Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
304
UXUS97 KBOU 290018
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1718 MST Friday, November 28, 2025
This forecast is for Saturday, November 29, 2025:
If the trigger temperature of 39.7 F/4.3 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 217 ft/min (1.1 m/s)
Maximum height of thermals.................. 7611 ft MSL (2295 ft AGL)
Forecast maximum temperature................... 31.0 F/-1.0 C
Time of trigger temperature.................... None
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................. 6787 ft MSL (1470 ft AGL)
Thermal soaring outlook for Sunday 11/30....... Poor
Wave Soaring Index............................. Good
Wave Soaring Index trend (to 1700 MST)......... No change
Height of stable layer (12-18K ft MSL)......... 17853 ft MSL (12537 ft AGL)
Weak PVA/NVA (through 1700 MST)................ Weak PVA
Potential height of wave....................... 34078 ft MSL (28762 ft AGL)
Wave soaring outlook for Sunday 11/30.......... Poor
Remarks...
Sunrise/Sunset.................... 07:00:03 / 16:35:53 MST
Total possible sunshine........... 9 hr 35 min 50 sec (575 min 50 sec)
Altitude of sun at 11:47:58 MST... 28.56 degrees
Upper air data from numerical model forecast valid on 11/29/2025 at 0500 MST
Freezing level.................. Entire airmass below 32 F / 0 C
Convective condensation level... 11732 ft MSL (6416 ft AGL)
Lifted condensation level....... 8531 ft MSL (3215 ft AGL)
Lifted index.................... +16.8
K index......................... +3.8
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 -58.0 -72.4 290 52 27 -0.5 -0.3 M M M M M
45000 -58.9 -74.0 285 68 35 -0.5 -0.3 M M M M M
40000 -60.3 -76.5 295 88 45 -1.0 -0.6 M M M M M
38000 -60.1 -76.2 300 95 49 3.9 2.2 M M M M M
36000 -57.7 -71.9 300 102 52 4.1 2.3 M M M M M
34000 -55.2 -67.4 305 108 55 4.3 2.4 M M M M M
32000 -50.8 -59.4 305 106 54 7.7 4.2 M M M M M
30000 -45.6 -50.1 305 102 53 7.7 4.2 31.4 88.5 23.9 M M
29000 -43.3 -45.9 310 99 51 7.7 4.2 30.4 86.7 23.4 M M
28000 -41.0 -41.8 310 96 49 7.7 4.2 29.6 85.3 23.1 M M
27000 -38.7 -37.7 310 93 48 7.7 4.2 28.9 84.0 22.9 M M
26000 -36.4 -33.5 315 89 46 7.9 4.3 28.1 82.6 22.5 M M
25000 -34.0 -29.2 315 85 44 7.9 4.3 27.4 81.3 22.2 M M
24000 -31.7 -25.1 315 80 41 7.8 4.3 26.7 80.1 22.0 M M
23000 -29.4 -20.9 315 76 39 7.1 3.9 25.9 78.6 21.6 M M
22000 -27.3 -17.1 320 73 38 7.1 3.9 24.9 76.8 21.0 M M
21000 -25.2 -13.4 320 70 36 7.4 4.0 24.0 75.2 20.5 M M
20000 -23.7 -10.7 315 62 32 3.9 2.1 22.2 72.0 19.2 M M
