Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
685
UXUS97 KBOU 021254
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0551 MST Tuesday, December 2, 2025
This forecast is for Tuesday, December 2, 2025:
If the trigger temperature of 52.5 F/11.4 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 141 ft/min (0.7 m/s)
Maximum height of thermals.................. 8230 ft MSL (2946 ft AGL)
Forecast maximum temperature................... 47.0 F/8.8 C
Time of trigger temperature.................... None
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Overcast thin high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 6571 ft MSL (1287 ft AGL)
Thermal soaring outlook for Wednesday 12/03.... Poor
Wave Soaring Index............................. Good
Wave Soaring Index trend (to 1700 MST)......... Becoming poor by 1500 MDT
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Weak PVA
Potential height of wave....................... 34790 ft MSL (29506 ft AGL)
Wave soaring outlook for Wednesday 12/03....... Poor
Remarks... Mountain wave this morning. Slightly warmer but mostly cloudy today.
Widespread snow late tonight and Wednesday morning.
Sunrise/Sunset.................... 07:03:02 / 16:35:10 MST
Total possible sunshine........... 9 hr 32 min 8 sec (572 min 8 sec)
Altitude of sun at 11:49:06 MST... 28.11 degrees
Upper air data from numerical model forecast valid on 12/02/2025 at 0500 MST
Freezing level.................. 5522 ft MSL (238 ft AGL)
Additional freezing level....... 7486 ft MSL (2202 ft AGL)
Convective condensation level... 20058 ft MSL (14774 ft AGL)
Lifted condensation level....... 13577 ft MSL (8293 ft AGL)
Lifted index.................... +12.9
K index......................... +8.2
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 -60.3 -76.5 295 29 15 0.7 0.4 M M M M M
45000 -59.4 -74.9 295 38 20 0.7 0.4 M M M M M
40000 -59.2 -74.6 285 52 27 0.0 0.0 M M M M M
38000 -58.6 -73.5 285 56 29 2.7 1.5 M M M M M
36000 -57.0 -70.6 290 58 30 2.6 1.4 M M M M M
34000 -55.2 -67.4 295 60 31 7.1 3.9 M M M M M
32000 -50.3 -58.5 295 57 29 8.2 4.5 M M M M M
30000 -45.3 -49.5 290 54 28 9.1 5.0 31.0 87.8 17.0 M M
29000 -42.0 -43.6 290 54 28 9.0 4.9 30.5 86.8 16.8 M M
28000 -39.3 -38.7 290 53 27 9.0 4.9 30.2 86.3 16.8 M M
27000 -36.6 -33.9 290 52 27 8.9 4.9 30.0 86.1 16.9 M M
26000 -34.0 -29.2 290 51 26 8.7 4.8 29.6 85.2 16.7 M M
25000 -31.4 -24.5 285 49 25 8.7 4.8 29.1 84.5 16.6 M M
24000 -28.8 -19.8 285 48 25 8.8 4.8 28.9 83.9 16.5 M M
23000 -26.3 -15.3 285 45 23 8.3 4.6 28.3 82.9 16.3 M M
