Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
442
UXUS97 KBOU 110300
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
2059 MDT Friday, October 10, 2025
This forecast is for Saturday, October 11, 2025:
If the trigger temperature of 74.4 F/23.5 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 175 ft/min (0.9 m/s)
Maximum height of thermals.................. 10335 ft MSL (5029 ft AGL)
Forecast maximum temperature................... 76.0 F/24.9 C
Time of trigger temperature.................... 1345 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 7951 ft MSL (2645 ft AGL)
Thermal soaring outlook for Sunday 10/12....... Fair
Wave Soaring Index............................. Poor
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....................... 39829 ft MSL (34523 ft AGL)
Wave soaring outlook for Sunday 10/12.......... Good
Remarks...
Sunrise/Sunset.................... 07:06:16 / 18:25:52 MDT
Total possible sunshine........... 11 hr 19 min 36 sec (679 min 36 sec)
Altitude of sun at 12:46:04 MDT... 42.79 degrees
Upper air data from numerical model forecast valid on 10/11/2025 at 0600 MDT
Freezing level.................. 15018 ft MSL (9712 ft AGL)
Convective condensation level... 13916 ft MSL (8610 ft AGL)
Lifted condensation level....... 12461 ft MSL (7154 ft AGL)
Lifted index.................... +1.3
K index......................... +27.9
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 -66.9 -88.4 260 49 25 4.0 2.2 M M M M M
45000 -60.0 -76.0 260 67 34 6.3 3.5 M M M M M
40000 -50.5 -58.9 260 81 42 5.7 3.1 M M M M M
38000 -47.1 -52.8 260 72 37 5.7 3.1 M M M M M
36000 -43.2 -45.8 255 63 32 5.6 3.1 M M M M M
34000 -39.3 -38.7 250 54 28 6.7 3.7 M M M M M
32000 -35.3 -31.5 245 45 23 6.5 3.6 M M M M M
30000 -30.3 -22.5 240 39 20 8.8 4.8 46.0 114.7 16.3 M M
29000 -27.7 -17.9 240 36 19 8.8 4.8 45.6 114.1 16.2 M M
28000 -25.1 -13.2 240 34 17 8.5 4.6 45.4 113.7 16.2 M M
27000 -22.9 -9.2 235 33 17 7.3 4.0 44.4 111.9 15.5 M M
26000 -20.7 -5.3 235 32 17 7.3 4.0 43.5 110.2 14.9 M M
25000 -18.5 -1.3 235 32 16 7.4 4.1 42.6 108.8 14.4 M M
24000 -16.5 2.3 235 31 16 6.5 3.5 41.5 106.7 13.6 M M
23000 -14.6 5.7 235 30 15 6.5 3.6 40.3 104.5 12.7 M M
22000 -12.7 9.1 230 28 15 6.5 3.6 39.2 102.5 11.9 M M
21000 -10.9 12.4 230 28 14 6.0 3.3 37.9 100.2 10.8 M M
20000 -9.2 15.4 230 28 14 6.1 3.3 36.5 97.8 9.8 M M
19500 -8.3 17.1 230 28 14 6.1 3.3 35.9 96.7 9.2 M M
19000 -7.4 18.7 230 28 14 6.0 3.3 35.3 95.6 8.8 M M