19500 -23.1 -9.6 315 58 30 3.9 2.1 21.2 70.1 18.4 M M
19000 -22.6 -8.7 310 54 28 3.9 2.1 20.1 68.2 17.7 M M
18500 -22.0 -7.6 310 50 26 4.0 2.2 19.1 66.4 16.9 M M
18000 -21.5 -6.7 305 46 24 2.1 1.1 18.1 64.5 16.1 M M
17500 -21.3 -6.3 300 45 23 1.6 0.9 16.6 61.9 14.9 M M
17000 -21.0 -5.8 300 43 22 2.0 1.1 15.2 59.4 13.8 M M
16500 -20.4 -4.7 300 43 22 3.0 1.7 13.4 56.2 12.3 M M
16000 -20.0 -4.0 295 43 22 4.2 2.3 12.3 54.2 11.3 M M
15500 -19.3 -2.7 295 44 23 5.2 2.8 11.5 52.8 10.7 M M
15000 -18.5 -1.3 300 45 23 5.8 3.2 10.8 51.4 10.0 M M
14500 -17.5 0.5 300 45 23 7.5 4.1 10.3 50.6 9.7 M M
14000 -16.4 2.5 300 45 23 7.5 4.1 10.0 49.9 9.4 M M
13500 -15.3 4.5 300 44 23 7.3 4.0 9.6 49.2 9.0 M M
13000 -14.2 6.4 305 43 22 7.3 4.0 9.2 48.5 8.7 M M
12500 -13.2 8.2 305 41 21 7.0 3.8 8.7 47.7 8.3 M M
12000 -12.2 10.0 305 39 20 7.0 3.8 8.3 46.9 7.9 M M
11500 -11.2 11.8 305 37 19 6.6 3.6 7.8 46.1 7.5 M M
11000 -10.2 13.6 305 35 18 6.5 3.6 7.3 45.2 7.1 M M
10500 -9.3 15.3 305 32 17 5.1 2.8 6.7 44.0 6.5 M M
10250 -8.9 16.0 305 30 16 6.1 3.3 6.3 43.4 6.2 M M
10000 -8.5 16.7 305 29 15 2.8 1.6 6.0 42.8 5.9 M M
9750 -8.4 16.9 305 27 14 2.6 1.5 5.3 41.6 5.2 M M
9500 -8.1 17.4 305 25 13 5.6 3.0 4.9 40.9 4.9 M M
9250 -7.7 18.1 310 22 12 5.2 2.9 4.6 40.2 4.5 M M
9000 -7.4 18.7 310 20 10 3.5 1.9 4.2 39.6 4.2 M M
8750 -7.3 18.9 320 18 9 1.0 0.5 3.6 38.5 3.6 M M
8500 -7.2 19.0 330 17 9 1.2 0.7 2.9 37.2 2.9 M M
8250 -7.1 19.2 340 16 8 0.5 0.2 2.2 36.0 2.2 M M
8000 -7.2 19.0 355 17 9 -1.6 -0.9 1.4 34.6 1.5 M M
7750 -7.3 18.9 005 20 10 -2.5 -1.4 0.5 32.9 0.6 M M
7500 -7.5 18.5 010 23 12 -2.5 -1.4 -0.4 31.2 -0.3 216 1.1
7250 -7.7 18.1 010 26 13 -2.4 -1.3 -1.4 29.5 -1.2 213 1.1
7000 -7.8 18.0 015 25 13 -2.3 -1.3 -2.3 27.9 -2.1 211 1.1
6750 -8.0 17.6 020 24 12 -2.2 -1.2 -3.2 26.2 -3.0 208 1.1
6500 -8.0 17.6 030 21 11 4.4 2.4 -3.9 24.9 -3.7 201 1.0
6250 -7.3 18.9 030 19 10 10.8 5.9 -4.0 24.7 -3.8 175 0.9
6000 -6.5 20.3 035 18 9 10.8 5.9 -4.0 24.9 -3.8 143 0.7
5750 -5.7 21.7 035 16 8 10.8 5.9 -3.9 25.0 -3.7 112 0.6
5500 -4.9 23.2 035 14 7 12.5 6.9 -3.8 25.2 -3.6 79 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/29/2025 at 0800 MST | 11/29/2025 at 1100 MST
|
CAPE... 0.0 LI... +11.6 | CAPE... 0.0 LI... +12.3
CINH... 0.0 K Index... -25.8 | CINH... 0.0 K Index... -29.9
|
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 -58.0 -72.4 280 51 26 -1.3 -0.7 | -57.5 -71.5 280 50 26 -2.1 -1.2
45000 -60.1 -76.2 280 65 34 -1.3 -0.7 | -60.9 -77.6 280 79 41 -2.1 -1.1
40000 -60.4 -76.7 290 82 42 -0.1 -0.0 | -62.1 -79.8 285 89 46 -0.6 -0.4
