Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
651
UXUS97 KBOU 161324
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0724 MDT Friday, May 16, 2025
This forecast is for Friday, May 16, 2025:
If the trigger temperature of 54.2 F/12.3 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1685 ft/min (8.6 m/s)
Maximum height of thermals.................. 23448 ft MSL (18134 ft AGL)
Forecast maximum temperature................... 73.0 F/23.2 C
Time of trigger temperature.................... 0800 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................. 19449 ft MSL (14134 ft AGL)
Thermal soaring outlook for Saturday 05/17..... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... Becoming good
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak NVA
Potential height of wave....................... 14437 ft MSL (9123 ft AGL)
Wave soaring outlook for Saturday 05/17........ Poor
Remarks...
Sunrise/Sunset.................... 05:43:19 / 20:08:26 MDT
Total possible sunshine........... 14 hr 25 min 7 sec (865 min 7 sec)
Altitude of sun at 12:55:53 MDT... 69.50 degrees
Upper air data from numerical model forecast valid on 05/16/2025 at 0600 MDT
Freezing level.................. 9513 ft MSL (4199 ft AGL)
Convective condensation level... 14999 ft MSL (9685 ft AGL)
Lifted condensation level....... 17475 ft MSL (12160 ft AGL)
Lifted index.................... -4.0
K index......................... +4.6
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 -53.4 -64.1 255 29 15 1.6 0.9 M M M M M
45000 -51.0 -59.8 265 33 17 0.1 0.1 M M M M M
40000 -51.6 -60.9 270 43 22 -0.4 -0.2 M M M M M
38000 -50.7 -59.3 270 45 23 3.9 2.2 M M M M M
36000 -48.0 -54.4 275 43 22 3.9 2.2 M M M M M
34000 -45.8 -50.4 280 43 22 2.5 1.3 M M M M M
32000 -44.2 -47.6 290 49 25 2.6 1.4 M M M M M
30000 -42.6 -44.7 295 56 29 3.7 2.1 34.6 94.2 8.8 M M
29000 -41.5 -42.7 295 58 30 3.7 2.0 32.0 89.6 7.0 M M
28000 -40.3 -40.5 295 60 31 3.7 2.0 29.6 85.3 5.2 M M
27000 -39.2 -38.6 295 62 32 3.4 1.9 27.4 81.3 3.6 M M
26000 -37.5 -35.5 295 59 30 6.6 3.6 25.8 78.4 2.4 M M
25000 -35.5 -31.9 290 54 28 6.6 3.6 24.5 76.2 1.4 M M
24000 -33.6 -28.5 290 49 25 6.5 3.6 23.4 74.2 0.5 M M
23000 -31.5 -24.7 290 44 23 7.1 3.9 22.4 72.3 -0.4 1649 8.4
22000 -29.4 -20.9 295 40 20 7.1 3.9 21.4 70.4 -1.2 1555 7.9
21000 -27.3 -17.1 295 35 18 7.2 3.9 20.5 68.9 -2.0 1462 7.4
20000 -24.9 -12.8 300 31 16 8.0 4.4 19.8 67.6 -2.6 1362 6.9
19500 -23.7 -10.7 305 30 15 8.0 4.4 19.4 67.0 -2.9 1311 6.7
19000 -22.5 -8.5 310 28 15 8.1 4.4 19.2 66.5 -3.2 1261 6.4
