Fort Smith
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Smith clear sky chart from 2005-11-05 to 2018-10-08.

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	11% 9% 4 8% 7% 4 6% 5% 5% 7% 30%	52459
	Night	9% 11% 5% 9% 8% 4 6% 6% 5% 6% 24%	50869
Transparency	Day	51% 7% 14% 19% 5%	52073
	Night	57% 7% 14% 15% 4	50760
Seeing	Day	14% 14% 23% 28% 15% 4	8544
	Night	13% 17% 23% 27% 14% 2	16706

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 15th	Day	10% 14% 6% 11% 7% 4 7% 11% 5% 6% 12%	970
	16th to end	Day	6% 15% 7% 11% 9% 6% 9% 7% 6% 5% 13%	1284
February	1st to 15th	Day	4 8% 6% 11% 11% 6% 10% 8% 6% 8% 18%	1397
	16th to end	Day	5% 12% 6% 12% 11% 6% 6% 5% 6% 6% 20%	1498
March	1st to 15th	Day	6% 11% 5% 8% 7% 4 5% 6% 5% 6% 31%	1940
	16th to end	Day	7% 9% 4 7% 8% 4 7% 6% 5% 6% 31%	2312
April	1st to 15th	Day	8% 8% 4 7% 5% 3 4 5% 5% 6% 39%	2524
	16th to end	Day	7% 7% 3 7% 5% 2 5% 5% 5% 7% 41%	2719
May	1st to 15th	Day	7% 7% 3 7% 5% 3 5% 5% 5% 8% 39%	2948
	16th to end	Day	11% 5% 3 5% 6% 2 5% 4 4 6% 43%	3409
June	1st to 15th	Day	13% 7% 3 7% 6% 4 5% 5% 5% 7% 31%	3315
	16th to end	Day	9% 5% 2 5% 6% 4 6% 6% 6% 8% 37%	3315
July	1st to 15th	Day	10% 6% 4 7% 7% 4 7% 6% 7% 8% 30%	3315
	16th to end	Day	9% 5% 2 6% 7% 4 7% 7% 6% 8% 32%	3389
August	1st to 15th	Day	11% 5% 2 7% 5% 3 5% 4 5% 7% 40%	2868
	16th to end	Day	20% 7% 3 5% 6% 4 5% 5% 6% 6% 27%	2823
September	1st to 15th	Day	16% 8% 3 6% 5% 3 4 4 5% 8% 32%	2460
	16th to end	Day	19% 12% 4 7% 6% 2 4 4 5% 6% 26%	2142
October	1st to 15th	Day	15% 14% 5% 7% 5% 3 4 4 6% 7% 24%	1807
	16th to end	Day	16% 22% 8% 9% 6% 3 5% 3 3 6% 14%	1584
November	1st to 15th	Day	15% 17% 7% 12% 8% 4 5% 3 4 4 17%	1307
	16th to end	Day	10% 17% 7% 15% 12% 5% 6% 4 4 4 11%	1118
December	1st to 15th	Day	9% 17% 7% 14% 11% 5% 7% 7% 5% 5% 8%	975
	16th to end	Day	8% 12% 7% 11% 11% 6% 7% 7% 6% 6% 12%	1040
January	1st to 15th	Night	8% 14% 6% 13% 10% 5% 7% 8% 6% 5% 12%	3299
	16th to end	Night	10% 15% 6% 10% 8% 5% 7% 7% 5% 5% 16%	3292
February	1st to 15th	Night	4 8% 4 10% 9% 7% 10% 10% 5% 7% 22%	2796
	16th to end	Night	4 12% 7% 11% 10% 5% 7% 4 6% 6% 23%	2262
March	1st to 15th	Night	4 10% 5% 9% 6% 4 5% 5% 6% 7% 34%	2349
	16th to end	Night	5% 8% 4 6% 6% 4 6% 5% 5% 7% 39%	2259
April	1st to 15th	Night	7% 11% 3 5% 4 2 3 5% 5% 9% 41%	1754
	16th to end	Night	6% 6% 2 6% 6% 3 6% 5% 7% 8% 40%	1514
May	1st to 15th	Night	7% 6% 3 8% 6% 4 6% 5% 6% 7% 37%	1332
	16th to end	Night	10% 5% 2 4 5% 2 4 3 5% 7% 46%	1055
June	1st to 15th	Night	11% 5% 4 8% 6% 3 5% 6% 5% 9% 33%	975
	16th to end	Night	6% 5% 2 5% 5% 5% 6% 7% 9% 7% 39%	975
July	1st to 15th	Night	11% 4 2 4 6% 4 5% 7% 6% 10% 34%	975
	16th to end	Night	6% 4 2 3 4 4 7% 7% 9% 11% 36%	1131
August	1st to 15th	Night	8% 5% 2 6% 6% 3 5% 6% 5% 8% 41%	1344
	16th to end	Night	14% 6% 2 6% 6% 4 5% 5% 7% 7% 31%	1729
September	1st to 15th	Night	16% 7% 2 5% 5% 3 5% 4 6% 8% 34%	1829
	16th to end	Night	17% 10% 3 5% 5% 3 5% 4 6% 8% 30%	2148
October	1st to 15th	Night	13% 12% 4 7% 6% 3 4 4 5% 6% 29%	2322
	16th to end	Night	16% 22% 7% 9% 6% 3 4 4 4 5% 14%	2628
November	1st to 15th	Night	14% 14% 7% 13% 9% 4 4 4 4 5% 17%	2878
	16th to end	Night	10% 14% 8% 14% 12% 7% 6% 6% 4 4 8%	3172
December	1st to 15th	Night	9% 15% 9% 14% 10% 5% 8% 7% 5% 4 7%	3315
	16th to end	Night	7% 13% 7% 13% 10% 5% 8% 8% 5% 5% 12%	3536

