Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
230
UXUS97 KGJT 121306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Sunday, October 12, 2025
This forecast is for Sunday, October 12, 2025:
If the trigger temperature of 63.6 F/17.6 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 399 ft/min (2.0 m/s)
Maximum height of thermals.................. 8639 ft MSL (3031 ft AGL)
Forecast maximum temperature................... 62.0 F/17.1 C
Time of trigger temperature.................... None
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................. 6930 ft MSL (1322 ft AGL)
Thermal soaring outlook for Monday 10/13....... Good
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:21:23 / 18:39:33 MDT
Total possible sunshine........... 11 hr 18 min 10 sec (678 min 10 sec)
Altitude of sun at 13:00:28 MDT... 43.18 degrees
Upper air data from rawinsonde observation taken on 10/12/2025 at 0600 MDT
Freezing level.................. 12208 ft MSL (6600 ft AGL)
Convective condensation level... 14410 ft MSL (8802 ft AGL)
Lifted condensation level....... 12372 ft MSL (6764 ft AGL)
Lifted index.................... +5.1
K index......................... +26.2
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 -61.5 -78.7 235 82 42 0.1 0.0 M M M M M
45000 -60.5 -76.9 235 116 60 4.8 2.6 M M M M M
40000 -53.2 -63.8 230 130 67 4.9 2.7 M M M M M
38000 -51.3 -60.3 230 119 61 2.9 1.6 M M M M M
36000 -49.3 -56.7 230 102 52 2.9 1.6 M M M M M
34000 -46.2 -51.2 230 92 48 7.7 4.2 M M M M M
32000 -41.5 -42.7 230 89 46 7.7 4.2 M M M M M
30000 -36.7 -34.1 230 84 43 8.3 4.6 38.6 101.4 16.6 M M
29000 -34.2 -29.6 230 81 42 8.3 4.6 38.0 100.3 16.3 M M
28000 -31.7 -25.1 230 78 40 8.3 4.6 37.5 99.5 16.1 M M
27000 -29.4 -20.9 230 76 39 7.0 3.9 36.8 98.3 15.8 M M
26000 -27.2 -17.0 230 73 38 7.1 3.9 35.8 96.4 15.2 M M
25000 -25.1 -13.2 225 70 36 7.1 3.9 34.8 94.6 14.6 M M
24000 -23.0 -9.4 225 67 35 6.5 3.6 33.9 93.0 14.0 M M
23000 -21.1 -6.0 220 64 33 6.3 3.5 32.5 90.6 13.0 M M
22000 -19.2 -2.6 220 61 31 6.3 3.5 31.3 88.4 12.1 M M
21000 -17.3 0.9 215 58 30 6.7 3.7 30.2 86.4 11.3 M M
20000 -14.8 5.4 215 56 29 6.7 3.7 28.8 83.8 10.2 M M
19500 -13.8 7.2 215 54 28 6.7 3.7 28.3 82.9 9.8 M M
19000 -12.9 8.8 215 53 27 6.7 3.7 27.8 82.1 9.4 M M
18500 -11.9 10.6 215 52 27 6.6 3.6 27.3 81.1 9.0 M M
18000 -10.9 12.4 215 50 26 6.7 3.7 26.7 80.1 8.6 M M
17500 -10.0 14.0 220 48 25 6.4 3.5 26.2 79.2 8.1 M M
