Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
192
UXUS97 KBOU 240035
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1835 MDT Thursday, July 23, 2026
This forecast is for Friday, July 24, 2026:
If the trigger temperature of 86.5 F/30.3 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1245 ft/min (6.3 m/s)
Maximum height of thermals.................. 16927 ft MSL (11502 ft AGL)
Forecast maximum temperature................... 95.0 F/35.5 C
Time of trigger temperature.................... 1130 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................. 13552 ft MSL (8127 ft AGL)
Thermal soaring outlook for Saturday 07/25..... Excellent
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....................... 15017 ft MSL (9592 ft AGL)
Wave soaring outlook for Saturday 07/25........ Poor
Remarks...
Sunrise/Sunset.................... 05:51:42 / 20:20:22 MDT
Total possible sunshine........... 14 hr 28 min 39 sec (868 min 39 sec)
Altitude of sun at 13:06:02 MDT... 69.93 degrees
Upper air data from numerical model forecast valid on 07/24/2026 at 0600 MDT
Freezing level.................. 17216 ft MSL (11791 ft AGL)
Convective condensation level... 15831 ft MSL (10406 ft AGL)
Lifted condensation level....... 16425 ft MSL (11000 ft AGL)
Lifted index.................... -1.5
K index......................... +25.1
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 -66.0 -86.8 290 32 16 2.6 1.5 77.6 171.7 25.2 M M
45000 -59.4 -74.9 290 38 20 6.9 3.8 65.3 149.5 19.1 M M
40000 -48.9 -56.0 290 38 20 7.3 4.0 59.2 138.6 16.4 M M
38000 -44.0 -47.2 285 34 17 7.3 4.0 56.7 134.1 15.1 M M
36000 -39.5 -39.1 280 30 15 8.6 4.7 55.1 131.3 14.3 M M
34000 -34.4 -29.9 285 30 15 8.5 4.7 53.9 129.1 13.8 M M
32000 -29.3 -20.7 290 29 15 7.4 4.1 53.1 127.6 13.5 M M
30000 -25.0 -13.0 295 22 11 7.1 3.9 50.9 123.6 12.2 M M
29000 -22.9 -9.2 300 19 10 7.1 3.9 50.0 122.0 11.6 M M
28000 -20.8 -5.4 305 16 8 6.6 3.6 48.9 120.1 10.9 M M
27000 -18.8 -1.8 315 14 7 6.6 3.6 47.7 117.8 10.0 M M
26000 -16.9 1.6 325 12 6 6.6 3.6 46.5 115.7 9.2 M M
25000 -14.9 5.2 340 11 6 7.4 4.1 45.5 113.9 8.5 M M
24000 -12.5 9.5 350 12 6 7.8 4.3 44.7 112.4 7.9 M M
23000 -9.6 14.7 005 14 7 7.8 4.3 43.8 110.8 7.3 M M
22000 -7.4 18.7 005 15 8 6.2 3.4 43.0 109.4 6.7 M M
21000 -5.6 21.9 360 15 7 6.3 3.5 41.7 107.1 5.6 M M
20000 -3.7 25.3 355 14 7 6.4 3.5 40.6 105.0 4.6 M M
19500 -2.8 27.0 350 14 7 4.8 2.6 40.0 104.0 4.1 M M
