Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
507
UXUS97 KBOU 180007
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1806 MDT Monday, August 17, 2026
This forecast is for Tuesday, August 18, 2026:
If the trigger temperature of 87.6 F/30.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1161 ft/min (5.9 m/s)
Maximum height of thermals.................. 17412 ft MSL (12114 ft AGL)
Forecast maximum temperature................... 93.0 F/34.3 C
Time of trigger temperature.................... 1145 MDT
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................. 10231 ft MSL (4934 ft AGL)
Thermal soaring outlook for Wednesday 08/19.... Good
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 46404 ft MSL (41106 ft AGL)
Wave soaring outlook for Wednesday 08/19....... Poor
Remarks...
Sunrise/Sunset.................... 06:14:47 / 19:51:46 MDT
Total possible sunshine........... 13 hr 36 min 59 sec (816 min 59 sec)
Altitude of sun at 13:03:17 MDT... 63.12 degrees
Upper air data from numerical model forecast valid on 08/18/2026 at 0600 MDT
Freezing level.................. 16313 ft MSL (11015 ft AGL)
Convective condensation level... 19069 ft MSL (13771 ft AGL)
Lifted condensation level....... 18379 ft MSL (13082 ft AGL)
Lifted index.................... +1.3
K index......................... +18.1
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 -65.4 -85.7 290 37 19 -0.8 -0.4 M M M M M
45000 -63.3 -81.9 285 53 27 5.6 3.1 M M M M M
40000 -54.2 -65.6 280 53 27 8.6 4.7 M M M M M
38000 -49.1 -56.4 280 49 25 8.6 4.7 M M M M M
36000 -43.9 -47.0 280 45 23 8.7 4.8 M M M M M
34000 -38.7 -37.7 275 42 22 8.8 4.8 M M M M M
32000 -32.8 -27.0 275 40 20 8.0 4.4 49.3 120.8 11.5 M M
30000 -28.6 -19.5 275 35 18 7.0 3.8 46.9 116.5 9.9 M M
29000 -26.6 -15.9 275 33 17 7.0 3.9 45.9 114.7 9.2 M M
28000 -24.3 -11.7 275 31 16 8.2 4.5 45.1 113.2 8.7 M M
27000 -21.9 -7.4 275 30 15 8.2 4.5 44.4 112.0 8.3 M M
26000 -19.4 -2.9 275 29 15 8.2 4.5 43.9 110.9 7.9 M M
25000 -17.0 1.4 270 27 14 7.8 4.3 43.4 110.0 7.6 M M
24000 -14.7 5.5 275 27 14 7.7 4.2 42.5 108.5 7.0 M M
23000 -12.3 9.9 275 27 14 7.7 4.2 41.7 107.1 6.5 M M
22000 -10.1 13.8 275 26 14 5.8 3.2 41.0 105.8 5.9 M M
21000 -8.5 16.7 280 25 13 5.4 3.0 39.3 102.8 4.5 M M
20000 -7.0 19.4 280 23 12 5.6 3.1 37.9 100.2 3.2 M M
19500 -6.2 20.8 280 23 12 5.6 3.1 37.2 99.0 2.6 M M
19000 -5.4 22.3 285 22 11 5.5 3.0 36.5 97.6 2.0 M M
18500 -4.6 23.7 285 21 11 5.4 3.0 35.7 96.3 1.3 M M
