Greenbrier State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greenbrier State Park clear sky chart from 2005-11-05 to 2017-09-14.

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
40%
15181
19%
46866
11%
15141
49%
15141
24%
29922

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
21%
717
19%
2414
8%
716
36%
716
17%
1571
January16th to endNight
21%
768
19%
2496
7%
768
37%
768
20%
1609
February1st to 15thNight
25%
703
18%
2287
6%
701
40%
701
19%
1442
February16th to endNight
19%
631
20%
1940
6%
631
36%
631
18%
1275
March1st to 15thNight
27%
720
20%
1989
9%
720
38%
720
23%
1329
March16th to endNight
25%
768
20%
2100
8%
768
35%
768
23%
1414
April1st to 15thNight
27%
718
16%
1796
5%
718
33%
718
25%
1242
April16th to endNight
40%
720
18%
1800
7%
720
44%
720
30%
1211
May1st to 15thNight
42%
531
17%
1611
11%
531
47%
531
22%
1099
May16th to endNight
53%
375
17%
1497
18%
374
59%
374
20%
913
June1st to 15thNight
56%
360
19%
1440
20%
360
62%
360
24%
830
June16th to endNight
59%
360
18%
1440
19%
360
65%
360
25%
831
July1st to 15thNight
56%
340
12%
1360
14%
340
59%
340
18%
866
July16th to endNight
73%
554
15%
1585
13%
521
76%
521
36%
920
August1st to 15thNight
69%
539
18%
1609
14%
536
70%
536
31%
993
August16th to endNight
66%
732
21%
1878
14%
732
67%
732
35%
1204
September1st to 15thNight
57%
716
24%
1790
13%
716
61%
716
35%
1161
September16th to endNight
54%
657
22%
1817
18%
657
58%
657
29%
1202
October1st to 15thNight
46%
660
23%
1980
19%
660
54%
660
27%
1274
October16th to endNight
38%
704
27%
2112
16%
704
53%
704
32%
1231
November1st to 15thNight
41%
700
24%
2215
18%
700
51%
700
28%
1340
November16th to endNight
33%
720
19%
2502
12%
720
45%
720
19%
1547
December1st to 15thNight
28%
720
16%
2520
7%
720
39%
720
16%
1683
December16th to endNight
24%
768
18%
2688
7%
768
39%
768
19%
1735

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
14%6%25%5%35%5%5%7%39%
47839
Night
14%5%25%43445%7%41%
47048
Cloud CoverDay
14%6%25%5%35%5%5%7%39%
47849
Night
14%5%25%43445%7%41%
47052
TransparencyDay
41%7%12%21%14%2
47539
Night
39%6%12%22%15%2
46866
SeeingDay
17%9%21%24%19%7%
5612
Night
17%9%27%31%13%1
15185

By Month

Percentage Cloud Cover NE (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
15%6%36%5%25%5%47%36%
1522
16th to endDay
15%8%35%4245%5%6%36%
1728
February1st to 15thDay
14%8%36%6%345%46%36%
1575
16th to endDay
13%7%37%6%25%35%439%
1533
March1st to 15thDay
15%6%35%5%34346%40%
1958
16th to endDay
17%7%36%6%23446%36%
2124
April1st to 15thDay
14%6%35%5%3435%7%40%
2152
16th to endDay
17%6%24423446%42%
2166
May1st to 15thDay
17%6%24435%5%6%8%34%
2342
16th to endDay
15%5%35%5%24448%37%
2618
June1st to 15thDay
12%423426%6%7%10%40%
2520
16th to endDay
10%4245%36%5%5%9%42%
2520
July1st to 15thDay
9%425%5%37%6%6%9%37%
2520
16th to endDay
7%425%5%37%7%8%11%36%
2473
August1st to 15thDay
10%5%25%6%47%6%7%9%34%
2340
16th to endDay
10%5%25%5%345%6%8%42%
2310
September1st to 15thDay
15%5%2342445%8%43%
2146
16th to endDay
15%5%25%6%3446%6%39%
1808
October1st to 15thDay
19%415%423346%44%
1650
16th to endDay
14%5%24424446%45%
1760
November1st to 15thDay
13%6%14424446%47%
1643
16th to endDay
19%5%25%5%2345%7%38%
1455
December1st to 15thDay
17%6%35%5%245%7%6%34%
1440
16th to endDay
17%6%26%445%46%6%35%
1536
January1st to 15thNight
17%7%25%42445%6%36%
2414
16th to endNight
14%8%25%5%2445%7%38%
2496
February1st to 15thNight
14%6%25%43446%7%40%
2285
16th to endNight
13%7%36%5%45%45%6%37%
1940
March1st to 15thNight
17%6%24435%45%6%40%
1977
16th to endNight
15%6%26%424347%41%
2100
April1st to 15thNight
13%6%45%5%35%46%6%38%
1796
16th to endNight
15%4245%2445%8%42%
1800
May1st to 15thNight
18%6%25%3345%5%8%36%
1611
16th to endNight
12%435%5%346%6%7%42%
1495
June1st to 15thNight
10%425%425%5%7%8%44%
1440
16th to endNight
8%3246%245%7%8%45%
1440
July1st to 15thNight
10%5%245%37%5%7%7%39%
1440
16th to endNight
6%214435%6%9%10%45%
1692
August1st to 15thNight
8%415%5%346%6%8%45%
1620
16th to endNight
10%415%4345%5%9%46%
1878
September1st to 15thNight
12%5%244335%5%7%47%
1790
16th to endNight
14%6%34434436%44%
1817
October1st to 15thNight
18%414424446%43%
1980
16th to endNight
14%5%1422325%6%50%
2112
November1st to 15thNight
14%6%2432334449%
2215
16th to endNight
16%434425%5%5%7%40%
2502
December1st to 15thNight
17%6%36%5%35%5%5%5%36%
2520
16th to endNight
17%6%25%425%45%7%36%
2688

