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 2018-02-22.

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
52%
14150
7%
48851
7%
14138
53%
14138
15%
35789

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
53%
966
8%
3648
8%
966
54%
966
15%
2595
January16th to endNight
53%
914
9%
3610
9%
914
54%
914
13%
2611
February1st to 15thNight
59%
801
16%
2985
16%
801
60%
801
22%
1880
February16th to endNight
51%
694
11%
2309
11%
694
51%
694
15%
1691
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
49%
349
0%
1066
0%
348
49%
348
9%
878
August16th to endNight
48%
556
0%
1460
0%
556
48%
556
15%
1163
September1st to 15thNight
54%
540
3%
1679
3%
540
54%
540
16%
1244
September16th to endNight
40%
542
4%
1959
5%
542
41%
542
9%
1566
October1st to 15thNight
45%
706
6%
2281
5%
706
45%
706
12%
1825
October16th to endNight
52%
816
6%
2769
6%
816
52%
816
14%
2094
November1st to 15thNight
48%
805
5%
3083
5%
805
48%
805
11%
2354
November16th to endNight
51%
887
11%
3462
13%
887
52%
887
13%
2516
December1st to 15thNight
46%
1065
8%
3751
8%
1065
47%
1065
12%
2864
December16th to endNight
52%
1136
6%
4160
6%
1136
53%
1136
11%
3154

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%27%
49522
Night
8%11%5%9%7%45%5%6%7%28%
48917
TransparencyDay
52%10%17%15%4
49088
Night
53%8%15%15%5%
48856
SeeingDay
14%315%25%28%12%
9244
Night
13%212%31%30%8%
14166

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
5%11%8%10%9%5%6%445%28%
632
16th to endDay
312%7%7%6%48%6%6%11%24%
966
February1st to 15thDay
410%6%11%7%35%5%5%6%33%
1209
16th to endDay
310%6%10%8%46%6%7%8%27%
1312
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
21%10%47%6%35%6%6%7%21%
2886
16th to endDay
18%9%38%6%35%46%8%24%
2741
September1st to 15thDay
16%9%46%7%346%6%7%26%
2280
16th to endDay
19%13%410%6%35%45%5%20%
2001
October1st to 15thDay
11%13%6%11%8%35%5%46%23%
1679
16th to endDay
10%13%39%8%345%7%8%25%
1452
November1st to 15thDay
8%10%7%11%10%47%5%6%6%21%
1105
16th to endDay
10%12%49%8%445%5%5%29%
815
December1st to 15thDay
8%16%6%9%7%35%5%7%6%23%
539
16th to endDay
313%6%11%8%36%6%6%6%26%
416
January1st to 15thNight
5%12%6%10%7%35%5%5%6%31%
3648
16th to endNight
5%11%6%10%7%37%6%6%7%26%
3610
February1st to 15thNight
210%6%9%6%3445%8%39%
2973
16th to endNight
411%5%9%8%5%6%5%48%28%
2309
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%38%7%5%7%5%6%7%17%
1071
16th to endNight
19%9%36%7%35%5%5%5%28%
1460
September1st to 15thNight
14%9%36%6%45%5%6%8%28%
1679
16th to endNight
16%11%5%9%7%45%6%45%23%
1959
October1st to 15thNight
12%13%5%9%8%45%6%6%6%23%
2281
16th to endNight
10%13%5%8%7%345%7%7%27%
2769
November1st to 15thNight
7%13%6%11%8%45%5%6%6%24%
3083
16th to endNight
9%12%5%10%7%36%45%7%27%
3462
December1st to 15thNight
7%14%6%11%6%45%45%7%25%
3751
16th to endNight
412%6%10%8%47%6%6%8%22%
4160

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
57%413%15%6%1
632
16th to endDay
51%8%16%15%7%
966
February1st to 15thDay
49%7%10%16%13%1
1209
16th to endDay
51%8%14%15%9%
1312
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
59%12%20%6%
2866
16th to endDay
55%13%19%9%1
2741
September1st to 15thDay
54%12%21%11%1
2280
16th to endDay
64%9%12%12%
2001
October1st to 15thDay
60%10%16%9%3
1679
16th to endDay
54%11%21%11%1
1452
November1st to 15thDay
59%9%16%11%1
1105
16th to endDay
55%8%13%17%5%
815
December1st to 15thDay
57%8%14%12%41
539
16th to endDay
54%10%19%11%3
416
January1st to 15thNight
52%7%14%17%5%2
3648
16th to endNight
55%7%14%16%6%
3610
February1st to 15thNight
43%5%11%21%15%3
2985
16th to endNight
53%7%12%16%8%
2309
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%16%8%
1066
16th to endNight
56%10%20%11%1
1460
September1st to 15thNight
52%9%23%13%1
1679
16th to endNight
61%11%12%13%2
1959
October1st to 15thNight
59%10%18%9%2
2281
16th to endNight
53%10%21%11%2
2769
November1st to 15thNight
57%9%17%13%
3083
16th to endNight
56%6%12%18%5%
3462
December1st to 15thNight
57%9%14%12%5%
3751
16th to endNight
56%10%17%11%3
4160

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%28%37%37%6%
45
16th to endDay
6%25%33%32%19%
123
February1st to 15thDay
9%47%21%32%23%
241
16th to endDay
9%5%19%32%25%8%
230
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
21%217%20%27%10%
494
16th to endDay
21%413%22%25%11%
523
September1st to 15thDay
20%314%24%22%15%
474
16th to endDay
26%8%15%21%16%11%
312
October1st to 15thDay
15%5%20%17%24%15%
270
16th to endDay
14%212%22%28%19%
288
November1st to 15thDay
16%11%33%27%11%
154
16th to endDay
15%224%37%20%
45
December1st to 15thDay
22%11%24%31%11%
45
16th to endDay
14%6%12%33%25%8%
48
January1st to 15thNight
11%212%33%28%10%
971
16th to endNight
10%311%38%29%7%
914
February1st to 15thNight
6%210%35%32%12%
809
16th to endNight
9%416%40%26%2
694
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
24%16%28%32%6%
349
16th to endNight
23%39%20%29%12%
556
September1st to 15thNight
18%211%26%29%11%
540
16th to endNight
21%416%24%29%4
542
October1st to 15thNight
17%417%25%29%6%
706
16th to endNight
16%110%30%31%10%
816
November1st to 15thNight
14%113%34%27%7%
805
16th to endNight
14%111%27%32%12%
887
December1st to 15thNight
13%413%30%26%10%
1065
16th to endNight
9%111%36%30%11%
1136
Page generated at 2018-02-23 07:21:30. Version ac04

Copyright 2018 A. Danko


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