Convective Snow Showers

[leicsnow]

Since I joined this forum I've heard a lot about "convective snow showers" and how they can benefit us from mid-February onwards in particular. What's the deal with them and how does this theory work?

[Harve]

I believe it's simply convective activity in cool, polar-maritime airstreams. There's focus on showers rather than thunderstorms. It's one of my favourite weather types.

[Thundery wintry showers]

It's generally a reference to those "sunshine and snow showers" setups with towering cumulus and cumulonimbus clouds. During the winter quarter most convection is generated by cold airmasses flowing over the comparitively warm North Sea. In a north-westerly flow it is mainly western areas that see the showers, while in a northerly flow it tends to be north and east-facing coasts, and in a north-easterly or easterly we get showers heading inland off the North Sea. Once we get into late February, though, the sun becomes strong enough to generate homegrown convection as the lowest layer of the atmosphere is heated up, generating a strong thermal contrast between the surface and upper atmosphere. In unstable northerly types this can result in snow showers developing across inland areas. Into March solar heating is capable of generating heavy and thundery showers as some of us noted on the 19th March 2007 and during Easter 2008.

There is, though, a common view that snow in late winter and spring is "useless" because the stronger sunshine, while generating convection, also helps to raise the surface temperatures enough to initiate quick thaws, and a lack of understanding of the fact that some enjoy the "enhanced homegrown convection" aspect.

[leicsnow]

It's generally a reference to those "sunshine and snow showers" setups with towering cumulus and cumulonimbus clouds. During the winter quarter most convection is generated by cold airmasses flowing over the comparitively warm North Sea. In a north-westerly flow it is mainly western areas that see the showers, while in a northerly flow it tends to be north and east-facing coasts, and in a north-easterly or easterly we get showers heading inland off the North Sea. Once we get into late February, though, the sun becomes strong enough to generate homegrown convection as the lowest layer of the atmosphere is heated up, generating a strong thermal contrast between the surface and upper atmosphere. In unstable northerly types this can result in snow showers developing across inland areas. Into March solar heating is capable of generating heavy and thundery showers as some of us noted on the 19th March 2007 and during Easter 2008.

There is, though, a common view that snow in late winter and spring is "useless" because the stronger sunshine, while generating convection, also helps to raise the surface temperatures enough to initiate quick thaws, and a lack of understanding of the fact that some enjoy the "enhanced homegrown convection" aspect.

Thanks, a very imformative post.

I think when we get snow in spring people are satisfied with the idea of just short-lived temporary snowcover, like in April 2008 when 4cm was reported widely even though it thawed by the next day.