Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
152
UXUS97 KGJT 071306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
606 AM MST Sunday, December 7, 2025
This forecast is for Sunday, December 7, 2025:
If the trigger temperature of 47.0 F/8.4 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 214 ft/min (1.1 m/s)
Maximum height of thermals.................. 8576 ft MSL (2969 ft AGL)
Forecast maximum temperature................... 44.0 F/7.1 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................. 6711 ft MSL (1104 ft AGL)
Thermal soaring outlook for Monday 12/08....... Fair
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:20:25 / 16:51:14 MST
Total possible sunshine........... 9 hr 30 min 49 sec (570 min 49 sec)
Altitude of sun at 12:05:50 MST... 28.17 degrees
Upper air data from rawinsonde observation taken on 12/07/2025 at 0500 MST
Freezing level.................. 5780 ft MSL (173 ft AGL)
Additional freezing level....... 7046 ft MSL (1439 ft AGL)
Convective condensation level... 14682 ft MSL (9075 ft AGL)
Lifted condensation level....... 11478 ft MSL (5871 ft AGL)
Lifted index.................... +9.1
K index......................... +16.8
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 -63.0 -81.4 290 52 27 2.5 1.4 M M M M M
45000 -59.3 -74.7 290 57 29 2.1 1.2 M M M M M
40000 -57.4 -71.3 295 53 27 1.2 0.7 M M M M M
38000 -56.1 -69.0 295 52 27 3.3 1.8 M M M M M
36000 -53.9 -65.0 300 53 28 3.3 1.8 M M M M M
34000 -51.8 -61.2 300 55 28 4.6 2.5 M M M M M
32000 -49.0 -56.2 295 60 31 4.6 2.5 M M M M M
30000 -45.9 -50.6 290 64 33 7.3 4.0 29.5 85.0 17.1 M M
29000 -43.7 -46.7 290 63 32 7.3 4.0 28.3 83.0 16.5 M M
28000 -41.6 -42.9 290 63 32 7.3 4.0 27.4 81.3 16.0 M M
27000 -39.4 -38.9 290 62 32 7.6 4.2 26.6 79.9 15.5 M M
26000 -37.0 -34.6 290 58 30 8.0 4.4 25.8 78.4 15.1 M M
25000 -34.6 -30.3 295 54 28 8.0 4.4 25.1 77.2 14.7 M M
24000 -32.2 -26.0 295 50 26 8.0 4.4 24.6 76.3 14.4 M M
23000 -29.9 -21.8 295 47 24 7.7 4.2 23.8 74.8 13.9 M M
22000 -27.6 -17.7 300 45 23 7.7 4.2 23.0 73.4 13.4 M M
21000 -24.8 -12.6 300 41 21 7.5 4.1 22.1 71.8 12.9 M M
20000 -22.6 -8.7 300 39 20 7.5 4.1 21.2 70.2 12.3 M M
19500 -21.4 -6.5 305 38 19 7.5 4.1 20.9 69.6 12.0 M M
19000 -20.3 -4.5 305 36 19 7.6 4.2 20.5 68.9 11.8 M M
18500 -19.3 -2.7 305 35 18 6.7 3.7 20.1 68.2 11.5 M M
18000 -18.2 -0.8 305 34 18 6.8 3.7 19.6 67.2 11.1 M M
17500 -17.2 1.0 305 33 17 6.3 3.4 19.1 66.3 10.7 M M
