Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
613
UXUS97 KBOU 121238
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0637 MDT Sunday, October 12, 2025
This forecast is for Sunday, October 12, 2025:
If the trigger temperature of 71.4 F/21.9 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 327 ft/min (1.7 m/s)
Maximum height of thermals.................. 9908 ft MSL (4622 ft AGL)
Forecast maximum temperature................... 73.0 F/23.2 C
Time of trigger temperature.................... 1300 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................. 6940 ft MSL (1654 ft AGL)
Thermal soaring outlook for Monday 10/13....... 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....................... 40255 ft MSL (34969 ft AGL)
Wave soaring outlook for Monday 10/13.......... Poor
Remarks...
Sunrise/Sunset.................... 07:07:17 / 18:24:21 MDT
Total possible sunshine........... 11 hr 17 min 3 sec (677 min 3 sec)
Altitude of sun at 12:45:49 MDT... 42.41 degrees
Upper air data from numerical model forecast valid on 10/12/2025 at 0600 MDT
Freezing level.................. 14944 ft MSL (9658 ft AGL)
Convective condensation level... 17064 ft MSL (11778 ft AGL)
Lifted condensation level....... 13918 ft MSL (8631 ft AGL)
Lifted index.................... +3.7
K index......................... +0.5
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 -65.2 -85.4 235 65 34 2.0 1.1 M M M M M
45000 -60.6 -77.1 240 97 50 6.4 3.5 M M M M M
40000 -50.9 -59.6 240 109 56 6.4 3.5 M M M M M
38000 -47.1 -52.8 235 107 55 6.4 3.5 M M M M M
36000 -43.3 -45.9 235 105 54 6.4 3.5 M M M M M
34000 -39.9 -39.8 230 97 50 5.1 2.8 M M M M M
32000 -36.5 -33.7 230 83 43 5.0 2.8 M M M M M
30000 -32.6 -26.7 230 73 37 7.5 4.1 43.4 110.0 15.6 M M
29000 -30.3 -22.5 230 69 35 7.5 4.1 42.5 108.4 15.1 M M
28000 -28.1 -18.6 230 65 33 7.5 4.1 41.7 107.0 14.7 M M
27000 -25.8 -14.4 230 61 32 7.4 4.0 40.8 105.4 14.2 M M
26000 -23.6 -10.5 230 59 30 7.4 4.0 39.8 103.7 13.6 M M
25000 -21.4 -6.5 225 56 29 7.4 4.0 39.0 102.2 13.1 M M
24000 -19.2 -2.6 225 54 28 7.0 3.9 38.1 100.6 12.5 M M
23000 -17.1 1.2 230 51 26 7.1 3.9 37.1 98.7 11.8 M M
22000 -15.0 5.0 230 49 25 7.1 3.9 36.1 97.1 11.1 M M
21000 -12.9 8.8 230 46 24 6.9 3.8 35.2 95.4 10.5 M M
20000 -10.8 12.6 230 43 22 6.9 3.8 34.1 93.5 9.7 M M
19500 -9.8 14.4 230 42 22 6.9 3.8 33.7 92.6 9.3 M M
19000 -8.8 16.2 230 41 21 6.9 3.8 33.2 91.8 9.0 M M
18500 -7.7 18.1 230 39 20 7.1 3.9 32.8 91.0 8.6 M M