18500 -20.7 -5.3 315 26 14 8.2 4.5 18.8 65.8 -3.5 1184 6.0
18000 -19.5 -3.1 315 26 13 8.2 4.5 18.5 65.3 -3.8 1133 5.8
17500 -18.2 -0.8 315 25 13 8.2 4.5 18.2 64.8 -4.1 1081 5.5
17000 -17.0 1.4 320 25 13 8.4 4.6 18.0 64.4 -4.3 1029 5.2
16500 -15.8 3.6 320 25 13 8.4 4.6 17.8 64.0 -4.6 976 5.0
16000 -14.5 5.9 320 25 13 8.0 4.4 17.5 63.5 -4.8 925 4.7
15500 -13.3 8.1 320 25 13 8.0 4.4 17.2 63.0 -5.1 874 4.4
15000 -12.1 10.2 320 26 13 8.1 4.4 16.9 62.5 -5.4 823 4.2
14500 -10.9 12.4 320 27 14 8.1 4.5 16.7 62.0 -5.7 772 3.9
14000 -9.7 14.5 320 28 14 8.1 4.5 16.4 61.5 -6.0 721 3.7
13500 -8.5 16.7 315 29 15 8.1 4.4 16.1 61.0 -6.3 670 3.4
13000 -7.3 18.9 315 30 16 8.0 4.4 15.9 60.5 -6.5 618 3.1
12500 -6.1 21.0 310 32 16 7.7 4.2 15.5 60.0 -6.9 569 2.9
12000 -5.0 23.0 310 34 17 7.6 4.2 15.2 59.4 -7.2 519 2.6
11500 -3.9 25.0 305 35 18 6.9 3.8 14.8 58.6 -7.7 473 2.4
11000 -2.9 26.8 305 37 19 6.6 3.6 14.4 57.8 -8.2 427 2.2
10500 -2.1 28.2 300 37 19 5.0 2.8 13.7 56.6 -8.9 388 2.0
10250 -1.7 28.9 300 37 19 5.5 3.0 13.3 56.0 -9.2 370 1.9
10000 -1.2 29.8 300 37 19 9.1 5.0 13.1 55.6 -9.5 347 1.8
9750 -0.5 31.1 300 37 19 8.7 4.8 13.1 55.6 -9.5 318 1.6
9500 0.0 32.0 295 37 19 6.0 3.3 12.9 55.2 -9.8 296 1.5
9250 0.5 32.9 295 36 19 7.1 3.9 12.6 54.7 -10.1 275 1.4
9000 1.0 33.8 295 36 18 5.5 3.0 12.4 54.3 -10.4 253 1.3
8750 1.4 34.5 295 35 18 6.4 3.5 12.0 53.7 -10.8 234 1.2
8500 1.9 35.4 295 33 17 8.5 4.6 11.9 53.4 -10.9 209 1.1
8250 2.5 36.5 295 32 16 7.5 4.1 11.8 53.2 -11.1 184 0.9
8000 3.0 37.4 295 31 16 6.1 3.4 11.5 52.8 -11.4 162 0.8
7750 3.5 38.3 290 29 15 7.6 4.1 11.3 52.3 -11.7 141 0.7
7500 4.2 39.6 290 27 14 9.9 5.4 11.2 52.2 -11.8 113 0.6
7250 4.8 40.6 290 24 13 8.0 4.4 11.2 52.1 -11.8 85 0.4
7000 5.3 41.5 290 23 12 5.7 3.1 10.9 51.7 -12.1 63 0.3
6750 5.8 42.4 290 21 11 8.8 4.8 10.7 51.3 -12.4 41 0.2
6500 6.6 43.9 290 18 9 11.1 6.1 10.8 51.4 -12.3 10 0.0
6250 7.3 45.1 290 15 8 8.2 4.5 10.8 51.4 -12.4 M M
6000 7.8 46.0 290 13 7 6.7 3.7 10.6 51.0 -12.6 M M
5750 8.4 47.1 290 10 5 8.3 4.5 10.4 50.7 -12.9 M M
5500 8.8 47.8 280 8 4 0.7 0.4 10.1 50.2 -13.2 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/16/2025 at 0900 MDT | 05/16/2025 at 1200 MDT
|
CAPE... 0.0 LI... +2.7 | CAPE... +2.5 LI... +2.1
CINH... -0.1 K Index... -1.9 | CINH... -0.1 K Index... +11.5
|
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 -53.8 -64.8 255 27 14 1.8 1.0 | -55.5 -67.9 255 30 15 0.8 0.5
45000 -51.1 -60.0 270 30 16 -0.1 -0.1 | -54.3 -65.7 280 39 20 -0.4 -0.2
40000 -52.0 -61.6 280 36 18 -0.6 -0.3 | -55.6 -68.1 290 42 22 -0.9 -0.5
