Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
490
UXUS97 KGJT 191307
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
707 AM MDT Saturday, July 19, 2025
This forecast is for Saturday, July 19, 2025:
If the trigger temperature of 82.6 F/28.1 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1471 ft/min (7.5 m/s)
Maximum height of thermals.................. 21104 ft MSL (15495 ft AGL)
Forecast maximum temperature................... 95.0 F/35.5 C
Time of trigger temperature.................... 1000 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................. 17851 ft MSL (12243 ft AGL)
Thermal soaring outlook for Sunday 07/20....... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:04:08 / 20:36:53 MDT
Total possible sunshine........... 14 hr 32 min 45 sec (872 min 45 sec)
Altitude of sun at 13:20:31 MDT... 71.05 degrees
Upper air data from rawinsonde observation taken on 07/19/2025 at 0600 MDT
Freezing level.................. 15670 ft MSL (10061 ft AGL)
Convective condensation level... 17223 ft MSL (11614 ft AGL)
Lifted condensation level....... 18894 ft MSL (13286 ft AGL)
Lifted index.................... -3.1
K index......................... +23.8
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 -65.0 -85.0 235 23 12 1.1 0.6 M M M M M
45000 -60.2 -76.4 230 38 19 6.6 3.6 M M M M M
40000 -50.3 -58.5 225 49 25 6.7 3.7 M M M M M
38000 -46.3 -51.3 230 50 26 6.7 3.7 M M M M M
36000 -42.3 -44.1 230 51 26 6.7 3.7 M M M M M
34000 -37.7 -35.9 230 50 26 7.8 4.3 M M M M M
32000 -32.5 -26.5 235 49 25 7.7 4.2 M M M M M
30000 -28.6 -19.5 235 44 23 6.4 3.5 46.5 115.7 8.8 M M
29000 -26.7 -16.1 235 42 22 6.4 3.5 45.2 113.4 7.9 M M
28000 -24.8 -12.6 240 39 20 5.8 3.2 44.0 111.2 7.1 M M
27000 -23.1 -9.6 240 37 19 5.8 3.2 42.4 108.3 5.8 M M
26000 -21.4 -6.5 240 35 18 5.9 3.2 40.9 105.7 4.7 M M
25000 -19.6 -3.3 240 33 17 6.1 3.4 39.6 103.3 3.7 M M
24000 -17.7 0.1 240 30 16 6.8 3.7 38.4 101.2 2.7 M M
23000 -15.6 3.9 245 27 14 6.8 3.7 37.3 99.2 1.8 M M
22000 -13.6 7.5 245 24 12 6.8 3.7 36.4 97.5 1.0 M M
21000 -11.7 10.9 245 21 11 6.7 3.7 35.2 95.4 -0.0 1469 7.5
20000 -9.7 14.5 245 19 10 6.8 3.7 34.2 93.5 -1.0 1381 7.0
19500 -8.8 16.2 245 17 9 6.8 3.7 33.7 92.7 -1.4 1337 6.8
19000 -7.7 18.1 245 16 8 7.3 4.0 33.3 91.9 -1.9 1292 6.6
18500 -6.7 19.9 245 16 8 7.3 4.0 32.8 91.1 -2.3 1246 6.3
18000 -5.1 22.8 245 15 8 7.2 4.0 32.2 90.0 -3.0 1177 6.0
17500 -4.1 24.6 245 14 7 7.3 4.0 31.8 89.2 -3.4 1131 5.7
