Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
046
UXUS97 KGJT 111306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Saturday, October 11, 2025
This forecast is for Saturday, October 11, 2025:
If the trigger temperature of 58.3 F/14.6 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 265 ft/min (1.3 m/s)
Maximum height of thermals.................. 14176 ft MSL (8569 ft AGL)
Forecast maximum temperature................... 69.0 F/21.0 C
Time of trigger temperature.................... 0930 MDT
Time of overdevelopment........................ None
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................. 11913 ft MSL (6306 ft AGL)
Thermal soaring outlook for Sunday 10/12....... Poor
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:20:24 / 18:41:03 MDT
Total possible sunshine........... 11 hr 20 min 39 sec (680 min 39 sec)
Altitude of sun at 13:00:43 MDT... 43.55 degrees
Upper air data from rawinsonde observation taken on 10/11/2025 at 0600 MDT
Freezing level.................. 11044 ft MSL (5437 ft AGL)
Convective condensation level... 10644 ft MSL (5037 ft AGL)
Lifted condensation level....... 12656 ft MSL (7049 ft AGL)
Lifted index.................... +0.6
K index......................... +16.6
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 -62.2 -80.0 235 68 35 3.1 1.7 M M M M M
45000 -56.9 -70.4 240 100 51 4.4 2.4 M M M M M
40000 -50.3 -58.5 235 134 69 4.4 2.4 M M M M M
38000 -47.5 -53.5 235 129 66 4.8 2.6 M M M M M
36000 -44.6 -48.3 235 121 62 4.8 2.6 M M M M M
34000 -41.8 -43.2 235 113 58 4.6 2.5 M M M M M
32000 -38.7 -37.7 235 102 52 4.6 2.5 M M M M M
30000 -35.3 -31.5 235 94 48 7.0 3.8 40.4 104.8 15.1 M M
29000 -33.2 -27.8 235 91 47 7.0 3.8 39.3 102.8 14.4 M M
28000 -31.1 -24.0 235 89 46 7.0 3.8 38.3 101.0 13.8 M M
27000 -29.0 -20.2 235 86 44 7.0 3.9 37.3 99.2 13.2 M M
26000 -26.9 -16.4 235 84 43 7.0 3.9 36.2 97.2 12.5 M M
25000 -24.8 -12.6 235 81 42 7.0 3.9 35.2 95.4 11.8 M M
24000 -22.7 -8.9 235 79 41 5.9 3.2 34.3 93.8 11.2 M M
23000 -21.2 -6.2 235 74 38 5.4 2.9 32.6 90.7 9.9 M M
22000 -19.6 -3.3 230 69 36 5.4 3.0 31.0 87.8 8.7 M M
21000 -18.0 -0.4 230 64 33 5.6 3.1 29.6 85.2 7.5 M M
20000 -16.4 2.5 230 57 30 5.7 3.1 28.0 82.4 6.2 M M
19500 -15.5 4.1 230 54 28 5.7 3.1 27.3 81.1 5.6 M M
19000 -14.7 5.5 230 51 26 5.8 3.2 26.6 79.9 5.0 M M
18500 -13.9 7.0 230 48 25 6.8 3.7 26.0 78.8 4.5 M M
18000 -12.2 10.0 230 45 23 7.7 4.2 25.4 77.8 4.0 M M
