Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
830
UXUS97 KGJT 171306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Tuesday, June 17, 2025
This forecast is for Tuesday, June 17, 2025:
If the trigger temperature of 87.0 F/30.6 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1952 ft/min (9.9 m/s)
Maximum height of thermals.................. 23624 ft MSL (18785 ft AGL)
Forecast maximum temperature................... 92.0 F/33.8 C
Time of trigger temperature.................... 1145 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................. 7873 ft MSL (3034 ft AGL)
Thermal soaring outlook for Wednesday 06/18.... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 05:47:46 / 20:42:38 MDT
Total possible sunshine........... 14 hr 54 min 52 sec (894 min 52 sec)
Altitude of sun at 13:15:12 MDT... 73.96 degrees
Upper air data from rawinsonde observation taken on 06/17/2025 at 0600 MDT
Freezing level.................. 15512 ft MSL (10673 ft AGL)
Convective condensation level... 21330 ft MSL (16491 ft AGL)
Lifted condensation level....... 21659 ft MSL (16820 ft AGL)
Lifted index.................... -1.4
K index......................... +7.1
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 -58.7 -73.7 270 32 17 5.4 3.0 97.6 207.6 37.2 M M
45000 -54.4 -65.9 275 51 26 5.9 3.2 80.2 176.4 29.0 M M
40000 -52.0 -61.6 260 70 36 2.3 1.3 61.1 142.0 18.4 M M
38000 -49.8 -57.6 265 58 30 4.8 2.6 54.5 130.1 14.4 M M
36000 -46.9 -52.4 270 65 33 4.7 2.6 50.2 122.4 11.8 M M
34000 -43.9 -47.0 260 64 33 2.4 1.3 46.2 115.1 9.2 M M
32000 -42.2 -44.0 255 36 19 -3.0 -1.6 40.4 104.8 5.2 M M
30000 -39.2 -38.6 245 38 20 8.0 4.4 36.5 97.8 2.4 M M
29000 -36.8 -34.2 240 40 20 8.0 4.4 35.9 96.5 1.9 M M
28000 -34.4 -29.9 230 39 20 7.9 4.3 35.2 95.3 1.4 M M
27000 -31.7 -25.1 225 40 21 9.5 5.2 34.9 94.8 1.2 M M
26000 -28.8 -19.8 225 38 20 10.0 5.5 35.0 94.9 1.2 M M
25000 -25.7 -14.3 220 39 20 9.2 5.1 35.2 95.4 1.4 M M
24000 -23.7 -10.7 220 38 19 6.6 3.6 34.1 93.3 0.4 M M
23000 -21.5 -6.7 225 35 18 9.3 5.1 33.3 92.0 -0.2 1894 9.6
22000 -18.7 -1.7 230 32 16 9.2 5.0 33.2 91.7 -0.3 1782 9.1
21000 -15.9 3.4 240 30 15 9.2 5.0 33.0 91.4 -0.5 1670 8.5
20000 -12.5 9.5 250 27 14 9.2 5.0 32.7 90.8 -0.7 1529 7.8
19500 -11.1 12.0 250 28 14 9.2 5.0 32.6 90.6 -0.9 1473 7.5
19000 -9.7 14.5 255 29 15 9.5 5.2 32.5 90.5 -0.9 1417 7.2
18500 -8.3 17.1 260 28 14 9.5 5.2 32.5 90.4 -1.0 1359 6.9
18000 -6.9 19.6 260 29 15 9.5 5.2 32.4 90.4 -1.0 1302 6.6
