Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
931
UXUS97 KBOU 241328
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0624 MST Monday, November 24, 2025
This forecast is for Monday, November 24, 2025:
If the trigger temperature of 54.1 F/12.3 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 568 ft/min (2.9 m/s)
Maximum height of thermals.................. 12252 ft MSL (6945 ft AGL)
Forecast maximum temperature................... 58.0 F/14.9 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................. 8101 ft MSL (2794 ft AGL)
Thermal soaring outlook for Tuesday 11/25...... Fair
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)................ Weak NVA
Potential height of wave....................... 17623 ft MSL (12316 ft AGL)
Wave soaring outlook for Tuesday 11/25......... Fair
Remarks...
Sunrise/Sunset.................... 06:54:48 / 16:37:49 MST
Total possible sunshine........... 9 hr 43 min 1 sec (583 min 1 sec)
Altitude of sun at 11:46:18 MST... 29.44 degrees
Upper air data from numerical model forecast valid on 11/24/2025 at 0500 MST
Freezing level.................. 9439 ft MSL (4132 ft AGL)
Convective condensation level... 16409 ft MSL (11102 ft AGL)
Lifted condensation level....... 14443 ft MSL (9136 ft AGL)
Lifted index.................... +5.4
K index......................... +6.7
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 -59.4 -74.9 275 25 13 1.9 1.1 M M M M M
45000 -56.5 -69.7 295 26 13 1.1 0.6 M M M M M
40000 -55.7 -68.3 330 31 16 0.6 0.3 M M M M M
38000 -54.8 -66.6 340 35 18 2.3 1.3 M M M M M
36000 -53.5 -64.3 350 39 20 2.3 1.3 M M M M M
34000 -51.3 -60.3 355 43 22 7.1 3.9 M M M M M
32000 -47.1 -52.8 355 42 22 7.0 3.9 M M M M M
30000 -42.9 -45.2 360 40 21 6.5 3.6 33.4 92.1 14.2 M M
29000 -41.0 -41.8 355 37 19 6.6 3.6 32.0 89.6 13.4 M M
28000 -39.0 -38.2 355 34 18 6.6 3.6 30.8 87.4 12.6 M M
27000 -37.0 -34.6 350 31 16 6.9 3.8 29.7 85.5 11.9 M M
26000 -34.8 -30.6 350 30 15 7.6 4.2 28.7 83.7 11.3 M M
25000 -32.5 -26.5 350 29 15 7.6 4.2 27.9 82.2 10.7 M M
24000 -30.2 -22.4 350 28 14 7.6 4.2 27.2 81.0 10.3 M M
23000 -28.0 -18.4 350 27 14 7.4 4.1 26.3 79.3 9.7 M M
22000 -25.8 -14.4 350 26 14 7.5 4.1 25.4 77.8 9.1 M M
21000 -23.6 -10.5 350 26 13 7.3 4.0 24.7 76.5 8.5 M M
20000 -21.4 -6.5 350 25 13 7.2 4.0 23.7 74.7 7.8 M M
19500 -20.4 -4.7 350 24 13 7.2 4.0 23.3 73.9 7.4 M M
19000 -19.3 -2.7 350 24 12 7.2 4.0 22.8 73.1 7.1 M M
18500 -18.2 -0.8 350 24 12 7.2 3.9 22.4 72.4 6.7 M M
