Walloper Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Walloper Lake 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% 11% 4 9% 6% 6% 6% 5% 6% 7% 33%	105533
	Night	6% 10% 4 10% 7% 6% 6% 5% 7% 8% 33%	102632
Transparency	Day	45% 7% 14% 21% 10% 2	105288
	Night	46% 7% 15% 21% 10% 2	102523
Seeing	Day	18% 16% 26% 23% 13% 4	15665
	Night	14% 16% 25% 27% 16% 3	24010

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	6% 14% 7% 16% 9% 8% 7% 5% 7% 7% 15%	2219
	11th to 20th	Day	5% 15% 6% 10% 7% 6% 5% 4 6% 10% 27%	2330
	21st to end	Day	3 16% 5% 13% 7% 7% 6% 6% 8% 9% 19%	2794
February	1st to 10th	Day	6% 17% 5% 14% 9% 5% 5% 6% 6% 6% 21%	1581
	11th to 20th	Day	4 15% 6% 12% 5% 5% 6% 6% 5% 8% 29%	1665
	21st to end	Day	2 14% 7% 15% 8% 8% 6% 5% 7% 5% 23%	1503
March	1st to 10th	Day	2 11% 5% 13% 8% 8% 9% 6% 9% 8% 22%	3138
	11th to 20th	Day	3 9% 3 9% 6% 6% 6% 5% 7% 7% 38%	3391
	21st to end	Day	4 16% 5% 13% 9% 7% 7% 5% 6% 7% 22%	4069
April	1st to 10th	Day	6% 14% 6% 12% 10% 9% 6% 5% 6% 7% 19%	2280
	11th to 20th	Day	7% 15% 6% 12% 8% 7% 6% 5% 5% 8% 22%	2257
	21st to end	Day	7% 16% 5% 11% 7% 6% 6% 5% 6% 8% 23%	2655
May	1st to 10th	Day	6% 12% 4 9% 6% 5% 6% 4 5% 7% 36%	4420
	11th to 20th	Day	8% 11% 4 11% 7% 6% 6% 5% 8% 10% 25%	4377
	21st to end	Day	13% 16% 6% 14% 7% 6% 5% 4 4 6% 18%	4813
June	1st to 10th	Day	17% 11% 3 9% 6% 6% 5% 5% 6% 7% 25%	3004
	11th to 20th	Day	16% 13% 5% 9% 7% 6% 6% 4 5% 6% 22%	3040
	21st to end	Day	12% 7% 3 8% 7% 5% 6% 5% 7% 8% 33%	3040
July	1st to 10th	Day	6% 5% 2 6% 4 4 5% 4 5% 6% 54%	4775
	11th to 20th	Day	4 4 1 4 4 4 4 4 5% 7% 60%	4690
	21st to end	Day	7% 5% 1 5% 4 4 4 4 6% 8% 51%	4790
August	1st to 10th	Day	4 3 2 5% 4 5% 5% 4 6% 7% 55%	4401
	11th to 20th	Day	4 4 2 7% 7% 7% 7% 5% 8% 8% 41%	4255
	21st to end	Day	9% 6% 2 7% 4 5% 5% 5% 7% 8% 41%	4308
September	1st to 10th	Day	9% 7% 2 6% 4 4 4 3 5% 7% 48%	2280
	11th to 20th	Day	12% 9% 3 7% 5% 5% 4 4 5% 6% 40%	2280
	21st to end	Day	12% 9% 3 8% 5% 5% 5% 5% 6% 8% 34%	2037
October	1st to 10th	Day	7% 9% 3 7% 5% 4 5% 4 6% 9% 41%	3180
	11th to 20th	Day	12% 13% 4 8% 5% 4 5% 4 6% 8% 33%	3107
	21st to end	Day	7% 13% 4 10% 5% 6% 5% 5% 7% 8% 30%	3101
November	1st to 10th	Day	10% 14% 4 13% 8% 6% 5% 4 4 6% 25%	1606
	11th to 20th	Day	6% 14% 4 8% 7% 7% 6% 5% 8% 7% 28%	1600
