Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
810
UXUS97 KGJT 151306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Friday, August 15, 2025
This forecast is for Friday, August 15, 2025:
If the trigger temperature of 74.2 F/23.5 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1061 ft/min (5.4 m/s)
Maximum height of thermals.................. 17995 ft MSL (12387 ft AGL)
Forecast maximum temperature................... 89.0 F/32.1 C
Time of trigger temperature.................... 0845 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast thin middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 15792 ft MSL (10184 ft AGL)
Thermal soaring outlook for Saturday 08/16..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:27:58 / 20:09:05 MDT
Total possible sunshine........... 13 hr 41 min 6 sec (821 min 6 sec)
Altitude of sun at 13:18:32 MDT... 64.34 degrees
Upper air data from rawinsonde observation taken on 08/15/2025 at 0600 MDT
Freezing level.................. 14767 ft MSL (9159 ft AGL)
Convective condensation level... 13399 ft MSL (7791 ft AGL)
Lifted condensation level....... 15617 ft MSL (10009 ft AGL)
Lifted index.................... -3.3
K index......................... +28.1
Height Temperature Wind Wind Spd Lapse Rate ConvectionT Thermal Lift Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft deg C deg F Index fpm m/s
--------------------------------------------------------------------------------
50000 -63.7 -82.7 225 20 10 0.8 0.4 M M M M M
45000 -60.0 -76.0 235 28 14 6.2 3.4 M M M M M
40000 -50.3 -58.5 230 39 20 5.8 3.2 M M M M M
38000 -46.8 -52.2 225 44 23 5.8 3.2 M M M M M
36000 -43.3 -45.9 220 50 26 6.1 3.3 M M M M M
34000 -38.7 -37.7 220 45 23 7.7 4.2 M M M M M
32000 -34.1 -29.4 225 40 20 7.6 4.2 M M M M M
30000 -29.5 -21.1 220 35 18 7.7 4.2 46.1 115.1 11.0 M M
29000 -27.2 -17.0 220 33 17 7.7 4.2 45.4 113.7 10.6 M M
28000 -24.9 -12.8 215 30 16 7.3 4.0 44.7 112.5 10.2 M M
27000 -22.8 -9.0 220 29 15 7.0 3.8 43.5 110.4 9.3 M M
26000 -20.7 -5.3 225 27 14 7.0 3.9 42.5 108.5 8.6 M M
25000 -18.6 -1.5 225 26 13 7.1 3.9 41.6 106.8 7.9 M M
24000 -16.7 1.9 225 24 12 6.4 3.5 40.3 104.6 7.0 M M
23000 -14.8 5.4 230 22 11 6.4 3.5 39.1 102.4 6.0 M M
22000 -12.4 9.7 230 20 10 6.4 3.5 37.7 99.9 4.9 M M
21000 -10.5 13.1 235 19 10 6.4 3.5 36.4 97.5 3.8 M M
20000 -8.7 16.3 240 18 9 6.4 3.5 35.3 95.5 2.8 M M
19500 -7.7 18.1 245 17 9 6.2 3.4 34.7 94.5 2.3 M M
19000 -7.0 19.4 250 16 8 4.3 2.4 33.9 93.1 1.6 M M
18500 -6.4 20.5 260 15 8 4.5 2.4 33.0 91.4 0.7 M M
18000 -5.8 21.6 270 14 7 5.0 2.7 32.1 89.8 -0.1 1057 5.4
17500 -5.0 23.0 280 13 7 5.2 2.9 31.3 88.4 -0.9 1021 5.2
17000 -4.3 24.3 295 14 7 5.5 3.0 30.6 87.1 -1.6 985 5.0
16500 -3.5 25.7 300 14 7 6.4 3.5 30.0 85.9 -2.2 944 4.8
