Northstar Ski Resort
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Northstar Ski Resort clear sky chart from 2005-11-05 to 2017-09-22.

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
46%
15196
25%
46922
18%
15166
55%
15166
31%
25871

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
43%
717
18%
2506
15%
716
50%
716
22%
1491
January16th to endNight
38%
768
21%
2520
15%
768
47%
768
20%
1547
February1st to 15thNight
35%
700
19%
2240
16%
700
42%
700
20%
1395
February16th to endNight
37%
632
22%
1895
15%
632
46%
632
22%
1207
March1st to 15thNight
36%
720
15%
2109
9%
720
44%
720
22%
1354
March16th to endNight
31%
768
17%
2025
9%
768
38%
768
23%
1305
April1st to 15thNight
35%
719
18%
1799
7%
719
40%
719
24%
1240
April16th to endNight
38%
720
20%
1800
8%
720
43%
720
31%
1097
May1st to 15thNight
40%
550
25%
1630
12%
550
51%
550
33%
848
May16th to endNight
47%
374
21%
1496
18%
374
55%
374
24%
761
June1st to 15thNight
51%
360
26%
1440
24%
360
65%
360
32%
650
June16th to endNight
56%
360
32%
1440
28%
360
75%
360
47%
511
July1st to 15thNight
72%
340
32%
1360
37%
340
80%
340
53%
473
July16th to endNight
68%
425
38%
1461
36%
399
81%
399
55%
553
August1st to 15thNight
65%
604
32%
1677
20%
601
71%
601
53%
818
August16th to endNight
66%
764
43%
1910
21%
764
73%
764
66%
889
September1st to 15thNight
70%
720
40%
1800
24%
720
76%
720
68%
839
September16th to endNight
59%
683
40%
1842
25%
683
71%
683
52%
889
October1st to 15thNight
53%
660
30%
1969
24%
660
64%
660
40%
1009
October16th to endNight
53%
704
32%
2132
24%
704
67%
704
40%
1059
November1st to 15thNight
51%
700
26%
2275
24%
700
57%
700
32%
1243
November16th to endNight
37%
720
25%
2388
18%
720
48%
720
25%
1318
December1st to 15thNight
34%
720
17%
2520
12%
720
43%
720
17%
1601
December16th to endNight
28%
768
20%
2688
14%
768
38%
768
15%
1774

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
36%24323346%59%
47974
Night
36%34323347%56%
47101
TransparencyDay
24%6%10%19%22%15%
47650
Night
26%7%11%21%21%12%
46924
SeeingDay
14%25%28%19%9%2
5794
Night
9%24%16%23%20%5%
15205

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
37%35%6%35%46%6%47%
1432
16th to endDay
413%5%5%4245%5%7%42%
1704
February1st to 15thDay
48%46%5%245%47%46%
1622
16th to endDay
313%7%7%42335%7%41%
1579
March1st to 15thDay
212%7%7%5%45%346%40%
1848
16th to endDay
312%45%5%235%5%8%41%
2199
April1st to 15thDay
313%46%4245%47%41%
2149
16th to endDay
49%3432425%5%54%
2160
May1st to 15thDay
45%1331335%7%59%
2318
16th to endDay
6%8%25%423346%49%
2615
June1st to 15thDay
5%414324346%59%
2520
16th to endDay
11111122479%
2520
July1st to 15thDay
11121223378%
2520
16th to endDay
21111222478%
2606
August1st to 15thDay
21221233477%
2274
16th to endDay
1111132382%
2292
September1st to 15thDay
11221123477%
2160
16th to endDay
33121123474%
1929
October1st to 15thDay
46%24212446%61%
1658
16th to endDay
45%1431235%6%61%
1738
November1st to 15thDay
45%24325%5%48%53%
1584
16th to endDay
38%3432346%11%48%
1571
December1st to 15thDay
310%47%5%35%37%8%40%
1440
16th to endDay
5%11%5%5%6%34446%40%
1536
January1st to 15thNight
27%46%5%3446%9%44%
2506
16th to endNight
39%5%5%5%25%6%5%6%45%
2520
February1st to 15thNight
27%47%7%35%46%8%41%
2230
16th to endNight
310%5%7%423448%44%
1895
March1st to 15thNight
110%46%5%35%5%6%8%42%
2109
16th to endNight
28%36%42446%8%47%
2025
April1st to 15thNight
48%45%5%26%5%7%8%41%
1799
16th to endNight
48%34213447%55%
1800
May1st to 15thNight
35%12323346%63%
1630
16th to endNight
47%24224349%54%
1496
June1st to 15thNight
3413223235%65%
1440
16th to endNight
11121222378%
1440
July1st to 15thNight
111111223478%
1440
16th to endNight
311121222378%
1561
August1st to 15thNight
221221233373%
1686
16th to endNight
1111224479%
1910
September1st to 15thNight
111111135%80%
1800
16th to endNight
221221223475%
1842
October1st to 15thNight
5%414322236%65%
1969
16th to endNight
3412222348%63%
2132
November1st to 15thNight
441432346%9%54%
2275
16th to endNight
27%35%42335%9%53%
2388
December1st to 15thNight
37%47%6%245%6%8%43%
2520
16th to endNight
212%5%8%5%35%447%40%
2688