38000 -51.5 -60.7 285 37 19 2.6 1.4 | -54.6 -66.3 295 46 24 3.2 1.8
36000 -49.7 -57.5 295 38 20 2.6 1.4 | -52.7 -62.9 305 51 26 3.2 1.8
34000 -48.0 -54.4 305 39 20 4.4 2.4 | -50.2 -58.4 310 55 28 7.3 4.0
32000 -45.5 -49.9 310 34 18 4.2 2.3 | -45.8 -50.4 305 51 26 7.3 4.0
30000 -42.8 -45.0 320 31 16 6.3 3.5 | -41.4 -42.5 300 46 24 7.8 4.3
29000 -40.9 -41.6 320 32 16 6.2 3.4 | -38.4 -37.1 300 43 22 7.8 4.3
28000 -39.1 -38.4 320 33 17 6.2 3.4 | -36.1 -33.0 300 40 21 7.9 4.3
27000 -37.2 -35.0 315 34 18 6.2 3.4 | -33.8 -28.8 295 38 19 7.4 4.1
26000 -35.3 -31.5 315 36 18 6.5 3.6 | -31.6 -24.9 300 38 20 7.4 4.0
25000 -33.3 -27.9 315 37 19 6.5 3.6 | -29.4 -20.9 300 38 20 7.4 4.0
24000 -31.4 -24.5 315 38 20 6.5 3.6 | -27.2 -17.0 305 38 20 6.9 3.8
23000 -29.4 -20.9 310 37 19 6.3 3.4 | -25.3 -13.5 300 38 20 6.3 3.5
22000 -27.6 -17.7 305 34 17 6.3 3.4 | -23.4 -10.1 295 38 20 6.3 3.5
21000 -25.7 -14.3 295 31 16 6.5 3.6 | -21.5 -6.7 295 38 19 5.3 2.9
20000 -23.0 -9.4 300 27 14 7.4 4.0 | -20.1 -4.2 295 35 18 4.9 2.7
19500 -21.9 -7.4 300 25 13 7.4 4.0 | -19.3 -2.7 295 33 17 5.0 2.7
19000 -20.8 -5.4 300 23 12 7.4 4.0 | -18.6 -1.5 295 32 16 5.0 2.7
18500 -19.7 -3.5 300 22 11 7.5 4.1 | -17.9 -0.2 300 30 15 5.6 3.0
18000 -18.5 -1.3 300 20 11 7.6 4.2 | -17.0 1.4 300 29 15 6.2 3.4
17500 -17.4 0.7 300 19 10 7.7 4.2 | -16.1 3.0 300 29 15 6.3 3.5
17000 -16.2 2.8 305 18 9 7.8 4.3 | -15.2 4.6 300 28 15 6.0 3.3
16500 -15.1 4.8 305 18 9 7.8 4.3 | -14.3 6.3 300 28 14 6.0 3.3
16000 -13.9 7.0 305 17 9 7.7 4.2 | -13.4 7.9 300 27 14 6.5 3.6
15500 -12.7 9.1 310 17 9 7.7 4.2 | -12.4 9.7 300 26 13 6.7 3.7
15000 -11.6 11.1 310 18 9 8.0 4.4 | -10.9 12.4 295 25 13 8.0 4.4
14500 -10.4 13.3 310 19 10 8.1 4.4 | -9.7 14.5 300 24 13 8.0 4.4
14000 -9.2 15.4 310 20 10 8.0 4.4 | -8.5 16.7 300 24 12 8.6 4.7
13500 -8.0 17.6 310 20 11 8.0 4.4 | -7.2 19.0 300 24 12 8.8 4.8
13000 -6.8 19.8 310 21 11 8.0 4.4 | -5.9 21.4 300 24 12 8.9 4.9
12500 -5.6 21.9 310 22 11 8.1 4.5 | -4.5 23.9 300 25 13 9.0 4.9
12000 -4.4 24.1 305 23 12 8.0 4.4 | -3.2 26.2 300 26 13 8.6 4.7
11500 -3.2 26.2 305 25 13 7.7 4.2 | -2.0 28.4 300 26 14 8.2 4.5
11000 -2.1 28.2 305 26 14 7.2 3.9 | -0.8 30.6 300 27 14 7.1 3.9
10500 -1.2 29.8 300 28 14 5.4 3.0 | 0.1 32.2 300 25 13 5.0 2.8
10250 -0.8 30.6 300 29 15 6.9 3.8 | 0.5 32.9 300 24 13 10.9 6.0
10000 -0.2 31.6 300 30 15 9.3 5.1 | 1.6 34.9 300 24 12 13.2 7.2
9750 0.5 32.9 300 31 16 7.7 4.2 | 2.3 36.1 300 23 12 8.5 4.6
9500 0.9 33.6 295 31 16 6.0 3.3 | 3.0 37.4 305 22 11 10.5 5.8
