Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
049
UXUS97 KBOU 221443
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0742 MST Saturday, November 22, 2025
This forecast is for Saturday, November 22, 2025:
If the trigger temperature of 59.0 F/15.0 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 371 ft/min (1.9 m/s)
Maximum height of thermals.................. 10212 ft MSL (4902 ft AGL)
Forecast maximum temperature................... 60.0 F/16.0 C
Time of trigger temperature.................... 1345 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................. 6971 ft MSL (1661 ft AGL)
Thermal soaring outlook for Sunday 11/23....... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... Trending the same
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Neither
Potential height of wave....................... 18838 ft MSL (13528 ft AGL)
Wave soaring outlook for Sunday 11/23.......... Poor
Remarks...
Sunrise/Sunset.................... 06:52:37 / 16:38:50 MST
Total possible sunshine........... 9 hr 46 min 13 sec (586 min 13 sec)
Altitude of sun at 11:45:44 MST... 29.84 degrees
Upper air data from numerical model forecast valid on 11/22/2025 at 0500 MST
Freezing level.................. 10590 ft MSL (5280 ft AGL)
Convective condensation level... 16342 ft MSL (11032 ft AGL)
Lifted condensation level....... 14100 ft MSL (8790 ft AGL)
Lifted index.................... +3.6
K index......................... +9.6
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 -60.2 -76.4 245 25 13 1.5 0.8 M M M M M
45000 -58.6 -73.5 260 25 13 0.7 0.4 M M M M M
40000 -56.9 -70.4 260 27 14 0.7 0.4 M M M M M
38000 -55.1 -67.2 265 22 12 4.2 2.3 M M M M M
36000 -52.6 -62.7 280 15 8 4.1 2.3 M M M M M
34000 -49.8 -57.6 305 10 5 6.3 3.5 M M M M M
32000 -46.0 -50.8 300 11 6 6.4 3.5 M M M M M
30000 -41.9 -43.4 300 12 6 5.2 2.9 34.1 93.3 13.9 M M
29000 -40.4 -40.7 295 11 6 5.2 2.9 32.2 90.0 12.7 M M
28000 -38.8 -37.8 295 10 5 5.2 2.9 30.5 86.9 11.5 M M
27000 -37.1 -34.8 295 9 5 7.7 4.2 29.1 84.3 10.5 M M
26000 -34.8 -30.6 295 7 4 7.6 4.2 28.1 82.7 10.0 M M
25000 -32.5 -26.5 305 5 3 7.6 4.2 27.4 81.3 9.4 M M
24000 -30.2 -22.4 310 3 2 8.5 4.7 26.7 80.1 9.0 M M
23000 -27.5 -17.5 290 5 3 8.8 4.9 26.3 79.3 8.8 M M
22000 -24.9 -12.8 285 8 4 8.8 4.9 26.0 78.8 8.6 M M
21000 -22.3 -8.1 280 10 5 8.1 4.4 25.7 78.2 8.4 M M
20000 -19.8 -3.6 290 12 6 8.2 4.5 25.0 77.1 8.0 M M
