Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
370
UXUS97 KGJT 181306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Saturday, October 18, 2025
This forecast is for Saturday, October 18, 2025:
If the trigger temperature of 64.5 F/18.1 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 275 ft/min (1.4 m/s)
Maximum height of thermals.................. 9428 ft MSL (3821 ft AGL)
Forecast maximum temperature................... 64.0 F/18.2 C
Time of trigger temperature.................... 1415 MDT
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................. 7692 ft MSL (2085 ft AGL)
Thermal soaring outlook for Sunday 10/19....... Fair
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:27:27 / 18:30:52 MDT
Total possible sunshine........... 11 hr 3 min 25 sec (663 min 25 sec)
Altitude of sun at 12:59:09 MDT... 40.97 degrees
Upper air data from rawinsonde observation taken on 10/18/2025 at 0600 MDT
Freezing level.................. 13844 ft MSL (8237 ft AGL)
Convective condensation level... 20344 ft MSL (14737 ft AGL)
Lifted condensation level....... 15010 ft MSL (9403 ft AGL)
Lifted index.................... +9.1
K index......................... +1.4
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 -66.3 -87.3 275 32 16 2.3 1.3 M M M M M
45000 -62.1 -79.8 275 41 21 4.1 2.2 M M M M M
40000 -55.9 -68.6 275 43 22 5.2 2.9 M M M M M
38000 -52.4 -62.3 280 43 22 5.9 3.3 M M M M M
36000 -48.8 -55.8 280 42 22 5.9 3.3 M M M M M
34000 -44.8 -48.6 280 42 22 7.1 3.9 M M M M M
32000 -40.0 -40.0 285 41 21 7.1 3.9 M M M M M
30000 -35.5 -31.9 285 41 21 7.9 4.3 39.4 102.9 16.4 M M
29000 -33.1 -27.6 285 42 22 7.9 4.3 38.7 101.6 16.1 M M
28000 -30.8 -23.4 285 42 22 7.9 4.3 38.1 100.6 15.8 M M
27000 -28.3 -18.9 280 43 22 8.3 4.5 37.4 99.4 15.4 M M
26000 -25.9 -14.6 280 43 22 8.3 4.5 36.8 98.3 15.1 M M
25000 -23.4 -10.1 280 43 22 8.3 4.5 36.3 97.4 14.9 M M
24000 -21.0 -5.8 280 44 22 7.6 4.2 35.6 96.2 14.5 M M
23000 -18.8 -1.8 280 44 23 7.6 4.2 34.8 94.7 14.0 M M
22000 -16.5 2.3 280 44 23 7.6 4.2 34.1 93.4 13.6 M M
21000 -14.3 6.3 280 43 22 7.1 3.9 33.2 91.8 13.0 M M
20000 -12.2 10.0 280 41 21 7.1 3.9 32.3 90.1 12.3 M M
19500 -11.1 12.0 280 40 20 7.1 3.9 31.9 89.3 12.0 M M
19000 -10.1 13.8 280 39 20 6.9 3.8 31.5 88.6 11.7 M M
18500 -8.6 16.5 280 37 19 6.6 3.6 30.6 87.1 11.0 M M
18000 -7.6 18.3 280 36 18 6.5 3.6 30.1 86.2 10.6 M M
