Detailed Predictions for: Chalk Bluffs
Launch Lat, Long, Altitude (f): 37.416328, -118.442829, 4500
LZ Altitude (f): 4220
Sounding

Station:

 KVBG

Date/Time UTC:

 250417/1200

Temp/Wind data from:

NOAA Digital Forecast

Site Forecasts
Time
(Local)		 High
Temp
Puddle
Temp
Wind
 (mph)		 Wind
 Gust		 Thermal
Ceiling
(ft)		 Soaring
Ceiling
(ft)		 Above
Launch
(ft)		 Thermal
Type		 Thermal
Index
(F)
12 Midnight Thu 54 54 NW 9 13 8893 8099 3599 Blue 13
1 AM Thu 53 53 NW 8 13 8863 7506 3006 Blue 12
2 AM Thu 51 51 NW 8 12 8172 6502 2002 Blue 10
3 AM Thu 51 51 NW 8 12 8172 6502 2002 Blue 10
4 AM Thu 48 48 NW 6 11 6513 6023 1523 Blue 7
5 AM Thu 48 48 NW 6 11 6513 6023 1523 Blue 7
6 AM Thu 47 47 NW 6 11 6353 5864 1364 Blue 6
7 AM Thu 46 46 NNW 8 11 6193 5704 1204 Blue 5
8 AM Thu 51 51 N 8 12 8172 6502 2002 Blue 10
9 AM Thu 55 57 N 9 13 8987 8889 4389 Blue 16
10 AM Thu 62 66 N 10 16 10547 9561 5061 Blue 25
11 AM Thu 65 70 N 10 18 12545 10799 6299 White 29
12 Noon Thu 67 73 N 13 23 13166 13166 8666 White 32
1 PM Thu 69 74 N 17 26 13373 13373 8873 White 33
2 PM Thu 69 73 N 19 28 13166 13166 8666 White 32
3 PM Thu 68 72 N 21 31 12959 12959 8459 White 31
4 PM Thu 68 70 N 23 32 12545 10799 6299 White 29
5 PM Thu 68 69 N 23 32 12337 10481 5981 White 28
6 PM Thu 64 64 NNW 21 31 9899 9279 4779 Blue 23
7 PM Thu 61 61 NNW 20 28 9291 9051 4551 Blue 20
8 PM Thu 57 57 NNW 18 25 8987 8889 4389 Blue 16
9 PM Thu 54 54 NNW 17 27 8893 8099 3599 Blue 13
10 PM Thu 51 51 NNW 13 23 8172 6502 2002 Blue 10
11 PM Thu 48 48 NW 12 19 6513 6023 1523 Blue 7
12 Midnight Fri 46 46 NNW 11 19 6193 5704 1204 Blue 5
1 AM Fri 45 45 NNW 11 18 6032 5366 866 Blue 4
2 AM Fri 43 43 NNW 11 18 5711 4500 0 Blue 2
3 AM Fri 41 41 NNW 11 18 4890 4500 0 Blue 0
4 AM Fri 40 40 NNW 11 17 4442 4500 0 Blue 0
5 AM Fri 38 38 NNW 11 17 4306 4500 0 Blue 0
6 AM Fri 37 37 N 13 19 4306 4500 0 Blue 0
7 AM Fri 39 39 N 14 20 4306 4500 0 Blue 0
8 AM Fri 42 43 NNW 14 20 5711 4500 0 Blue 2
9 AM Fri 46 48 NNW 16 23 6513 6023 1523 Blue 7
10 AM Fri 50 54 N 17 25 8893 8099 3599 Blue 13
11 AM Fri 54 60 N 18 27 9215 8979 4479 Blue 19
12 Noon Fri 57 64 N 20 29 9899 9279 4779 Blue 23
1 PM Fri 60 67 N 23 32 10868 9846 5346 Blue 26
2 PM Fri 62 68 N 24 33 12129 10161 5661 White 27
3 PM Fri 63 68 N 25 34 12129 10161 5661 White 27
4 PM Fri 63 66 N 25 34 10547 9561 5061 Blue 25
5 PM Fri 62 63 N 25 34 9611 9203 4703 Blue 22
6 PM Fri 59 59 N 24 33 9139 8949 4449 Blue 18
7 PM Fri 56 56 N 20 31 8953 8858 4358 Blue 15
8 PM Fri 52 52 N 18 28 8703 6888 2388 White 11
