Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
670
UXUS97 KBOU 140112
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1912 MDT Monday, October 13, 2025
This forecast is for Tuesday, October 14, 2025:
If the trigger temperature of 64.4 F/18.0 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 403 ft/min (2.0 m/s)
Maximum height of thermals.................. 11763 ft MSL (6445 ft AGL)
Forecast maximum temperature................... 75.0 F/24.3 C
Time of trigger temperature.................... 1130 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................. 10323 ft MSL (5006 ft AGL)
Thermal soaring outlook for Wednesday 10/15.... Good
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... Little change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak NVA
Potential height of wave....................... 18098 ft MSL (12780 ft AGL)
Wave soaring outlook for Wednesday 10/15....... Poor
Remarks... Stronger southwest flow aloft Tuesday and Wednesday. Warmer.
Sunrise/Sunset.................... 07:09:21 / 18:21:20 MDT
Total possible sunshine........... 11 hr 12 min 0 sec (672 min 0 sec)
Altitude of sun at 12:45:20 MDT... 41.66 degrees
Upper air data from numerical model forecast valid on 10/14/2025 at 0600 MDT
Freezing level.................. 15024 ft MSL (9706 ft AGL)
Convective condensation level... 15692 ft MSL (10374 ft AGL)
Lifted condensation level....... 13289 ft MSL (7971 ft AGL)
Lifted index.................... +0.6
K index......................... +14.4
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 -66.9 -88.4 225 64 33 2.7 1.5 M M M M M
45000 -61.4 -78.5 225 89 46 5.9 3.2 M M M M M
40000 -52.5 -62.5 220 101 52 7.4 4.1 M M M M M
38000 -48.1 -54.6 225 99 51 7.3 4.0 M M M M M
36000 -43.7 -46.7 225 98 51 7.3 4.0 M M M M M
34000 -39.2 -38.6 225 96 49 7.6 4.1 M M M M M
32000 -34.7 -30.5 225 93 48 7.6 4.2 M M M M M
30000 -30.5 -22.9 225 85 44 5.4 3.0 46.2 115.2 16.9 M M
29000 -28.9 -20.0 220 80 41 5.4 3.0 44.5 112.2 15.9 M M
28000 -27.3 -17.1 220 75 39 5.5 3.0 43.0 109.5 14.9 M M
27000 -25.5 -13.9 220 68 35 5.9 3.2 41.4 106.6 13.8 M M
26000 -23.8 -10.8 215 60 31 5.9 3.2 39.9 103.9 12.8 M M
25000 -22.0 -7.6 215 53 27 5.9 3.2 38.6 101.4 11.8 M M
24000 -20.0 -4.0 215 48 25 7.2 3.9 37.4 99.3 11.0 M M
23000 -17.9 -0.2 215 46 24 7.3 4.0 36.4 97.6 10.3 M M
22000 -15.7 3.7 215 44 23 7.3 4.0 35.6 96.1 9.7 M M
21000 -13.4 7.9 215 43 22 8.3 4.5 35.0 94.9 9.2 M M
20000 -10.9 12.4 215 42 21 8.3 4.5 34.4 93.9 8.8 M M
