Atmospheric pressure and sap flow.

[madmapler]

I've heard a several of theories about sap flow being affected by wind direction, air pressure and what not. I thought this might be a good thread to clarify what is fact and what is myth. Frankly, I wouldn't mind understanding things a little better myself. I look mainly at the forecast temps. and expect to be making syrup accordingly and it's not always the case. I can count on sunny days (above freezing) but am not clear how much is attributed to the suns warmth or atmospheric pressure. I'm aware of the little ditty about wind direction(wind from the west, sap flows best... yada yada...) but I don't really know why. I don't recall seeing much posted on the subject either. Any insights or observations welcome.

[katmike]

I had an observation that occurred several years ago. One morning I was wondering the woods, checking things out and surprised that the trees were running like crazy even though it wasn't warm (<40F) nor was the sun shining. The previous days' collections wasn't anything memorable, so I thought a bit odd. We were expecting a snowstorm about 12-24 hours away, so I kind of theorized the approaching low-pressure center was the main cause, but under similar circumstance more recently, that did not happen like I was hoping. Perhaps sometimes Mother Nature gives an assist with low pressure if other factors (?) cooperate in the situation I described?