Detailed Predictions for: Chalk Bluffs
Launch Altitude (f): 4500
LZ Altitude (f): 4220
Sounding

Station:

KVBG

Date/Time:

21 AUG 2019

Temp/Wind data from:

NOAA Digital Forecast

Site Forecasts
Time
(Local)
High
Temp

Puddle
Temp

Wind
(mph)
Thermal
Ceiling

(ft)
Soaring
Ceiling

(ft)
Above
Launch

(ft)
Thermal
Type
Thermal
Index

(F)
5 AM Wed 60 60 W 3 4275 4500 0 Blue 0
6 AM Wed 59 59 W 3 4275 4500 0 Blue 0
7 AM Wed 56 56 NW 3 4275 4500 0 Blue 0
8 AM Wed 67 67 NW 3 4275 4500 0 Blue 0
9 AM Wed 75 77 W 3 4743 4500 0 Blue 0
10 AM Wed 80 84 S 2 6794 5489 989 Blue 6
11 AM Wed 85 90 SE 2 10731 8793 4293 Blue 12
12 Noon Wed 89 95 SE 3 13539 11787 7287 Blue 17
1 PM Wed 91 98 S 3 14901 13402 8902 Blue 20
2 PM Wed 94 100 S 5 15761 14313 9813 Blue 22
3 PM Wed 95 100 S 5 15761 14313 9813 Blue 22
4 PM Wed 96 99 S 5 15336 13863 9363 Blue 21
5 PM Wed 96 98 S 5 14901 13402 8902 Blue 20
6 PM Wed 95 95 S 5 13539 11787 7287 Blue 17
7 PM Wed 90 90 S 6 10731 8793 4293 Blue 12
8 PM Wed 84 84 SW 6 6794 5489 989 Blue 6
9 PM Wed 79 79 SW 6 4955 4650 150 Blue 1
10 PM Wed 77 77 W 6 4743 4500 0 Blue 0
11 PM Wed 75 75 W 6 4559 4500 0 Blue 0
12 Midnight Thu 71 71 W 5 4275 4500 0 Blue 0
1 AM Thu 68 68 W 5 4275 4500 0 Blue 0
2 AM Thu 65 65 W 3 4275 4500 0 Blue 0
3 AM Thu 61 61 W 3 4275 4500 0 Blue 0
4 AM Thu 60 60 W 5 4275 4500 0 Blue 0
5 AM Thu 58 58 W 5 4275 4500 0 Blue 0
6 AM Thu 57 57 NW 5 4275 4500 0 Blue 0
7 AM Thu 60 60 NW 3 4275 4500 0 Blue 0
8 AM Thu 68 68 NW 3 4275 4500 0 Blue 0
9 AM Thu 74 76 W 3 4651 4500 0 Blue 0
10 AM Thu 80 84 S 3 6794 5489 989 Blue 6
11 AM Thu 85 91 S 3 11339 9416 4916 Blue 13
12 Noon Thu 89 96 S 3 14004 12344 7844 Blue 18
1 PM Thu 91 98 SE 3 14901 13402 8902 Blue 20
2 PM Thu 93 100 SE 3 15761 14313 9813 Blue 22
3 PM Thu 94 100 S 5 15761 14313 9813 Blue 22
4 PM Thu 95 99 S 6 15336 13863 9363 Blue 21
5 PM Thu 94 96 S 7 14004 12344 7844 Blue 18
6 PM Thu 91 91 S 8 11339 9416 4916 Blue 13
7 PM Thu 87 87 S 8 8882 6740 2240 Blue 9
8 PM Thu 83 83 S 8 6013 5190 690 Blue 5
9 PM Thu 80 80 SW 8 5198 4742 242 Blue 2
10 PM Thu 77 77 W 7 4743 4500 0 Blue 0
11 PM Thu 74 74 NW 6 4467 4500 0 Blue 0
12 Midnight Fri 70 70 NW 6 4275 4500 0 Blue 0
1 AM Fri 66 66 NW 5 4275 4500 0 Blue 0
2 AM Fri 63 63 W 5 4275 4500 0 Blue 0
3 AM Fri 59 59 W 3 4275 4500 0 Blue 0
4 AM Fri 57 57 W 3 4275 4500 0 Blue 0
5 AM Fri 57 57 SW 2 4275 4500 0 Blue 0
6 AM Fri 59 59 SW 2 4275 4500 0 Blue 0
7 AM Fri 63 63 SW 2 4275 4500 0 Blue 0
8 AM Fri 68 68 S 2 4275 4500 0 Blue 0
9 AM Fri 74 76 S 3 4651 4500 0 Blue 0
10 AM Fri 80 84 S 5 6794 5489 989 Blue 6
11 AM Fri 86 91 SE 6 11339 9416 4916 Blue 13
12 Noon Fri 90 96 SE 7 14004 12344 7844 Blue 18
1 PM Fri 93 100 SE 9 15761 14313 9813 Blue 22
2 PM Fri 95 101 SE 10 16178 14753 10253 Blue 23
3 PM Fri 96 101 SE 10 16178 14753 10253 Blue 23
4 PM Fri 96 99 S 10 15336 13863 9363 Blue 21
5 PM Fri 95 97 S 10 14458 12882 8382 Blue 19
6 PM Fri 92 92 S 10 11922 10015 5515 Blue 14
7 PM Fri 88 88 S 10 9513 7460 2960 Blue 10
8 PM Fri 85 85 S 10 7527 5706 1206 Blue 7
9 PM Fri 82 82 S 9 5714 4953 453 Blue 4
10 PM Fri 79 79 W 7 4955 4650 150 Blue 1
11 PM Fri 76 76 W 6 4651 4500 0 Blue 0
12 Midnight Sat 72 72 W 5 4284 4500 0 Blue 0