16000 -2.6 27.3 300 13 7 6.3 3.5 29.4 84.9 -2.8 902 4.6
15500 -1.6 29.1 295 13 7 7.5 4.1 28.9 84.0 -3.3 858 4.4
15000 -0.5 31.1 290 12 6 7.6 4.1 28.5 83.4 -3.7 810 4.1
14500 0.6 33.1 280 12 6 7.4 4.1 28.2 82.7 -4.1 762 3.9
14000 1.7 35.1 270 11 6 7.4 4.1 27.8 82.0 -4.5 715 3.6
13500 2.8 37.0 260 11 6 7.4 4.0 27.4 81.3 -4.9 668 3.4
13000 3.8 38.8 255 11 6 7.4 4.0 27.0 80.6 -5.3 622 3.2
12500 4.9 40.8 250 11 5 7.5 4.1 26.6 79.9 -5.7 575 2.9
12000 6.0 42.8 245 10 5 8.0 4.4 26.3 79.4 -6.1 526 2.7
11500 7.2 45.0 245 9 5 7.8 4.3 26.1 78.9 -6.4 477 2.4
11000 8.2 46.8 245 9 4 6.9 3.8 25.6 78.1 -6.9 431 2.2
10500 9.2 48.6 245 8 4 9.5 5.2 25.2 77.3 -7.4 387 2.0
10250 10.0 50.0 245 7 4 10.0 5.5 25.3 77.5 -7.3 355 1.8
10000 10.6 51.1 240 7 3 6.7 3.7 25.1 77.2 -7.5 331 1.7
9750 11.1 52.0 235 6 3 8.3 4.6 24.9 76.9 -7.7 307 1.6
9500 11.7 53.1 230 6 3 5.3 2.9 24.8 76.6 -7.9 283 1.4
9250 12.0 53.6 225 5 3 5.4 3.0 24.3 75.8 -8.4 266 1.4
9000 12.5 54.5 215 5 2 8.0 4.4 24.2 75.5 -8.6 242 1.2
8750 13.1 55.6 205 4 2 7.7 4.2 24.0 75.2 -8.8 218 1.1
8500 13.6 56.5 195 4 2 6.3 3.5 23.8 74.9 -8.9 194 1.0
8250 14.0 57.2 185 4 2 5.1 2.8 23.5 74.2 -9.3 175 0.9
8000 14.4 57.9 175 4 2 6.2 3.4 23.2 73.7 -9.7 155 0.8
7750 14.9 58.8 165 4 2 6.4 3.5 22.9 73.2 -10.0 134 0.7
7500 15.3 59.5 160 4 2 5.5 3.0 22.6 72.7 -10.3 114 0.6
7250 15.7 60.3 155 5 2 4.7 2.6 22.3 72.1 -10.7 96 0.5
7000 16.0 60.8 150 5 3 5.3 2.9 21.9 71.4 -11.1 78 0.4
6750 16.4 61.5 145 5 3 4.2 2.3 21.5 70.8 -11.5 60 0.3
6500 16.6 61.9 140 5 3 1.8 1.0 21.0 69.8 -12.1 47 0.2
6250 16.6 61.9 140 5 3 0.5 0.3 20.4 68.6 -12.8 39 0.2
6000 16.6 61.9 135 5 3 3.6 2.0 19.7 67.5 -13.5 30 0.2
5750 16.8 62.2 125 5 2 -2.8 -1.5 19.2 66.5 -14.1 18 0.1
5500 M M M M M M M M M M M M
5250 M M M M M M M M M M M M
5000 M M M M M M M M M M M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/15/2025 at 0900 MDT | 08/15/2025 at 1200 MDT
|
CAPE... +0.1 LI... -0.3 | CAPE... +41.9 LI... -0.6
CINH... -1.3 K Index... +27.0 | CINH... -34.3 K Index... +28.3
|
Height Temperature Wnd WndSpd Lapse Rate | Temperature Wnd WndSpd Lapse Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft | deg C deg F Dir kt m/s C/km F/kft
--------------------------------------------------------------------------------
50000 -63.5 -82.3 250 18 9 0.2 0.1 | -63.5 -82.3 245 18 9 -0.1 -0.1
45000 -60.6 -77.1 245 25 13 5.9 3.3 | -60.8 -77.4 245 26 13 6.4 3.5
40000 -51.8 -61.2 235 27 14 5.3 2.9 | -51.1 -60.0 225 32 16 5.0 2.8
38000 -48.2 -54.8 235 31 16 5.3 2.9 | -48.1 -54.6 225 34 18 5.0 2.8
36000 -45.1 -49.2 230 34 18 5.6 3.0 | -45.0 -49.0 225 37 19 5.3 2.9
34000 -40.4 -40.7 225 30 16 8.1 4.4 | -40.4 -40.7 215 33 17 7.9 4.4
32000 -35.6 -32.1 215 27 14 7.9 4.4 | -35.6 -32.1 205 30 15 7.8 4.3
30000 -30.9 -23.6 205 24 13 7.8 4.3 | -31.1 -24.0 200 28 15 7.6 4.2