18000 -6.7 19.9 235 37 19 7.1 3.9 32.3 90.1 8.2 M M
17500 -5.6 21.9 235 36 18 7.1 3.9 31.8 89.3 7.9 M M
17000 -4.5 23.9 235 35 18 7.3 4.0 31.4 88.5 7.5 M M
16500 -3.5 25.7 235 34 18 7.3 4.0 31.0 87.8 7.2 M M
16000 -2.4 27.7 235 33 17 6.8 3.7 30.6 87.0 6.8 M M
15500 -0.9 30.4 240 32 16 6.8 3.7 29.8 85.7 6.2 M M
15000 0.1 32.2 240 30 15 6.9 3.8 29.3 84.8 5.8 M M
14500 1.1 34.0 235 28 14 6.9 3.8 28.9 83.9 5.3 M M
14000 2.1 35.8 235 26 13 7.0 3.9 28.4 83.1 4.9 M M
13500 3.2 37.8 240 25 13 7.0 3.9 27.9 82.3 4.5 M M
13000 4.2 39.6 240 24 13 6.7 3.7 27.5 81.5 4.1 M M
12500 5.1 41.2 245 25 13 6.3 3.4 26.9 80.5 3.5 M M
12000 6.0 42.8 250 26 14 6.2 3.4 26.4 79.5 3.0 M M
11500 6.8 44.2 255 29 15 6.1 3.3 25.8 78.4 2.4 M M
11000 7.7 45.9 255 31 16 5.7 3.1 25.2 77.4 1.8 M M
10500 8.3 46.9 260 33 17 4.0 2.2 24.4 75.9 0.9 M M
10250 8.5 47.3 260 33 17 4.9 2.7 24.0 75.1 0.5 M M
10000 8.9 48.0 260 34 18 5.8 3.2 23.6 74.5 0.1 M M
9750 9.3 48.7 260 34 17 5.6 3.1 23.3 74.0 -0.3 313 1.6
9500 9.7 49.5 260 33 17 5.8 3.2 23.0 73.4 -0.6 293 1.5
9250 10.1 50.2 260 32 16 5.3 2.9 22.7 72.8 -0.9 274 1.4
9000 10.4 50.7 265 31 16 5.3 2.9 22.3 72.2 -1.3 256 1.3
8750 10.8 51.4 265 29 15 6.7 3.7 22.0 71.6 -1.6 236 1.2
8500 11.3 52.3 265 27 14 7.2 4.0 21.8 71.3 -1.9 213 1.1
8250 11.9 53.4 265 25 13 6.9 3.8 21.6 70.9 -2.1 190 1.0
8000 12.4 54.3 265 23 12 7.5 4.1 21.4 70.5 -2.3 168 0.9
7750 13.0 55.4 265 21 11 8.0 4.4 21.3 70.3 -2.4 143 0.7
7500 13.5 56.3 265 18 9 7.8 4.3 21.1 70.0 -2.6 118 0.6
7250 14.1 57.4 260 16 8 7.7 4.2 21.0 69.7 -2.7 93 0.5
7000 14.7 58.5 260 14 7 6.8 3.7 20.8 69.4 -2.9 69 0.4
6750 15.2 59.4 260 13 7 7.2 3.9 20.6 69.0 -3.2 47 0.2
6500 15.8 60.4 250 11 5 9.0 4.9 20.4 68.8 -3.3 21 0.1
6250 16.4 61.5 245 8 4 5.7 3.1 20.3 68.6 -3.4 M M
6000 16.5 61.7 230 7 4 -0.8 -0.4 19.7 67.5 -4.0 M M
5750 16.5 61.7 215 7 4 2.5 1.4 19.0 66.1 -4.8 M M
5500 16.4 61.5 205 6 3 -13.9 -7.6 18.2 64.7 -5.7 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/12/2025 at 0900 MDT | 10/12/2025 at 1200 MDT
|
CAPE... 0.0 LI... +3.4 | CAPE... 0.0 LI... +3.5
CINH... 0.0 K Index... +11.2 | CINH... -0.1 K Index... +5.3
|
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 -65.3 -85.5 235 78 40 2.2 1.2 | -66.2 -87.2 235 85 44 2.3 1.3
45000 -61.1 -78.0 240 104 53 6.0 3.3 | -61.7 -79.1 235 106 55 6.7 3.7
40000 -51.7 -61.1 230 119 61 6.5 3.6 | -51.2 -60.2 230 120 62 6.9 3.8
38000 -47.5 -53.5 230 117 60 6.9 3.8 | -46.9 -52.4 230 120 62 7.2 3.9