17000 -16.4 2.5 310 32 17 6.0 3.3 18.4 65.1 10.1 M M
16500 -15.5 4.1 310 32 16 6.0 3.3 17.8 64.0 9.6 M M
16000 -14.7 5.5 310 31 16 5.9 3.2 17.1 62.8 9.0 M M
15500 -13.8 7.2 310 30 16 5.9 3.2 16.5 61.7 8.5 M M
15000 -12.9 8.8 310 29 15 6.5 3.5 15.9 60.6 8.0 M M
14500 -11.9 10.6 310 29 15 6.5 3.5 15.3 59.6 7.5 M M
14000 -11.0 12.2 310 28 14 5.8 3.2 14.7 58.5 7.0 M M
13500 -10.2 13.6 310 27 14 5.8 3.2 14.1 57.3 6.4 M M
13000 -9.3 15.3 305 26 13 5.3 2.9 13.4 56.1 5.8 M M
12500 -8.6 16.5 305 25 13 5.2 2.9 12.7 54.8 5.2 M M
12000 -7.8 18.0 305 24 12 6.0 3.3 12.0 53.6 4.5 M M
11500 -6.9 19.6 300 22 11 6.2 3.4 11.4 52.5 4.0 M M
11000 -6.0 21.2 300 20 10 5.4 3.0 10.8 51.5 3.4 M M
10500 -5.2 22.6 295 18 9 4.8 2.6 10.1 50.2 2.8 M M
10250 -4.8 23.4 295 17 9 6.8 3.7 9.7 49.5 2.4 M M
10000 -4.3 24.3 290 15 8 6.5 3.5 9.6 49.2 2.3 M M
9750 -3.9 25.0 290 14 7 4.0 2.2 9.2 48.5 1.9 M M
9500 -3.6 25.5 285 12 6 5.1 2.8 8.8 47.8 1.5 M M
9250 -3.2 26.2 285 11 6 3.0 1.7 8.4 47.1 1.2 M M
9000 -3.0 26.6 280 10 5 3.6 2.0 7.8 46.0 0.6 M M
8750 -2.6 27.3 275 9 4 6.0 3.3 7.5 45.4 0.3 M M
8500 -2.2 28.0 270 7 4 5.2 2.9 7.1 44.8 -0.0 213 1.1
8250 -1.8 28.8 265 6 3 5.0 2.7 6.8 44.2 -0.3 194 1.0
8000 -1.4 29.5 255 5 3 4.9 2.7 6.4 43.5 -0.7 175 0.9
7750 -1.0 30.2 240 4 2 5.5 3.0 6.0 42.9 -1.0 156 0.8
7500 -0.6 30.9 220 3 2 4.5 2.5 5.7 42.3 -1.4 137 0.7
7250 -0.3 31.5 190 4 2 3.5 1.9 5.2 41.4 -1.8 121 0.6
7000 -0.0 32.0 170 5 3 4.3 2.3 4.8 40.6 -2.3 105 0.5
6750 0.3 32.5 160 5 3 3.4 1.9 4.4 39.9 -2.7 88 0.4
6500 0.4 32.7 155 6 3 1.1 0.6 3.8 38.8 -3.3 76 0.4
6250 0.4 32.7 150 6 3 0.0 0.0 3.1 37.5 -4.0 68 0.3
6000 0.5 32.9 145 7 3 1.6 0.9 2.4 36.3 -4.7 59 0.3
5750 0.5 32.9 140 6 3 -3.7 -2.0 1.7 35.0 -5.4 52 0.3
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 * * * * * *
12/07/2025 at 0800 MST | 12/07/2025 at 1100 MST
|
CAPE... 0.0 LI... +8.4 | CAPE... 0.0 LI... +8.0
CINH... -0.2 K Index... -13.0 | CINH... 0.0 K Index... -10.2
|
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 -62.5 -80.5 300 58 30 2.5 1.4 | -62.8 -81.0 295 61 32 3.1 1.7
45000 -58.7 -73.7 300 81 42 2.1 1.1 | -58.2 -72.8 295 76 39 2.2 1.2
40000 -58.5 -73.3 305 86 44 0.1 0.0 | -58.8 -73.8 300 80 41 -0.5 -0.3
38000 -57.0 -70.6 310 90 46 4.4 2.4 | -57.5 -71.5 305 81 42 4.4 2.4
36000 -54.4 -65.9 315 94 48 4.4 2.4 | -54.9 -66.8 305 82 42 4.4 2.4
34000 -51.4 -60.5 315 97 50 7.5 4.1 | -51.9 -61.4 310 83 43 7.3 4.0
