Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
679
UXUS97 KGJT 201306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Sunday, July 20, 2025
This forecast is for Sunday, July 20, 2025:
If the trigger temperature of 82.2 F/27.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1586 ft/min (8.1 m/s)
Maximum height of thermals.................. 20590 ft MSL (14982 ft AGL)
Forecast maximum temperature................... 96.0 F/36.0 C
Time of trigger temperature.................... 0930 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................. 18390 ft MSL (12782 ft AGL)
Thermal soaring outlook for Monday 07/21....... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:04:56 / 20:36:11 MDT
Total possible sunshine........... 14 hr 31 min 15 sec (871 min 15 sec)
Altitude of sun at 13:20:34 MDT... 70.86 degrees
Upper air data from rawinsonde observation taken on 07/20/2025 at 0600 MDT
Freezing level.................. 15492 ft MSL (9884 ft AGL)
Convective condensation level... 16647 ft MSL (11039 ft AGL)
Lifted condensation level....... 18982 ft MSL (13374 ft AGL)
Lifted index.................... -2.0
K index......................... +26.1
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 -65.2 -85.4 225 17 9 0.7 0.4 M M M M M
45000 -61.6 -78.9 220 25 13 6.1 3.3 M M M M M
40000 -52.1 -61.8 235 37 19 7.4 4.1 M M M M M
38000 -47.1 -52.8 235 42 22 7.5 4.1 M M M M M
36000 -42.6 -44.7 230 46 24 7.5 4.1 M M M M M
34000 -38.1 -36.6 230 45 23 7.5 4.1 M M M M M
32000 -33.5 -28.3 225 44 23 8.1 4.4 M M M M M
30000 -29.1 -20.4 225 39 20 7.5 4.1 46.2 115.1 8.0 M M
29000 -26.8 -16.2 220 36 18 7.6 4.1 45.4 113.7 7.5 M M
28000 -24.6 -12.3 220 33 17 7.3 4.0 44.6 112.4 6.9 M M
27000 -22.5 -8.5 220 30 16 7.3 4.0 43.6 110.4 6.1 M M
26000 -20.3 -4.5 220 28 14 7.3 4.0 42.6 108.7 5.4 M M
25000 -18.2 -0.8 225 25 13 7.3 4.0 41.8 107.3 4.8 M M
24000 -16.2 2.8 225 26 13 6.8 3.7 40.7 105.2 3.8 M M
23000 -14.2 6.4 220 27 14 6.8 3.7 39.6 103.2 2.9 M M
22000 -12.2 10.0 220 27 14 6.7 3.7 38.6 101.5 2.0 M M
21000 -10.2 13.6 215 23 12 5.5 3.0 36.7 98.1 0.4 M M
20000 -8.6 16.5 210 20 10 5.5 3.0 35.3 95.5 -0.9 1332 6.8
19500 -7.8 18.0 210 18 9 5.5 3.0 34.6 94.2 -1.5 1293 6.6
19000 -7.0 19.4 205 16 8 5.1 2.8 33.8 92.8 -2.2 1256 6.4
18500 -6.2 20.8 205 13 7 5.1 2.8 33.0 91.4 -2.9 1218 6.2
18000 -5.5 22.1 200 11 6 5.6 3.1 32.2 90.0 -3.7 1181 6.0