1 AM Sat 68 68 W 3 4275 4500 0 Blue 0
2 AM Sat 65 65 W 2 4275 4500 0 Blue 0
3 AM Sat 61 61 SW 2 4275 4500 0 Blue 0
4 AM Sat 59 59 SW 2 4275 4500 0 Blue 0
5 AM Sat 59 59 SW 2 4275 4500 0 Blue 0
6 AM Sat 61 61 SW 2 4275 4500 0 Blue 0
7 AM Sat 65 65 SW 2 4275 4500 0 Blue 0
8 AM Sat 70 70 S 2 4275 4500 0 Blue 0
9 AM Sat 76 77 S 2 4743 4500 0 Blue 0
10 AM Sat 81 83 S 3 6013 5190 690 Blue 5
11 AM Sat 86 89 SE 5 10120 8142 3642 Blue 11
12 Noon Sat 90 95 SE 6 13539 11787 7287 Blue 17
1 PM Sat 93 99 SE 7 15336 13863 9363 Blue 21
2 PM Sat 95 101 SE 8 16178 14753 10253 Blue 23
3 PM Sat 96 101 SE 9 16178 14753 10253 Blue 23
4 PM Sat 97 100 S 10 15761 14313 9813 Blue 22
5 PM Sat 96 98 S 10 14901 13402 8902 Blue 20
6 PM Sat 94 94 S 9 13028 11210 6710 Blue 16
7 PM Sat 90 90 S 8 10731 8793 4293 Blue 12
8 PM Sat 86 86 S 7 8221 5975 1475 Blue 8
9 PM Sat 82 82 SW 6 5714 4953 453 Blue 4
10 PM Sat 79 79 W 6 4955 4650 150 Blue 1
11 PM Sat 76 76 W 5 4651 4500 0 Blue 0
12 Midnight Sun 72 72 W 3 4284 4500 0 Blue 0
1 AM Sun 69 69 W 3 4275 4500 0 Blue 0
2 AM Sun 66 66 W 2 4275 4500 0 Blue 0
3 AM Sun 62 62 W 2 4275 4500 0 Blue 0
4 AM Sun 60 60 W 2 4275 4500 0 Blue 0
5 AM Sun 60 60 W 2 4275 4500 0 Blue 0
6 AM Sun 62 62 W 2 4275 4500 0 Blue 0
7 AM Sun 66 66 W 2 4275 4500 0 Blue 0
8 AM Sun 71 71 W 2 4275 4500 0 Blue 0
9 AM Sun 77 79 W 2 4955 4650 150 Blue 1
10 AM Sun 82 86 S 3 8221 5975 1475 Blue 8
11 AM Sun 87 93 S 3 12485 10609 6109 Blue 15
12 Noon Sun 91 98 S 5 14901 13402 8902 Blue 20
1 PM Sun 94 101 S 5 16178 14753 10253 Blue 23
2 PM Sun 96 103 SW 6 16988 15605 11105 Blue 25
3 PM Sun 97 102 SW 7 16587 15183 10683 Blue 24
4 PM Sun 98 102 S 8 16587 15183 10683 Blue 24
5 PM Sun 97 99 S 8 15336 13863 9363 Blue 21
6 PM Sun 94 94 S 8 13028 11210 6710 Blue 16
7 PM Sun 91 91 S 7 11339 9416 4916 Blue 13
8 PM Sun 87 87 SW 6 8882 6740 2240 Blue 9
9 PM Sun 83 83 SW 6 6013 5190 690 Blue 5
10 PM Sun 80 80 W 6 5198 4742 242 Blue 2
11 PM Sun 77 77 NW 6 4743 4500 0 Blue 0
12 Midnight Mon 74 74 W 5 4467 4500 0 Blue 0
1 AM Mon 71 71 W 5 4275 4500 0 Blue 0
2 AM Mon 67 67 W 3 4275 4500 0 Blue 0
3 AM Mon 63 63 W 3 4275 4500 0 Blue 0
4 AM Mon 61 61 W 2 4275 4500 0 Blue 0
5 AM Mon 60 60 W 2 4275 4500 0 Blue 0
6 AM Mon 62 62 W 2 4275 4500 0 Blue 0
7 AM Mon 66 66 NW 2 4275 4500 0 Blue 0
8 AM Mon 72 72 NW 2 4284 4500 0 Blue 0
9 AM Mon 77 77 W 2 4743 4500 0 Blue 0
10 AM Mon 83 84 S 3 6794 5489 989 Blue 6
11 AM Mon 88 90 S 3 10731 8793 4293 Blue 12
12 Noon Mon 91 93 S 5 12485 10609 6109 Blue 15
1 PM Mon 94 96 S 5 14004 12344 7844 Blue 18
2 PM Mon 96 98 S 6 14901 13402 8902 Blue 20
3 PM Mon 97 98 S 7 14901 13402 8902 Blue 20
4 PM Mon 98 99 S 7 15336 13863 9363 Blue 21
5 PM Mon 97 97 S 7 14458 12882 8382 Blue 19
6 PM Mon 94 94 S 6 13028 11210 6710 Blue 16
7 PM Mon 90 90 S 6 10731 8793 4293 Blue 12
8 PM Mon 87 87 S 5 8882 6740 2240 Blue 9
9 PM Mon 84 84 S 5 6794 5489 989 Blue 6
10 PM Mon 81 81 W 6 5496 4833 333 Blue 3
11 PM Mon 79 79 W 6 4955 4650 150 Blue 1
12 Midnight Tue 75 75 W 6 4559 4500 0 Blue 0
1 AM Tue 71 71 W 5 4275 4500 0 Blue 0
2 AM Tue 67 67 W 5 4275 4500 0 Blue 0
3 AM Tue 63 63 W 5 4275 4500 0 Blue 0
4 AM Tue 61 61 W 5 4275 4500 0 Blue 0

