Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
Versions:
1
2
463
UXUS97 KGJT 131306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Friday, June 13, 2025
This forecast is for Friday, June 13, 2025:
If the trigger temperature of 81.9 F/27.7 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1702 ft/min (8.6 m/s)
Maximum height of thermals.................. 23249 ft MSL (17642 ft AGL)
Forecast maximum temperature................... 96.0 F/36.0 C
Time of trigger temperature.................... 0945 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................. 17815 ft MSL (12208 ft AGL)
Thermal soaring outlook for Saturday 06/14..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 05:47:31 / 20:41:10 MDT
Total possible sunshine........... 14 hr 53 min 38 sec (893 min 38 sec)
Altitude of sun at 13:14:21 MDT... 73.85 degrees
Upper air data from rawinsonde observation taken on 06/13/2025 at 0600 MDT
Freezing level.................. 15890 ft MSL (10283 ft AGL)
Convective condensation level... 21962 ft MSL (16355 ft AGL)
Lifted condensation level....... 22441 ft MSL (16834 ft AGL)
Lifted index.................... -1.2
K index......................... +9.5
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 -60.5 -76.9 240 25 13 2.4 1.3 M M M M M
45000 -57.4 -71.3 245 29 15 0.7 0.4 M M M M M
40000 -55.9 -68.6 260 30 16 6.3 3.5 M M M M M
38000 -52.4 -62.3 260 32 16 5.8 3.2 M M M M M
36000 -49.0 -56.2 260 33 17 5.8 3.2 M M M M M
34000 -44.9 -48.8 260 33 17 7.2 3.9 M M M M M
32000 -40.6 -41.1 255 33 17 7.2 4.0 M M M M M
30000 -35.1 -31.2 255 33 17 8.6 4.7 38.6 101.4 2.2 M M
29000 -32.5 -26.5 255 33 17 8.6 4.7 38.2 100.7 1.9 M M
28000 -30.0 -22.0 255 33 17 8.6 4.7 37.9 100.2 1.7 M M
27000 -27.4 -17.3 255 33 17 8.6 4.7 37.3 99.2 1.3 M M
26000 -24.8 -12.6 255 33 17 8.6 4.7 36.9 98.4 1.0 M M
25000 -22.2 -8.0 255 34 17 8.6 4.7 36.6 97.8 0.7 M M
24000 -19.7 -3.5 255 33 17 8.5 4.7 36.0 96.9 0.3 M M
23000 -17.1 1.2 255 32 17 8.5 4.7 35.6 96.0 -0.1 1679 8.5
22000 -14.6 5.7 255 31 16 8.4 4.6 35.2 95.4 -0.4 1573 8.0
21000 -12.2 10.0 250 30 15 7.9 4.3 34.5 94.1 -1.0 1472 7.5
20000 -9.9 14.2 245 28 15 7.9 4.3 33.9 93.0 -1.6 1372 7.0
19500 -8.7 16.3 245 27 14 7.9 4.4 33.6 92.5 -1.8 1322 6.7
19000 -7.5 18.5 240 27 14 7.6 4.2 33.3 91.9 -2.1 1272 6.5
18500 -6.4 20.5 240 26 13 7.6 4.2 32.9 91.2 -2.5 1224 6.2
18000 -4.7 23.5 235 24 13 8.1 4.4 32.4 90.3 -3.0 1151 5.8
17500 -3.5 25.7 235 23 12 8.1 4.5 32.1 89.8 -3.2 1100 5.6
