Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
390
UXUS97 KGJT 071859
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
0703 MDT Tuesday, October 7, 2025
This forecast is for Tuesday, October 7, 2025:
If the trigger temperature of 70.2 F/21.2 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 991 ft/min (5.0 m/s)
Maximum height of thermals.................. 16647 ft MSL (11039 ft AGL)
Forecast maximum temperature................... 79.0 F/26.6 C
Time of trigger temperature.................... 1130 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................. 11922 ft MSL (6314 ft AGL)
Thermal soaring outlook for Wednesday 10/08....
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:17:27 / 18:45:35 MDT
Total possible sunshine........... 11 hr 28 min 8 sec (688 min 8 sec)
Altitude of sun at 13:01:31 MDT... 44.68 degrees
Upper air data from numerical model forecast valid on 10/07/2025 at 0600 MDT
Freezing level.................. 13557 ft MSL (7949 ft AGL)
Convective condensation level... 16022 ft MSL (10414 ft AGL)
Lifted condensation level....... 16352 ft MSL (10744 ft AGL)
Lifted index.................... -0.1
K index......................... +12.9
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 -64.2 -83.6 265 49 25 3.3 1.8 M M M M M
45000 -58.2 -72.8 265 60 31 5.7 3.1 M M M M M
40000 -49.8 -57.6 265 65 34 3.8 2.1 M M M M M
38000 -47.8 -54.0 265 60 31 3.4 1.9 M M M M M
36000 -45.8 -50.4 265 55 28 3.4 1.9 M M M M M
34000 -43.3 -45.9 265 51 26 4.5 2.5 M M M M M
32000 -40.3 -40.5 265 48 25 4.5 2.5 M M M M M
30000 -36.2 -33.2 265 45 23 7.9 4.3 38.4 101.2 9.4 M M
29000 -33.9 -29.0 265 44 22 7.9 4.3 37.7 99.9 8.9 M M
28000 -31.5 -24.7 265 42 22 7.9 4.3 37.1 98.9 8.6 M M
27000 -29.1 -20.4 265 40 21 8.0 4.4 36.4 97.5 8.1 M M
26000 -26.7 -16.1 265 38 20 8.0 4.4 35.7 96.2 7.6 M M
25000 -24.4 -11.9 265 36 19 8.0 4.4 35.1 95.1 7.2 M M
24000 -22.1 -7.8 260 34 18 7.4 4.1 34.3 93.7 6.7 M M
23000 -19.8 -3.6 260 33 17 7.4 4.1 33.4 92.1 6.0 M M
22000 -17.6 0.3 255 31 16 7.5 4.1 32.6 90.7 5.4 M M
21000 -15.7 3.7 255 30 15 6.0 3.3 31.5 88.6 4.5 M M
20000 -13.9 7.0 250 29 15 6.0 3.3 30.1 86.2 3.4 M M
19500 -13.0 8.6 250 29 15 6.0 3.3 29.5 85.1 2.9 M M
19000 -12.1 10.2 250 29 15 6.2 3.4 28.9 84.0 2.4 M M
18500 -10.7 12.7 245 28 15 6.5 3.6 28.0 82.4 1.6 M M
18000 -9.7 14.5 245 28 15 6.7 3.7 27.5 81.5 1.1 M M
17500 -8.7 16.3 245 28 15 6.9 3.8 27.0 80.6 0.7 M M
