Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
174
UXUS97 KBOU 080110
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1809 MST Friday, November 7, 2025
This forecast is for Saturday, November 8, 2025:
If the trigger temperature of 50.1 F/10.0 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 443 ft/min (2.3 m/s)
Maximum height of thermals.................. 11466 ft MSL (6165 ft AGL)
Forecast maximum temperature................... 56.0 F/13.8 C
Time of trigger temperature.................... 1045 MST
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................. 9428 ft MSL (4127 ft AGL)
Thermal soaring outlook for Sunday 11/09....... Poor
Wave Soaring Index............................. Good
Wave Soaring Index trend (to 1700 MST)......... Decreasing
Height of stable layer (12-18K ft MSL)......... 14388 ft MSL (9087 ft AGL)
Weak PVA/NVA (through 1700 MST)................ Neither
Potential height of wave....................... 38700 ft MSL (33399 ft AGL)
Wave soaring outlook for Sunday 11/09.......... Poor
Remarks...
Sunrise/Sunset.................... 06:36:47 / 16:49:39 MST
Total possible sunshine........... 10 hr 12 min 52 sec (612 min 52 sec)
Altitude of sun at 11:43:13 MST... 33.29 degrees
Upper air data from numerical model forecast valid on 11/08/2025 at 0500 MST
Freezing level.................. 8398 ft MSL (3097 ft AGL)
Convective condensation level... 14435 ft MSL (9134 ft AGL)
Lifted condensation level....... 12771 ft MSL (7469 ft AGL)
Lifted index.................... +6.7
K index......................... -7.9
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 -62.7 -80.9 290 66 34 2.3 1.3 M M M M M
45000 -59.2 -74.6 290 71 37 1.5 0.8 M M M M M
40000 -61.0 -77.8 300 98 50 -1.2 -0.7 M M M M M
38000 -58.8 -73.8 300 103 53 7.2 4.0 M M M M M
36000 -54.5 -66.1 300 105 54 7.2 4.0 M M M M M
34000 -50.2 -58.4 300 106 54 7.1 3.9 M M M M M
32000 -45.9 -50.6 305 102 53 7.1 3.9 M M M M M
30000 -41.8 -43.2 305 98 51 6.3 3.5 35.4 95.7 16.6 M M
29000 -39.9 -39.8 310 95 49 6.4 3.5 34.0 93.1 15.7 M M
28000 -37.5 -35.5 310 91 47 6.4 3.5 32.4 90.2 14.7 M M
27000 -35.5 -31.9 315 88 45 7.7 4.2 31.3 88.3 14.0 M M
26000 -33.1 -27.6 310 85 44 8.1 4.4 30.5 86.9 13.6 M M
25000 -30.7 -23.3 310 82 42 8.1 4.4 29.9 85.8 13.2 M M
24000 -28.3 -18.9 310 80 41 8.0 4.4 29.4 84.9 13.0 M M
23000 -25.9 -14.6 305 78 40 7.9 4.3 28.6 83.4 12.5 M M
22000 -23.6 -10.5 305 77 39 7.9 4.3 27.9 82.2 12.1 M M
21000 -21.3 -6.3 305 75 39 7.0 3.8 27.3 81.1 11.6 M M
