Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
124
UXUS97 KGJT 181306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Wednesday, June 18, 2025
This forecast is for Wednesday, June 18, 2025:
If the trigger temperature of 80.5 F/26.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1139 ft/min (5.8 m/s)
Maximum height of thermals.................. 17876 ft MSL (13037 ft AGL)
Forecast maximum temperature................... 94.0 F/34.9 C
Time of trigger temperature.................... 1015 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................. 15071 ft MSL (10232 ft AGL)
Thermal soaring outlook for Thursday 06/19..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 05:47:54 / 20:42:56 MDT
Total possible sunshine........... 14 hr 55 min 2 sec (895 min 2 sec)
Altitude of sun at 13:15:25 MDT... 73.97 degrees
Upper air data from rawinsonde observation taken on 06/18/2025 at 0600 MDT
Freezing level.................. 15252 ft MSL (10413 ft AGL)
Convective condensation level... 21022 ft MSL (16183 ft AGL)
Lifted condensation level....... 19671 ft MSL (14832 ft AGL)
Lifted index.................... +2.4
K index......................... +5.4
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 -65.9 -86.6 295 36 19 3.3 1.8 84.1 183.4 28.8 M M
45000 -60.0 -76.0 300 47 24 5.2 2.9 69.5 157.1 21.8 M M
40000 -52.0 -61.6 300 55 28 7.0 3.8 59.1 138.4 16.4 M M
38000 -48.3 -54.9 300 53 27 6.2 3.4 56.0 132.9 14.8 M M
36000 -44.2 -47.6 305 50 26 7.2 3.9 53.5 128.2 13.3 M M
34000 -38.8 -37.8 300 44 23 6.8 3.8 51.8 125.2 12.5 M M
32000 -35.1 -31.2 310 40 21 1.8 1.0 48.8 119.8 10.6 M M
30000 -31.1 -24.0 310 38 20 7.9 4.3 46.4 115.6 9.1 M M
29000 -28.7 -19.7 305 40 21 6.9 3.8 45.7 114.2 8.6 M M
28000 -26.7 -16.1 305 39 20 9.0 5.0 44.5 112.1 7.8 M M
27000 -24.1 -11.4 300 35 18 8.5 4.7 44.2 111.5 7.6 M M
26000 -21.9 -7.4 310 38 20 8.0 4.4 43.3 109.9 7.0 M M
25000 -19.5 -3.1 310 37 19 7.7 4.2 42.5 108.6 6.5 M M
24000 -16.9 1.6 310 37 19 9.0 4.9 42.1 107.8 6.2 M M
23000 -14.6 5.7 305 37 19 7.5 4.1 41.4 106.5 5.7 M M
22000 -12.4 9.7 305 36 18 6.2 3.4 40.4 104.8 5.0 M M
21000 -10.5 13.1 320 31 16 6.4 3.5 39.2 102.6 4.0 M M
20000 -8.5 16.7 320 31 16 8.0 4.4 38.2 100.8 3.2 M M
19500 -7.6 18.3 320 30 15 3.4 1.9 37.5 99.5 2.6 M M
19000 -7.0 19.4 325 28 14 5.2 2.8 36.5 97.8 1.8 M M
18500 -5.6 21.9 310 25 13 6.9 3.8 35.6 96.1 1.0 M M
18000 -5.0 23.0 295 27 14 -5.0 -2.7 34.5 94.1 0.1 M M
17500 -5.8 21.6 295 25 13 4.2 2.3 32.1 89.8 -2.1 1146 5.8
