Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
788
UXUS97 KBOU 171315
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0715 MDT Friday, October 17, 2025
This forecast is for Friday, October 17, 2025:
If the trigger temperature of 56.9 F/13.9 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 613 ft/min (3.1 m/s)
Maximum height of thermals.................. 13292 ft MSL (7998 ft AGL)
Forecast maximum temperature................... 66.0 F/19.3 C
Time of trigger temperature.................... 1100 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................. 10993 ft MSL (5698 ft AGL)
Thermal soaring outlook for Saturday 10/18..... Fair
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....................... 34639 ft MSL (29345 ft AGL)
Wave soaring outlook for Saturday 10/18........ Good
Remarks... Cold front passage expected Saturday morning
Sunrise/Sunset.................... 07:12:28 / 18:16:55 MDT
Total possible sunshine........... 11 hr 4 min 27 sec (664 min 27 sec)
Altitude of sun at 12:44:42 MDT... 40.55 degrees
Upper air data from numerical model forecast valid on 10/17/2025 at 0600 MDT
Freezing level.................. 10302 ft MSL (5008 ft AGL)
Convective condensation level... 15161 ft MSL (9867 ft AGL)
Lifted condensation level....... 14385 ft MSL (9091 ft AGL)
Lifted index.................... +4.9
K index......................... -4.0
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 -60.6 -77.1 230 33 17 2.5 1.4 M M M M M
45000 -56.4 -69.5 225 48 25 4.5 2.5 M M M M M
40000 -49.5 -57.1 230 58 30 4.5 2.5 M M M M M
38000 -48.2 -54.8 230 62 32 1.3 0.7 M M M M M
36000 -47.5 -53.5 225 66 34 1.3 0.7 M M M M M
34000 -45.4 -49.7 225 69 36 6.0 3.3 M M M M M
32000 -41.9 -43.4 225 71 36 6.0 3.3 M M M M M
30000 -37.7 -35.9 230 72 37 8.5 4.7 39.1 102.3 15.2 M M
29000 -35.1 -31.2 230 72 37 8.5 4.6 38.5 101.3 15.0 M M
28000 -32.6 -26.7 230 72 37 8.5 4.7 38.1 100.6 14.8 M M
27000 -30.2 -22.4 230 72 37 6.1 3.3 37.5 99.5 14.6 M M
26000 -28.4 -19.1 230 71 37 6.0 3.3 36.0 96.7 13.5 M M
25000 -26.6 -15.9 235 71 36 6.0 3.3 34.6 94.2 12.6 M M
24000 -24.8 -12.6 235 70 36 6.0 3.3 33.3 92.0 11.7 M M
23000 -23.0 -9.4 235 63 33 5.9 3.2 31.8 89.2 10.5 M M
22000 -21.3 -6.3 235 57 29 5.9 3.2 30.4 86.7 9.5 M M
21000 -19.5 -3.1 235 51 26 6.0 3.3 29.1 84.4 8.5 M M
20000 -17.6 0.3 240 44 23 6.0 3.3 27.7 81.9 7.4 M M
19500 -16.7 1.9 240 41 21 6.0 3.3 27.0 80.7 6.9 M M
19000 -15.8 3.6 240 37 19 6.0 3.3 26.4 79.6 6.5 M M
