Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
630
UXUS97 KGJT 011306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Wednesday, October 1, 2025
This forecast is for Wednesday, October 1, 2025:
If the trigger temperature of 71.8 F/22.1 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 693 ft/min (3.5 m/s)
Maximum height of thermals.................. 13820 ft MSL (8212 ft AGL)
Forecast maximum temperature................... 78.0 F/26.0 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................. 10247 ft MSL (4639 ft AGL)
Thermal soaring outlook for Thursday 10/02..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:10:46 / 18:56:30 MDT
Total possible sunshine........... 11 hr 45 min 45 sec (705 min 45 sec)
Altitude of sun at 13:03:38 MDT... 47.37 degrees
Upper air data from rawinsonde observation taken on 10/01/2025 at 0600 MDT
Freezing level.................. 14678 ft MSL (9070 ft AGL)
Convective condensation level... 18857 ft MSL (13249 ft AGL)
Lifted condensation level....... 16043 ft MSL (10435 ft AGL)
Lifted index.................... +4.1
K index......................... +7.9
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 -66.8 -88.2 250 35 18 1.2 0.7 M M M M M
45000 -63.2 -81.8 245 37 19 5.5 3.0 M M M M M
40000 -54.7 -66.5 235 35 18 8.1 4.4 M M M M M
38000 -49.9 -57.8 240 33 17 8.1 4.4 M M M M M
36000 -45.0 -49.0 245 31 16 8.1 4.4 M M M M M
34000 -39.9 -39.8 245 30 15 7.4 4.1 M M M M M
32000 -35.5 -31.9 245 29 15 7.4 4.0 M M M M M
30000 -31.2 -24.2 240 32 16 7.1 3.9 44.0 111.2 14.1 M M
29000 -29.1 -20.4 235 33 17 7.1 3.9 43.0 109.4 13.5 M M
28000 -27.0 -16.6 235 34 18 7.4 4.1 42.2 107.9 13.0 M M
27000 -24.7 -12.5 235 33 17 7.7 4.2 41.2 106.2 12.4 M M
26000 -22.4 -8.3 230 32 16 7.7 4.2 40.5 104.8 11.9 M M
25000 -20.1 -4.2 230 31 16 7.7 4.2 39.8 103.6 11.5 M M
24000 -17.7 0.1 235 30 15 7.8 4.3 39.0 102.2 11.0 M M
23000 -15.4 4.3 235 29 15 7.8 4.3 38.2 100.8 10.5 M M
22000 -13.1 8.4 240 28 15 7.7 4.2 37.6 99.7 10.0 M M
21000 -11.1 12.0 245 26 14 6.4 3.5 36.5 97.6 9.2 M M
20000 -8.8 16.2 250 24 12 6.4 3.5 35.0 95.0 8.0 M M
19500 -7.8 18.0 250 23 12 6.3 3.5 34.5 94.1 7.6 M M
19000 -7.0 19.4 250 22 11 5.6 3.1 33.8 92.8 7.0 M M
18500 -6.1 21.0 250 22 11 5.6 3.1 33.1 91.6 6.4 M M
18000 -5.3 22.5 250 22 11 5.7 3.1 32.4 90.3 5.8 M M
17500 -4.4 24.1 245 21 11 5.8 3.2 31.7 89.1 5.2 M M
