Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
877
UXUS97 KGJT 101306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Sunday, August 10, 2025
This forecast is for Sunday, August 10, 2025:
If the trigger temperature of 77.1 F/25.1 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1129 ft/min (5.7 m/s)
Maximum height of thermals.................. 18305 ft MSL (12697 ft AGL)
Forecast maximum temperature................... 90.0 F/32.7 C
Time of trigger temperature.................... 0945 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................. 15763 ft MSL (10155 ft AGL)
Thermal soaring outlook for Monday 08/11....... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:23:24 / 20:15:28 MDT
Total possible sunshine........... 13 hr 52 min 4 sec (832 min 4 sec)
Altitude of sun at 13:19:26 MDT... 65.82 degrees
Upper air data from rawinsonde observation taken on 08/10/2025 at 0600 MDT
Freezing level.................. 14970 ft MSL (9362 ft AGL)
Convective condensation level... 23210 ft MSL (17602 ft AGL)
Lifted condensation level....... 21128 ft MSL (15519 ft AGL)
Lifted index.................... +3.9
K index......................... +7.4
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 -62.3 -80.1 335 15 8 -0.2 -0.1 M M M M M
45000 -60.8 -77.4 330 28 14 3.9 2.1 M M M M M
40000 -54.5 -66.1 325 35 18 7.2 3.9 M M M M M
38000 -50.3 -58.5 325 34 17 7.1 3.9 M M M M M
36000 -45.5 -49.9 325 32 17 7.2 3.9 M M M M M
34000 -40.9 -41.6 325 30 16 7.7 4.2 M M M M M
32000 -36.3 -33.3 325 28 15 7.5 4.1 M M M M M
30000 -31.1 -24.0 330 28 15 8.9 4.9 44.0 111.1 8.9 M M
29000 -28.4 -19.1 330 28 15 8.9 4.9 43.7 110.6 8.8 M M
28000 -25.8 -14.4 330 29 15 8.4 4.6 43.4 110.2 8.7 M M
27000 -23.4 -10.1 330 28 14 8.1 4.4 42.7 108.8 8.2 M M
26000 -20.9 -5.6 330 28 14 8.1 4.4 42.0 107.7 7.8 M M
25000 -18.5 -1.3 330 27 14 8.2 4.5 41.5 106.7 7.5 M M
24000 -16.6 2.1 330 27 14 6.1 3.3 40.3 104.5 6.5 M M
23000 -14.8 5.4 335 27 14 6.2 3.4 38.9 102.0 5.4 M M
22000 -13.0 8.6 335 28 14 6.3 3.5 37.7 99.9 4.4 M M
21000 -11.1 12.0 340 27 14 6.5 3.5 36.5 97.6 3.4 M M
20000 -8.7 16.3 340 25 13 6.4 3.5 35.0 95.1 2.1 M M
19500 -7.8 18.0 340 25 13 6.1 3.4 34.5 94.1 1.7 M M
19000 -7.0 19.4 340 23 12 4.5 2.4 33.7 92.7 1.0 M M
18500 -6.4 20.5 340 22 11 4.5 2.5 32.8 91.0 0.2 M M
18000 -5.7 21.7 340 21 11 5.4 3.0 32.0 89.5 -0.6 1100 5.6
17500 -4.8 23.4 345 20 10 5.6 3.1 31.2 88.2 -1.2 1061 5.4
17000 -4.0 24.8 345 19 10 5.8 3.2 30.6 87.0 -1.8 1021 5.2
16500 -3.0 26.6 345 18 9 6.7 3.7 30.0 86.0 -2.4 977 5.0