	21st to end	Day	7% 15% 4 10% 8% 6% 7% 6% 7% 8% 23%	1503
December	1st to 10th	Day	4 11% 5% 13% 9% 9% 7% 5% 7% 7% 24%	1330
	11th to 20th	Day	3 13% 6% 13% 8% 6% 6% 6% 7% 9% 21%	1499
	21st to end	Day	4 12% 5% 12% 9% 8% 7% 6% 9% 8% 20%	2215
January	1st to 10th	Night	5% 15% 6% 15% 9% 8% 7% 5% 7% 7% 16%	4726
	11th to 20th	Night	5% 14% 6% 14% 7% 6% 5% 5% 7% 9% 23%	4566
	21st to end	Night	4 11% 5% 14% 7% 8% 8% 6% 9% 8% 19%	4862
February	1st to 10th	Night	6% 16% 5% 13% 8% 6% 6% 5% 6% 7% 23%	2596
	11th to 20th	Night	4 12% 5% 11% 7% 6% 7% 4 6% 7% 31%	2402
	21st to end	Night	3 11% 6% 15% 8% 7% 6% 5% 6% 8% 25%	1950
March	1st to 10th	Night	2 10% 3 9% 8% 7% 8% 6% 9% 11% 27%	3736
	11th to 20th	Night	2 6% 3 6% 5% 5% 6% 6% 8% 9% 43%	3587
	21st to end	Night	5% 12% 5% 10% 8% 6% 7% 5% 6% 7% 29%	3583
April	1st to 10th	Night	4 11% 4 11% 8% 7% 6% 5% 7% 7% 31%	1900
	11th to 20th	Night	3 11% 4 11% 8% 7% 7% 6% 5% 6% 31%	1871
	21st to end	Night	4 11% 3 9% 6% 5% 5% 6% 7% 8% 35%	1525
May	1st to 10th	Night	6% 13% 4 8% 6% 5% 6% 3 6% 7% 38%	2540
	11th to 20th	Night	5% 9% 4 10% 6% 5% 5% 5% 8% 10% 32%	2516
	21st to end	Night	8% 10% 3 10% 7% 6% 5% 5% 6% 8% 31%	2762
June	1st to 10th	Night	13% 8% 3 8% 6% 5% 5% 5% 6% 9% 31%	1169
	11th to 20th	Night	10% 10% 3 8% 7% 6% 6% 5% 7% 8% 29%	1140
	21st to end	Night	6% 8% 3 7% 5% 4 4 4 6% 8% 44%	1140
July	1st to 10th	Night	7% 5% 2 5% 5% 3 4 3 5% 7% 54%	2180
	11th to 20th	Night	3 3 1 3 3 3 4 3 6% 6% 66%	2270
	21st to end	Night	5% 3 2 5% 4 3 3 4 5% 7% 57%	2762
August	1st to 10th	Night	4 4 2 5% 4 4 5% 3 6% 8% 56%	2529
	11th to 20th	Night	4 4 2 6% 5% 5% 6% 5% 9% 9% 45%	2560
	21st to end	Night	8% 6% 3 7% 4 5% 5% 4 5% 7% 45%	3365
September	1st to 10th	Night	6% 6% 1 6% 3 3 4 3 5% 7% 54%	1900
	11th to 20th	Night	8% 6% 2 7% 4 5% 5% 5% 6% 7% 46%	1900
	21st to end	Night	9% 8% 4 7% 5% 4 4 3 6% 8% 42%	2142
October	1st to 10th	Night	8% 9% 3 8% 5% 5% 4 4 6% 7% 43%	3800
	11th to 20th	Night	12% 11% 3 8% 5% 4 4 5% 6% 8% 34%	3828
	21st to end	Night	6% 11% 4 11% 6% 6% 5% 4 5% 6% 35%	4457
November	1st to 10th	Night	9% 14% 4 10% 7% 6% 6% 5% 6% 7% 24%	2690
	11th to 20th	Night	5% 13% 5% 11% 9% 6% 6% 5% 6% 7% 28%	2800
	21st to end	Night	6% 15% 4 10% 8% 8% 6% 6% 6% 7% 24%	2870
December	1st to 10th	Night	5% 12% 5% 11% 8% 7% 6% 6% 6% 8% 27%	2850
