Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
264
UXUS97 KBOU 070024
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1723 MST Saturday, December 6, 2025
This forecast is for Sunday, December 7, 2025:
If the trigger temperature of 43.2 F/6.2 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 473 ft/min (2.4 m/s)
Maximum height of thermals.................. 11179 ft MSL (5871 ft AGL)
Forecast maximum temperature................... 45.0 F/7.7 C
Time of trigger temperature.................... 1145 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................. 7072 ft MSL (1764 ft AGL)
Thermal soaring outlook for Monday 12/08....... Poor
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Neither
Potential height of wave....................... 15873 ft MSL (10565 ft AGL)
Wave soaring outlook for Monday 12/08.......... Poor
Remarks...
Sunrise/Sunset.................... 07:07:39 / 16:34:42 MST
Total possible sunshine........... 9 hr 27 min 3 sec (567 min 3 sec)
Altitude of sun at 11:51:10 MST... 27.50 degrees
Upper air data from numerical model forecast valid on 12/07/2025 at 0500 MST
Freezing level.................. 5521 ft MSL (213 ft AGL)
Additional freezing level....... 6623 ft MSL (1315 ft AGL)
Convective condensation level... 13740 ft MSL (8432 ft AGL)
Lifted condensation level....... 13379 ft MSL (8070 ft AGL)
Lifted index.................... +9.2
K index......................... -2.5
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 -60.8 -77.4 290 60 31 1.8 1.0 M M M M M
45000 -58.2 -72.8 290 60 31 1.8 1.0 M M M M M
40000 -52.8 -63.0 300 65 33 3.6 2.0 M M M M M
38000 -50.9 -59.6 305 67 34 2.2 1.2 M M M M M
36000 -49.6 -57.3 310 67 35 2.2 1.2 M M M M M
34000 -48.3 -54.9 315 68 35 2.2 1.2 M M M M M
32000 -46.7 -52.1 315 72 37 2.7 1.5 M M M M M
30000 -45.1 -49.2 320 77 39 2.6 1.4 M M M M M
29000 -43.0 -45.4 320 78 40 6.1 3.4 31.1 87.9 18.0 M M
28000 -41.2 -42.2 320 79 41 6.1 3.4 29.6 85.3 17.2 M M
27000 -39.3 -38.7 325 81 42 6.1 3.4 28.3 83.0 16.4 M M
26000 -37.6 -35.7 320 78 40 5.5 3.0 26.8 80.3 15.4 M M
25000 -36.0 -32.8 320 73 38 5.5 3.0 25.1 77.2 14.2 M M
24000 -34.3 -29.7 320 68 35 5.5 3.0 23.6 74.5 13.2 M M
23000 -32.8 -27.0 320 61 31 4.4 2.4 21.9 71.4 11.9 M M
22000 -31.5 -24.7 315 53 27 4.4 2.4 19.9 67.8 10.4 M M
21000 -30.2 -22.4 310 44 23 4.3 2.4 18.0 64.4 9.0 M M
20000 -28.6 -19.5 310 39 20 5.7 3.1 16.4 61.5 7.7 M M
19500 -27.7 -17.9 310 38 19 5.7 3.2 15.7 60.2 7.2 M M
19000 -26.9 -16.4 315 36 19 5.7 3.2 15.0 58.9 6.6 M M