17000 -3.6 25.5 245 20 11 5.8 3.2 31.0 87.9 4.7 M M
16500 -2.7 27.1 240 20 10 5.8 3.2 30.4 86.7 4.1 M M
16000 -1.9 28.6 235 19 10 5.9 3.2 29.7 85.5 3.5 M M
15500 -1.1 30.0 235 19 10 4.9 2.7 29.0 84.2 2.8 M M
15000 -0.4 31.3 230 18 9 5.0 2.7 28.2 82.7 2.1 M M
14500 0.3 32.5 230 18 9 4.2 2.3 27.4 81.3 1.3 M M
14000 0.8 33.4 225 17 9 3.9 2.2 26.4 79.5 0.3 M M
13500 1.2 34.2 225 16 8 4.9 2.7 25.4 77.8 -0.7 673 3.4
13000 2.0 35.6 225 15 8 6.2 3.4 24.8 76.7 -1.3 634 3.2
12500 2.9 37.2 225 14 7 6.9 3.8 24.3 75.7 -2.0 594 3.0
12000 4.0 39.2 225 13 6 8.5 4.7 24.0 75.2 -2.3 544 2.8
11500 5.3 41.5 225 11 6 8.4 4.6 23.8 74.8 -2.5 492 2.5
11000 6.5 43.7 230 10 5 8.1 4.5 23.5 74.4 -2.7 441 2.2
10500 7.7 45.9 230 9 5 9.4 5.1 23.3 73.9 -3.0 390 2.0
10250 8.5 47.3 225 9 5 9.6 5.3 23.3 74.0 -3.0 360 1.8
10000 9.1 48.4 220 9 4 8.0 4.4 23.2 73.8 -3.1 334 1.7
9750 9.7 49.5 220 8 4 8.8 4.8 23.1 73.6 -3.2 308 1.6
9500 10.4 50.7 215 8 4 7.1 3.9 23.0 73.4 -3.3 281 1.4
9250 10.8 51.4 210 8 4 6.9 3.8 22.7 72.9 -3.6 259 1.3
9000 11.4 52.5 205 8 4 8.1 4.5 22.6 72.6 -3.7 234 1.2
8750 12.0 53.6 195 8 4 8.1 4.4 22.4 72.4 -3.9 209 1.1
8500 12.6 54.7 190 8 4 7.0 3.9 22.3 72.1 -4.0 184 0.9
8250 13.1 55.6 185 9 4 5.8 3.2 22.0 71.6 -4.3 163 0.8
8000 13.5 56.3 175 9 5 6.0 3.3 21.7 71.1 -4.6 142 0.7
7750 14.0 57.2 170 9 5 5.9 3.3 21.4 70.6 -4.9 121 0.6
7500 14.4 57.9 165 10 5 4.4 2.4 21.1 70.0 -5.2 102 0.5
7250 14.6 58.3 160 11 5 3.1 1.7 20.6 69.1 -5.7 86 0.4
7000 14.9 58.8 155 11 6 4.1 2.2 20.1 68.3 -6.2 71 0.4
6750 15.2 59.4 150 11 5 1.4 0.8 19.7 67.4 -6.6 56 0.3
6500 15.1 59.2 145 10 5 -2.9 -1.6 18.8 65.9 -7.5 51 0.3
6250 14.8 58.6 135 9 5 -4.3 -2.4 17.8 64.1 -8.5 52 0.3
6000 14.5 58.1 130 8 4 -0.6 -0.4 16.8 62.3 -9.5 52 0.3
5750 14.3 57.7 120 8 4 -10.7 -5.9 15.9 60.7 -10.5 52 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 * * * * * *
10/01/2025 at 0900 MDT | 10/01/2025 at 1200 MDT
|
CAPE... 0.0 LI... +1.9 | CAPE... +0.4 LI... +3.0
CINH... 0.0 K Index... +21.1 | CINH... -0.4 K Index... +16.6
|
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 -83.6 260 32 16 2.1 1.2 | -64.6 -84.3 260 32 17 1.6 0.9
45000 -60.1 -76.2 265 37 19 4.4 2.4 | -61.3 -78.3 265 42 22 4.1 2.2
40000 -53.4 -64.1 285 58 30 7.1 3.9 | -54.9 -66.8 280 52 27 7.8 4.3
38000 -49.3 -56.7 290 56 29 6.9 3.8 | -50.5 -58.9 280 51 26 7.4 4.1
36000 -44.6 -48.3 300 55 28 6.9 3.8 | -45.5 -49.9 285 50 26 7.4 4.0