19000 -2.3 27.9 350 14 7 4.0 2.2 38.9 102.1 3.2 M M
18500 -1.8 28.8 350 13 7 4.0 2.2 38.0 100.3 2.3 M M
18000 -1.2 29.8 350 13 7 5.7 3.1 37.1 98.8 1.5 M M
17500 -0.4 31.3 350 13 7 5.7 3.1 36.4 97.5 0.7 M M
17000 0.4 32.7 350 13 7 6.2 3.4 35.7 96.3 0.1 M M
16500 1.3 34.3 345 13 7 6.6 3.6 35.2 95.3 -0.5 1007 5.1
16000 2.2 36.0 335 14 7 6.7 3.7 34.7 94.4 -1.0 964 4.9
15500 3.2 37.8 335 15 8 7.0 3.8 34.2 93.6 -1.5 920 4.7
15000 4.2 39.6 330 15 8 6.9 3.8 33.7 92.7 -2.0 876 4.4
14500 5.3 41.5 330 16 8 8.1 4.5 33.4 92.1 -2.4 830 4.2
14000 6.4 43.5 330 16 8 8.2 4.5 33.1 91.6 -2.7 780 4.0
13500 7.6 45.7 330 16 8 8.7 4.8 32.9 91.2 -3.0 730 3.7
13000 8.9 48.0 325 15 8 9.0 4.9 32.7 90.9 -3.2 677 3.4
12500 10.1 50.2 325 14 7 9.1 5.0 32.6 90.7 -3.4 624 3.2
12000 11.5 52.7 320 13 7 9.3 5.1 32.5 90.6 -3.5 568 2.9
11500 12.9 55.2 320 12 6 9.2 5.0 32.5 90.5 -3.6 513 2.6
11000 14.2 57.6 310 11 6 8.8 4.8 32.3 90.2 -3.8 459 2.3
10500 15.5 59.9 305 10 5 7.4 4.0 32.2 90.0 -4.0 405 2.1
10250 16.0 60.8 300 10 5 7.6 4.2 32.0 89.6 -4.2 383 1.9
10000 16.6 61.9 300 9 5 9.6 5.3 31.9 89.5 -4.3 356 1.8
9750 17.3 63.1 300 9 5 9.3 5.1 31.9 89.4 -4.3 328 1.7
9500 18.0 64.4 300 9 5 8.5 4.7 31.9 89.3 -4.4 300 1.5
9250 18.5 65.3 300 9 5 7.2 4.0 31.7 89.1 -4.6 276 1.4
9000 19.1 66.4 300 9 5 8.1 4.4 31.5 88.7 -4.8 252 1.3
8750 19.7 67.5 300 9 4 8.9 4.9 31.4 88.6 -4.9 226 1.1
8500 20.3 68.5 300 8 4 7.7 4.2 31.3 88.4 -5.0 200 1.0
8250 21.2 70.2 300 8 4 6.3 3.5 30.8 87.5 -5.5 158 0.8
8000 21.8 71.2 295 8 4 8.0 4.4 30.6 87.1 -5.8 135 0.7
7750 22.3 72.1 295 7 4 5.4 2.9 30.4 86.8 -6.0 112 0.6
7500 22.5 72.5 290 7 4 2.6 1.4 29.9 85.9 -6.5 97 0.5
7250 22.7 72.9 290 7 4 2.7 1.5 29.4 85.0 -7.0 84 0.4
7000 22.9 73.2 285 7 3 1.2 0.7 28.8 83.9 -7.6 73 0.4
6750 22.9 73.2 275 7 3 -0.4 -0.2 28.1 82.6 -8.4 65 0.3
6500 22.8 73.0 270 6 3 -1.3 -0.7 27.3 81.2 -9.2 61 0.3
6250 22.7 72.9 260 6 3 -0.5 -0.3 26.5 79.7 -10.1 56 0.3
6000 22.5 72.5 255 6 3 -4.5 -2.5 25.7 78.2 -11.0 53 0.3
5750 21.8 71.2 245 5 3 -13.1 -7.2 24.2 75.6 -12.4 67 0.3
5500 21.0 69.8 235 4 2 -0.4 -0.2 22.8 73.0 -14.0 84 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
07/24/2026 at 0900 MDT | 07/24/2026 at 1200 MDT
|
CAPE... +5.2 LI... +2.0 | CAPE... +13.6 LI... +1.8
CINH... -22.1 K Index... +22.9 | CINH... -41.5 K Index... +23.1
|
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 -66.1 -87.0 285 33 17 2.2 1.2 | -65.9 -86.6 285 30 15 2.4 1.3
45000 -59.5 -75.1 285 42 22 7.4 4.1 | -59.3 -74.7 285 37 19 7.1 3.9