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
32%10%14%24%14%2
1432
16th to endDay
38%8%11%17%15%8%
1704
February1st to 15thDay
36%7%15%21%15%4
1622
16th to endDay
39%8%13%24%12%2
1579
March1st to 15thDay
38%13%13%15%15%3
1848
16th to endDay
34%12%20%18%11%3
2199
April1st to 15thDay
38%7%16%20%14%2
2149
16th to endDay
29%6%14%27%18%3
2160
May1st to 15thDay
22%5%13%31%22%3
2318
16th to endDay
33%5%12%24%20%4
2619
June1st to 15thDay
22%5%10%21%26%13%
2520
16th to endDay
9%25%17%37%26%
2520
July1st to 15thDay
9%2410%25%47%
2371
16th to endDay
11%2311%22%48%
2443
August1st to 15thDay
12%2411%26%42%
2258
16th to endDay
9%2211%39%35%
2292
September1st to 15thDay
10%25%12%36%31%
2160
16th to endDay
14%36%25%32%17%
1929
October1st to 15thDay
23%49%25%27%9%
1658
16th to endDay
22%5%12%25%24%9%
1738
November1st to 15thDay
28%8%14%23%17%7%
1584
16th to endDay
28%8%13%24%21%2
1571
December1st to 15thDay
39%10%13%21%14%
1440
16th to endDay
43%9%10%14%18%2
1536
January1st to 15thNight
32%10%14%21%17%3
2506
16th to endNight
35%8%12%16%16%10%
2520
February1st to 15thNight
34%10%13%22%12%5%
2241
16th to endNight
34%11%13%24%13%3
1895
March1st to 15thNight
34%11%16%18%13%6%
2109
16th to endNight
29%13%19%21%13%3
2025
April1st to 15thNight
37%10%15%23%12%1
1799
16th to endNight
27%7%18%26%16%3
1800
May1st to 15thNight
21%5%12%30%25%4
1631
16th to endNight
27%6%14%28%17%4
1496
June1st to 15thNight
19%7%8%24%26%13%
1440
16th to endNight
11%26%18%34%25%
1440
July1st to 15thNight
10%249%27%45%
1360
16th to endNight
11%2410%23%47%
1461
August1st to 15thNight
15%3412%25%38%
1677
16th to endNight
8%2314%38%32%
1910
September1st to 15thNight
8%16%13%39%29%
1800
16th to endNight
14%26%23%34%18%
1842
October1st to 15thNight
21%48%29%27%7%
1969
16th to endNight
19%5%11%27%30%6%
2132
November1st to 15thNight
26%7%13%25%19%7%
2275
16th to endNight
26%9%12%26%21%4
2388
December1st to 15thNight
37%11%12%21%14%2
2520
16th to endNight
42%9%10%16%16%3
2688

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
40%18%26%10%31
60
16th to endDay
24%29%16%17%9%2
232
February1st to 15thDay
17%31%22%19%8%
245
16th to endDay
22%28%27%15%5%
238
March1st to 15thDay
24%36%15%11%8%2
270
16th to endDay
22%36%19%16%4
288
April1st to 15thDay
24%30%25%12%6%
269
16th to endDay
17%37%27%12%41
270
May1st to 15thDay
15%34%24%19%41
288
16th to endDay
18%25%22%17%11%3
330
June1st to 15thDay
16%26%28%19%7%1
315
16th to endDay
5%23%35%22%8%4
315
July1st to 15thDay
318%37%27%11%1
305
16th to endDay
121%37%25%9%4
327
August1st to 15thDay
5%20%38%22%9%3
315
16th to endDay
215%36%24%16%5%
332
September1st to 15thDay
6%15%34%26%15%1
315
16th to endDay
9%19%32%23%14%1
280
October1st to 15thDay
11%26%26%20%12%3
255
16th to endDay
19%25%26%15%12%
250
November1st to 15thDay
12%14%18%13%35%5%
90
16th to endDay
14%34%14%27%8%
81
December1st to 15thDay
28%33%23%10%5%
60
16th to endDay
25%17%23%21%9%3
64
January1st to 15thNight
9%25%17%23%16%8%
720
16th to endNight
11%27%19%20%15%5%
768
February1st to 15thNight
13%27%19%21%14%4
704
16th to endNight
14%27%17%21%13%5%
632
March1st to 15thNight
15%29%16%18%16%4
720
16th to endNight
13%35%18%16%14%1
768
April1st to 15thNight
12%31%19%22%13%1
719
16th to endNight
11%30%17%20%14%4
720
May1st to 15thNight
7%29%20%22%15%3
551
16th to endNight
8%24%16%22%22%5%
375
June1st to 15thNight
5%23%16%27%23%3
360
16th to endNight
322%16%30%26%1
360
July1st to 15thNight
112%10%37%35%2
340
16th to endNight
217%8%31%33%6%
425
August1st to 15thNight
312%15%32%31%5%
604
16th to endNight
112%16%33%30%5%
764
September1st to 15thNight
112%14%29%35%7%
720
16th to endNight
5%17%15%25%26%10%
683
October1st to 15thNight
9%17%15%25%22%8%
660
16th to endNight
11%17%15%25%21%9%
704
November1st to 15thNight
8%22%15%22%23%7%
700
16th to endNight
12%31%16%19%16%4
720
December1st to 15thNight
16%28%18%20%13%3
720
16th to endNight
15%30%22%17%10%3
768
Page generated at 2017-09-23 03:43:35. Version ac04

Copyright 2017 A. Danko


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