17500 -4.6 23.7 200 9 5 5.7 3.1 31.5 88.8 -4.3 1141 5.8
17000 -3.8 25.2 200 8 4 6.5 3.6 30.8 87.5 -5.0 1101 5.6
16500 -2.6 27.3 200 6 3 8.9 4.9 30.6 87.1 -5.2 1050 5.3
16000 -1.3 29.7 205 5 3 8.8 4.8 30.4 86.8 -5.4 996 5.1
15500 0.1 32.2 210 5 2 9.4 5.2 30.3 86.6 -5.5 940 4.8
15000 1.5 34.7 215 5 2 9.3 5.1 30.3 86.5 -5.6 884 4.5
14500 2.9 37.2 225 5 2 9.4 5.2 30.2 86.4 -5.7 827 4.2
14000 4.3 39.7 225 5 3 9.5 5.2 30.2 86.3 -5.8 770 3.9
13500 5.7 42.3 230 6 3 9.6 5.2 30.1 86.2 -5.9 713 3.6
13000 7.1 44.8 235 6 3 9.6 5.3 30.1 86.2 -5.9 655 3.3
12500 8.6 47.5 235 7 4 9.5 5.2 30.1 86.2 -6.0 597 3.0
12000 9.9 49.8 235 8 4 8.9 4.9 30.0 86.0 -6.1 542 2.8
11500 11.2 52.2 235 9 4 8.7 4.8 29.9 85.7 -6.3 487 2.5
11000 12.4 54.3 240 9 5 7.4 4.1 29.6 85.2 -6.6 437 2.2
10500 13.6 56.5 245 10 5 9.9 5.4 29.3 84.7 -6.9 386 2.0
10250 14.4 57.9 245 11 5 9.1 5.0 29.3 84.8 -6.9 356 1.8
10000 14.9 58.8 245 11 6 7.2 4.0 29.2 84.5 -7.1 331 1.7
9750 15.5 59.9 245 11 6 7.6 4.2 29.0 84.2 -7.2 307 1.6
9500 16.1 61.0 245 11 6 8.0 4.4 28.8 83.9 -7.4 283 1.4
9250 16.7 62.1 245 11 6 7.8 4.3 28.7 83.7 -7.6 257 1.3
9000 17.2 63.0 245 11 6 7.0 3.8 28.5 83.3 -7.8 234 1.2
8750 17.7 63.9 240 10 5 7.4 4.1 28.3 83.0 -8.0 211 1.1
8500 18.3 64.9 240 10 5 6.6 3.6 28.1 82.6 -8.2 187 1.0
8250 18.7 65.7 235 9 5 5.6 3.1 27.8 82.1 -8.5 167 0.8
8000 19.1 66.4 230 8 4 5.8 3.2 27.5 81.5 -8.9 147 0.7
7750 19.6 67.3 225 8 4 6.0 3.3 27.2 81.0 -9.2 127 0.6
7500 20.0 68.0 220 7 4 5.3 2.9 26.9 80.4 -9.5 106 0.5
7250 20.3 68.5 205 7 3 4.3 2.4 26.5 79.7 -9.9 89 0.5
7000 20.6 69.1 200 6 3 4.1 2.3 26.1 79.0 -10.4 72 0.4
6750 20.9 69.6 195 6 3 3.9 2.1 25.7 78.2 -10.9 57 0.3
6500 21.1 70.0 190 6 3 1.9 1.0 25.2 77.3 -11.4 42 0.2
6250 21.2 70.2 175 6 3 -0.6 -0.3 24.5 76.0 -12.1 34 0.2
6000 21.2 70.2 160 6 3 4.1 2.3 23.8 74.8 -12.8 25 0.1
5750 21.6 70.9 150 6 3 0.6 0.4 23.4 74.1 -13.2 7 0.0
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 * * * * * *
07/20/2025 at 0900 MDT | 07/20/2025 at 1200 MDT
|
CAPE... +7.6 LI... -0.6 | CAPE... +79.8 LI... -0.6
CINH... -40.6 K Index... +21.6 | CINH... -21.4 K Index... +21.4
|
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 -64.9 -84.8 230 19 10 1.6 0.9 | -64.6 -84.3 225 22 12 1.8 1.0
45000 -60.5 -76.9 225 34 17 5.9 3.2 | -60.1 -76.2 220 33 17 5.8 3.2
40000 -50.8 -59.4 230 48 25 7.3 4.0 | -50.8 -59.4 225 43 22 6.5 3.6
38000 -46.4 -51.5 225 51 26 7.3 4.0 | -46.9 -52.4 225 48 25 6.5 3.6