36000 -43.4 -46.1 230 115 59 6.9 3.8 | -42.7 -44.9 230 121 62 7.2 3.9
34000 -39.9 -39.8 230 106 55 5.0 2.8 | -39.1 -38.4 225 114 59 5.0 2.7
32000 -36.9 -34.4 230 91 47 5.0 2.8 | -36.1 -33.0 230 101 52 5.0 2.7
30000 -32.8 -27.0 230 79 41 7.1 3.9 | -32.2 -26.0 230 92 47 6.8 3.7
29000 -30.7 -23.3 230 76 39 7.1 3.9 | -30.1 -22.2 230 90 46 6.8 3.7
28000 -28.5 -19.3 230 73 37 7.1 3.9 | -28.1 -18.6 230 88 45 6.8 3.7
27000 -26.4 -15.5 230 70 36 7.0 3.9 | -26.2 -15.2 230 86 44 6.1 3.4
26000 -24.3 -11.7 230 67 35 7.0 3.9 | -24.3 -11.7 235 83 43 6.1 3.4
25000 -22.2 -8.0 230 65 34 7.0 3.9 | -22.5 -8.5 235 80 41 6.1 3.4
24000 -20.1 -4.2 230 63 32 6.9 3.8 | -20.7 -5.3 235 77 39 5.9 3.2
23000 -18.1 -0.6 230 60 31 6.9 3.8 | -18.9 -2.0 235 72 37 5.9 3.2
22000 -16.0 3.2 230 58 30 6.9 3.8 | -17.1 1.2 235 68 35 5.9 3.2
21000 -14.0 6.8 230 55 28 6.3 3.5 | -15.4 4.3 235 64 33 6.1 3.3
20000 -12.1 10.2 230 52 27 6.4 3.5 | -13.5 7.7 240 61 31 6.1 3.3
19500 -11.1 12.0 235 50 26 6.4 3.5 | -12.6 9.3 240 59 30 6.1 3.3
19000 -10.2 13.6 235 49 25 6.4 3.5 | -11.7 10.9 240 57 29 6.1 3.3
18500 -9.3 15.3 235 47 24 5.8 3.2 | -10.8 12.6 240 55 29 6.2 3.4
18000 -8.4 16.9 235 45 23 5.7 3.1 | -9.9 14.2 240 54 28 6.3 3.4
17500 -7.6 18.3 235 44 22 5.8 3.2 | -9.0 15.8 240 53 27 6.3 3.4
17000 -6.7 19.9 235 42 22 6.2 3.4 | -8.0 17.6 240 52 27 6.2 3.4
16500 -5.8 21.6 235 41 21 6.2 3.4 | -6.7 19.9 240 50 26 6.2 3.4
16000 -4.4 24.1 240 39 20 6.8 3.7 | -5.8 21.6 240 48 25 5.9 3.2
15500 -3.4 25.9 240 37 19 6.8 3.7 | -5.0 23.0 240 47 24 6.0 3.3
15000 -2.4 27.7 240 36 19 6.7 3.7 | -4.1 24.6 240 45 23 5.8 3.2
14500 -1.4 29.5 240 35 18 6.7 3.7 | -3.3 26.1 240 43 22 5.9 3.2
14000 -0.5 31.1 240 34 17 6.7 3.7 | -2.5 27.5 240 41 21 6.2 3.4
13500 0.5 32.9 245 32 16 6.7 3.7 | -1.6 29.1 240 38 20 6.3 3.4
13000 1.5 34.7 245 30 16 6.0 3.3 | -0.7 30.7 240 36 18 6.3 3.5
12500 2.2 36.0 250 31 16 5.4 3.0 | 0.1 32.2 240 32 16 6.3 3.5
12000 3.0 37.4 255 31 16 5.2 2.9 | 1.0 33.8 240 28 14 6.4 3.5
11500 3.6 38.5 255 30 15 4.9 2.7 | 1.9 35.4 240 26 14 6.4 3.5
11000 4.3 39.7 260 28 15 4.6 2.5 | 2.9 37.2 240 25 13 5.7 3.1
10500 4.9 40.8 265 26 14 3.4 1.9 | 3.5 38.3 240 22 11 3.8 2.1
10250 5.2 41.4 270 26 13 6.6 3.6 | 3.8 38.8 240 20 10 7.1 3.9
10000 5.8 42.4 270 25 13 8.7 4.8 | 4.5 40.1 245 21 11 9.0 5.0
9750 6.3 43.3 270 24 12 6.7 3.7 | 5.1 41.2 245 20 11 6.6 3.6
9500 6.8 44.2 275 22 11 6.4 3.5 | 5.5 41.9 250 20 10 6.5 3.6
9250 7.3 45.1 275 20 10 7.6 4.2 | 6.0 42.8 250 19 10 7.0 3.9
