Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
669
UXUS97 KGJT 111305
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
705 AM MDT Monday, August 11, 2025
This forecast is for Monday, August 11, 2025:
If the trigger temperature of 81.6 F/27.6 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1117 ft/min (5.7 m/s)
Maximum height of thermals.................. 17890 ft MSL (12282 ft AGL)
Forecast maximum temperature................... 92.0 F/33.8 C
Time of trigger temperature.................... 1100 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................. 14476 ft MSL (8868 ft AGL)
Thermal soaring outlook for Tuesday 08/12...... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:24:19 / 20:14:14 MDT
Total possible sunshine........... 13 hr 49 min 55 sec (829 min 55 sec)
Altitude of sun at 13:19:16 MDT... 65.53 degrees
Upper air data from rawinsonde observation taken on 08/11/2025 at 0600 MDT
Freezing level.................. 16009 ft MSL (10401 ft AGL)
Convective condensation level... 20705 ft MSL (15097 ft AGL)
Lifted condensation level....... 19752 ft MSL (14144 ft AGL)
Lifted index.................... +1.1
K index......................... +10.1
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 -63.9 -83.0 360 10 5 -1.4 -0.8 M M M M M
45000 -63.2 -81.8 010 15 8 5.0 2.7 M M M M M
40000 -55.2 -67.4 025 22 12 8.0 4.4 M M M M M
38000 -50.4 -58.7 025 24 12 8.1 4.4 M M M M M
36000 -44.9 -48.8 030 25 13 8.5 4.7 M M M M M
34000 -39.5 -39.1 035 24 12 9.0 4.9 M M M M M
32000 -34.1 -29.4 045 23 12 9.1 5.0 M M M M M
30000 -29.5 -21.1 040 18 9 7.5 4.1 45.5 113.8 9.3 M M
29000 -27.3 -17.1 040 15 8 7.5 4.1 44.7 112.4 8.8 M M
28000 -25.1 -13.2 035 13 7 7.1 3.9 43.9 111.0 8.3 M M
27000 -23.0 -9.4 030 12 6 7.0 3.9 42.7 108.9 7.4 M M
26000 -20.9 -5.6 030 10 5 7.1 3.9 41.7 107.1 6.7 M M
25000 -18.7 -1.7 025 9 5 7.1 3.9 40.8 105.5 6.0 M M
24000 -16.6 2.1 025 9 4 7.2 3.9 39.8 103.6 5.2 M M
23000 -14.5 5.9 025 8 4 7.2 3.9 38.9 101.9 4.5 M M
22000 -12.4 9.7 025 7 3 7.2 4.0 38.0 100.5 3.8 M M
21000 -9.6 14.7 030 7 4 7.2 4.0 36.8 98.3 2.9 M M
20000 -7.4 18.7 035 7 4 7.2 4.0 36.0 96.8 2.2 M M
19500 -6.3 20.7 040 7 4 6.6 3.6 35.6 96.1 1.9 M M
19000 -5.5 22.1 040 6 3 5.6 3.1 34.9 94.8 1.3 M M
18500 -4.7 23.5 045 5 3 5.5 3.0 34.2 93.5 0.6 M M
18000 -3.8 25.2 050 4 2 6.4 3.5 33.5 92.3 0.0 M M
17500 -2.9 26.8 060 3 1 6.5 3.6 32.9 91.3 -0.5 1077 5.5