17000 -9.1 15.6 215 47 24 6.3 3.4 25.6 78.1 7.5 M M
16500 -8.2 17.2 215 45 23 6.3 3.4 25.0 77.0 7.0 M M
16000 -7.4 18.7 215 44 22 6.0 3.3 24.4 75.9 6.4 M M
15500 -6.5 20.3 215 42 22 5.9 3.2 23.8 74.8 5.8 M M
15000 -5.6 21.9 215 41 21 7.3 4.0 23.2 73.8 5.3 M M
14500 -4.6 23.7 210 40 20 7.3 4.0 22.8 73.1 4.9 M M
14000 -3.6 25.5 210 38 20 7.1 3.9 22.4 72.3 4.5 M M
13500 -2.5 27.5 210 37 19 7.1 3.9 22.0 71.5 4.1 M M
13000 -1.5 29.3 205 36 18 6.9 3.8 21.5 70.8 3.7 M M
12500 -0.6 30.9 205 34 18 6.7 3.7 21.0 69.9 3.2 M M
12000 0.4 32.7 205 32 17 6.9 3.8 20.6 69.0 2.7 M M
11500 1.4 34.5 200 30 16 7.1 3.9 20.1 68.2 2.3 M M
11000 2.5 36.5 200 28 15 7.1 3.9 19.7 67.5 1.9 M M
10500 3.5 38.3 200 26 13 7.3 4.0 19.3 66.7 1.4 M M
10250 4.1 39.4 200 25 13 8.3 4.6 19.1 66.5 1.3 M M
10000 4.7 40.5 195 24 12 7.7 4.2 19.0 66.2 1.2 M M
9750 5.2 41.4 195 23 12 7.1 3.9 18.8 65.9 1.0 M M
9500 5.8 42.4 195 22 11 6.8 3.7 18.6 65.5 0.8 M M
9250 6.3 43.3 190 21 11 8.5 4.6 18.4 65.1 0.6 M M
9000 7.0 44.6 190 20 10 6.9 3.8 18.3 65.0 0.6 M M
8750 7.3 45.1 185 19 10 4.3 2.4 17.9 64.3 0.2 M M
8500 7.7 45.9 180 19 10 4.7 2.6 17.6 63.6 -0.1 193 1.0
8250 8.1 46.6 175 18 9 5.8 3.2 17.2 62.9 -0.4 174 0.9
8000 8.6 47.5 170 17 9 4.8 2.6 16.9 62.4 -0.7 153 0.8
7750 8.9 48.0 165 15 8 2.6 1.4 16.4 61.5 -1.2 137 0.7
7500 9.1 48.4 160 14 7 3.4 1.9 15.9 60.6 -1.6 122 0.6
7250 9.4 48.9 155 13 7 2.5 1.4 15.4 59.7 -2.1 106 0.5
7000 9.6 49.3 150 13 7 1.5 0.8 14.8 58.6 -2.6 93 0.5
6750 9.7 49.5 145 12 6 1.5 0.8 14.2 57.5 -3.2 82 0.4
6500 9.9 49.8 135 11 5 1.4 0.8 13.5 56.4 -3.8 70 0.4
6250 9.9 49.8 130 9 5 -4.0 -2.2 12.8 55.0 -4.6 64 0.3
6000 9.3 48.7 120 8 4 -9.6 -5.3 11.4 52.6 -5.9 73 0.4
5750 8.6 47.5 110 6 3 -7.5 -4.1 10.0 50.1 -7.3 87 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 * * * * * *
10/12/2025 at 0900 MDT | 10/12/2025 at 1200 MDT
|
CAPE... +3.1 LI... +6.1 | CAPE... 0.0 LI... +6.4
CINH... -2.7 K Index... -0.3 | CINH... -0.1 K Index... -22.9
|
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 -79.6 225 67 35 3.5 1.9 | -62.0 -79.6 225 73 38 3.3 1.8
45000 -56.5 -69.7 235 103 53 4.6 2.5 | -56.9 -70.4 235 106 55 4.5 2.4
40000 -49.3 -56.7 235 138 71 4.7 2.6 | -49.8 -57.6 230 140 72 4.5 2.5
38000 -47.0 -52.6 235 135 70 3.6 2.0 | -47.1 -52.8 235 138 71 4.5 2.5
36000 -44.8 -48.6 235 129 66 3.6 2.0 | -44.4 -47.9 235 133 69 4.5 2.5