38000 -59.8 -75.6 295 89 46 3.9 2.1 | -61.5 -78.7 285 93 48 5.1 2.8
36000 -57.4 -71.3 295 96 49 4.0 2.2 | -58.3 -72.9 285 97 50 5.2 2.9
34000 -55.0 -67.0 295 103 53 4.5 2.5 | -55.2 -67.4 285 102 52 5.7 3.1
32000 -51.0 -59.8 300 99 51 6.9 3.8 | -51.1 -60.0 285 97 50 7.0 3.9
30000 -46.3 -51.3 300 95 49 8.4 4.6 | -46.2 -51.2 285 90 47 8.4 4.6
29000 -43.8 -46.8 300 92 47 8.4 4.6 | -43.8 -46.8 285 87 45 8.3 4.5
28000 -41.3 -42.3 300 89 46 8.4 4.6 | -41.3 -42.3 290 83 43 8.3 4.5
27000 -38.8 -37.8 300 87 45 8.4 4.6 | -38.8 -37.8 290 79 41 8.3 4.6
26000 -36.3 -33.3 300 84 43 8.3 4.5 | -36.5 -33.7 290 77 39 7.7 4.2
25000 -33.8 -28.8 300 81 42 8.3 4.5 | -34.2 -29.6 290 74 38 7.7 4.2
24000 -31.3 -24.3 305 78 40 8.3 4.6 | -31.9 -25.4 295 72 37 7.7 4.2
23000 -29.1 -20.4 305 75 39 6.7 3.7 | -29.6 -21.3 295 69 36 7.4 4.1
22000 -27.2 -17.0 305 72 37 6.6 3.6 | -27.4 -17.3 295 65 34 7.4 4.1
21000 -25.2 -13.4 305 69 36 6.8 3.7 | -25.2 -13.4 295 61 32 7.5 4.1
20000 -23.4 -10.1 305 65 34 5.5 3.0 | -23.4 -10.1 295 59 30 5.3 2.9
19500 -22.6 -8.7 305 63 33 5.5 3.0 | -22.7 -8.9 300 58 30 5.3 2.9
19000 -21.8 -7.2 310 62 32 5.5 3.0 | -21.9 -7.4 300 57 29 5.3 2.9
18500 -21.0 -5.8 310 60 31 5.6 3.0 | -21.1 -6.0 300 56 29 5.2 2.9
18000 -20.2 -4.4 310 58 30 4.7 2.6 | -20.3 -4.5 300 55 29 5.8 3.2
17500 -19.5 -3.1 310 56 29 4.7 2.6 | -19.4 -2.9 305 55 28 5.7 3.2
17000 -18.8 -1.8 305 54 28 4.7 2.6 | -18.1 -0.6 305 54 28 5.1 2.8
16500 -17.7 0.1 305 50 26 4.7 2.6 | -17.4 0.7 305 53 27 5.2 2.9
16000 -17.0 1.4 305 48 25 4.5 2.5 | -16.6 2.1 305 52 27 4.8 2.6
15500 -16.4 2.5 305 48 25 4.4 2.4 | -15.9 3.4 305 51 26 4.6 2.5
15000 -15.7 3.7 305 48 25 3.9 2.2 | -15.2 4.6 305 50 26 4.1 2.2
14500 -15.2 4.6 305 48 25 3.1 1.7 | -14.7 5.5 305 49 25 3.4 1.9
14000 -14.8 5.4 305 47 24 3.0 1.7 | -14.2 6.4 305 48 25 3.3 1.8
13500 -14.3 6.3 305 47 24 2.9 1.6 | -13.8 7.2 305 47 24 2.7 1.5
13000 -13.9 7.0 305 47 24 2.9 1.6 | -13.4 7.9 305 46 23 2.6 1.4
12500 -13.5 7.7 305 47 24 2.8 1.5 | -13.0 8.6 305 43 22 2.1 1.2
12000 -13.1 8.4 305 45 23 2.9 1.6 | -12.7 9.1 305 41 21 2.1 1.2
11500 -12.7 9.1 305 43 22 3.3 1.8 | -12.5 9.5 305 37 19 1.7 0.9
11000 -12.2 10.0 305 40 21 3.4 1.9 | -12.2 10.0 305 33 17 1.8 1.0
10500 -11.7 10.9 305 36 18 3.7 2.0 | -12.0 10.4 310 29 15 1.9 1.0
10250 -11.4 11.5 305 33 17 4.3 2.4 | -11.8 10.8 310 26 14 2.6 1.4
10000 -11.2 11.8 305 31 16 2.0 1.1 | -11.7 10.9 315 24 12 -0.1 -0.1
9750 -11.1 12.0 305 30 16 1.9 1.1 | -11.8 10.8 315 23 12 0.4 0.2
9500 -10.8 12.6 310 27 14 4.2 2.3 | -11.6 11.1 320 21 11 3.6 2.0