40000 -48.6 -55.5 295 40 20 6.9 3.8 | -48.1 -54.6 290 32 16 7.3 4.0
38000 -43.9 -47.0 290 34 17 6.9 3.8 | -43.7 -46.7 290 31 16 7.3 4.0
36000 -39.6 -39.3 285 29 15 8.6 4.7 | -39.3 -38.7 285 29 15 8.0 4.4
34000 -34.5 -30.1 285 27 14 8.5 4.7 | -34.5 -30.1 285 26 13 8.0 4.4
32000 -29.4 -20.9 285 25 13 7.4 4.0 | -29.7 -21.5 290 23 12 7.7 4.2
30000 -25.1 -13.2 290 18 9 7.2 3.9 | -25.1 -13.2 285 18 9 7.6 4.2
29000 -23.0 -9.4 290 15 8 7.2 3.9 | -22.8 -9.0 280 16 8 7.6 4.2
28000 -20.9 -5.6 295 12 6 6.5 3.6 | -20.7 -5.3 280 13 7 6.2 3.4
27000 -18.9 -2.0 305 10 5 6.5 3.6 | -18.8 -1.8 280 10 5 6.3 3.4
26000 -17.0 1.4 320 8 4 6.5 3.6 | -16.9 1.6 275 6 3 6.3 3.4
25000 -15.0 5.0 335 7 4 7.6 4.2 | -15.0 5.0 270 3 2 7.5 4.1
24000 -12.0 10.4 360 7 4 7.9 4.4 | -12.0 10.4 275 2 1 7.9 4.3
23000 -9.6 14.7 015 8 4 7.9 4.4 | -9.7 14.5 295 1 0 7.9 4.3
22000 -7.3 18.9 025 9 5 7.0 3.8 | -7.4 18.7 005 1 1 6.9 3.8
21000 -5.2 22.6 020 10 5 7.1 3.9 | -5.3 22.5 005 3 2 7.0 3.8
20000 -3.1 26.4 015 12 6 7.1 3.9 | -3.2 26.2 005 5 2 7.1 3.9
19500 -2.2 28.0 010 12 6 5.2 2.8 | -2.2 28.0 005 5 3 5.7 3.1
19000 -1.5 29.3 360 11 6 4.5 2.5 | -1.5 29.3 350 6 3 5.4 2.9
18500 -0.9 30.4 355 10 5 4.6 2.5 | -0.7 30.7 340 6 3 5.4 2.9
18000 -0.3 31.5 345 10 5 3.8 2.1 | 0.1 32.2 330 7 3 5.3 2.9
17500 0.2 32.4 335 10 5 3.9 2.2 | 0.8 33.4 325 8 4 5.3 2.9
17000 0.7 33.3 330 11 5 4.8 2.6 | 1.6 34.9 325 9 5 5.0 2.7
16500 1.4 34.5 330 12 6 5.3 2.9 | 2.2 36.0 325 11 6 4.9 2.7
16000 2.1 35.8 330 13 7 5.6 3.1 | 2.8 37.0 325 13 7 5.2 2.9
15500 3.0 37.4 335 15 8 6.7 3.7 | 3.5 38.3 325 14 7 6.0 3.3
15000 3.9 39.0 340 16 8 6.6 3.6 | 4.3 39.7 325 14 7 6.0 3.3
14500 4.9 40.8 340 18 9 8.1 4.4 | 5.2 41.4 325 14 7 8.9 4.9
14000 6.0 42.8 340 19 10 8.1 4.4 | 6.5 43.7 325 13 7 8.8 4.8
13500 7.2 45.0 345 20 10 8.7 4.8 | 7.7 45.9 325 13 7 9.0 4.9
13000 8.5 47.3 340 19 10 8.9 4.9 | 9.1 48.4 330 12 6 9.0 5.0
12500 9.7 49.5 340 19 10 9.3 5.1 | 10.4 50.7 330 11 6 9.3 5.1
12000 11.2 52.2 340 18 9 9.6 5.3 | 11.8 53.2 335 11 6 9.5 5.2
11500 12.6 54.7 340 17 9 9.6 5.3 | 13.2 55.8 335 10 5 9.5 5.2
11000 14.0 57.2 340 16 8 9.6 5.2 | 14.6 58.3 340 10 5 9.6 5.3
10500 15.4 59.7 340 16 8 8.4 4.6 | 16.1 61.0 340 10 5 8.6 4.7
10250 16.0 60.8 340 15 8 8.6 4.7 | 16.7 62.1 340 9 5 8.9 4.9
10000 16.7 62.1 340 15 8 10.2 5.6 | 17.4 63.3 345 9 5 10.4 5.7
9750 17.4 63.3 340 14 7 10.2 5.6 | 18.2 64.8 345 9 5 10.4 5.7
9500 18.2 64.8 340 14 7 8.7 4.8 | 18.9 66.0 350 9 5 9.0 4.9
