Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
577
UXUS97 KGJT 161306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Wednesday, July 16, 2025
This forecast is for Wednesday, July 16, 2025:
If the trigger temperature of 82.2 F/27.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1587 ft/min (8.1 m/s)
Maximum height of thermals.................. 22487 ft MSL (16880 ft AGL)
Forecast maximum temperature................... 98.0 F/37.1 C
Time of trigger temperature.................... 0915 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................. 19442 ft MSL (13835 ft AGL)
Thermal soaring outlook for Thursday 07/17..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:01:48 / 20:38:47 MDT
Total possible sunshine........... 14 hr 37 min 0 sec (877 min 0 sec)
Altitude of sun at 13:20:17 MDT... 71.58 degrees
Upper air data from rawinsonde observation taken on 07/16/2025 at 0600 MDT
Freezing level.................. 15875 ft MSL (10268 ft AGL)
Convective condensation level... 16697 ft MSL (11090 ft AGL)
Lifted condensation level....... 19030 ft MSL (13423 ft AGL)
Lifted index.................... -4.4
K index......................... +21.3
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 -64.5 -84.1 265 25 13 1.9 1.0 M M M M M
45000 -60.2 -76.4 255 35 18 4.9 2.7 M M M M M
40000 -52.6 -62.7 250 52 27 6.6 3.6 M M M M M
38000 -48.6 -55.5 245 52 27 6.7 3.7 M M M M M
36000 -44.1 -47.4 240 54 28 7.2 3.9 M M M M M
34000 -39.0 -38.2 245 51 26 8.6 4.7 M M M M M
32000 -33.8 -28.8 245 48 25 8.6 4.7 M M M M M
30000 -29.5 -21.1 245 40 21 6.9 3.8 45.7 114.2 6.8 M M
29000 -27.5 -17.5 250 36 19 6.9 3.8 44.6 112.3 6.1 M M
28000 -25.4 -13.7 250 33 17 6.8 3.7 43.6 110.6 5.4 M M
27000 -23.4 -10.1 255 30 15 6.7 3.7 42.4 108.3 4.4 M M
26000 -21.4 -6.5 255 27 14 6.7 3.7 41.2 106.2 3.6 M M
25000 -19.3 -2.7 260 24 12 6.8 3.7 40.2 104.4 2.8 M M
24000 -17.4 0.7 265 21 11 6.2 3.4 38.9 102.0 1.7 M M
23000 -15.6 3.9 270 18 10 6.3 3.4 37.6 99.6 0.6 M M
22000 -13.8 7.2 275 16 8 6.3 3.5 36.4 97.6 -0.4 1554 7.9
21000 -11.8 10.8 280 14 7 6.7 3.7 35.3 95.5 -1.4 1466 7.4
20000 -9.3 15.3 280 12 6 6.7 3.7 33.9 93.1 -2.6 1354 6.9
19500 -8.3 17.1 285 12 6 6.8 3.7 33.5 92.2 -3.0 1310 6.7
19000 -7.3 18.9 290 11 6 7.1 3.9 33.0 91.3 -3.5 1264 6.4
18500 -6.3 20.7 295 11 5 7.0 3.8 32.5 90.5 -3.9 1218 6.2
18000 -5.2 22.6 305 11 5 8.1 4.4 32.1 89.8 -4.3 1171 5.9
17500 -4.0 24.8 310 11 5 8.3 4.5 31.8 89.3 -4.6 1120 5.7
