Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
088
UXUS97 KBOU 170115
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1914 MDT Monday, June 16, 2025
This forecast is for Tuesday, June 17, 2025:
If the trigger temperature of 78.8 F/26.0 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 8782 ft MSL (3500 ft AGL)
Forecast maximum temperature................... 77.0 F/25.5 C
Time of trigger temperature.................... None
Time of overdevelopment........................ 1200 MDT
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 7492 ft MSL (2210 ft AGL)
Thermal soaring outlook for Wednesday 06/18.... 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)................ Weak PVA
Potential height of wave....................... 25236 ft MSL (19954 ft AGL)
Wave soaring outlook for Wednesday 06/18....... Poor
Remarks...
Sunrise/Sunset.................... 05:31:01 / 20:30:04 MDT
Total possible sunshine........... 14 hr 59 min 3 sec (899 min 3 sec)
Altitude of sun at 13:00:33 MDT... 73.63 degrees
Upper air data from numerical model forecast valid on 06/17/2025 at 0600 MDT
Freezing level.................. 15319 ft MSL (10037 ft AGL)
Convective condensation level... 14961 ft MSL (9679 ft AGL)
Lifted condensation level....... 13013 ft MSL (7731 ft AGL)
Lifted index.................... -4.2
K index......................... +15.9
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 -60.3 -76.5 270 37 19 2.0 1.1 M M M M M
45000 -57.0 -70.6 260 51 26 2.5 1.4 M M M M M
40000 -53.2 -63.8 255 57 29 3.8 2.1 M M M M M
38000 -50.2 -58.4 255 54 28 5.1 2.8 M M M M M
36000 -47.1 -52.8 255 52 27 5.1 2.8 M M M M M
34000 -44.3 -47.7 255 46 24 4.2 2.3 M M M M M
32000 -41.5 -42.7 245 36 19 4.2 2.3 M M M M M
30000 -37.5 -35.5 245 35 18 8.0 4.4 37.2 98.9 9.2 M M
29000 -35.2 -31.4 245 36 18 8.0 4.4 36.5 97.7 8.8 M M
28000 -32.8 -27.0 245 37 19 8.0 4.4 35.9 96.7 8.4 M M
27000 -30.3 -22.5 245 38 19 8.4 4.6 35.3 95.5 8.0 M M
26000 -27.8 -18.0 245 39 20 8.4 4.6 34.8 94.6 7.7 M M
25000 -25.3 -13.5 245 40 20 8.4 4.6 34.3 93.8 7.4 M M
24000 -22.8 -9.0 245 40 20 8.4 4.6 33.8 92.9 7.0 M M
23000 -20.3 -4.5 250 39 20 8.4 4.6 33.3 91.9 6.6 M M
22000 -17.9 -0.2 250 38 19 8.4 4.6 32.8 91.1 6.3 M M
21000 -15.4 4.3 255 36 18 8.3 4.6 32.3 90.2 5.9 M M
20000 -12.9 8.8 255 33 17 8.3 4.6 31.8 89.3 5.5 M M
19500 -11.6 11.1 255 32 16 8.4 4.6 31.6 88.9 5.4 M M
19000 -10.4 13.3 260 30 16 8.5 4.7 31.4 88.5 5.2 M M
