Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
771
UXUS97 KBOU 300121
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1921 MDT Friday, August 29, 2025
This forecast is for Saturday, August 30, 2025:
If the trigger temperature of 69.1 F/20.6 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 641 ft/min (3.3 m/s)
Maximum height of thermals.................. 13650 ft MSL (8359 ft AGL)
Forecast maximum temperature................... 79.0 F/26.6 C
Time of trigger temperature.................... 1030 MDT
Time of overdevelopment........................ 1430 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................. 11349 ft MSL (6058 ft AGL)
Thermal soaring outlook for Sunday 08/31....... Good
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....................... 16387 ft MSL (11096 ft AGL)
Wave soaring outlook for Sunday 08/31.......... Poor
Remarks...
Sunrise/Sunset.................... 06:26:16 / 19:33:38 MDT
Total possible sunshine........... 13 hr 7 min 22 sec (787 min 22 sec)
Altitude of sun at 12:59:57 MDT... 58.93 degrees
Upper air data from numerical model forecast valid on 08/30/2025 at 0600 MDT
Freezing level.................. 14267 ft MSL (8976 ft AGL)
Convective condensation level... 10712 ft MSL (5421 ft AGL)
Lifted condensation level....... 12354 ft MSL (7063 ft AGL)
Lifted index.................... -4.0
K index......................... +27.7
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 -63.9 -83.0 245 36 19 2.0 1.1 M M M M M
45000 -58.9 -74.0 245 58 30 6.2 3.4 M M M M M
40000 -49.5 -57.1 250 77 40 6.8 3.7 M M M M M
38000 -45.4 -49.7 245 78 40 6.8 3.7 M M M M M
36000 -41.3 -42.3 245 80 41 6.8 3.7 M M M M M
34000 -36.6 -33.9 245 76 39 7.0 3.8 M M M M M
32000 -32.4 -26.3 245 72 37 7.1 3.9 M M M M M
30000 -29.3 -20.7 245 59 30 4.7 2.6 47.7 117.8 16.4 M M
29000 -27.9 -18.2 250 51 26 4.7 2.6 45.7 114.3 15.1 M M
28000 -26.5 -15.7 255 44 22 4.7 2.6 43.9 111.1 13.9 M M
27000 -25.1 -13.2 255 39 20 4.6 2.6 41.8 107.3 12.4 M M
26000 -23.8 -10.8 260 35 18 4.7 2.6 39.9 103.7 11.0 M M
25000 -22.4 -8.3 260 31 16 4.2 2.3 38.1 100.5 9.6 M M
24000 -20.0 -4.0 260 29 15 9.2 5.0 37.3 99.1 9.1 M M
23000 -17.3 0.9 260 28 15 9.2 5.0 37.1 98.7 9.0 M M
22000 -14.6 5.7 260 27 14 9.2 5.1 36.9 98.4 9.0 M M
21000 -12.0 10.4 260 26 14 8.2 4.5 36.4 97.5 8.6 M M
20000 -9.6 14.7 265 25 13 8.2 4.5 35.8 96.5 8.2 M M
19500 -8.4 16.9 265 25 13 8.3 4.5 35.6 96.1 8.0 M M
19000 -7.3 18.9 265 24 12 5.9 3.2 35.3 95.5 7.8 M M
