Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
811
UXUS97 KBOU 221236
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0632 MDT Friday, August 22, 2025
This forecast is for Friday, August 22, 2025:
If the trigger temperature of 85.7 F/29.8 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 208 ft/min (1.1 m/s)
Maximum height of thermals.................. 9761 ft MSL (4406 ft AGL)
Forecast maximum temperature................... 87.0 F/31.0 C
Time of trigger temperature.................... 1300 MDT
Time of overdevelopment........................ 1500 MDT
Middle/high clouds during soaring window....... Overcast thin high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 8468 ft MSL (3113 ft AGL)
Thermal soaring outlook for Saturday 08/23..... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 16181 ft MSL (10826 ft AGL)
Wave soaring outlook for Saturday 08/23........ Poor
Remarks... Turning cooler through Saturday. Areas of stratus by tonight.
Moderate northwest flow aloft developing.
Sunrise/Sunset.................... 06:18:47 / 19:45:43 MDT
Total possible sunshine........... 13 hr 26 min 56 sec (806 min 56 sec)
Altitude of sun at 13:02:15 MDT... 61.72 degrees
Upper air data from numerical model forecast valid on 08/22/2025 at 0600 MDT
Freezing level.................. 16852 ft MSL (11497 ft AGL)
Convective condensation level... 16144 ft MSL (10789 ft AGL)
Lifted condensation level....... 14767 ft MSL (9412 ft AGL)
Lifted index.................... -2.9
K index......................... +24.1
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 -66.0 -86.8 285 27 14 0.3 0.2 M M M M M
45000 -62.0 -79.6 285 41 21 6.7 3.7 M M M M M
40000 -51.7 -61.1 285 43 22 7.6 4.2 M M M M M
38000 -47.1 -52.8 285 38 20 7.6 4.2 M M M M M
36000 -42.5 -44.5 290 33 17 7.7 4.2 M M M M M
34000 -37.3 -35.1 290 27 14 7.8 4.3 M M M M M
32000 -32.6 -26.7 290 21 11 8.3 4.5 49.7 121.4 14.2 M M
30000 -27.9 -18.2 285 17 9 7.8 4.3 47.9 118.2 13.2 M M
29000 -25.6 -14.1 280 15 8 7.8 4.3 47.2 117.0 12.8 M M
28000 -23.5 -10.3 280 13 7 5.6 3.1 46.3 115.3 12.2 M M
27000 -21.8 -7.2 285 12 6 5.8 3.2 44.7 112.4 11.1 M M
26000 -20.1 -4.2 290 11 6 5.9 3.2 43.2 109.8 10.0 M M
25000 -18.3 -0.9 295 10 5 6.1 3.4 41.9 107.4 9.0 M M
24000 -16.5 2.3 305 12 6 6.3 3.4 40.5 104.9 7.9 M M
23000 -14.7 5.5 310 13 7 6.3 3.5 39.2 102.6 6.8 M M
22000 -12.9 8.8 315 15 8 7.8 4.3 38.2 100.7 5.9 M M
21000 -10.4 13.3 310 15 8 8.4 4.6 37.6 99.7 5.4 M M
20000 -8.0 17.6 305 14 7 8.4 4.6 37.1 98.8 5.0 M M
19500 -6.1 21.0 305 14 7 8.3 4.5 36.8 98.3 4.8 M M