19500 -18.6 -1.5 290 13 7 8.2 4.5 24.8 76.6 7.8 M M
19000 -17.4 0.7 295 14 7 8.2 4.5 24.5 76.1 7.7 M M
18500 -16.2 2.8 295 15 8 7.3 4.0 24.2 75.6 7.4 M M
18000 -15.2 4.6 295 15 8 7.2 3.9 23.8 74.8 7.1 M M
17500 -14.1 6.6 300 15 8 6.9 3.8 23.3 74.0 6.7 M M
17000 -13.1 8.4 300 15 8 6.4 3.5 22.8 73.0 6.3 M M
16500 -11.7 10.9 300 13 7 6.4 3.5 21.9 71.5 5.5 M M
16000 -10.8 12.6 305 12 6 6.4 3.5 21.3 70.4 5.0 M M
15500 -9.9 14.2 310 11 6 6.5 3.5 20.8 69.4 4.5 M M
15000 -8.9 16.0 310 11 5 6.9 3.8 20.3 68.5 4.1 M M
14500 -7.9 17.8 315 10 5 6.9 3.8 19.8 67.6 3.6 M M
14000 -6.9 19.6 320 10 5 6.8 3.7 19.3 66.8 3.2 M M
13500 -5.9 21.4 320 9 5 6.9 3.8 18.8 65.9 2.7 M M
13000 -4.9 23.2 325 9 5 6.6 3.6 18.4 65.0 2.3 M M
12500 -3.9 25.0 325 8 4 6.6 3.6 17.8 64.1 1.8 M M
12000 -3.0 26.6 325 7 4 6.8 3.7 17.3 63.2 1.3 M M
11500 -2.0 28.4 325 6 3 6.7 3.7 16.9 62.4 0.8 M M
11000 -0.9 30.4 320 6 3 8.1 4.5 16.5 61.7 0.4 M M
10500 0.3 32.5 315 5 3 9.5 5.2 16.2 61.2 0.2 M M
10250 0.9 33.6 310 5 2 3.2 1.7 16.1 61.0 0.0 M M
10000 0.9 33.6 300 4 2 4.5 2.5 15.4 59.7 -0.6 362 1.8
9750 1.7 35.1 300 5 2 11.5 6.3 15.4 59.8 -0.6 332 1.7
9500 2.5 36.5 295 5 3 10.7 5.9 15.5 59.8 -0.6 302 1.5
9250 3.2 37.8 295 5 3 6.6 3.6 15.5 59.9 -0.5 271 1.4
9000 3.5 38.3 300 5 3 4.0 2.2 15.0 59.0 -1.0 256 1.3
8750 4.0 39.2 295 6 3 8.5 4.6 14.8 58.6 -1.2 233 1.2
8500 4.6 40.3 290 6 3 8.5 4.7 14.7 58.5 -1.3 206 1.0
8250 5.2 41.4 290 7 3 6.1 3.4 14.5 58.2 -1.5 182 0.9
8000 5.6 42.1 290 7 4 4.8 2.7 14.2 57.5 -1.8 163 0.8
7750 6.0 42.8 290 7 4 7.8 4.3 13.9 57.0 -2.1 143 0.7
7500 6.7 44.1 280 8 4 7.6 4.2 13.8 56.8 -2.2 116 0.6
7250 7.1 44.8 280 8 4 4.8 2.7 13.5 56.3 -2.5 96 0.5
7000 7.4 45.3 275 8 4 4.8 2.7 13.1 55.6 -2.9 78 0.4
6750 7.8 46.0 275 8 4 4.9 2.7 12.7 54.9 -3.3 60 0.3
6500 8.0 46.4 260 8 4 -0.2 -0.1 12.2 54.0 -3.8 46 0.2
6250 7.7 45.9 250 8 4 -4.9 -2.7 11.2 52.2 -4.8 47 0.2
6000 7.5 45.5 245 8 4 -1.3 -0.7 10.2 50.4 -5.9 48 0.2
5750 7.2 45.0 235 9 4 -11.0 -6.1 9.2 48.6 -6.9 49 0.2
5500 5.4 41.7 225 7 3 -35.7 -19.6 6.7 44.1 -9.4 95 0.5
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/22/2025 at 0800 MST | 11/22/2025 at 1100 MST
|
CAPE... 0.0 LI... +4.7 | CAPE... 0.0 LI... +4.8
CINH... -0.1 K Index... +6.2 | CINH... -0.0 K Index... +1.4
|
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 -60.7 -77.3 260 26 13 1.1 0.6 | -61.7 -79.1 260 25 13 1.2 0.7
45000 -59.0 -74.2 265 27 14 0.5 0.3 | -59.9 -75.8 260 28 15 0.3 0.2
