Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
891
UXUS97 KBOU 101306
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0706 MDT Friday, October 10, 2025
This forecast is for Friday, October 10, 2025:
If the trigger temperature of 78.7 F/26.0 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 19 ft/min (0.1 m/s)
Maximum height of thermals.................. 7607 ft MSL (2282 ft AGL)
Forecast maximum temperature................... 76.0 F/24.9 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................. 6480 ft MSL (1154 ft AGL)
Thermal soaring outlook for Saturday 10/11..... Fair
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....................... 17368 ft MSL (12043 ft AGL)
Wave soaring outlook for Saturday 10/11........ Poor
Remarks...
Sunrise/Sunset.................... 07:05:15 / 18:27:24 MDT
Total possible sunshine........... 11 hr 22 min 9 sec (682 min 9 sec)
Altitude of sun at 12:46:19 MDT... 43.17 degrees
Upper air data from numerical model forecast valid on 10/10/2025 at 0600 MDT
Freezing level.................. 14728 ft MSL (9403 ft AGL)
Convective condensation level... 18033 ft MSL (12708 ft AGL)
Lifted condensation level....... 15468 ft MSL (10142 ft AGL)
Lifted index.................... +4.3
K index......................... +20.6
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 -66.8 -88.2 280 46 24 4.2 2.3 M M M M M
45000 -58.9 -74.0 275 65 34 6.6 3.6 M M M M M
40000 -49.6 -57.3 270 86 44 3.1 1.7 M M M M M
38000 -47.8 -54.0 270 71 37 3.0 1.6 M M M M M
36000 -46.1 -51.0 265 57 29 2.6 1.4 M M M M M
34000 -41.5 -42.7 260 49 25 8.6 4.7 M M M M M
32000 -36.4 -33.5 255 42 22 8.4 4.6 M M M M M
30000 -31.2 -24.2 260 33 17 7.5 4.1 44.7 112.4 15.3 M M
29000 -29.0 -20.2 265 29 15 7.5 4.1 43.9 110.9 14.8 M M
28000 -26.8 -16.2 270 25 13 6.5 3.6 43.0 109.5 14.4 M M
27000 -25.0 -13.0 265 21 11 6.2 3.4 41.6 106.8 13.4 M M
26000 -23.1 -9.6 255 18 9 6.2 3.4 40.2 104.4 12.5 M M
25000 -21.2 -6.2 245 14 7 6.5 3.6 39.0 102.3 11.7 M M
24000 -18.9 -2.0 235 15 8 7.9 4.3 38.2 100.8 11.1 M M
23000 -16.5 2.3 235 16 8 7.9 4.3 37.5 99.5 10.7 M M
22000 -14.2 6.4 230 16 8 7.3 4.0 36.9 98.5 10.4 M M
21000 -12.3 9.9 230 15 8 6.1 3.4 35.6 96.1 9.3 M M
20000 -10.6 12.9 230 14 7 6.3 3.4 34.4 93.8 8.3 M M
19500 -9.7 14.5 230 13 7 6.4 3.5 33.8 92.8 7.8 M M
19000 -8.8 16.2 225 13 7 6.0 3.3 33.2 91.7 7.2 M M
18500 -7.9 17.8 225 12 6 6.0 3.3 32.5 90.6 6.7 M M