17000 -1.9 28.6 075 2 1 6.8 3.7 32.4 90.3 -1.0 1035 5.3
16500 -0.9 30.4 115 1 1 7.1 3.9 31.9 89.5 -1.5 989 5.0
16000 0.1 32.2 150 2 1 7.1 3.9 31.5 88.7 -1.9 943 4.8
15500 1.2 34.2 155 2 1 7.8 4.3 31.1 88.0 -2.3 896 4.5
15000 2.3 36.1 150 3 1 7.7 4.2 30.8 87.4 -2.7 847 4.3
14500 3.5 38.3 145 3 2 8.2 4.5 30.5 86.9 -3.0 798 4.1
14000 4.7 40.5 135 3 2 8.3 4.5 30.2 86.4 -3.3 747 3.8
13500 5.9 42.6 125 3 2 8.6 4.7 30.0 86.0 -3.6 696 3.5
13000 7.2 45.0 115 4 2 8.8 4.8 29.9 85.7 -3.8 643 3.3
12500 8.4 47.1 110 4 2 8.7 4.8 29.7 85.5 -4.0 590 3.0
12000 9.7 49.5 105 4 2 8.4 4.6 29.5 85.1 -4.2 538 2.7
11500 10.9 51.6 105 5 2 8.2 4.5 29.3 84.7 -4.5 487 2.5
11000 12.0 53.6 105 5 3 7.7 4.2 29.0 84.2 -4.8 438 2.2
10500 13.2 55.8 105 5 3 9.5 5.2 28.7 83.7 -5.1 388 2.0
10250 14.0 57.2 100 6 3 9.2 5.1 28.7 83.7 -5.1 358 1.8
10000 14.6 58.3 100 6 3 7.6 4.2 28.6 83.5 -5.3 333 1.7
9750 15.1 59.2 100 6 3 8.5 4.7 28.5 83.2 -5.4 307 1.6
9500 15.7 60.3 100 6 3 6.7 3.7 28.3 83.0 -5.6 282 1.4
9250 16.2 61.2 100 7 4 6.2 3.4 28.0 82.4 -5.9 262 1.3
9000 16.7 62.1 095 7 4 7.4 4.0 27.8 82.1 -6.1 238 1.2
8750 17.3 63.1 095 7 4 7.4 4.1 27.6 81.7 -6.3 215 1.1
8500 17.8 64.0 095 7 4 6.0 3.3 27.4 81.4 -6.5 191 1.0
8250 18.1 64.6 095 7 4 4.0 2.2 27.0 80.7 -6.9 173 0.9
8000 18.4 65.1 095 7 4 4.0 2.2 26.6 79.9 -7.3 157 0.8
7750 18.7 65.7 095 7 4 4.3 2.3 26.1 79.1 -7.8 140 0.7
7500 19.0 66.2 095 7 3 2.2 1.2 25.7 78.2 -8.2 125 0.6
7250 19.1 66.4 100 7 3 0.2 0.1 25.0 77.0 -8.9 116 0.6
7000 19.1 66.4 105 6 3 1.4 0.8 24.3 75.8 -9.6 106 0.5
6750 19.2 66.6 105 6 3 0.1 0.0 23.7 74.6 -10.3 97 0.5
6500 19.1 66.4 105 6 3 -3.4 -1.9 22.8 73.0 -11.2 93 0.5
6250 18.7 65.7 105 6 3 -6.8 -3.7 21.7 71.0 -12.3 97 0.5
6000 18.4 65.1 105 6 3 2.2 1.2 20.6 69.1 -13.4 100 0.5
5750 18.7 65.7 105 6 3 -3.2 -1.8 20.2 68.3 -13.9 84 0.4
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 * * * * * *
08/11/2025 at 0900 MDT | 08/11/2025 at 1200 MDT
|
CAPE... 0.0 LI... +4.5 | CAPE... 0.0 LI... +5.1
CINH... 0.0 K Index... +15.3 | CINH... -1.6 K Index... +14.9
|
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 -61.1 -78.0 355 14 7 0.4 0.2 | -61.2 -78.2 360 12 6 0.3 0.2
45000 -59.3 -74.7 350 21 11 3.2 1.7 | -59.7 -75.5 360 18 9 2.7 1.5
40000 -54.1 -65.4 345 29 15 6.5 3.6 | -54.6 -66.3 015 26 14 7.0 3.8
38000 -49.8 -57.6 345 27 14 6.4 3.5 | -50.4 -58.7 015 27 14 7.0 3.8
36000 -46.0 -50.8 345 25 13 6.3 3.5 | -46.2 -51.2 020 28 14 7.0 3.9