18000 -3.8 25.2 290 21 11 6.7 3.7 35.1 95.1 0.7 M M
17500 -2.8 27.0 290 21 11 7.1 3.9 34.6 94.3 0.2 M M
17000 -1.8 28.8 290 21 11 7.4 4.0 34.2 93.5 -0.3 1134 5.8
16500 -0.7 30.7 295 21 11 7.9 4.3 33.8 92.9 -0.7 1087 5.5
16000 1.0 33.8 295 20 10 8.3 4.5 33.4 92.0 -1.1 1013 5.1
15500 2.3 36.1 300 20 10 8.9 4.9 33.2 91.7 -1.3 960 4.9
15000 3.6 38.5 300 19 10 8.9 4.9 33.1 91.5 -1.5 906 4.6
14500 5.0 41.0 300 18 9 9.4 5.2 33.0 91.3 -1.6 850 4.3
14000 6.3 43.3 300 18 9 9.4 5.2 32.9 91.2 -1.7 794 4.0
13500 7.7 45.9 300 17 9 9.0 5.0 32.8 91.1 -1.8 738 3.7
13000 9.1 48.4 300 16 8 9.0 4.9 32.7 90.9 -1.9 682 3.5
12500 10.4 50.7 300 15 8 9.1 5.0 32.6 90.7 -2.0 627 3.2
12000 11.8 53.2 300 14 7 9.2 5.0 32.5 90.5 -2.1 570 2.9
11500 13.2 55.8 300 13 7 8.9 4.9 32.4 90.3 -2.2 514 2.6
11000 14.5 58.1 300 13 6 8.7 4.8 32.3 90.1 -2.3 460 2.3
10500 15.8 60.4 300 12 6 3.7 2.0 32.0 89.7 -2.5 407 2.1
10250 16.0 60.8 300 12 6 6.2 3.4 31.5 88.6 -3.0 393 2.0
10000 16.9 62.4 300 11 6 12.8 7.0 31.6 88.9 -2.9 360 1.8
9750 17.7 63.9 305 11 6 11.3 6.2 31.7 89.1 -2.8 327 1.7
9500 18.5 65.3 305 11 5 8.7 4.8 31.8 89.3 -2.7 296 1.5
9250 19.0 66.2 305 10 5 6.3 3.5 31.6 88.8 -2.9 273 1.4
9000 19.6 67.3 305 10 5 8.2 4.5 31.4 88.5 -3.1 250 1.3
8750 20.2 68.4 305 10 5 8.5 4.7 31.3 88.3 -3.3 223 1.1
8500 20.8 69.4 305 10 5 7.3 4.0 31.2 88.1 -3.4 198 1.0
8250 21.3 70.3 305 10 5 6.5 3.6 30.9 87.7 -3.6 176 0.9
8000 21.8 71.2 305 10 5 7.1 3.9 30.7 87.2 -3.9 153 0.8
7750 22.3 72.1 310 10 5 5.7 3.2 30.5 86.8 -4.1 131 0.7
7500 22.5 72.5 310 10 5 2.3 1.3 30.0 86.0 -4.6 116 0.6
7250 22.6 72.7 315 10 5 0.6 0.3 29.4 84.8 -5.3 107 0.5
7000 22.6 72.7 315 10 5 2.4 1.3 28.7 83.7 -6.0 99 0.5
6750 22.7 72.9 320 10 5 -2.5 -1.4 28.1 82.5 -6.7 89 0.5
6500 22.1 71.8 325 9 5 -8.7 -4.8 26.8 80.3 -8.1 101 0.5
6250 21.3 70.3 335 8 4 -8.6 -4.7 25.4 77.8 -9.6 117 0.6
6000 20.5 68.9 345 7 4 -7.2 -4.0 24.1 75.3 -11.1 133 0.7
5750 19.9 67.8 335 6 3 -9.3 -5.1 22.8 73.0 -12.5 144 0.7
5500 18.8 65.8 300 3 2 -16.6 -9.1 21.1 69.9 -14.4 169 0.9
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/18/2026 at 0900 MDT | 08/18/2026 at 1200 MDT
|
CAPE... 0.0 LI... +1.6 | CAPE... +7.8 LI... +0.3
CINH... -3.8 K Index... +18.6 | CINH... -21.5 K Index... +23.3
|
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 -64.6 -84.3 295 37 19 -0.5 -0.3 | -64.2 -83.6 290 37 19 -0.1 -0.1
45000 -62.7 -80.9 290 47 24 4.8 2.6 | -62.1 -79.8 285 46 24 4.5 2.5
40000 -54.6 -66.3 275 44 22 8.5 4.7 | -54.4 -65.9 275 46 24 8.4 4.6
