Welsh Mountain Community Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Welsh Mountain Community Center clear sky chart from 2005-11-06 to 2024-12-09.

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	15% 7% 2 7% 4 4 5% 4 6% 7% 39%	101646
	Night	15% 7% 3 6% 4 4 4 4 5% 7% 41%	98157
Transparency	Day	41% 6% 12% 23% 15% 3	105221
	Night	41% 6% 11% 23% 16% 3	102658
Seeing	Day	20% 15% 28% 22% 11% 3	15036
	Night	18% 14% 31% 27% 10% 1	24406

By Month

Percentage Cloud Cover NE (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	14% 9% 3 7% 4 4 4 3 4 6% 43%	2517
	11th to 20th	Day	14% 12% 3 11% 4 5% 4 3 5% 6% 33%	2680
	21st to end	Day	19% 10% 3 9% 5% 4 4 3 4 5% 33%	3124
February	1st to 10th	Day	15% 9% 4 6% 5% 3 4 4 7% 6% 38%	1710
	11th to 20th	Day	15% 9% 3 6% 5% 4 4 3 5% 7% 39%	1761
	21st to end	Day	18% 12% 2 8% 4 3 4 2 4 6% 37%	1570
March	1st to 10th	Day	24% 7% 2 6% 4 4 4 3 4 7% 35%	3209
	11th to 20th	Day	10% 7% 2 6% 5% 5% 6% 4 6% 8% 42%	3480
	21st to end	Day	22% 8% 2 6% 3 3 3 2 4 5% 43%	3988
April	1st to 10th	Day	15% 8% 3 6% 5% 4 4 4 6% 7% 39%	2280
	11th to 20th	Day	14% 7% 2 7% 4 4 4 4 5% 7% 43%	2254
	21st to end	Day	16% 6% 3 6% 4 5% 4 4 6% 7% 40%	2280
May	1st to 10th	Day	28% 7% 2 6% 4 4 4 3 5% 7% 29%	4080
	11th to 20th	Day	23% 9% 3 8% 5% 4 4 3 6% 7% 27%	4398
	21st to end	Day	11% 5% 2 6% 4 4 4 4 6% 8% 45%	4837
June	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 4 7% 9% 39%	2660
	11th to 20th	Day	12% 5% 2 7% 6% 5% 5% 4 7% 9% 38%	2660
	21st to end	Day	11% 4 2 5% 4 5% 5% 3 7% 10% 42%	2660
July	1st to 10th	Day	7% 5% 2 6% 5% 5% 7% 5% 8% 11% 37%	4440
	11th to 20th	Day	9% 6% 2 6% 5% 5% 6% 5% 8% 9% 39%	4440
	21st to end	Day	12% 8% 3 8% 5% 6% 6% 5% 6% 8% 33%	4628
August	1st to 10th	Day	17% 7% 3 7% 5% 5% 6% 4 6% 7% 33%	4104
	11th to 20th	Day	13% 6% 2 7% 4 4 5% 4 7% 8% 40%	3801
	21st to end	Day	10% 5% 2 6% 4 4 4 4 6% 8% 47%	4180
September	1st to 10th	Day	14% 6% 2 6% 4 4 4 3 5% 5% 45%	2280
	11th to 20th	Day	11% 5% 2 5% 4 4 3 3 5% 8% 50%	2280
	21st to end	Day	18% 9% 3 6% 4 5% 4 4 5% 6% 37%	2037
October	1st to 10th	Day	15% 7% 2 7% 3 4 3 4 6% 6% 44%	1900
	11th to 20th	Day	15% 6% 2 5% 4 3 4 3 4 6% 47%	1900
	21st to end	Day	17% 6% 2 5% 3 3 4 3 5% 6% 45%	2070
November	1st to 10th	Day	11% 7% 3 5% 3 2 3 3 4 7% 51%	1761
	11th to 20th	Day	14% 7% 2 5% 4 4 3 3 6% 6% 46%	1800