	11th to 20th	Night	6% 16% 7% 15% 9% 7% 6% 4 6% 6% 19%	3688
	21st to end	Night	4 13% 5% 12% 9% 7% 6% 6% 8% 7% 24%	5470

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% 8% 13% 13% 3	2219
	11th to 20th	Day	53% 6% 18% 14% 4 6%	2352
	21st to end	Day	57% 12% 16% 11% 4	2794
February	1st to 10th	Day	60% 6% 12% 14% 7% 1	1581
	11th to 20th	Day	51% 7% 15% 16% 10% 1	1674
	21st to end	Day	58% 5% 14% 15% 8%	1503
March	1st to 10th	Day	50% 8% 14% 19% 8%	3138
	11th to 20th	Day	41% 5% 19% 27% 7%	3391
	21st to end	Day	55% 8% 16% 13% 8%	4069
April	1st to 10th	Day	60% 8% 12% 16% 5%	2280
	11th to 20th	Day	56% 7% 9% 16% 11% 2	2257
	21st to end	Day	55% 7% 13% 16% 9%	2655
May	1st to 10th	Day	43% 6% 10% 29% 11% 1	4420
	11th to 20th	Day	44% 10% 15% 25% 6%	4380
	21st to end	Day	61% 9% 12% 14% 4	4814
June	1st to 10th	Day	54% 7% 11% 15% 10% 4	3004
	11th to 20th	Day	60% 6% 10% 16% 8%	3040
	21st to end	Day	45% 6% 14% 21% 12% 2	3040
July	1st to 10th	Day	27% 6% 8% 22% 22% 15%	4701
	11th to 20th	Day	22% 5% 9% 26% 28% 10%	4609
	21st to end	Day	28% 6% 15% 26% 18% 8%	4639
August	1st to 10th	Day	24% 6% 11% 30% 26% 2	4384
	11th to 20th	Day	33% 11% 20% 24% 10% 2	4297
	21st to end	Day	36% 6% 19% 29% 8% 1	4307
September	1st to 10th	Day	36% 5% 14% 29% 14% 3	2280
	11th to 20th	Day	43% 4 12% 25% 13% 3	2280
	21st to end	Day	44% 7% 17% 19% 10% 2	2037
October	1st to 10th	Day	39% 5% 21% 26% 8% 1	3180
	11th to 20th	Day	48% 5% 14% 26% 6%	3107
	21st to end	Day	48% 9% 17% 21% 4	3101
November	1st to 10th	Day	58% 6% 11% 17% 6% 1	1606
	11th to 20th	Day	52% 7% 16% 18% 7% 1	1600
	21st to end	Day	55% 7% 16% 16% 6% 1	1503
December	1st to 10th	Day	56% 9% 15% 17% 3	1330
	11th to 20th	Day	58% 8% 18% 11% 5%	1501
	21st to end	Day	55% 8% 17% 16% 3	2215
January	1st to 10th	Night	62% 8% 15% 11% 4	4726
	11th to 20th	Night	56% 4 15% 14% 5% 6%	4606
	21st to end	Night	55% 12% 17% 12% 3	4862
February	1st to 10th	Night	58% 5% 13% 15% 6% 1	2596
	11th to 20th	Night	49% 6% 16% 19% 9% 2	2404
	21st to end	Night	54% 6% 14% 17% 9%	1950
March	1st to 10th	Night	43% 10% 15% 22% 11%	3736
	11th to 20th	Night	32% 5% 21% 30% 12%	3588
	21st to end	Night	50% 7% 14% 18% 10%	3583
April	1st to 10th	Night	47% 7% 18% 20% 7%	1900
	11th to 20th	Night	49% 8% 13% 19% 11%	1871
	21st to end	Night	44% 5% 15% 24% 12% 1	1525
May	1st to 10th	Night	44% 6% 9% 26% 14% 1	2540