17000 -2.8 27.0 315 11 6 8.5 4.6 31.6 88.9 -4.9 1069 5.4
16500 -1.5 29.3 315 11 6 8.9 4.9 31.4 88.6 -5.1 1016 5.2
16000 -0.2 31.6 310 11 6 8.9 4.9 31.3 88.3 -5.3 962 4.9
15500 1.1 34.0 310 11 6 9.2 5.1 31.2 88.1 -5.5 908 4.6
15000 2.5 36.5 305 10 5 9.2 5.1 31.1 88.0 -5.6 853 4.3
14500 3.8 38.8 305 10 5 9.0 4.9 31.0 87.8 -5.8 797 4.1
14000 5.1 41.2 300 10 5 8.9 4.9 30.9 87.5 -6.0 743 3.8
13500 6.5 43.7 295 9 5 8.9 4.9 30.7 87.3 -6.1 689 3.5
13000 7.8 46.0 295 9 5 8.9 4.9 30.6 87.0 -6.3 635 3.2
12500 9.1 48.4 290 8 4 8.8 4.8 30.4 86.8 -6.5 581 3.0
12000 10.3 50.5 285 8 4 8.7 4.8 30.3 86.5 -6.7 528 2.7
11500 11.6 52.9 275 7 4 8.6 4.7 30.1 86.2 -7.0 475 2.4
11000 12.7 54.9 265 7 4 7.4 4.1 29.8 85.7 -7.3 427 2.2
10500 13.9 57.0 260 7 3 10.0 5.5 29.6 85.2 -7.7 378 1.9
10250 14.6 58.3 255 6 3 8.5 4.7 29.6 85.3 -7.7 348 1.8
10000 15.1 59.2 245 5 3 6.1 3.4 29.3 84.8 -8.0 327 1.7
9750 15.6 60.1 240 5 2 6.6 3.6 29.1 84.4 -8.2 305 1.5
9500 16.0 60.8 225 4 2 7.2 3.9 28.9 83.9 -8.5 283 1.4
9250 16.6 61.9 220 4 2 7.0 3.8 28.7 83.6 -8.7 259 1.3
9000 17.1 62.8 210 4 2 6.0 3.3 28.4 83.1 -9.0 238 1.2
8750 17.5 63.5 195 5 2 6.3 3.5 28.1 82.6 -9.3 217 1.1
8500 18.0 64.4 185 5 3 5.9 3.3 27.9 82.2 -9.6 196 1.0
8250 18.4 65.1 180 6 3 4.9 2.7 27.5 81.6 -9.9 176 0.9
8000 18.7 65.7 175 6 3 4.2 2.3 27.1 80.8 -10.4 159 0.8
7750 19.0 66.2 170 7 3 4.8 2.6 26.7 80.1 -10.8 142 0.7
7500 19.3 66.7 165 7 4 2.9 1.6 26.3 79.3 -11.2 126 0.6
7250 19.4 66.9 155 7 3 0.6 0.4 25.7 78.2 -12.0 117 0.6
7000 19.4 66.9 145 7 3 1.9 1.0 25.0 77.0 -12.7 108 0.5
6750 19.6 67.3 135 6 3 2.8 1.5 24.5 76.0 -13.3 96 0.5
6500 19.7 67.5 130 6 3 -1.0 -0.6 23.8 74.9 -13.9 85 0.4
6250 19.4 66.9 120 6 3 -5.3 -2.9 22.8 73.1 -15.0 87 0.4
6000 19.1 66.4 115 6 3 1.2 0.6 21.8 71.3 -16.0 88 0.4
5750 19.3 66.7 110 6 3 -2.7 -1.5 21.3 70.3 -16.7 76 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 * * * * * *
07/16/2025 at 0900 MDT | 07/16/2025 at 1200 MDT
|
CAPE... +3.6 LI... 0.0 | CAPE... +223.7 LI... -1.2
CINH... -5.6 K Index... +23.5 | CINH... -35.0 K Index... +24.6
|
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 -63.1 -81.6 265 21 11 0.5 0.3 | -62.8 -81.0 245 22 11 1.5 0.8
45000 -60.1 -76.2 250 34 17 5.5 3.0 | -59.2 -74.6 245 36 19 4.6 2.5
40000 -51.8 -61.2 250 44 23 5.9 3.2 | -51.7 -61.1 250 46 24 6.3 3.4
38000 -47.9 -54.2 250 42 22 5.9 3.2 | -47.9 -54.2 250 45 23 6.3 3.4
36000 -44.3 -47.7 250 40 21 5.9 3.2 | -44.1 -47.4 250 44 23 6.3 3.4
