Elbow Falls
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elbow Falls clear sky chart from 2005-11-06 to 2024-10-25.

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% 9% 3 9% 5% 5% 5% 4 7% 8% 37%	101810
	Night	4 8% 3 8% 5% 5% 5% 5% 7% 9% 41%	97078
Transparency	Day	41% 8% 15% 22% 12% 2	101562
	Night	36% 8% 17% 23% 13% 3	96973
Seeing	Day	16% 23% 31% 20% 8% 2	15271
	Night	11% 23% 32% 23% 9% 2	24275

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	3 3 11% 7% 6% 7% 5% 10% 13% 35%	2219
	11th to 20th	Day	5% 4 12% 6% 5% 6% 5% 8% 11% 39%	2333
	21st to end	Day	6% 4 10% 5% 6% 6% 5% 8% 10% 41%	2794
February	1st to 10th	Day	6% 3 10% 8% 9% 7% 5% 10% 9% 33%	1520
	11th to 20th	Day	1 7% 4 11% 7% 7% 7% 6% 8% 10% 32%	1626
	21st to end	Day	1 7% 4 16% 10% 6% 5% 5% 7% 8% 31%	1570
March	1st to 10th	Day	5% 3 11% 8% 7% 6% 5% 8% 10% 37%	3138
	11th to 20th	Day	1 9% 5% 8% 5% 4 4 3 7% 9% 45%	3410
	21st to end	Day	2 13% 9% 21% 8% 4 4 4 5% 7% 23%	3943
April	1st to 10th	Day	4 15% 7% 11% 6% 6% 5% 4 7% 8% 26%	2299
	11th to 20th	Day	5% 17% 6% 13% 6% 4 5% 4 7% 7% 25%	2440
	21st to end	Day	7% 17% 6% 10% 6% 4 4 4 5% 8% 29%	2470
May	1st to 10th	Day	11% 25% 4 7% 5% 4 4 3 5% 6% 24%	4314
	11th to 20th	Day	7% 11% 4 7% 6% 5% 6% 6% 9% 9% 29%	4680
	21st to end	Day	14% 13% 3 8% 6% 6% 6% 4 7% 8% 25%	5161
June	1st to 10th	Day	17% 11% 3 8% 6% 5% 4 4 6% 8% 26%	2850
	11th to 20th	Day	21% 11% 4 10% 6% 5% 5% 4 6% 5% 24%	2850
	21st to end	Day	11% 8% 3 7% 6% 5% 6% 5% 6% 8% 34%	2850
July	1st to 10th	Day	8% 6% 2 6% 5% 5% 6% 4 6% 7% 46%	4740
	11th to 20th	Day	6% 4 2 5% 4 5% 6% 5% 7% 9% 48%	4740
	21st to end	Day	4 4 2 5% 3 5% 5% 4 6% 8% 54%	4917
August	1st to 10th	Day	11% 7% 2 7% 5% 4 5% 4 8% 9% 37%	4401
	11th to 20th	Day	10% 5% 2 7% 5% 6% 5% 4 6% 8% 41%	4115
	21st to end	Day	9% 6% 2 5% 4 4 4 4 7% 8% 47%	4521
September	1st to 10th	Day	10% 8% 2 6% 4 4 4 4 6% 7% 46%	2323
	11th to 20th	Day	11% 9% 2 6% 4 4 4 5% 6% 7% 42%	2103
	21st to end	Day	7% 8% 3 6% 4 4 5% 5% 7% 8% 44%	2090
October	1st to 10th	Day	8% 10% 3 7% 5% 5% 4 3 7% 8% 39%	2043
	11th to 20th	Day	4 10% 3 7% 5% 4 5% 4 7% 8% 42%	1720
	21st to end	Day	2 10% 4 10% 5% 5% 5% 4 8% 8% 39%	1822
November	1st to 10th	Day	2 11% 5% 10% 6% 4 5% 4 7% 8% 37%	1603
	11th to 20th	Day	1 6% 3 8% 6% 4 4 4 7% 12% 45%	1421
	21st to end	Day	1 7% 2 9% 7% 5% 5% 5% 6% 9% 44%	1330
December	1st to 10th	Day	1 5% 3 11% 6% 5% 5% 5% 8% 11% 39%	1330
	11th to 20th	Day	1 6% 3 10% 7% 6% 6% 6% 7% 9% 38%	1682
	21st to end	Day	7% 4 9% 5% 6% 5% 4 7% 8% 45%	2442
January	1st to 10th	Night	5% 4 13% 7% 6% 7% 6% 9% 11% 32%	4726
	11th to 20th	Night	5% 3 10% 6% 6% 7% 6% 10% 10% 37%	4595
	21st to end	Night	1 7% 4 9% 6% 6% 6% 5% 7% 10% 40%	4862
February	1st to 10th	Night	1 6% 3 10% 8% 6% 7% 6% 7% 9% 37%	2660
	11th to 20th	Night	1 7% 5% 11% 7% 5% 6% 5% 7% 9% 37%	2436
	21st to end	Night	1 6% 4 11% 8% 8% 6% 6% 7% 8% 36%	1884