18000 -7.1 19.2 220 12 6 6.1 3.3 31.9 89.5 6.1 M M
17500 -6.2 20.8 215 12 6 6.2 3.4 31.3 88.3 5.5 M M
17000 -5.3 22.5 210 13 7 6.1 3.4 30.7 87.2 5.0 M M
16500 -3.9 25.0 200 14 7 6.8 3.7 29.9 85.8 4.2 M M
16000 -2.9 26.8 195 14 7 7.0 3.8 29.4 84.9 3.8 M M
15500 -1.8 28.8 190 14 7 8.7 4.8 29.1 84.4 3.5 M M
15000 -0.5 31.1 185 14 7 8.6 4.7 28.9 84.0 3.4 M M
14500 0.8 33.4 180 14 7 8.9 4.9 28.7 83.7 3.2 M M
14000 2.2 36.0 180 14 7 8.8 4.9 28.6 83.5 3.1 M M
13500 3.5 38.3 180 14 7 9.0 4.9 28.5 83.2 3.0 M M
13000 4.8 40.6 180 14 7 9.0 5.0 28.3 83.0 2.9 M M
12500 6.2 43.2 180 14 7 8.8 4.8 28.2 82.8 2.9 M M
12000 7.5 45.5 180 15 8 8.7 4.7 28.0 82.5 2.7 M M
11500 8.8 47.8 180 16 8 8.5 4.7 27.9 82.2 2.6 M M
11000 10.0 50.0 180 16 8 8.2 4.5 27.7 81.8 2.4 M M
10500 11.3 52.3 180 17 9 4.7 2.6 27.5 81.4 2.2 M M
10250 11.5 52.7 180 17 9 4.7 2.6 26.9 80.4 1.6 M M
10000 12.1 53.8 180 17 9 10.5 5.8 26.8 80.3 1.6 M M
9750 12.9 55.2 180 18 9 11.0 6.0 26.9 80.4 1.6 M M
9500 13.7 56.7 180 18 9 8.0 4.4 26.9 80.5 1.7 M M
9250 14.1 57.4 180 18 9 4.7 2.6 26.6 79.9 1.4 M M
9000 14.6 58.3 185 18 9 8.3 4.6 26.3 79.4 1.1 M M
8750 15.3 59.5 180 18 9 10.4 5.7 26.3 79.4 1.1 M M
8500 16.0 60.8 180 17 9 7.4 4.1 26.3 79.3 1.1 M M
8250 16.4 61.5 185 17 9 5.6 3.1 26.0 78.8 0.8 M M
8000 16.9 62.4 185 16 8 6.7 3.7 25.7 78.3 0.5 M M
7750 17.4 63.3 185 15 8 6.3 3.5 25.5 77.9 0.3 M M
7500 17.7 63.9 185 14 7 3.8 2.1 25.2 77.3 -0.1 114 0.6
7250 17.9 64.2 185 13 7 2.1 1.1 24.6 76.3 -0.6 101 0.5
7000 18.1 64.6 185 11 6 4.5 2.5 24.1 75.4 -1.2 88 0.4
6750 18.4 65.1 190 10 5 0.8 0.4 23.7 74.6 -1.6 72 0.4
6500 18.1 64.6 190 8 4 -5.6 -3.0 22.7 72.8 -2.6 73 0.4
6250 17.7 63.9 195 6 3 -5.2 -2.8 21.5 70.7 -3.8 79 0.4
6000 17.2 63.0 210 4 2 -6.1 -3.3 20.4 68.7 -5.0 85 0.4
5750 16.5 61.7 235 3 2 -14.6 -8.0 18.9 66.1 -6.4 98 0.5
5500 15.0 59.0 225 2 1 -26.1 -14.3 16.6 61.9 -8.8 138 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/10/2025 at 0900 MDT | 10/10/2025 at 1200 MDT
|
CAPE... 0.0 LI... +1.2 | CAPE... +0.2 LI... +1.0
CINH... -0.2 K Index... +23.7 | CINH... -0.2 K Index... +25.7
|
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 -66.7 -88.1 275 46 24 4.7 2.6 | -67.8 -90.0 270 51 26 4.6 2.5
45000 -58.6 -73.5 275 66 34 6.3 3.4 | -59.6 -75.3 270 72 37 6.4 3.5
40000 -49.7 -57.5 265 83 43 3.4 1.8 | -50.4 -58.7 265 78 40 4.2 2.3
38000 -47.7 -53.9 265 70 36 3.3 1.8 | -47.9 -54.2 265 68 35 4.2 2.3
36000 -45.7 -50.3 265 58 30 2.9 1.6 | -45.4 -49.7 265 58 30 3.8 2.1
