Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
170
UXUS97 KGJT 091306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
606 AM MST Sunday, November 9, 2025
This forecast is for Sunday, November 9, 2025:
If the trigger temperature of 62.9 F/17.2 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 245 ft/min (1.2 m/s)
Maximum height of thermals.................. 8856 ft MSL (3248 ft AGL)
Forecast maximum temperature................... 60.0 F/16.0 C
Time of trigger temperature.................... None
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................. 7451 ft MSL (1843 ft AGL)
Thermal soaring outlook for Monday 11/10....... Fair
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:51:14 / 17:04:40 MST
Total possible sunshine........... 10 hr 13 min 26 sec (613 min 26 sec)
Altitude of sun at 11:57:57 MST... 33.79 degrees
Upper air data from rawinsonde observation taken on 11/09/2025 at 0500 MST
Freezing level.................. 12769 ft MSL (7161 ft AGL)
Convective condensation level... 23496 ft MSL (17888 ft AGL)
Lifted condensation level....... 16499 ft MSL (10891 ft AGL)
Lifted index.................... +13.0
K index......................... +3.8
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 -68.5 -91.3 330 56 29 -1.5 -0.8 M M M M M
45000 -69.2 -92.6 340 50 26 5.3 2.9 M M M M M
40000 -61.3 -78.3 340 53 27 6.2 3.4 M M M M M
38000 -56.7 -70.1 340 51 26 7.7 4.2 M M M M M
36000 -51.5 -60.7 350 50 25 7.8 4.3 M M M M M
34000 -46.3 -51.3 350 46 24 8.8 4.8 M M M M M
32000 -41.1 -42.0 350 42 22 8.8 4.8 M M M M M
30000 -36.0 -32.8 350 39 20 8.4 4.6 39.3 102.7 18.0 M M
29000 -33.5 -28.3 350 37 19 8.4 4.6 38.8 101.8 17.8 M M
28000 -30.9 -23.6 350 36 18 8.4 4.6 38.4 101.1 17.7 M M
27000 -28.5 -19.3 350 35 18 8.0 4.4 37.6 99.7 17.3 M M
26000 -26.1 -15.0 355 35 18 8.0 4.4 36.9 98.5 17.0 M M
25000 -23.8 -10.8 355 35 18 8.0 4.4 36.4 97.5 16.7 M M
24000 -21.4 -6.5 355 35 18 7.8 4.3 35.6 96.1 16.3 M M
23000 -19.1 -2.4 360 34 17 7.8 4.3 34.9 94.8 15.9 M M
22000 -16.7 1.9 360 33 17 7.9 4.3 34.2 93.6 15.5 M M
21000 -14.2 6.4 005 31 16 6.7 3.7 32.9 91.3 14.6 M M
20000 -12.2 10.0 005 29 15 6.7 3.7 31.9 89.4 13.8 M M
19500 -11.2 11.8 005 29 15 6.7 3.7 31.4 88.5 13.5 M M
19000 -10.3 13.5 005 28 14 5.4 3.0 30.7 87.3 13.0 M M
18500 -9.5 14.9 005 27 14 5.6 3.0 30.0 86.0 12.4 M M
18000 -8.7 16.3 005 26 13 5.2 2.9 29.3 84.7 11.8 M M
17500 -8.0 17.6 360 25 13 5.0 2.8 28.5 83.2 11.1 M M
17000 -7.2 19.0 360 24 12 5.1 2.8 27.7 81.8 10.5 M M
16500 -6.5 20.3 355 23 12 5.4 3.0 26.9 80.4 9.8 M M
16000 -5.7 21.7 355 22 11 5.4 3.0 26.2 79.1 9.2 M M
15500 -4.9 23.2 350 21 11 5.9 3.3 25.5 77.9 8.6 M M
15000 -4.0 24.8 345 20 10 5.9 3.3 24.8 76.7 8.0 M M
14500 -3.1 26.4 340 19 10 5.9 3.2 24.2 75.6 7.5 M M
14000 -2.2 28.0 335 18 9 5.9 3.2 23.6 74.4 7.0 M M
