Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
876
UXUS97 KGJT 211306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Monday, July 21, 2025
This forecast is for Monday, July 21, 2025:
If the trigger temperature of 78.8 F/26.0 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1425 ft/min (7.2 m/s)
Maximum height of thermals.................. 19412 ft MSL (13804 ft AGL)
Forecast maximum temperature................... 94.0 F/34.9 C
Time of trigger temperature.................... 0845 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................. 17194 ft MSL (11586 ft AGL)
Thermal soaring outlook for Tuesday 07/22...... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:05:45 / 20:35:28 MDT
Total possible sunshine........... 14 hr 29 min 42 sec (869 min 42 sec)
Altitude of sun at 13:20:37 MDT... 70.67 degrees
Upper air data from rawinsonde observation taken on 07/21/2025 at 0600 MDT
Freezing level.................. 15317 ft MSL (9709 ft AGL)
Convective condensation level... 14753 ft MSL (9145 ft AGL)
Lifted condensation level....... 17165 ft MSL (11557 ft AGL)
Lifted index.................... -2.7
K index......................... +29.5
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 -65.3 -85.5 220 18 9 -0.2 -0.1 M M M M M
45000 -62.8 -81.0 220 27 14 5.7 3.1 M M M M M
40000 -53.7 -64.7 220 34 18 8.5 4.7 M M M M M
38000 -48.5 -55.3 220 35 18 8.6 4.7 M M M M M
36000 -42.7 -44.9 215 35 18 8.6 4.7 M M M M M
34000 -37.6 -35.7 220 34 17 8.6 4.7 M M M M M
32000 -32.4 -26.3 220 33 17 8.9 4.9 M M M M M
30000 -27.8 -18.0 220 30 16 7.6 4.1 47.6 117.6 10.0 M M
29000 -25.6 -14.1 220 29 15 7.6 4.1 46.8 116.2 9.5 M M
28000 -23.3 -9.9 220 28 14 7.2 3.9 46.0 114.9 9.1 M M
27000 -21.2 -6.2 220 28 14 7.1 3.9 44.9 112.8 8.2 M M
26000 -19.1 -2.4 220 27 14 7.1 3.9 43.9 111.0 7.5 M M
25000 -17.0 1.4 220 27 14 7.1 3.9 43.0 109.4 6.9 M M
24000 -15.2 4.6 215 27 14 6.1 3.3 41.6 106.9 5.8 M M
23000 -13.4 7.9 215 27 14 6.1 3.4 40.3 104.5 4.7 M M
22000 -11.6 11.1 215 28 14 6.2 3.4 39.1 102.3 3.6 M M
21000 -10.0 14.0 215 27 14 5.5 3.0 37.5 99.6 2.3 M M
20000 -8.1 17.4 215 26 13 5.5 3.0 35.7 96.2 0.6 M M
19500 -7.3 18.9 220 26 13 5.6 3.0 35.0 95.0 -0.0 1224 6.2
19000 -6.5 20.3 220 25 13 5.4 3.0 34.3 93.7 -0.7 1186 6.0
18500 -5.7 21.7 220 25 13 5.5 3.0 33.5 92.3 -1.4 1148 5.8
18000 -5.0 23.0 220 24 13 5.9 3.3 32.8 91.1 -2.1 1110 5.6
17500 -4.1 24.6 220 23 12 6.1 3.4 32.2 89.9 -2.7 1069 5.4