20000 -19.3 -2.7 305 73 38 6.7 3.7 26.1 79.0 10.8 M M
19500 -18.3 -0.9 305 73 37 6.7 3.7 25.6 78.1 10.4 M M
19000 -17.2 1.0 305 72 37 6.7 3.7 25.1 77.2 10.0 M M
18500 -16.2 2.8 305 71 36 6.1 3.4 24.6 76.3 9.7 M M
18000 -15.4 4.3 305 68 35 5.5 3.0 23.9 75.0 9.1 M M
17500 -14.6 5.7 310 65 34 5.3 2.9 23.1 73.6 8.5 M M
17000 -13.7 7.3 310 62 32 6.6 3.6 22.5 72.5 8.0 M M
16500 -12.7 9.1 310 58 30 6.5 3.6 21.9 71.5 7.5 M M
16000 -11.8 10.8 305 55 28 5.3 2.9 21.3 70.4 7.1 M M
15500 -11.1 12.0 310 52 27 4.7 2.6 20.5 68.9 6.3 M M
15000 -10.1 13.8 310 49 25 3.2 1.8 19.1 66.4 5.2 M M
14500 -9.7 14.5 305 46 24 3.1 1.7 18.0 64.5 4.2 M M
14000 -9.2 15.4 305 43 22 4.1 2.3 17.0 62.6 3.2 M M
13500 -8.5 16.7 305 41 21 4.6 2.5 16.1 61.0 2.4 M M
13000 -7.9 17.8 305 40 21 6.1 3.3 15.3 59.6 1.7 M M
12500 -6.8 19.8 305 45 23 7.1 3.9 14.9 58.8 1.3 M M
12000 -5.8 21.6 305 49 25 5.6 3.1 14.5 58.1 0.9 M M
11500 -5.2 22.6 300 50 26 4.3 2.4 13.6 56.4 -0.0 441 2.2
11000 -4.6 23.7 295 51 26 5.4 3.0 12.7 54.9 -0.9 409 2.1
10500 -3.7 25.3 295 47 24 6.7 3.7 12.2 53.9 -1.5 367 1.9
10250 -3.3 26.1 295 46 23 5.1 2.8 11.9 53.4 -1.8 346 1.8
10000 -3.0 26.6 295 44 23 3.7 2.1 11.5 52.6 -2.2 331 1.7
9750 -2.7 27.1 295 42 22 5.6 3.1 11.0 51.9 -2.6 313 1.6
9500 -2.2 28.0 300 39 20 6.1 3.4 10.8 51.4 -2.9 293 1.5
9250 -1.8 28.8 300 36 19 6.0 3.3 10.5 50.8 -3.3 273 1.4
9000 -1.4 29.5 300 34 18 6.6 3.6 10.2 50.3 -3.5 252 1.3
8750 -0.8 30.6 300 32 16 7.7 4.2 10.0 50.0 -3.8 229 1.2
8500 -0.2 31.6 305 29 15 8.4 4.6 9.9 49.7 -3.9 204 1.0
8250 0.4 32.7 305 27 14 7.2 4.0 9.7 49.5 -4.0 179 0.9
8000 0.8 33.4 310 24 12 6.0 3.3 9.5 49.0 -4.3 157 0.8
7750 1.3 34.3 315 22 11 6.7 3.7 9.2 48.6 -4.6 136 0.7
7500 1.8 35.2 320 20 10 6.9 3.8 9.0 48.2 -4.8 113 0.6
7250 2.3 36.1 330 18 9 5.6 3.1 8.7 47.7 -5.1 91 0.5
7000 2.7 36.9 340 17 9 5.2 2.8 8.4 47.1 -5.4 73 0.4
6750 3.1 37.6 355 18 9 4.8 2.7 8.0 46.5 -5.8 54 0.3
6500 3.3 37.9 005 18 9 -0.0 -0.0 7.5 45.5 -6.3 40 0.2
6250 3.1 37.6 015 17 9 -3.4 -1.8 6.6 43.8 -7.3 38 0.2
6000 2.8 37.0 030 16 8 -2.6 -1.4 5.6 42.1 -8.2 38 0.2
5750 2.6 36.7 045 16 8 -3.2 -1.7 4.7 40.4 -9.2 38 0.2
5500 2.3 36.1 055 12 6 -4.0 -2.2 3.7 38.6 -10.2 38 0.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/08/2025 at 0800 MST | 11/08/2025 at 1100 MST
|
CAPE... 0.0 LI... +10.1 | CAPE... 0.0 LI... +11.4
CINH... 0.0 K Index... -17.4 | CINH... 0.0 K Index... -25.9
|
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 -61.9 -79.4 290 67 35 2.0 1.1 | -60.9 -77.6 295 65 34 1.6 0.9
45000 -59.0 -74.2 280 69 35 1.2 0.6 | -58.4 -73.1 290 68 35 1.1 0.6
