Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
575
UXUS97 KBOU 301329
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0728 MDT Saturday, August 30, 2025
This forecast is for Saturday, August 30, 2025:
If the trigger temperature of 69.2 F/20.7 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 912 ft/min (4.6 m/s)
Maximum height of thermals.................. 14251 ft MSL (8926 ft AGL)
Forecast maximum temperature................... 79.0 F/26.6 C
Time of trigger temperature.................... 1045 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 11567 ft MSL (6242 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)................ Neither
Potential height of wave....................... 36122 ft MSL (30797 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.................. 13897 ft MSL (8572 ft AGL)
Convective condensation level... 10932 ft MSL (5607 ft AGL)
Lifted condensation level....... 12534 ft MSL (7209 ft AGL)
Lifted index.................... -4.3
K index......................... +29.8
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 -64.2 -83.6 245 36 18 1.6 0.9 M M M M M
45000 -59.4 -74.9 250 61 31 6.7 3.7 M M M M M
40000 -49.2 -56.6 250 76 39 7.1 3.9 M M M M M
38000 -45.0 -49.0 245 79 40 7.1 3.9 M M M M M
36000 -40.7 -41.3 245 81 42 7.1 3.9 M M M M M
34000 -36.4 -33.5 245 77 40 6.1 3.3 M M M M M
32000 -32.8 -27.0 245 71 36 6.1 3.3 M M M M M
30000 -30.3 -22.5 250 57 30 3.6 2.0 46.6 115.9 15.6 M M
29000 -29.2 -20.6 255 50 25 3.6 2.0 44.2 111.6 13.9 M M
28000 -28.1 -18.6 255 42 22 4.0 2.2 42.0 107.6 12.4 M M
27000 -26.5 -15.7 255 37 19 5.7 3.1 40.2 104.4 11.1 M M
26000 -24.8 -12.6 260 34 17 5.7 3.1 38.7 101.6 10.0 M M
25000 -23.1 -9.6 260 30 15 5.5 3.0 37.3 99.1 9.0 M M
24000 -20.7 -5.3 260 28 14 9.2 5.1 36.6 97.9 8.5 M M
23000 -17.9 -0.2 260 27 14 9.3 5.1 36.4 97.6 8.4 M M
22000 -15.1 4.8 260 26 14 9.6 5.3 36.3 97.4 8.4 M M
21000 -12.9 8.8 260 24 12 7.2 3.9 35.5 96.0 7.8 M M
20000 -10.8 12.6 265 21 11 7.2 4.0 34.6 94.3 7.0 M M
19500 -9.7 14.5 265 20 10 7.3 4.0 34.2 93.6 6.7 M M
19000 -8.7 16.3 265 18 10 6.2 3.4 33.8 92.9 6.3 M M
18500 -7.5 18.5 260 17 9 5.6 3.1 32.7 90.9 5.3 M M
18000 -6.8 19.8 260 16 8 5.3 2.9 32.0 89.6 4.7 M M
17500 -6.1 21.0 260 15 8 5.1 2.8 31.2 88.1 3.9 M M
17000 -5.4 22.3 260 14 7 5.2 2.9 30.4 86.7 3.2 M M
16500 -4.6 23.7 260 14 7 6.1 3.3 29.7 85.5 2.5 M M