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 15th	Day	66% 9% 11% 9% 2	970
	16th to end	Day	68% 4 11% 11% 2	1284
February	1st to 15th	Day	60% 7% 12% 15% 4	1397
	16th to end	Day	63% 5% 11% 16% 3	1498
March	1st to 15th	Day	52% 6% 13% 22% 4	1940
	16th to end	Day	50% 7% 13% 21% 6%	2313
April	1st to 15th	Day	44% 6% 13% 25% 10%	2524
	16th to end	Day	41% 5% 12% 31% 7%	2719
May	1st to 15th	Day	42% 6% 13% 23% 13%	2948
	16th to end	Day	40% 5% 10% 23% 18%	3414
June	1st to 15th	Day	49% 7% 12% 21% 8%	3315
	16th to end	Day	42% 9% 16% 23% 8%	3315
July	1st to 15th	Day	48% 9% 16% 20% 4	3136
	16th to end	Day	45% 11% 19% 21% 2	3194
August	1st to 15th	Day	41% 9% 20% 22% 5%	2850
	16th to end	Day	53% 10% 19% 15% 1	2823
September	1st to 15th	Day	50% 9% 22% 15% 1	2460
	16th to end	Day	56% 7% 17% 14% 2	2142
October	1st to 15th	Day	58% 8% 18% 14%	1807
	16th to end	Day	71% 8% 11% 7%	1584
November	1st to 15th	Day	69% 7% 9% 9% 2	1307
	16th to end	Day	75% 6% 9% 6% 1	1118
December	1st to 15th	Day	75% 7% 9% 7%	975
	16th to end	Day	67% 7% 11% 11% 1	1040
January	1st to 15th	Night	68% 6% 10% 11% 1	3299
	16th to end	Night	66% 6% 10% 11% 4	3292
February	1st to 15th	Night	57% 6% 16% 15% 3	2808
	16th to end	Night	59% 5% 14% 14% 4	2262
March	1st to 15th	Night	47% 6% 15% 23% 5%	2349
	16th to end	Night	43% 6% 15% 24% 9%	2262
April	1st to 15th	Night	40% 6% 13% 25% 13%	1754
	16th to end	Night	38% 6% 13% 30% 10%	1514
May	1st to 15th	Night	42% 8% 11% 22% 14%	1333
	16th to end	Night	37% 4 10% 24% 22% 1	1055
June	1st to 15th	Night	45% 8% 13% 23% 7%	975
	16th to end	Night	37% 9% 17% 24% 10%	975
July	1st to 15th	Night	39% 11% 18% 24% 5%	925
	16th to end	Night	32% 12% 26% 26% 2	1063
August	1st to 15th	Night	38% 9% 19% 25% 6% 1	1337
	16th to end	Night	48% 10% 18% 19% 2	1729
September	1st to 15th	Night	45% 9% 24% 16% 4	1829
	16th to end	Night	50% 8% 20% 14% 4	2148
October	1st to 15th	Night	53% 8% 18% 17% 1	2322
	16th to end	Night	72% 8% 11% 7%	2628
November	1st to 15th	Night	69% 6% 11% 10% 1	2878
	16th to end	Night	77% 7% 8% 6%	3172
December	1st to 15th	Night	76% 8% 8% 6%	3315
	16th to end	Night	68% 8% 11% 9% 1	3536

