Knudson Forestry Service Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Knudson Forestry Service Road clear sky chart from 2005-11-06 to 2024-01-15.

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	8% 10% 4 8% 8% 4 6% 6% 6% 7% 33%	74682
	Night	6% 10% 5% 8% 8% 4 6% 6% 6% 8% 32%	75060
Transparency	Day	48% 9% 14% 18% 9% 2	74373
	Night	48% 10% 16% 18% 8% 1	74887
Seeing	Day	17% 17% 29% 22% 12% 4	14031
	Night	14% 11% 26% 31% 16% 2	22712

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	7% 13% 6% 12% 11% 5% 8% 6% 8% 7% 17%	1329
	11th to 20th	Day	4 10% 6% 12% 8% 5% 8% 8% 7% 9% 24%	1452
	21st to end	Day	6% 13% 6% 11% 9% 4 6% 5% 7% 9% 25%	1584
February	1st to 10th	Day	6% 15% 7% 13% 9% 4 7% 6% 5% 7% 19%	1526
	11th to 20th	Day	4 15% 7% 13% 9% 4 5% 7% 6% 8% 22%	1575
	21st to end	Day	3 12% 8% 15% 12% 5% 5% 6% 6% 8% 20%	1428
March	1st to 10th	Day	4 12% 6% 10% 9% 6% 7% 7% 7% 8% 24%	1800
	11th to 20th	Day	5% 16% 6% 10% 8% 5% 9% 6% 6% 8% 22%	1926
	21st to end	Day	7% 14% 6% 11% 9% 5% 8% 6% 8% 9% 17%	2315
April	1st to 10th	Day	7% 13% 6% 10% 9% 6% 8% 7% 7% 7% 21%	2160
	11th to 20th	Day	8% 12% 5% 11% 8% 5% 6% 6% 6% 8% 26%	2132
	21st to end	Day	8% 14% 5% 8% 7% 4 7% 6% 6% 8% 26%	2480
May	1st to 10th	Day	9% 10% 4 7% 8% 5% 5% 5% 5% 7% 35%	2520
	11th to 20th	Day	8% 10% 5% 6% 8% 4 6% 6% 7% 9% 31%	2477
	21st to end	Day	13% 10% 3 8% 8% 4 6% 6% 6% 7% 29%	2723
June	1st to 10th	Day	15% 8% 4 8% 7% 4 6% 6% 5% 7% 31%	2612
	11th to 20th	Day	14% 8% 4 7% 8% 4 5% 6% 6% 7% 31%	2880
	21st to end	Day	9% 6% 3 7% 7% 4 5% 6% 6% 8% 40%	2731
July	1st to 10th	Day	6% 5% 2 6% 6% 3 5% 5% 5% 8% 50%	2700
	11th to 20th	Day	5% 3 2 4 4 3 4 5% 6% 7% 57%	2612
	21st to end	Day	3 2 1 2 3 2 3 4 5% 8% 67%	2741
August	1st to 10th	Day	5% 4 1 4 5% 2 4 5% 5% 7% 57%	2507
	11th to 20th	Day	5% 3 1 4 4 2 5% 4 5% 7% 58%	2410
	21st to end	Day	6% 6% 2 5% 6% 3 5% 6% 6% 9% 46%	2439
September	1st to 10th	Day	9% 5% 3 6% 6% 4 4 3 5% 6% 50%	2160
	11th to 20th	Day	8% 8% 3 7% 7% 4 5% 6% 5% 6% 41%	2160
	21st to end	Day	13% 9% 3 7% 5% 3 4 4 6% 8% 37%	1931
October	1st to 10th	Day	10% 12% 4 8% 7% 4 5% 6% 5% 6% 35%	1800
	11th to 20th	Day	9% 12% 5% 9% 7% 5% 5% 6% 6% 7% 30%	1787
	21st to end	Day	10% 11% 5% 9% 9% 5% 7% 6% 5% 8% 27%	1782
November	1st to 10th	Day	9% 14% 8% 10% 9% 5% 7% 6% 5% 6% 22%	1547