17500 -11.1 12.0 230 43 22 7.2 4.0 25.1 77.2 3.7 M M
17000 -10.1 13.8 235 42 22 6.8 3.7 24.6 76.3 3.3 M M
16500 -9.1 15.6 235 41 21 6.8 3.7 24.1 75.4 2.8 M M
16000 -8.1 17.4 235 39 20 6.0 3.3 23.5 74.3 2.3 M M
15500 -7.3 18.9 235 38 20 6.2 3.4 22.9 73.2 1.7 M M
15000 -6.4 20.5 240 37 19 5.3 2.9 22.3 72.1 1.1 M M
14500 -5.7 21.7 240 36 18 5.2 2.9 21.5 70.7 0.4 M M
14000 -5.0 23.0 240 34 18 5.4 2.9 20.8 69.4 -0.3 648 3.3
13500 -4.2 24.4 240 33 17 5.5 3.0 20.1 68.1 -1.0 611 3.1
13000 -3.5 25.7 245 32 17 5.8 3.2 19.4 66.9 -1.7 573 2.9
12500 -2.6 27.3 245 31 16 6.3 3.5 18.8 65.8 -2.3 532 2.7
12000 -1.7 28.9 250 30 16 6.2 3.4 18.3 64.9 -2.9 491 2.5
11500 -0.8 30.6 250 29 15 6.0 3.3 17.7 63.8 -3.5 450 2.3
11000 0.1 32.2 255 27 14 5.7 3.1 17.1 62.7 -4.1 409 2.1
10500 0.8 33.4 255 26 13 5.4 2.9 16.3 61.4 -4.9 373 1.9
10250 1.2 34.2 260 25 13 7.1 3.9 16.0 60.9 -5.1 351 1.8
10000 1.8 35.2 260 25 13 7.4 4.1 15.9 60.6 -5.4 328 1.7
9750 2.3 36.1 265 24 12 7.2 4.0 15.7 60.2 -5.6 305 1.5
9500 2.8 37.0 265 23 12 7.1 3.9 15.5 59.9 -5.8 282 1.4
9250 3.4 38.1 265 22 11 7.7 4.2 15.3 59.5 -6.0 258 1.3
9000 4.0 39.2 270 22 11 7.5 4.1 15.1 59.3 -6.2 233 1.2
8750 4.5 40.1 270 21 11 7.0 3.8 14.9 58.9 -6.4 211 1.1
8500 5.0 41.0 270 20 10 6.7 3.7 14.7 58.5 -6.6 188 1.0
8250 5.5 41.9 275 19 10 8.4 4.6 14.5 58.1 -6.9 166 0.8
8000 6.1 43.0 275 18 9 8.1 4.4 14.5 58.0 -6.9 139 0.7
7750 6.6 43.9 280 17 9 5.8 3.2 14.2 57.6 -7.2 117 0.6
7500 7.0 44.6 280 16 8 6.9 3.8 13.9 57.1 -7.5 96 0.5
7250 7.5 45.5 285 16 8 4.9 2.7 13.7 56.6 -7.8 75 0.4
7000 7.8 46.0 285 15 8 5.1 2.8 13.3 55.9 -8.3 59 0.3
6750 8.3 46.9 285 14 7 7.1 3.9 13.0 55.4 -8.6 38 0.2
6500 8.7 47.7 285 13 7 6.4 3.5 12.8 55.0 -8.9 17 0.1
6250 9.2 48.6 285 12 6 8.1 4.5 12.6 54.6 -9.1 M M
6000 9.7 49.5 285 10 5 5.7 3.1 12.4 54.4 -9.3 M M
5750 9.8 49.6 285 8 4 -2.3 -1.2 11.8 53.3 -10.0 M M
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 * * * * * *
10/11/2025 at 0900 MDT | 10/11/2025 at 1200 MDT
|
CAPE... +15.5 LI... +0.8 | CAPE... +54.0 LI... +0.4
CINH... -14.0 K Index... +26.6 | CINH... -8.4 K Index... +25.7
|
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 -66.6 -87.9 240 61 31 3.3 1.8 | -66.3 -87.3 235 61 32 2.6 1.4
45000 -60.5 -76.9 245 86 45 6.3 3.5 | -60.6 -77.1 240 88 45 6.7 3.7
40000 -51.1 -60.0 240 93 48 5.6 3.1 | -50.6 -59.1 235 95 49 6.5 3.6
38000 -47.7 -53.9 235 82 42 5.7 3.1 | -46.7 -52.1 230 89 46 6.5 3.6
