Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
457
UXUS97 KGJT 091306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Thursday, October 9, 2025
This forecast is for Thursday, October 9, 2025:
If the trigger temperature of 67.1 F/19.5 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 506 ft/min (2.6 m/s)
Maximum height of thermals.................. 14681 ft MSL (9073 ft AGL)
Forecast maximum temperature................... 79.0 F/26.6 C
Time of trigger temperature.................... 0945 MDT
Time of overdevelopment........................ 1200 MDT
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 12727 ft MSL (7118 ft AGL)
Thermal soaring outlook for Friday 10/10....... Poor
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:18:26 / 18:44:04 MDT
Total possible sunshine........... 11 hr 25 min 38 sec (685 min 38 sec)
Altitude of sun at 13:01:15 MDT... 44.30 degrees
Upper air data from rawinsonde observation taken on 10/09/2025 at 0600 MDT
Freezing level.................. 13754 ft MSL (8146 ft AGL)
Convective condensation level... 10158 ft MSL (4550 ft AGL)
Lifted condensation level....... 12634 ft MSL (7025 ft AGL)
Lifted index.................... -1.8
K index......................... +27.3
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 -67.0 -88.6 255 54 28 4.0 2.2 M M M M M
45000 -59.8 -75.6 255 77 39 6.1 3.3 M M M M M
40000 -51.0 -59.8 250 81 42 4.5 2.5 M M M M M
38000 -48.3 -54.9 245 72 37 4.4 2.4 M M M M M
36000 -45.6 -50.1 245 63 32 4.2 2.3 M M M M M
34000 -41.1 -42.0 240 55 28 8.3 4.6 M M M M M
32000 -36.1 -33.0 240 46 24 8.4 4.6 M M M M M
30000 -30.3 -22.5 235 38 19 8.6 4.7 45.1 113.2 14.4 M M
29000 -27.8 -18.0 235 34 17 8.7 4.8 44.7 112.5 14.3 M M
28000 -25.2 -13.4 230 30 16 7.7 4.2 44.4 111.9 14.2 M M
27000 -23.1 -9.6 230 29 15 7.3 4.0 43.3 110.0 13.4 M M
26000 -21.0 -5.8 230 28 15 7.3 4.0 42.4 108.3 12.8 M M
25000 -18.8 -1.8 230 27 14 7.3 4.0 41.6 106.8 12.3 M M
24000 -16.8 1.8 230 27 14 7.0 3.8 40.5 104.9 11.5 M M
23000 -14.7 5.5 225 28 14 7.0 3.8 39.5 103.0 10.7 M M
22000 -12.7 9.1 225 28 14 7.0 3.8 38.6 101.4 10.0 M M
21000 -11.1 12.0 220 27 14 5.1 2.8 37.0 98.6 8.7 M M
20000 -9.7 14.5 215 26 13 5.1 2.8 35.3 95.6 7.4 M M
19500 -8.9 16.0 215 26 13 5.1 2.8 34.6 94.2 6.7 M M
19000 -8.2 17.2 210 25 13 5.7 3.1 33.8 92.9 6.1 M M
18500 -7.3 18.9 210 25 13 5.9 3.2 33.2 91.7 5.5 M M
18000 -6.1 21.0 210 25 13 5.7 3.1 32.2 89.9 4.6 M M