32000 -47.0 -52.6 320 95 49 7.4 4.0 | -47.5 -53.5 315 85 44 7.3 4.0
30000 -42.5 -44.5 320 94 48 7.7 4.2 | -43.1 -45.6 315 87 45 7.5 4.1
29000 -40.2 -40.4 320 92 47 7.7 4.2 | -40.8 -41.4 315 86 44 7.5 4.1
28000 -37.9 -36.2 320 90 46 7.7 4.2 | -38.5 -37.3 315 85 44 7.5 4.1
27000 -35.6 -32.1 320 88 46 7.5 4.1 | -36.3 -33.3 320 85 44 7.5 4.1
26000 -33.7 -28.7 320 85 44 6.3 3.5 | -34.1 -29.4 315 80 41 7.4 4.1
25000 -31.3 -24.3 320 81 42 6.3 3.5 | -31.3 -24.3 315 75 39 7.5 4.1
24000 -29.4 -20.9 320 78 40 5.9 3.3 | -29.1 -20.4 315 70 36 6.5 3.6
23000 -27.8 -18.0 320 74 38 5.4 3.0 | -27.3 -17.1 315 67 34 6.0 3.3
22000 -26.2 -15.2 315 69 36 5.4 3.0 | -25.5 -13.9 310 63 33 6.1 3.3
21000 -24.5 -12.1 315 65 33 6.1 3.4 | -23.7 -10.7 310 60 31 5.1 2.8
20000 -22.6 -8.7 320 61 31 6.2 3.4 | -22.2 -8.0 310 56 29 5.2 2.8
19500 -21.7 -7.1 320 59 30 6.2 3.4 | -21.4 -6.5 305 54 28 5.2 2.8
19000 -20.7 -5.3 320 57 29 6.2 3.4 | -20.7 -5.3 305 53 27 5.1 2.8
18500 -19.8 -3.6 320 55 28 6.9 3.8 | -19.8 -3.6 305 51 26 6.4 3.5
18000 -18.7 -1.7 320 54 28 7.2 3.9 | -18.8 -1.8 305 48 25 6.5 3.6
17500 -17.6 0.3 325 52 27 7.1 3.9 | -17.8 -0.0 310 46 24 6.7 3.7
17000 -16.6 2.1 325 50 26 6.9 3.8 | -16.8 1.8 310 44 23 6.9 3.8
16500 -15.5 4.1 325 48 25 7.1 3.9 | -15.7 3.7 310 42 22 6.9 3.8
16000 -14.6 5.7 325 46 24 5.3 2.9 | -14.7 5.5 310 40 21 7.2 4.0
15500 -13.8 7.2 325 43 22 5.3 2.9 | -13.6 7.5 310 38 19 7.3 4.0
15000 -13.0 8.6 325 41 21 4.4 2.4 | -12.6 9.3 310 36 18 5.7 3.1
14500 -12.4 9.7 325 38 19 4.0 2.2 | -11.7 10.9 310 33 17 5.5 3.0
14000 -11.8 10.8 320 35 18 3.3 1.8 | -10.9 12.4 310 31 16 4.5 2.5
13500 -11.5 11.3 320 31 16 2.6 1.4 | -10.3 13.5 310 29 15 4.0 2.2
13000 -11.1 12.0 315 28 14 2.2 1.2 | -9.8 14.4 310 26 13 3.3 1.8
12500 -10.9 12.4 315 25 13 1.8 1.0 | -9.4 15.1 310 23 12 2.9 1.6
12000 -10.6 12.9 310 21 11 2.8 1.5 | -9.0 15.8 310 20 10 2.6 1.4
11500 -10.0 14.0 305 18 9 4.6 2.5 | -8.6 16.5 305 18 9 2.5 1.4
11000 -9.4 15.1 300 15 8 5.2 2.9 | -8.3 17.1 295 15 8 3.9 2.1
10500 -8.5 16.7 295 13 7 6.0 3.3 | -7.6 18.3 290 14 7 4.8 2.6
10250 -8.1 17.4 295 12 6 5.9 3.2 | -7.3 18.9 285 13 7 4.7 2.6
10000 -7.7 18.1 290 12 6 5.9 3.2 | -6.9 19.6 285 13 7 5.0 2.7
9750 -7.2 19.0 290 11 6 7.2 4.0 | -6.5 20.3 280 13 7 6.3 3.5
9500 -6.6 20.1 290 10 5 8.0 4.4 | -6.0 21.2 275 12 6 6.8 3.7
9250 -6.1 21.0 290 9 5 7.9 4.3 | -5.6 21.9 270 11 6 6.9 3.8
9000 -4.9 23.2 285 8 4 7.9 4.3 | -5.0 23.0 265 11 5 7.4 4.1
