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 2024-11-30.

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	7% 10% 4 9% 6% 5% 5% 4 6% 7% 36%	105590
	Night	6% 11% 4 10% 6% 6% 6% 5% 6% 7% 33%	102548
Transparency	Day	45% 8% 14% 18% 11% 3	105347
	Night	46% 10% 16% 18% 8% 2	102437
Seeing	Day	17% 17% 29% 22% 12% 4	15235
	Night	14% 11% 26% 31% 16% 2	23754

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% 19% 6% 16% 8% 6% 7% 4 6% 6% 14%	2219
	11th to 20th	Day	3 14% 6% 15% 7% 7% 5% 4 6% 7% 25%	2483
	21st to end	Day	5% 14% 7% 16% 10% 7% 6% 5% 6% 8% 17%	2794
February	1st to 10th	Day	6% 17% 7% 14% 8% 6% 6% 4 5% 7% 19%	1611
	11th to 20th	Day	4 15% 6% 14% 8% 5% 6% 5% 6% 8% 22%	1665
	21st to end	Day	3 15% 6% 17% 10% 7% 5% 4 6% 7% 19%	1515
March	1st to 10th	Day	3 11% 5% 14% 9% 7% 8% 6% 7% 7% 24%	3138
	11th to 20th	Day	3 12% 3 9% 6% 6% 7% 5% 7% 8% 35%	3397
	21st to end	Day	8% 16% 5% 12% 8% 7% 6% 5% 7% 7% 20%	4065
April	1st to 10th	Day	7% 14% 5% 12% 8% 8% 7% 5% 7% 7% 20%	2280
	11th to 20th	Day	7% 13% 4 11% 7% 6% 6% 4 6% 8% 27%	2252
	21st to end	Day	8% 15% 5% 10% 6% 6% 6% 5% 7% 8% 25%	2619
May	1st to 10th	Day	6% 11% 4 7% 5% 5% 5% 4 5% 8% 39%	4420
	11th to 20th	Day	6% 9% 3 8% 5% 5% 6% 5% 7% 10% 34%	4377
	21st to end	Day	16% 17% 4 9% 6% 5% 5% 4 5% 6% 23%	4813
June	1st to 10th	Day	14% 9% 3 9% 6% 6% 6% 5% 5% 7% 31%	2758
	11th to 20th	Day	13% 9% 3 8% 7% 5% 6% 4 6% 7% 31%	3040
	21st to end	Day	9% 7% 2 8% 5% 5% 5% 4 6% 8% 39%	2882
July	1st to 10th	Day	3 3 1 4 3 3 3 3 3 6% 67%	4740
	11th to 20th	Day	3 3 1 3 2 2 3 2 4 5% 71%	4582
	21st to end	Day	5% 4 1 4 3 3 3 3 5% 8% 61%	4790
August	1st to 10th	Day	3 2 1 4 3 4 4 4 5% 7% 63%	4401
	11th to 20th	Day	5% 4 2 6% 5% 4 6% 5% 6% 7% 51%	4213
	21st to end	Day	8% 6% 3 8% 6% 5% 6% 4 5% 6% 43%	4282
September	1st to 10th	Day	8% 6% 3 7% 4 5% 4 3 5% 6% 51%	2280
	11th to 20th	Day	8% 8% 3 9% 6% 5% 4 5% 5% 6% 41%	2280
	21st to end	Day	13% 10% 3 8% 4 4 4 3 6% 8% 36%	2037
October	1st to 10th	Day	10% 12% 3 8% 5% 5% 5% 5% 6% 7% 35%	3180
	11th to 20th	Day	15% 11% 4 9% 5% 5% 5% 4 6% 6% 30%	3135
	21st to end	Day	9% 13% 5% 11% 7% 6% 6% 4 6% 8% 24%	3101
November	1st to 10th	Day	9% 16% 6% 12% 7% 7% 6% 4 4 6% 22%	1630
	11th to 20th	Day	7% 16% 6% 11% 8% 7% 6% 6% 5% 6% 23%	1600
	21st to end	Day	7% 14% 5% 11% 8% 6% 6% 6% 7% 8% 22%	1595
December	1st to 10th	Day	5% 14% 5% 13% 8% 9% 6% 5% 7% 7% 20%	1356
	11th to 20th	Day	5% 12% 6% 14% 10% 10% 10% 5% 7% 6% 16%	1641
	21st to end	Day	5% 15% 6% 15% 10% 8% 8% 5% 8% 6% 14%	2419
January	1st to 10th	Night	7% 18% 6% 16% 9% 8% 7% 5% 6% 6% 12%	4726
	11th to 20th	Night	4 14% 6% 12% 8% 7% 6% 5% 7% 6% 26%	4412
	21st to end	Night	6% 13% 6% 15% 10% 8% 9% 6% 7% 7% 14%	4862
