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

Station:

KVBG

Date/Time:

18 SEP 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 47 47 NW 3 3989 4500 0 Blue 0
6 AM Wed 45 45 NW 3 3989 4500 0 Blue 0
7 AM Wed 43 43 N 3 3989 4500 0 Blue 0
8 AM Wed 51 51 N 3 3989 4500 0 Blue 0
9 AM Wed 61 62 NE 3 4552 4500 0 Blue 0
10 AM Wed 67 70 SE 3 6310 5574 1074 Blue 6
11 AM Wed 71 76 S 5 8651 7211 2711 Blue 12
12 Noon Wed 75 81 S 6 11174 10905 6405 Blue 17
1 PM Wed 78 84 SW 7 11559 11150 6650 Blue 20
2 PM Wed 80 85 SW 8 11865 11256 6756 Blue 21
3 PM Wed 81 85 SW 10 11865 11256 6756 Blue 21
4 PM Wed 82 84 SW 13 11559 11150 6650 Blue 20
5 PM Wed 80 81 SW 14 11174 10905 6405 Blue 17
6 PM Wed 77 77 SW 14 10670 8118 3618 Blue 13
7 PM Wed 71 71 W 13 6622 5781 1281 Blue 7
8 PM Wed 67 67 W 12 5582 4952 452 Blue 3
9 PM Wed 65 65 W 12 5165 4551 51 Blue 1
10 PM Wed 61 61 NW 10 4350 4500 0 Blue 0
11 PM Wed 58 58 NW 10 3989 4500 0 Blue 0
12 Midnight Thu 55 55 NW 9 3989 4500 0 Blue 0
1 AM Thu 53 53 NW 9 3989 4500 0 Blue 0
2 AM Thu 50 50 NW 8 3989 4500 0 Blue 0
3 AM Thu 46 46 NW 8 3989 4500 0 Blue 0
4 AM Thu 45 45 NW 7 3989 4500 0 Blue 0
5 AM Thu 44 44 NW 7 3989 4500 0 Blue 0
6 AM Thu 42 42 NW 6 3989 4500 0 Blue 0
7 AM Thu 42 42 NW 5 3989 4500 0 Blue 0
8 AM Thu 49 49 NW 5 3989 4500 0 Blue 0
9 AM Thu 58 59 NW 5 3989 4500 0 Blue 0
10 AM Thu 62 64 N 6 4955 4500 0 Blue 0
11 AM Thu 66 69 N 6 5997 5367 867 Blue 5
12 Noon Thu 68 72 N 6 6931 5987 1487 Blue 8
1 PM Thu 70 75 NW 6 8400 6907 2407 Blue 11
2 PM Thu 71 76 NW 7 8651 7211 2711 Blue 12
3 PM Thu 72 76 NW 8 8651 7211 2711 Blue 12
4 PM Thu 72 74 N 10 8148 6600 2100 Blue 10
5 PM Thu 70 71 N 12 6622 5781 1281 Blue 7
6 PM Thu 67 67 N 12 5582 4952 452 Blue 3
7 PM Thu 62 62 N 12 4552 4500 0 Blue 0
8 PM Thu 58 58 NW 10 3989 4500 0 Blue 0
9 PM Thu 55 55 NW 9 3989 4500 0 Blue 0
10 PM Thu 53 53 NW 9 3989 4500 0 Blue 0
11 PM Thu 51 51 NW 8 3989 4500 0 Blue 0
12 Midnight Fri 49 49 NW 7 3989 4500 0 Blue 0
1 AM Fri 46 46 NW 7 3989 4500 0 Blue 0
2 AM Fri 43 43 NW 6 3989 4500 0 Blue 0
3 AM Fri 40 40 NW 5 3989 4500 0 Blue 0
4 AM Fri 38 38 NW 5 3989 4500 0 Blue 0
5 AM Fri 37 37 NW 3 3989 4500 0 Blue 0
6 AM Fri 38 38 NW 3 3989 4500 0 Blue 0
7 AM Fri 41 41 NW 3 3989 4500 0 Blue 0
8 AM Fri 45 45 NW 3 3989 4500 0 Blue 0
9 AM Fri 51 52 NW 3 3989 4500 0 Blue 0
10 AM Fri 57 60 N 3 4146 4500 0 Blue 0
11 AM Fri 62 66 NE 3 5374 4752 252 Blue 2
12 Noon Fri 66 72 E 5 6931 5987 1487 Blue 8
1 PM Fri 69 75 SE 5 8400 6907 2407 Blue 11
2 PM Fri 71 76 S 6 8651 7211 2711 Blue 12
3 PM Fri 73 77 SE 6 10670 8118 3618 Blue 13
4 PM Fri 75 78 E 6 10920 8368 3868 Blue 14
5 PM Fri 74 75 NE 6 8400 6907 2407 Blue 11
6 PM Fri 71 71 NE 6 6622 5781 1281 Blue 7
7 PM Fri 66 66 E 6 5374 4752 252 Blue 2
8 PM Fri 62 62 E 6 4552 4500 0 Blue 0
9 PM Fri 59 59 NE 6 3989 4500 0 Blue 0
10 PM Fri 58 58 N 5 3989 4500 0 Blue 0
11 PM Fri 56 56 NW 5 3989 4500 0 Blue 0
12 Midnight Sat 53 53 NW 5 3989 4500 0 Blue 0
1 AM Sat 50 50 NW 3 3989 4500 0 Blue 0
2 AM Sat 47 47 NW 3 3989 4500 0 Blue 0
3 AM Sat 44 44 NW 3 3989 4500 0 Blue 0