34000 -42.3 -44.1 235 123 63 5.1 2.8 | -41.7 -43.1 235 127 66 4.6 2.5
32000 -39.2 -38.6 235 117 60 5.1 2.8 | -39.0 -38.2 235 119 61 4.6 2.5
30000 -36.1 -33.0 235 110 57 5.4 3.0 | -36.2 -33.2 235 109 56 4.8 2.6
29000 -34.5 -30.1 235 106 54 5.4 3.0 | -34.7 -30.5 235 103 53 4.8 2.6
28000 -32.8 -27.0 235 101 52 5.4 3.0 | -33.3 -27.9 240 97 50 4.8 2.6
27000 -31.2 -24.2 235 97 50 5.8 3.2 | -31.8 -25.2 240 91 47 5.3 2.9
26000 -28.9 -20.0 240 89 46 6.0 3.3 | -30.2 -22.4 240 84 43 5.5 3.0
25000 -27.1 -16.8 240 83 43 6.0 3.3 | -28.1 -18.6 245 75 38 5.5 3.0
24000 -25.3 -13.5 240 77 40 6.6 3.6 | -26.4 -15.5 245 68 35 6.6 3.6
23000 -23.3 -9.9 245 72 37 6.7 3.7 | -24.4 -11.9 245 62 32 6.8 3.7
22000 -21.2 -6.2 245 67 34 6.7 3.7 | -22.3 -8.1 250 56 29 6.8 3.7
21000 -19.2 -2.6 250 63 32 7.3 4.0 | -20.2 -4.4 250 52 27 7.9 4.3
20000 -17.0 1.4 250 60 31 7.2 4.0 | -17.9 -0.2 250 50 26 7.8 4.3
19500 -15.9 3.4 245 59 31 7.3 4.0 | -16.7 1.9 250 49 25 7.8 4.3
19000 -14.8 5.4 245 58 30 7.3 4.0 | -15.5 4.1 255 48 25 7.8 4.3
18500 -13.8 7.2 245 57 29 5.9 3.2 | -14.4 6.1 255 47 24 7.3 4.0
18000 -13.0 8.6 245 55 28 5.6 3.0 | -13.3 8.1 255 45 23 7.2 3.9
17500 -12.2 10.0 245 53 27 5.3 2.9 | -12.2 10.0 255 44 22 6.7 3.7
17000 -11.5 11.3 245 51 26 4.1 2.3 | -11.3 11.7 260 41 21 5.4 3.0
16500 -10.9 12.4 250 49 25 4.3 2.4 | -10.5 13.1 260 39 20 5.7 3.1
16000 -10.3 13.5 250 47 24 3.5 1.9 | -9.8 14.4 260 36 19 3.4 1.9
15500 -9.8 14.4 250 44 23 3.5 1.9 | -9.3 15.3 260 33 17 3.5 1.9
15000 -9.3 15.3 250 41 21 4.0 2.2 | -8.8 16.2 265 31 16 3.5 1.9
14500 -8.7 16.3 250 39 20 4.3 2.4 | -8.3 17.1 265 28 15 3.6 2.0
14000 -8.2 17.2 250 36 19 4.8 2.6 | -7.7 18.1 265 26 13 3.9 2.1
13500 -7.4 18.7 255 35 18 5.5 3.0 | -7.1 19.2 265 24 12 4.3 2.4
13000 -6.6 20.1 255 33 17 5.7 3.1 | -6.5 20.3 270 22 11 4.7 2.6
12500 -5.7 21.7 260 31 16 6.3 3.5 | -5.7 21.7 270 20 10 5.4 3.0
12000 -4.8 23.4 260 29 15 6.2 3.4 | -4.9 23.2 270 17 9 5.5 3.0
11500 -3.9 25.0 265 27 14 6.0 3.3 | -4.1 24.6 270 15 8 5.8 3.2
11000 -3.0 26.6 270 24 12 6.0 3.3 | -3.2 26.2 270 13 7 5.8 3.2
10500 -2.1 28.2 270 22 11 5.9 3.2 | -2.4 27.7 275 11 6 5.6 3.1
10250 -1.7 28.9 275 21 11 6.1 3.3 | -2.0 28.4 275 11 5 6.1 3.4
10000 -1.2 29.8 275 20 10 7.8 4.3 | -1.5 29.3 275 9 5 8.1 4.5
9750 -0.6 30.9 280 19 10 7.4 4.1 | -0.9 30.4 270 8 4 8.2 4.5
9500 -0.1 31.8 280 18 9 6.1 3.4 | -0.4 31.3 275 7 4 7.3 4.0
9250 0.4 32.7 285 17 9 6.2 3.4 | 0.2 32.4 275 6 3 7.5 4.1