16000 -3.7 25.3 260 13 7 6.0 3.3 29.1 84.4 1.9 M M
15500 -2.9 26.8 260 12 6 6.1 3.4 28.5 83.3 1.3 M M
15000 -2.0 28.4 265 12 6 6.2 3.4 27.9 82.2 0.7 M M
14500 -1.1 30.0 270 12 6 6.6 3.6 27.3 81.1 0.2 M M
14000 -0.1 31.8 275 11 6 6.9 3.8 26.8 80.3 -0.3 684 3.5
13500 0.9 33.6 280 11 6 6.8 3.7 26.4 79.5 -0.8 640 3.3
13000 1.8 35.2 285 11 5 6.5 3.6 25.8 78.5 -1.3 597 3.0
12500 2.7 36.9 290 10 5 6.3 3.5 25.3 77.6 -1.8 554 2.8
12000 3.6 38.5 295 10 5 5.6 3.1 24.7 76.4 -2.5 514 2.6
11500 4.4 39.9 305 10 5 5.9 3.2 24.0 75.3 -3.1 475 2.4
11000 5.4 41.7 310 9 5 7.0 3.9 23.5 74.4 -3.6 431 2.2
10500 6.4 43.5 315 9 5 5.5 3.0 23.1 73.6 -4.1 386 2.0
10250 6.7 44.1 315 9 5 3.5 1.9 22.7 72.8 -4.5 370 1.9
10000 7.0 44.6 320 9 5 7.4 4.1 22.3 72.1 -4.9 352 1.8
9750 7.7 45.9 325 9 5 10.2 5.6 22.3 72.1 -5.0 324 1.6
9500 8.4 47.1 330 9 5 8.1 4.4 22.2 72.0 -5.0 296 1.5
9250 8.9 48.0 335 10 5 4.5 2.5 22.0 71.6 -5.3 275 1.4
9000 9.2 48.6 335 10 5 6.0 3.3 21.6 70.8 -5.7 257 1.3
8750 9.8 49.6 340 10 5 9.2 5.0 21.4 70.6 -5.9 232 1.2
8500 10.4 50.7 345 10 5 6.9 3.8 21.3 70.4 -6.0 207 1.1
8250 10.8 51.4 350 10 5 4.9 2.7 21.0 69.8 -6.4 188 1.0
8000 11.1 52.0 350 10 5 5.3 2.9 20.7 69.2 -6.7 169 0.9
7750 11.5 52.7 355 10 5 5.7 3.2 20.3 68.6 -7.1 151 0.8
7500 11.9 53.4 355 10 5 5.2 2.9 20.0 68.0 -7.5 132 0.7
7250 12.2 54.0 360 10 5 4.4 2.4 19.6 67.3 -7.9 114 0.6
7000 12.6 54.7 360 11 5 5.2 2.8 19.2 66.6 -8.3 97 0.5
6750 13.0 55.4 360 11 5 8.2 4.5 19.0 66.2 -8.6 76 0.4
6500 13.6 56.5 360 10 5 8.0 4.4 18.9 66.1 -8.7 51 0.3
6250 14.1 57.4 360 9 5 6.8 3.7 18.7 65.7 -9.0 29 0.1
6000 14.6 58.3 355 9 5 5.4 3.0 18.5 65.3 -9.3 8 0.0
5750 14.9 58.8 355 9 5 4.4 2.4 18.1 64.5 -9.8 M M
5500 15.3 59.5 355 7 3 8.7 4.8 17.8 64.1 -10.1 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/30/2025 at 0900 MDT | 08/30/2025 at 1200 MDT
|
CAPE... +553.4 LI... -1.9 | CAPE... +639.7 LI... -2.6
CINH... -17.1 K Index... +28.2 | CINH... -2.9 K Index... +26.2
|
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 -63.4 -82.1 250 39 20 2.7 1.5 | -62.4 -80.3 250 42 22 3.1 1.7
45000 -58.0 -72.4 250 64 33 5.7 3.2 | -56.9 -70.4 255 63 32 4.9 2.7
40000 -49.2 -56.6 250 85 44 6.9 3.8 | -49.3 -56.7 255 78 40 6.6 3.6
38000 -45.1 -49.2 250 85 44 6.9 3.8 | -45.4 -49.7 260 75 39 6.5 3.6
36000 -41.0 -41.8 250 85 44 6.8 3.7 | -41.6 -42.9 260 73 38 6.4 3.5
34000 -37.8 -36.0 250 74 38 3.9 2.1 | -38.8 -37.8 260 61 31 3.2 1.8
