Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
984
UXUS97 KGJT 311306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Thursday, July 31, 2025
This forecast is for Thursday, July 31, 2025:
If the trigger temperature of 82.0 F/27.8 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1898 ft/min (9.6 m/s)
Maximum height of thermals.................. 24601 ft MSL (18993 ft AGL)
Forecast maximum temperature................... 94.0 F/34.9 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................. 19735 ft MSL (14127 ft AGL)
Thermal soaring outlook for Friday 08/01....... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:14:21 / 20:26:42 MDT
Total possible sunshine........... 14 hr 12 min 21 sec (852 min 21 sec)
Altitude of sun at 13:20:31 MDT... 68.47 degrees
Upper air data from rawinsonde observation taken on 07/31/2025 at 0600 MDT
Freezing level.................. 15486 ft MSL (9878 ft AGL)
Convective condensation level... 17598 ft MSL (11990 ft AGL)
Lifted condensation level....... 19483 ft MSL (13875 ft AGL)
Lifted index.................... -5.2
K index......................... +14.5
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 -60.6 -77.1 260 28 15 3.2 1.7 M M M M M
45000 -55.2 -67.4 260 46 24 4.6 2.5 M M M M M
40000 -48.4 -55.1 260 61 31 3.5 1.9 M M M M M
38000 -46.4 -51.5 260 61 31 3.5 1.9 M M M M M
36000 -44.0 -47.2 260 61 31 3.4 1.9 M M M M M
34000 -41.2 -42.2 260 57 29 4.9 2.7 M M M M M
32000 -38.2 -36.8 260 53 27 4.7 2.6 M M M M M
30000 -34.1 -29.4 260 48 25 7.2 4.0 40.3 104.6 4.5 M M
29000 -32.0 -25.6 255 46 24 7.3 4.0 39.4 102.9 3.8 M M
28000 -29.8 -21.6 255 43 22 6.8 3.7 38.5 101.4 3.2 M M
27000 -27.9 -18.2 255 41 21 6.6 3.6 37.2 99.0 2.1 M M
26000 -25.9 -14.6 255 38 20 6.6 3.6 36.0 96.8 1.2 M M
25000 -23.9 -11.0 250 36 18 6.8 3.7 35.0 94.9 0.3 M M
24000 -21.6 -6.9 250 34 17 7.9 4.3 34.1 93.4 -0.4 1844 9.4
23000 -19.3 -2.7 245 32 17 7.9 4.3 33.4 92.2 -1.0 1745 8.9
22000 -17.0 1.4 245 30 16 7.9 4.4 32.9 91.1 -1.5 1645 8.4
21000 -14.6 5.7 240 29 15 8.1 4.4 32.2 89.9 -2.2 1545 7.9
20000 -11.7 10.9 235 28 14 8.2 4.5 31.5 88.7 -2.9 1420 7.2
19500 -10.5 13.1 235 27 14 8.3 4.5 31.3 88.3 -3.2 1370 7.0
19000 -9.3 15.3 230 26 13 8.3 4.6 31.0 87.8 -3.5 1319 6.7
18500 -8.1 17.4 230 25 13 8.3 4.5 30.8 87.4 -3.7 1268 6.4
18000 -6.8 19.8 230 23 12 9.0 4.9 30.6 87.0 -3.9 1215 6.2
17500 -5.5 22.1 230 22 11 8.9 4.9 30.4 86.8 -4.1 1160 5.9
17000 -4.1 24.6 235 21 11 9.1 5.0 30.3 86.5 -4.2 1105 5.6
