Fairbanks
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fairbanks clear sky chart from 2005-11-05 to 2017-08-12.

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
52%
13175
7%
45970
6%
13163
53%
13163
15%
33596

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
51%
868
7%
3366
6%
868
53%
868
13%
2426
January16th to endNight
55%
823
10%
3333
9%
823
56%
823
14%
2386
February1st to 15thNight
58%
726
15%
2751
14%
726
59%
726
21%
1759
February16th to endNight
52%
659
12%
2212
12%
659
53%
659
16%
1599
March1st to 15thNight
53%
577
15%
2188
17%
577
57%
577
19%
1419
March16th to endNight
60%
581
13%
2011
14%
581
61%
581
23%
1247
April1st to 15thNight
52%
539
3%
1583
3%
539
52%
539
17%
1187
April16th to endNight
63%
505
0%
1288
0%
505
63%
505
30%
874
May1st to 15thNight
59%
266
0%
987
0%
266
59%
266
17%
673
May16th to endNight
60%
187
0%
687
0%
187
60%
187
20%
445
June1st to 15thNight
50%
180
0%
398
0%
180
50%
180
17%
323
June16th to endNight
60%
180
0%
360
0%
180
60%
180
23%
293
July1st to 15thNight
59%
170
0%
410
0%
170
59%
170
17%
327
July16th to endNight
43%
188
0%
717
0%
177
42%
177
8%
566
August1st to 15thNight
50%
341
0%
1042
0%
340
50%
340
9%
854
August16th to endNight
49%
509
0%
1337
0%
509
49%
509
17%
1046
September1st to 15thNight
55%
495
3%
1539
3%
495
55%
495
17%
1127
September16th to endNight
41%
495
4%
1795
5%
495
42%
495
9%
1430
October1st to 15thNight
45%
636
6%
2091
5%
636
46%
636
12%
1660
October16th to endNight
52%
736
6%
2538
6%
736
53%
736
14%
1911
November1st to 15thNight
49%
730
5%
2840
5%
730
49%
730
12%
2140
November16th to endNight
49%
800
10%
3195
11%
800
51%
800
12%
2332
December1st to 15thNight
46%
960
8%
3462
7%
960
47%
960
12%
2642
December16th to endNight
52%
1024
5%
3840
4%
1024
52%
1024
10%
2930

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
11%9%48%7%46%5%6%7%28%
48124
Night
8%11%5%9%7%46%5%6%7%28%
46036
TransparencyDay
51%10%17%15%4
47690
Night
52%9%16%15%5%
45975
SeeingDay
14%315%25%28%12%
8775
Night
12%212%31%31%8%
13191

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%12%8%10%9%47%44426%
583
16th to endDay
311%6%7%6%49%6%6%12%25%
891
February1st to 15thDay
310%6%12%7%36%6%6%6%30%
1113
16th to endDay
310%6%10%8%46%6%7%8%28%
1262
March1st to 15thDay
49%5%7%7%5%6%46%6%35%
1770
16th to endDay
36%48%6%35%46%6%42%
2208
April1st to 15thDay
5%12%6%8%7%5%7%5%7%8%26%
2364
16th to endDay
35%26%7%47%6%6%10%37%
2670
May1st to 15thDay
6%8%5%8%8%47%6%6%7%30%
2964
16th to endDay
8%6%36%6%46%6%8%9%33%
3424
June1st to 15thDay
13%8%5%8%8%47%6%5%7%24%
3561
16th to endDay
13%6%36%6%36%6%7%9%31%
3600
July1st to 15thDay
13%7%37%7%47%6%8%8%25%
3524
16th to endDay
20%9%48%7%46%6%6%7%18%
3404
August1st to 15thDay
20%10%47%6%35%6%6%7%22%
2825
16th to endDay
18%8%37%6%35%46%8%26%
2512
September1st to 15thDay
17%9%46%7%345%6%7%27%
2090
16th to endDay
18%14%410%6%35%45%5%21%
1835
October1st to 15thDay
10%13%6%10%8%35%5%46%24%
1539
16th to endDay
10%12%38%8%345%7%8%26%
1332
November1st to 15thDay
8%10%7%11%10%46%5%6%6%23%
1018
16th to endDay
10%11%48%8%45%45%5%29%
753
December1st to 15thDay
8%15%6%9%6%25%6%7%7%25%
498
16th to endDay
312%7%10%8%37%6%6%6%26%
384
January1st to 15thNight
6%13%6%10%7%35%5%6%6%29%
3366
16th to endNight
411%5%10%7%47%6%6%8%27%
3333
February1st to 15thNight
210%6%10%6%35%45%8%37%
2739
16th to endNight
411%5%9%8%5%6%5%5%8%29%
2212
March1st to 15thNight
310%5%9%7%35%45%6%37%
2188
16th to endNight
49%46%4446%5%5%44%
2011
April1st to 15thNight
5%11%5%8%8%46%5%6%8%27%
1583
16th to endNight
45%27%7%46%5%8%8%39%
1288
May1st to 15thNight
6%7%37%7%5%7%6%6%9%31%
986
16th to endNight
9%7%346%35%6%6%8%36%
687
June1st to 15thNight
9%10%310%9%38%5%6%9%23%
398
16th to endNight
11%7%18%6%48%6%6%10%27%
360
July1st to 15thNight
11%5%45%8%37%8%8%11%24%
436
16th to endNight
21%9%5%7%7%347%5%7%20%
765
August1st to 15thNight
20%8%37%7%5%7%6%6%7%18%
1047
16th to endNight
19%9%46%6%245%45%30%
1337
September1st to 15thNight
14%9%36%6%45%5%6%8%30%
1539
16th to endNight
14%11%5%10%7%45%7%45%23%
1795
October1st to 15thNight
12%13%5%9%7%45%6%5%6%23%
2091
16th to endNight
10%14%5%7%7%345%7%7%27%
2538
November1st to 15thNight
8%12%6%11%8%45%5%6%6%25%
2840
16th to endNight
9%11%5%11%7%35%45%6%27%
3195
December1st to 15thNight
8%14%6%11%6%45%45%6%25%
3462
16th to endNight
412%6%10%8%48%6%6%8%21%
3840