8750 -4.3 24.3 285 7 4 7.4 4.1 | -4.5 23.9 260 10 5 7.3 4.0
8500 -3.7 25.3 280 6 3 7.6 4.2 | -3.4 25.9 255 8 4 6.8 3.7
8250 -3.2 26.2 280 6 3 8.1 4.4 | -3.0 26.6 255 7 4 6.2 3.4
8000 -2.6 27.3 280 6 3 6.7 3.7 | -2.5 27.5 250 6 3 7.2 3.9
7750 -2.2 28.0 270 4 2 5.5 3.0 | -1.9 28.6 245 5 3 6.6 3.6
7500 -1.7 28.9 255 3 2 5.9 3.2 | -1.5 29.3 235 4 2 4.9 2.7
7250 -1.3 29.7 245 3 2 6.5 3.6 | -1.2 29.8 225 3 1 4.0 2.2
7000 -0.8 30.6 235 3 1 4.3 2.4 | -0.8 30.6 205 2 1 6.9 3.8
6750 -0.6 30.9 195 2 1 2.8 1.5 | -0.2 31.6 195 2 1 9.1 5.0
6500 -0.4 31.3 175 3 1 3.1 1.7 | 0.4 32.7 185 2 1 8.2 4.5
6250 -0.1 31.8 155 3 2 4.9 2.7 | 1.0 33.8 175 2 1 7.4 4.1
6000 0.1 32.2 145 4 2 -2.7 -1.5 | 1.6 34.9 155 2 1 9.8 5.4
5750 -0.8 30.6 130 3 2 -22.2 -12.2 | 2.6 36.7 140 2 1 17.4 9.5
5500 -1.9 28.6 110 3 2 7.8 4.3 | 3.7 38.7 135 2 1 5.3 2.9
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
12/07/2025 at 1400 MST | 12/07/2025 at 1700 MST
|
CAPE... 0.0 LI... +8.1 | CAPE... 0.0 LI... +8.2
CINH... -0.1 K Index... +1.8 | CINH... -0.1 K Index... +7.9
|
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 -63.0 -81.4 290 59 30 3.4 1.8 | -63.1 -81.6 290 58 30 3.1 1.7
45000 -57.9 -72.2 290 73 37 2.2 1.2 | -58.4 -73.1 295 71 37 2.1 1.2
40000 -58.9 -74.0 295 80 41 -0.7 -0.4 | -59.0 -74.2 295 82 42 -0.4 -0.2
38000 -57.8 -72.0 300 82 42 3.7 2.0 | -57.9 -72.2 295 84 43 3.6 1.9
36000 -55.6 -68.1 305 83 43 3.7 2.0 | -55.7 -68.3 300 85 44 3.6 2.0
34000 -52.8 -63.0 305 85 44 7.6 4.2 | -53.1 -63.6 305 86 44 7.5 4.1
32000 -48.3 -54.9 305 85 44 7.6 4.2 | -48.6 -55.5 305 85 44 7.5 4.1
30000 -43.6 -46.5 310 86 44 8.1 4.5 | -44.0 -47.2 305 84 43 8.0 4.4
29000 -41.2 -42.2 310 86 44 8.2 4.5 | -41.6 -42.9 305 83 43 8.1 4.4
28000 -38.7 -37.7 310 86 44 8.2 4.5 | -39.1 -38.4 305 82 42 8.1 4.4
27000 -36.3 -33.3 310 85 44 7.9 4.3 | -36.7 -34.1 305 81 42 8.0 4.4
26000 -34.0 -29.2 310 82 42 7.4 4.1 | -34.4 -29.9 305 78 40 7.8 4.3
25000 -31.3 -24.3 310 78 40 7.4 4.1 | -31.5 -24.7 310 74 38 7.8 4.3
24000 -29.1 -20.4 310 75 38 7.0 3.8 | -29.1 -20.4 310 70 36 7.4 4.1
23000 -27.1 -16.8 310 71 36 6.8 3.7 | -27.0 -16.6 310 67 34 7.3 4.0
22000 -25.0 -13.0 310 66 34 6.8 3.7 | -24.8 -12.6 310 63 33 7.3 4.0
21000 -23.1 -9.6 310 62 32 5.3 2.9 | -22.7 -8.9 310 60 31 6.3 3.5
20000 -21.5 -6.7 305 58 30 5.5 3.0 | -20.8 -5.4 310 57 29 6.4 3.5
19500 -20.7 -5.3 305 56 29 5.5 3.0 | -19.8 -3.6 310 56 29 6.5 3.5
19000 -19.9 -3.8 305 54 28 5.5 3.0 | -18.9 -2.0 310 54 28 6.6 3.6
