Random Snow Shower

[Northern Block]

Hi,

Just thought I would post the below. Unfortunately I can't remember the exact date I took this but I believe it was April 2007.

The location was around 10 miles west of Cambridge when i first noticed the cloud. The temperature according to the car was 6 degrees. I crossed the path of the storn just about a mile or so outside Cambridge. The temperature dropped to zero from 6 degrees within a mile and a half of the cloud and the centre and you can see the dusting it left within the space of minutes. The wind had picked up from almost nothing to quite strong as well underneath the cloud. Unfortunately no sooner than the cloud appeared it left over the fields and the snow rapidly melted on the originally warm ground.

I've never seen a single cell like this before or since so any explanation would be very interesting.

[Thundery wintry showers]

My guess is that it's an isolated cumulonimbus cell triggered by localised convective uplift somewhere- remember that cumulus and cumulonimbus clouds form from rising parcels of air, and that subsidence surrounding the air parcels gives rise to the clear intervals in between the showers. I've definitely seen isolated cells like that on numerous occasions, and while I don't recall any such instances when it was cold enough for snow, the processes will be the same.

If the month was April chances are it was either 2006 or 2008- April 2007 was the warmest April in record and had no "sunshine and snow showers" setups except possibly in Shetland. If the year was 2007, it is most likely to be the 19th or 20th March.