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

Station:

KVBG

Date/Time:

12Z 23 SEP 2017

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 Sat 36 36 NW 7 3999 4500 0 Blue 0
6 AM Sat 35 35 NW 7 3999 4500 0 Blue 0
7 AM Sat 35 35 NW 6 3999 4500 0 Blue 0
8 AM Sat 43 43 N 6 3999 4500 0 Blue 0
9 AM Sat 51 52 N 7 7575 4904 404 Blue 3
10 AM Sat 55 57 N 8 8656 8034 3534 Blue 8
11 AM Sat 59 63 N 7 10234 9235 4735 Blue 14
12 Noon Sat 62 66 N 8 10863 10193 5693 Blue 17
1 PM Sat 65 70 N 10 11606 10999 6499 Blue 21
2 PM Sat 67 71 N 12 11794 11186 6686 Blue 22
3 PM Sat 67 70 N 13 11606 10999 6499 Blue 21
4 PM Sat 67 69 N 14 11418 10818 6318 Blue 20
5 PM Sat 62 63 N 15 10234 9235 4735 Blue 14
6 PM Sat 61 61 N 16 9481 8826 4326 Blue 12
7 PM Sat 56 56 N 13 8457 7839 3339 Blue 7
8 PM Sat 52 52 NW 10 7575 4904 404 Blue 3
9 PM Sat 50 50 NW 10 5816 4500 0 Blue 1
10 PM Sat 48 48 NW 9 3999 4500 0 Blue 0
11 PM Sat 45 45 NW 7 3999 4500 0 Blue 0
12 Midnight Sun 43 43 NW 7 3999 4500 0 Blue 0
1 AM Sun 42 42 NW 7 3999 4500 0 Blue 0
2 AM Sun 40 40 NW 6 3999 4500 0 Blue 0
3 AM Sun 38 38 NW 6 3999 4500 0 Blue 0
4 AM Sun 35 35 NW 6 3999 4500 0 Blue 0
5 AM Sun 34 34 NW 5 3999 4500 0 Blue 0
6 AM Sun 33 33 NW 5 3999 4500 0 Blue 0
7 AM Sun 34 34 NW 5 3999 4500 0 Blue 0
8 AM Sun 43 43 NW 5 3999 4500 0 Blue 0
9 AM Sun 54 55 NW 6 8258 7492 2992 Blue 6
10 AM Sun 60 63 N 6 10234 9235 4735 Blue 14
11 AM Sun 66 70 N 7 11606 10999 6499 Blue 21
12 Noon Sun 70 75 N 8 12835 11934 7434 Blue 26
1 PM Sun 74 79 N 8 14945 13240 8740 White 30
2 PM Sun 76 81 N 9 15356 14350 9850 White 32
3 PM Sun 75 79 N 10 14945 13240 8740 White 30
4 PM Sun 76 78 N 10 14551 12668 8168 Blue 29
5 PM Sun 71 72 N 10 11981 11374 6874 Blue 23
6 PM Sun 69 69 N 10 11418 10818 6318 Blue 20
7 PM Sun 63 63 NW 9 10234 9235 4735 Blue 14
8 PM Sun 59 59 NW 8 9057 8431 3931 Blue 10
9 PM Sun 58 58 NW 7 8855 8233 3733 Blue 9
10 PM Sun 55 55 NW 7 8258 7492 2992 Blue 6
11 PM Sun 52 52 NW 6 7575 4904 404 Blue 3
12 Midnight Mon 49 49 NW 5 4918 4500 0 Blue 0
1 AM Mon 48 48 NW 5 3999 4500 0 Blue 0
2 AM Mon 46 46 NW 5 3999 4500 0 Blue 0
3 AM Mon 43 43 NW 5 3999 4500 0 Blue 0
4 AM Mon 40 40 NW 6 3999 4500 0 Blue 0
5 AM Mon 39 39 NW 6 3999 4500 0 Blue 0
6 AM Mon 38 38 NW 6 3999 4500 0 Blue 0
7 AM Mon 38 38 NW 6 3999 4500 0 Blue 0
8 AM Mon 47 47 NW 6 3999 4500 0 Blue 0
9 AM Mon 57 58 NW 6 8855 8233 3733 Blue 9
10 AM Mon 63 65 N 7 10654 9893 5393 Blue 16
11 AM Mon 68 72 N 7 11981 11374 6874 Blue 23
12 Noon Mon 71 76 N 6 13409 12111 7611 Blue 27
1 PM Mon 75 80 N 5 15151 13786 9286 White 31
2 PM Mon 77 81 N 5 15356 14350 9850 White 32
3 PM Mon 76 79 N 6 14945 13240 8740 White 30
4 PM Mon 77 79 N 7 14945 13240 8740 White 30
5 PM Mon 72 73 N 8 12156 11561 7061 Blue 24
6 PM Mon 71 71 N 8 11794 11186 6686 Blue 22
7 PM Mon 65 65 NW 7 10654 9893 5393 Blue 16
8 PM Mon 61 61 NW 7 9481 8826 4326 Blue 12
9 PM Mon 59 59 NW 7 9057 8431 3931 Blue 10
10 PM Mon 56 56 NW 7 8457 7839 3339 Blue 7
11 PM Mon 53 53 W 7 7861 5778 1278 Blue 4
12 Midnight Tue 50 50 W 7 5816 4500 0 Blue 1
1 AM Tue 49 49 W 7 4918 4500 0 Blue 0
2 AM Tue 47 47 W 7 3999 4500 0 Blue 0
3 AM Tue 45 45 W 6 3999 4500 0 Blue 0
4 AM Tue 42 42 NW 6 3999 4500 0 Blue 0
