Grasslands National Park (West)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grasslands National Park (West) clear sky chart from 2005-11-05 to 2017-09-23.

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
42%
15670
15%
46781
10%
15633
47%
15633
25%
30574

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
32%
895
11%
2685
6%
895
37%
895
18%
1933
January16th to endNight
28%
952
15%
2735
6%
952
37%
952
18%
1959
February1st to 15thNight
40%
697
12%
2288
9%
696
45%
696
20%
1543
February16th to endNight
40%
632
13%
2035
10%
632
45%
632
18%
1446
March1st to 15thNight
39%
720
13%
2068
7%
720
44%
720
23%
1438
March16th to endNight
34%
726
13%
2070
7%
726
39%
726
19%
1511
April1st to 15thNight
40%
539
15%
1798
11%
539
46%
539
22%
1165
April16th to endNight
39%
540
16%
1585
12%
540
43%
540
22%
1092
May1st to 15thNight
48%
539
14%
1440
9%
539
50%
539
31%
934
May16th to endNight
40%
542
9%
1477
5%
540
42%
540
22%
1055
June1st to 15thNight
47%
360
6%
1260
5%
360
50%
360
23%
777
June16th to endNight
54%
360
8%
1260
8%
360
57%
360
33%
669
July1st to 15thNight
60%
340
10%
1190
9%
340
62%
340
37%
609
July16th to endNight
62%
485
18%
1339
12%
454
67%
454
50%
666
August1st to 15thNight
64%
539
18%
1495
14%
536
68%
536
47%
803
August16th to endNight
61%
573
28%
1764
22%
573
67%
573
43%
929
September1st to 15thNight
58%
540
21%
1800
21%
540
62%
540
35%
975
September16th to endNight
53%
618
27%
1891
20%
618
62%
618
37%
1050
October1st to 15thNight
43%
660
21%
1980
12%
660
51%
660
28%
1228
October16th to endNight
42%
778
20%
2197
10%
778
50%
778
27%
1426
November1st to 15thNight
34%
875
19%
2450
9%
875
42%
875
26%
1588
November16th to endNight
32%
900
15%
2520
8%
900
38%
900
23%
1749
December1st to 15thNight
33%
900
9%
2574
5%
900
36%
900
15%
1966
December16th to endNight
31%
960
13%
2880
6%
960
39%
960
18%
2063

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
9%7%36%5%35%5%5%7%40%
48155
Night
7%7%36%6%35%5%5%8%40%
46937
Cloud CoverDay
9%7%36%5%35%5%5%7%40%
48156
Night
7%7%36%6%35%5%5%7%40%
46939
TransparencyDay
41%6%15%23%10%1
47815
Night
40%6%15%23%11%1
46781
SeeingDay
13%7%27%30%17%3
6146
Night
11%6%31%35%13%1
15683

By Month

Percentage Cloud Cover NW (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
6%11%5%9%6%5%6%6%47%30%
1253
16th to endDay
210%48%9%5%7%6%6%8%29%
1497
February1st to 15thDay
9%9%6%10%8%5%7%5%47%26%
1575
16th to endDay
5%13%5%10%11%5%7%5%5%7%22%
1438
March1st to 15thDay
48%410%8%46%7%7%8%30%
1890
16th to endDay
9%10%5%11%6%36%46%8%27%
2153
April1st to 15thDay
11%7%36%7%45%46%9%32%
2150
16th to endDay
15%9%46%434447%35%
2373
May1st to 15thDay
11%8%35%6%34446%39%
2511
16th to endDay
20%7%36%5%35%45%7%31%
2634
June1st to 15thDay
14%6%35%5%46%5%5%7%35%
2700
16th to endDay
7%314425%6%7%9%45%
2700
July1st to 15thDay
4313435%5%6%9%53%
2700
16th to endDay
321332346%7%60%
2736
August1st to 15thDay
6%42442446%7%51%
2457
16th to endDay
6%21332345%7%60%
2438
September1st to 15thDay
9%424434446%51%
2160
16th to endDay
13%5%2321345%6%51%
1904
October1st to 15thDay
11%8%35%42445%7%42%
1650
16th to endDay
7%9%345%25%5%6%8%41%
1661
November1st to 15thDay
6%8%36%5%25%5%6%7%42%
1408
16th to endDay
7%9%47%5%35%6%5%8%35%
1440
December1st to 15thDay
8%10%7%12%11%5%5%5%5%6%22%
1383
16th to endDay
5%11%5%11%9%5%5%5%7%5%28%
1344
January1st to 15thNight
6%8%5%8%7%37%6%5%8%32%
2685
16th to endNight
48%49%8%46%5%6%8%32%
2735
February1st to 15thNight
6%8%47%7%36%5%5%7%36%
2277
16th to endNight
5%10%5%10%7%345%5%7%31%
2035
March1st to 15thNight
5%7%49%6%45%5%6%9%35%
2068
16th to endNight
8%10%48%6%45%6%6%9%29%
2067
April1st to 15thNight
8%7%35%5%35%46%7%39%
1798
16th to endNight
12%7%36%6%35%46%6%36%
1585
May1st to 15thNight
9%7%344245%6%7%44%
1439
16th to endNight
14%7%26%6%35%5%6%6%35%
1477
June1st to 15thNight
13%5%35%4335%6%7%41%
1260
16th to endNight
6%414425%45%10%51%
1260
July1st to 15thNight
432442446%7%56%
1260
16th to endNight
321332445%8%60%
1432
August1st to 15thNight
431332235%8%59%
1503
16th to endNight
6%313313446%60%
1764
September1st to 15thNight
8%5%23423446%55%
1800
16th to endNight
9%42431235%9%53%
1891
October1st to 15thNight
8%6%25%42445%7%46%
1980
16th to endNight
8%8%244245%6%9%43%
2197
November1st to 15thNight
7%7%36%435%5%5%7%44%
2450
16th to endNight
6%9%48%7%3445%8%37%
2520
December1st to 15thNight
5%10%6%9%10%5%6%5%5%7%26%
2574
16th to endNight
7%9%48%7%46%6%6%8%30%
2880

