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

Station:

KVBG

Date/Time:

25 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 Sun 62 62 NW 6 2592 4500 0 Blue 0
6 AM Sun 61 61 NW 6 2592 4500 0 Blue 0
7 AM Sun 60 60 NW 5 2592 4500 0 Blue 0
8 AM Sun 69 69 N 2 3284 4500 0 Blue 0
9 AM Sun 76 78 E 2 5149 4534 34 Blue 1
10 AM Sun 82 86 E 2 11333 7752 3252 Blue 9
11 AM Sun 85 90 SE 2 11520 11369 6869 Blue 13
12 Noon Sun 89 96 S 3 13303 12319 7819 Blue 19
1 PM Sun 92 99 S 3 13895 13247 8747 Blue 22
2 PM Sun 95 102 S 6 15154 13835 9335 Blue 25
3 PM Sun 96 102 S 6 15154 13835 9335 Blue 25
4 PM Sun 97 101 S 6 14367 13639 9139 Blue 24
5 PM Sun 96 98 S 6 13698 13050 8550 Blue 21
6 PM Sun 95 95 SE 7 13105 11623 7123 Blue 18
7 PM Sun 91 91 SE 6 11566 11417 6917 Blue 14
8 PM Sun 86 86 NE 1 11333 7752 3252 Blue 9
9 PM Sun 83 83 NW 2 7809 6656 2156 Blue 6
10 PM Sun 81 81 NW 3 6773 5145 645 Blue 4
11 PM Sun 79 79 W 2 6554 4740 240 Blue 2
12 Midnight Mon 75 75 NW 3 4535 4500 0 Blue 0
1 AM Mon 73 73 NW 5 4120 4500 0 Blue 0
2 AM Mon 68 68 W 6 3074 4500 0 Blue 0
3 AM Mon 65 65 NW 5 2592 4500 0 Blue 0
4 AM Mon 64 64 NW 5 2592 4500 0 Blue 0
5 AM Mon 63 63 NW 5 2592 4500 0 Blue 0
6 AM Mon 61 61 NW 5 2592 4500 0 Blue 0
7 AM Mon 64 64 W 5 2592 4500 0 Blue 0
8 AM Mon 72 72 W 1 3912 4500 0 Blue 0
9 AM Mon 79 81 N 1 6773 5145 645 Blue 4
10 AM Mon 85 89 N 1 11474 11322 6822 Blue 12
11 AM Mon 89 95 S 0 13105 11623 7123 Blue 18
12 Noon Mon 93 100 S 2 14091 13443 8943 Blue 23
1 PM Mon 95 101 SE 6 14367 13639 9139 Blue 24
2 PM Mon 97 102 SE 9 15154 13835 9335 Blue 25
3 PM Mon 98 102 SE 10 15154 13835 9335 Blue 25
4 PM Mon 98 100 SE 10 14091 13443 8943 Blue 23
5 PM Mon 97 98 SE 10 13698 13050 8550 Blue 21
6 PM Mon 94 94 SE 10 12907 11556 7056 Blue 17
7 PM Mon 90 90 S 9 11520 11369 6869 Blue 13
8 PM Mon 86 86 S 9 11333 7752 3252 Blue 9
9 PM Mon 83 83 SW 9 7809 6656 2156 Blue 6
10 PM Mon 80 80 W 8 6663 4945 445 Blue 3
11 PM Mon 78 78 NW 8 5149 4534 34 Blue 1
12 Midnight Tue 75 75 NW 7 4535 4500 0 Blue 0
1 AM Tue 71 71 NW 7 3703 4500 0 Blue 0
2 AM Tue 67 67 NW 6 2863 4500 0 Blue 0
3 AM Tue 64 64 NW 6 2592 4500 0 Blue 0
4 AM Tue 61 61 W 5 2592 4500 0 Blue 0
5 AM Tue 60 60 W 5 2592 4500 0 Blue 0
6 AM Tue 62 62 W 5 2592 4500 0 Blue 0
7 AM Tue 65 65 NW 5 2592 4500 0 Blue 0
8 AM Tue 71 71 NW 5 3703 4500 0 Blue 0
9 AM Tue 77 79 W 5 6554 4740 240 Blue 2
10 AM Tue 84 88 S 5 11427 11275 6775 Blue 11
11 AM Tue 90 95 SE 6 13105 11623 7123 Blue 18
12 Noon Tue 93 100 SE 8 14091 13443 8943 Blue 23
1 PM Tue 95 102 SE 10 15154 13835 9335 Blue 25
2 PM Tue 97 103 SE 13 15884 14030 9530 Blue 26
3 PM Tue 98 103 SE 14 15884 14030 9530 Blue 26
4 PM Tue 99 103 S 14 15884 14030 9530 Blue 26
5 PM Tue 98 100 S 13 14091 13443 8943 Blue 23
6 PM Tue 95 95 S 12 13105 11623 7123 Blue 18
7 PM Tue 90 90 S 10 11520 11369 6869 Blue 13
8 PM Tue 86 86 S 9 11333 7752 3252 Blue 9
9 PM Tue 83 83 S 9 7809 6656 2156 Blue 6
10 PM Tue 81 81 SW 8 6773 5145 645 Blue 4
11 PM Tue 78 78 SW 8 5149 4534 34 Blue 1
12 Midnight Wed 74 74 SW 7 4328 4500 0 Blue 0
1 AM Wed 70 70 W 6 3494 4500 0 Blue 0
2 AM Wed 66 66 W 5 2652 4500 0 Blue 0
