BWCA temp adjustments Boundary Waters Winter Camping and Activities
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spirit2189
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02/09/2015 12:41PM   (Thread Older Than 3 Years)
I'm curious for planning purposes. When typical weather forecasts predict a given temp, it is not based upon temps experienced when standing/traveling on a large frozen body of water. What generically could someone expect in terms of a temp adjustment from standard weather forecast temp data and actual on top of some frozen lake in the boundary waters?
 
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OldFingers57
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02/09/2015 12:57PM  
I would imagine it may be a few degrees colder, but so would being on a snow pack landscape as opposed to barren ground.
spirit2189
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02/09/2015 01:05PM  
OK thanks for the intel. I would have guessed much colder like maybe 10 degrees different?
OldFingers57
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02/09/2015 01:51PM  
Other conditions will affect the temp. too like wind. Ask Whitewolf he may know more about this from being a meteorologist.
SevenofNine
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02/09/2015 01:52PM  
If it's a low lying area you can always expect it to be colder. By how much I wouldn't know. To me wind is a killer when it comes to tolerance for the cold. Wind and cold will find every chink in your armor.
02/09/2015 03:18PM  
Be interesting to see what our resident weather expert says.......I'll guess that it doesn't make much if any difference, if we're talking about frozen, snow covered ground and frozen snow covered lakes. However, wind chill will have a big impact.

I don't think the ice affects the air temperature as much as the air temperature affects the ice.

02/10/2015 12:12PM  
quote SevenofNine: "If it's a low lying area you can always expect it to be colder. By how much I wouldn't know. To me wind is a killer when it comes to tolerance for the cold. Wind and cold will find every chink in your armor."


This...is my opinion too.
02/11/2015 02:01AM  
double post-- sorry.
02/11/2015 02:01AM  
quote spirit2189: "I'm curious for planning purposes. When typical weather forecasts predict a given temp, it is not based upon temps experienced when standing/traveling on a large frozen body of water. What generically could someone expect in terms of a temp adjustment from standard weather forecast temp data and actual on top of some frozen lake in the boundary waters?"


Great question! Official temperature measured at many sites across the US (sadly many at airports-- that is for another time) is taken at the 5-6' level-- more commonly called the 2M temp. Temperature forecasts by NOAA/NWS are made for the 2 meter level-- nearly all forecasts issued by Noaa/NWS in and around large cities are made for the actual temperature sensor located at the nearest airport so their forecast can verify or .. bust.

As far as a "real feel" under your conditions above- those above pretty much nailed it. Obviously as mentioned-- wind chill is huge. Many on here likely remember the "old" wind chill chart that was replaced in 2001 with the "new wind chill chart. The reason??? Wind is "officially" measured at the 10 meter level (at airports again). 10 meters because of the effect that height has on the aviation community (take off and landing). The old wind chill used the 10 meter level-- which due to frictional effect of the earth -- is usually several knots or mph higher then at human face level. So a algorthim was developed that converts the 10 meter wind speed to a more representable speed at human face level -- hence the new wind chill chart. I have always thought that dampness affects us also with the wind chill-- by how much I don't know-- but a wind driven cold rain at 35F to myself is much more miserable then the same wind with snow at 28F. Probably has something to do with the specific heat of water. old/new wind chill calculator

As far as the actual temperature being different in your ?-- not much. Maybe a few degrees cooler at most as mentioned by oldfingers. This mainly due to being away from concrete/buildings etc-- but it can work the other way also. However, as mentioned -- cold air is more dense then warm air and sinks. On calm,clear skies/cold nights-- lower lying areas will get colder/faster then surrounding- higher terrain. I have seen 10F+ changes both ways (actually just a few nights ago--- -17F to -7F within one valley-- less then 50' drop/rise. It doesn't take much for cold air to funnel-- but the winds must be very light to calm otherwise the wind "mixes" the air column and and then little change will be noticed-- if at all. This is also partly explains why snow can accumulate with 2 meter temps above 0C -- say 34F. On Super Bowl weekend-- here in Des Moines we received 11.6" of snowfall--- 85% occurred with a 2 meter temp of 34F-- but 1" above the ground (frozen) the temps was just barely colder then 0C-- and the falling snow was allowed to accumulate.
I hope this helps.
OldFingers57
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02/11/2015 07:13AM  
White Wolf Thanks for the explaination. I enjoy reading and learning all the info you put out about the weather.
02/11/2015 10:56AM  
Thanks, O Great Weather Kahuna........

Not that it means a lot in the BWCA, because it is basically low humidity winter location, but I've always experienced feeling colder with higher humidity.

I lived in Germany when I was in the Army. The winter temperature rarely got below the 20's, but it was a humid cold. It would chill you to the bone.
02/11/2015 11:03AM  
i agree that dampness or humidity is a critical factor in the 'feel' of cold tempts. -10f in alaska and the west is much different than the feel of -10f in the midwest. that's just based on experience, no science.
 
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