19000 -4.9 23.2 300 13 7 8.3 4.5 36.6 97.8 4.5 M M
18500 -3.7 25.3 295 13 7 8.2 4.5 36.3 97.4 4.3 M M
18000 -2.5 27.5 290 13 6 7.9 4.4 36.0 96.8 4.0 M M
17500 -1.4 29.5 285 12 6 7.9 4.4 35.7 96.3 3.8 M M
17000 -0.2 31.6 280 12 6 8.6 4.7 35.4 95.8 3.5 M M
16500 1.1 34.0 270 12 6 8.7 4.8 35.3 95.5 3.4 M M
16000 2.4 36.3 265 12 6 8.7 4.8 35.1 95.2 3.3 M M
15500 3.7 38.7 255 12 6 8.5 4.7 34.9 94.8 3.1 M M
15000 5.0 41.0 250 13 7 8.5 4.7 34.7 94.5 3.0 M M
14500 6.3 43.3 240 13 7 8.3 4.6 34.5 94.1 2.8 M M
14000 7.5 45.5 235 13 7 8.3 4.6 34.2 93.6 2.6 M M
13500 8.8 47.8 230 13 7 8.5 4.7 34.0 93.3 2.4 M M
13000 10.1 50.2 220 13 7 8.5 4.7 33.8 92.9 2.3 M M
12500 11.4 52.5 215 13 7 8.7 4.8 33.7 92.6 2.1 M M
12000 12.7 54.9 210 13 7 8.7 4.8 33.5 92.3 2.0 M M
11500 14.0 57.2 210 13 7 8.3 4.6 33.3 92.0 1.8 M M
11000 15.1 59.2 215 13 7 7.7 4.2 33.0 91.5 1.5 M M
10500 16.3 61.3 215 12 6 3.4 1.9 32.8 91.0 1.2 M M
10250 16.3 61.3 215 13 7 2.8 1.5 32.1 89.7 0.5 M M
10000 16.8 62.2 220 13 7 8.1 4.4 31.8 89.3 0.3 M M
9750 17.3 63.1 225 12 6 7.5 4.1 31.6 88.9 0.0 M M
9500 17.7 63.9 230 12 6 4.8 2.6 31.4 88.6 -0.2 289 1.5
9250 17.8 64.0 235 12 6 1.3 0.7 30.8 87.5 -0.8 278 1.4
9000 17.9 64.2 235 12 6 2.2 1.2 30.2 86.4 -1.5 267 1.4
8750 18.1 64.6 245 11 6 2.5 1.4 29.6 85.4 -2.1 257 1.3
8500 18.2 64.8 250 10 5 0.9 0.5 29.1 84.3 -2.7 246 1.2
8250 18.1 64.6 255 9 5 -0.8 -0.5 28.3 82.9 -3.5 241 1.2
8000 18.0 64.4 265 9 5 0.5 0.3 27.5 81.5 -4.3 236 1.2
7750 18.1 64.6 275 8 4 1.8 1.0 26.9 80.3 -5.0 227 1.2
7500 18.2 64.8 285 8 4 1.5 0.8 26.2 79.2 -5.7 217 1.1
7250 18.2 64.8 295 7 4 0.8 0.4 25.6 78.0 -6.4 208 1.1
7000 18.2 64.8 310 7 4 1.9 1.0 24.9 76.9 -7.1 200 1.0
6750 18.4 65.1 315 7 4 4.8 2.6 24.4 76.0 -7.6 187 0.9
6500 18.8 65.8 320 6 3 5.3 2.9 24.1 75.4 -8.0 168 0.9
6250 19.1 66.4 325 6 3 4.0 2.2 23.7 74.7 -8.5 151 0.8
6000 19.4 66.9 330 5 3 5.3 2.9 23.3 74.0 -8.9 135 0.7
5750 19.7 67.5 340 4 2 0.9 0.5 22.9 73.2 -9.3 118 0.6
5500 19.4 66.9 335 2 1 -9.2 -5.0 21.8 71.3 -10.4 120 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/22/2025 at 0900 MDT | 08/22/2025 at 1200 MDT
|
CAPE... +80.2 LI... -0.5 | CAPE... +464.2 LI... -2.1
CINH... -441.4 K Index... +24.6 | CINH... -149.6 K Index... +24.8
|
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 -66.4 -87.5 290 27 14 1.4 0.7 | -66.6 -87.9 290 25 13 0.7 0.4
45000 -61.4 -78.5 290 38 20 6.7 3.7 | -62.0 -79.6 285 35 18 7.0 3.8
40000 -51.2 -60.2 285 40 20 7.3 4.0 | -51.5 -60.7 280 42 21 7.2 4.0
38000 -46.9 -52.4 285 36 18 7.3 4.0 | -47.1 -52.8 280 41 21 7.2 4.0
