Flaming Gorge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flaming Gorge Observatory clear sky chart from 2005-11-06 to 2024-01-17.

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 Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(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

By Month

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 Forecast	Data Points
Cloud Cover	Day	4 5% 2 5% 5% 3 5% 6% 6% 9% 49%	74694
	Night	3 5% 2 4 4 3 4 5% 6% 9% 54%	75153
Transparency	Day	21% 40% 8% 14% 12% 5%	74413
	Night	18% 39% 10% 16% 13% 5%	74955
Seeing	Day	7% 11% 26% 30% 19% 5%	14317
	Night	6% 7% 27% 39% 19% 2	24609

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	1 5% 2 6% 5% 3 5% 6% 8% 10% 47%	1644
	11th to 20th	Day	2 5% 3 7% 7% 4 5% 6% 6% 9% 46%	1674
	21st to end	Day	1 7% 3 6% 5% 3 5% 6% 6% 8% 48%	1782
February	1st to 10th	Day	2 5% 3 6% 6% 3 5% 5% 7% 10% 47%	1620
	11th to 20th	Day	2 5% 3 7% 5% 4 6% 5% 6% 9% 47%	1575
	21st to end	Day	2 6% 2 6% 5% 5% 6% 7% 7% 9% 44%	1448
March	1st to 10th	Day	3 7% 3 6% 6% 3 5% 5% 7% 10% 46%	1980
	11th to 20th	Day	4 7% 3 6% 5% 4 5% 6% 7% 11% 43%	1980
	21st to end	Day	3 9% 4 7% 7% 4 4 5% 6% 9% 41%	2178
April	1st to 10th	Day	3 7% 4 6% 5% 4 5% 6% 7% 10% 43%	2096
	11th to 20th	Day	7% 9% 3 6% 5% 3 5% 5% 6% 9% 41%	2131
	21st to end	Day	6% 7% 2 5% 5% 3 6% 7% 7% 9% 43%	2340
May	1st to 10th	Day	6% 6% 2 5% 6% 3 6% 6% 7% 10% 42%	2340
	11th to 20th	Day	7% 6% 2 4 5% 4 5% 7% 8% 10% 44%	2314
	21st to end	Day	5% 5% 2 5% 6% 4 7% 7% 8% 10% 40%	2724
June	1st to 10th	Day	4 4 2 4 5% 3 6% 6% 7% 9% 51%	2520
	11th to 20th	Day	5% 4 1 4 4 3 4 5% 5% 8% 56%	2520
	21st to end	Day	3 3 2 4 5% 4 4 5% 6% 8% 58%	2520
July	1st to 10th	Day	3 3 2 4 6% 4 7% 7% 8% 8% 47%	2520
	11th to 20th	Day	4 3 2 4 5% 5% 7% 7% 7% 9% 47%	2343
	21st to end	Day	3 4 2 5% 6% 4 6% 8% 8% 10% 44%	2545
August	1st to 10th	Day	4 4 2 5% 8% 4 7% 7% 7% 9% 43%	2328
	11th to 20th	Day	4 4 2 4 5% 4 5% 6% 7% 8% 50%	2299
	21st to end	Day	4 4 2 5% 5% 4 5% 5% 6% 8% 52%	2462
September	1st to 10th	Day	4 3 1 3 4 4 3 5% 6% 6% 60%	2160
	11th to 20th	Day	4 3 1 3 5% 3 4 4 6% 8% 59%	2016
	21st to end	Day	5% 3 2 3 4 3 3 3 4 5% 66%	1977
October	1st to 10th	Day	6% 5% 2 5% 3 2 3 3 5% 7% 58%	1800
	11th to 20th	Day	4 4 2 3 4 3 3 4 4 8% 62%	1800
	21st to end	Day	4 5% 2 3 4 3 4 5% 6% 7% 58%	1980
