Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
604
UXUS97 KBOU 290119
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1918 MDT Saturday, June 28, 2025
This forecast is for Sunday, June 29, 2025:
If the trigger temperature of 84.7 F/29.3 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 507 ft/min (2.6 m/s)
Maximum height of thermals.................. 11538 ft MSL (6219 ft AGL)
Forecast maximum temperature................... 87.0 F/31.0 C
Time of trigger temperature.................... 1200 MDT
Time of overdevelopment........................ 1500 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 7457 ft MSL (2138 ft AGL)
Thermal soaring outlook for Monday 06/30....... 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)................ Weak PVA
Potential height of wave....................... 16654 ft MSL (11335 ft AGL)
Wave soaring outlook for Monday 06/30.......... Fair
Remarks...
Sunrise/Sunset.................... 05:34:31 / 20:31:40 MDT
Total possible sunshine........... 14 hr 57 min 9 sec (897 min 9 sec)
Altitude of sun at 13:03:06 MDT... 73.40 degrees
Upper air data from numerical model forecast valid on 06/29/2025 at 0600 MDT
Freezing level.................. 15920 ft MSL (10601 ft AGL)
Convective condensation level... 18741 ft MSL (13422 ft AGL)
Lifted condensation level....... 17991 ft MSL (12672 ft AGL)
Lifted index.................... -0.7
K index......................... +16.1
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 -60.4 -76.7 265 27 14 2.4 1.3 M M M M M
45000 -57.1 -70.8 265 30 15 1.6 0.9 M M M M M
40000 -54.4 -65.9 255 26 13 4.9 2.7 M M M M M
38000 -51.6 -60.9 260 22 12 4.6 2.5 M M M M M
36000 -48.8 -55.8 260 19 10 4.8 2.6 M M M M M
34000 -43.8 -46.8 255 16 8 8.3 4.5 M M M M M
32000 -38.8 -37.8 250 14 7 8.3 4.5 M M M M M
30000 -34.0 -29.2 245 13 7 7.9 4.4 40.9 105.7 7.9 M M
29000 -31.6 -24.9 240 12 6 7.9 4.4 40.3 104.5 7.5 M M
28000 -29.2 -20.6 235 11 6 7.7 4.2 39.7 103.5 7.1 M M
27000 -27.0 -16.6 240 10 5 7.6 4.2 38.8 101.8 6.5 M M
26000 -24.7 -12.5 250 9 4 7.7 4.2 38.0 100.3 5.9 M M
25000 -22.4 -8.3 260 8 4 7.7 4.2 37.3 99.1 5.4 M M
24000 -20.1 -4.2 275 7 4 7.7 4.2 36.4 97.6 4.7 M M
23000 -17.9 -0.2 295 7 4 7.7 4.2 35.7 96.2 4.1 M M
22000 -15.6 3.9 310 8 4 7.9 4.3 35.0 95.1 3.5 M M
21000 -13.2 8.2 305 8 4 8.1 4.5 34.4 93.9 3.0 M M
20000 -10.8 12.6 300 8 4 8.1 4.5 33.8 92.8 2.5 M M
19500 -9.6 14.7 295 8 4 8.1 4.5 33.6 92.4 2.3 M M