34000 -40.3 -40.5 305 53 27 7.3 4.0 | -40.8 -41.4 290 46 24 7.9 4.3
32000 -35.9 -32.6 310 51 26 7.3 4.0 | -36.1 -33.0 295 41 21 7.8 4.3
30000 -31.8 -25.2 310 48 25 6.9 3.8 | -31.6 -24.9 295 38 19 7.5 4.1
29000 -29.7 -21.5 310 46 24 6.9 3.8 | -29.3 -20.7 295 36 18 7.5 4.1
28000 -27.6 -17.7 310 44 23 6.9 3.8 | -27.1 -16.8 290 34 18 7.5 4.1
27000 -25.7 -14.3 305 41 21 6.4 3.5 | -24.9 -12.8 290 33 17 7.3 4.0
26000 -23.8 -10.8 300 38 20 6.4 3.5 | -22.7 -8.9 290 32 16 7.3 4.0
25000 -21.9 -7.4 300 36 18 6.4 3.5 | -20.5 -4.9 290 30 16 7.3 4.0
24000 -19.9 -3.8 295 34 17 6.6 3.6 | -18.3 -0.9 290 29 15 7.5 4.1
23000 -18.0 -0.4 290 32 16 6.6 3.6 | -16.0 3.2 290 28 15 7.5 4.1
22000 -15.5 4.1 285 29 15 6.6 3.6 | -13.2 8.2 290 27 14 6.9 3.8
21000 -13.7 7.3 280 28 14 6.2 3.4 | -11.8 10.8 285 25 13 4.5 2.5
20000 -11.9 10.6 275 27 14 6.2 3.4 | -10.4 13.3 280 22 11 4.6 2.5
19500 -11.0 12.2 275 27 14 6.3 3.5 | -9.8 14.4 280 21 11 4.5 2.5
19000 -10.1 13.8 270 26 14 6.1 3.3 | -9.1 15.6 275 20 10 5.3 2.9
18500 -9.2 15.4 270 25 13 6.0 3.3 | -8.3 17.1 275 19 10 5.3 2.9
18000 -8.3 17.1 270 24 12 5.5 3.0 | -7.6 18.3 270 19 10 5.4 3.0
17500 -7.7 18.1 270 22 11 3.8 2.1 | -6.8 19.8 265 18 9 5.6 3.1
17000 -7.1 19.2 265 20 10 3.8 2.1 | -5.9 21.4 265 17 9 5.8 3.2
16500 -6.5 20.3 260 19 10 4.4 2.4 | -5.3 22.5 260 16 8 2.8 1.5
16000 -5.9 21.4 255 18 9 4.5 2.5 | -4.9 23.2 255 15 8 3.0 1.6
15500 -5.3 22.5 250 18 9 5.2 2.9 | -4.5 23.9 245 15 8 4.1 2.2
15000 -4.5 23.9 245 17 9 5.8 3.2 | -3.8 25.2 245 15 8 4.7 2.6
14500 -3.7 25.3 245 17 9 6.2 3.4 | -3.2 26.2 240 15 8 5.4 3.0
14000 -2.7 27.1 245 17 9 7.2 3.9 | -2.3 27.9 235 15 8 6.8 3.7
13500 -1.7 28.9 240 17 9 7.2 4.0 | -1.4 29.5 235 14 7 6.9 3.8
13000 -0.6 30.9 240 17 9 8.2 4.5 | -0.3 31.5 230 14 7 8.2 4.5
12500 0.6 33.1 240 16 8 8.2 4.5 | 0.9 33.6 230 14 7 8.1 4.5
12000 1.8 35.2 240 15 7 8.8 4.8 | 2.1 35.8 230 13 7 8.6 4.7
11500 3.1 37.6 240 13 7 8.8 4.8 | 3.4 38.1 230 12 6 8.6 4.7
11000 4.4 39.9 240 12 6 9.0 5.0 | 4.7 40.5 230 11 6 9.2 5.0
10500 5.7 42.3 240 11 6 9.0 4.9 | 6.0 42.8 230 10 5 8.6 4.7
10250 6.3 43.3 240 10 5 7.2 3.9 | 6.6 43.9 230 10 5 6.9 3.8
10000 6.9 44.4 240 10 5 7.9 4.3 | 7.2 45.0 230 9 5 8.8 4.8
9750 7.6 45.7 235 9 5 9.8 5.4 | 7.9 46.2 230 9 4 10.8 5.9
9500 8.3 46.9 230 8 4 9.2 5.1 | 8.7 47.7 230 8 4 10.2 5.6
9250 8.9 48.0 225 7 4 8.1 4.5 | 9.4 48.9 230 8 4 8.3 4.6
