Glacier Basin Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Glacier Basin Campground clear sky chart from 2005-11-05 to 2017-12-20.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
32%
16383
25%
48062
9%
16336
47%
16336
28%
26204

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
17%
900
24%
2506
5%
895
35%
895
22%
1303
January16th to endNight
14%
804
29%
2532
5%
804
40%
804
22%
1251
February1st to 15thNight
11%
701
21%
2274
3%
697
33%
697
16%
1201
February16th to endNight
11%
632
25%
1894
2%
632
34%
632
18%
1026
March1st to 15thNight
21%
720
25%
2094
6%
720
39%
720
23%
1116
March16th to endNight
23%
693
23%
2037
6%
693
39%
693
24%
1125
April1st to 15thNight
23%
539
20%
1798
7%
539
40%
539
23%
974
April16th to endNight
29%
540
21%
1800
10%
540
45%
540
21%
1030
May1st to 15thNight
35%
540
17%
1575
7%
540
45%
540
23%
1005
May16th to endNight
44%
563
17%
1498
8%
561
52%
561
30%
931
June1st to 15thNight
50%
540
21%
1440
11%
540
58%
540
42%
783
June16th to endNight
64%
540
27%
1440
19%
540
70%
540
54%
738
July1st to 15thNight
66%
510
17%
1360
13%
510
70%
510
36%
833
July16th to endNight
73%
564
22%
1450
20%
531
74%
531
39%
844
August1st to 15thNight
70%
539
19%
1640
17%
536
73%
536
38%
900
August16th to endNight
68%
573
27%
1910
26%
573
73%
573
36%
1035
September1st to 15thNight
57%
540
26%
1800
21%
540
68%
540
34%
979
September16th to endNight
58%
552
34%
1932
26%
552
70%
552
39%
934
October1st to 15thNight
34%
720
27%
2160
11%
720
48%
720
30%
1162
October16th to endNight
26%
789
32%
2325
9%
789
45%
789
30%
1233
November1st to 15thNight
21%
950
29%
2470
7%
950
36%
950
30%
1347
November16th to endNight
15%
975
32%
2642
5%
975
38%
975
26%
1373
December1st to 15thNight
12%
975
21%
2730
2%
975
29%
975
19%
1477
December16th to endNight
13%
984
22%
2755
3%
984
31%
984
17%
1604

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
5%6%35%5%35%5%6%8%44%
48792
Night
242432445%9%55%
48237
TransparencyDay
32%8%14%23%15%4
48469
Night
24%6%17%27%18%5%
48062
SeeingDay
10%23%31%21%10%2
6160
Night
6%29%27%22%12%2
16386

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
336%325%48%11%50%
1432
16th to endDay
335%4245%6%9%53%
1704
February1st to 15thDay
436%5%36%5%6%10%46%
1588
16th to endDay
5%45%5%35%5%8%13%42%
1580
March1st to 15thDay
16%35%5%35%5%6%8%47%
1863
16th to endDay
39%46%435%6%7%11%37%
2187
April1st to 15thDay
39%45%5%35%6%5%10%40%
2150
16th to endDay
8%13%47%6%35%5%5%7%31%
2160
May1st to 15thDay
10%11%46%5%345%5%7%33%
2373
16th to endDay
9%8%36%6%47%6%6%8%31%
2616
June1st to 15thDay
5%4245%35%6%6%9%44%
2520
16th to endDay
2324425%5%6%8%52%
2520
July1st to 15thDay
8%5%37%6%36%6%5%7%39%
2520
16th to endDay
6%5%37%6%47%7%7%7%35%
2617
August1st to 15thDay
10%7%38%7%35%5%5%8%34%
2310
16th to endDay
8%5%27%7%45%6%5%6%39%
2292
September1st to 15thDay
9%4245%35%5%5%6%48%
2160
16th to endDay
6%5%245%24445%54%
2024
October1st to 15thDay
5%5%2442445%7%52%
1800
16th to endDay
36%2442445%6%55%
1886
November1st to 15thDay
142442445%9%56%
1718
16th to endDay
325%42346%11%54%
1644
December1st to 15thDay
337%4345%5%10%50%
1560
16th to endDay
1326%6%3447%12%45%
1568
January1st to 15thNight
22342347%11%58%
2506
16th to endNight
31332345%11%59%
2532
February1st to 15thNight
425%42345%11%54%
2263
16th to endNight
5%344335%5%10%54%
1894
March1st to 15thNight
142432446%12%54%
2094
16th to endNight
35%3322346%10%53%
2037
April1st to 15thNight
26%24425%45%7%53%
1798
16th to endNight
7%10%232335%5%9%48%
1800
May1st to 15thNight
8%8%244345%5%7%44%
1574
16th to endNight
5%6%245%25%45%9%47%
1497
June1st to 15thNight
32132235%6%7%60%
1440
16th to endNight
12123136%6%8%63%
1440
July1st to 15thNight
43245%26%5%7%10%48%
1440
16th to endNight
3424445%45%7%53%
1549
August1st to 15thNight
43124346%7%9%51%
1649
16th to endNight
43145%4445%7%53%
1910
September1st to 15thNight
7%414324347%55%
1800
16th to endNight
441232335%5%63%
1932
October1st to 15thNight
5%413423349%57%
2160
16th to endNight
342431335%9%59%
2325
November1st to 15thNight
131432345%9%61%
2470
16th to endNight
31431345%12%58%
2642
December1st to 15thNight
415%31335%11%58%
2730
16th to endNight
436%5%2446%10%51%
2755