17000 -2.3 27.9 230 22 11 8.0 4.4 31.8 89.3 -3.5 1049 5.3
16500 -1.2 29.8 230 21 11 7.6 4.2 31.5 88.7 -3.9 1001 5.1
16000 -0.1 31.8 230 20 11 7.6 4.2 31.2 88.1 -4.2 953 4.8
15500 1.1 34.0 230 20 10 8.4 4.6 30.9 87.5 -4.6 903 4.6
15000 2.3 36.1 230 19 10 8.4 4.6 30.6 87.1 -4.8 852 4.3
14500 3.5 38.3 230 19 10 8.6 4.7 30.4 86.8 -5.1 801 4.1
14000 4.8 40.6 235 18 9 8.6 4.7 30.2 86.4 -5.3 748 3.8
13500 6.1 43.0 235 18 9 8.6 4.7 30.1 86.1 -5.5 695 3.5
13000 7.3 45.1 235 17 9 8.5 4.7 29.8 85.7 -5.8 643 3.3
12500 8.6 47.5 235 16 8 8.5 4.6 29.6 85.4 -6.0 591 3.0
12000 9.8 49.6 235 16 8 8.4 4.6 29.4 85.0 -6.3 539 2.7
11500 11.1 52.0 235 15 8 8.4 4.6 29.2 84.6 -6.5 487 2.5
11000 12.2 54.0 235 14 7 7.7 4.2 29.0 84.1 -6.8 436 2.2
10500 13.5 56.3 235 13 7 10.0 5.5 28.7 83.7 -7.0 384 2.0
10250 14.2 57.6 235 12 6 9.0 5.0 28.8 83.8 -7.0 354 1.8
10000 14.8 58.6 235 12 6 7.3 4.0 28.6 83.5 -7.2 330 1.7
9750 15.4 59.7 235 11 6 7.5 4.1 28.4 83.2 -7.4 305 1.6
9500 16.0 60.8 235 11 5 8.3 4.6 28.3 82.9 -7.6 281 1.4
9250 16.6 61.9 235 10 5 8.1 4.4 28.2 82.7 -7.6 254 1.3
9000 17.2 63.0 230 9 5 6.8 3.8 28.0 82.4 -7.9 230 1.2
8750 17.7 63.9 230 9 4 7.4 4.1 27.8 82.0 -8.1 207 1.1
8500 18.2 64.8 225 8 4 6.4 3.5 27.6 81.7 -8.3 183 0.9
8250 18.6 65.5 220 7 4 5.1 2.8 27.3 81.1 -8.6 163 0.8
8000 19.0 66.2 210 7 4 5.2 2.8 26.9 80.4 -9.0 144 0.7
7750 19.4 66.9 205 7 4 5.4 2.9 26.6 79.8 -9.3 125 0.6
7500 19.8 67.6 195 7 4 5.1 2.8 26.2 79.2 -9.7 105 0.5
7250 20.2 68.4 185 8 4 4.4 2.4 25.9 78.5 -10.0 87 0.4
7000 20.5 68.9 175 9 5 2.8 1.6 25.4 77.7 -10.5 72 0.4
6750 20.7 69.3 170 9 5 3.7 2.0 24.9 76.8 -11.1 58 0.3
6500 20.9 69.6 165 9 5 -2.6 -1.4 24.3 75.7 -11.7 45 0.2
6250 20.2 68.4 155 8 4 -11.1 -6.1 22.9 73.3 -13.0 57 0.3
6000 19.7 67.5 145 8 4 0.9 0.5 21.7 71.0 -14.3 66 0.3
5750 19.8 67.6 130 7 4 -7.6 -4.2 21.1 70.0 -15.0 54 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 * * * * * *
06/13/2025 at 0900 MDT | 06/13/2025 at 1200 MDT
|
CAPE... 0.0 LI... +1.8 | CAPE... 0.0 LI... +1.6
CINH... -1.4 K Index... +10.8 | CINH... -1.4 K Index... +12.4
|
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 -60.8 -77.4 280 14 7 2.1 1.1 | -61.3 -78.3 275 14 7 2.1 1.1
45000 -58.2 -72.8 285 15 8 0.7 0.4 | -58.5 -73.3 275 14 7 1.2 0.6
40000 -56.4 -69.5 265 14 7 8.0 4.4 | -56.1 -69.0 255 16 8 7.2 4.0
38000 -51.9 -61.4 255 19 10 7.5 4.1 | -52.0 -61.6 260 17 9 6.8 3.7
36000 -47.4 -53.3 250 23 12 7.5 4.1 | -47.9 -54.2 260 19 10 6.8 3.7