March	1st to 10th	Night	3 3 11% 8% 6% 6% 6% 9% 10% 37%	3736
	11th to 20th	Night	1 7% 4 7% 5% 3 4 4 6% 9% 50%	3569
	21st to end	Night	1 14% 8% 16% 6% 5% 3 4 6% 7% 29%	3707
April	1st to 10th	Night	3 12% 5% 10% 6% 4 6% 4 6% 9% 35%	1881
	11th to 20th	Night	5% 11% 5% 12% 4 5% 5% 4 7% 8% 34%	1691
	21st to end	Night	3 12% 6% 10% 6% 5% 4 4 6% 7% 36%	1710
May	1st to 10th	Night	9% 21% 5% 9% 5% 4 3 3 5% 5% 30%	2646
	11th to 20th	Night	6% 10% 4 8% 6% 6% 5% 4 7% 9% 35%	2213
	21st to end	Night	12% 12% 3 7% 5% 5% 5% 4 6% 8% 33%	2414
June	1st to 10th	Night	12% 13% 3 7% 5% 4 4 5% 6% 7% 34%	1330
	11th to 20th	Night	18% 11% 3 7% 6% 4 5% 4 5% 7% 32%	1330
	21st to end	Night	8% 5% 1 6% 5% 4 5% 5% 7% 8% 47%	1330
July	1st to 10th	Night	5% 5% 2 4 4 4 5% 4 6% 7% 54%	2220
	11th to 20th	Night	5% 4 1 3 4 3 4 5% 6% 8% 57%	2220
	21st to end	Night	5% 3 1 3 3 3 3 3 6% 5% 64%	2631
August	1st to 10th	Night	10% 10% 2 5% 4 3 4 4 7% 8% 43%	2529
	11th to 20th	Night	6% 5% 2 5% 4 5% 5% 4 7% 9% 49%	2720
	21st to end	Night	8% 4 1 4 3 4 4 4 7% 9% 52%	3146
September	1st to 10th	Night	9% 7% 2 5% 3 3 4 4 5% 7% 52%	1854
	11th to 20th	Night	11% 8% 2 6% 3 3 3 4 7% 8% 46%	2076
	21st to end	Night	7% 7% 2 5% 3 4 4 3 6% 8% 50%	2090
October	1st to 10th	Night	7% 9% 4 6% 4 4 5% 4 6% 6% 46%	2137
	11th to 20th	Night	4 8% 4 7% 4 4 4 3 7% 9% 46%	2457
	21st to end	Night	3 8% 3 10% 5% 5% 5% 5% 8% 10% 39%	2639
November	1st to 10th	Night	2 9% 4 9% 5% 5% 5% 5% 7% 9% 39%	2457
	11th to 20th	Night	1 6% 4 6% 5% 4 5% 5% 7% 12% 46%	2758
	21st to end	Night	1 8% 3 8% 6% 4 5% 4 8% 10% 42%	2850
December	1st to 10th	Night	1 6% 4 9% 6% 6% 5% 5% 8% 10% 40%	2850
	11th to 20th	Night	1 5% 3 10% 6% 7% 6% 5% 8% 11% 37%	3510
	21st to end	Night	1 7% 4 10% 6% 5% 6% 4 7% 8% 42%	5214

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	36% 9% 15% 24% 13% 3	2219
	11th to 20th	Day	37% 7% 14% 19% 17% 6%	2355
	21st to end	Day	33% 9% 18% 29% 9% 2	2794
February	1st to 10th	Day	41% 9% 15% 21% 11% 3	1520
	11th to 20th	Day	40% 9% 16% 22% 10% 3	1635
	21st to end	Day	48% 8% 14% 17% 12% 2	1570
March	1st to 10th	Day	36% 7% 19% 17% 19% 2	3138
	11th to 20th	Day	32% 6% 26% 22% 12% 1	3411
	21st to end	Day	57% 7% 12% 15% 8%	3943
April	1st to 10th	Day	52% 8% 17% 15% 7%	2299
	11th to 20th	Day	53% 8% 13% 18% 7% 1	2440
	21st to end	Day	53% 7% 15% 18% 7% 1	2470
May	1st to 10th	Day	59% 6% 11% 18% 5%	4314
	11th to 20th	Day	43% 10% 15% 24% 8%	4684
	21st to end	Day	52% 10% 13% 15% 11%	5162
June	1st to 10th	Day	54% 8% 12% 15% 9% 1	2850
	11th to 20th	Day	57% 9% 11% 14% 8% 1	2850
	21st to end	Day	43% 10% 14% 20% 11% 2	2850
July	1st to 10th	Day	33% 8% 11% 20% 25% 4	4666
	11th to 20th	Day	28% 10% 12% 28% 18% 3	4659
	21st to end	Day	25% 7% 10% 25% 26% 7%	4762
August	1st to 10th	Day	39% 9% 12% 27% 11% 1	4384
	11th to 20th	Day	37% 9% 18% 28% 7% 1	4156
	21st to end	Day	30% 7% 17% 32% 12% 1	4520
