Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
459
UXUS97 KGJT 031306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Thursday, July 3, 2025
This forecast is for Thursday, July 3, 2025:
If the trigger temperature of 71.5 F/22.0 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 780 ft/min (4.0 m/s)
Maximum height of thermals.................. 17170 ft MSL (11561 ft AGL)
Forecast maximum temperature................... 85.0 F/29.9 C
Time of trigger temperature.................... 0745 MDT
Time of overdevelopment........................ 1000 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................. 13951 ft MSL (8342 ft AGL)
Thermal soaring outlook for Friday 07/04....... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 05:53:13 / 20:43:48 MDT
Total possible sunshine........... 14 hr 50 min 35 sec (890 min 35 sec)
Altitude of sun at 13:18:30 MDT... 73.30 degrees
Upper air data from rawinsonde observation taken on 07/03/2025 at 0600 MDT
Freezing level.................. 14454 ft MSL (8845 ft AGL)
Convective condensation level... 12315 ft MSL (6706 ft AGL)
Lifted condensation level....... 14064 ft MSL (8455 ft AGL)
Lifted index.................... -4.9
K index......................... +28.1
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 -62.4 -80.3 220 28 15 3.3 1.8 M M M M M
45000 -56.1 -69.0 225 37 19 5.5 3.0 M M M M M
40000 -48.0 -54.4 230 41 21 4.8 2.6 M M M M M
38000 -45.1 -49.2 235 38 20 4.8 2.6 M M M M M
36000 -42.3 -44.1 235 36 18 4.7 2.6 M M M M M
34000 -38.9 -38.0 235 32 17 5.9 3.2 M M M M M
32000 -34.9 -30.8 235 28 14 5.6 3.1 M M M M M
30000 -30.4 -22.7 240 26 14 7.9 4.3 44.9 112.9 11.8 M M
29000 -28.1 -18.6 245 26 13 7.9 4.3 44.3 111.7 11.4 M M
28000 -25.7 -14.3 250 25 13 7.2 3.9 43.7 110.7 11.1 M M
27000 -23.8 -10.8 250 24 12 6.3 3.5 42.3 108.1 10.1 M M
26000 -22.0 -7.6 250 22 11 6.3 3.5 41.0 105.7 9.1 M M
25000 -20.1 -4.2 250 20 10 6.3 3.5 39.8 103.6 8.2 M M
24000 -18.1 -0.6 255 19 10 6.9 3.8 38.7 101.6 7.3 M M
23000 -16.1 3.0 255 18 9 6.9 3.8 37.6 99.7 6.5 M M
22000 -14.0 6.8 260 16 8 7.1 3.9 36.7 98.0 5.8 M M
21000 -12.2 10.0 265 14 7 6.2 3.4 35.4 95.8 4.8 M M
20000 -10.3 13.5 265 12 6 6.2 3.4 34.2 93.5 3.7 M M
19500 -9.4 15.1 265 11 6 6.2 3.4 33.6 92.5 3.2 M M
19000 -8.5 16.7 270 10 5 5.6 3.0 33.0 91.4 2.7 M M
18500 -7.4 18.7 280 10 5 5.2 2.8 31.8 89.2 1.6 M M
18000 -6.6 20.1 290 10 5 5.6 3.1 31.0 87.9 1.0 M M