36000 -43.9 -47.0 225 71 37 5.6 3.1 | -42.8 -45.0 230 85 44 6.5 3.6
34000 -39.5 -39.1 225 65 33 7.8 4.3 | -38.4 -37.1 220 75 39 6.5 3.6
32000 -34.8 -30.6 220 60 31 7.9 4.3 | -34.5 -30.1 210 67 34 6.6 3.6
30000 -30.0 -22.0 220 56 29 8.2 4.5 | -30.2 -22.4 210 62 32 7.8 4.3
29000 -27.5 -17.5 220 55 28 8.2 4.5 | -27.9 -18.2 210 59 31 7.8 4.3
28000 -25.1 -13.2 220 54 28 8.4 4.6 | -25.6 -14.1 210 57 29 7.9 4.3
27000 -22.9 -9.2 220 52 27 7.1 3.9 | -23.6 -10.5 215 56 29 6.2 3.4
26000 -20.8 -5.4 220 49 25 7.1 3.9 | -21.8 -7.2 220 55 28 6.2 3.4
25000 -18.7 -1.7 215 47 24 7.1 3.9 | -19.9 -3.8 225 54 28 6.2 3.4
24000 -16.8 1.8 215 45 23 6.1 3.3 | -18.1 -0.6 230 53 27 6.0 3.3
23000 -15.0 5.0 215 43 22 6.1 3.3 | -16.4 2.5 230 50 26 6.0 3.3
22000 -12.8 9.0 215 40 21 6.1 3.4 | -14.2 6.4 235 46 24 6.0 3.3
21000 -11.1 12.0 215 39 20 5.7 3.1 | -12.3 9.9 235 43 22 6.3 3.4
20000 -9.4 15.1 215 38 20 5.7 3.1 | -10.5 13.1 230 41 21 6.3 3.5
19500 -8.6 16.5 215 38 19 5.7 3.1 | -9.6 14.7 230 41 21 6.3 3.5
19000 -7.8 18.0 215 37 19 5.7 3.1 | -8.7 16.3 230 40 20 6.3 3.5
18500 -7.0 19.4 215 37 19 5.6 3.1 | -7.8 18.0 230 39 20 6.3 3.5
18000 -6.2 20.8 215 36 19 5.6 3.1 | -6.9 19.6 230 38 19 6.4 3.5
17500 -5.4 22.3 215 36 18 5.1 2.8 | -6.0 21.2 230 36 19 5.6 3.0
17000 -4.7 23.5 215 35 18 5.2 2.8 | -5.2 22.6 230 35 18 5.6 3.1
16500 -3.9 25.0 215 34 18 5.2 2.8 | -4.4 24.1 230 33 17 5.5 3.0
16000 -3.2 26.2 215 33 17 5.1 2.8 | -3.7 25.3 230 32 16 5.3 2.9
15500 -2.5 27.5 215 32 16 5.1 2.8 | -2.9 26.8 230 30 16 5.3 2.9
15000 -1.8 28.8 215 31 16 4.8 2.6 | -2.2 28.0 230 29 15 5.3 2.9
14500 -1.1 30.0 215 30 15 4.9 2.7 | -1.4 29.5 230 28 14 5.3 2.9
14000 -0.5 31.1 215 29 15 3.5 1.9 | -0.7 30.7 230 27 14 5.3 2.9
13500 0.0 32.0 215 27 14 3.5 1.9 | 0.1 32.2 230 26 13 5.3 2.9
13000 0.6 33.1 220 26 13 4.8 2.6 | 0.8 33.4 230 25 13 5.6 3.1
12500 1.3 34.3 220 24 12 5.1 2.8 | 1.6 34.9 230 24 13 5.7 3.1
12000 2.1 35.8 220 22 12 6.2 3.4 | 2.5 36.5 230 23 12 5.9 3.3
11500 3.0 37.4 225 21 11 6.7 3.7 | 3.4 38.1 235 22 12 6.1 3.3
11000 4.0 39.2 225 19 10 6.0 3.3 | 4.2 39.6 235 21 11 5.9 3.2
10500 4.8 40.6 230 17 9 5.1 2.8 | 5.1 41.2 235 21 11 5.3 2.9
10250 5.1 41.2 230 16 8 7.2 3.9 | 5.5 41.9 235 20 10 7.3 4.0
10000 5.7 42.3 230 16 8 7.3 4.0 | 6.1 43.0 235 18 9 7.3 4.0
9750 6.1 43.0 230 15 8 5.3 2.9 | 6.5 43.7 235 17 9 5.2 2.9
9500 6.5 43.7 230 14 7 6.0 3.3 | 6.9 44.4 235 17 9 5.8 3.2
9250 6.9 44.4 230 13 7 5.3 2.9 | 7.3 45.1 235 16 8 5.7 3.1
