Things are looking interesting in the weather world over the next few days, so I thought I'd do a proper post...
First up, images from tonight - Apr 6- (yesterday when this posts)... Surface winds (NE, cold) -
NE winds in southern ON (and southern Great Lakes)
Surface winds + temperature from the same time:
Just above freezing, but mainly due to lake water...
Now we'll look at 850mb winds (roughly 1500m up off the surface)
850mb winds on Apr 6 at 9:30ish pm... Note the strong southerly flow hitting the southern great lakes! I'm not sure how high passerines fly, but I do know they don't fly along the surface...
850mb winds with 850mb temperature overlay... Note that the air is fairly warm right up to the southern Great Lakes, all the way back to the gulf of mexico
Finally, a surface map from the same time (roughly):
Almost-sorta looks like zonal flow?! But the Jet is a bit messy... Anyways, the point of this weather bit is to show that warm southerly air often rides above the surface conditions, so even though we have 3-4 days of NE winds and cool temperatures, conditions are ripe for migration just south of us... In terms of nocturnal migrants, I would expect them to continue flying (with new arrivals possible at places like Pelee or Long Point) - even though the conventional wisdom would be to expect them when the temperatures start to increase...
Other weather news - I don't really feel right issuing a "rarity alert" for later this week, but it's possible that we could see some good birds from some upcoming weather. Most notably is the potential for a severe weather outbreak mid-late week... The exact requirements for a "rarity event" under these circumstances elude me (on a local level) - but overall birders around the Great Lakes should be keeping their eyes peeled as we go forwards...
Severe outlook... Major historical outbreaks of Tornadoes have directly corresponded to mega rare birds in southern Ontario in the late april - may period... But I'm still trying to figure out what exactly we should be looking for in order to get these birds into our borders!
I can say that a severe outbreak is tied to a strong kink in the jet with powerful winds aloft (and often a strong temperature gradient) - so needless to say, that can get birds moving! This system may be a bit too far south to get southern Ontario in on the action, but time will tell... If it comes close enough, we could be in for another serious "surge" in migration.
How far north the subtropical jet will travel is important! Although great birds often correlate to nice weather on weekends - simply because people are out looking... I'll take any excuse I can get!
This Thurs-Fri storm will "wrap around" with an occluded front for Saturday/Sunday ish - meaning we should see some nice/normal weekend weather... Another system is possible on Monday for another "migration surge" (if we're lucky)... Watch this space! And go birding!