17000 -7.7 18.1 245 28 15 6.9 3.8 26.5 79.7 0.2 M M
16500 -6.6 20.1 240 28 15 7.8 4.3 26.1 79.0 -0.2 968 4.9
16000 -5.5 22.1 240 28 15 7.7 4.2 25.7 78.3 -0.5 920 4.7
15500 -4.4 24.1 240 28 15 7.6 4.2 25.4 77.7 -0.8 871 4.4
15000 -3.3 26.1 240 28 15 7.7 4.2 25.0 77.1 -1.2 824 4.2
14500 -2.2 28.0 240 28 14 7.9 4.4 24.7 76.5 -1.6 776 3.9
14000 -1.0 30.2 235 27 14 8.3 4.5 24.4 76.0 -1.9 726 3.7
13500 0.2 32.4 235 26 13 8.4 4.6 24.2 75.6 -2.1 675 3.4
13000 1.4 34.5 235 25 13 8.5 4.7 24.0 75.2 -2.4 624 3.2
12500 2.7 36.9 235 23 12 8.5 4.7 23.8 74.9 -2.6 572 2.9
12000 3.8 38.8 235 21 11 8.2 4.5 23.6 74.4 -2.9 522 2.7
11500 5.0 41.0 230 19 10 8.3 4.6 23.4 74.0 -3.3 473 2.4
11000 6.0 42.8 225 18 9 7.0 3.8 23.0 73.4 -3.7 428 2.2
10500 6.9 44.4 225 17 9 9.8 5.4 22.5 72.6 -4.3 384 2.0
10250 7.8 46.0 220 16 8 10.2 5.6 22.7 72.8 -4.2 353 1.8
10000 8.3 46.9 220 15 8 6.7 3.7 22.5 72.5 -4.4 329 1.7
9750 8.8 47.8 215 15 8 8.2 4.5 22.3 72.2 -4.6 305 1.6
9500 9.4 48.9 215 15 8 5.7 3.1 22.1 71.9 -4.8 282 1.4
9250 9.7 49.5 210 15 8 5.3 2.9 21.7 71.1 -5.2 264 1.3
9000 10.2 50.4 210 14 7 7.1 3.9 21.5 70.7 -5.4 241 1.2
8750 10.7 51.3 205 14 7 6.9 3.8 21.3 70.3 -5.6 219 1.1
8500 11.3 52.3 200 13 7 6.0 3.3 21.1 69.9 -5.9 196 1.0
8250 11.6 52.9 195 13 7 4.3 2.4 20.7 69.2 -6.2 177 0.9
8000 12.0 53.6 190 13 7 4.2 2.3 20.3 68.5 -6.6 159 0.8
7750 12.3 54.1 185 12 6 4.8 2.6 19.9 67.8 -7.0 142 0.7
7500 12.7 54.9 180 12 6 3.3 1.8 19.5 67.0 -7.4 124 0.6
7250 12.9 55.2 170 12 6 1.7 0.9 18.9 66.0 -7.9 110 0.6
7000 13.1 55.6 160 12 6 2.3 1.3 18.3 64.9 -8.5 97 0.5
6750 13.3 55.9 160 11 6 1.2 0.7 17.7 63.9 -9.1 84 0.4
6500 13.3 55.9 150 10 5 -1.6 -0.9 17.0 62.5 -9.8 77 0.4
6250 13.1 55.6 145 9 4 -5.4 -3.0 16.0 60.7 -10.8 75 0.4
6000 12.9 55.2 135 8 4 4.3 2.4 15.0 59.0 -11.7 73 0.4
5750 13.4 56.1 125 7 4 -0.9 -0.5 14.8 58.6 -12.0 51 0.3
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 * * * * * *
10/07/2025 at 0900 MDT | 10/07/2025 at 1200 MDT
|
CAPE... 0.0 LI... +1.1 | CAPE... +8.6 LI... +1.7
CINH... 0.0 K Index... +6.9 | CINH... -15.9 K Index... +0.9
|
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 -64.2 -83.6 265 44 23 3.5 1.9 | -64.5 -84.1 265 47 24 3.4 1.9
45000 -58.0 -72.4 265 57 29 5.2 2.9 | -58.6 -73.5 265 63 33 5.6 3.1
40000 -50.3 -58.5 265 60 31 4.3 2.4 | -50.3 -58.5 265 64 33 4.6 2.5
38000 -47.8 -54.0 265 58 30 4.2 2.3 | -47.6 -53.7 265 61 31 4.5 2.5
36000 -45.3 -49.5 265 57 29 4.2 2.3 | -44.5 -48.1 265 58 30 4.5 2.5