18000 -17.2 1.0 350 24 12 6.9 3.8 22.0 71.5 6.4 M M
17500 -16.2 2.8 350 24 13 7.0 3.8 21.5 70.7 6.0 M M
17000 -14.6 5.7 350 25 13 6.6 3.6 20.7 69.3 5.3 M M
16500 -13.6 7.5 350 26 13 6.7 3.7 20.2 68.4 4.9 M M
16000 -12.7 9.1 350 26 13 5.9 3.3 19.6 67.3 4.4 M M
15500 -11.8 10.8 350 26 14 6.0 3.3 19.0 66.2 3.9 M M
15000 -10.9 12.4 350 27 14 5.4 2.9 18.3 65.0 3.3 M M
14500 -10.2 13.6 350 27 14 5.2 2.9 17.6 63.6 2.6 M M
14000 -9.4 15.1 350 27 14 5.4 3.0 16.8 62.3 2.0 M M
13500 -8.6 16.5 350 27 14 5.7 3.1 16.2 61.1 1.3 M M
13000 -7.7 18.1 345 26 14 6.1 3.3 15.5 59.9 0.7 M M
12500 -6.8 19.8 345 26 13 6.7 3.7 15.0 58.9 0.2 M M
12000 -5.8 21.6 345 25 13 6.9 3.8 14.5 58.1 -0.3 541 2.7
11500 -4.7 23.5 345 24 12 7.4 4.1 14.1 57.4 -0.7 494 2.5
11000 -3.6 25.5 345 23 12 6.9 3.8 13.7 56.7 -1.0 446 2.3
10500 -2.6 27.3 345 23 12 5.6 3.1 13.2 55.7 -1.6 403 2.0
10250 -2.2 28.0 345 22 12 8.8 4.8 12.9 55.2 -1.8 382 1.9
10000 -1.4 29.5 345 22 11 10.8 5.9 13.0 55.4 -1.7 350 1.8
9750 -0.7 30.7 345 22 11 7.9 4.3 12.9 55.3 -1.8 322 1.6
9500 -0.1 31.8 345 22 11 7.6 4.2 12.8 55.0 -2.0 298 1.5
9250 0.4 32.7 350 21 11 7.3 4.0 12.6 54.7 -2.1 273 1.4
9000 0.9 33.6 350 21 11 6.2 3.4 12.4 54.3 -2.4 251 1.3
8750 1.4 34.5 350 21 11 7.3 4.0 12.1 53.8 -2.6 229 1.2
8500 2.0 35.6 350 20 10 8.5 4.7 12.0 53.6 -2.8 204 1.0
8250 2.6 36.7 350 19 10 7.9 4.3 11.9 53.4 -2.9 178 0.9
8000 3.2 37.8 350 18 9 7.5 4.1 11.7 53.1 -3.1 153 0.8
7750 3.8 38.8 345 17 9 7.4 4.0 11.5 52.8 -3.2 130 0.7
7500 4.3 39.7 345 16 8 8.0 4.4 11.4 52.5 -3.4 105 0.5
7250 4.9 40.8 340 16 8 5.6 3.1 11.2 52.2 -3.6 82 0.4
7000 5.1 41.2 340 15 8 3.2 1.8 10.7 51.3 -4.1 66 0.3
6750 5.4 41.7 340 14 7 4.5 2.5 10.3 50.5 -4.5 50 0.3
6500 5.7 42.3 335 12 6 3.6 2.0 9.9 49.8 -5.0 33 0.2
6250 5.9 42.6 335 10 5 1.4 0.8 9.3 48.8 -5.6 21 0.1
6000 6.0 42.8 335 8 4 0.8 0.4 8.7 47.6 -6.2 12 0.1
5750 6.0 42.8 335 6 3 1.2 0.7 8.0 46.4 -6.9 2 0.0
5500 5.9 42.6 310 4 2 -9.6 -5.2 7.1 44.8 -7.8 0 0.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/24/2025 at 0800 MST | 11/24/2025 at 1100 MST
|
CAPE... 0.0 LI... +6.0 | CAPE... 0.0 LI... +6.0
CINH... -0.1 K Index... +1.5 | CINH... -0.2 K Index... +1.9
|
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 -59.6 -75.3 265 30 15 2.1 1.1 | -60.1 -76.2 260 33 17 2.3 1.3
45000 -56.5 -69.7 275 31 16 0.7 0.4 | -56.5 -69.7 270 42 22 0.8 0.5
40000 -56.5 -69.7 300 30 15 0.0 0.0 | -56.1 -69.0 280 40 20 0.2 0.1
38000 -55.6 -68.1 310 31 16 3.0 1.6 | -55.5 -67.9 285 38 20 2.0 1.1