17000 -4.5 23.9 290 22 12 9.3 5.1 31.9 89.3 -2.4 1094 5.6
16500 -3.2 26.2 300 20 10 9.2 5.0 31.8 89.2 -2.5 1038 5.3
16000 -1.8 28.8 305 20 10 9.1 5.0 31.7 89.0 -2.6 982 5.0
15500 -0.4 31.3 305 16 8 8.6 4.7 31.6 88.8 -2.7 926 4.7
15000 0.6 33.1 275 11 6 2.7 1.5 31.1 87.9 -3.2 882 4.5
14500 0.9 33.6 275 11 6 6.0 3.3 30.0 85.9 -4.4 858 4.4
14000 1.6 34.9 315 4 2 5.4 3.0 29.2 84.6 -5.2 822 4.2
13500 2.4 36.3 350 4 2 8.0 4.4 28.6 83.5 -5.9 783 4.0
13000 3.7 38.7 330 4 2 9.1 5.0 28.5 83.4 -6.0 728 3.7
12500 5.1 41.2 345 5 3 9.2 5.0 28.5 83.2 -6.1 672 3.4
12000 6.5 43.7 335 6 3 9.2 5.0 28.4 83.1 -6.2 616 3.1
11500 7.8 46.0 350 5 3 9.2 5.0 28.3 82.9 -6.3 561 2.8
11000 9.2 48.6 010 5 3 9.2 5.0 28.2 82.7 -6.5 505 2.6
10500 10.6 51.1 070 8 4 9.1 5.0 28.0 82.5 -6.6 449 2.3
10250 11.2 52.2 060 13 6 9.0 4.9 28.0 82.4 -6.7 422 2.1
10000 11.9 53.4 045 18 9 8.9 4.9 27.9 82.3 -6.8 394 2.0
9750 12.6 54.7 045 18 9 9.0 4.9 27.9 82.2 -6.9 367 1.9
9500 13.2 55.8 040 16 8 9.0 4.9 27.8 82.1 -7.0 340 1.7
9250 13.9 57.0 035 14 7 9.6 4.9 27.7 81.9 -7.1 313 1.6
9000 14.5 58.1 025 12 6 9.0 4.9 27.7 81.8 -7.1 286 1.5
8750 15.2 59.4 030 13 7 8.9 4.9 27.6 81.7 -7.2 258 1.3
8500 15.9 60.6 040 14 7 9.2 5.1 27.5 81.6 -7.3 231 1.2
8250 16.5 61.7 050 17 9 8.0 4.4 27.5 81.5 -7.4 204 1.0
8000 16.8 62.2 035 13 7 -1.3 -0.7 27.1 80.7 -7.9 188 1.0
7750 16.7 62.1 025 14 7 2.9 1.6 26.1 79.0 -8.8 185 0.9
7500 17.4 63.3 015 13 7 11.5 6.3 26.1 79.0 -8.8 156 0.8
7250 18.1 64.6 015 13 6 9.2 5.0 26.1 79.0 -8.8 127 0.6
7000 18.8 65.8 020 12 6 9.8 5.4 26.1 79.0 -8.8 98 0.5
6750 19.5 67.1 020 11 5 9.6 5.3 26.1 79.0 -8.9 69 0.3
6500 20.3 68.5 030 9 5 9.7 5.3 26.1 79.0 -8.9 40 0.2
6250 21.0 69.8 040 9 4 9.7 5.3 26.1 79.0 -9.0 11 0.1
6000 21.7 71.1 050 7 4 9.5 5.2 26.1 79.0 -9.0 M M
5750 22.4 72.3 040 5 3 10.1 5.6 26.1 78.9 -9.0 M M
5500 23.1 73.6 020 5 3 7.9 4.3 26.1 78.9 -9.1 M M
5250 23.7 74.7 360 4 2 9.4 5.2 25.9 78.6 -9.3 M M
5000 24.1 75.4 305 5 2 -5.0 -2.7 25.6 78.1 -9.6 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/18/2025 at 0900 MDT | 06/18/2025 at 1200 MDT
|
CAPE... 0.0 LI... +5.1 | CAPE... 0.0 LI... +4.7
CINH... -1.6 K Index... -4.2 | CINH... -0.1 K Index... 0.0
|
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 -64.3 -83.7 280 29 15 1.1 0.6 | -63.9 -83.0 275 23 12 2.0 1.1
45000 -60.6 -77.1 290 42 22 5.7 3.1 | -59.7 -75.5 285 30 15 4.6 2.5
40000 -52.0 -61.6 295 43 22 6.2 3.4 | -52.6 -62.7 295 35 18 6.4 3.5
