Molalla
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Molalla clear sky chart from 2005-11-05 to 2018-02-13.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
45%
15263
12%
48828
12%
15237
47%
15237
18%
34885

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
33%
777
9%
2716
8%
776
36%
776
10%
2160
January16th to endNight
34%
832
11%
2801
11%
832
37%
832
12%
2144
February1st to 15thNight
35%
744
7%
2444
6%
744
36%
744
10%
1977
February16th to endNight
30%
632
10%
1999
7%
632
35%
632
11%
1550
March1st to 15thNight
31%
720
5%
2046
4%
720
32%
720
11%
1686
March16th to endNight
30%
768
6%
2078
5%
768
31%
768
10%
1751
April1st to 15thNight
32%
719
6%
1799
4%
719
33%
719
13%
1506
April16th to endNight
42%
614
9%
1694
6%
614
43%
614
16%
1301
May1st to 15thNight
48%
386
13%
1466
15%
386
51%
386
18%
958
May16th to endNight
47%
375
8%
1496
12%
374
48%
374
12%
1098
June1st to 15thNight
49%
360
7%
1440
11%
360
50%
360
14%
1010
June16th to endNight
53%
360
11%
1440
17%
360
55%
360
21%
878
July1st to 15thNight
77%
340
17%
1360
28%
340
79%
340
43%
585
July16th to endNight
83%
376
28%
1416
40%
354
87%
354
53%
545
August1st to 15thNight
83%
520
26%
1594
25%
518
85%
518
54%
736
August16th to endNight
76%
664
31%
1810
23%
664
77%
664
52%
948
September1st to 15thNight
75%
720
27%
1800
17%
720
76%
720
57%
968
September16th to endNight
64%
716
25%
1973
22%
716
65%
716
33%
1235
October1st to 15thNight
51%
720
16%
2160
16%
720
53%
720
24%
1447
October16th to endNight
43%
768
14%
2334
14%
768
44%
768
17%
1711
November1st to 15thNight
30%
760
8%
2590
8%
760
32%
760
10%
2074
November16th to endNight
37%
780
6%
2730
7%
780
38%
780
10%
2138
December1st to 15thNight
38%
780
11%
2730
10%
780
40%
780
13%
2053
December16th to endNight
28%
832
6%
2912
7%
832
29%
832
7%
2426

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 ForecastData
Points
Cloud CoverDay
21%7%35%5%24446%33%
49231
Night
22%8%35%5%24345%34%
48996
Cloud CoverDay
22%8%36%5%24445%33%
49231
Night
23%8%35%423345%33%
49000
TransparencyDay
52%411%16%10%2
48902
Night
53%411%16%10%3
48829
SeeingDay
26%8%21%26%13%3
6046
Night
28%5%12%28%22%3
15275

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
34%9%46%6%35%43417%
1552
16th to endDay
29%9%36%5%35%445%21%
1773
February1st to 15thDay
30%10%47%5%345%46%16%
1685
16th to endDay
28%11%48%7%3344319%
1475
March1st to 15thDay
31%11%36%7%35%45%5%14%
1913
16th to endDay
31%11%47%6%35%445%14%
2145
April1st to 15thDay
26%12%46%7%35%45%5%17%
2149
16th to endDay
24%9%36%7%3445%6%22%
2265
May1st to 15thDay
21%7%36%424336%34%
2484
16th to endDay
26%7%245%35%45%6%27%
2615
June1st to 15thDay
23%8%46%6%35%45%7%26%
2520
16th to endDay
14%6%35%5%35%45%6%40%
2520
July1st to 15thDay
5%312322346%63%
2520
16th to endDay
6%312212235%67%
2657
August1st to 15thDay
331332345%7%61%
2355
16th to endDay
6%413323336%60%
2391
September1st to 15thDay
7%313323246%62%
2160
16th to endDay
16%5%36%5%23346%41%
1983
October1st to 15thDay
20%6%26%4245%48%33%
1800
16th to endDay
25%6%36%7%3446%6%26%
1890
November1st to 15thDay
34%9%38%5%33346%16%
1595
16th to endDay
29%8%47%7%345%5%417%
1560
December1st to 15thDay
26%11%46%7%2445%422%
1560
16th to endDay
35%12%36%5%24445%14%
1664
January1st to 15thNight
31%10%47%6%3434419%
2716
16th to endNight
29%8%36%5%33345%24%
2801
February1st to 15thNight
28%10%47%5%35%445%19%
2432
16th to endNight
26%11%46%5%24335%25%
1999
March1st to 15thNight
30%10%45%434446%20%
2046
16th to endNight
27%11%48%6%3445%6%17%
2074
April1st to 15thNight
27%11%5%6%5%3445%5%20%
1799
16th to endNight
24%9%35%42435%6%29%
1694
May1st to 15thNight
17%7%26%5%2345%6%37%
1466
16th to endNight
23%6%26%6%35%45%7%28%
1496
June1st to 15thNight
20%7%45%5%34436%34%
1440
16th to endNight
13%7%25%6%24335%45%
1440
July1st to 15thNight
4112312345%69%
1440
16th to endNight
311212235%74%
1512
August1st to 15thNight
2312222338%67%
1602
16th to endNight
4313212225%69%
1810
September1st to 15thNight
6%212212235%69%
1800
16th to endNight
14%32332445%7%49%
1973
October1st to 15thNight
18%6%25%5%33345%42%
2160
16th to endNight
23%7%26%423446%33%
2334
November1st to 15thNight
34%8%25%5%3445%5%20%
2590
16th to endNight
28%9%35%6%3444424%
2730
December1st to 15thNight
28%9%46%424346%25%
2730
16th to endNight
32%12%47%7%2333416%
2912