9 PM Fri 49 49 NNW 14 25 6941 6183 1683 Blue 8
10 PM Fri 47 47 NNW 12 20 6353 5864 1364 Blue 6
11 PM Fri 45 45 NW 10 17 6032 5366 866 Blue 4
12 Midnight Sat 43 43 NW 9 14 5711 4500 0 Blue 2
1 AM Sat 40 40 NW 8 12 4442 4500 0 Blue 0
2 AM Sat 38 38 NW 8 11 4306 4500 0 Blue 0
3 AM Sat 36 36 NW 6 10 4306 4500 0 Blue 0
4 AM Sat 34 34 NW 6 9 4306 4500 0 Blue 0
5 AM Sat 34 34 NW 5 8 4306 4500 0 Blue 0
6 AM Sat 35 35 NW 4 6 4306 4500 0 Blue 0
7 AM Sat 37 37 NW 4 6 4306 4500 0 Blue 0
8 AM Sat 41 42 NW 3 6 5382 4500 0 Blue 1
9 AM Sat 47 49 NNW 2 6 6941 6183 1683 Blue 8
10 AM Sat 53 57 N 2 6 8987 8889 4389 Blue 16
11 AM Sat 59 65 N 2 6 10224 9355 4855 Blue 24
12 Noon Sat 63 70 NNE 2 8 12545 10799 6299 White 29
1 PM Sat 67 74 NNE 3 10 13373 13373 8873 White 33
2 PM Sat 69 75 NNE 4 11 13579 13579 9079 White 34
3 PM Sat 71 76 N 5 12 13785 13785 9285 White 35
4 PM Sat 73 76 WNW 6 14 13785 13785 9285 White 35
5 PM Sat 73 74 W 6 14 13373 13373 8873 White 33
6 PM Sat 71 71 WSW 6 13 12752 12752 8252 White 30
7 PM Sat 69 69 S 5 12 12337 10481 5981 White 28
8 PM Sat 65 65 SSE 5 11 10224 9355 4855 Blue 24
9 PM Sat 61 61 S 5 10 9291 9051 4551 Blue 20
10 PM Sat 58 58 SW 4 9 9063 8919 4419 Blue 17
11 PM Sat 54 54 WSW 4 8 8893 8099 3599 Blue 13
12 Midnight Sun 51 51 W 4 6 8172 6502 2002 Blue 10
1 AM Sun 48 48 W 4 6 6513 6023 1523 Blue 7
2 AM Sun 46 46 W 4 6 6193 5704 1204 Blue 5
3 AM Sun 44 44 W 4 6 5871 4882 382 Blue 3
4 AM Sun 42 42 W 4 6 5382 4500 0 Blue 1
5 AM Sun 42 42 W 4 6 5382 4500 0 Blue 1
6 AM Sun 43 43 W 4 6 5711 4500 0 Blue 2
7 AM Sun 45 45 W 3 6 6032 5366 866 Blue 4
8 AM Sun 49 50 W 3 6 7569 6343 1843 Blue 9
9 AM Sun 54 56 WSW 3 8 8953 8858 4358 Blue 15
10 AM Sun 61 65 S 3 9 10224 9355 4855 Blue 24
11 AM Sun 66 72 SE 4 10 12959 12959 8459 White 31
12 Noon Sun 70 77 SE 5 11 13990 13990 9490 White 36
1 PM Sun 72 79 SSE 6 13 14400 14400 9900 White 38
2 PM Sun 74 80 SSE 8 14 14604 14604 10104 White 39
3 PM Sun 75 79 SSE 9 16 14400 14400 9900 White 38
4 PM Sun 76 78 S 10 18 14195 14195 9695 White 37
5 PM Sun 75 76 S 11 18 13785 13785 9285 White 35
6 PM Sun 72 72 SSW 11 17 12959 12959 8459 White 31
7 PM Sun 69 69 WSW 10 16 12337 10481 5981 White 28
8 PM Sun 65 65 W 9 14 10224 9355 4855 Blue 24
9 PM Sun 62 62 W 9 13 9368 9127 4627 Blue 21
10 PM Sun 59 59 W 8 13 9139 8949 4449 Blue 18
11 PM Sun 56 56 W 8 12 8953 8858 4358 Blue 15
12 Midnight Mon 53 53 W 8 11 8863 7506 3006 Blue 12
1 AM Mon 50 50 WNW 6 11 7569 6343 1843 Blue 9
2 AM Mon 48 48 WNW 6 10 6513 6023 1523 Blue 7
3 AM Mon 45 45 WNW 6 9 6032 5366 866 Blue 4