17500 -5.8 21.6 295 11 5 5.8 3.2 30.4 86.6 0.3 M M
17000 -5.0 23.0 305 12 6 5.9 3.2 29.7 85.5 -0.3 959 4.9
16500 -4.1 24.6 305 13 6 6.9 3.8 29.2 84.5 -0.9 917 4.7
16000 -3.1 26.4 305 14 7 6.8 3.7 28.7 83.6 -1.4 873 4.4
15500 -2.1 28.2 310 15 7 7.3 4.0 28.2 82.8 -1.9 829 4.2
15000 -1.1 30.0 305 15 8 7.4 4.1 27.8 82.1 -2.3 782 4.0
14500 -0.0 32.0 305 16 8 7.7 4.2 27.5 81.4 -2.7 735 3.7
14000 1.1 34.0 300 17 9 8.0 4.4 27.2 80.9 -3.0 686 3.5
13500 2.3 36.1 300 18 9 8.2 4.5 26.9 80.4 -3.3 637 3.2
13000 3.5 38.3 295 18 9 8.6 4.7 26.7 80.0 -3.6 585 3.0
12500 4.8 40.6 295 18 9 8.4 4.6 26.5 79.7 -3.8 533 2.7
12000 5.9 42.6 290 18 9 7.0 3.8 26.1 79.0 -4.2 485 2.5
11500 6.9 44.4 285 17 9 7.0 3.8 25.7 78.3 -4.6 440 2.2
11000 7.7 45.9 280 16 8 5.2 2.9 25.1 77.2 -5.3 400 2.0
10500 8.5 47.3 275 15 8 7.1 3.9 24.4 75.9 -6.0 363 1.8
10250 9.0 48.2 270 15 8 7.2 4.0 24.3 75.7 -6.2 339 1.7
10000 9.4 48.9 265 14 7 5.0 2.7 23.9 75.1 -6.6 320 1.6
9750 9.8 49.6 265 13 7 5.7 3.1 23.6 74.5 -6.9 302 1.5
9500 10.1 50.2 260 13 7 5.1 2.8 23.3 73.9 -7.3 283 1.4
9250 10.5 50.9 260 12 6 5.5 3.0 22.9 73.2 -7.7 265 1.3
9000 10.9 51.6 260 11 6 6.2 3.4 22.6 72.7 -8.0 245 1.2
8750 11.3 52.3 255 10 5 6.0 3.3 22.3 72.2 -8.3 225 1.1
8500 11.8 53.2 255 9 5 5.8 3.2 22.0 71.7 -8.7 205 1.0
8250 12.2 54.0 250 8 4 5.6 3.1 21.7 71.1 -9.0 186 0.9
8000 12.6 54.7 245 7 3 5.7 3.2 21.4 70.5 -9.4 167 0.8
7750 13.0 55.4 235 5 3 6.0 3.3 21.1 70.0 -9.7 147 0.7
7500 13.4 56.1 225 4 2 5.5 3.0 20.8 69.5 -10.0 127 0.6
7250 13.7 56.7 205 4 2 4.9 2.7 20.5 68.8 -10.5 110 0.6
7000 14.0 57.2 190 4 2 5.1 2.8 20.1 68.2 -10.9 92 0.5
6750 14.4 57.9 175 4 2 4.9 2.7 19.7 67.5 -11.3 75 0.4
6500 14.7 58.5 165 4 2 4.3 2.4 19.4 66.8 -11.7 58 0.3
6250 15.0 59.0 155 4 2 3.2 1.8 18.9 66.0 -12.2 43 0.2
6000 15.2 59.4 145 5 2 6.1 3.3 18.5 65.3 -12.7 27 0.1
5750 15.6 60.1 140 5 2 1.4 0.8 18.2 64.7 -13.1 8 0.0
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 * * * * * *
07/03/2025 at 0900 MDT | 07/03/2025 at 1200 MDT
|
CAPE... +73.8 LI... -0.7 | CAPE... +113.6 LI... -1.2
CINH... -38.9 K Index... +29.1 | CINH... -27.3 K Index... +30.1
|
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 -63.3 -81.9 210 26 14 3.0 1.6 | -63.1 -81.6 200 29 15 2.7 1.5
45000 -57.3 -71.1 210 37 19 5.3 2.9 | -57.3 -71.1 200 42 22 5.5 3.0
40000 -49.4 -56.9 215 50 26 4.8 2.6 | -49.2 -56.6 210 52 27 4.2 2.3
38000 -46.5 -51.7 215 45 23 4.8 2.6 | -46.7 -52.1 210 48 25 4.2 2.3