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
33%10%47%5%2432420%
1552
16th to endDay
30%9%36%5%23445%24%
1773
February1st to 15thDay
31%10%47%6%245%46%17%
1685
16th to endDay
28%13%47%7%3433419%
1475
March1st to 15thDay
32%12%37%7%35%445%14%
1913
16th to endDay
32%13%5%8%5%35%435%13%
2145
April1st to 15thDay
28%14%47%6%3445%5%16%
2149
16th to endDay
25%11%38%6%34346%21%
2265
May1st to 15thDay
22%9%36%423336%33%
2484
16th to endDay
28%8%36%5%34346%25%
2615
June1st to 15thDay
25%9%47%5%34445%26%
2520
16th to endDay
16%7%35%43435%5%38%
2520
July1st to 15thDay
6%312323346%62%
2520
16th to endDay
7%312212235%65%
2657
August1st to 15thDay
421432345%6%60%
2355
16th to endDay
6%423323346%59%
2391
September1st to 15thDay
7%313312347%60%
2160
16th to endDay
16%7%25%5%23445%41%
1983
October1st to 15thDay
21%7%35%4245%5%7%33%
1800
16th to endDay
26%7%36%43345%5%28%
1890
November1st to 15thDay
36%7%48%5%23346%16%
1595
16th to endDay
29%10%48%6%3444420%
1560
December1st to 15thDay
27%10%46%6%24445%23%
1560
16th to endDay
36%12%36%42343417%
1664
January1st to 15thNight
31%10%37%5%3434420%
2716
16th to endNight
30%9%36%5%23345%24%
2801
February1st to 15thNight
29%11%36%5%35%446%19%
2432
16th to endNight
28%11%46%5%24345%23%
1999
March1st to 15thNight
29%12%45%5%3445%5%19%
2046
16th to endNight
28%13%5%6%5%3445%6%16%
2078
April1st to 15thNight
27%14%47%4245%45%19%
1799
16th to endNight
24%10%35%42435%6%28%
1694
May1st to 15thNight
19%8%45%42445%5%36%
1466
16th to endNight
24%7%36%6%345%5%7%26%
1496
June1st to 15thNight
21%9%35%43444434%
1440
16th to endNight
14%8%25%5%24335%44%
1440
July1st to 15thNight
421331234468%
1440
16th to endNight
3112211345%73%
1512
August1st to 15thNight
13322225%8%66%
1602
16th to endNight
4223312235%68%
1810
September1st to 15thNight
6%31221223469%
1800
16th to endNight
15%41342435%6%47%
1973
October1st to 15thNight
19%7%25%423345%41%
2160
16th to endNight
24%7%25%5%23446%32%
2334
November1st to 15thNight
35%8%26%5%24446%19%
2590
16th to endNight
30%9%36%5%3443324%
2730
December1st to 15thNight
28%9%46%424346%25%
2730
16th to endNight
34%13%47%42333417%
2912