34000 -41.3 -42.3 260 49 25 8.2 4.5 | -40.8 -41.4 260 51 26 8.3 4.5
32000 -35.7 -32.3 250 41 21 8.9 4.9 | -35.2 -31.4 255 45 23 8.9 4.9
30000 -30.9 -23.6 245 35 18 8.1 4.5 | -30.1 -22.2 255 40 21 8.5 4.7
29000 -28.5 -19.3 240 33 17 8.1 4.5 | -27.6 -17.7 255 38 19 8.5 4.7
28000 -26.1 -15.0 235 30 15 6.7 3.7 | -25.1 -13.2 255 35 18 7.4 4.0
27000 -24.3 -11.7 235 26 14 6.4 3.5 | -23.0 -9.4 255 32 17 7.1 3.9
26000 -22.4 -8.3 225 23 12 6.4 3.5 | -20.9 -5.6 245 29 15 7.1 3.9
25000 -20.5 -4.9 220 20 10 6.5 3.5 | -18.9 -2.0 240 27 14 7.0 3.9
24000 -18.5 -1.3 215 19 10 6.7 3.7 | -17.0 1.4 235 26 13 6.1 3.4
23000 -16.5 2.3 210 18 9 6.7 3.7 | -15.2 4.6 225 25 13 6.2 3.4
22000 -14.5 5.9 205 17 9 6.6 3.6 | -13.5 7.7 215 25 13 6.1 3.3
21000 -12.6 9.3 200 16 8 6.3 3.5 | -11.8 10.8 210 25 13 5.7 3.1
20000 -10.8 12.6 200 15 8 6.3 3.5 | -10.1 13.8 205 24 12 5.7 3.1
19500 -9.8 14.4 200 15 8 6.4 3.5 | -9.3 15.3 200 24 12 5.8 3.2
19000 -9.0 15.8 200 15 8 5.6 3.1 | -8.5 16.7 195 24 12 5.0 2.7
18500 -8.2 17.2 195 15 8 5.7 3.1 | -7.8 18.0 195 24 12 5.0 2.7
18000 -7.4 18.7 190 15 8 5.9 3.2 | -7.1 19.2 190 24 12 5.1 2.8
17500 -6.5 20.3 185 16 8 6.2 3.4 | -5.9 21.4 185 24 13 5.5 3.0
17000 -5.2 22.6 180 18 9 6.8 3.7 | -5.1 22.8 185 25 13 5.5 3.0
16500 -4.1 24.6 180 18 9 7.4 4.0 | -4.3 24.3 180 25 13 5.5 3.0
16000 -3.0 26.6 180 19 10 7.5 4.1 | -3.5 25.7 180 26 13 5.5 3.0
15500 -1.8 28.8 180 20 10 8.5 4.6 | -2.7 27.1 180 26 13 5.8 3.2
15000 -0.6 30.9 180 20 10 8.4 4.6 | -1.8 28.8 175 27 14 5.7 3.1
14500 0.7 33.3 180 21 11 8.4 4.6 | -0.8 30.6 175 27 14 7.7 4.2
14000 1.9 35.4 180 21 11 8.4 4.6 | 0.3 32.5 175 27 14 7.9 4.3
13500 3.2 37.8 180 22 11 8.6 4.7 | 1.5 34.7 175 27 14 8.6 4.7
13000 4.4 39.9 180 22 11 8.6 4.7 | 2.9 37.2 180 27 14 9.0 4.9
12500 5.7 42.3 180 22 11 8.6 4.7 | 4.2 39.6 180 27 14 9.1 5.0
12000 7.0 44.6 185 22 12 8.6 4.7 | 5.6 42.1 180 26 13 9.3 5.1
11500 8.3 46.9 185 22 12 8.5 4.7 | 6.9 44.4 185 25 13 9.1 5.0
11000 9.5 49.1 185 22 11 8.3 4.5 | 8.2 46.8 185 23 12 8.5 4.7
10500 10.8 51.4 185 22 11 4.8 2.6 | 9.5 49.1 190 22 11 5.2 2.8
10250 11.0 51.8 185 21 11 4.2 2.3 | 9.7 49.5 190 21 11 4.7 2.6
10000 11.6 52.9 185 21 11 10.4 5.7 | 10.3 50.5 190 21 11 10.5 5.8
9750 12.4 54.3 185 20 10 11.4 6.3 | 11.1 52.0 195 20 10 11.6 6.4
9500 13.2 55.8 190 20 10 7.5 4.1 | 11.9 53.4 195 19 10 8.5 4.6
9250 13.5 56.3 190 19 10 3.4 1.9 | 12.3 54.1 200 18 9 4.8 2.6
9000 13.9 57.0 190 18 9 6.8 3.7 | 12.8 55.0 200 18 9 7.6 4.2