36000 -42.5 -44.5 280 32 16 7.5 4.1 | -42.8 -45.0 275 40 20 7.6 4.2
34000 -37.2 -35.0 280 25 13 7.9 4.3 | -38.0 -36.4 275 32 16 8.0 4.4
32000 -32.5 -26.5 270 19 10 8.4 4.6 | -32.6 -26.7 265 24 12 8.4 4.6
30000 -27.6 -17.7 275 17 9 8.1 4.5 | -27.9 -18.2 260 22 11 7.8 4.3
29000 -25.2 -13.4 275 16 8 8.1 4.5 | -25.5 -13.9 260 21 11 7.8 4.3
28000 -23.0 -9.4 275 15 8 5.9 3.2 | -23.3 -9.9 260 20 10 6.5 3.6
27000 -21.2 -6.2 275 15 8 6.1 3.3 | -21.4 -6.5 265 20 10 6.6 3.6
26000 -19.4 -2.9 270 14 7 6.1 3.3 | -19.4 -2.9 270 21 11 6.6 3.6
25000 -17.6 0.3 265 14 7 5.5 3.0 | -17.5 0.5 275 21 11 6.1 3.3
24000 -16.1 3.0 275 13 7 5.2 2.9 | -15.8 3.6 280 21 11 5.9 3.2
23000 -14.6 5.7 290 13 7 5.3 2.9 | -14.0 6.8 280 21 11 5.9 3.3
22000 -13.0 8.6 300 14 7 7.5 4.1 | -12.3 9.9 285 21 11 7.3 4.0
21000 -10.6 12.9 300 14 7 8.3 4.5 | -10.0 14.0 285 20 10 7.8 4.3
20000 -8.2 17.2 305 14 7 8.3 4.6 | -7.8 18.0 285 19 10 7.8 4.3
19500 -7.0 19.4 305 14 7 8.3 4.5 | -6.7 19.9 285 18 9 7.7 4.2
19000 -5.3 22.5 305 14 7 8.0 4.4 | -5.6 21.9 285 17 9 7.3 4.0
18500 -4.1 24.6 300 13 7 8.0 4.4 | -4.6 23.7 285 16 8 7.3 4.0
18000 -2.9 26.8 300 13 7 8.3 4.6 | -2.9 26.8 285 14 7 8.5 4.7
17500 -1.7 28.9 295 13 7 8.3 4.5 | -1.6 29.1 285 14 7 8.4 4.6
17000 -0.4 31.3 295 13 7 8.8 4.8 | -0.4 31.3 285 13 7 8.5 4.7
16500 0.9 33.6 290 13 7 8.9 4.9 | 0.9 33.6 285 13 7 8.5 4.7
16000 2.2 36.0 290 12 6 8.8 4.8 | 2.1 35.8 290 13 6 8.5 4.6
15500 3.5 38.3 285 12 6 8.6 4.7 | 3.4 38.1 290 12 6 8.3 4.6
15000 4.8 40.6 280 12 6 8.6 4.7 | 4.6 40.3 290 12 6 8.3 4.6
14500 6.1 43.0 275 12 6 8.4 4.6 | 5.8 42.4 290 11 6 7.9 4.3
14000 7.4 45.3 270 11 6 8.5 4.6 | 7.0 44.6 295 10 5 8.0 4.4
13500 8.6 47.5 265 11 6 8.4 4.6 | 8.2 46.8 295 9 5 7.7 4.2
13000 9.9 49.8 265 10 5 8.4 4.6 | 9.3 48.7 295 8 4 7.7 4.2
12500 11.1 52.0 260 10 5 8.2 4.5 | 10.4 50.7 295 7 4 7.4 4.1
12000 12.3 54.1 260 10 5 8.1 4.5 | 11.5 52.7 300 6 3 7.3 4.0
11500 13.5 56.3 260 10 5 7.5 4.1 | 12.5 54.5 310 5 3 6.5 3.6
11000 14.5 58.1 260 9 5 6.9 3.8 | 13.4 56.1 325 5 2 5.9 3.3
10500 15.5 59.9 265 9 5 2.6 1.4 | 14.2 57.6 340 5 2 3.3 1.8
10250 15.5 59.9 275 9 5 2.5 1.4 | 14.4 57.9 340 5 3 3.3 1.8
10000 16.0 60.8 275 9 4 7.9 4.3 | 14.8 58.6 350 5 3 6.3 3.5
9750 16.5 61.7 275 8 4 7.4 4.0 | 15.1 59.2 355 6 3 5.8 3.2
9500 17.0 62.6 275 8 4 4.4 2.4 | 15.5 59.9 360 6 3 4.1 2.2
9250 17.1 62.8 280 8 4 1.3 0.7 | 15.7 60.3 005 7 3 2.7 1.5
9000 17.2 63.0 285 7 4 2.7 1.5 | 15.9 60.6 005 7 4 4.6 2.5
8750 17.4 63.3 285 7 3 2.8 1.6 | 16.2 61.2 005 7 4 5.4 2.9
8500 17.5 63.5 290 6 3 1.4 0.7 | 16.5 61.7 005 8 4 5.6 3.1
