lillooet temps and adiabatic lapse rate

[Don_Serl]

dru's posting of the weather for lillooet provides a perfect opportunity to put lillooet townsite temperatures in context with temps at the routes.

 

the dry adiabatic lapse rate (the rate at which dry air cools when its pressure is lowered at higher altitude) is close to 10ºC/1000m. fully saturated air cools at only 5.5ºC/1000m. 'average' atmospheric lapse rate is about 6.5ºC/1000m [3.5ºF/1000 ft].

 

except for honeyman, etc and the seton lake climbs, most stuff around lillooet is significantly higher than town:

 

*** lillooet lies just below 300m

 

*** marble canyon is at 800m, thus might be expected to be about 3-4ºC cooler. but M/C is also more 'interior', therefore generally colder; plus the air has dried out after passing over the coast mtns, so the lapse rate is closer to the dry figure. i reckon M/C runs 6-8ºC cooler than lillooet.

 

*** oregon jack experiences the same interior benefits, and is at nearly 1200m. temps are probably 8-10ºC below lillooet.

 

*** the valley bottom on the duffey lake road lies between about 550m [synchronicity] and 750m [rambles] in the ice climbing areas. many of the routes lie 200m or more up the hillside. the air tends to be fairly saturated except in arctic outflows. expect typical temps 3-5ºC colder than lillooet.

 

*** phair creek climbs lie between about 800m [just walkin' the dog] and 1200m [phairwell to arms], so are 3-6ºC colder than town. too bad it's so sketchy to get there!

 

*** the bridge river valley lies at between 500m [old dogs, new picks] and 600m [tezaghi dam]. the air is drier than the duffey, but not fully interior dry. expect temps about 2-4ºC colder than lillooet. luckily many of the 'big' routes (capricorn, night 'n gale, shriek of the sheep) are way up at 1100m or 1200m, so experience temps about 6ºC colder than lillooet.

 

too complex? simple rule: drop 5ºC off the town temp to reckon climb temp...

 

cheers,

[Alex]

So a little quick math

 

"Sunday .. Sunny. Low minus 16. High minus 7."

 

Sunday, your approach in the dark will be frigid and your headlamp batteries will be dead anyway. Might as well get plastered Sat night and sleep in.

[Dru]

1) If you check the weather forecast for Clinton (please no jokes ) it is usually pretty close to Marble Canyon conditions, as measured at Butterfly Springs store.

 

2)You can check the actually measured temperatures for Lillooet on the same webpage as the text forecast. They are usually colder than forecast when it's cold.

 

This is because 3) the Lillooet forecast is a regional forecast. It's almost always nearly exactly the same as the Lytton forecast. But when cold air dominates Lillooet is usually getting a colder outflow than Lytton and tends to be 2-3C colder as actually measured although its only about 50-100m higher in elevation (I think - I didn't look this figure up.).

 

4) The amount of sun recieved will also affectr local microclimates. MC climbs are in the shade all day and hence local air temp will often be a few degrees colder than, say, a south facing cliff of a similar elevation. EVEN THOUGH air temp should be measured in the shade to be accurate... a big chunk of sun warmed south facing rock can warm the air around it. This is why Twilight Teirs isnt in as much as Nigh N Gale even though both are at roughly similar elevations... but you knew that right!