Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
559
UXUS97 KGJT 281306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
606 AM MST Friday, November 28, 2025
This forecast is for Friday, November 28, 2025:
If the trigger temperature of 43.4 F/6.3 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 419 ft/min (2.1 m/s)
Maximum height of thermals.................. 13629 ft MSL (8022 ft AGL)
Forecast maximum temperature................... 53.0 F/12.1 C
Time of trigger temperature.................... 1000 MST
Time of overdevelopment........................ 1400 MST
Middle/high clouds during soaring window....... Broken/overcast thin middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 11735 ft MSL (6128 ft AGL)
Thermal soaring outlook for Saturday 11/29..... Fair
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:11:55 / 16:52:37 MST
Total possible sunshine........... 9 hr 40 min 41 sec (580 min 41 sec)
Altitude of sun at 12:02:16 MST... 29.44 degrees
Upper air data from rawinsonde observation taken on 11/28/2025 at 0500 MST
Freezing level.................. 5691 ft MSL (84 ft AGL)
Additional freezing level....... 6839 ft MSL (1232 ft AGL)
Convective condensation level... 11983 ft MSL (6376 ft AGL)
Lifted condensation level....... 13213 ft MSL (7605 ft AGL)
Lifted index.................... +7.0
K index......................... -15.3
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 -59.8 -75.6 290 49 25 -0.2 -0.1 M M M M M
45000 -60.1 -76.2 290 70 36 -0.1 -0.1 M M M M M
40000 -61.8 -79.2 295 85 44 -1.2 -0.7 M M M M M
38000 -60.9 -77.6 295 89 46 5.0 2.8 M M M M M
36000 -57.9 -72.2 300 90 47 5.0 2.7 M M M M M
34000 -54.7 -66.5 305 91 47 7.9 4.3 M M M M M
32000 -50.1 -58.2 305 84 43 7.6 4.2 M M M M M
30000 -45.5 -49.9 305 77 40 8.5 4.7 29.9 85.9 13.7 M M
29000 -43.0 -45.4 305 75 39 8.5 4.6 29.3 84.8 13.4 M M
28000 -40.4 -40.7 305 73 38 8.5 4.6 28.8 83.9 13.2 M M
27000 -37.9 -36.2 305 72 37 8.5 4.6 28.5 83.2 13.1 M M
26000 -35.4 -31.7 305 70 36 8.4 4.6 27.9 82.1 12.8 M M
25000 -32.9 -27.2 305 68 35 8.4 4.6 27.3 81.2 12.5 M M
24000 -30.4 -22.7 310 66 34 8.4 4.6 26.9 80.4 12.3 M M
23000 -27.9 -18.2 310 64 33 8.2 4.5 26.3 79.3 12.0 M M
22000 -25.4 -13.7 310 61 32 8.2 4.5 25.7 78.3 11.6 M M
21000 -22.4 -8.3 315 58 30 6.1 3.3 25.0 77.0 11.2 M M
20000 -20.7 -5.3 315 55 28 5.6 3.1 23.4 74.2 10.0 M M
19500 -19.9 -3.8 315 53 27 5.6 3.1 22.7 72.9 9.5 M M
19000 -19.0 -2.2 320 51 26 5.6 3.1 22.0 71.7 8.9 M M
18500 -18.2 -0.8 320 49 25 4.8 2.6 21.4 70.4 8.4 M M