	11th to 20th	Night	41% 10% 16% 26% 7%	2516
	21st to end	Night	47% 8% 17% 22% 6%	2762
June	1st to 10th	Night	45% 6% 14% 23% 8% 3	1169
	11th to 20th	Night	48% 6% 15% 22% 8%	1140
	21st to end	Night	37% 5% 17% 25% 14% 2	1140
July	1st to 10th	Night	28% 5% 10% 20% 25% 11%	2145
	11th to 20th	Night	16% 4 9% 31% 32% 7%	2228
	21st to end	Night	24% 5% 13% 28% 16% 14%	2674
August	1st to 10th	Night	25% 6% 11% 26% 30% 3	2521
	11th to 20th	Night	29% 9% 17% 28% 13% 2	2584
	21st to end	Night	34% 7% 22% 26% 10% 1	3365
September	1st to 10th	Night	29% 4 16% 32% 16% 3	1900
	11th to 20th	Night	34% 5% 16% 26% 14% 4	1900
	21st to end	Night	39% 6% 19% 21% 12% 2	2142
October	1st to 10th	Night	38% 6% 20% 28% 8%	3800
	11th to 20th	Night	46% 5% 13% 27% 8%	3828
	21st to end	Night	46% 6% 17% 26% 5%	4457
November	1st to 10th	Night	55% 7% 15% 15% 7% 1	2690
	11th to 20th	Night	54% 8% 15% 15% 8% 1	2800
	21st to end	Night	57% 6% 16% 13% 7% 1	2870
December	1st to 10th	Night	53% 7% 15% 19% 5%	2850
	11th to 20th	Night	66% 8% 12% 11% 4	3685
	21st to end	Night	55% 7% 16% 16% 5%	5470

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	16% 25% 26% 19% 9% 6%	180
	11th to 20th	Day	14% 18% 27% 23% 14% 3	180
	21st to end	Day	16% 21% 30% 19% 12% 2	198
February	1st to 10th	Day	19% 24% 31% 21% 5%	241
	11th to 20th	Day	15% 26% 29% 21% 9% 1	365
	21st to end	Day	16% 21% 31% 18% 12% 2	350
March	1st to 10th	Day	20% 25% 25% 19% 11% 1	460
	11th to 20th	Day	18% 24% 27% 18% 10% 3	460
	21st to end	Day	20% 25% 26% 17% 9% 3	506
April	1st to 10th	Day	24% 20% 27% 21% 6% 2	460
	11th to 20th	Day	20% 24% 23% 20% 11% 3	452
	21st to end	Day	22% 17% 31% 19% 8% 3	460
May	1st to 10th	Day	22% 16% 25% 26% 9% 3	463
	11th to 20th	Day	19% 12% 19% 28% 17% 5%	488
	21st to end	Day	21% 12% 24% 26% 14% 4	529
June	1st to 10th	Day	24% 18% 25% 21% 10% 1	834
	11th to 20th	Day	23% 12% 26% 24% 13% 2	870
	21st to end	Day	15% 11% 27% 25% 18% 4	870
July	1st to 10th	Day	13% 14% 25% 30% 15% 4	693
	11th to 20th	Day	10% 13% 27% 29% 16% 5%	644
	21st to end	Day	7% 8% 21% 37% 21% 6%	531
August	1st to 10th	Day	7% 6% 24% 30% 26% 8%	487
	11th to 20th	Day	8% 10% 25% 29% 20% 8%	477
	21st to end	Day	13% 12% 27% 29% 14% 5%	539
September	1st to 10th	Day	16% 13% 24% 27% 16% 4	490
	11th to 20th	Day	21% 14% 23% 23% 15% 4	490