17500 -5.5 22.1 265 26 13 9.5 5.2 32.4 90.3 -1.1 1245 6.3
17000 -4.0 24.8 265 24 12 9.5 5.2 32.4 90.2 -1.1 1187 6.0
16500 -2.6 27.3 255 21 11 9.5 5.2 32.3 90.1 -1.2 1130 5.7
16000 -1.2 29.8 255 22 11 9.5 5.2 32.2 90.0 -1.2 1073 5.4
15500 0.2 32.4 260 20 10 9.5 5.2 32.2 89.9 -1.3 1015 5.2
15000 1.6 34.9 270 18 9 9.2 5.0 32.1 89.8 -1.4 958 4.9
14500 2.9 37.2 260 16 8 8.9 4.9 32.0 89.5 -1.5 904 4.6
14000 4.3 39.7 260 17 9 8.9 4.9 31.8 89.3 -1.7 850 4.3
13500 5.6 42.1 260 17 9 8.8 4.8 31.7 89.0 -1.9 795 4.0
13000 6.9 44.4 255 18 9 9.6 5.2 31.6 88.8 -2.0 740 3.8
12500 8.4 47.1 255 18 9 9.6 5.3 31.5 88.8 -2.0 682 3.5
12000 9.8 49.6 260 17 9 9.6 5.3 31.5 88.8 -2.0 624 3.2
11500 11.2 52.2 260 18 9 9.6 5.3 31.5 88.7 -2.1 566 2.9
11000 12.7 54.9 255 17 9 9.6 5.3 31.5 88.7 -2.1 508 2.6
10500 14.1 57.4 260 16 8 9.7 5.3 31.4 88.6 -2.2 451 2.3
10250 14.8 58.6 260 16 8 9.3 5.1 31.4 88.5 -2.2 422 2.1
10000 15.5 59.9 270 18 9 8.7 4.8 31.3 88.4 -2.3 394 2.0
9750 16.1 61.0 270 18 9 8.7 4.8 31.3 88.3 -2.3 367 1.9
9500 16.8 62.2 270 18 9 8.7 4.8 31.2 88.1 -2.4 340 1.7
9250 17.4 63.3 265 19 10 8.7 4.8 31.1 88.0 -2.5 313 1.6
9000 18.1 64.6 265 20 10 8.7 4.8 31.0 87.9 -2.6 286 1.5
8750 18.8 65.8 265 20 10 8.7 4.8 30.9 87.7 -2.7 259 1.3
8500 19.4 66.9 265 19 10 8.7 4.8 30.9 87.5 -2.8 232 1.2
8250 20.1 68.2 260 18 9 8.7 4.7 30.8 87.4 -2.9 205 1.0
8000 20.7 69.3 260 17 9 8.9 4.9 30.7 87.2 -2.9 178 0.9
7750 21.4 70.5 260 17 9 8.1 4.4 30.6 87.1 -3.0 151 0.8
7500 21.9 71.4 265 16 8 6.7 3.7 30.4 86.7 -3.2 128 0.6
7250 22.4 72.3 275 15 7 6.5 3.5 30.2 86.3 -3.5 106 0.5
7000 22.9 73.2 285 14 7 6.5 3.6 29.9 85.8 -3.8 84 0.4
6750 23.3 73.9 290 15 8 6.5 3.6 29.7 85.4 -4.0 62 0.3
6500 23.8 74.8 300 16 8 6.6 3.6 29.4 84.9 -4.3 41 0.2
6250 24.2 75.6 310 17 9 1.2 0.7 29.0 84.3 -4.7 23 0.1
6000 24.1 75.4 320 15 7 1.3 0.7 28.2 82.8 -5.5 19 0.1
5750 24.4 75.9 325 14 7 5.0 2.8 27.8 82.1 -6.0 2 0.0
5500 24.7 76.5 335 13 7 6.9 3.8 27.5 81.5 -6.4 M M
5250 25.3 77.5 340 12 6 5.1 2.8 27.3 81.2 -6.6 M M
5000 25.1 77.2 010 8 4 -12.0 -6.6 26.4 79.5 -7.5 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/17/2025 at 0900 MDT | 06/17/2025 at 1200 MDT
|
CAPE... +39.8 LI... +0.8 | CAPE... +137.0 LI... -0.8
CINH... -39.2 K Index... +13.9 | CINH... -10.9 K Index... +18.8
|
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 -59.8 -75.6 285 33 17 1.9 1.0 | -59.4 -74.9 295 34 18 2.1 1.2
45000 -56.3 -69.3 290 47 24 4.0 2.2 | -55.9 -68.6 305 46 24 3.0 1.7
40000 -50.2 -58.4 285 51 26 3.8 2.1 | -51.4 -60.5 305 59 31 3.3 1.8
