Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
399
UXUS97 KGJT 061306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
606 AM MST Saturday, December 6, 2025
This forecast is for Saturday, December 6, 2025:
If the trigger temperature of 39.6 F/4.2 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 464 ft/min (2.4 m/s)
Maximum height of thermals.................. 11799 ft MSL (6193 ft AGL)
Forecast maximum temperature................... 45.0 F/7.7 C
Time of trigger temperature.................... 1100 MST
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................. 9494 ft MSL (3888 ft AGL)
Thermal soaring outlook for Sunday 12/07....... Good
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:19:33 / 16:51:15 MST
Total possible sunshine........... 9 hr 31 min 42 sec (571 min 42 sec)
Altitude of sun at 12:05:24 MST... 28.29 degrees
Upper air data from rawinsonde observation taken on 12/06/2025 at 0500 MST
Freezing level.................. Entire airmass below 32 F / 0 C
Convective condensation level... 12299 ft MSL (6693 ft AGL)
Lifted condensation level....... 11978 ft MSL (6372 ft AGL)
Lifted index.................... +11.6
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 -62.9 -81.2 300 64 33 3.3 1.8 M M M M M
45000 -57.9 -72.2 300 79 41 2.5 1.4 M M M M M
40000 -57.4 -71.3 310 93 48 0.3 0.2 M M M M M
38000 -56.0 -68.8 310 99 51 3.7 2.1 M M M M M
36000 -53.8 -64.8 315 104 54 3.8 2.1 M M M M M
34000 -51.2 -60.2 315 108 56 7.0 3.9 M M M M M
32000 -47.1 -52.8 320 105 54 6.8 3.7 M M M M M
30000 -42.9 -45.2 325 103 53 7.6 4.2 33.4 92.2 19.7 M M
29000 -40.6 -41.1 325 102 52 7.6 4.2 32.5 90.5 19.2 M M
28000 -38.3 -36.9 325 100 52 7.6 4.2 31.7 89.0 18.8 M M
27000 -36.1 -33.0 325 99 51 7.6 4.2 31.0 87.8 18.5 M M
26000 -33.9 -29.0 325 96 49 7.1 3.9 29.9 85.8 17.9 M M
25000 -31.8 -25.2 325 92 47 7.1 3.9 28.9 83.9 17.3 M M
24000 -29.7 -21.5 325 88 45 7.3 4.0 28.0 82.3 16.7 M M
23000 -28.0 -18.4 325 82 42 5.3 2.9 26.5 79.6 15.7 M M
22000 -26.4 -15.5 320 75 39 5.4 2.9 24.8 76.7 14.5 M M
21000 -24.3 -11.7 320 67 35 7.0 3.9 23.0 73.5 13.2 M M
20000 -22.0 -7.6 320 65 34 7.3 4.0 22.1 71.8 12.6 M M
19500 -20.9 -5.6 325 64 33 7.4 4.0 21.7 71.1 12.3 M M
19000 -19.8 -3.6 325 63 33 7.4 4.0 21.3 70.4 12.1 M M
18500 -18.7 -1.7 325 62 32 7.0 3.9 20.9 69.7 11.8 M M
18000 -17.7 0.1 325 61 31 6.9 3.8 20.4 68.8 11.4 M M
17500 -16.7 1.9 325 60 31 6.8 3.7 19.9 67.9 11.1 M M
