Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
289
UXUS97 KBOU 180136
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1935 MDT Friday, October 17, 2025
This forecast is for Saturday, October 18, 2025:
If the trigger temperature of 60.9 F/16.0 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 241 ft/min (1.2 m/s)
Maximum height of thermals.................. 10795 ft MSL (5511 ft AGL)
Forecast maximum temperature................... 62.0 F/17.1 C
Time of trigger temperature.................... 1200 MDT
Time of overdevelopment........................ None
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................. 7241 ft MSL (1957 ft AGL)
Thermal soaring outlook for Sunday 10/19....... Good
Wave Soaring Index............................. Fair
Wave Soaring Index trend (to 1800 MDT)......... Trending the same
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 45581 ft MSL (40297 ft AGL)
Wave soaring outlook for Sunday 10/19.......... Good
Remarks...
Sunrise/Sunset.................... 07:13:31 / 18:15:29 MDT
Total possible sunshine........... 11 hr 1 min 58 sec (661 min 58 sec)
Altitude of sun at 12:44:30 MDT... 40.19 degrees
Upper air data from numerical model forecast valid on 10/18/2025 at 0600 MDT
Freezing level.................. 10891 ft MSL (5607 ft AGL)
Convective condensation level... 16478 ft MSL (11194 ft AGL)
Lifted condensation level....... 14122 ft MSL (8838 ft AGL)
Lifted index.................... +3.5
K index......................... +10.4
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 -60.7 -77.3 280 41 21 2.6 1.4 M M M M M
45000 -56.7 -70.1 285 51 26 3.8 2.1 M M M M M
40000 -50.8 -59.4 290 53 27 3.7 2.0 M M M M M
38000 -48.6 -55.5 295 53 27 3.6 2.0 M M M M M
36000 -46.4 -51.5 300 54 28 3.6 2.0 M M M M M
34000 -44.4 -47.9 300 54 28 2.5 1.4 M M M M M
32000 -42.9 -45.2 300 52 27 2.5 1.4 M M M M M
30000 -41.0 -41.8 300 50 26 5.7 3.1 35.8 96.4 14.4 M M
29000 -39.3 -38.7 300 47 24 5.7 3.1 34.1 93.4 13.3 M M
28000 -37.1 -34.8 295 44 23 5.7 3.1 32.2 89.9 12.0 M M
27000 -35.3 -31.5 295 41 21 7.3 4.0 30.9 87.6 11.1 M M
26000 -33.1 -27.6 290 40 20 7.4 4.1 29.9 85.8 10.4 M M
25000 -30.9 -23.6 290 38 20 7.5 4.1 29.0 84.2 9.8 M M
24000 -28.7 -19.7 290 36 19 8.0 4.4 28.3 82.9 9.3 M M
23000 -26.2 -15.2 285 35 18 8.4 4.6 27.7 81.8 8.9 M M
22000 -23.7 -10.7 285 33 17 8.4 4.6 27.2 81.0 8.6 M M
21000 -21.3 -6.3 280 31 16 8.1 4.4 26.8 80.2 8.3 M M
20000 -18.8 -1.8 285 31 16 8.1 4.4 26.1 79.0 7.8 M M
19500 -17.6 0.3 285 31 16 8.1 4.4 25.8 78.5 7.6 M M