February	1st to 10th	Night	7% 18% 6% 14% 7% 6% 6% 5% 6% 7% 19%	2565
	11th to 20th	Night	3 16% 6% 12% 7% 6% 6% 4 5% 6% 28%	2402
	21st to end	Night	6% 12% 6% 15% 8% 5% 6% 5% 7% 8% 22%	1938
March	1st to 10th	Night	2 10% 5% 12% 8% 6% 7% 6% 8% 9% 27%	3736
	11th to 20th	Night	2 10% 3 7% 5% 5% 6% 6% 7% 10% 39%	3565
	21st to end	Night	7% 15% 4 11% 7% 6% 6% 5% 7% 7% 24%	3587
April	1st to 10th	Night	4 12% 5% 10% 8% 5% 7% 6% 6% 8% 30%	1900
	11th to 20th	Night	5% 10% 4 10% 6% 7% 6% 5% 7% 7% 32%	1879
	21st to end	Night	8% 12% 3 8% 7% 7% 6% 5% 6% 8% 31%	1558
May	1st to 10th	Night	6% 11% 3 8% 5% 6% 3 4 6% 7% 41%	2540
	11th to 20th	Night	5% 11% 3 7% 4 4 5% 3 6% 9% 42%	2516
	21st to end	Night	10% 18% 4 8% 6% 5% 6% 4 6% 7% 27%	2762
June	1st to 10th	Night	8% 10% 3 7% 7% 5% 6% 5% 7% 8% 35%	1407
	11th to 20th	Night	9% 10% 2 6% 7% 5% 6% 5% 6% 9% 36%	1140
	21st to end	Night	6% 6% 2 7% 4 4 4 4 7% 9% 48%	1287
July	1st to 10th	Night	3 3 1 2 3 2 3 3 5% 5% 69%	2220
	11th to 20th	Night	2 2 1 2 2 2 2 2 5% 6% 75%	2375
	21st to end	Night	3 3 1 3 2 3 2 4 5% 7% 68%	2762
August	1st to 10th	Night	1 2 1 3 2 3 4 4 6% 9% 64%	2529
	11th to 20th	Night	2 3 2 4 3 4 4 3 6% 10% 58%	2615
	21st to end	Night	13% 6% 2 6% 4 4 4 3 5% 7% 46%	3392
September	1st to 10th	Night	5% 4 2 5% 3 4 4 4 6% 8% 56%	1900
	11th to 20th	Night	8% 6% 2 5% 4 3 5% 4 6% 7% 49%	1900
	21st to end	Night	10% 8% 3 8% 4 5% 4 5% 6% 8% 39%	2142
October	1st to 10th	Night	9% 11% 3 8% 5% 5% 5% 4 6% 8% 36%	3800
	11th to 20th	Night	16% 11% 3 8% 5% 4 5% 4 6% 8% 31%	3801
	21st to end	Night	10% 16% 5% 9% 5% 5% 5% 5% 5% 6% 29%	4457
November	1st to 10th	Night	10% 15% 5% 10% 7% 7% 6% 4 6% 7% 23%	2663
	11th to 20th	Night	7% 15% 4 12% 7% 7% 7% 5% 5% 7% 23%	2800
	21st to end	Night	6% 15% 5% 12% 8% 6% 6% 5% 7% 8% 20%	2800
December	1st to 10th	Night	5% 14% 6% 12% 9% 7% 6% 6% 6% 7% 23%	2800
	11th to 20th	Night	5% 16% 6% 16% 9% 8% 7% 5% 6% 7% 15%	3546
	21st to end	Night	6% 13% 6% 14% 9% 8% 8% 6% 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	63% 11% 13% 9% 3	2219
	11th to 20th	Day	55% 9% 16% 11% 3 5%	2507
	21st to end	Day	61% 11% 13% 11% 4	2794
February	1st to 10th	Day	63% 11% 11% 9% 6% 1	1611
	11th to 20th	Day	57% 11% 15% 10% 7% 1	1674
	21st to end	Day	62% 9% 13% 13% 3	1515
March	1st to 10th	Day	54% 9% 11% 16% 9% 1	3138
	11th to 20th	Day	42% 10% 19% 24% 5%	3397
	21st to end	Day	60% 10% 13% 9% 8%	4065
April	1st to 10th	Day	61% 10% 15% 13% 1	2280
	11th to 20th	Day	53% 9% 13% 14% 10% 1	2252
	21st to end	Day	54% 9% 16% 13% 7%	2619
May	1st to 10th	Day	41% 7% 16% 26% 10% 1	4420
	11th to 20th	Day	42% 8% 22% 23% 5%	4380
	21st to end	Day	62% 7% 15% 13% 3	4814
June	1st to 10th	Day	52% 8% 13% 16% 7% 3	2758
	11th to 20th	Day	52% 9% 15% 18% 6%	3040
	21st to end	Day	41% 8% 17% 21% 11% 1	2882
