Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
167
UXUS97 KGJT 131306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Monday, October 13, 2025
This forecast is for Monday, October 13, 2025:
If the trigger temperature of 63.4 F/17.5 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 107 ft/min (0.5 m/s)
Maximum height of thermals.................. 9843 ft MSL (4235 ft AGL)
Forecast maximum temperature................... 64.0 F/18.2 C
Time of trigger temperature.................... 1445 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 7059 ft MSL (1451 ft AGL)
Thermal soaring outlook for Tuesday 10/14...... Good
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:22:23 / 18:38:04 MDT
Total possible sunshine........... 11 hr 15 min 41 sec (675 min 41 sec)
Altitude of sun at 13:00:14 MDT... 42.80 degrees
Upper air data from rawinsonde observation taken on 10/13/2025 at 0600 MDT
Freezing level.................. 12744 ft MSL (7136 ft AGL)
Convective condensation level... 11019 ft MSL (5411 ft AGL)
Lifted condensation level....... 10449 ft MSL (4841 ft AGL)
Lifted index.................... -0.5
K index......................... +25.8
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 -63.3 -81.9 215 66 34 1.6 0.9 M M M M M
45000 -59.9 -75.8 220 103 53 5.0 2.7 M M M M M
40000 -52.4 -62.3 220 120 62 5.4 3.0 M M M M M
38000 -48.6 -55.5 215 122 63 6.4 3.5 M M M M M
36000 -44.7 -48.5 215 123 63 6.4 3.5 M M M M M
34000 -40.5 -40.9 215 120 62 6.3 3.5 M M M M M
32000 -36.7 -34.1 215 115 59 6.3 3.5 M M M M M
30000 -33.7 -28.7 215 101 52 3.9 2.2 42.3 108.1 18.6 M M
29000 -32.5 -26.5 215 91 47 4.0 2.2 39.9 103.9 17.0 M M
28000 -31.3 -24.3 215 80 41 4.1 2.2 37.8 100.1 15.5 M M
27000 -29.7 -21.5 215 73 37 6.9 3.8 36.2 97.1 14.4 M M
26000 -27.6 -17.7 215 68 35 7.0 3.8 35.1 95.1 13.7 M M
25000 -25.5 -13.9 215 64 33 7.0 3.8 34.1 93.4 13.1 M M
24000 -23.5 -10.3 215 60 31 7.1 3.9 33.1 91.7 12.4 M M
23000 -21.3 -6.3 215 58 30 7.1 3.9 32.1 89.8 11.7 M M
22000 -19.2 -2.6 215 57 29 7.1 3.9 31.2 88.2 11.1 M M
21000 -17.0 1.4 215 55 28 7.8 4.3 30.4 86.7 10.5 M M
20000 -14.1 6.6 210 54 28 7.8 4.3 29.5 85.1 9.8 M M
19500 -13.0 8.6 210 53 27 7.8 4.3 29.2 84.5 9.6 M M
19000 -11.8 10.8 210 52 27 7.4 4.1 28.9 84.0 9.4 M M
18500 -10.8 12.6 210 51 26 7.1 3.9 28.4 83.1 9.0 M M
18000 -9.8 14.4 210 50 26 7.2 3.9 27.9 82.3 8.6 M M
17500 -8.8 16.2 210 48 25 6.1 3.3 27.4 81.3 8.1 M M