19000 -16.4 2.5 285 31 16 8.1 4.4 25.6 78.0 7.5 M M
18500 -15.2 4.6 290 31 16 7.6 4.2 25.3 77.6 7.3 M M
18000 -14.1 6.6 290 30 16 7.4 4.0 24.9 76.8 6.9 M M
17500 -13.1 8.4 290 30 15 7.3 4.0 24.5 76.0 6.6 M M
17000 -12.0 10.4 295 30 15 6.8 3.8 24.0 75.2 6.2 M M
16500 -11.0 12.2 295 29 15 6.9 3.8 23.5 74.3 5.8 M M
16000 -10.0 14.0 300 29 15 6.7 3.7 23.0 73.5 5.4 M M
15500 -9.0 15.8 300 29 15 6.7 3.7 22.5 72.5 5.0 M M
15000 -8.0 17.6 300 29 15 6.4 3.5 22.0 71.6 4.5 M M
14500 -7.1 19.2 300 28 14 6.0 3.3 21.4 70.5 4.0 M M
14000 -5.8 21.6 305 26 13 5.7 3.1 20.4 68.8 3.2 M M
13500 -4.9 23.2 305 25 13 5.7 3.1 19.8 67.6 2.5 M M
13000 -4.1 24.6 305 23 12 5.9 3.3 19.1 66.4 1.9 M M
12500 -3.2 26.2 305 21 11 6.1 3.3 18.5 65.3 1.4 M M
12000 -2.3 27.9 305 20 10 6.9 3.8 17.9 64.3 0.8 M M
11500 -1.2 29.8 305 19 10 7.5 4.1 17.6 63.7 0.5 M M
11000 -0.1 31.8 305 19 10 7.0 3.8 17.2 63.0 0.1 M M
10500 0.9 33.6 305 19 10 5.7 3.1 16.7 62.1 -0.3 409 2.1
10250 1.4 34.5 305 20 10 10.5 5.8 16.5 61.7 -0.6 387 2.0
10000 2.4 36.3 305 20 10 11.7 6.4 16.8 62.2 -0.3 350 1.8
9750 3.0 37.4 305 22 11 7.6 4.1 16.7 62.0 -0.4 324 1.6
9500 3.6 38.5 300 24 12 9.2 5.0 16.6 61.8 -0.5 297 1.5
9250 4.3 39.7 300 26 13 6.9 3.8 16.5 61.7 -0.6 271 1.4
9000 4.7 40.5 300 28 14 5.0 2.7 16.2 61.1 -0.9 252 1.3
8750 5.1 41.2 300 29 15 6.3 3.5 15.8 60.5 -1.3 232 1.2
8500 5.6 42.1 295 29 15 7.5 4.1 15.6 60.1 -1.5 210 1.1
8250 6.1 43.0 295 30 15 5.4 3.0 15.4 59.7 -1.8 188 1.0
8000 6.3 43.3 295 29 15 3.4 1.9 14.9 58.9 -2.2 173 0.9
7750 6.6 43.9 295 27 14 6.3 3.5 14.5 58.2 -2.6 156 0.8
7500 7.2 45.0 295 25 13 8.2 4.5 14.4 57.9 -2.8 132 0.7
7250 7.8 46.0 295 22 12 7.1 3.9 14.2 57.6 -3.0 107 0.5
7000 8.3 46.9 295 21 11 6.6 3.6 14.0 57.2 -3.2 85 0.4
6750 8.8 47.8 295 19 10 7.0 3.9 13.8 56.8 -3.5 63 0.3
6500 9.3 48.7 295 17 9 5.5 3.0 13.5 56.4 -3.7 40 0.2
6250 9.5 49.1 295 15 7 2.2 1.2 13.1 55.6 -4.2 25 0.1
6000 9.7 49.5 290 12 6 1.5 0.8 12.5 54.4 -4.8 14 0.1
5750 9.8 49.6 285 10 5 1.0 0.5 11.9 53.3 -5.4 3 0.0
5500 9.6 49.3 265 6 3 -7.3 -4.0 11.0 51.7 -6.3 1 0.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/18/2025 at 0900 MDT | 10/18/2025 at 1200 MDT
|
CAPE... 0.0 LI... +3.1 | CAPE... +43.2 LI... +1.0
CINH... -0.1 K Index... +12.7 | CINH... -1.7 K Index... +12.7
|
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 -60.8 -77.4 290 43 22 3.6 2.0 | -61.7 -79.1 285 45 23 1.9 1.0
45000 -55.2 -67.4 300 66 34 3.2 1.8 | -57.8 -72.0 285 66 34 6.6 3.6
40000 -50.4 -58.7 290 68 35 3.2 1.8 | -47.8 -54.0 305 59 30 6.5 3.6