18500 -9.1 15.6 260 29 15 8.7 4.8 31.2 88.2 5.1 M M
18000 -7.8 18.0 260 28 14 8.7 4.8 31.0 87.9 5.0 M M
17500 -6.4 20.5 260 27 14 9.2 5.1 30.9 87.6 4.9 M M
17000 -5.1 22.8 260 26 13 9.2 5.1 30.8 87.5 4.8 M M
16500 -3.7 25.3 260 25 13 9.3 5.1 30.7 87.3 4.7 M M
16000 -2.3 27.9 260 24 12 9.4 5.1 30.7 87.2 4.7 M M
15500 -0.2 31.6 260 22 12 9.4 5.2 30.6 87.0 4.7 M M
15000 1.2 34.2 260 21 11 9.4 5.2 30.5 86.9 4.6 M M
14500 2.7 36.9 255 20 10 9.4 5.2 30.5 86.9 4.6 M M
14000 4.1 39.4 255 18 9 9.4 5.1 30.4 86.7 4.6 M M
13500 5.5 41.9 255 17 9 9.3 5.1 30.4 86.6 4.6 M M
13000 6.8 44.2 255 14 7 8.9 4.9 30.2 86.4 4.5 M M
12500 8.1 46.6 255 12 6 9.0 4.9 30.1 86.2 4.4 M M
12000 9.4 48.9 250 10 5 8.4 4.6 29.9 85.9 4.2 M M
11500 10.6 51.1 255 7 4 8.7 4.8 29.7 85.5 4.0 M M
11000 11.7 53.1 255 5 2 6.2 3.4 29.4 84.8 3.6 M M
10500 12.6 54.7 260 3 1 7.4 4.0 28.8 83.9 3.1 M M
10250 13.1 55.6 270 2 1 2.8 1.5 28.6 83.4 2.8 M M
10000 13.0 55.4 275 1 1 2.5 1.4 27.8 82.1 2.0 M M
9750 13.4 56.1 000 0 0 6.7 3.7 27.5 81.5 1.6 M M
9500 13.7 56.7 060 1 1 6.6 3.6 27.2 81.0 1.3 M M
9250 14.1 57.4 070 3 1 3.7 2.0 27.0 80.5 0.9 M M
9000 14.2 57.6 070 3 1 3.3 1.8 26.4 79.4 0.3 M M
8750 14.6 58.3 070 2 1 6.4 3.5 26.1 78.9 -0.1 244 1.2
8500 15.0 59.0 070 2 1 5.9 3.3 25.7 78.3 -0.4 225 1.1
8250 15.3 59.5 065 2 1 2.8 1.5 25.4 77.7 -0.8 207 1.1
8000 15.4 59.7 025 1 1 -0.4 -0.2 24.7 76.4 -1.5 198 1.0
7750 15.4 59.7 335 2 1 0.1 0.0 23.9 75.1 -2.2 191 1.0
7500 15.3 59.5 305 2 1 -0.4 -0.2 23.2 73.7 -3.0 185 0.9
7250 15.2 59.4 310 3 2 -0.9 -0.5 22.4 72.3 -3.8 181 0.9
7000 15.0 59.0 330 3 2 -0.9 -0.5 21.5 70.8 -4.8 179 0.9
6750 14.8 58.6 345 4 2 -3.6 -2.0 20.7 69.2 -5.8 179 0.9
6500 14.4 57.9 350 4 2 -0.5 -0.3 19.7 67.4 -6.9 184 0.9
6250 14.6 58.3 345 5 2 5.0 2.7 19.2 66.5 -7.4 169 0.9
6000 15.0 59.0 345 5 2 4.6 2.5 18.8 65.8 -7.8 151 0.8
5750 15.3 59.5 345 5 3 4.4 2.4 18.4 65.1 -8.2 133 0.7
5500 15.6 60.1 345 4 2 2.3 1.3 17.9 64.3 -8.7 118 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/17/2025 at 0900 MDT | 06/17/2025 at 1200 MDT
|
CAPE... +1442.2 LI... -4.3 | CAPE... +2094.9 LI... -6.7
CINH... -168.2 K Index... +17.4 | CINH... -42.1 K Index... +23.0
|
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 -59.1 -74.4 275 33 17 2.0 1.1 | -58.5 -73.3 285 32 17 1.9 1.1
45000 -56.0 -68.8 270 43 22 2.4 1.3 | -55.4 -67.7 280 42 21 2.6 1.4
40000 -52.4 -62.3 260 48 25 2.9 1.6 | -51.5 -60.7 265 41 21 2.7 1.5
38000 -50.0 -58.0 260 47 24 4.1 2.2 | -49.7 -57.5 270 41 21 3.0 1.7