	11th to 20th	Day	7% 15% 6% 9% 9% 5% 6% 8% 5% 6% 23%	1520
	21st to end	Day	7% 13% 5% 9% 10% 5% 6% 7% 7% 8% 24%	1520
December	1st to 10th	Day	6% 12% 6% 12% 9% 7% 7% 7% 7% 7% 20%	1356
	11th to 20th	Day	5% 11% 6% 12% 11% 8% 10% 7% 7% 7% 16%	1641
	21st to end	Day	5% 14% 7% 13% 12% 6% 8% 7% 8% 6% 14%	2419
January	1st to 10th	Night	9% 15% 6% 12% 10% 6% 8% 7% 7% 7% 14%	2836
	11th to 20th	Night	5% 12% 5% 11% 9% 6% 8% 8% 6% 9% 20%	2593
	21st to end	Night	6% 12% 6% 10% 8% 5% 7% 8% 8% 9% 21%	2772
February	1st to 10th	Night	7% 16% 6% 12% 9% 5% 7% 6% 6% 7% 20%	2430
	11th to 20th	Night	4 15% 7% 11% 8% 5% 7% 5% 5% 6% 28%	2272
	21st to end	Night	6% 11% 6% 13% 9% 4 7% 6% 6% 9% 23%	1827
March	1st to 10th	Night	4 11% 5% 11% 9% 4 7% 7% 7% 8% 27%	2160
	11th to 20th	Night	4 11% 4 8% 8% 5% 6% 7% 8% 9% 30%	2029
	21st to end	Night	7% 12% 5% 9% 9% 4 6% 6% 7% 7% 26%	2040
April	1st to 10th	Night	3 10% 5% 9% 8% 4 7% 8% 6% 9% 30%	1800
	11th to 20th	Night	6% 10% 4 9% 6% 5% 8% 6% 8% 8% 31%	1779
	21st to end	Night	8% 10% 4 6% 9% 4 6% 6% 6% 9% 32%	1477
May	1st to 10th	Night	7% 9% 3 7% 7% 4 5% 5% 6% 7% 39%	1440
	11th to 20th	Night	6% 7% 3 6% 6% 3 6% 6% 8% 9% 39%	1416
	21st to end	Night	10% 9% 3 6% 6% 3 6% 4 5% 9% 40%	1552
June	1st to 10th	Night	9% 8% 4 6% 7% 4 6% 6% 7% 8% 35%	1333
	11th to 20th	Night	9% 8% 3 5% 7% 4 5% 6% 6% 9% 37%	1080
	21st to end	Night	5% 5% 2 5% 5% 3 4 5% 7% 9% 49%	1219
July	1st to 10th	Night	5% 4 1 3 5% 3 4 5% 6% 7% 57%	1260
	11th to 20th	Night	3 3 2 3 2 2 4 4 7% 9% 62%	1345
	21st to end	Night	3 2 1 2 2 2 2 4 4 7% 73%	1576
August	1st to 10th	Night	2 3 1 3 3 2 4 5% 5% 7% 65%	1432
	11th to 20th	Night	2 3 2 2 3 2 4 4 5% 7% 66%	1486
	21st to end	Night	6% 4 2 4 5% 3 4 5% 7% 8% 52%	1916
September	1st to 10th	Night	5% 4 2 4 4 3 4 5% 6% 8% 55%	1800
	11th to 20th	Night	9% 6% 2 4 4 2 5% 5% 6% 8% 49%	1800
	21st to end	Night	10% 8% 3 6% 5% 4 4 5% 6% 8% 40%	2028
October	1st to 10th	Night	7% 9% 3 8% 6% 3 4 5% 5% 7% 41%	2160
	11th to 20th	Night	10% 10% 3 8% 7% 3 6% 5% 5% 7% 35%	2172
	21st to end	Night	11% 13% 5% 7% 6% 4 5% 6% 5% 7% 31%	2574
November	1st to 10th	Night	10% 14% 5% 8% 8% 5% 6% 6% 6% 7% 24%	2526
	11th to 20th	Night	7% 14% 5% 10% 8% 5% 7% 6% 6% 7% 25%	2660
	21st to end	Night	6% 13% 6% 11% 9% 5% 6% 6% 7% 8% 21%	2660
December	1st to 10th	Night	5% 12% 6% 10% 10% 6% 6% 7% 6% 7% 23%	2800