	21st to end	Day	15% 7% 2 5% 4 4 5% 4 5% 7% 42%	1615
December	1st to 10th	Day	17% 9% 3 7% 5% 4 4 3 5% 6% 38%	1584
	11th to 20th	Day	19% 9% 2 5% 5% 3 4 3 5% 6% 40%	1906
	21st to end	Day	16% 8% 3 8% 6% 5% 5% 4 5% 6% 33%	2772
January	1st to 10th	Night	15% 7% 3 6% 5% 5% 4 4 5% 6% 40%	4429
	11th to 20th	Night	18% 8% 2 6% 4 3 4 3 5% 6% 40%	4277
	21st to end	Night	21% 9% 3 8% 4 3 3 3 4 5% 37%	4532
February	1st to 10th	Night	17% 8% 3 6% 5% 4 4 3 5% 6% 39%	2470
	11th to 20th	Night	17% 8% 3 7% 4 4 4 4 5% 5% 40%	2305
	21st to end	Night	17% 8% 3 7% 4 4 4 4 6% 6% 39%	1884
March	1st to 10th	Night	21% 10% 2 6% 4 4 4 3 4 5% 37%	3628
	11th to 20th	Night	10% 6% 2 7% 4 4 4 3 5% 6% 49%	3479
	21st to end	Night	14% 9% 3 7% 4 3 3 3 3 4 47%	3643
April	1st to 10th	Night	16% 8% 2 6% 5% 4 4 3 7% 7% 39%	1900
	11th to 20th	Night	14% 6% 3 6% 4 4 4 3 5% 8% 42%	1875
	21st to end	Night	16% 7% 3 6% 4 3 4 3 6% 7% 43%	1900
May	1st to 10th	Night	24% 7% 3 7% 5% 4 4 3 5% 8% 31%	2889
	11th to 20th	Night	24% 10% 3 7% 5% 4 4 4 5% 7% 28%	2495
	21st to end	Night	12% 6% 2 6% 3 4 4 4 6% 10% 43%	2738
June	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 6% 8% 43%	1520
	11th to 20th	Night	11% 6% 2 5% 4 5% 5% 4 7% 10% 40%	1520
	21st to end	Night	10% 6% 2 5% 3 4 5% 4 8% 10% 43%	1520
July	1st to 10th	Night	7% 5% 2 6% 6% 6% 7% 5% 7% 9% 40%	2520
	11th to 20th	Night	8% 6% 2 7% 5% 6% 5% 5% 8% 10% 36%	2520
	21st to end	Night	13% 8% 2 6% 5% 5% 5% 4 7% 8% 38%	2921
August	1st to 10th	Night	17% 8% 3 6% 5% 4 5% 4 6% 7% 35%	2825
	11th to 20th	Night	12% 8% 3 7% 5% 4 4 4 5% 7% 41%	2994
	21st to end	Night	10% 5% 2 5% 3 4 4 4 7% 7% 48%	3476
September	1st to 10th	Night	13% 6% 3 7% 3 4 4 3 5% 6% 47%	1900
	11th to 20th	Night	11% 6% 2 5% 3 3 4 3 5% 7% 52%	1900
	21st to end	Night	18% 7% 2 7% 4 4 4 4 5% 6% 41%	2140
October	1st to 10th	Night	19% 8% 3 6% 3 3 4 2 4 6% 43%	2280
	11th to 20th	Night	14% 6% 2 6% 3 3 4 4 5% 6% 49%	2280
	21st to end	Night	17% 5% 2 5% 3 3 3 3 5% 7% 48%	2527
November	1st to 10th	Night	10% 5% 2 5% 3 3 4 3 5% 6% 53%	2537
	11th to 20th	Night	14% 8% 2 6% 3 3 4 3 5% 6% 45%	2600
	21st to end	Night	13% 6% 2 5% 5% 4 5% 4 6% 6% 44%	2782
December	1st to 10th	Night	18% 7% 2 6% 6% 4 4 4 5% 6% 38%	2779
	11th to 20th	Night	17% 6% 2 8% 4 4 4 3 5% 6% 41%	3288
	21st to end	Night	16% 8% 3 7% 5% 4 4 5% 6% 8% 34%	4884