17000 -15.7 3.7 325 58 30 6.0 3.3 19.3 66.8 10.6 M M
16500 -14.8 5.4 320 56 29 6.3 3.4 18.7 65.7 10.1 M M
16000 -14.0 6.8 320 54 28 3.7 2.0 17.9 64.3 9.5 M M
15500 -13.5 7.7 320 51 26 3.6 2.0 16.9 62.4 8.6 M M
15000 -13.0 8.6 320 49 25 2.1 1.2 15.8 60.5 7.7 M M
14500 -12.8 9.0 320 45 23 1.3 0.7 14.4 57.9 6.5 M M
14000 -12.6 9.3 320 42 21 1.1 0.6 13.0 55.4 5.2 M M
13500 -12.5 9.5 315 38 20 0.9 0.5 11.5 52.8 3.9 M M
13000 -12.4 9.7 315 34 18 1.5 0.8 10.1 50.2 2.5 M M
12500 -12.1 10.2 315 31 16 3.0 1.7 8.9 48.1 1.4 M M
12000 -11.7 10.9 310 28 14 3.5 1.9 7.8 46.1 0.4 M M
11500 -11.1 12.0 310 24 13 4.5 2.5 6.9 44.5 -0.5 445 2.3
11000 -10.4 13.3 305 21 11 4.6 2.5 6.1 43.0 -1.3 411 2.1
10500 -9.7 14.5 300 20 10 4.3 2.4 5.3 41.6 -2.1 375 1.9
10250 -9.3 15.3 300 19 10 7.6 4.2 5.0 40.9 -2.4 356 1.8
10000 -8.7 16.3 295 17 9 8.8 4.9 5.0 40.9 -2.5 328 1.7
9750 -8.1 17.4 295 16 8 6.4 3.5 4.7 40.5 -2.7 306 1.6
9500 -7.6 18.3 290 15 8 7.4 4.1 4.5 40.1 -3.0 283 1.4
9250 -7.1 19.2 290 14 7 5.9 3.2 4.3 39.7 -3.2 260 1.3
9000 -6.7 19.9 290 14 7 6.7 3.7 4.0 39.2 -3.5 241 1.2
8750 -6.1 21.0 285 13 7 8.5 4.7 3.8 38.9 -3.7 215 1.1
8500 -5.5 22.1 280 12 6 8.2 4.5 3.7 38.7 -3.8 190 1.0
8250 -4.9 23.2 275 10 5 7.6 4.2 3.6 38.5 -3.9 164 0.8
8000 -4.4 24.1 280 10 5 6.7 3.7 3.4 38.1 -4.2 141 0.7
7750 -3.9 25.0 275 8 4 6.8 3.7 3.2 37.7 -4.4 119 0.6
7500 -3.4 25.9 270 7 4 6.7 3.7 2.9 37.3 -4.6 97 0.5
7250 -2.9 26.8 265 6 3 7.3 4.0 2.7 36.9 -4.9 74 0.4
7000 -2.4 27.7 260 5 2 5.9 3.3 2.5 36.5 -5.1 51 0.3
6750 -2.0 28.4 250 4 2 4.6 2.5 2.1 35.8 -5.5 33 0.2
6500 -1.7 28.9 235 3 1 1.3 0.7 1.7 35.0 -6.0 17 0.1
6250 -1.9 28.6 190 2 1 -3.9 -2.1 0.8 33.4 -6.8 14 0.1
6000 -2.0 28.4 155 3 2 4.0 2.2 -0.1 31.9 -7.7 11 0.1
5750 -1.5 29.3 140 3 2 4.1 2.2 -0.3 31.5 -8.0 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 * * * * * *
12/06/2025 at 0800 MST | 12/06/2025 at 1100 MST
|
CAPE... 0.0 LI... +2.6 | CAPE... +0.3 LI... +3.3
CINH... -0.1 K Index... +19.7 | CINH... 0.0 K Index... +12.8
|
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 -61.2 -78.2 295 63 32 2.3 1.3 | -60.9 -77.6 290 59 30 2.7 1.5
45000 -57.6 -71.7 290 77 39 2.2 1.2 | -56.6 -69.9 290 81 42 2.0 1.1
40000 -54.3 -65.7 305 95 49 2.2 1.2 | -53.8 -64.8 300 99 51 1.8 1.0
38000 -52.6 -62.7 310 103 53 3.2 1.7 | -52.2 -62.0 300 101 52 3.6 1.9
36000 -50.7 -59.3 310 110 56 3.2 1.7 | -50.1 -58.2 305 97 50 3.6 2.0
34000 -48.5 -55.3 310 115 59 7.1 3.9 | -47.9 -54.2 310 94 49 4.7 2.6
