I received this question by e-mail today:
"I just saw something weird today that I hadn't thought about before.. I know there can be sun-showers, rain on a mainly clear day, but walking to work this afternoon it was snowing even though the sky was pretty much blue and clear, except at the horizon.
I hadn't really thought about it before, but I wonder how that happens.. if it's clear, I'd assume high pressure, but for it to snow, even flurries, I'd expect lower pressure...
Just wondering if you know how this happens.. "

My response:
Here's what I think you might have seen taking place:
The terminal velocity of a raindrop is much greater than that of a snowflake. Therefore, a snowflake may reach the surface well after the cloud that produced it has passed away. Also, wind can easily waft snowflakes a significant horizontal distance. This is especially true of small snowflakes that have a low density (the kind that you likely saw this afternoon).
Clouds that produce snowfall can dissipate rapidly and/or move downwind after producing snow. This can cause snow to be observed at the surface while the sky is partly cloudy or clear.

You wouldn't know it looking out the window right now (noon on Friday), but there is a system heading our way. There may be quite a bit of snow falling over night tonight and into tomorrow morning. I'll be updating more later. In the meantime, take a look at this.

1 school proactively cancelled,
1 daycare proactively cancelled,
3 people in my house with the flu,

= I won't be able to make it in today.

The Midterm Test will still be held today, however, as I am making arrangements to have someone else in the Geography Department proctor the test. If you are unable to come for whatever reasons (weather or illness), I will give you the option to write the test next Wednesday (Feb. 20: Reading Week) at 10:30 am. Please e-mail me if you are unable to make it today and want to write the make-up test.

Here's a map of the forecast tracks for low pressure systems across Canada this week. Obviously we're interested in the series of lines that indicate a low pressure system moving across our region. The lines all indicate that we'll have precipitation for some period of time on Wednesday: not a doubt. The question now is which track it takes: each coloured line shows a potential track (as predicted by various models): if the system tracks off the coast (i.e. the green line), then we would expect snowfall: being on the western side of the low, and the air would be coming from the northeast (counter-clockwise around the low pressure: classic nor'easter). If the system tracks to the west of Nova Scotia (i.e the blue line), then we might expect more in the way of rain or sleet (air flowing from the south and east, bringing warmer temperatures). You'll notice that the temperature range is wide for Wednesday (-10 to +4): this range is indicative of the uncertainty of the specific track. Some forecasters are starting to tend towards the offshore track which could mean heavy snow (see post below).

Fun stuff!

Environment Canada is officially using the term "heavy snow" for Wednesday, although you hvae to hunt to find it on their web site. Scrol down to Halifax on this link.

Thundersnow was observed in Yarmouth during the storm last night. What is it? You can read about it here or listen here.

According to Brett Anderson at Accuweather:

More snow into the East this weekend
This same storm that forms along the Arctic cold front will spread a band of light to moderate snow across Ontario and into southern Quebec late Friday night and into Saturday. I will detail accumulations in a later post. As the Arctic air wraps in behind the storm Saturday night and into Sunday morning there will be an outbreak of moderate to heavy lake-effect snow in the typical snow belt regions southeast of Georgian Bay and Lake Huron. Strong winds and snow will make for difficult travel and could create blizzard-like conditions.
As the storm hits the Atlantic Ocean Saturday night it will begin to rapidly intensify and slow its forward speed. What does this mean? It means there is the potential for another snowstorm from central and southern New Brunswick through PEI and northern Nova Scotia Saturday night and into Sunday. Southern Nova Scotia might have to deal with a mix of rain and snow Saturday night before it changes to all snow on Sunday. The storm will likely bring snow to southeastern Newfoundland early Sunday before going over to rain, while western Newfoundland could experience a moderate snowstorm.

Read what is going on in these regions of the US today. A series of rare winter season tornadoes have already occured and there is the potential for further outbreaks.

Someone in the class e-mailed this link today. Take a look at it:"NASA DATA LINK POLLUTION TO RAINY SUMMER DAYS IN THE SOUTHEAST"

You can find the jet stream image every day from this site if you'd like!

Or check this site for another perspective.

Just as we were starting to enjoy the sunshine (even I am getting tired of the storms!)
http://www.weatheroffice.gc.ca/city/pages/ns-19_metric_e.html