18500 -26.0 -14.8 315 35 18 5.8 3.2 14.3 57.8 6.1 M M
18000 -25.2 -13.4 315 32 17 5.6 3.1 13.6 56.6 5.5 M M
17500 -24.3 -11.7 310 28 15 5.6 3.1 12.9 55.2 4.9 M M
17000 -23.5 -10.3 305 25 13 6.1 3.3 12.2 54.0 4.3 M M
16500 -22.5 -8.5 305 22 11 6.8 3.7 11.7 53.0 3.9 M M
16000 -21.5 -6.7 305 20 10 6.7 3.7 11.2 52.1 3.4 M M
15500 -20.2 -4.4 290 16 8 5.5 3.0 10.2 50.3 2.5 M M
15000 -19.4 -2.9 275 15 8 6.2 3.4 9.4 49.0 1.9 M M
14500 -18.4 -1.1 275 13 7 7.2 3.9 9.0 48.2 1.5 M M
14000 -17.3 0.9 275 11 6 7.4 4.0 8.6 47.4 1.1 M M
13500 -16.2 2.8 280 11 5 7.8 4.3 8.2 46.8 0.8 M M
13000 -15.0 5.0 290 11 5 8.1 4.4 7.9 46.2 0.5 M M
12500 -13.7 7.3 295 12 6 9.2 5.1 7.8 46.0 0.3 M M
12000 -12.3 9.9 300 14 7 9.0 5.0 7.7 45.8 0.3 M M
11500 -11.0 12.2 310 17 9 8.5 4.7 7.5 45.5 0.1 M M
11000 -9.8 14.4 315 20 10 8.5 4.6 7.3 45.2 -0.1 449 2.3
10500 -8.5 16.7 315 22 12 8.1 4.5 7.1 44.8 -0.3 397 2.0
10250 -7.9 17.8 315 24 12 9.1 5.0 7.0 44.6 -0.4 371 1.9
10000 -7.3 18.9 310 25 13 5.5 3.0 6.9 44.4 -0.5 346 1.8
9750 -7.0 19.4 310 26 13 6.3 3.5 6.4 43.6 -0.9 329 1.7
9500 -6.3 20.7 310 27 14 10.6 5.8 6.4 43.6 -1.0 300 1.5
9250 -5.5 22.1 310 29 15 9.4 5.1 6.4 43.6 -1.0 271 1.4
9000 -4.9 23.2 310 30 15 8.0 4.4 6.4 43.5 -1.0 244 1.2
8750 -4.4 24.1 310 31 16 7.0 3.8 6.2 43.1 -1.2 221 1.1
8500 -3.8 25.2 305 33 17 7.7 4.2 6.0 42.8 -1.4 197 1.0
8250 -3.3 26.1 305 34 18 7.1 3.9 5.8 42.5 -1.6 173 0.9
8000 -2.8 27.0 300 35 18 7.0 3.8 5.6 42.1 -1.8 151 0.8
7750 -2.3 27.9 300 35 18 5.6 3.1 5.3 41.6 -2.1 129 0.7
7500 -1.9 28.6 300 34 18 4.4 2.4 5.0 40.9 -2.5 112 0.6
7250 -1.6 29.1 295 33 17 6.8 3.7 4.6 40.3 -2.9 93 0.5
7000 -1.0 30.2 295 32 16 7.8 4.3 4.5 40.0 -3.0 68 0.3
6750 -0.4 31.3 295 30 15 8.8 4.8 4.3 39.8 -3.2 44 0.2
6500 0.2 32.4 295 28 14 6.4 3.5 4.2 39.6 -3.3 17 0.1
6250 0.5 32.9 290 25 13 2.1 1.1 3.8 38.8 -3.8 2 0.0
6000 0.7 33.3 290 21 11 3.5 1.9 3.2 37.8 -4.3 M M
5750 0.8 33.4 285 18 9 -0.8 -0.5 2.7 36.8 -4.9 M M
5500 0.2 32.4 275 13 7 -16.2 -8.9 1.4 34.4 -6.3 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
12/07/2025 at 0800 MST | 12/07/2025 at 1100 MST
|
CAPE... 0.0 LI... +7.5 | CAPE... 0.0 LI... +8.8
CINH... 0.0 K Index... -3.6 | CINH... 0.0 K Index... -5.6
|
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 -60.3 -76.5 290 54 28 2.2 1.2 | -61.2 -78.2 290 57 30 2.3 1.3
45000 -56.8 -70.2 295 63 33 2.2 1.2 | -57.5 -71.5 300 72 37 2.3 1.3
40000 -53.6 -64.5 305 75 39 2.1 1.1 | -55.0 -67.0 305 81 42 1.6 0.9
38000 -52.4 -62.3 310 80 41 1.9 1.0 | -54.1 -65.4 310 87 45 1.3 0.7
