Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
726
UXUS97 KBOU 200153
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1951 MDT Saturday, April 19, 2025
This forecast is for Sunday, April 20, 2025:
If the trigger temperature of 47.5 F/8.6 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 905 ft/min (4.6 m/s)
Maximum height of thermals.................. 16407 ft MSL (11124 ft AGL)
Forecast maximum temperature................... 62.0 F/17.1 C
Time of trigger temperature.................... 0945 MDT
Time of overdevelopment........................ 1400 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 13374 ft MSL (8092 ft AGL)
Thermal soaring outlook for Monday 04/21....... 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)................ Weak NVA
Potential height of wave....................... 30569 ft MSL (25286 ft AGL)
Wave soaring outlook for Monday 04/21.......... Poor
Remarks...
Sunrise/Sunset.................... 06:13:42 / 19:42:50 MDT
Total possible sunshine........... 13 hr 29 min 8 sec (809 min 8 sec)
Altitude of sun at 12:58:16 MDT... 62.03 degrees
Upper air data from numerical model forecast valid on 04/20/2025 at 0600 MDT
Freezing level.................. 7518 ft MSL (2235 ft AGL)
Convective condensation level... 14106 ft MSL (8823 ft AGL)
Lifted condensation level....... 15226 ft MSL (9943 ft AGL)
Lifted index.................... +2.9
K index......................... -6.8
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 -58.4 -73.1 265 25 13 0.1 0.1 M M M M M
45000 -58.2 -72.8 265 27 14 0.1 0.1 M M M M M
40000 -57.9 -72.2 295 26 14 0.2 0.1 M M M M M
38000 -56.5 -69.7 305 28 15 4.5 2.5 M M M M M
36000 -53.8 -64.8 310 31 16 4.5 2.5 M M M M M
34000 -51.0 -59.8 320 35 18 6.4 3.5 M M M M M
32000 -47.1 -52.8 330 38 19 6.5 3.6 M M M M M
30000 -43.2 -45.8 335 41 21 6.6 3.6 34.5 94.1 13.3 M M
29000 -41.2 -42.2 335 40 21 6.5 3.6 33.1 91.5 12.4 M M
28000 -39.3 -38.7 340 40 20 6.5 3.6 31.8 89.2 11.6 M M
27000 -36.8 -34.2 340 39 20 6.5 3.6 30.4 86.8 10.7 M M
26000 -34.9 -30.8 340 38 20 6.3 3.4 29.0 84.2 9.7 M M
25000 -33.1 -27.6 340 37 19 6.3 3.4 27.7 81.8 8.8 M M
24000 -31.2 -24.2 340 36 19 6.3 3.5 26.5 79.7 7.9 M M
23000 -29.4 -20.9 335 33 17 6.1 3.3 25.1 77.2 6.9 M M
22000 -27.5 -17.5 330 29 15 6.1 3.3 23.7 74.7 5.8 M M
21000 -25.7 -14.3 320 26 13 6.1 3.4 22.5 72.6 4.9 M M
20000 -23.9 -11.0 315 24 12 6.2 3.4 21.2 70.1 3.8 M M
19500 -23.0 -9.4 315 23 12 6.2 3.4 20.5 69.0 3.3 M M
19000 -22.1 -7.8 315 22 12 6.2 3.4 19.9 67.9 2.8 M M