18000 -17.6 0.3 320 47 24 4.3 2.3 20.4 68.7 7.6 M M
17500 -16.9 1.6 320 45 23 4.2 2.3 19.4 67.0 6.8 M M
17000 -16.4 2.5 320 43 22 3.7 2.0 18.4 65.2 6.0 M M
16500 -15.8 3.6 320 41 21 3.7 2.0 17.4 63.4 5.1 M M
16000 -15.2 4.6 320 39 20 3.8 2.1 16.4 61.5 4.2 M M
15500 -14.7 5.5 320 36 19 3.8 2.1 15.4 59.7 3.3 M M
15000 -14.1 6.6 320 34 17 3.9 2.1 14.4 58.0 2.4 M M
14500 -13.5 7.7 320 31 16 3.9 2.2 13.4 56.2 1.5 M M
14000 -13.0 8.6 320 28 14 3.9 2.2 12.5 54.5 0.7 M M
13500 -12.4 9.7 320 25 13 3.9 2.1 11.5 52.7 -0.3 610 3.1
13000 -11.9 10.6 325 22 11 4.3 2.4 10.6 51.0 -1.2 579 2.9
12500 -11.2 11.8 325 19 10 5.2 2.9 9.8 49.6 -1.9 543 2.8
12000 -10.4 13.3 330 16 8 5.7 3.1 9.1 48.3 -2.7 506 2.6
11500 -9.5 14.9 330 15 8 6.8 3.7 8.5 47.4 -3.2 462 2.3
11000 -8.5 16.7 335 14 7 6.3 3.4 8.1 46.5 -3.7 418 2.1
10500 -7.7 18.1 345 13 7 4.9 2.7 7.4 45.3 -4.4 379 1.9
10250 -7.3 18.9 345 13 7 7.9 4.3 7.1 44.7 -4.7 359 1.8
10000 -6.6 20.1 350 13 7 9.2 5.1 7.1 44.7 -4.7 331 1.7
9750 -6.0 21.2 350 13 7 7.0 3.8 6.9 44.4 -4.9 307 1.6
9500 -5.5 22.1 355 13 6 8.0 4.4 6.7 44.1 -5.1 283 1.4
9250 -4.9 23.2 355 12 6 6.2 3.4 6.5 43.8 -5.3 259 1.3
9000 -4.5 23.9 355 13 7 6.5 3.6 6.2 43.2 -5.7 239 1.2
8750 -3.9 25.0 355 12 6 8.1 4.5 6.1 42.9 -5.8 214 1.1
8500 -3.3 26.1 355 12 6 8.2 4.5 5.9 42.7 -6.0 189 1.0
8250 -2.8 27.0 350 11 6 6.2 3.4 5.8 42.4 -6.2 165 0.8
8000 -2.4 27.7 350 10 5 5.8 3.2 5.4 41.8 -6.5 146 0.7
7750 -1.9 28.6 345 9 5 7.7 4.2 5.2 41.4 -6.8 123 0.6
7500 -1.3 29.7 340 8 4 7.0 3.9 5.0 41.1 -7.0 99 0.5
7250 -0.8 30.6 335 8 4 5.5 3.0 4.8 40.6 -7.2 77 0.4
7000 -0.5 31.1 335 7 4 5.4 3.0 4.4 40.0 -7.6 59 0.3
6750 -0.0 32.0 330 6 3 7.0 3.8 4.2 39.5 -7.9 37 0.2
6500 0.5 32.9 325 6 3 5.5 3.0 3.9 39.1 -8.2 16 0.1
6250 0.8 33.4 330 5 2 3.3 1.8 3.5 38.3 -8.6 M M
6000 1.1 34.0 335 3 2 6.4 3.5 3.1 37.6 -9.1 M M
5750 1.5 34.7 340 2 1 -0.6 -0.3 2.7 36.9 -9.4 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 * * * * * *
11/28/2025 at 0800 MST | 11/28/2025 at 1100 MST
|
CAPE... 0.0 LI... +1.1 | CAPE... 0.0 LI... +1.7
CINH... -0.0 K Index... +13.2 | CINH... -0.1 K Index... +10.9
|
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 -60.9 -77.6 285 53 27 1.1 0.6 | -60.1 -76.2 280 50 26 1.0 0.6
45000 -59.2 -74.6 275 58 30 0.9 0.5 | -58.5 -73.3 275 63 32 1.0 0.6
40000 -60.8 -77.4 275 59 30 -1.2 -0.6 | -60.4 -76.7 275 61 32 -1.4 -0.8
38000 -60.2 -76.4 270 57 30 4.1 2.3 | -60.1 -76.2 275 62 32 3.8 2.1
36000 -57.5 -71.5 270 53 27 4.1 2.3 | -57.8 -72.0 270 64 33 3.7 2.0