17500 -6.7 19.9 280 35 18 6.4 3.5 29.5 85.1 10.2 M M
17000 -5.8 21.6 280 34 17 6.4 3.5 29.0 84.1 9.7 M M
16500 -4.8 23.4 280 33 17 6.2 3.4 28.4 83.1 9.2 M M
16000 -3.9 25.0 280 32 16 6.2 3.4 27.8 82.0 8.7 M M
15500 -3.0 26.6 280 31 16 6.3 3.5 27.2 81.0 8.2 M M
15000 -2.0 28.4 280 30 15 6.4 3.5 26.6 80.0 7.7 M M
14500 -1.1 30.0 275 29 15 6.2 3.4 26.1 79.0 7.3 M M
14000 -0.2 31.6 275 27 14 6.0 3.3 25.5 77.9 6.8 M M
13500 0.7 33.3 275 26 13 5.9 3.2 24.9 76.8 6.2 M M
13000 1.5 34.7 275 25 13 5.1 2.8 24.2 75.5 5.6 M M
12500 2.2 36.0 270 23 12 5.2 2.8 23.4 74.1 4.9 M M
12000 2.9 37.2 265 22 11 4.2 2.3 22.6 72.7 4.2 M M
11500 3.5 38.3 260 21 11 4.3 2.3 21.7 71.1 3.3 M M
11000 4.2 39.6 260 20 10 4.4 2.4 20.9 69.5 2.5 M M
10500 4.8 40.6 255 18 9 4.4 2.4 20.0 68.0 1.7 M M
10250 5.1 41.2 250 17 9 4.8 2.6 19.6 67.3 1.3 M M
10000 5.5 41.9 250 16 8 5.0 2.7 19.2 66.6 0.9 M M
9750 5.8 42.4 245 15 8 4.9 2.7 18.8 65.9 0.5 M M
9500 6.2 43.2 240 14 7 4.9 2.7 18.5 65.2 0.2 M M
9250 6.5 43.7 240 13 7 5.0 2.7 18.1 64.6 -0.2 265 1.3
9000 6.9 44.4 235 12 6 5.0 2.7 17.7 63.9 -0.6 247 1.3
8750 7.2 45.0 225 10 5 5.2 2.9 17.4 63.2 -0.9 228 1.2
8500 7.6 45.7 215 9 5 4.4 2.4 17.0 62.6 -1.3 210 1.1
8250 7.9 46.2 205 8 4 2.9 1.6 16.5 61.7 -1.8 195 1.0
8000 8.1 46.6 190 8 4 3.2 1.7 16.0 60.8 -2.3 181 0.9
7750 8.3 46.9 185 8 4 3.5 1.9 15.5 59.9 -2.8 166 0.8
7500 8.6 47.5 175 8 4 3.8 2.1 15.0 59.1 -3.2 151 0.8
7250 8.9 48.0 165 9 5 4.3 2.4 14.6 58.3 -3.7 134 0.7
7000 9.2 48.6 160 11 5 3.7 2.0 14.2 57.5 -4.1 118 0.6
6750 9.4 48.9 160 11 5 1.7 0.9 13.7 56.6 -4.6 104 0.5
6500 9.4 48.9 155 10 5 -1.5 -0.8 12.9 55.3 -5.4 97 0.5
6250 9.2 48.6 150 10 5 -5.7 -3.1 11.9 53.5 -6.4 97 0.5
6000 8.9 48.0 145 9 5 4.0 2.2 11.0 51.7 -7.4 97 0.5
5750 9.4 48.9 135 8 4 1.5 0.8 10.8 51.4 -7.6 74 0.4
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 * * * * * *
10/18/2025 at 0900 MDT | 10/18/2025 at 1200 MDT
|
CAPE... 0.0 LI... +5.9 | CAPE... 0.0 LI... +8.8
CINH... -0.0 K Index... +10.0 | CINH... -0.1 K Index... -5.5
|
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 -63.6 -82.5 295 41 21 3.4 1.9 | -64.2 -83.6 285 37 19 3.8 2.1
45000 -58.1 -72.6 295 52 27 5.1 2.8 | -58.6 -73.5 290 47 24 3.5 1.9
40000 -50.5 -58.9 310 70 36 5.1 2.8 | -53.3 -63.9 305 74 38 3.6 2.0
38000 -49.5 -57.1 315 71 37 0.7 0.4 | -51.7 -61.1 310 72 37 2.2 1.2
36000 -49.1 -56.4 325 72 37 0.7 0.4 | -50.4 -58.7 315 67 35 2.2 1.2