18500 -21.1 -6.0 310 22 11 6.2 3.4 19.4 66.9 2.3 M M
18000 -20.2 -4.4 310 21 11 6.3 3.4 18.8 65.8 1.8 M M
17500 -19.3 -2.7 310 20 10 6.3 3.4 18.2 64.7 1.2 M M
17000 -18.3 -0.9 315 19 10 6.2 3.4 17.6 63.6 0.7 M M
16500 -17.4 0.7 315 18 9 6.2 3.4 16.9 62.5 0.2 M M
16000 -16.5 2.3 320 17 9 6.5 3.6 16.4 61.5 -0.3 877 4.5
15500 -15.5 4.1 320 16 8 6.8 3.7 15.8 60.5 -0.8 832 4.2
15000 -14.5 5.9 320 15 8 6.8 3.7 15.4 59.6 -1.2 786 4.0
14500 -13.5 7.7 325 14 7 6.7 3.7 14.8 58.7 -1.7 742 3.8
14000 -12.5 9.5 325 13 7 6.7 3.7 14.3 57.8 -2.2 697 3.5
13500 -11.1 12.0 325 12 6 6.2 3.4 13.5 56.3 -3.0 633 3.2
13000 -10.1 13.8 325 11 6 6.2 3.4 12.9 55.3 -3.5 591 3.0
12500 -9.2 15.4 330 11 5 6.3 3.5 12.3 54.2 -4.1 548 2.8
12000 -8.3 17.1 330 10 5 6.2 3.4 11.8 53.2 -4.7 506 2.6
11500 -7.4 18.7 325 10 5 6.1 3.3 11.2 52.1 -5.3 465 2.4
11000 -6.6 20.1 325 11 5 6.5 3.6 10.6 51.1 -5.9 424 2.2
10500 -5.6 21.9 320 11 6 7.2 4.0 10.2 50.3 -6.4 379 1.9
10250 -5.1 22.8 320 11 6 5.9 3.2 9.9 49.9 -6.6 357 1.8
10000 -4.7 23.5 320 11 6 4.1 2.2 9.5 49.2 -7.1 340 1.7
9750 -4.4 24.1 320 11 6 6.6 3.6 9.2 48.5 -7.4 321 1.6
9500 -3.8 25.2 320 10 5 8.8 4.8 9.0 48.2 -7.6 296 1.5
9250 -3.2 26.2 320 10 5 7.1 3.9 8.9 48.0 -7.8 271 1.4
9000 -2.8 27.0 320 10 5 4.6 2.5 8.6 47.5 -8.1 251 1.3
8750 -2.4 27.7 320 9 5 5.9 3.2 8.2 46.8 -8.5 234 1.2
8500 -1.9 28.6 320 8 4 7.8 4.3 8.0 46.4 -8.7 211 1.1
8250 -1.4 29.5 320 6 3 6.6 3.6 7.8 46.1 -9.0 188 1.0
8000 -1.0 30.2 320 6 3 5.4 3.0 7.5 45.5 -9.3 168 0.9
7750 -0.5 31.1 315 5 3 7.1 3.9 7.2 45.0 -9.6 147 0.7
7500 0.1 32.2 315 4 2 8.1 4.5 7.1 44.8 -9.8 122 0.6
7250 0.6 33.1 310 4 2 6.2 3.4 6.9 44.4 -10.0 99 0.5
7000 1.0 33.8 305 4 2 4.9 2.7 6.6 43.8 -10.4 80 0.4
6750 1.4 34.5 300 4 2 6.9 3.8 6.2 43.2 -10.7 61 0.3
6500 1.9 35.4 290 4 2 4.3 2.3 6.0 42.9 -11.0 38 0.2
6250 2.0 35.6 280 4 2 0.2 0.1 5.4 41.7 -11.7 28 0.1
6000 2.0 35.6 270 4 2 1.6 0.9 4.7 40.5 -12.4 19 0.1
5750 2.1 35.8 260 4 2 -0.6 -0.3 4.1 39.3 -13.1 10 0.1
5500 1.8 35.2 235 3 2 -6.6 -3.6 3.1 37.5 -14.1 12 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/20/2025 at 0900 MDT | 04/20/2025 at 1200 MDT
|
CAPE... 0.0 LI... +7.1 | CAPE... +1.7 LI... +5.6
CINH... -0.0 K Index... -2.8 | CINH... -0.2 K Index... +5.5
|
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 -57.4 -71.3 265 25 13 0.2 0.1 | -58.3 -72.9 260 27 14 1.2 0.6
45000 -57.0 -70.6 275 35 18 0.3 0.2 | -56.6 -69.9 270 33 17 1.3 0.7
40000 -57.8 -72.0 275 28 14 -0.5 -0.3 | -56.9 -70.4 275 35 18 -0.3 -0.2
