Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
661
UXUS97 KGJT 041307
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
707 AM MDT Saturday, October 4, 2025
This forecast is for Saturday, October 4, 2025:
If the trigger temperature of 58.0 F/14.4 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 767 ft/min (3.9 m/s)
Maximum height of thermals.................. 15169 ft MSL (9560 ft AGL)
Forecast maximum temperature................... 70.0 F/21.6 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................. 13238 ft MSL (7629 ft AGL)
Thermal soaring outlook for Sunday 10/05....... Good
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:13:36 / 18:51:47 MDT
Total possible sunshine........... 11 hr 38 min 10 sec (698 min 10 sec)
Altitude of sun at 13:02:41 MDT... 46.21 degrees
Upper air data from rawinsonde observation taken on 10/04/2025 at 0600 MDT
Freezing level.................. 10725 ft MSL (5116 ft AGL)
Convective condensation level... 14939 ft MSL (9330 ft AGL)
Lifted condensation level....... 15325 ft MSL (9716 ft AGL)
Lifted index.................... +2.6
K index......................... +7.2
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 -60.6 -77.1 240 48 25 3.5 1.9 M M M M M
45000 -55.6 -68.1 240 57 29 2.1 1.2 M M M M M
40000 -52.5 -62.5 245 74 38 2.1 1.1 M M M M M
38000 -50.9 -59.6 245 74 38 2.9 1.6 M M M M M
36000 -48.9 -56.0 245 71 37 2.9 1.6 M M M M M
34000 -46.3 -51.3 245 67 35 6.6 3.6 M M M M M
32000 -42.4 -44.3 245 62 32 6.6 3.6 M M M M M
30000 -38.2 -36.8 245 57 29 7.4 4.0 37.5 99.6 12.4 M M
29000 -36.0 -32.8 245 55 29 7.4 4.0 36.5 97.7 11.8 M M
28000 -33.8 -28.8 245 54 28 7.4 4.0 35.6 96.2 11.2 M M
27000 -31.6 -24.9 245 52 27 7.6 4.2 34.8 94.7 10.7 M M
26000 -29.4 -20.9 250 51 26 7.6 4.2 33.9 93.0 10.1 M M
25000 -27.1 -16.8 250 49 25 7.6 4.2 33.1 91.6 9.6 M M
24000 -24.8 -12.6 250 47 24 7.4 4.0 32.4 90.4 9.1 M M
23000 -22.7 -8.9 250 44 23 7.1 3.9 31.3 88.4 8.3 M M
22000 -20.6 -5.1 250 42 22 7.1 3.9 30.4 86.7 7.6 M M
21000 -18.5 -1.3 250 40 20 6.6 3.6 29.5 85.0 6.9 M M
20000 -16.1 3.0 250 37 19 6.5 3.6 27.9 82.3 5.7 M M
19500 -15.1 4.8 250 36 18 6.5 3.6 27.4 81.3 5.2 M M
19000 -14.2 6.4 250 35 18 6.5 3.6 26.8 80.3 4.8 M M
18500 -13.2 8.2 250 34 17 6.1 3.4 26.3 79.3 4.3 M M
18000 -12.3 9.9 250 33 17 6.1 3.4 25.6 78.1 3.8 M M
17500 -11.3 11.7 245 32 17 5.8 3.2 25.0 77.1 3.3 M M
17000 -10.5 13.1 245 31 16 5.2 2.9 24.3 75.7 2.7 M M