19000 -8.4 16.9 290 7 4 8.3 4.6 33.3 92.0 2.0 M M
18500 -6.6 20.1 285 7 3 8.3 4.6 33.0 91.3 1.7 M M
18000 -5.3 22.5 280 6 3 8.6 4.7 32.7 90.9 1.5 M M
17500 -4.0 24.8 275 6 3 8.7 4.7 32.5 90.6 1.3 M M
17000 -2.8 27.0 275 5 3 9.0 4.9 32.4 90.2 1.2 M M
16500 -1.4 29.5 275 4 2 9.3 5.1 32.3 90.1 1.1 M M
16000 0.0 32.0 280 4 2 9.4 5.1 32.2 90.0 1.0 M M
15500 1.4 34.5 285 4 2 9.1 5.0 32.1 89.8 0.9 M M
15000 2.8 37.0 290 3 2 9.1 5.0 32.0 89.6 0.8 M M
14500 4.1 39.4 300 4 2 9.4 5.2 31.9 89.5 0.8 M M
14000 5.5 41.9 305 4 2 9.4 5.2 31.9 89.4 0.7 M M
13500 6.9 44.4 310 4 2 8.9 4.9 31.8 89.3 0.6 M M
13000 8.2 46.8 315 5 2 8.7 4.8 31.6 88.9 0.5 M M
12500 9.5 49.1 320 5 3 8.7 4.8 31.5 88.7 0.3 M M
12000 10.8 51.4 320 5 3 8.7 4.8 31.3 88.3 0.1 M M
11500 12.1 53.8 320 6 3 8.5 4.7 31.1 88.0 -0.0 500 2.5
11000 13.3 55.9 325 6 3 8.0 4.4 30.9 87.6 -0.3 449 2.3
10500 14.6 58.3 325 6 3 4.6 2.5 30.7 87.2 -0.5 397 2.0
10250 14.8 58.6 325 6 3 5.4 3.0 30.1 86.2 -1.0 383 1.9
10000 15.5 59.9 325 7 3 10.6 5.8 30.1 86.2 -1.0 355 1.8
9750 16.2 61.2 320 7 3 9.5 5.2 30.1 86.2 -1.1 326 1.7
9500 16.9 62.4 320 7 3 8.6 4.7 30.1 86.1 -1.1 297 1.5
9250 17.4 63.3 320 7 4 6.8 3.7 29.9 85.8 -1.3 274 1.4
9000 17.9 64.2 320 7 4 7.4 4.1 29.7 85.4 -1.5 252 1.3
8750 18.5 65.3 320 7 4 7.9 4.4 29.5 85.1 -1.7 227 1.2
8500 19.1 66.4 320 8 4 7.6 4.2 29.4 84.9 -1.8 202 1.0
8250 19.6 67.3 320 8 4 7.6 4.2 29.2 84.6 -2.0 179 0.9
8000 20.1 68.2 325 8 4 6.9 3.8 29.0 84.2 -2.2 156 0.8
7750 20.6 69.1 325 9 4 6.2 3.4 28.8 83.8 -2.5 135 0.7
7500 21.0 69.8 325 9 5 4.8 2.6 28.5 83.2 -2.8 115 0.6
7250 21.3 70.3 330 10 5 3.5 1.9 28.0 82.4 -3.3 99 0.5
7000 21.6 70.9 330 10 5 4.3 2.4 27.6 81.6 -3.8 84 0.4
6750 21.8 71.2 330 11 5 3.0 1.7 27.1 80.8 -4.2 68 0.3
6500 21.9 71.4 330 11 5 0.0 0.0 26.5 79.7 -4.9 57 0.3
6250 21.8 71.2 325 10 5 -4.2 -2.3 25.6 78.1 -5.8 55 0.3
6000 21.6 70.9 325 9 5 5.9 3.3 24.7 76.5 -6.7 52 0.3
5750 22.1 71.8 325 9 5 -6.4 -3.5 24.5 76.0 -6.9 30 0.2
5500 19.5 67.1 300 5 3 -58.6 -32.1 21.3 70.3 -10.3 100 0.5
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/29/2025 at 0900 MDT | 06/29/2025 at 1200 MDT
|
CAPE... +74.8 LI... +0.8 | CAPE... +571.2 LI... -2.1
CINH... -202.8 K Index... +17.5 | CINH... -30.1 K Index... +23.9
|
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 -60.5 -76.9 265 28 14 1.6 0.9 | -61.0 -77.8 270 24 12 1.5 0.8
45000 -57.9 -72.2 265 27 14 2.0 1.1 | -58.2 -72.8 270 24 13 2.7 1.5
40000 -54.6 -66.3 265 21 11 5.1 2.8 | -53.8 -64.8 270 22 11 5.6 3.1