34000 -40.2 -40.4 240 37 19 6.9 3.8 | -40.3 -40.5 240 39 20 6.4 3.5
32000 -36.1 -33.0 230 35 18 6.7 3.7 | -36.4 -33.5 225 35 18 6.2 3.4
30000 -31.6 -24.9 230 30 15 7.6 4.1 | -32.0 -25.6 225 32 16 7.7 4.2
29000 -29.4 -20.9 235 27 14 7.6 4.1 | -29.7 -21.5 225 30 15 7.7 4.2
28000 -27.1 -16.8 235 25 13 7.4 4.1 | -27.4 -17.3 230 28 14 7.2 4.0
27000 -24.9 -12.8 240 24 12 7.3 4.0 | -25.4 -13.7 230 24 13 6.7 3.7
26000 -22.7 -8.9 250 23 12 7.3 4.0 | -23.4 -10.1 235 21 11 6.7 3.7
25000 -20.5 -4.9 255 22 11 7.3 4.0 | -21.4 -6.5 245 18 9 6.6 3.6
24000 -17.8 -0.0 260 22 11 7.5 4.1 | -18.8 -1.8 250 18 9 7.2 3.9
23000 -15.6 3.9 260 22 11 7.5 4.1 | -16.7 1.9 250 18 9 7.2 4.0
22000 -13.4 7.9 260 22 11 7.0 3.9 | -14.6 5.7 255 19 10 7.4 4.1
21000 -11.4 11.5 260 22 11 6.9 3.8 | -12.4 9.7 255 19 10 7.5 4.1
20000 -9.4 15.1 260 21 11 6.9 3.8 | -10.2 13.6 255 19 10 7.6 4.2
19500 -8.4 16.9 260 21 11 7.1 3.9 | -9.1 15.6 255 20 10 7.8 4.3
19000 -7.3 18.9 265 20 10 7.8 4.3 | -7.9 17.8 255 19 10 8.6 4.7
18500 -6.2 20.8 265 20 10 7.7 4.2 | -6.7 19.9 255 19 10 8.5 4.7
18000 -5.0 23.0 270 19 10 8.3 4.6 | -5.4 22.3 260 18 9 8.6 4.7
17500 -3.8 25.2 270 19 10 8.5 4.7 | -4.1 24.6 260 17 9 8.7 4.8
17000 -2.6 27.3 275 18 9 8.6 4.7 | -2.8 27.0 260 17 9 8.8 4.8
16500 -1.3 29.7 275 18 9 8.9 4.9 | -1.5 29.3 260 16 8 9.2 5.0
16000 0.0 32.0 275 18 9 8.9 4.9 | -0.1 31.8 265 16 8 9.2 5.0
15500 1.3 34.3 275 18 9 8.7 4.8 | 1.2 34.2 265 16 8 9.1 5.0
15000 2.6 36.7 275 18 9 8.7 4.8 | 2.6 36.7 265 15 8 9.1 5.0
14500 3.8 38.8 275 18 9 8.4 4.6 | 3.9 39.0 265 15 8 9.1 5.0
14000 5.0 41.0 270 18 9 8.3 4.6 | 5.3 41.5 265 15 8 9.0 5.0
13500 6.2 43.2 270 18 9 8.3 4.5 | 6.6 43.9 265 15 8 9.0 4.9
13000 7.4 45.3 265 18 9 8.2 4.5 | 7.9 46.2 265 15 8 8.9 4.9
12500 8.7 47.7 265 18 9 8.2 4.5 | 9.2 48.6 265 14 7 8.9 4.9
12000 9.9 49.8 260 18 9 8.1 4.5 | 10.5 50.9 265 14 7 8.8 4.9
11500 11.1 52.0 255 17 9 8.1 4.5 | 11.8 53.2 260 14 7 8.8 4.9
11000 12.2 54.0 255 17 9 7.2 4.0 | 13.0 55.4 260 14 7 7.7 4.2
10500 13.3 55.9 255 16 8 8.8 4.8 | 14.1 57.4 260 14 7 11.5 6.3
10250 14.0 57.2 250 16 8 9.0 4.9 | 15.1 59.2 260 13 7 12.3 6.8
10000 14.6 58.3 250 15 8 7.0 3.9 | 15.8 60.4 260 13 7 7.8 4.3
9750 15.1 59.2 245 14 7 7.6 4.1 | 16.4 61.5 260 13 7 9.2 5.0
9500 15.7 60.3 245 14 7 7.4 4.1 | 17.1 62.8 260 12 6 8.4 4.6
9250 16.2 61.2 245 13 7 7.5 4.1 | 17.7 63.9 260 12 6 7.2 3.9
9000 16.8 62.2 245 13 7 7.2 4.0 | 18.2 64.8 260 11 6 8.4 4.6