8250 17.5 63.5 295 6 3 0.3 0.2 | 16.9 62.4 005 8 4 5.4 3.0
8000 17.5 63.5 300 6 3 0.7 0.4 | 17.3 63.1 005 8 4 7.3 4.0
7750 17.5 63.5 315 5 3 0.6 0.4 | 17.9 64.2 005 8 4 9.2 5.0
7500 17.4 63.3 330 5 3 0.5 0.3 | 18.5 65.3 005 8 4 8.2 4.5
7250 17.4 63.3 340 6 3 0.3 0.2 | 19.0 66.2 005 9 4 6.7 3.7
7000 17.4 63.3 350 6 3 1.0 0.6 | 19.6 67.3 005 9 4 11.0 6.0
6750 17.5 63.5 360 7 4 5.7 3.1 | 20.6 69.1 005 9 4 14.0 7.7
6500 18.1 64.6 005 7 4 8.1 4.4 | 21.5 70.7 005 9 4 10.8 5.9
6250 18.6 65.5 005 7 4 7.9 4.3 | 22.3 72.1 005 8 4 10.9 6.0
6000 19.2 66.6 005 7 4 5.9 3.2 | 23.1 73.6 005 8 4 9.6 5.3
5750 19.6 67.3 010 7 4 10.0 5.5 | 23.9 75.0 005 8 4 17.1 9.4
5500 20.9 69.6 005 7 3 23.3 12.8 | 25.8 78.4 360 8 4 33.2 18.2
08/22/2025 at 1500 MDT | 08/22/2025 at 1800 MDT
|
CAPE... +951.4 LI... -3.7 | CAPE... +500.9 LI... -2.4
CINH... -19.0 K Index... +30.1 | CINH... -55.4 K Index... +31.3
|
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 -66.0 -86.8 285 26 13 0.8 0.4 | -66.1 -87.0 285 29 15 0.7 0.4
45000 -61.5 -78.7 285 36 18 6.6 3.6 | -62.0 -79.6 280 40 21 6.2 3.4
40000 -51.3 -60.3 290 42 22 7.6 4.1 | -52.2 -62.0 280 40 21 8.0 4.4
38000 -46.7 -52.1 285 45 23 7.6 4.1 | -47.4 -53.3 275 38 19 8.0 4.4
36000 -42.2 -44.0 280 48 25 7.5 4.1 | -42.6 -44.7 275 35 18 8.2 4.5
34000 -37.1 -34.8 280 42 22 7.5 4.1 | -37.0 -34.6 270 34 18 8.3 4.6
32000 -32.6 -26.7 275 37 19 8.2 4.5 | -32.0 -25.6 270 34 17 8.8 4.9
30000 -28.0 -18.4 280 33 17 7.8 4.3 | -27.2 -17.0 270 32 17 8.1 4.4
29000 -25.6 -14.1 280 31 16 7.8 4.3 | -24.8 -12.6 275 31 16 8.1 4.4
28000 -23.4 -10.1 280 30 15 6.8 3.7 | -22.5 -8.5 275 31 16 6.9 3.8
27000 -21.4 -6.5 280 29 15 6.9 3.8 | -20.5 -4.9 275 30 15 6.9 3.8
26000 -19.4 -2.9 280 28 14 6.9 3.8 | -18.5 -1.3 275 29 15 7.0 3.8
25000 -17.3 0.9 280 27 14 6.7 3.7 | -16.4 2.5 280 29 15 6.7 3.7
24000 -15.4 4.3 280 26 13 6.6 3.6 | -14.5 5.9 280 29 15 6.6 3.6
23000 -13.5 7.7 280 26 13 6.6 3.6 | -12.6 9.3 280 29 15 6.6 3.6
22000 -11.6 11.1 280 25 13 6.6 3.6 | -10.7 12.7 280 29 15 6.2 3.4
21000 -9.7 14.5 275 23 12 6.7 3.7 | -9.0 15.8 275 28 15 6.1 3.3
20000 -7.8 18.0 275 21 11 6.7 3.7 | -7.2 19.0 275 28 14 6.1 3.3
19500 -6.8 19.8 275 20 10 6.8 3.7 | -6.3 20.7 275 28 14 6.1 3.4
19000 -5.8 21.6 275 19 10 7.3 4.0 | -5.4 22.3 275 27 14 6.6 3.6
18500 -4.2 24.4 275 18 9 7.3 4.0 | -4.5 23.9 275 26 13 6.6 3.6
18000 -3.1 26.4 275 18 9 7.6 4.2 | -3.1 26.4 275 24 12 5.9 3.2
17500 -2.0 28.4 275 17 9 7.6 4.2 | -2.2 28.0 270 22 11 5.9 3.2
17000 -0.9 30.4 275 17 9 8.0 4.4 | -1.4 29.5 270 20 11 6.4 3.5