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
69%37%11%6%1
1552
16th to endDay
63%38%10%8%4
1773
February1st to 15thDay
67%6%10%9%5%
1685
16th to endDay
69%5%8%9%7%
1475
March1st to 15thDay
73%48%9%3
1913
16th to endDay
74%5%9%8%2
2145
April1st to 15thDay
70%5%12%8%2
2149
16th to endDay
64%5%11%11%5%1
2265
May1st to 15thDay
53%312%20%8%
2484
16th to endDay
60%6%14%15%2
2619
June1st to 15thDay
60%5%14%14%4
2520
16th to endDay
46%417%22%6%2
2520
July1st to 15thDay
23%414%27%23%5%
2371
16th to endDay
20%39%27%31%7%
2490
August1st to 15thDay
22%5%16%30%19%5%
2338
16th to endDay
25%5%12%30%20%5%
2391
September1st to 15thDay
24%311%26%21%12%
2160
16th to endDay
45%413%17%13%5%
1983
October1st to 15thDay
50%5%10%19%10%3
1800
16th to endDay
56%5%10%12%12%1
1890
November1st to 15thDay
70%410%11%3
1595
16th to endDay
67%5%8%7%9%
1560
December1st to 15thDay
62%6%8%12%8%1
1560
16th to endDay
71%48%10%4
1664
January1st to 15thNight
67%49%9%7%2
2716
16th to endNight
62%38%10%8%5%
2801
February1st to 15thNight
66%5%10%9%5%1
2444
16th to endNight
63%411%11%7%1
1999
March1st to 15thNight
66%5%10%11%4
2046
16th to endNight
68%6%10%11%2
2078
April1st to 15thNight
67%412%9%4
1799
16th to endNight
57%6%15%13%42
1694
May1st to 15thNight
48%415%20%8%3
1467
16th to endNight
57%6%15%14%41
1496
June1st to 15thNight
53%6%15%17%5%
1440
16th to endNight
43%318%22%7%2
1440
July1st to 15thNight
20%314%29%24%7%
1360
16th to endNight
14%310%30%31%9%
1416
August1st to 15thNight
16%316%37%17%7%
1594
16th to endNight
20%312%36%18%7%
1810
September1st to 15thNight
20%213%27%21%14%
1800
16th to endNight
37%414%22%14%7%
1973
October1st to 15thNight
46%39%19%16%4
2160
16th to endNight
52%7%9%11%14%3
2334
November1st to 15thNight
66%411%10%6%
2590
16th to endNight
64%5%8%7%10%3
2730
December1st to 15thNight
60%49%13%10%2
2730
16th to endNight
71%48%9%4
2912

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
31%6%18%18%18%5%
90
16th to endDay
41%7%14%20%14%1
205
February1st to 15thDay
38%8%22%21%7%1
273
16th to endDay
37%13%25%17%6%
221
March1st to 15thDay
48%15%21%12%2
270
16th to endDay
45%10%23%15%4
288
April1st to 15thDay
36%13%21%15%9%2
269
16th to endDay
37%12%25%13%7%2
270
May1st to 15thDay
30%11%22%24%8%1
288
16th to endDay
30%6%18%26%14%4
330
June1st to 15thDay
24%9%23%23%15%3
315
16th to endDay
16%7%26%33%13%2
315
July1st to 15thDay
7%420%40%22%3
305
16th to endDay
7%223%42%18%4
327
August1st to 15thDay
6%220%40%23%6%
315
16th to endDay
7%421%36%23%6%
332
September1st to 15thDay
10%6%22%36%20%4
315
16th to endDay
20%7%22%30%17%1
315
October1st to 15thDay
28%6%22%25%13%3
315
16th to endDay
33%7%18%23%11%5%
306
November1st to 15thDay
36%17%17%21%4
106
16th to endDay
40%11%23%11%10%4
90
December1st to 15thDay
38%14%15%11%13%6%
90
16th to endDay
46%416%15%14%2
96
January1st to 15thNight
37%7%11%21%19%1
780
16th to endNight
35%6%12%25%16%3
832
February1st to 15thNight
35%6%13%26%16%1
752
16th to endNight
36%10%15%22%14%
632
March1st to 15thNight
38%9%14%24%11%1
720
16th to endNight
36%8%16%24%13%1
768
April1st to 15thNight
36%8%14%25%14%1
719
16th to endNight
32%413%27%18%4
614
May1st to 15thNight
24%5%15%29%22%2
387
16th to endNight
27%210%29%27%2
375
June1st to 15thNight
27%313%32%21%2
360
16th to endNight
18%413%34%27%1
360
July1st to 15thNight
6%17%37%44%2
340
16th to endNight
416%45%38%3
376
August1st to 15thNight
31427%52%10%
520
16th to endNight
5%38%34%39%8%
664
September1st to 15thNight
8%10%32%39%8%
720
16th to endNight
19%18%33%33%4
716
October1st to 15thNight
22%5%13%29%25%4
720
16th to endNight
29%314%26%20%5%
768
November1st to 15thNight
39%8%13%28%10%
760
16th to endNight
35%9%10%26%15%1
780
December1st to 15thNight
36%312%28%15%2
780
16th to endNight
41%8%12%22%12%1
832
Page generated at 2018-02-13 17:46:05. Version ac04

Copyright 2018 A. Danko


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