22000 -23.8 -10.8 285 41 21 8.3 4.6 27.8 82.0 16.0 M M
21000 -21.3 -6.3 285 38 19 7.9 4.3 27.3 81.2 15.8 M M
20000 -19.3 -2.7 285 34 17 6.7 3.7 26.2 79.2 15.0 M M
19500 -18.3 -0.9 285 32 16 6.8 3.7 25.7 78.3 14.7 M M
19000 -17.3 0.9 285 30 15 6.8 3.7 25.2 77.4 14.3 M M
18500 -16.3 2.7 290 28 14 6.8 3.7 24.7 76.5 13.9 M M
18000 -15.3 4.5 290 26 14 6.4 3.5 24.2 75.5 13.5 M M
17500 -14.4 6.1 290 26 13 6.4 3.5 23.6 74.5 13.1 M M
17000 -13.4 7.9 295 25 13 6.1 3.3 23.0 73.5 12.7 M M
16500 -12.6 9.3 295 23 12 5.9 3.2 22.4 72.3 12.1 M M
16000 -11.7 10.9 300 21 11 5.6 3.1 21.7 71.1 11.6 M M
15500 -11.0 12.2 300 19 10 4.4 2.4 20.9 69.6 10.9 M M
15000 -10.3 13.5 305 17 9 4.6 2.5 20.0 68.0 10.2 M M
14500 -9.4 15.1 310 15 8 3.7 2.0 18.6 65.4 8.9 M M
14000 -8.9 16.0 310 13 7 3.9 2.2 17.6 63.6 8.1 M M
13500 -8.2 17.2 310 11 6 4.9 2.7 16.7 62.1 7.3 M M
13000 -7.5 18.5 315 9 5 5.1 2.8 15.9 60.6 6.6 M M
12500 -6.5 20.3 315 8 4 7.6 4.2 15.4 59.7 6.2 M M
12000 -5.4 22.3 320 8 4 7.5 4.1 15.0 59.0 5.9 M M
11500 -4.2 24.4 320 9 5 9.2 5.1 14.8 58.6 5.7 M M
11000 -2.8 27.0 325 12 6 8.9 4.9 14.7 58.5 5.6 M M
10500 -1.9 28.6 320 16 8 4.4 2.4 14.2 57.5 5.1 M M
10250 -1.5 29.3 315 18 9 5.1 2.8 13.8 56.8 4.8 M M
10000 -1.2 29.8 315 21 11 4.3 2.3 13.4 56.1 4.4 M M
9750 -0.9 30.4 310 23 12 2.3 1.3 12.9 55.2 4.0 M M
9500 -0.8 30.6 305 25 13 1.4 0.8 12.2 54.0 3.4 M M
9250 -0.7 30.7 300 27 14 2.0 1.1 11.6 52.9 2.8 M M
9000 -0.5 31.1 300 28 15 0.5 0.3 11.0 51.8 2.2 M M
8750 -0.6 30.9 295 29 15 -0.4 -0.2 10.2 50.3 1.4 M M
8500 -0.5 31.1 295 28 15 0.4 0.2 9.4 49.0 0.7 M M
8250 -0.5 31.1 290 28 14 -0.1 -0.0 8.7 47.7 0.0 M M
8000 -0.5 31.1 290 27 14 1.6 0.9 8.0 46.4 -0.7 233 1.2
7750 -0.2 31.6 285 24 12 3.3 1.8 7.5 45.4 -1.2 219 1.1
7500 -0.0 32.0 280 21 11 2.9 1.6 6.9 44.5 -1.7 204 1.0
7250 0.2 32.4 280 18 9 3.8 2.1 6.4 43.6 -2.2 190 1.0
7000 0.6 33.1 270 15 8 5.7 3.1 6.1 42.9 -2.5 171 0.9
6750 1.1 34.0 265 12 6 6.3 3.5 5.8 42.4 -2.8 150 0.8
6500 1.6 34.9 255 10 5 6.8 3.8 5.5 41.9 -3.1 128 0.6
6250 1.9 35.4 240 8 4 0.7 0.4 5.2 41.3 -3.4 109 0.6
6000 1.8 35.2 225 8 4 -2.5 -1.4 4.2 39.6 -4.3 107 0.5
5750 1.6 34.9 215 9 4 -6.4 -3.5 3.3 37.9 -5.3 106 0.5
5500 0.2 32.4 205 10 5 -35.7 -19.6 1.2 34.1 -7.4 141 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
12/02/2025 at 0800 MST | 12/02/2025 at 1100 MST
|
CAPE... 0.0 LI... +3.9 | CAPE... 0.0 LI... +4.7
CINH... 0.0 K Index... +15.8 | CINH... 0.0 K Index... +7.7
|
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 -59.7 -75.5 285 27 14 1.8 1.0 | -59.8 -75.6 270 30 16 2.6 1.4