18500 -14.9 5.2 240 34 17 4.9 2.7 25.9 78.5 6.0 M M
18000 -14.3 6.3 240 29 15 3.8 2.1 24.8 76.6 5.1 M M
17500 -13.5 7.7 250 21 11 5.7 3.1 23.3 73.9 3.8 M M
17000 -12.4 9.7 250 19 10 7.2 3.9 22.8 73.1 3.4 M M
16500 -11.3 11.7 255 16 8 7.3 4.0 22.4 72.4 3.1 M M
16000 -10.2 13.6 260 15 8 7.5 4.1 22.0 71.6 2.7 M M
15500 -9.1 15.6 260 14 7 7.6 4.2 21.6 71.0 2.4 M M
15000 -8.1 17.4 260 13 7 6.4 3.5 21.2 70.2 2.0 M M
14500 -7.1 19.2 260 13 7 6.5 3.6 20.6 69.2 1.5 M M
14000 -6.2 20.8 255 13 7 5.5 3.0 20.1 68.1 0.9 M M
13500 -5.4 22.3 250 13 7 5.2 2.9 19.3 66.7 0.2 M M
13000 -4.7 23.5 245 14 7 5.6 3.1 18.6 65.4 -0.5 586 3.0
12500 -3.8 25.2 240 14 7 6.0 3.3 17.9 64.3 -1.1 546 2.8
12000 -3.0 26.6 240 14 7 5.9 3.2 17.3 63.2 -1.7 505 2.6
11500 -2.1 28.2 240 13 7 5.8 3.2 16.7 62.0 -2.4 466 2.4
11000 -1.3 29.7 240 12 6 6.4 3.5 16.1 60.9 -3.0 426 2.2
10500 -0.3 31.5 240 11 6 7.6 4.1 15.6 60.0 -3.5 382 1.9
10250 0.2 32.4 240 11 6 3.9 2.1 15.3 59.6 -3.8 360 1.8
10000 0.3 32.5 240 11 6 4.6 2.5 14.8 58.6 -4.4 347 1.8
9750 0.9 33.6 240 10 5 8.8 4.8 14.6 58.3 -4.5 323 1.6
9500 1.5 34.7 245 10 5 7.8 4.3 14.5 58.0 -4.7 298 1.5
9250 2.1 35.8 250 10 5 7.4 4.1 14.3 57.8 -4.9 273 1.4
9000 2.5 36.5 255 10 5 6.3 3.4 14.1 57.4 -5.1 251 1.3
8750 3.0 37.4 260 11 5 6.8 3.8 13.8 56.9 -5.4 230 1.2
8500 3.5 38.3 265 11 6 7.2 3.9 13.6 56.5 -5.6 207 1.0
8250 4.1 39.4 270 12 6 7.5 4.1 13.4 56.2 -5.8 184 0.9
8000 4.6 40.3 275 13 7 7.9 4.4 13.3 55.9 -6.0 159 0.8
7750 5.2 41.4 275 13 7 7.0 3.8 13.1 55.6 -6.2 135 0.7
7500 5.7 42.3 275 13 7 6.4 3.5 12.9 55.2 -6.5 114 0.6
7250 6.1 43.0 275 13 7 7.8 4.3 12.7 54.8 -6.7 91 0.5
7000 6.8 44.2 275 11 6 8.4 4.6 12.6 54.6 -6.9 66 0.3
6750 7.4 45.3 275 10 5 9.3 5.1 12.5 54.4 -7.0 40 0.2
6500 8.0 46.4 275 9 5 7.8 4.3 12.4 54.4 -7.1 12 0.1
6250 8.5 47.3 275 8 4 4.4 2.4 12.1 53.8 -7.4 M M
6000 8.8 47.8 275 7 4 4.6 2.5 11.7 53.1 -7.9 M M
5750 9.1 48.4 275 6 3 3.3 1.8 11.3 52.4 -8.3 M M
5500 9.0 48.2 270 4 2 -9.9 -5.4 10.4 50.8 -9.2 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/17/2025 at 0900 MDT | 10/17/2025 at 1200 MDT
|
CAPE... 0.0 LI... +6.3 | CAPE... 0.0 LI... +4.9
CINH... 0.0 K Index... -9.9 | CINH... 0.0 K Index... -12.8
|
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 -60.2 -76.4 240 31 16 2.5 1.3 | -60.0 -76.0 240 31 16 2.7 1.5
45000 -56.2 -69.2 240 41 21 4.4 2.4 | -55.8 -68.4 235 44 22 3.5 1.9
40000 -49.5 -57.1 230 49 25 4.4 2.4 | -50.5 -58.9 235 48 25 3.5 1.9