38000 -51.7 -61.1 265 18 9 4.8 2.7 | -50.6 -59.1 280 19 10 5.4 2.9
36000 -48.8 -55.8 265 15 8 4.9 2.7 | -47.4 -53.3 290 17 9 5.4 3.0
34000 -43.9 -47.0 265 13 7 8.0 4.4 | -43.0 -45.4 285 16 8 6.9 3.8
32000 -39.1 -38.4 265 11 6 8.0 4.4 | -38.9 -38.0 275 17 9 6.8 3.7
30000 -34.5 -30.1 265 9 5 7.6 4.2 | -34.2 -29.6 275 15 8 8.0 4.4
29000 -32.2 -26.0 265 8 4 7.6 4.2 | -31.8 -25.2 275 14 7 8.0 4.4
28000 -29.9 -21.8 265 7 4 7.6 4.2 | -29.5 -21.1 275 13 7 7.3 4.0
27000 -27.7 -17.9 260 6 3 7.6 4.2 | -27.4 -17.3 260 13 6 6.8 3.7
26000 -25.4 -13.7 255 5 3 7.7 4.2 | -25.4 -13.7 250 12 6 6.8 3.7
25000 -23.1 -9.6 245 4 2 7.7 4.2 | -23.4 -10.1 240 12 6 6.9 3.8
24000 -20.8 -5.4 265 4 2 8.0 4.4 | -21.1 -6.0 240 12 6 7.9 4.3
23000 -18.5 -1.3 285 4 2 8.0 4.4 | -18.8 -1.8 240 12 6 8.0 4.4
22000 -16.1 3.0 300 5 3 8.1 4.5 | -16.5 2.3 240 11 6 8.1 4.5
21000 -13.7 7.3 305 6 3 8.2 4.5 | -14.1 6.6 245 10 5 8.2 4.5
20000 -11.3 11.7 305 6 3 8.2 4.5 | -11.7 10.9 255 10 5 8.2 4.5
19500 -10.1 13.8 305 6 3 8.1 4.5 | -10.5 13.1 260 10 5 8.1 4.5
19000 -8.8 16.2 305 6 3 8.8 4.8 | -9.2 15.4 265 9 5 8.9 4.9
18500 -7.5 18.5 310 6 3 8.8 4.8 | -7.9 17.8 265 9 5 8.8 4.9
18000 -6.2 20.8 310 5 3 8.9 4.9 | -5.9 21.4 270 9 4 9.2 5.1
17500 -4.1 24.6 315 5 3 9.1 5.0 | -4.5 23.9 275 9 4 9.2 5.0
17000 -2.8 27.0 320 5 3 9.1 5.0 | -3.2 26.2 280 9 5 8.8 4.8
16500 -1.4 29.5 320 5 2 9.1 5.0 | -1.9 28.6 285 9 4 8.5 4.7
16000 -0.1 31.8 325 5 2 9.1 5.0 | -0.7 30.7 285 8 4 8.5 4.7
15500 1.3 34.3 325 5 3 9.2 5.0 | 0.6 33.1 290 8 4 8.5 4.6
15000 2.6 36.7 330 6 3 9.2 5.0 | 1.8 35.2 300 8 4 8.4 4.6
14500 4.0 39.2 335 6 3 8.8 4.8 | 3.1 37.6 305 9 4 8.8 4.8
14000 5.3 41.5 340 7 4 8.8 4.8 | 4.3 39.7 315 9 5 8.8 4.8
13500 6.6 43.9 340 8 4 8.8 4.8 | 5.6 42.1 320 9 5 8.8 4.8
13000 7.9 46.2 345 8 4 8.8 4.8 | 6.9 44.4 330 10 5 8.8 4.8
12500 9.2 48.6 345 9 5 9.0 4.9 | 8.1 46.6 335 11 6 8.4 4.6
12000 10.5 50.9 345 10 5 9.1 5.0 | 9.4 48.9 340 12 6 8.2 4.5
11500 11.9 53.4 345 10 5 9.0 5.0 | 10.6 51.1 345 13 7 7.9 4.3
11000 13.2 55.8 345 11 6 8.7 4.8 | 11.7 53.1 355 13 7 7.4 4.1
10500 14.5 58.1 345 11 6 4.5 2.5 | 12.9 55.2 005 13 7 4.2 2.3
10250 14.7 58.5 345 11 6 5.2 2.9 | 13.1 55.6 005 13 7 5.8 3.2
10000 15.4 59.7 345 12 6 11.4 6.3 | 13.8 56.8 015 13 7 11.4 6.2
9750 16.2 61.2 345 12 6 10.2 5.6 | 14.5 58.1 025 13 7 10.4 5.7
9500 16.9 62.4 345 12 6 9.0 4.9 | 15.2 59.4 030 13 7 8.8 4.8
9250 17.5 63.5 345 12 6 7.3 4.0 | 15.8 60.4 030 14 7 7.7 4.2