34000 -42.6 -44.7 265 52 27 3.9 2.1 | -42.0 -43.6 260 51 26 4.0 2.2
32000 -40.2 -40.4 260 46 24 4.0 2.2 | -39.6 -39.3 255 44 23 4.1 2.3
30000 -36.0 -32.8 260 42 22 8.5 4.7 | -35.4 -31.7 250 40 21 8.1 4.5
29000 -33.4 -28.1 260 41 21 8.5 4.7 | -33.0 -27.4 250 39 20 8.1 4.5
28000 -30.9 -23.6 260 39 20 8.6 4.7 | -30.6 -23.1 250 38 19 8.1 4.5
27000 -28.5 -19.3 260 38 20 7.6 4.2 | -28.2 -18.8 245 37 19 7.9 4.3
26000 -26.3 -15.3 260 37 19 7.6 4.2 | -25.8 -14.4 245 36 18 7.9 4.3
25000 -24.0 -11.2 255 36 18 7.6 4.2 | -23.4 -10.1 245 35 18 7.9 4.3
24000 -21.7 -7.1 255 35 18 7.7 4.2 | -21.1 -6.0 245 33 17 7.5 4.1
23000 -19.4 -2.9 255 34 17 7.8 4.3 | -18.9 -2.0 245 32 16 7.5 4.1
22000 -17.1 1.2 255 33 17 7.9 4.3 | -16.6 2.1 250 31 16 7.6 4.2
21000 -15.1 4.8 255 32 16 6.1 3.3 | -14.6 5.7 245 30 15 6.3 3.4
20000 -13.2 8.2 250 31 16 6.1 3.3 | -12.3 9.9 245 29 15 6.3 3.4
19500 -11.9 10.6 250 30 15 6.0 3.3 | -11.4 11.5 245 29 15 6.2 3.4
19000 -10.9 12.4 250 29 15 6.8 3.7 | -10.4 13.3 245 28 15 6.7 3.7
18500 -9.9 14.2 245 28 14 6.7 3.7 | -9.4 15.1 245 28 14 6.6 3.6
18000 -8.9 16.0 245 27 14 6.4 3.5 | -8.4 16.9 245 28 14 6.4 3.5
17500 -8.0 17.6 245 27 14 6.0 3.3 | -7.5 18.5 245 28 14 6.1 3.3
17000 -7.1 19.2 240 26 14 6.0 3.3 | -6.6 20.1 245 28 14 6.0 3.3
16500 -6.2 20.8 240 26 13 6.6 3.6 | -5.7 21.7 240 28 14 6.3 3.4
16000 -5.2 22.6 240 26 14 6.5 3.6 | -4.7 23.5 240 28 14 6.2 3.4
15500 -4.3 24.3 235 27 14 7.1 3.9 | -3.8 25.2 240 28 14 6.7 3.7
15000 -3.2 26.2 235 26 14 7.3 4.0 | -2.8 27.0 235 27 14 6.9 3.8
14500 -2.2 28.0 235 26 14 7.8 4.3 | -1.8 28.8 230 27 14 7.3 4.0
14000 -1.0 30.2 230 26 13 8.2 4.5 | -0.7 30.7 230 26 13 7.7 4.2
13500 0.1 32.2 230 25 13 8.5 4.6 | 0.4 32.7 225 26 13 8.1 4.4
13000 1.4 34.5 230 24 12 8.8 4.8 | 1.6 34.9 225 25 13 8.7 4.8
12500 2.6 36.7 230 23 12 8.8 4.8 | 2.8 37.0 220 24 12 8.8 4.8
12000 3.9 39.0 225 22 11 9.0 4.9 | 4.1 39.4 220 23 12 8.8 4.8
11500 5.2 41.4 225 21 11 8.8 4.9 | 5.4 41.7 220 22 11 8.6 4.7
11000 6.3 43.3 220 19 10 6.9 3.8 | 6.5 43.7 215 20 11 7.2 4.0
10500 7.2 45.0 220 17 9 9.0 4.9 | 7.5 45.5 215 19 10 10.0 5.5
10250 8.0 46.4 215 17 9 9.3 5.1 | 8.3 46.9 215 19 10 10.0 5.5
10000 8.5 47.3 215 16 8 6.5 3.5 | 8.8 47.8 215 18 9 6.3 3.4
9750 9.0 48.2 210 15 8 8.1 4.4 | 9.3 48.7 210 17 9 8.0 4.4
9500 9.5 49.1 210 15 8 4.5 2.5 | 9.8 49.6 210 16 8 5.0 2.7
9250 9.7 49.5 210 15 7 3.7 2.0 | 10.1 50.2 210 15 8 5.7 3.1
9000 10.1 50.2 205 14 7 6.4 3.5 | 10.7 51.3 210 14 7 8.7 4.8