34000 -43.0 -45.4 250 25 13 7.2 3.9 | -43.5 -46.3 265 20 10 7.7 4.2
32000 -38.7 -37.7 255 26 14 7.2 3.9 | -38.8 -37.8 265 21 11 7.7 4.2
30000 -34.0 -29.2 260 27 14 8.2 4.5 | -34.0 -29.2 270 22 11 8.1 4.5
29000 -31.5 -24.7 260 27 14 8.2 4.5 | -31.6 -24.9 270 22 12 8.1 4.5
28000 -29.1 -20.4 265 27 14 8.2 4.5 | -29.2 -20.6 270 23 12 8.1 4.4
27000 -26.8 -16.2 265 26 13 7.3 4.0 | -26.9 -16.4 265 22 12 7.5 4.1
26000 -24.7 -12.5 270 26 13 7.3 4.0 | -24.6 -12.3 265 21 11 7.5 4.1
25000 -22.5 -8.5 270 25 13 7.3 4.0 | -22.4 -8.3 265 21 11 7.5 4.1
24000 -19.8 -3.6 270 24 12 7.1 3.9 | -19.5 -3.1 260 19 10 7.7 4.2
23000 -17.7 0.1 265 24 12 7.1 3.9 | -17.2 1.0 260 19 10 7.7 4.2
22000 -15.5 4.1 260 23 12 7.0 3.8 | -14.9 5.2 260 18 9 7.4 4.1
21000 -13.6 7.5 250 22 12 6.6 3.6 | -12.9 8.8 250 18 9 6.6 3.6
20000 -11.6 11.1 240 22 11 6.6 3.6 | -10.9 12.4 245 18 9 6.7 3.7
19500 -10.7 12.7 235 22 11 6.5 3.6 | -10.0 14.0 240 18 9 6.6 3.6
19000 -9.6 14.7 235 23 12 8.2 4.5 | -9.0 15.8 235 18 9 7.0 3.8
18500 -8.4 16.9 230 23 12 8.2 4.5 | -7.9 17.8 235 18 9 7.0 3.9
18000 -7.3 18.9 230 23 12 8.5 4.7 | -6.9 19.6 230 18 9 7.4 4.1
17500 -5.9 21.4 225 23 12 9.0 4.9 | -5.8 21.6 225 17 9 8.0 4.4
17000 -4.6 23.7 225 23 12 9.0 4.9 | -4.6 23.7 225 17 9 8.0 4.4
16500 -3.3 26.1 225 23 12 9.2 5.1 | -3.4 25.9 220 17 9 8.7 4.8
16000 -1.9 28.6 225 22 11 9.2 5.1 | -2.1 28.2 220 17 9 8.7 4.8
15500 -0.5 31.1 225 22 11 9.2 5.0 | -0.8 30.6 220 17 9 8.9 4.9
15000 0.8 33.4 225 21 11 9.1 5.0 | 0.5 32.9 220 17 9 9.0 5.0
14500 2.2 36.0 225 20 10 9.1 5.0 | 1.9 35.4 220 17 9 9.1 5.0
14000 3.5 38.3 225 19 10 9.1 5.0 | 3.2 37.8 220 16 8 9.2 5.1
13500 4.9 40.8 225 18 9 9.1 5.0 | 4.6 40.3 220 16 8 9.3 5.1
13000 6.2 43.2 225 17 9 8.9 4.9 | 6.0 42.8 220 16 8 9.4 5.1
12500 7.5 45.5 230 16 8 8.9 4.9 | 7.4 45.3 220 15 8 9.4 5.1
12000 8.8 47.8 230 15 8 8.8 4.8 | 8.8 47.8 220 15 8 9.4 5.2
11500 10.2 50.4 230 14 7 9.0 5.0 | 10.2 50.4 220 15 8 9.6 5.2
11000 11.3 52.3 230 14 7 6.8 3.7 | 11.5 52.7 220 14 7 8.0 4.4
10500 12.4 54.3 235 13 7 7.6 4.2 | 12.6 54.7 220 13 7 10.0 5.5
10250 13.0 55.4 235 13 7 10.9 6.0 | 13.5 56.3 220 14 7 12.3 6.7
10000 13.9 57.0 235 13 7 9.6 5.3 | 14.4 57.9 225 14 7 9.8 5.4
9750 14.4 57.9 230 12 6 7.3 4.0 | 15.0 59.0 225 13 7 8.9 4.9
9500 15.0 59.0 230 12 6 8.4 4.6 | 15.7 60.3 225 13 7 9.6 5.3
9250 15.6 60.1 230 12 6 6.4 3.5 | 16.4 61.5 225 13 7 7.8 4.3
9000 16.0 60.8 230 11 6 6.1 3.3 | 16.9 62.4 225 12 6 8.1 4.5
8750 16.6 61.9 225 11 6 7.6 4.2 | 17.7 63.9 225 12 6 10.1 5.5