16000 -2.0 28.4 350 17 9 6.6 3.6 29.5 85.0 -2.8 932 4.7
15500 -1.0 30.2 350 17 8 6.8 3.7 29.0 84.1 -3.3 887 4.5
15000 0.0 32.0 355 16 8 6.8 3.7 28.5 83.3 -3.8 842 4.3
14500 1.0 33.8 360 16 8 7.1 3.9 28.0 82.4 -4.2 796 4.0
14000 2.1 35.8 005 16 8 7.3 4.0 27.6 81.7 -4.7 750 3.8
13500 3.1 37.6 005 16 8 7.8 4.3 27.2 80.9 -5.1 704 3.6
13000 4.3 39.7 005 16 8 8.4 4.6 27.0 80.5 -5.4 653 3.3
12500 5.6 42.1 010 16 8 8.4 4.6 26.8 80.2 -5.6 601 3.1
12000 6.8 44.2 010 15 8 8.4 4.6 26.5 79.7 -5.9 549 2.8
11500 8.1 46.6 015 15 8 8.2 4.5 26.3 79.4 -6.1 497 2.5
11000 9.2 48.6 020 14 7 7.7 4.2 26.0 78.8 -6.5 447 2.3
10500 10.4 50.7 020 12 6 10.4 5.7 25.7 78.2 -6.8 398 2.0
10250 11.3 52.3 025 12 6 11.2 6.2 25.8 78.5 -6.6 363 1.8
10000 11.9 53.4 025 11 6 8.1 4.4 25.8 78.4 -6.7 336 1.7
9750 12.6 54.7 025 11 6 9.4 5.1 25.7 78.3 -6.8 309 1.6
9500 13.3 55.9 025 10 5 7.4 4.0 25.6 78.1 -6.9 282 1.4
9250 13.8 56.8 030 10 5 7.3 4.0 25.4 77.7 -7.2 259 1.3
9000 14.4 57.9 030 9 5 8.9 4.9 25.3 77.5 -7.3 233 1.2
8750 15.1 59.2 035 9 5 8.7 4.8 25.2 77.4 -7.4 206 1.0
8500 15.7 60.3 035 8 4 8.0 4.4 25.1 77.2 -7.5 179 0.9
8250 16.2 61.2 040 8 4 6.4 3.5 24.9 76.9 -7.7 155 0.8
8000 16.7 62.1 040 8 4 5.8 3.2 24.6 76.3 -7.9 134 0.7
7750 17.1 62.8 045 7 4 6.1 3.3 24.3 75.8 -8.3 113 0.6
7500 17.6 63.7 055 7 3 3.9 2.1 24.0 75.2 -8.6 93 0.5
7250 17.8 64.0 055 6 3 1.8 1.0 23.4 74.2 -9.1 80 0.4
7000 17.9 64.2 065 6 3 3.2 1.7 22.9 73.2 -9.7 67 0.3
6750 18.2 64.8 070 5 3 0.9 0.5 22.3 72.2 -10.3 54 0.3
6500 18.0 64.4 080 5 3 -4.9 -2.7 21.4 70.6 -11.2 51 0.3
6250 17.5 63.5 085 5 3 -9.6 -5.2 20.2 68.3 -12.5 60 0.3
6000 17.0 62.6 090 6 3 1.0 0.6 18.9 66.1 -13.7 67 0.3
5750 17.3 63.1 095 5 3 -2.0 -1.1 18.5 65.3 -14.2 50 0.3
5500 M M M M M M M M M M M M
5250 M M M M M M M M M M M M
5000 M M M M M M M M M M M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/10/2025 at 0900 MDT | 08/10/2025 at 1200 MDT
|
CAPE... 0.0 LI... +4.2 | CAPE... 0.0 LI... +4.7
CINH... 0.0 K Index... +6.4 | CINH... -0.1 K Index... +2.3
|
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 -58.7 -73.7 335 14 7 1.4 0.7 | -59.3 -74.7 335 15 8 1.1 0.6
45000 -56.8 -70.2 325 24 12 0.9 0.5 | -57.7 -71.9 335 32 16 0.8 0.5
40000 -55.3 -67.5 335 40 20 5.3 2.9 | -56.0 -68.8 345 63 33 7.7 4.2
38000 -52.0 -61.6 335 38 20 5.5 3.0 | -51.9 -61.4 340 54 28 6.9 3.8
36000 -48.3 -54.9 335 37 19 5.4 2.9 | -47.3 -53.1 330 44 23 6.8 3.7
34000 -43.7 -46.7 330 34 18 8.2 4.5 | -42.4 -44.3 325 39 20 8.4 4.6
32000 -38.8 -37.8 320 32 17 8.1 4.5 | -37.4 -35.3 315 35 18 8.2 4.5