38000 -48.2 -54.8 285 54 28 2.9 1.6 | -48.8 -55.8 305 58 30 3.9 2.1
36000 -46.5 -51.7 285 57 29 2.8 1.5 | -46.5 -51.7 305 56 29 3.9 2.1
34000 -43.7 -46.7 285 57 29 5.9 3.2 | -43.3 -45.9 300 54 28 6.0 3.3
32000 -40.1 -40.2 285 55 28 5.9 3.2 | -39.7 -39.5 300 51 26 6.0 3.3
30000 -36.4 -33.5 285 50 26 6.4 3.5 | -35.7 -32.3 300 48 25 7.1 3.9
29000 -34.5 -30.1 280 47 24 6.4 3.5 | -33.6 -28.5 295 47 24 7.1 3.9
28000 -32.6 -26.7 280 44 22 6.4 3.5 | -31.5 -24.7 295 45 23 7.1 3.9
27000 -30.8 -23.4 280 39 20 5.6 3.1 | -29.4 -20.9 295 43 22 6.8 3.7
26000 -29.2 -20.6 275 34 17 5.7 3.1 | -27.4 -17.3 290 40 21 6.8 3.7
25000 -27.5 -17.5 270 29 15 5.8 3.2 | -25.4 -13.7 290 37 19 6.8 3.7
24000 -24.8 -12.6 265 27 14 8.6 4.7 | -23.0 -9.4 285 32 17 6.1 3.3
23000 -22.3 -8.1 265 27 14 8.6 4.7 | -21.2 -6.2 280 29 15 6.1 3.4
22000 -19.7 -3.5 265 28 14 8.6 4.7 | -19.4 -2.9 275 25 13 6.0 3.3
21000 -17.0 1.4 270 28 15 9.3 5.1 | -17.0 1.4 275 23 12 8.6 4.7
20000 -14.3 6.3 270 28 15 9.3 5.1 | -14.5 5.9 275 22 11 8.6 4.7
19500 -12.9 8.8 270 28 15 9.3 5.1 | -13.2 8.2 275 21 11 8.7 4.7
19000 -11.5 11.3 270 28 14 9.5 5.2 | -11.9 10.6 280 20 10 9.1 5.0
18500 -10.1 13.8 270 28 14 9.5 5.2 | -10.6 12.9 280 20 10 9.2 5.0
18000 -8.7 16.3 270 27 14 9.5 5.2 | -9.2 15.4 280 19 10 9.2 5.1
17500 -7.2 19.0 270 27 14 9.4 5.2 | -7.9 17.8 280 18 9 9.3 5.1
17000 -5.8 21.6 270 26 13 9.4 5.2 | -6.5 20.3 285 18 9 9.3 5.1
16500 -4.4 24.1 270 25 13 9.3 5.1 | -5.1 22.8 285 17 9 9.4 5.1
16000 -3.1 26.4 270 23 12 9.3 5.1 | -3.7 25.3 285 17 9 9.4 5.1
15500 -1.7 28.9 270 22 11 9.3 5.1 | -2.3 27.9 290 16 8 9.4 5.2
15000 -0.3 31.5 270 20 10 9.3 5.1 | -0.9 30.4 290 15 8 9.5 5.2
14500 1.1 34.0 270 19 10 9.3 5.1 | 0.5 32.9 290 15 8 9.5 5.2
14000 2.4 36.3 270 17 9 9.1 5.0 | 1.9 35.4 290 14 7 9.3 5.1
13500 3.8 38.8 265 16 8 9.1 5.0 | 3.2 37.8 295 13 7 9.3 5.1
13000 5.2 41.4 265 15 8 9.3 5.1 | 4.6 40.3 295 13 6 9.2 5.1
12500 6.5 43.7 265 14 7 9.3 5.1 | 6.0 42.8 300 12 6 9.3 5.1
12000 7.9 46.2 270 13 7 8.4 4.6 | 7.4 45.3 300 11 6 9.2 5.1
11500 9.1 48.4 270 12 6 8.5 4.6 | 8.7 47.7 305 11 5 9.3 5.1
11000 10.3 50.5 275 11 6 6.5 3.5 | 10.0 50.0 310 10 5 7.7 4.2
10500 11.2 52.2 275 10 5 6.1 3.3 | 11.1 52.0 315 9 5 8.4 4.6
10250 11.7 53.1 280 10 5 9.7 5.3 | 11.9 53.4 315 9 5 12.2 6.7
10000 12.6 54.7 285 8 4 9.8 5.4 | 12.8 55.0 315 9 5 11.2 6.2
9750 13.1 55.6 290 8 4 7.0 3.8 | 13.5 56.3 320 9 5 8.8 4.8
9500 13.7 56.7 295 7 4 8.2 4.5 | 14.2 57.6 320 9 5 9.7 5.3