8500 17.6 63.7 215 10 5 7.0 3.8 | 19.1 66.4 230 11 6 8.6 4.7
8250 18.1 64.6 210 9 5 6.2 3.4 | 19.7 67.5 230 10 5 9.1 5.0
8000 18.6 65.5 205 9 4 6.0 3.3 | 20.5 68.9 230 10 5 10.9 6.0
7750 19.0 66.2 200 8 4 6.0 3.3 | 21.3 70.3 230 10 5 10.4 5.7
7500 19.4 66.9 195 8 4 5.2 2.9 | 22.0 71.6 230 10 5 8.8 4.8
7250 19.8 67.6 185 8 4 5.3 2.9 | 22.6 72.7 235 10 5 8.6 4.7
7000 20.3 68.5 180 8 4 7.4 4.1 | 23.3 73.9 235 10 5 11.1 6.1
6750 20.8 69.4 180 8 4 8.5 4.7 | 24.2 75.6 235 10 5 11.7 6.4
6500 21.5 70.7 175 7 4 8.5 4.7 | 25.1 77.2 235 10 5 10.8 5.9
6250 22.1 71.8 165 7 4 8.9 4.9 | 25.9 78.6 235 9 5 11.3 6.2
6000 22.7 72.9 160 7 3 7.7 4.2 | 26.6 79.9 235 9 5 7.9 4.4
5750 23.3 73.9 170 6 3 11.8 6.4 | 27.3 81.1 235 9 4 13.2 7.2
5500 25.2 77.4 155 5 3 47.5 26.1 | 30.3 86.5 240 8 4 88.5 48.6
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
06/13/2025 at 1500 MDT | 06/13/2025 at 1800 MDT
|
CAPE... 0.0 LI... +0.6 | CAPE... 0.0 LI... +1.4
CINH... -0.0 K Index... +12.2 | CINH... -0.6 K Index... +8.6
|
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 -61.3 -78.3 265 14 7 1.9 1.0 | -60.9 -77.6 240 12 6 1.9 1.0
45000 -58.7 -73.7 265 16 8 1.1 0.6 | -58.4 -73.1 255 14 7 0.9 0.5
40000 -56.4 -69.5 255 15 8 7.2 4.0 | -56.3 -69.3 255 15 8 7.2 4.0
38000 -52.3 -62.1 260 15 8 6.9 3.8 | -52.2 -62.0 250 16 8 6.8 3.7
36000 -48.1 -54.6 265 16 8 6.9 3.8 | -48.1 -54.6 245 17 9 6.8 3.7
34000 -43.5 -46.3 265 18 9 7.9 4.3 | -43.6 -46.5 250 19 10 7.7 4.2
32000 -38.8 -37.8 265 20 10 7.9 4.3 | -39.0 -38.2 260 22 11 7.8 4.3
30000 -34.0 -29.2 265 22 11 7.9 4.3 | -34.2 -29.6 265 24 12 8.0 4.4
29000 -31.7 -25.1 270 23 12 7.9 4.3 | -31.8 -25.2 265 25 13 8.0 4.4
28000 -29.3 -20.7 270 24 12 7.9 4.4 | -29.4 -20.9 270 25 13 8.0 4.4
27000 -26.9 -16.4 270 24 12 8.0 4.4 | -26.4 -15.5 270 25 13 7.9 4.3
26000 -24.5 -12.1 270 23 12 8.0 4.4 | -24.1 -11.4 270 25 13 7.9 4.3
25000 -21.5 -6.7 270 23 12 8.0 4.4 | -21.7 -7.1 270 25 13 7.9 4.4
24000 -19.1 -2.4 270 22 11 7.9 4.3 | -19.3 -2.7 270 23 12 8.2 4.5
23000 -16.7 1.9 265 21 11 7.9 4.3 | -16.8 1.8 270 21 11 8.2 4.5
22000 -14.4 6.1 265 20 10 7.3 4.0 | -14.3 6.3 270 20 10 7.9 4.4
21000 -12.5 9.5 255 19 10 6.2 3.4 | -12.1 10.2 260 19 10 7.6 4.1
20000 -10.7 12.7 245 18 9 6.4 3.5 | -9.8 14.4 250 18 9 7.6 4.2
19500 -9.8 14.4 240 18 9 6.3 3.5 | -8.7 16.3 245 18 9 7.6 4.2
19000 -8.7 16.3 235 18 9 8.3 4.6 | -7.6 18.3 240 18 9 7.6 4.2
18500 -7.6 18.3 230 18 9 8.2 4.5 | -6.5 20.3 235 18 9 7.7 4.2