November	1st to 10th	Day	4 5% 2 3 4 2 3 5% 5% 9% 59%	1788
	11th to 20th	Day	3 5% 2 4 5% 3 4 4 5% 8% 58%	1530
	21st to end	Day	1 5% 3 6% 5% 2 5% 5% 6% 8% 53%	1520
December	1st to 10th	Day	1 6% 3 4 6% 3 5% 5% 7% 11% 49%	1520
	11th to 20th	Day	1 5% 3 4 4 3 5% 6% 8% 12% 48%	1926
	21st to end	Day	2 8% 4 7% 7% 4 5% 6% 6% 10% 41%	2794
January	1st to 10th	Night	2 6% 3 5% 6% 3 5% 5% 6% 9% 50%	2537
	11th to 20th	Night	1 5% 3 5% 6% 3 5% 5% 6% 9% 51%	2430
	21st to end	Night	1 8% 4 6% 5% 3 5% 5% 6% 7% 49%	2574
February	1st to 10th	Night	1 5% 2 5% 4 3 5% 6% 7% 10% 51%	2340
	11th to 20th	Night	2 6% 3 6% 5% 3 5% 5% 6% 10% 49%	2272
	21st to end	Night	1 6% 4 7% 5% 3 4 5% 7% 10% 49%	1804
March	1st to 10th	Night	3 7% 3 6% 5% 3 5% 6% 6% 8% 48%	1980
	11th to 20th	Night	3 6% 3 5% 4 3 5% 6% 7% 9% 50%	1980
	21st to end	Night	4 8% 3 6% 7% 3 5% 6% 6% 7% 46%	2178
April	1st to 10th	Night	4 6% 3 5% 5% 3 5% 5% 6% 8% 51%	1864
	11th to 20th	Night	6% 10% 3 6% 5% 2 5% 5% 5% 8% 45%	1773
	21st to end	Night	4 6% 2 4 4 3 6% 6% 7% 8% 50%	1620
May	1st to 10th	Night	7% 5% 2 4 5% 2 5% 5% 5% 9% 51%	1620
	11th to 20th	Night	6% 5% 1 4 4 3 4 4 6% 11% 52%	1581
	21st to end	Night	5% 4 2 4 5% 3 5% 6% 7% 11% 50%	1552
June	1st to 10th	Night	2 2 1 2 4 3 5% 5% 7% 10% 59%	1440
	11th to 20th	Night	4 2 1 2 3 3 2 4 7% 9% 63%	1440
	21st to end	Night	3 3 1 2 3 2 4 4 5% 6% 68%	1440
July	1st to 10th	Night	2 2 1 3 4 3 5% 5% 7% 9% 59%	1440
	11th to 20th	Night	3 2 1 3 4 2 4 6% 7% 10% 59%	1612
	21st to end	Night	2 2 1 3 4 3 5% 7% 9% 9% 55%	1773
August	1st to 10th	Night	2 2 1 4 4 2 3 5% 7% 9% 60%	1611
	11th to 20th	Night	2 2 1 3 4 2 4 5% 7% 8% 62%	1602
	21st to end	Night	2 2 1 3 3 2 5% 4 6% 7% 65%	1894
September	1st to 10th	Night	3 2 1 2 3 2 3 3 4 7% 72%	1800
	11th to 20th	Night	3 2 1 2 3 2 3 4 5% 7% 68%	1940
	21st to end	Night	3 3 1 3 4 2 3 3 3 6% 69%	1981
October	1st to 10th	Night	4 4 2 4 4 3 3 4 5% 7% 60%	2160
	11th to 20th	Night	3 4 2 3 3 2 3 3 4 7% 66%	2160
	21st to end	Night	4 5% 2 4 4 2 2 3 4 7% 61%	2376
November	1st to 10th	Night	3 5% 2 3 3 3 4 4 5% 9% 59%	2286
	11th to 20th	Night	2 4 2 5% 4 3 4 5% 5% 9% 58%	2629
	21st to end	Night	2 6% 3 5% 4 3 4 5% 6% 7% 56%	2660
December	1st to 10th	Night	1 5% 3 6% 6% 3 5% 4 6% 8% 50%	2660
	11th to 20th	Night	2 7% 3 6% 5% 3 5% 5% 9% 11% 43%	3271
	21st to end	Night	2 8% 5% 7% 6% 3 5% 6% 8% 10% 41%	4873