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
15%6%36%5%35%6%47%36%
1522
16th to endDay
15%9%35%42445%6%37%
1728
February1st to 15thDay
14%9%35%6%345%46%36%
1575
16th to endDay
13%7%37%6%25%35%5%39%
1533
March1st to 15thDay
15%7%26%5%34446%40%
1969
16th to endDay
17%7%36%6%24446%37%
2123
April1st to 15thDay
15%5%35%5%3445%7%40%
2152
16th to endDay
17%6%245%2345%6%42%
2166
May1st to 15thDay
17%6%24425%5%6%8%34%
2342
16th to endDay
15%6%35%5%3445%8%37%
2618
June1st to 15thDay
12%423436%5%7%10%40%
2520
16th to endDay
9%5%145%35%5%6%9%42%
2520
July1st to 15thDay
9%5%25%6%37%6%6%9%37%
2520
16th to endDay
7%425%5%47%6%8%11%36%
2473
August1st to 15thDay
10%5%25%6%46%7%7%9%34%
2340
16th to endDay
10%5%25%5%345%7%7%42%
2310
September1st to 15thDay
15%42342445%7%44%
2146
16th to endDay
15%5%25%6%3345%7%39%
1808
October1st to 15thDay
19%314423347%44%
1650
16th to endDay
14%5%35%424445%45%
1760
November1st to 15thDay
13%7%14423446%47%
1643
16th to endDay
18%5%25%5%14447%38%
1455
December1st to 15thDay
17%6%35%5%25%47%6%35%
1440
16th to endDay
17%6%26%435%46%6%36%
1536
January1st to 15thNight
17%7%26%43445%6%37%
2414
16th to endNight
15%8%25%42445%7%38%
2496
February1st to 15thNight
14%6%25%42445%7%41%
2278
16th to endNight
13%7%26%445%45%7%37%
1940
March1st to 15thNight
17%6%24435%45%6%40%
1989
16th to endNight
15%6%26%43435%6%41%
2100
April1st to 15thNight
12%7%35%5%35%45%6%38%
1796
16th to endNight
15%5%245%2445%8%42%
1800
May1st to 15thNight
18%6%25%3345%5%8%36%
1610
16th to endNight
12%435%4245%6%7%42%
1495
June1st to 15thNight
9%425%43447%8%44%
1440
16th to endNight
8%315%5%25%5%6%8%45%
1440
July1st to 15thNight
10%5%246%37%6%6%8%38%
1440
16th to endNight
6%224426%6%8%10%46%
1692
August1st to 15thNight
9%415%5%346%6%8%45%
1620
16th to endNight
10%415%43445%8%46%
1878
September1st to 15thNight
12%6%1432345%7%47%
1790
16th to endNight
14%6%34425%336%44%
1817
October1st to 15thNight
18%41443435%6%43%
1980
16th to endNight
14%41422435%6%50%
2112
November1st to 15thNight
14%6%25%32334449%
2215
16th to endNight
16%5%34425%5%5%7%40%
2502
December1st to 15thNight
17%5%35%5%35%5%5%5%36%
2520
16th to endNight
17%6%25%5%25%5%5%8%36%
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
44%6%12%21%11%1
1523
16th to endDay
44%413%22%11%2
1728
February1st to 15thDay
46%6%12%21%10%1
1577
16th to endDay
45%413%23%11%1
1533
March1st to 15thDay
43%5%12%22%13%2
1969
16th to endDay
47%5%11%18%14%2
2124
April1st to 15thDay
42%5%12%19%16%3
2152
16th to endDay
42%5%8%19%19%5%
2166
May1st to 15thDay
45%8%12%19%14%1
2342
16th to endDay
43%7%13%21%11%2
2622
June1st to 15thDay
35%10%14%23%14%
2520
16th to endDay
35%9%15%22%15%1
2520
July1st to 15thDay
40%9%13%18%14%2
2371
16th to endDay
36%9%15%21%14%2
2317
August1st to 15thDay
42%9%13%18%14%1
2327
16th to endDay
37%6%14%25%13%2
2310
September1st to 15thDay
38%6%12%19%21%2
2146
16th to endDay
43%5%9%20%18%2
1808
October1st to 15thDay
40%5%10%24%16%2
1650
16th to endDay
38%5%11%25%17%1
1760
November1st to 15thDay
36%5%13%21%17%5%
1643
16th to endDay
43%412%25%12%1
1455