40000 -58.2 -72.8 265 31 16 0.6 0.3 | -59.3 -74.7 260 34 17 0.4 0.2
38000 -56.5 -69.7 265 21 11 4.1 2.3 | -57.3 -71.1 260 25 13 4.7 2.6
36000 -54.0 -65.2 265 5 3 4.1 2.2 | -54.5 -66.1 255 12 6 4.7 2.6
34000 -50.8 -59.4 080 9 5 8.0 4.4 | -50.9 -59.6 185 2 1 8.5 4.7
32000 -45.4 -49.7 070 21 11 8.0 4.4 | -45.2 -49.4 105 12 6 8.5 4.7
30000 -40.8 -41.4 065 22 11 7.2 4.0 | -40.0 -40.0 105 14 7 8.7 4.8
29000 -38.6 -37.5 065 15 8 7.2 4.0 | -37.4 -35.3 105 11 6 8.7 4.8
28000 -36.5 -33.7 065 9 5 7.2 4.0 | -34.8 -30.6 110 8 4 8.7 4.7
27000 -34.4 -29.9 060 3 2 5.6 3.1 | -32.5 -26.5 135 4 2 6.6 3.6
26000 -32.7 -26.9 320 1 0 5.8 3.2 | -30.4 -22.7 245 6 3 6.7 3.7
25000 -31.0 -23.8 260 4 2 5.7 3.2 | -28.4 -19.1 260 14 7 6.7 3.7
24000 -29.2 -20.6 255 7 3 7.7 4.2 | -26.5 -15.7 265 20 10 5.5 3.0
23000 -26.8 -16.2 255 7 4 8.0 4.4 | -24.8 -12.6 265 18 9 5.5 3.0
22000 -24.4 -11.9 255 8 4 8.0 4.4 | -23.2 -9.8 265 17 9 5.6 3.1
21000 -22.0 -7.6 260 8 4 8.4 4.6 | -21.3 -6.3 265 15 8 7.8 4.3
20000 -19.5 -3.1 275 8 4 8.3 4.6 | -19.0 -2.2 265 13 7 7.7 4.2
19500 -18.2 -0.8 280 9 5 8.4 4.6 | -17.8 -0.0 265 12 6 7.7 4.2
19000 -17.0 1.4 285 9 5 8.5 4.6 | -16.6 2.1 265 11 6 7.7 4.2
18500 -15.8 3.6 290 10 5 7.3 4.0 | -15.5 4.1 270 10 5 7.7 4.2
18000 -14.7 5.5 295 10 5 7.3 4.0 | -14.3 6.3 270 10 5 7.7 4.2
17500 -13.6 7.5 300 11 5 7.1 3.9 | -13.2 8.2 270 9 5 7.3 4.0
17000 -12.6 9.3 305 11 5 6.7 3.7 | -12.2 10.0 270 9 4 7.0 3.9
16500 -11.1 12.0 315 11 5 6.5 3.5 | -11.1 12.0 275 8 4 6.9 3.8
16000 -10.2 13.6 320 10 5 6.3 3.5 | -9.8 14.4 275 7 4 5.9 3.2
15500 -9.3 15.3 325 10 5 6.2 3.4 | -8.9 16.0 275 6 3 5.7 3.1
15000 -8.4 16.9 325 9 5 5.9 3.2 | -8.2 17.2 275 6 3 5.2 2.9
14500 -7.5 18.5 330 9 4 6.0 3.3 | -7.4 18.7 280 5 3 5.3 2.9
14000 -6.6 20.1 335 8 4 6.5 3.6 | -6.6 20.1 280 4 2 5.6 3.1
13500 -5.7 21.7 335 7 4 6.5 3.6 | -5.8 21.6 280 3 2 5.6 3.1
13000 -4.8 23.4 340 7 4 6.2 3.4 | -5.0 23.0 280 2 1 6.2 3.4
12500 -3.9 25.0 340 6 3 6.1 3.4 | -4.1 24.6 280 1 1 6.0 3.3
12000 -2.9 26.8 345 6 3 7.0 3.8 | -3.1 26.4 255 1 0 7.4 4.1
11500 -1.9 28.6 345 5 2 6.9 3.8 | -2.0 28.4 175 1 0 7.2 4.0
11000 -0.8 30.6 345 4 2 8.0 4.4 | -0.9 30.4 160 1 1 8.1 4.4
10500 0.3 32.5 355 3 1 9.1 5.0 | 0.3 32.5 165 3 1 8.4 4.6
10250 0.9 33.6 360 2 1 3.2 1.8 | 0.8 33.4 165 3 2 3.0 1.7
10000 1.0 33.8 010 1 1 4.7 2.6 | 0.9 33.6 160 4 2 5.6 3.1
9750 1.8 35.2 005 1 1 11.6 6.4 | 1.7 35.1 165 4 2 12.2 6.7
9500 2.5 36.5 355 1 0 9.9 5.5 | 2.5 36.5 165 4 2 9.7 5.3
9250 3.2 37.8 345 1 0 6.2 3.4 | 3.1 37.6 170 5 2 6.1 3.3