34000 -47.1 -52.8 330 76 39 6.2 3.4 | -47.4 -53.3 320 67 35 7.4 4.0
32000 -43.3 -45.9 330 85 44 6.2 3.4 | -43.0 -45.4 325 72 37 7.4 4.1
30000 -39.0 -38.2 335 90 46 8.6 4.7 | -38.3 -36.9 330 73 38 8.2 4.5
29000 -36.4 -33.5 335 89 46 8.6 4.7 | -35.9 -32.6 325 72 37 8.2 4.5
28000 -33.8 -28.8 335 89 46 8.6 4.7 | -33.4 -28.1 325 71 37 8.2 4.5
27000 -31.3 -24.3 335 87 45 8.0 4.4 | -31.0 -23.8 325 70 36 7.8 4.3
26000 -28.9 -20.0 330 85 44 8.1 4.4 | -28.6 -19.5 325 68 35 7.8 4.3
25000 -26.5 -15.7 330 83 43 8.1 4.4 | -26.3 -15.3 330 66 34 7.8 4.3
24000 -24.1 -11.4 325 81 42 7.4 4.1 | -23.9 -11.0 330 65 34 8.7 4.7
23000 -21.3 -6.3 325 79 41 7.3 4.0 | -20.7 -5.3 325 64 33 8.6 4.7
22000 -19.1 -2.4 325 77 40 7.2 4.0 | -18.1 -0.6 325 64 33 8.6 4.7
21000 -17.4 0.7 320 73 37 4.7 2.6 | -15.9 3.4 320 64 33 6.9 3.8
20000 -16.0 3.2 320 66 34 4.6 2.5 | -13.8 7.2 325 63 32 6.8 3.8
19500 -15.3 4.5 320 63 33 4.6 2.5 | -12.8 9.0 325 62 32 6.8 3.7
19000 -14.6 5.7 320 60 31 4.6 2.5 | -11.8 10.8 325 62 32 6.1 3.3
18500 -14.0 6.8 320 56 29 3.9 2.2 | -11.0 12.2 325 59 31 4.4 2.4
18000 -13.5 7.7 320 53 27 4.0 2.2 | -10.4 13.3 325 57 29 4.5 2.5
17500 -12.8 9.0 320 49 25 5.4 2.9 | -9.7 14.5 325 54 28 4.0 2.2
17000 -12.0 10.4 320 46 24 5.7 3.1 | -9.1 15.6 325 51 26 3.9 2.2
16500 -11.2 11.8 320 43 22 5.9 3.2 | -8.6 16.5 325 48 25 3.9 2.1
16000 -10.3 13.5 315 40 21 6.2 3.4 | -8.0 17.6 325 44 23 3.8 2.1
15500 -9.4 15.1 315 38 19 6.2 3.4 | -7.4 18.7 325 41 21 3.8 2.1
15000 -8.4 16.9 315 35 18 6.6 3.6 | -6.8 19.8 325 37 19 4.4 2.4
14500 -7.5 18.5 315 32 17 6.6 3.6 | -6.2 20.8 325 33 17 4.3 2.4
14000 -6.5 20.3 315 30 15 5.8 3.2 | -5.5 22.1 320 30 15 5.4 2.9
13500 -5.7 21.7 315 27 14 5.8 3.2 | -4.8 23.4 320 27 14 5.3 2.9
13000 -4.8 23.4 315 24 12 5.6 3.1 | -4.0 24.8 315 24 12 6.0 3.3
12500 -4.0 24.8 315 21 11 5.6 3.1 | -3.1 26.4 315 22 11 6.2 3.4
12000 -3.2 26.2 315 19 10 5.7 3.1 | -2.2 28.0 310 19 10 5.5 3.0
11500 -2.4 27.7 310 17 9 5.8 3.2 | -1.5 29.3 310 17 9 5.3 2.9
11000 -1.5 29.3 310 15 8 5.7 3.1 | -0.7 30.7 305 15 8 5.4 2.9
10500 -0.7 30.7 305 14 7 5.8 3.2 | 0.0 32.0 300 14 7 5.4 2.9
10250 -0.3 31.5 305 13 7 4.9 2.7 | 0.4 32.7 295 13 7 5.5 3.0
10000 0.0 32.0 305 14 7 5.5 3.0 | 0.8 33.4 295 13 7 5.7 3.2
9750 0.5 32.9 305 13 7 6.6 3.6 | 1.3 34.3 295 12 6 5.8 3.2
9500 1.0 33.8 300 12 6 6.5 3.6 | 1.7 35.1 295 12 6 5.8 3.2
9250 1.4 34.5 300 11 6 6.0 3.3 | 2.1 35.8 290 11 6 5.9 3.2
9000 1.8 35.2 295 10 5 5.5 3.0 | 2.5 36.5 290 11 6 6.3 3.5