17000 -3.2 26.2 220 22 12 6.3 3.4 31.6 88.8 -3.3 1028 5.2
16500 -2.3 27.9 220 21 11 6.9 3.8 31.0 87.9 -3.9 985 5.0
16000 -1.3 29.7 220 19 10 6.8 3.7 30.6 87.0 -4.4 941 4.8
15500 -0.3 31.5 220 17 9 7.6 4.2 30.1 86.2 -4.8 896 4.6
15000 0.8 33.4 220 16 8 7.6 4.2 29.8 85.6 -5.2 848 4.3
14500 1.9 35.4 220 14 7 7.9 4.3 29.4 85.0 -5.6 801 4.1
14000 3.1 37.6 220 12 6 8.1 4.4 29.2 84.5 -5.9 751 3.8
13500 4.2 39.6 225 11 6 8.3 4.6 28.9 84.0 -6.2 701 3.6
13000 5.5 41.9 225 10 5 8.8 4.8 28.7 83.7 -6.5 647 3.3
12500 6.8 44.2 230 9 5 8.8 4.8 28.6 83.4 -6.6 594 3.0
12000 8.1 46.6 240 9 5 8.7 4.8 28.4 83.2 -6.8 540 2.7
11500 9.4 48.9 245 9 5 8.7 4.8 28.3 82.9 -7.0 486 2.5
11000 10.6 51.1 245 9 4 7.4 4.0 28.0 82.4 -7.3 436 2.2
10500 11.8 53.2 250 9 4 9.8 5.4 27.7 81.8 -7.7 387 2.0
10250 12.5 54.5 250 9 4 9.3 5.1 27.7 81.9 -7.6 356 1.8
10000 13.1 55.6 250 9 4 7.4 4.1 27.6 81.7 -7.8 331 1.7
9750 13.7 56.7 250 8 4 7.8 4.3 27.4 81.4 -8.0 307 1.6
9500 14.3 57.7 250 8 4 8.2 4.5 27.3 81.1 -8.2 282 1.4
9250 14.9 58.8 250 8 4 8.0 4.4 27.2 80.9 -8.3 256 1.3
9000 15.4 59.7 250 8 4 7.3 4.0 27.0 80.6 -8.5 232 1.2
8750 16.0 60.8 250 7 4 7.7 4.2 26.8 80.3 -8.7 208 1.1
8500 16.5 61.7 250 7 4 6.7 3.7 26.7 80.0 -8.9 184 0.9
8250 17.0 62.6 245 6 3 6.2 3.4 26.4 79.5 -9.2 163 0.8
8000 17.5 63.5 240 6 3 6.8 3.7 26.1 79.1 -9.4 141 0.7
7750 18.0 64.4 230 5 3 7.1 3.9 25.9 78.7 -9.7 119 0.6
7500 18.5 65.3 220 4 2 6.2 3.4 25.7 78.3 -9.9 96 0.5
7250 18.9 66.0 200 4 2 4.9 2.7 25.4 77.7 -10.3 76 0.4
7000 19.3 66.7 190 5 2 5.1 2.8 25.0 77.0 -10.6 58 0.3
6750 19.7 67.5 180 5 3 6.1 3.3 24.7 76.4 -11.0 38 0.2
6500 20.0 68.0 170 5 3 2.2 1.2 24.3 75.8 -11.4 20 0.1
6250 20.0 68.0 160 6 3 -2.6 -1.4 23.5 74.4 -12.2 15 0.1
6000 20.0 68.0 150 6 3 4.3 2.3 22.8 73.0 -13.0 8 0.0
5750 20.3 68.5 140 6 3 -1.1 -0.6 22.4 72.3 -13.4 M M
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 * * * * * *
07/21/2025 at 0900 MDT | 07/21/2025 at 1200 MDT
|
CAPE... 0.0 LI... +1.2 | CAPE... +0.3 LI... +0.6
CINH... 0.0 K Index... +24.6 | CINH... -1.5 K Index... +26.0
|
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 -65.3 -85.5 220 19 10 0.7 0.4 | -65.1 -85.2 215 24 12 0.5 0.3
45000 -61.8 -79.2 220 31 16 6.1 3.3 | -61.8 -79.2 220 35 18 5.9 3.2
40000 -51.9 -61.4 230 37 19 7.6 4.2 | -52.1 -61.8 230 38 19 7.7 4.2
38000 -47.3 -53.1 225 38 19 7.6 4.2 | -47.5 -53.5 225 38 19 7.7 4.2
36000 -42.7 -44.9 220 39 20 7.9 4.3 | -42.9 -45.2 220 38 20 7.9 4.4
34000 -37.6 -35.7 220 40 21 8.6 4.7 | -37.9 -36.2 220 38 20 8.4 4.6