17500 -5.3 22.5 210 24 12 5.6 3.1 31.4 88.6 4.0 M M
17000 -4.5 23.9 210 24 12 5.5 3.0 30.8 87.4 3.3 M M
16500 -3.7 25.3 210 24 12 4.8 2.7 30.0 85.9 2.6 M M
16000 -3.0 26.6 210 23 12 4.9 2.7 29.1 84.5 1.9 M M
15500 -2.3 27.9 210 23 12 5.0 2.7 28.3 83.0 1.1 M M
15000 -1.6 29.1 205 23 12 5.0 2.7 27.6 81.6 0.4 M M
14500 -0.9 30.4 205 23 12 4.7 2.6 26.8 80.2 -0.4 689 3.5
14000 -0.3 31.5 205 23 12 4.6 2.5 25.9 78.6 -1.2 655 3.3
13500 0.4 32.7 200 23 12 5.0 2.7 25.1 77.2 -2.0 620 3.2
13000 1.2 34.2 195 23 12 5.5 3.0 24.4 75.9 -2.7 582 3.0
12500 2.0 35.6 195 23 12 5.9 3.2 23.7 74.7 -3.3 544 2.8
12000 2.9 37.2 190 23 12 7.0 3.8 23.2 73.8 -3.9 500 2.5
11500 3.9 39.0 190 23 12 6.9 3.8 22.8 73.0 -4.3 456 2.3
11000 4.9 40.8 190 23 12 6.6 3.6 22.3 72.1 -4.9 412 2.1
10500 5.8 42.4 190 23 12 6.6 3.6 21.8 71.2 -5.4 369 1.9
10250 6.3 43.3 185 22 11 6.8 3.7 21.6 70.8 -5.7 348 1.8
10000 6.8 44.2 185 22 11 6.8 3.7 21.3 70.4 -5.9 326 1.7
9750 7.2 45.0 185 21 11 6.9 3.8 21.1 70.0 -6.2 304 1.5
9500 7.7 45.9 185 21 11 6.6 3.6 20.9 69.6 -6.4 282 1.4
9250 8.2 46.8 180 20 10 5.8 3.2 20.6 69.1 -6.7 261 1.3
9000 8.6 47.5 180 19 10 5.6 3.1 20.3 68.5 -7.1 242 1.2
8750 9.0 48.2 175 18 10 5.8 3.2 20.0 67.9 -7.4 222 1.1
8500 9.4 48.9 175 18 9 5.1 2.8 19.7 67.4 -7.7 203 1.0
8250 9.7 49.5 170 16 8 4.6 2.5 19.3 66.7 -8.1 186 0.9
8000 10.1 50.2 170 15 8 5.4 3.0 18.9 66.0 -8.5 167 0.9
7750 10.5 50.9 165 14 7 5.5 3.0 18.6 65.4 -8.9 149 0.8
7500 10.8 51.4 165 13 7 5.5 3.0 18.3 64.9 -9.3 130 0.7
7250 11.2 52.2 160 11 6 5.4 3.0 17.9 64.3 -9.6 111 0.6
7000 11.6 52.9 155 10 5 6.2 3.4 17.6 63.7 -10.0 92 0.5
6750 12.0 53.6 155 8 4 6.1 3.4 17.4 63.3 -10.3 72 0.4
6500 12.4 54.3 150 7 4 5.3 2.9 17.1 62.7 -10.7 53 0.3
6250 12.8 55.0 140 6 3 5.2 2.9 16.7 62.1 -11.1 35 0.2
6000 13.1 55.6 125 5 2 5.8 3.2 16.4 61.5 -11.5 17 0.1
5750 13.6 56.5 120 4 2 7.3 4.0 16.2 61.1 -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 * * * * * *
10/09/2025 at 0900 MDT | 10/09/2025 at 1200 MDT
|
CAPE... +0.7 LI... -1.4 | CAPE... +160.7 LI... -1.6
CINH... -3.5 K Index... +29.0 | CINH... -43.5 K Index... +30.4
|
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 -66.0 -86.8 250 55 28 3.6 1.9 | -66.2 -87.2 250 57 29 3.8 2.1
45000 -59.5 -75.1 255 79 41 6.3 3.5 | -59.4 -74.9 255 83 43 6.4 3.5
40000 -49.9 -57.8 245 88 45 4.4 2.4 | -49.8 -57.6 250 93 48 3.9 2.2
38000 -47.3 -53.1 245 78 40 4.3 2.4 | -47.5 -53.5 250 81 41 3.9 2.1
36000 -44.7 -48.5 250 69 35 4.3 2.3 | -45.1 -49.2 245 68 35 3.7 2.0
