Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
272
UXUS97 KBOU 241311
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0711 MDT Sunday, August 24, 2025
This forecast is for Sunday, August 24, 2025:
If the trigger temperature of 82.4 F/28.0 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 30 ft/min (0.2 m/s)
Maximum height of thermals.................. 8586 ft MSL (3265 ft AGL)
Forecast maximum temperature................... 80.0 F/27.1 C
Time of trigger temperature.................... None
Time of overdevelopment........................ 1000 MDT
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................. 7297 ft MSL (1976 ft AGL)
Thermal soaring outlook for Monday 08/25....... Poor
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT).........
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 21767 ft MSL (16446 ft AGL)
Wave soaring outlook for Monday 08/25.......... Poor
Remarks...
Sunrise/Sunset.................... 06:20:39 / 19:42:46 MDT
Total possible sunshine........... 13 hr 22 min 7 sec (802 min 7 sec)
Altitude of sun at 13:01:43 MDT... 61.04 degrees
Upper air data from numerical model forecast valid on 08/24/2025 at 0600 MDT
Freezing level.................. 15911 ft MSL (10590 ft AGL)
Convective condensation level... 13780 ft MSL (8459 ft AGL)
Lifted condensation level....... 12061 ft MSL (6740 ft AGL)
Lifted index.................... -3.0
K index......................... +11.3
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 -64.7 -84.5 310 38 20 1.2 0.6 M M M M M
45000 -61.3 -78.3 305 53 27 4.7 2.6 M M M M M
40000 -53.3 -63.9 300 62 32 7.6 4.2 M M M M M
38000 -48.8 -55.8 300 59 30 7.6 4.2 M M M M M
36000 -44.2 -47.6 300 56 29 7.7 4.2 M M M M M
34000 -39.2 -38.6 305 54 28 8.4 4.6 M M M M M
32000 -34.2 -29.6 310 53 27 8.4 4.6 M M M M M
30000 -29.8 -21.6 310 48 25 7.3 4.0 46.7 116.1 15.2 M M
29000 -27.1 -16.8 310 45 23 7.3 4.0 45.6 114.1 14.6 M M
28000 -24.9 -12.8 310 42 22 6.8 3.8 44.7 112.5 14.0 M M
27000 -22.9 -9.2 310 40 20 6.9 3.8 43.5 110.3 13.2 M M
26000 -20.8 -5.4 310 37 19 6.9 3.8 42.5 108.4 12.5 M M
25000 -18.8 -1.8 315 35 18 7.1 3.9 41.5 106.8 11.9 M M
24000 -16.6 2.1 315 32 17 7.2 4.0 40.5 104.9 11.2 M M
23000 -14.4 6.1 315 30 16 7.2 4.0 39.6 103.3 10.6 M M
22000 -12.3 9.9 320 28 15 6.1 3.3 38.8 101.8 10.0 M M
21000 -10.8 12.6 325 27 14 5.1 2.8 37.0 98.7 8.6 M M
20000 -9.3 15.3 335 25 13 5.1 2.8 35.4 95.8 7.3 M M