DISCLAIMER: These estimates are intended to assist in daily site selection only.  No warranty is made concerning the accuracy of these estimates.  These estimates cannot be used to determine if conditions are safe for flying.  Conditions should be evaluated at the launch site by experienced pilots before launching.

Sounding: This is the site at which the weather balloon was released.  If the flying site predicted is far from the sounding site, the estimate is not valid.  Also, the sounding is done at 12Z (4AM PST).  If a front comes through, the sounding is no longer valid. The sounding becomes less valid later in the day.

Thermal Ceiling: the lower of the height at which the thermal stops rising and the cloud level.  We can't fly into the clouds, so it doesn't matter how much higher the thermal goes.  Remember that we can't get to the top of the thermal because of our sink rate.  Our upper limit will be lower than the reported ceiling.

Soaring Ceiling: We will stop going up when the thermal is rising just fast enough to offset our sink.  It is estimated that this happens when the temperature difference between the thermal and the surrounding air is about 2 degrees F. This number is an estimate of the maximum altitude we might reach if we start at launch height, and should be more reflective of our chances of soaring than the thermal top. Please let me know how this compares with actually flying, and I will adjust it as necessary.

Above Launch: The difference between how high we might get and how high we start. This estimate does not account for ridge lift.

High Temp: This estimate is taken from the National Weather Service website.  Puddle temperatures can exceed this temperature. 

Puddle Temp: This estimate is based on the High Temp and the National Weather Service estimate of cloudiness, and the angle of the sun.  When the sun is directly overhead on a sunny day, the puddle temp is esimated to be 25 degrees warmer than the high ambient temperature. This estimate now includes a rigorous calculation of the Sun Angle, and accounts for the seasonal differences in zenith and daylight hours.

Wind: This estimate is taken from the National Weather Service website.

Thermal Type: Blue (no cloud formation) or White (Cloud formation)

Thermal Index: This is the maximum difference in temperature between the rising packet of air (the thermal) and the surrounding air.  The difference in temperature is responsible for the buoyancy of the thermal, and larger temperature differences mean faster rising thermals.  A value of about 10 F or greater often means that the conditions are soarable.  Values above 20 could indicate rowdy thermals.

Validity of estimate: Many factors (including strong wind, fronts, cloud shadows, incorrectly predicted temperatures, etc) can affect the validity of the estimates. 

Author: Tad Hurst

Supported By: Alan Crouse ac_soaring@yahoo.com