19500 -9.7 14.5 215 41 21 8.3 4.5 34.2 93.5 8.7 M M
19000 -8.5 16.7 215 40 21 8.2 4.5 34.0 93.2 8.5 M M
18500 -7.3 18.9 220 41 21 7.9 4.4 33.7 92.6 8.3 M M
18000 -6.1 21.0 220 43 22 8.0 4.4 33.3 92.0 8.1 M M
17500 -5.0 23.0 225 44 22 6.9 3.8 33.0 91.3 7.8 M M
17000 -4.0 24.8 225 42 22 6.8 3.7 32.5 90.4 7.3 M M
16500 -2.5 27.5 225 40 20 7.0 3.8 31.7 89.1 6.7 M M
16000 -1.5 29.3 225 39 20 6.9 3.8 31.2 88.2 6.3 M M
15500 -0.5 31.1 230 38 20 5.9 3.2 30.8 87.4 5.8 M M
15000 0.2 32.4 225 35 18 5.1 2.8 30.0 86.0 5.1 M M
14500 0.8 33.4 225 33 17 4.9 2.7 29.2 84.6 4.3 M M
14000 1.4 34.5 225 30 15 3.9 2.1 28.3 82.9 3.4 M M
13500 1.9 35.4 230 28 14 4.0 2.2 27.3 81.2 2.5 M M
13000 2.5 36.5 230 26 13 5.4 3.0 26.5 79.7 1.7 M M
12500 3.3 37.9 230 24 12 5.3 2.9 25.8 78.4 0.9 M M
12000 4.0 39.2 230 24 12 5.8 3.2 25.1 77.2 0.3 M M
11500 4.8 40.6 230 26 13 6.2 3.4 24.5 76.1 -0.4 379 1.9
11000 5.4 41.7 230 26 13 1.6 0.9 23.6 74.4 -1.3 347 1.8
10500 5.6 42.1 225 24 13 1.8 1.0 22.3 72.1 -2.6 327 1.7
10250 5.6 42.1 225 24 12 1.0 0.6 21.7 71.0 -3.2 318 1.6
10000 5.7 42.3 225 23 12 1.2 0.6 20.9 69.7 -3.9 309 1.6
9750 5.8 42.4 220 22 12 2.2 1.2 20.3 68.6 -4.6 298 1.5
9500 5.9 42.6 220 22 11 1.8 1.0 19.7 67.5 -5.2 287 1.5
9250 6.0 42.8 215 21 11 2.5 1.3 19.1 66.4 -5.8 277 1.4
9000 6.3 43.3 215 19 10 2.8 1.5 18.6 65.5 -6.3 262 1.3
8750 6.5 43.7 215 17 9 2.5 1.4 18.0 64.4 -6.9 249 1.3
8500 6.7 44.1 215 15 8 2.4 1.3 17.5 63.4 -7.4 236 1.2
8250 6.8 44.2 215 13 7 1.2 0.7 16.9 62.4 -8.0 223 1.1
8000 6.9 44.4 220 11 6 0.4 0.2 16.2 61.1 -8.7 213 1.1
7750 7.0 44.6 220 9 5 -0.4 -0.2 15.4 59.8 -9.4 205 1.0
7500 6.9 44.4 225 7 4 0.0 0.0 14.6 58.3 -10.1 198 1.0
7250 7.0 44.6 230 6 3 1.9 1.0 14.0 57.2 -10.8 188 1.0
7000 7.2 45.0 230 6 3 1.9 1.0 13.4 56.1 -11.4 176 0.9
6750 7.3 45.1 230 6 3 3.0 1.6 12.8 55.1 -12.0 164 0.8
6500 7.6 45.7 225 6 3 3.7 2.0 12.3 54.2 -12.5 148 0.8
6250 7.8 46.0 225 5 2 3.2 1.8 11.9 53.3 -13.0 134 0.7
6000 8.1 46.6 225 4 2 3.6 2.0 11.4 52.5 -13.5 119 0.6
5750 8.3 46.9 225 3 1 2.6 1.5 10.9 51.6 -14.0 104 0.5
5500 8.4 47.1 245 2 1 1.0 0.5 10.3 50.5 -14.7 94 0.5
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/14/2025 at 0900 MDT | 10/14/2025 at 1200 MDT
|
CAPE... 0.0 LI... +3.4 | CAPE... 0.0 LI... +3.6
CINH... 0.0 K Index... +8.9 | CINH... 0.0 K Index... -6.2
|
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 -67.0 -88.6 220 53 27 3.1 1.7 | -66.7 -88.1 225 54 28 3.5 1.9
45000 -61.2 -78.2 225 82 42 5.4 3.0 | -60.6 -77.1 225 83 43 4.8 2.6