19500 -8.6 16.5 340 25 13 5.2 2.9 34.7 94.4 6.6 M M
19000 -7.6 18.3 340 24 12 7.9 4.3 34.2 93.5 6.2 M M
18500 -6.4 20.5 345 22 11 7.7 4.2 33.8 92.8 6.0 M M
18000 -5.2 22.6 345 21 11 7.7 4.2 33.5 92.2 5.8 M M
17500 -4.1 24.6 350 20 10 7.6 4.2 33.1 91.6 5.5 M M
17000 -2.9 26.8 350 19 10 7.6 4.2 32.7 90.9 5.2 M M
16500 -1.7 28.9 350 18 9 8.2 4.5 32.4 90.4 4.9 M M
16000 -0.5 31.1 350 17 9 8.1 4.4 32.1 89.9 4.7 M M
15500 1.4 34.5 350 15 8 9.0 4.9 31.8 89.3 4.5 M M
15000 2.7 36.9 350 14 7 9.0 4.9 31.7 89.1 4.4 M M
14500 4.0 39.2 350 13 7 9.0 4.9 31.6 88.9 4.3 M M
14000 5.4 41.7 350 12 6 9.0 5.0 31.5 88.6 4.1 M M
13500 6.7 44.1 355 10 5 8.6 4.7 31.3 88.4 4.0 M M
13000 7.9 46.2 360 8 4 8.6 4.7 31.1 88.0 3.8 M M
12500 9.1 48.4 010 6 3 8.5 4.6 31.0 87.7 3.6 M M
12000 10.3 50.5 005 5 3 8.4 4.6 30.7 87.3 3.3 M M
11500 11.4 52.5 005 4 2 8.1 4.5 30.5 86.9 3.0 M M
11000 12.5 54.5 350 4 2 7.7 4.2 30.2 86.4 2.6 M M
10500 13.5 56.3 335 4 2 4.7 2.6 29.9 85.9 2.2 M M
10250 13.8 56.8 330 4 2 6.3 3.5 29.4 85.0 1.7 M M
10000 14.4 57.9 325 4 2 11.7 6.4 29.5 85.1 1.6 M M
9750 15.1 59.2 315 3 2 11.8 6.5 29.6 85.3 1.6 M M
9500 15.8 60.4 305 3 2 8.3 4.6 29.7 85.5 1.6 M M
9250 16.1 61.0 295 3 2 4.0 2.2 29.4 84.8 1.1 M M
9000 16.4 61.5 285 3 2 4.9 2.7 29.0 84.1 0.7 M M
8750 16.7 62.1 270 4 2 4.9 2.7 28.6 83.5 0.3 M M
8500 17.0 62.6 265 4 2 3.9 2.1 28.2 82.8 -0.1 225 1.1
8250 17.2 63.0 265 4 2 3.1 1.7 27.7 81.8 -0.6 212 1.1
8000 17.4 63.3 265 5 2 2.9 1.6 27.2 80.9 -1.2 198 1.0
7750 17.6 63.7 265 5 2 2.1 1.1 26.6 79.9 -1.7 186 0.9
7500 17.7 63.9 270 5 2 1.4 0.8 26.0 78.8 -2.3 175 0.9
7250 17.7 63.9 280 5 2 1.0 0.6 25.4 77.6 -3.0 166 0.8
7000 17.8 64.0 290 5 2 1.5 0.8 24.7 76.5 -3.7 158 0.8
6750 17.8 64.0 300 5 2 -0.2 -0.1 24.1 75.3 -4.4 150 0.8
6500 17.6 63.7 305 5 3 -2.2 -1.2 23.2 73.7 -5.3 147 0.7
6250 17.4 63.3 310 6 3 -2.9 -1.6 22.3 72.1 -6.3 146 0.7
6000 17.2 63.0 310 6 3 -0.6 -0.4 21.4 70.4 -7.3 146 0.7
5750 17.3 63.1 310 6 3 2.9 1.6 20.7 69.3 -7.9 136 0.7
5500 17.5 63.5 300 4 2 2.0 1.1 20.2 68.4 -8.5 123 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/24/2025 at 0900 MDT | 08/24/2025 at 1200 MDT
|
CAPE... +318.7 LI... -2.9 | CAPE... +824.8 LI... -4.2
CINH... -283.2 K Index... +17.9 | CINH... -120.1 K Index... +25.2
|
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 -64.4 -83.9 310 39 20 1.0 0.6 | -64.9 -84.8 310 40 21 1.5 0.8
45000 -61.3 -78.3 310 53 27 4.3 2.4 | -61.3 -78.3 305 54 28 4.7 2.6
40000 -53.7 -64.7 305 58 30 7.9 4.4 | -53.4 -64.1 305 56 29 7.5 4.1