18500 -6.6 20.1 230 28 14 5.8 3.2 34.6 94.4 8.2 M M
18000 -5.3 22.5 230 28 14 5.9 3.2 33.6 92.5 7.3 M M
17500 -4.5 23.9 230 27 14 6.2 3.4 33.0 91.4 6.8 M M
17000 -3.6 25.5 230 27 14 6.2 3.4 32.4 90.3 6.2 M M
16500 -2.7 27.1 230 26 13 6.2 3.4 31.8 89.3 5.7 M M
16000 -1.7 28.9 230 25 13 6.3 3.4 31.2 88.2 5.2 M M
15500 -0.8 30.6 230 24 12 6.7 3.7 30.6 87.2 4.7 M M
15000 0.2 32.4 230 23 12 7.0 3.8 30.2 86.3 4.2 M M
14500 1.2 34.2 230 22 11 7.2 3.9 29.7 85.5 3.8 M M
14000 2.4 36.3 230 21 11 7.9 4.3 29.4 84.9 3.5 M M
13500 3.5 38.3 230 21 11 7.9 4.3 29.1 84.3 3.3 M M
13000 4.6 40.3 230 20 10 6.3 3.4 28.6 83.5 2.9 M M
12500 5.5 41.9 230 19 10 6.4 3.5 28.1 82.6 2.4 M M
12000 6.5 43.7 230 18 9 7.0 3.9 27.6 81.7 1.9 M M
11500 7.5 45.5 225 17 9 7.1 3.9 27.1 80.9 1.4 M M
11000 8.4 47.1 225 16 8 5.2 2.9 26.6 79.9 0.9 M M
10500 9.2 48.6 225 15 8 4.3 2.4 25.9 78.6 0.2 M M
10250 9.6 49.3 225 15 8 8.9 4.9 25.5 78.0 -0.1 368 1.9
10000 10.4 50.7 225 14 7 9.5 5.2 25.7 78.2 -0.1 336 1.7
9750 10.8 51.4 225 13 7 5.0 2.8 25.4 77.7 -0.4 316 1.6
9500 11.2 52.2 220 12 6 6.8 3.7 25.1 77.1 -0.6 295 1.5
9250 11.7 53.1 220 12 6 4.3 2.4 24.8 76.6 -0.9 275 1.4
9000 11.9 53.4 220 11 6 4.5 2.5 24.3 75.8 -1.4 260 1.3
8750 12.4 54.3 220 11 5 6.5 3.6 24.0 75.2 -1.7 239 1.2
8500 12.8 55.0 225 10 5 6.3 3.5 23.7 74.7 -2.0 219 1.1
8250 13.2 55.8 225 9 5 4.3 2.4 23.5 74.2 -2.3 199 1.0
8000 13.4 56.1 225 9 4 2.4 1.3 22.9 73.2 -2.9 185 0.9
7750 13.6 56.5 225 8 4 3.1 1.7 22.4 72.3 -3.4 172 0.9
7500 13.8 56.8 230 7 4 2.8 1.6 21.9 71.4 -3.9 158 0.8
7250 14.0 57.2 235 6 3 2.1 1.2 21.3 70.4 -4.5 146 0.7
7000 14.1 57.4 240 5 3 1.7 0.9 20.7 69.3 -5.1 135 0.7
6750 14.3 57.7 245 4 2 2.3 1.2 20.1 68.2 -5.7 123 0.6
6500 14.4 57.9 265 3 2 1.0 0.6 19.5 67.2 -6.3 111 0.6
6250 14.4 57.9 280 3 1 -0.7 -0.4 18.8 65.8 -7.1 105 0.5
6000 14.3 57.7 295 3 1 -0.7 -0.4 18.0 64.4 -7.9 99 0.5
5750 14.3 57.7 305 3 1 0.2 0.1 17.2 63.0 -8.6 92 0.5
5500 14.3 57.7 320 2 1 -1.5 -0.8 16.5 61.7 -9.4 86 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/11/2025 at 0900 MDT | 10/11/2025 at 1200 MDT
|
CAPE... 0.0 LI... +0.6 | CAPE... +21.0 LI... +0.2
CINH... -1.0 K Index... +27.1 | CINH... -25.3 K Index... +28.2
|
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 -66.5 -87.7 255 45 23 4.1 2.3 | -66.9 -88.4 250 51 26 3.8 2.1
45000 -59.5 -75.1 255 65 33 6.0 3.3 | -60.3 -76.5 255 74 38 6.0 3.3
40000 -50.5 -58.9 255 85 44 5.6 3.1 | -51.3 -60.3 255 85 44 6.0 3.3