8750 2.3 36.1 290 9 5 6.1 3.4 | 3.0 37.4 285 10 5 6.7 3.7
8500 2.7 36.9 285 8 4 6.5 3.6 | 3.5 38.3 285 9 5 6.9 3.8
8250 3.2 37.8 280 6 3 5.4 3.0 | 4.3 39.7 280 7 4 4.6 2.5
8000 4.0 39.2 270 6 3 6.8 3.7 | 4.8 40.6 275 7 3 8.9 4.9
7750 4.5 40.1 255 5 2 7.5 4.1 | 5.5 41.9 275 6 3 9.5 5.2
7500 5.0 41.0 245 4 2 6.0 3.3 | 6.1 43.0 270 5 3 6.4 3.5
7250 5.4 41.7 240 4 2 5.0 2.8 | 6.5 43.7 270 5 2 4.6 2.5
7000 5.9 42.6 230 4 2 7.6 4.2 | 7.0 44.6 270 4 2 12.5 6.9
6750 6.5 43.7 210 4 2 6.7 3.7 | 8.2 46.8 270 4 2 13.0 7.1
6500 6.8 44.2 200 3 2 3.7 2.0 | 8.8 47.8 275 3 2 7.2 3.9
6250 7.1 44.8 190 3 2 4.4 2.4 | 9.4 48.9 280 3 2 7.7 4.2
6000 7.4 45.3 175 3 2 4.4 2.4 | 10.0 50.0 290 3 1 12.0 6.6
5750 7.7 45.9 170 3 1 3.3 1.8 | 11.3 52.3 280 3 1 23.7 13.0
5500 7.6 45.7 150 2 1 -8.1 -4.5 | 12.6 54.7 290 3 1 -0.1 -0.1
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
10/18/2025 at 1500 MDT | 10/18/2025 at 1800 MDT
|
CAPE... 0.0 LI... +8.8 | CAPE... 0.0 LI... +8.4
CINH... -0.0 K Index... -8.7 | CINH... -0.1 K Index... -6.4
|
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 -63.6 -82.5 295 38 20 4.1 2.3 | -64.6 -84.3 300 41 21 3.7 2.0
45000 -58.0 -72.4 300 45 23 1.6 0.9 | -59.4 -74.9 305 49 25 2.2 1.2
40000 -55.4 -67.7 305 71 36 2.4 1.3 | -56.0 -68.8 310 62 32 3.8 2.1
38000 -53.1 -63.6 305 66 34 3.9 2.2 | -52.8 -63.0 315 62 32 5.3 2.9
36000 -50.7 -59.3 310 61 32 3.9 2.2 | -49.7 -57.5 315 61 31 5.2 2.9
34000 -47.1 -52.8 310 60 31 7.6 4.2 | -45.8 -50.4 310 59 31 7.2 3.9
32000 -42.5 -44.5 305 62 32 7.6 4.2 | -41.5 -42.7 305 58 30 7.2 3.9
30000 -37.7 -35.9 305 62 32 8.5 4.6 | -37.0 -34.6 305 56 29 8.0 4.4
29000 -35.1 -31.2 305 60 31 8.5 4.6 | -34.6 -30.3 305 55 28 8.0 4.4
28000 -32.6 -26.7 305 59 31 8.5 4.6 | -32.2 -26.0 300 54 28 8.0 4.4
27000 -30.2 -22.4 305 58 30 8.0 4.4 | -29.8 -21.6 300 53 27 7.8 4.3
26000 -27.8 -18.0 310 56 29 8.0 4.4 | -27.5 -17.5 300 52 27 7.8 4.3
25000 -25.4 -13.7 310 54 28 8.0 4.4 | -24.6 -12.3 295 51 26 7.8 4.3
24000 -22.4 -8.3 315 51 26 7.9 4.3 | -22.2 -8.0 295 49 25 8.1 4.4
23000 -20.1 -4.2 315 48 25 7.9 4.3 | -19.8 -3.6 300 46 24 8.1 4.4
22000 -17.7 0.1 320 45 23 7.8 4.3 | -17.4 0.7 300 44 23 8.0 4.4
21000 -15.2 4.6 320 45 23 8.5 4.7 | -14.9 5.2 300 42 22 8.4 4.6
20000 -12.7 9.1 320 46 24 8.5 4.7 | -12.4 9.7 305 40 21 8.4 4.6
19500 -11.4 11.5 320 46 24 8.5 4.6 | -11.2 11.8 305 39 20 8.4 4.6