30000 -34.0 -29.2 310 29 15 7.9 4.3 | -32.6 -26.7 310 33 17 7.9 4.3
29000 -31.6 -24.9 310 28 14 7.9 4.3 | -30.2 -22.4 305 33 17 7.9 4.3
28000 -29.2 -20.6 300 27 14 7.8 4.3 | -27.9 -18.2 305 32 16 7.4 4.1
27000 -27.0 -16.6 300 26 13 7.5 4.1 | -25.9 -14.6 305 30 15 6.3 3.5
26000 -24.7 -12.5 300 26 13 7.5 4.1 | -24.0 -11.2 300 28 14 6.3 3.5
25000 -22.5 -8.5 300 25 13 7.5 4.1 | -22.1 -7.8 300 26 13 6.3 3.4
24000 -20.4 -4.7 295 25 13 6.7 3.7 | -20.0 -4.0 295 24 13 7.1 3.9
23000 -18.4 -1.1 290 25 13 6.7 3.7 | -17.3 0.9 290 23 12 7.1 3.9
22000 -16.8 1.8 285 25 13 7.0 3.8 | -15.2 4.6 285 22 11 7.0 3.8
21000 -13.8 7.2 280 27 14 7.3 4.0 | -13.2 8.2 280 23 12 6.8 3.7
20000 -11.7 10.9 275 29 15 7.3 4.0 | -11.1 12.0 275 23 12 6.8 3.7
19500 -10.6 12.9 275 30 15 7.4 4.1 | -10.1 13.8 275 24 12 6.8 3.7
19000 -9.5 14.9 275 31 16 8.0 4.4 | -9.1 15.6 270 24 12 7.2 4.0
18500 -8.3 17.1 270 31 16 8.0 4.4 | -8.0 17.6 270 24 12 7.2 4.0
18000 -7.2 19.0 270 32 17 8.4 4.6 | -7.0 19.4 270 25 13 7.2 4.0
17500 -5.9 21.4 270 32 17 8.6 4.7 | -5.9 21.4 270 25 13 7.3 4.0
17000 -4.6 23.7 270 32 17 8.6 4.7 | -4.9 23.2 270 25 13 7.4 4.0
16500 -3.4 25.9 270 32 16 8.3 4.6 | -3.8 25.2 270 24 13 7.7 4.2
16000 -2.1 28.2 270 31 16 8.4 4.6 | -2.6 27.3 270 24 12 7.7 4.2
15500 -0.9 30.4 270 30 15 7.8 4.3 | -1.5 29.3 270 23 12 7.7 4.2
15000 0.2 32.4 270 28 15 7.7 4.2 | -0.4 31.3 270 22 11 7.7 4.2
14500 1.4 34.5 275 27 14 7.4 4.1 | 0.8 33.4 270 20 11 7.7 4.2
14000 2.4 36.3 275 24 12 7.3 4.0 | 1.9 35.4 275 19 10 7.7 4.2
13500 3.5 38.3 275 22 11 7.2 4.0 | 3.0 37.4 275 17 9 7.8 4.3
13000 4.6 40.3 275 19 10 7.2 4.0 | 4.2 39.6 275 15 8 8.0 4.4
12500 5.7 42.3 280 17 9 7.3 4.0 | 5.4 41.7 280 13 7 8.0 4.4
12000 6.8 44.2 280 15 8 7.3 4.0 | 6.6 43.9 285 12 6 8.2 4.5
11500 7.9 46.2 280 13 7 7.3 4.0 | 7.8 46.0 285 11 5 8.2 4.5
11000 9.0 48.2 280 11 5 7.7 4.2 | 9.1 48.4 290 10 5 8.5 4.7
10500 10.2 50.4 280 9 4 6.1 3.3 | 10.4 50.7 290 9 5 5.9 3.3
10250 10.6 51.1 285 8 4 5.7 3.1 | 10.7 51.3 295 9 5 6.8 3.7
10000 11.1 52.0 290 7 4 8.4 4.6 | 11.5 52.7 295 9 5 10.8 5.9
9750 11.8 53.2 295 6 3 8.6 4.7 | 12.2 54.0 295 9 4 9.9 5.4
9500 12.4 54.3 300 5 3 8.2 4.5 | 13.0 55.4 300 8 4 9.7 5.3
9250 13.0 55.4 310 4 2 6.7 3.7 | 13.6 56.5 300 8 4 8.4 4.6
9000 13.5 56.3 325 4 2 6.9 3.8 | 14.3 57.7 300 8 4 8.8 4.8
8750 14.0 57.2 345 4 2 8.0 4.4 | 15.0 59.0 300 8 4 9.7 5.3
8500 14.6 58.3 360 5 2 7.3 4.0 | 15.7 60.3 305 8 4 9.0 5.0
8250 15.1 59.2 010 5 3 6.2 3.4 | 16.9 62.4 300 8 4 9.0 4.9
8000 16.1 61.0 020 6 3 8.3 4.5 | 17.7 63.9 300 8 4 12.0 6.6