16500 -2.7 27.1 235 20 10 9.2 5.0 30.2 86.4 -4.3 1048 5.3
16000 -1.3 29.7 235 19 10 9.2 5.0 30.1 86.2 -4.3 991 5.0
15500 0.1 32.2 240 18 9 9.2 5.1 30.0 86.0 -4.4 934 4.7
15000 1.5 34.7 240 18 9 9.2 5.1 29.9 85.9 -4.5 877 4.5
14500 2.9 37.2 240 17 9 9.3 5.1 29.9 85.8 -4.6 820 4.2
14000 4.3 39.7 245 16 8 9.3 5.1 29.8 85.6 -4.7 763 3.9
13500 5.7 42.3 245 16 8 9.3 5.1 29.7 85.5 -4.8 707 3.6
13000 7.1 44.8 245 15 8 9.3 5.1 29.6 85.3 -4.9 650 3.3
12500 8.5 47.3 245 14 7 9.0 4.9 29.6 85.2 -4.9 594 3.0
12000 9.8 49.6 250 14 7 8.8 4.8 29.4 84.9 -5.1 540 2.7
11500 11.1 52.0 250 13 7 8.8 4.8 29.3 84.7 -5.3 485 2.5
11000 12.4 54.3 250 13 6 9.2 5.0 29.1 84.4 -5.5 432 2.2
10500 13.5 56.3 245 12 6 6.9 3.8 28.7 83.7 -5.9 384 2.0
10250 14.1 57.4 245 12 6 8.8 4.8 28.6 83.5 -6.0 358 1.8
10000 14.7 58.5 240 12 6 8.2 4.5 28.5 83.3 -6.2 333 1.7
9750 15.3 59.5 235 12 6 8.7 4.8 28.4 83.2 -6.3 307 1.6
9500 15.9 60.6 235 11 6 6.1 3.4 28.3 82.9 -6.4 282 1.4
9250 16.2 61.2 230 11 6 5.3 2.9 27.9 82.2 -6.9 265 1.3
9000 16.7 62.1 225 11 6 6.9 3.8 27.7 81.8 -7.2 244 1.2
8750 17.1 62.8 215 12 6 6.4 3.5 27.4 81.3 -7.5 223 1.1
8500 17.6 63.7 210 12 6 5.1 2.8 27.1 80.8 -7.8 203 1.0
8250 17.8 64.0 200 12 6 4.0 2.2 26.7 80.1 -8.3 187 1.0
8000 18.1 64.6 195 12 6 4.4 2.4 26.3 79.3 -8.8 172 0.9
7750 18.4 65.1 190 12 6 3.4 1.9 25.8 78.5 -9.2 157 0.8
7500 18.5 65.3 180 12 6 1.0 0.5 25.3 77.5 -9.9 146 0.7
7250 18.4 65.1 170 13 7 0.1 0.0 24.5 76.2 -10.7 140 0.7
7000 18.4 65.1 165 13 7 2.7 1.5 23.9 75.0 -11.4 132 0.7
6750 18.6 65.5 160 13 7 -0.4 -0.2 23.3 74.0 -12.0 121 0.6
6500 18.3 64.9 155 11 6 -5.2 -2.8 22.3 72.1 -13.1 123 0.6
6250 17.9 64.2 145 10 5 -3.7 -2.0 21.2 70.2 -14.3 127 0.6
6000 17.6 63.7 135 8 4 -4.2 -2.3 20.2 68.4 -15.4 129 0.7
5750 16.8 62.2 125 7 4 -17.8 -9.8 18.8 65.8 -16.8 143 0.7
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 * * * * * *
07/31/2025 at 0900 MDT | 07/31/2025 at 1200 MDT
|
CAPE... +168.5 LI... -2.5 | CAPE... +897.8 LI... -3.1
CINH... -218.6 K Index... +30.4 | CINH... -16.1 K Index... +31.0
|
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 -59.9 -75.8 250 24 12 2.9 1.6 | -59.8 -75.6 250 27 14 3.3 1.8
45000 -56.1 -69.0 250 39 20 1.8 1.0 | -55.6 -68.1 250 42 21 1.6 0.9
40000 -52.8 -63.0 245 47 24 5.4 3.0 | -52.7 -62.9 250 49 25 5.2 2.8
38000 -49.6 -57.3 240 48 25 5.4 3.0 | -49.6 -57.3 245 49 25 5.2 2.8
36000 -46.0 -50.8 235 50 26 5.5 3.0 | -46.2 -51.2 245 49 25 5.3 2.9