9250 14.3 57.7 300 7 3 6.3 3.4 | 14.9 58.8 320 9 5 8.4 4.6
9000 14.7 58.5 305 6 3 6.5 3.6 | 15.5 59.9 320 8 4 9.1 5.0
8750 15.3 59.5 310 6 3 8.2 4.5 | 16.3 61.3 320 8 4 10.6 5.8
8500 16.5 61.7 320 5 3 6.5 3.6 | 17.8 64.0 320 8 4 8.8 4.8
8250 16.9 62.4 330 5 3 5.9 3.2 | 18.4 65.1 320 8 4 8.9 4.9
8000 17.4 63.3 335 5 2 7.4 4.1 | 19.2 66.6 320 8 4 11.2 6.1
7750 17.9 64.2 335 5 2 7.9 4.4 | 20.0 68.0 320 8 4 11.3 6.2
7500 18.5 65.3 340 5 3 5.8 3.2 | 20.8 69.4 320 8 4 8.7 4.8
7250 18.8 65.8 345 4 2 4.6 2.5 | 21.3 70.3 320 8 4 7.4 4.1
7000 19.3 66.7 350 4 2 8.6 4.7 | 22.0 71.6 320 7 4 11.1 6.1
6750 20.0 68.0 345 4 2 10.1 5.5 | 22.9 73.2 320 7 4 12.0 6.6
6500 20.7 69.3 345 3 2 9.1 5.0 | 23.8 74.8 320 7 4 10.9 6.0
6250 21.4 70.5 350 3 2 9.2 5.1 | 24.6 76.3 320 7 4 11.2 6.1
6000 22.1 71.8 355 3 1 8.0 4.4 | 25.4 77.7 315 7 3 8.2 4.5
5750 22.7 72.9 340 3 1 11.5 6.3 | 26.0 78.8 320 6 3 13.9 7.6
5500 24.6 76.3 345 2 1 50.6 27.8 | 29.2 84.6 320 6 3 90.7 49.7
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
06/17/2025 at 1500 MDT | 06/17/2025 at 1800 MDT
|
CAPE... +42.0 LI... -0.5 | CAPE... +0.7 LI... +0.5
CINH... -3.5 K Index... +14.5 | CINH... 0.0 K Index... +11.2
|
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 -60.6 -77.1 310 40 21 1.8 1.0 | -61.8 -79.2 305 41 21 2.1 1.1
45000 -57.4 -71.3 315 58 30 3.3 1.8 | -58.1 -72.6 315 55 29 3.7 2.0
40000 -52.1 -61.8 315 66 34 5.3 2.9 | -52.0 -61.6 320 65 33 5.6 3.1
38000 -49.0 -56.2 315 62 32 5.1 2.8 | -48.7 -55.7 320 64 33 5.5 3.0
36000 -45.9 -50.6 310 58 30 5.1 2.8 | -45.4 -49.7 320 63 32 5.6 3.1
34000 -42.0 -43.6 315 57 29 7.2 4.0 | -41.5 -42.7 320 60 31 6.9 3.8
32000 -37.6 -35.7 315 56 29 7.2 4.0 | -37.3 -35.1 320 57 29 6.9 3.8
30000 -33.3 -27.9 320 53 27 7.1 3.9 | -33.0 -27.4 320 52 27 7.4 4.1
29000 -31.2 -24.2 320 51 26 7.1 3.9 | -30.8 -23.4 320 49 25 7.4 4.1
28000 -29.1 -20.4 320 48 25 7.2 3.9 | -28.6 -19.5 320 47 24 7.5 4.1
27000 -27.2 -17.0 315 45 23 5.9 3.2 | -26.5 -15.7 315 45 23 6.8 3.7
26000 -25.4 -13.7 315 42 22 5.9 3.2 | -23.9 -11.0 315 42 22 6.8 3.7
25000 -23.2 -9.8 310 38 20 5.8 3.2 | -21.9 -7.4 315 41 21 6.9 3.8
24000 -21.4 -6.5 305 34 18 6.2 3.4 | -20.0 -4.0 310 38 19 6.2 3.4
23000 -19.6 -3.3 305 30 16 6.3 3.5 | -18.1 -0.6 310 35 18 6.2 3.4
22000 -17.7 0.1 305 26 14 6.4 3.5 | -16.3 2.7 305 32 16 6.3 3.5
21000 -15.6 3.9 305 23 12 7.6 4.1 | -14.2 6.4 300 28 14 7.1 3.9
20000 -13.3 8.1 305 20 11 7.6 4.2 | -12.2 10.0 295 23 12 7.2 4.0
19500 -12.2 10.0 305 19 10 7.5 4.1 | -11.2 11.8 290 21 11 7.3 4.0