7750 16.7 62.1 020 7 4 6.6 3.6 | 18.5 65.3 305 7 4 10.0 5.5
7500 17.1 62.8 020 7 4 4.4 2.4 | 19.2 66.6 305 8 4 7.4 4.1
7250 17.5 63.5 025 7 4 5.0 2.8 | 19.8 67.6 300 8 4 8.8 4.8
7000 17.9 64.2 025 7 4 7.4 4.1 | 20.5 68.9 300 7 4 12.9 7.1
6750 18.5 65.3 020 6 3 7.3 4.0 | 21.6 70.9 305 7 4 12.1 6.6
6500 19.0 66.2 020 6 3 6.1 3.4 | 22.3 72.1 305 7 4 10.0 5.5
6250 19.4 66.9 020 5 3 5.5 3.0 | 23.1 73.6 300 7 4 9.1 5.0
6000 19.9 67.8 020 5 2 9.7 5.3 | 23.8 74.8 300 7 4 13.9 7.6
5750 21.0 69.8 020 4 2 20.8 11.4 | 25.4 77.7 300 6 3 29.0 15.9
5500 22.3 72.1 020 4 2 5.6 3.1 | 27.4 81.3 300 6 3 15.5 8.5
5250 M M M M M M M | M M M M M M M
5000 M M M M M M M | M M M M M M M
08/10/2025 at 1500 MDT | 08/10/2025 at 1800 MDT
|
CAPE... 0.0 LI... +3.8 | CAPE... 0.0 LI... +3.1
CINH... 0.0 K Index... -0.1 | CINH... -0.7 K Index... +4.8
|
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 -59.7 -75.5 340 18 9 1.0 0.6 | -60.7 -77.3 350 22 11 0.6 0.3
45000 -58.0 -72.4 340 37 19 1.6 0.9 | -59.0 -74.2 355 41 21 2.4 1.3
40000 -55.1 -67.2 345 62 32 7.2 3.9 | -54.9 -66.8 360 65 34 7.8 4.3
38000 -50.7 -59.3 340 54 28 6.6 3.6 | -49.8 -57.6 360 62 32 7.5 4.1
36000 -46.8 -52.2 340 48 25 6.5 3.5 | -45.3 -49.5 360 60 31 7.5 4.1
34000 -42.3 -44.1 335 41 21 7.6 4.1 | -40.6 -41.1 360 51 26 7.9 4.3
32000 -37.8 -36.0 325 34 17 7.4 4.1 | -35.9 -32.6 360 42 22 7.9 4.3
30000 -32.8 -27.0 315 34 17 8.5 4.7 | -31.3 -24.3 355 35 18 7.5 4.1
29000 -30.3 -22.5 315 35 18 8.5 4.7 | -29.1 -20.4 350 31 16 7.5 4.1
28000 -27.8 -18.0 315 36 19 8.1 4.4 | -26.9 -16.4 345 28 15 7.3 4.0
27000 -25.6 -14.1 315 35 18 7.2 3.9 | -24.8 -12.6 340 27 14 7.1 3.9
26000 -23.5 -10.3 310 33 17 7.2 4.2 | -22.7 -8.9 340 27 14 7.1 3.9
25000 -21.4 -6.5 310 32 16 7.4 4.1 | -20.6 -5.1 335 26 13 7.2 4.0
24000 -19.6 -3.3 305 29 15 5.1 2.8 | -18.6 -1.5 335 25 13 6.5 3.6
23000 -17.7 0.1 300 24 12 5.1 2.8 | -16.2 2.8 330 24 12 6.5 3.6
22000 -16.1 3.0 295 20 10 6.6 3.6 | -14.3 6.3 325 23 12 6.2 3.4
21000 -13.7 7.3 290 20 10 8.0 4.4 | -12.5 9.5 320 21 11 6.0 3.3
20000 -11.3 11.7 285 19 10 8.0 4.4 | -10.6 12.9 320 19 10 6.0 3.3
19500 -10.0 14.0 280 19 10 7.9 4.3 | -9.7 14.5 315 19 10 6.1 3.3
19000 -9.0 15.8 280 19 10 6.4 3.5 | -8.8 16.2 315 18 9 6.4 3.5
18500 -8.0 17.6 280 18 9 6.6 3.6 | -7.8 18.0 315 18 9 6.3 3.5
18000 -7.0 19.4 280 18 9 6.8 3.7 | -6.9 19.6 315 18 9 6.6 3.6
17500 -6.0 21.2 280 17 9 6.9 3.8 | -5.9 21.4 315 17 9 6.8 3.7
17000 -5.0 23.0 280 16 8 7.1 3.9 | -4.9 23.2 320 16 8 6.9 3.8
16500 -3.9 25.0 280 15 8 7.9 4.4 | -3.8 25.2 320 16 8 8.3 4.6