36000 -51.3 -60.3 315 86 44 1.9 1.0 | -53.4 -64.1 315 96 49 1.3 0.7
34000 -50.2 -58.4 320 92 47 2.0 1.1 | -52.6 -62.7 320 105 54 2.5 1.4
32000 -48.5 -55.3 325 95 49 2.8 1.5 | -49.4 -56.9 325 99 51 4.9 2.7
30000 -46.5 -51.7 325 99 51 5.6 3.1 | -46.4 -51.5 330 93 48 6.5 3.5
29000 -44.6 -48.3 325 96 50 6.4 3.5 | -44.5 -48.1 325 90 46 6.4 3.5
28000 -42.7 -44.9 325 94 48 6.4 3.5 | -42.6 -44.7 325 88 45 6.4 3.5
27000 -40.8 -41.4 325 92 47 6.3 3.5 | -40.7 -41.3 325 85 44 6.2 3.4
26000 -38.7 -37.7 330 89 46 7.5 4.1 | -38.6 -37.5 325 81 42 7.4 4.1
25000 -36.5 -33.7 330 86 45 7.5 4.1 | -36.4 -33.5 325 77 40 7.4 4.0
24000 -34.2 -29.6 330 84 43 7.5 4.1 | -34.2 -29.6 325 73 38 7.4 4.0
23000 -32.0 -25.6 330 80 41 7.5 4.1 | -31.9 -25.4 325 69 36 7.6 4.2
22000 -29.8 -21.6 330 76 39 7.5 4.1 | -29.7 -21.5 325 66 34 7.6 4.2
21000 -27.5 -17.5 330 72 37 7.7 4.2 | -27.4 -17.3 325 62 32 7.6 4.2
20000 -25.8 -14.4 330 65 34 5.0 2.7 | -25.1 -13.2 325 60 31 7.5 4.1
19500 -25.1 -13.2 330 62 32 5.0 2.7 | -24.0 -11.2 325 58 30 7.5 4.1
19000 -24.4 -11.9 330 58 30 5.0 2.8 | -22.9 -9.2 325 57 29 7.5 4.1
18500 -23.6 -10.5 330 55 28 5.2 2.8 | -21.8 -7.2 325 55 28 7.5 4.1
18000 -23.0 -9.4 325 51 26 3.4 1.9 | -20.5 -4.9 325 53 28 5.3 2.9
17500 -22.4 -8.3 325 48 25 3.5 1.9 | -19.7 -3.5 325 52 27 5.1 2.8
17000 -21.6 -6.9 325 43 22 4.9 2.7 | -19.0 -2.2 325 50 26 3.9 2.1
16500 -20.9 -5.6 325 40 21 4.8 2.6 | -18.4 -1.1 325 48 25 4.0 2.2
16000 -20.2 -4.4 325 37 19 5.1 2.8 | -17.9 -0.2 325 45 23 3.8 2.1
15500 -19.4 -2.9 325 35 18 5.2 2.8 | -17.3 0.9 325 43 22 3.8 2.1
15000 -18.6 -1.5 325 33 17 5.4 3.0 | -16.7 1.9 320 41 21 4.3 2.4
14500 -17.8 -0.0 325 31 16 5.5 3.0 | -16.1 3.0 320 38 20 4.5 2.5
14000 -17.0 1.4 320 28 14 5.7 3.1 | -15.4 4.3 320 36 18 5.0 2.7
13500 -16.1 3.0 320 27 14 5.9 3.3 | -14.6 5.7 320 34 18 5.4 2.9
13000 -15.2 4.6 325 27 14 6.4 3.5 | -13.8 7.2 320 33 17 5.4 2.9
12500 -14.2 6.4 325 26 13 7.2 4.0 | -13.0 8.6 320 31 16 5.4 3.0
12000 -13.1 8.4 325 25 13 7.4 4.1 | -12.3 9.9 320 28 15 6.2 3.4
11500 -12.0 10.4 325 26 13 7.8 4.3 | -11.2 11.8 320 28 14 7.2 3.9
11000 -10.8 12.6 325 28 14 8.0 4.4 | -10.1 13.8 325 28 14 7.1 3.9
10500 -9.6 14.7 320 28 14 8.4 4.6 | -9.1 15.6 320 26 13 7.3 4.0
10250 -9.0 15.8 320 28 15 7.9 4.4 | -8.6 16.5 320 25 13 5.8 3.2
10000 -8.5 16.7 320 28 14 4.7 2.6 | -8.3 17.1 320 24 12 3.9 2.2
9750 -8.2 17.2 320 28 14 7.4 4.1 | -7.9 17.8 320 23 12 7.3 4.0
9500 -7.4 18.7 320 29 15 11.8 6.5 | -7.2 19.0 315 23 12 10.2 5.6
9250 -6.6 20.1 315 30 16 9.6 5.3 | -6.5 20.3 315 23 12 8.2 4.5