32000 -44.5 -48.1 310 111 57 6.8 3.7 | -45.0 -49.0 310 87 45 4.7 2.6
30000 -40.5 -40.9 305 106 55 5.6 3.1 | -42.1 -43.8 310 80 41 6.3 3.4
29000 -38.9 -38.0 305 101 52 5.4 3.0 | -40.2 -40.4 310 77 40 6.5 3.6
28000 -37.3 -35.1 305 97 50 5.4 3.0 | -38.2 -36.8 310 74 38 6.5 3.6
27000 -35.2 -31.4 300 91 47 5.5 3.0 | -35.8 -32.4 310 70 36 6.5 3.6
26000 -33.6 -28.5 300 87 45 5.7 3.1 | -33.8 -28.8 305 71 36 6.6 3.6
25000 -31.9 -25.4 300 84 43 5.7 3.1 | -31.8 -25.2 305 72 37 6.6 3.6
24000 -30.2 -22.4 300 80 41 5.6 3.1 | -29.9 -21.8 300 73 38 6.8 3.7
23000 -28.0 -18.4 300 78 40 7.8 4.3 | -28.3 -18.9 300 74 38 5.0 2.7
22000 -25.7 -14.3 300 76 39 7.7 4.3 | -26.8 -16.2 295 74 38 5.0 2.8
21000 -23.4 -10.1 300 74 38 7.1 3.9 | -25.3 -13.5 295 75 38 5.3 2.9
20000 -21.6 -6.9 300 71 37 6.0 3.3 | -23.6 -10.5 295 71 37 5.8 3.2
19500 -20.7 -5.3 300 70 36 6.0 3.3 | -22.7 -8.9 295 69 36 5.8 3.2
19000 -19.8 -3.6 300 69 36 6.0 3.3 | -21.8 -7.2 295 67 35 5.8 3.2
18500 -18.9 -2.0 295 68 35 5.7 3.1 | -21.0 -5.8 295 65 34 5.9 3.2
18000 -18.2 -0.8 295 66 34 3.9 2.1 | -20.0 -4.0 295 63 33 6.6 3.6
17500 -17.6 0.3 295 64 33 3.9 2.1 | -19.1 -2.4 295 61 32 6.6 3.6
17000 -17.0 1.4 295 62 32 5.6 3.1 | -18.1 -0.6 295 59 30 6.1 3.4
16500 -16.1 3.0 295 60 31 5.8 3.2 | -17.2 1.0 300 57 29 6.1 3.3
16000 -15.3 4.5 295 57 29 6.1 3.3 | -16.3 2.7 300 54 28 6.0 3.3
15500 -14.3 6.3 295 54 28 6.4 3.5 | -15.4 4.3 300 51 26 5.9 3.3
15000 -13.4 7.9 295 51 26 6.5 3.6 | -14.6 5.7 295 48 25 5.9 3.3
14500 -12.4 9.7 295 49 25 7.0 3.9 | -13.7 7.3 295 46 24 6.0 3.3
14000 -11.4 11.5 295 47 24 7.0 3.8 | -12.8 9.0 295 44 23 6.0 3.3
13500 -10.3 13.5 295 46 24 7.0 3.9 | -11.9 10.6 295 42 22 6.7 3.7
13000 -9.3 15.3 295 45 23 7.1 3.9 | -10.9 12.4 295 41 21 6.6 3.6
12500 -8.3 17.1 295 44 23 6.2 3.4 | -9.9 14.2 295 41 21 6.8 3.7
12000 -7.4 18.7 295 44 23 6.4 3.5 | -8.9 16.0 295 41 21 6.9 3.8
11500 -6.5 20.3 295 43 22 5.7 3.1 | -8.0 17.6 295 40 21 5.8 3.2
11000 -5.7 21.7 290 41 21 6.0 3.3 | -7.1 19.2 295 39 20 6.0 3.3
10500 -5.0 23.0 290 39 20 3.8 2.1 | -6.4 20.5 295 38 19 5.1 2.8
10250 -4.7 23.5 290 38 20 3.5 1.9 | -6.0 21.2 295 37 19 4.8 2.6
10000 -4.4 24.1 285 37 19 5.6 3.0 | -5.6 21.9 295 36 19 6.3 3.5
9750 -3.9 25.0 280 35 18 5.2 2.8 | -5.1 22.8 295 33 17 6.7 3.7
9500 -3.7 25.3 280 33 17 2.7 1.5 | -4.7 23.5 295 31 16 5.4 3.0
9250 -3.2 26.2 275 29 15 3.2 1.8 | -4.3 24.3 290 29 15 5.9 3.2
9000 -2.9 26.8 270 29 15 3.9 2.1 | -3.5 25.7 290 27 14 4.6 2.5