9000 0.8 33.4 285 16 8 7.1 3.9 | 0.7 33.3 275 6 3 7.7 4.2
8750 1.9 35.4 295 14 7 6.5 3.5 | 1.3 34.3 285 5 3 8.4 4.6
8500 2.3 36.1 295 13 7 6.5 3.6 | 2.5 36.5 285 4 2 8.0 4.4
8250 2.8 37.0 300 12 6 5.9 3.2 | 3.0 37.4 290 4 2 6.3 3.5
8000 3.2 37.8 305 11 6 7.0 3.8 | 3.5 38.3 295 4 2 8.7 4.8
7750 3.8 38.8 305 10 5 8.4 4.6 | 4.3 39.7 295 3 2 11.6 6.4
7500 4.4 39.9 310 9 4 7.1 3.9 | 5.0 41.0 300 3 2 8.8 4.8
7250 4.8 40.6 310 8 4 5.6 3.1 | 5.5 41.9 295 3 2 5.8 3.2
7000 5.2 41.4 310 7 4 7.0 3.8 | 6.1 43.0 295 3 2 10.5 5.8
6750 5.8 42.4 320 5 3 8.3 4.5 | 7.0 44.6 295 3 2 13.3 7.3
6500 6.3 43.3 325 4 2 7.6 4.1 | 7.9 46.2 295 3 2 9.9 5.4
6250 6.9 44.4 325 3 2 7.7 4.2 | 8.5 47.3 295 3 2 8.9 4.9
6000 7.4 45.3 330 3 1 6.9 3.8 | 9.2 48.6 295 3 2 9.5 5.2
5750 7.9 46.2 355 2 1 8.2 4.5 | 10.0 50.0 300 3 1 14.6 8.0
5500 9.0 48.2 345 1 1 28.4 15.6 | 11.8 53.2 295 3 2 39.4 21.6
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
10/12/2025 at 1500 MDT | 10/12/2025 at 1800 MDT
|
CAPE... 0.0 LI... +5.5 | CAPE... 0.0 LI... +3.8
CINH... -0.3 K Index... -18.4 | 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 -62.6 -80.7 225 79 41 2.8 1.5 | -61.9 -79.4 230 81 42 2.4 1.3
45000 -58.0 -72.4 235 108 55 4.7 2.6 | -58.1 -72.6 235 109 56 3.9 2.1
40000 -50.5 -58.9 230 138 71 4.8 2.6 | -52.2 -62.0 230 134 69 3.9 2.2
38000 -47.9 -54.2 235 135 69 4.3 2.4 | -49.7 -57.5 230 130 67 4.2 2.3
36000 -45.3 -49.5 235 129 66 4.3 2.4 | -46.9 -52.4 235 119 61 4.2 2.3
34000 -42.7 -44.9 235 121 62 4.4 2.4 | -44.3 -47.7 235 109 56 4.8 2.6
32000 -40.0 -40.0 240 110 57 4.4 2.4 | -41.4 -42.5 240 99 51 4.8 2.6
30000 -37.0 -34.6 240 100 52 6.2 3.4 | -37.9 -36.2 240 89 46 7.3 4.0
29000 -35.2 -31.4 245 95 49 6.2 3.4 | -35.8 -32.4 245 86 44 7.3 4.0
28000 -33.3 -27.9 245 90 46 6.2 3.4 | -33.6 -28.5 245 82 42 7.3 4.0
27000 -31.5 -24.7 245 85 44 6.2 3.4 | -31.4 -24.5 245 78 40 7.1 3.9
26000 -29.6 -21.3 245 79 41 6.2 3.4 | -29.3 -20.7 245 74 38 7.1 3.9
25000 -27.7 -17.9 245 73 38 6.2 3.4 | -27.1 -16.8 245 70 36 7.1 3.9
24000 -25.4 -13.7 245 66 34 5.4 3.0 | -25.0 -13.0 245 66 34 6.7 3.7
23000 -23.8 -10.8 250 59 30 5.4 3.0 | -22.7 -8.9 245 59 30 6.3 3.4
22000 -22.2 -8.0 250 52 27 5.4 3.0 | -20.8 -5.4 245 53 27 6.2 3.4
21000 -20.4 -4.7 250 46 24 7.5 4.1 | -19.0 -2.2 245 47 24 5.5 3.0
20000 -18.2 -0.8 250 44 22 7.3 4.0 | -17.3 0.9 245 41 21 5.6 3.1
19500 -17.1 1.2 250 42 22 7.3 4.0 | -16.5 2.3 245 38 20 5.6 3.0