34000 -41.5 -42.7 250 62 32 5.5 3.0 | -41.3 -42.3 250 62 32 6.9 3.8
32000 -38.2 -36.8 250 56 29 5.6 3.1 | -37.2 -35.0 250 57 29 6.8 3.7
30000 -34.1 -29.4 245 48 25 7.2 4.0 | -33.4 -28.1 245 50 26 6.3 3.5
29000 -32.0 -25.6 245 44 23 7.2 4.0 | -31.5 -24.7 245 47 24 6.3 3.5
28000 -29.8 -21.6 240 40 21 7.4 4.0 | -29.6 -21.3 245 43 22 6.6 3.6
27000 -27.5 -17.5 240 37 19 7.9 4.3 | -27.4 -17.3 245 39 20 7.5 4.1
26000 -25.1 -13.2 245 35 18 7.9 4.3 | -25.2 -13.4 240 34 18 7.5 4.1
25000 -22.8 -9.0 245 32 16 7.9 4.4 | -22.9 -9.2 235 29 15 7.6 4.1
24000 -20.1 -4.2 245 30 15 7.2 3.9 | -20.2 -4.4 235 27 14 7.3 4.0
23000 -17.9 -0.2 240 29 15 7.2 3.9 | -18.0 -0.4 230 26 13 7.4 4.1
22000 -15.8 3.6 240 28 14 6.5 3.6 | -15.9 3.4 230 25 13 6.9 3.8
21000 -14.2 6.4 235 28 14 5.7 3.1 | -14.0 6.8 225 24 12 6.4 3.5
20000 -12.5 9.5 235 27 14 5.8 3.2 | -12.2 10.0 225 24 12 6.5 3.6
19500 -11.7 10.9 235 27 14 5.8 3.2 | -11.3 11.7 225 24 12 6.5 3.6
19000 -10.8 12.6 235 26 14 6.6 3.6 | -10.3 13.5 225 23 12 6.8 3.7
18500 -9.9 14.2 230 25 13 6.5 3.6 | -9.3 15.3 225 22 11 6.8 3.7
18000 -8.9 16.0 230 24 12 6.7 3.7 | -8.3 17.1 220 21 11 6.6 3.6
17500 -8.0 17.6 230 23 12 6.7 3.7 | -7.4 18.7 220 20 10 6.6 3.6
17000 -7.0 19.4 225 22 11 6.9 3.8 | -6.4 20.5 220 20 10 6.6 3.6
16500 -6.0 21.2 225 21 11 7.5 4.1 | -5.5 22.1 220 19 10 6.8 3.7
16000 -4.9 23.2 225 20 10 7.5 4.1 | -4.5 23.9 220 19 10 6.8 3.7
15500 -3.8 25.2 220 19 10 7.6 4.2 | -3.5 25.7 215 18 9 6.9 3.8
15000 -2.7 27.1 220 19 10 7.6 4.2 | -2.5 27.5 215 18 9 6.9 3.8
14500 -1.6 29.1 220 18 9 7.6 4.2 | -1.5 29.3 215 18 9 6.9 3.8
14000 -0.5 31.1 220 18 9 7.6 4.2 | -0.5 31.1 210 18 9 7.0 3.8
13500 0.6 33.1 225 17 9 7.9 4.3 | 0.5 32.9 210 18 9 7.4 4.1
13000 1.8 35.2 225 17 9 8.1 4.4 | 1.6 34.9 210 17 9 7.9 4.3
12500 3.0 37.4 230 16 8 8.2 4.5 | 2.8 37.0 210 17 9 8.2 4.5
12000 4.2 39.6 230 16 8 8.2 4.5 | 4.1 39.4 215 16 8 8.7 4.8
11500 5.4 41.7 230 17 9 8.1 4.5 | 5.3 41.5 215 16 8 8.6 4.7
11000 6.6 43.9 230 16 8 7.8 4.3 | 6.6 43.9 215 15 8 8.4 4.6
10500 7.7 45.9 230 16 8 7.3 4.0 | 7.8 46.0 215 14 7 8.1 4.4
10250 8.2 46.8 230 15 8 6.8 3.7 | 8.4 47.1 215 14 7 7.9 4.3
10000 8.8 47.8 230 14 7 7.7 4.2 | 9.0 48.2 215 13 7 8.5 4.7
9750 9.3 48.7 225 14 7 8.1 4.4 | 9.7 49.5 210 12 6 8.7 4.8
9500 9.9 49.8 220 14 7 7.9 4.3 | 10.3 50.5 210 12 6 8.5 4.7
9250 10.5 50.9 220 14 7 8.2 4.5 | 10.9 51.6 210 11 6 8.6 4.7
9000 11.1 52.0 225 13 7 6.9 3.8 | 11.5 52.7 210 11 5 7.8 4.3