4 AM Mon 44 44 WNW 5 9 5871 4882 382 Blue 3
5 AM Mon 43 43 WNW 5 8 5711 4500 0 Blue 2
6 AM Mon 44 44 WNW 4 6 5871 4882 382 Blue 3
7 AM Mon 46 46 WNW 4 6 6193 5704 1204 Blue 5
8 AM Mon 50 51 WNW 3 6 8172 6502 2002 Blue 10
9 AM Mon 55 57 W 3 6 8987 8889 4389 Blue 16
10 AM Mon 62 66 S 3 8 10547 9561 5061 Blue 25
11 AM Mon 67 72 SE 3 9 12959 12959 8459 White 31
12 Noon Mon 71 77 SSE 4 11 13990 13990 9490 White 36
1 PM Mon 73 79 SSE 5 12 14400 14400 9900 White 38
2 PM Mon 75 81 S 6 14 14804 14804 10304 White 40
3 PM Mon 76 80 S 8 16 14604 14604 10104 White 39
4 PM Mon 76 79 SW 9 17 14400 14400 9900 White 38
5 PM Mon 75 76 WSW 10 17 13785 13785 9285 White 35
6 PM Mon 72 72 W 10 17 12959 12959 8459 White 31
7 PM Mon 68 68 WNW 9 16 12129 10161 5661 White 27
8 PM Mon 64 64 WNW 8 14 9899 9279 4779 Blue 23
9 PM Mon 61 61 WNW 8 13 9291 9051 4551 Blue 20
10 PM Mon 59 59 WNW 8 13 9139 8949 4449 Blue 18
11 PM Mon 57 57 WNW 8 12 8987 8889 4389 Blue 16
12 Midnight Tue 54 54 WNW 8 12 8893 8099 3599 Blue 13
1 AM Tue 51 51 WNW 6 11 8172 6502 2002 Blue 10
2 AM Tue 49 49 WNW 6 11 6941 6183 1683 Blue 8
3 AM Tue 46 46 WNW 6 10 6193 5704 1204 Blue 5
4 AM Tue 45 45 WNW 5 10 6032 5366 866 Blue 4
5 AM Tue 44 44 WNW 5 9 5871 4882 382 Blue 3
6 AM Tue 44 44 WNW 5 8 5871 4882 382 Blue 3
7 AM Tue 46 46 WNW 4 8 6193 5704 1204 Blue 5
8 AM Tue 50 51 WNW 4 8 8172 6502 2002 Blue 10
9 AM Tue 56 58 WSW 4 8 9063 8919 4419 Blue 17
10 AM Tue 62 66 S 4 9 10547 9561 5061 Blue 25
11 AM Tue 68 73 SE 4 10 13166 13166 8666 White 32
12 Noon Tue 72 78 SE 5 12 14195 14195 9695 White 37
1 PM Tue 75 81 SSE 6 13 14804 14804 10304 White 40
2 PM Tue 76 82 SSE 8 16 15003 15003 10503 White 41
3 PM Tue 77 81 S 9 17 14804 14804 10304 White 40
4 PM Tue 77 79 SSW 10 19 14400 14400 9900 White 38
5 PM Tue 76 77 SW 11 19 13990 13990 9490 White 36
6 PM Tue 73 73 SW 11 18 13166 13166 8666 White 32
7 PM Tue 70 70 WSW 11 17 12545 10799 6299 White 29
8 PM Tue 66 66 WSW 10 16 10547 9561 5061 Blue 25
9 PM Tue 63 63 W 10 14 9611 9203 4703 Blue 22
10 PM Tue 60 60 W 9 14 9215 8979 4479 Blue 19

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 or WeatherAPI.com website.  Puddle temperatures can exceed this temperature. 

Puddle Temp: This estimate is based on the High Temp and the National Weather Service or WeatherAPI.com 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 or WeatherAPI.com website.

Wind Gust: This estimate is taken from the National Weather Service or WeatherAPI.com 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 [email protected]