	21st to end	Day	23% 16% 26% 23% 11% 2	490
October	1st to 10th	Day	22% 15% 24% 20% 15% 4	490
	11th to 20th	Day	22% 20% 23% 18% 14% 2	461
	21st to end	Day	22% 19% 25% 21% 11% 2	330
November	1st to 10th	Day	26% 20% 25% 18% 10% 1	220
	11th to 20th	Day	25% 23% 24% 12% 12% 4	200
	21st to end	Day	21% 18% 29% 17% 10% 6%	199
December	1st to 10th	Day	14% 14% 27% 21% 19% 6%	180
	11th to 20th	Day	13% 26% 29% 16% 11% 6%	180
	21st to end	Day	14% 14% 32% 27% 10% 4	198
January	1st to 10th	Night	21% 21% 23% 24% 10% 2	850
	11th to 20th	Night	14% 14% 25% 31% 14% 1	810
	21st to end	Night	11% 18% 26% 29% 14% 2	836
February	1st to 10th	Night	17% 17% 23% 29% 11% 3	760
	11th to 20th	Night	13% 17% 24% 31% 15% 1	744
	21st to end	Night	12% 18% 26% 25% 18% 2	628
March	1st to 10th	Night	12% 22% 23% 25% 15% 3	760
	11th to 20th	Night	12% 24% 27% 21% 14% 2	760
	21st to end	Night	14% 19% 27% 23% 13% 4	836
April	1st to 10th	Night	13% 18% 25% 26% 16% 3	760
	11th to 20th	Night	12% 20% 26% 26% 15% 1	743
	21st to end	Night	9% 20% 33% 24% 11% 2	385
May	1st to 10th	Night	14% 13% 26% 30% 15% 3	380
	11th to 20th	Night	10% 10% 25% 37% 14% 3	374
	21st to end	Night	16% 6% 28% 27% 20% 2	411
June	1st to 10th	Night	16% 13% 31% 28% 11% 2	380
	11th to 20th	Night	14% 13% 32% 26% 12% 4	380
	21st to end	Night	8% 12% 30% 27% 19% 3	380
July	1st to 10th	Night	9% 7% 28% 36% 18% 2	370
	11th to 20th	Night	8% 9% 30% 32% 21% 1	368
	21st to end	Night	7% 4 27% 34% 25% 4	416
August	1st to 10th	Night	7% 5% 20% 33% 30% 6%	378
	11th to 20th	Night	8% 4 25% 27% 31% 5%	413
	21st to end	Night	11% 9% 24% 30% 22% 4	755
September	1st to 10th	Night	10% 9% 23% 27% 26% 5%	760
	11th to 20th	Night	13% 8% 20% 23% 27% 8%	760
	21st to end	Night	17% 17% 21% 24% 17% 4	760
October	1st to 10th	Night	13% 15% 23% 27% 19% 4	760
	11th to 20th	Night	16% 18% 21% 24% 17% 3	760
	21st to end	Night	17% 19% 27% 23% 12% 2	836
November	1st to 10th	Night	20% 18% 28% 25% 8% 1	780
	11th to 20th	Night	18% 24% 24% 22% 12% 1	800
	21st to end	Night	16% 18% 25% 25% 12% 3	870
December	1st to 10th	Night	13% 15% 24% 29% 15% 3	950
	11th to 20th	Night	15% 20% 27% 27% 10% 1	1010
	21st to end	Night	15% 19% 26% 28% 10% 2	1087

Page generated at 2024-11-27 14:30:55. Version ac07

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