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
6%11%5%11%6%36%6%5%6%30%
1253
16th to endDay
310%48%9%6%7%7%6%8%29%
1497
February1st to 15thDay
9%9%6%10%9%46%5%46%26%
1575
16th to endDay
6%12%6%10%10%46%6%6%6%22%
1438
March1st to 15thDay
48%5%10%7%46%6%6%9%30%
1890
16th to endDay
8%10%6%10%6%35%5%5%9%27%
2154
April1st to 15thDay
11%8%36%6%45%6%5%9%33%
2150
16th to endDay
15%10%36%5%2445%7%35%
2373
May1st to 15thDay
12%9%25%6%24446%40%
2511
16th to endDay
20%6%36%5%35%5%5%7%31%
2634
June1st to 15thDay
15%5%346%36%5%5%8%35%
2700
16th to endDay
7%324435%5%8%9%45%
2700
July1st to 15thDay
5%214425%5%6%8%53%
2700
16th to endDay
321332435%7%61%
2736
August1st to 15thDay
7%415%33445%7%51%
2457
16th to endDay
6%21332345%8%59%
2438
September1st to 15thDay
9%6%145%24445%52%
2160
16th to endDay
13%5%1321335%6%50%
1904
October1st to 15thDay
10%8%36%42435%8%42%
1650
16th to endDay
7%10%25%425%5%6%8%41%
1661
November1st to 15thDay
7%8%45%5%25%5%5%8%41%
1408
16th to endDay
7%9%47%5%35%5%5%8%36%
1440
December1st to 15thDay
8%10%7%12%10%46%6%5%6%21%
1383
16th to endDay
5%10%6%12%9%46%5%6%6%27%
1344
January1st to 15thNight
6%8%5%9%7%46%6%6%7%32%
2685
16th to endNight
48%5%9%8%46%6%6%8%32%
2735
February1st to 15thNight
6%7%48%8%36%5%5%8%35%
2277
16th to endNight
5%10%6%11%7%45%5%5%8%31%
2035
March1st to 15thNight
5%7%5%7%6%46%5%6%9%36%
2068
16th to endNight
8%9%5%8%6%35%6%6%9%30%
2070
April1st to 15thNight
8%6%35%5%35%5%6%7%41%
1798
16th to endNight
12%7%36%6%36%45%6%36%
1585
May1st to 15thNight
9%7%145%25%36%6%45%
1439
16th to endNight
15%7%26%6%345%5%7%34%
1476
June1st to 15thNight
15%425%425%46%8%41%
1260
16th to endNight
7%42333445%9%52%
1260
July1st to 15thNight
5%2134245%5%8%55%
1260
16th to endNight
32123235%6%8%60%
1432
August1st to 15thNight
5%31332335%8%59%
1503
16th to endNight
7%21322235%5%61%
1764
September1st to 15thNight
9%423423345%55%
1800
16th to endNight
9%5%1432236%7%53%
1891
October1st to 15thNight
8%6%25%43445%7%46%
1980
16th to endNight
9%7%344245%6%8%42%
2197
November1st to 15thNight
7%7%45%6%25%45%7%44%
2450
16th to endNight
6%9%38%7%35%5%5%8%37%
2520
December1st to 15thNight
5%10%5%10%10%47%5%6%7%25%
2574
16th to endNight
6%10%48%7%35%6%6%9%30%
2880