38000 -48.1 -54.6 230 54 28 1.4 0.8 | -48.7 -55.7 235 52 27 2.7 1.5
36000 -47.2 -53.0 230 59 31 1.4 0.8 | -47.1 -52.8 235 58 30 2.7 1.5
34000 -45.4 -49.7 230 64 33 5.1 2.8 | -44.9 -48.8 230 66 34 4.4 2.4
32000 -42.3 -44.1 230 67 35 5.1 2.8 | -42.3 -44.1 235 73 38 4.3 2.4
30000 -38.6 -37.5 230 70 36 8.4 4.6 | -39.0 -38.2 235 77 40 7.6 4.2
29000 -36.0 -32.8 230 71 36 8.4 4.6 | -36.7 -34.1 230 76 39 7.6 4.1
28000 -33.5 -28.3 230 71 37 8.4 4.6 | -34.4 -29.9 230 75 38 7.6 4.2
27000 -31.1 -24.0 230 72 37 5.7 3.1 | -32.2 -26.0 230 73 37 5.8 3.2
26000 -29.5 -21.1 235 69 36 5.6 3.1 | -30.6 -23.1 230 69 35 5.6 3.1
25000 -27.8 -18.0 235 67 35 5.6 3.1 | -28.9 -20.0 230 64 33 5.6 3.1
24000 -26.1 -15.0 235 65 34 6.3 3.5 | -27.2 -17.0 230 60 31 6.5 3.6
23000 -24.0 -11.2 235 60 31 6.9 3.8 | -25.0 -13.0 230 55 28 7.4 4.1
22000 -21.9 -7.4 240 54 28 6.9 3.8 | -22.7 -8.9 235 50 26 7.5 4.1
21000 -19.9 -3.8 240 48 25 6.0 3.3 | -20.5 -4.9 235 45 23 6.5 3.6
20000 -18.1 -0.6 240 42 21 5.9 3.2 | -18.6 -1.5 235 39 20 6.4 3.5
19500 -17.2 1.0 240 38 20 5.9 3.2 | -17.6 0.3 240 36 18 6.4 3.5
19000 -16.3 2.7 240 35 18 5.9 3.2 | -16.7 1.9 240 32 17 6.4 3.5
18500 -15.5 4.1 240 32 16 5.3 2.9 | -15.7 3.7 245 29 15 6.4 3.5
18000 -14.7 5.5 245 28 14 4.9 2.7 | -14.8 5.4 245 27 14 6.3 3.5
17500 -13.6 7.5 245 22 11 6.3 3.5 | -13.3 8.1 250 23 12 7.2 4.0
17000 -12.5 9.5 245 20 10 7.1 3.9 | -12.1 10.2 250 22 11 7.8 4.3
16500 -11.5 11.3 245 18 9 7.3 4.0 | -11.0 12.2 250 21 11 7.9 4.3
16000 -10.3 13.5 245 17 9 8.0 4.4 | -9.8 14.4 250 20 10 8.1 4.5
15500 -9.1 15.6 245 16 8 8.0 4.4 | -8.6 16.5 250 19 10 8.2 4.5
15000 -8.0 17.6 245 15 8 7.3 4.0 | -7.4 18.7 250 18 9 6.6 3.6
14500 -6.9 19.6 245 15 8 7.4 4.1 | -6.5 20.3 250 18 9 6.7 3.7
14000 -5.8 21.6 250 14 7 6.5 3.6 | -5.5 22.1 250 17 9 5.9 3.2
13500 -4.9 23.2 250 14 7 6.4 3.5 | -4.6 23.7 250 17 9 5.8 3.2
13000 -4.0 24.8 250 14 7 6.2 3.4 | -3.8 25.2 250 16 8 5.4 3.0
12500 -3.1 26.4 245 14 7 6.1 3.3 | -3.0 26.6 250 15 8 5.3 2.9
12000 -2.2 28.0 245 14 7 5.7 3.1 | -2.3 27.9 250 14 7 5.6 3.1
11500 -1.4 29.5 240 13 7 5.5 3.0 | -1.4 29.5 250 13 7 5.8 3.2
11000 -0.6 30.9 240 13 7 5.6 3.1 | -0.6 30.9 255 12 6 5.9 3.2
10500 0.2 32.4 240 12 6 6.2 3.4 | 0.3 32.5 260 11 6 5.7 3.1
10250 0.6 33.1 240 12 6 4.0 2.2 | 0.7 33.3 260 11 6 6.9 3.8
10000 0.9 33.6 240 12 6 4.9 2.7 | 1.3 34.3 265 11 6 8.1 4.5
9750 1.4 34.5 240 11 6 7.7 4.2 | 1.8 35.2 270 11 6 7.8 4.3
9500 1.9 35.4 245 10 5 7.1 3.9 | 2.4 36.3 275 12 6 8.1 4.4