18500 -19.1 -2.4 305 52 27 6.3 3.4 | -18.0 -0.4 310 53 27 5.4 3.0
18000 -18.1 -0.6 305 50 26 6.3 3.5 | -17.2 1.0 310 51 26 5.4 2.9
17500 -17.2 1.0 305 48 25 6.0 3.3 | -16.4 2.5 310 49 25 5.2 2.9
17000 -16.4 2.5 300 46 24 5.3 2.9 | -15.7 3.7 310 46 24 5.0 2.7
16500 -15.6 3.9 300 44 23 5.3 2.9 | -15.0 5.0 310 44 23 5.0 2.7
16000 -14.8 5.4 300 42 22 5.2 2.8 | -14.2 6.4 310 42 22 5.2 2.8
15500 -14.0 6.8 300 40 21 5.2 2.8 | -13.5 7.7 310 40 21 5.2 2.9
15000 -13.1 8.4 300 38 20 5.8 3.2 | -12.7 9.1 310 38 20 4.6 2.5
14500 -12.2 10.0 300 36 19 5.9 3.2 | -12.1 10.2 310 37 19 4.6 2.5
14000 -11.3 11.7 300 34 17 6.1 3.4 | -11.4 11.5 305 35 18 5.1 2.8
13500 -10.3 13.5 300 32 16 6.2 3.4 | -10.5 13.1 305 32 17 5.4 2.9
13000 -9.4 15.1 300 29 15 5.3 2.9 | -9.7 14.5 300 30 16 5.3 2.9
12500 -8.7 16.3 300 27 14 4.7 2.6 | -8.9 16.0 300 28 14 5.2 2.9
12000 -8.0 17.6 300 25 13 4.0 2.2 | -8.1 17.4 295 25 13 5.3 2.9
11500 -7.5 18.5 295 22 11 3.4 1.9 | -7.3 18.9 290 23 12 5.4 2.9
11000 -7.0 19.4 290 18 9 3.8 2.1 | -6.5 20.3 285 21 11 5.1 2.8
10500 -6.5 20.3 285 16 8 4.2 2.3 | -5.8 21.6 280 18 9 4.9 2.7
10250 -6.2 20.8 280 15 8 4.1 2.2 | -5.4 22.3 275 17 9 5.0 2.8
10000 -5.9 21.4 275 14 7 4.9 2.7 | -5.0 23.0 270 16 8 5.4 3.0
9750 -5.5 22.1 270 14 7 6.2 3.4 | -4.6 23.7 270 15 8 5.6 3.1
9500 -5.0 23.0 265 12 6 6.4 3.5 | -4.2 24.4 265 13 7 5.2 2.9
9250 -4.6 23.7 260 11 6 6.6 3.6 | -3.8 25.2 260 12 6 6.3 3.5
9000 -4.1 24.6 260 10 5 6.9 3.8 | -3.3 26.1 255 11 6 7.9 4.3
8750 -3.6 25.5 255 10 5 7.2 4.0 | -2.2 28.0 245 10 5 6.6 3.6
8500 -2.5 27.5 245 7 4 6.8 3.7 | -1.7 28.9 240 9 4 6.7 3.7
8250 -2.0 28.4 245 6 3 6.1 3.4 | -1.3 29.7 235 8 4 6.7 3.7
8000 -1.6 29.1 245 6 3 7.1 3.9 | -0.8 30.6 230 7 4 6.2 3.4
7750 -1.0 30.2 235 5 2 7.4 4.0 | -0.4 31.3 225 6 3 5.7 3.1
7500 -0.5 31.1 230 4 2 6.7 3.7 | 0.1 32.2 210 5 3 6.0 3.3
7250 -0.0 32.0 220 3 1 6.0 3.3 | 0.5 32.9 200 5 2 6.1 3.4
7000 0.5 32.9 200 2 1 8.2 4.5 | 1.0 33.8 185 4 2 5.7 3.1
6750 1.2 34.2 195 3 1 9.8 5.4 | 1.4 34.5 180 4 2 6.3 3.5
6500 1.9 35.4 195 2 1 8.9 4.9 | 1.9 35.4 170 4 2 6.7 3.7
6250 2.5 36.5 190 2 1 8.8 4.8 | 2.4 36.3 160 4 2 8.3 4.6
6000 3.2 37.8 185 2 1 10.2 5.6 | 2.9 37.2 150 4 2 1.4 0.8
5750 4.1 39.4 150 2 1 13.9 7.6 | 2.4 36.3 150 3 1 -14.7 -8.1
5500 5.0 41.0 145 1 1 7.0 3.8 | 2.0 35.6 135 3 1 21.7 11.9
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.
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