34000 -42.2 -44.0 235 44 23 6.3 3.5 | -42.4 -44.3 245 43 22 6.5 3.6
32000 -38.4 -37.1 235 38 20 6.1 3.3 | -38.5 -37.3 240 37 19 6.3 3.5
30000 -33.9 -29.0 230 31 16 7.8 4.3 | -34.0 -29.2 240 32 16 7.6 4.2
29000 -31.5 -24.7 230 28 14 7.9 4.3 | -31.8 -25.2 235 29 15 7.6 4.2
28000 -29.2 -20.6 230 25 13 7.5 4.1 | -29.5 -21.1 235 27 14 7.6 4.2
27000 -27.0 -16.6 225 24 12 7.5 4.1 | -27.2 -17.0 235 26 13 7.6 4.2
26000 -24.8 -12.6 225 23 12 7.5 4.1 | -25.0 -13.0 230 25 13 7.6 4.2
25000 -22.6 -8.7 225 22 11 7.5 4.1 | -22.7 -8.9 230 25 13 7.6 4.2
24000 -20.4 -4.7 225 22 11 7.4 4.1 | -20.4 -4.7 225 24 13 7.9 4.3
23000 -18.2 -0.8 225 22 11 7.5 4.1 | -18.1 -0.6 225 24 12 7.9 4.3
22000 -15.5 4.1 220 21 11 8.2 4.5 | -15.2 4.6 220 24 12 8.1 4.4
21000 -13.1 8.4 220 20 10 8.2 4.5 | -12.8 9.0 220 23 12 8.2 4.5
20000 -10.7 12.7 215 18 9 8.3 4.5 | -10.4 13.3 215 23 12 8.2 4.5
19500 -9.5 14.9 210 18 9 8.1 4.4 | -9.3 15.3 215 23 12 8.2 4.5
19000 -8.4 16.9 210 17 9 7.9 4.3 | -8.1 17.4 215 22 11 8.1 4.4
18500 -7.2 19.0 210 16 8 7.9 4.3 | -6.9 19.6 210 22 11 8.1 4.4
18000 -6.0 21.2 210 16 8 8.2 4.5 | -5.7 21.7 210 22 11 8.4 4.6
17500 -4.8 23.4 210 15 8 8.2 4.5 | -4.5 23.9 210 21 11 8.3 4.6
17000 -3.6 25.5 210 14 7 8.2 4.5 | -3.3 26.1 210 21 11 8.2 4.5
16500 -2.4 27.7 210 14 7 8.2 4.5 | -2.1 28.2 210 20 10 8.2 4.5
16000 -1.2 29.8 210 13 7 8.3 4.5 | -1.0 30.2 215 19 10 8.2 4.5
15500 -0.0 32.0 215 13 7 8.6 4.7 | 0.2 32.4 215 18 9 8.2 4.5
15000 1.2 34.2 215 13 7 8.5 4.7 | 1.4 34.5 215 17 9 8.2 4.5
14500 2.5 36.5 215 13 7 9.0 4.9 | 2.6 36.7 215 17 9 8.6 4.7
14000 3.8 38.8 220 13 7 9.0 4.9 | 3.9 39.0 220 16 8 8.5 4.7
13500 5.1 41.2 220 13 7 8.7 4.8 | 5.2 41.4 220 16 8 8.9 4.9
13000 6.4 43.5 220 14 7 8.6 4.7 | 6.5 43.7 220 15 8 9.0 4.9
12500 7.6 45.7 220 14 7 8.3 4.5 | 7.8 46.0 220 14 7 9.1 5.0
12000 8.8 47.8 215 15 8 8.1 4.4 | 9.1 48.4 220 14 7 9.1 5.0
11500 10.0 50.0 215 15 8 7.9 4.3 | 10.5 50.9 220 13 7 9.1 5.0
11000 11.1 52.0 215 16 8 7.6 4.2 | 11.8 53.2 220 13 7 9.0 4.9
10500 12.2 54.0 215 16 8 7.2 4.0 | 13.1 55.6 215 12 6 9.3 5.1
10250 12.7 54.9 215 16 8 7.0 3.9 | 13.8 56.8 220 11 6 9.4 5.1
10000 13.2 55.8 210 16 8 7.5 4.1 | 14.4 57.9 220 11 6 9.2 5.1
9750 13.8 56.8 210 16 8 7.3 4.0 | 15.1 59.2 220 11 6 9.0 4.9
9500 14.3 57.7 210 16 8 7.7 4.2 | 15.8 60.4 215 11 6 10.0 5.5
9250 14.9 58.8 205 15 8 7.9 4.3 | 16.6 61.9 220 10 5 10.4 5.7
9000 15.4 59.7 205 15 8 6.9 3.8 | 17.3 63.1 220 10 5 8.6 4.7
8750 15.9 60.6 200 15 8 6.3 3.4 | 17.8 64.0 215 10 5 8.0 4.4