38000 -48.3 -54.9 300 44 23 6.2 3.4 | -48.7 -55.7 300 37 19 6.5 3.5
36000 -44.1 -47.4 305 46 24 6.1 3.4 | -44.3 -47.7 305 40 21 6.5 3.6
34000 -40.1 -40.2 305 43 22 6.7 3.7 | -40.1 -40.2 305 41 21 7.1 3.9
32000 -36.1 -33.0 305 40 21 6.7 3.7 | -35.9 -32.6 305 43 22 7.1 3.9
30000 -31.8 -25.2 305 38 20 7.4 4.0 | -31.5 -24.7 305 39 20 7.3 4.0
29000 -29.6 -21.3 305 37 19 7.4 4.0 | -29.3 -20.7 300 36 19 7.3 4.0
28000 -27.4 -17.3 300 36 19 7.8 4.3 | -27.1 -16.8 300 34 17 7.6 4.2
27000 -24.9 -12.8 305 35 18 8.3 4.6 | -24.7 -12.5 300 32 16 7.9 4.3
26000 -22.4 -8.3 305 34 18 8.3 4.6 | -22.4 -8.3 300 29 15 7.9 4.3
25000 -19.9 -3.8 305 33 17 8.4 4.6 | -20.0 -4.0 300 27 14 8.0 4.4
24000 -17.6 0.3 310 32 17 7.3 4.0 | -17.8 -0.0 305 26 13 7.2 4.0
23000 -15.5 4.1 310 31 16 7.3 4.0 | -15.6 3.9 310 25 13 7.2 4.0
22000 -12.7 9.1 320 30 15 6.9 3.8 | -13.0 8.6 310 24 12 7.2 3.9
21000 -10.8 12.6 320 29 15 6.6 3.6 | -10.8 12.6 315 24 12 7.2 3.9
20000 -8.8 16.2 320 28 14 6.6 3.6 | -8.7 16.3 315 24 12 7.2 3.9
19500 -7.8 18.0 320 27 14 6.6 3.6 | -7.6 18.3 315 24 12 7.1 3.9
19000 -6.9 19.6 320 26 14 5.5 3.0 | -6.6 20.1 315 24 12 6.3 3.5
18500 -6.1 21.0 320 26 13 5.6 3.1 | -5.7 21.7 315 24 12 6.4 3.5
18000 -5.3 22.5 320 25 13 6.3 3.4 | -4.7 23.5 315 24 12 6.9 3.8
17500 -4.3 24.3 315 24 12 6.7 3.7 | -3.7 25.3 315 24 12 7.0 3.9
17000 -3.3 26.1 315 23 12 6.8 3.7 | -2.6 27.3 315 24 12 7.0 3.8
16500 -2.3 27.9 315 22 11 6.0 3.3 | -1.7 28.9 315 22 12 6.3 3.5
16000 -1.4 29.5 315 21 11 6.1 3.3 | -0.7 30.7 320 21 11 6.4 3.5
15500 -0.5 31.1 315 19 10 5.8 3.2 | 0.2 32.4 320 19 10 6.4 3.5
15000 0.3 32.5 320 17 9 5.8 3.2 | 1.1 34.0 325 17 9 6.4 3.5
14500 1.1 34.0 320 14 7 6.0 3.3 | 2.1 35.8 325 15 8 6.5 3.5
14000 2.0 35.6 325 12 6 6.3 3.4 | 3.0 37.4 330 13 7 6.5 3.6
13500 2.9 37.2 335 10 5 6.5 3.6 | 4.0 39.2 335 11 6 6.8 3.7
13000 3.9 39.0 340 9 5 7.4 4.1 | 5.0 41.0 340 9 5 7.5 4.1
12500 4.9 40.8 350 8 4 7.4 4.1 | 6.1 43.0 350 8 4 7.6 4.2
12000 6.1 43.0 360 8 4 8.0 4.4 | 7.3 45.1 360 7 3 8.3 4.5
11500 7.2 45.0 005 9 5 7.9 4.4 | 8.5 47.3 010 6 3 8.2 4.5
11000 8.4 47.1 010 9 5 8.2 4.5 | 9.7 49.5 015 5 3 8.3 4.5
10500 9.6 49.3 015 10 5 6.5 3.5 | 10.9 51.6 020 5 2 5.5 3.0
10250 10.0 50.0 015 10 5 6.2 3.4 | 11.2 52.2 025 4 2 6.6 3.6
10000 10.6 51.1 020 10 5 9.5 5.2 | 12.0 53.6 025 4 2 11.1 6.1
9750 11.4 52.5 020 10 5 9.8 5.4 | 12.7 54.9 025 4 2 10.0 5.5
9500 12.1 53.8 025 10 5 9.7 5.3 | 13.5 56.3 020 4 2 10.0 5.5
9250 12.8 55.0 030 10 5 8.4 4.6 | 14.1 57.4 020 3 2 8.7 4.8