5 AM Tue 41 41 NW 5 3999 4500 0 Blue 0
6 AM Tue 40 40 NW 5 3999 4500 0 Blue 0
7 AM Tue 41 41 NW 5 3999 4500 0 Blue 0
8 AM Tue 50 50 NW 5 5816 4500 0 Blue 1
9 AM Tue 61 62 N 5 10023 9024 4524 Blue 13
10 AM Tue 67 70 N 5 11606 10999 6499 Blue 21
11 AM Tue 73 77 N 5 13959 12283 7783 Blue 28
12 Noon Tue 77 82 N 5 15562 14919 10419 White 33
1 PM Tue 81 87 N 5 16563 16563 12063 White 38
2 PM Tue 83 88 N 5 16765 16765 12265 White 39
3 PM Tue 82 86 N 5 16358 16358 11858 White 37
4 PM Tue 83 85 N 5 16151 16151 11651 White 36
5 PM Tue 78 79 N 5 14945 13240 8740 White 30
6 PM Tue 76 76 N 5 13409 12111 7611 Blue 27
7 PM Tue 70 70 N 3 11606 10999 6499 Blue 21
8 PM Tue 66 66 N 3 10863 10193 5693 Blue 17
9 PM Tue 64 64 N 3 10444 9445 4945 Blue 15
10 PM Tue 61 61 NW 2 9481 8826 4326 Blue 12
11 PM Tue 58 58 NW 2 8855 8233 3733 Blue 9
12 Midnight Wed 55 55 NW 2 8258 7492 2992 Blue 6
1 AM Wed 54 54 NW 2 8058 6714 2214 Blue 5
2 AM Wed 52 52 NW 2 7575 4904 404 Blue 3
3 AM Wed 49 49 NW 3 4918 4500 0 Blue 0
4 AM Wed 47 47 NW 3 3999 4500 0 Blue 0
5 AM Wed 45 45 NW 3 3999 4500 0 Blue 0
6 AM Wed 44 44 NW 3 3999 4500 0 Blue 0
7 AM Wed 44 44 N 3 3999 4500 0 Blue 0
8 AM Wed 54 54 N 2 8058 6714 2214 Blue 5
9 AM Wed 64 65 N 2 10654 9893 5393 Blue 16
10 AM Wed 69 72 NE 2 11981 11374 6874 Blue 23
11 AM Wed 75 79 NE 2 14945 13240 8740 White 30
12 Noon Wed 78 83 NE 2 15756 15466 10966 White 34
1 PM Wed 82 87 NE 3 16563 16563 12063 White 38
2 PM Wed 84 89 E 3 16964 16964 12464 White 40
3 PM Wed 83 87 E 3 16563 16563 12063 White 38
4 PM Wed 84 86 E 5 16358 16358 11858 White 37
5 PM Wed 79 80 E 5 15151 13786 9286 White 31
6 PM Wed 77 77 E 5 13959 12283 7783 Blue 28
7 PM Wed 71 71 SE 5 11794 11186 6686 Blue 22
8 PM Wed 67 67 SE 5 11040 10402 5902 Blue 18
9 PM Wed 66 66 S 3 10863 10193 5693 Blue 17
10 PM Wed 63 63 S 3 10234 9235 4735 Blue 14
11 PM Wed 60 60 S 3 9269 8629 4129 Blue 11
12 Midnight Thu 57 57 SW 3 8656 8034 3534 Blue 8
1 AM Thu 56 56 SW 3 8457 7839 3339 Blue 7
2 AM Thu 54 54 W 2 8058 6714 2214 Blue 5
3 AM Thu 51 51 W 2 6786 4500 0 Blue 2
4 AM Thu 48 48 W 2 3999 4500 0 Blue 0
5 AM Thu 47 47 NW 2 3999 4500 0 Blue 0
6 AM Thu 46 46 NW 2 3999 4500 0 Blue 0
7 AM Thu 46 46 N 2 3999 4500 0 Blue 0
8 AM Thu 56 56 N 2 8457 7839 3339 Blue 7
9 AM Thu 66 67 NE 2 11040 10402 5902 Blue 18
10 AM Thu 71 74 NE 2 12329 11747 7247 Blue 25
11 AM Thu 77 81 E 2 15356 14350 9850 White 32
12 Noon Thu 80 85 E 3 16151 16151 11651 White 36
1 PM Thu 84 89 E 3 16964 16964 12464 White 40
2 PM Thu 86 91 E 5 17360 17360 12860 White 42
3 PM Thu 85 89 SE 6 16964 16964 12464 White 40
4 PM Thu 86 88 SE 7 16765 16765 12265 White 39
5 PM Thu 81 82 SE 7 15562 14919 10419 White 33
6 PM Thu 79 79 S 7 14945 13240 8740 White 30
7 PM Thu 73 73 S 6 12156 11561 7061 Blue 24
8 PM Thu 69 69 S 6 11418 10818 6318 Blue 20
9 PM Thu 67 67 S 5 11040 10402 5902 Blue 18
10 PM Thu 64 64 S 5 10444 9445 4945 Blue 15
11 PM Thu 61 61 SW 3 9481 8826 4326 Blue 12
12 Midnight Fri 57 57 SW 3 8656 8034 3534 Blue 8
1 AM Fri 56 56 SW 2 8457 7839 3339 Blue 7
2 AM Fri 54 54 W 2 8058 6714 2214 Blue 5
3 AM Fri 51 51 W 2 6786 4500 0 Blue 2
4 AM Fri 49 49 W 2 4918 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