9250 -10.6 12.9 315 23 12 3.7 2.0 | -11.4 11.5 325 18 9 2.8 1.5
9000 -10.3 13.5 320 21 11 2.0 1.1 | -11.2 11.8 335 17 9 0.6 0.3
8750 -10.3 13.5 325 19 10 0.9 0.5 | -11.2 11.8 345 15 8 2.7 1.5
8500 -10.2 13.6 335 19 10 1.6 0.9 | -10.8 12.6 350 15 8 6.5 3.6
8250 -10.1 13.8 340 19 10 1.5 0.8 | -10.3 13.5 355 15 8 6.0 3.3
8000 -9.9 14.2 350 19 10 0.9 0.5 | -9.9 14.2 360 14 7 5.5 3.0
7750 -9.8 14.4 355 21 11 2.7 1.5 | -9.4 15.1 005 14 7 7.4 4.1
7500 -9.5 14.9 360 20 10 5.1 2.8 | -8.8 16.2 005 13 7 9.7 5.3
7250 -9.2 15.4 360 18 9 4.1 2.2 | -8.1 17.4 010 13 7 9.0 4.9
7000 -8.9 16.0 010 16 8 2.0 1.1 | -7.4 18.7 010 13 7 7.8 4.3
6750 -8.7 16.3 015 14 7 6.2 3.4 | -6.8 19.8 010 13 7 11.1 6.1
6500 -8.0 17.6 020 12 6 9.4 5.2 | -5.8 21.6 010 13 7 12.0 6.6
6250 -7.4 18.7 025 10 5 8.0 4.4 | -5.1 22.8 010 12 6 9.8 5.4
6000 -6.8 19.8 035 8 4 8.0 4.4 | -4.3 24.3 010 12 6 9.1 5.0
5750 -6.2 20.8 050 6 3 9.4 5.2 | -3.6 25.5 010 12 6 14.0 7.7
5500 -5.4 22.3 040 5 3 13.1 7.2 | -2.0 28.4 010 11 5 26.3 14.5
11/29/2025 at 1400 MST | 11/29/2025 at 1700 MST
|
CAPE... 0.0 LI... +11.3 | CAPE... 0.0 LI... +10.5
CINH... 0.0 K Index... -21.9 | CINH... 0.0 K Index... -18.3
|
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 -59.2 -74.6 280 60 31 -1.0 -0.6 | -59.4 -74.9 285 59 31 -0.7 -0.4
45000 -60.7 -77.3 280 83 43 -1.0 -0.6 | -60.6 -77.1 285 82 42 -0.7 -0.4
40000 -62.3 -80.1 275 97 50 -1.0 -0.6 | -60.9 -77.6 280 93 48 -0.2 -0.1
38000 -61.7 -79.1 275 100 52 5.6 3.1 | -60.2 -76.4 275 97 50 4.1 2.3
36000 -58.3 -72.9 275 102 52 5.7 3.1 | -57.7 -71.9 275 98 50 4.2 2.3
34000 -54.9 -66.8 275 103 53 6.4 3.5 | -55.1 -67.2 275 98 51 5.3 2.9
32000 -50.4 -58.7 280 98 51 7.5 4.1 | -50.7 -59.3 275 95 49 7.6 4.2
30000 -45.9 -50.6 280 94 48 7.5 4.1 | -45.6 -50.1 275 90 46 7.3 4.0
29000 -43.2 -45.8 280 87 45 7.1 3.9 | -43.4 -46.1 280 85 44 7.1 3.9
28000 -41.1 -42.0 285 81 42 7.2 3.9 | -41.3 -42.3 280 80 41 7.1 3.9
27000 -39.0 -38.2 285 76 39 7.1 3.9 | -39.1 -38.4 285 75 39 7.2 3.9
26000 -36.6 -33.9 285 73 38 8.2 4.5 | -37.0 -34.6 285 71 37 7.0 3.9
25000 -34.2 -29.6 290 71 37 8.2 4.5 | -34.9 -30.8 290 68 35 7.0 3.9
24000 -31.7 -25.1 290 69 35 8.3 4.6 | -32.8 -27.0 290 65 33 7.1 3.9
23000 -29.6 -21.3 290 66 34 6.6 3.6 | -30.8 -23.4 295 61 32 6.4 3.5
22000 -27.6 -17.7 295 62 32 6.6 3.6 | -28.9 -20.0 295 58 30 6.4 3.5
21000 -25.6 -14.1 295 59 30 6.6 3.6 | -27.0 -16.6 300 55 28 6.4 3.5
20000 -23.8 -10.8 295 57 29 5.9 3.2 | -24.9 -12.8 300 53 27 7.0 3.8
19500 -22.9 -9.2 295 55 29 5.9 3.2 | -23.9 -11.0 300 52 27 7.0 3.8
19000 -22.0 -7.6 300 54 28 5.9 3.2 | -22.8 -9.0 305 51 26 7.0 3.9