40000 -61.5 -78.7 295 94 48 -1.7 -0.9 | -60.9 -77.6 300 90 46 -1.7 -0.9
38000 -59.3 -74.7 300 97 50 7.5 4.1 | -59.0 -74.2 300 94 48 6.8 3.7
36000 -54.9 -66.8 300 95 49 7.5 4.1 | -54.9 -66.8 300 93 48 6.8 3.7
34000 -50.4 -58.7 300 94 48 7.0 3.8 | -50.9 -59.6 300 93 48 6.1 3.4
32000 -46.2 -51.2 305 93 48 7.0 3.8 | -47.2 -53.0 305 90 46 6.1 3.4
30000 -42.1 -43.8 310 93 48 6.3 3.5 | -43.4 -46.1 310 87 45 7.2 3.9
29000 -39.8 -39.6 310 90 46 6.3 3.5 | -40.7 -41.3 310 84 43 7.2 3.9
28000 -37.9 -36.2 310 88 45 6.3 3.5 | -38.6 -37.5 305 82 42 7.2 3.9
27000 -35.9 -32.6 310 86 44 8.5 4.6 | -36.4 -33.5 305 80 41 8.5 4.7
26000 -33.2 -27.8 310 82 42 8.8 4.8 | -33.8 -28.8 305 79 40 8.6 4.7
25000 -30.6 -23.1 315 79 41 8.8 4.8 | -31.3 -24.3 300 77 40 8.6 4.7
24000 -28.0 -18.4 315 76 39 8.5 4.7 | -28.7 -19.7 300 76 39 9.0 5.0
23000 -25.5 -13.9 310 75 39 8.1 4.5 | -25.9 -14.6 300 76 39 9.3 5.1
22000 -23.1 -9.6 310 74 38 8.2 4.5 | -23.1 -9.6 305 75 39 9.3 5.1
21000 -20.7 -5.3 305 74 38 6.4 3.5 | -20.4 -4.7 305 74 38 7.5 4.1
20000 -18.9 -2.0 310 76 39 6.1 3.3 | -18.2 -0.8 310 73 38 7.4 4.1
19500 -18.0 -0.4 310 77 40 6.1 3.3 | -17.1 1.2 310 72 37 7.4 4.1
19000 -17.1 1.2 310 78 40 6.1 3.3 | -15.9 3.4 310 72 37 7.4 4.1
18500 -16.2 2.8 310 79 41 6.2 3.4 | -14.9 5.2 310 71 37 5.5 3.0
18000 -15.3 4.5 310 76 39 6.2 3.4 | -14.2 6.4 315 69 35 4.4 2.4
17500 -14.4 6.1 310 73 37 6.3 3.4 | -13.6 7.5 315 66 34 4.3 2.4
17000 -13.5 7.7 310 70 36 5.3 2.9 | -13.0 8.6 315 63 33 4.0 2.2
16500 -12.7 9.1 310 67 35 5.5 3.0 | -12.4 9.7 315 60 31 4.0 2.2
16000 -11.9 10.6 310 65 33 5.0 2.7 | -11.7 10.9 315 57 29 4.2 2.3
15500 -11.1 12.0 310 60 31 4.9 2.7 | -10.8 12.6 315 53 27 4.3 2.4
15000 -10.1 13.8 310 54 28 4.2 2.3 | -10.2 13.6 315 49 25 3.4 1.9
14500 -9.4 15.1 310 50 26 4.3 2.3 | -9.7 14.5 315 46 24 3.4 1.9
14000 -8.8 16.2 310 46 23 4.3 2.4 | -9.1 15.6 315 42 22 4.5 2.5
13500 -8.2 17.2 310 41 21 4.3 2.4 | -8.4 16.9 315 38 20 4.7 2.6
13000 -7.5 18.5 310 38 19 5.7 3.1 | -7.7 18.1 315 35 18 4.5 2.5
12500 -6.5 20.3 310 36 19 6.3 3.4 | -7.1 19.2 310 33 17 4.4 2.4
12000 -5.6 21.9 310 35 18 5.3 2.9 | -6.4 20.5 310 31 16 6.0 3.3
11500 -5.0 23.0 310 36 19 4.6 2.6 | -5.4 22.3 310 32 17 6.8 3.7
11000 -4.3 24.3 305 37 19 4.1 2.3 | -4.5 23.9 310 33 17 3.6 2.0
10500 -3.8 25.2 305 40 20 4.1 2.3 | -4.2 24.4 310 32 16 2.6 1.5
10250 -3.5 25.7 300 41 21 3.2 1.7 | -4.1 24.6 310 31 16 1.9 1.0
10000 -3.3 26.1 300 41 21 2.3 1.3 | -3.9 25.0 305 30 16 2.8 1.6
9750 -3.2 26.2 300 40 20 3.7 2.0 | -3.7 25.3 310 29 15 4.9 2.7