36000 -53.8 -64.8 320 32 16 3.0 1.6 | -54.2 -65.6 290 36 18 2.0 1.1
34000 -51.2 -60.2 325 33 17 6.9 3.8 | -52.6 -62.7 295 34 17 8.1 4.4
32000 -47.0 -52.6 330 32 16 7.0 3.8 | -47.6 -53.7 300 33 17 7.4 4.1
30000 -42.7 -44.9 335 31 16 7.3 4.0 | -43.1 -45.6 305 33 17 7.7 4.2
29000 -40.5 -40.9 335 31 16 7.3 4.0 | -40.8 -41.4 305 32 16 7.7 4.2
28000 -38.3 -36.9 335 30 16 7.3 4.0 | -38.5 -37.3 305 31 16 7.7 4.2
27000 -36.1 -33.0 335 30 16 7.4 4.1 | -36.2 -33.2 310 30 15 7.8 4.3
26000 -33.9 -29.0 335 29 15 7.5 4.1 | -33.8 -28.8 310 29 15 8.0 4.4
25000 -31.7 -25.1 335 28 14 7.5 4.1 | -31.4 -24.5 310 27 14 8.0 4.4
24000 -29.4 -20.9 335 27 14 7.4 4.1 | -29.1 -20.4 315 26 13 7.8 4.3
23000 -27.2 -17.0 340 26 13 7.3 4.0 | -26.9 -16.4 315 23 12 7.2 4.0
22000 -25.0 -13.0 340 25 13 7.3 4.0 | -24.7 -12.5 315 21 11 7.2 4.0
21000 -22.9 -9.2 340 24 12 7.1 3.9 | -22.6 -8.7 320 19 10 7.0 3.8
20000 -20.8 -5.4 345 24 12 7.0 3.8 | -20.6 -5.1 325 19 10 6.8 3.7
19500 -19.7 -3.5 345 24 12 7.0 3.8 | -19.5 -3.1 325 19 10 6.8 3.7
19000 -18.7 -1.7 345 24 12 7.0 3.8 | -18.5 -1.3 325 19 10 6.8 3.7
18500 -17.7 0.1 345 24 12 6.9 3.8 | -17.5 0.5 330 19 10 6.9 3.8
18000 -16.7 1.9 345 24 12 6.7 3.7 | -16.5 2.3 330 19 10 7.0 3.9
17500 -15.2 4.6 350 24 13 6.8 3.7 | -15.4 4.3 330 19 10 7.0 3.9
17000 -14.1 6.6 350 25 13 6.9 3.8 | -13.8 7.2 330 20 10 7.1 3.9
16500 -13.1 8.4 350 25 13 6.9 3.8 | -12.8 9.0 330 20 10 7.1 3.9
16000 -12.1 10.2 350 25 13 6.5 3.6 | -11.7 10.9 330 20 10 6.8 3.8
15500 -11.2 11.8 345 25 13 6.6 3.6 | -10.7 12.7 330 21 11 6.9 3.8
15000 -10.2 13.6 345 25 13 5.8 3.2 | -9.7 14.5 330 21 11 6.2 3.4
14500 -9.4 15.1 345 25 13 5.8 3.2 | -8.8 16.2 330 21 11 6.1 3.3
14000 -8.5 16.7 345 25 13 5.5 3.0 | -7.9 17.8 330 21 11 5.5 3.0
13500 -7.8 18.0 345 24 12 5.3 2.9 | -7.2 19.0 325 21 11 5.2 2.9
13000 -7.0 19.4 340 24 12 5.4 3.0 | -6.4 20.5 325 21 11 5.2 2.8
12500 -6.2 20.8 340 23 12 5.6 3.1 | -5.6 21.9 325 20 10 5.1 2.8
12000 -5.3 22.5 345 22 11 5.9 3.2 | -4.9 23.2 325 19 10 5.5 3.0
11500 -4.4 24.1 345 21 11 6.3 3.4 | -4.0 24.8 325 17 9 6.0 3.3
11000 -3.5 25.7 345 20 10 6.6 3.6 | -3.1 26.4 325 16 8 5.6 3.1
10500 -2.4 27.7 350 19 10 7.9 4.4 | -2.3 27.9 325 15 8 4.4 2.4
10250 -1.9 28.6 350 19 10 3.1 1.7 | -1.9 28.6 325 14 7 8.6 4.7
10000 -1.8 28.8 350 19 10 4.4 2.4 | -1.1 30.0 325 14 7 9.9 5.4
9750 -1.2 29.8 350 18 9 10.1 5.5 | -0.6 30.9 325 13 7 6.5 3.6
9500 -0.5 31.1 350 18 9 8.8 4.8 | -0.0 32.0 325 13 7 7.6 4.2
9250 0.2 32.4 350 17 9 8.3 4.6 | 0.5 32.9 330 12 6 6.7 3.7
