Not all cold fronts are created equally...

[Bryan Guarente]

COBirders,

There is a cold front coming through tomorrow.  I think if you were to ask COBirders whether a cold front meant good birds in Fall or not, I think most would say yes, especially if the front comes with precipitation.  Go birding in bad weather!

On the East slope, tomorrow's cold front won't be wet nor cold, just cooler with some cloud cover.  On the West slope, it will be a different story in terms of precipitation.  Definitely expecting precipitation.  Hopefully this will help with some of the wildfire situations.  

So today, I am going to try something different.  Here is the forecast graphic for tomorrow after the frontal passage (map is from 3pm local time).  If you were at my CFO presentation the other day, you would know some of the things to look for in terms of good weather for migrants.  Does this look like it will be a good day to get long-distance migrants from Canada?  Should we expect dispersing migrants affected by Hurricane Delta?  Should we be thinking about tropical species coming up from Mexico and the southwest US?  Where do you see the flow pattern coming from that would dictate the birds we might expect?

https://earth.nullschool.net/#2020/10/11/2100Z/wind/isobaric/850hPa/orthographic=-105.11,40.20,1064/loc=-105,40

The green circle on that map is around Boulder, CO.  Anyone want to play along and give your weather forecast for migrants based on this map?  Are you expecting turnover of birds?  Are you expecting most birds to stay put, but add other species to the mix with the frontal passage?  Is this going to be the pattern that drives even more corvids out onto the Plains?  

Harder challenge: anyone want to venture a guess about what birds to expect based on the flow pattern?  

All of the previous questions will be answered by the weather and the birds tomorrow into Monday, but I will wrap up some thoughts later this evening based on what folks have stated to me privately (paraphrased or summarized only) and publicly, plus some of my own words to help move the conversation along.

Thanks for playing along,

Bryan 

Bryan Guarente

Meteorologist/Instructional Designer

UCAR/The COMET Program

Boulder, CO

[rjpa...@gmail.com]

Looks like a good day for more Mountain Chickadees, Mountain Bluebirds, and Stellar's Jays.  Cassin's Finches?  But I wouldn't bet on  northern, eastern, or southern rarities in Boulder tomorrow.  (and what's that huge low up in northern Canada?)

[Dave Hyde]

Hi Bryan – I expect the three White-crowned sparrows that have been enjoying the free lunch here near Storm Mountain in Larimer County since Oct 1^st to be gone by Monday! I think the juncos will remain, though. :)  - Dave Hyde, Larimer Cty.

 

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[Bryan Guarente]

COBirders,

I got some responses to my inquiry about what this next cold front might bring.  Nobody thought this was going to be bringing Canadian, Mexican, or eastern migrants to CO.  Most responses suggested that the birds in place right now would move out with the passage.  Those responses seemed to be more about altitudinal migrants though including my corvid question.  My favorite response was that we should expect murrelets!  It's a wonderful thought, but I am highly doubtful of a movement of murrelets into our location from this flow pattern. However, that does bring up a good point about where this cold front is coming from.  

The idea that murrelets were suggested is likely because this front is coming from the Pacific.  Winds are coming from the west with this system.  This is a different type of cold frontal passage for us in CO.  They happen more in winter than in fall like we will experience today.  Birds that could move this direction would likely be migrants moving southward along the West Coast at this time of year but following the wind patterns inland instead of along the coast because these are going to be quite strong winds.  This is one of the hardest sets of migrants to get to show up in CO.  The Rockies do a great job of blocking migrants from coming this way.  So I am not expecting much of a change in migrants with this frontal passage.  

I also believe that some of the altitudinal migrants that come into our area at this time of year might make their numbers more well known (juncos for instance).  Get out before the winds blast us later today if you want to get your birding in.  

If you are hoping for northern migrants, look no further than Thursday of this week: https://earth.nullschool.net/#2020/10/15/0300Z/wind/isobaric/850hPa/orthographic=-105.11,40.20,1064/loc=-105.113,40.203. Northern migrants should be flooding the eastern 2/3rds of the US.  I might get a chance to write again before then, but my time is limited this week, so this is your fair warning.

Thanks,

Bryan

Bryan Guarente

Meteorologist/Instructional Designer

UCAR/The COMET Program

Boulder, CO

[Steven Brown]

Hey COBIrders,

I didn’t know what to expect this morning for banding birds at Clear Spring Ranch - but I expected I might see some warblers.  Woohoo!  Today I only banded 10 birds early, before I got blown out by the West Winds, but those 10 included 4 Ruby-crowned Kinglets (not a surprise, I’ve had about 30 in the last week). The surprises were a juv PALM WARBLER (only my 2nd banded at CSR), and a wayward juv N. Waterthrush - the latest I’ve ever had here by over A MONTH. Did they come from Canada???? Won’t know.  Isn’t science fun?

We’ll see now what the front leaves behind tomorrow. Can’t wait!

Happy Migration,

Steve Brown

COS

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