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

Station:

KVBG

Date/Time:

27 MAY 2018

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 47 47 NW 10 4203 4500 0 Blue 0
6 AM Sun 49 49 NW 12 4203 4500 0 Blue 0
7 AM Sun 54 54 N 13 4772 4500 0 Blue 2
8 AM Sun 59 60 N 13 6500 6073 1573 Blue 8
9 AM Sun 64 67 N 13 8169 7404 2904 Blue 15
10 AM Sun 69 73 N 12 9696 8901 4401 Blue 21
11 AM Sun 73 78 N 12 11197 10263 5763 Blue 26
12 Noon Sun 76 82 N 10 12011 11341 6841 Blue 30
1 PM Sun 78 84 N 10 12922 11709 7209 Blue 32
2 PM Sun 80 86 N 10 13862 12244 7744 White 34
3 PM Sun 80 84 N 12 12922 11709 7209 Blue 32
4 PM Sun 79 82 N 14 12011 11341 6841 Blue 30
5 PM Sun 77 78 N 15 11197 10263 5763 Blue 26
6 PM Sun 75 75 N 14 10444 9403 4903 Blue 23
7 PM Sun 72 72 N 13 9445 8647 4147 Blue 20
8 PM Sun 69 69 N 12 8683 7880 3380 Blue 17
9 PM Sun 67 67 N 10 8169 7404 2904 Blue 15
10 PM Sun 64 64 NW 10 7425 6649 2149 Blue 12
11 PM Sun 61 61 NW 9 6660 6196 1696 Blue 9
12 Midnight Mon 59 59 NW 9 6339 5511 1011 Blue 7
1 AM Mon 56 56 NW 8 5565 4677 177 Blue 4
2 AM Mon 53 53 NW 8 4678 4500 0 Blue 1
3 AM Mon 50 50 NW 8 4220 4500 0 Blue 0
4 AM Mon 48 48 NW 8 4203 4500 0 Blue 0
5 AM Mon 49 49 NW 8 4203 4500 0 Blue 0
6 AM Mon 53 53 NW 8 4678 4500 0 Blue 1
7 AM Mon 59 59 NW 8 6339 5511 1011 Blue 7
8 AM Mon 65 66 NW 8 7910 7190 2690 Blue 14
9 AM Mon 71 74 NW 8 9947 9153 4653 Blue 22
10 AM Mon 75 80 N 8 11569 10970 6470 Blue 28
11 AM Mon 79 85 N 8 13441 11947 7447 Blue 33
12 Noon Mon 82 89 N 8 14485 13787 9287 White 37
1 PM Mon 85 92 N 9 15094 15094 10594 White 40
2 PM Mon 87 94 N 9 15497 15497 10997 White 42
3 PM Mon 88 93 N 10 15295 15295 10795 White 41
4 PM Mon 88 92 N 12 15094 15094 10594 White 40
5 PM Mon 87 89 N 12 14485 13787 9287 White 37
6 PM Mon 84 85 N 10 13441 11947 7447 Blue 33
7 PM Mon 80 80 N 9 11569 10970 6470 Blue 28
8 PM Mon 76 76 N 8 10824 9653 5153 Blue 24
9 PM Mon 73 73 NW 7 9696 8901 4401 Blue 21
10 PM Mon 70 70 NW 7 8938 8137 3637 Blue 18
11 PM Mon 67 67 W 7 8169 7404 2904 Blue 15
12 Midnight Tue 64 64 W 7 7425 6649 2149 Blue 12
1 AM Tue 61 61 W 7 6660 6196 1696 Blue 9
2 AM Tue 58 58 W 7 6203 4858 358 Blue 6
3 AM Tue 54 54 W 6 4772 4500 0 Blue 2
4 AM Tue 51 51 W 6 4404 4500 0 Blue 0
5 AM Tue 51 51 W 5 4404 4500 0 Blue 0
6 AM Tue 54 54 W 5 4772 4500 0 Blue 2
7 AM Tue 60 60 SW 3 6500 6073 1573 Blue 8
8 AM Tue 67 68 S 3 8426 7622 3122 Blue 16
9 AM Tue 74 77 S 3 11011 9902 5402 Blue 25
10 AM Tue 80 84 SE 3 12922 11709 7209 Blue 32
11 AM Tue 84 89 SE 3 14485 13787 9287 White 37
12 Noon Tue 87 92 SE 5 15094 15094 10594 White 40
1 PM Tue 88 93 S 5 15295 15295 10795 White 41
2 PM Tue 89 94 S 6 15497 15497 10997 White 42
3 PM Tue 90 94 S 7 15497 15497 10997 White 42
4 PM Tue 90 92 S 8 15094 15094 10594 White 40
5 PM Tue 89 90 SW 8 14689 14272 9772 White 38
6 PM Tue 86 86 SW 8 13862 12244 7744 White 34
7 PM Tue 82 82 SW 7 12011 11341 6841 Blue 30
8 PM Tue 78 78 SW 7 11197 10263 5763 Blue 26
9 PM Tue 74 74 SW 7 9947 9153 4653 Blue 22
10 PM Tue 70 70 W 6 8938 8137 3637 Blue 18
11 PM Tue 68 68 W 6 8426 7622 3122 Blue 16
12 Midnight Wed 65 65 W 6 7649 6826 2326 Blue 13
1 AM Wed 62 62 W 6 6856 6329 1829 Blue 10
2 AM Wed 60 60 W 6 6500 6073 1573 Blue 8