32000 -32.4 -26.3 225 42 21 8.9 4.9 | -32.9 -27.2 220 39 20 8.5 4.7
30000 -28.8 -19.8 225 37 19 5.7 3.1 | -28.8 -19.8 220 36 19 6.6 3.6
29000 -27.1 -16.8 225 34 17 5.7 3.1 | -26.8 -16.2 220 34 18 6.6 3.6
28000 -25.4 -13.7 220 31 16 6.5 3.6 | -24.9 -12.8 220 32 17 6.8 3.7
27000 -23.3 -9.9 220 29 15 7.0 3.8 | -22.8 -9.0 220 29 15 6.9 3.8
26000 -21.3 -6.3 220 27 14 7.0 3.8 | -20.8 -5.4 220 27 14 6.9 3.8
25000 -19.2 -2.6 220 25 13 7.1 3.9 | -18.8 -1.8 215 24 12 7.0 3.8
24000 -16.8 1.8 220 24 12 6.7 3.7 | -16.4 2.5 215 23 12 6.4 3.5
23000 -14.8 5.4 220 24 12 6.7 3.7 | -14.5 5.9 210 22 11 6.5 3.5
22000 -12.9 8.8 220 23 12 6.6 3.6 | -12.6 9.3 210 22 11 6.5 3.6
21000 -10.9 12.4 215 21 11 6.6 3.6 | -10.7 12.7 210 22 12 6.6 3.6
20000 -9.0 15.8 205 19 10 6.6 3.6 | -8.8 16.2 210 23 12 6.6 3.6
19500 -8.1 17.4 200 18 9 6.6 3.6 | -7.9 17.8 210 24 12 6.6 3.6
19000 -7.1 19.2 195 16 8 6.2 3.4 | -6.9 19.6 210 23 12 6.5 3.5
18500 -6.2 20.8 190 15 8 6.2 3.4 | -6.0 21.2 210 23 12 6.5 3.6
18000 -5.3 22.5 180 13 7 6.2 3.4 | -5.1 22.8 205 22 11 6.3 3.4
17500 -4.4 24.1 175 12 6 6.2 3.4 | -4.2 24.4 200 21 11 6.2 3.4
17000 -3.5 25.7 170 11 6 6.4 3.5 | -3.3 26.1 200 20 10 6.4 3.5
16500 -2.4 27.7 170 10 5 7.6 4.2 | -2.3 27.9 195 18 9 7.1 3.9
16000 -1.3 29.7 170 9 5 7.4 4.1 | -1.2 29.8 195 17 9 7.0 3.8
15500 -0.1 31.8 175 8 4 8.6 4.7 | -0.1 31.8 195 16 8 8.5 4.7
15000 1.1 34.0 180 7 4 8.6 4.7 | 1.2 34.2 195 15 8 8.5 4.7
14500 2.4 36.3 185 7 4 8.8 4.8 | 2.5 36.5 195 14 7 8.7 4.8
14000 3.8 38.8 195 7 3 8.9 4.9 | 3.8 38.8 195 13 7 8.8 4.8
13500 5.1 41.2 205 7 3 9.0 4.9 | 5.1 41.2 200 13 7 8.8 4.8
13000 6.4 43.5 210 7 4 9.1 5.0 | 6.4 43.5 200 12 6 8.8 4.8
12500 7.8 46.0 220 7 4 9.0 4.9 | 7.7 45.9 205 11 6 8.8 4.8
12000 9.1 48.4 225 8 4 8.6 4.7 | 9.0 48.2 205 11 6 8.8 4.8
11500 10.4 50.7 225 8 4 8.6 4.7 | 10.3 50.5 210 10 5 8.8 4.8
11000 11.7 53.1 230 8 4 8.6 4.7 | 11.6 52.9 220 10 5 8.6 4.7
10500 13.0 55.4 235 9 4 6.5 3.6 | 12.9 55.2 225 10 5 7.2 3.9
10250 13.4 56.1 240 9 4 7.0 3.9 | 13.4 56.1 230 9 5 7.4 4.1
10000 14.1 57.4 240 9 5 10.2 5.6 | 14.1 57.4 235 9 5 9.6 5.2
9750 14.8 58.6 235 9 5 9.4 5.1 | 14.8 58.6 235 10 5 8.9 4.9
9500 15.5 59.9 235 9 5 9.5 5.2 | 15.5 59.9 240 10 5 9.3 5.1
9250 16.2 61.2 240 10 5 8.5 4.7 | 16.1 61.0 245 10 5 9.4 5.1
9000 16.8 62.2 240 10 5 7.7 4.2 | 16.8 62.2 245 10 5 8.4 4.6
8750 17.4 63.3 235 10 5 7.8 4.3 | 17.4 63.3 250 11 5 7.9 4.3
8500 18.5 65.3 235 10 5 7.1 3.9 | 18.6 65.5 250 11 6 6.8 3.7
