#cbcmar Good afternoon, so certainly some messy weather moving through the Maritimes today. Weve seen drifting and accumulating snow, a turn to rain for some as temperatures spiked upwards in the warm southerly winds, and even a few reports of a rare meteorological phenomena known as thunder snow! The reports of thunder snow came from around Saint John, NB early this morning and Weymouth, NS this afternoon. Thunder snow is relatively easy to explain, it occurs when we get enough convection (upward vertical motion) to produce lightning and thunder while temperatures remain cold enough that the primary type of precipitation that is falling is snow. This situation can develop in a number of ways but today its all about the much warmer air in the southerly winds colliding with the much colder Arctic air mass in place yesterday. You see warm, moist air is actually significantly less dense than cold, dry air. As the warm air arrived today it initially slid up and over the cold air much like a ramp. It also increases instability (the tendency for air to rise) in the atmosphere and all of a sudden weve got enough lift and vertical motion to get some lightning and thunder going on! Ive only been fortunate enough to experience thunder snow twice in person. Now as for whats left of the current messy system. The rounds of snow (and rain) will continue to clear the Maritimes west to east as we move into and through this evening. I estimate that the steadiest precipitation will clear Moncton and southeastern New Brunswick by 5 pm, Kings County PEI by 7 pm, mainland Nova Scotia by 9 pm (western areas a few hours sooner), and Cape Breton by 11 pm. As the system clears our winds turn west bringing very cold air back to the Maritimes. Just before sunrise tomorrow most temperatures in New Brunswick will be between -18 and -10, for PEI -12 to -8, and for Nova Scotia -12 to -4. Any slushy accumulations still around overnight will freeze solid and youll want to watch for ice on Saturday. Best to give the driveway a quick scrape this evening, even if theres just a coating. Of course those in southeastern New Brunswick and western areas of PEI will have to do some shoveling as they are seeing some of the higher snowfall amounts. The images Ive attached along with this post include some forecast guidance snapshots of how the last of this system will play out tonight and the fall in temperatures following it. Ive also includes and image showing the temperature/wind direction trend (not a forecast, just a trend) at Fredericton, Charlottetown, and Halifax. For more updates like my page here on facebook and follow me on twitter @kalinCBC.
Posted on: Fri, 09 Jan 2015 17:21:54 +0000
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