17000 -3.0 26.6 245 14 7 7.8 4.3 31.4 88.5 -3.8 1085 5.5
16500 -1.8 28.8 250 13 7 8.3 4.5 31.1 88.0 -4.1 1034 5.3
16000 -0.6 30.9 255 13 6 8.3 4.6 30.9 87.6 -4.4 982 5.0
15500 0.6 33.1 260 12 6 8.8 4.8 30.7 87.2 -4.6 930 4.7
15000 1.9 35.4 265 12 6 8.7 4.8 30.5 86.9 -4.8 877 4.5
14500 3.2 37.8 270 11 6 9.0 5.0 30.4 86.7 -5.0 823 4.2
14000 4.5 40.1 270 11 5 9.0 5.0 30.2 86.4 -5.1 768 3.9
13500 5.9 42.6 275 10 5 9.1 5.0 30.1 86.3 -5.3 713 3.6
13000 7.3 45.1 275 10 5 9.2 5.0 30.1 86.1 -5.4 658 3.3
12500 8.6 47.5 280 9 5 9.2 5.1 30.0 86.0 -5.5 602 3.1
12000 10.0 50.0 280 9 5 9.2 5.1 29.9 85.8 -5.6 546 2.8
11500 11.4 52.5 280 8 4 8.9 4.9 29.8 85.7 -5.7 490 2.5
11000 12.6 54.7 275 8 4 7.9 4.3 29.6 85.2 -6.0 439 2.2
10500 13.9 57.0 275 8 4 10.1 5.5 29.4 85.0 -6.2 385 2.0
10250 14.6 58.3 270 7 4 8.9 4.9 29.4 85.0 -6.2 356 1.8
10000 15.2 59.4 270 7 4 7.7 4.2 29.3 84.7 -6.3 331 1.7
9750 15.8 60.4 270 7 3 8.4 4.6 29.2 84.5 -6.5 306 1.6
9500 16.4 61.5 265 6 3 7.1 3.9 29.0 84.3 -6.6 281 1.4
9250 16.8 62.2 265 6 3 6.9 3.8 28.8 83.8 -6.9 260 1.3
9000 17.4 63.3 265 5 3 7.8 4.3 28.6 83.5 -7.1 236 1.2
8750 17.9 64.2 260 5 2 7.9 4.3 28.5 83.2 -7.3 212 1.1
8500 18.5 65.3 250 4 2 6.5 3.5 28.3 82.9 -7.5 188 1.0
8250 18.9 66.0 245 3 2 5.2 2.9 28.0 82.3 -7.9 169 0.9
8000 19.3 66.7 225 3 2 5.9 3.2 27.6 81.8 -8.2 150 0.8
7750 19.7 67.5 200 3 1 5.9 3.3 27.3 81.2 -8.5 130 0.7
7500 20.1 68.2 180 3 2 5.3 2.9 27.1 80.7 -8.9 110 0.6
7250 20.5 68.9 165 4 2 4.4 2.4 26.7 80.0 -9.3 92 0.5
7000 20.8 69.4 155 5 3 4.3 2.3 26.3 79.3 -9.7 75 0.4
6750 21.1 70.0 150 5 3 3.1 1.7 25.8 78.5 -10.1 59 0.3
6500 21.2 70.2 140 5 3 -0.7 -0.4 25.2 77.3 -10.8 48 0.2
6250 21.0 69.8 130 6 3 -4.4 -2.4 24.2 75.6 -11.7 46 0.2
6000 20.8 69.4 120 6 3 3.3 1.8 23.3 74.0 -12.6 44 0.2
5750 21.1 70.0 115 6 3 -4.0 -2.2 22.9 73.2 -13.1 28 0.1
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 * * * * * *
07/19/2025 at 0900 MDT | 07/19/2025 at 1200 MDT
|
CAPE... +42.0 LI... -1.5 | CAPE... +147.0 LI... -1.9
CINH... -106.9 K Index... +23.2 | CINH... -12.2 K Index... +19.3
|
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 -64.8 -84.6 235 22 11 1.4 0.8 | -65.0 -85.0 230 27 14 1.2 0.7
45000 -60.2 -76.4 240 39 20 5.9 3.2 | -60.4 -76.7 230 43 22 6.1 3.4
40000 -51.0 -59.8 245 51 26 7.7 4.2 | -50.7 -59.3 230 48 25 7.9 4.4
38000 -46.3 -51.3 240 54 28 7.7 4.2 | -45.9 -50.6 230 51 26 7.9 4.4
36000 -41.7 -43.1 235 57 29 7.7 4.2 | -41.2 -42.2 235 53 28 7.7 4.2