9000 13.3 55.9 030 9 5 7.8 4.3 | 14.8 58.6 025 3 2 9.3 5.1
8750 13.9 57.0 035 9 5 8.4 4.6 | 15.5 59.9 025 3 2 10.4 5.7
8500 14.5 58.1 035 9 4 7.9 4.3 | 16.2 61.2 020 3 2 9.7 5.3
8250 15.4 59.7 040 9 5 6.1 3.3 | 16.9 62.4 025 3 1 7.1 3.9
8000 15.9 60.6 045 8 4 7.7 4.2 | 17.4 63.3 025 3 1 8.9 4.9
7750 16.4 61.5 045 7 4 6.1 3.3 | 19.2 66.6 020 2 1 10.7 5.8
7500 16.7 62.1 050 7 4 3.1 1.7 | 19.8 67.6 025 2 1 7.5 4.1
7250 16.9 62.4 055 7 3 3.6 2.0 | 20.4 68.7 025 2 1 8.3 4.6
7000 17.3 63.1 060 6 3 9.1 5.0 | 21.1 70.0 025 2 1 12.6 6.9
6750 18.1 64.6 060 5 3 9.5 5.2 | 22.1 71.8 020 2 1 12.0 6.6
6500 18.7 65.7 065 5 2 6.9 3.8 | 22.9 73.2 025 2 1 9.8 5.4
6250 19.2 66.6 065 4 2 6.8 3.8 | 23.6 74.5 025 1 1 9.3 5.1
6000 19.8 67.6 070 4 2 10.7 5.9 | 24.4 75.9 025 1 1 13.7 7.5
5750 21.0 69.8 070 3 2 21.7 11.9 | 25.9 78.6 015 1 1 28.2 15.5
5500 22.5 72.5 075 3 2 10.9 6.0 | 28.1 82.6 015 1 0 23.9 13.1
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
06/18/2025 at 1500 MDT | 06/18/2025 at 1800 MDT
|
CAPE... 0.0 LI... +4.3 | CAPE... 0.0 LI... +3.2
CINH... 0.0 K Index... +4.7 | CINH... -0.8 K Index... +5.6
|
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 -64.3 -83.7 275 24 12 2.2 1.2 | -64.5 -84.1 290 25 13 1.8 1.0
45000 -60.0 -76.0 285 26 13 4.3 2.3 | -60.6 -77.1 295 29 15 4.5 2.5
40000 -53.3 -63.9 295 29 15 6.8 3.7 | -53.6 -64.5 300 29 15 6.8 3.7
38000 -49.2 -56.6 300 31 16 6.9 3.8 | -49.4 -56.9 300 29 15 6.9 3.8
36000 -44.5 -48.1 305 34 18 7.0 3.8 | -44.8 -48.6 305 30 15 7.1 3.9
34000 -40.1 -40.2 305 38 19 7.4 4.1 | -40.1 -40.2 300 32 17 7.8 4.3
32000 -35.7 -32.3 300 41 21 7.3 4.0 | -35.4 -31.7 300 35 18 7.7 4.2
30000 -31.1 -24.0 300 37 19 7.8 4.3 | -30.7 -23.3 300 32 16 8.0 4.4
29000 -28.7 -19.7 300 35 18 7.8 4.3 | -28.3 -18.9 295 30 15 8.0 4.4
28000 -26.4 -15.5 300 32 17 7.3 4.0 | -25.9 -14.6 295 28 14 7.1 3.9
27000 -24.3 -11.7 300 29 15 7.0 3.9 | -23.9 -11.0 295 24 13 6.7 3.7
26000 -22.2 -8.0 300 26 13 7.0 3.9 | -21.9 -7.4 295 21 11 6.7 3.6
25000 -20.1 -4.2 300 22 12 7.0 3.9 | -19.9 -3.8 295 18 9 6.7 3.7
24000 -17.9 -0.2 300 21 11 7.3 4.0 | -17.8 -0.0 295 17 9 7.1 3.9
23000 -15.7 3.7 300 20 10 7.3 4.0 | -15.2 4.6 290 16 8 7.1 3.9
22000 -13.0 8.6 300 19 10 7.7 4.2 | -13.0 8.6 285 15 8 7.8 4.3
21000 -10.7 12.7 300 19 10 7.8 4.3 | -10.7 12.7 290 14 7 8.0 4.4
20000 -8.3 17.1 305 19 10 7.8 4.3 | -8.3 17.1 290 14 7 8.0 4.4
19500 -7.2 19.0 305 19 10 7.7 4.2 | -7.1 19.2 290 14 7 7.9 4.3
19000 -6.1 21.0 305 19 10 7.4 4.1 | -5.9 21.4 295 13 7 7.6 4.2