19000 -10.1 13.8 320 47 24 7.7 4.2 | -9.9 14.2 310 38 20 7.8 4.3
18500 -9.1 15.6 320 47 24 6.9 3.8 | -8.8 16.2 310 37 19 7.4 4.1
18000 -8.1 17.4 320 47 24 7.2 3.9 | -7.7 18.1 315 36 19 7.5 4.1
17500 -7.2 19.0 325 46 24 4.3 2.3 | -6.7 19.9 315 35 18 5.4 3.0
17000 -6.5 20.3 325 46 23 4.5 2.5 | -5.9 21.4 315 35 18 5.6 3.1
16500 -5.9 21.4 325 45 23 3.6 2.0 | -5.0 23.0 320 34 18 4.7 2.6
16000 -5.4 22.3 325 42 22 3.0 1.6 | -4.4 24.1 320 33 17 4.2 2.3
15500 -5.0 23.0 325 40 20 3.0 1.7 | -3.8 25.2 325 32 17 4.0 2.2
15000 -4.5 23.9 325 37 19 3.4 1.9 | -3.3 26.1 325 31 16 3.4 1.8
14500 -4.0 24.8 325 33 17 3.4 1.9 | -2.8 27.0 325 29 15 3.4 1.8
14000 -3.5 25.7 325 30 16 3.4 1.9 | -2.2 28.0 325 27 14 3.6 2.0
13500 -3.0 26.6 320 27 14 3.3 1.8 | -1.7 28.9 325 25 13 3.5 1.9
13000 -2.4 27.7 320 23 12 4.4 2.4 | -1.2 29.8 325 23 12 4.1 2.3
12500 -1.8 28.8 320 21 11 4.4 2.4 | -0.6 30.9 320 20 10 4.1 2.2
12000 -1.1 30.0 315 18 9 5.5 3.0 | 0.1 32.2 320 18 9 5.2 2.9
11500 -0.3 31.5 315 15 8 5.7 3.1 | 0.9 33.6 315 15 8 5.3 2.9
11000 0.5 32.9 310 13 7 6.5 3.5 | 1.7 35.1 315 13 7 6.1 3.4
10500 1.5 34.7 305 11 6 6.7 3.7 | 2.5 36.5 305 11 6 6.2 3.4
10250 1.9 35.4 305 10 5 6.1 3.4 | 3.0 37.4 305 10 5 6.5 3.6
10000 2.4 36.3 305 10 5 6.7 3.7 | 3.5 38.3 305 10 5 7.2 4.0
9750 2.9 37.2 305 9 5 7.8 4.3 | 4.0 39.2 300 9 4 7.6 4.2
9500 3.5 38.3 305 8 4 7.6 4.2 | 4.5 40.1 295 8 4 7.2 3.9
9250 4.0 39.2 300 8 4 7.5 4.1 | 5.1 41.2 290 7 4 8.7 4.8
9000 4.5 40.1 300 8 4 7.2 4.0 | 6.3 43.3 285 6 3 6.5 3.5
8750 5.1 41.2 300 7 4 7.3 4.0 | 6.8 44.2 280 6 3 6.6 3.6
8500 5.6 42.1 300 6 3 7.4 4.0 | 7.3 45.1 280 5 3 7.1 3.9
8250 6.5 43.7 300 6 3 5.7 3.1 | 7.8 46.0 280 5 3 7.6 4.2
8000 7.0 44.6 300 5 3 9.5 5.2 | 8.4 47.1 280 5 3 7.9 4.3
7750 7.8 46.0 295 5 2 9.7 5.3 | 9.0 48.2 280 4 2 7.6 4.2
7500 8.4 47.1 300 4 2 6.9 3.8 | 9.5 49.1 280 4 2 6.8 3.7
7250 8.8 47.8 300 5 2 5.7 3.1 | 10.0 50.0 280 4 2 6.4 3.5
7000 9.4 48.9 300 4 2 12.4 6.8 | 10.5 50.9 280 4 2 8.5 4.7
6750 10.5 50.9 300 4 2 12.3 6.8 | 11.2 52.2 280 3 2 8.7 4.8
6500 11.1 52.0 300 4 2 7.3 4.0 | 11.7 53.1 285 3 1 7.2 4.0
6250 11.7 53.1 305 4 2 7.7 4.2 | 12.2 54.0 295 3 1 7.9 4.3
6000 12.3 54.1 305 4 2 12.1 6.7 | 12.8 55.0 305 2 1 7.2 4.0
5750 13.7 56.7 305 4 2 23.9 13.1 | 13.2 55.8 295 2 1 4.7 2.6
5500 15.0 59.0 305 4 2 1.4 0.8 | 13.3 55.9 320 2 1 1.2 0.7
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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