9250 2.4 36.3 245 10 5 6.7 3.7 | 3.0 37.4 280 13 6 7.5 4.1
9000 2.8 37.0 250 10 5 6.0 3.3 | 3.4 38.1 285 13 7 5.6 3.1
8750 3.3 37.9 255 10 5 6.8 3.7 | 3.8 38.8 285 11 6 5.0 2.7
8500 3.8 38.8 260 10 5 7.2 4.0 | 4.2 39.6 280 10 5 4.9 2.7
8250 4.3 39.7 265 11 5 6.9 3.8 | 4.5 40.1 280 8 4 6.3 3.4
8000 4.8 40.6 270 12 6 6.4 3.5 | 5.1 41.2 280 7 4 8.6 4.7
7750 5.3 41.5 275 13 7 5.9 3.2 | 5.7 42.3 280 6 3 9.5 5.2
7500 5.7 42.3 275 14 7 5.6 3.1 | 6.4 43.5 280 6 3 9.9 5.4
7250 6.1 43.0 275 15 7 6.7 3.7 | 7.2 45.0 280 6 3 10.3 5.7
7000 6.6 43.9 270 13 7 7.2 3.9 | 8.0 46.4 280 6 3 11.0 6.0
6750 7.1 44.8 270 12 6 7.3 4.0 | 8.8 47.8 280 6 3 9.6 5.2
6500 7.7 45.9 270 11 6 6.6 3.6 | 9.4 48.9 280 6 3 9.5 5.2
6250 8.1 46.6 265 9 5 5.4 3.0 | 10.2 50.4 280 6 3 11.0 6.0
6000 8.5 47.3 260 8 4 5.7 3.1 | 11.1 52.0 280 6 3 11.0 6.0
5750 8.9 48.0 250 6 3 4.8 2.6 | 11.9 53.4 280 6 3 11.3 6.2
5500 9.2 48.6 230 5 3 3.6 2.0 | 12.9 55.2 280 5 3 17.3 9.5
10/17/2025 at 1500 MDT | 10/17/2025 at 1800 MDT
|
CAPE... 0.0 LI... +2.6 | CAPE... 0.0 LI... +2.1
CINH... 0.0 K Index... +2.8 | CINH... 0.0 K Index... +6.1
|
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 -59.8 -75.6 245 30 15 2.5 1.4 | -59.6 -75.3 255 30 16 2.0 1.1
45000 -55.9 -68.6 245 38 19 3.5 1.9 | -56.1 -69.0 255 32 17 3.6 2.0
40000 -50.5 -58.9 245 41 21 3.6 2.0 | -50.7 -59.3 260 32 16 3.6 2.0
38000 -48.5 -55.3 240 45 23 3.4 1.8 | -48.9 -56.0 265 29 15 2.9 1.6
36000 -46.5 -51.7 240 49 25 3.4 1.8 | -47.1 -52.8 270 25 13 2.9 1.6
34000 -44.1 -47.4 240 54 28 3.8 2.1 | -45.3 -49.5 290 20 11 3.3 1.8
32000 -41.9 -43.4 235 59 30 3.8 2.1 | -43.0 -45.4 335 20 10 3.4 1.8
30000 -39.0 -38.2 235 63 32 6.5 3.6 | -40.1 -40.2 355 27 14 7.6 4.2
29000 -37.1 -34.8 235 63 32 6.5 3.6 | -37.9 -36.2 005 29 15 7.6 4.2
28000 -35.1 -31.2 235 63 32 6.6 3.6 | -35.6 -32.1 005 31 16 7.7 4.2
27000 -33.2 -27.8 235 62 32 6.0 3.3 | -33.3 -27.9 010 33 17 7.8 4.3
26000 -31.4 -24.5 240 58 30 5.8 3.2 | -30.9 -23.6 010 31 16 7.8 4.3
25000 -29.7 -21.5 240 54 28 5.8 3.2 | -28.6 -19.5 010 29 15 7.8 4.3
24000 -27.9 -18.2 240 49 25 6.3 3.4 | -26.3 -15.3 010 26 14 6.8 3.7
23000 -25.9 -14.6 240 45 23 7.0 3.8 | -24.6 -12.3 355 21 11 5.5 3.0
22000 -23.8 -10.8 240 41 21 7.0 3.8 | -22.9 -9.2 340 17 9 5.5 3.0
21000 -21.7 -7.1 245 36 19 7.1 3.9 | -21.2 -6.2 315 16 8 6.2 3.4
20000 -19.5 -3.1 245 30 16 7.1 3.9 | -19.3 -2.7 295 17 9 6.4 3.5
19500 -18.5 -1.3 250 27 14 7.1 3.9 | -18.3 -0.9 285 17 9 6.4 3.5
19000 -17.4 0.7 255 25 13 7.1 3.9 | -17.4 0.7 280 19 10 6.4 3.5