9000 0.7 33.3 350 17 9 6.9 3.8 | 1.0 33.8 330 12 6 6.7 3.7
8750 1.2 34.2 350 17 9 8.2 4.5 | 1.6 34.9 330 11 6 8.3 4.5
8500 1.9 35.4 350 16 8 9.8 5.4 | 2.2 36.0 335 10 5 9.3 5.1
8250 2.6 36.7 350 16 8 8.1 4.4 | 2.9 37.2 335 10 5 8.1 4.5
8000 3.1 37.6 350 15 8 6.1 3.3 | 3.4 38.1 335 9 5 6.8 3.7
7750 3.6 38.5 345 14 7 7.2 3.9 | 3.9 39.0 335 8 4 7.8 4.3
7500 4.2 39.6 345 13 7 8.2 4.5 | 4.6 40.3 335 8 4 8.6 4.7
7250 4.7 40.5 340 12 6 6.2 3.4 | 5.1 41.2 335 7 3 7.0 3.8
7000 5.1 41.2 335 11 6 4.7 2.6 | 5.6 42.1 330 6 3 5.2 2.9
6750 5.5 41.9 325 10 5 6.0 3.3 | 6.0 42.8 325 5 3 8.7 4.7
6500 5.9 42.6 320 10 5 3.3 1.8 | 6.8 44.2 325 4 2 10.2 5.6
6250 5.9 42.6 315 8 4 -1.3 -0.7 | 7.4 45.3 320 3 2 8.4 4.6
6000 5.8 42.4 310 7 3 -1.1 -0.6 | 8.1 46.6 320 2 1 7.6 4.2
5750 5.7 42.3 295 5 3 -2.7 -1.5 | 8.7 47.7 315 2 1 10.6 5.8
5500 5.2 41.4 275 4 2 -11.7 -6.4 | 9.8 49.6 320 2 1 19.0 10.4
11/24/2025 at 1400 MST | 11/24/2025 at 1700 MST
|
CAPE... 0.0 LI... +4.8 | CAPE... 0.0 LI... +3.7
CINH... -0.0 K Index... +4.9 | CINH... 0.0 K Index... +9.7
|
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 -60.4 -76.7 255 39 20 1.9 1.0 | -60.4 -76.7 255 46 23 2.3 1.3
45000 -57.5 -71.5 265 49 25 0.9 0.5 | -56.9 -70.4 255 52 27 2.2 1.2
40000 -56.7 -70.1 270 46 23 0.5 0.3 | -56.9 -70.4 260 56 29 -0.0 -0.0
38000 -55.9 -68.6 275 44 23 2.2 1.2 | -56.3 -69.3 265 57 29 2.1 1.2
36000 -54.5 -66.1 280 44 22 2.2 1.2 | -55.0 -67.0 265 56 29 2.1 1.2
34000 -52.8 -63.0 285 43 22 7.9 4.3 | -53.3 -63.9 270 55 29 8.0 4.4
32000 -48.4 -55.1 280 41 21 7.3 4.0 | -48.9 -56.0 270 50 26 7.4 4.1
30000 -43.4 -46.1 280 39 20 7.7 4.2 | -43.9 -47.0 270 45 23 7.3 4.0
29000 -41.1 -42.0 280 38 19 7.7 4.2 | -41.7 -43.1 270 42 22 7.3 4.0
28000 -38.8 -37.8 280 36 19 7.7 4.2 | -39.5 -39.1 275 40 21 7.3 4.0
27000 -36.5 -33.7 280 35 18 7.6 4.2 | -37.3 -35.1 275 38 20 7.3 4.0
26000 -34.2 -29.6 280 33 17 7.5 4.1 | -35.1 -31.2 280 36 19 7.3 4.0
25000 -32.0 -25.6 280 31 16 7.5 4.1 | -33.0 -27.4 280 34 18 7.3 4.0
24000 -29.7 -21.5 285 29 15 7.5 4.1 | -30.8 -23.4 285 32 17 7.4 4.0
23000 -27.5 -17.5 285 28 14 7.5 4.1 | -28.6 -19.5 285 31 16 7.5 4.1
22000 -25.3 -13.5 285 26 14 7.5 4.1 | -26.3 -15.3 285 29 15 7.5 4.1
21000 -23.0 -9.4 290 25 13 7.3 4.0 | -24.1 -11.4 290 28 14 7.5 4.1
20000 -20.9 -5.6 290 24 12 7.2 4.0 | -21.9 -7.4 290 27 14 7.5 4.1
19500 -19.8 -3.6 295 23 12 7.2 4.0 | -20.8 -5.4 290 27 14 7.5 4.1
19000 -18.7 -1.7 295 23 12 7.2 4.0 | -19.7 -3.5 295 26 14 7.5 4.1