8500 16.4 61.5 195 14 7 6.8 3.7 | 18.4 65.1 215 10 5 8.5 4.6
8250 16.9 62.4 190 14 7 7.0 3.8 | 19.7 67.5 215 8 4 9.6 5.2
8000 17.9 64.2 185 14 7 6.9 3.8 | 20.5 68.9 215 8 4 10.8 5.9
7750 18.4 65.1 185 14 7 6.2 3.4 | 21.2 70.2 215 8 4 9.1 5.0
7500 18.8 65.8 175 14 7 5.5 3.0 | 21.8 71.2 215 7 4 7.9 4.3
7250 19.2 66.6 170 14 7 6.6 3.6 | 22.5 72.5 215 7 3 9.4 5.2
7000 19.8 67.6 170 13 7 7.1 3.9 | 23.3 73.9 210 7 3 11.7 6.4
6750 20.2 68.4 165 12 6 5.4 2.9 | 24.1 75.4 210 7 3 10.8 5.9
6500 20.6 69.1 160 11 6 5.3 2.9 | 24.9 76.8 210 6 3 10.7 5.9
6250 20.9 69.6 155 10 5 3.6 2.0 | 25.6 78.1 210 5 3 8.3 4.5
6000 21.2 70.2 150 12 6 5.2 2.9 | 26.3 79.3 210 6 3 14.2 7.8
5750 21.9 71.4 145 10 5 13.7 7.5 | 28.0 82.4 210 5 2 32.0 17.6
5500 22.5 72.5 140 8 4 -2.9 -1.6 | 29.7 85.5 215 4 2 -1.9 -1.0
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
07/31/2025 at 1500 MDT | 07/31/2025 at 1800 MDT
|
CAPE... +558.3 LI... -1.8 | CAPE... +277.0 LI... -1.0
CINH... -137.9 K Index... +30.4 | CINH... -109.4 K Index... +21.9
|
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 -59.6 -75.3 255 30 16 3.2 1.8 | -60.1 -76.2 260 31 16 2.8 1.5
45000 -55.8 -68.4 250 44 23 1.1 0.6 | -56.0 -68.8 255 49 25 2.7 1.5
40000 -53.4 -64.1 240 43 22 5.9 3.2 | -51.6 -60.9 245 51 26 4.7 2.6
38000 -49.4 -56.9 240 39 20 6.0 3.3 | -48.4 -55.1 240 51 26 4.7 2.6
36000 -45.8 -50.4 240 37 19 6.3 3.5 | -45.6 -50.1 235 51 26 5.0 2.8
34000 -41.4 -42.5 240 34 17 7.5 4.1 | -41.6 -42.9 235 46 24 6.8 3.7
32000 -36.9 -34.4 240 31 16 7.8 4.3 | -37.5 -35.5 235 42 21 6.6 3.6
30000 -32.3 -26.1 235 29 15 7.6 4.2 | -33.1 -27.6 235 37 19 7.5 4.1
29000 -30.0 -22.0 235 29 15 7.6 4.2 | -30.8 -23.4 230 34 18 7.5 4.1
28000 -27.8 -18.0 230 28 14 7.0 3.8 | -28.6 -19.5 230 32 17 7.7 4.3
27000 -25.8 -14.4 230 28 14 6.8 3.8 | -26.3 -15.3 230 31 16 7.8 4.3
26000 -23.7 -10.7 230 27 14 6.9 3.8 | -23.9 -11.0 225 30 15 7.8 4.3
25000 -21.7 -7.1 230 27 14 7.0 3.9 | -21.6 -6.9 225 28 15 7.7 4.2
24000 -19.5 -3.1 225 27 14 7.6 4.2 | -19.4 -2.9 225 28 14 7.5 4.1
23000 -16.7 1.9 225 27 14 7.7 4.2 | -16.6 2.1 225 27 14 7.5 4.1
22000 -14.5 5.9 225 26 13 7.7 4.2 | -14.4 6.1 225 27 14 7.7 4.2
21000 -12.2 10.0 225 26 13 7.7 4.2 | -12.1 10.2 225 27 14 7.8 4.3
20000 -10.0 14.0 225 25 13 7.8 4.3 | -9.8 14.4 225 26 14 7.9 4.3
19500 -8.8 16.2 225 25 13 7.9 4.3 | -8.7 16.3 225 26 13 8.4 4.6
19000 -7.7 18.1 225 24 12 7.9 4.3 | -7.4 18.7 230 26 13 8.7 4.8
18500 -6.5 20.3 225 24 12 8.0 4.4 | -6.2 20.8 230 26 13 8.7 4.8