9250 18.7 65.7 335 13 7 7.1 3.9 | 19.6 67.3 350 9 5 8.4 4.6
9000 19.3 66.7 335 12 6 8.2 4.5 | 20.3 68.5 350 9 4 10.1 5.6
8750 19.9 67.8 330 10 5 9.1 5.0 | 21.0 69.8 355 9 4 10.6 5.8
8500 20.5 68.9 325 9 5 7.1 3.9 | 21.8 71.2 355 8 4 9.6 5.3
8250 21.2 70.2 320 8 4 5.5 3.0 | 23.1 73.6 360 8 4 9.9 5.4
8000 21.7 71.1 315 7 3 6.6 3.6 | 23.9 75.0 005 8 4 11.6 6.4
7750 22.1 71.8 310 6 3 4.4 2.4 | 24.7 76.5 005 8 4 10.1 5.5
7500 22.3 72.1 305 5 3 2.5 1.4 | 25.4 77.7 005 8 4 9.0 4.9
7250 22.5 72.5 300 4 2 3.0 1.7 | 26.1 79.0 010 8 4 9.8 5.4
7000 22.7 72.9 290 4 2 4.1 2.2 | 26.9 80.4 010 7 4 10.9 6.0
6750 23.1 73.6 285 3 2 7.0 3.8 | 27.7 81.9 010 7 4 10.7 5.9
6500 23.7 74.7 280 3 2 8.5 4.7 | 28.5 83.3 015 7 4 10.8 5.9
6250 24.3 75.7 275 3 1 7.2 3.9 | 29.3 84.7 015 7 4 9.4 5.2
6000 24.9 76.8 265 3 1 11.2 6.1 | 30.1 86.2 015 7 3 15.0 8.2
5750 26.1 79.0 265 2 1 21.1 11.6 | 31.7 89.1 020 6 3 30.2 16.6
5500 27.4 81.3 265 2 1 7.5 4.1 | 33.8 92.8 020 6 3 13.4 7.3
07/24/2026 at 1500 MDT | 07/24/2026 at 1800 MDT
|
CAPE... +68.3 LI... -0.1 | CAPE... +45.1 LI... -0.8
CINH... -22.3 K Index... +28.5 | CINH... -8.2 K Index... +29.1
|
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 -65.9 -86.6 285 31 16 2.2 1.2 | -66.0 -86.8 285 33 17 2.1 1.2
45000 -59.4 -74.9 290 37 19 7.1 3.9 | -59.6 -75.3 290 40 20 7.1 3.9
40000 -48.0 -54.4 295 29 15 7.8 4.3 | -48.1 -54.6 285 30 15 8.0 4.4
38000 -43.3 -45.9 295 31 16 7.8 4.3 | -43.3 -45.9 295 31 16 8.0 4.4
36000 -38.6 -37.5 295 31 16 7.6 4.2 | -38.6 -37.5 300 31 16 7.5 4.1
34000 -34.1 -29.4 285 26 14 7.6 4.2 | -34.1 -29.4 295 26 14 7.5 4.1
32000 -29.5 -21.1 280 22 11 7.7 4.2 | -29.6 -21.3 290 22 11 8.2 4.5
30000 -24.9 -12.8 280 19 10 7.7 4.2 | -24.6 -12.3 290 22 11 8.2 4.5
29000 -22.6 -8.7 280 17 9 7.6 4.2 | -22.2 -8.0 285 21 11 8.2 4.5
28000 -20.5 -4.9 280 15 8 6.1 3.4 | -20.0 -4.0 285 21 11 6.2 3.4
27000 -18.7 -1.7 265 13 7 6.1 3.4 | -18.1 -0.6 280 20 10 6.2 3.4
26000 -16.9 1.6 255 11 6 6.1 3.4 | -16.3 2.7 270 19 10 6.2 3.4
25000 -15.0 5.0 240 10 5 7.3 4.0 | -14.0 6.8 265 18 9 6.3 3.4
24000 -12.2 10.0 235 8 4 7.5 4.1 | -12.1 10.2 265 17 9 6.4 3.5
23000 -9.9 14.2 235 7 4 7.5 4.1 | -10.3 13.5 265 15 8 6.5 3.6
22000 -7.8 18.0 245 6 3 6.0 3.3 | -8.5 16.7 265 14 7 6.4 3.5
21000 -6.0 21.2 265 7 4 6.1 3.4 | -6.7 19.9 275 14 7 6.5 3.6
20000 -4.2 24.4 275 9 5 6.2 3.4 | -4.9 23.2 285 15 8 6.6 3.6
19500 -3.4 25.9 280 11 6 6.0 3.3 | -3.9 25.0 290 15 8 7.3 4.0
19000 -2.6 27.3 280 15 8 6.3 3.4 | -2.9 26.8 290 14 7 7.4 4.1