29000 -28.5 -19.3 205 23 12 7.8 4.3 | -28.8 -19.8 200 28 14 7.6 4.2
28000 -26.2 -15.2 200 22 12 7.3 4.0 | -26.5 -15.7 195 27 14 7.3 4.0
27000 -24.1 -11.4 200 21 11 7.0 3.8 | -24.4 -11.9 195 26 13 7.2 3.9
26000 -22.1 -7.8 200 19 10 7.0 3.9 | -22.3 -8.1 195 25 13 7.2 3.9
25000 -20.0 -4.0 205 17 9 7.1 3.9 | -20.2 -4.4 195 24 12 7.2 4.0
24000 -18.1 -0.6 205 18 9 6.4 3.5 | -17.6 0.3 200 22 11 6.9 3.8
23000 -15.7 3.7 210 19 10 6.4 3.5 | -15.6 3.9 205 21 11 6.9 3.8
22000 -13.8 7.2 215 20 11 6.8 3.7 | -13.6 7.5 210 20 11 7.0 3.8
21000 -11.8 10.8 215 22 11 6.9 3.8 | -11.5 11.3 210 20 10 7.1 3.9
20000 -9.8 14.4 215 24 12 6.9 3.8 | -9.5 14.9 210 20 10 7.1 3.9
19500 -8.8 16.2 215 24 13 7.0 3.9 | -8.4 16.9 210 20 10 7.1 3.9
19000 -7.8 18.0 215 24 12 7.2 4.0 | -7.4 18.7 210 19 10 7.2 4.0
18500 -6.7 19.9 210 24 12 7.2 3.9 | -6.3 20.7 205 18 9 7.3 4.0
18000 -5.6 21.9 210 23 12 8.0 4.4 | -5.3 22.5 205 17 9 7.2 3.9
17500 -4.4 24.1 210 22 11 8.2 4.5 | -4.3 24.3 200 16 8 7.2 4.0
17000 -3.2 26.2 205 21 11 8.2 4.5 | -3.2 26.2 200 15 8 7.4 4.1
16500 -2.1 28.2 205 19 10 8.0 4.4 | -2.1 28.2 195 14 7 8.0 4.4
16000 -0.9 30.4 200 18 9 8.0 4.4 | -0.9 30.4 195 13 7 7.9 4.3
15500 0.3 32.5 200 17 9 8.0 4.4 | 0.3 32.5 190 12 6 8.9 4.9
15000 1.4 34.5 200 15 8 8.0 4.4 | 1.6 34.9 190 11 6 8.9 4.9
14500 2.6 36.7 200 14 7 8.5 4.7 | 3.0 37.4 185 10 5 9.0 4.9
14000 3.9 39.0 200 13 7 8.8 4.8 | 4.3 39.7 185 9 5 9.0 5.0
13500 5.2 41.4 200 12 6 8.8 4.8 | 5.7 42.3 185 9 4 9.1 5.0
13000 6.5 43.7 205 10 5 8.7 4.8 | 7.0 44.6 185 8 4 9.1 5.0
12500 7.8 46.0 205 9 5 8.7 4.7 | 8.3 46.9 190 8 4 9.1 5.0
12000 9.1 48.4 210 8 4 8.3 4.6 | 9.7 49.5 190 7 4 9.0 4.9
11500 10.3 50.5 215 7 4 8.3 4.6 | 11.0 51.8 195 6 3 8.9 4.9
11000 11.6 52.9 220 6 3 8.3 4.6 | 12.3 54.1 195 6 3 8.7 4.8
10500 12.8 55.0 225 5 3 6.8 3.7 | 13.7 56.7 200 5 3 6.8 3.7
10250 13.3 55.9 230 5 3 7.1 3.9 | 14.1 57.4 200 4 2 7.3 4.0
10000 14.0 57.2 235 5 2 9.3 5.1 | 14.8 58.6 205 4 2 10.2 5.6
9750 14.6 58.3 235 4 2 8.7 4.8 | 15.5 59.9 210 4 2 9.5 5.2
9500 15.3 59.5 240 4 2 8.8 4.8 | 16.2 61.2 215 4 2 9.5 5.2
9250 15.9 60.6 245 4 2 8.0 4.4 | 16.9 62.4 215 3 2 9.0 4.9
9000 16.5 61.7 245 3 2 7.6 4.2 | 17.6 63.7 220 3 2 9.0 4.9
8750 17.0 62.6 250 3 2 7.7 4.2 | 18.3 64.9 225 3 2 9.3 5.1
8500 18.1 64.6 255 2 1 5.9 3.3 | 19.6 67.3 230 3 1 6.8 3.7
8250 18.6 65.5 245 2 1 6.5 3.6 | 20.1 68.2 235 2 1 8.5 4.6
8000 19.1 66.4 240 2 1 8.5 4.7 | 20.8 69.4 240 2 1 11.1 6.1
7750 19.7 67.5 230 1 1 6.5 3.6 | 21.6 70.9 240 2 1 9.7 5.3
7500 20.1 68.2 190 1 1 3.8 2.1 | 22.3 72.1 245 2 1 8.3 4.6
7250 20.4 68.7 170 2 1 4.2 2.3 | 22.9 73.2 250 2 1 9.1 5.0
7000 20.8 69.4 155 3 1 6.1 3.4 | 23.7 74.7 250 2 1 12.0 6.6
6750 21.3 70.3 140 3 1 6.1 3.4 | 24.6 76.3 250 2 1 11.6 6.4
6500 21.7 71.1 140 3 2 5.3 2.9 | 25.4 77.7 250 2 1 10.3 5.7