34000 -41.5 -42.7 345 24 12 7.6 4.2 | -41.1 -42.0 015 28 14 8.6 4.7
32000 -36.9 -34.4 345 23 12 7.5 4.1 | -35.9 -32.6 010 27 14 8.6 4.7
30000 -31.7 -25.1 340 25 13 8.9 4.9 | -31.0 -23.8 360 27 14 8.2 4.5
29000 -29.1 -20.4 335 26 13 8.9 4.9 | -28.5 -19.3 355 27 14 8.2 4.5
28000 -26.4 -15.5 335 27 14 8.4 4.6 | -26.0 -14.8 355 27 14 7.6 4.2
27000 -24.0 -11.2 335 27 14 8.0 4.4 | -23.9 -11.0 350 27 14 7.2 3.9
26000 -21.6 -6.9 335 28 14 8.0 4.4 | -21.7 -7.1 350 28 14 7.2 3.9
25000 -19.2 -2.6 335 28 15 8.2 4.5 | -19.6 -3.3 350 29 15 7.2 3.9
24000 -16.7 1.9 340 26 13 6.3 3.5 | -16.9 1.6 350 26 13 7.1 3.9
23000 -14.9 5.2 345 24 12 6.3 3.5 | -14.8 5.4 350 23 12 7.1 3.9
22000 -13.0 8.6 345 22 11 6.5 3.6 | -12.7 9.1 350 20 11 7.3 4.0
21000 -11.1 12.0 350 21 11 6.6 3.6 | -10.5 13.1 355 19 10 7.3 4.0
20000 -9.1 15.6 350 21 11 6.6 3.6 | -8.4 16.9 355 17 9 7.3 4.0
19500 -8.1 17.4 350 20 11 6.5 3.6 | -7.3 18.9 355 17 9 7.2 4.0
19000 -7.4 18.7 350 20 10 4.5 2.5 | -6.3 20.7 360 16 8 5.9 3.2
18500 -6.7 19.9 350 19 10 4.7 2.6 | -5.5 22.1 360 15 8 6.0 3.3
18000 -6.0 21.2 350 18 9 4.5 2.5 | -4.6 23.7 360 14 7 4.7 2.6
17500 -5.4 22.3 345 18 9 4.5 2.5 | -4.1 24.6 355 14 7 4.2 2.3
17000 -4.8 23.4 345 17 9 4.7 2.6 | -3.5 25.7 355 13 7 4.2 2.3
16500 -4.0 24.8 340 17 9 6.0 3.3 | -2.9 26.8 355 13 6 4.1 2.2
16000 -3.2 26.2 340 17 9 5.8 3.2 | -2.3 27.9 350 13 6 3.9 2.2
15500 -2.2 28.0 340 17 9 7.8 4.3 | -1.6 29.1 350 12 6 6.5 3.6
15000 -1.0 30.2 340 16 8 7.9 4.3 | -0.7 30.7 345 12 6 6.6 3.6
14500 0.1 32.2 340 16 8 8.2 4.5 | 0.3 32.5 345 12 6 7.7 4.2
14000 1.4 34.5 345 15 8 8.4 4.6 | 1.5 34.7 345 12 6 8.3 4.6
13500 2.6 36.7 350 14 7 8.5 4.7 | 2.8 37.0 345 12 6 8.6 4.7
13000 3.9 39.0 350 13 7 8.7 4.8 | 4.1 39.4 345 11 6 9.1 5.0
12500 5.2 41.4 360 12 6 8.7 4.8 | 5.5 41.9 350 11 6 9.1 5.0
12000 6.5 43.7 005 12 6 8.7 4.8 | 6.8 44.2 350 10 5 9.1 5.0
11500 7.8 46.0 005 11 6 8.7 4.8 | 8.2 46.8 350 10 5 9.1 5.0
11000 9.1 48.4 010 10 5 8.5 4.7 | 9.6 49.3 350 9 5 9.2 5.1
10500 10.4 50.7 015 10 5 7.7 4.2 | 11.0 51.8 350 8 4 6.4 3.5
10250 10.9 51.6 015 10 5 7.1 3.9 | 11.3 52.3 350 8 4 7.0 3.8
10000 11.5 52.7 015 9 5 8.3 4.6 | 12.1 53.8 350 7 4 11.1 6.1
9750 12.2 54.0 015 9 4 8.6 4.7 | 12.9 55.2 350 7 4 10.2 5.6
9500 12.8 55.0 015 8 4 8.3 4.5 | 13.7 56.7 345 7 4 9.8 5.4
9250 13.4 56.1 020 8 4 7.6 4.2 | 14.3 57.7 345 6 3 8.0 4.4
9000 14.0 57.2 020 7 4 6.4 3.5 | 14.9 58.8 345 6 3 8.6 4.7
8750 14.4 57.9 020 7 3 6.0 3.3 | 15.6 60.1 345 6 3 9.9 5.4