September	1st to 10th	Day	36% 6% 13% 26% 15% 3	2323
	11th to 20th	Day	39% 6% 16% 24% 13% 2	2103
	21st to end	Day	35% 10% 16% 25% 13% 2	2090
October	1st to 10th	Day	41% 7% 13% 26% 12% 1	2043
	11th to 20th	Day	37% 9% 17% 22% 13% 2	1720
	21st to end	Day	39% 9% 16% 21% 13% 2	1822
November	1st to 10th	Day	43% 9% 15% 19% 12% 2	1603
	11th to 20th	Day	31% 9% 22% 25% 11% 2	1421
	21st to end	Day	35% 8% 21% 22% 9% 4	1330
December	1st to 10th	Day	36% 8% 22% 17% 15% 3	1330
	11th to 20th	Day	37% 11% 17% 25% 10% 2	1684
	21st to end	Day	34% 8% 11% 24% 17% 7%	2442
January	1st to 10th	Night	39% 11% 15% 21% 11% 3	4726
	11th to 20th	Night	36% 9% 15% 17% 14% 9%	4635
	21st to end	Night	35% 10% 19% 22% 13% 1	4862
February	1st to 10th	Night	40% 8% 14% 20% 14% 3	2660
	11th to 20th	Night	40% 9% 18% 18% 12% 3	2437
	21st to end	Night	41% 7% 13% 21% 15% 3	1884
March	1st to 10th	Night	35% 7% 20% 18% 18% 2	3736
	11th to 20th	Night	29% 6% 24% 24% 16% 1	3569
	21st to end	Night	51% 8% 11% 22% 7% 1	3707
April	1st to 10th	Night	44% 8% 16% 18% 13% 1	1881
	11th to 20th	Night	46% 7% 16% 21% 9% 1	1691
	21st to end	Night	46% 8% 14% 22% 8% 2	1710
May	1st to 10th	Night	54% 7% 12% 22% 6%	2646
	11th to 20th	Night	39% 9% 16% 29% 7%	2213
	21st to end	Night	46% 8% 15% 19% 11%	2414
June	1st to 10th	Night	46% 10% 13% 22% 9% 1	1330
	11th to 20th	Night	50% 8% 14% 17% 11% 1	1330
	21st to end	Night	31% 10% 18% 28% 12% 1	1330
July	1st to 10th	Night	26% 8% 15% 25% 21% 5%	2185
	11th to 20th	Night	22% 8% 16% 32% 19% 4	2178
	21st to end	Night	20% 6% 12% 28% 26% 8%	2548
August	1st to 10th	Night	34% 9% 14% 31% 11% 2	2521
	11th to 20th	Night	28% 8% 25% 28% 9% 1	2745
	21st to end	Night	25% 8% 22% 31% 12% 1	3146
September	1st to 10th	Night	31% 6% 17% 28% 15% 3	1854
	11th to 20th	Night	35% 7% 15% 26% 13% 4	2076
	21st to end	Night	32% 6% 18% 27% 15% 2	2090
October	1st to 10th	Night	37% 7% 15% 25% 15% 1	2137
	11th to 20th	Night	33% 7% 18% 26% 13% 2	2457
	21st to end	Night	37% 8% 16% 24% 13% 1	2639
November	1st to 10th	Night	39% 11% 17% 20% 12% 2	2457
	11th to 20th	Night	31% 9% 19% 25% 15% 2	2758
	21st to end	Night	35% 8% 20% 21% 12% 4	2850
December	1st to 10th	Night	36% 9% 16% 22% 12% 5%	2850
	11th to 20th	Night	36% 10% 21% 22% 10% 1	3507
	21st to end	Night	36% 7% 13% 23% 14% 7%	5214

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	8% 29% 28% 24% 7% 3	180
	11th to 20th	Day	8% 24% 38% 23% 6% 1	180
	21st to end	Day	7% 37% 35% 12% 7% 3	198
February	1st to 10th	Day	14% 28% 36% 14% 6% 2	180
	11th to 20th	Day	9% 25% 41% 15% 9%	252
	21st to end	Day	13% 26% 32% 21% 7%	382
March	1st to 10th	Day	11% 32% 35% 15% 5% 2	460
	11th to 20th	Day	10% 31% 35% 17% 5% 2	460
	21st to end	Day	13% 30% 32% 17% 5% 2	506
April	1st to 10th	Day	16% 30% 35% 14% 4	460
	11th to 20th	Day	15% 26% 31% 18% 8% 2	452
	21st to end	Day	20% 28% 25% 17% 8% 2	460