36000 -47.6 -53.7 260 45 23 4.1 2.2 | -47.8 -54.0 270 41 21 3.1 1.7
34000 -44.5 -48.1 255 40 21 4.9 2.7 | -44.9 -48.8 270 38 20 5.3 2.9
32000 -41.5 -42.7 250 33 17 4.9 2.7 | -41.7 -43.1 260 34 18 5.3 2.9
30000 -38.0 -36.4 250 30 16 6.6 3.6 | -38.0 -36.4 255 29 15 6.9 3.8
29000 -36.0 -32.8 250 30 15 6.6 3.6 | -35.9 -32.6 255 27 14 6.9 3.8
28000 -34.0 -29.2 250 29 15 6.5 3.5 | -33.9 -29.0 255 24 12 6.8 3.8
27000 -31.6 -24.9 250 30 16 8.8 4.9 | -31.5 -24.7 255 24 12 8.5 4.7
26000 -28.9 -20.0 250 33 17 8.9 4.9 | -29.0 -20.2 260 26 13 8.5 4.7
25000 -26.3 -15.3 255 35 18 8.9 4.9 | -26.4 -15.5 265 28 14 8.6 4.7
24000 -23.7 -10.7 255 36 18 8.4 4.6 | -23.9 -11.0 265 29 15 8.5 4.7
23000 -21.2 -6.2 255 34 18 8.4 4.6 | -21.4 -6.5 265 30 15 8.5 4.7
22000 -18.7 -1.7 255 33 17 8.4 4.6 | -18.9 -2.0 265 30 16 8.5 4.7
21000 -16.1 3.0 255 31 16 9.0 5.0 | -16.4 2.5 265 30 15 8.4 4.6
20000 -13.4 7.9 255 29 15 9.1 5.0 | -13.9 7.0 265 28 14 8.4 4.6
19500 -12.1 10.2 260 28 15 9.1 5.0 | -12.6 9.3 265 27 14 8.4 4.6
19000 -10.7 12.7 260 27 14 9.2 5.1 | -11.4 11.5 265 26 13 8.7 4.8
18500 -9.3 15.3 255 27 14 9.5 5.2 | -9.3 15.3 265 25 13 9.4 5.2
18000 -7.9 17.8 255 26 13 9.5 5.2 | -7.9 17.8 265 25 13 9.5 5.2
17500 -5.7 21.7 255 25 13 9.5 5.2 | -6.4 20.5 265 24 13 9.6 5.3
17000 -4.3 24.3 255 24 13 9.4 5.2 | -5.0 23.0 265 24 12 9.6 5.3
16500 -2.9 26.8 255 24 12 9.6 5.3 | -3.6 25.5 265 23 12 9.5 5.2
16000 -1.4 29.5 255 23 12 9.6 5.3 | -2.2 28.0 265 23 12 9.5 5.2
15500 0.0 32.0 255 23 12 9.4 5.2 | -0.7 30.7 265 22 11 9.2 5.1
15000 1.4 34.5 255 22 11 9.3 5.1 | 0.6 33.1 265 21 11 9.0 5.0
14500 2.8 37.0 255 21 11 9.2 5.1 | 1.9 35.4 265 20 10 8.9 4.9
14000 4.2 39.6 255 20 10 9.0 4.9 | 3.2 37.8 265 19 10 8.6 4.7
13500 5.5 41.9 250 19 10 9.0 4.9 | 4.5 40.1 265 17 9 8.6 4.7
13000 6.8 44.2 250 18 9 8.2 4.5 | 5.7 42.3 265 16 8 8.1 4.5
12500 8.0 46.4 250 16 8 8.4 4.6 | 6.9 44.4 265 14 7 8.4 4.6
12000 9.0 48.2 245 15 8 6.8 3.7 | 8.0 46.4 265 12 6 6.3 3.5
11500 10.0 50.0 240 13 7 7.3 4.0 | 8.8 47.8 265 10 5 6.7 3.7
11000 10.8 51.4 240 12 6 4.0 2.2 | 9.5 49.1 265 8 4 3.0 1.7
10500 11.3 52.3 235 11 6 3.4 1.9 | 9.8 49.6 265 6 3 2.5 1.4
10250 11.6 52.9 235 10 5 7.1 3.9 | 10.0 50.0 270 5 3 5.1 2.8
10000 12.1 53.8 230 8 4 7.1 3.9 | 10.3 50.5 295 3 2 6.4 3.5
9750 12.3 54.1 230 7 4 3.3 1.8 | 10.6 51.1 315 2 1 4.6 2.5
9500 12.5 54.5 225 6 3 4.9 2.7 | 10.9 51.6 345 2 1 5.6 3.1
9250 12.7 54.9 220 5 2 3.2 1.8 | 11.1 52.0 010 3 2 3.9 2.1