8750 14.5 58.1 190 17 9 8.6 4.7 | 13.4 56.1 205 17 9 9.6 5.3
8500 15.1 59.2 190 16 8 5.6 3.1 | 14.1 57.4 210 16 8 6.5 3.6
8250 15.4 59.7 190 15 8 3.7 2.0 | 14.4 57.9 210 15 8 4.3 2.3
8000 15.7 60.3 190 14 7 5.1 2.8 | 14.8 58.6 210 14 7 5.4 3.0
7750 16.1 61.0 190 12 6 4.8 2.6 | 15.2 59.4 215 13 7 5.3 2.9
7500 16.3 61.3 190 10 5 2.0 1.1 | 15.6 60.1 220 11 6 3.2 1.7
7250 16.4 61.5 190 9 5 0.2 0.1 | 15.7 60.3 220 9 5 1.5 0.8
7000 16.5 61.7 190 8 4 3.0 1.6 | 15.9 60.6 225 7 4 3.6 2.0
6750 16.7 62.1 190 6 3 0.2 0.1 | 16.4 61.5 230 5 3 7.1 3.9
6500 16.4 61.5 195 4 2 -5.2 -2.8 | 16.9 62.4 235 4 2 6.7 3.7
6250 16.1 61.0 210 3 1 -3.6 -2.0 | 17.3 63.1 250 3 2 6.1 3.4
6000 15.7 60.3 250 2 1 -7.0 -3.8 | 17.8 64.0 275 2 1 4.3 2.4
5750 15.1 59.2 295 2 1 -5.0 -2.8 | 18.1 64.6 315 3 2 9.1 5.0
5500 15.2 59.4 305 2 1 7.4 4.1 | 19.4 66.9 320 3 2 23.4 12.8
10/10/2025 at 1500 MDT | 10/10/2025 at 1800 MDT
|
CAPE... +0.3 LI... +0.6 | CAPE... +1.7 LI... -0.3
CINH... -0.5 K Index... +28.8 | CINH... -4.9 K Index... +28.9
|
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 -67.5 -89.5 270 51 26 4.2 2.3 | -67.3 -89.1 270 52 27 4.1 2.3
45000 -59.7 -75.5 270 70 36 6.6 3.6 | -60.1 -76.2 270 71 36 6.5 3.5
40000 -50.2 -58.4 265 77 40 4.7 2.6 | -50.4 -58.7 265 80 41 4.4 2.4
38000 -47.4 -53.3 260 68 35 4.7 2.6 | -47.7 -53.9 260 70 36 4.4 2.4
36000 -44.6 -48.3 260 60 31 4.4 2.4 | -45.1 -49.2 260 60 31 4.0 2.2
34000 -40.3 -40.5 255 51 26 7.7 4.2 | -40.4 -40.7 255 51 26 8.5 4.7
32000 -35.7 -32.3 250 42 21 7.5 4.1 | -35.3 -31.5 255 44 22 8.3 4.6
30000 -30.2 -22.4 245 38 19 8.3 4.5 | -29.9 -21.8 250 38 19 8.1 4.4
29000 -27.8 -18.0 245 37 19 8.3 4.5 | -27.5 -17.5 250 35 18 8.1 4.4
28000 -25.3 -13.5 245 36 18 7.5 4.1 | -25.1 -13.2 250 33 17 7.5 4.1
27000 -23.2 -9.8 245 33 17 7.3 4.0 | -22.9 -9.2 245 32 16 7.3 4.0
26000 -21.1 -6.0 245 31 16 7.3 4.0 | -20.8 -5.4 245 31 16 7.3 4.0
25000 -18.9 -2.0 245 29 15 7.2 4.0 | -18.6 -1.5 240 30 15 7.3 4.0
24000 -17.0 1.4 245 27 14 6.5 3.6 | -16.7 1.9 240 28 14 6.3 3.5
23000 -15.0 5.0 250 26 13 6.6 3.6 | -14.9 5.2 235 25 13 6.3 3.5
22000 -13.1 8.4 250 25 13 6.5 3.6 | -13.0 8.6 235 23 12 6.3 3.5
21000 -11.3 11.7 250 23 12 6.1 3.4 | -11.3 11.7 235 21 11 5.9 3.2
20000 -9.5 14.9 255 22 11 6.2 3.4 | -9.6 14.7 235 18 9 5.9 3.2
19500 -8.7 16.3 255 22 11 6.2 3.4 | -8.8 16.2 235 17 9 5.9 3.2
19000 -7.8 18.0 255 21 11 5.7 3.1 | -7.9 17.8 235 16 8 5.9 3.2