16500 -9.8 14.4 245 31 16 5.3 2.9 23.5 74.3 2.0 M M
16000 -9.0 15.8 245 30 15 4.7 2.6 22.7 72.8 1.3 M M
15500 -8.4 16.9 245 29 15 4.8 2.6 21.8 71.3 0.5 M M
15000 -7.7 18.1 245 27 14 4.6 2.5 21.0 69.8 -0.3 753 3.8
14500 -7.1 19.2 245 26 13 4.6 2.5 20.1 68.2 -1.2 720 3.7
14000 -6.4 20.5 240 24 12 5.5 3.0 19.3 66.8 -2.0 686 3.5
13500 -5.6 21.9 240 22 12 6.0 3.3 18.7 65.6 -2.7 646 3.3
13000 -4.7 23.5 240 21 11 6.4 3.5 18.1 64.5 -3.3 605 3.1
12500 -3.7 25.3 240 19 10 6.9 3.8 17.6 63.7 -3.8 561 2.8
12000 -2.7 27.1 235 18 9 7.0 3.9 17.1 62.8 -4.3 516 2.6
11500 -1.7 28.9 235 16 8 7.2 4.0 16.7 62.1 -4.7 469 2.4
11000 -0.6 30.9 235 14 7 7.0 3.8 16.3 61.4 -5.1 422 2.1
10500 0.4 32.7 235 13 6 6.5 3.6 15.8 60.4 -5.7 378 1.9
10250 0.9 33.6 230 12 6 8.0 4.4 15.6 60.1 -5.9 355 1.8
10000 1.5 34.7 230 11 6 7.8 4.3 15.5 59.8 -6.0 328 1.7
9750 2.1 35.8 225 10 5 6.7 3.7 15.2 59.4 -6.2 305 1.6
9500 2.6 36.7 225 9 5 6.9 3.8 15.0 59.0 -6.5 283 1.4
9250 3.1 37.6 215 8 4 6.9 3.8 14.8 58.6 -6.7 260 1.3
9000 3.6 38.5 215 7 4 7.0 3.8 14.6 58.2 -6.9 237 1.2
8750 4.1 39.4 215 7 3 6.9 3.8 14.3 57.8 -7.2 214 1.1
8500 4.6 40.3 210 6 3 7.2 4.0 14.1 57.4 -7.4 192 1.0
8250 5.1 41.2 205 5 3 6.1 3.3 13.9 57.0 -7.7 169 0.9
8000 5.5 41.9 205 5 2 5.5 3.0 13.6 56.4 -8.0 150 0.8
7750 6.0 42.8 205 4 2 6.1 3.4 13.3 55.9 -8.3 129 0.7
7500 6.4 43.5 205 4 2 6.3 3.4 13.0 55.4 -8.6 108 0.6
7250 6.9 44.4 205 3 2 5.1 2.8 12.7 54.9 -8.9 88 0.4
7000 7.2 45.0 195 2 1 4.9 2.7 12.3 54.1 -9.4 71 0.4
6750 7.6 45.7 195 2 1 6.3 3.4 12.0 53.6 -9.7 50 0.3
6500 8.0 46.4 190 2 1 5.1 2.8 11.7 53.1 -10.0 30 0.2
6250 8.3 46.9 165 2 1 0.8 0.5 11.2 52.2 -10.5 15 0.1
6000 8.3 46.9 140 2 1 3.0 1.7 10.5 50.9 -11.3 7 0.0
5750 8.6 47.5 125 3 1 -1.9 -1.1 10.0 50.0 -11.8 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 * * * * * *
10/04/2025 at 0900 MDT | 10/04/2025 at 1200 MDT
|
CAPE... +572.2 LI... -4.0 | CAPE... +373.6 LI... -3.2
CINH... -25.8 K Index... +24.6 | CINH... -2.2 K Index... +26.4
|
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 -59.8 -75.6 225 45 23 2.2 1.2 | -59.2 -74.6 230 43 22 2.1 1.1
45000 -56.0 -68.8 225 68 35 3.4 1.9 | -55.4 -67.7 225 68 35 4.5 2.5
40000 -50.9 -59.6 220 85 44 3.5 1.9 | -48.6 -55.5 220 81 42 4.6 2.5
38000 -48.9 -56.0 215 87 45 3.1 1.7 | -46.3 -51.3 215 83 43 3.6 2.0
36000 -47.1 -52.8 210 88 45 3.1 1.7 | -44.2 -47.6 210 84 43 3.6 2.0
34000 -44.5 -48.1 210 90 46 5.8 3.2 | -42.1 -43.8 205 86 44 3.4 1.9
32000 -41.1 -42.0 210 92 47 5.7 3.2 | -40.0 -40.0 205 88 45 3.4 1.9