36000 -43.7 -46.7 210 40 21 4.4 2.4 | -44.2 -47.6 205 44 23 3.6 2.0
34000 -39.0 -38.2 200 34 17 8.2 4.5 | -39.3 -38.7 200 40 21 8.6 4.7
32000 -34.0 -29.2 190 28 15 8.0 4.4 | -34.1 -29.4 195 36 19 8.4 4.6
30000 -29.4 -20.9 185 26 13 7.5 4.1 | -29.4 -20.9 195 34 17 7.8 4.3
29000 -27.2 -17.0 180 25 13 7.5 4.1 | -27.1 -16.8 190 32 17 7.8 4.3
28000 -24.9 -12.8 180 24 12 7.4 4.0 | -24.7 -12.5 190 31 16 7.6 4.2
27000 -22.4 -8.3 180 23 12 6.9 3.8 | -22.1 -7.8 190 29 15 7.0 3.9
26000 -20.3 -4.5 175 22 12 6.9 3.8 | -20.1 -4.2 185 28 14 7.0 3.9
25000 -18.2 -0.8 175 22 11 6.8 3.7 | -18.0 -0.4 185 26 13 7.0 3.8
24000 -16.4 2.5 175 21 11 6.3 3.5 | -16.0 3.2 180 25 13 6.6 3.6
23000 -14.5 5.9 180 20 10 6.3 3.5 | -14.1 6.6 180 24 13 6.6 3.6
22000 -12.7 9.1 180 19 10 6.4 3.5 | -12.2 10.0 175 24 12 6.4 3.5
21000 -10.8 12.6 180 18 9 6.4 3.5 | -10.4 13.3 170 22 12 6.0 3.3
20000 -8.9 16.0 180 16 8 6.4 3.5 | -8.7 16.3 165 21 11 6.0 3.3
19500 -8.0 17.6 180 15 8 6.5 3.6 | -7.8 18.0 165 21 11 6.0 3.3
19000 -7.1 19.2 180 15 7 6.1 3.3 | -6.9 19.6 160 20 10 6.0 3.3
18500 -6.2 20.8 180 14 7 6.1 3.4 | -6.0 21.2 155 19 10 6.0 3.3
18000 -5.3 22.5 180 13 7 6.4 3.5 | -5.2 22.6 155 18 9 6.1 3.3
17500 -4.4 24.1 180 12 6 6.7 3.7 | -4.3 24.3 150 17 9 6.1 3.4
17000 -3.4 25.9 180 11 6 6.7 3.7 | -3.4 25.9 145 16 8 6.1 3.3
16500 -2.4 27.7 175 10 5 7.3 4.0 | -2.5 27.5 140 15 8 6.5 3.6
16000 -1.3 29.7 175 9 5 7.3 4.0 | -1.6 29.1 140 13 7 6.6 3.6
15500 -0.3 31.5 175 8 4 7.8 4.3 | -0.6 30.9 140 12 6 6.9 3.8
15000 0.9 33.6 175 7 4 8.0 4.4 | 0.4 32.7 140 11 5 7.1 3.9
14500 2.1 35.8 170 7 3 8.1 4.4 | 1.4 34.5 140 9 5 7.3 4.0
14000 3.2 37.8 170 6 3 8.2 4.5 | 2.5 36.5 140 8 4 7.6 4.2
13500 4.4 39.9 170 6 3 8.1 4.5 | 3.6 38.5 140 6 3 7.6 4.2
13000 5.6 42.1 175 5 3 7.8 4.3 | 4.7 40.5 145 5 3 7.3 4.0
12500 6.7 44.1 180 4 2 7.8 4.3 | 5.8 42.4 160 4 2 7.3 4.0
12000 7.9 46.2 185 4 2 7.4 4.1 | 6.8 44.2 190 3 1 7.4 4.0
11500 9.0 48.2 195 3 1 7.5 4.1 | 7.9 46.2 230 3 2 7.5 4.1
11000 10.0 50.0 210 3 1 6.6 3.6 | 8.9 48.0 250 4 2 6.4 3.5
10500 11.0 51.8 220 3 1 6.2 3.4 | 9.8 49.6 260 6 3 6.2 3.4
10250 11.5 52.7 225 3 1 8.7 4.8 | 10.4 50.7 265 7 4 10.1 5.5
10000 12.2 54.0 235 3 2 8.8 4.8 | 11.2 52.2 265 8 4 10.1 5.6
9750 12.7 54.9 235 3 2 6.3 3.5 | 11.8 53.2 265 9 5 6.9 3.8
9500 13.2 55.8 240 4 2 7.2 3.9 | 12.4 54.3 265 10 5 8.1 4.4
9250 13.7 56.7 240 4 2 6.3 3.5 | 13.4 56.1 270 12 6 7.4 4.0
9000 14.7 58.5 235 3 2 6.7 3.7 | 14.0 57.2 270 12 6 9.1 5.0