38000 -49.0 -56.2 305 55 28 7.9 4.3 | -48.9 -56.0 305 56 29 7.5 4.1
36000 -44.2 -47.6 305 53 27 8.0 4.4 | -44.4 -47.9 300 55 28 7.8 4.3
34000 -39.3 -38.7 310 50 26 8.3 4.6 | -39.3 -38.7 305 48 25 8.6 4.7
32000 -34.3 -29.7 310 47 24 8.2 4.5 | -34.2 -29.6 310 42 21 8.5 4.7
30000 -28.8 -19.8 315 44 23 8.1 4.4 | -29.2 -20.6 305 38 20 8.2 4.5
29000 -26.4 -15.5 315 43 22 8.1 4.4 | -26.2 -15.2 305 36 19 8.2 4.5
28000 -24.2 -11.6 315 42 21 6.1 3.3 | -23.9 -11.0 305 35 18 6.5 3.5
27000 -22.3 -8.1 310 38 20 6.3 3.5 | -21.9 -7.4 305 33 17 6.7 3.7
26000 -20.4 -4.7 310 35 18 6.4 3.5 | -19.9 -3.8 305 31 16 6.7 3.7
25000 -18.6 -1.5 310 32 17 6.2 3.4 | -18.0 -0.4 305 30 15 5.8 3.2
24000 -16.8 1.8 310 31 16 6.0 3.3 | -16.6 2.1 305 29 15 4.9 2.7
23000 -15.1 4.8 315 31 16 6.0 3.3 | -15.2 4.6 305 29 15 5.0 2.7
22000 -13.3 8.1 315 30 15 6.3 3.4 | -13.7 7.3 305 29 15 6.2 3.4
21000 -11.4 11.5 315 29 15 6.5 3.6 | -11.7 10.9 305 27 14 7.1 3.9
20000 -9.6 14.7 320 28 14 6.5 3.6 | -9.6 14.7 305 25 13 7.2 3.9
19500 -8.6 16.5 320 27 14 6.5 3.6 | -8.6 16.5 305 24 12 7.2 4.0
19000 -7.7 18.1 320 26 13 6.0 3.3 | -7.6 18.3 305 23 12 7.4 4.1
18500 -6.8 19.8 325 24 12 6.1 3.4 | -6.5 20.3 300 23 12 7.4 4.1
18000 -5.9 21.4 325 22 11 7.9 4.3 | -5.4 22.3 300 22 11 7.6 4.2
17500 -4.6 23.7 325 20 10 8.9 4.9 | -4.3 24.3 295 21 11 7.7 4.2
17000 -3.3 26.1 320 18 9 8.9 4.9 | -3.2 26.2 295 20 10 7.7 4.2
16500 -2.0 28.4 325 17 9 8.0 4.4 | -2.0 28.4 295 18 9 8.6 4.7
16000 -0.1 31.8 330 15 8 8.3 4.5 | -0.0 32.0 295 16 8 8.4 4.6
15500 1.2 34.2 330 13 7 8.9 4.9 | 1.2 34.2 290 15 8 8.1 4.4
15000 2.5 36.5 335 12 6 8.9 4.9 | 2.4 36.3 290 13 7 8.1 4.4
14500 3.8 38.8 340 10 5 8.8 4.8 | 3.7 38.7 290 13 6 8.4 4.6
14000 5.2 41.4 340 8 4 8.9 4.9 | 4.9 40.8 285 12 6 8.4 4.6
13500 6.6 43.9 345 6 3 8.9 4.9 | 6.2 43.2 285 11 6 8.4 4.6
13000 8.0 46.4 340 4 2 9.1 5.0 | 7.4 45.3 285 11 6 8.4 4.6
12500 9.4 48.9 330 3 2 8.3 4.6 | 8.6 47.5 290 10 5 8.1 4.5
12000 10.6 51.1 310 3 1 7.9 4.3 | 9.8 49.6 290 10 5 8.0 4.4
11500 11.7 53.1 285 3 1 7.7 4.2 | 11.0 51.8 290 10 5 7.6 4.1
11000 12.8 55.0 285 3 2 7.5 4.1 | 12.0 53.6 295 9 5 7.1 3.9
10500 13.8 56.8 280 3 2 4.5 2.5 | 13.0 55.4 295 8 4 4.2 2.3
10250 14.0 57.2 280 3 2 4.8 2.6 | 13.1 55.6 300 8 4 3.3 1.8
10000 14.5 58.1 285 3 2 9.8 5.4 | 13.5 56.3 305 8 4 7.1 3.9
9750 15.1 59.2 290 3 2 10.3 5.7 | 13.9 57.0 310 8 4 7.6 4.2
9500 15.6 60.1 290 4 2 7.5 4.1 | 14.3 57.7 315 8 4 4.0 2.2