34000 -54.4 -65.9 270 49 25 8.5 4.6 | -54.9 -66.8 265 66 34 8.1 4.4
32000 -49.4 -56.9 270 46 24 8.4 4.6 | -50.2 -58.4 270 60 31 7.9 4.3
30000 -44.5 -48.1 270 44 22 7.5 4.1 | -45.5 -49.9 270 55 28 7.8 4.3
29000 -42.2 -44.0 270 43 22 7.6 4.1 | -43.1 -45.6 270 54 28 7.9 4.3
28000 -39.9 -39.8 270 43 22 7.6 4.1 | -40.8 -41.4 270 53 27 7.9 4.3
27000 -37.7 -35.9 270 43 22 7.1 3.9 | -38.4 -37.1 270 51 27 7.7 4.2
26000 -35.7 -32.3 270 43 22 6.5 3.6 | -36.2 -33.2 270 50 26 7.3 4.0
25000 -33.8 -28.8 270 42 22 6.5 3.6 | -34.0 -29.2 275 49 25 7.3 4.0
24000 -31.9 -25.4 270 42 22 6.7 3.7 | -31.9 -25.4 275 47 24 7.3 4.0
23000 -29.7 -21.5 270 41 21 7.4 4.1 | -29.8 -21.6 275 46 24 7.0 3.8
22000 -27.0 -16.6 270 40 20 7.4 4.1 | -27.7 -17.9 275 44 23 7.0 3.8
21000 -24.7 -12.5 275 38 20 7.8 4.3 | -25.0 -13.0 275 42 22 8.1 4.5
20000 -22.4 -8.3 275 36 19 7.8 4.3 | -22.7 -8.9 275 41 21 8.0 4.4
19500 -21.3 -6.3 275 35 18 7.8 4.3 | -21.5 -6.7 275 40 21 8.0 4.4
19000 -20.1 -4.2 275 35 18 7.7 4.2 | -20.3 -4.5 270 39 20 8.0 4.4
18500 -18.9 -2.0 275 33 17 8.8 4.8 | -19.1 -2.4 270 39 20 8.6 4.7
18000 -17.6 0.3 275 32 17 8.8 4.8 | -17.8 -0.0 270 38 19 8.6 4.7
17500 -16.3 2.7 275 31 16 9.0 4.9 | -16.5 2.3 270 37 19 8.6 4.7
17000 -14.9 5.2 275 30 16 9.2 5.0 | -15.2 4.6 270 36 18 8.7 4.8
16500 -13.5 7.7 275 29 15 9.2 5.1 | -13.9 7.0 270 35 18 8.7 4.8
16000 -12.2 10.0 275 28 15 9.2 5.0 | -12.6 9.3 270 34 18 8.6 4.7
15500 -10.8 12.6 275 28 14 9.2 5.0 | -11.3 11.7 270 33 17 8.6 4.7
15000 -9.4 15.1 270 27 14 8.8 4.8 | -10.1 13.8 270 33 17 8.5 4.6
14500 -8.1 17.4 270 26 13 8.8 4.8 | -8.8 16.2 270 32 16 8.5 4.6
14000 -6.8 19.8 270 25 13 8.4 4.6 | -7.5 18.5 270 31 16 8.3 4.6
13500 -5.6 21.9 270 25 13 8.3 4.6 | -6.3 20.7 265 30 16 8.3 4.5
13000 -4.4 24.1 270 24 12 7.5 4.1 | -5.1 22.8 265 30 15 7.8 4.3
12500 -3.4 25.9 265 24 12 6.9 3.8 | -4.0 24.8 265 29 15 7.3 4.0
12000 -2.3 27.9 265 23 12 6.3 3.4 | -3.0 26.6 265 28 14 6.6 3.6
11500 -1.6 29.1 260 23 12 5.6 3.0 | -2.2 28.0 260 26 13 5.2 2.9
11000 -0.8 30.6 255 22 11 5.1 2.8 | -1.4 29.5 255 25 13 4.7 2.6
10500 -0.1 31.8 250 21 11 5.1 2.8 | -0.9 30.4 250 23 12 3.5 1.9
10250 0.2 32.4 250 20 11 2.4 1.3 | -0.6 30.9 250 23 12 4.5 2.4
10000 0.3 32.5 250 21 11 2.4 1.3 | -0.2 31.6 245 22 11 5.5 3.0
9750 0.6 33.1 245 20 10 4.9 2.7 | 0.1 32.2 245 20 10 4.4 2.4
9500 0.9 33.6 245 18 9 4.4 2.4 | 0.4 32.7 240 19 10 3.7 2.0
9250 1.3 34.3 240 17 9 4.0 2.2 | 0.7 33.3 240 18 9 3.8 2.1
9000 1.5 34.7 240 16 8 2.5 1.4 | 0.9 33.6 235 17 9 3.6 2.0