17000 -8.0 17.6 210 46 24 6.2 3.4 26.8 80.2 7.6 M M
16500 -7.1 19.2 210 44 23 6.2 3.4 26.2 79.1 7.0 M M
16000 -6.2 20.8 210 42 22 6.2 3.4 25.6 78.0 6.5 M M
15500 -5.4 22.3 205 40 21 6.4 3.5 25.0 77.0 5.9 M M
15000 -4.4 24.1 210 39 20 7.2 3.9 24.5 76.1 5.5 M M
14500 -3.4 25.9 210 39 20 7.2 4.0 24.1 75.3 5.0 M M
14000 -2.4 27.7 210 39 20 6.5 3.6 23.6 74.5 4.6 M M
13500 -1.4 29.5 210 40 21 6.5 3.6 23.1 73.5 4.1 M M
13000 -0.5 31.1 210 41 21 6.7 3.7 22.6 72.6 3.6 M M
12500 0.5 32.9 210 41 21 6.7 3.7 22.1 71.7 3.1 M M
12000 1.4 34.5 210 41 21 6.0 3.3 21.5 70.8 2.7 M M
11500 2.3 36.1 205 42 21 5.8 3.2 20.9 69.6 2.0 M M
11000 3.1 37.6 205 42 22 5.5 3.0 20.3 68.5 1.4 M M
10500 3.9 39.0 205 43 22 6.1 3.4 19.6 67.2 0.7 M M
10250 4.4 39.9 205 42 22 7.4 4.0 19.3 66.8 0.5 M M
10000 4.8 40.6 200 42 21 6.3 3.5 19.1 66.4 0.3 M M
9750 5.2 41.4 200 41 21 5.7 3.1 18.8 65.9 -0.1 303 1.5
9500 5.6 42.1 200 40 21 5.8 3.2 18.5 65.3 -0.4 283 1.4
9250 6.0 42.8 200 39 20 6.1 3.3 18.2 64.8 -0.7 264 1.3
9000 6.5 43.7 195 37 19 6.7 3.7 17.9 64.3 -1.0 243 1.2
8750 7.0 44.6 195 35 18 6.8 3.7 17.7 63.9 -1.3 221 1.1
8500 7.5 45.5 195 33 17 6.9 3.8 17.5 63.5 -1.5 199 1.0
8250 7.9 46.2 190 32 16 6.6 3.6 17.3 63.1 -1.8 178 0.9
8000 8.4 47.1 190 30 15 6.5 3.6 17.0 62.6 -2.0 156 0.8
7750 8.9 48.0 190 28 14 6.6 3.6 16.8 62.2 -2.3 135 0.7
7500 9.4 48.9 185 25 13 6.6 3.6 16.5 61.8 -2.5 113 0.6
7250 9.9 49.8 180 23 12 7.5 4.1 16.3 61.4 -2.8 91 0.5
7000 10.4 50.7 180 22 11 6.4 3.5 16.2 61.1 -3.0 67 0.3
6750 10.8 51.4 175 20 10 5.4 3.0 15.8 60.5 -3.3 48 0.2
6500 11.2 52.2 170 18 9 4.3 2.4 15.5 59.9 -3.7 29 0.1
6250 11.4 52.5 165 15 8 1.2 0.7 15.0 58.9 -4.2 16 0.1
6000 11.5 52.7 160 13 6 3.1 1.7 14.3 57.8 -4.8 6 0.0
5750 11.7 53.1 150 10 5 0.6 0.3 13.8 56.9 -5.4 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 * * * * * *
10/13/2025 at 0900 MDT | 10/13/2025 at 1200 MDT
|
CAPE... 0.0 LI... -0.5 | CAPE... +0.4 LI... +0.4
CINH... -0.2 K Index... +28.2 | CINH... 0.0 K Index... +27.9
|
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 -61.6 -78.9 230 79 41 0.9 0.5 | -62.9 -81.2 235 81 42 1.0 0.6
45000 -59.5 -75.1 235 113 58 4.9 2.7 | -60.4 -76.7 235 111 57 5.7 3.1
40000 -52.2 -62.0 230 124 64 4.9 2.7 | -51.4 -60.5 230 129 66 4.9 2.7
38000 -50.5 -58.9 230 112 58 1.8 1.0 | -49.9 -57.8 225 113 58 2.4 1.3
36000 -49.4 -56.9 230 98 50 1.9 1.0 | -48.5 -55.3 225 97 50 2.4 1.3
34000 -46.5 -51.7 225 89 46 7.9 4.3 | -45.5 -49.9 225 85 44 7.4 4.0