9250 15.9 60.6 295 4 2 4.2 2.3 | 14.3 57.7 325 8 4 0.8 0.4
9000 16.1 61.0 295 4 2 5.3 2.9 | 14.4 57.9 330 9 5 0.8 0.4
8750 16.4 61.5 295 4 2 5.5 3.0 | 14.3 57.7 340 10 5 -0.2 -0.1
8500 16.6 61.9 295 4 2 2.7 1.5 | 14.3 57.7 345 11 6 0.3 0.1
8250 16.7 62.1 300 5 2 0.5 0.3 | 14.2 57.6 350 11 6 0.5 0.3
8000 16.7 62.1 305 5 2 0.7 0.4 | 14.1 57.4 355 12 6 0.0 0.0
7750 16.7 62.1 305 5 3 -0.7 -0.4 | 14.1 57.4 355 13 7 1.0 0.5
7500 16.5 61.7 315 5 3 -2.4 -1.3 | 14.2 57.6 360 13 7 3.8 2.1
7250 16.2 61.2 325 6 3 -3.0 -1.7 | 14.4 57.9 005 13 7 5.1 2.8
7000 16.0 60.8 330 7 4 -3.1 -1.7 | 14.7 58.5 005 13 7 3.8 2.1
6750 15.7 60.3 335 8 4 0.4 0.2 | 15.0 59.0 010 13 7 7.1 3.9
6500 15.9 60.6 340 9 4 4.1 2.2 | 15.7 60.3 010 13 7 11.2 6.1
6250 16.1 61.0 340 9 4 3.3 1.8 | 16.5 61.7 010 13 7 9.8 5.4
6000 16.4 61.5 345 9 4 5.1 2.8 | 17.3 63.1 010 13 6 12.6 6.9
5750 17.0 62.6 345 8 4 13.9 7.6 | 18.5 65.3 010 12 6 21.3 11.7
5500 18.4 65.1 345 8 4 23.1 12.7 | 20.4 68.7 010 12 6 27.9 15.3
08/24/2025 at 1500 MDT | 08/24/2025 at 1800 MDT
|
CAPE... +804.5 LI... -4.3 | CAPE... +703.3 LI... -2.3
CINH... -56.2 K Index... +27.3 | CINH... 0.0 K Index... +29.4
|
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 -64.6 -84.3 310 39 20 1.4 0.8 | -65.7 -86.3 305 43 22 0.7 0.4
45000 -60.6 -77.1 305 57 29 4.7 2.6 | -62.7 -80.9 285 54 28 4.8 2.6
40000 -52.9 -63.2 305 67 34 7.5 4.1 | -53.8 -64.8 255 62 32 9.6 5.3
38000 -48.5 -55.3 300 64 33 7.4 4.1 | -48.1 -54.6 255 59 30 9.6 5.3
36000 -44.0 -47.2 300 60 31 7.7 4.2 | -42.3 -44.1 255 56 29 8.9 4.9
34000 -38.9 -38.0 295 55 28 8.7 4.8 | -37.3 -35.1 260 50 26 8.4 4.6
32000 -33.7 -28.7 290 49 25 8.7 4.8 | -32.2 -26.0 265 45 23 9.1 5.0
30000 -28.4 -19.1 295 43 22 7.7 4.2 | -27.6 -17.7 270 40 21 7.9 4.3
29000 -26.1 -15.0 295 40 21 7.8 4.3 | -25.2 -13.4 275 38 20 7.9 4.3
28000 -23.8 -10.8 295 38 20 7.0 3.8 | -22.9 -9.2 280 36 18 7.2 4.0
27000 -21.7 -7.1 295 37 19 7.1 3.9 | -20.8 -5.4 280 33 17 7.1 3.9
26000 -19.6 -3.3 295 36 19 7.1 3.9 | -18.7 -1.7 280 29 15 7.2 3.9
25000 -17.5 0.5 295 35 18 6.5 3.6 | -16.6 2.1 285 26 14 7.1 3.9
24000 -15.9 3.4 295 34 18 5.8 3.2 | -14.7 5.5 285 24 12 6.2 3.4
23000 -14.2 6.4 295 33 17 5.9 3.2 | -12.5 9.5 290 21 11 6.3 3.4
22000 -12.5 9.5 295 32 17 6.0 3.3 | -10.7 12.7 295 19 10 6.0 3.3
21000 -10.8 12.6 300 28 15 6.0 3.3 | -8.9 16.0 300 16 8 6.0 3.3
20000 -9.0 15.8 300 24 13 6.0 3.3 | -7.2 19.0 310 13 7 6.0 3.3
19500 -8.2 17.2 300 23 12 6.0 3.3 | -6.3 20.7 315 12 6 5.9 3.3