36000 -42.1 -43.8 225 53 27 7.4 4.0 | -43.0 -45.4 225 52 27 6.9 3.8
34000 -37.5 -35.5 230 51 26 7.7 4.2 | -38.1 -36.6 225 51 26 8.2 4.5
32000 -32.9 -27.2 230 49 25 7.7 4.2 | -33.1 -27.6 230 49 25 8.2 4.5
30000 -28.6 -19.5 230 44 23 7.0 3.8 | -28.7 -19.7 230 44 22 7.2 4.0
29000 -26.5 -15.7 235 41 21 7.0 3.8 | -26.5 -15.7 230 41 21 7.2 4.0
28000 -24.4 -11.9 235 39 20 5.8 3.2 | -24.4 -11.9 230 38 20 6.0 3.3
27000 -23.0 -9.4 235 34 17 4.7 2.6 | -22.8 -9.0 230 34 17 5.2 2.8
26000 -21.3 -6.3 240 28 14 4.8 2.6 | -20.9 -5.6 230 28 15 5.2 2.9
25000 -19.9 -3.8 240 23 12 5.4 2.9 | -19.3 -2.7 230 24 12 5.2 2.9
24000 -18.1 -0.6 240 22 11 6.0 3.3 | -17.8 -0.0 235 22 11 5.3 2.9
23000 -16.4 2.5 240 21 11 6.0 3.3 | -16.2 2.8 235 19 10 5.4 3.0
22000 -14.6 5.7 245 20 10 6.6 3.6 | -14.6 5.7 240 17 9 6.8 3.7
21000 -12.6 9.3 245 19 10 6.8 3.7 | -12.5 9.5 245 18 9 7.4 4.1
20000 -10.6 12.9 245 17 9 6.9 3.8 | -10.3 13.5 245 18 9 7.4 4.1
19500 -9.6 14.7 245 17 9 7.0 3.8 | -9.2 15.4 245 18 9 7.4 4.1
19000 -8.6 16.5 250 16 8 7.4 4.0 | -8.1 17.4 250 18 9 7.3 4.0
18500 -7.5 18.5 250 15 8 7.4 4.0 | -7.1 19.2 250 17 9 7.4 4.0
18000 -6.4 20.5 255 14 7 7.6 4.2 | -6.0 21.2 250 16 8 7.8 4.3
17500 -5.3 22.5 255 13 7 7.7 4.2 | -4.8 23.4 250 15 8 7.9 4.3
17000 -4.1 24.6 260 12 6 7.9 4.3 | -3.7 25.3 250 14 7 8.0 4.4
16500 -2.9 26.8 265 12 6 8.7 4.8 | -2.5 27.5 250 13 7 8.4 4.6
16000 -1.6 29.1 270 11 6 8.6 4.7 | -1.2 29.8 250 12 6 8.4 4.6
15500 -0.2 31.6 270 11 5 9.3 5.1 | 0.0 32.0 255 11 5 8.7 4.8
15000 1.1 34.0 275 10 5 9.3 5.1 | 1.3 34.3 255 10 5 8.7 4.8
14500 2.5 36.5 280 10 5 9.3 5.1 | 2.6 36.7 260 9 5 9.1 5.0
14000 3.9 39.0 280 10 5 9.3 5.1 | 4.0 39.2 260 8 4 9.3 5.1
13500 5.3 41.5 280 10 5 9.3 5.1 | 5.4 41.7 265 8 4 9.3 5.1
13000 6.7 44.1 280 10 5 9.4 5.1 | 6.8 44.2 270 8 4 9.3 5.1
12500 8.1 46.6 280 10 5 9.3 5.1 | 8.2 46.8 270 7 4 9.4 5.2
12000 9.4 48.9 280 10 5 9.1 5.0 | 9.6 49.3 275 7 4 9.6 5.3
11500 10.7 51.3 280 9 5 9.0 4.9 | 11.0 51.8 275 7 4 9.6 5.3
11000 12.0 53.6 275 9 5 8.5 4.6 | 12.5 54.5 280 7 4 9.3 5.1
10500 13.3 55.9 270 9 5 6.1 3.3 | 13.9 57.0 280 7 3 6.6 3.6
10250 13.6 56.5 270 9 5 6.4 3.5 | 14.3 57.7 285 7 3 7.2 3.9
10000 14.3 57.7 265 9 4 9.8 5.4 | 15.0 59.0 285 7 3 11.2 6.1
9750 14.9 58.8 265 8 4 9.1 5.0 | 15.8 60.4 285 6 3 10.3 5.7
9500 15.6 60.1 265 8 4 8.6 4.7 | 16.6 61.9 285 6 3 9.8 5.4
9250 16.1 61.0 260 8 4 6.8 3.7 | 17.2 63.0 285 6 3 8.4 4.6
9000 17.1 62.8 250 7 3 7.4 4.1 | 17.9 64.2 290 6 3 9.1 5.0