38000 -57.1 -70.8 280 25 13 3.2 1.7 | -56.6 -69.9 275 33 17 1.8 1.0
36000 -55.2 -67.4 285 24 12 3.2 1.7 | -55.5 -67.9 270 27 14 1.8 1.0
34000 -53.1 -63.6 295 23 12 6.9 3.8 | -54.1 -65.4 265 22 11 6.9 3.8
32000 -48.8 -55.8 305 23 12 7.3 4.0 | -49.7 -57.5 270 22 11 7.3 4.0
30000 -43.9 -47.0 320 25 13 7.5 4.1 | -44.7 -48.5 280 23 12 8.1 4.4
29000 -41.6 -42.9 320 27 14 7.5 4.1 | -42.3 -44.1 285 22 11 8.1 4.5
28000 -39.3 -38.7 320 28 15 7.5 4.1 | -39.8 -39.6 290 22 11 8.1 4.5
27000 -37.1 -34.8 320 30 15 7.6 4.1 | -37.4 -35.3 295 22 11 7.9 4.3
26000 -34.8 -30.6 325 30 15 7.6 4.2 | -35.1 -31.2 300 22 11 7.6 4.2
25000 -32.5 -26.5 330 30 16 7.6 4.2 | -32.9 -27.2 305 22 11 7.6 4.2
24000 -30.3 -22.5 330 30 16 7.6 4.2 | -30.6 -23.1 315 22 11 7.6 4.2
23000 -28.2 -18.8 330 30 15 6.9 3.8 | -28.3 -18.9 315 22 11 7.9 4.3
22000 -26.1 -15.0 330 28 15 6.9 3.8 | -25.9 -14.6 315 22 11 7.9 4.3
21000 -24.0 -11.2 330 27 14 6.7 3.7 | -23.6 -10.5 315 22 11 7.5 4.1
20000 -22.1 -7.8 330 27 14 6.3 3.4 | -21.4 -6.5 320 23 12 7.1 3.9
19500 -21.2 -6.2 330 26 14 6.3 3.4 | -20.4 -4.7 320 23 12 7.1 3.9
19000 -20.3 -4.5 325 26 13 6.3 3.4 | -19.3 -2.7 320 23 12 7.1 3.9
18500 -19.3 -2.7 325 26 13 6.1 3.3 | -18.2 -0.8 320 24 12 6.7 3.7
18000 -18.5 -1.3 325 25 13 4.8 2.6 | -17.4 0.7 325 24 12 5.5 3.0
17500 -17.8 -0.0 325 25 13 4.9 2.7 | -16.6 2.1 325 24 12 5.6 3.0
17000 -17.1 1.2 325 24 12 4.3 2.4 | -15.8 3.6 325 23 12 4.7 2.6
16500 -16.5 2.3 330 23 12 4.3 2.4 | -15.1 4.8 325 23 12 4.7 2.6
16000 -15.5 4.1 330 21 11 4.8 2.7 | -14.4 6.1 325 23 12 4.5 2.5
15500 -14.8 5.4 330 20 10 4.8 2.6 | -13.5 7.7 325 22 11 4.3 2.4
15000 -14.1 6.6 330 19 10 5.6 3.1 | -12.8 9.0 320 21 11 5.0 2.8
14500 -13.2 8.2 330 18 9 5.8 3.2 | -12.1 10.2 320 20 10 5.2 2.8
14000 -12.3 9.9 330 18 9 6.3 3.5 | -11.3 11.7 320 19 10 5.6 3.1
13500 -11.4 11.5 335 17 9 6.6 3.6 | -10.5 13.1 315 18 9 5.8 3.2
13000 -10.4 13.3 335 16 8 6.9 3.8 | -9.6 14.7 315 18 9 6.3 3.4
12500 -9.3 15.3 335 15 8 7.3 4.0 | -8.6 16.5 315 17 9 6.7 3.7
12000 -8.2 17.2 340 14 7 7.6 4.2 | -7.7 18.1 315 16 8 7.5 4.1
11500 -7.0 19.4 340 14 7 8.0 4.4 | -6.4 20.5 315 15 8 8.3 4.6
11000 -5.8 21.6 340 13 7 8.0 4.4 | -5.2 22.6 315 14 7 8.7 4.8
10500 -4.7 23.5 335 12 6 8.3 4.5 | -3.9 25.0 315 14 7 10.1 5.5
10250 -4.1 24.6 335 12 6 6.3 3.4 | -3.2 26.2 315 13 7 4.4 2.4
10000 -3.7 25.3 335 11 6 5.2 2.8 | -3.0 26.6 315 13 6 5.8 3.2
9750 -3.2 26.2 330 11 6 8.1 4.4 | -2.2 28.0 315 12 6 12.4 6.8
9500 -2.6 27.3 330 11 6 9.3 5.1 | -1.4 29.5 315 12 6 11.2 6.1