30000 -37.4 -35.3 205 92 47 6.9 3.8 | -37.6 -35.7 200 90 46 5.3 2.9
29000 -35.3 -31.5 205 90 46 6.9 3.8 | -36.0 -32.8 200 90 46 5.4 3.0
28000 -33.2 -27.8 200 88 46 6.9 3.8 | -34.4 -29.9 200 91 47 5.4 3.0
27000 -30.7 -23.3 200 86 44 6.3 3.5 | -32.3 -26.1 200 90 47 5.3 2.9
26000 -28.8 -19.8 200 83 43 6.4 3.5 | -30.7 -23.3 200 88 45 5.3 2.9
25000 -26.9 -16.4 200 81 42 6.4 3.5 | -29.1 -20.4 200 86 44 5.4 2.9
24000 -25.0 -13.0 195 78 40 6.1 3.4 | -27.5 -17.5 200 83 43 5.6 3.1
23000 -23.2 -9.8 195 76 39 6.1 3.4 | -25.8 -14.4 200 78 40 5.7 3.1
22000 -21.4 -6.5 200 73 37 6.2 3.4 | -24.1 -11.4 200 73 38 5.7 3.1
21000 -19.5 -3.1 200 70 36 6.5 3.6 | -22.3 -8.1 205 68 35 7.0 3.8
20000 -17.6 0.3 200 67 35 6.5 3.6 | -20.3 -4.5 205 64 33 7.0 3.9
19500 -16.7 1.9 200 66 34 6.5 3.6 | -19.2 -2.6 205 61 32 7.1 3.9
19000 -15.7 3.7 200 64 33 6.5 3.5 | -18.2 -0.8 205 59 30 7.1 3.9
18500 -14.7 5.5 200 63 32 7.0 3.8 | -17.2 1.0 205 57 29 7.2 3.9
18000 -13.7 7.3 200 62 32 7.0 3.8 | -16.1 3.0 205 55 28 7.3 4.0
17500 -12.7 9.1 205 60 31 7.3 4.0 | -15.1 4.8 205 53 28 7.5 4.1
17000 -11.6 11.1 205 59 30 7.7 4.2 | -13.9 7.0 205 52 27 8.5 4.7
16500 -10.4 13.3 205 57 29 7.7 4.2 | -12.6 9.3 205 51 26 8.5 4.6
16000 -9.2 15.4 205 56 29 8.3 4.6 | -11.4 11.5 205 49 25 8.7 4.8
15500 -8.0 17.6 205 54 28 8.3 4.5 | -10.1 13.8 205 48 25 8.7 4.8
15000 -6.8 19.8 205 53 27 8.4 4.6 | -8.8 16.2 205 47 24 8.7 4.8
14500 -5.6 21.9 205 51 26 8.4 4.6 | -7.6 18.3 205 46 24 8.7 4.7
14000 -4.3 24.3 205 49 25 8.4 4.6 | -6.3 20.7 205 45 23 8.6 4.7
13500 -3.1 26.4 205 48 25 8.4 4.6 | -5.1 22.8 205 43 22 8.6 4.7
13000 -1.9 28.6 205 46 24 8.5 4.6 | -3.8 25.2 200 42 22 8.7 4.7
12500 -0.6 30.9 205 44 23 8.6 4.7 | -2.5 27.5 200 41 21 8.9 4.9
12000 0.6 33.1 205 43 22 8.6 4.7 | -1.2 29.8 200 39 20 9.0 4.9
11500 1.9 35.4 205 41 21 8.6 4.7 | 0.1 32.2 200 38 20 9.1 5.0
11000 3.1 37.6 200 40 20 8.4 4.6 | 1.4 34.5 200 37 19 9.0 4.9
10500 4.3 39.7 205 39 20 7.4 4.0 | 2.7 36.9 200 36 18 7.8 4.3
10250 4.9 40.8 205 39 20 9.2 5.0 | 3.3 37.9 200 35 18 9.8 5.4
10000 5.6 42.1 200 38 20 10.4 5.7 | 4.1 39.4 200 35 18 11.7 6.4
9750 6.3 43.3 200 37 19 8.9 4.9 | 4.9 40.8 200 35 18 10.2 5.6
9500 6.9 44.4 200 37 19 8.6 4.7 | 5.7 42.3 200 35 18 9.6 5.3
9250 8.2 46.8 200 36 18 9.2 5.1 | 6.4 43.5 200 34 18 9.8 5.3
9000 8.8 47.8 200 34 17 9.2 5.0 | 7.9 46.2 205 34 17 9.8 5.4
8750 9.5 49.1 200 33 17 8.9 4.9 | 8.6 47.5 205 33 17 9.8 5.4