9000 9.5 49.1 220 7 4 6.9 3.8 | 10.0 50.0 230 7 3 8.1 4.5
8750 10.0 50.0 215 6 3 7.0 3.8 | 10.7 51.3 225 6 3 9.5 5.2
8500 10.5 50.9 200 6 3 6.8 3.7 | 11.4 52.5 225 6 3 8.8 4.8
8250 11.5 52.7 185 6 3 6.0 3.3 | 12.5 54.5 220 4 2 7.8 4.3
8000 12.0 53.6 175 6 3 7.2 3.9 | 13.2 55.8 215 4 2 10.8 5.9
7750 12.5 54.5 165 6 3 6.3 3.4 | 14.0 57.2 215 4 2 9.9 5.4
7500 12.9 55.2 160 7 3 4.7 2.6 | 14.6 58.3 215 4 2 8.0 4.4
7250 13.3 55.9 160 7 4 4.8 2.7 | 15.3 59.5 210 3 2 8.5 4.7
7000 13.6 56.5 155 8 4 5.9 3.2 | 16.0 60.8 210 3 2 11.9 6.6
6750 14.1 57.4 150 7 3 4.9 2.7 | 16.9 62.4 215 3 2 11.8 6.5
6500 14.4 57.9 145 7 3 3.6 2.0 | 17.7 63.9 210 3 2 10.1 5.5
6250 14.7 58.5 140 7 3 3.7 2.0 | 18.5 65.3 205 3 1 9.4 5.1
6000 15.0 59.0 140 6 3 5.9 3.2 | 19.2 66.6 205 2 1 12.9 7.1
5750 15.6 60.1 130 4 2 10.1 5.5 | 20.6 69.1 210 2 1 25.0 13.7
5500 16.1 61.0 115 4 2 -1.4 -0.7 | 22.4 72.3 205 2 1 15.9 8.7
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
10/01/2025 at 1500 MDT | 10/01/2025 at 1800 MDT
|
CAPE... +0.8 LI... +3.0 | CAPE... 0.0 LI... +3.2
CINH... -1.2 K Index... +17.8 | CINH... -0.2 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 -65.3 -85.5 265 31 16 1.4 0.7 | -66.5 -87.7 265 30 15 1.3 0.7
45000 -61.9 -79.4 270 43 22 5.1 2.8 | -62.7 -80.9 275 40 21 6.1 3.4
40000 -54.2 -65.6 275 48 25 6.7 3.7 | -53.5 -64.3 280 43 22 6.2 3.4
38000 -50.2 -58.4 275 49 25 6.6 3.6 | -49.8 -57.6 275 44 22 6.2 3.4
36000 -45.8 -50.4 275 51 26 6.5 3.5 | -45.6 -50.1 275 45 23 6.0 3.3
34000 -41.2 -42.2 275 46 24 7.8 4.3 | -41.3 -42.3 270 44 23 7.5 4.1
32000 -36.5 -33.7 280 40 21 7.8 4.3 | -36.8 -34.2 270 43 22 7.4 4.1
30000 -31.7 -25.1 280 37 19 8.2 4.5 | -31.9 -25.4 270 39 20 8.2 4.5
29000 -29.2 -20.6 280 35 18 8.2 4.5 | -29.5 -21.1 270 36 19 8.2 4.5
28000 -26.8 -16.2 285 34 17 8.1 4.4 | -27.0 -16.6 270 34 18 8.3 4.6
27000 -24.4 -11.9 285 33 17 7.8 4.3 | -24.5 -12.1 270 32 16 8.5 4.6
26000 -22.1 -7.8 285 33 17 7.8 4.3 | -22.0 -7.6 275 30 15 8.5 4.6
25000 -19.8 -3.6 285 32 17 7.8 4.3 | -19.4 -2.9 275 28 14 8.6 4.7
24000 -17.5 0.5 285 31 16 7.4 4.1 | -17.2 1.0 275 26 13 7.2 4.0
23000 -14.7 5.5 280 28 15 7.4 4.1 | -15.0 5.0 275 24 12 7.2 4.0
22000 -12.5 9.5 280 26 14 6.7 3.7 | -12.3 9.9 275 22 11 6.6 3.6
21000 -11.0 12.2 275 23 12 5.0 2.7 | -10.6 12.9 270 21 11 5.6 3.1
20000 -9.5 14.9 270 20 10 5.0 2.8 | -9.0 15.8 260 21 11 5.6 3.1
19500 -8.8 16.2 265 19 10 5.1 2.8 | -8.1 17.4 260 21 11 5.8 3.2