8750 17.3 63.1 240 12 6 7.0 3.8 | 19.6 67.3 260 10 5 9.4 5.1
8500 17.8 64.0 235 11 6 7.0 3.8 | 20.3 68.5 260 9 5 7.8 4.3
8250 18.8 65.8 225 9 5 6.4 3.5 | 20.8 69.4 265 9 4 8.8 4.8
8000 19.3 66.7 220 9 4 6.9 3.8 | 21.6 70.9 265 8 4 10.8 5.9
7750 19.8 67.6 210 8 4 6.4 3.5 | 22.4 72.3 265 8 4 9.8 5.4
7500 20.2 68.4 200 7 4 5.3 2.9 | 23.1 73.6 265 8 4 8.5 4.7
7250 20.6 69.1 195 7 4 5.6 3.1 | 23.7 74.7 270 8 4 9.0 4.9
7000 21.1 70.0 185 7 4 7.9 4.3 | 24.5 76.1 270 7 4 11.5 6.3
6750 21.7 71.1 180 7 3 8.9 4.9 | 25.3 77.5 265 7 4 11.6 6.4
6500 22.4 72.3 175 7 3 8.7 4.8 | 26.2 79.2 270 7 4 10.8 5.9
6250 23.0 73.4 170 7 3 8.4 4.6 | 27.0 80.6 270 7 4 10.4 5.7
6000 23.6 74.5 165 6 3 9.3 5.1 | 27.7 81.9 275 7 3 10.6 5.8
5750 24.5 76.1 165 6 3 15.9 8.7 | 28.8 83.8 270 6 3 20.9 11.5
5500 26.1 79.0 160 5 3 28.5 15.6 | 31.5 88.7 280 6 3 58.9 32.3
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
07/16/2025 at 1500 MDT | 07/16/2025 at 1800 MDT
|
CAPE... +165.1 LI... -0.4 | CAPE... +136.5 LI... -0.4
CINH... -21.7 K Index... +20.3 | CINH... -21.9 K Index... +21.3
|
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 -63.3 -81.9 240 25 13 1.3 0.7 | -63.6 -82.5 250 26 13 1.5 0.8
45000 -59.8 -75.6 245 38 20 4.8 2.6 | -59.8 -75.6 245 39 20 5.1 2.8
40000 -51.9 -61.4 250 46 24 6.7 3.7 | -51.6 -60.9 245 47 24 6.5 3.6
38000 -47.9 -54.2 250 45 23 6.7 3.7 | -47.7 -53.9 245 47 24 6.5 3.6
36000 -43.8 -46.8 245 45 23 6.7 3.7 | -43.8 -46.8 245 46 24 6.5 3.6
34000 -39.8 -39.6 240 40 21 6.7 3.7 | -39.6 -39.3 240 44 22 6.9 3.8
32000 -35.8 -32.4 230 37 19 6.6 3.6 | -35.5 -31.9 230 42 21 6.9 3.8
30000 -31.5 -24.7 225 33 17 7.2 4.0 | -31.4 -24.5 230 37 19 6.8 3.7
29000 -29.3 -20.7 230 31 16 7.3 4.0 | -29.3 -20.7 230 35 18 6.8 3.7
28000 -27.2 -17.0 230 29 15 7.2 4.0 | -27.3 -17.1 230 32 17 7.0 3.9
27000 -25.0 -13.0 230 26 14 7.2 4.0 | -25.1 -13.2 235 28 15 7.3 4.0
26000 -22.9 -9.2 235 24 12 7.2 4.0 | -23.0 -9.4 240 25 13 7.3 4.0
25000 -20.8 -5.4 245 22 11 7.2 4.0 | -20.8 -5.4 245 21 11 7.4 4.0
24000 -18.0 -0.4 245 20 10 7.4 4.0 | -18.2 -0.8 250 19 10 7.2 4.3
23000 -15.9 3.4 245 19 10 7.4 4.1 | -16.0 3.2 255 17 9 7.2 4.0
22000 -13.7 7.3 250 18 9 7.3 4.0 | -13.8 7.2 260 15 8 7.8 4.3
21000 -11.5 11.3 250 17 9 7.3 4.0 | -11.5 11.3 260 15 8 8.1 4.4
20000 -9.4 15.1 255 17 9 7.3 4.0 | -9.1 15.6 265 15 7 8.1 4.4
19500 -8.3 17.1 255 16 8 7.6 4.2 | -7.9 17.8 265 14 7 8.2 4.5