July	1st to 10th	Day	20% 4 9% 21% 27% 18%	4666
	11th to 20th	Day	16% 5% 9% 22% 33% 16%	4501
	21st to end	Day	20% 6% 15% 30% 21% 8%	4639
August	1st to 10th	Day	19% 6% 12% 25% 30% 8%	4384
	11th to 20th	Day	29% 9% 23% 26% 11% 3	4255
	21st to end	Day	37% 9% 15% 24% 14% 1	4281
September	1st to 10th	Day	35% 6% 13% 26% 16% 4	2280
	11th to 20th	Day	42% 7% 11% 20% 17% 3	2280
	21st to end	Day	45% 8% 16% 17% 11% 3	2037
October	1st to 10th	Day	45% 8% 17% 24% 6%	3180
	11th to 20th	Day	52% 7% 11% 22% 7% 1	3135
	21st to end	Day	54% 11% 15% 15% 5%	3101
November	1st to 10th	Day	63% 8% 13% 12% 4	1630
	11th to 20th	Day	59% 10% 13% 12% 6% 1	1600
	21st to end	Day	55% 13% 11% 14% 5% 1	1595
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	64% 12% 12% 9% 2	4726
	11th to 20th	Night	55% 9% 15% 13% 5% 4	4450
	21st to end	Night	59% 16% 12% 9% 4	4862
February	1st to 10th	Night	62% 10% 11% 12% 4	2565
	11th to 20th	Night	56% 8% 14% 14% 7% 1	2404
	21st to end	Night	57% 9% 12% 16% 5%	1938
March	1st to 10th	Night	45% 11% 14% 17% 12% 1	3736
	11th to 20th	Night	36% 10% 22% 28% 4	3566
	21st to end	Night	53% 11% 15% 15% 6%	3587
April	1st to 10th	Night	49% 12% 19% 17% 3	1900
	11th to 20th	Night	46% 9% 19% 17% 8% 1	1879
	21st to end	Night	49% 9% 17% 16% 8%	1558
May	1st to 10th	Night	41% 7% 19% 26% 7%	2540
	11th to 20th	Night	38% 9% 23% 23% 7%	2516
	21st to end	Night	55% 10% 16% 16% 3	2762
June	1st to 10th	Night	45% 9% 17% 19% 7% 3	1407
	11th to 20th	Night	42% 12% 19% 20% 7%	1140
	21st to end	Night	32% 9% 25% 23% 10% 1	1287
July	1st to 10th	Night	17% 6% 11% 24% 27% 15%	2185
	11th to 20th	Night	11% 4 13% 25% 33% 14%	2333
	21st to end	Night	16% 5% 16% 31% 21% 12%	2674
August	1st to 10th	Night	15% 6% 15% 30% 30% 4	2521
	11th to 20th	Night	20% 9% 31% 27% 11% 3	2639
	21st to end	Night	36% 8% 18% 24% 12% 2	3392
September	1st to 10th	Night	26% 8% 18% 29% 17% 3	1900
	11th to 20th	Night	33% 7% 15% 23% 17% 5%	1900
	21st to end	Night	41% 10% 18% 20% 9% 2	2142
October	1st to 10th	Night	43% 9% 19% 23% 6%	3800
	11th to 20th	Night	49% 9% 13% 22% 7%	3801
	21st to end	Night	51% 9% 16% 19% 4	4457
November	1st to 10th	Night	58% 11% 13% 12% 5%	2663
	11th to 20th	Night	55% 13% 14% 13% 5% 1	2800
	21st to end	Night	57% 13% 13% 10% 6% 1	2800
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	11% 11% 24% 34% 14% 6%	180
	21st to end	Day	12% 15% 28% 29% 15% 1	198
February	1st to 10th	Day	24% 21% 30% 18% 5% 1	271
	11th to 20th	Day	19% 21% 29% 21% 5% 3	365
	21st to end	Day	18% 22% 33% 17% 9% 1	357
March	1st to 10th	Day	20% 21% 28% 20% 9% 2	460
	11th to 20th	Day	19% 21% 24% 20% 12% 4	460
	21st to end	Day	23% 23% 25% 17% 9% 3	506
April	1st to 10th	Day	25% 20% 32% 15% 8% 1	460