18500 -21.1 -6.0 300 53 27 6.0 3.3 | -21.8 -7.2 305 50 26 7.1 3.9
18000 -20.3 -4.5 300 52 27 4.6 2.5 | -20.8 -5.4 305 49 25 5.7 3.1
17500 -19.6 -3.3 300 52 27 4.7 2.6 | -20.0 -4.0 305 48 25 5.8 3.2
17000 -18.9 -2.0 300 51 26 5.8 3.2 | -19.1 -2.4 305 47 24 5.4 3.0
16500 -17.9 -0.2 305 51 26 6.4 3.5 | -18.3 -0.9 305 46 24 5.3 2.9
16000 -17.0 1.4 305 51 26 6.4 3.5 | -17.5 0.5 305 45 23 5.3 2.9
15500 -16.0 3.2 305 51 26 6.2 3.4 | -16.3 2.7 305 44 23 5.7 3.1
15000 -14.7 5.5 305 51 26 5.8 3.2 | -15.4 4.3 305 43 22 5.3 2.9
14500 -13.8 7.2 310 50 26 5.4 3.0 | -14.7 5.5 305 42 22 5.0 2.7
14000 -13.0 8.6 310 49 25 4.4 2.4 | -13.9 7.0 310 41 21 4.7 2.6
13500 -12.6 9.3 310 47 24 2.5 1.4 | -13.3 8.1 305 39 20 4.3 2.4
13000 -12.2 10.0 305 45 23 2.3 1.2 | -12.6 9.3 305 37 19 4.2 2.3
12500 -12.0 10.4 305 42 22 1.7 0.9 | -12.1 10.2 305 36 18 3.7 2.0
12000 -11.7 10.9 305 39 20 1.5 0.8 | -11.5 11.3 300 34 18 3.6 2.0
11500 -11.6 11.1 300 35 18 0.9 0.5 | -11.0 12.2 295 31 16 3.3 1.8
11000 -11.5 11.3 300 31 16 -0.3 -0.1 | -10.5 13.1 290 28 14 2.8 1.5
10500 -11.8 10.8 300 24 12 -2.5 -1.4 | -10.3 13.5 285 24 13 1.8 1.0
10250 -12.0 10.4 300 20 10 -2.8 -1.5 | -10.1 13.8 285 23 12 2.1 1.1
10000 -12.2 10.0 300 16 8 -0.8 -0.4 | -10.0 14.0 285 21 11 0.6 0.3
9750 -12.2 10.0 305 14 7 0.5 0.3 | -10.1 13.8 285 20 10 -0.5 -0.3
9500 -12.2 10.0 315 10 5 -0.9 -0.5 | -10.1 13.8 280 16 8 -0.1 -0.1
9250 -12.3 9.9 345 7 3 1.2 0.6 | -10.1 13.8 275 13 7 0.1 0.1
9000 -12.0 10.4 010 6 3 5.3 2.9 | -10.1 13.8 270 10 5 -0.1 -0.1
8750 -11.5 11.3 015 6 3 9.3 5.1 | -10.1 13.8 265 8 4 2.5 1.4
8500 -10.7 12.7 020 6 3 11.5 6.3 | -9.8 14.4 255 6 3 4.7 2.6
8250 -9.8 14.4 025 6 3 10.1 5.6 | -9.4 15.1 230 4 2 5.8 3.2
8000 -9.1 15.6 025 6 3 9.0 5.0 | -8.9 16.0 205 2 1 7.0 3.8
7750 -8.4 16.9 025 6 3 9.7 5.3 | -8.4 16.9 160 2 1 7.6 4.2
7500 -7.7 18.1 025 6 3 10.0 5.5 | -7.7 18.1 135 3 1 9.4 5.1
7250 -7.0 19.4 025 6 3 10.1 5.5 | -7.0 19.4 120 4 2 9.7 5.3
7000 -6.2 20.8 025 6 3 9.8 5.4 | -6.3 20.7 110 4 2 10.1 5.5
6750 -5.5 22.1 025 6 3 10.8 5.9 | -5.5 22.1 105 5 3 9.1 5.0
6500 -4.6 23.7 030 6 3 10.8 5.9 | -4.9 23.2 105 6 3 9.0 4.9
6250 -3.9 25.0 030 6 3 10.2 5.6 | -4.2 24.4 100 6 3 9.5 5.2
6000 -3.1 26.4 030 6 3 9.6 5.3 | -3.4 25.9 100 7 4 9.9 5.4
5750 -2.3 27.9 030 6 3 13.4 7.3 | -2.7 27.1 100 7 4 9.0 4.9
5500 -1.0 30.2 030 6 3 22.0 12.1 | -2.2 28.0 100 6 3 5.4 2.9
________________________________________________________________________________
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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