9000 7.3 45.1 230 11 6 5.4 3.0 | 7.7 45.9 235 16 8 5.6 3.1
8750 7.7 45.9 230 10 5 5.8 3.2 | 8.1 46.6 230 15 8 5.3 2.9
8500 8.1 46.6 230 10 5 5.8 3.2 | 8.4 47.1 230 13 7 5.6 3.1
8250 8.9 48.0 230 8 4 4.9 2.7 | 9.1 48.4 225 11 6 4.3 2.3
8000 9.2 48.6 230 7 4 5.1 2.8 | 9.4 48.9 220 10 5 5.1 2.8
7750 9.6 49.3 225 6 3 5.6 3.1 | 9.8 49.6 215 9 4 6.3 3.4
7500 10.0 50.0 225 5 3 4.7 2.6 | 10.2 50.4 210 7 4 4.3 2.3
7250 10.2 50.4 220 5 3 3.8 2.1 | 10.4 50.7 200 6 3 2.0 1.1
7000 10.6 51.1 210 4 2 5.4 3.0 | 10.6 51.1 185 5 2 5.7 3.1
6750 11.0 51.8 205 4 2 6.0 3.3 | 11.1 52.0 170 4 2 8.3 4.6
6500 11.3 52.3 190 3 2 4.2 2.3 | 11.6 52.9 150 3 2 6.3 3.5
6250 11.6 52.9 170 3 1 2.7 1.5 | 12.0 53.6 130 4 2 5.0 2.7
6000 11.8 53.2 150 3 2 5.7 3.1 | 12.4 54.3 115 4 2 8.0 4.4
5750 12.4 54.3 135 3 1 9.9 5.5 | 13.2 55.8 120 3 2 14.4 7.9
5500 12.7 54.9 120 2 1 -7.5 -4.1 | 14.2 57.6 110 4 2 9.7 5.3
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
10/11/2025 at 1500 MDT | 10/11/2025 at 1800 MDT
|
CAPE... +279.9 LI... -1.6 | CAPE... +428.1 LI... -2.2
CINH... -2.9 K Index... +27.3 | CINH... -10.5 K Index... +25.6
|
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 -66.1 -87.0 235 66 34 2.5 1.4 | -65.2 -85.4 235 68 35 2.5 1.4
45000 -60.9 -77.6 240 90 46 6.9 3.8 | -60.1 -76.2 240 91 47 6.7 3.7
40000 -50.1 -58.2 235 97 50 7.2 3.9 | -49.6 -57.3 235 98 51 5.7 3.1
38000 -45.8 -50.4 235 95 49 7.1 3.9 | -46.2 -51.2 235 98 50 5.8 3.2
36000 -41.5 -42.7 235 94 48 7.1 3.9 | -42.7 -44.9 235 97 50 5.8 3.2
34000 -38.2 -36.8 230 86 44 4.7 2.6 | -39.5 -39.1 235 88 46 5.0 2.8
32000 -35.4 -31.7 230 74 38 4.7 2.6 | -36.5 -33.7 235 75 39 5.0 2.8
30000 -31.8 -25.2 230 67 35 6.9 3.8 | -32.6 -26.7 240 67 34 7.7 4.2
29000 -29.7 -21.5 225 65 33 6.9 3.8 | -30.3 -22.5 240 64 33 7.7 4.2
28000 -27.6 -17.7 225 63 32 6.9 3.8 | -28.0 -18.4 240 62 32 7.7 4.2
27000 -25.5 -13.9 225 61 32 7.2 4.0 | -25.8 -14.4 240 59 31 6.8 3.7
26000 -22.8 -9.0 225 61 31 7.3 4.0 | -23.8 -10.8 240 57 29 6.8 3.7
25000 -20.7 -5.3 230 60 31 7.2 4.0 | -21.3 -6.3 240 53 27 6.8 3.7
24000 -18.7 -1.7 230 57 29 6.3 3.4 | -19.3 -2.7 240 51 26 6.4 3.5
23000 -16.8 1.8 230 53 27 6.2 3.4 | -17.4 0.7 240 49 25 6.4 3.5
22000 -14.9 5.2 235 48 25 6.2 3.4 | -15.5 4.1 240 47 24 6.4 3.5
21000 -13.1 8.4 240 44 23 6.4 3.5 | -13.6 7.5 240 44 23 6.5 3.5
20000 -11.2 11.8 240 39 20 6.5 3.6 | -11.7 10.9 240 40 21 6.5 3.6
19500 -10.3 13.5 240 36 19 6.5 3.6 | -10.7 12.7 240 39 20 6.5 3.6
