May 1st, 2015

The high pressure center
over IL.

Fellow Illinoisans,

First of all, happy May! To use the words of BirdCast, May will bring "locally very heavy flights," ensuring to add many species to our year lists and completely alter ecosystems in the process. Tonight, we have a slight prequel to those flights.

Tonight's winds. Click to
view live.

Winds, both aloft and on the surface level, are confused and weak tonight. The reasons for this include a high pressure center sitting right on top of the Prairie State. Winds, even if weak, rotate clockwise around high pressure centers. The presence of a high pressure center in Illinois means that winds will be moving in a different direction anywhere around that center. These 360 degrees of wind variation are visible on the earth wind map.

Migration at the time of this
post.

What do these winds mean for migration? Right now, it appears that winds have very little influence on where birds are moving aloft, meaning that a number of other factors could be at play that are much harder to predict. Regardless, a south-to-north gradient of migration exists overhead tonight: Southern Illinois is currently witness to moderate to heavy concentrations, while Northern Illinois is currently witness to minimal concentrations. Concentrations over Central Illinois are somewhere in between (radar). This gradient may stay in place throughout the night, resulting in obvious arrivals/influxes in Southern Illinois, and marginal arrivals/influxes in Northern Illinois. The gradient may also be altered as decisive, southerly winds expand into Illinois as the night progresses. In that case, arrivals/influxes will be obvious in Southern as well as most of Western Illinois. We'll see what happens.

Regardless of that, Saturday's forecast remains as exciting as it was yesterday. Strong, southerly winds are forecast for Saturday night, making the aforementioned "very heavy flights" extremely likely. Sunday should be an extremely exciting time to bird, especially given the forecast temperatures. Sunday night is still forecast to be as favorable, while Monday night, favorable winds are forecast to be limited to Southern and Central Illinois. That's that for the forecast.

Winds forecast for Saturday night: southerly and favorable.

If you're curious about just what will be out there this weekend, I recommend reading the latest BirdCast National Migration Forecast here. After that, check out this perpetually useful eBird Page, displaying frequency data specific to Illinois.

With that, I bid you all a good night and good birding!