9250 -2.0 28.4 325 11 6 8.1 4.4 | -0.6 30.9 315 12 6 9.6 5.3
9000 -1.4 29.5 325 11 6 5.8 3.2 | 0.0 32.0 315 12 6 7.2 4.0
8750 -1.0 30.2 320 10 5 6.5 3.6 | 0.6 33.1 310 11 6 9.3 5.1
8500 -0.5 31.1 315 10 5 8.2 4.5 | 1.4 34.5 310 11 6 10.9 6.0
8250 0.1 32.2 315 9 5 6.5 3.6 | 2.2 36.0 310 11 6 8.8 4.8
8000 0.5 32.9 310 9 4 4.7 2.6 | 2.7 36.9 305 10 5 7.1 3.9
7750 0.9 33.6 305 8 4 6.4 3.5 | 3.3 37.9 300 10 5 9.7 5.3
7500 1.4 34.5 295 7 4 7.5 4.1 | 4.1 39.4 300 10 5 11.0 6.0
7250 1.9 35.4 290 7 4 6.2 3.4 | 4.9 40.8 295 9 5 8.8 4.8
7000 2.3 36.1 285 7 4 4.7 2.6 | 5.4 41.7 295 9 5 7.0 3.8
6750 2.7 36.9 285 7 4 8.4 4.6 | 6.1 43.0 295 9 4 11.4 6.3
6500 3.5 38.3 275 7 4 9.3 5.1 | 7.1 44.8 295 9 4 12.8 7.0
6250 4.0 39.2 270 7 3 6.3 3.5 | 7.9 46.2 295 8 4 10.1 5.6
6000 4.4 39.9 265 6 3 5.8 3.2 | 8.6 47.5 300 8 4 9.5 5.2
5750 4.9 40.8 260 6 3 9.0 4.9 | 9.4 48.9 300 7 4 12.9 7.1
5500 5.9 42.6 255 6 3 18.3 10.0 | 10.7 51.3 300 7 4 24.5 13.4
04/20/2025 at 1500 MDT | 04/20/2025 at 1800 MDT
|
CAPE... +15.9 LI... +2.4 | CAPE... +8.5 LI... +0.6
CINH... -0.9 K Index... +17.6 | CINH... -18.3 K Index... +21.1
|
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 -59.5 -75.1 255 31 16 1.0 0.6 | -59.3 -74.7 260 33 17 0.2 0.1
45000 -57.9 -72.2 265 39 20 1.1 0.6 | -59.0 -74.2 270 43 22 0.1 0.1
40000 -56.6 -69.9 280 40 21 0.8 0.4 | -56.9 -70.4 285 51 26 1.4 0.8
38000 -55.7 -68.3 280 39 20 2.3 1.3 | -55.7 -68.3 290 52 27 2.9 1.6
36000 -54.3 -65.7 280 36 19 2.3 1.3 | -53.9 -65.0 290 51 26 2.9 1.6
34000 -52.7 -62.9 275 33 17 5.4 3.0 | -52.0 -61.6 295 49 25 6.6 3.6
32000 -49.5 -57.1 270 29 15 5.4 3.0 | -48.2 -54.8 295 47 24 6.3 3.4
30000 -46.1 -51.0 270 26 13 8.1 4.5 | -44.4 -47.9 295 45 23 6.2 3.4
29000 -43.2 -45.8 270 25 13 7.8 4.3 | -42.1 -43.8 295 40 21 6.2 3.4
28000 -40.9 -41.6 275 25 13 7.8 4.3 | -40.3 -40.5 295 36 19 6.2 3.4
27000 -38.5 -37.3 275 25 13 8.2 4.5 | -38.4 -37.1 290 33 17 6.7 3.7
26000 -36.0 -32.8 280 24 12 8.4 4.6 | -36.3 -33.3 290 31 16 7.2 3.9
25000 -33.5 -28.3 285 24 12 8.5 4.6 | -34.2 -29.6 285 30 15 7.2 4.0
24000 -31.0 -23.8 285 23 12 8.3 4.6 | -32.0 -25.6 285 28 14 7.4 4.1
23000 -28.6 -19.5 290 24 12 7.9 4.3 | -29.6 -21.3 285 28 14 8.0 4.4
22000 -26.3 -15.3 290 24 12 7.9 4.3 | -27.3 -17.1 290 27 14 8.0 4.4
21000 -24.0 -11.2 295 24 12 7.4 4.1 | -24.9 -12.8 290 27 14 7.9 4.3
20000 -21.8 -7.2 300 24 12 7.2 4.0 | -22.6 -8.7 290 26 14 7.8 4.3
19500 -20.8 -5.4 305 24 13 7.2 4.0 | -21.4 -6.5 290 26 13 7.8 4.3
19000 -19.7 -3.5 305 25 13 7.2 4.0 | -20.3 -4.5 295 26 13 7.8 4.3