9250 1.4 34.5 295 31 16 6.6 3.6 | 3.7 38.7 305 22 11 7.1 3.9
9000 1.8 35.2 295 30 16 5.5 3.0 | 4.2 39.6 305 20 11 7.6 4.2
8750 2.3 36.1 295 29 15 6.8 3.7 | 4.9 40.8 305 20 10 11.3 6.2
8500 2.9 37.2 295 27 14 8.7 4.8 | 5.8 42.4 305 20 10 11.2 6.2
8250 3.5 38.3 295 26 13 7.8 4.3 | 6.6 43.9 305 19 10 9.7 5.3
8000 4.0 39.2 295 24 12 6.7 3.7 | 7.2 45.0 310 19 10 8.3 4.5
7750 4.5 40.1 295 22 11 8.4 4.6 | 7.9 46.2 310 18 9 10.4 5.7
7500 5.2 41.4 295 21 11 10.4 5.7 | 8.7 47.7 310 18 9 12.0 6.6
7250 6.0 42.8 295 19 10 8.7 4.8 | 9.6 49.3 310 18 9 9.0 5.0
7000 6.5 43.7 295 18 9 6.8 3.7 | 10.1 50.2 310 17 9 6.6 3.6
6750 7.1 44.8 295 17 9 10.0 5.5 | 10.7 51.3 315 17 9 11.3 6.2
6500 8.0 46.4 295 15 8 12.3 6.8 | 11.7 53.1 310 17 9 12.9 7.1
6250 8.8 47.8 295 14 7 10.0 5.5 | 12.6 54.7 315 16 8 10.2 5.6
6000 9.5 49.1 295 13 7 9.3 5.1 | 13.3 55.9 315 15 8 9.5 5.2
5750 10.2 50.4 300 12 6 9.7 5.3 | 14.0 57.2 315 15 8 11.1 6.1
5500 11.1 52.0 295 11 6 14.4 7.9 | 15.1 59.2 315 14 7 21.0 11.5
05/16/2025 at 1500 MDT | 05/16/2025 at 1800 MDT
|
CAPE... +22.2 LI... +0.9 | CAPE... +25.3 LI... +0.1
CINH... -2.4 K Index... +19.1 | CINH... -13.5 K Index... +20.0
|
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 -56.2 -69.2 245 24 12 0.2 0.1 | -56.8 -70.2 245 31 16 0.7 0.4
45000 -56.0 -68.8 255 24 12 -1.6 -0.9 | -55.9 -68.6 255 38 19 -2.0 -1.1
40000 -59.0 -74.2 275 60 31 -1.9 -1.0 | -59.4 -74.9 265 66 34 -2.0 -1.1
38000 -57.3 -71.1 275 63 32 5.3 2.9 | -57.4 -71.3 265 69 35 5.7 3.1
36000 -54.1 -65.4 280 61 31 5.3 2.9 | -54.0 -65.2 265 67 35 5.7 3.1
34000 -50.4 -58.7 285 58 30 8.4 4.6 | -50.0 -58.0 265 65 33 8.5 4.6
32000 -45.3 -49.5 285 56 29 8.5 4.6 | -44.9 -48.8 265 59 30 8.5 4.6
30000 -39.6 -39.3 285 54 28 8.5 4.7 | -39.2 -38.6 265 54 28 8.4 4.6
29000 -37.1 -34.8 285 52 27 8.5 4.7 | -36.7 -34.1 265 52 27 8.4 4.6
28000 -34.5 -30.1 285 51 26 8.6 4.7 | -34.2 -29.6 265 50 26 8.4 4.6
27000 -32.1 -25.8 290 49 25 7.0 3.8 | -31.7 -25.1 270 49 25 7.6 4.2
26000 -29.9 -21.8 285 47 24 7.2 3.9 | -29.5 -21.1 270 47 24 7.7 4.2
25000 -27.8 -18.0 285 44 23 7.2 3.9 | -27.2 -17.0 270 46 24 7.7 4.2
24000 -25.7 -14.3 285 42 22 6.7 3.7 | -25.0 -13.0 270 44 23 6.2 3.4
23000 -23.8 -10.8 285 40 20 6.5 3.6 | -23.2 -9.8 275 42 21 6.0 3.3
22000 -21.8 -7.2 285 38 19 6.6 3.6 | -21.4 -6.5 275 39 20 6.0 3.3
21000 -19.9 -3.8 285 36 18 5.3 2.9 | -19.7 -3.5 275 37 19 5.5 3.0
20000 -18.4 -1.1 285 33 17 5.3 2.9 | -18.1 -0.6 275 35 18 5.6 3.1
19500 -17.6 0.3 280 32 17 5.4 2.9 | -17.2 1.0 270 34 18 5.6 3.1
19000 -16.8 1.8 280 31 16 5.4 2.9 | -16.4 2.5 270 33 17 5.6 3.1