9000 12.8 55.0 225 5 2 2.7 1.5 | 11.4 52.5 015 4 2 5.1 2.8
8750 13.1 55.6 230 4 2 3.5 1.9 | 11.9 53.4 025 5 2 7.4 4.1
8500 13.3 55.9 240 3 1 4.0 2.2 | 12.4 54.3 030 6 3 7.3 4.0
8250 13.5 56.3 260 2 1 0.6 0.3 | 12.9 55.2 030 7 4 5.5 3.0
8000 13.3 55.9 290 1 1 -2.3 -1.2 | 13.1 55.6 030 8 4 5.4 2.9
7750 13.1 55.6 330 2 1 -1.0 -0.5 | 13.6 56.5 030 8 4 8.2 4.5
7500 12.9 55.2 355 3 1 -0.5 -0.3 | 14.1 57.4 030 9 4 8.2 4.5
7250 12.9 55.2 005 4 2 2.2 1.2 | 14.7 58.5 035 9 5 7.5 4.1
7000 13.1 55.6 010 4 2 4.0 2.2 | 15.2 59.4 035 9 5 7.6 4.2
6750 13.5 56.3 015 5 2 7.8 4.3 | 15.9 60.6 030 9 5 10.9 6.0
6500 14.1 57.4 015 5 3 9.8 5.4 | 16.7 62.1 035 9 5 11.7 6.4
6250 14.7 58.5 010 5 3 8.3 4.6 | 17.5 63.5 035 9 5 10.0 5.5
6000 15.4 59.7 010 5 3 8.0 4.4 | 18.2 64.8 035 9 5 9.6 5.3
5750 16.0 60.8 005 5 3 10.9 6.0 | 19.0 66.2 030 9 5 11.7 6.4
5500 17.1 62.8 010 5 3 18.7 10.2 | 20.1 68.2 035 9 4 20.9 11.5
06/17/2025 at 1500 MDT | 06/17/2025 at 1800 MDT
|
CAPE... +1158.0 LI... -4.2 | CAPE... +634.3 LI... -2.2
CINH... -6.8 K Index... +28.0 | CINH... -79.0 K Index... +26.6
|
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 -58.8 -73.8 290 33 17 1.9 1.0 | -59.1 -74.4 300 37 19 2.0 1.1
45000 -56.0 -68.8 290 43 22 1.8 1.0 | -55.9 -68.6 305 45 23 2.6 1.4
40000 -53.3 -63.9 290 38 20 2.7 1.5 | -52.0 -61.6 310 48 25 3.4 1.9
38000 -50.5 -58.9 280 32 17 4.8 2.7 | -48.9 -56.0 305 45 23 4.7 2.6
36000 -47.2 -53.0 270 26 14 4.8 2.7 | -46.0 -50.8 305 42 22 4.7 2.6
34000 -43.6 -46.5 265 26 13 6.6 3.6 | -43.0 -45.4 295 37 19 5.2 2.9
32000 -39.6 -39.3 260 27 14 6.6 3.6 | -39.8 -39.6 285 32 17 5.2 2.9
30000 -35.2 -31.4 255 28 14 7.9 4.3 | -35.8 -32.4 275 32 16 7.7 4.2
29000 -32.8 -27.0 255 28 15 7.9 4.3 | -33.5 -28.3 270 33 17 7.7 4.2
28000 -30.5 -22.9 255 29 15 7.9 4.4 | -31.2 -24.2 270 34 17 7.7 4.2
27000 -28.3 -18.9 255 29 15 7.0 3.8 | -28.9 -20.0 270 34 18 7.7 4.2
26000 -26.2 -15.2 255 29 15 7.0 3.8 | -26.6 -15.9 275 35 18 7.7 4.2
25000 -24.2 -11.6 250 29 15 7.0 3.8 | -24.3 -11.7 280 35 18 7.7 4.2
24000 -22.0 -7.6 250 30 15 7.3 4.0 | -22.0 -7.6 285 36 18 7.7 4.2
23000 -19.9 -3.8 250 29 15 7.3 4.0 | -19.7 -3.5 285 35 18 7.7 4.2
22000 -17.8 -0.0 250 29 15 7.3 4.0 | -17.4 0.7 285 35 18 7.7 4.2
21000 -15.1 4.8 255 28 15 7.0 3.8 | -14.6 5.7 290 34 17 7.5 4.1
20000 -13.1 8.4 260 28 14 7.0 3.8 | -12.3 9.9 290 33 17 7.5 4.1
19500 -12.1 10.2 265 27 14 7.0 3.8 | -11.2 11.8 295 32 17 7.5 4.1
19000 -11.1 12.0 265 27 14 7.1 3.9 | -10.1 13.8 295 32 16 7.9 4.3
