Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
907
UXUS97 KGJT 291306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
606 AM MST Saturday, November 29, 2025
This forecast is for Saturday, November 29, 2025:
If the trigger temperature of 47.7 F/8.7 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 307 ft/min (1.6 m/s)
Maximum height of thermals.................. 9809 ft MSL (4203 ft AGL)
Forecast maximum temperature................... 48.0 F/9.3 C
Time of trigger temperature.................... 1300 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................. 7192 ft MSL (1586 ft AGL)
Thermal soaring outlook for Sunday 11/30....... Poor
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:12:56 / 16:52:19 MST
Total possible sunshine........... 9 hr 39 min 23 sec (579 min 23 sec)
Altitude of sun at 12:02:37 MST... 29.27 degrees
Upper air data from rawinsonde observation taken on 11/29/2025 at 0500 MST
Freezing level.................. 7873 ft MSL (2267 ft AGL)
Convective condensation level... 16099 ft MSL (10493 ft AGL)
Lifted condensation level....... 13369 ft MSL (7763 ft AGL)
Lifted index.................... +8.3
K index......................... -5.5
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 -58.7 -73.7 280 49 25 0.4 0.2 M M M M M
45000 -58.1 -72.6 275 62 32 0.3 0.2 M M M M M
40000 -59.7 -75.5 270 67 34 -1.2 -0.7 M M M M M
38000 -60.0 -76.0 265 69 35 1.9 1.0 M M M M M
36000 -58.8 -73.8 270 68 35 2.0 1.1 M M M M M
34000 -57.2 -71.0 270 68 35 6.9 3.8 M M M M M
32000 -52.2 -62.0 270 65 33 8.4 4.6 M M M M M
30000 -47.2 -53.0 275 61 31 8.9 4.9 27.8 82.0 14.2 M M
29000 -44.5 -48.1 275 58 30 8.8 4.8 27.3 81.1 14.0 M M
28000 -41.9 -43.4 275 54 28 8.8 4.8 26.9 80.4 13.9 M M
27000 -39.3 -38.7 275 51 26 8.9 4.9 26.6 80.0 13.8 M M
26000 -36.9 -34.4 270 49 25 7.8 4.3 25.9 78.7 13.4 M M
25000 -34.6 -30.3 270 49 25 7.8 4.3 25.2 77.3 13.0 M M
24000 -32.2 -26.0 265 48 25 7.8 4.3 24.5 76.1 12.6 M M
23000 -30.0 -22.0 265 48 25 7.1 3.9 23.6 74.5 12.0 M M
22000 -27.9 -18.2 265 47 24 7.1 3.9 22.6 72.7 11.3 M M
21000 -25.8 -14.4 260 46 24 7.2 3.9 21.8 71.2 10.7 M M
20000 -23.7 -10.7 260 44 23 6.9 3.8 20.7 69.3 9.9 M M
19500 -22.7 -8.9 260 43 22 6.9 3.8 20.2 68.4 9.5 M M
19000 -21.1 -6.0 260 41 21 6.8 3.8 19.5 67.1 9.0 M M
18500 -20.1 -4.2 260 40 20 6.5 3.6 19.0 66.3 8.7 M M
18000 -19.2 -2.6 260 38 20 6.1 3.4 18.4 65.1 8.2 M M
17500 -18.3 -0.9 260 37 19 6.0 3.3 17.8 64.0 7.7 M M