	11th to 20th	Day	21% 21% 28% 18% 8% 4	452
	21st to end	Day	22% 24% 25% 18% 7% 3	460
May	1st to 10th	Day	17% 20% 32% 20% 9% 3	463
	11th to 20th	Day	19% 16% 27% 23% 12% 3	488
	21st to end	Day	22% 16% 26% 22% 10% 3	529
June	1st to 10th	Day	19% 22% 32% 18% 8% 1	588
	11th to 20th	Day	20% 20% 32% 17% 9% 2	870
	21st to end	Day	14% 18% 31% 21% 13% 3	712
July	1st to 10th	Day	11% 13% 37% 24% 13% 2	671
	11th to 20th	Day	10% 14% 34% 25% 12% 4	575
	21st to end	Day	6% 14% 32% 27% 15% 6%	531
August	1st to 10th	Day	7% 11% 27% 29% 18% 8%	487
	11th to 20th	Day	8% 11% 27% 29% 17% 8%	477
	21st to end	Day	11% 17% 32% 21% 13% 6%	539
September	1st to 10th	Day	14% 14% 27% 23% 15% 6%	490
	11th to 20th	Day	14% 15% 24% 27% 17% 3	490
	21st to end	Day	21% 18% 25% 20% 12% 4	490
October	1st to 10th	Day	21% 16% 25% 18% 15% 6%	490
	11th to 20th	Day	23% 19% 18% 21% 14% 4	476
	21st to end	Day	22% 16% 26% 25% 8% 2	330
November	1st to 10th	Day	20% 16% 31% 24% 8% 1	233
	11th to 20th	Day	24% 18% 26% 17% 14% 3	200
	21st to end	Day	17% 13% 28% 22% 14% 7%	199
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% 11% 32% 29% 14% 1	767
	21st to end	Night	13% 13% 29% 31% 12% 2	836
February	1st to 10th	Night	18% 14% 26% 30% 9% 2	760
	11th to 20th	Night	12% 13% 28% 32% 13% 2	744
	21st to end	Night	15% 13% 26% 28% 16% 1	628
March	1st to 10th	Night	13% 12% 29% 28% 17% 2	760
	11th to 20th	Night	14% 12% 32% 27% 13% 3	760
	21st to end	Night	16% 13% 29% 27% 13% 2	836
April	1st to 10th	Night	13% 14% 24% 33% 14% 2	760
	11th to 20th	Night	13% 15% 29% 27% 15% 1	751
	21st to end	Night	16% 14% 24% 34% 11% 1	418
May	1st to 10th	Night	10% 12% 27% 33% 17% 2	380
	11th to 20th	Night	9% 6% 22% 38% 24% 2	374
	21st to end	Night	15% 7% 24% 32% 21% 1	411
June	1st to 10th	Night	11% 12% 26% 38% 12% 1	380
	11th to 20th	Night	13% 12% 29% 28% 16% 1	380
	21st to end	Night	8% 10% 26% 32% 22% 2	380
July	1st to 10th	Night	7% 7% 20% 40% 24% 2	370
	11th to 20th	Night	5% 8% 24% 41% 21% 1	368
	21st to end	Night	3 6% 22% 40% 28% 1	416
August	1st to 10th	Night	4 3 17% 40% 33% 2	378
	11th to 20th	Night	3 3 17% 38% 34% 4	442
	21st to end	Night	10% 8% 22% 35% 23% 2	769
September	1st to 10th	Night	8% 7% 24% 33% 24% 5%	760
	11th to 20th	Night	12% 6% 20% 25% 28% 8%	760
	21st to end	Night	17% 9% 23% 30% 18% 3	760
October	1st to 10th	Night	14% 10% 21% 33% 20% 3	760
	11th to 20th	Night	18% 10% 24% 28% 18% 2	760
	21st to end	Night	21% 15% 23% 27% 12% 2	836
November	1st to 10th	Night	21% 11% 31% 28% 8% 1	780
	11th to 20th	Night	21% 15% 28% 23% 11% 2	800
	21st to end	Night	16% 15% 27% 27% 13% 3	800
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

Page generated at 2024-11-27 14:30:51. Version ac07

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