18500 -6.6 20.1 265 22 11 5.2 2.8 34.4 94.0 7.0 M M
18000 -5.9 21.4 265 20 10 5.4 2.9 33.6 92.5 6.2 M M
17500 -5.2 22.6 265 18 10 5.4 3.0 32.9 91.2 5.5 M M
17000 -4.1 24.6 270 17 9 5.6 3.1 31.8 89.2 4.4 M M
16500 -3.4 25.9 275 17 9 5.2 2.9 31.0 87.9 3.7 M M
16000 -2.6 27.3 280 16 8 5.3 2.9 30.3 86.5 3.0 M M
15500 -1.9 28.6 285 15 8 5.8 3.2 29.6 85.2 2.3 M M
15000 -1.1 30.0 290 15 8 5.8 3.2 28.9 84.0 1.7 M M
14500 -0.2 31.6 295 15 8 5.7 3.1 28.3 82.9 1.1 M M
14000 0.5 32.9 305 15 8 5.6 3.1 27.6 81.6 0.4 M M
13500 1.3 34.3 315 15 8 5.4 3.0 26.9 80.4 -0.3 624 3.2
13000 2.1 35.8 320 15 8 5.2 2.8 26.1 79.0 -1.0 588 3.0
12500 2.8 37.0 330 15 8 5.5 3.0 25.4 77.7 -1.8 551 2.8
12000 3.7 38.7 335 15 8 6.5 3.6 24.8 76.7 -2.4 509 2.6
11500 4.6 40.3 335 15 8 6.4 3.5 24.3 75.8 -2.9 466 2.4
11000 5.5 41.9 340 15 8 5.8 3.2 23.7 74.7 -3.5 425 2.2
10500 6.4 43.5 340 15 8 4.8 2.6 23.1 73.6 -4.1 384 1.9
10250 6.7 44.1 345 15 8 4.0 2.2 22.6 72.7 -4.5 368 1.9
10000 7.1 44.8 345 15 8 7.3 4.0 22.3 72.1 -4.9 348 1.8
9750 7.7 45.9 345 15 8 9.5 5.2 22.2 72.0 -5.0 322 1.6
9500 8.4 47.1 350 15 8 7.7 4.2 22.2 71.9 -5.1 295 1.5
9250 8.8 47.8 350 15 8 4.9 2.7 21.9 71.4 -5.3 274 1.4
9000 9.2 48.6 355 14 7 6.4 3.5 21.5 70.7 -5.7 256 1.3
8750 9.7 49.5 355 14 7 9.2 5.0 21.4 70.5 -5.9 231 1.2
8500 10.3 50.5 360 14 7 7.1 3.9 21.3 70.3 -6.1 206 1.0
8250 10.7 51.3 360 13 7 5.2 2.9 21.0 69.8 -6.4 188 1.0
8000 11.1 52.0 005 13 6 6.0 3.3 20.7 69.2 -6.8 169 0.9
7750 11.5 52.7 005 12 6 6.8 3.7 20.4 68.7 -7.1 149 0.8
7500 11.9 53.4 010 11 6 6.6 3.6 20.2 68.3 -7.4 128 0.7
7250 12.4 54.3 010 11 5 6.2 3.4 19.9 67.8 -7.7 107 0.5
7000 12.8 55.0 010 10 5 6.2 3.4 19.7 67.4 -8.0 87 0.4
6750 13.2 55.8 015 9 5 5.9 3.2 19.4 66.9 -8.4 67 0.3
6500 13.7 56.7 010 8 4 6.3 3.5 19.1 66.4 -8.6 45 0.2
6250 14.3 57.7 005 7 4 6.8 3.7 18.8 65.9 -8.8 21 0.1
6000 14.8 58.6 355 6 3 6.0 3.3 18.6 65.5 -9.0 M M
5750 15.1 59.2 340 4 2 3.1 1.7 18.2 64.8 -9.5 M M
5500 15.1 59.2 305 2 1 0.5 0.3 17.6 63.7 -10.3 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/30/2025 at 0900 MDT | 08/30/2025 at 1200 MDT
|
CAPE... +167.1 LI... +0.4 | CAPE... +335.9 LI... -1.3
CINH... -19.7 K Index... +28.1 | CINH... -0.2 K Index... +26.4
|
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 -62.4 -80.3 245 34 17 2.0 1.1 | -62.2 -80.0 250 35 18 2.0 1.1
45000 -57.7 -71.9 250 57 29 5.6 3.1 | -57.6 -71.7 250 58 30 5.5 3.0
40000 -49.1 -56.4 255 81 42 6.9 3.8 | -49.1 -56.4 260 77 40 6.7 3.7