38000 -48.5 -55.3 295 70 36 3.0 1.6 | -46.4 -51.5 305 69 35 0.6 0.3
36000 -46.8 -52.2 305 74 38 3.0 1.6 | -46.0 -50.8 310 84 43 0.6 0.3
34000 -45.0 -49.0 310 77 39 3.1 1.7 | -45.4 -49.7 315 97 50 2.5 1.4
32000 -43.1 -45.6 315 72 37 3.1 1.7 | -43.8 -46.8 325 106 54 2.5 1.4
30000 -40.8 -41.4 315 68 35 4.7 2.6 | -40.8 -41.4 330 115 59 8.8 4.8
29000 -39.4 -38.9 315 66 34 4.7 2.6 | -38.2 -36.8 330 114 59 8.8 4.8
28000 -38.0 -36.4 315 65 33 4.7 2.6 | -35.6 -32.1 330 113 58 8.8 4.8
27000 -36.5 -33.7 315 63 32 6.3 3.5 | -33.0 -27.4 330 112 57 6.4 3.5
26000 -34.5 -30.1 315 57 30 6.8 3.7 | -31.2 -24.2 325 106 54 6.1 3.3
25000 -32.4 -26.3 315 52 27 6.8 3.7 | -29.4 -20.9 325 100 51 6.1 3.3
24000 -30.4 -22.7 310 47 24 7.5 4.1 | -27.5 -17.5 320 94 48 5.4 3.0
23000 -27.9 -18.2 310 45 23 8.3 4.6 | -26.2 -15.2 320 87 45 4.6 2.5
22000 -25.5 -13.9 310 43 22 8.3 4.6 | -24.8 -12.6 320 81 42 4.6 2.5
21000 -23.0 -9.4 305 41 21 8.1 4.4 | -23.4 -10.1 315 74 38 5.3 2.9
20000 -20.6 -5.1 305 40 21 8.1 4.4 | -21.8 -7.2 315 66 34 5.4 3.0
19500 -19.4 -2.9 305 40 21 8.1 4.5 | -21.0 -5.8 315 62 32 5.4 3.0
19000 -18.2 -0.8 305 40 21 8.1 4.5 | -20.2 -4.4 315 59 30 5.4 3.0
18500 -17.0 1.4 305 40 21 7.9 4.3 | -19.3 -2.7 315 55 28 6.2 3.4
18000 -15.9 3.4 305 40 21 7.7 4.2 | -18.4 -1.1 310 53 27 6.6 3.6
17500 -14.7 5.5 305 40 21 7.7 4.2 | -17.4 0.7 310 50 26 6.7 3.7
17000 -13.6 7.5 305 39 20 7.3 4.0 | -16.4 2.5 310 48 25 6.8 3.7
16500 -12.5 9.5 305 39 20 7.4 4.1 | -15.4 4.3 310 46 24 6.8 3.7
16000 -10.9 12.4 305 38 19 7.1 3.9 | -14.4 6.1 310 44 23 7.1 3.9
15500 -9.9 14.2 305 37 19 7.1 3.9 | -12.8 9.0 305 42 21 7.1 3.9
15000 -8.8 16.2 305 36 18 6.9 3.8 | -11.8 10.8 305 40 21 7.3 4.0
14500 -7.8 18.0 305 34 18 7.0 3.8 | -10.7 12.7 305 39 20 7.2 4.0
14000 -6.8 19.8 305 34 17 7.1 3.9 | -9.6 14.7 305 38 20 7.7 4.2
13500 -5.7 21.7 310 33 17 7.1 3.9 | -8.5 16.7 305 38 19 7.6 4.2
13000 -4.7 23.5 310 33 17 7.3 4.0 | -7.4 18.7 305 37 19 8.2 4.5
12500 -3.6 25.5 310 33 17 7.4 4.1 | -6.1 21.0 305 37 19 8.3 4.5
12000 -2.5 27.5 305 33 17 6.9 3.8 | -4.9 23.2 305 36 19 8.5 4.6
11500 -1.5 29.3 305 34 17 6.7 3.7 | -3.7 25.3 305 37 19 8.5 4.7
11000 -0.5 31.1 305 34 18 6.7 3.7 | -2.4 27.7 305 36 19 8.6 4.7
10500 0.5 32.9 305 35 18 7.5 4.1 | -1.2 29.8 305 34 17 9.7 5.3
10250 1.0 33.8 305 35 18 3.7 2.1 | -0.5 31.1 305 32 17 4.0 2.2
10000 1.1 34.0 300 35 18 4.3 2.3 | -0.4 31.3 305 32 16 6.1 3.3
9750 1.7 35.1 300 35 18 8.2 4.5 | 0.5 32.9 305 31 16 12.8 7.0
9500 2.2 36.0 300 34 18 7.6 4.2 | 1.3 34.3 310 30 15 12.1 6.6