17000 -17.3 0.9 260 36 19 7.1 3.9 17.2 63.0 7.3 M M
16500 -16.2 2.8 260 35 18 7.0 3.8 16.8 62.2 6.9 M M
16000 -15.2 4.6 255 34 18 6.7 3.7 16.3 61.3 6.5 M M
15500 -14.2 6.4 255 34 17 6.6 3.6 15.8 60.4 6.1 M M
15000 -13.2 8.2 250 34 17 6.0 3.3 15.3 59.5 5.7 M M
14500 -12.4 9.7 250 33 17 5.1 2.8 14.5 58.1 5.0 M M
14000 -11.7 10.9 245 33 17 5.0 2.7 13.7 56.7 4.3 M M
13500 -11.0 12.2 245 34 17 4.6 2.5 12.9 55.2 3.5 M M
13000 -10.3 13.5 240 34 17 4.9 2.7 12.1 53.7 2.7 M M
12500 -9.6 14.7 240 34 17 6.1 3.3 11.4 52.5 2.1 M M
12000 -8.7 16.3 240 33 17 6.2 3.4 10.8 51.4 1.5 M M
11500 -7.7 18.1 235 32 16 8.0 4.4 10.4 50.7 1.1 M M
11000 -6.5 20.3 230 30 15 7.7 4.2 10.1 50.1 0.8 M M
10500 -5.4 22.3 230 27 14 6.7 3.7 9.7 49.4 0.4 M M
10250 -4.9 23.2 230 26 13 8.1 4.4 9.5 49.0 0.2 M M
10000 -4.2 24.4 225 25 13 8.6 4.7 9.4 48.9 0.1 M M
9750 -3.6 25.5 225 24 12 7.0 3.9 9.2 48.6 -0.0 305 1.5
9500 -3.1 26.4 220 23 12 6.7 3.7 9.0 48.2 -0.2 282 1.4
9250 -2.6 27.3 220 22 12 7.1 3.9 8.8 47.8 -0.5 259 1.3
9000 -2.1 28.2 215 21 11 6.8 3.7 8.6 47.4 -0.7 236 1.2
8750 -1.6 29.1 215 21 11 6.2 3.4 8.3 46.9 -0.9 215 1.1
8500 -1.2 29.8 210 20 10 6.5 3.6 8.0 46.5 -1.2 193 1.0
8250 -0.7 30.7 210 19 10 5.5 3.0 7.8 46.0 -1.5 172 0.9
8000 -0.3 31.5 205 19 10 5.1 2.8 7.4 45.3 -1.8 154 0.8
7750 0.1 32.2 200 18 9 5.7 3.1 7.1 44.7 -2.1 134 0.7
7500 0.5 32.9 200 17 9 5.7 3.1 6.8 44.2 -2.5 114 0.6
7250 0.9 33.6 195 16 8 5.2 2.8 6.5 43.6 -2.8 94 0.5
7000 1.3 34.3 185 16 8 4.2 2.3 6.1 42.9 -3.2 77 0.4
6750 1.6 34.9 180 15 8 4.4 2.4 5.6 42.1 -3.6 60 0.3
6500 1.9 35.4 175 14 7 3.6 2.0 5.2 41.4 -4.0 43 0.2
6250 2.0 35.6 170 12 6 -2.9 -1.6 4.6 40.2 -4.7 33 0.2
6000 1.7 35.1 160 10 5 -2.5 -1.4 3.5 38.3 -5.7 35 0.2
5750 1.7 35.1 150 9 4 2.5 1.4 2.8 37.1 -6.4 25 0.1
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 * * * * * *
11/29/2025 at 0800 MST | 11/29/2025 at 1100 MST
|
CAPE... 0.0 LI... +8.1 | CAPE... 0.0 LI... +8.1
CINH... 0.0 K Index... -19.2 | CINH... -0.1 K Index... -14.8
|
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 -60.8 -77.4 285 52 27 -0.1 -0.0 | -60.7 -77.3 280 57 29 0.1 0.0
45000 -60.9 -77.6 285 65 33 0.0 0.0 | -60.5 -76.9 280 68 35 0.1 0.1
40000 -63.3 -81.9 285 85 44 -1.7 -0.9 | -62.7 -80.9 275 81 42 -1.5 -0.8
38000 -62.1 -79.8 285 89 46 6.5 3.5 | -61.6 -78.9 275 83 43 5.9 3.2
36000 -58.2 -72.8 285 87 45 6.5 3.5 | -58.0 -72.4 275 83 43 5.9 3.2
34000 -54.3 -65.7 290 85 44 7.8 4.3 | -54.3 -65.7 275 82 42 8.4 4.6