45000 -57.1 -70.8 285 34 18 1.8 1.0 | -56.0 -68.8 270 39 20 2.5 1.4
40000 -60.6 -77.1 280 60 31 -2.7 -1.5 | -62.4 -80.3 265 68 35 -4.6 -2.5
38000 -60.6 -77.1 280 66 34 4.5 2.5 | -62.8 -81.0 265 77 40 6.3 3.4
36000 -58.0 -72.4 285 67 34 4.4 2.4 | -58.4 -73.1 265 76 39 6.5 3.6
34000 -55.1 -67.2 290 67 35 7.8 4.3 | -54.4 -65.9 265 75 39 7.8 4.3
32000 -50.0 -58.0 285 62 32 8.7 4.7 | -49.7 -57.5 265 71 37 7.8 4.3
30000 -44.8 -48.6 285 57 30 8.2 4.5 | -45.0 -49.0 270 67 35 8.7 4.8
29000 -42.4 -44.3 285 55 28 7.9 4.3 | -42.4 -44.3 270 65 33 8.5 4.7
28000 -39.5 -39.1 280 53 27 7.9 4.3 | -39.9 -39.8 270 62 32 8.5 4.7
27000 -37.1 -34.8 280 51 26 8.1 4.4 | -37.3 -35.1 270 60 31 8.6 4.7
26000 -34.6 -30.3 280 50 26 8.6 4.7 | -34.9 -30.8 270 58 30 7.9 4.3
25000 -32.0 -25.6 280 49 25 8.6 4.7 | -32.6 -26.7 275 55 28 7.9 4.3
24000 -29.5 -21.1 280 47 24 8.7 4.8 | -30.2 -22.4 275 53 27 7.9 4.4
23000 -27.2 -17.0 280 45 23 7.6 4.1 | -28.0 -18.4 275 49 25 7.2 4.0
22000 -24.9 -12.8 280 43 22 7.6 4.2 | -25.8 -14.4 280 45 23 7.2 4.0
21000 -22.7 -8.9 280 40 21 7.4 4.1 | -23.7 -10.7 285 41 21 7.2 4.0
20000 -20.7 -5.3 285 37 19 6.8 3.8 | -21.6 -6.9 285 37 19 6.7 3.7
19500 -19.6 -3.3 285 35 18 6.9 3.8 | -20.6 -5.1 290 35 18 6.7 3.7
19000 -18.6 -1.5 285 33 17 6.9 3.8 | -19.6 -3.3 290 34 17 6.7 3.7
18500 -17.6 0.3 285 31 16 6.9 3.8 | -18.1 -0.6 295 31 16 6.7 3.7
18000 -16.7 1.9 285 29 15 5.8 3.2 | -17.1 1.2 295 29 15 6.6 3.6
17500 -15.8 3.6 285 27 14 5.9 3.2 | -16.1 3.0 300 27 14 6.6 3.6
17000 -15.0 5.0 285 25 13 5.7 3.1 | -15.1 4.8 300 26 13 6.7 3.7
16500 -14.2 6.4 285 23 12 5.5 3.0 | -14.1 6.6 305 24 12 6.7 3.7
16000 -13.4 7.9 285 21 11 5.5 3.0 | -13.2 8.2 305 23 12 6.6 3.6
15500 -12.6 9.3 285 20 10 5.1 2.8 | -12.2 10.0 310 21 11 6.6 3.6
15000 -11.5 11.3 290 18 9 5.2 2.9 | -11.2 11.8 310 20 10 6.8 3.7
14500 -10.7 12.7 290 16 8 5.3 2.9 | -10.2 13.6 310 19 10 7.2 3.9
14000 -9.9 14.2 290 14 7 5.9 3.3 | -9.1 15.6 315 18 9 7.2 4.0
13500 -8.8 16.2 295 14 7 7.7 4.2 | -8.0 17.6 315 17 9 7.6 4.1
13000 -7.7 18.1 300 13 7 7.9 4.3 | -6.9 19.6 320 17 9 7.6 4.2
12500 -6.3 20.7 310 14 7 9.8 5.4 | -5.8 21.6 320 18 9 6.1 3.4
12000 -4.9 23.2 315 15 8 9.6 5.3 | -4.9 23.2 320 19 10 6.5 3.5
11500 -3.6 25.5 320 18 9 7.7 4.2 | -4.1 24.6 315 19 10 4.3 2.4
11000 -2.5 27.5 320 20 10 7.6 4.2 | -3.5 25.7 315 20 10 4.5 2.5
10500 -1.7 28.9 320 22 11 3.5 1.9 | -2.8 27.0 310 21 11 4.1 2.3
10250 -1.4 29.5 315 22 12 3.8 2.1 | -2.5 27.5 310 21 11 4.0 2.2
10000 -1.1 30.0 315 23 12 4.3 2.4 | -2.2 28.0 305 22 11 4.7 2.6
9750 -0.8 30.6 315 24 13 3.2 1.7 | -1.9 28.6 305 23 12 4.5 2.4