8750 1.7 35.1 235 15 8 3.1 1.7 | 1.2 34.2 235 15 8 4.2 2.3
8500 1.9 35.4 235 13 7 4.2 2.3 | 1.5 34.7 235 14 7 4.9 2.7
8250 2.2 36.0 230 12 6 3.1 1.7 | 2.1 35.8 225 10 5 2.5 1.4
8000 2.5 36.5 220 9 5 3.7 2.0 | 2.3 36.1 220 8 4 5.1 2.8
7750 2.9 37.2 215 8 4 5.5 3.0 | 2.9 37.2 220 8 4 8.0 4.4
7500 3.3 37.9 205 7 4 4.1 2.2 | 3.4 38.1 215 7 4 5.4 3.0
7250 3.5 38.3 200 7 3 2.9 1.6 | 3.6 38.5 210 5 3 2.3 1.3
7000 3.8 38.8 195 6 3 4.8 2.6 | 3.9 39.0 205 4 2 7.4 4.1
6750 4.2 39.6 190 6 3 4.4 2.4 | 4.7 40.5 210 4 2 10.7 5.9
6500 4.4 39.9 180 5 3 1.6 0.9 | 5.4 41.7 210 4 2 7.8 4.3
6250 4.5 40.1 175 5 2 1.4 0.8 | 5.9 42.6 215 3 1 6.8 3.7
6000 4.6 40.3 165 4 2 1.2 0.7 | 6.4 43.5 225 2 1 8.9 4.9
5750 4.4 39.9 150 2 1 -9.2 -5.1 | 7.3 45.1 220 3 1 15.4 8.5
5500 2.3 36.1 115 1 1 -55.8 -30.6 | 8.6 47.5 240 2 1 16.8 9.2
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
11/28/2025 at 1400 MST | 11/28/2025 at 1700 MST
|
CAPE... 0.0 LI... +2.0 | CAPE... 0.0 LI... +0.3
CINH... 0.0 K Index... +14.4 | CINH... -0.2 K Index... +17.8
|
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 -59.9 -75.8 280 48 25 0.5 0.3 | -59.0 -74.2 280 45 23 1.0 0.6
45000 -59.2 -74.6 275 58 30 0.5 0.3 | -57.5 -71.5 280 52 27 1.0 0.5
40000 -60.1 -76.2 280 66 34 -0.7 -0.4 | -59.7 -75.5 280 69 36 -1.7 -0.9
38000 -59.4 -74.9 280 69 36 3.9 2.1 | -59.2 -74.6 280 76 39 5.1 2.8
36000 -57.1 -70.8 280 71 37 3.9 2.1 | -56.1 -69.0 290 83 43 5.1 2.8
34000 -54.7 -66.5 275 72 37 6.2 3.4 | -53.1 -63.6 295 91 47 5.3 2.9
32000 -50.7 -59.3 275 68 35 6.5 3.6 | -49.8 -57.6 290 85 44 5.4 3.0
30000 -46.7 -52.1 275 65 33 8.6 4.7 | -46.5 -51.7 280 81 42 7.1 3.9
29000 -44.2 -47.6 275 64 33 8.4 4.6 | -44.2 -47.6 280 80 41 7.5 4.1
28000 -41.6 -42.9 275 63 32 8.4 4.6 | -42.0 -43.6 280 79 41 7.5 4.1
27000 -39.1 -38.4 275 62 32 8.5 4.7 | -39.8 -39.6 275 78 40 7.5 4.1
26000 -36.3 -33.3 275 60 31 7.4 4.0 | -37.0 -34.6 275 74 38 7.2 3.9
25000 -34.1 -29.4 275 58 30 7.4 4.0 | -34.9 -30.8 280 70 36 7.2 3.9
24000 -31.9 -25.4 275 57 29 7.5 4.1 | -32.7 -26.9 280 65 34 7.2 3.9
23000 -29.6 -21.3 275 55 28 7.6 4.2 | -30.5 -22.9 280 62 32 7.4 4.1
22000 -27.4 -17.3 275 53 27 7.7 4.2 | -28.3 -18.9 275 58 30 7.5 4.1
21000 -25.1 -13.2 275 51 26 7.9 4.3 | -26.1 -15.0 275 55 28 7.5 4.1
20000 -22.7 -8.9 275 49 25 7.9 4.4 | -23.9 -11.0 275 53 27 7.5 4.1
19500 -21.5 -6.7 275 48 25 8.0 4.4 | -22.8 -9.0 275 52 27 7.6 4.1
19000 -20.3 -4.5 275 47 24 8.0 4.4 | -21.6 -6.9 275 52 27 7.6 4.2