18500 -18.7 -1.7 310 25 13 6.7 3.7 | -19.1 -2.4 295 26 13 7.5 4.1
18000 -17.8 -0.0 310 25 13 6.0 3.3 | -18.0 -0.4 295 25 13 7.2 4.0
17500 -16.9 1.6 315 25 13 6.1 3.3 | -17.0 1.4 295 25 13 7.2 4.0
17000 -16.1 3.0 315 25 13 5.3 2.9 | -16.0 3.2 295 25 13 6.7 3.7
16500 -15.3 4.5 315 24 13 5.4 3.0 | -15.0 5.0 295 25 13 6.7 3.7
16000 -14.5 5.9 315 24 12 5.8 3.2 | -14.0 6.8 295 25 13 6.9 3.8
15500 -13.7 7.3 315 23 12 6.0 3.3 | -12.9 8.8 295 24 12 7.0 3.8
15000 -12.9 8.8 315 22 11 6.4 3.5 | -11.9 10.6 295 23 12 7.4 4.0
14500 -11.9 10.6 315 21 11 6.9 3.8 | -10.8 12.6 295 23 12 7.8 4.3
14000 -10.9 12.4 310 20 10 7.2 3.9 | -9.1 15.6 295 22 12 7.9 4.4
13500 -9.1 15.6 310 18 9 8.1 4.5 | -7.9 17.8 295 22 11 8.0 4.4
13000 -7.9 17.8 310 18 9 8.3 4.6 | -6.7 19.9 295 22 11 8.2 4.5
12500 -6.7 19.9 310 17 9 8.4 4.6 | -5.5 22.1 295 22 11 8.3 4.5
12000 -5.4 22.3 310 17 9 8.8 4.8 | -4.2 24.4 295 21 11 8.7 4.8
11500 -4.1 24.6 310 16 8 9.0 4.9 | -2.9 26.8 295 21 11 8.9 4.9
11000 -2.7 27.1 310 16 8 9.3 5.1 | -1.6 29.1 295 21 11 8.9 4.9
10500 -1.4 29.5 310 16 8 10.7 5.9 | -0.3 31.5 295 21 11 10.0 5.5
10250 -0.7 30.7 310 16 8 3.8 2.1 | 0.4 32.7 300 21 11 4.5 2.5
10000 -0.6 30.9 310 16 8 5.3 2.9 | 0.5 32.9 300 20 10 5.8 3.2
9750 0.3 32.5 310 16 8 13.1 7.2 | 1.3 34.3 300 20 10 11.9 6.5
9500 1.1 34.0 310 16 8 12.0 6.6 | 2.1 35.8 300 19 10 11.2 6.1
9250 2.0 35.6 310 16 8 8.6 4.7 | 2.9 37.2 300 18 9 8.0 4.4
9000 2.4 36.3 310 15 8 6.9 3.8 | 3.4 38.1 300 17 9 6.9 3.8
8750 3.1 37.6 310 15 8 11.0 6.1 | 4.1 39.4 300 17 8 10.8 5.9
8500 3.9 39.0 310 15 8 12.1 6.7 | 4.9 40.8 300 16 8 11.6 6.3
8250 4.8 40.6 310 14 7 9.4 5.1 | 5.7 42.3 300 15 8 8.8 4.8
8000 5.3 41.5 310 14 7 7.5 4.1 | 6.2 43.2 300 14 7 7.0 3.9
7750 6.0 42.8 310 14 7 11.2 6.1 | 6.9 44.4 305 14 7 10.9 6.0
7500 6.9 44.4 310 14 7 11.8 6.4 | 7.8 46.0 305 14 7 11.6 6.3
7250 7.7 45.9 310 14 7 8.5 4.7 | 8.5 47.3 305 14 7 9.0 5.0
7000 8.2 46.8 310 13 7 6.5 3.5 | 9.1 48.4 305 14 7 7.7 4.2
6750 8.9 48.0 310 13 7 12.7 7.0 | 9.8 49.6 305 13 7 11.4 6.3
6500 10.0 50.0 310 13 7 13.4 7.3 | 10.8 51.4 310 13 7 11.5 6.3
6250 10.7 51.3 310 13 6 9.0 4.9 | 11.5 52.7 310 13 7 8.7 4.7
6000 11.4 52.5 315 12 6 8.6 4.7 | 12.1 53.8 310 13 6 8.5 4.7
5750 12.1 53.8 315 12 6 13.1 7.2 | 12.8 55.0 310 12 6 11.2 6.1
5500 13.5 56.3 315 11 5 25.8 14.2 | 13.8 56.8 315 11 5 16.8 9.2
________________________________________________________________________________
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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