9000 3.5 38.3 335 1 0 4.3 2.4 | 3.5 38.3 165 5 3 5.2 2.9
8750 4.0 39.2 310 1 0 8.3 4.5 | 4.0 39.2 170 5 2 8.9 4.9
8500 4.6 40.3 295 2 1 8.0 4.4 | 4.7 40.5 170 4 2 7.6 4.2
8250 5.1 41.2 295 2 1 5.7 3.2 | 5.1 41.2 175 4 2 4.8 2.6
8000 5.5 41.9 300 3 1 4.9 2.7 | 5.5 41.9 180 3 2 4.7 2.6
7750 5.9 42.6 300 4 2 7.6 4.2 | 5.9 42.6 185 3 1 7.7 4.2
7500 6.5 43.7 290 4 2 6.4 3.5 | 6.5 43.7 185 2 1 6.7 3.7
7250 6.8 44.2 290 5 2 3.5 1.9 | 6.8 44.2 210 1 0 4.1 2.3
7000 7.1 44.8 295 5 3 4.0 2.2 | 7.1 44.8 280 1 0 4.4 2.4
6750 7.4 45.3 295 5 3 4.2 2.3 | 7.5 45.5 320 1 1 8.5 4.7
6500 7.6 45.7 280 6 3 1.5 0.8 | 8.3 46.9 335 1 1 9.6 5.3
6250 7.6 45.7 275 6 3 -0.7 -0.4 | 8.9 48.0 350 1 1 7.2 4.0
6000 7.6 45.7 270 6 3 -0.4 -0.2 | 9.4 48.9 015 1 0 6.3 3.5
5750 7.2 45.0 260 6 3 -13.0 -7.1 | 9.9 49.8 010 1 0 9.8 5.4
5500 5.5 41.9 235 4 2 -31.1 -17.1 | 11.1 52.0 020 1 0 21.1 11.6
11/22/2025 at 1400 MST | 11/22/2025 at 1700 MST
|
CAPE... 0.0 LI... +4.9 | CAPE... 0.0 LI... +6.1
CINH... -0.0 K Index... -8.6 | CINH... -0.1 K Index... -4.6
|
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 -62.3 -80.1 255 28 14 0.6 0.3 | -63.8 -82.8 260 27 14 -0.0 -0.0
45000 -61.3 -78.3 255 34 17 1.0 0.5 | -63.7 -82.7 255 35 18 1.5 0.8
40000 -59.8 -75.6 255 41 21 1.1 0.6 | -61.5 -78.7 250 44 23 1.6 0.9
38000 -57.4 -71.3 260 39 20 5.2 2.9 | -58.3 -72.9 250 45 23 6.6 3.6
36000 -54.3 -65.7 260 35 18 5.2 2.9 | -54.3 -65.7 255 46 24 6.6 3.6
34000 -50.5 -58.9 265 31 16 8.3 4.5 | -49.9 -57.8 255 45 23 8.2 4.5
32000 -45.6 -50.1 260 25 13 8.3 4.5 | -45.0 -49.0 260 42 22 8.2 4.5
30000 -39.9 -39.8 260 22 11 8.4 4.6 | -39.5 -39.1 260 38 20 8.1 4.5
29000 -37.4 -35.3 260 22 11 8.4 4.6 | -37.1 -34.8 260 37 19 8.1 4.5
28000 -34.9 -30.8 260 23 12 8.4 4.6 | -34.6 -30.3 260 36 18 8.1 4.5
27000 -32.4 -26.3 265 25 13 8.1 4.5 | -32.1 -25.8 260 35 18 8.5 4.6
26000 -30.0 -22.0 265 30 16 8.1 4.5 | -29.6 -21.3 260 34 18 8.5 4.7
25000 -27.5 -17.5 270 35 18 8.1 4.5 | -27.1 -16.8 260 33 17 8.5 4.7
24000 -25.2 -13.4 270 38 19 6.2 3.4 | -24.6 -12.3 260 32 17 7.9 4.3
23000 -23.3 -9.9 270 32 17 6.4 3.5 | -22.2 -8.0 265 30 15 8.0 4.4
22000 -21.4 -6.5 270 27 14 6.4 3.5 | -19.8 -3.6 265 27 14 7.9 4.3
21000 -19.5 -3.1 275 23 12 6.2 3.4 | -17.7 0.1 265 24 13 5.7 3.1
20000 -17.6 0.3 270 19 10 6.3 3.4 | -16.0 3.2 260 21 11 5.7 3.1
19500 -16.7 1.9 270 16 8 6.2 3.4 | -15.1 4.8 255 19 10 5.7 3.1
19000 -15.8 3.6 270 14 7 6.1 3.4 | -14.3 6.3 255 17 9 5.7 3.1