38000 -45.0 -49.0 250 83 43 6.9 3.8 | -45.1 -49.2 255 75 38 6.7 3.7
36000 -40.3 -40.5 250 86 44 7.2 3.9 | -40.6 -41.1 255 72 37 6.9 3.8
34000 -37.3 -35.1 250 76 39 4.7 2.6 | -38.1 -36.6 260 62 32 3.7 2.0
32000 -34.5 -30.1 250 65 34 4.6 2.6 | -35.9 -32.6 260 52 27 3.7 2.0
30000 -31.5 -24.7 255 51 26 5.1 2.8 | -32.7 -26.9 265 42 21 5.8 3.2
29000 -30.0 -22.0 260 44 23 5.1 2.8 | -31.0 -23.8 265 37 19 5.8 3.2
28000 -28.5 -19.3 265 37 19 5.4 3.0 | -29.3 -20.7 270 32 16 6.1 3.4
27000 -26.6 -15.9 265 33 17 6.5 3.6 | -27.1 -16.8 270 30 15 7.3 4.0
26000 -24.6 -12.3 265 31 16 6.5 3.6 | -24.9 -12.8 270 28 15 7.3 4.0
25000 -22.6 -8.7 270 28 14 6.4 3.5 | -22.8 -9.0 270 27 14 7.3 4.0
24000 -20.3 -4.5 270 27 14 8.5 4.6 | -20.4 -4.7 270 25 13 8.2 4.5
23000 -17.8 -0.0 265 27 14 8.5 4.6 | -17.9 -0.2 270 25 13 8.2 4.5
22000 -15.2 4.6 265 27 14 8.5 4.7 | -15.4 4.3 270 24 12 8.4 4.6
21000 -12.8 9.0 265 25 13 8.2 4.5 | -13.3 8.1 270 22 12 6.8 3.7
20000 -10.3 13.5 270 24 12 8.2 4.5 | -11.3 11.7 275 21 11 6.9 3.8
19500 -9.1 15.6 270 23 12 8.3 4.5 | -10.4 13.3 275 21 11 7.0 3.8
19000 -8.0 17.6 270 22 11 6.4 3.5 | -9.4 15.1 280 20 10 6.6 3.6
18500 -7.2 19.0 275 20 10 5.8 3.2 | -8.1 17.4 285 18 10 6.6 3.6
18000 -6.4 20.5 275 18 9 5.9 3.3 | -7.2 19.0 290 18 9 6.5 3.6
17500 -5.3 22.5 285 16 8 5.3 2.9 | -6.3 20.7 295 18 9 6.5 3.6
17000 -4.6 23.7 290 15 8 5.3 2.9 | -5.3 22.5 305 18 9 6.6 3.6
16500 -3.9 25.0 295 15 8 4.9 2.7 | -4.3 24.3 305 18 9 7.2 4.0
16000 -3.2 26.2 305 14 7 4.9 2.7 | -3.2 26.2 310 18 9 7.3 4.0
15500 -2.5 27.5 310 14 7 5.6 3.1 | -2.2 28.0 310 18 9 6.5 3.6
15000 -1.7 28.9 315 14 7 5.7 3.1 | -1.3 29.7 315 18 9 6.5 3.5
14500 -0.9 30.4 320 14 7 5.3 2.9 | -0.4 31.3 315 18 9 5.9 3.2
14000 -0.2 31.6 325 14 7 5.1 2.8 | 0.4 32.7 315 18 9 5.5 3.0
13500 0.5 32.9 330 14 7 5.6 3.1 | 1.2 34.2 320 18 9 5.3 2.9
13000 1.4 34.5 330 15 8 6.5 3.5 | 1.9 35.4 320 18 9 4.9 2.7
12500 2.3 36.1 330 15 8 6.4 3.5 | 2.5 36.5 320 18 9 4.9 2.7
12000 3.2 37.8 330 16 8 6.3 3.4 | 3.2 37.8 320 18 9 4.9 2.7
11500 4.1 39.4 330 16 8 6.2 3.4 | 3.9 39.0 325 18 9 5.4 3.0
11000 5.0 41.0 335 16 8 6.0 3.3 | 4.8 40.6 325 19 10 7.2 3.9
10500 5.8 42.4 340 15 8 4.4 2.4 | 5.8 42.4 330 19 10 5.4 3.0
10250 6.0 42.8 340 15 8 2.9 1.6 | 6.1 43.0 330 19 10 3.3 1.8
10000 6.4 43.5 340 15 8 7.3 4.0 | 6.4 43.5 330 19 10 6.7 3.7
9750 7.1 44.8 345 14 7 10.2 5.6 | 7.0 44.6 335 19 10 8.8 4.8
9500 7.8 46.0 345 14 7 7.8 4.3 | 7.5 45.5 335 19 10 6.9 3.8
9250 8.2 46.8 345 14 7 4.7 2.6 | 7.9 46.2 340 19 10 4.1 2.2