19000 -8.1 17.4 260 18 9 4.3 2.4 | -7.4 18.7 255 21 11 4.0 2.2
18500 -7.4 18.7 255 18 9 4.4 2.4 | -6.8 19.8 255 20 10 4.2 2.3
18000 -6.8 19.8 255 18 9 4.6 2.5 | -6.2 20.8 255 20 10 4.5 2.4
17500 -6.1 21.0 250 18 9 4.9 2.7 | -5.5 22.1 255 19 10 4.7 2.6
17000 -5.4 22.3 250 17 9 4.9 2.7 | -4.9 23.2 250 18 9 4.8 2.6
16500 -4.8 23.4 245 16 8 4.3 2.4 | -4.1 24.6 245 17 9 5.3 2.9
16000 -4.2 24.4 240 15 8 4.4 2.4 | -3.4 25.9 240 15 8 5.3 2.9
15500 -3.6 25.5 230 14 7 5.0 2.8 | -2.7 27.1 230 14 7 5.7 3.1
15000 -2.8 27.0 225 14 7 5.4 3.0 | -1.8 28.8 225 14 7 5.9 3.2
14500 -2.1 28.2 220 13 7 6.2 3.4 | -1.0 30.2 215 14 7 6.3 3.5
14000 -1.1 30.0 215 13 7 7.5 4.1 | -0.1 31.8 215 14 7 6.9 3.8
13500 -0.1 31.8 215 12 6 7.6 4.2 | 0.8 33.4 210 13 7 7.2 4.0
13000 1.1 34.0 210 11 6 8.3 4.6 | 2.0 35.6 205 13 7 8.5 4.7
12500 2.3 36.1 210 10 5 8.3 4.6 | 3.2 37.8 205 12 6 8.5 4.7
12000 3.5 38.3 210 9 5 8.5 4.7 | 4.5 40.1 205 11 6 8.9 4.9
11500 4.8 40.6 215 9 4 8.5 4.7 | 5.8 42.4 205 10 5 8.8 4.8
11000 6.1 43.0 215 8 4 8.8 4.8 | 7.1 44.8 210 9 5 8.8 4.8
10500 7.4 45.3 220 7 4 7.7 4.2 | 8.4 47.1 215 8 4 7.4 4.0
10250 7.9 46.2 225 6 3 6.8 3.7 | 8.9 48.0 215 7 4 6.9 3.8
10000 8.5 47.3 230 6 3 9.3 5.1 | 9.5 49.1 220 6 3 9.6 5.3
9750 9.3 48.7 235 6 3 10.3 5.7 | 10.3 50.5 225 6 3 10.0 5.5
9500 10.0 50.0 240 6 3 10.0 5.5 | 11.0 51.8 225 6 3 9.8 5.4
9250 10.7 51.3 245 5 3 8.6 4.7 | 11.7 53.1 235 5 3 8.2 4.5
9000 11.3 52.3 260 5 2 8.6 4.7 | 12.3 54.1 245 4 2 8.3 4.5
8750 12.0 53.6 260 5 3 9.7 5.3 | 13.0 55.4 250 4 2 9.6 5.3
8500 13.4 56.1 265 5 3 8.0 4.4 | 13.7 56.7 255 4 2 8.8 4.8
8250 14.0 57.2 275 5 3 9.0 5.0 | 14.2 57.6 265 4 2 6.5 3.6
8000 14.8 58.6 275 5 3 11.9 6.6 | 15.4 59.7 290 4 2 10.5 5.7
7750 15.7 60.3 270 6 3 10.4 5.7 | 16.2 61.2 285 4 2 9.2 5.1
7500 16.3 61.3 275 6 3 7.8 4.3 | 16.7 62.1 290 5 2 7.0 3.9
7250 16.9 62.4 285 6 3 8.3 4.5 | 17.3 63.1 305 5 3 7.5 4.1
7000 17.6 63.7 285 6 3 11.8 6.5 | 17.9 64.2 305 5 3 11.0 6.0
6750 18.6 65.5 275 6 3 11.6 6.4 | 18.8 65.8 295 5 2 11.1 6.1
6500 19.3 66.7 285 6 3 9.9 5.4 | 19.5 67.1 300 5 3 9.3 5.1
6250 20.1 68.2 290 6 3 9.3 5.1 | 20.3 68.5 310 5 3 9.6 5.3
6000 20.8 69.4 295 6 3 12.7 7.0 | 21.0 69.8 310 5 3 9.5 5.2
5750 22.2 72.0 285 6 3 24.2 13.3 | 21.7 71.1 305 4 2 11.4 6.3
5500 24.0 75.2 300 6 3 18.1 10.0 | 22.7 72.9 320 5 2 13.5 7.4
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