19000 -7.1 19.2 260 16 8 8.5 4.7 | -6.7 19.9 265 14 7 8.6 4.7
18500 -5.9 21.4 260 16 8 8.5 4.7 | -5.4 22.3 265 14 7 8.6 4.7
18000 -4.6 23.7 260 16 8 8.8 4.8 | -4.2 24.4 265 14 7 8.9 4.9
17500 -3.3 26.1 260 16 8 8.9 4.9 | -2.9 26.8 265 14 7 9.1 5.0
17000 -2.0 28.4 260 16 8 8.9 4.9 | -1.5 29.3 265 14 7 9.1 5.0
16500 -0.7 30.7 265 15 8 9.0 4.9 | -0.2 31.6 265 14 7 9.2 5.1
16000 0.7 33.3 265 15 8 9.0 4.9 | 1.2 34.2 265 14 7 9.2 5.1
15500 2.0 35.6 265 15 8 9.5 5.2 | 2.6 36.7 265 14 7 9.4 5.1
15000 3.4 38.1 265 14 7 9.5 5.2 | 4.0 39.2 265 14 7 9.4 5.1
14500 4.8 40.6 265 14 7 9.5 5.2 | 5.3 41.5 265 14 7 9.3 5.1
14000 6.2 43.2 260 14 7 9.5 5.2 | 6.7 44.1 270 14 7 9.3 5.1
13500 7.7 45.9 260 14 7 9.4 5.2 | 8.1 46.6 270 13 7 9.3 5.1
13000 9.0 48.2 260 14 7 9.4 5.1 | 9.5 49.1 270 13 7 9.3 5.1
12500 10.4 50.7 260 14 7 9.4 5.2 | 10.9 51.6 270 12 6 9.3 5.1
12000 11.8 53.2 260 14 7 9.5 5.2 | 12.3 54.1 270 12 6 9.4 5.2
11500 13.3 55.9 260 14 7 9.5 5.2 | 13.7 56.7 270 12 6 9.6 5.2
11000 14.5 58.1 260 14 7 7.8 4.3 | 14.9 58.8 275 11 6 7.7 4.2
10500 15.6 60.1 260 15 8 12.3 6.7 | 16.0 60.8 280 11 5 11.7 6.4
10250 16.8 62.2 255 14 7 13.3 7.3 | 17.1 62.8 275 10 5 13.0 7.1
10000 17.4 63.3 255 15 7 8.1 4.5 | 17.8 64.0 275 10 5 8.7 4.8
9750 18.1 64.6 255 15 8 9.6 5.3 | 18.5 65.3 280 10 5 9.7 5.3
9500 18.8 65.8 255 15 8 8.9 4.9 | 19.2 66.6 280 10 5 9.8 5.4
9250 19.4 66.9 255 15 8 7.8 4.3 | 19.9 67.8 280 10 5 8.7 4.8
9000 20.0 68.0 255 15 8 9.0 4.9 | 20.5 68.9 280 10 5 9.1 5.0
8750 20.7 69.3 255 15 8 10.4 5.7 | 22.1 71.8 280 9 5 10.4 5.7
8500 21.5 70.7 250 14 7 10.0 5.5 | 22.8 73.0 280 9 5 8.9 4.9
8250 22.7 72.9 250 15 8 8.9 4.9 | 23.4 74.1 280 10 5 9.1 5.0
8000 23.5 74.3 250 14 7 11.1 6.1 | 24.2 75.6 280 9 5 10.8 5.9
7750 24.3 75.7 250 14 7 10.1 5.5 | 25.0 77.0 280 9 5 10.3 5.7
7500 25.0 77.0 245 14 7 8.0 4.4 | 25.7 78.3 280 9 5 8.6 4.7
7250 25.6 78.1 250 14 7 8.3 4.5 | 26.3 79.3 280 9 5 8.5 4.7
7000 26.3 79.3 245 14 7 11.7 6.4 | 27.1 80.8 280 9 5 10.9 6.0
6750 27.2 81.0 245 13 7 11.6 6.4 | 27.9 82.2 280 8 4 11.2 6.2
6500 28.0 82.4 245 13 7 10.0 5.5 | 28.7 83.7 280 8 4 10.4 5.7
6250 28.7 83.7 245 13 7 10.1 5.5 | 29.5 85.1 285 8 4 10.7 5.9
6000 29.5 85.1 245 13 6 8.9 4.9 | 30.2 86.4 285 8 4 7.8 4.3
5750 30.3 86.5 240 11 6 17.4 9.5 | 30.8 87.4 280 7 4 10.2 5.6
5500 33.3 91.9 245 11 6 77.2 42.4 | 33.0 91.4 290 7 4 62.3 34.2
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.
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