18500 -14.7 5.5 265 13 7 8.0 4.4 | -13.4 7.9 250 16 8 6.1 3.3
18000 -13.5 7.7 265 13 7 7.8 4.3 | -12.5 9.5 245 14 7 6.1 3.3
17500 -12.4 9.7 260 13 6 7.4 4.1 | -11.6 11.1 245 14 7 6.2 3.4
17000 -11.3 11.7 260 12 6 7.2 3.9 | -10.6 12.9 240 13 7 6.3 3.4
16500 -10.2 13.6 255 12 6 7.0 3.9 | -9.7 14.5 240 13 6 6.2 3.4
16000 -9.3 15.3 255 11 6 6.0 3.3 | -8.8 16.2 240 12 6 5.5 3.0
15500 -8.3 17.1 250 11 6 6.2 3.4 | -8.0 17.6 235 12 6 5.6 3.1
15000 -7.5 18.5 250 11 6 5.3 2.9 | -6.9 19.6 240 13 6 4.6 2.5
14500 -6.3 20.7 245 11 6 5.3 2.9 | -6.2 20.8 240 13 7 4.6 2.5
14000 -5.6 21.9 245 10 5 4.9 2.7 | -5.6 21.9 240 13 7 4.5 2.5
13500 -4.9 23.2 240 10 5 5.0 2.7 | -5.0 23.0 240 13 7 4.6 2.5
13000 -4.2 24.4 240 10 5 5.2 2.9 | -4.3 24.3 235 12 6 5.0 2.8
12500 -3.5 25.7 235 9 5 5.1 2.8 | -3.6 25.5 230 12 6 4.9 2.7
12000 -2.7 27.1 225 8 4 6.4 3.5 | -2.8 27.0 225 11 6 7.0 3.8
11500 -1.7 28.9 215 7 4 6.2 3.4 | -1.8 28.8 215 10 5 6.7 3.7
11000 -0.7 30.7 205 7 3 7.6 4.2 | -0.8 30.6 205 10 5 7.4 4.1
10500 0.3 32.5 195 7 3 8.1 4.4 | 0.3 32.5 200 9 5 7.7 4.2
10250 0.8 33.4 190 7 4 2.2 1.2 | 0.7 33.3 195 9 5 2.4 1.3
10000 0.9 33.6 185 7 4 5.2 2.9 | 0.9 33.6 195 10 5 5.7 3.1
9750 1.7 35.1 180 7 4 12.7 7.0 | 1.7 35.1 190 9 5 12.8 7.0
9500 2.5 36.5 175 7 4 10.3 5.6 | 2.5 36.5 180 9 5 10.2 5.6
9250 3.2 37.8 170 7 4 6.0 3.3 | 3.1 37.6 175 9 5 6.5 3.5
9000 3.5 38.3 170 7 4 5.7 3.1 | 3.5 38.3 170 9 4 6.0 3.3
8750 4.1 39.4 165 7 4 11.0 6.1 | 4.2 39.6 165 8 4 10.3 5.6
8500 5.0 41.0 160 7 4 9.4 5.2 | 4.9 40.8 155 9 4 9.2 5.0
8250 5.5 41.9 150 7 3 5.6 3.1 | 5.5 41.9 150 9 4 6.4 3.5
8000 5.9 42.6 145 7 3 5.5 3.0 | 5.9 42.6 145 9 5 6.3 3.5
7750 6.4 43.5 135 7 3 10.2 5.6 | 6.5 43.7 140 9 5 8.7 4.8
7500 7.2 45.0 125 6 3 9.5 5.2 | 7.1 44.8 130 10 5 7.2 3.9
7250 7.7 45.9 125 6 3 6.2 3.4 | 7.5 45.5 125 11 5 4.6 2.5
7000 8.2 46.8 120 6 3 6.9 3.8 | 7.9 46.2 120 11 6 5.0 2.8
6750 8.8 47.8 120 6 3 11.7 6.4 | 8.3 46.9 115 12 6 7.2 4.0
6500 9.9 49.8 115 6 3 12.4 6.8 | 8.9 48.0 105 12 6 7.9 4.3
6250 10.6 51.1 110 6 3 9.9 5.4 | 9.4 48.9 100 11 6 6.4 3.5
6000 11.4 52.5 110 6 3 7.9 4.3 | 9.9 49.8 095 11 6 6.3 3.4
5750 11.9 53.4 110 6 3 9.6 5.3 | 10.2 50.4 095 12 6 1.6 0.9
5500 13.1 55.6 110 5 3 21.6 11.9 | 10.1 50.2 090 9 4 -3.9 -2.2
________________________________________________________________________________
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.
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