4 AM Sat 42 42 NW 2 3989 4500 0 Blue 0
5 AM Sat 41 41 NW 2 3989 4500 0 Blue 0
6 AM Sat 42 42 NW 2 3989 4500 0 Blue 0
7 AM Sat 45 45 NW 2 3989 4500 0 Blue 0
8 AM Sat 50 50 NW 2 3989 4500 0 Blue 0
9 AM Sat 55 56 N 2 3989 4500 0 Blue 0
10 AM Sat 61 64 E 2 4955 4500 0 Blue 0
11 AM Sat 66 70 SE 2 6310 5574 1074 Blue 6
12 Noon Sat 70 76 SE 3 8651 7211 2711 Blue 12
1 PM Sat 73 79 SE 5 10994 8617 4117 Blue 15
2 PM Sat 76 81 SE 6 11174 10905 6405 Blue 17
3 PM Sat 78 82 SE 6 11280 10978 6478 Blue 18
4 PM Sat 80 83 E 6 11387 11052 6552 Blue 19
5 PM Sat 79 80 E 6 11068 10556 6056 Blue 16
6 PM Sat 75 75 E 6 8400 6907 2407 Blue 11
7 PM Sat 69 69 SE 6 5997 5367 867 Blue 5
8 PM Sat 64 64 SE 6 4955 4500 0 Blue 0
9 PM Sat 62 62 SE 6 4552 4500 0 Blue 0
10 PM Sat 60 60 S 5 4146 4500 0 Blue 0
11 PM Sat 59 59 S 5 3989 4500 0 Blue 0
12 Midnight Sun 56 56 S 3 3989 4500 0 Blue 0
1 AM Sun 53 53 SW 3 3989 4500 0 Blue 0
2 AM Sun 50 50 SW 2 3989 4500 0 Blue 0
3 AM Sun 47 47 SW 2 3989 4500 0 Blue 0
4 AM Sun 45 45 W 2 3989 4500 0 Blue 0
5 AM Sun 45 45 W 2 3989 4500 0 Blue 0
6 AM Sun 46 46 W 2 3989 4500 0 Blue 0
7 AM Sun 49 49 SW 2 3989 4500 0 Blue 0
8 AM Sun 53 53 SW 2 3989 4500 0 Blue 0
9 AM Sun 59 60 S 2 4146 4500 0 Blue 0
10 AM Sun 67 69 S 2 5997 5367 867 Blue 5
11 AM Sun 73 77 SE 3 10670 8118 3618 Blue 13
12 Noon Sun 77 81 S 5 11174 10905 6405 Blue 17
1 PM Sun 79 84 S 7 11559 11150 6650 Blue 20
2 PM Sun 81 85 S 8 11865 11256 6756 Blue 21
3 PM Sun 82 85 S 9 11865 11256 6756 Blue 21
4 PM Sun 83 85 SW 10 11865 11256 6756 Blue 21
5 PM Sun 82 83 SW 10 11387 11052 6552 Blue 19
6 PM Sun 78 78 SW 10 10920 8368 3868 Blue 14
7 PM Sun 73 73 SW 9 7238 6291 1791 Blue 9
8 PM Sun 68 68 SW 8 5790 5160 660 Blue 4
9 PM Sun 65 65 SW 7 5165 4551 51 Blue 1
10 PM Sun 62 62 W 7 4552 4500 0 Blue 0
11 PM Sun 60 60 W 6 4146 4500 0 Blue 0
12 Midnight Mon 57 57 W 6 3989 4500 0 Blue 0
1 AM Mon 54 54 W 5 3989 4500 0 Blue 0
2 AM Mon 51 51 W 5 3989 4500 0 Blue 0
3 AM Mon 48 48 W 5 3989 4500 0 Blue 0
4 AM Mon 46 46 W 3 3989 4500 0 Blue 0
5 AM Mon 45 45 W 3 3989 4500 0 Blue 0
6 AM Mon 45 45 W 3 3989 4500 0 Blue 0
7 AM Mon 47 47 W 5 3989 4500 0 Blue 0
8 AM Mon 51 51 W 5 3989 4500 0 Blue 0
9 AM Mon 57 58 NW 5 3989 4500 0 Blue 0
10 AM Mon 64 66 N 6 5374 4752 252 Blue 2
11 AM Mon 69 72 N 6 6931 5987 1487 Blue 8
12 Noon Mon 73 76 N 7 8651 7211 2711 Blue 12
1 PM Mon 74 77 N 7 10670 8118 3618 Blue 13
2 PM Mon 76 79 N 8 10994 8617 4117 Blue 15
3 PM Mon 77 79 N 9 10994 8617 4117 Blue 15
4 PM Mon 78 79 N 10 10994 8617 4117 Blue 15
5 PM Mon 77 77 N 10 10670 8118 3618 Blue 13
6 PM Mon 73 73 N 10 7238 6291 1791 Blue 9
7 PM Mon 67 67 N 10 5582 4952 452 Blue 3
8 PM Mon 62 62 N 9 4552 4500 0 Blue 0
9 PM Mon 59 59 N 8 3989 4500 0 Blue 0
10 PM Mon 58 58 N 8 3989 4500 0 Blue 0
11 PM Mon 56 56 N 7 3989 4500 0 Blue 0
12 Midnight Tue 54 54 N 6 3989 4500 0 Blue 0
1 AM Tue 51 51 N 6 3989 4500 0 Blue 0
2 AM Tue 48 48 N 5 3989 4500 0 Blue 0
3 AM Tue 45 45 N 5 3989 4500 0 Blue 0
4 AM Tue 43 43 N 3 3989 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