38000 -47.1 -52.8 255 79 40 5.7 3.1 | -47.6 -53.7 250 74 38 6.0 3.3
36000 -43.7 -46.7 250 72 37 5.7 3.1 | -44.0 -47.2 245 63 32 6.1 3.3
34000 -39.2 -38.6 250 60 31 7.0 3.8 | -39.6 -39.3 240 54 28 7.9 4.3
32000 -35.0 -31.0 245 49 25 6.8 3.7 | -34.3 -29.7 235 46 24 7.7 4.2
30000 -30.3 -22.5 235 43 22 8.1 4.4 | -29.6 -21.3 235 45 23 7.9 4.3
29000 -27.9 -18.2 235 41 21 8.1 4.5 | -27.2 -17.0 235 44 23 7.9 4.3
28000 -25.5 -13.9 230 39 20 8.0 4.4 | -24.9 -12.8 235 44 23 7.8 4.3
27000 -23.2 -9.8 230 38 19 7.5 4.1 | -22.7 -8.9 235 45 23 7.3 4.0
26000 -21.0 -5.8 230 37 19 7.5 4.1 | -20.5 -4.9 235 45 23 7.3 4.0
25000 -18.8 -1.8 225 36 19 7.6 4.2 | -18.4 -1.1 235 45 23 7.4 4.0
24000 -16.8 1.8 225 35 18 6.5 3.5 | -16.4 2.5 235 45 23 6.6 3.6
23000 -14.9 5.2 225 34 17 6.5 3.6 | -14.4 6.1 230 45 23 6.6 3.6
22000 -13.0 8.6 225 33 17 6.5 3.6 | -12.5 9.5 230 45 23 6.7 3.7
21000 -11.2 11.8 225 32 16 6.2 3.4 | -10.7 12.7 230 44 22 5.8 3.2
20000 -9.4 15.1 225 30 16 6.2 3.4 | -9.0 15.8 230 42 21 5.8 3.2
19500 -8.5 16.7 220 30 15 6.2 3.4 | -8.2 17.2 230 40 21 5.9 3.2
19000 -7.6 18.3 220 29 15 6.2 3.4 | -7.3 18.9 230 39 20 5.8 3.2
18500 -6.7 19.9 220 29 15 6.1 3.3 | -6.5 20.3 230 39 20 5.5 3.0
18000 -5.8 21.6 220 28 15 6.1 3.4 | -5.7 21.7 230 38 19 5.5 3.0
17500 -5.0 23.0 215 28 14 5.6 3.1 | -4.9 23.2 230 37 19 5.8 3.2
17000 -4.2 24.4 215 27 14 5.6 3.1 | -4.1 24.6 230 36 19 5.8 3.2
16500 -2.9 26.8 215 27 14 5.7 3.1 | -2.8 27.0 230 35 18 5.9 3.3
16000 -2.1 28.2 215 26 13 5.7 3.1 | -1.9 28.6 225 34 18 6.0 3.3
15500 -1.3 29.7 215 25 13 6.0 3.3 | -1.1 30.0 225 33 17 6.0 3.3
15000 -0.4 31.3 215 24 13 6.3 3.5 | -0.2 31.6 225 32 17 6.2 3.4
14500 0.5 32.9 220 23 12 6.4 3.5 | 0.7 33.3 220 31 16 6.2 3.4
14000 1.5 34.7 220 22 11 6.6 3.6 | 1.7 35.1 220 30 15 6.9 3.8
13500 2.5 36.5 220 21 11 6.6 3.6 | 2.7 36.9 220 29 15 6.8 3.7
13000 3.5 38.3 220 20 10 7.4 4.0 | 3.7 38.7 220 29 15 7.1 3.9
12500 4.6 40.3 220 19 10 7.3 4.0 | 4.7 40.5 215 28 15 7.1 3.9
12000 5.7 42.3 215 18 9 7.6 4.2 | 5.7 42.3 215 28 14 7.1 3.9
11500 6.8 44.2 215 17 9 7.6 4.2 | 6.8 44.2 215 27 14 7.2 3.9
11000 7.9 46.2 215 17 9 7.3 4.0 | 7.8 46.0 210 27 14 6.2 3.4
10500 9.0 48.2 215 16 8 8.3 4.5 | 8.7 47.7 210 27 14 5.2 2.8
10250 9.5 49.1 210 16 8 3.5 1.9 | 9.1 48.4 210 27 14 9.4 5.2
10000 9.6 49.3 210 15 8 4.4 2.4 | 9.9 49.8 210 25 13 10.0 5.5
9750 10.3 50.5 210 14 7 9.4 5.2 | 10.4 50.7 210 24 13 5.9 3.3
9500 10.9 51.6 210 14 7 9.1 5.0 | 10.9 51.6 205 24 12 7.6 4.2
9250 11.5 52.7 210 14 7 5.4 3.0 | 11.4 52.5 205 23 12 5.0 2.7