8750 15.2 59.4 235 3 2 6.8 3.7 | 14.6 58.3 270 13 6 9.1 5.0
8500 15.7 60.3 235 3 2 5.5 3.0 | 15.3 59.5 270 13 7 6.9 3.8
8250 16.0 60.8 240 3 2 5.2 2.8 | 15.7 60.3 270 14 7 7.6 4.2
8000 16.5 61.7 235 3 1 6.5 3.5 | 16.5 61.7 270 14 7 11.1 6.1
7750 16.9 62.4 230 3 1 6.0 3.3 | 17.3 63.1 270 14 7 10.5 5.8
7500 17.3 63.1 230 3 2 3.8 2.1 | 18.0 64.4 270 14 7 7.7 4.2
7250 17.5 63.5 240 3 1 3.6 1.9 | 18.5 65.3 275 15 8 7.1 3.9
7000 17.9 64.2 240 3 1 8.7 4.8 | 19.1 66.4 275 15 8 11.9 6.5
6750 18.7 65.7 225 3 2 9.6 5.3 | 20.1 68.2 270 14 7 12.5 6.9
6500 19.2 66.6 235 3 1 7.2 4.0 | 20.9 69.6 275 14 7 10.2 5.6
6250 19.7 67.5 255 3 1 6.9 3.8 | 21.7 71.1 275 15 8 10.0 5.5
6000 20.3 68.5 265 3 1 10.3 5.6 | 22.5 72.5 275 15 8 10.9 6.0
5750 21.3 70.3 230 2 1 18.8 10.3 | 23.5 74.3 275 13 6 20.7 11.4
5500 22.7 72.9 270 2 1 13.4 7.4 | 26.1 79.0 280 13 7 56.3 30.9
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
07/03/2025 at 1500 MDT | 07/03/2025 at 1800 MDT
|
CAPE... +240.2 LI... -1.5 | CAPE... +371.3 LI... -1.6
CINH... -44.1 K Index... +29.2 | CINH... -29.4 K Index... +29.8
|
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 -62.6 -80.7 205 29 15 3.3 1.8 | -62.6 -80.7 205 30 16 3.2 1.7
45000 -57.1 -70.8 205 46 24 3.9 2.2 | -57.1 -70.8 205 46 23 4.2 2.3
40000 -50.8 -59.4 200 53 28 6.1 3.3 | -50.6 -59.1 195 46 23 5.8 3.2
38000 -47.2 -53.0 195 51 26 6.1 3.4 | -47.1 -52.8 190 42 22 5.8 3.2
36000 -43.0 -45.4 190 49 25 6.8 3.7 | -43.2 -45.8 175 40 20 6.7 3.7
34000 -38.0 -36.4 190 45 23 8.4 4.6 | -38.0 -36.4 175 39 20 8.8 4.8
32000 -33.0 -27.4 195 40 21 8.3 4.6 | -32.8 -27.0 175 39 20 8.7 4.8
30000 -28.6 -19.5 195 36 18 7.3 4.0 | -28.1 -18.6 180 36 18 7.7 4.2
29000 -26.4 -15.5 195 33 17 7.3 4.0 | -25.8 -14.4 180 34 17 7.7 4.2
28000 -24.2 -11.6 195 31 16 7.4 4.0 | -23.6 -10.5 185 32 16 7.0 3.8
27000 -22.0 -7.6 195 31 16 7.4 4.1 | -21.7 -7.1 190 29 15 6.4 3.5
26000 -19.9 -3.8 195 32 16 7.4 4.1 | -19.8 -3.6 190 27 14 6.4 3.5
25000 -17.7 0.1 195 32 16 7.6 4.2 | -17.9 -0.2 195 25 13 6.3 3.5
24000 -15.7 3.7 195 30 16 6.7 3.7 | -15.9 3.4 200 24 12 7.0 3.9
23000 -13.7 7.3 195 28 15 6.7 3.7 | -13.9 7.0 205 24 12 7.1 3.9
22000 -11.3 11.7 190 26 13 6.3 3.5 | -11.3 11.7 205 24 12 6.5 3.6
21000 -9.6 14.7 185 24 12 5.9 3.2 | -9.6 14.7 210 23 12 5.9 3.2
20000 -7.9 17.8 185 22 11 5.9 3.2 | -7.9 17.8 210 23 12 6.0 3.3
19500 -7.1 19.2 180 21 11 6.0 3.3 | -7.1 19.2 210 22 11 6.0 3.3