40000 -52.9 -63.2 220 94 48 7.6 4.2 | -53.1 -63.6 225 96 49 7.5 4.1
38000 -48.4 -55.1 220 94 49 7.5 4.1 | -48.7 -55.7 225 96 49 7.3 4.0
36000 -43.9 -47.0 220 95 49 7.5 4.1 | -44.3 -47.7 220 96 49 7.3 4.0
34000 -39.2 -38.6 220 94 48 7.8 4.3 | -39.7 -39.5 220 95 49 7.8 4.3
32000 -34.6 -30.3 220 93 48 7.8 4.3 | -35.0 -31.0 220 94 49 7.8 4.3
30000 -30.1 -22.2 220 89 46 6.1 3.3 | -30.2 -22.4 220 91 47 6.8 3.7
29000 -28.3 -18.9 220 86 45 6.1 3.3 | -28.2 -18.8 220 89 46 6.8 3.7
28000 -26.5 -15.7 220 84 43 6.0 3.3 | -26.1 -15.0 225 87 45 6.5 3.6
27000 -24.9 -12.8 220 78 40 5.1 2.8 | -24.6 -12.3 225 79 41 5.0 2.8
26000 -23.4 -10.1 220 71 37 5.1 2.8 | -23.1 -9.6 220 71 37 5.0 2.8
25000 -21.8 -7.2 220 64 33 5.1 2.8 | -21.6 -6.9 220 63 33 4.9 2.7
24000 -20.0 -4.0 220 59 31 7.0 3.8 | -19.6 -3.3 220 59 30 7.2 3.9
23000 -17.9 -0.2 220 55 29 7.0 3.8 | -17.5 0.5 220 56 29 7.2 3.9
22000 -15.8 3.6 220 51 26 7.0 3.8 | -15.3 4.5 225 54 28 7.2 3.9
21000 -13.6 7.5 225 48 25 7.1 3.9 | -13.2 8.2 225 51 26 7.2 4.0
20000 -11.5 11.3 225 45 23 7.1 3.9 | -11.0 12.2 225 47 24 7.2 4.0
19500 -10.5 13.1 225 44 22 7.1 3.9 | -9.9 14.2 225 45 23 7.2 4.0
19000 -9.4 15.1 225 42 22 7.3 4.0 | -8.8 16.2 225 43 22 7.1 3.9
18500 -8.3 17.1 225 41 21 7.5 4.1 | -7.8 18.0 225 42 21 6.9 3.8
18000 -7.2 19.0 225 40 21 7.6 4.1 | -6.8 19.8 225 40 21 7.0 3.9
17500 -6.1 21.0 225 40 21 6.7 3.7 | -5.8 21.6 225 39 20 6.1 3.3
17000 -5.1 22.8 225 42 21 6.8 3.7 | -4.9 23.2 225 37 19 6.2 3.4
16500 -4.2 24.4 225 43 22 6.8 3.8 | -4.0 24.8 225 36 19 6.5 3.6
16000 -2.7 27.1 225 42 21 6.8 3.8 | -2.9 26.8 225 34 18 6.7 3.7
15500 -1.7 28.9 220 40 21 6.8 3.7 | -1.9 28.6 220 33 17 6.7 3.7
15000 -0.7 30.7 220 38 20 6.9 3.8 | -0.5 31.1 220 33 17 6.4 3.5
14500 0.3 32.5 220 35 18 6.9 3.8 | 0.5 32.9 220 33 17 6.4 3.5
14000 1.3 34.3 220 33 17 7.0 3.8 | 1.4 34.5 215 31 16 6.5 3.6
13500 2.3 36.1 220 30 16 7.0 3.8 | 2.3 36.1 215 29 15 6.8 3.7
13000 3.2 37.8 220 28 14 6.5 3.6 | 3.4 38.1 215 28 14 8.0 4.4
12500 4.1 39.4 220 26 13 6.6 3.6 | 4.6 40.3 215 27 14 8.0 4.4
12000 5.1 41.2 225 25 13 6.4 3.5 | 5.8 42.4 220 28 14 8.3 4.5
11500 6.0 42.8 230 25 13 6.5 3.6 | 7.1 44.8 225 30 15 8.3 4.6
11000 6.8 44.2 235 24 13 5.4 3.0 | 8.0 46.4 225 32 16 4.8 2.6
10500 7.6 45.7 235 22 12 6.0 3.3 | 8.6 47.5 225 33 17 5.1 2.8
10250 7.9 46.2 235 22 11 3.1 1.7 | 8.9 48.0 230 34 17 2.3 1.2
10000 8.0 46.4 235 21 11 2.2 1.2 | 9.0 48.2 230 33 17 2.4 1.3
9750 8.3 46.9 235 21 11 4.3 2.3 | 9.2 48.6 230 31 16 4.7 2.6
9500 8.5 47.3 235 20 10 3.8 2.1 | 9.4 48.9 230 29 15 4.1 2.3
