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Bill O
04-12-2009, 08:51 PM
April (+/- a week) doesn't fail to disappoint with the year's lowest relative humidity. At least in this part of the world.

Over the past few years I have noticed that April consistently creates the lowest RH. Today my weather station dropped to around 20% as the dewpoint fell close to 10F. In recent years I have recorded RH values below 10% in April.

This happens when a Canadian (Arctic air mass) invades the region. April's strong sunlight easily warms the air mass, but northerly winds prevent moisture from building. This leads to very dry weather and low RH values.

Not as exciting as a world record wind, but it's what happened in your backyard today.

JimS
04-13-2009, 09:05 AM
Exactly right on the whys of this weather. Another factor that plays into the lack of moisture is the lack of both snowpack and living leaf material. Transporation from leaves adds moisture to the air in the summer, but right now, all we have are twigs...

Unfortunately, low humidity with the dry leaves on the ground combine to create brush fire season. Last year, one big brushfire swept up mount major in alton, with little damage. This year, alton wasn't so lucky...

http://www.unionleader.com/article.aspx?headline=Wind-whipped+fire+tears+through+landmark+conference+cen ter&articleId=9ccc1b62-7e84-43cb-886b-7c6287765145

Brad
04-13-2009, 12:23 PM
And fire danger was posted as HIGH today with the high winds.

Bill O
04-13-2009, 05:42 PM
This morning the temps dropped to just above 32F, but a large brackish pond near my parent's house was covered in fresh ice. Another result of the dry weather.