May	1st to 10th	Day	22% 19% 27% 21% 10% 3	463
	11th to 20th	Day	22% 13% 24% 25% 13% 2	661
	21st to end	Day	26% 14% 22% 21% 14% 2	734
June	1st to 10th	Day	21% 20% 30% 19% 8% 1	680
	11th to 20th	Day	26% 21% 23% 20% 8% 1	680
	21st to end	Day	16% 17% 29% 24% 11% 4	680
July	1st to 10th	Day	14% 13% 32% 24% 15% 3	671
	11th to 20th	Day	13% 18% 29% 26% 11% 3	668
	21st to end	Day	8% 15% 37% 26% 10% 3	606
August	1st to 10th	Day	14% 18% 30% 26% 11% 1	487
	11th to 20th	Day	13% 17% 31% 27% 9% 3	477
	21st to end	Day	18% 17% 32% 22% 9% 2	539
September	1st to 10th	Day	17% 25% 30% 20% 7% 2	490
	11th to 20th	Day	19% 19% 31% 23% 6% 1	490
	21st to end	Day	21% 32% 26% 15% 5% 1	490
October	1st to 10th	Day	17% 23% 29% 19% 10% 1	443
	11th to 20th	Day	15% 27% 32% 18% 6% 1	300
	21st to end	Day	19% 32% 32% 13% 5% 1	311
November	1st to 10th	Day	16% 34% 32% 11% 6% 1	270
	11th to 20th	Day	18% 31% 37% 12% 2	223
	21st to end	Day	14% 34% 26% 12% 8% 6%	180
December	1st to 10th	Day	11% 31% 36% 14% 7% 2	180
	11th to 20th	Day	6% 36% 40% 16% 2 1	180
	21st to end	Day	11% 20% 43% 16% 7% 3	198
January	1st to 10th	Night	11% 32% 38% 15% 3	950
	11th to 20th	Night	6% 33% 39% 18% 2 2	884
	21st to end	Night	8% 34% 36% 16% 6%	836
February	1st to 10th	Night	8% 29% 31% 19% 10% 3	760
	11th to 20th	Night	8% 27% 35% 21% 9%	744
	21st to end	Night	8% 20% 35% 24% 12% 2	628
March	1st to 10th	Night	6% 25% 38% 21% 8% 2	760
	11th to 20th	Night	7% 26% 37% 23% 7% 1	760
	21st to end	Night	9% 20% 30% 29% 10% 3	836
April	1st to 10th	Night	11% 21% 30% 27% 9% 1	741
	11th to 20th	Night	12% 19% 33% 26% 9% 1	563
	21st to end	Night	13% 18% 32% 26% 10% 1	570
May	1st to 10th	Night	15% 13% 27% 31% 14% 1	447
	11th to 20th	Night	14% 12% 27% 26% 18% 3	374
	21st to end	Night	25% 12% 21% 24% 18% 1	411
June	1st to 10th	Night	19% 14% 25% 28% 11% 3	380
	11th to 20th	Night	23% 13% 25% 26% 13%	380
	21st to end	Night	11% 12% 27% 28% 19% 1	380
July	1st to 10th	Night	13% 8% 20% 37% 20% 2	370
	11th to 20th	Night	11% 10% 29% 34% 15% 2	368
	21st to end	Night	8% 10% 23% 37% 19% 2	416
August	1st to 10th	Night	13% 6% 19% 34% 25% 3	378
	11th to 20th	Night	10% 9% 24% 32% 22% 3	509
	21st to end	Night	12% 13% 26% 31% 16% 2	627
September	1st to 10th	Night	13% 13% 27% 29% 14% 4	714
	11th to 20th	Night	15% 12% 28% 26% 13% 6%	760
	21st to end	Night	14% 25% 29% 20% 9% 3	760
October	1st to 10th	Night	14% 18% 30% 26% 9% 2	760
	11th to 20th	Night	12% 24% 32% 24% 7% 1	760
	21st to end	Night	10% 30% 34% 20% 5% 1	812
November	1st to 10th	Night	10% 30% 41% 13% 5% 1	792
	11th to 20th	Night	10% 37% 36% 14% 1 1	950
	21st to end	Night	9% 34% 36% 15% 5% 2	950
December	1st to 10th	Night	8% 31% 36% 16% 8% 1	950
	11th to 20th	Night	5% 34% 38% 17% 5% 1	950
	21st to end	Night	7% 30% 39% 17% 7% 1	1045

Page generated at 2024-10-22 18:21:04. Version ac07

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