6250 22.1 71.8 140 4 2 4.9 2.7 | 26.2 79.2 255 2 1 9.7 5.3
6000 22.5 72.5 135 4 2 8.4 4.6 | 27.0 80.6 255 2 1 12.6 6.9
5750 23.4 74.1 130 3 2 17.2 9.4 | 28.3 82.9 255 2 1 24.7 13.5
5500 24.6 76.3 125 4 2 7.4 4.1 | 30.4 86.7 265 2 1 29.2 16.0
5250 M M M M M M M | M M M M M M M
5000 M M M M M M M | M M M M M M M
08/15/2025 at 1500 MDT | 08/15/2025 at 1800 MDT
|
CAPE... +75.1 LI... -0.5 | CAPE... +142.9 LI... -1.2
CINH... -37.1 K Index... +29.4 | CINH... -68.6 K Index... +30.5
|
Height Temperature Wnd WndSpd Lapse Rate | Temperature Wnd WndSpd Lapse Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft | deg C deg F Dir kt m/s C/km F/kft
--------------------------------------------------------------------------------
50000 -63.7 -82.7 240 20 10 0.2 0.1 | -63.7 -82.7 240 18 9 0.8 0.4
45000 -60.5 -76.9 235 25 13 6.6 3.6 | -59.7 -75.5 230 24 12 5.9 3.2
40000 -50.6 -59.1 220 34 17 4.4 2.4 | -51.0 -59.8 215 31 16 5.1 2.8
38000 -48.0 -54.4 215 35 18 4.4 2.4 | -47.9 -54.2 210 32 17 5.1 2.8
36000 -45.4 -49.7 215 37 19 4.9 2.7 | -44.8 -48.6 205 34 17 5.5 3.0
34000 -40.5 -40.9 210 35 18 8.4 4.6 | -40.0 -40.0 200 32 17 8.3 4.5
32000 -35.4 -31.7 200 33 17 8.2 4.5 | -35.0 -31.0 190 31 16 8.1 4.4
30000 -30.6 -23.1 200 27 14 8.1 4.4 | -30.1 -22.2 190 29 15 8.2 4.5
29000 -28.2 -18.8 195 25 13 8.1 4.5 | -27.6 -17.7 190 29 15 8.2 4.5
28000 -25.8 -14.4 195 22 11 7.6 4.2 | -25.2 -13.4 190 28 14 7.7 4.2
27000 -23.6 -10.5 190 21 11 7.3 4.0 | -22.5 -8.5 190 26 14 7.4 4.1
26000 -20.9 -5.6 190 21 11 7.3 4.0 | -20.3 -4.5 190 25 13 7.4 4.1
25000 -18.8 -1.8 190 20 10 7.1 3.9 | -18.1 -0.6 190 24 13 7.0 3.8
24000 -16.7 1.9 185 20 10 6.9 3.8 | -16.2 2.8 190 23 12 6.7 3.7
23000 -14.7 5.5 185 20 10 6.9 3.8 | -14.2 6.4 195 22 11 6.7 3.7
22000 -12.6 9.3 185 20 10 7.1 3.9 | -12.3 9.9 195 20 10 6.3 3.5
21000 -10.6 12.9 185 20 10 7.1 3.9 | -10.5 13.1 195 19 10 6.1 3.4
20000 -8.5 16.7 180 19 10 7.1 3.9 | -8.7 16.3 195 19 10 6.2 3.4
19500 -7.5 18.5 180 19 10 7.0 3.9 | -7.8 18.0 195 18 9 6.2 3.4
19000 -6.5 20.3 180 19 10 6.5 3.6 | -6.9 19.6 195 17 9 6.4 3.5
18500 -5.5 22.1 180 19 10 6.6 3.6 | -6.0 21.2 195 17 9 6.4 3.5
18000 -4.6 23.7 180 18 9 6.8 3.8 | -5.0 23.0 195 16 8 6.7 3.7
17500 -3.6 25.5 180 18 9 6.9 3.8 | -4.1 24.6 200 15 8 6.8 3.7
17000 -2.6 27.3 180 17 9 7.0 3.8 | -3.1 26.4 200 13 7 6.9 3.8
16500 -1.6 29.1 180 16 8 7.1 3.9 | -2.1 28.2 200 12 6 7.2 3.9
16000 -0.5 31.1 180 15 8 7.1 3.9 | -1.1 30.0 200 10 5 7.2 4.0
15500 0.5 32.9 180 14 7 7.6 4.2 | -0.0 32.0 200 9 4 6.8 3.7
15000 1.6 34.9 180 13 7 7.6 4.2 | 0.9 33.6 200 8 4 6.8 3.7
14500 2.8 37.0 185 12 6 8.3 4.5 | 1.9 35.4 200 7 4 7.6 4.2
14000 4.0 39.2 190 11 6 8.6 4.7 | 3.1 37.6 205 7 3 8.1 4.4
13500 5.3 41.5 190 11 6 8.8 4.8 | 4.3 39.7 205 7 3 8.4 4.6
13000 6.6 43.9 195 10 5 9.0 4.9 | 5.7 42.3 210 7 3 8.9 4.9