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
22%8%28%25%12%3
1433
16th to endDay
22%7%20%30%14%4
1704
February1st to 15thDay
29%9%22%27%8%2
1588
16th to endDay
28%8%16%30%14%2
1580
March1st to 15thDay
30%7%17%27%15%2
1863
16th to endDay
34%8%16%26%11%3
2187
April1st to 15thDay
34%9%14%22%14%4
2150
16th to endDay
46%7%13%20%10%1
2160
May1st to 15thDay
45%8%13%20%10%
2373
16th to endDay
42%11%14%18%9%2
2620
June1st to 15thDay
31%10%15%17%18%6%
2520
16th to endDay
25%8%10%21%25%8%
2520
July1st to 15thDay
38%9%13%15%13%10%
2371
16th to endDay
38%11%14%19%9%6%
2453
August1st to 15thDay
42%12%10%14%13%6%
2295
16th to endDay
37%9%11%19%18%3
2292
September1st to 15thDay
31%8%10%19%20%8%
2160
16th to endDay
28%6%9%25%27%2
2024
October1st to 15thDay
29%8%10%23%24%3
1800
16th to endDay
24%6%11%29%21%5%
1886
November1st to 15thDay
21%7%18%24%23%4
1718
16th to endDay
22%5%16%32%18%4
1644
December1st to 15thDay
27%8%20%28%12%1
1560
16th to endDay
26%10%18%27%13%3
1568
January1st to 15thNight
18%7%26%27%16%3
2506
16th to endNight
20%5%20%30%18%4
2532
February1st to 15thNight
23%7%23%31%12%2
2274
16th to endNight
24%5%19%27%18%4
1894
March1st to 15thNight
21%6%18%31%19%2
2094
16th to endNight
25%6%16%33%15%2
2037
April1st to 15thNight
28%6%16%28%15%4
1798
16th to endNight
32%5%15%28%16%1
1800
May1st to 15thNight
36%9%16%24%12%1
1575
16th to endNight
31%8%17%25%14%2
1498
June1st to 15thNight
20%7%17%25%19%8%
1440
16th to endNight
15%6%11%27%26%12%
1440
July1st to 15thNight
27%11%15%21%14%9%
1360
16th to endNight
26%8%15%26%14%8%
1450
August1st to 15thNight
23%9%20%19%18%8%
1640
16th to endNight
27%6%11%23%24%5%
1910
September1st to 15thNight
28%6%12%20%20%11%
1800
16th to endNight
21%6%9%33%25%4
1932
October1st to 15thNight
24%5%13%25%23%7%
2160
16th to endNight
24%414%28%24%4
2325
November1st to 15thNight
19%6%16%26%23%7%
2470
16th to endNight
18%415%33%22%4
2642
December1st to 15thNight
21%7%24%27%15%3
2730
16th to endNight
26%8%20%27%14%1
2755

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
6%30%33%13%14%2
90
16th to endDay
239%34%20%3
96
February1st to 15thDay
6%62%21%10%
90
16th to endDay
6%46%25%17%3
81
March1st to 15thDay
13%45%28%9%3
153
16th to endDay
13%40%38%6%1
288
April1st to 15thDay
12%40%31%9%4
269
16th to endDay
25%36%24%10%3
270
May1st to 15thDay
16%23%32%16%8%1
414
16th to endDay
15%16%31%21%12%1
517
June1st to 15thDay
6%17%30%26%16%3
495
16th to endDay
310%39%24%16%5%
495
July1st to 15thDay
10%430%28%16%8%
475
16th to endDay
6%428%32%19%7%
476
August1st to 15thDay
13%11%37%28%8%
315
16th to endDay
8%8%34%36%10%2
332
September1st to 15thDay
10%17%35%25%10%1
315
16th to endDay
8%21%35%19%12%3
197
October1st to 15thDay
8%26%31%21%8%2
135
16th to endDay
10%35%28%20%22
144
November1st to 15thDay
5%35%23%16%16%2
135
16th to endDay
8%56%28%6%
135
December1st to 15thDay
5%59%25%8%1
135
16th to endDay
52%27%17%1
108
January1st to 15thNight
6%47%26%12%5%2
900
16th to endNight
5%46%31%12%4
804
February1st to 15thNight
349%30%13%4
704
16th to endNight
5%48%29%13%2
632
March1st to 15thNight
443%27%15%8%
720
16th to endNight
7%35%31%21%3
693
April1st to 15thNight
8%26%37%21%5%
539
16th to endNight
13%26%27%22%8%1
540
May1st to 15thNight
15%14%29%26%13%1
540
16th to endNight
9%11%26%33%17%2
563
June1st to 15thNight
5%9%30%34%17%2
540
16th to endNight
26%22%37%26%3
540
July1st to 15thNight
5%214%38%32%6%
510
16th to endNight
410%35%41%7%
564
August1st to 15thNight
5%113%42%33%3
539
16th to endNight
5%314%35%33%8%
573
September1st to 15thNight
8%5%21%32%23%7%
540
16th to endNight
7%10%21%34%19%6%
552
October1st to 15thNight
8%25%27%24%11%2
720
16th to endNight
6%29%34%17%8%3
789
November1st to 15thNight
439%32%16%6%1
950
16th to endNight
346%31%15%3
975
December1st to 15thNight
5%48%30%11%2
975
16th to endNight
348%29%13%4
984
Page generated at 2017-12-21 05:04:54. Version ac04

Copyright 2017 A. Danko


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