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
52%9%12%18%5%
1253
16th to endDay
50%8%18%16%41
1497
February1st to 15thDay
58%6%15%14%5%
1575
16th to endDay
59%6%15%11%6%
1438
March1st to 15thDay
48%9%20%15%4
1890
16th to endDay
52%8%17%17%3
2154
April1st to 15thDay
47%7%16%20%7%
2150
16th to endDay
48%5%15%22%6%1
2373
May1st to 15thDay
44%5%12%27%10%
2511
16th to endDay
51%7%14%18%7%
2638
June1st to 15thDay
46%7%16%20%9%
2700
16th to endDay
31%8%18%30%10%
2700
July1st to 15thDay
27%6%15%30%16%3
2541
16th to endDay
21%5%13%30%23%5%
2566
August1st to 15thDay
30%7%15%28%15%3
2441
16th to endDay
23%5%13%33%20%4
2438
September1st to 15thDay
33%412%28%15%4
2160
16th to endDay
33%5%11%30%16%2
1904
October1st to 15thDay
40%5%17%26%9%
1650
16th to endDay
39%7%19%26%6%
1661
November1st to 15thDay
40%6%19%25%6%
1408
16th to endDay
46%7%19%17%8%
1440
December1st to 15thDay
61%9%12%15%
1383
16th to endDay
54%8%18%13%4
1344
January1st to 15thNight
48%9%17%19%4
2685
16th to endNight
48%7%16%19%6%1
2735
February1st to 15thNight
46%6%19%19%6%1
2288
16th to endNight
50%7%14%18%8%
2035
March1st to 15thNight
43%9%19%19%7%
2068
16th to endNight
49%8%16%20%5%
2070
April1st to 15thNight
41%8%15%24%10%
1798
16th to endNight
47%5%12%22%10%2
1585
May1st to 15thNight
37%6%12%28%14%
1440
16th to endNight
48%6%13%20%10%
1477
June1st to 15thNight
41%5%16%23%12%1
1260
16th to endNight
28%5%20%30%13%
1260
July1st to 15thNight
25%6%13%29%20%4
1190
16th to endNight
19%417%29%23%5%
1339
August1st to 15thNight
23%416%33%18%3
1495
16th to endNight
23%5%8%28%25%7%
1764
September1st to 15thNight
30%410%26%19%7%
1800
16th to endNight
29%411%30%20%3
1891
October1st to 15thNight
36%7%15%25%14%1
1980
16th to endNight
36%8%15%26%11%
2197
November1st to 15thNight
39%5%17%24%10%1
2450
16th to endNight
45%6%20%18%8%
2520
December1st to 15thNight
55%7%17%16%3
2574
16th to endNight
48%8%17%19%5%
2880

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
10%318%21%31%15%
60
16th to endDay
18%5%26%17%31%1
87
February1st to 15thDay
17%11%34%26%10%
90
16th to endDay
18%7%27%34%9%2
81
March1st to 15thDay
8%12%40%27%11%
180
16th to endDay
11%12%39%25%9%1
288
April1st to 15thDay
15%19%30%25%8%
269
16th to endDay
23%8%28%26%11%1
312
May1st to 15thDay
18%5%24%29%17%4
468
16th to endDay
20%8%25%23%17%5%
517
June1st to 15thDay
16%7%29%27%16%2
495
16th to endDay
10%7%28%30%18%3
495
July1st to 15thDay
7%323%40%20%5%
475
16th to endDay
4327%38%22%3
515
August1st to 15thDay
9%324%35%20%7%
430
16th to endDay
9%5%21%32%23%6%
332
September1st to 15thDay
13%6%26%35%12%5%
315
16th to endDay
16%6%28%26%19%3
226
October1st to 15thDay
28%6%21%27%11%4
90
16th to endDay
14%7%26%27%19%5%
96
November1st to 15thDay
11%437%28%17%
90
16th to endDay
8%13%31%28%14%3
90
December1st to 15thDay
9%432%38%7%7%
81
16th to endDay
15%7%40%21%12%1
64
January1st to 15thNight
10%10%35%30%10%2
900
16th to endNight
7%12%38%29%10%1
952
February1st to 15thNight
9%6%32%33%15%2
704
16th to endNight
9%5%30%36%15%2
632
March1st to 15thNight
8%6%35%34%13%1
720
16th to endNight
12%7%35%33%9%1
726
April1st to 15thNight
12%5%36%34%10%
539
16th to endNight
17%7%28%35%11%
540
May1st to 15thNight
13%428%38%12%1
540
16th to endNight
18%6%27%30%15%1
542
June1st to 15thNight
17%5%23%37%15%1
360
16th to endNight
9%427%41%16%
360
July1st to 15thNight
5%226%48%15%
340
16th to endNight
4226%47%17%
485
August1st to 15thNight
7%122%43%23%2
539
16th to endNight
8%323%41%22%1
573
September1st to 15thNight
11%222%37%24%1
540
16th to endNight
11%427%37%18%1
618
October1st to 15thNight
11%6%31%33%14%1
660
16th to endNight
14%7%29%38%10%
778
November1st to 15thNight
11%10%37%27%12%1
875
16th to endNight
11%8%37%34%8%
900
December1st to 15thNight
10%7%31%34%14%1
900
16th to endNight
13%6%35%30%13%2
960
Page generated at 2017-09-24 07:15:55. Version ac04

Copyright 2017 A. Danko


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