18500 -7.0 19.4 250 21 11 5.6 3.1 | -7.1 19.2 235 15 8 5.9 3.2
18000 -6.2 20.8 250 21 11 5.6 3.0 | -6.2 20.8 235 14 7 5.9 3.3
17500 -5.4 22.3 245 22 11 5.2 2.8 | -5.3 22.5 240 14 7 6.0 3.3
17000 -4.7 23.5 240 22 11 5.2 2.8 | -4.5 23.9 240 13 7 6.0 3.3
16500 -3.6 25.5 235 22 11 5.3 2.9 | -3.6 25.5 240 13 6 5.8 3.2
16000 -2.8 27.0 230 22 11 5.2 2.9 | -2.4 27.7 240 11 6 5.8 3.2
15500 -2.0 28.4 225 22 11 6.2 3.4 | -1.6 29.1 235 11 5 5.5 3.0
15000 -1.1 30.0 220 21 11 6.1 3.3 | -0.8 30.6 230 10 5 5.5 3.0
14500 -0.2 31.6 215 20 11 6.7 3.7 | 0.0 32.0 225 10 5 6.0 3.3
14000 0.8 33.4 210 20 10 6.9 3.8 | 0.9 33.6 215 11 6 6.2 3.4
13500 1.8 35.2 210 20 10 7.9 4.3 | 1.7 35.1 210 11 6 6.8 3.7
13000 3.1 37.6 205 19 10 8.7 4.8 | 2.8 37.0 200 12 6 7.5 4.1
12500 4.4 39.9 200 19 10 8.7 4.7 | 3.9 39.0 195 14 7 7.8 4.3
12000 5.7 42.3 200 18 9 8.5 4.7 | 5.1 41.2 190 15 7 8.2 4.5
11500 6.9 44.4 195 18 9 8.5 4.6 | 6.3 43.3 190 15 8 8.2 4.5
11000 8.1 46.6 195 17 9 8.0 4.4 | 7.5 45.5 185 16 8 8.0 4.4
10500 9.4 48.9 190 17 9 4.3 2.4 | 8.8 47.8 185 15 8 4.5 2.5
10250 9.5 49.1 185 17 9 4.6 2.5 | 8.9 48.0 180 15 8 4.4 2.4
10000 10.2 50.4 185 17 9 11.0 6.0 | 9.6 49.3 180 15 8 10.8 5.9
9750 11.0 51.8 180 16 8 11.2 6.2 | 10.4 50.7 180 14 7 11.6 6.4
9500 11.8 53.2 175 15 8 9.0 4.9 | 11.3 52.3 180 14 7 9.3 5.1
9250 12.3 54.1 175 15 8 5.6 3.1 | 11.8 53.2 175 13 7 5.4 3.0
9000 12.8 55.0 170 14 7 8.2 4.5 | 12.2 54.0 175 12 6 7.5 4.1
8750 13.5 56.3 170 14 7 11.1 6.1 | 12.9 55.2 175 12 6 10.4 5.7
8500 14.3 57.7 165 13 7 7.9 4.3 | 13.6 56.5 170 11 6 7.7 4.2
8250 14.7 58.5 165 12 6 4.8 2.6 | 14.0 57.2 170 10 5 5.0 2.7
8000 15.2 59.4 165 11 6 7.0 3.9 | 14.4 57.9 165 8 4 6.2 3.4
7750 15.8 60.4 160 10 5 9.3 5.1 | 15.0 59.0 165 7 4 7.9 4.4
7500 16.4 61.5 160 9 5 6.5 3.5 | 15.5 59.9 165 6 3 6.0 3.3
7250 16.8 62.2 155 8 4 3.6 2.0 | 15.8 60.4 165 5 2 3.8 2.1
7000 17.1 62.8 155 6 3 5.9 3.3 | 16.2 61.2 175 3 2 5.2 2.9
6750 17.7 63.9 145 5 3 10.2 5.6 | 16.7 62.1 185 2 1 8.5 4.7
6500 18.5 65.3 140 5 2 9.3 5.1 | 17.4 63.3 210 2 1 8.7 4.8
6250 19.1 66.4 135 4 2 7.8 4.3 | 17.9 64.2 255 2 1 6.8 3.7
6000 19.6 67.3 130 3 1 6.2 3.4 | 18.4 65.1 285 2 1 8.4 4.6
5750 20.1 68.2 105 2 1 9.2 5.0 | 19.0 66.2 300 3 1 8.0 4.4
5500 21.2 70.2 090 2 1 21.2 11.6 | 19.5 67.1 300 3 1 4.4 2.4
________________________________________________________________________________
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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