18000 -5.4 22.3 225 23 12 7.6 4.1 | -4.9 23.2 230 25 13 9.2 5.0
17500 -4.3 24.3 225 23 12 7.6 4.2 | -3.5 25.7 230 25 13 9.2 5.0
17000 -3.2 26.2 225 22 11 7.9 4.4 | -2.2 28.0 235 25 13 9.1 5.0
16500 -2.0 28.4 225 22 11 8.2 4.5 | -0.8 30.6 235 25 13 9.1 5.0
16000 -0.8 30.6 225 21 11 8.2 4.5 | 0.5 32.9 235 25 13 9.1 5.0
15500 0.4 32.7 230 21 11 8.7 4.8 | 1.9 35.4 235 24 13 9.3 5.1
15000 1.7 35.1 230 21 11 8.7 4.8 | 3.3 37.9 240 24 12 9.3 5.1
14500 3.0 37.4 230 20 10 9.1 5.0 | 4.6 40.3 240 24 12 9.1 5.0
14000 4.4 39.9 230 20 10 9.1 5.0 | 6.0 42.8 240 23 12 9.1 5.0
13500 5.7 42.3 230 19 10 9.2 5.1 | 7.3 45.1 240 23 12 9.0 4.9
13000 7.1 44.8 235 19 10 9.3 5.1 | 8.7 47.7 240 22 11 9.0 4.9
12500 8.4 47.1 235 18 9 9.1 5.0 | 10.0 50.0 245 21 11 8.9 4.9
12000 9.8 49.6 235 17 9 9.0 5.0 | 11.3 52.3 245 20 10 8.8 4.8
11500 11.1 52.0 235 17 9 9.0 4.9 | 12.6 54.7 245 19 10 8.8 4.8
11000 12.4 54.3 240 16 8 8.9 4.9 | 13.9 57.0 245 18 9 8.6 4.7
10500 13.7 56.7 240 15 8 8.3 4.6 | 15.2 59.4 245 17 9 7.2 4.0
10250 14.3 57.7 245 15 8 8.3 4.6 | 15.6 60.1 245 16 8 7.9 4.3
10000 15.0 59.0 245 14 7 9.1 5.0 | 16.4 61.5 245 16 8 10.3 5.6
9750 15.6 60.1 245 14 7 8.8 4.8 | 17.1 62.8 245 15 8 9.7 5.3
9500 16.3 61.3 245 14 7 9.3 5.1 | 17.8 64.0 245 14 7 9.7 5.3
9250 17.0 62.6 250 13 7 9.2 5.1 | 18.5 65.3 245 14 7 9.1 5.0
9000 17.6 63.7 250 13 7 7.6 4.2 | 19.1 66.4 245 13 7 8.6 4.7
8750 18.1 64.6 250 12 6 6.8 3.7 | 20.4 68.7 245 12 6 8.1 4.5
8500 19.2 66.6 255 11 6 7.7 4.2 | 20.9 69.6 245 11 6 7.6 4.2
8250 19.7 67.5 260 11 6 6.9 3.8 | 21.5 70.7 245 11 5 7.3 4.0
8000 20.1 68.2 260 10 5 5.9 3.3 | 22.0 71.6 245 9 5 7.3 4.0
7750 20.6 69.1 265 8 4 5.9 3.2 | 22.5 72.5 240 7 4 6.2 3.4
7500 21.0 69.8 270 8 4 6.0 3.3 | 22.9 73.2 240 7 3 5.2 2.9
7250 21.4 70.5 275 8 4 5.6 3.1 | 23.3 73.9 240 6 3 5.1 2.8
7000 21.7 71.1 275 8 4 5.1 2.8 | 23.6 74.5 240 5 3 5.1 2.8
6750 22.1 71.8 275 7 3 5.6 3.1 | 24.0 75.2 235 4 2 8.1 4.5
6500 22.4 72.3 280 7 4 6.6 3.6 | 24.7 76.5 240 4 2 10.4 5.7
6250 22.8 73.0 280 7 4 4.4 2.4 | 25.4 77.7 245 4 2 8.4 4.6
6000 23.1 73.6 265 6 3 8.0 4.4 | 26.0 78.8 245 4 2 10.7 5.9
5750 24.1 75.4 275 5 3 20.1 11.1 | 27.1 80.8 240 3 1 19.9 10.9
5500 25.0 77.0 285 5 3 -3.0 -1.7 | 28.5 83.3 250 2 1 13.9 7.6
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
________________________________________________________________________________
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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