32000 -49.6 -57.3 290 80 41 7.7 4.2 | -49.4 -56.9 275 80 41 8.2 4.5
30000 -45.0 -49.0 295 74 38 8.4 4.6 | -44.5 -48.1 280 77 40 8.1 4.4
29000 -42.5 -44.5 295 72 37 8.4 4.6 | -42.1 -43.8 280 75 38 8.1 4.4
28000 -40.0 -40.0 295 69 36 8.4 4.6 | -39.6 -39.3 280 72 37 8.1 4.4
27000 -37.5 -35.5 295 67 34 8.3 4.6 | -37.2 -35.0 285 70 36 8.0 4.4
26000 -35.1 -31.2 295 65 33 7.8 4.3 | -35.0 -31.0 285 68 35 7.1 3.9
25000 -32.8 -27.0 295 63 33 7.8 4.3 | -32.9 -27.2 285 65 34 7.1 3.9
24000 -30.5 -22.9 295 61 32 8.0 4.4 | -30.2 -22.4 285 62 32 6.9 3.8
23000 -27.9 -18.2 295 58 30 6.5 3.6 | -28.3 -18.9 290 59 30 6.6 3.6
22000 -26.0 -14.8 295 54 28 6.5 3.6 | -26.3 -15.3 290 56 29 6.6 3.6
21000 -24.1 -11.4 295 51 26 6.1 3.3 | -24.4 -11.9 295 53 27 5.9 3.2
20000 -22.2 -8.0 300 46 24 6.0 3.3 | -22.7 -8.9 295 48 25 5.8 3.2
19500 -21.3 -6.3 300 44 23 6.0 3.3 | -21.8 -7.2 295 46 24 5.8 3.2
19000 -20.4 -4.7 300 42 22 6.0 3.3 | -20.9 -5.6 295 43 22 5.7 3.2
18500 -19.5 -3.1 300 40 21 6.4 3.5 | -20.1 -4.2 300 41 21 6.1 3.4
18000 -18.5 -1.3 305 38 20 6.5 3.6 | -19.1 -2.4 300 39 20 6.3 3.5
17500 -17.6 0.3 305 36 19 6.5 3.6 | -18.2 -0.8 300 37 19 6.3 3.5
17000 -16.6 2.1 310 34 18 6.4 3.5 | -17.2 1.0 305 36 18 6.6 3.6
16500 -15.6 3.9 310 33 17 6.4 3.5 | -16.2 2.8 305 34 18 6.6 3.6
16000 -14.7 5.5 315 32 16 6.5 3.6 | -15.2 4.6 305 33 17 6.9 3.8
15500 -13.7 7.3 315 30 16 6.5 3.6 | -14.1 6.6 310 31 16 6.9 3.8
15000 -12.7 9.1 320 29 15 6.4 3.5 | -13.1 8.4 310 30 16 6.7 3.7
14500 -11.8 10.8 320 28 14 6.3 3.4 | -12.1 10.2 315 28 15 6.6 3.6
14000 -10.8 12.6 325 27 14 5.6 3.1 | -11.1 12.0 315 27 14 6.1 3.4
13500 -10.1 13.8 325 25 13 4.6 2.5 | -10.2 13.6 315 25 13 5.6 3.1
13000 -9.4 15.1 325 24 12 3.9 2.1 | -9.4 15.1 320 22 12 5.0 2.8
12500 -9.1 15.6 325 21 11 2.0 1.1 | -8.8 16.2 325 20 10 4.1 2.2
12000 -8.8 16.2 325 18 9 2.2 1.2 | -8.2 17.2 325 18 9 3.6 2.0
11500 -8.5 16.7 325 15 8 2.4 1.3 | -7.8 18.0 325 15 8 2.7 1.5
11000 -8.2 17.2 330 11 6 3.3 1.8 | -7.4 18.7 325 12 6 3.2 1.8
10500 -7.6 18.3 335 9 5 5.0 2.7 | -6.9 19.6 325 10 5 4.0 2.2
10250 -7.2 19.0 340 9 4 5.5 3.0 | -6.6 20.1 325 8 4 3.9 2.2
10000 -6.8 19.8 350 8 4 3.4 1.9 | -6.4 20.5 325 7 4 3.8 2.1
9750 -6.6 20.1 350 8 4 4.8 2.6 | -6.0 21.2 325 6 3 5.5 3.0
9500 -6.1 21.0 360 8 4 8.0 4.4 | -5.6 21.9 330 5 3 6.9 3.8
9250 -5.6 21.9 010 9 4 7.2 3.9 | -5.1 22.8 340 4 2 6.5 3.6
9000 -5.0 23.0 020 9 5 7.4 4.0 | -4.6 23.7 345 4 2 6.5 3.5
8750 -4.5 23.9 025 10 5 6.9 3.8 | -4.1 24.6 350 3 2 6.3 3.5
