Winter Thunderstorm Ingredients

Due to my overwhelming interest and lack of school and research Im turning to the pros here on stormtrack to find out what It takes for Winter thunderstorms to fire off. Of course its no suprise that the Gulf Coast states and florida still get there fair share of thunderstorms due to proper daytime heating and the subtropical influence. But I find myself questioning what Fires off thunderstorms or better yet, Thundersnow when typically as far as I understand, the Ground is frozen, therefore lack of Surface heating or elimination of surface heating altogether. The last thundersnow episode that occured from MI to NY this last weekend put out frequent lightning and Im looking to find out what caused this disturbance. What were the main ingredients for this Event. The only thing I can think of that helped was a Southerly Subtropical Influence and the Northerly Clipper influence combining together and somehow bypassing the surface heating factor.

Thanks in advance for all feedback...

-gerrit
 
You need to move past the mis-understanding the ground needs to be "hot" to produce a thunderstorm. After all, it's hot in Phoenix every day but they don't get thunderstorms.

The ground just needs to be warmer than the air above it. To be more precise, it needs to be potentially warmer than the air above it since its almost always colder the higher up you go.

I'll let you go from there. Just think how warm the surface of Lake Ontario is compared to the air at 6000'.

Oh, and you need moisture and all that good stuff, but I'm not writing this paper for you.
 
Hey Bill thanks for the reply. I do understand the main ingredients needed for a Thunderstorm. Was mostly under the impression that Surface heating was a main factor (warm under cold air). It was hard to fathom that the freezing ground could be warm enough to create an unstable environment. I thought maybe there was something I was missing.

-gerrit
 
Since I did not recieve the reply I was looking for. Let me be specific.

My area of Southeastern Idaho for the last 3 years I lived here has not recieved a thunderstorm during winter. From my Understanding The ground has been too cold during Upper level Low storms, therefore not having an unstable environment. What baffles me is the Fact that Thundersnow occurs pretty often in the plains and near the great lakes. What I understand is that the last Thundersnow occured after a decent arctic air intrusion. This led me to believe the ground was frozen, but there was still enough warming to lead to an unstable air mass. As for forecast maps & models what do you look for to determine that the enviornment is unstable. Will the Lifted Index indicate this instability even tho the Ground is frozen?

thanks..
 
First of all, the actual ground temperature has very little to do with the amount of instability present; You need to look at a deeper mixed layer.

Thundersnow is usually the result of mid level conditional instability, not the convective instability typically found when the boundary layer is a lot warmer / moister than the air above it. Lake effect snow is an exception - that's convective instability. You have 45F temperatures over the lake with extremely cold air a short distance above it. That can create lake induced CAPE in excess of 1500J/KG, which is sufficient for lightning.

There is no single parameter to determine thundersnow. You really need to analyze cross sections, thete-e patterns, vertical lift, and other parameters. Outside of the lake effect snowbelts or other areas with significant topographical influences, thundersnow is very rare.
 
Thundersnow is a fairly uncommon event, and I'd say its very rare in the plains. Much more common in a nor'easter than in the plains. Its a little confusing because you are talking about thunderstorms and thundersnow. While they both produce thunder, they are different.

Everytime I have seen thundersnow has been at night, so daytime heating isn't an issue. Several times in rapidly developing nor'easters. Intense synoptic scale lift coupled with orographics and convergence, but still nothing on the scale of lift generated in a summer thunderstorm.

The other time I saw thundersnow was again at night in Salt Lake City. That was a synoptic scale event with major lake enhancement.

Soundings might be good to look at. Yes, the lifted index still works if the ground is frozen, but I'm not sure its going to help. The LI might not be significant as thundersnow tends to be shallow, and by 500mb you're completely above the storm.
 
The best place in a synoptic storm to find thundersnow is usually within the comma head under a TROWAL, or in extreme cases you will have traditional thunderstorms fire up along a cold front and they will be advected along the front and into the comma head region maintaining themselves with the presence of a strong low level jet. This in many ways is similar to the TROWAL, another location where thundersnow is sometimes found can be the triple point, there is usually a good deal of mixing and forcing in their region which may assists in the development of convection.

Upslope snows also produce thunder sometimes depending on the temperature and moisture levels in the air being forced up along the mountain.

One of the key elements for thundersnow I would argue is the presence or existence of graupel. It is generally accepted that lightning becomes possible once the cloud top temperatures reach -30C or below, after that point you can be assured the upper portion of the storm is entirely glaciated and there is no liquid water present. Graupel which falls through the storm from the upper portions into the mid portions help to maintain a small temperature difference in the storm and it is theorized it also helps to separate or somehow carry the potential energy building up a charge in the storm cell or a portion of the cloud.

This site explains it properly here
http://www.met.tamu.edu/class/Metr304/Severedir/LightningDir/lightning-stu.html

Some other good links,
http://www.wrh.noaa.gov/wrh/02TAs/0213/index.html
http://www.crh.noaa.gov/lsx/science/pdfppt/thun_prox_soundings.ppt
http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0434(2002)017%3C1290:ACOTEO%3E2.0.CO%3B2
 
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