19000 -9.4 15.1 240 34 17 6.5 3.6 | -9.8 14.4 240 37 19 6.4 3.5
18500 -8.4 16.9 240 33 17 6.4 3.5 | -8.9 16.0 240 36 18 5.9 3.2
18000 -7.5 18.5 240 31 16 6.5 3.5 | -8.0 17.6 235 35 18 6.0 3.3
17500 -6.6 20.1 240 30 16 6.3 3.5 | -7.2 19.0 235 34 17 6.6 3.6
17000 -5.8 21.6 240 30 15 6.3 3.5 | -6.2 20.8 235 33 17 6.8 3.7
16500 -4.9 23.2 245 29 15 6.2 3.4 | -5.3 22.5 235 32 17 6.7 3.7
16000 -4.0 24.8 245 29 15 5.8 3.2 | -4.4 24.1 235 32 16 6.1 3.3
15500 -3.2 26.2 245 28 14 5.8 3.2 | -3.5 25.7 235 31 16 6.2 3.4
15000 -2.3 27.9 245 28 14 5.9 3.2 | -2.6 27.3 235 31 16 6.2 3.4
14500 -1.5 29.3 245 27 14 5.9 3.2 | -1.7 28.9 240 30 15 6.3 3.4
14000 -0.7 30.7 240 26 14 5.8 3.2 | -0.8 30.6 240 29 15 6.4 3.5
13500 0.2 32.4 240 26 13 5.8 3.2 | 0.1 32.2 240 28 14 6.5 3.6
13000 1.0 33.8 240 25 13 6.0 3.3 | 1.0 33.8 240 27 14 6.5 3.5
12500 1.8 35.2 240 24 12 6.1 3.3 | 1.9 35.4 235 26 13 6.4 3.5
12000 2.7 36.9 235 22 12 6.0 3.3 | 2.8 37.0 235 24 13 6.3 3.5
11500 3.5 38.3 235 21 11 5.9 3.2 | 3.6 38.5 230 23 12 6.0 3.3
11000 4.3 39.7 230 20 10 5.4 3.0 | 4.5 40.1 230 22 11 5.8 3.2
10500 5.0 41.0 230 19 10 3.9 2.2 | 5.2 41.4 225 21 11 4.6 2.5
10250 5.3 41.5 225 18 9 6.8 3.7 | 5.6 42.1 225 20 11 6.9 3.8
10000 5.9 42.6 225 17 9 8.2 4.5 | 6.1 43.0 220 19 10 8.5 4.6
9750 6.4 43.5 220 16 8 5.9 3.2 | 6.7 44.1 215 19 10 6.8 3.7
9500 6.8 44.2 220 15 8 5.7 3.1 | 7.1 44.8 215 18 9 6.6 3.6
9250 7.2 45.0 215 14 7 6.4 3.5 | 7.6 45.7 215 17 9 6.9 3.8
9000 8.1 46.6 210 13 7 6.3 3.4 | 8.1 46.6 210 16 8 8.0 4.4
8750 8.6 47.5 205 12 6 6.2 3.4 | 8.7 47.7 210 16 8 8.2 4.5
8500 9.0 48.2 200 11 6 5.9 3.2 | 9.8 49.6 205 15 8 8.0 4.4
8250 9.4 48.9 200 10 5 5.6 3.1 | 10.4 50.7 205 14 7 7.3 4.0
8000 9.8 49.6 195 9 5 6.8 3.7 | 10.9 51.6 200 12 6 7.3 4.0
7750 10.4 50.7 190 9 4 7.8 4.3 | 11.4 52.5 200 12 6 8.1 4.4
7500 10.9 51.6 190 8 4 6.9 3.8 | 12.0 53.6 195 11 6 7.3 4.0
7250 11.4 52.5 185 7 4 6.1 3.3 | 12.5 54.5 190 10 5 5.5 3.0
7000 11.9 53.4 180 7 3 8.9 4.9 | 12.9 55.2 185 9 5 7.4 4.1
6750 12.7 54.9 180 7 3 11.4 6.3 | 13.5 56.3 185 9 4 9.9 5.4
6500 13.4 56.1 180 6 3 9.3 5.1 | 14.2 57.6 180 8 4 8.0 4.4
6250 14.0 57.2 175 6 3 8.0 4.4 | 14.7 58.5 170 7 4 6.1 3.4
6000 14.7 58.5 170 5 3 9.0 4.9 | 15.2 59.4 155 6 3 7.9 4.3
5750 15.4 59.7 175 5 3 12.8 7.0 | 15.8 60.4 165 6 3 9.8 5.4
5500 16.8 62.2 165 4 2 29.5 16.2 | 16.2 61.2 145 4 2 -1.5 -0.8
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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