9500 -0.6 30.9 310 25 13 1.4 0.8 | -1.6 29.1 300 24 12 3.4 1.8
9250 -0.5 31.1 310 25 13 2.4 1.3 | -1.3 29.7 300 25 13 4.0 2.2
9000 -0.4 31.3 305 26 13 0.2 0.1 | -1.1 30.0 300 26 13 2.5 1.4
8750 -0.4 31.3 300 25 13 -0.4 -0.2 | -0.9 30.4 295 24 12 2.3 1.3
8500 -0.4 31.3 300 26 13 1.3 0.7 | -0.7 30.7 290 25 13 3.5 1.9
8250 -0.3 31.5 295 27 14 0.8 0.4 | -0.5 31.1 290 26 13 3.3 1.8
8000 -0.2 31.6 290 28 14 1.3 0.7 | -0.2 31.6 285 27 14 2.9 1.6
7750 -0.1 31.8 290 24 13 1.3 0.7 | -0.0 32.0 280 23 12 3.2 1.7
7500 0.0 32.0 285 21 11 0.6 0.3 | 0.3 32.5 275 20 10 3.6 2.0
7250 0.1 32.2 280 18 9 2.1 1.2 | 0.5 32.9 270 18 9 4.2 2.3
7000 0.4 32.7 275 15 8 5.1 2.8 | 1.0 33.8 265 15 8 7.8 4.3
6750 0.8 33.4 270 12 6 6.5 3.6 | 1.7 35.1 255 12 6 8.2 4.5
6500 1.4 34.5 260 9 5 7.2 3.9 | 2.2 36.0 250 10 5 7.0 3.9
6250 1.8 35.2 250 8 4 2.8 1.5 | 2.8 37.0 240 9 5 6.4 3.5
6000 1.8 35.2 235 7 4 0.1 0.1 | 3.2 37.8 235 8 4 6.4 3.5
5750 1.9 35.4 220 7 4 -1.2 -0.7 | 3.7 38.7 230 7 3 3.6 2.0
5500 1.2 34.2 205 9 4 -21.4 -11.8 | 3.8 38.8 220 5 3 1.5 0.8
12/02/2025 at 1400 MST | 12/02/2025 at 1700 MST
|
CAPE... 0.0 LI... +4.9 | CAPE... 0.0 LI... +4.1
CINH... 0.0 K Index... +4.8 | CINH... 0.0 K Index... +12.5
|
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 -60.4 -76.7 265 40 21 2.3 1.2 | -58.9 -74.0 255 37 19 1.4 0.8
45000 -57.0 -70.6 270 58 30 2.2 1.2 | -56.9 -70.4 265 54 28 1.3 0.7
40000 -58.6 -73.5 265 75 38 -1.5 -0.8 | -58.4 -73.1 260 83 43 -1.3 -0.7
38000 -58.8 -73.8 265 82 42 3.0 1.7 | -58.6 -73.5 260 94 49 3.6 2.0
36000 -56.9 -70.4 265 91 47 3.2 1.7 | -56.4 -69.5 260 101 52 3.6 2.0
34000 -54.6 -66.3 265 101 52 5.8 3.2 | -54.0 -65.2 260 109 56 5.1 2.8
32000 -50.5 -58.9 265 90 46 6.9 3.8 | -50.1 -58.2 255 96 50 6.5 3.6
30000 -46.2 -51.2 260 79 41 9.0 4.9 | -46.1 -51.0 250 84 43 8.4 4.6
29000 -43.4 -46.1 260 77 40 9.2 5.1 | -43.3 -45.9 250 78 40 9.3 5.1
28000 -40.7 -41.3 260 74 38 9.2 5.1 | -40.6 -41.1 250 73 38 9.3 5.1
27000 -37.9 -36.2 260 72 37 9.3 5.1 | -37.8 -36.0 245 68 35 9.3 5.1
26000 -35.4 -31.7 255 67 35 7.8 4.3 | -35.6 -32.1 245 62 32 5.9 3.3
25000 -33.1 -27.6 255 62 32 7.8 4.3 | -33.8 -28.8 250 55 28 5.9 3.2
24000 -30.8 -23.4 255 56 29 7.8 4.3 | -32.1 -25.8 255 48 25 5.9 3.2
23000 -28.6 -19.5 255 50 26 6.6 3.6 | -30.2 -22.4 260 43 22 6.8 3.7
22000 -26.7 -16.1 260 43 22 6.6 3.6 | -28.2 -18.8 265 40 21 6.8 3.8
21000 -24.7 -12.5 265 36 19 6.5 3.6 | -26.1 -15.0 270 38 19 6.9 3.8
20000 -22.7 -8.9 270 31 16 7.0 3.9 | -24.1 -11.4 270 35 18 6.7 3.7
19500 -21.6 -6.9 270 29 15 7.0 3.9 | -23.1 -9.6 275 33 17 6.7 3.7