18500 -16.4 2.5 260 22 11 7.3 4.0 | -16.4 2.5 275 20 10 7.4 4.0
18000 -15.2 4.6 260 21 11 7.5 4.1 | -15.2 4.6 270 20 10 8.2 4.5
17500 -14.1 6.6 260 21 11 7.5 4.1 | -14.0 6.8 270 20 10 8.3 4.5
17000 -12.3 9.9 265 20 10 8.3 4.5 | -12.8 9.0 265 19 10 7.9 4.4
16500 -11.1 12.0 260 19 10 8.2 4.5 | -11.0 12.2 265 19 10 7.9 4.3
16000 -10.0 14.0 260 19 10 7.1 3.9 | -9.9 14.2 265 19 10 7.2 4.0
15500 -8.9 16.0 260 18 9 7.2 4.0 | -8.8 16.2 265 21 11 7.4 4.1
15000 -7.9 17.8 260 18 9 6.4 3.5 | -7.8 18.0 260 22 11 6.2 3.4
14500 -7.0 19.4 260 18 9 6.4 3.5 | -7.0 19.4 260 22 12 6.3 3.5
14000 -6.0 21.2 260 19 10 6.9 3.8 | -6.1 21.0 255 23 12 6.2 3.4
13500 -5.0 23.0 265 19 10 7.1 3.9 | -5.2 22.6 255 22 11 6.3 3.4
13000 -4.0 24.8 265 20 10 6.3 3.4 | -4.3 24.3 255 21 11 6.7 3.7
12500 -3.2 26.2 270 20 11 5.8 3.2 | -3.3 26.1 260 20 10 7.0 3.8
12000 -2.4 27.7 275 21 11 5.9 3.2 | -2.3 27.9 260 18 9 7.5 4.1
11500 -1.5 29.3 280 19 10 6.0 3.3 | -1.1 30.0 260 17 9 7.9 4.3
11000 -0.7 30.7 285 18 9 5.8 3.2 | 0.1 32.2 265 15 8 7.4 4.1
10500 0.2 32.4 290 14 7 4.8 2.6 | 1.1 34.0 270 14 7 6.5 3.5
10250 0.6 33.1 290 12 6 8.7 4.8 | 1.6 34.9 275 14 7 8.8 4.8
10000 1.4 34.5 295 10 5 10.5 5.8 | 2.3 36.1 275 13 7 9.6 5.3
9750 2.0 35.6 295 9 5 8.0 4.4 | 3.0 37.4 280 12 6 7.8 4.3
9500 2.6 36.7 295 8 4 8.6 4.7 | 3.6 38.5 280 11 6 8.1 4.4
9250 3.3 37.9 300 8 4 8.8 4.8 | 4.2 39.6 285 10 5 8.6 4.7
9000 4.0 39.2 300 7 4 9.8 5.4 | 4.8 40.6 285 9 5 8.8 4.8
8750 4.7 40.5 300 7 4 10.1 5.5 | 5.4 41.7 290 8 4 8.1 4.5
8500 5.5 41.9 300 7 4 9.8 5.4 | 6.0 42.8 290 8 4 7.7 4.2
8250 6.2 43.2 300 7 4 10.6 5.8 | 6.6 43.9 295 7 4 9.1 5.0
8000 7.0 44.6 300 7 4 11.0 6.0 | 7.4 45.3 300 7 3 10.7 5.9
7750 7.8 46.0 305 7 4 9.5 5.2 | 8.2 46.8 300 6 3 9.3 5.1
7500 8.5 47.3 305 7 4 8.5 4.7 | 8.8 47.8 300 6 3 8.1 4.4
7250 9.1 48.4 305 7 4 10.1 5.5 | 9.5 49.1 305 6 3 9.6 5.3
7000 10.0 50.0 305 7 4 11.3 6.2 | 10.2 50.4 305 6 3 10.8 5.9
6750 10.8 51.4 305 7 4 9.7 5.3 | 11.0 51.8 305 6 3 9.4 5.1
6500 11.4 52.5 305 7 3 9.5 5.2 | 11.7 53.1 310 6 3 9.1 5.0
6250 12.2 54.0 305 7 3 11.0 6.0 | 12.4 54.3 310 5 3 10.3 5.7
6000 13.1 55.6 305 6 3 11.7 6.4 | 13.2 55.8 310 5 3 11.0 6.0
5750 13.9 57.0 305 6 3 9.9 5.4 | 14.0 57.2 310 5 3 9.5 5.2
5500 14.7 58.5 305 6 3 12.9 7.1 | 14.6 58.3 315 5 2 5.9 3.2
________________________________________________________________________________
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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