December1st to 15thDay
45%8%15%19%9%1
1440
16th to endDay
45%7%13%22%10%
1536
January1st to 15thNight
44%5%12%20%13%3
2414
16th to endNight
42%5%14%24%11%1
2496
February1st to 15thNight
40%6%13%23%14%1
2287
16th to endNight
43%6%12%23%13%1
1940
March1st to 15thNight
41%5%12%27%10%1
1989
16th to endNight
42%5%11%21%15%2
2100
April1st to 15thNight
44%5%11%20%15%3
1796
16th to endNight
39%5%11%20%16%6%
1800
May1st to 15thNight
44%7%9%21%14%2
1611
16th to endNight
39%8%14%21%14%2
1497
June1st to 15thNight
34%8%12%26%16%1
1440
16th to endNight
33%9%12%24%16%2
1440
July1st to 15thNight
41%10%14%17%11%4
1360
16th to endNight
27%9%21%21%17%2
1585
August1st to 15thNight
34%7%16%22%17%2
1609
16th to endNight
33%7%13%24%18%3
1878
September1st to 15thNight
34%6%13%20%21%3
1790
16th to endNight
41%5%8%21%19%3
1817
October1st to 15thNight
41%5%10%23%17%2
1980
16th to endNight
32%411%30%19%1
2112
November1st to 15thNight
37%48%24%18%6%
2215
16th to endNight
40%5%12%21%16%3
2502
December1st to 15thNight
46%7%12%21%10%1
2520
16th to endNight
43%6%16%21%10%1
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
28%30%21%13%6%
75
16th to endDay
28%30%28%11%2
96
February1st to 15thDay
21%31%37%10%
90
16th to endDay
20%18%37%21%2
192
March1st to 15thDay
17%19%28%28%7%
270
16th to endDay
19%13%31%25%7%2
288
April1st to 15thDay
18%15%25%23%13%2
270
16th to endDay
23%5%26%17%19%7%
270
May1st to 15thDay
26%15%21%17%13%5%
288
16th to endDay
21%5%16%23%24%8%
331
June1st to 15thDay
15%326%22%22%9%
315
16th to endDay
12%6%22%28%22%6%
315
July1st to 15thDay
13%222%27%25%8%
305
16th to endDay
8%18%33%31%15%
326
August1st to 15thDay
13%116%25%29%14%
313
16th to endDay
10%8%32%26%21%
332
September1st to 15thDay
16%6%17%17%25%17%
310
16th to endDay
22%214%27%21%12%
254
October1st to 15thDay
20%6%13%30%22%6%
255
16th to endDay
12%13%26%30%15%1
272
November1st to 15thDay
15%10%26%23%21%2
246
16th to endDay
26%18%21%18%10%4
75
December1st to 15thDay
15%31%26%10%11%5%
60
16th to endDay
28%10%34%23%3
64
January1st to 15thNight
20%16%35%23%3
720
16th to endNight
19%16%38%24%1
768
February1st to 15thNight
18%17%33%27%2
704
16th to endNight
19%19%36%22%1
631
March1st to 15thNight
22%13%33%26%4
720
16th to endNight
17%14%37%23%5%
768
April1st to 15thNight
16%14%38%25%4
718
16th to endNight
18%9%27%31%12%
720
May1st to 15thNight
22%5%24%34%13%
531
16th to endNight
16%220%38%20%1
375
June1st to 15thNight
11%222%37%25%1
360
16th to endNight
9%120%48%20%
360
July1st to 15thNight
12%117%40%27%1
340
16th to endNight
6%112%42%32%4
554
August1st to 15thNight
12%8%47%28%2
539
16th to endNight
12%211%40%28%4
732
September1st to 15thNight
14%119%33%28%2
716
16th to endNight
18%217%32%28%2
657
October1st to 15thNight
20%5%21%29%20%2
660
16th to endNight
17%8%33%30%9%
704
November1st to 15thNight
14%8%29%33%11%1
700
16th to endNight
19%15%27%28%8%
720
December1st to 15thNight
21%12%32%26%7%
720
16th to endNight
21%9%38%27%2
768
Page generated at 2017-09-15 10:29:57. Version ac04

Copyright 2017 A. Danko


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