18500 -16.0 3.2 280 30 15 5.7 3.1 | -15.6 3.9 270 32 16 6.0 3.3
18000 -15.2 4.6 280 30 15 5.9 3.2 | -14.7 5.5 270 31 16 6.1 3.3
17500 -14.3 6.3 280 29 15 6.0 3.3 | -13.8 7.2 270 30 15 6.3 3.5
17000 -13.4 7.9 280 29 15 6.9 3.8 | -12.8 9.0 265 29 15 7.2 4.0
16500 -12.4 9.7 280 29 15 6.8 3.8 | -11.7 10.9 265 28 14 7.1 3.9
16000 -10.8 12.6 280 29 15 7.3 4.0 | -10.0 14.0 265 27 14 8.4 4.6
15500 -9.7 14.5 280 29 15 7.2 4.0 | -8.7 16.3 265 26 13 8.4 4.6
15000 -8.6 16.5 280 29 15 7.7 4.2 | -7.5 18.5 265 25 13 8.4 4.6
14500 -7.5 18.5 280 28 14 7.6 4.2 | -6.2 20.8 265 24 12 8.4 4.6
14000 -6.3 20.7 280 27 14 8.6 4.7 | -5.0 23.0 265 23 12 8.9 4.9
13500 -5.1 22.8 280 26 13 8.6 4.7 | -3.7 25.3 265 22 12 8.9 4.9
13000 -3.8 25.2 280 25 13 8.9 4.9 | -2.4 27.7 265 22 11 8.9 4.9
12500 -2.4 27.7 285 23 12 9.0 4.9 | -1.0 30.2 270 21 11 8.9 4.9
12000 -1.1 30.0 285 22 11 9.3 5.1 | 0.3 32.5 270 20 10 9.1 5.0
11500 0.3 32.5 285 21 11 9.4 5.2 | 1.6 34.9 275 19 10 9.1 5.0
11000 1.7 35.1 285 20 10 8.5 4.7 | 3.0 37.4 275 18 9 8.0 4.4
10500 2.9 37.2 290 20 10 6.9 3.8 | 4.1 39.4 280 18 9 6.4 3.5
10250 3.5 38.3 290 20 10 12.4 6.8 | 4.7 40.5 280 18 9 11.8 6.5
10000 4.6 40.3 290 20 10 13.5 7.4 | 5.7 42.3 285 18 9 13.1 7.2
9750 5.3 41.5 290 19 10 8.6 4.7 | 6.5 43.7 285 18 9 8.4 4.6
9500 6.1 43.0 290 19 10 10.4 5.7 | 7.2 45.0 285 18 9 10.3 5.7
9250 6.8 44.2 295 19 10 7.9 4.3 | 7.9 46.2 285 18 9 7.4 4.0
9000 7.3 45.1 295 19 10 8.5 4.7 | 8.3 46.9 285 18 9 8.0 4.4
8750 8.1 46.6 295 19 10 10.9 6.0 | 9.1 48.4 290 18 9 10.8 5.9
8500 8.9 48.0 295 19 10 10.6 5.8 | 9.9 49.8 290 18 9 10.4 5.7
8250 9.7 49.5 295 19 10 9.6 5.3 | 10.6 51.1 290 18 9 9.3 5.1
8000 10.3 50.5 295 19 10 9.0 4.9 | 11.3 52.3 290 18 9 8.6 4.7
7750 11.0 51.8 295 19 10 10.2 5.6 | 12.0 53.6 295 18 9 10.2 5.6
7500 11.8 53.2 300 19 10 11.1 6.1 | 12.8 55.0 295 18 9 10.8 5.9
7250 12.6 54.7 300 18 9 9.1 5.0 | 13.5 56.3 295 18 9 8.7 4.8
7000 13.2 55.8 300 18 9 7.7 4.2 | 14.1 57.4 295 18 9 7.2 4.0
6750 13.9 57.0 300 18 9 10.8 5.9 | 14.7 58.5 295 18 9 10.8 5.9
6500 14.8 58.6 300 18 9 12.0 6.6 | 15.6 60.1 295 17 9 11.8 6.5
6250 15.6 60.1 300 17 9 10.5 5.8 | 16.4 61.5 300 17 9 9.8 5.4
6000 16.4 61.5 305 17 9 10.4 5.7 | 17.1 62.8 300 17 9 9.2 5.1
5750 17.2 63.0 305 17 9 9.9 5.4 | 17.8 64.0 300 16 8 10.3 5.7
5500 18.0 64.4 305 15 8 16.4 9.0 | 18.7 65.7 300 14 7 14.4 7.9
________________________________________________________________________________
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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