32000 -41.8 -43.2 225 86 44 7.9 4.3 | -41.1 -42.0 220 78 40 7.4 4.0
30000 -37.1 -34.8 225 82 42 7.8 4.3 | -36.6 -33.9 220 73 38 7.9 4.3
29000 -34.7 -30.5 225 79 41 7.8 4.3 | -34.2 -29.6 220 71 37 7.9 4.3
28000 -32.4 -26.3 225 77 40 7.9 4.3 | -31.9 -25.4 220 69 36 7.9 4.3
27000 -30.1 -22.2 225 75 39 7.2 3.9 | -29.5 -21.1 220 67 35 7.7 4.2
26000 -28.0 -18.4 220 72 37 7.2 4.0 | -27.2 -17.0 215 66 34 7.8 4.3
25000 -25.8 -14.4 220 70 36 7.2 4.0 | -24.9 -12.8 215 65 33 7.8 4.3
24000 -23.2 -9.8 220 67 34 6.6 3.6 | -22.1 -7.8 215 63 32 7.4 4.1
23000 -21.2 -6.2 215 64 33 6.7 3.7 | -19.8 -3.6 215 61 31 7.5 4.1
22000 -19.2 -2.6 215 62 32 6.7 3.7 | -17.6 0.3 210 60 31 7.5 4.1
21000 -17.2 1.0 215 60 31 7.1 3.9 | -15.5 4.1 210 58 30 7.0 3.8
20000 -15.1 4.8 215 57 29 7.2 3.9 | -13.5 7.7 210 57 29 7.0 3.9
19500 -14.1 6.6 215 55 29 7.2 3.9 | -12.5 9.5 210 56 29 7.1 3.9
19000 -13.1 8.4 215 54 28 7.2 4.0 | -11.5 11.3 210 55 28 7.1 3.9
18500 -12.0 10.4 215 53 27 7.3 4.0 | -10.6 12.9 210 54 28 5.8 3.2
18000 -10.9 12.4 215 51 26 7.3 4.0 | -9.7 14.5 210 53 27 6.0 3.3
17500 -9.9 14.2 215 50 26 6.9 3.8 | -8.9 16.0 215 52 27 5.7 3.1
17000 -8.9 16.0 215 48 25 6.6 3.6 | -8.1 17.4 215 51 26 5.6 3.1
16500 -8.0 17.6 215 46 24 6.6 3.6 | -7.3 18.9 215 49 25 5.6 3.1
16000 -7.1 19.2 215 45 23 6.0 3.3 | -6.4 20.5 215 47 24 5.9 3.2
15500 -6.2 20.8 215 43 22 6.0 3.3 | -5.6 21.9 215 45 23 5.9 3.2
15000 -5.3 22.5 215 41 21 6.1 3.4 | -4.7 23.5 215 43 22 6.4 3.5
14500 -4.4 24.1 215 39 20 6.2 3.4 | -3.8 25.2 220 40 21 6.4 3.5
14000 -3.6 25.5 215 37 19 6.2 3.4 | -2.9 26.8 220 38 19 6.1 3.3
13500 -2.7 27.1 215 35 18 6.2 3.4 | -2.0 28.4 220 35 18 5.9 3.2
13000 -1.8 28.8 215 33 17 6.2 3.4 | -1.2 29.8 215 33 17 5.7 3.1
12500 -0.9 30.4 215 31 16 6.1 3.4 | -0.4 31.3 215 30 16 5.5 3.0
12000 -0.0 32.0 215 30 15 6.2 3.4 | 0.4 32.7 215 28 15 5.7 3.1
11500 0.9 33.6 210 29 15 6.3 3.4 | 1.2 34.2 215 26 14 6.0 3.3
11000 1.8 35.2 210 28 14 5.9 3.3 | 2.1 35.8 215 25 13 5.5 3.0
10500 2.5 36.5 205 27 14 4.9 2.7 | 2.8 37.0 215 23 12 4.3 2.4
10250 2.9 37.2 205 27 14 6.0 3.3 | 3.1 37.6 215 23 12 5.7 3.1
10000 3.4 38.1 205 26 13 7.1 3.9 | 3.6 38.5 210 22 11 6.6 3.6
9750 3.9 39.0 200 25 13 6.4 3.5 | 4.0 39.2 210 21 11 5.3 2.9
9500 4.3 39.7 200 24 12 5.9 3.3 | 4.4 39.9 205 20 10 4.8 2.7
9250 4.8 40.6 195 24 12 6.4 3.5 | 4.7 40.5 205 19 10 5.5 3.0
9000 5.2 41.4 195 23 12 5.0 2.7 | 5.1 41.2 200 18 9 3.3 1.8