9000 8.6 47.5 350 14 7 6.4 3.5 | 8.2 46.8 340 18 9 6.3 3.4
8750 9.2 48.6 350 14 7 8.9 4.9 | 8.8 47.8 345 17 9 8.8 4.8
8500 9.8 49.6 350 14 7 7.7 4.2 | 9.4 48.9 350 16 8 8.3 4.6
8250 10.3 50.5 350 14 7 6.7 3.7 | 10.0 50.0 355 15 8 8.2 4.5
8000 10.8 51.4 355 14 7 7.5 4.1 | 10.6 51.1 355 14 7 8.9 4.9
7750 11.4 52.5 355 14 7 8.6 4.7 | 11.3 52.3 360 14 7 10.6 5.8
7500 12.0 53.6 355 13 7 8.0 4.4 | 12.1 53.8 360 14 7 10.7 5.8
7250 12.5 54.5 350 12 6 7.5 4.1 | 12.9 55.2 360 14 7 10.5 5.7
7000 13.0 55.4 350 10 5 7.0 3.8 | 13.7 56.7 360 14 7 9.9 5.4
6750 13.5 56.3 350 9 5 7.3 4.0 | 14.4 57.9 360 13 7 9.4 5.2
6500 14.1 57.4 345 8 4 9.2 5.1 | 15.1 59.2 360 13 7 10.4 5.7
6250 14.8 58.6 340 7 3 9.5 5.2 | 15.9 60.6 360 13 7 10.5 5.8
6000 15.5 59.9 330 5 3 9.6 5.3 | 16.7 62.1 360 13 7 11.3 6.2
5750 16.4 61.5 325 5 2 13.7 7.5 | 17.8 64.0 360 13 6 19.1 10.5
5500 17.6 63.7 320 5 2 19.9 10.9 | 19.6 67.3 360 12 6 29.0 15.9
08/30/2025 at 1500 MDT | 08/30/2025 at 1800 MDT
|
CAPE... +309.6 LI... -2.2 | CAPE... +417.1 LI... -2.2
CINH... -12.4 K Index... +26.5 | CINH... -2.7 K Index... +31.2
|
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 -62.6 -80.7 255 37 19 2.1 1.1 | -62.9 -81.2 265 38 20 2.0 1.1
45000 -57.9 -72.2 260 56 29 5.5 3.0 | -58.5 -73.3 270 56 29 5.0 2.7
40000 -49.5 -57.1 265 67 34 7.1 3.9 | -50.8 -59.4 270 70 36 7.2 4.0
38000 -45.2 -49.4 270 68 35 7.1 3.9 | -46.5 -51.7 275 71 37 7.2 3.9
36000 -41.0 -41.8 270 70 36 7.0 3.8 | -42.2 -44.0 275 73 37 7.1 3.9
34000 -37.9 -36.2 270 60 31 3.9 2.1 | -38.2 -36.8 275 64 33 5.5 3.0
32000 -35.5 -31.9 270 49 25 3.9 2.1 | -34.9 -30.8 280 55 28 5.5 3.0
30000 -32.3 -26.1 270 42 22 5.7 3.1 | -31.9 -25.4 285 47 24 5.0 2.8
29000 -30.6 -23.1 275 39 20 5.7 3.1 | -30.3 -22.5 285 43 22 5.0 2.8
28000 -28.9 -20.0 275 37 19 6.3 3.5 | -28.8 -19.8 290 39 20 5.6 3.1
27000 -26.6 -15.9 275 35 18 8.0 4.4 | -26.8 -16.2 290 38 19 7.0 3.9
26000 -24.2 -11.6 280 33 17 8.0 4.4 | -24.7 -12.5 290 36 19 7.0 3.9
25000 -21.8 -7.2 280 31 16 8.2 4.5 | -22.5 -8.5 295 35 18 7.2 3.9
24000 -20.0 -4.0 280 29 15 5.0 2.7 | -20.7 -5.3 295 32 17 5.7 3.1
23000 -18.5 -1.3 285 27 14 5.0 2.8 | -19.0 -2.2 300 30 15 5.8 3.2
22000 -17.0 1.4 285 25 13 4.9 2.7 | -17.3 0.9 305 27 14 5.9 3.2
21000 -14.9 5.2 290 24 12 8.2 4.5 | -14.9 5.2 305 27 14 8.9 4.9
20000 -12.5 9.5 295 23 12 8.2 4.5 | -12.3 9.9 305 27 14 9.0 4.9
19500 -11.3 11.7 300 22 12 8.3 4.6 | -11.0 12.2 305 27 14 9.1 5.0
19000 -10.1 13.8 300 22 11 8.4 4.6 | -9.8 14.4 305 27 14 7.4 4.0