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 15th	Day	10% 11% 30% 37% 10% 1	90
	16th to end	Day	22% 4 28% 22% 14% 7%	96
February	1st to 15th	Day	11% 8% 34% 32% 8% 4	90
	16th to end	Day	7% 4 29% 40% 11% 6%	110
March	1st to 15th	Day	10% 16% 30% 23% 12% 5%	262
	16th to end	Day	10% 15% 35% 28% 7% 3	352
April	1st to 15th	Day	13% 16% 31% 22% 11% 5%	329
	16th to end	Day	11% 20% 24% 29% 11% 2	451
May	1st to 15th	Day	11% 20% 23% 27% 14% 2	543
	16th to end	Day	10% 17% 21% 31% 16% 3	761
June	1st to 15th	Day	16% 18% 24% 26% 10% 2	765
	16th to end	Day	10% 15% 18% 30% 19% 5%	765
July	1st to 15th	Day	13% 14% 17% 32% 16% 6%	735
	16th to end	Day	11% 14% 17% 27% 22% 6%	770
August	1st to 15th	Day	11% 9% 15% 29% 23% 10%	549
	16th to end	Day	21% 10% 25% 27% 12% 2	456
September	1st to 15th	Day	23% 13% 25% 21% 12% 3	375
	16th to end	Day	21% 12% 27% 22% 13% 1	372
October	1st to 15th	Day	28% 3 21% 29% 10% 5%	157
	16th to end	Day	40% 2 29% 15% 9%	144
November	1st to 15th	Day	14% 7% 36% 22% 17% 1	96
	16th to end	Day	21% 5% 23% 31% 18%	90
December	1st to 15th	Day	22% 6% 26% 27% 12% 4	90
	16th to end	Day	1 32% 31% 20% 14%	96
January	1st to 15th	Night	12% 21% 27% 26% 9% 2	1020
	16th to end	Night	15% 19% 27% 24% 9% 2	1072
February	1st to 15th	Night	6% 20% 27% 28% 11% 4	898
	16th to end	Night	7% 19% 31% 28% 11%	684
March	1st to 15th	Night	7% 20% 23% 29% 16% 3	780
	16th to end	Night	7% 20% 24% 29% 16% 2	825
April	1st to 15th	Night	11% 20% 24% 27% 13% 2	584
	16th to end	Night	8% 22% 23% 30% 14% 1	489
May	1st to 15th	Night	8% 21% 23% 31% 13% 1	390
	16th to end	Night	11% 17% 19% 35% 14% 1	407
June	1st to 15th	Night	12% 20% 22% 28% 13% 2	390
	16th to end	Night	8% 16% 16% 31% 26% 1	390
July	1st to 15th	Night	10% 12% 16% 30% 25% 4	370
	16th to end	Night	7% 15% 10% 33% 26% 6%	408
August	1st to 15th	Night	10% 10% 13% 34% 24% 5%	384
	16th to end	Night	17% 10% 21% 30% 18% 3	548
September	1st to 15th	Night	18% 11% 21% 28% 17% 3	594
	16th to end	Night	19% 13% 24% 26% 13% 1	776
October	1st to 15th	Night	20% 13% 20% 27% 13% 3	752
	16th to end	Night	26% 14% 21% 24% 12% 1	900
November	1st to 15th	Night	16% 19% 25% 25% 11% 2	950
	16th to end	Night	16% 20% 22% 24% 13% 2	987
December	1st to 15th	Night	15% 20% 27% 26% 7% 2	1020
	16th to end	Night	10% 18% 25% 23% 16% 5%	1088

Page generated at 2018-10-09 08:39:16. Version ac04

Copyright 2018 A. Danko