38000 -49.5 -57.1 275 41 21 8.5 4.7 | -49.4 -56.9 275 43 22 8.3 4.6
36000 -44.4 -47.9 275 39 20 8.5 4.7 | -44.4 -47.9 280 40 21 8.4 4.6
34000 -39.3 -38.7 280 38 20 8.6 4.7 | -39.4 -38.9 280 39 20 8.4 4.6
32000 -33.5 -28.3 280 37 19 8.4 4.6 | -33.7 -28.7 280 37 19 8.7 4.8
30000 -29.0 -20.2 275 35 18 7.6 4.2 | -28.9 -20.0 275 35 18 7.9 4.4
29000 -26.8 -16.2 275 34 18 7.6 4.2 | -26.6 -15.9 275 35 18 7.9 4.4
28000 -24.5 -12.1 275 33 17 7.5 4.1 | -24.3 -11.7 275 34 17 7.5 4.1
27000 -22.3 -8.1 275 33 17 7.5 4.1 | -22.1 -7.8 270 34 17 7.5 4.1
26000 -20.0 -4.0 270 32 16 7.5 4.1 | -19.8 -3.6 265 33 17 7.5 4.1
25000 -17.8 -0.0 270 31 16 7.6 4.2 | -17.6 0.3 265 33 17 6.8 3.7
24000 -15.5 4.1 270 29 15 7.7 4.2 | -15.7 3.7 265 31 16 6.4 3.5
23000 -13.1 8.4 270 28 14 7.7 4.2 | -13.8 7.2 270 29 15 6.4 3.5
22000 -10.9 12.4 270 26 13 6.0 3.3 | -11.9 10.6 275 27 14 6.2 3.4
21000 -9.3 15.3 275 24 12 5.6 3.1 | -10.1 13.8 275 25 13 6.2 3.4
20000 -7.7 18.1 280 22 12 5.7 3.1 | -8.3 17.1 275 24 13 6.2 3.4
19500 -6.8 19.8 285 22 11 5.8 3.2 | -7.4 18.7 275 24 12 6.3 3.5
19000 -6.0 21.2 285 21 11 6.2 3.4 | -6.5 20.3 275 24 12 6.8 3.7
18500 -5.1 22.8 290 21 11 6.2 3.4 | -5.5 22.1 275 24 12 6.8 3.7
18000 -4.2 24.4 290 21 11 7.1 3.9 | -4.6 23.7 275 24 12 7.4 4.1
17500 -2.6 27.3 295 21 11 7.4 4.1 | -3.0 26.6 275 23 12 7.6 4.1
17000 -1.5 29.3 295 21 11 8.1 4.5 | -1.8 28.8 280 23 12 8.4 4.6
16500 -0.3 31.5 295 21 11 8.3 4.6 | -0.6 30.9 280 23 12 8.6 4.7
16000 0.9 33.6 295 21 11 8.5 4.7 | 0.6 33.1 280 22 12 8.7 4.8
15500 2.2 36.0 295 21 11 8.8 4.9 | 1.9 35.4 280 22 11 8.9 4.9
15000 3.5 38.3 295 21 11 8.9 4.9 | 3.3 37.9 280 22 11 8.9 4.9
14500 4.8 40.6 295 20 11 9.2 5.0 | 4.6 40.3 285 21 11 9.2 5.0
14000 6.2 43.2 295 20 10 9.2 5.0 | 6.0 42.8 285 20 10 9.2 5.0
13500 7.5 45.5 295 20 10 8.8 4.8 | 7.4 45.3 285 20 10 9.1 5.0
13000 8.8 47.8 295 19 10 8.8 4.8 | 8.7 47.7 285 19 10 9.1 5.0
12500 10.1 50.2 295 18 9 8.6 4.7 | 10.1 50.2 285 18 9 9.2 5.0
12000 11.4 52.5 295 17 9 8.6 4.7 | 11.5 52.7 285 17 9 9.2 5.0
11500 12.7 54.9 295 16 8 8.1 4.4 | 12.8 55.0 285 15 8 8.7 4.8
11000 13.9 57.0 290 14 7 7.7 4.2 | 14.1 57.4 285 14 7 8.5 4.7
10500 15.0 59.0 290 13 7 3.8 2.1 | 15.3 59.5 285 12 6 3.5 1.9
10250 15.2 59.4 290 13 7 5.0 2.8 | 15.5 59.9 290 13 7 6.0 3.3
10000 15.8 60.4 285 12 6 9.6 5.3 | 16.3 61.3 290 11 6 11.8 6.5
9750 16.4 61.5 285 10 5 8.5 4.7 | 17.1 62.8 285 9 5 10.4 5.7
9500 17.0 62.6 280 9 5 6.3 3.5 | 17.8 64.0 285 8 4 7.4 4.0
9250 17.3 63.1 275 8 4 4.5 2.5 | 18.2 64.8 290 7 4 5.6 3.1