8500 -4.0 24.8 030 10 5 6.7 3.7 | -3.7 25.3 010 3 2 6.3 3.5
8250 -3.5 25.7 035 11 6 6.7 3.7 | -2.8 27.0 035 4 2 5.8 3.2
8000 -2.6 27.3 045 12 6 7.7 4.2 | -2.3 27.9 040 4 2 7.6 4.2
7750 -1.9 28.6 045 11 6 9.3 5.1 | -1.7 28.9 045 4 2 9.0 4.9
7500 -1.3 29.7 045 11 6 7.4 4.0 | -1.1 30.0 045 5 2 7.9 4.3
7250 -0.8 30.6 050 11 6 5.7 3.1 | -0.5 31.1 050 5 3 6.4 3.5
7000 -0.3 31.5 055 12 6 8.5 4.7 | 0.0 32.0 050 5 3 10.4 5.7
6750 0.4 32.7 055 9 5 8.4 4.6 | 1.0 33.8 050 5 2 11.8 6.5
6500 0.8 33.4 055 8 4 5.0 2.7 | 1.7 35.1 050 5 3 9.1 5.0
6250 1.2 34.2 060 7 4 6.7 3.7 | 2.4 36.3 050 5 3 9.1 5.0
6000 1.6 34.9 070 7 4 1.6 0.9 | 3.1 37.6 050 5 3 11.2 6.1
5750 1.2 34.2 070 4 2 -13.1 -7.2 | 4.2 39.6 050 4 2 18.1 9.9
5500 0.3 32.5 080 2 1 -4.7 -2.6 | 5.5 41.9 050 4 2 13.5 7.4
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
11/29/2025 at 1400 MST | 11/29/2025 at 1700 MST
|
CAPE... 0.0 LI... +6.7 | CAPE... 0.0 LI... +6.2
CINH... -0.1 K Index... -4.6 | CINH... 0.0 K Index... -5.0
|
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 -60.9 -77.6 280 64 33 -0.0 -0.0 | -60.3 -76.5 285 62 32 0.1 0.1
45000 -61.0 -77.8 275 80 41 0.0 0.0 | -60.1 -76.2 280 78 40 0.2 0.1
40000 -62.6 -80.7 270 87 45 -1.2 -0.7 | -62.1 -79.8 270 89 46 -1.4 -0.8
38000 -61.4 -78.5 270 87 45 6.1 3.4 | -61.2 -78.2 265 91 47 5.6 3.1
36000 -57.8 -72.0 270 86 44 6.1 3.4 | -57.8 -72.0 265 89 46 5.6 3.1
34000 -54.0 -65.2 270 83 43 8.1 4.4 | -54.3 -65.7 265 86 44 7.8 4.3
32000 -49.2 -56.6 270 80 41 7.9 4.3 | -49.7 -57.5 270 81 42 7.7 4.2
30000 -44.5 -48.1 270 76 39 7.8 4.3 | -45.1 -49.2 270 77 40 7.6 4.2
29000 -42.2 -44.0 275 75 38 7.9 4.3 | -42.9 -45.2 270 74 38 7.5 4.1
28000 -39.8 -39.6 275 73 38 7.9 4.3 | -40.6 -41.1 275 71 37 7.5 4.1
27000 -37.5 -35.5 275 72 37 7.8 4.3 | -38.4 -37.1 275 69 35 7.6 4.2
26000 -35.5 -31.9 280 69 35 6.4 3.5 | -36.4 -33.5 275 64 33 6.3 3.5
25000 -33.6 -28.5 280 65 34 6.4 3.5 | -34.5 -30.1 280 59 31 6.3 3.5
24000 -31.7 -25.1 280 62 32 6.4 3.5 | -32.7 -26.9 285 55 28 6.4 3.5
23000 -29.3 -20.7 285 57 29 6.3 3.4 | -30.3 -22.5 290 49 25 6.2 3.4
22000 -27.5 -17.5 290 53 27 6.3 3.5 | -28.5 -19.3 295 45 23 6.2 3.4
21000 -25.6 -14.1 295 49 25 6.3 3.4 | -26.6 -15.9 300 41 21 7.0 3.8
20000 -23.7 -10.7 295 45 23 6.3 3.4 | -24.4 -11.9 300 39 20 7.2 4.0
19500 -22.8 -9.0 295 43 22 6.3 3.4 | -23.4 -10.1 305 38 20 7.2 4.0
19000 -21.9 -7.4 300 42 21 6.3 3.4 | -22.3 -8.1 305 37 19 7.3 4.0
18500 -20.9 -5.6 300 40 20 6.7 3.7 | -21.2 -6.2 305 36 19 7.3 4.0