	11th to 20th	Night	5% 15% 7% 13% 10% 6% 8% 7% 6% 6% 16%	3546
	21st to end	Night	6% 13% 6% 12% 11% 6% 8% 7% 8% 7% 16%	5264

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	62% 12% 14% 9% 4 1	1329
	11th to 20th	Day	53% 13% 15% 13% 4 2	1452
	21st to end	Day	55% 8% 14% 16% 7%	1584
February	1st to 10th	Day	62% 11% 12% 8% 6% 1	1526
	11th to 20th	Day	58% 10% 15% 10% 6% 1	1584
	21st to end	Day	61% 8% 13% 13% 3	1428
March	1st to 10th	Day	54% 11% 15% 13% 6% 1	1800
	11th to 20th	Day	59% 10% 13% 13% 4	1926
	21st to end	Day	61% 10% 16% 10% 2	2315
April	1st to 10th	Day	61% 10% 15% 13% 1	2160
	11th to 20th	Day	55% 9% 13% 13% 10% 1	2132
	21st to end	Day	54% 9% 16% 13% 7%	2480
May	1st to 10th	Day	48% 8% 18% 17% 8% 1	2520
	11th to 20th	Day	48% 10% 17% 19% 5%	2480
	21st to end	Day	54% 7% 15% 18% 5%	2724
June	1st to 10th	Day	53% 8% 13% 16% 7% 3	2612
	11th to 20th	Day	52% 9% 15% 18% 6%	2880
	21st to end	Day	41% 8% 17% 21% 11% 1	2731
July	1st to 10th	Day	33% 7% 14% 24% 17% 5%	2626
	11th to 20th	Day	26% 8% 15% 28% 20% 3	2531
	21st to end	Day	18% 4 13% 32% 27% 7%	2589
August	1st to 10th	Day	26% 6% 16% 26% 20% 6%	2490
	11th to 20th	Day	25% 7% 17% 28% 19% 5%	2410
	21st to end	Day	33% 8% 16% 28% 13% 2	2439
September	1st to 10th	Day	35% 6% 13% 27% 15% 3	2160
	11th to 20th	Day	43% 7% 10% 20% 18% 3	2160
	21st to end	Day	45% 8% 15% 18% 11% 3	1931
October	1st to 10th	Day	49% 8% 13% 23% 7%	1800
	11th to 20th	Day	52% 9% 13% 18% 6% 1	1787
	21st to end	Day	55% 9% 14% 18% 5%	1782
November	1st to 10th	Day	63% 8% 13% 11% 5%	1547
	11th to 20th	Day	59% 10% 13% 12% 6% 1	1520
	21st to end	Day	54% 13% 12% 14% 6% 1	1520
December	1st to 10th	Day	59% 11% 13% 12% 4	1356
	11th to 20th	Day	59% 14% 14% 10% 4	1643
	21st to end	Day	62% 13% 12% 11% 2	2419
January	1st to 10th	Night	63% 12% 11% 10% 3	2836
	11th to 20th	Night	56% 13% 12% 12% 4 2	2593
	21st to end	Night	54% 10% 14% 14% 6% 1	2772
February	1st to 10th	Night	61% 10% 11% 13% 4	2430
	11th to 20th	Night	57% 8% 14% 14% 6% 1	2274
	21st to end	Night	56% 9% 12% 17% 6%	1827
March	1st to 10th	Night	52% 10% 17% 13% 8%	2160
	11th to 20th	Night	46% 13% 18% 18% 5%	2030
	21st to end	Night	54% 11% 17% 15% 3	2040
April	1st to 10th	Night	48% 12% 20% 17% 4	1800
	11th to 20th	Night	47% 9% 19% 16% 8%	1779