8750 11.9 53.4 210 12 6 6.6 3.6 | 12.1 53.8 205 10 5 6.9 3.8
8500 12.5 54.5 210 12 6 7.6 4.2 | 12.6 54.7 200 9 5 7.5 4.1
8250 13.0 55.4 205 12 6 7.0 3.8 | 13.7 56.7 195 8 4 7.9 4.3
8000 13.5 56.3 200 11 6 6.0 3.3 | 14.3 57.7 190 8 4 8.0 4.4
7750 13.9 57.0 195 11 5 5.6 3.1 | 14.8 58.6 190 7 4 7.4 4.1
7500 14.4 57.9 190 11 6 5.6 3.1 | 15.4 59.7 180 7 4 6.6 3.6
7250 14.8 58.6 185 11 6 5.7 3.1 | 15.9 60.6 175 7 3 8.0 4.4
7000 15.2 59.4 180 11 6 5.0 2.8 | 16.6 61.9 175 6 3 10.6 5.8
6750 15.6 60.1 170 9 5 4.1 2.2 | 17.4 63.3 175 6 3 9.9 5.4
6500 15.9 60.6 165 8 4 4.4 2.4 | 18.0 64.4 170 6 3 9.6 5.3
6250 16.2 61.2 160 8 4 3.4 1.9 | 18.7 65.7 170 5 3 7.0 3.9
6000 16.4 61.5 150 8 4 1.0 0.6 | 19.2 66.6 140 6 3 8.7 4.8
5750 16.5 61.7 135 6 3 -0.0 -0.0 | 20.2 68.4 140 6 3 20.3 11.1
5500 16.5 61.7 110 4 2 1.0 0.5 | 21.3 70.3 140 5 3 -2.9 -1.6
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
10/09/2025 at 1500 MDT | 10/09/2025 at 1800 MDT
|
CAPE... +199.4 LI... -1.7 | CAPE... +101.8 LI... -1.3
CINH... -35.0 K Index... +29.9 | CINH... -69.2 K Index... +29.1
|
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 -66.4 -87.5 255 58 30 3.5 1.9 | -66.7 -88.1 255 57 29 3.4 1.9
45000 -60.0 -76.0 255 83 43 6.4 3.5 | -60.2 -76.4 255 82 42 6.6 3.6
40000 -50.3 -58.5 250 90 46 4.1 2.3 | -50.3 -58.5 250 92 47 4.2 2.3
38000 -47.9 -54.2 250 79 41 4.1 2.2 | -47.8 -54.0 250 85 44 4.1 2.3
36000 -45.4 -49.7 245 69 35 3.8 2.1 | -45.3 -49.5 245 78 40 3.8 2.1
34000 -41.4 -42.5 245 63 33 7.2 4.0 | -41.3 -42.3 250 69 35 7.2 3.9
32000 -37.1 -34.8 245 59 30 7.1 3.9 | -37.0 -34.6 255 59 30 7.1 3.9
30000 -32.9 -27.2 245 53 27 6.9 3.8 | -32.5 -26.5 255 52 27 7.5 4.1
29000 -30.8 -23.4 245 50 26 6.9 3.8 | -30.3 -22.5 255 48 25 7.5 4.1
28000 -28.7 -19.7 250 48 24 7.0 3.8 | -28.1 -18.6 255 45 23 7.2 4.0
27000 -26.6 -15.9 245 43 22 7.2 3.9 | -26.0 -14.8 250 39 20 6.7 3.7
26000 -24.5 -12.1 245 38 19 7.2 3.9 | -24.0 -11.2 250 33 17 6.7 3.7
25000 -21.8 -7.2 240 31 16 7.1 3.9 | -21.6 -6.9 245 25 13 7.0 3.8
24000 -19.7 -3.5 235 29 15 7.2 3.9 | -19.4 -2.9 240 22 12 7.4 4.1
23000 -17.6 0.3 230 26 14 7.2 4.0 | -17.2 1.0 235 20 11 7.4 4.1
22000 -15.5 4.1 230 24 12 7.1 3.9 | -15.0 5.0 230 19 10 7.0 3.9
21000 -13.5 7.7 225 22 12 6.9 3.8 | -13.0 8.6 225 17 9 6.7 3.7
20000 -11.5 11.3 220 21 11 6.9 3.8 | -11.1 12.0 220 16 8 6.7 3.7
19500 -10.5 13.1 215 20 10 6.9 3.8 | -10.1 13.8 215 16 8 6.7 3.7
19000 -9.6 14.7 215 20 10 6.0 3.3 | -9.1 15.6 210 16 8 6.6 3.6