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	16% 43% 16% 17% 7%	1645
	11th to 20th	Day	21% 44% 11% 14% 8% 2	1674
	21st to end	Day	23% 41% 14% 14% 5% 2	1782
February	1st to 10th	Day	24% 40% 10% 16% 9% 1	1620
	11th to 20th	Day	26% 40% 10% 14% 9% 1	1584
	21st to end	Day	22% 40% 12% 16% 8% 2	1448
March	1st to 10th	Day	22% 40% 12% 18% 7% 1	1980
	11th to 20th	Day	23% 40% 15% 14% 6% 1	1980
	21st to end	Day	29% 41% 10% 13% 6% 1	2178
April	1st to 10th	Day	26% 39% 10% 12% 11% 3	2096
	11th to 20th	Day	26% 40% 7% 16% 10% 1	2134
	21st to end	Day	22% 41% 7% 19% 10% 1	2340
May	1st to 10th	Day	25% 39% 7% 15% 13% 2	2340
	11th to 20th	Day	21% 43% 7% 17% 8% 3	2317
	21st to end	Day	24% 42% 6% 17% 9% 2	2724
June	1st to 10th	Day	20% 39% 10% 16% 11% 5%	2520
	11th to 20th	Day	18% 39% 5% 10% 18% 10%	2520
	21st to end	Day	15% 38% 4 10% 18% 14%	2520
July	1st to 10th	Day	20% 40% 5% 8% 15% 12%	2451
	11th to 20th	Day	21% 40% 6% 8% 12% 13%	2273
	21st to end	Day	21% 43% 7% 10% 12% 8%	2404
August	1st to 10th	Day	25% 40% 6% 9% 12% 8%	2313
	11th to 20th	Day	20% 38% 5% 10% 16% 11%	2299
	21st to end	Day	19% 40% 5% 10% 17% 9%	2462
September	1st to 10th	Day	17% 38% 5% 9% 15% 16%	2160
	11th to 20th	Day	17% 38% 7% 12% 16% 10%	2016
	21st to end	Day	12% 36% 4 16% 25% 7%	1977
October	1st to 10th	Day	19% 40% 5% 17% 15% 4	1800
	11th to 20th	Day	17% 38% 8% 22% 14% 2	1800
	21st to end	Day	17% 38% 10% 19% 14% 2	1980
November	1st to 10th	Day	16% 43% 10% 16% 12% 2	1788
	11th to 20th	Day	16% 44% 12% 15% 12% 1	1530
	21st to end	Day	18% 41% 8% 17% 13% 3	1520
December	1st to 10th	Day	19% 43% 13% 12% 10% 3	1520
	11th to 20th	Day	19% 36% 14% 21% 10%	1924
	21st to end	Day	27% 30% 12% 14% 11% 7%	2794
January	1st to 10th	Night	20% 43% 13% 17% 7%	2537
	11th to 20th	Night	17% 43% 12% 17% 9% 2	2430
	21st to end	Night	22% 40% 14% 16% 6% 3	2574
February	1st to 10th	Night	18% 39% 12% 19% 10% 1	2340
	11th to 20th	Night	22% 40% 10% 16% 11% 2	2273
	21st to end	Night	20% 39% 13% 16% 9% 3	1804
March	1st to 10th	Night	21% 39% 13% 18% 9% 1	1980
	11th to 20th	Night	19% 38% 14% 19% 7% 1	1980
	21st to end	Night	23% 40% 13% 17% 6% 1	2178
April	1st to 10th	Night	21% 39% 9% 14% 13% 4	1864
	11th to 20th	Night	23% 39% 9% 16% 12% 1	1773
	21st to end	Night	18% 40% 10% 22% 10%	1620
May	1st to 10th	Night	21% 38% 7% 17% 15% 2	1620
	11th to 20th	Night	15% 39% 9% 23% 10% 3	1582
	21st to end	Night	18% 40% 8% 19% 13% 2	1552
June	1st to 10th	Night	17% 39% 11% 18% 12% 4	1440
	11th to 20th	Night	15% 38% 3 12% 19% 13%	1440
	21st to end	Night	10% 39% 4 9% 23% 17%	1440
July	1st to 10th	Night	14% 39% 6% 9% 18% 15%	1400
	11th to 20th	Night	14% 39% 6% 12% 14% 16%	1559
	21st to end	Night	14% 42% 8% 13% 14% 10%	1674
August	1st to 10th	Night	16% 40% 7% 12% 17% 9%	1602
	11th to 20th	Night	13% 39% 5% 10% 19% 15%	1602
	21st to end	Night	11% 38% 6% 12% 19% 14%	1894
September	1st to 10th	Night	11% 36% 5% 11% 19% 18%	1800
	11th to 20th	Night	11% 38% 8% 17% 16% 10%	1940
	21st to end	Night	10% 36% 4 16% 27% 6%	1981
October	1st to 10th	Night	15% 39% 7% 20% 15% 5%	2160
	11th to 20th	Night	16% 36% 7% 23% 16% 2	2160
	21st to end	Night	16% 39% 9% 19% 15% 3	2376
November	1st to 10th	Night	16% 43% 8% 15% 14% 3	2286
	11th to 20th	Night	15% 43% 13% 19% 10% 1	2629
	21st to end	Night	16% 40% 9% 18% 14% 4	2660
December	1st to 10th	Night	19% 42% 13% 14% 9% 3	2660
	11th to 20th	Night	23% 38% 12% 18% 9% 1	3272
	21st to end	Night	26% 28% 13% 15% 11% 7%	4873

