Yesterday afternoon at 12:02 Julian Bray started a new hashtag #uksnow on Twitter with the post 

#UKSNOW Starting thread as Met Office Alerts are usually rubbish! RT and tweet conditions to#UKSNOW and if stuck in snowdrift!

Hashtags are a community determined way of identifying a topic on twitter and provide a quick way to search for comment on a topic and to track trends. Anyone can create a hashtag just by typing it into a posting (I started #geocommunity as a hashtag for this year’s conference) then it is over to the viral transmission of the tag to determine its use.

People started responding with local reports and less than half an hour later someone incorporated their postcode in their update. Just over an hour after the hashtag had been initiated Paul Clarke suggested an informal standard for reporting the progress of the anticipated snow storm
paul_clarke: snow? tag with #uksnow and 1st part postcode then some bright spark will mashup amazing time/snow map. or something
A few minutes later Paul posted a slightly more refined version
paul_clarke#uksnow [1st part postcode] [n/10] on a notional #snowscale to give mashing a chance
Gradually this informal format was tweeted and picked up by more and more of the twitter community, by the end of the evening as the snow started to come down heavily about half the posts were using the format. At the time of writing #uksnow is the second most posted topic after the Superbowl with over 3600 posts.
Now I don’t normally post on trends in the social networks but there is a postcode in this informal format and Ben Marsh put together this mashup which searches for tweets with #uksnow and maps them by postcode. It builds up cumulatively as the tweets come through each minute so you may not see much if you are reading this a few days after posting. Here is a screengrab from this morning.

An impressive example of how a social network can be an almost instantaneous  means for crowdsourcing observations. There is a lot of potential in this, how about #ukcrunchfeel [1st part of postcode] [n/10] where n is your level of optimism today on a scale of 0 – depressed to 10 euphoric? Loads of opportunities here.
The buses aren’t running today, no cars getting up or down the hill I live on, school closed and kids gone tobogganning. Still snowing
#uksnow N10 3/10