18000 -6.4 20.5 225 18 9 8.6 4.7 | -5.4 22.3 230 19 10 8.2 4.5
17500 -5.0 23.0 225 17 9 9.1 5.0 | -4.1 24.6 225 19 10 8.8 4.8
17000 -3.7 25.3 225 17 9 9.1 5.0 | -2.8 27.0 225 19 10 8.8 4.8
16500 -2.3 27.9 220 17 9 9.3 5.1 | -1.5 29.3 225 18 9 9.3 5.1
16000 -0.9 30.4 220 17 9 9.3 5.1 | -0.1 31.8 225 18 9 9.3 5.1
15500 0.5 32.9 220 17 9 9.3 5.1 | 1.3 34.3 225 18 9 9.3 5.1
15000 1.9 35.4 220 16 8 9.3 5.1 | 2.7 36.9 225 17 9 9.3 5.1
14500 3.2 37.8 220 16 8 9.3 5.1 | 4.1 39.4 225 17 9 9.3 5.1
14000 4.6 40.3 220 16 8 9.4 5.1 | 5.5 41.9 225 17 9 9.3 5.1
13500 6.0 42.8 220 15 8 9.4 5.1 | 6.9 44.4 230 16 8 9.3 5.1
13000 7.4 45.3 220 15 8 9.3 5.1 | 8.3 46.9 230 16 8 9.1 5.0
12500 8.8 47.8 220 15 8 9.3 5.1 | 9.6 49.3 230 16 8 9.1 5.0
12000 10.2 50.4 220 14 7 9.4 5.1 | 11.0 51.8 230 15 8 9.5 5.2
11500 11.6 52.9 225 14 7 9.5 5.2 | 12.5 54.5 235 15 8 9.7 5.3
11000 12.9 55.2 225 14 7 7.8 4.3 | 13.8 56.8 235 14 7 7.8 4.3
10500 14.1 57.4 230 13 7 10.0 5.5 | 14.9 58.8 240 14 7 9.6 5.3
10250 15.0 59.0 230 13 7 12.4 6.8 | 15.8 60.4 240 14 7 11.9 6.5
10000 15.8 60.4 230 13 7 10.0 5.5 | 16.6 61.9 240 14 7 9.7 5.3
9750 16.5 61.7 230 13 7 9.2 5.1 | 17.3 63.1 240 14 7 8.8 4.8
9500 17.2 63.0 230 13 6 9.7 5.3 | 18.6 65.5 245 13 7 7.9 4.3
9250 17.9 64.2 235 12 6 8.5 4.6 | 19.2 66.6 245 13 7 8.4 4.6
9000 19.3 66.7 235 12 6 10.8 5.9 | 19.9 67.8 250 13 7 10.2 5.6
8750 20.1 68.2 235 12 6 10.8 5.9 | 20.6 69.1 250 13 7 9.8 5.4
8500 20.9 69.6 235 12 6 9.1 5.0 | 21.4 70.5 250 13 7 9.6 5.3
8250 21.5 70.7 240 12 6 9.2 5.1 | 22.1 71.8 255 13 7 9.7 5.3
8000 22.3 72.1 240 12 6 11.1 6.1 | 22.8 73.0 255 13 7 10.1 5.6
7750 23.1 73.6 240 12 6 10.7 5.9 | 23.6 74.5 255 12 6 10.3 5.6
7500 23.9 75.0 240 12 6 9.0 5.0 | 24.3 75.7 255 12 6 8.7 4.8
7250 24.5 76.1 245 12 6 8.6 4.7 | 24.9 76.8 255 13 7 8.3 4.5
7000 25.2 77.4 245 12 6 10.9 6.0 | 25.6 78.1 255 13 6 10.5 5.8
6750 26.1 79.0 240 11 6 11.4 6.3 | 26.5 79.7 255 12 6 11.0 6.1
6500 26.9 80.4 240 11 6 10.9 6.0 | 27.3 81.1 255 12 6 10.5 5.8
6250 27.7 81.9 245 11 6 11.4 6.3 | 28.1 82.6 260 12 6 10.8 5.9
6000 28.5 83.3 245 11 6 7.6 4.2 | 28.8 83.8 260 12 6 8.0 4.4
5750 29.1 84.4 240 10 5 12.7 7.0 | 29.4 84.9 255 11 5 9.9 5.4
5500 32.3 90.1 250 10 5 94.2 51.7 | 31.4 88.5 260 10 5 58.6 32.1
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
________________________________________________________________________________
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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