8750 10.6 51.1 200 14 7 6.0 3.3 | 11.2 52.2 205 13 7 8.4 4.6
8500 11.0 51.8 195 13 7 5.2 2.8 | 11.8 53.2 205 13 7 6.6 3.6
8250 11.3 52.3 190 14 7 3.6 2.0 | 12.2 54.0 205 12 6 5.7 3.1
8000 11.6 52.9 185 14 7 3.5 1.9 | 12.8 55.0 200 10 5 8.2 4.5
7750 11.8 53.2 180 13 7 3.8 2.1 | 13.4 56.1 200 10 5 8.5 4.7
7500 12.1 53.8 175 12 6 2.4 1.3 | 14.0 57.2 200 9 5 8.4 4.6
7250 12.2 54.0 165 12 6 1.0 0.5 | 14.7 58.5 200 9 4 8.6 4.7
7000 12.4 54.3 160 12 6 3.3 1.8 | 15.4 59.7 200 8 4 9.8 5.4
6750 12.7 54.9 160 11 6 3.3 1.8 | 16.1 61.0 200 8 4 10.7 5.8
6500 12.9 55.2 155 10 5 0.7 0.4 | 16.9 62.4 195 7 4 10.5 5.7
6250 12.9 55.2 145 9 4 -0.9 -0.5 | 17.7 63.9 195 7 4 11.1 6.1
6000 13.0 55.4 140 7 4 3.8 2.1 | 18.5 65.3 195 7 3 8.8 4.8
5750 13.6 56.5 130 7 3 11.0 6.0 | 19.2 66.6 195 6 3 12.1 6.6
5500 M M 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 M M
5000 M M M M M M M | M M M M M M M
10/07/2025 at 1500 MDT | 10/07/2025 at 1800 MDT
|
CAPE... +95.7 LI... +0.3 | CAPE... +65.4 LI... -0.1
CINH... -16.5 K Index... +18.0 | CINH... -24.9 K Index... +17.1
|
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 -64.8 -84.6 260 47 24 3.5 1.9 | -65.4 -85.7 260 46 24 3.7 2.0
45000 -58.7 -73.7 265 64 33 5.9 3.2 | -58.9 -74.0 265 61 31 6.1 3.4
40000 -50.0 -58.0 260 73 37 4.4 2.4 | -49.8 -57.6 260 77 40 3.9 2.2
38000 -47.3 -53.1 265 67 34 4.5 2.5 | -47.3 -53.1 260 69 36 4.2 2.3
36000 -44.3 -47.7 265 60 31 4.5 2.5 | -44.5 -48.1 255 60 31 4.1 2.3
34000 -41.2 -42.2 265 53 27 5.4 3.0 | -40.9 -41.6 255 54 28 6.5 3.5
32000 -37.9 -36.2 265 45 23 5.4 3.0 | -37.0 -34.6 260 49 25 6.5 3.6
30000 -34.1 -29.4 260 40 21 6.8 3.8 | -33.0 -27.4 260 42 22 6.8 3.8
29000 -32.0 -25.6 255 38 20 6.8 3.8 | -30.9 -23.6 260 39 20 6.8 3.8
28000 -30.0 -22.0 250 36 19 6.8 3.8 | -28.9 -20.0 255 36 19 6.9 3.8
27000 -27.8 -18.0 245 35 18 7.5 4.1 | -26.6 -15.9 255 34 18 7.7 4.2
26000 -25.5 -13.9 245 33 17 7.5 4.1 | -24.3 -11.7 255 33 17 7.7 4.2
25000 -23.3 -9.9 240 31 16 7.5 4.1 | -22.0 -7.6 255 31 16 7.8 4.3
24000 -21.1 -6.0 240 30 15 7.4 4.1 | -19.9 -3.8 255 30 15 6.3 3.4
23000 -18.8 -1.8 235 28 14 7.4 4.1 | -18.1 -0.6 250 29 15 6.2 3.4
22000 -16.6 2.1 235 26 14 7.5 4.1 | -16.2 2.8 245 28 14 6.3 3.5
21000 -14.6 5.7 235 26 13 6.1 3.3 | -14.5 5.9 240 28 14 5.1 2.8
20000 -12.4 9.7 235 26 14 6.1 3.3 | -12.6 9.3 240 28 15 5.2 2.8
19500 -11.5 11.3 235 27 14 6.1 3.3 | -11.9 10.6 240 29 15 5.0 2.8