8500 10.1 50.2 200 32 16 9.0 5.0 | 9.3 48.7 205 33 17 9.7 5.3
8250 10.8 51.4 200 31 16 8.6 4.7 | 10.0 50.0 205 32 17 9.9 5.5
8000 11.4 52.5 200 31 16 8.7 4.7 | 10.8 51.4 205 32 16 9.9 5.4
7750 12.0 53.6 195 29 15 9.2 5.1 | 11.5 52.7 205 31 16 9.7 5.3
7500 12.7 54.9 195 28 14 8.4 4.6 | 12.2 54.0 205 30 16 9.6 5.3
7250 13.2 55.8 195 27 14 6.1 3.4 | 12.9 55.2 205 30 15 8.6 4.7
7000 13.6 56.5 190 27 14 7.2 3.9 | 13.6 56.5 205 30 16 9.5 5.2
6750 14.3 57.7 190 24 12 9.3 5.1 | 14.4 57.9 205 29 15 10.7 5.9
6500 14.9 58.8 185 21 11 7.8 4.3 | 15.1 59.2 205 27 14 10.6 5.8
6250 15.4 59.7 180 20 10 6.8 3.7 | 16.0 60.8 205 27 14 11.8 6.5
6000 15.9 60.6 175 19 10 6.8 3.7 | 16.8 62.2 205 27 14 9.0 5.0
5750 16.4 61.5 175 16 8 9.0 5.0 | 17.4 63.3 205 24 12 10.3 5.7
5500 17.4 63.3 170 13 7 23.5 12.9 | 19.5 67.1 205 20 10 59.9 32.8
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
10/04/2025 at 1500 MDT | 10/04/2025 at 1800 MDT
|
CAPE... +160.9 LI... -1.4 | CAPE... +15.1 LI... +0.5
CINH... -6.2 K Index... +27.0 | CINH... -16.5 K Index... +16.7
|
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 -59.0 -74.2 230 43 22 2.4 1.3 | -59.6 -75.3 230 37 19 3.1 1.7
45000 -54.5 -66.1 235 62 32 5.4 3.0 | -54.4 -65.9 245 50 26 4.8 2.7
40000 -46.4 -51.5 235 63 33 5.4 3.0 | -47.1 -52.8 255 55 28 4.8 2.7
38000 -44.1 -47.4 235 65 33 3.3 1.8 | -44.8 -48.6 260 56 29 3.7 2.0
36000 -42.1 -43.8 230 66 34 3.3 1.8 | -42.6 -44.7 260 58 30 3.7 2.0
34000 -40.2 -40.4 225 67 34 2.7 1.5 | -40.6 -41.1 260 57 29 2.5 1.4
32000 -38.6 -37.5 220 63 32 2.7 1.5 | -39.0 -38.2 265 54 28 2.5 1.4
30000 -37.0 -34.6 220 60 31 2.3 1.3 | -37.5 -35.5 270 49 25 3.2 1.7
29000 -36.3 -33.3 215 60 31 2.3 1.3 | -36.5 -33.7 275 45 23 3.2 1.7
28000 -35.7 -32.3 215 59 30 2.3 1.3 | -35.6 -32.1 285 41 21 3.2 1.8
27000 -34.7 -30.5 215 59 30 4.8 2.6 | -34.2 -29.6 295 38 19 6.2 3.4
26000 -33.0 -27.4 215 59 30 5.6 3.1 | -32.2 -26.0 295 38 19 6.8 3.7
25000 -31.3 -24.3 210 58 30 5.7 3.1 | -30.1 -22.2 295 38 19 6.8 3.7
24000 -29.7 -21.5 210 58 30 6.3 3.5 | -28.1 -18.6 295 37 19 6.8 3.7
23000 -27.5 -17.5 210 55 29 7.2 3.9 | -26.1 -15.0 290 37 19 6.7 3.7
22000 -25.4 -13.7 210 53 27 7.2 3.9 | -24.1 -11.4 285 36 18 6.7 3.7
21000 -23.3 -9.9 210 50 26 7.1 3.9 | -22.1 -7.8 280 35 18 6.0 3.3
20000 -21.2 -6.2 210 46 24 7.1 3.9 | -20.4 -4.7 275 32 16 5.9 3.3
19500 -20.1 -4.2 210 44 23 7.1 3.9 | -19.5 -3.1 270 30 16 5.9 3.3
19000 -19.1 -2.4 210 42 22 7.1 3.9 | -18.6 -1.5 265 29 15 5.9 3.3