32000 -35.5 -31.9 250 60 31 3.9 2.2 | -36.9 -34.4 260 47 24 3.3 1.8
30000 -32.6 -26.7 255 47 24 5.3 2.9 | -33.7 -28.7 260 37 19 6.0 3.3
29000 -31.0 -23.8 255 40 21 5.3 2.9 | -31.9 -25.4 265 33 17 6.0 3.3
28000 -29.4 -20.9 260 34 17 5.6 3.0 | -30.1 -22.2 265 29 15 6.3 3.5
27000 -27.5 -17.5 260 31 16 6.8 3.7 | -27.9 -18.2 265 27 14 7.5 4.1
26000 -25.4 -13.7 260 29 15 6.8 3.7 | -25.7 -14.3 270 26 13 7.5 4.1
25000 -23.4 -10.1 260 27 14 6.7 3.7 | -23.5 -10.3 270 25 13 7.5 4.1
24000 -21.1 -6.0 260 26 13 8.4 4.6 | -21.1 -6.0 270 24 12 7.9 4.3
23000 -18.5 -1.3 260 25 13 8.4 4.6 | -18.8 -1.8 270 24 12 7.9 4.3
22000 -16.0 3.2 260 25 13 8.6 4.7 | -16.4 2.5 270 23 12 8.0 4.4
21000 -13.8 7.2 260 23 12 7.1 3.9 | -14.3 6.3 270 22 11 6.9 3.8
20000 -11.8 10.8 260 20 10 7.2 4.0 | -12.3 9.9 270 20 10 6.9 3.8
19500 -10.7 12.7 265 19 10 7.3 4.0 | -11.3 11.7 275 19 10 7.0 3.8
19000 -9.7 14.5 265 18 9 6.2 3.4 | -10.4 13.3 275 18 9 6.3 3.5
18500 -8.5 16.7 270 16 8 5.8 3.2 | -9.5 14.9 280 17 9 6.1 3.3
18000 -7.7 18.1 275 15 8 6.0 3.3 | -8.2 17.2 285 16 8 6.2 3.4
17500 -6.8 19.8 275 14 7 6.1 3.4 | -7.3 18.9 290 16 8 6.3 3.5
17000 -5.9 21.4 280 14 7 6.1 3.4 | -6.3 20.7 295 16 8 6.4 3.5
16500 -5.1 22.8 285 14 7 5.7 3.1 | -5.4 22.3 300 16 8 6.7 3.7
16000 -4.3 24.3 285 13 7 5.7 3.1 | -4.4 24.1 300 15 8 6.7 3.7
15500 -3.5 25.7 290 13 7 6.2 3.4 | -3.5 25.7 305 15 8 6.4 3.5
15000 -2.6 27.3 295 13 7 6.3 3.4 | -2.5 27.5 310 15 8 6.4 3.5
14500 -1.7 28.9 300 13 6 6.2 3.4 | -1.6 29.1 315 14 7 6.6 3.6
14000 -0.8 30.6 310 12 6 6.1 3.4 | -0.6 30.9 315 14 7 6.7 3.7
13500 0.1 32.2 315 12 6 6.1 3.4 | 0.3 32.5 320 14 7 6.9 3.8
13000 1.0 33.8 325 12 6 6.1 3.4 | 1.4 34.5 325 13 7 7.1 3.9
12500 1.9 35.4 335 13 7 6.4 3.5 | 2.4 36.3 325 13 7 7.3 4.0
12000 2.9 37.2 345 13 7 7.2 3.9 | 3.5 38.3 330 12 6 7.5 4.1
11500 3.9 39.0 350 14 7 7.3 4.0 | 4.5 40.1 335 12 6 7.5 4.1
11000 5.0 41.0 355 14 7 7.7 4.2 | 5.6 42.1 340 11 6 7.4 4.1
10500 6.1 43.0 355 14 7 5.8 3.2 | 6.7 44.1 340 11 5 5.2 2.9
10250 6.4 43.5 355 14 7 3.7 2.0 | 6.9 44.4 345 10 5 3.8 2.1
10000 6.8 44.2 355 14 7 7.9 4.3 | 7.4 45.3 345 10 5 8.1 4.4
9750 7.5 45.5 355 14 7 10.6 5.8 | 8.0 46.4 350 9 5 9.9 5.4
9500 8.2 46.8 355 14 7 7.9 4.4 | 8.6 47.5 350 9 5 7.6 4.2
9250 8.6 47.5 355 14 7 4.9 2.7 | 9.0 48.2 355 8 4 4.2 2.3
9000 9.0 48.2 355 13 7 6.1 3.4 | 9.4 48.9 355 8 4 7.6 4.2
8750 9.5 49.1 355 12 6 7.8 4.3 | 10.1 50.2 355 7 3 11.0 6.0