9000 18.1 64.6 345 12 6 8.4 4.6 | 16.5 61.7 035 14 7 11.0 6.0
8750 18.7 65.7 345 12 6 9.0 4.9 | 17.4 63.3 035 14 7 12.3 6.8
8500 19.4 66.9 345 12 6 7.6 4.2 | 18.2 64.8 035 14 7 10.4 5.7
8250 19.9 67.8 345 11 6 6.5 3.5 | 18.9 66.0 035 14 7 8.9 4.9
8000 20.4 68.7 345 11 6 6.7 3.7 | 19.6 67.3 035 14 7 10.1 5.5
7750 20.9 69.6 345 11 6 6.6 3.6 | 20.4 68.7 035 14 7 10.8 5.9
7500 21.3 70.3 345 11 6 6.2 3.4 | 21.2 70.2 035 14 7 10.3 5.6
7250 21.8 71.2 345 10 5 6.0 3.3 | 22.0 71.6 035 14 7 10.2 5.6
7000 22.2 72.0 340 9 5 6.1 3.4 | 22.7 72.9 035 14 7 9.8 5.4
6750 22.7 72.9 340 8 4 6.1 3.4 | 23.5 74.3 035 14 7 9.8 5.4
6500 23.1 73.6 335 7 4 5.8 3.2 | 24.2 75.6 035 14 7 10.6 5.8
6250 23.5 74.3 330 6 3 6.6 3.6 | 25.0 77.0 035 13 7 10.6 5.8
6000 23.9 75.0 320 4 2 3.4 1.9 | 25.8 78.4 035 13 7 11.3 6.2
5750 24.2 75.6 295 3 2 6.8 3.7 | 26.8 80.2 035 13 7 17.9 9.8
5500 25.2 77.4 285 3 1 21.6 11.9 | 28.5 83.3 035 12 6 26.5 14.5
06/29/2025 at 1500 MDT | 06/29/2025 at 1800 MDT
|
CAPE... +1593.8 LI... -5.3 | CAPE... +1422.0 LI... -4.9
CINH... 0.0 K Index... +32.0 | CINH... -4.2 K Index... +32.2
|
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 -60.8 -77.4 270 25 13 1.7 0.9 | -61.0 -77.8 280 24 12 1.3 0.7
45000 -58.1 -72.6 270 29 15 2.1 1.2 | -58.9 -74.0 285 25 13 1.8 1.0
40000 -54.5 -66.1 270 27 14 6.0 3.3 | -55.6 -68.1 280 27 14 7.0 3.9
38000 -51.1 -60.0 275 25 13 5.7 3.1 | -51.5 -60.7 275 28 15 6.8 3.7
36000 -47.2 -53.0 280 23 12 5.5 3.0 | -46.9 -52.4 265 31 16 7.0 3.8
34000 -42.8 -45.0 280 21 11 7.6 4.2 | -41.9 -43.4 270 29 15 8.5 4.7
32000 -38.2 -36.8 280 20 10 7.5 4.1 | -36.8 -34.2 280 26 14 8.5 4.6
30000 -33.4 -28.1 280 20 10 8.2 4.5 | -32.0 -25.6 290 24 12 7.9 4.4
29000 -30.9 -23.6 280 20 10 8.2 4.5 | -29.6 -21.3 300 23 12 7.9 4.4
28000 -28.5 -19.3 275 20 10 7.4 4.1 | -27.2 -17.0 305 22 11 7.2 4.0
27000 -26.4 -15.5 275 19 10 7.0 3.8 | -25.1 -13.2 305 21 11 7.0 3.8
26000 -24.4 -11.9 275 18 9 7.0 3.9 | -23.1 -9.6 305 21 11 7.0 3.8
25000 -22.3 -8.1 275 18 9 7.1 3.9 | -21.0 -5.8 305 21 11 7.0 3.8
24000 -20.2 -4.4 270 16 8 7.0 3.8 | -18.9 -2.0 305 20 11 6.9 3.8
23000 -18.1 -0.6 265 15 8 7.0 3.8 | -16.8 1.8 305 20 10 6.9 3.8
22000 -16.1 3.0 260 14 7 7.3 4.0 | -14.8 5.4 305 20 10 7.1 3.9
21000 -13.7 7.3 265 14 7 8.1 4.4 | -12.6 9.3 310 19 10 7.4 4.1
20000 -11.3 11.7 265 14 7 8.1 4.4 | -10.4 13.3 310 19 10 7.5 4.1
19500 -10.1 13.8 270 14 7 8.1 4.5 | -9.4 15.1 310 18 9 7.6 4.1
19000 -9.0 15.8 270 13 7 7.9 4.4 | -8.3 17.1 310 17 9 7.6 4.1