8500 15.3 59.5 025 5 3 4.1 2.2 | 16.9 62.4 345 5 3 6.2 3.4
8250 15.6 60.1 030 5 3 4.3 2.4 | 17.4 63.3 340 4 2 7.9 4.3
8000 16.0 60.8 035 4 2 5.6 3.1 | 18.2 64.8 340 4 2 11.6 6.4
7750 16.4 61.5 045 4 2 4.3 2.4 | 19.0 66.2 340 4 2 9.4 5.2
7500 16.6 61.9 055 4 2 2.7 1.5 | 19.6 67.3 335 4 2 6.7 3.7
7250 16.8 62.2 065 3 2 3.5 1.9 | 20.1 68.2 335 3 2 8.2 4.5
7000 17.2 63.0 075 4 2 6.5 3.6 | 20.9 69.6 330 3 2 12.6 6.9
6750 17.7 63.9 080 3 2 6.7 3.7 | 21.9 71.4 330 3 2 12.0 6.6
6500 18.2 64.8 090 3 2 5.3 2.9 | 22.6 72.7 325 3 2 9.9 5.4
6250 18.6 65.5 095 3 2 5.2 2.8 | 23.4 74.1 320 3 1 9.1 5.0
6000 19.1 66.4 100 3 2 10.6 5.8 | 24.2 75.6 315 3 1 14.4 7.9
5750 20.3 68.5 100 3 2 20.8 11.4 | 25.8 78.4 320 3 1 29.7 16.3
5500 21.4 70.5 105 3 2 -0.7 -0.4 | 27.8 82.0 310 2 1 14.3 7.8
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
08/11/2025 at 1500 MDT | 08/11/2025 at 1800 MDT
|
CAPE... 0.0 LI... +3.4 | CAPE... +0.1 LI... +1.1
CINH... 0.0 K Index... +16.3 | CINH... -0.4 K Index... +19.9
|
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 -62.0 -79.6 360 9 5 0.1 0.1 | -62.1 -79.8 360 11 6 -0.1 -0.1
45000 -60.5 -76.9 010 16 8 3.4 1.9 | -60.8 -77.4 015 19 10 3.2 1.8
40000 -54.4 -65.9 025 33 17 6.9 3.8 | -54.7 -66.5 040 41 21 7.9 4.3
38000 -50.2 -58.4 020 29 15 6.9 3.8 | -50.0 -58.0 035 39 20 7.9 4.3
36000 -46.0 -50.8 015 26 13 7.1 3.9 | -45.2 -49.4 030 36 19 8.0 4.4
34000 -40.9 -41.6 015 26 13 8.6 4.7 | -40.3 -40.5 025 34 18 8.2 4.5
32000 -35.8 -32.4 015 27 14 8.5 4.7 | -35.4 -31.7 020 32 17 8.2 4.5
30000 -30.8 -23.4 015 27 14 8.3 4.5 | -30.6 -23.1 015 28 14 8.0 4.4
29000 -28.3 -18.9 015 26 14 8.3 4.5 | -28.2 -18.8 015 25 13 8.0 4.4
28000 -25.8 -14.4 015 26 13 7.8 4.3 | -25.8 -14.4 015 23 12 7.8 4.3
27000 -23.6 -10.5 015 25 13 7.5 4.1 | -23.5 -10.3 015 22 11 7.7 4.2
26000 -21.3 -6.3 010 25 13 7.5 4.1 | -21.2 -6.2 015 21 11 7.7 4.2
25000 -19.1 -2.4 010 24 13 7.5 4.1 | -18.3 -0.9 015 20 10 6.9 3.8
24000 -16.5 2.3 005 22 12 6.9 3.8 | -16.4 2.5 010 18 9 6.5 3.6
23000 -14.4 6.1 005 21 11 6.9 3.8 | -14.5 5.9 010 16 8 6.5 3.6
22000 -12.3 9.9 360 19 10 6.8 3.7 | -12.5 9.5 005 15 8 5.9 3.3
21000 -10.3 13.5 360 17 8 6.8 3.7 | -10.8 12.6 005 13 7 5.8 3.2
20000 -8.3 17.1 360 14 7 6.8 3.7 | -9.2 15.4 010 12 6 5.9 3.2
19500 -7.3 18.9 360 13 7 6.7 3.7 | -8.3 17.1 010 11 6 6.0 3.3
19000 -6.4 20.5 360 13 7 6.3 3.5 | -7.5 18.5 010 11 6 6.1 3.3
18500 -5.5 22.1 360 13 7 6.4 3.5 | -6.6 20.1 010 11 6 6.1 3.3
