Asheville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Asheville clear sky chart from 2005-11-05 to 2018-01-12.

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
46%
16085
19%
48360
13%
16044
53%
16044
23%
31349

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
28%
764
20%
2472
9%
761
41%
761
17%
1542
January16th to endNight
25%
768
21%
2496
9%
768
40%
768
19%
1580
February1st to 15thNight
26%
703
21%
2178
9%
701
40%
701
22%
1331
February16th to endNight
23%
631
22%
1893
9%
631
35%
631
18%
1213
March1st to 15thNight
29%
720
21%
2010
11%
720
38%
720
22%
1327
March16th to endNight
30%
768
15%
2112
8%
768
36%
768
21%
1453
April1st to 15thNight
34%
715
20%
1970
9%
715
44%
715
26%
1212
April16th to endNight
46%
540
21%
1620
13%
540
53%
540
25%
1033
May1st to 15thNight
45%
540
14%
1620
7%
540
50%
540
22%
1094
May16th to endNight
61%
561
14%
1684
10%
561
63%
561
26%
1089
June1st to 15thNight
65%
540
11%
1620
9%
540
67%
540
23%
1089
June16th to endNight
72%
540
14%
1620
12%
540
73%
540
29%
1037
July1st to 15thNight
71%
510
9%
1530
8%
510
71%
510
22%
1095
July16th to endNight
73%
564
12%
1595
10%
531
75%
531
24%
1097
August1st to 15thNight
67%
539
12%
1609
11%
536
68%
536
21%
1144
August16th to endNight
69%
605
16%
1827
15%
605
69%
605
20%
1308
September1st to 15thNight
58%
720
17%
1980
15%
720
59%
720
22%
1402
September16th to endNight
58%
717
21%
1980
18%
717
60%
717
26%
1315
October1st to 15thNight
51%
720
26%
2061
21%
720
57%
720
29%
1299
October16th to endNight
47%
768
31%
2304
22%
768
60%
768
32%
1319
November1st to 15thNight
51%
760
26%
2405
21%
760
60%
760
28%
1421
November16th to endNight
44%
780
26%
2535
19%
780
55%
780
25%
1501
December1st to 15thNight
36%
780
20%
2535
13%
780
46%
780
20%
1617
December16th to endNight
31%
832
19%
2704
12%
832
41%
832
16%
1831

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%6%36%6%35%5%6%7%37%
48975
Night
9%5%25%5%35%5%6%8%41%
48557
TransparencyDay
42%9%12%17%13%3
48676
Night
37%9%13%19%15%3
48360
SeeingDay
16%10%20%22%18%12%
5875
Night
15%11%20%27%20%3
16089

By Month

Percentage Cloud Cover SE (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
10%6%36%5%4446%7%40%
1710
16th to endDay
10%7%25%4345%48%44%
1728
February1st to 15thDay
10%7%25%6%35%45%7%42%
1681
16th to endDay
9%6%35%5%2445%7%42%
1580
March1st to 15thDay
13%7%25%5%3446%7%40%
1948
16th to endDay
14%7%45%5%345%6%7%36%
2111
April1st to 15thDay
10%5%145%25%46%9%43%
1987
16th to endDay
13%6%25%435%5%46%41%
2340
May1st to 15thDay
11%6%47%6%35%46%7%36%
2331
16th to endDay
10%5%25%6%46%6%6%8%35%
2431
June1st to 15thDay
8%5%36%7%5%7%7%8%9%28%
2340
16th to endDay
7%425%6%5%7%7%7%9%34%
2340
July1st to 15thDay
10%7%38%8%48%7%8%9%24%
2340
16th to endDay
9%436%7%48%8%7%10%28%
2465
August1st to 15thDay
10%7%37%7%5%6%7%8%10%25%
2340
16th to endDay
11%6%36%7%5%7%8%7%8%26%
2360
September1st to 15thDay
12%6%37%8%45%5%7%7%31%
1980
16th to endDay
14%6%25%5%46%6%6%6%35%
1980
October1st to 15thDay
12%424323445%51%
1899
16th to endDay
10%5%2442233456%
1920
November1st to 15thDay
7%5%245%24446%51%
1782
16th to endDay
12%5%34414346%48%
1755
December1st to 15thDay
10%6%27%6%46%5%5%6%39%
1755
16th to endDay
13%8%36%6%36%447%36%
1872
January1st to 15thNight
9%6%25%5%36%5%6%7%41%
2472
16th to endNight
12%7%35%5%35%5%5%6%39%
2496
February1st to 15thNight
9%8%24425%45%8%42%
2169
16th to endNight
10%5%35%6%45%5%5%7%39%
1893
March1st to 15thNight
11%6%36%5%245%6%7%41%
2010
16th to endNight
11%7%25%5%4445%7%39%
2112
April1st to 15thNight
8%5%345%245%5%8%46%
1970
16th to endNight
9%5%26%5%34348%46%
1620
May1st to 15thNight
10%5%36%5%45%46%8%38%
1619
16th to endNight
6%425%5%36%5%6%11%41%
1682
June1st to 15thNight
6%5%345%26%6%9%14%35%
1620
16th to endNight
6%423435%6%9%10%43%
1620
July1st to 15thNight
6%6%26%5%47%6%7%10%35%
1620
16th to endNight
5%4346%46%5%8%11%37%
1703
August1st to 15thNight
7%426%5%45%6%7%10%36%
1620
16th to endNight
8%6%25%6%47%6%7%10%34%
1827
September1st to 15thNight
10%427%6%45%6%5%8%38%
1980
16th to endNight
11%5%36%42445%6%45%
1980
October1st to 15thNight
10%42442445%6%49%
2061
16th to endNight
9%41432435%455%
2304
November1st to 15thNight
9%42442445%6%50%
2405
16th to endNight
10%5%3433445%6%48%
2535
December1st to 15thNight
12%6%35%5%35%6%5%7%38%
2535
16th to endNight
14%8%46%5%35%5%6%7%32%
2704