19000 -6.3 20.7 180 20 10 5.4 3.0 | -6.2 20.8 210 22 11 5.9 3.3
18500 -5.5 22.1 175 19 10 5.5 3.0 | -5.4 22.3 210 21 11 5.9 3.3
18000 -4.7 23.5 175 18 9 5.5 3.0 | -4.5 23.9 210 20 11 5.8 3.2
17500 -3.9 25.0 170 18 9 5.5 3.0 | -3.7 25.3 210 20 10 5.7 3.1
17000 -3.1 26.4 165 17 9 5.4 3.0 | -2.9 26.8 210 19 10 5.7 3.1
16500 -2.3 27.9 160 17 9 6.1 3.4 | -2.1 28.2 205 18 9 5.6 3.1
16000 -1.4 29.5 160 17 9 6.0 3.3 | -1.3 29.7 205 18 9 5.7 3.1
15500 -0.5 31.1 155 16 8 6.7 3.7 | -0.5 31.1 205 17 9 5.6 3.1
15000 0.5 32.9 155 15 8 7.0 3.9 | 0.3 32.5 205 16 8 5.6 3.1
14500 1.6 34.9 155 14 7 7.0 3.9 | 1.1 34.0 200 15 8 5.8 3.2
14000 2.6 36.7 155 12 6 7.0 3.8 | 2.0 35.6 200 15 8 6.3 3.5
13500 3.6 38.5 155 10 5 7.0 3.9 | 2.9 37.2 195 14 7 6.3 3.5
13000 4.6 40.3 160 8 4 7.4 4.1 | 3.8 38.8 195 13 7 6.7 3.7
12500 5.7 42.3 170 6 3 7.4 4.1 | 4.8 40.6 195 12 6 6.8 3.7
12000 6.7 44.1 185 5 3 7.2 3.9 | 5.7 42.3 195 11 6 6.5 3.5
11500 7.7 45.9 210 5 2 7.4 4.0 | 6.6 43.9 195 10 5 6.5 3.6
11000 8.7 47.7 235 5 3 5.6 3.1 | 7.5 45.5 195 9 4 6.3 3.5
10500 9.5 49.1 255 6 3 5.6 3.1 | 8.4 47.1 195 8 4 6.4 3.5
10250 9.9 49.8 260 7 4 6.2 3.4 | 8.9 48.0 195 7 4 6.0 3.3
10000 10.3 50.5 260 9 4 6.2 3.4 | 9.3 48.7 195 7 3 5.8 3.2
9750 10.7 51.3 260 10 5 5.8 3.2 | 9.7 49.5 195 6 3 6.2 3.4
9500 11.1 52.0 265 10 5 5.4 3.0 | 10.2 50.4 195 6 3 5.3 2.9
9250 11.5 52.7 265 11 6 7.4 4.1 | 10.6 51.1 195 5 3 8.5 4.7
9000 12.1 53.8 275 12 6 7.1 3.9 | 11.3 52.3 200 5 2 7.8 4.3
8750 12.5 54.5 270 13 7 4.9 2.7 | 11.6 52.9 205 4 2 4.2 2.3
8500 12.9 55.2 270 14 7 5.3 2.9 | 12.0 53.6 215 3 2 5.2 2.8
8250 13.3 55.9 270 16 8 6.5 3.6 | 12.8 55.0 230 3 1 6.7 3.7
8000 14.4 57.9 275 17 9 8.4 4.6 | 13.2 55.8 230 3 1 7.4 4.1
7750 15.0 59.0 270 17 9 8.6 4.7 | 13.8 56.8 235 2 1 7.4 4.0
7500 15.6 60.1 270 18 9 8.8 4.8 | 14.2 57.6 235 2 1 6.4 3.5
7250 16.3 61.3 270 18 9 9.2 5.0 | 14.7 58.5 225 2 1 6.5 3.5
7000 17.0 62.6 270 18 9 10.2 5.6 | 15.2 59.4 220 2 1 9.9 5.4
6750 17.8 64.0 270 17 9 11.2 6.2 | 16.0 60.8 225 2 1 10.3 5.6
6500 18.6 65.5 270 17 9 11.6 6.4 | 16.6 61.9 220 1 1 8.4 4.6
6250 19.5 67.1 270 17 9 11.3 6.2 | 17.3 63.1 205 1 1 8.2 4.5
6000 20.3 68.5 270 17 9 11.4 6.2 | 17.9 64.2 190 1 1 10.2 5.6
5750 21.3 70.3 270 15 8 20.9 11.5 | 18.8 65.8 210 1 1 15.7 8.6
5500 24.1 75.4 275 15 8 58.5 32.1 | 19.9 67.8 165 1 0 13.9 7.6
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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