18000 -4.6 23.7 005 13 7 5.7 3.1 | -5.7 21.7 010 11 6 7.7 4.2
17500 -3.8 25.2 005 13 7 5.6 3.1 | -4.5 23.9 010 12 6 8.0 4.4
17000 -3.1 26.4 005 13 7 5.8 3.2 | -3.4 25.9 010 12 6 8.3 4.5
16500 -2.2 28.0 005 13 7 6.5 3.6 | -2.1 28.2 005 12 6 8.9 4.9
16000 -1.2 29.8 360 13 6 6.4 3.5 | -0.8 30.6 005 12 6 8.8 4.8
15500 -0.2 31.6 360 12 6 7.7 4.3 | 0.5 32.9 005 12 6 9.3 5.1
15000 0.9 33.6 360 12 6 7.7 4.2 | 1.9 35.4 005 12 6 9.3 5.1
14500 2.0 35.6 360 12 6 8.4 4.6 | 3.2 37.8 005 12 6 9.3 5.1
14000 3.3 37.9 355 12 6 8.7 4.8 | 4.6 40.3 005 12 6 9.4 5.1
13500 4.6 40.3 355 11 6 8.9 4.9 | 6.0 42.8 005 12 6 9.5 5.2
13000 6.0 42.8 355 11 6 9.2 5.1 | 7.5 45.5 005 12 6 9.7 5.3
12500 7.4 45.3 355 11 6 9.3 5.1 | 8.9 48.0 005 11 6 9.6 5.3
12000 8.8 47.8 350 10 5 9.4 5.1 | 10.4 50.7 360 11 6 9.6 5.3
11500 10.2 50.4 350 10 5 9.4 5.1 | 11.8 53.2 360 11 6 9.5 5.2
11000 11.6 52.9 345 9 5 9.3 5.1 | 13.1 55.6 360 11 5 8.8 4.8
10500 13.0 55.4 340 9 5 7.5 4.1 | 14.5 58.1 360 10 5 10.5 5.8
10250 13.5 56.3 335 8 4 8.1 4.4 | 15.3 59.5 360 10 5 11.0 6.0
10000 14.2 57.6 335 8 4 10.9 6.0 | 16.0 60.8 355 10 5 8.9 4.9
9750 15.0 59.0 335 8 4 10.2 5.6 | 16.7 62.1 355 10 5 9.5 5.2
9500 15.8 60.4 330 8 4 10.2 5.6 | 17.4 63.3 355 9 5 9.3 5.1
9250 16.5 61.7 330 8 4 9.7 5.3 | 18.1 64.6 355 9 5 9.2 5.1
9000 17.2 63.0 325 8 4 9.7 5.3 | 18.8 65.8 355 9 4 9.2 5.0
8750 18.0 64.4 325 7 4 9.9 5.4 | 20.2 68.4 350 8 4 9.1 5.0
8500 19.4 66.9 320 7 4 8.1 4.4 | 20.9 69.6 350 8 4 8.1 4.5
8250 20.0 68.0 315 7 4 9.5 5.2 | 21.5 70.7 350 8 4 9.1 5.0
8000 20.8 69.4 315 7 4 11.8 6.5 | 22.2 72.0 350 8 4 10.7 5.9
7750 21.7 71.1 315 7 3 10.2 5.6 | 23.0 73.4 350 8 4 9.8 5.4
7500 22.3 72.1 315 7 3 8.3 4.6 | 23.7 74.7 350 8 4 8.6 4.7
7250 23.0 73.4 305 7 3 9.2 5.0 | 24.3 75.7 350 7 4 9.1 5.0
7000 23.8 74.8 305 6 3 12.1 6.6 | 25.1 77.2 350 7 4 11.1 6.1
6750 24.7 76.5 310 6 3 11.7 6.4 | 25.9 78.6 345 7 4 11.1 6.1
6500 25.5 77.9 305 6 3 10.6 5.8 | 26.7 80.1 345 7 4 10.5 5.7
6250 26.3 79.3 295 6 3 9.7 5.3 | 27.5 81.5 350 7 3 10.2 5.6
6000 27.1 80.8 295 6 3 13.2 7.2 | 28.3 82.9 350 7 3 10.1 5.5
5750 28.5 83.3 300 6 3 27.5 15.1 | 29.2 84.6 345 6 3 15.6 8.6
5500 30.9 87.6 290 6 3 30.8 16.9 | 30.9 87.6 350 6 3 32.7 17.9
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
________________________________________________________________________________
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.
042613