9000 11.7 53.1 205 13 7 4.2 2.3 | 11.7 53.1 205 23 12 4.8 2.6
8750 12.2 54.0 210 12 6 7.4 4.1 | 12.2 54.0 205 21 11 6.8 3.8
8500 12.7 54.9 215 12 6 6.7 3.7 | 12.7 54.9 200 20 10 6.7 3.7
8250 13.2 55.8 215 11 6 5.1 2.8 | 13.1 55.6 200 18 10 5.3 2.9
8000 13.4 56.1 215 10 5 3.5 1.9 | 13.4 56.1 200 18 9 4.2 2.3
7750 13.7 56.7 215 9 5 4.2 2.3 | 13.8 56.8 200 17 9 5.2 2.9
7500 14.0 57.2 220 8 4 3.6 2.0 | 14.2 57.6 195 15 8 5.5 3.0
7250 14.2 57.6 220 8 4 2.0 1.1 | 14.5 58.1 190 13 7 3.4 1.9
7000 14.2 57.6 220 7 4 1.1 0.6 | 14.7 58.5 190 12 6 2.1 1.2
6750 14.3 57.7 220 6 3 1.5 0.8 | 14.9 58.8 185 10 5 5.6 3.1
6500 14.4 57.9 225 5 3 -0.4 -0.2 | 15.4 59.7 180 8 4 7.2 3.9
6250 14.2 57.6 230 4 2 -2.1 -1.2 | 15.9 60.6 175 6 3 6.4 3.5
6000 14.0 57.2 230 4 2 -2.6 -1.4 | 16.3 61.3 165 5 2 5.9 3.3
5750 13.8 56.8 235 3 2 1.2 0.6 | 16.8 62.2 150 4 2 8.9 4.9
5500 14.2 57.6 230 2 1 8.3 4.6 | 17.7 63.9 130 3 1 16.8 9.2
10/11/2025 at 1500 MDT | 10/11/2025 at 1800 MDT
|
CAPE... +265.1 LI... -1.2 | CAPE... +32.9 LI... -0.3
CINH... -34.0 K Index... +28.1 | CINH... -100.1 K Index... +25.4
|
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 -67.0 -88.6 245 56 29 3.5 1.9 | -66.8 -88.2 245 59 30 3.2 1.7
45000 -60.4 -76.7 250 78 40 6.1 3.4 | -60.5 -76.9 255 80 41 6.6 3.6
40000 -51.1 -60.0 245 86 44 6.9 3.8 | -50.6 -59.1 245 86 44 6.9 3.8
38000 -47.0 -52.6 245 80 41 6.8 3.8 | -46.5 -51.7 245 84 43 6.8 3.8
36000 -42.9 -45.2 240 74 38 6.8 3.7 | -42.4 -44.3 245 81 42 6.8 3.7
34000 -38.9 -38.0 235 64 33 6.7 3.7 | -38.8 -37.8 240 73 38 5.6 3.1
32000 -34.4 -29.9 225 54 28 6.8 3.7 | -35.4 -31.7 230 63 33 5.6 3.1
30000 -29.7 -21.5 225 50 26 8.2 4.5 | -30.3 -22.5 225 60 31 8.7 4.7
29000 -27.3 -17.1 225 49 25 8.3 4.5 | -27.7 -17.9 225 59 31 8.7 4.8
28000 -24.8 -12.6 225 48 25 8.3 4.5 | -25.2 -13.4 225 59 30 8.8 4.9
27000 -22.7 -8.9 225 47 24 7.0 3.8 | -23.0 -9.4 230 56 29 6.8 3.8
26000 -20.6 -5.1 230 45 23 7.0 3.9 | -20.9 -5.6 235 51 26 6.9 3.8
25000 -18.6 -1.5 230 44 22 7.0 3.9 | -18.9 -2.0 240 48 25 6.9 3.8
24000 -16.6 2.1 235 42 22 6.2 3.4 | -16.9 1.6 245 46 24 6.4 3.5
23000 -14.8 5.4 240 41 21 6.1 3.4 | -15.0 5.0 245 45 23 6.4 3.5
22000 -13.0 8.6 240 39 20 6.2 3.4 | -13.2 8.2 245 44 23 6.5 3.5
21000 -11.2 11.8 245 39 20 6.4 3.5 | -11.2 11.8 250 42 22 6.7 3.6
20000 -9.3 15.3 245 38 19 6.4 3.5 | -9.3 15.3 250 39 20 6.7 3.7
19500 -8.4 16.9 245 37 19 6.4 3.5 | -8.3 17.1 250 38 19 6.7 3.7
19000 -7.4 18.7 245 37 19 6.4 3.5 | -7.3 18.9 250 36 19 6.7 3.7