9250 2.7 36.9 300 34 17 6.2 3.4 | 2.2 36.0 310 28 15 8.4 4.6
9000 3.1 37.6 295 33 17 5.7 3.1 | 2.6 36.7 310 28 14 7.0 3.8
8750 3.6 38.5 295 32 16 8.1 4.5 | 3.4 38.1 310 28 14 11.6 6.4
8500 4.3 39.7 295 30 16 8.9 4.9 | 4.2 39.6 310 27 14 11.6 6.3
8250 4.9 40.8 295 29 15 7.3 4.0 | 5.0 41.0 310 27 14 9.1 5.0
8000 5.3 41.5 295 27 14 6.1 3.4 | 5.6 42.1 310 26 14 7.9 4.3
7750 5.9 42.6 295 25 13 8.9 4.9 | 6.3 43.3 310 26 13 11.2 6.2
7500 6.6 43.9 295 23 12 9.9 5.5 | 7.2 45.0 310 25 13 10.9 6.0
7250 7.3 45.1 295 22 11 7.6 4.2 | 7.9 46.2 315 25 13 8.2 4.5
7000 7.7 45.9 295 20 10 6.0 3.3 | 8.5 47.3 310 25 13 7.5 4.1
6750 8.3 46.9 295 18 9 8.8 4.9 | 9.2 48.6 310 25 13 12.3 6.8
6500 9.0 48.2 295 15 8 8.7 4.8 | 10.2 50.4 315 23 12 12.6 6.9
6250 9.5 49.1 295 13 7 6.0 3.3 | 11.0 51.8 315 23 12 9.4 5.1
6000 9.9 49.8 295 10 5 6.0 3.3 | 11.7 53.1 315 22 12 9.3 5.1
5750 10.4 50.7 295 8 4 6.5 3.6 | 12.5 54.5 315 22 11 13.3 7.3
5500 10.9 51.6 285 5 3 7.2 4.0 | 13.8 56.8 315 19 10 23.8 13.1
10/18/2025 at 1500 MDT | 10/18/2025 at 1800 MDT
|
CAPE... +5.8 LI... +6.4 | CAPE... 0.0 LI... +9.6
CINH... -0.1 K Index... +6.9 | CINH... 0.0 K Index... -6.5
|
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 -61.2 -78.2 295 49 25 2.2 1.2 | -62.1 -79.8 295 48 24 2.6 1.4
45000 -56.9 -70.4 290 66 34 6.5 3.5 | -57.8 -72.0 290 51 26 4.7 2.6
40000 -47.2 -53.0 315 81 42 6.2 3.4 | -50.7 -59.3 315 85 44 4.6 2.5
38000 -47.1 -52.8 315 85 44 -2.2 -1.2 | -50.3 -58.5 315 85 44 -0.6 -0.3
36000 -48.5 -55.3 310 87 45 -2.2 -1.2 | -50.6 -59.1 315 80 41 -0.6 -0.3
34000 -48.5 -55.3 310 89 46 5.1 2.8 | -49.2 -56.6 315 77 40 7.6 4.2
32000 -45.4 -49.7 325 92 47 5.2 2.9 | -44.1 -47.4 320 78 40 7.6 4.2
30000 -40.9 -41.6 330 96 49 8.9 4.9 | -39.3 -38.7 320 78 40 8.3 4.6
29000 -38.3 -36.9 330 96 50 8.9 4.9 | -36.8 -34.2 320 77 40 8.3 4.6
28000 -35.6 -32.1 325 97 50 8.9 4.9 | -34.3 -29.7 320 76 39 8.3 4.6
27000 -32.9 -27.2 325 97 50 9.1 5.0 | -31.8 -25.2 320 76 39 8.3 4.6
26000 -30.2 -22.4 325 96 50 9.1 5.0 | -29.4 -20.9 320 75 39 8.3 4.6
25000 -27.4 -17.3 325 95 49 9.1 5.0 | -26.9 -16.4 320 74 38 8.4 4.6
24000 -24.8 -12.6 325 95 49 8.2 4.5 | -24.4 -11.9 320 73 38 8.1 4.4
23000 -22.4 -8.3 325 93 48 7.9 4.3 | -21.9 -7.4 315 72 37 8.1 4.5
22000 -20.0 -4.0 325 92 47 7.9 4.3 | -19.5 -3.1 315 70 36 8.1 4.5
21000 -17.9 -0.2 320 90 46 4.2 2.3 | -17.1 1.2 315 70 36 7.4 4.1
20000 -16.6 2.1 320 86 44 4.4 2.4 | -14.9 5.2 315 70 36 7.5 4.1
19500 -15.9 3.4 320 84 43 4.4 2.4 | -13.8 7.2 315 70 36 7.5 4.1
19000 -15.3 4.5 320 83 43 4.5 2.4 | -12.7 9.1 315 70 36 7.7 4.2