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
60%412%14%6%1
583
16th to endDay
50%9%17%15%6%
891
February1st to 15thDay
50%8%11%18%10%1
1113
16th to endDay
50%8%14%15%10%
1262
March1st to 15thDay
46%7%13%20%9%2
1770
16th to endDay
40%6%19%19%12%1
2208
April1st to 15thDay
52%9%16%18%2
2364
16th to endDay
39%9%18%26%6%1
2670
May1st to 15thDay
49%9%13%23%3
2964
16th to endDay
42%10%17%19%9%
3428
June1st to 15thDay
57%10%15%14%2
3561
16th to endDay
47%12%20%17%2
3600
July1st to 15thDay
51%14%20%12%1
3321
16th to endDay
61%14%17%6%
3189
August1st to 15thDay
58%12%21%6%
2805
16th to endDay
53%13%21%10%1
2512
September1st to 15thDay
53%11%22%11%1
2090
16th to endDay
63%9%13%12%1
1835
October1st to 15thDay
59%10%16%10%3
1539
16th to endDay
53%11%21%12%1
1332
November1st to 15thDay
58%9%17%12%1
1018
16th to endDay
55%8%13%18%3
753
December1st to 15thDay
55%9%15%12%5%1
498
16th to endDay
53%10%20%11%2
384
January1st to 15thNight
53%8%14%16%5%2
3366
16th to endNight
53%7%15%16%6%
3333
February1st to 15thNight
44%5%12%22%12%1
2751
16th to endNight
52%7%12%17%8%
2212
March1st to 15thNight
45%5%12%21%10%3
2188
16th to endNight
40%6%15%20%15%1
2016
April1st to 15thNight
51%9%16%19%2
1583
16th to endNight
38%9%21%23%7%
1288
May1st to 15thNight
45%11%15%25%2
987
16th to endNight
43%7%16%21%10%
687
June1st to 15thNight
56%10%15%15%2
398
16th to endNight
50%12%18%17%1
360
July1st to 15thNight
47%18%19%12%2
410
16th to endNight
60%11%18%9%
717
August1st to 15thNight
61%12%17%8%
1042
16th to endNight
54%9%21%12%1
1337
September1st to 15thNight
50%10%24%13%1
1539
16th to endNight
60%11%12%13%2
1795
October1st to 15thNight
59%10%18%9%3
2091
16th to endNight
53%11%22%10%2
2538
November1st to 15thNight
56%9%18%14%
2840
16th to endNight
56%6%13%18%4
3195
December1st to 15thNight
57%9%14%12%5%
3462
16th to endNight
56%11%17%11%3
3840

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%3340%33%10%
30
16th to endDay
5%2433%32%19%
101
February1st to 15thDay
8%48%21%32%24%
209
16th to endDay
9%419%31%25%8%
211
March1st to 15thDay
7%414%35%25%12%
240
16th to endDay
6%113%28%35%13%
391
April1st to 15thDay
10%5%16%30%29%8%
442
16th to endDay
3218%32%32%10%
450
May1st to 15thDay
10%6%16%27%30%9%
468
16th to endDay
11%5%18%30%25%7%
764
June1st to 15thDay
15%221%27%24%8%
855
16th to endDay
12%212%21%34%16%
855
July1st to 15thDay
14%29%24%33%15%
793
16th to endDay
21%214%22%25%13%
694
August1st to 15thDay
20%218%20%27%10%
475
16th to endDay
21%314%22%26%11%
443
September1st to 15thDay
20%213%24%23%15%
406
16th to endDay
26%9%15%19%17%12%
264
October1st to 15thDay
13%319%18%27%17%
225
16th to endDay
15%212%20%27%20%
240
November1st to 15thDay
16%9%29%31%13%
127
16th to endDay
23%316%33%23%
30
December1st to 15thDay
13%6%20%43%16%
30
16th to endDay
12%9%12%31%21%12%
32
January1st to 15thNight
11%212%33%28%11%
873
16th to endNight
9%311%39%30%6%
823
February1st to 15thNight
6%211%36%31%11%
734
16th to endNight
9%415%40%27%2
659
March1st to 15thNight
8%316%39%27%3
577
16th to endNight
8%215%29%32%11%
582
April1st to 15thNight
10%217%31%33%4
539
16th to endNight
6%212%33%39%5%
505
May1st to 15thNight
8%312%29%37%6%
267
16th to endNight
12%412%35%28%5%
188
June1st to 15thNight
15%118%28%31%4
180
16th to endNight
15%27%23%40%11%
180
July1st to 15thNight
12%210%27%39%8%
170
16th to endNight
24%5%9%22%30%6%
188
August1st to 15thNight
23%16%28%33%6%
341
16th to endNight
22%310%20%28%13%
509
September1st to 15thNight
18%211%26%29%11%
495
16th to endNight
19%416%25%29%4
495
October1st to 15thNight
16%416%24%31%5%
636
16th to endNight
16%110%30%31%9%
736
November1st to 15thNight
13%113%32%29%8%
730
16th to endNight
15%111%26%32%13%
800
December1st to 15thNight
14%413%27%28%11%
960
16th to endNight
8%111%35%30%12%
1024
Page generated at 2017-08-13 10:16:44. Version ac04

Copyright 2017 A. Danko


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