9250 8.7 47.7 235 19 10 1.9 1.1 | 9.6 49.3 230 28 14 3.0 1.7
9000 8.8 47.8 235 19 10 0.6 0.3 | 9.7 49.5 230 26 13 1.9 1.1
8750 8.8 47.8 230 18 9 1.6 0.9 | 9.8 49.6 225 24 12 1.9 1.1
8500 8.9 48.0 230 16 8 1.1 0.6 | 9.9 49.8 225 22 11 2.3 1.3
8250 8.9 48.0 225 15 8 -0.2 -0.1 | 10.0 50.0 220 20 10 3.0 1.6
8000 8.8 47.8 225 14 7 -1.0 -0.6 | 10.2 50.4 215 17 9 3.4 1.9
7750 8.7 47.7 225 12 6 -2.6 -1.4 | 10.4 50.7 210 15 7 3.2 1.8
7500 8.5 47.3 220 11 6 -2.6 -1.4 | 10.7 51.3 200 12 6 4.9 2.7
7250 8.4 47.1 220 10 5 -1.1 -0.6 | 11.1 52.0 195 9 5 6.6 3.6
7000 8.3 46.9 215 9 5 -1.3 -0.7 | 11.6 52.9 185 7 4 6.3 3.5
6750 8.2 46.8 215 8 4 -1.4 -0.8 | 12.1 53.8 175 5 3 9.3 5.1
6500 8.1 46.6 215 7 3 1.0 0.6 | 12.9 55.2 170 4 2 11.1 6.1
6250 8.3 46.9 215 5 3 3.2 1.7 | 13.7 56.7 170 4 2 10.6 5.8
6000 8.5 47.3 215 4 2 1.8 1.0 | 14.5 58.1 170 3 2 9.6 5.3
5750 8.7 47.7 215 3 2 5.0 2.8 | 15.3 59.5 170 3 2 13.4 7.4
5500 9.4 48.9 215 2 1 14.3 7.8 | 16.7 62.1 175 3 1 23.9 13.1
10/14/2025 at 1500 MDT | 10/14/2025 at 1800 MDT
|
CAPE... 0.0 LI... +0.4 | CAPE... +16.2 LI... -0.8
CINH... 0.0 K Index... +4.1 | CINH... -16.8 K Index... +7.2
|
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 -66.7 -88.1 225 57 29 4.4 2.4 | -66.6 -87.9 225 59 30 4.5 2.5
45000 -59.8 -75.6 225 79 41 4.2 2.3 | -59.8 -75.6 225 76 39 4.6 2.6
40000 -53.3 -63.9 225 96 49 7.3 4.0 | -52.6 -62.7 220 90 46 7.0 3.8
38000 -49.0 -56.2 225 96 49 7.1 3.9 | -48.5 -55.3 225 91 47 6.8 3.8
36000 -44.8 -48.6 225 96 49 7.1 3.9 | -44.4 -47.9 225 91 47 6.9 3.8
34000 -40.2 -40.4 225 95 49 7.9 4.3 | -39.9 -39.8 225 90 47 7.6 4.1
32000 -35.4 -31.7 220 94 48 7.9 4.3 | -34.8 -30.6 225 89 46 7.5 4.1
30000 -30.8 -23.4 225 86 44 6.2 3.4 | -30.8 -23.4 225 80 41 6.4 3.5
29000 -29.0 -20.2 225 81 42 6.2 3.4 | -28.9 -20.0 225 74 38 6.4 3.5
28000 -27.1 -16.8 225 77 39 6.3 3.5 | -26.9 -16.4 225 68 35 6.4 3.5
27000 -25.1 -13.2 225 68 35 6.6 3.6 | -25.0 -13.0 225 63 32 6.4 3.5
26000 -23.1 -9.6 225 58 30 6.6 3.6 | -23.1 -9.6 225 57 29 6.4 3.5
25000 -21.2 -6.2 225 49 25 6.5 3.6 | -21.1 -6.0 225 51 26 6.3 3.5
24000 -18.9 -2.0 225 45 23 8.1 4.4 | -18.9 -2.0 225 45 23 7.8 4.3
23000 -16.5 2.3 225 43 22 8.1 4.4 | -16.6 2.1 220 40 20 7.8 4.3
22000 -14.0 6.8 230 42 22 8.3 4.6 | -14.3 6.3 220 34 18 8.1 4.4
21000 -12.0 10.4 230 42 22 6.1 3.3 | -12.5 9.5 220 33 17 5.1 2.8
20000 -10.2 13.6 225 42 22 6.1 3.4 | -11.0 12.2 220 34 18 5.2 2.8
19500 -9.3 15.3 225 42 22 6.1 3.4 | -10.2 13.6 220 35 18 5.2 2.9
19000 -8.4 16.9 225 42 22 5.6 3.1 | -9.5 14.9 220 35 18 6.3 3.5