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	42% 4 13% 25% 12% 3	2518
	11th to 20th	Day	51% 4 10% 19% 13% 3	2680
	21st to end	Day	51% 6% 12% 22% 9% 1	3124
February	1st to 10th	Day	45% 5% 15% 24% 11% 2	1710
	11th to 20th	Day	45% 5% 9% 25% 14% 2	1770
	21st to end	Day	49% 4 10% 20% 13% 4	1570
March	1st to 10th	Day	48% 5% 9% 27% 10% 2	3212
	11th to 20th	Day	37% 5% 11% 27% 16% 4	3480
	21st to end	Day	46% 5% 8% 19% 20% 3	3988
April	1st to 10th	Day	43% 6% 12% 20% 15% 5%	2280
	11th to 20th	Day	40% 6% 11% 21% 17% 4	2254
	21st to end	Day	42% 6% 12% 19% 17% 4	2280
May	1st to 10th	Day	53% 6% 9% 19% 10% 2	4092
	11th to 20th	Day	55% 7% 12% 17% 8% 1	4402
	21st to end	Day	35% 7% 13% 26% 17% 2	4837
June	1st to 10th	Day	39% 8% 12% 24% 15% 2	2660
	11th to 20th	Day	41% 8% 13% 24% 12% 3	2660
	21st to end	Day	36% 9% 14% 25% 15% 1	2660
July	1st to 10th	Day	37% 11% 15% 21% 13% 3	4370
	11th to 20th	Day	37% 9% 16% 23% 13% 1	4365
	21st to end	Day	47% 8% 9% 18% 16% 1	4480
August	1st to 10th	Day	48% 8% 12% 22% 9%	4091
	11th to 20th	Day	38% 7% 11% 29% 14% 1	3839
	21st to end	Day	33% 7% 11% 28% 19% 2	4180
September	1st to 10th	Day	40% 6% 11% 20% 20% 4	2280
	11th to 20th	Day	33% 5% 9% 26% 23% 4	2280
	21st to end	Day	48% 5% 8% 18% 20% 2	2037
October	1st to 10th	Day	37% 4 8% 19% 28% 5%	3160
	11th to 20th	Day	26% 5% 12% 26% 23% 8%	3140
	21st to end	Day	25% 3 12% 27% 28% 4	3384
November	1st to 10th	Day	34% 3 13% 25% 20% 4	1761
	11th to 20th	Day	37% 5% 10% 25% 20% 2	1800
	21st to end	Day	40% 6% 11% 30% 11% 2	1615
December	1st to 10th	Day	46% 5% 15% 21% 12% 1	1584
	11th to 20th	Day	43% 4 14% 28% 10% 1	1906
	21st to end	Day	49% 6% 14% 21% 10% 1	2772
January	1st to 10th	Night	43% 4 11% 27% 12% 3	4429
	11th to 20th	Night	44% 4 12% 25% 13% 2	4277
	21st to end	Night	49% 4 8% 27% 10% 2	4532
February	1st to 10th	Night	45% 5% 12% 25% 11% 2	2470
	11th to 20th	Night	45% 5% 9% 20% 18% 3	2307
	21st to end	Night	45% 5% 10% 21% 15% 5%	1884
March	1st to 10th	Night	48% 5% 9% 24% 13% 2	3638
	11th to 20th	Night	34% 4 13% 30% 16% 2	3480
	21st to end	Night	42% 4 7% 18% 24% 5%	3643
April	1st to 10th	Night	43% 5% 11% 20% 17% 4	1900
	11th to 20th	Night	39% 7% 11% 21% 19% 4	1875
	21st to end	Night	41% 5% 10% 22% 18% 5%	1900
May	1st to 10th	Night	52% 7% 9% 19% 11% 2	2896
	11th to 20th	Night	55% 8% 12% 13% 10% 1	2496
	21st to end	Night	36% 8% 15% 22% 16% 3	2739
June	1st to 10th	Night	39% 7% 11% 23% 19% 1	1520
	11th to 20th	Night	38% 9% 13% 24% 15% 1	1520
	21st to end	Night	33% 8% 16% 26% 15% 2	1520
July	1st to 10th	Night	38% 10% 16% 18% 13% 4	2480
	11th to 20th	Night	39% 9% 17% 21% 13% 1	2472
	21st to end	Night	42% 8% 13% 18% 18% 1	2828
August	1st to 10th	Night	46% 8% 17% 19% 9% 1	2814
	11th to 20th	Night	41% 7% 11% 25% 14% 1	3022
	21st to end	Night	33% 7% 12% 30% 18% 1	3476
September	1st to 10th	Night	38% 6% 10% 21% 21% 4	1900
	11th to 20th	Night	32% 5% 10% 24% 26% 4	1900
	21st to end	Night	44% 6% 8% 20% 21% 2	2140
October	1st to 10th	Night	44% 4 9% 20% 21% 2	3800
	11th to 20th	Night	25% 4 10% 28% 27% 5%	3779
	21st to end	Night	25% 4 11% 32% 23% 4	4151
November	1st to 10th	Night	32% 4 12% 26% 21% 5%	2537
	11th to 20th	Night	39% 5% 9% 23% 20% 5%	2600
	21st to end	Night	37% 5% 13% 27% 16% 2	2782
December	1st to 10th	Night	45% 5% 12% 23% 14% 1	2779
	11th to 20th	Night	42% 5% 13% 21% 16% 3	3288
	21st to end	Night	45% 7% 14% 22% 11% 1	4884