8500 10.0 50.0 355 11 6 6.3 3.4 | 10.8 51.4 360 6 3 8.6 4.7
8250 10.4 50.7 355 11 5 4.9 2.7 | 11.3 52.3 360 5 3 6.9 3.8
8000 10.8 51.4 350 10 5 5.8 3.2 | 11.8 53.2 360 5 3 8.9 4.9
7750 11.2 52.2 350 9 5 6.8 3.7 | 12.6 54.7 005 5 2 10.9 6.0
7500 11.6 52.9 350 8 4 6.1 3.4 | 13.3 55.9 005 4 2 9.4 5.1
7250 12.0 53.6 355 7 4 5.0 2.8 | 13.9 57.0 005 4 2 7.2 4.0
7000 12.3 54.1 355 6 3 6.3 3.5 | 14.5 58.1 005 4 2 10.5 5.8
6750 12.8 55.0 355 6 3 8.8 4.8 | 15.4 59.7 010 4 2 13.2 7.2
6500 13.5 56.3 355 5 3 8.5 4.7 | 16.3 61.3 010 4 2 10.7 5.9
6250 14.0 57.2 350 4 2 8.1 4.4 | 17.1 62.8 010 4 2 10.4 5.7
6000 14.6 58.3 350 4 2 6.7 3.7 | 17.8 64.0 010 3 2 8.4 4.6
5750 15.1 59.2 345 3 2 9.5 5.2 | 18.5 65.3 015 3 2 13.3 7.3
5500 16.1 61.0 345 3 1 19.2 10.6 | 20.0 68.0 015 3 2 28.4 15.6
08/30/2025 at 1500 MDT | 08/30/2025 at 1800 MDT
|
CAPE... +599.7 LI... -3.1 | CAPE... +731.1 LI... -3.0
CINH... -0.4 K Index... +30.1 | CINH... -18.0 K Index... +29.9
|
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 -62.3 -80.1 255 43 22 2.6 1.4 | -62.6 -80.7 270 43 22 1.9 1.0
45000 -57.3 -71.1 260 60 31 5.0 2.8 | -58.4 -73.1 270 60 31 4.9 2.7
40000 -49.6 -57.3 265 68 35 6.6 3.6 | -50.8 -59.4 270 67 34 7.2 3.9
38000 -45.7 -50.3 265 69 36 6.5 3.6 | -46.5 -51.7 270 66 34 7.1 3.9
36000 -41.8 -43.2 270 70 36 6.4 3.5 | -42.3 -44.1 275 66 34 7.0 3.8
34000 -39.1 -38.4 270 58 30 3.1 1.7 | -38.8 -37.8 275 58 30 4.6 2.5
32000 -37.2 -35.0 270 44 23 3.3 1.8 | -36.1 -33.0 280 47 24 4.5 2.5
30000 -33.8 -28.8 270 36 18 6.6 3.6 | -32.9 -27.2 280 39 20 5.6 3.1
29000 -31.8 -25.2 275 32 17 6.6 3.6 | -31.2 -24.2 280 35 18 5.6 3.1
28000 -29.8 -21.6 275 29 15 6.8 3.7 | -29.5 -21.1 280 31 16 6.1 3.4
27000 -27.6 -17.7 280 28 14 7.5 4.1 | -27.3 -17.1 280 29 15 7.4 4.1
26000 -25.4 -13.7 280 26 13 7.5 4.1 | -25.1 -13.2 285 27 14 7.4 4.1
25000 -23.2 -9.8 285 25 13 7.6 4.1 | -22.9 -9.2 285 25 13 7.5 4.1
24000 -21.0 -5.8 285 24 12 7.3 4.0 | -20.7 -5.3 285 24 12 7.2 4.0
23000 -18.8 -1.8 285 23 12 7.4 4.0 | -18.6 -1.5 290 23 12 7.2 4.0
22000 -16.7 1.9 280 23 12 7.5 4.1 | -16.5 2.3 290 23 12 7.3 4.0
21000 -14.7 5.5 285 22 11 6.6 3.6 | -14.3 6.3 295 22 12 7.4 4.0
20000 -12.7 9.1 285 21 11 6.7 3.7 | -12.1 10.2 295 23 12 7.4 4.1
19500 -11.8 10.8 290 21 11 6.7 3.7 | -11.1 12.0 295 23 12 7.4 4.1
19000 -10.8 12.6 290 21 11 6.4 3.5 | -10.0 14.0 295 23 12 6.7 3.7
18500 -9.9 14.2 295 20 10 6.3 3.5 | -9.1 15.6 295 24 12 6.5 3.6