18500 -1.8 28.8 280 19 10 6.9 3.8 | -1.8 28.8 290 13 7 7.4 4.1
18000 -0.8 30.6 285 20 10 7.9 4.4 | -0.8 30.6 290 11 6 6.9 3.8
17500 0.2 32.4 285 20 10 8.0 4.4 | 0.2 32.4 285 9 4 6.9 3.8
17000 1.3 34.3 285 19 10 8.1 4.5 | 1.3 34.3 285 6 3 8.8 4.8
16500 2.5 36.5 290 16 8 8.1 4.5 | 2.7 36.9 285 5 3 9.4 5.1
16000 3.7 38.7 295 14 7 8.3 4.5 | 4.1 39.4 285 4 2 9.4 5.2
15500 4.9 40.8 300 12 6 8.7 4.8 | 5.5 41.9 285 3 2 9.5 5.2
15000 6.2 43.2 305 10 5 8.7 4.8 | 7.0 44.6 285 3 1 9.5 5.2
14500 7.5 45.5 310 8 4 8.8 4.8 | 8.4 47.1 290 2 1 9.6 5.3
14000 8.8 47.8 315 7 4 8.7 4.8 | 9.8 49.6 290 2 1 9.6 5.3
13500 10.1 50.2 325 6 3 9.3 5.1 | 11.3 52.3 300 1 1 9.8 5.3
13000 11.5 52.7 330 6 3 9.4 5.2 | 12.7 54.9 310 1 1 9.8 5.4
12500 12.9 55.2 335 5 3 9.6 5.3 | 14.2 57.6 325 1 0 9.8 5.4
12000 14.4 57.9 340 5 3 9.7 5.3 | 15.6 60.1 345 1 0 9.7 5.3
11500 15.9 60.6 350 5 3 9.6 5.3 | 17.1 62.8 010 1 0 9.6 5.3
11000 17.3 63.1 355 5 3 9.5 5.2 | 18.5 65.3 025 1 1 9.5 5.2
10500 18.7 65.7 360 5 3 8.7 4.8 | 19.9 67.8 040 1 1 10.1 5.5
10250 19.3 66.7 005 5 2 9.0 4.9 | 20.7 69.3 045 1 1 10.2 5.6
10000 20.1 68.2 005 5 2 10.2 5.6 | 21.4 70.5 045 2 1 9.4 5.2
9750 20.8 69.4 010 5 3 10.1 5.5 | 22.2 72.0 050 2 1 9.9 5.4
9500 21.6 70.9 015 5 3 9.3 5.1 | 22.9 73.2 050 2 1 9.0 4.9
9250 22.2 72.0 015 5 3 9.2 5.0 | 23.5 74.3 055 2 1 9.1 5.0
9000 23.0 73.4 020 5 3 10.1 5.6 | 24.3 75.7 055 2 1 10.0 5.5
8750 23.7 74.7 020 5 3 10.3 5.6 | 25.0 77.0 055 3 1 10.0 5.5
8500 25.1 77.2 030 5 3 8.2 4.5 | 26.4 79.5 060 3 2 8.6 4.7
8250 25.8 78.4 030 5 3 10.0 5.5 | 27.1 80.8 060 3 2 9.9 5.4
8000 26.6 79.9 035 5 3 11.7 6.4 | 27.9 82.2 060 3 2 11.2 6.2
7750 27.4 81.3 035 5 3 10.3 5.7 | 28.7 83.7 065 4 2 10.1 5.5
7500 28.2 82.8 035 6 3 9.1 5.0 | 29.4 84.9 065 4 2 8.8 4.9
7250 28.9 84.0 040 6 3 9.8 5.4 | 30.1 86.2 065 4 2 9.4 5.2
7000 29.6 85.3 040 6 3 11.0 6.0 | 30.8 87.4 065 4 2 10.8 5.9
6750 30.5 86.9 045 6 3 10.8 5.9 | 31.6 88.9 065 5 2 10.5 5.7
6500 31.3 88.3 045 6 3 10.7 5.9 | 32.4 90.3 065 5 2 10.0 5.5
6250 32.0 89.6 045 6 3 9.7 5.3 | 33.2 91.8 065 5 3 9.8 5.4
6000 32.8 91.0 045 6 3 13.5 7.4 | 33.9 93.0 065 5 3 11.3 6.2
5750 34.3 93.7 050 6 3 27.0 14.8 | 35.0 95.0 065 5 3 17.3 9.5
5500 36.6 97.9 050 5 3 29.0 15.9 | 36.5 97.7 065 5 2 23.7 13.0
________________________________________________________________________________
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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