to very heavy snow - got 4-5" in 3 hours, with the thundersnow hitting as soon as it flipped to all snow.

 

That was back at home - and I also distinctly remember the HRRR nailing that band.

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I'm not that confident we'll have thundersnow. The dynamics for this event are pretty good but they are not extreme like those you would see with strong cyclogenesis. I guess it's a possiblity. Keep an eye out for graupel though, which indicates the potential for charge separation within the cloud.

 

It's definitely a cool thing to experience; I've seen it several times with lake-effect.

That's what I saw this am. Graupel mixed with the flakes.

 

First time I've seen it is Blizzard of 83, then during an intense cold frontal passage in like 84 or 85, then during the Superstorm. Also saw it during the early Jan 1994 storm. I also have seen it several times with frontal passages. The most amazing was in Jan 2003, half hour that looked like blizzard crossed with a severe t-storm. Mallow should have seen that.

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