19000 -10.6 12.9 235 27 14 6.1 3.3 | -11.0 12.2 240 29 15 6.6 3.6
18500 -9.7 14.5 240 28 14 6.1 3.3 | -10.1 13.8 240 29 15 6.5 3.6
18000 -8.8 16.2 240 28 15 6.4 3.5 | -9.1 15.6 240 30 15 6.9 3.8
17500 -7.8 18.0 240 29 15 6.8 3.7 | -8.1 17.4 240 30 15 7.2 3.9
17000 -6.8 19.8 240 29 15 6.8 3.7 | -7.0 19.4 240 30 15 7.2 4.0
16500 -5.8 21.6 240 29 15 7.3 4.0 | -5.9 21.4 240 29 15 8.5 4.6
16000 -4.8 23.4 240 29 15 7.4 4.0 | -4.7 23.5 240 29 15 8.4 4.6
15500 -3.7 25.3 235 29 15 8.0 4.4 | -3.5 25.7 240 28 14 8.3 4.6
15000 -2.5 27.5 235 28 14 8.2 4.5 | -2.3 27.9 235 26 14 8.3 4.6
14500 -1.4 29.5 230 27 14 8.3 4.6 | -1.1 30.0 230 25 13 8.1 4.5
14000 -0.2 31.6 225 25 13 8.4 4.6 | 0.0 32.0 230 23 12 8.0 4.4
13500 1.0 33.8 220 24 12 8.6 4.7 | 1.1 34.0 225 22 11 8.4 4.6
13000 2.3 36.1 220 22 11 9.0 5.0 | 2.4 36.3 220 20 11 9.4 5.1
12500 3.6 38.5 215 21 11 9.1 5.0 | 3.8 38.8 220 19 10 9.4 5.1
12000 4.9 40.8 215 20 10 9.1 5.0 | 5.2 41.4 220 19 10 9.4 5.2
11500 6.2 43.2 215 19 10 9.0 5.0 | 6.6 43.9 220 18 9 9.4 5.1
11000 7.5 45.5 215 18 9 8.1 4.4 | 7.9 46.2 220 18 9 8.8 4.8
10500 8.7 47.7 215 17 9 11.3 6.2 | 9.2 48.6 220 17 9 11.3 6.2
10250 9.6 49.3 215 16 8 11.7 6.4 | 10.1 50.2 220 17 9 11.2 6.1
10000 10.3 50.5 215 16 8 7.5 4.1 | 10.8 51.4 225 16 8 7.9 4.3
9750 10.9 51.6 215 15 8 9.4 5.2 | 11.4 52.5 225 15 8 9.2 5.1
9500 11.5 52.7 215 14 7 5.9 3.2 | 12.1 53.8 225 15 8 7.2 3.9
9250 11.9 53.4 215 13 7 6.2 3.4 | 12.5 54.5 225 14 7 7.4 4.0
9000 12.5 54.5 220 12 6 9.4 5.2 | 13.2 55.8 225 13 7 9.2 5.0
8750 13.2 55.8 220 11 6 9.0 4.9 | 13.8 56.8 230 12 6 9.1 5.0
8500 13.8 56.8 220 10 5 7.4 4.1 | 14.5 58.1 230 11 6 7.7 4.2
8250 14.3 57.7 225 9 5 7.2 3.9 | 15.0 59.0 230 10 5 6.8 3.7
8000 15.0 59.0 225 9 5 9.7 5.3 | 15.6 60.1 235 9 5 8.1 4.4
7750 15.7 60.3 230 9 4 10.0 5.5 | 16.2 61.2 240 8 4 8.4 4.6
7500 16.4 61.5 235 8 4 9.3 5.1 | 16.8 62.2 245 7 3 7.5 4.1
7250 17.1 62.8 235 8 4 8.9 4.9 | 17.3 63.1 255 6 3 6.9 3.8
7000 17.8 64.0 235 8 4 10.2 5.6 | 17.9 64.2 260 6 3 8.5 4.7
6750 18.6 65.5 240 8 4 10.7 5.9 | 18.5 65.3 265 5 3 9.2 5.1
6500 19.4 66.9 240 7 4 10.3 5.7 | 19.2 66.6 270 5 3 9.1 5.0
6250 20.2 68.4 240 7 4 10.6 5.8 | 19.9 67.8 275 5 2 9.4 5.1
6000 20.9 69.6 245 7 4 8.9 4.9 | 20.6 69.1 280 5 2 8.5 4.7
5750 21.6 70.9 245 6 3 11.9 6.5 | 21.1 70.0 285 4 2 6.4 3.5
5500 M M 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 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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