18500 -8.7 16.3 215 19 10 6.0 3.3 | -8.2 17.2 205 16 8 6.6 3.6
18000 -7.8 18.0 210 19 10 6.5 3.6 | -7.2 19.0 205 16 8 6.5 3.6
17500 -6.9 19.6 210 19 10 6.7 3.7 | -6.3 20.7 200 16 8 6.5 3.6
17000 -5.9 21.4 210 19 10 6.8 3.7 | -5.3 22.5 195 16 8 6.6 3.6
16500 -4.9 23.2 210 19 10 7.1 3.9 | -4.4 24.1 190 16 8 6.8 3.7
16000 -3.9 25.0 205 19 10 7.1 3.9 | -3.4 25.9 190 16 8 6.7 3.7
15500 -2.8 27.0 205 19 10 7.1 3.9 | -2.4 27.7 185 15 8 7.6 4.2
15000 -1.8 28.8 205 18 9 7.1 3.9 | -1.3 29.7 185 15 8 7.7 4.2
14500 -0.7 30.7 205 18 9 7.2 4.0 | -0.2 31.6 185 15 8 8.1 4.5
14000 0.3 32.5 205 18 9 7.3 4.0 | 1.0 33.8 185 14 7 8.3 4.6
13500 1.4 34.5 205 17 9 7.6 4.1 | 2.2 36.0 180 14 7 8.3 4.5
13000 2.5 36.5 205 16 8 7.9 4.3 | 3.4 38.1 180 13 7 8.2 4.5
12500 3.7 38.7 205 14 7 8.1 4.4 | 4.6 40.3 175 12 6 8.3 4.6
12000 4.9 40.8 205 13 7 8.4 4.6 | 5.9 42.6 175 11 6 8.7 4.8
11500 6.1 43.0 205 11 6 8.4 4.6 | 7.1 44.8 175 10 5 8.7 4.8
11000 7.3 45.1 205 10 5 8.6 4.7 | 8.4 47.1 170 9 5 8.7 4.8
10500 8.6 47.5 210 9 4 7.8 4.3 | 9.7 49.5 165 8 4 7.7 4.2
10250 9.1 48.4 210 8 4 7.7 4.2 | 10.2 50.4 165 8 4 7.8 4.3
10000 9.7 49.5 215 8 4 9.0 4.9 | 10.9 51.6 165 7 4 9.5 5.2
9750 11.1 52.0 220 6 3 9.0 5.0 | 11.6 52.9 160 6 3 9.3 5.1
9500 11.7 53.1 220 6 3 9.0 5.0 | 12.3 54.1 155 6 3 9.3 5.1
9250 12.4 54.3 225 5 3 8.8 4.8 | 13.0 55.4 150 5 3 9.2 5.1
9000 13.0 55.4 225 5 3 8.7 4.8 | 13.6 56.5 145 5 3 8.4 4.6
8750 13.7 56.7 230 5 2 8.4 4.6 | 14.8 58.6 135 4 2 8.0 4.4
8500 14.3 57.7 235 4 2 7.6 4.2 | 15.4 59.7 125 3 2 8.0 4.4
8250 14.8 58.6 240 3 1 8.3 4.6 | 16.0 60.8 120 3 1 8.0 4.4
8000 15.5 59.9 240 3 1 9.3 5.1 | 16.6 61.9 110 2 1 7.9 4.3
7750 16.2 61.2 240 3 1 8.6 4.7 | 17.2 63.0 105 2 1 8.2 4.5
7500 16.8 62.2 250 2 1 7.7 4.2 | 17.8 64.0 095 2 1 8.3 4.6
7250 17.4 63.3 260 1 1 8.5 4.7 | 18.4 65.1 085 2 1 8.4 4.6
7000 18.0 64.4 265 1 1 9.5 5.2 | 19.0 66.2 085 1 1 9.0 5.0
6750 18.7 65.7 260 1 1 8.2 4.5 | 19.7 67.5 090 1 1 9.1 5.0
6500 19.3 66.7 285 1 0 7.1 3.9 | 20.4 68.7 080 1 0 9.1 5.0
6250 19.8 67.6 315 1 0 7.4 4.1 | 21.1 70.0 070 1 0 8.6 4.7
6000 20.4 68.7 275 1 1 9.8 5.4 | 21.6 70.9 070 1 0 7.3 4.0
5750 21.3 70.3 320 1 0 14.1 7.7 | 22.1 71.8 000 0 0 7.0 3.8
5500 22.2 72.0 360 1 1 6.4 3.5 | 22.7 72.9 000 0 0 9.5 5.2
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
________________________________________________________________________________
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.
042613