18000 -9.0 15.8 295 20 10 6.4 3.5 | -7.7 18.1 295 25 13 6.1 3.4
17500 -7.4 18.7 300 20 10 7.3 4.0 | -6.8 19.8 295 25 13 6.0 3.3
17000 -6.4 20.5 305 20 10 7.3 4.0 | -6.0 21.2 295 26 13 6.0 3.3
16500 -5.3 22.5 305 20 10 7.0 3.9 | -5.1 22.8 300 26 13 6.1 3.3
16000 -4.3 24.3 305 20 10 7.1 3.9 | -4.3 24.3 300 25 13 6.1 3.3
15500 -3.3 26.1 310 19 10 6.7 3.7 | -3.4 25.9 305 24 12 6.9 3.8
15000 -2.4 27.7 310 18 9 6.7 3.7 | -2.4 27.7 305 22 11 6.8 3.8
14500 -1.4 29.5 310 17 9 7.2 3.9 | -1.4 29.5 305 20 10 7.4 4.1
14000 -0.3 31.5 315 16 8 7.4 4.0 | -0.3 31.5 305 18 9 7.6 4.2
13500 0.7 33.3 315 15 8 7.3 4.0 | 0.8 33.4 305 17 9 7.6 4.2
13000 1.8 35.2 320 14 7 7.3 4.0 | 1.8 35.2 310 16 8 7.6 4.2
12500 2.8 37.0 320 14 7 7.5 4.1 | 2.9 37.2 310 15 8 7.8 4.3
12000 4.0 39.2 320 13 7 8.0 4.4 | 4.1 39.4 310 13 7 8.2 4.5
11500 5.1 41.2 325 12 6 8.1 4.4 | 5.3 41.5 315 12 6 8.1 4.4
11000 6.3 43.3 330 10 5 8.2 4.5 | 6.5 43.7 320 10 5 7.8 4.3
10500 7.5 45.5 335 8 4 4.7 2.6 | 7.6 45.7 335 9 4 4.4 2.4
10250 7.7 45.9 335 8 4 4.8 2.7 | 7.8 46.0 335 8 4 4.1 2.3
10000 8.4 47.1 340 8 4 11.7 6.4 | 8.4 47.1 340 8 4 11.1 6.1
9750 9.3 48.7 340 8 4 12.7 7.0 | 9.3 48.7 345 8 4 12.7 7.0
9500 10.1 50.2 345 7 4 10.0 5.5 | 10.1 50.2 355 8 4 9.6 5.2
9250 10.7 51.3 345 7 4 6.6 3.6 | 10.6 51.1 360 8 4 5.4 3.0
9000 11.2 52.2 345 7 3 9.9 5.4 | 11.1 52.0 005 8 4 8.8 4.8
8750 12.1 53.8 350 7 3 12.7 6.9 | 11.9 53.4 005 8 4 11.9 6.5
8500 13.0 55.4 350 6 3 9.8 5.4 | 12.7 54.9 010 8 4 8.8 4.8
8250 13.6 56.5 350 6 3 7.5 4.1 | 13.2 55.8 015 8 4 6.5 3.6
8000 14.2 57.6 350 6 3 9.7 5.3 | 13.7 56.7 020 9 5 8.1 4.4
7750 15.0 59.0 355 6 3 11.7 6.4 | 14.4 57.9 025 9 5 9.1 5.0
7500 15.8 60.4 355 6 3 9.7 5.3 | 15.0 59.0 025 9 5 7.7 4.2
7250 16.5 61.7 355 6 3 7.7 4.2 | 15.4 59.7 030 10 5 6.2 3.4
7000 17.1 62.8 355 6 3 10.1 5.6 | 15.9 60.6 035 10 5 8.2 4.5
6750 18.0 64.4 355 6 3 12.7 7.0 | 16.6 61.9 035 10 5 10.6 5.8
6500 18.9 66.0 360 6 3 11.0 6.0 | 17.3 63.1 035 10 5 9.1 5.0
6250 19.6 67.3 360 6 3 10.2 5.6 | 17.9 64.2 035 10 5 8.4 4.6
6000 20.4 68.7 360 5 3 9.0 5.0 | 18.5 65.3 035 10 5 7.7 4.2
5750 21.1 70.0 360 5 3 13.9 7.6 | 19.1 66.4 040 10 5 10.1 5.5
5500 22.6 72.7 360 5 3 26.5 14.5 | 20.1 68.2 040 9 5 17.1 9.4
________________________________________________________________________________
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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