	21st to end	Night	48% 10% 17% 17% 8%	1477
May	1st to 10th	Night	43% 9% 22% 18% 7% 1	1440
	11th to 20th	Night	39% 12% 21% 21% 7%	1416
	21st to end	Night	45% 8% 18% 24% 5%	1552
June	1st to 10th	Night	45% 9% 18% 19% 7% 3	1333
	11th to 20th	Night	42% 12% 20% 20% 7%	1080
	21st to end	Night	31% 9% 26% 23% 10% 1	1219
July	1st to 10th	Night	27% 9% 16% 27% 17% 4	1225
	11th to 20th	Night	18% 6% 21% 34% 17% 3	1303
	21st to end	Night	12% 5% 17% 32% 29% 6%	1488
August	1st to 10th	Night	19% 7% 18% 29% 20% 7%	1424
	11th to 20th	Night	17% 7% 21% 30% 20% 5%	1486
	21st to end	Night	28% 8% 19% 28% 15% 2	1916
September	1st to 10th	Night	27% 8% 18% 29% 16% 3	1800
	11th to 20th	Night	33% 7% 15% 23% 18% 5%	1800
	21st to end	Night	40% 10% 18% 21% 9% 3	2028
October	1st to 10th	Night	42% 8% 17% 24% 9%	2160
	11th to 20th	Night	48% 10% 13% 20% 9%	2172
	21st to end	Night	51% 9% 13% 20% 6%	2574
November	1st to 10th	Night	58% 11% 14% 12% 5%	2526
	11th to 20th	Night	55% 13% 14% 13% 5% 1	2660
	21st to end	Night	57% 13% 13% 10% 6% 2	2660
December	1st to 10th	Night	58% 10% 13% 14% 4 1	2800
	11th to 20th	Night	62% 13% 11% 10% 3	3543
	21st to end	Night	58% 13% 13% 14% 3	5264

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	13% 18% 29% 20% 17% 4	180
	11th to 20th	Day	12% 11% 24% 34% 13% 6%	168
	21st to end	Day	13% 16% 30% 26% 15% 1	176
February	1st to 10th	Day	26% 22% 30% 18% 4	246
	11th to 20th	Day	21% 22% 29% 21% 5% 2	335
	21st to end	Day	16% 21% 34% 18% 10% 1	324
March	1st to 10th	Day	21% 22% 29% 18% 8% 2	420
	11th to 20th	Day	20% 21% 26% 19% 10% 4	420
	21st to end	Day	24% 23% 25% 17% 8% 2	462
April	1st to 10th	Day	24% 19% 31% 16% 8% 1	420
	11th to 20th	Day	21% 22% 27% 17% 8% 4	412
	21st to end	Day	21% 25% 26% 18% 7% 4	420
May	1st to 10th	Day	17% 20% 33% 18% 9% 3	423
	11th to 20th	Day	18% 16% 27% 23% 13% 4	448
	21st to end	Day	21% 16% 26% 22% 11% 4	485
June	1st to 10th	Day	18% 22% 33% 17% 8% 1	542
	11th to 20th	Day	19% 20% 32% 17% 10% 2	810
	21st to end	Day	13% 18% 32% 21% 13% 3	661
July	1st to 10th	Day	11% 13% 37% 24% 13% 2	621
	11th to 20th	Day	11% 15% 35% 26% 10% 3	530
	21st to end	Day	5% 13% 31% 28% 16% 7%	487
August	1st to 10th	Day	8% 11% 27% 28% 17% 9%	447
	11th to 20th	Day	8% 11% 28% 28% 18% 7%	437
	21st to end	Day	11% 17% 32% 21% 14% 6%	495