9500 -2.9 26.8 300 38 19 4.7 2.6 | -3.3 26.1 310 27 14 5.7 3.1
9250 -2.6 27.3 305 35 18 4.0 2.2 | -3.0 26.6 310 25 13 3.8 2.1
9000 -2.4 27.7 305 32 17 3.1 1.7 | -2.8 27.0 310 22 11 1.6 0.9
8750 -2.1 28.2 305 29 15 3.8 2.1 | -2.7 27.1 315 19 10 2.8 1.5
8500 -1.9 28.6 305 25 13 4.4 2.4 | -2.5 27.5 320 15 8 3.4 1.9
8250 -1.6 29.1 310 22 11 4.4 2.4 | -2.2 28.0 330 12 6 4.6 2.5
8000 -1.2 29.8 310 19 10 4.5 2.5 | -1.8 28.8 335 9 5 5.5 3.0
7750 -0.9 30.4 315 16 8 4.5 2.4 | -1.5 29.3 350 6 3 6.1 3.4
7500 -0.6 30.9 320 14 7 4.6 2.5 | -1.0 30.2 010 5 3 8.3 4.6
7250 -0.3 31.5 330 13 6 4.8 2.7 | -0.3 31.5 020 5 2 9.5 5.2
7000 0.1 32.2 340 12 6 5.1 2.8 | 0.4 32.7 020 5 2 9.9 5.5
6750 0.5 32.9 355 12 6 4.3 2.3 | 1.1 34.0 025 5 2 8.9 4.9
6500 0.7 33.3 005 12 6 1.0 0.5 | 1.8 35.2 030 5 2 9.3 5.1
6250 0.6 33.1 015 8 4 -0.2 -0.1 | 2.6 36.7 030 5 2 11.1 6.1
6000 0.6 33.1 040 4 2 -1.1 -0.6 | 3.3 37.9 030 4 2 9.3 5.1
5750 0.6 33.1 100 4 2 3.8 2.1 | 4.1 39.4 030 4 2 14.7 8.0
5500 1.3 34.3 135 4 2 16.9 9.3 | 5.7 42.3 030 4 2 26.6 14.6
11/08/2025 at 1400 MST | 11/08/2025 at 1700 MST
|
CAPE... 0.0 LI... +11.1 | CAPE... 0.0 LI... +11.2
CINH... 0.0 K Index... -24.3 | CINH... 0.0 K Index... -17.2
|
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 -61.2 -78.2 305 66 34 1.3 0.7 | -60.9 -77.6 305 65 34 1.7 1.0
45000 -59.2 -74.6 300 79 41 1.2 0.7 | -58.3 -72.9 305 75 39 1.6 0.9
40000 -60.9 -77.6 300 95 49 -1.2 -0.7 | -59.5 -75.1 305 75 38 -0.8 -0.5
38000 -59.5 -75.1 300 96 50 5.5 3.0 | -58.3 -72.9 305 78 40 4.3 2.4
36000 -56.2 -69.2 300 94 49 5.5 3.0 | -55.7 -68.3 310 85 44 4.3 2.4
34000 -52.8 -63.0 295 92 47 6.4 3.5 | -53.0 -63.4 315 90 47 5.8 3.2
32000 -49.0 -56.2 300 84 43 6.3 3.5 | -49.5 -57.1 320 85 44 5.8 3.2
30000 -44.9 -48.8 305 77 40 8.8 4.8 | -45.6 -50.1 320 80 41 9.3 5.1
29000 -41.6 -42.9 305 76 39 8.8 4.8 | -42.2 -44.0 315 76 39 9.2 5.1
28000 -39.0 -38.2 305 75 38 8.8 4.8 | -39.4 -38.9 310 74 38 9.2 5.1
27000 -36.4 -33.5 305 73 38 8.7 4.8 | -36.7 -34.1 310 73 37 8.8 4.8
26000 -33.8 -28.8 305 73 37 8.7 4.8 | -34.0 -29.2 310 71 36 8.8 4.8
25000 -31.2 -24.2 305 72 37 8.7 4.8 | -31.4 -24.5 310 69 36 8.8 4.8
24000 -28.6 -19.5 305 71 37 8.6 4.7 | -28.8 -19.8 310 67 35 8.9 4.9
23000 -26.1 -15.0 305 70 36 8.6 4.7 | -26.1 -15.0 310 66 34 9.0 4.9
22000 -23.5 -10.3 305 69 36 8.6 4.7 | -23.4 -10.1 310 65 34 9.0 4.9
21000 -21.0 -5.8 305 68 35 8.2 4.5 | -20.9 -5.6 305 65 33 6.9 3.8
20000 -18.5 -1.3 310 67 34 8.2 4.5 | -18.8 -1.8 310 65 34 6.9 3.8
19500 -17.3 0.9 310 66 34 8.2 4.5 | -17.8 -0.0 310 65 34 6.9 3.8