18500 -14.7 5.5 320 80 41 1.5 0.8 | -11.7 10.9 320 70 36 5.1 2.8
18000 -14.7 5.5 320 73 38 0.3 0.2 | -10.9 12.4 320 68 35 5.1 2.8
17500 -14.7 5.5 315 66 34 0.4 0.2 | -10.1 13.8 320 67 34 4.9 2.7
17000 -14.5 5.9 315 59 30 2.1 1.2 | -9.4 15.1 320 64 33 4.7 2.6
16500 -14.2 6.4 310 52 27 1.8 1.0 | -8.7 16.3 320 62 32 5.0 2.8
16000 -13.7 7.3 305 46 24 5.1 2.8 | -8.3 17.1 320 59 30 1.3 0.7
15500 -12.6 9.3 300 42 21 5.3 2.9 | -8.0 17.6 325 56 29 1.6 0.9
15000 -11.7 10.9 300 40 20 7.1 3.9 | -7.5 18.5 320 51 26 3.3 1.8
14500 -10.6 12.9 300 38 20 6.8 3.8 | -7.0 19.4 315 47 24 3.2 1.7
14000 -9.6 14.7 300 37 19 8.0 4.4 | -6.5 20.3 315 44 23 4.4 2.4
13500 -8.4 16.9 300 35 18 8.0 4.4 | -5.9 21.4 310 42 22 4.2 2.3
13000 -7.2 19.0 300 33 17 7.9 4.3 | -5.2 22.6 305 40 21 5.7 3.2
12500 -6.1 21.0 300 31 16 7.9 4.3 | -4.3 24.3 300 38 20 5.6 3.1
12000 -4.9 23.2 300 29 15 8.2 4.5 | -3.4 25.9 295 36 19 7.8 4.3
11500 -3.7 25.3 300 28 14 8.3 4.5 | -2.2 28.0 295 34 18 8.0 4.4
11000 -2.5 27.5 305 26 13 8.5 4.6 | -1.1 30.0 295 32 17 7.4 4.1
10500 -1.2 29.8 305 24 12 9.6 5.3 | -0.0 32.0 295 30 15 8.3 4.5
10250 -0.6 30.9 310 23 12 3.9 2.1 | 0.5 32.9 295 28 15 3.8 2.1
10000 -0.5 31.1 310 23 12 4.6 2.5 | 0.6 33.1 295 28 14 3.1 1.7
9750 0.2 32.4 315 22 11 10.5 5.8 | 1.1 34.0 300 26 13 7.3 4.0
9500 0.9 33.6 315 21 11 9.9 5.4 | 1.6 34.9 300 23 12 7.1 3.9
9250 1.6 34.9 320 20 10 6.5 3.6 | 2.0 35.6 305 20 11 3.9 2.1
9000 1.9 35.4 325 19 10 4.2 2.3 | 2.1 35.8 305 19 10 1.6 0.9
8750 2.4 36.3 330 18 9 7.8 4.3 | 2.4 36.3 310 17 9 4.6 2.5
8500 3.0 37.4 340 18 9 8.2 4.5 | 2.7 36.9 320 14 7 4.6 2.5
8250 3.5 38.3 345 17 9 7.2 4.0 | 2.9 37.2 325 12 6 2.2 1.2
8000 4.0 39.2 350 17 9 6.9 3.8 | 3.0 37.4 335 10 5 1.2 0.7
7750 4.6 40.3 355 18 9 9.5 5.2 | 3.2 37.8 350 9 5 3.1 1.7
7500 5.4 41.7 360 18 9 10.0 5.5 | 3.5 38.3 015 8 4 5.1 2.8
7250 6.1 43.0 005 18 9 8.4 4.6 | 3.9 39.0 025 8 4 5.8 3.2
7000 6.7 44.1 005 18 9 8.1 4.4 | 4.3 39.7 035 8 4 4.7 2.6
6750 7.4 45.3 010 19 10 10.7 5.9 | 4.7 40.5 045 8 4 8.6 4.7
6500 8.2 46.8 010 19 10 10.9 6.0 | 5.5 41.9 060 9 5 10.1 5.5
6250 8.9 48.0 015 19 10 9.1 5.0 | 6.1 43.0 065 9 5 8.0 4.4
6000 9.6 49.3 015 18 9 8.3 4.5 | 6.7 44.1 070 9 5 6.7 3.7
5750 10.3 50.5 015 18 9 14.0 7.7 | 7.1 44.8 070 10 5 6.8 3.7
5500 11.9 53.4 015 17 9 27.7 15.2 | 7.9 46.2 070 9 4 13.7 7.5
________________________________________________________________________________
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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