18500 -7.2 19.0 270 12 6 7.9 4.3 | -7.2 19.0 310 15 8 7.7 4.2
18000 -6.0 21.2 270 12 6 8.7 4.8 | -5.6 21.9 310 12 6 8.4 4.6
17500 -4.8 23.4 270 11 5 8.7 4.8 | -4.4 24.1 305 10 5 8.3 4.6
17000 -3.5 25.7 270 10 5 8.7 4.8 | -3.2 26.2 300 7 4 8.0 4.4
16500 -2.2 28.0 275 9 4 8.7 4.8 | -2.0 28.4 285 5 3 7.7 4.2
16000 -1.0 30.2 280 8 4 8.6 4.7 | -0.9 30.4 255 4 2 7.7 4.2
15500 0.2 32.4 285 7 3 7.9 4.4 | 0.2 32.4 230 4 2 7.7 4.2
15000 1.4 34.5 290 6 3 8.1 4.4 | 1.4 34.5 210 5 3 7.7 4.2
14500 2.5 36.5 300 5 3 7.2 3.9 | 2.5 36.5 200 6 3 8.0 4.4
14000 3.6 38.5 315 5 3 7.2 4.0 | 3.5 38.3 190 5 3 8.1 4.5
13500 4.6 40.3 335 5 3 7.7 4.2 | 4.6 40.3 180 5 3 8.2 4.5
13000 5.6 42.1 355 6 3 8.1 4.4 | 5.7 42.3 165 4 2 8.3 4.6
12500 6.6 43.9 010 8 4 8.8 4.8 | 6.7 44.1 150 3 2 8.8 4.8
12000 7.9 46.2 015 9 5 9.2 5.1 | 8.1 46.6 155 3 2 9.1 5.0
11500 9.2 48.6 020 10 5 9.7 5.3 | 9.4 48.9 160 3 1 9.3 5.1
11000 10.7 51.3 020 10 5 9.8 5.4 | 10.8 51.4 165 2 1 9.2 5.0
10500 12.2 54.0 020 10 5 4.6 2.5 | 12.3 54.1 175 2 1 4.0 2.2
10250 12.4 54.3 020 10 5 5.9 3.2 | 12.4 54.3 175 2 1 5.7 3.1
10000 13.3 55.9 020 10 5 13.6 7.5 | 13.3 55.9 180 2 1 13.7 7.5
9750 14.2 57.6 020 10 5 12.1 6.6 | 14.2 57.6 185 2 1 12.3 6.7
9500 15.1 59.2 020 10 5 10.4 5.7 | 15.1 59.2 190 2 1 9.8 5.4
9250 15.7 60.3 020 10 5 8.5 4.7 | 15.7 60.3 195 3 1 7.3 4.0
9000 16.4 61.5 020 10 5 10.3 5.7 | 16.4 61.5 200 3 1 10.6 5.8
8750 17.2 63.0 020 10 5 10.7 5.9 | 17.2 63.0 205 3 1 11.6 6.4
8500 18.0 64.4 015 10 5 10.6 5.8 | 18.0 64.4 210 3 2 10.1 5.6
8250 18.8 65.8 015 11 5 11.0 6.0 | 18.7 65.7 215 3 2 9.3 5.1
8000 19.6 67.3 015 11 5 9.9 5.4 | 19.5 67.1 215 3 2 9.6 5.2
7750 20.3 68.5 015 11 5 9.0 5.0 | 20.2 68.4 220 4 2 9.6 5.3
7500 21.0 69.8 015 11 5 10.2 5.6 | 20.9 69.6 220 4 2 9.8 5.4
7250 21.8 71.2 015 11 5 10.8 5.9 | 21.7 71.1 225 4 2 9.9 5.4
7000 22.6 72.7 015 11 5 10.4 5.7 | 22.4 72.3 225 4 2 9.9 5.4
6750 23.4 74.1 015 11 5 10.0 5.5 | 23.1 73.6 225 4 2 9.8 5.3
6500 24.1 75.4 015 11 5 10.3 5.7 | 23.8 74.8 230 4 2 9.7 5.3
6250 24.9 76.8 015 11 5 9.8 5.4 | 24.6 76.3 230 4 2 9.3 5.1
6000 25.7 78.3 015 10 5 12.3 6.7 | 25.3 77.5 230 4 2 10.8 5.9
5750 26.8 80.2 015 10 5 20.1 11.0 | 26.3 79.3 230 4 2 15.8 8.7
5500 28.5 83.3 015 10 5 25.3 13.9 | 27.6 81.7 230 4 2 19.7 10.8
________________________________________________________________________________
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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