9000 17.7 63.9 275 7 4 6.6 3.6 | 18.8 65.8 290 6 3 8.8 4.8
8750 18.2 64.8 270 6 3 7.2 3.9 | 19.4 66.9 290 5 2 9.2 5.1
8500 18.7 65.7 265 5 3 5.3 2.9 | 20.1 68.2 295 4 2 7.3 4.0
8250 19.0 66.2 265 4 2 4.3 2.4 | 20.5 68.9 300 3 2 5.6 3.1
8000 19.3 66.7 260 3 1 4.8 2.6 | 21.0 69.8 310 2 1 8.3 4.6
7750 19.6 67.3 265 3 1 3.8 2.1 | 21.7 71.1 320 2 1 9.4 5.2
7500 19.9 67.8 270 3 2 2.5 1.4 | 22.3 72.1 340 2 1 6.6 3.6
7250 20.0 68.0 270 3 2 1.1 0.6 | 22.7 72.9 010 2 1 4.8 2.7
7000 20.1 68.2 275 3 2 5.0 2.8 | 23.1 73.6 030 2 1 9.1 5.0
6750 20.6 69.1 275 4 2 6.0 3.3 | 23.9 75.0 035 3 1 12.9 7.1
6500 20.8 69.4 275 3 2 2.2 1.2 | 24.7 76.5 035 3 2 10.5 5.8
6250 20.9 69.6 270 3 2 2.3 1.3 | 25.5 77.9 035 3 2 10.6 5.8
6000 21.1 70.0 265 2 1 3.0 1.7 | 26.3 79.3 035 3 2 9.0 5.0
5750 21.4 70.5 265 3 1 9.1 5.0 | 27.0 80.6 040 4 2 15.1 8.3
5500 22.3 72.1 260 2 1 16.7 9.2 | 28.7 83.7 040 4 2 29.9 16.4
08/18/2026 at 1500 MDT | 08/18/2026 at 1800 MDT
|
CAPE... +803.8 LI... -3.2 | CAPE... +893.7 LI... -3.0
CINH... -19.7 K Index... +30.7 | CINH... -34.7 K Index... +31.1
|
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 -64.1 -83.4 285 38 19 0.1 0.1 | -64.5 -84.1 285 36 19 -0.1 -0.1
45000 -61.7 -79.1 285 50 26 4.4 2.4 | -62.3 -80.1 285 47 24 4.5 2.5
40000 -54.2 -65.6 280 51 26 8.1 4.4 | -54.7 -66.5 280 47 24 8.6 4.7
38000 -49.3 -56.7 275 48 25 8.1 4.4 | -49.5 -57.1 280 46 23 8.5 4.7
36000 -44.5 -48.1 270 46 24 8.4 4.6 | -44.4 -47.9 280 45 23 8.5 4.7
34000 -39.2 -38.6 270 44 23 8.9 4.9 | -39.4 -38.9 275 44 23 8.4 4.6
32000 -33.1 -27.6 275 42 22 9.0 4.9 | -33.7 -28.7 275 43 22 8.8 4.9
30000 -28.4 -19.1 270 36 19 7.9 4.3 | -28.8 -19.8 275 41 21 8.2 4.5
29000 -26.0 -14.8 270 34 17 7.9 4.3 | -26.4 -15.5 275 40 21 8.2 4.5
28000 -23.7 -10.7 265 32 17 7.3 4.0 | -24.0 -11.2 275 39 20 7.6 4.2
27000 -21.5 -6.7 270 33 17 7.3 4.0 | -21.7 -7.1 275 39 20 7.6 4.2
26000 -19.3 -2.7 270 34 18 7.3 4.0 | -19.4 -2.9 275 38 20 7.6 4.2
25000 -17.1 1.2 275 35 18 6.5 3.6 | -17.2 1.0 270 38 19 6.5 3.6
24000 -15.3 4.5 270 35 18 6.2 3.4 | -15.5 4.1 270 37 19 6.0 3.3
23000 -13.6 7.5 270 35 18 6.3 3.5 | -13.7 7.3 265 37 19 6.0 3.3
22000 -11.8 10.8 270 36 18 6.2 3.4 | -11.9 10.6 265 36 19 6.9 3.8
21000 -10.0 14.0 270 36 18 6.1 3.4 | -9.9 14.2 260 34 18 7.2 3.9
20000 -8.2 17.2 270 36 18 6.2 3.4 | -7.8 18.0 255 33 17 7.3 4.0
19500 -7.3 18.9 270 36 18 6.5 3.5 | -6.8 19.8 250 32 16 7.5 4.1
19000 -6.3 20.7 265 34 18 7.6 4.2 | -5.7 21.7 250 30 16 8.1 4.4