34000 -36.3 -33.3 230 57 29 8.0 4.4 | -36.8 -34.2 225 52 27 7.2 4.0
32000 -31.5 -24.7 225 57 29 8.5 4.7 | -32.4 -26.3 220 51 26 7.1 3.9
30000 -27.2 -17.0 225 54 28 7.0 3.8 | -28.3 -18.9 220 50 26 6.9 3.8
29000 -25.1 -13.2 225 52 27 7.0 3.8 | -26.2 -15.2 225 49 25 6.9 3.8
28000 -23.1 -9.6 230 50 26 5.4 2.9 | -24.2 -11.6 225 48 25 6.5 3.6
27000 -21.6 -6.9 230 46 24 5.0 2.7 | -21.8 -7.2 225 45 23 6.2 3.4
26000 -20.1 -4.2 230 42 22 5.0 2.7 | -19.9 -3.8 225 42 22 6.2 3.4
25000 -18.6 -1.5 225 38 19 5.0 2.7 | -18.0 -0.4 230 39 20 5.9 3.2
24000 -17.1 1.2 225 35 18 5.2 2.9 | -16.3 2.7 230 36 19 5.6 3.1
23000 -15.6 3.9 225 33 17 5.3 2.9 | -14.6 5.7 230 34 17 5.6 3.1
22000 -14.0 6.8 230 31 16 5.5 3.0 | -12.9 8.8 230 31 16 5.4 3.0
21000 -11.7 10.9 230 29 15 6.3 3.5 | -11.4 11.5 230 29 15 5.3 2.9
20000 -9.9 14.2 235 27 14 6.4 3.5 | -9.8 14.4 235 27 14 5.3 2.9
19500 -9.0 15.8 240 27 14 6.7 3.7 | -9.0 15.8 235 26 13 5.6 3.1
19000 -8.0 17.6 240 26 13 7.3 4.0 | -8.1 17.4 235 25 13 6.9 3.8
18500 -6.9 19.6 245 25 13 7.3 4.0 | -7.1 19.2 235 24 12 6.9 3.8
18000 -5.9 21.4 245 25 13 7.7 4.2 | -6.1 21.0 240 23 12 7.9 4.3
17500 -4.7 23.5 245 24 13 7.8 4.3 | -4.9 23.2 240 23 12 8.1 4.5
17000 -3.6 25.5 250 24 12 7.9 4.3 | -3.7 25.3 240 22 11 8.3 4.5
16500 -2.4 27.7 245 23 12 8.2 4.5 | -2.5 27.5 240 21 11 8.7 4.8
16000 -1.2 29.8 245 23 12 8.2 4.5 | -1.2 29.8 240 21 11 8.7 4.8
15500 -0.0 32.0 245 23 12 8.5 4.7 | 0.1 32.2 240 20 11 8.8 4.8
15000 1.2 34.2 245 22 12 8.5 4.7 | 1.4 34.5 245 20 10 8.8 4.8
14500 2.5 36.5 245 22 11 8.6 4.7 | 2.6 36.7 245 19 10 8.5 4.7
14000 3.7 38.7 245 22 11 8.6 4.7 | 3.9 39.0 245 19 10 8.5 4.6
13500 5.0 41.0 245 21 11 8.7 4.8 | 5.1 41.2 245 18 9 8.5 4.7
13000 6.3 43.3 245 20 10 8.9 4.9 | 6.3 43.3 245 18 9 8.6 4.7
12500 7.6 45.7 245 20 10 8.8 4.8 | 7.6 45.7 245 17 9 8.7 4.8
12000 8.8 47.8 245 19 10 8.7 4.8 | 8.9 48.0 245 16 8 9.0 4.9
11500 10.0 50.0 245 18 9 8.6 4.7 | 10.2 50.4 245 16 8 9.0 4.9
11000 11.3 52.3 245 17 9 8.3 4.5 | 11.5 52.7 250 15 8 9.0 4.9
10500 12.5 54.5 245 16 8 6.8 3.7 | 12.8 55.0 250 15 8 7.1 3.9
10250 12.9 55.2 245 16 8 6.8 3.7 | 13.2 55.8 250 15 8 7.6 4.2
10000 13.5 56.3 240 15 8 8.9 4.9 | 14.0 57.2 255 15 8 10.5 5.8
9750 14.1 57.4 240 14 7 8.4 4.6 | 14.7 58.5 255 14 7 9.8 5.4
9500 14.7 58.5 240 13 7 8.2 4.5 | 15.4 59.7 255 14 7 9.7 5.3
9250 15.2 59.4 235 12 6 7.2 4.0 | 16.7 62.1 260 13 7 8.9 4.9
9000 15.7 60.3 235 11 6 6.7 3.7 | 17.4 63.3 260 13 7 9.2 5.1