18500 -7.7 18.1 225 39 20 5.2 2.8 | -8.4 16.9 220 34 17 7.1 3.9
18000 -6.9 19.6 225 37 19 5.1 2.8 | -7.3 18.9 220 32 16 7.0 3.9
17500 -6.1 21.0 220 33 17 5.9 3.2 | -6.2 20.8 220 30 15 8.2 4.5
17000 -5.2 22.6 220 30 15 5.8 3.2 | -4.9 23.2 225 28 15 8.1 4.5
16500 -4.3 24.3 215 26 14 7.1 3.9 | -3.7 25.3 225 27 14 8.2 4.5
16000 -3.2 26.2 215 26 13 7.8 4.3 | -2.5 27.5 230 27 14 8.1 4.5
15500 -2.0 28.4 215 25 13 7.9 4.3 | -0.8 30.6 235 28 14 6.2 3.4
15000 -0.8 30.6 220 26 13 8.1 4.5 | 0.0 32.0 235 28 14 5.9 3.3
14500 1.0 33.8 230 29 15 7.4 4.1 | 0.9 33.6 235 27 14 5.2 2.9
14000 2.0 35.6 230 29 15 6.8 3.8 | 1.4 34.5 230 25 13 4.6 2.5
13500 3.0 37.4 235 29 15 6.3 3.5 | 1.9 35.4 225 24 12 5.3 2.9
13000 3.6 38.5 230 29 15 4.5 2.5 | 2.6 36.7 220 22 11 6.5 3.6
12500 4.1 39.4 225 29 15 5.1 2.8 | 3.4 38.1 210 21 11 7.0 3.8
12000 4.7 40.5 215 26 13 5.5 3.0 | 4.6 40.3 205 20 10 9.4 5.2
11500 5.3 41.5 205 23 12 5.9 3.2 | 6.0 42.8 200 19 10 9.3 5.1
11000 6.5 43.7 200 21 11 9.8 5.4 | 7.4 45.3 200 19 10 9.7 5.3
10500 8.0 46.4 195 21 11 7.2 3.9 | 8.9 48.0 200 19 10 6.9 3.8
10250 8.4 47.1 195 20 10 5.7 3.1 | 9.3 48.7 200 18 10 4.9 2.7
10000 9.0 48.2 195 20 10 10.5 5.8 | 9.8 49.6 195 17 9 9.8 5.4
9750 9.9 49.8 195 19 10 12.1 6.7 | 10.6 51.1 190 16 8 11.2 6.2
9500 10.7 51.3 190 18 9 10.9 6.0 | 11.4 52.5 185 15 8 10.2 5.6
9250 11.4 52.5 190 17 9 6.9 3.8 | 12.1 53.8 185 13 7 7.4 4.0
9000 11.9 53.4 190 16 8 7.1 3.9 | 12.6 54.7 180 12 6 7.5 4.1
8750 12.5 54.5 185 14 7 9.6 5.3 | 13.2 55.8 175 10 5 9.3 5.1
8500 13.2 55.8 180 12 6 8.2 4.5 | 13.8 56.8 165 9 5 8.1 4.4
8250 13.7 56.7 175 10 5 6.5 3.6 | 14.4 57.9 160 7 4 6.2 3.4
8000 14.2 57.6 170 7 4 6.8 3.7 | 14.8 58.6 150 6 3 6.6 3.6
7750 14.7 58.5 160 5 3 7.9 4.4 | 15.4 59.7 140 5 2 8.4 4.6
7500 15.3 59.5 150 3 2 8.6 4.7 | 16.0 60.8 130 4 2 7.7 4.2
7250 16.0 60.8 150 2 1 9.2 5.0 | 16.5 61.7 110 3 1 6.7 3.7
7000 16.7 62.1 145 2 1 9.2 5.1 | 17.0 62.6 080 2 1 7.0 3.8
6750 17.4 63.3 140 1 1 10.0 5.5 | 17.6 63.7 045 2 1 7.9 4.3
6500 18.1 64.6 135 1 0 10.2 5.6 | 18.2 64.8 025 3 2 8.5 4.7
6250 18.9 66.0 000 0 0 10.2 5.6 | 18.8 65.8 010 4 2 8.3 4.5
6000 19.7 67.5 000 0 0 9.4 5.2 | 19.4 66.9 360 5 2 8.7 4.8
5750 20.4 68.7 000 0 0 12.8 7.0 | 20.1 68.2 355 6 3 7.5 4.1
5500 21.7 71.1 355 1 0 21.4 11.8 | 20.4 68.7 350 5 3 3.9 2.1
________________________________________________________________________________
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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