9000 7.9 46.2 275 20 10 8.8 4.8 | 6.6 43.9 255 20 10 6.3 3.4
8750 8.5 47.3 280 18 10 8.0 4.4 | 7.0 44.6 260 18 9 5.2 2.8
8500 9.1 48.4 280 17 9 7.7 4.2 | 7.4 45.3 265 17 9 5.3 2.9
8250 9.7 49.5 285 15 8 7.9 4.3 | 7.8 46.0 275 16 8 5.9 3.2
8000 10.3 50.5 290 14 7 8.5 4.7 | 8.3 46.9 280 15 8 8.8 4.8
7750 10.9 51.6 295 13 7 8.4 4.6 | 9.0 48.2 280 13 7 9.3 5.1
7500 11.5 52.7 295 12 6 8.0 4.4 | 9.6 49.3 285 13 7 8.1 4.5
7250 12.1 53.8 300 11 6 7.8 4.3 | 10.3 50.5 290 13 7 8.7 4.8
7000 12.6 54.7 305 11 5 7.2 3.9 | 10.9 51.6 290 13 7 9.2 5.1
6750 13.2 55.8 310 11 5 7.6 4.2 | 11.6 52.9 295 12 6 10.0 5.5
6500 13.8 56.8 315 9 5 8.6 4.7 | 12.4 54.3 295 12 6 10.4 5.7
6250 14.4 57.9 325 8 4 6.7 3.7 | 13.2 55.8 295 12 6 10.9 6.0
6000 14.8 58.6 325 7 4 6.0 3.3 | 14.0 57.2 300 12 6 12.1 6.7
5750 15.2 59.4 320 6 3 1.8 1.0 | 14.9 58.8 300 11 6 9.4 5.1
5500 14.8 58.6 330 4 2 -8.3 -4.6 | 15.6 60.1 300 11 6 12.7 6.9
10/12/2025 at 1500 MDT | 10/12/2025 at 1800 MDT
|
CAPE... 0.0 LI... +3.1 | CAPE... 0.0 LI... +0.8
CINH... 0.0 K Index... -0.1 | CINH... 0.0 K Index... +6.9
|
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 -65.2 -85.4 235 87 45 2.3 1.3 | -63.8 -82.8 240 85 44 1.7 1.0
45000 -60.8 -77.4 240 113 58 5.8 3.2 | -60.4 -76.7 240 117 60 5.3 2.9
40000 -52.0 -61.6 230 129 66 5.8 3.2 | -52.4 -62.3 235 134 69 5.2 2.9
38000 -47.6 -53.7 230 128 66 6.7 3.7 | -49.0 -56.2 230 130 67 5.9 3.2
36000 -43.5 -46.3 230 126 65 6.7 3.7 | -45.0 -49.0 235 123 63 5.9 3.2
34000 -40.0 -40.0 230 119 61 5.4 2.9 | -41.5 -42.7 235 116 60 5.7 3.1
32000 -36.7 -34.1 230 109 56 5.4 2.9 | -38.1 -36.6 235 107 55 5.7 3.1
30000 -33.2 -27.8 235 102 52 6.5 3.6 | -34.6 -30.3 240 98 51 6.0 3.3
29000 -31.2 -24.2 235 100 51 6.5 3.6 | -32.8 -27.0 240 94 48 6.0 3.3
28000 -29.3 -20.7 235 97 50 6.5 3.6 | -31.0 -23.8 245 89 46 6.0 3.3
27000 -27.4 -17.3 235 94 48 5.3 2.9 | -29.2 -20.6 245 85 44 6.6 3.6
26000 -25.8 -14.4 235 89 46 5.4 3.0 | -27.2 -17.0 245 81 42 6.5 3.6
25000 -24.2 -11.6 240 84 43 5.4 3.0 | -25.2 -13.4 245 77 40 6.5 3.6
24000 -22.6 -8.7 240 79 41 5.6 3.1 | -23.3 -9.9 245 73 37 5.7 3.1
23000 -20.9 -5.6 240 73 38 5.6 3.1 | -21.7 -7.1 245 67 34 5.4 3.0
22000 -19.2 -2.6 240 67 34 5.6 3.1 | -20.0 -4.0 245 61 31 5.4 3.0
21000 -17.5 0.5 240 61 31 6.0 3.3 | -18.4 -1.1 245 55 28 4.9 2.7
20000 -15.7 3.7 240 56 29 6.0 3.3 | -17.0 1.4 245 48 25 4.9 2.7
19500 -14.3 6.3 240 52 27 6.0 3.3 | -16.3 2.7 245 44 23 4.9 2.7
19000 -13.4 7.9 240 49 25 6.0 3.3 | -15.2 4.6 240 39 20 5.2 2.9