19000 -16.0 3.2 250 41 21 7.3 4.0 | -15.7 3.7 245 35 18 5.4 3.0
18500 -14.9 5.2 250 40 20 7.8 4.3 | -14.8 5.4 245 33 17 7.2 3.9
18000 -13.8 7.2 255 39 20 7.8 4.3 | -13.7 7.3 245 31 16 7.1 3.9
17500 -12.6 9.3 255 38 19 7.7 4.2 | -12.6 9.3 245 30 15 7.3 4.0
17000 -11.5 11.3 255 36 19 7.4 4.1 | -11.5 11.3 245 29 15 7.6 4.2
16500 -10.4 13.3 255 35 18 7.5 4.1 | -10.4 13.3 245 28 14 7.6 4.2
16000 -9.3 15.3 260 33 17 6.7 3.7 | -9.2 15.4 245 27 14 7.5 4.1
15500 -8.3 17.1 260 31 16 6.8 3.7 | -8.1 17.4 245 26 13 7.5 4.1
15000 -7.3 18.9 260 28 15 5.6 3.1 | -7.0 19.4 245 25 13 7.0 3.9
14500 -6.5 20.3 255 26 13 5.4 3.0 | -6.0 21.2 245 23 12 7.0 3.8
14000 -5.7 21.7 255 23 12 4.9 2.7 | -4.9 23.2 240 22 11 6.5 3.6
13500 -5.0 23.0 255 21 11 4.6 2.5 | -4.0 24.8 240 21 11 6.2 3.4
13000 -4.4 24.1 250 19 10 4.6 2.5 | -3.1 26.4 235 19 10 6.0 3.3
12500 -3.7 25.3 245 17 9 4.8 2.7 | -2.3 27.9 230 18 9 5.8 3.2
12000 -3.0 26.6 240 15 8 5.2 2.8 | -1.5 29.3 220 17 9 5.9 3.3
11500 -2.2 28.0 235 13 7 6.0 3.3 | -0.6 30.9 215 16 8 6.1 3.4
11000 -1.3 29.7 230 12 6 5.9 3.2 | 0.2 32.4 205 15 8 6.2 3.4
10500 -0.5 31.1 230 11 6 5.4 3.0 | 1.0 33.8 200 14 7 5.3 2.9
10250 -0.1 31.8 230 10 5 6.9 3.8 | 1.4 34.5 195 13 7 7.4 4.1
10000 0.5 32.9 225 9 4 8.7 4.8 | 2.0 35.6 195 12 6 9.1 5.0
9750 1.1 34.0 225 7 4 7.8 4.3 | 2.6 36.7 190 11 5 7.1 3.9
9500 1.6 34.9 225 6 3 7.1 3.9 | 3.1 37.6 190 10 5 6.4 3.5
9250 2.1 35.8 225 6 3 7.4 4.0 | 3.6 38.5 185 9 5 6.9 3.8
9000 2.6 36.7 225 5 2 6.3 3.4 | 4.1 39.4 180 8 4 5.7 3.1
8750 3.1 37.6 230 4 2 7.1 3.9 | 4.4 39.9 180 7 4 6.2 3.4
8500 4.3 39.7 230 3 1 7.4 4.1 | 5.6 42.1 175 5 3 7.2 4.0
8250 4.8 40.6 240 2 1 5.6 3.1 | 6.1 43.0 165 4 2 6.5 3.6
8000 5.2 41.4 260 2 1 8.4 4.6 | 6.6 43.9 160 4 2 6.6 3.6
7750 6.0 42.8 265 1 1 11.6 6.4 | 7.1 44.8 155 2 1 7.3 4.0
7500 6.8 44.2 275 1 1 8.8 4.8 | 7.6 45.7 140 1 1 6.6 3.6
7250 7.3 45.1 300 1 1 5.6 3.1 | 8.1 46.6 125 1 0 5.6 3.1
7000 7.8 46.0 315 2 1 10.1 5.5 | 8.6 47.5 000 0 0 8.4 4.6
6750 8.7 47.7 305 1 1 13.3 7.3 | 9.3 48.7 000 0 0 10.6 5.8
6500 9.6 49.3 300 1 1 9.8 5.4 | 10.1 50.2 355 1 1 8.6 4.7
6250 10.2 50.4 315 2 1 8.3 4.6 | 10.6 51.1 340 2 1 7.3 4.0
6000 10.9 51.6 325 2 1 9.3 5.1 | 11.2 52.2 335 2 1 8.9 4.9
5750 11.7 53.1 305 1 1 14.3 7.8 | 11.9 53.4 335 1 1 9.9 5.4
5500 13.4 56.1 330 2 1 36.5 20.0 | 12.2 54.0 325 2 1 -1.0 -0.6
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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