16000 -2.7 27.1 285 15 8 7.9 4.3 | -2.5 27.5 320 15 8 8.2 4.5
15500 -1.5 29.3 285 14 7 8.1 4.4 | -1.3 29.7 325 14 7 8.8 4.8
15000 -0.3 31.5 285 13 7 8.1 4.4 | 0.0 32.0 325 13 7 8.9 4.9
14500 0.9 33.6 290 13 6 8.4 4.6 | 1.3 34.3 325 13 7 9.1 5.0
14000 2.1 35.8 290 12 6 8.5 4.7 | 2.7 36.9 325 13 6 9.3 5.1
13500 3.4 38.1 290 12 6 8.7 4.8 | 4.1 39.4 325 12 6 9.3 5.1
13000 4.7 40.5 290 12 6 8.9 4.9 | 5.5 41.9 325 12 6 9.4 5.2
12500 6.0 42.8 295 11 6 8.9 4.9 | 6.9 44.4 325 12 6 9.4 5.2
12000 7.4 45.3 295 11 6 9.2 5.0 | 8.3 46.9 325 12 6 9.5 5.2
11500 8.8 47.8 295 11 6 9.2 5.0 | 9.8 49.6 325 12 6 9.5 5.2
11000 10.1 50.2 300 11 6 9.2 5.1 | 11.2 52.2 325 11 6 9.3 5.1
10500 11.5 52.7 300 11 6 6.5 3.6 | 12.6 54.7 325 11 6 7.2 4.0
10250 11.9 53.4 300 11 6 7.2 4.0 | 13.0 55.4 325 11 6 7.8 4.3
10000 12.7 54.9 300 11 6 11.4 6.3 | 13.8 56.8 320 11 6 11.0 6.1
9750 13.5 56.3 300 11 6 10.4 5.7 | 14.6 58.3 320 11 6 10.2 5.6
9500 14.3 57.7 300 11 6 10.1 5.5 | 15.4 59.7 320 11 6 10.2 5.6
9250 15.0 59.0 300 11 6 8.7 4.8 | 16.1 61.0 320 11 6 9.2 5.1
9000 15.6 60.1 300 11 6 9.5 5.2 | 16.8 62.2 320 11 6 9.1 5.0
8750 16.4 61.5 300 11 6 10.6 5.8 | 17.5 63.5 315 11 6 9.6 5.3
8500 17.2 63.0 300 11 6 9.7 5.3 | 18.8 65.8 315 11 6 7.8 4.3
8250 17.8 64.0 300 11 6 7.8 4.3 | 19.4 66.9 315 11 6 8.8 4.8
8000 19.2 66.6 300 11 6 12.1 6.6 | 20.2 68.4 315 11 6 10.7 5.9
7750 20.1 68.2 300 11 5 10.2 5.6 | 21.0 69.8 315 11 5 9.7 5.3
7500 20.8 69.4 300 11 5 8.0 4.4 | 21.6 70.9 310 11 6 8.3 4.5
7250 21.4 70.5 295 11 6 9.1 5.0 | 22.3 72.1 310 11 6 8.8 4.8
7000 22.2 72.0 295 11 5 12.4 6.8 | 23.0 73.4 310 11 5 11.5 6.3
6750 23.1 73.6 300 10 5 11.7 6.4 | 23.9 75.0 310 10 5 11.3 6.2
6500 23.9 75.0 295 10 5 10.3 5.7 | 24.7 76.5 310 10 5 10.2 5.6
6250 24.7 76.5 295 10 5 9.3 5.1 | 25.4 77.7 310 10 5 9.9 5.4
6000 25.4 77.7 295 10 5 13.7 7.5 | 26.2 79.2 310 10 5 10.7 5.9
5750 27.0 80.6 295 9 5 28.7 15.8 | 27.2 81.0 310 9 5 17.6 9.6
5500 29.1 84.4 295 9 5 20.6 11.3 | 28.8 83.8 305 9 4 26.9 14.7
5250 M M M M M M M | M M M M M M M
5000 M M M M M M M | M M M M M M M
________________________________________________________________________________
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 at Walker Field in Grand
Junction, Colorado at
North Latitude: 39 deg 07 min 00.001 sec
West Longitude: 108 deg 31 min 59.998 sec
Elevation: 4839 feet (1475 meters)
and may not be representative of other areas along the Western Slope of
Colorado. 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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