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	4 12% 24% 37% 19% 3	270
	11th to 20th	Day	6% 12% 27% 38% 16%	258
	21st to end	Day	5% 7% 34% 39% 14% 2	264
February	1st to 10th	Day	6% 20% 44% 22% 7% 1	240
	11th to 20th	Day	4 11% 41% 30% 13% 2	240
	21st to end	Day	5% 14% 32% 41% 9% 1	274
March	1st to 10th	Day	6% 13% 39% 31% 9% 2	420
	11th to 20th	Day	9% 12% 31% 33% 15% 1	420
	21st to end	Day	11% 19% 31% 27% 11%	462
April	1st to 10th	Day	11% 20% 26% 24% 17% 2	420
	11th to 20th	Day	15% 19% 33% 24% 8% 1	412
	21st to end	Day	14% 19% 27% 24% 14% 3	420
May	1st to 10th	Day	10% 17% 30% 26% 13% 3	423
	11th to 20th	Day	11% 14% 27% 28% 14% 5%	461
	21st to end	Day	11% 9% 23% 27% 23% 6%	679
June	1st to 10th	Day	5% 9% 23% 31% 26% 6%	630
	11th to 20th	Day	6% 13% 28% 30% 21% 2	630
	21st to end	Day	4 9% 25% 32% 23% 6%	630
July	1st to 10th	Day	4 3 17% 33% 33% 10%	621
	11th to 20th	Day	6% 5% 28% 29% 23% 9%	446
	21st to end	Day	5% 3 19% 30% 31% 12%	487
August	1st to 10th	Day	6% 5% 20% 34% 25% 11%	447
	11th to 20th	Day	6% 5% 22% 30% 26% 10%	437
	21st to end	Day	6% 6% 22% 31% 24% 11%	495
September	1st to 10th	Day	7% 8% 23% 28% 21% 12%	450
	11th to 20th	Day	8% 11% 26% 28% 18% 9%	450
	21st to end	Day	7% 14% 21% 25% 25% 7%	447
October	1st to 10th	Day	9% 10% 21% 25% 28% 7%	270
	11th to 20th	Day	7% 14% 20% 30% 24% 6%	270
	21st to end	Day	8% 14% 28% 32% 16% 2	297
November	1st to 10th	Day	7% 21% 24% 27% 16% 5%	270
	11th to 20th	Day	7% 12% 27% 38% 11% 6%	270
	21st to end	Day	5% 11% 22% 40% 17% 5%	270
December	1st to 10th	Day	6% 10% 27% 40% 16% 2	270
	11th to 20th	Day	4 11% 27% 44% 13% 1	270
	21st to end	Day	7% 10% 40% 26% 13% 3	297
January	1st to 10th	Night	6% 10% 30% 36% 16% 2	840
	11th to 20th	Night	5% 12% 32% 34% 15% 2	748
	21st to end	Night	6% 8% 34% 39% 10% 2	792
February	1st to 10th	Night	4 13% 39% 34% 9% 2	720
	11th to 20th	Night	4 8% 38% 37% 12% 1	704
	21st to end	Night	4 6% 39% 44% 7% 1	592
March	1st to 10th	Night	6% 8% 33% 42% 10% 2	720
	11th to 20th	Night	5% 8% 27% 44% 16% 1	720
	21st to end	Night	7% 9% 37% 36% 10%	792
April	1st to 10th	Night	8% 11% 32% 38% 10%	604
	11th to 20th	Night	13% 12% 30% 34% 11% 1	533
	21st to end	Night	8% 12% 30% 34% 14% 1	540
May	1st to 10th	Night	9% 9% 28% 36% 15% 2	540
	11th to 20th	Night	10% 4 20% 39% 24% 3	531
	21st to end	Night	7% 5% 26% 35% 24% 3	584
June	1st to 10th	Night	4 6% 22% 39% 27% 2	540
	11th to 20th	Night	5% 7% 28% 41% 18%	540
	21st to end	Night	3 3 16% 44% 31% 2	540
July	1st to 10th	Night	4 1 11% 40% 41% 3	525
	11th to 20th	Night	3 2 12% 45% 35% 3	522
	21st to end	Night	4 1 7% 40% 43% 5%	591
August	1st to 10th	Night	4 1 12% 43% 37% 3	537
	11th to 20th	Night	4 1 11% 43% 38% 2	534
	21st to end	Night	2 2 14% 40% 38% 4	594
September	1st to 10th	Night	4 3 15% 42% 31% 5%	540
	11th to 20th	Night	3 3 18% 42% 27% 7%	680
	21st to end	Night	6% 5% 20% 35% 26% 9%	720
October	1st to 10th	Night	6% 5% 26% 37% 23% 3	720
	11th to 20th	Night	6% 7% 27% 37% 20% 4	720
	21st to end	Night	7% 7% 30% 37% 17% 3	792
November	1st to 10th	Night	6% 8% 28% 38% 17% 3	740
	11th to 20th	Night	5% 11% 33% 36% 12% 2	919
	21st to end	Night	6% 10% 28% 37% 16% 2	950
December	1st to 10th	Night	5% 8% 33% 43% 11% 1	950
	11th to 20th	Night	6% 8% 35% 39% 10% 1	950
	21st to end	Night	6% 11% 38% 34% 9% 2	1045

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