8750 -2.6 27.3 265 27 14 4.4 2.4 | -3.2 26.2 285 24 12 4.7 2.6
8500 -2.3 27.9 265 24 12 4.1 2.3 | -2.8 27.0 280 21 11 4.6 2.5
8250 -1.9 28.6 260 21 11 4.7 2.6 | -2.5 27.5 275 19 10 4.9 2.7
8000 -1.5 29.3 255 22 11 5.0 2.8 | -2.1 28.2 275 19 10 5.8 3.2
7750 -1.2 29.8 255 19 10 4.8 2.6 | -1.6 29.1 270 17 9 6.2 3.4
7500 -0.8 30.6 250 16 8 4.6 2.5 | -1.2 29.8 270 15 7 6.1 3.4
7250 -0.5 31.1 250 13 7 2.8 1.5 | -0.7 30.7 270 13 7 5.3 2.9
7000 -0.3 31.5 250 11 6 3.7 2.0 | -0.3 31.5 265 13 7 7.2 3.9
6750 0.1 32.2 250 9 4 6.0 3.3 | 0.3 32.5 265 11 6 9.4 5.1
6500 0.5 32.9 245 6 3 4.3 2.3 | 1.0 33.8 265 9 4 7.0 3.9
6250 0.7 33.3 250 4 2 2.3 1.2 | 1.4 34.5 265 7 4 5.1 2.8
6000 0.9 33.6 260 2 1 5.0 2.8 | 1.8 35.2 270 5 3 7.4 4.0
5750 1.4 34.5 235 2 1 3.9 2.1 | 2.6 36.7 260 6 3 12.8 7.0
5500 0.5 32.9 000 0 0 -36.5 -20.0 | 3.6 38.5 275 3 2 13.8 7.6
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
12/06/2025 at 1400 MST | 12/06/2025 at 1700 MST
|
CAPE... +24.9 LI... +4.2 | CAPE... +1.4 LI... +5.9
CINH... -1.5 K Index... -1.3 | CINH... -3.9 K Index... -3.3
|
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 -61.2 -78.2 290 60 31 2.7 1.5 | -61.3 -78.3 290 60 31 2.9 1.6
45000 -57.1 -70.8 290 85 44 2.7 1.5 | -57.2 -71.0 290 83 43 2.8 1.6
40000 -53.0 -63.4 295 94 48 2.6 1.4 | -53.4 -64.1 300 84 43 2.2 1.2
38000 -51.6 -60.9 300 96 49 2.3 1.3 | -52.2 -62.0 305 87 45 1.9 1.0
36000 -50.2 -58.4 305 96 50 2.3 1.3 | -51.0 -59.8 315 95 49 1.9 1.0
34000 -48.7 -55.7 310 98 50 4.3 2.4 | -49.7 -57.5 320 103 53 5.2 2.8
32000 -45.9 -50.6 310 92 48 4.6 2.5 | -46.3 -51.3 315 97 50 5.7 3.1
30000 -43.1 -45.6 305 88 45 7.0 3.8 | -42.9 -45.2 315 91 47 6.0 3.3
29000 -40.9 -41.6 305 87 45 7.4 4.0 | -41.1 -42.0 315 88 45 6.0 3.3
28000 -38.7 -37.7 305 85 44 7.4 4.0 | -39.3 -38.7 315 85 44 6.0 3.3
27000 -36.5 -33.7 305 84 43 7.4 4.1 | -37.5 -35.5 310 82 42 5.9 3.2
26000 -34.3 -29.7 305 84 43 7.2 3.9 | -35.5 -31.9 310 80 41 7.4 4.0
25000 -31.6 -24.9 310 84 43 7.2 3.9 | -32.7 -26.9 310 78 40 7.4 4.1
24000 -29.4 -20.9 310 84 43 7.3 4.0 | -30.5 -22.9 310 77 39 7.4 4.0
23000 -27.4 -17.3 310 82 42 6.6 3.6 | -28.3 -18.9 310 75 39 7.4 4.1
22000 -25.4 -13.7 310 80 41 6.6 3.6 | -26.1 -15.0 315 73 38 7.4 4.1
21000 -23.5 -10.3 310 78 40 5.8 3.2 | -23.8 -10.8 315 72 37 6.5 3.6
20000 -22.4 -8.3 310 72 37 3.2 1.7 | -22.4 -8.3 315 67 35 4.3 2.4
19500 -21.9 -7.4 310 69 35 3.2 1.7 | -21.8 -7.2 315 65 33 4.3 2.4
19000 -21.4 -6.5 310 66 34 3.2 1.7 | -21.1 -6.0 315 62 32 4.3 2.4