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
39%7%11%20%16%4
1711
16th to endDay
37%412%24%16%5%
1728
February1st to 15thDay
39%5%10%21%19%2
1683
16th to endDay
37%6%15%20%16%3
1580
March1st to 15thDay
40%6%9%21%16%4
1948
16th to endDay
44%8%14%16%13%2
2112
April1st to 15thDay
35%7%13%23%16%4
1987
16th to endDay
41%8%10%19%16%4
2340
May1st to 15thDay
45%10%12%18%11%1
2331
16th to endDay
43%13%14%17%9%1
2435
June1st to 15thDay
46%14%18%14%5%
2340
16th to endDay
42%13%15%14%12%1
2340
July1st to 15thDay
51%13%16%11%6%
2201
16th to endDay
45%15%18%12%6%1
2310
August1st to 15thDay
50%15%14%13%5%1
2327
16th to endDay
49%14%14%15%5%1
2360
September1st to 15thDay
49%9%13%14%10%3
1980
16th to endDay
46%9%11%14%15%2
1980
October1st to 15thDay
34%5%12%18%22%6%
1899
16th to endDay
31%47%23%23%10%
1920
November1st to 15thDay
32%5%8%18%25%8%
1782
16th to endDay
35%5%7%21%24%6%
1755
December1st to 15thDay
41%7%10%20%16%4
1755
16th to endDay
45%6%11%18%14%4
1872
January1st to 15thNight
37%8%12%18%18%4
2472
16th to endNight
40%6%10%19%18%4
2496
February1st to 15thNight
37%5%12%22%17%4
2178
16th to endNight
39%6%12%22%16%2
1893
March1st to 15thNight
39%7%12%18%17%4
2010
16th to endNight
43%8%13%21%11%1
2112
April1st to 15thNight
33%6%14%24%17%3
1970
16th to endNight
36%7%13%20%18%3
1620
May1st to 15thNight
41%10%15%20%11%
1620
16th to endNight
34%12%20%22%8%1
1684
June1st to 15thNight
35%16%23%20%4
1620
16th to endNight
31%13%21%19%12%1
1620
July1st to 15thNight
40%15%19%15%8%1
1530
16th to endNight
34%16%22%17%7%1
1595
August1st to 15thNight
38%16%18%13%11%
1609
16th to endNight
41%15%15%20%5%1
1827
September1st to 15thNight
43%11%12%18%11%2
1980
16th to endNight
40%7%12%18%19%1
1980
October1st to 15thNight
35%7%11%20%21%3
2061
16th to endNight
30%5%8%21%26%7%
2304
November1st to 15thNight
33%6%7%19%23%8%
2405
16th to endNight
33%6%8%21%22%7%
2535
December1st to 15thNight
40%7%13%17%15%5%
2535
16th to endNight
45%7%11%17%13%3
2704

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
27%20%34%13%3
123
16th to endDay
21%41%22%11%2
96
February1st to 15thDay
20%44%27%7%
90
16th to endDay
24%40%23%8%2
81
March1st to 15thDay
20%20%27%23%7%
238
16th to endDay
19%16%29%22%9%1
288
April1st to 15thDay
16%16%24%24%15%3
270
16th to endDay
17%8%25%22%17%7%
270
May1st to 15thDay
13%19%20%23%12%9%
288
16th to endDay
15%5%21%21%17%18%
331
June1st to 15thDay
13%317%23%22%19%
315
16th to endDay
10%421%20%22%20%
315
July1st to 15thDay
10%117%20%25%24%
305
16th to endDay
7%9%23%33%25%
326
August1st to 15thDay
17%313%23%18%23%
313
16th to endDay
11%12%25%25%24%
332
September1st to 15thDay
14%49%24%28%18%
315
16th to endDay
15%315%26%25%13%
314
October1st to 15thDay
18%7%16%25%23%7%
315
16th to endDay
17%11%18%29%17%5%
336
November1st to 15thDay
19%9%28%26%13%3
200
16th to endDay
16%19%29%20%12%2
135
December1st to 15thDay
22%20%38%14%2
135
16th to endDay
30%15%39%12%1
144
January1st to 15thNight
21%21%25%24%6%
765
16th to endNight
20%19%32%25%2
768
February1st to 15thNight
19%20%30%26%3
704
16th to endNight
17%27%29%22%2
631
March1st to 15thNight
17%19%30%26%5%
720
16th to endNight
18%15%32%23%10%
768
April1st to 15thNight
14%21%26%25%11%1
715
16th to endNight
14%12%20%33%17%1
540
May1st to 15thNight
15%8%23%32%17%2
540
16th to endNight
10%415%29%33%7%
563
June1st to 15thNight
8%114%31%34%9%
540
16th to endNight
6%110%28%42%10%
540
July1st to 15thNight
10%16%25%47%8%
510
16th to endNight
7%15%21%47%16%
564
August1st to 15thNight
11%28%24%43%10%
539
16th to endNight
10%17%26%45%8%
605
September1st to 15thNight
12%314%25%37%7%
720
16th to endNight
16%413%31%28%5%
717
October1st to 15thNight
15%8%19%25%23%6%
720
16th to endNight
13%11%22%30%18%3
768
November1st to 15thNight
13%9%21%32%19%3
760
16th to endNight
18%14%19%31%15%1
780
December1st to 15thNight
18%14%24%31%8%1
780
16th to endNight
21%16%26%28%6%
832
Page generated at 2018-01-12 22:01:30. Version ac04

Copyright 2018 A. Danko


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