18500 -12.5 9.5 240 47 24 6.8 3.8 | -14.2 6.4 240 36 19 7.8 4.3
18000 -11.4 11.5 240 46 24 6.8 3.7 | -13.0 8.6 235 35 18 7.6 4.2
17500 -10.4 13.3 240 44 23 6.9 3.8 | -11.9 10.6 235 33 17 8.1 4.4
17000 -9.4 15.1 240 43 22 7.0 3.8 | -10.6 12.9 230 32 17 8.2 4.5
16500 -8.4 16.9 240 41 21 7.0 3.9 | -9.4 15.1 230 31 16 8.3 4.5
16000 -7.3 18.9 240 40 20 7.4 4.1 | -8.2 17.2 230 31 16 8.2 4.5
15500 -6.2 20.8 240 38 20 7.5 4.1 | -7.0 19.4 225 30 15 8.3 4.6
15000 -5.1 22.8 235 37 19 6.8 3.7 | -5.8 21.6 225 29 15 7.8 4.3
14500 -4.1 24.6 235 35 18 6.9 3.8 | -4.7 23.5 225 27 14 7.9 4.4
14000 -3.2 26.2 235 34 17 6.4 3.5 | -3.5 25.7 220 25 13 8.0 4.4
13500 -2.2 28.0 235 31 16 6.4 3.5 | -2.4 27.7 220 24 12 8.1 4.4
13000 -1.3 29.7 230 29 15 6.4 3.5 | -1.2 29.8 215 22 11 8.5 4.7
12500 -0.4 31.3 235 26 14 6.5 3.6 | 0.1 32.2 215 20 10 8.7 4.8
12000 0.5 32.9 235 24 12 7.2 4.0 | 1.4 34.5 215 18 9 7.9 4.4
11500 1.6 34.9 235 21 11 7.9 4.3 | 2.4 36.3 210 16 8 7.4 4.1
11000 2.8 37.0 235 18 9 7.5 4.1 | 3.4 38.1 205 13 7 6.4 3.5
10500 3.8 38.8 235 15 8 6.3 3.4 | 4.3 39.7 195 10 5 5.2 2.9
10250 4.3 39.7 235 14 7 9.9 5.4 | 4.7 40.5 190 8 4 7.4 4.1
10000 5.2 41.4 245 13 7 11.2 6.1 | 5.4 41.7 185 7 3 9.0 5.0
9750 5.9 42.6 245 12 6 8.5 4.7 | 6.0 42.8 180 5 3 7.8 4.3
9500 6.5 43.7 250 11 6 9.2 5.1 | 6.6 43.9 170 4 2 8.4 4.6
9250 7.2 45.0 255 10 5 9.0 4.9 | 7.3 45.1 155 2 1 7.3 4.0
9000 7.9 46.2 260 9 5 9.3 5.1 | 7.8 46.0 085 3 1 7.8 4.3
8750 8.6 47.5 265 9 5 9.6 5.3 | 8.5 47.3 070 3 2 9.0 4.9
8500 9.3 48.7 265 9 5 9.5 5.2 | 9.1 48.4 055 3 2 8.8 4.8
8250 10.1 50.2 270 9 5 9.8 5.4 | 9.8 49.6 045 4 2 8.5 4.7
8000 10.8 51.4 275 9 4 10.1 5.5 | 10.4 50.7 040 6 3 8.5 4.7
7750 11.6 52.9 280 8 4 9.7 5.3 | 11.1 52.0 040 7 4 9.1 5.0
7500 12.3 54.1 280 8 4 9.7 5.3 | 11.8 53.2 040 7 4 9.7 5.3
7250 13.0 55.4 280 8 4 9.2 5.1 | 12.5 54.5 035 7 4 8.1 4.5
7000 13.7 56.7 285 8 4 8.8 4.8 | 13.0 55.4 035 9 5 6.7 3.7
6750 14.4 57.9 285 8 4 10.3 5.7 | 13.6 56.5 035 11 5 10.1 5.6
6500 15.2 59.4 290 8 4 11.3 6.2 | 14.5 58.1 035 10 5 11.6 6.4
6250 16.0 60.8 290 8 4 10.6 5.8 | 15.3 59.5 035 9 5 9.3 5.1
6000 16.8 62.2 290 8 4 10.9 6.0 | 15.9 60.6 040 11 6 8.3 4.5
5750 17.6 63.7 295 8 4 9.0 4.9 | 16.6 61.9 040 12 6 9.6 5.3
5500 18.3 64.9 295 7 4 12.4 6.8 | 17.3 63.1 040 9 5 8.8 4.8
________________________________________________________________________________
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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