18500 -10.0 14.0 270 27 14 7.1 3.9 | -9.0 15.8 295 31 16 7.9 4.4
18000 -9.0 15.8 275 27 14 7.2 3.9 | -7.8 18.0 295 31 16 7.9 4.3
17500 -7.9 17.8 275 27 14 7.6 4.1 | -6.7 19.9 295 30 16 7.5 4.1
17000 -6.8 19.8 280 26 13 7.5 4.1 | -5.6 21.9 300 29 15 7.6 4.2
16500 -5.7 21.7 280 26 13 8.2 4.5 | -4.5 23.9 300 28 15 7.5 4.1
16000 -4.4 24.1 285 25 13 8.4 4.6 | -3.4 25.9 300 27 14 7.5 4.1
15500 -3.2 26.2 285 25 13 8.4 4.6 | -2.3 27.9 305 26 14 7.4 4.1
15000 -1.9 28.6 290 25 13 8.4 4.6 | -1.3 29.7 305 25 13 7.2 4.0
14500 -0.7 30.7 290 24 12 8.4 4.6 | -0.2 31.6 305 24 13 7.2 4.0
14000 0.5 32.9 295 23 12 8.2 4.5 | 0.8 33.4 305 23 12 7.1 3.9
13500 1.7 35.1 300 22 11 8.3 4.6 | 1.8 35.2 305 22 11 7.2 4.0
13000 2.8 37.0 305 21 11 6.8 3.7 | 2.8 37.0 310 19 10 6.5 3.6
12500 3.8 38.8 310 20 10 7.1 3.9 | 3.7 38.7 310 17 9 6.7 3.7
12000 4.7 40.5 315 19 10 4.6 2.5 | 4.6 40.3 320 14 7 5.8 3.2
11500 5.3 41.5 320 17 9 4.4 2.4 | 5.4 41.7 330 12 6 5.8 3.2
11000 5.9 42.6 325 16 8 5.4 3.0 | 6.2 43.2 345 11 6 5.7 3.1
10500 6.6 43.9 335 15 8 5.0 2.8 | 7.0 44.6 355 12 6 5.1 2.8
10250 7.0 44.6 340 14 7 7.9 4.4 | 7.4 45.3 005 12 6 7.9 4.4
10000 7.7 45.9 345 14 7 9.5 5.2 | 8.1 46.6 010 13 7 8.7 4.8
9750 8.2 46.8 350 15 8 7.8 4.3 | 8.6 47.5 010 14 7 6.3 3.5
9500 8.8 47.8 355 16 8 8.5 4.6 | 9.1 48.4 015 14 7 7.1 3.9
9250 9.3 48.7 005 16 8 7.5 4.1 | 9.6 49.3 015 15 8 6.4 3.5
9000 9.8 49.6 005 17 9 7.0 3.8 | 10.0 50.0 015 15 8 6.4 3.5
8750 10.3 50.5 010 17 9 7.3 4.0 | 10.5 50.9 020 15 8 7.0 3.8
8500 10.9 51.6 010 17 9 7.2 4.0 | 11.0 51.8 020 15 8 7.0 3.8
8250 11.4 52.5 015 17 9 7.3 4.0 | 11.4 52.5 025 15 8 6.5 3.6
8000 11.9 53.4 015 17 9 7.5 4.1 | 11.9 53.4 025 15 8 6.0 3.3
7750 12.5 54.5 020 17 9 7.7 4.2 | 12.3 54.1 025 14 7 6.1 3.3
7500 13.0 55.4 020 17 9 7.7 4.2 | 12.7 54.9 025 13 7 6.5 3.6
7250 13.6 56.5 020 17 9 7.3 4.0 | 13.3 55.9 030 12 6 8.3 4.5
7000 14.1 57.4 025 17 9 7.1 3.9 | 13.9 57.0 030 12 6 9.2 5.0
6750 14.6 58.3 025 17 9 7.2 3.9 | 14.6 58.3 030 11 6 9.5 5.2
6500 15.2 59.4 025 17 9 7.6 4.2 | 15.3 59.5 030 11 6 10.0 5.5
6250 15.7 60.3 025 16 8 8.4 4.6 | 16.0 60.8 030 11 5 10.0 5.5
6000 16.3 61.3 025 15 8 8.3 4.5 | 16.8 62.2 030 10 5 9.8 5.4
5750 16.9 62.4 025 15 8 9.2 5.0 | 17.5 63.5 030 10 5 10.5 5.8
5500 17.8 64.0 025 13 7 15.3 8.4 | 18.4 65.1 030 9 5 14.3 7.8
________________________________________________________________________________
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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