19000 -20.5 -4.9 275 27 14 7.0 3.9 | -22.1 -7.8 275 31 16 6.7 3.7
18500 -19.5 -3.1 280 25 13 7.0 3.8 | -21.1 -6.0 275 29 15 6.7 3.7
18000 -18.4 -1.1 285 23 12 7.2 3.9 | -20.2 -4.4 275 27 14 6.0 3.3
17500 -16.8 1.8 290 20 10 7.2 4.0 | -19.3 -2.7 275 24 12 5.7 3.1
17000 -15.7 3.7 290 19 10 6.9 3.8 | -18.0 -0.4 275 20 10 6.1 3.3
16500 -14.7 5.5 290 17 9 6.9 3.8 | -17.1 1.2 275 18 9 6.2 3.4
16000 -13.7 7.3 295 16 8 6.7 3.7 | -16.2 2.8 275 16 8 6.5 3.5
15500 -12.7 9.1 295 15 8 6.5 3.6 | -15.2 4.6 270 14 7 6.9 3.8
15000 -11.8 10.8 300 13 7 6.4 3.5 | -14.2 6.4 270 12 6 6.8 3.7
14500 -10.9 12.4 305 12 6 5.8 3.2 | -13.2 8.2 265 11 6 6.0 3.3
14000 -10.0 14.0 305 11 5 5.9 3.2 | -12.3 9.9 265 10 5 6.1 3.3
13500 -9.2 15.4 310 9 5 5.5 3.0 | -11.4 11.5 265 10 5 6.1 3.3
13000 -8.4 16.9 315 8 4 5.4 3.0 | -10.5 13.1 270 9 5 6.1 3.4
12500 -7.5 18.5 315 8 4 6.2 3.4 | -9.6 14.7 275 9 5 6.1 3.4
12000 -6.6 20.1 310 7 4 6.1 3.4 | -8.7 16.3 275 9 5 5.9 3.2
11500 -5.7 21.7 305 8 4 6.6 3.6 | -7.7 18.1 285 9 5 8.6 4.7
11000 -4.7 23.5 300 10 5 6.7 3.7 | -6.4 20.5 290 11 5 8.7 4.8
10500 -3.8 25.2 295 12 6 5.4 3.0 | -5.3 22.5 295 13 6 6.5 3.6
10250 -3.4 25.9 295 13 7 5.0 2.7 | -4.8 23.4 295 14 7 6.1 3.3
10000 -3.0 26.6 295 15 8 7.0 3.9 | -4.3 24.3 295 15 8 8.7 4.8
9750 -2.5 27.5 290 16 8 6.4 3.5 | -3.6 25.5 300 16 8 8.5 4.7
9500 -2.2 28.0 290 18 9 3.9 2.1 | -3.1 26.4 300 18 9 5.6 3.1
9250 -1.8 28.8 285 20 10 4.6 2.5 | -2.7 27.1 300 19 10 6.4 3.5
9000 -1.5 29.3 285 21 11 4.4 2.4 | -2.2 28.0 295 20 10 6.2 3.4
8750 -1.2 29.8 285 22 11 4.3 2.4 | -1.8 28.8 300 21 11 5.3 2.9
8500 -0.9 30.4 285 20 10 4.4 2.4 | -1.4 29.5 300 20 10 4.8 2.6
8250 -0.6 30.9 285 18 9 4.0 2.2 | -1.1 30.0 300 20 10 4.4 2.4
8000 -0.2 31.6 285 17 9 5.8 3.2 | -0.7 30.7 300 19 10 6.5 3.6
7750 0.3 32.5 285 13 7 7.6 4.2 | -0.1 31.8 305 17 9 7.1 3.9
7500 0.8 33.4 285 11 6 7.0 3.8 | 0.3 32.5 310 15 8 5.4 2.9
7250 1.4 34.5 290 9 5 7.3 4.0 | 0.7 33.3 315 13 7 6.1 3.4
7000 2.0 35.6 290 7 4 9.8 5.4 | 1.2 34.2 320 11 6 8.1 4.4
6750 2.8 37.0 290 7 4 10.3 5.6 | 1.9 35.4 330 10 5 8.7 4.8
6500 3.5 38.3 295 7 3 8.7 4.7 | 2.5 36.5 335 9 5 8.0 4.4
6250 4.2 39.6 295 7 3 9.9 5.4 | 3.1 37.6 345 9 5 8.1 4.4
6000 5.0 41.0 295 6 3 11.0 6.1 | 3.7 38.7 355 8 4 8.0 4.4
5750 5.8 42.4 295 6 3 10.3 5.6 | 4.3 39.7 005 8 4 7.7 4.2
5500 6.6 43.9 300 6 3 11.5 6.3 | 4.8 40.6 020 7 4 3.8 2.1
________________________________________________________________________________
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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