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	28% 29% 27% 14% 2 1	180
	11th to 20th	Day	29% 29% 31% 10% 1	225
	21st to end	Day	24% 31% 30% 13% 2 1	297
February	1st to 10th	Day	24% 30% 33% 9% 2 1	270
	11th to 20th	Day	31% 26% 36% 7% 2	368
	21st to end	Day	34% 20% 30% 13% 3	382
March	1st to 10th	Day	25% 25% 32% 16% 3	460
	11th to 20th	Day	27% 27% 31% 11% 3 1	460
	21st to end	Day	28% 20% 32% 14% 4 1	506
April	1st to 10th	Day	26% 23% 31% 14% 5% 1	460
	11th to 20th	Day	22% 23% 29% 17% 7% 2	452
	21st to end	Day	27% 17% 34% 16% 5% 1	460
May	1st to 10th	Day	27% 21% 24% 21% 6% 2	463
	11th to 20th	Day	21% 16% 31% 22% 9% 2	487
	21st to end	Day	16% 11% 27% 24% 19% 3	529
June	1st to 10th	Day	14% 13% 30% 25% 15% 3	490
	11th to 20th	Day	16% 11% 28% 29% 13% 2	490
	21st to end	Day	14% 8% 29% 31% 13% 4	490
July	1st to 10th	Day	13% 5% 20% 33% 21% 8%	485
	11th to 20th	Day	6% 4 24% 38% 23% 5%	484
	21st to end	Day	12% 7% 28% 31% 17% 4	532
August	1st to 10th	Day	13% 5% 26% 28% 21% 7%	486
	11th to 20th	Day	12% 7% 19% 35% 20% 8%	479
	21st to end	Day	13% 5% 22% 32% 19% 8%	539
September	1st to 10th	Day	17% 9% 21% 28% 17% 9%	490
	11th to 20th	Day	14% 6% 24% 28% 17% 10%	490
	21st to end	Day	25% 14% 22% 22% 13% 4	490
October	1st to 10th	Day	22% 8% 27% 23% 15% 4	490
	11th to 20th	Day	17% 15% 31% 22% 13% 2	490
	21st to end	Day	17% 16% 37% 21% 8% 2	528
November	1st to 10th	Day	17% 16% 31% 24% 10% 3	395
	11th to 20th	Day	19% 22% 33% 20% 6%	400
	21st to end	Day	25% 21% 31% 18% 5%	215
December	1st to 10th	Day	22% 28% 34% 13% 2 1	196
	11th to 20th	Day	29% 27% 28% 12% 4	180
	21st to end	Day	25% 23% 32% 15% 5% 1	198
January	1st to 10th	Night	17% 23% 41% 16% 3	760
	11th to 20th	Night	25% 19% 33% 20% 3	760
	21st to end	Night	17% 22% 41% 18% 2	836
February	1st to 10th	Night	21% 20% 38% 20% 1	760
	11th to 20th	Night	24% 26% 36% 12% 1	743
	21st to end	Night	24% 22% 37% 15% 2	628
March	1st to 10th	Night	20% 21% 36% 19% 4	760
	11th to 20th	Night	22% 22% 34% 17% 5%	760
	21st to end	Night	20% 16% 40% 18% 5%	836
April	1st to 10th	Night	22% 19% 38% 18% 4	760
	11th to 20th	Night	19% 15% 36% 24% 6%	751
	21st to end	Night	20% 16% 33% 24% 7%	760
May	1st to 10th	Night	21% 13% 31% 28% 7%	613
	11th to 20th	Night	19% 11% 33% 29% 8%	374
	21st to end	Night	14% 6% 27% 38% 13% 1	411
June	1st to 10th	Night	14% 4 28% 41% 13%	380
	11th to 20th	Night	12% 5% 27% 45% 11%	380
	21st to end	Night	11% 3 26% 48% 11%	380
July	1st to 10th	Night	11% 3 22% 42% 20% 1	370
	11th to 20th	Night	8% 3 18% 45% 24% 1	368
	21st to end	Night	12% 3 20% 42% 21% 2	523
August	1st to 10th	Night	11% 3 15% 46% 23% 2	567
	11th to 20th	Night	13% 5% 14% 41% 25% 2	683
	21st to end	Night	14% 3 18% 39% 23% 3	836
September	1st to 10th	Night	15% 4 26% 33% 19% 3	760
	11th to 20th	Night	12% 5% 20% 36% 24% 4	760
	21st to end	Night	20% 7% 22% 30% 18% 2	760
October	1st to 10th	Night	22% 8% 23% 29% 14% 3	760
	11th to 20th	Night	17% 12% 31% 28% 11% 1	760
	21st to end	Night	19% 13% 33% 26% 10%	836
November	1st to 10th	Night	13% 13% 35% 28% 11% 1	780
	11th to 20th	Night	18% 19% 30% 25% 6% 1	800
	21st to end	Night	16% 20% 35% 21% 7%	800
December	1st to 10th	Night	23% 18% 35% 18% 6%	795
	11th to 20th	Night	19% 19% 38% 21% 4	760
	21st to end	Night	20% 18% 37% 23% 2	836

Page generated at 2024-12-06 03:54:47. Version ac07

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