8750 17.6 63.7 245 6 3 6.5 3.6 | 19.3 66.7 285 6 3 9.0 4.9
8500 18.1 64.6 235 6 3 4.9 2.7 | 19.8 67.6 285 6 3 6.7 3.7
8250 18.4 65.1 230 6 3 5.6 3.1 | 20.3 68.5 290 5 3 8.7 4.8
8000 18.9 66.0 220 5 3 7.3 4.0 | 21.1 70.0 285 5 3 11.9 6.5
7750 19.4 66.9 210 5 2 6.2 3.4 | 21.9 71.4 285 5 3 9.7 5.3
7500 19.8 67.6 200 5 2 4.6 2.5 | 22.5 72.5 285 5 3 7.4 4.1
7250 20.2 68.4 195 5 3 5.6 3.1 | 23.1 73.6 290 5 3 8.9 4.9
7000 20.7 69.3 185 5 3 9.1 5.0 | 23.9 75.0 290 5 2 13.2 7.2
6750 21.4 70.5 180 5 2 9.0 4.9 | 24.9 76.8 280 5 2 11.9 6.5
6500 22.0 71.6 175 4 2 7.3 4.0 | 25.7 78.3 285 5 2 9.7 5.3
6250 22.6 72.7 170 4 2 7.1 3.9 | 26.4 79.5 290 5 2 9.0 5.0
6000 23.2 73.8 165 4 2 11.1 6.1 | 27.2 81.0 290 5 2 13.7 7.5
5750 24.3 75.7 160 3 2 21.1 11.6 | 28.7 83.7 285 4 2 28.9 15.8
5500 25.7 78.3 160 3 2 7.0 3.9 | 30.9 87.6 295 4 2 20.7 11.3
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
07/20/2025 at 1500 MDT | 07/20/2025 at 1800 MDT
|
CAPE... +23.4 LI... -0.1 | CAPE... +14.6 LI... +0.5
CINH... -5.9 K Index... +20.6 | CINH... -12.8 K Index... +19.8
|
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 -64.5 -84.1 230 25 13 1.6 0.9 | -64.6 -84.3 240 25 13 1.2 0.6
45000 -60.3 -76.5 225 37 19 5.7 3.1 | -60.7 -77.3 235 38 19 5.8 3.2
40000 -51.0 -59.8 220 44 23 6.6 3.6 | -51.4 -60.5 225 45 23 6.8 3.7
38000 -47.1 -52.8 225 47 24 6.6 3.6 | -47.3 -53.1 230 47 24 6.8 3.7
36000 -43.1 -45.6 230 50 26 6.9 3.8 | -43.3 -45.9 230 50 26 7.1 3.9
34000 -38.4 -37.1 225 48 25 7.9 4.3 | -38.5 -37.3 230 48 25 7.9 4.4
32000 -33.7 -28.7 225 47 24 7.8 4.3 | -33.8 -28.8 230 46 24 7.8 4.3
30000 -29.2 -20.6 230 44 23 7.4 4.0 | -29.2 -20.6 230 43 22 7.6 4.1
29000 -27.0 -16.6 230 43 22 7.4 4.0 | -26.9 -16.4 230 42 22 7.6 4.2
28000 -24.8 -12.6 235 41 21 6.5 3.6 | -24.7 -12.5 235 41 21 6.4 3.5
27000 -23.0 -9.4 235 36 19 6.0 3.3 | -23.0 -9.4 235 36 18 5.8 3.2
26000 -20.8 -5.4 235 30 15 6.0 3.3 | -20.8 -5.4 235 30 15 5.8 3.2
25000 -19.0 -2.2 235 25 13 5.8 3.2 | -19.0 -2.2 235 25 13 6.1 3.4
24000 -17.3 0.9 235 21 11 5.7 3.1 | -17.1 1.2 235 22 11 6.4 3.5
23000 -15.7 3.7 235 17 9 5.7 3.1 | -15.3 4.5 230 19 10 6.5 3.5
22000 -14.0 6.8 235 14 7 6.8 3.7 | -13.4 7.9 230 16 8 7.0 3.9
21000 -11.9 10.6 235 14 7 7.3 4.0 | -11.3 11.7 230 14 7 7.2 4.0
20000 -9.8 14.4 240 14 7 7.3 4.0 | -9.2 15.4 235 13 7 7.3 4.0
19500 -8.7 16.3 240 13 7 7.6 4.1 | -8.1 17.4 235 12 6 7.5 4.1