3 AM Wed 63 63 W 5 2592 4500 0 Blue 0
4 AM Wed 61 61 W 5 2592 4500 0 Blue 0
5 AM Wed 61 61 W 5 2592 4500 0 Blue 0
6 AM Wed 63 63 SW 5 2592 4500 0 Blue 0
7 AM Wed 67 67 S 5 2863 4500 0 Blue 0
8 AM Wed 72 72 S 5 3912 4500 0 Blue 0
9 AM Wed 78 80 S 5 6663 4945 445 Blue 3
10 AM Wed 84 88 S 6 11427 11275 6775 Blue 11
11 AM Wed 89 94 SE 7 12907 11556 7056 Blue 17
12 Noon Wed 93 100 S 9 14091 13443 8943 Blue 23
1 PM Wed 95 102 S 12 15154 13835 9335 Blue 25
2 PM Wed 96 103 S 13 15884 14030 9530 Blue 26
3 PM Wed 97 103 S 14 15884 14030 9530 Blue 26
4 PM Wed 97 100 S 13 14091 13443 8943 Blue 23
5 PM Wed 95 97 S 13 13501 12852 8352 Blue 20
6 PM Wed 92 92 S 12 11663 11464 6964 Blue 15
7 PM Wed 88 88 SW 12 11427 11275 6775 Blue 11
8 PM Wed 84 84 SW 10 10335 6765 2265 Blue 7
9 PM Wed 81 81 SW 9 6773 5145 645 Blue 4
10 PM Wed 79 79 W 9 6554 4740 240 Blue 2
11 PM Wed 76 76 W 8 4742 4500 0 Blue 0
12 Midnight Thu 72 72 W 7 3912 4500 0 Blue 0
1 AM Thu 69 69 W 7 3284 4500 0 Blue 0
2 AM Thu 65 65 W 6 2592 4500 0 Blue 0
3 AM Thu 62 62 W 6 2592 4500 0 Blue 0
4 AM Thu 60 60 W 6 2592 4500 0 Blue 0
5 AM Thu 59 59 W 6 2592 4500 0 Blue 0
6 AM Thu 60 60 W 6 2592 4500 0 Blue 0
7 AM Thu 64 64 SW 6 2592 4500 0 Blue 0
8 AM Thu 69 69 SW 6 3284 4500 0 Blue 0
9 AM Thu 75 77 S 5 4948 4500 0 Blue 0
10 AM Thu 81 85 SE 5 11286 7205 2705 Blue 8
11 AM Thu 86 92 SE 5 11663 11464 6964 Blue 15
12 Noon Thu 90 97 SE 6 13501 12852 8352 Blue 20
1 PM Thu 93 100 S 8 14091 13443 8943 Blue 23
2 PM Thu 95 102 S 10 15154 13835 9335 Blue 25
3 PM Thu 96 102 S 12 15154 13835 9335 Blue 25
4 PM Thu 96 100 SW 12 14091 13443 8943 Blue 23
5 PM Thu 95 97 SW 12 13501 12852 8352 Blue 20
6 PM Thu 92 92 SW 12 11663 11464 6964 Blue 15
7 PM Thu 88 88 SW 10 11427 11275 6775 Blue 11
8 PM Thu 84 84 SW 9 10335 6765 2265 Blue 7
9 PM Thu 81 81 SW 8 6773 5145 645 Blue 4
10 PM Thu 78 78 W 8 5149 4534 34 Blue 1
11 PM Thu 76 76 W 7 4742 4500 0 Blue 0
12 Midnight Fri 72 72 W 7 3912 4500 0 Blue 0
1 AM Fri 69 69 W 6 3284 4500 0 Blue 0
2 AM Fri 65 65 W 6 2592 4500 0 Blue 0
3 AM Fri 62 62 W 6 2592 4500 0 Blue 0
4 AM Fri 60 60 W 5 2592 4500 0 Blue 0
5 AM Fri 59 59 W 5 2592 4500 0 Blue 0
6 AM Fri 61 61 W 5 2592 4500 0 Blue 0
7 AM Fri 64 64 W 5 2592 4500 0 Blue 0
8 AM Fri 68 68 W 5 3074 4500 0 Blue 0
9 AM Fri 74 76 W 3 4742 4500 0 Blue 0
10 AM Fri 80 84 S 3 10335 6765 2265 Blue 7
11 AM Fri 85 90 S 3 11520 11369 6869 Blue 13
12 Noon Fri 89 96 S 6 13303 12319 7819 Blue 19
1 PM Fri 92 99 S 8 13895 13247 8747 Blue 22
2 PM Fri 95 102 S 10 15154 13835 9335 Blue 25
3 PM Fri 96 102 S 12 15154 13835 9335 Blue 25
4 PM Fri 96 100 S 10 14091 13443 8943 Blue 23
5 PM Fri 95 97 S 10 13501 12852 8352 Blue 20
6 PM Fri 92 92 S 10 11663 11464 6964 Blue 15
7 PM Fri 88 88 S 9 11427 11275 6775 Blue 11
8 PM Fri 84 84 S 9 10335 6765 2265 Blue 7
9 PM Fri 81 81 SW 8 6773 5145 645 Blue 4
10 PM Fri 79 79 SW 8 6554 4740 240 Blue 2
11 PM Fri 76 76 W 7 4742 4500 0 Blue 0
12 Midnight Sat 73 73 W 7 4120 4500 0 Blue 0
1 AM Sat 69 69 W 6 3284 4500 0 Blue 0
2 AM Sat 65 65 W 6 2592 4500 0 Blue 0
3 AM Sat 61 61 W 6 2592 4500 0 Blue 0
4 AM Sat 59 59 W 5 2592 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