18500 -6.5 20.3 245 36 19 6.5 3.5 | -6.2 20.8 250 34 18 7.4 4.1
18000 -5.6 21.9 245 35 18 6.5 3.5 | -5.2 22.6 250 33 17 7.3 4.0
17500 -4.6 23.7 245 35 18 6.3 3.4 | -4.1 24.6 250 31 16 6.9 3.8
17000 -3.7 25.3 245 34 18 6.1 3.4 | -3.1 26.4 250 30 15 6.5 3.6
16500 -2.9 26.8 245 34 17 6.1 3.4 | -2.2 28.0 250 29 15 6.5 3.6
16000 -1.6 29.1 250 33 17 6.0 3.3 | -1.4 29.5 250 27 14 4.8 2.7
15500 -0.7 30.7 250 33 17 5.9 3.3 | -0.4 31.3 255 25 13 5.0 2.7
15000 0.1 32.2 250 31 16 5.8 3.2 | 0.3 32.5 255 23 12 4.8 2.6
14500 0.9 33.6 250 29 15 5.7 3.1 | 0.9 33.6 255 21 11 4.6 2.5
14000 1.8 35.2 250 27 14 6.5 3.6 | 1.7 35.1 255 18 9 7.0 3.8
13500 2.7 36.9 250 25 13 6.4 3.5 | 2.6 36.7 255 16 8 6.8 3.7
13000 3.7 38.7 250 23 12 7.3 4.0 | 3.7 38.7 255 13 7 7.8 4.3
12500 4.8 40.6 245 22 11 7.4 4.1 | 4.8 40.6 255 11 6 8.0 4.4
12000 5.9 42.6 240 21 11 7.7 4.2 | 6.0 42.8 250 10 5 8.3 4.6
11500 7.0 44.6 235 20 10 7.8 4.3 | 7.2 45.0 250 9 4 8.5 4.6
11000 8.1 46.6 230 19 10 6.7 3.7 | 8.4 47.1 255 7 4 7.8 4.3
10500 9.0 48.2 225 19 10 5.8 3.2 | 9.5 49.1 255 6 3 7.1 3.9
10250 9.5 49.1 220 19 10 10.0 5.5 | 10.1 50.2 260 6 3 9.2 5.1
10000 10.3 50.5 220 18 9 10.2 5.6 | 10.8 51.4 260 6 3 9.0 5.0
9750 10.9 51.6 215 17 9 6.8 3.7 | 11.3 52.3 265 5 3 7.0 3.8
9500 11.4 52.5 215 17 9 7.2 4.0 | 11.9 53.4 270 5 3 7.4 4.1
9250 11.9 53.4 210 17 9 8.9 4.9 | 12.4 54.3 270 5 2 7.7 4.2
9000 12.7 54.9 210 16 8 9.6 5.2 | 13.0 55.4 275 5 2 7.9 4.3
8750 13.3 55.9 205 16 8 7.9 4.3 | 13.6 56.5 275 4 2 7.4 4.1
8500 13.9 57.0 205 15 8 8.6 4.7 | 14.1 57.4 275 4 2 7.8 4.3
8250 14.5 58.1 205 15 8 7.4 4.1 | 14.7 58.5 275 4 2 6.8 3.7
8000 15.0 59.0 200 15 8 7.4 4.1 | 15.1 59.2 280 3 2 6.2 3.4
7750 15.6 60.1 200 14 7 8.7 4.8 | 15.6 60.1 290 3 1 7.3 4.0
7500 16.2 61.2 200 13 6 9.1 5.0 | 16.1 61.0 295 2 1 8.0 4.4
7250 16.9 62.4 200 11 6 7.6 4.2 | 16.7 62.1 305 2 1 6.5 3.6
7000 17.4 63.3 200 11 5 6.5 3.6 | 17.1 62.8 320 2 1 4.2 2.3
6750 17.9 64.2 200 10 5 9.4 5.1 | 17.4 63.3 340 3 1 5.0 2.7
6500 18.7 65.7 200 8 4 10.8 5.9 | 17.8 64.0 355 3 2 6.6 3.6
6250 19.4 66.9 200 7 4 9.3 5.1 | 18.2 64.8 005 4 2 4.0 2.2
6000 20.1 68.2 200 6 3 8.5 4.7 | 18.3 64.9 005 5 2 1.0 0.5
5750 20.7 69.3 205 5 3 9.4 5.2 | 18.5 65.3 005 5 3 5.9 3.2
5500 21.5 70.7 205 4 2 11.7 6.4 | 19.1 66.4 360 5 2 10.7 5.9
________________________________________________________________________________
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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