8750 16.2 61.2 235 10 5 6.9 3.8 | 18.1 64.6 260 12 6 8.9 4.9
8500 16.7 62.1 230 9 5 6.3 3.4 | 18.7 65.7 260 12 6 7.5 4.1
8250 17.1 62.8 230 8 4 4.6 2.6 | 19.2 66.6 265 12 6 9.1 5.0
8000 18.0 64.4 225 7 4 8.9 4.9 | 20.0 68.0 265 12 6 11.7 6.4
7750 18.6 65.5 225 6 3 6.2 3.4 | 20.8 69.4 265 11 6 9.9 5.4
7500 18.9 66.0 225 5 3 2.9 1.6 | 21.5 70.7 265 11 6 7.8 4.3
7250 19.2 66.6 225 4 2 4.8 2.6 | 22.1 71.8 270 11 6 8.9 4.9
7000 19.7 67.5 225 4 2 9.8 5.4 | 22.9 73.2 270 11 6 12.4 6.8
6750 20.5 68.9 220 3 2 9.3 5.1 | 23.8 74.8 270 10 5 11.9 6.5
6500 21.0 69.8 230 3 1 6.8 3.7 | 24.6 76.3 270 10 5 10.6 5.8
6250 21.5 70.7 240 2 1 6.8 3.8 | 25.4 77.7 275 10 5 9.5 5.2
6000 22.1 71.8 245 2 1 11.2 6.2 | 26.2 79.2 275 10 5 14.1 7.7
5750 23.3 73.9 235 2 1 21.2 11.6 | 27.8 82.0 275 9 5 30.2 16.5
5500 24.6 76.3 265 1 1 4.6 2.6 | 30.1 86.2 280 9 5 23.5 12.9
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
07/19/2025 at 1500 MDT | 07/19/2025 at 1800 MDT
|
CAPE... +3.9 LI... +0.4 | CAPE... +19.3 LI... +0.6
CINH... -9.1 K Index... +16.6 | CINH... -6.2 K Index... +18.0
|
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 -64.9 -84.8 235 31 16 1.2 0.7 | -64.8 -84.6 240 30 16 1.5 0.8
45000 -60.5 -76.9 230 48 25 6.1 3.4 | -60.0 -76.0 235 46 24 6.2 3.4
40000 -50.9 -59.6 225 54 28 7.8 4.3 | -50.5 -58.9 225 53 27 7.5 4.1
38000 -46.2 -51.2 225 52 27 7.8 4.3 | -46.0 -50.8 225 52 27 7.5 4.1
36000 -41.0 -41.8 230 50 26 7.4 4.0 | -40.9 -41.6 225 51 26 7.1 3.9
34000 -36.7 -34.1 225 49 25 7.1 3.9 | -36.8 -34.2 225 49 25 6.8 3.8
32000 -32.4 -26.3 225 48 24 7.9 4.4 | -32.7 -26.9 225 48 25 7.7 4.2
30000 -28.1 -18.6 220 47 24 7.2 4.0 | -28.4 -19.1 225 46 24 7.3 4.0
29000 -26.0 -14.8 220 46 24 7.3 4.0 | -26.2 -15.2 230 45 23 7.4 4.0
28000 -23.9 -11.0 220 45 23 6.0 3.3 | -24.1 -11.4 230 44 23 6.0 3.3
27000 -22.1 -7.8 225 42 21 5.9 3.2 | -22.3 -8.1 235 41 21 5.9 3.3
26000 -20.4 -4.7 230 39 20 5.9 3.2 | -20.6 -5.1 235 37 19 5.9 3.3
25000 -18.6 -1.5 235 36 18 5.9 3.2 | -18.8 -1.8 235 34 18 6.0 3.3
24000 -16.8 1.8 235 34 17 6.0 3.3 | -16.9 1.6 240 31 16 6.1 3.4
23000 -15.0 5.0 235 32 16 6.0 3.3 | -15.1 4.8 240 27 14 6.2 3.4
22000 -12.7 9.1 235 29 15 6.2 3.4 | -12.7 9.1 240 23 12 6.6 3.6
21000 -10.8 12.6 235 27 14 6.3 3.4 | -10.7 12.7 240 22 11 6.7 3.7
20000 -9.0 15.8 235 25 13 6.3 3.5 | -8.8 16.2 245 20 10 6.8 3.7
19500 -8.1 17.4 235 24 12 6.5 3.6 | -7.8 18.0 245 19 10 7.0 3.9