8750 5.9 42.6 190 21 11 5.2 2.9 | 5.3 41.5 195 17 9 2.9 1.6
8500 6.3 43.3 185 20 10 4.9 2.7 | 5.6 42.1 190 15 8 4.8 2.6
8250 6.7 44.1 185 19 10 4.3 2.4 | 6.2 43.2 180 13 7 3.5 1.9
8000 7.0 44.6 180 19 10 3.9 2.1 | 6.4 43.5 175 13 7 3.7 2.0
7750 7.3 45.1 175 17 9 4.1 2.3 | 6.8 44.2 170 12 6 4.5 2.5
7500 7.6 45.7 165 15 8 3.8 2.1 | 7.1 44.8 160 11 5 3.9 2.1
7250 7.9 46.2 160 15 8 3.1 1.7 | 7.3 45.1 155 11 5 3.1 1.7
7000 8.2 46.8 160 15 8 3.6 2.0 | 7.6 45.7 150 11 6 3.8 2.1
6750 8.5 47.3 155 12 6 4.2 2.3 | 7.9 46.2 145 9 5 4.4 2.4
6500 8.8 47.8 145 10 5 2.8 1.6 | 8.2 46.8 140 8 4 4.0 2.2
6250 8.9 48.0 140 9 5 1.2 0.7 | 8.5 47.3 135 7 4 3.2 1.8
6000 9.1 48.4 130 9 5 3.5 1.9 | 8.8 47.8 130 6 3 5.4 3.0
5750 9.3 48.7 120 6 3 1.7 0.9 | 9.3 48.7 125 5 3 8.1 4.5
5500 8.5 47.3 095 5 2 -35.7 -19.6 | 9.4 48.9 100 4 2 -11.4 -6.2
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
10/13/2025 at 1500 MDT | 10/13/2025 at 1800 MDT
|
CAPE... +23.3 LI... -1.0 | CAPE... +100.8 LI... -0.7
CINH... -1.6 K Index... +28.8 | CINH... -3.8 K Index... +26.1
|
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 -63.0 -81.4 230 82 42 1.2 0.6 | -63.6 -82.5 230 79 41 1.4 0.8
45000 -60.3 -76.5 230 111 57 5.6 3.0 | -60.5 -76.9 230 108 55 5.5 3.0
40000 -51.6 -60.9 225 127 65 5.1 2.8 | -51.9 -61.4 225 125 64 5.5 3.0
38000 -49.0 -56.2 225 118 61 4.3 2.4 | -48.6 -55.5 225 121 62 5.4 3.0
36000 -46.4 -51.5 225 108 56 4.3 2.4 | -45.4 -49.7 225 117 60 5.4 3.0
34000 -43.5 -46.3 225 95 49 5.3 2.9 | -42.3 -44.1 220 106 55 4.7 2.6
32000 -40.3 -40.5 220 79 41 5.3 2.9 | -39.5 -39.1 220 90 47 4.7 2.6
30000 -36.4 -33.5 215 69 35 8.0 4.4 | -35.8 -32.4 215 79 41 7.6 4.2
29000 -34.0 -29.2 215 67 35 8.0 4.4 | -33.6 -28.5 215 76 39 7.6 4.2
28000 -31.7 -25.1 215 66 34 8.0 4.4 | -31.3 -24.3 215 73 38 7.6 4.2
27000 -29.3 -20.7 210 64 33 7.7 4.2 | -29.0 -20.2 210 70 36 7.6 4.1
26000 -27.0 -16.6 215 64 33 7.7 4.2 | -26.2 -15.2 215 68 35 7.6 4.1
25000 -24.2 -11.6 215 63 32 7.7 4.2 | -23.9 -11.0 215 67 34 7.6 4.1
24000 -21.9 -7.4 215 62 32 7.2 4.0 | -21.7 -7.1 215 65 33 7.0 3.8
23000 -19.8 -3.6 215 60 31 7.3 4.0 | -19.6 -3.3 215 63 32 7.0 3.9
22000 -17.6 0.3 215 59 30 7.3 4.0 | -17.5 0.5 215 61 31 7.0 3.9
21000 -15.6 3.9 215 58 30 6.7 3.7 | -15.4 4.3 215 59 31 7.1 3.9
20000 -13.6 7.5 215 56 29 6.7 3.7 | -13.3 8.1 215 58 30 7.2 3.9
19500 -12.6 9.3 215 56 29 6.8 3.7 | -12.2 10.0 215 57 29 7.2 3.9
19000 -11.7 10.9 215 55 28 6.8 3.7 | -11.1 12.0 215 56 29 7.2 3.9