September	1st to 10th	Day	15% 16% 28% 23% 13% 4	450
	11th to 20th	Day	15% 15% 24% 25% 18% 3	450
	21st to end	Day	20% 19% 25% 20% 12% 4	450
October	1st to 10th	Day	20% 16% 25% 17% 16% 6%	450
	11th to 20th	Day	23% 19% 19% 21% 14% 5%	437
	21st to end	Day	24% 15% 24% 25% 9% 3	297
November	1st to 10th	Day	19% 15% 32% 25% 8% 1	210
	11th to 20th	Day	22% 17% 26% 17% 15% 3	180
	21st to end	Day	17% 13% 29% 21% 13% 7%	180
December	1st to 10th	Day	20% 12% 16% 27% 17% 8%	180
	11th to 20th	Day	17% 12% 31% 26% 12% 3	180
	21st to end	Day	15% 8% 30% 34% 11% 2	198
January	1st to 10th	Night	20% 14% 28% 26% 9% 2	850
	11th to 20th	Night	12% 12% 32% 29% 14% 1	743
	21st to end	Night	13% 13% 30% 31% 12% 2	792
February	1st to 10th	Night	19% 15% 26% 30% 9% 2	720
	11th to 20th	Night	13% 14% 28% 32% 13% 2	704
	21st to end	Night	14% 13% 27% 29% 16% 1	592
March	1st to 10th	Night	13% 13% 29% 27% 16% 2	720
	11th to 20th	Night	14% 12% 33% 26% 13% 3	720
	21st to end	Night	16% 13% 29% 26% 14% 2	792
April	1st to 10th	Night	12% 13% 24% 34% 15% 2	720
	11th to 20th	Night	13% 14% 29% 27% 15% 1	711
	21st to end	Night	15% 13% 25% 34% 11% 2	397
May	1st to 10th	Night	10% 12% 26% 33% 16% 3	360
	11th to 20th	Night	9% 5% 20% 39% 25% 2	354
	21st to end	Night	15% 7% 23% 32% 22% 2	389
June	1st to 10th	Night	11% 11% 26% 38% 13% 1	360
	11th to 20th	Night	13% 12% 29% 29% 16% 1	360
	21st to end	Night	7% 9% 26% 32% 23% 2	360
July	1st to 10th	Night	7% 7% 21% 39% 24% 2	350
	11th to 20th	Night	5% 9% 25% 40% 20% 1	348
	21st to end	Night	3 5% 22% 40% 29% 1	394
August	1st to 10th	Night	4 3 17% 39% 34% 3	358
	11th to 20th	Night	4 3 18% 38% 34% 3	418
	21st to end	Night	9% 8% 23% 35% 24% 2	728
September	1st to 10th	Night	8% 7% 25% 33% 23% 5%	720
	11th to 20th	Night	12% 5% 20% 24% 29% 9%	720
	21st to end	Night	16% 9% 23% 30% 18% 4	720
October	1st to 10th	Night	14% 9% 20% 33% 21% 3	720
	11th to 20th	Night	18% 10% 25% 28% 19% 2	720
	21st to end	Night	21% 14% 23% 27% 12% 2	792
November	1st to 10th	Night	21% 11% 32% 28% 8% 1	740
	11th to 20th	Night	21% 15% 28% 23% 11% 2	760
	21st to end	Night	17% 15% 26% 26% 13% 3	760
December	1st to 10th	Night	13% 11% 28% 32% 13% 2	900
	11th to 20th	Night	17% 11% 31% 31% 10% 1	961
	21st to end	Night	16% 12% 30% 33% 8%	959

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