18500 -8.9 16.0 300 22 11 8.4 4.6 | -8.8 16.2 305 27 14 7.1 3.9
18000 -7.6 18.3 305 22 11 8.3 4.6 | -7.8 18.0 305 26 13 7.0 3.8
17500 -6.0 21.2 305 22 12 7.0 3.9 | -6.5 20.3 305 25 13 6.0 3.3
17000 -5.0 23.0 310 23 12 6.9 3.8 | -5.6 21.9 310 24 12 6.4 3.5
16500 -4.1 24.6 315 23 12 6.4 3.5 | -4.6 23.7 310 23 12 7.5 4.1
16000 -3.2 26.2 315 23 12 6.4 3.5 | -3.5 25.7 310 23 12 7.5 4.1
15500 -2.3 27.9 320 23 12 6.4 3.5 | -2.5 27.5 310 22 11 7.1 3.9
15000 -1.4 29.5 320 24 12 6.4 3.5 | -1.5 29.3 310 22 11 7.2 3.9
14500 -0.4 31.3 325 24 12 6.6 3.6 | -0.4 31.3 310 21 11 6.9 3.8
14000 0.5 32.9 325 24 13 6.6 3.6 | 0.6 33.1 310 21 11 6.8 3.7
13500 1.5 34.7 330 25 13 6.9 3.8 | 1.5 34.7 315 20 10 6.3 3.5
13000 2.6 36.7 330 25 13 7.1 3.9 | 2.4 36.3 315 20 10 6.0 3.3
12500 3.6 38.5 330 25 13 7.1 3.9 | 3.2 37.8 320 19 10 6.2 3.4
12000 4.6 40.3 330 24 12 7.1 3.9 | 4.1 39.4 330 16 8 6.5 3.6
11500 5.6 42.1 330 23 12 7.0 3.8 | 5.1 41.2 340 13 7 7.0 3.9
11000 6.6 43.9 330 20 10 6.4 3.5 | 6.2 43.2 350 12 6 7.9 4.3
10500 7.5 45.5 330 17 9 4.0 2.2 | 7.3 45.1 355 11 6 4.7 2.6
10250 7.7 45.9 330 16 8 3.0 1.6 | 7.5 45.5 355 11 6 4.8 2.6
10000 8.1 46.6 330 14 7 7.7 4.2 | 8.2 46.8 360 11 6 11.3 6.2
9750 8.6 47.5 340 12 6 8.9 4.9 | 9.0 48.2 360 11 6 12.4 6.8
9500 9.2 48.6 345 9 5 7.9 4.3 | 9.9 49.8 360 11 6 10.2 5.6
9250 9.7 49.5 350 9 5 6.4 3.5 | 10.5 50.9 360 11 6 7.7 4.2
9000 10.2 50.4 350 9 4 9.3 5.1 | 11.2 52.2 360 11 6 10.5 5.8
8750 11.1 52.0 350 8 4 12.2 6.7 | 12.1 53.8 360 11 6 12.6 6.9
8500 11.9 53.4 350 8 4 10.5 5.8 | 12.9 55.2 360 11 6 10.3 5.7
8250 12.6 54.7 355 8 4 10.0 5.5 | 13.6 56.5 360 11 6 8.7 4.8
8000 13.4 56.1 355 8 4 9.9 5.4 | 14.3 57.7 360 11 6 9.8 5.4
7750 14.1 57.4 355 8 4 9.6 5.3 | 15.1 59.2 360 11 6 10.7 5.9
7500 14.8 58.6 355 8 4 9.9 5.4 | 15.9 60.6 360 11 6 10.2 5.6
7250 15.6 60.1 355 8 4 10.1 5.5 | 16.6 61.9 360 11 6 9.7 5.3
7000 16.3 61.3 355 8 4 10.0 5.5 | 17.4 63.3 360 11 6 10.1 5.5
6750 17.1 62.8 355 8 4 10.3 5.7 | 18.1 64.6 360 11 5 9.9 5.4
6500 17.9 64.2 355 8 4 10.7 5.9 | 18.8 65.8 360 11 5 9.7 5.3
6250 18.7 65.7 355 7 4 10.5 5.8 | 19.5 67.1 360 10 5 9.0 4.9
6000 19.5 67.1 355 7 4 11.1 6.1 | 20.3 68.5 360 10 5 11.4 6.3
5750 20.5 68.9 355 7 4 18.0 9.9 | 21.3 70.3 360 10 5 15.3 8.4
5500 22.2 72.0 355 7 4 27.5 15.1 | 22.4 72.3 360 9 5 14.5 8.0
________________________________________________________________________________
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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