19000 -7.5 18.5 240 13 7 8.2 4.5 | -7.0 19.4 235 12 6 8.1 4.5
18500 -6.3 20.7 245 13 7 8.1 4.5 | -5.8 21.6 235 11 6 8.1 4.5
18000 -5.1 22.8 245 13 6 8.7 4.8 | -4.6 23.7 240 11 6 8.6 4.7
17500 -3.8 25.2 245 12 6 8.8 4.8 | -3.3 26.1 240 11 6 8.6 4.7
17000 -2.5 27.5 245 12 6 8.8 4.8 | -2.0 28.4 240 11 5 8.8 4.8
16500 -1.2 29.8 250 12 6 8.9 4.9 | -0.7 30.7 245 10 5 9.3 5.1
16000 0.1 32.2 250 11 6 8.9 4.9 | 0.7 33.3 245 10 5 9.2 5.1
15500 1.4 34.5 250 11 6 9.1 5.0 | 2.1 35.8 245 10 5 9.5 5.2
15000 2.8 37.0 250 11 5 9.1 5.0 | 3.5 38.3 245 10 5 9.5 5.2
14500 4.1 39.4 250 10 5 9.2 5.1 | 5.0 41.0 250 10 5 9.5 5.2
14000 5.5 41.9 255 10 5 9.3 5.1 | 6.4 43.5 250 10 5 9.5 5.2
13500 6.9 44.4 255 10 5 9.2 5.0 | 7.8 46.0 250 10 5 9.4 5.2
13000 8.3 46.9 255 10 5 9.1 5.0 | 9.2 48.6 250 9 5 9.3 5.1
12500 9.6 49.3 260 9 5 9.2 5.0 | 10.6 51.1 255 9 5 9.4 5.1
12000 11.0 51.8 260 9 5 9.4 5.1 | 12.0 53.6 255 9 5 9.4 5.2
11500 12.4 54.3 260 8 4 9.2 5.1 | 13.4 56.1 255 9 5 9.3 5.1
11000 13.7 56.7 265 8 4 8.4 4.6 | 14.7 58.5 260 9 4 7.7 4.2
10500 15.0 59.0 270 8 4 10.2 5.6 | 15.8 60.4 260 9 4 12.0 6.6
10250 15.8 60.4 265 8 4 10.8 5.9 | 16.9 62.4 255 9 4 13.0 7.1
10000 16.5 61.7 265 8 4 9.0 4.9 | 17.6 63.7 255 8 4 8.0 4.4
9750 17.2 63.0 265 8 4 9.4 5.2 | 18.3 64.9 255 8 4 9.5 5.2
9500 17.9 64.2 265 7 4 9.5 5.2 | 18.9 66.0 255 8 4 8.6 4.7
9250 18.6 65.5 270 8 4 10.0 5.5 | 19.6 67.3 260 8 4 8.0 4.4
9000 19.4 66.9 270 8 4 9.8 5.3 | 20.2 68.4 260 8 4 9.2 5.0
8750 20.8 69.4 265 8 4 9.5 5.2 | 21.7 71.1 255 7 4 9.8 5.4
8500 21.5 70.7 265 8 4 8.6 4.7 | 22.4 72.3 255 7 4 8.7 4.8
8250 22.1 71.8 270 8 4 9.6 5.3 | 23.0 73.4 260 7 4 9.0 4.9
8000 22.9 73.2 265 8 4 11.0 6.1 | 23.7 74.7 255 7 4 10.0 5.5
7750 23.7 74.7 260 8 4 10.0 5.5 | 24.4 75.9 250 7 4 9.5 5.2
7500 24.4 75.9 260 8 4 8.6 4.7 | 25.1 77.2 250 7 4 8.6 4.7
7250 25.0 77.0 265 8 4 9.1 5.0 | 25.7 78.3 255 7 4 8.9 4.9
7000 25.8 78.4 265 8 4 11.2 6.2 | 26.5 79.7 250 7 4 10.5 5.8
6750 26.7 80.1 255 8 4 11.2 6.2 | 27.3 81.1 245 7 4 10.8 5.9
6500 27.5 81.5 260 8 4 10.8 5.9 | 28.1 82.6 245 7 4 10.4 5.7
6250 28.3 82.9 260 8 4 10.0 5.5 | 28.8 83.8 250 7 4 10.3 5.6
6000 29.1 84.4 265 8 4 12.4 6.8 | 29.6 85.3 250 7 4 9.2 5.1
5750 30.4 86.7 255 7 4 25.2 13.8 | 30.3 86.5 245 6 3 13.4 7.4
5500 32.9 91.2 265 7 4 41.4 22.7 | 32.2 90.0 255 6 3 42.9 23.5
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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