9000 -6.0 21.2 315 30 16 6.9 3.8 | -6.0 21.2 315 22 11 6.3 3.4
8750 -5.5 22.1 315 30 15 7.3 4.0 | -5.5 22.1 315 21 11 7.7 4.2
8500 -4.8 23.4 315 30 15 9.1 5.0 | -4.8 23.4 310 21 11 9.2 5.1
8250 -4.2 24.4 310 30 16 7.9 4.3 | -4.2 24.4 310 21 11 8.2 4.5
8000 -3.7 25.3 310 29 15 6.7 3.7 | -3.6 25.5 310 20 10 7.1 3.9
7750 -3.2 26.2 310 28 14 8.4 4.6 | -3.1 26.4 305 19 10 9.1 5.0
7500 -2.5 27.5 310 27 14 9.3 5.1 | -2.3 27.9 305 19 10 9.8 5.4
7250 -1.8 28.8 310 26 14 8.1 4.4 | -1.7 28.9 305 18 9 8.3 4.6
7000 -1.2 29.8 310 25 13 7.1 3.9 | -1.1 30.0 300 17 9 7.3 4.0
6750 -0.7 30.7 310 23 12 9.8 5.4 | -0.5 31.1 300 16 8 10.7 5.9
6500 0.1 32.2 305 22 11 8.3 4.6 | 0.5 32.9 300 16 8 11.7 6.4
6250 0.5 32.9 305 19 10 4.0 2.2 | 1.2 34.2 300 15 8 9.3 5.1
6000 0.9 33.6 305 16 8 7.0 3.9 | 1.9 35.4 300 13 7 9.3 5.1
5750 1.2 34.2 300 13 7 -0.7 -0.4 | 2.6 36.7 300 12 6 11.7 6.4
5500 0.4 32.7 285 9 5 -20.6 -11.3 | 3.7 38.7 295 10 5 17.7 9.7
12/07/2025 at 1400 MST | 12/07/2025 at 1700 MST
|
CAPE... 0.0 LI... +8.3 | CAPE... 0.0 LI... +8.3
CINH... 0.0 K Index... -15.4 | CINH... 0.0 K Index... -8.2
|
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 -61.6 -78.9 290 58 30 2.3 1.3 | -61.9 -79.4 290 64 33 2.5 1.3
45000 -58.0 -72.4 295 70 36 2.2 1.2 | -58.0 -72.4 295 71 36 2.1 1.1
40000 -56.8 -70.2 305 83 43 0.7 0.4 | -57.8 -72.0 300 85 44 0.1 0.1
38000 -56.1 -69.0 305 89 46 2.0 1.1 | -57.1 -70.8 300 91 47 2.6 1.4
36000 -54.9 -66.8 310 97 50 2.0 1.1 | -55.6 -68.1 305 97 50 2.5 1.4
34000 -53.6 -64.5 315 104 53 4.5 2.5 | -54.0 -65.2 305 102 53 5.6 3.1
32000 -49.3 -56.7 315 98 50 6.5 3.5 | -49.9 -57.8 310 99 51 6.8 3.7
30000 -45.4 -49.7 320 93 48 6.9 3.8 | -45.2 -49.4 310 94 49 8.0 4.4
29000 -43.3 -45.9 320 89 46 6.9 3.8 | -42.9 -45.2 310 89 46 8.0 4.4
28000 -41.2 -42.2 320 85 44 6.9 3.8 | -40.5 -40.9 310 84 43 8.0 4.4
27000 -39.2 -38.6 320 82 42 6.9 3.8 | -38.1 -36.6 310 79 41 7.7 4.2
26000 -36.9 -34.4 320 79 40 7.7 4.2 | -36.0 -32.8 310 74 38 7.0 3.8
25000 -34.6 -30.3 320 75 39 7.7 4.2 | -33.9 -29.0 305 68 35 7.0 3.8
24000 -32.3 -26.1 320 72 37 7.9 4.3 | -31.8 -25.2 305 63 32 7.0 3.8
23000 -30.3 -22.5 320 68 35 6.2 3.4 | -29.6 -21.3 305 60 31 7.6 4.2
22000 -28.5 -19.3 315 62 32 6.2 3.4 | -27.4 -17.3 305 59 30 7.6 4.2
21000 -26.6 -15.9 315 57 29 6.6 3.6 | -25.1 -13.2 310 58 30 7.2 3.9
20000 -24.4 -11.9 315 53 27 7.4 4.1 | -23.1 -9.6 305 55 28 6.6 3.6
19500 -23.3 -9.9 315 51 26 7.4 4.1 | -22.1 -7.8 305 53 28 6.6 3.6
19000 -22.2 -8.0 315 50 26 7.4 4.1 | -21.2 -6.2 305 52 27 6.6 3.6