18500 -18.0 -0.4 210 40 21 7.8 4.3 | -17.7 0.1 265 28 14 6.7 3.7
18000 -16.8 1.8 210 39 20 8.2 4.5 | -16.7 1.9 260 27 14 7.1 3.9
17500 -15.6 3.9 210 37 19 8.3 4.6 | -15.6 3.9 255 26 13 7.1 3.9
17000 -14.3 6.3 210 36 19 8.8 4.8 | -14.5 5.9 250 26 13 7.4 4.1
16500 -13.0 8.6 210 35 18 8.8 4.9 | -13.4 7.9 250 26 13 7.4 4.1
16000 -11.8 10.8 205 34 18 8.4 4.6 | -12.3 9.9 245 26 13 7.6 4.2
15500 -10.5 13.1 205 33 17 8.4 4.6 | -11.2 11.8 240 26 13 7.7 4.2
15000 -9.3 15.3 205 33 17 8.4 4.6 | -10.1 13.8 240 26 14 8.0 4.4
14500 -8.1 17.4 205 32 17 8.3 4.6 | -8.8 16.2 240 27 14 8.3 4.5
14000 -6.8 19.8 210 32 16 8.4 4.6 | -7.6 18.3 235 27 14 8.5 4.7
13500 -5.6 21.9 210 31 16 8.7 4.8 | -6.3 20.7 235 27 14 8.9 4.9
13000 -4.3 24.3 210 31 16 9.1 5.0 | -5.0 23.0 235 27 14 8.9 4.9
12500 -3.0 26.6 215 30 16 13.7 7.5 | -3.7 25.3 235 26 14 8.9 4.9
12000 -1.7 28.9 215 30 15 77.2 42.4 | -2.4 27.7 240 26 14 8.9 4.9
11500 7.0 44.6 230 28 14 -19.0 -10.4 | -1.0 30.2 240 26 14 9.0 4.9
11000 7.0 44.6 230 28 14 -1.1 -0.6 | 0.3 32.5 240 26 14 8.9 4.9
10500 7.1 44.8 230 28 14 0.1 0.0 | 1.5 34.7 245 26 13 6.8 3.8
10250 7.1 44.8 230 28 14 0.2 0.1 | 2.0 35.6 245 26 13 9.0 4.9
10000 7.1 44.8 230 28 14 0.2 0.1 | 2.8 37.0 245 26 13 11.8 6.5
9750 7.1 44.8 230 28 14 0.1 0.1 | 4.3 39.7 245 26 13 8.5 4.7
9500 7.1 44.8 230 28 14 0.3 0.2 | 5.0 41.0 245 26 13 8.5 4.7
9250 7.1 44.8 230 28 14 2.2 1.2 | 5.6 42.1 245 26 13 10.1 5.6
9000 7.5 45.5 230 27 14 8.0 4.4 | 6.4 43.5 245 25 13 10.5 5.8
8750 8.2 46.8 230 27 14 9.7 5.3 | 7.1 44.8 245 25 13 9.0 4.9
8500 8.9 48.0 230 27 14 9.2 5.0 | 7.8 46.0 250 25 13 9.5 5.2
8250 9.6 49.3 235 26 13 9.5 5.2 | 8.5 47.3 250 24 13 9.2 5.0
8000 10.3 50.5 235 25 13 9.5 5.2 | 9.2 48.6 250 25 13 9.5 5.2
7750 11.0 51.8 235 25 13 9.3 5.1 | 10.0 50.0 250 24 12 10.0 5.5
7500 11.7 53.1 235 24 12 9.3 5.1 | 10.7 51.3 250 23 12 9.6 5.3
7250 12.3 54.1 240 23 12 8.0 4.4 | 11.3 52.3 250 23 12 7.8 4.3
7000 12.9 55.2 240 23 12 9.1 5.0 | 11.9 53.4 250 23 12 8.9 4.9
6750 13.7 56.7 240 22 11 10.7 5.9 | 12.7 54.9 250 22 11 10.9 6.0
6500 14.5 58.1 245 20 10 10.4 5.7 | 13.5 56.3 250 20 10 10.2 5.6
6250 15.3 59.5 245 20 10 11.6 6.4 | 14.2 57.6 250 20 10 10.4 5.7
6000 16.1 61.0 245 20 10 9.3 5.1 | 15.0 59.0 250 20 10 9.0 4.9
5750 16.7 62.1 245 18 10 10.2 5.6 | 15.6 60.1 250 17 9 8.4 4.6
5500 19.3 66.7 250 16 8 51.0 28.0 | 16.7 62.1 250 14 7 26.9 14.7
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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