12500 8.0 46.4 200 10 5 9.0 4.9 | 7.0 44.6 215 7 4 8.8 4.8
12000 9.3 48.7 210 9 5 9.0 4.9 | 8.2 46.8 220 8 4 8.4 4.6
11500 10.6 51.1 215 9 5 8.9 4.9 | 9.5 49.1 225 9 4 8.4 4.6
11000 11.9 53.4 225 9 5 8.3 4.6 | 10.8 51.4 230 10 5 8.8 4.8
10500 13.2 55.8 235 9 5 6.5 3.6 | 12.1 53.8 230 11 5 8.1 4.4
10250 13.6 56.5 240 9 5 7.1 3.9 | 12.7 54.9 235 12 6 8.5 4.7
10000 14.3 57.7 240 10 5 10.0 5.5 | 13.4 56.1 235 12 6 9.8 5.4
9750 15.0 59.0 245 10 5 9.3 5.1 | 14.1 57.4 235 12 6 9.3 5.1
9500 15.7 60.3 245 11 6 9.4 5.2 | 15.6 60.1 235 13 7 10.6 5.8
9250 16.4 61.5 250 11 6 9.2 5.1 | 16.3 61.3 235 13 7 9.4 5.2
9000 17.8 64.0 255 12 6 9.4 5.2 | 17.0 62.6 235 13 7 8.3 4.6
8750 18.5 65.3 250 12 6 9.2 5.1 | 17.6 63.7 230 13 7 8.8 4.8
8500 19.1 66.4 255 12 6 8.2 4.5 | 18.3 64.9 230 13 7 9.1 5.0
8250 19.8 67.6 260 13 7 9.2 5.1 | 18.9 66.0 230 14 7 9.2 5.0
8000 20.5 68.9 255 13 7 11.0 6.1 | 19.6 67.3 230 14 7 9.2 5.1
7750 21.3 70.3 255 13 6 9.7 5.3 | 20.3 68.5 225 13 7 8.6 4.7
7500 22.0 71.6 255 13 7 7.9 4.3 | 20.9 69.6 220 13 7 7.5 4.1
7250 22.6 72.7 260 14 7 8.7 4.8 | 21.4 70.5 220 14 7 7.9 4.3
7000 23.3 73.9 260 13 7 11.9 6.5 | 22.1 71.8 215 14 7 9.8 5.4
6750 24.3 75.7 255 13 7 11.6 6.3 | 22.8 73.0 205 13 6 8.6 4.7
6500 25.0 77.0 260 13 7 10.2 5.6 | 23.3 73.9 210 13 7 6.9 3.8
6250 25.8 78.4 260 13 7 9.7 5.3 | 23.8 74.8 210 13 7 6.7 3.7
6000 26.6 79.9 260 13 7 12.0 6.6 | 24.2 75.6 205 13 7 5.7 3.1
5750 27.8 82.0 255 12 6 22.4 12.3 | 24.7 76.5 200 10 5 10.0 5.5
5500 29.7 85.5 260 12 6 27.3 15.0 | 25.8 78.4 205 9 5 24.0 13.2
5250 M M M M M M M | M M M M M M M
5000 M M M M M M M | M M M M M M M
________________________________________________________________________________
This product is issued twice per day, once by approximately 0630 MST/0730 MDT
(1330 UTC) and again by approximately 1830 MST/1930 MDT (0130 UTC). It is not
continuously monitored nor updated after its initial issuance.
The information contained herein is based on rawinsonde observation and/or
numerical weather prediction model data taken at Walker Field in Grand
Junction, Colorado at
North Latitude: 39 deg 07 min 00.001 sec
West Longitude: 108 deg 31 min 59.998 sec
Elevation: 4839 feet (1475 meters)
and may not be representative of other areas along the Western Slope of
Colorado. Note that some elevations in numerical weather prediction models
differ from actual station elevations, which can lead to data which appear
to be below ground. Erroneous data such as these should not be used.
The content and format of this report as well as the issuance times are subject
to change without prior notice. Comments and suggestions are welcome and should
be directed to one of the addresses or phone numbers shown at the bottom of this