18500 -21.0 -5.8 310 63 32 3.2 1.7 | -20.5 -4.9 315 60 31 4.1 2.3
18000 -20.5 -4.9 310 60 31 3.2 1.7 | -20.1 -4.2 315 56 29 1.7 0.9
17500 -20.0 -4.0 310 56 29 3.1 1.7 | -19.8 -3.6 315 52 27 1.8 1.0
17000 -19.5 -3.1 310 53 27 4.4 2.4 | -19.5 -3.1 315 49 25 2.9 1.6
16500 -18.8 -1.8 310 51 26 4.7 2.6 | -19.0 -2.2 315 46 23 3.2 1.8
16000 -18.1 -0.6 310 48 25 5.1 2.8 | -18.6 -1.5 315 43 22 4.0 2.2
15500 -17.3 0.9 310 46 24 5.7 3.1 | -17.8 -0.0 315 40 21 5.0 2.7
15000 -16.4 2.5 310 45 23 5.8 3.2 | -17.1 1.2 315 38 19 5.2 2.9
14500 -15.5 4.1 310 43 22 6.7 3.7 | -16.2 2.8 315 36 18 6.1 3.4
14000 -14.6 5.7 310 42 22 6.6 3.6 | -15.4 4.3 315 34 17 6.1 3.4
13500 -13.6 7.5 305 41 21 7.1 3.9 | -14.4 6.1 315 32 16 7.2 4.0
13000 -12.5 9.5 305 39 20 7.0 3.8 | -13.3 8.1 315 31 16 7.1 3.9
12500 -11.5 11.3 305 37 19 7.6 4.2 | -12.2 10.0 310 29 15 7.7 4.2
12000 -10.4 13.3 305 36 19 7.5 4.1 | -11.1 12.0 310 28 15 7.6 4.2
11500 -9.3 15.3 305 35 18 7.9 4.3 | -9.9 14.2 310 27 14 8.6 4.7
11000 -8.1 17.4 305 34 17 8.0 4.4 | -8.7 16.3 305 26 14 8.6 4.7
10500 -7.1 19.2 305 32 16 6.5 3.6 | -7.6 18.3 305 25 13 7.0 3.8
10250 -6.6 20.1 305 31 16 5.6 3.1 | -7.1 19.2 305 25 13 6.0 3.3
10000 -6.1 21.0 300 30 16 9.7 5.3 | -6.6 20.1 305 24 12 10.3 5.7
9750 -5.3 22.5 300 28 14 10.3 5.7 | -5.6 21.9 305 24 12 11.6 6.4
9500 -4.7 23.5 300 26 13 6.7 3.7 | -5.0 23.0 305 23 12 8.1 4.4
9250 -4.2 24.4 300 24 13 7.6 4.1 | -4.3 24.3 305 22 12 9.4 5.1
9000 -3.6 25.5 300 23 12 7.9 4.3 | -3.1 26.4 300 21 11 8.2 4.5
8750 -2.5 27.5 295 21 11 7.2 4.0 | -2.4 27.7 300 20 10 9.6 5.3
8500 -2.0 28.4 295 18 9 7.2 4.0 | -1.7 28.9 300 19 10 9.3 5.1
8250 -1.4 29.5 290 16 8 7.9 4.4 | -1.0 30.2 300 19 10 9.2 5.0
8000 -0.8 30.6 295 17 9 8.4 4.6 | -0.4 31.3 300 19 10 8.8 4.8
7750 -0.2 31.6 295 15 8 8.0 4.4 | 0.3 32.5 295 17 9 8.7 4.8
7500 0.4 32.7 290 13 7 8.1 4.4 | 0.9 33.6 295 16 8 8.6 4.7
7250 1.0 33.8 295 13 7 7.5 4.1 | 1.5 34.7 295 16 8 8.5 4.7
7000 1.5 34.7 295 14 7 8.9 4.9 | 2.2 36.0 295 16 8 8.1 4.5
6750 2.3 36.1 295 12 6 10.3 5.7 | 2.7 36.9 290 13 7 7.9 4.3
6500 3.0 37.4 290 10 5 10.0 5.5 | 3.3 37.9 290 11 6 8.5 4.6
6250 3.8 38.8 295 11 5 11.0 6.0 | 4.0 39.2 290 11 6 9.3 5.1
6000 4.6 40.3 295 11 6 8.5 4.7 | 4.7 40.5 290 11 6 7.5 4.1
5750 5.1 41.2 295 9 5 7.6 4.2 | 4.8 40.6 285 7 4 -5.0 -2.7
5500 6.5 43.7 290 7 4 41.2 22.6 | 3.3 37.9 275 4 2 -39.7 -21.8
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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