16500 0.3 32.5 275 15 8 8.1 4.4 | -0.5 31.1 270 19 10 6.5 3.6
16000 1.5 34.7 275 14 7 8.0 4.4 | 0.5 32.9 265 17 9 6.3 3.5
15500 2.7 36.9 275 12 6 7.9 4.3 | 1.3 34.3 265 15 8 5.8 3.2
15000 3.8 38.8 280 11 6 8.0 4.4 | 2.2 36.0 260 13 7 5.7 3.1
14500 4.9 40.8 285 9 5 6.9 3.8 | 3.1 37.6 260 12 6 7.0 3.8
14000 5.9 42.6 290 7 4 7.0 3.8 | 4.1 39.4 260 10 5 6.8 3.7
13500 7.0 44.6 300 6 3 7.1 3.9 | 5.1 41.2 260 8 4 7.6 4.1
13000 8.0 46.4 310 5 3 7.1 3.9 | 6.2 43.2 265 6 3 7.6 4.2
12500 9.0 48.2 325 5 2 7.0 3.8 | 7.3 45.1 275 4 2 7.6 4.2
12000 10.0 50.0 340 5 2 7.0 3.8 | 8.4 47.1 305 3 2 7.6 4.1
11500 11.0 51.8 350 5 2 6.7 3.7 | 9.4 48.9 345 4 2 7.4 4.1
11000 11.9 53.4 005 6 3 6.5 3.5 | 10.4 50.7 010 6 3 7.3 4.0
10500 12.7 54.9 015 7 4 1.9 1.0 | 11.4 52.5 020 8 4 4.7 2.6
10250 12.8 55.0 020 8 4 5.4 3.0 | 11.7 53.1 015 7 4 5.5 3.0
10000 13.6 56.5 020 9 4 13.1 7.2 | 12.3 54.1 015 9 4 9.0 4.9
9750 14.4 57.9 020 9 5 11.5 6.3 | 12.9 55.2 020 10 5 8.6 4.7
9500 15.1 59.2 020 9 5 9.0 5.0 | 13.5 56.3 020 11 6 7.4 4.0
9250 15.7 60.3 020 10 5 7.2 4.0 | 13.9 57.0 020 12 6 6.3 3.5
9000 16.3 61.3 020 10 5 10.3 5.6 | 14.5 58.1 020 13 6 7.8 4.3
8750 17.1 62.8 020 10 5 11.0 6.0 | 15.1 59.2 015 13 7 8.1 4.4
8500 17.9 64.2 020 10 5 9.7 5.3 | 15.6 60.1 015 14 7 6.0 3.3
8250 18.5 65.3 020 10 5 8.6 4.7 | 16.0 60.8 015 15 8 4.6 2.5
8000 19.2 66.6 020 10 5 10.3 5.7 | 16.3 61.3 015 16 8 6.3 3.5
7750 20.0 68.0 020 10 5 11.1 6.1 | 16.9 62.4 010 17 9 6.5 3.6
7500 20.8 69.4 020 10 5 9.2 5.0 | 17.2 63.0 010 17 9 4.5 2.5
7250 21.4 70.5 020 10 5 7.9 4.3 | 17.5 63.5 010 18 9 3.3 1.8
7000 22.1 71.8 020 11 5 10.7 5.9 | 17.8 64.0 005 19 10 6.4 3.5
6750 23.0 73.4 020 10 5 12.6 6.9 | 18.4 65.1 005 19 10 9.4 5.1
6500 23.8 74.8 020 10 5 10.5 5.7 | 18.9 66.0 360 19 10 8.6 4.7
6250 24.6 76.3 020 10 5 10.0 5.5 | 19.5 67.1 360 18 9 8.6 4.7
6000 25.3 77.5 020 10 5 10.6 5.8 | 20.1 68.2 360 17 9 9.5 5.2
5750 26.3 79.3 020 10 5 18.4 10.1 | 21.0 69.8 360 17 9 12.7 7.0
5500 28.1 82.6 020 10 5 29.6 16.3 | 22.0 71.6 360 15 8 15.3 8.4
________________________________________________________________________________
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 near the old Stapleton
Airport site in Denver, Colorado at
North Latitude: 39 deg 46 min 5.016 sec
West Longitude: 104 deg 52 min 9.984 sec
Elevation: 5285 feet (1611 meters)
and may not be representative of other areas along the Front Range of the
Colorado Rocky Mountains. 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.
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