page. To expedite a response to comments, be sure to mention your interest in
the soaring forecast.
DEFINITIONS:
CAPE (Convective Available Potential Energy) - An integrated measure of the
energy available for convective development, also known as the positive
area on a thermodynamic diagram. Units are Joules per kilogram. Larger
values are indicative of greater instability and the possibility of
stronger convective activity, including thunderstorms. Values around or
greater than 1000 suggest the possibility of severe weather should
convective activity develop.
CINH (Convective Inhibition) - An integrated measure of the amount of energy
needed to initiate convective activity, also known as the negative area on
a thermodynamic diagram. Units are Joules per kilogram. The more negative
this number, the more energy is required to initiate convection. This
inhibitive energy can be overcome through surface heating, cooling aloft,
lifting mechanisms (orographic, frontal, gravity waves, etc.)
Convective Condensation Level - The height to which an air parcel possessing the
average saturation mixing ratio in the lowest 4000 feet of the airmass,
if heated sufficiently from below, will rise dry adiabatically until it
just becomes saturated. It estimates the base of cumulus clouds that are
produced by surface heating only.
Convection Temperature (ConvectionT) - The surface temperature required to make
the airmass dry adiabatic up to the given level. It can be considered a
"trigger temperature" for that level.
Freezing Level - The height where the temperature is zero degrees Celsius.
Height of Stable Layer - The height (between 12,000 and 18,000 feet above
mean sea level) where the smallest lapse rate exists. The location and
existence of this feature is important in the generation of mountain
waves.
K Index - A measure of stability which combines the temperature difference
between approximately 5,000 and 18,000 feet above the surface, the amount
of moisture at approximately 5,000 feet above the surface, and a measure
of the dryness at approximately 10,000 feet above the surface. Larger
positive numbers indicate more instability and a greater likelihood of
thunderstorm development. One interpretation of K index values regarding
soaring in the western United States is given in WMO Technical Note 158
and is reproduced in the following table:
below -10 no or weak thermals
-10 to 5 dry thermals or 1/8 cumulus with moderate thermals
5 to 15 good soaring conditions
15 to 20 good soaring conditions with occasional showers
20 to 30 excellent soaring conditions, but increasing
probability of showers and thunderstorms
above 30 more than 60 percent probability of thunderstorms
Lapse Rate - The change with height of the temperature. Negative values indicate
inversions.