18500 -10.7 12.7 215 54 28 6.9 3.8 | -10.2 13.6 215 55 28 6.4 3.5
18000 -9.7 14.5 215 53 27 6.9 3.8 | -9.2 15.4 215 54 28 6.5 3.6
17500 -8.7 16.3 215 52 27 6.5 3.6 | -8.3 17.1 215 53 27 6.4 3.5
17000 -7.8 18.0 215 51 26 6.4 3.5 | -7.4 18.7 215 52 27 6.4 3.5
16500 -6.9 19.6 210 50 26 6.3 3.5 | -6.5 20.3 215 51 26 6.4 3.5
16000 -6.0 21.2 210 48 25 6.0 3.3 | -5.6 21.9 215 49 25 6.1 3.3
15500 -5.1 22.8 210 46 24 6.1 3.3 | -4.8 23.4 215 47 24 6.2 3.4
15000 -4.2 24.4 210 44 23 6.1 3.3 | -4.0 24.8 215 46 24 6.0 3.3
14500 -3.4 25.9 210 42 22 6.1 3.4 | -3.1 26.4 215 44 23 6.0 3.3
14000 -2.5 27.5 210 40 20 6.3 3.5 | -2.3 27.9 210 42 22 6.2 3.4
13500 -1.6 29.1 210 38 19 6.4 3.5 | -1.4 29.5 210 41 21 6.3 3.5
13000 -0.7 30.7 210 35 18 6.2 3.4 | -0.5 31.1 210 39 20 6.4 3.5
12500 0.2 32.4 210 33 17 6.1 3.3 | 0.4 32.7 210 38 19 6.4 3.5
12000 1.0 33.8 210 31 16 6.1 3.3 | 1.3 34.3 205 36 19 6.6 3.6
11500 1.9 35.4 205 29 15 6.2 3.4 | 2.3 36.1 205 35 18 6.9 3.8
11000 2.8 37.0 205 27 14 5.9 3.3 | 3.3 37.9 205 33 17 6.4 3.5
10500 3.6 38.5 205 25 13 5.2 2.9 | 4.0 39.2 200 32 16 4.6 2.5
10250 4.0 39.2 205 24 13 5.6 3.1 | 4.4 39.9 200 31 16 7.1 3.9
10000 4.4 39.9 205 23 12 5.3 2.9 | 5.0 41.0 200 29 15 8.5 4.6
9750 4.7 40.5 200 22 11 4.4 2.4 | 5.5 41.9 195 28 14 5.8 3.2
9500 5.0 41.0 200 20 10 4.4 2.4 | 5.9 42.6 195 27 14 5.3 2.9
9250 5.3 41.5 200 19 10 4.1 2.3 | 6.6 43.9 195 24 12 5.6 3.1
9000 5.6 42.1 195 18 9 5.0 2.8 | 7.0 44.6 190 22 11 4.7 2.6
8750 6.3 43.3 190 15 8 3.4 1.9 | 7.3 45.1 185 20 10 3.8 2.1
8500 6.5 43.7 180 13 7 3.6 2.0 | 7.6 45.7 180 18 9 4.0 2.2
8250 6.8 44.2 175 13 6 3.1 1.7 | 7.9 46.2 180 17 9 4.8 2.7
8000 7.0 44.6 175 12 6 4.3 2.3 | 8.3 46.9 175 16 8 5.1 2.8
7750 7.4 45.3 165 11 5 5.3 2.9 | 8.6 47.5 170 14 7 4.5 2.5
7500 7.8 46.0 160 9 5 4.7 2.6 | 9.0 48.2 165 12 6 5.1 2.8
7250 8.1 46.6 155 9 5 3.7 2.0 | 9.4 48.9 160 11 6 6.2 3.4
7000 8.4 47.1 155 9 5 5.3 2.9 | 9.8 49.6 155 10 5 5.4 2.9
6750 8.8 47.8 145 7 4 6.9 3.8 | 10.1 50.2 145 8 4 4.5 2.5
6500 9.3 48.7 130 6 3 5.1 2.8 | 10.5 50.9 130 7 3 4.4 2.4
6250 9.6 49.3 125 5 3 3.2 1.8 | 10.7 51.3 120 6 3 3.5 1.9
6000 9.9 49.8 115 5 3 6.3 3.5 | 11.0 51.8 110 6 3 5.3 2.9
5750 10.5 50.9 105 3 2 10.5 5.8 | 11.5 52.7 105 4 2 6.9 3.8
5500 10.9 51.6 080 4 2 -6.5 -3.6 | 11.6 52.9 085 4 2 -8.9 -4.9
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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