8250 19.0 66.2 235 10 5 7.4 4.1 | 19.1 66.4 255 11 6 8.0 4.4
8000 19.6 67.3 230 10 5 8.3 4.6 | 19.8 67.6 255 11 6 10.2 5.6
7750 20.2 68.4 220 9 5 7.6 4.2 | 20.5 68.9 255 12 6 9.0 4.9
7500 20.7 69.3 220 10 5 6.5 3.5 | 21.1 70.0 260 12 6 7.1 3.9
7250 21.2 70.2 215 10 5 6.6 3.6 | 21.6 70.9 260 11 6 7.6 4.2
7000 21.7 71.1 215 9 5 8.1 4.4 | 22.3 72.1 260 11 6 10.4 5.7
6750 22.3 72.1 205 8 4 7.7 4.2 | 23.1 73.6 260 11 6 10.8 5.9
6500 22.9 73.2 205 7 3 6.8 3.7 | 23.9 75.0 265 11 6 10.1 5.5
6250 23.4 74.1 200 6 3 6.7 3.7 | 24.6 76.3 265 11 6 9.4 5.2
6000 23.9 75.0 195 5 2 7.9 4.3 | 25.4 77.7 265 10 5 11.3 6.2
5750 24.6 76.3 190 4 2 12.4 6.8 | 26.5 79.7 265 10 5 22.0 12.1
5500 25.6 78.1 160 2 1 12.7 7.0 | 28.7 83.7 270 9 5 34.1 18.7
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
07/21/2025 at 1500 MDT | 07/21/2025 at 1800 MDT
|
CAPE... +19.4 LI... +0.2 | CAPE... +26.8 LI... -0.8
CINH... -1.2 K Index... +28.0 | CINH... -6.9 K Index... +29.5
|
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 -84.8 210 27 14 0.4 0.2 | -65.3 -85.5 215 25 13 -0.1 -0.1
45000 -61.8 -79.2 220 39 20 5.9 3.2 | -62.4 -80.3 220 38 20 6.5 3.5
40000 -52.1 -61.8 230 40 21 7.5 4.1 | -51.9 -61.4 225 39 20 7.7 4.2
38000 -47.6 -53.7 225 38 20 7.5 4.1 | -47.3 -53.1 225 36 19 7.7 4.2
36000 -43.1 -45.6 225 36 18 7.7 4.2 | -42.7 -44.9 225 34 17 7.7 4.2
34000 -38.3 -36.9 225 36 19 8.0 4.4 | -38.0 -36.4 225 33 17 7.9 4.3
32000 -33.5 -28.3 220 37 19 8.0 4.4 | -33.2 -27.8 225 32 16 7.8 4.3
30000 -29.0 -20.2 220 36 18 7.5 4.1 | -28.7 -19.7 220 33 17 7.6 4.2
29000 -26.7 -16.1 220 35 18 7.5 4.1 | -26.4 -15.5 220 33 17 7.6 4.2
28000 -24.5 -12.1 220 35 18 7.0 3.8 | -24.2 -11.6 215 33 17 7.1 3.9
27000 -22.5 -8.5 220 33 17 6.8 3.7 | -22.1 -7.8 215 32 17 6.9 3.8
26000 -20.5 -4.9 215 32 16 6.8 3.7 | -20.1 -4.2 220 31 16 6.9 3.8
25000 -18.5 -1.3 215 30 16 6.9 3.8 | -18.1 -0.6 220 30 16 7.0 3.8
24000 -16.1 3.0 210 28 15 6.7 3.7 | -15.6 3.9 215 29 15 6.8 3.7
23000 -14.1 6.6 205 27 14 6.8 3.7 | -13.6 7.5 210 28 14 6.8 3.7
22000 -12.2 10.0 200 25 13 6.6 3.6 | -11.6 11.1 205 27 14 6.4 3.5
21000 -10.3 13.5 200 24 13 6.5 3.6 | -9.8 14.4 200 27 14 6.2 3.4
20000 -8.4 16.9 200 24 12 6.6 3.6 | -8.1 17.4 200 27 14 6.2 3.4
19500 -7.4 18.7 200 23 12 6.6 3.6 | -7.2 19.0 195 27 14 6.3 3.5
19000 -6.5 20.3 200 23 12 6.7 3.7 | -6.2 20.8 195 26 13 6.8 3.8
18500 -5.5 22.1 200 22 11 6.7 3.7 | -5.3 22.5 200 25 13 6.8 3.7