18500 -5.2 22.6 265 33 17 7.7 4.2 | -4.5 23.9 250 29 15 8.1 4.5
18000 -4.2 24.4 260 31 16 8.1 4.4 | -3.4 25.9 250 27 14 7.6 4.2
17500 -3.0 26.6 260 29 15 8.2 4.5 | -2.3 27.9 250 26 13 7.5 4.1
17000 -1.8 28.8 255 27 14 8.2 4.5 | -1.3 29.7 250 24 13 7.4 4.1
16500 -0.1 31.8 255 25 13 8.1 4.4 | -0.2 31.6 250 24 12 7.3 4.0
16000 1.1 34.0 250 23 12 8.3 4.5 | 1.4 34.5 250 23 12 7.6 4.2
15500 2.4 36.3 245 22 11 8.7 4.8 | 2.6 36.7 250 22 11 8.2 4.5
15000 3.7 38.7 240 20 10 8.7 4.8 | 3.8 38.8 250 21 11 8.2 4.5
14500 5.0 41.0 240 19 10 8.2 4.5 | 4.9 40.8 250 19 10 6.6 3.6
14000 6.2 43.2 235 17 9 8.3 4.5 | 5.9 42.6 245 17 9 7.0 3.8
13500 7.4 45.3 230 14 7 7.4 4.1 | 6.7 44.1 245 15 8 4.4 2.4
13000 8.5 47.3 225 11 6 7.4 4.1 | 7.2 45.0 245 11 6 4.4 2.4
12500 9.5 49.1 215 7 4 6.9 3.8 | 7.8 46.0 250 8 4 6.0 3.3
12000 10.4 50.7 185 2 1 6.8 3.7 | 8.7 47.7 265 5 2 6.4 3.5
11500 11.4 52.5 070 4 2 8.4 4.6 | 9.6 49.3 320 3 2 6.9 3.8
11000 12.7 54.9 055 7 4 9.1 5.0 | 10.6 51.1 015 5 2 7.1 3.9
10500 13.9 57.0 050 11 5 4.7 2.6 | 11.6 52.9 030 8 4 2.2 1.2
10250 14.2 57.6 050 11 6 7.8 4.3 | 11.8 53.2 030 9 4 6.5 3.5
10000 15.1 59.2 050 11 6 13.5 7.4 | 12.7 54.9 035 10 5 13.9 7.6
9750 16.0 60.8 050 11 6 12.1 6.6 | 13.6 56.5 035 11 5 11.8 6.5
9500 16.9 62.4 050 12 6 9.4 5.2 | 14.4 57.9 035 11 6 9.8 5.4
9250 17.5 63.5 045 12 6 8.0 4.4 | 15.0 59.0 035 12 6 8.5 4.7
9000 18.2 64.8 045 12 6 10.6 5.8 | 15.8 60.4 035 12 6 11.0 6.0
8750 19.0 66.2 045 12 6 11.1 6.1 | 16.6 61.9 035 12 6 11.5 6.3
8500 19.8 67.6 045 12 6 10.5 5.8 | 17.4 63.3 035 12 6 10.1 5.5
8250 20.6 69.1 045 12 6 10.3 5.6 | 18.1 64.6 035 12 6 9.3 5.1
8000 21.3 70.3 045 13 7 10.4 5.7 | 18.9 66.0 035 12 6 10.4 5.7
7750 22.1 71.8 045 13 7 10.4 5.7 | 19.7 67.5 035 12 6 10.7 5.8
7500 22.8 73.0 045 13 7 10.2 5.6 | 20.4 68.7 035 12 6 9.7 5.3
7250 23.6 74.5 045 13 7 10.4 5.7 | 21.1 70.0 035 12 6 9.3 5.1
7000 24.4 75.9 045 13 7 9.6 5.3 | 21.9 71.4 030 12 6 10.2 5.6
6750 25.1 77.2 040 13 7 9.7 5.3 | 22.6 72.7 030 13 6 10.4 5.7
6500 25.8 78.4 040 13 7 10.7 5.9 | 23.4 74.1 030 13 6 9.9 5.5
6250 26.6 79.9 040 13 7 10.8 5.9 | 24.1 75.4 030 12 6 9.8 5.4
6000 27.4 81.3 040 13 7 10.5 5.8 | 24.9 76.8 030 12 6 10.7 5.9
5750 28.4 83.1 040 13 7 16.5 9.1 | 25.8 78.4 030 12 6 14.1 7.8
5500 30.0 86.0 040 13 7 27.2 14.9 | 26.9 80.4 030 11 6 16.9 9.3
________________________________________________________________________________
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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