19000 -16.1 3.0 310 65 34 8.2 4.5 | -16.8 1.8 310 66 34 7.0 3.8
18500 -14.9 5.2 310 65 33 6.3 3.5 | -15.8 3.6 310 66 34 5.5 3.0
18000 -14.1 6.6 315 63 33 5.4 3.0 | -15.1 4.8 310 62 32 4.8 2.6
17500 -13.3 8.1 315 62 32 5.3 2.9 | -14.4 6.1 310 59 30 4.7 2.6
17000 -12.6 9.3 315 59 31 4.1 2.3 | -13.7 7.3 310 57 29 3.7 2.0
16500 -11.9 10.6 315 56 29 4.3 2.3 | -13.1 8.4 310 55 29 4.0 2.2
16000 -11.3 11.7 315 53 27 3.6 2.0 | -12.7 9.1 310 53 27 1.8 1.0
15500 -10.5 13.1 315 50 26 3.5 1.9 | -12.4 9.7 310 50 26 1.7 0.9
15000 -10.0 14.0 315 48 25 3.2 1.8 | -12.0 10.4 305 45 23 2.0 1.1
14500 -9.5 14.9 310 46 23 3.3 1.8 | -11.7 10.9 305 41 21 1.8 1.0
14000 -9.0 15.8 310 43 22 3.4 1.9 | -11.3 11.7 300 38 19 4.6 2.5
13500 -8.5 16.7 305 39 20 3.4 1.9 | -10.6 12.9 300 34 18 4.6 2.6
13000 -8.0 17.6 305 35 18 4.1 2.2 | -10.0 14.0 295 31 16 4.3 2.4
12500 -7.4 18.7 305 33 17 4.3 2.4 | -9.4 15.1 295 27 14 4.3 2.4
12000 -6.7 19.9 300 31 16 5.3 2.9 | -8.8 16.2 295 22 11 4.0 2.2
11500 -5.9 21.4 305 29 15 5.7 3.2 | -8.2 17.2 300 16 8 3.8 2.1
11000 -5.2 22.6 305 27 14 3.7 2.0 | -7.6 18.3 315 11 5 6.6 3.6
10500 -4.8 23.4 305 20 10 3.4 1.8 | -6.6 20.1 335 9 5 7.6 4.2
10250 -4.6 23.7 310 17 9 1.7 0.9 | -6.1 21.0 345 8 4 3.8 2.1
10000 -4.5 23.9 310 15 8 3.4 1.9 | -5.9 21.4 350 8 4 4.4 2.4
9750 -4.1 24.6 315 13 6 7.1 3.9 | -5.3 22.5 355 9 4 10.8 5.9
9500 -3.5 25.7 325 10 5 7.5 4.1 | -4.4 24.1 360 9 5 11.2 6.1
9250 -3.0 26.6 345 7 4 6.0 3.3 | -3.7 25.3 005 10 5 9.4 5.1
9000 -2.7 27.1 350 6 3 4.8 2.7 | -3.0 26.6 010 10 5 8.3 4.6
8750 -2.3 27.9 360 5 3 7.4 4.0 | -2.3 27.9 015 11 6 10.0 5.5
8500 -1.7 28.9 010 5 2 8.6 4.7 | -1.6 29.1 015 11 6 10.6 5.8
8250 -1.1 30.0 020 5 2 9.1 5.0 | -0.8 30.6 015 12 6 10.3 5.6
8000 -0.3 31.5 020 5 2 9.7 5.3 | -0.0 32.0 020 12 6 10.4 5.7
7750 0.4 32.7 020 5 2 9.5 5.2 | 0.7 33.3 020 12 6 9.5 5.2
7500 1.1 34.0 020 5 2 9.8 5.4 | 1.4 34.5 020 12 6 9.4 5.2
7250 1.8 35.2 020 4 2 10.2 5.6 | 2.2 36.0 020 12 6 10.1 5.6
7000 2.6 36.7 020 4 2 10.5 5.7 | 2.9 37.2 020 13 6 10.3 5.6
6750 3.4 38.1 020 4 2 9.4 5.2 | 3.7 38.7 025 13 7 9.0 4.9
6500 4.0 39.2 020 4 2 9.4 5.1 | 4.3 39.7 025 13 7 8.7 4.8
6250 4.8 40.6 020 4 2 10.8 5.9 | 5.0 41.0 025 13 6 9.7 5.3
6000 5.6 42.1 020 4 2 9.2 5.0 | 5.7 42.3 025 12 6 10.1 5.6
5750 6.3 43.3 020 4 2 14.1 7.7 | 6.4 43.5 030 11 6 7.4 4.1
5500 7.8 46.0 020 4 2 24.8 13.6 | 6.7 44.1 030 8 4 0.3 0.2
________________________________________________________________________________
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.
042613