18500 -19.2 -2.6 270 46 24 7.8 4.3 | -20.5 -4.9 275 51 26 7.5 4.1
18000 -18.0 -0.4 270 46 24 7.8 4.3 | -19.4 -2.9 275 50 26 7.3 4.0
17500 -16.9 1.6 270 45 23 7.8 4.3 | -18.4 -1.1 275 48 25 7.3 4.0
17000 -15.7 3.7 270 45 23 8.1 4.4 | -17.2 1.0 275 47 24 7.7 4.3
16500 -14.5 5.9 270 44 23 8.0 4.4 | -16.1 3.0 270 46 24 7.7 4.2
16000 -13.3 8.1 265 43 22 8.2 4.5 | -14.9 5.2 270 45 23 8.1 4.4
15500 -12.0 10.4 265 42 22 8.2 4.5 | -13.7 7.3 270 44 23 8.2 4.5
15000 -10.8 12.6 265 41 21 8.1 4.5 | -12.5 9.5 270 43 22 8.4 4.6
14500 -9.6 14.7 265 40 20 8.1 4.4 | -11.2 11.8 270 42 21 8.8 4.8
14000 -8.4 16.9 265 38 20 8.1 4.5 | -9.9 14.2 270 41 21 8.8 4.8
13500 -7.1 19.2 265 37 19 8.3 4.6 | -8.6 16.5 270 39 20 8.6 4.7
13000 -5.9 21.4 260 35 18 8.2 4.5 | -7.3 18.9 270 38 20 8.6 4.7
12500 -4.7 23.5 260 34 17 8.0 4.4 | -6.0 21.2 270 37 19 8.3 4.6
12000 -3.5 25.7 260 32 16 7.8 4.3 | -4.8 23.4 270 36 18 8.4 4.6
11500 -2.4 27.7 260 30 15 6.6 3.6 | -3.6 25.5 265 34 18 7.6 4.2
11000 -1.5 29.3 255 28 14 6.5 3.5 | -2.5 27.5 260 32 16 7.7 4.2
10500 -0.7 30.7 250 26 14 4.0 2.2 | -1.5 29.3 260 30 16 6.3 3.5
10250 -0.4 31.3 250 26 13 4.5 2.5 | -1.0 30.2 255 30 15 6.6 3.6
10000 -0.0 32.0 245 24 13 7.5 4.1 | -0.5 31.1 255 29 15 8.8 4.8
9750 0.5 32.9 240 22 12 7.3 4.0 | 0.2 32.4 250 27 14 8.6 4.7
9500 0.9 33.6 240 21 11 5.2 2.8 | 0.7 33.3 250 26 13 6.9 3.8
9250 1.3 34.3 235 20 10 6.1 3.3 | 1.3 34.3 250 24 13 7.6 4.2
9000 1.8 35.2 235 19 10 4.7 2.6 | 2.2 36.0 245 21 11 6.0 3.3
8750 2.1 35.8 235 18 9 5.0 2.7 | 2.7 36.9 245 19 10 6.4 3.5
8500 2.9 37.2 230 14 7 6.2 3.4 | 3.1 37.6 245 18 9 6.4 3.5
8250 3.3 37.9 225 12 6 3.7 2.0 | 3.6 38.5 245 16 8 5.9 3.2
8000 3.6 38.5 225 10 5 4.5 2.5 | 4.0 39.2 250 16 8 5.2 2.8
7750 4.1 39.4 225 9 5 7.5 4.1 | 4.4 39.9 250 14 7 5.2 2.9
7500 4.6 40.3 225 7 4 5.8 3.2 | 4.8 40.6 250 12 6 5.1 2.8
7250 4.9 40.8 230 6 3 2.5 1.4 | 5.1 41.2 255 10 5 4.4 2.4
7000 5.1 41.2 245 4 2 7.2 4.0 | 5.5 41.9 265 9 5 5.2 2.9
6750 6.0 42.8 250 4 2 12.5 6.8 | 5.9 42.6 270 8 4 6.3 3.5
6500 6.8 44.2 250 4 2 8.9 4.9 | 6.4 43.5 280 6 3 5.7 3.1
6250 7.3 45.1 270 3 2 7.0 3.8 | 6.8 44.2 295 6 3 4.8 2.6
6000 7.9 46.2 295 3 2 9.0 4.9 | 7.1 44.8 315 7 3 6.8 3.8
5750 8.8 47.8 265 3 2 14.2 7.8 | 7.6 45.7 310 5 3 4.4 2.4
5500 10.1 50.2 300 3 2 20.5 11.3 | 6.8 44.2 330 4 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
________________________________________________________________________________
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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