19000 -7.2 19.0 300 21 11 7.8 4.3 | -5.5 22.1 320 12 6 5.8 3.2
18500 -6.1 21.0 300 20 10 7.7 4.2 | -4.7 23.5 325 11 6 5.9 3.2
18000 -5.0 23.0 300 19 10 7.4 4.1 | -3.9 25.0 330 11 6 4.7 2.6
17500 -3.9 25.0 300 19 10 7.1 3.9 | -3.3 26.1 335 11 6 4.5 2.5
17000 -2.9 26.8 305 18 9 7.1 3.9 | -2.6 27.3 345 11 6 4.3 2.4
16500 -1.3 29.7 305 18 9 7.6 4.2 | -2.0 28.4 345 11 6 3.8 2.1
16000 -0.1 31.8 305 18 9 7.7 4.2 | -1.5 29.3 350 11 6 3.7 2.0
15500 1.1 34.0 310 17 9 8.6 4.7 | -0.8 30.6 350 10 5 5.5 3.0
15000 2.4 36.3 310 17 9 8.6 4.7 | -0.0 32.0 350 9 5 5.4 3.0
14500 3.6 38.5 310 16 8 8.2 4.5 | 0.8 33.4 350 9 5 6.6 3.6
14000 4.8 40.6 315 15 8 8.3 4.5 | 1.8 35.2 345 8 4 7.0 3.8
13500 6.0 42.8 320 14 7 8.0 4.4 | 2.8 37.0 340 8 4 7.2 4.0
13000 7.2 45.0 320 13 7 7.9 4.4 | 3.9 39.0 330 7 4 7.5 4.1
12500 8.4 47.1 320 12 6 7.3 4.0 | 5.0 41.0 320 7 4 7.2 4.0
12000 9.3 48.7 325 10 5 6.8 3.7 | 5.9 42.6 305 7 4 6.6 3.6
11500 10.3 50.5 325 9 5 5.9 3.2 | 6.9 44.4 295 8 4 6.4 3.5
11000 11.0 51.8 330 8 4 4.6 2.5 | 7.7 45.9 290 8 4 5.6 3.1
10500 11.6 52.9 340 7 3 2.8 1.5 | 8.5 47.3 285 8 4 4.7 2.6
10250 11.6 52.9 340 6 3 0.8 0.4 | 8.8 47.8 280 9 4 4.3 2.4
10000 11.7 53.1 345 6 3 2.3 1.3 | 9.2 48.6 280 9 5 6.6 3.6
9750 11.8 53.2 355 5 3 2.4 1.3 | 9.7 49.5 275 9 5 7.7 4.2
9500 11.9 53.4 005 5 3 2.4 1.3 | 10.2 50.4 275 9 5 6.5 3.6
9250 11.9 53.4 015 5 2 2.2 1.2 | 10.5 50.9 270 9 5 4.7 2.6
9000 12.0 53.6 025 4 2 3.7 2.0 | 10.9 51.6 270 9 5 5.5 3.0
8750 12.2 54.0 040 5 2 5.1 2.8 | 11.3 52.3 265 9 4 6.6 3.6
8500 12.4 54.3 050 5 3 4.9 2.7 | 11.7 53.1 265 8 4 6.0 3.3
8250 12.8 55.0 055 6 3 5.1 2.8 | 12.1 53.8 265 6 3 5.8 3.2
8000 13.1 55.6 055 6 3 4.6 2.5 | 12.5 54.5 265 5 2 5.5 3.0
7750 13.5 56.3 055 7 4 4.5 2.5 | 12.8 55.0 265 3 2 4.5 2.5
7500 13.8 56.8 050 7 4 6.2 3.4 | 13.1 55.6 285 2 1 4.9 2.7
7250 14.3 57.7 045 8 4 7.3 4.0 | 13.4 56.1 330 2 1 5.6 3.1
7000 14.9 58.8 040 8 4 6.4 3.5 | 13.8 56.8 355 4 2 4.9 2.7
6750 15.3 59.5 035 9 5 7.9 4.4 | 14.1 57.4 005 5 3 4.6 2.5
6500 16.0 60.8 035 9 5 10.5 5.7 | 14.4 57.9 005 6 3 6.2 3.4
6250 16.8 62.2 030 9 5 10.1 5.6 | 14.9 58.8 005 7 3 5.9 3.2
6000 17.6 63.7 030 9 5 11.6 6.3 | 15.3 59.5 005 7 4 9.2 5.0
5750 18.7 65.7 030 9 4 19.6 10.7 | 16.2 61.2 005 7 4 14.7 8.1
5500 20.5 68.9 030 9 4 28.4 15.6 | 17.2 63.0 005 6 3 13.4 7.4
________________________________________________________________________________
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.
042613