3 AM Wed 57 57 W 6 6079 4771 271 Blue 5
4 AM Wed 54 54 W 6 4772 4500 0 Blue 2
5 AM Wed 54 54 W 6 4772 4500 0 Blue 2
6 AM Wed 56 56 W 6 5565 4677 177 Blue 4
7 AM Wed 60 60 SW 6 6500 6073 1573 Blue 8
8 AM Wed 66 67 SW 5 8169 7404 2904 Blue 15
9 AM Wed 72 74 S 5 9947 9153 4653 Blue 22
10 AM Wed 77 81 S 5 11754 11156 6656 Blue 29
11 AM Wed 82 87 SE 6 14071 12774 8274 White 35
12 Noon Wed 86 91 SE 8 14891 14891 10391 White 39
1 PM Wed 88 93 S 10 15295 15295 10795 White 41
2 PM Wed 89 94 S 13 15497 15497 10997 White 42
3 PM Wed 89 93 SW 15 15295 15295 10795 White 41
4 PM Wed 88 90 SW 16 14689 14272 9772 White 38
5 PM Wed 86 87 SW 17 14071 12774 8274 White 35
6 PM Wed 83 83 SW 16 12386 11525 7025 Blue 31
7 PM Wed 80 80 SW 15 11569 10970 6470 Blue 28
8 PM Wed 76 76 SW 13 10824 9653 5153 Blue 24
9 PM Wed 72 72 SW 10 9445 8647 4147 Blue 20
10 PM Wed 68 68 SW 9 8426 7622 3122 Blue 16
11 PM Wed 64 64 SW 7 7425 6649 2149 Blue 12
12 Midnight Thu 60 60 SW 6 6500 6073 1573 Blue 8
1 AM Thu 56 56 SW 6 5565 4677 177 Blue 4
2 AM Thu 53 53 W 6 4678 4500 0 Blue 1
3 AM Thu 51 51 W 6 4404 4500 0 Blue 0
4 AM Thu 50 50 W 6 4220 4500 0 Blue 0
5 AM Thu 51 51 W 6 4404 4500 0 Blue 0
6 AM Thu 53 53 W 6 4678 4500 0 Blue 1
7 AM Thu 57 57 SW 5 6079 4771 271 Blue 5
8 AM Thu 62 63 S 5 7209 6489 1989 Blue 11
9 AM Thu 68 70 S 5 8938 8137 3637 Blue 18
10 AM Thu 73 77 SE 5 11011 9902 5402 Blue 25
11 AM Thu 77 83 SE 6 12386 11525 7025 Blue 31
12 Noon Thu 80 86 SE 8 13862 12244 7744 White 34
1 PM Thu 82 88 S 10 14278 13288 8788 White 36
2 PM Thu 83 89 S 13 14485 13787 9287 White 37
3 PM Thu 83 87 S 15 14071 12774 8274 White 35
4 PM Thu 82 85 SW 17 13441 11947 7447 Blue 33
5 PM Thu 80 81 SW 18 11754 11156 6656 Blue 29
6 PM Thu 77 77 SW 18 11011 9902 5402 Blue 25
7 PM Thu 74 74 W 17 9947 9153 4653 Blue 22
8 PM Thu 71 71 W 15 9192 8393 3893 Blue 19
9 PM Thu 67 67 W 14 8169 7404 2904 Blue 15
10 PM Thu 63 63 W 12 7209 6489 1989 Blue 11
11 PM Thu 59 59 W 10 6339 5511 1011 Blue 7
12 Midnight Fri 55 55 W 9 4859 4584 84 Blue 3
1 AM Fri 51 51 NW 9 4404 4500 0 Blue 0
2 AM Fri 48 48 NW 9 4203 4500 0 Blue 0
3 AM Fri 46 46 NW 9 4203 4500 0 Blue 0
4 AM Fri 45 45 NW 8 4203 4500 0 Blue 0
5 AM Fri 46 46 NW 8 4203 4500 0 Blue 0
6 AM Fri 49 49 NW 7 4203 4500 0 Blue 0
7 AM Fri 53 53 N 6 4678 4500 0 Blue 1
8 AM Fri 58 59 N 6 6339 5511 1011 Blue 7
9 AM Fri 64 67 N 5 8169 7404 2904 Blue 15
10 AM Fri 69 73 NE 3 9696 8901 4401 Blue 21
11 AM Fri 74 80 NE 3 11569 10970 6470 Blue 28
12 Noon Fri 78 84 E 3 12922 11709 7209 Blue 32
1 PM Fri 80 87 E 3 14071 12774 8274 White 35
2 PM Fri 82 88 SE 5 14278 13288 8788 White 36
3 PM Fri 83 88 S 5 14278 13288 8788 White 36
4 PM Fri 83 86 S 6 13862 12244 7744 White 34
5 PM Fri 82 84 SW 6 12922 11709 7209 Blue 32
6 PM Fri 80 81 SW 6 11754 11156 6656 Blue 29
7 PM Fri 77 77 SW 6 11011 9902 5402 Blue 25
8 PM Fri 74 74 W 6 9947 9153 4653 Blue 22
9 PM Fri 70 70 W 6 8938 8137 3637 Blue 18
10 PM Fri 66 66 W 6 7910 7190 2690 Blue 14
11 PM Fri 62 62 W 6 6856 6329 1829 Blue 10
12 Midnight Sat 58 58 W 6 6203 4858 358 Blue 6
1 AM Sat 54 54 W 6 4772 4500 0 Blue 2
2 AM Sat 51 51 W 6 4404 4500 0 Blue 0
3 AM Sat 50 50 W 5 4220 4500 0 Blue 0
4 AM Sat 49 49 W 5 4203 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