18000 -4.5 23.9 205 21 11 6.9 3.8 | -4.3 24.3 200 24 12 7.1 3.9
17500 -3.5 25.7 205 21 11 6.9 3.8 | -3.2 26.2 200 23 12 7.2 4.0
17000 -2.5 27.5 205 20 10 6.9 3.8 | -2.2 28.0 205 22 11 7.3 4.0
16500 -1.5 29.3 205 19 10 6.8 3.8 | -1.1 30.0 205 21 11 7.5 4.1
16000 -0.5 31.1 205 19 10 6.8 3.7 | -0.1 31.8 210 20 10 7.5 4.1
15500 0.5 32.9 205 18 9 7.7 4.2 | 1.1 34.0 210 19 10 8.4 4.6
15000 1.7 35.1 205 17 9 7.7 4.2 | 2.3 36.1 215 18 9 8.5 4.6
14500 2.9 37.2 210 17 8 8.4 4.6 | 3.6 38.5 215 17 9 8.8 4.8
14000 4.2 39.6 210 16 8 8.8 4.8 | 4.9 40.8 215 16 8 9.0 4.9
13500 5.5 41.9 215 16 8 8.9 4.9 | 6.2 43.2 220 15 8 9.1 5.0
13000 6.9 44.4 215 15 8 9.2 5.1 | 7.6 45.7 220 15 8 9.2 5.1
12500 8.2 46.8 220 15 8 9.3 5.1 | 9.0 48.2 225 14 7 9.2 5.1
12000 9.6 49.3 220 15 8 9.6 5.3 | 10.4 50.7 230 14 7 9.2 5.1
11500 11.1 52.0 225 14 7 9.6 5.3 | 11.7 53.1 230 13 7 9.3 5.1
11000 12.4 54.3 230 14 7 8.5 4.7 | 13.0 55.4 235 13 7 8.4 4.6
10500 13.6 56.5 230 14 7 10.5 5.8 | 14.3 57.7 240 12 6 9.8 5.4
10250 14.5 58.1 235 14 7 11.0 6.0 | 15.1 59.2 240 12 6 10.1 5.5
10000 15.2 59.4 235 13 7 8.6 4.7 | 15.8 60.4 245 12 6 8.5 4.7
9750 15.9 60.6 235 13 7 9.2 5.1 | 16.4 61.5 245 12 6 9.0 4.9
9500 16.6 61.9 240 13 7 9.1 5.0 | 17.1 62.8 250 12 6 8.7 4.8
9250 17.3 63.1 240 13 7 9.2 5.1 | 17.7 63.9 250 12 6 9.7 5.3
9000 17.9 64.2 245 13 7 8.8 4.8 | 19.1 66.4 260 12 6 8.1 4.4
8750 19.2 66.6 245 12 6 8.6 4.7 | 19.7 67.5 260 12 6 8.6 4.7
8500 19.8 67.6 250 11 6 6.9 3.8 | 20.4 68.7 260 12 6 7.6 4.2
8250 20.3 68.5 250 11 6 7.5 4.1 | 20.9 69.6 270 12 6 8.4 4.6
8000 20.9 69.6 250 10 5 9.2 5.0 | 21.6 70.9 270 11 6 9.8 5.4
7750 21.6 70.9 255 10 5 8.7 4.8 | 22.3 72.1 270 11 6 9.3 5.1
7500 22.2 72.0 255 10 5 8.1 4.4 | 23.0 73.4 270 11 6 8.4 4.6
7250 22.8 73.0 255 10 5 8.7 4.8 | 23.6 74.5 275 12 6 8.7 4.8
7000 23.6 74.5 255 10 5 11.3 6.2 | 24.3 75.7 275 12 6 10.6 5.8
6750 24.4 75.9 255 9 5 11.5 6.3 | 25.2 77.4 275 11 6 11.1 6.1
6500 25.3 77.5 255 9 5 10.7 5.9 | 26.0 78.8 275 11 6 10.6 5.8
6250 26.1 79.0 255 9 5 10.3 5.7 | 26.8 80.2 275 11 6 10.9 6.0
6000 26.8 80.2 255 9 5 10.6 5.8 | 27.5 81.5 280 11 6 8.2 4.5
5750 27.8 82.0 260 8 4 19.6 10.8 | 28.1 82.6 275 9 5 10.5 5.7
5500 30.3 86.5 260 8 4 50.8 27.9 | 30.2 86.4 285 9 5 57.1 31.3
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
________________________________________________________________________________
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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