18000 -19.9 -3.8 300 38 19 6.9 3.8 | -20.1 -4.2 305 35 18 7.4 4.0
17500 -18.8 -1.8 305 36 18 6.9 3.8 | -19.0 -2.2 305 34 18 7.3 4.0
17000 -17.8 -0.0 305 34 18 6.5 3.6 | -17.9 -0.2 310 33 17 7.2 4.0
16500 -16.9 1.6 305 33 17 6.5 3.6 | -16.8 1.8 310 32 16 7.3 4.0
16000 -15.8 3.6 310 31 16 7.2 4.0 | -15.8 3.6 310 30 16 7.1 3.9
15500 -14.8 5.4 310 31 16 7.2 4.0 | -14.7 5.5 310 29 15 7.1 3.9
15000 -13.7 7.3 315 30 15 7.3 4.0 | -13.6 7.5 315 28 14 7.2 3.9
14500 -12.5 9.5 315 29 15 7.4 4.0 | -12.5 9.5 315 27 14 7.2 4.0
14000 -11.4 11.5 315 28 14 7.1 3.9 | -11.5 11.3 315 25 13 7.1 3.9
13500 -10.4 13.3 315 26 14 6.7 3.7 | -10.4 13.3 320 23 12 6.9 3.8
13000 -9.4 15.1 315 25 13 6.2 3.4 | -9.4 15.1 320 21 11 6.5 3.6
12500 -8.6 16.5 315 22 11 5.2 2.8 | -8.5 16.7 320 19 10 5.6 3.1
12000 -7.8 18.0 315 20 10 4.9 2.7 | -7.7 18.1 320 16 8 5.5 3.0
11500 -7.1 19.2 315 17 9 4.4 2.4 | -6.9 19.6 320 13 7 4.8 2.7
11000 -6.5 20.3 315 14 7 4.3 2.4 | -6.2 20.8 315 10 5 5.0 2.8
10500 -5.9 21.4 315 11 6 4.2 2.3 | -5.4 22.3 315 8 4 5.5 3.0
10250 -5.6 21.9 315 10 5 4.2 2.3 | -5.0 23.0 315 6 3 5.5 3.0
10000 -5.3 22.5 315 8 4 4.4 2.4 | -4.6 23.7 310 5 3 5.5 3.0
9750 -5.0 23.0 315 8 4 5.5 3.0 | -4.2 24.4 310 5 2 6.3 3.5
9500 -4.5 23.9 320 6 3 6.1 3.4 | -3.7 25.3 310 3 2 7.0 3.8
9250 -4.1 24.6 325 5 3 5.9 3.3 | -3.2 26.2 305 2 1 6.9 3.8
9000 -3.7 25.3 330 4 2 6.4 3.5 | -2.7 27.1 300 1 0 7.8 4.3
8750 -3.2 26.2 340 3 2 7.6 4.2 | -1.6 29.1 000 0 0 6.4 3.5
8500 -2.6 27.3 350 3 2 8.5 4.7 | -1.1 30.0 110 1 1 6.7 3.7
8250 -2.0 28.4 005 3 1 7.4 4.0 | -0.6 30.9 105 2 1 6.6 3.6
8000 -1.0 30.2 025 3 2 8.6 4.7 | -0.1 31.8 100 2 1 7.3 4.0
7750 -0.2 31.6 025 3 2 11.2 6.1 | 0.5 32.9 100 3 1 8.0 4.4
7500 0.5 32.9 025 3 2 8.4 4.6 | 1.0 33.8 100 3 2 7.2 3.9
7250 1.0 33.8 030 3 2 5.6 3.1 | 1.5 34.7 095 4 2 5.9 3.2
7000 1.5 34.7 035 3 2 10.7 5.9 | 2.0 35.6 095 4 2 8.1 4.4
6750 2.5 36.5 030 3 2 13.0 7.1 | 2.7 36.9 090 4 2 9.6 5.3
6500 3.3 37.9 030 3 2 9.5 5.2 | 3.4 38.1 090 4 2 8.3 4.6
6250 4.0 39.2 035 3 2 9.6 5.3 | 4.0 39.2 090 4 2 9.3 5.1
6000 4.8 40.6 035 3 2 10.7 5.9 | 4.6 40.3 085 4 2 5.8 3.2
5750 5.7 42.3 030 3 1 15.6 8.6 | 4.6 40.3 090 2 1 -6.2 -3.4
5500 7.1 44.8 035 3 1 19.3 10.6 | 3.9 39.0 085 2 1 -7.8 -4.3
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
________________________________________________________________________________
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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