18500 -21.1 -6.0 310 48 25 7.6 4.1 | -20.2 -4.4 305 50 26 6.6 3.6
18000 -19.9 -3.8 310 47 24 8.3 4.6 | -19.2 -2.6 305 49 25 6.5 3.6
17500 -18.6 -1.5 310 48 25 8.4 4.6 | -18.2 -0.8 305 47 24 6.5 3.6
17000 -17.0 1.4 310 48 25 6.6 3.6 | -17.3 0.9 305 45 23 6.3 3.4
16500 -16.0 3.2 310 48 25 6.8 3.7 | -16.3 2.7 305 43 22 6.2 3.4
16000 -15.1 4.8 310 47 24 4.7 2.6 | -14.9 5.2 305 40 21 5.2 2.9
15500 -14.4 6.1 310 45 23 4.9 2.7 | -14.1 6.6 305 37 19 5.4 2.9
15000 -13.7 7.3 310 42 21 3.8 2.1 | -13.3 8.1 305 35 18 4.9 2.7
14500 -13.2 8.2 310 38 20 3.5 1.9 | -12.6 9.3 305 32 16 4.8 2.6
14000 -12.6 9.3 310 35 18 4.0 2.2 | -11.9 10.6 305 29 15 4.6 2.5
13500 -12.0 10.4 310 32 16 4.3 2.4 | -11.2 11.8 305 27 14 4.5 2.5
13000 -11.4 11.5 310 29 15 3.8 2.1 | -10.5 13.1 305 24 13 4.4 2.4
12500 -10.9 12.4 310 25 13 3.3 1.8 | -9.9 14.2 300 21 11 4.5 2.4
12000 -10.5 13.1 305 21 11 5.0 2.7 | -9.2 15.4 300 18 9 6.0 3.3
11500 -9.4 15.1 310 19 10 7.0 3.8 | -8.1 17.4 300 20 10 7.3 4.0
11000 -8.4 16.9 310 17 9 6.6 3.6 | -7.1 19.2 300 21 11 6.4 3.5
10500 -7.5 18.5 305 16 8 6.4 3.5 | -6.2 20.8 295 23 12 6.0 3.3
10250 -7.0 19.4 305 15 8 5.4 3.0 | -5.8 21.6 290 23 12 4.8 2.6
10000 -6.7 19.9 300 15 8 3.7 2.0 | -5.5 22.1 290 24 12 3.1 1.7
9750 -6.4 20.5 300 16 8 5.3 2.9 | -5.3 22.5 285 23 12 4.4 2.4
9500 -5.9 21.4 295 16 8 6.8 3.7 | -4.9 23.2 280 21 11 5.5 3.0
9250 -5.5 22.1 295 17 9 6.7 3.7 | -4.6 23.7 270 20 10 5.7 3.1
9000 -4.9 23.2 295 17 9 7.3 4.0 | -4.1 24.6 265 19 10 6.8 3.7
8750 -4.4 24.1 290 17 8 7.5 4.1 | -3.6 25.5 265 18 9 7.7 4.2
8500 -3.8 25.2 290 16 8 7.6 4.2 | -3.0 26.6 265 17 9 8.2 4.5
8250 -3.3 26.1 290 15 7 7.7 4.2 | -2.4 27.7 260 15 8 8.2 4.5
8000 -2.7 27.1 290 14 7 7.9 4.3 | -1.7 28.9 260 14 7 8.7 4.8
7750 -2.1 28.2 290 13 6 7.9 4.4 | -1.1 30.0 255 13 7 7.3 4.0
7500 -1.5 29.3 290 12 6 7.8 4.3 | -0.7 30.7 250 11 6 6.0 3.3
7250 -1.0 30.2 290 10 5 7.4 4.0 | -0.2 31.6 245 10 5 6.4 3.5
7000 -0.4 31.3 290 8 4 7.5 4.1 | 0.3 32.5 240 9 5 6.4 3.5
6750 0.1 32.2 285 7 3 6.6 3.6 | 0.8 33.4 235 9 4 6.1 3.3
6500 0.6 33.1 275 5 3 8.3 4.6 | 1.2 34.2 225 8 4 6.1 3.3
6250 1.4 34.5 270 4 2 10.6 5.8 | 1.7 35.1 215 8 4 6.2 3.4
6000 2.1 35.8 265 4 2 9.8 5.4 | 2.1 35.8 205 8 4 6.9 3.8
5750 2.9 37.2 260 3 2 10.7 5.9 | 2.6 36.7 195 8 4 4.2 2.3
5500 3.7 38.7 255 3 2 12.8 7.0 | 2.6 36.7 190 7 4 -2.5 -1.4
________________________________________________________________________________
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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