18500 -5.0 23.0 310 19 10 7.4 4.1 | -4.8 23.4 295 12 6 7.7 4.2
18000 -3.9 25.0 310 19 10 6.8 3.7 | -3.7 25.3 300 12 6 7.5 4.1
17500 -2.9 26.8 310 18 9 6.7 3.7 | -2.6 27.3 305 11 6 7.5 4.1
17000 -1.9 28.6 315 17 9 6.7 3.7 | -1.5 29.3 310 11 5 7.6 4.2
16500 -1.0 30.2 315 15 8 6.7 3.7 | -0.4 31.3 310 10 5 8.0 4.4
16000 -0.0 32.0 315 14 7 6.7 3.7 | 0.8 33.4 315 10 5 8.0 4.4
15500 1.0 33.8 320 12 6 7.5 4.1 | 2.0 35.6 320 9 5 8.2 4.5
15000 2.1 35.8 320 10 5 7.5 4.1 | 3.2 37.8 320 9 4 8.2 4.5
14500 3.2 37.8 320 9 4 7.9 4.3 | 4.4 39.9 320 8 4 8.4 4.6
14000 4.4 39.9 320 7 4 8.1 4.5 | 5.7 42.3 320 7 4 8.5 4.7
13500 5.6 42.1 320 6 3 8.3 4.5 | 6.9 44.4 320 6 3 8.7 4.8
13000 6.9 44.4 320 5 3 8.5 4.7 | 8.2 46.8 320 6 3 8.9 4.9
12500 8.1 46.6 320 4 2 8.6 4.7 | 9.5 49.1 320 6 3 9.0 4.9
12000 9.4 48.9 320 4 2 9.0 5.0 | 10.9 51.6 320 5 3 9.4 5.2
11500 10.8 51.4 315 4 2 9.0 4.9 | 12.3 54.1 315 5 3 9.3 5.1
11000 12.0 53.6 315 3 2 8.2 4.5 | 13.5 56.3 315 5 3 7.7 4.2
10500 13.2 55.8 315 3 2 11.0 6.0 | 14.6 58.3 320 5 2 12.3 6.7
10250 14.2 57.6 310 3 2 11.7 6.4 | 15.8 60.4 310 5 2 13.3 7.3
10000 14.9 58.8 310 3 2 8.5 4.7 | 16.5 61.7 310 5 2 8.0 4.4
9750 15.6 60.1 310 3 2 9.4 5.2 | 17.1 62.8 310 5 2 9.6 5.3
9500 16.2 61.2 310 3 2 8.9 4.9 | 17.8 64.0 310 5 2 8.5 4.6
9250 16.9 62.4 305 3 2 8.4 4.6 | 18.4 65.1 310 4 2 7.2 4.0
9000 17.5 63.5 300 3 2 9.3 5.1 | 19.0 66.2 310 4 2 9.1 5.0
8750 18.2 64.8 300 3 2 10.1 5.5 | 19.8 67.6 305 5 2 10.7 5.9
8500 19.0 66.2 300 3 2 9.7 5.3 | 20.5 68.9 305 5 2 10.0 5.5
8250 20.2 68.4 295 3 2 9.2 5.0 | 21.7 71.1 300 5 2 8.4 4.6
8000 21.0 69.8 295 3 2 12.2 6.7 | 22.5 72.5 300 5 2 10.7 5.9
7750 21.9 71.4 295 3 2 10.3 5.6 | 23.3 73.9 300 5 2 9.6 5.2
7500 22.5 72.5 295 3 2 7.7 4.2 | 23.9 75.0 295 5 2 7.9 4.3
7250 23.1 73.6 290 3 2 8.3 4.5 | 24.5 76.1 295 5 2 8.4 4.6
7000 23.8 74.8 290 3 2 12.3 6.8 | 25.2 77.4 295 5 2 11.7 6.4
6750 24.8 76.6 290 3 2 12.0 6.6 | 26.1 79.0 295 5 2 11.5 6.3
6500 25.6 78.1 285 3 2 10.2 5.6 | 26.9 80.4 295 5 2 9.9 5.4
6250 26.4 79.5 285 3 2 9.9 5.4 | 27.6 81.7 290 5 2 9.8 5.4
6000 27.1 80.8 280 3 2 12.2 6.7 | 28.3 82.9 290 5 2 9.5 5.2
5750 28.4 83.1 285 3 2 24.7 13.5 | 29.2 84.6 290 4 2 15.1 8.3
5500 30.9 87.6 280 3 2 42.3 23.2 | 31.0 87.8 290 4 2 39.5 21.7
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
________________________________________________________________________________
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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