Lifted Condensation Level - The height to which an air parcel possessing the
average dew point in the lowest 4000 feet of the airmass and the forecast
maximum temperature must be lifted dry adiabatically to attain saturation.
Lifted Index (LI) - The difference between the environmental temperature at a
level approximately 18,000 feet above the surface and the temperature of
an air parcel lifted dry adiabatically from the surface to its lifted
condensation level and then pseudoadiabatically thereafter to this same
level. The parcel`s initial temperature is the forecast maximum
temperature and its dew point is the average dew point in the lowest 4000
feet of the airmass. Negative values are indicative of instability with
positive values showing stable conditions.
Lift Rate - An experimental estimate of the strength of thermals. It is
computed the same way as the maximum rate of lift but uses the actual
level rather than the maximum height of thermals in the calculation.
Also, none of the empirical adjustments based on cloudiness and K-index
are applied to these calculations.
Maximum Height of Thermals - The height where the dry adiabat through the
forecast maximum temperature intersects the environmental temperature.
Maximum Rate of Lift - An estimate of the maximum strength of thermals. It
is computed from an empirical formula which combines the expected maximum
height of thermals with the difference in the environmental temperatures
between the maximum height of thermals and the temperature 4,000 feet
above the ground. After this computation, further empirical adjustments
are made based on the value of the K-index and the amount and opacity of
middle and high level cloudiness expected between the time of trigger
temperature and the time of overdevelopment.
Middle/High Clouds - The amount and opacity of middle (altostratus, altocumulus)
or high (cirrus, cirrostratus, cirrocumulus) clouds. Broken means that
between 60% and 90% of the sky is covered by the cloud, with overcast
conditions occurring when more than 90% of the sky is covered by the cloud.
Thin implies that the clouds are predominantly transparent, meaning that
some sunlight is reaching the ground, in contrast to opaque which suggests
that little sunlight is reaching the ground.
Potential Height of Wave - The minimum of the following two heights:
1. Level above the height of stable layer (or 14,000 feet if none exists)
where the wind direction changes by 30 degrees or more
2. Level above the height of stable layer (or 14,000 feet if none exists)
where the wind speed no longer increases with height
PVA/NVA - Positive vorticity advection (PVA)/negative vorticity advection (NVA)
on the 500 millibar isobaric surface (approximately 18,000 feet above mean
sea level). Weak PVA has been shown to assist in mountain wave soaring.
Soaring Window - The time between the time the trigger temperature is reached
and the time of overdevelopment.
Thermal Index - The difference between the environmental temperature and the
temperature at a particular level determined by following the dry adiabat
through the forecast maximum temperature up to that level. Negative values
are indicative of thermal lift.
Thermal Soaring Index - An adjective rating (for sailplanes) based on the
computed maximum rate of lift, and the wind speed and middle and high
cloud cover expected during the soaring window (the time of the trigger
temperature and the time of overdevelopment) according to the following:
Maximum rate of lift Adjective Rating
>= 800 fpm Excellent
>= 400 and < 800 fpm Good
>= 200 and < 400 fpm Fair
< 200 fpm Poor
Time of Overdevelopment - The time one or more of the following phenomena,
which essentially shut off thermal lift, is expected to occur:
1. formation of broken to overcast convective cloud cover
2. formation of scattered to numerous downbursts
3. initiation of widespread precipitation
Time of Trigger Temperature - The time the surface temperature is expected to
reach the trigger temperature.
Trigger Temperature - The surface temperature required to make the first 4000
feet of the atmosphere dry adiabatic.
Wave Soaring Index - An empirical, adjective rating (for sailplanes) which
attempts to combine a variety of phenomena important in mountain wave
soaring into a single index number. Objective points are assigned to
these phenomena: wind speed and direction at 14,000 ft MSL, the static
stability in the 12,000-18,000 ft MSL layer, the wind speed gradient above
the stable layer, jet stream location and frontal and upper trough
movements.
042613