19000 -11.0 12.2 305 18 9 8.8 4.8 | -10.0 14.0 290 19 10 8.5 4.7
18500 -9.7 14.5 305 17 9 8.9 4.9 | -8.8 16.2 290 19 10 8.6 4.7
18000 -8.4 16.9 305 17 9 9.0 4.9 | -7.5 18.5 295 18 9 8.7 4.8
17500 -7.0 19.4 305 16 8 9.2 5.0 | -6.1 21.0 295 17 9 9.0 4.9
17000 -5.7 21.7 305 16 8 9.2 5.0 | -4.8 23.4 300 16 8 9.0 4.9
16500 -4.3 24.3 305 16 8 9.4 5.2 | -3.4 25.9 300 16 8 9.4 5.1
16000 -2.9 26.8 305 15 8 9.4 5.2 | -2.0 28.4 300 15 8 9.4 5.1
15500 -1.5 29.3 305 15 8 9.5 5.2 | -0.6 30.9 305 15 8 9.4 5.2
15000 -0.1 31.8 305 15 8 9.5 5.2 | 0.8 33.4 305 15 8 9.4 5.2
14500 1.3 34.3 305 15 8 9.5 5.2 | 2.2 36.0 305 15 8 9.5 5.2
14000 2.7 36.9 305 15 8 9.5 5.2 | 3.6 38.5 305 15 7 9.6 5.2
13500 4.2 39.6 305 15 7 9.5 5.2 | 5.1 41.2 310 14 7 9.6 5.2
13000 5.6 42.1 305 14 7 9.5 5.2 | 6.5 43.7 310 14 7 9.5 5.2
12500 7.0 44.6 305 14 7 9.4 5.2 | 7.9 46.2 310 14 7 9.5 5.2
12000 8.4 47.1 305 14 7 9.7 5.3 | 9.3 48.7 310 14 7 9.6 5.2
11500 9.8 49.6 305 14 7 9.9 5.4 | 10.8 51.4 310 14 7 9.7 5.3
11000 11.2 52.2 305 14 7 8.0 4.4 | 12.1 53.8 310 14 7 8.0 4.4
10500 12.4 54.3 305 14 7 9.2 5.1 | 13.3 55.9 310 14 7 9.1 5.0
10250 13.2 55.8 305 14 7 12.7 7.0 | 14.1 57.4 310 14 7 12.2 6.7
10000 14.1 57.4 305 14 7 11.2 6.1 | 15.0 59.0 315 14 7 10.8 5.9
9750 14.8 58.6 305 14 7 9.2 5.0 | 15.7 60.3 315 14 7 8.9 4.9
9500 15.6 60.1 305 13 7 10.1 5.5 | 16.4 61.5 315 13 7 9.7 5.3
9250 16.3 61.3 305 13 7 8.5 4.7 | 17.1 62.8 310 13 7 8.4 4.6
9000 16.9 62.4 310 13 7 9.1 5.0 | 18.4 65.1 310 13 7 10.2 5.6
8750 18.4 65.1 310 13 7 10.8 5.9 | 19.2 66.6 315 13 7 10.3 5.6
8500 19.2 66.6 310 13 7 9.0 4.9 | 19.9 67.8 315 13 7 8.7 4.8
8250 19.8 67.6 310 13 6 9.2 5.0 | 20.5 68.9 315 13 7 8.9 4.9
8000 20.6 69.1 310 12 6 11.2 6.1 | 21.3 70.3 315 13 6 10.5 5.8
7750 21.4 70.5 310 12 6 11.1 6.1 | 22.1 71.8 315 12 6 10.5 5.8
7500 22.2 72.0 310 12 6 8.7 4.8 | 22.8 73.0 315 12 6 8.8 4.8
7250 22.8 73.0 310 12 6 7.7 4.2 | 23.4 74.1 315 12 6 8.0 4.4
7000 23.5 74.3 310 11 6 11.2 6.1 | 24.1 75.4 315 12 6 10.5 5.7
6750 24.4 75.9 310 11 6 11.9 6.5 | 24.9 76.8 315 11 6 11.1 6.1
6500 25.2 77.4 310 11 6 10.8 5.9 | 25.7 78.3 315 11 6 10.6 5.8
6250 26.0 78.8 310 10 5 11.2 6.1 | 26.5 79.7 315 11 6 11.0 6.0
6000 26.8 80.2 310 10 5 8.0 4.4 | 27.3 81.1 315 11 6 8.2 4.5
5750 27.4 81.3 310 10 5 13.7 7.5 | 27.9 82.2 315 10 5 10.2 5.6
5500 30.6 87.1 310 9 4 91.1 50.0 | 30.0 86.0 320 9 5 59.8 32.8
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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