19000 -7.1 19.2 235 23 12 6.8 3.7 | -6.7 19.9 250 18 9 7.4 4.1
18500 -6.1 21.0 240 21 11 6.7 3.7 | -5.6 21.9 250 17 9 7.4 4.1
18000 -5.1 22.8 240 20 10 8.0 4.4 | -4.5 23.9 250 16 8 8.2 4.5
17500 -3.9 25.0 240 19 10 8.1 4.5 | -3.3 26.1 250 15 8 8.2 4.5
17000 -2.7 27.1 240 19 10 8.4 4.6 | -2.2 28.0 250 14 7 8.5 4.7
16500 -1.5 29.3 240 18 9 8.8 4.8 | -0.9 30.4 255 14 7 8.8 4.8
16000 -0.2 31.6 240 18 9 8.8 4.9 | 0.4 32.7 255 13 7 8.8 4.8
15500 1.1 34.0 245 17 9 8.6 4.7 | 1.7 35.1 255 13 7 8.9 4.9
15000 2.3 36.1 245 17 9 8.6 4.7 | 3.0 37.4 255 13 7 8.9 4.9
14500 3.6 38.5 245 17 9 9.1 5.0 | 4.3 39.7 255 13 7 9.1 5.0
14000 5.0 41.0 245 16 8 9.2 5.1 | 5.7 42.3 255 13 7 9.1 5.0
13500 6.3 43.3 250 16 8 9.3 5.1 | 7.0 44.6 255 13 7 9.2 5.0
13000 7.7 45.9 250 16 8 9.3 5.1 | 8.4 47.1 260 13 7 9.2 5.1
12500 9.1 48.4 250 16 8 9.3 5.1 | 9.7 49.5 260 13 7 9.3 5.1
12000 10.4 50.7 250 16 8 9.3 5.1 | 11.1 52.0 260 13 7 9.4 5.2
11500 11.8 53.2 250 16 8 9.3 5.1 | 12.5 54.5 260 13 7 9.2 5.1
11000 13.2 55.8 255 16 8 9.1 5.0 | 13.8 56.8 265 13 7 8.6 4.7
10500 14.5 58.1 255 16 8 7.3 4.0 | 15.1 59.2 265 13 6 10.8 5.9
10250 15.0 59.0 255 16 8 7.8 4.3 | 16.0 60.8 265 13 6 11.4 6.2
10000 15.7 60.3 255 16 8 10.6 5.8 | 16.7 62.1 265 13 6 8.8 4.8
9750 16.5 61.7 255 15 8 9.9 5.5 | 17.4 63.3 265 12 6 9.6 5.3
9500 17.2 63.0 260 15 8 9.9 5.4 | 18.1 64.6 265 12 6 9.0 5.0
9250 17.9 64.2 260 15 8 9.5 5.2 | 18.7 65.7 265 12 6 8.9 4.9
9000 18.6 65.5 260 15 8 9.8 5.4 | 19.4 66.9 265 12 6 9.4 5.2
8750 19.3 66.7 260 15 8 10.1 5.5 | 20.1 68.2 270 12 6 9.7 5.3
8500 20.1 68.2 260 15 8 9.6 5.3 | 20.8 69.4 270 12 6 9.4 5.2
8250 21.3 70.3 260 15 8 9.6 5.3 | 22.1 71.8 265 12 6 9.5 5.2
8000 22.2 72.0 265 15 8 11.9 6.5 | 22.9 73.2 270 12 6 11.3 6.2
7750 23.0 73.4 265 15 8 9.9 5.4 | 23.7 74.7 270 12 6 9.9 5.4
7500 23.7 74.7 265 15 8 7.7 4.2 | 24.4 75.9 270 12 6 8.2 4.5
7250 24.3 75.7 265 15 8 9.0 5.0 | 25.0 77.0 265 12 6 9.0 4.9
7000 25.1 77.2 265 15 8 12.8 7.0 | 25.7 78.3 270 12 6 11.6 6.4
6750 26.0 78.8 265 14 7 12.0 6.6 | 26.6 79.9 270 12 6 11.2 6.2
6500 26.8 80.2 265 14 7 10.4 5.7 | 27.4 81.3 270 12 6 10.2 5.6
6250 27.6 81.7 270 14 7 9.6 5.3 | 28.2 82.8 270 12 6 9.9 5.4
6000 28.4 83.1 270 14 7 13.2 7.3 | 28.9 84.0 270 11 6 10.6 5.8
5750 29.8 85.6 270 13 7 28.2 15.5 | 29.9 85.8 270 10 5 17.7 9.7
5500 32.3 90.1 270 13 6 32.9 18.1 | 31.6 88.9 270 10 5 30.5 16.7
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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