18500 -17.6 0.3 300 23 12 7.3 4.0 | -18.5 -1.3 295 26 13 7.4 4.1
18000 -16.5 2.3 300 22 11 7.4 4.1 | -17.5 0.5 295 25 13 7.4 4.0
17500 -15.4 4.3 305 22 11 7.4 4.1 | -16.4 2.5 300 25 13 7.4 4.0
17000 -14.3 6.3 305 22 11 7.4 4.1 | -15.3 4.5 300 25 13 7.3 4.0
16500 -13.2 8.2 310 22 11 7.4 4.1 | -14.2 6.4 300 24 13 7.3 4.0
16000 -12.1 10.2 310 21 11 7.1 3.9 | -12.6 9.3 305 24 12 7.3 4.0
15500 -10.6 12.9 310 21 11 7.0 3.9 | -11.5 11.3 305 24 12 7.3 4.0
15000 -9.6 14.7 315 21 11 6.5 3.6 | -10.4 13.3 305 23 12 7.4 4.0
14500 -8.6 16.5 315 21 11 6.5 3.6 | -9.3 15.3 305 23 12 7.4 4.0
14000 -7.6 18.3 310 21 11 6.4 3.5 | -8.2 17.2 310 23 12 7.3 4.0
13500 -6.7 19.9 310 21 11 6.3 3.5 | -7.1 19.2 310 23 12 7.2 4.0
13000 -5.8 21.6 310 21 11 6.3 3.5 | -6.0 21.2 310 22 12 7.3 4.0
12500 -4.8 23.4 305 21 11 6.3 3.5 | -5.0 23.0 305 22 11 7.3 4.0
12000 -3.9 25.0 305 21 11 6.5 3.6 | -3.9 25.0 305 22 11 7.2 4.0
11500 -2.9 26.8 305 20 10 6.7 3.7 | -2.8 27.0 305 21 11 7.1 3.9
11000 -1.9 28.6 300 19 10 6.1 3.3 | -1.7 28.9 305 20 11 6.6 3.6
10500 -1.1 30.0 300 17 9 4.5 2.4 | -0.8 30.6 305 20 10 5.1 2.8
10250 -0.7 30.7 300 17 9 9.1 5.0 | -0.4 31.3 305 19 10 10.1 5.6
10000 0.2 32.4 300 15 8 10.5 5.7 | 0.6 33.1 300 19 10 11.6 6.4
9750 0.8 33.4 300 14 7 6.6 3.6 | 1.2 34.2 300 19 10 7.5 4.1
9500 1.3 34.3 300 13 7 8.0 4.4 | 1.9 35.4 305 19 10 8.9 4.9
9250 1.9 35.4 300 12 6 6.3 3.5 | 2.5 36.5 305 19 10 7.3 4.0
9000 2.3 36.1 300 11 6 6.1 3.3 | 3.0 37.4 305 19 10 6.9 3.8
8750 2.8 37.0 300 10 5 8.6 4.7 | 3.6 38.5 305 19 10 8.7 4.8
8500 3.5 38.3 300 9 5 9.8 5.4 | 4.3 39.7 300 20 10 9.5 5.2
8250 4.2 39.6 300 8 4 8.0 4.4 | 4.9 40.8 300 21 11 8.2 4.5
8000 4.7 40.5 300 7 4 6.2 3.4 | 5.5 41.9 300 21 11 6.7 3.7
7750 5.2 41.4 300 7 3 9.1 5.0 | 6.0 42.8 300 20 10 8.1 4.4
7500 6.0 42.8 300 6 3 11.4 6.2 | 6.6 43.9 295 19 10 9.2 5.0
7250 6.8 44.2 305 5 3 8.2 4.5 | 7.3 45.1 295 19 10 7.6 4.2
7000 7.2 45.0 305 5 2 5.4 2.9 | 7.8 46.0 295 17 9 6.2 3.4
6750 7.8 46.0 305 4 2 11.0 6.0 | 8.3 46.9 295 16 8 8.8 4.8
6500 8.8 47.8 305 4 2 13.1 7.2 | 9.0 48.2 295 14 7 9.3 5.1
6250 9.6 49.3 310 3 2 9.3 5.1 | 9.6 49.3 295 11 6 6.5 3.6
6000 10.3 50.5 315 3 1 8.4 4.6 | 10.0 50.0 295 9 5 6.5 3.5
5750 10.9 51.6 320 2 1 10.4 5.7 | 10.5 50.9 295 7 4 5.3 2.9
5500 11.9 53.4 320 2 1 15.9 8.7 | 10.6 51.1 290 5 3 -4.5 -2.5
________________________________________________________________________________
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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