13500 -1.4 29.5 330 18 9 6.0 3.3 22.9 73.3 6.4 M M
13000 -0.4 31.3 330 17 9 6.1 3.4 22.3 72.2 5.9 M M
12500 0.5 32.9 325 16 8 6.2 3.4 21.8 71.2 5.4 M M
12000 1.4 34.5 320 15 8 6.2 3.4 21.2 70.2 4.9 M M
11500 2.4 36.3 320 13 7 5.8 3.2 20.6 69.2 4.4 M M
11000 3.1 37.6 315 12 6 5.1 2.8 19.9 67.9 3.7 M M
10500 3.9 39.0 310 10 5 5.1 2.8 19.2 66.6 3.1 M M
10250 4.3 39.7 310 9 5 4.5 2.4 18.8 65.9 2.7 M M
10000 4.6 40.3 310 8 4 3.9 2.1 18.4 65.0 2.3 M M
9750 4.9 40.8 305 7 4 4.2 2.3 17.9 64.2 1.9 M M
9500 5.2 41.4 300 6 3 3.3 1.8 17.5 63.4 1.4 M M
9250 5.4 41.7 300 5 3 2.5 1.4 16.9 62.4 0.9 M M
9000 5.6 42.1 295 4 2 3.0 1.6 16.4 61.5 0.4 M M
8750 5.8 42.4 290 3 2 2.9 1.6 15.8 60.5 -0.1 242 1.2
8500 6.1 43.0 280 2 1 2.6 1.4 15.3 59.5 -0.6 228 1.2
8250 6.2 43.2 260 1 1 2.4 1.3 14.7 58.5 -1.1 215 1.1
8000 6.5 43.7 210 1 0 2.7 1.5 14.2 57.5 -1.7 202 1.0
7750 6.7 44.1 170 1 1 2.8 1.5 13.6 56.6 -2.2 188 1.0
7500 6.9 44.4 150 2 1 2.7 1.5 13.1 55.6 -2.7 174 0.9
7250 7.1 44.8 145 3 1 2.8 1.5 12.6 54.6 -3.3 161 0.8
7000 7.3 45.1 140 4 2 2.3 1.3 12.0 53.7 -3.8 147 0.7
6750 7.4 45.3 130 4 2 -0.4 -0.2 11.4 52.5 -4.4 137 0.7
6500 7.2 45.0 125 4 2 -2.8 -1.5 10.5 50.9 -5.3 134 0.7
6250 7.1 44.8 125 5 2 0.0 0.0 9.6 49.3 -6.2 131 0.7
6000 6.9 44.4 120 5 3 -8.9 -4.9 8.7 47.7 -7.1 128 0.7
5750 5.3 41.5 115 4 2 -35.1 -19.3 6.4 43.5 -9.5 170 0.9
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 * * * * * *
11/09/2025 at 0800 MST | 11/09/2025 at 1100 MST
|
CAPE... 0.0 LI... +9.7 | CAPE... 0.0 LI... +8.6
CINH... -0.1 K Index... -6.9 | CINH... -0.1 K Index... -6.0
|
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 -66.9 -88.4 330 62 32 -1.4 -0.8 | -68.3 -90.9 335 66 34 -1.9 -1.0
45000 -68.6 -91.5 340 69 35 3.8 2.1 | -70.4 -94.7 340 71 37 5.2 2.9
40000 -63.2 -81.8 345 67 35 3.7 2.0 | -62.6 -80.7 345 64 33 5.5 3.0
38000 -58.4 -73.1 345 64 33 8.4 4.6 | -57.9 -72.2 345 60 31 8.0 4.4
36000 -53.4 -64.1 345 61 31 8.4 4.6 | -53.1 -63.6 345 55 28 8.0 4.4
34000 -48.4 -55.1 345 59 30 8.2 4.5 | -48.2 -54.8 345 52 27 8.4 4.6
32000 -43.4 -46.1 340 58 30 8.2 4.5 | -43.1 -45.6 340 50 26 8.4 4.6
30000 -38.6 -37.5 340 56 29 7.9 4.3 | -38.2 -36.8 340 48 24 8.1 4.5
29000 -36.2 -33.2 340 53 27 7.9 4.3 | -35.7 -32.3 340 46 24 8.1 4.5
28000 -33.8 -28.8 340 51 26 7.9 4.3 | -33.3 -27.9 340 45 23 8.1 4.5
27000 -31.5 -24.7 335 49 25 7.6 4.2 | -30.8 -23.4 335 44 22 8.2 4.5
26000 -28.7 -19.7 330 47 24 7.6 4.2 | -27.8 -18.0 335 42 22 8.2 4.5
25000 -26.4 -15.5 325 46 24 7.6 4.2 | -25.3 -13.5 335 41 21 8.4 4.6
24000 -24.2 -11.6 325 45 23 7.1 3.9 | -23.2 -9.8 330 40 21 6.5 3.5
23000 -22.1 -7.8 325 43 22 7.1 3.9 | -21.3 -6.3 330 39 20 6.5 3.5
22000 -19.9 -3.8 325 42 21 7.1 3.9 | -19.3 -2.7 330 38 20 6.5 3.5
21000 -17.7 0.1 325 40 20 7.6 4.2 | -17.4 0.7 330 37 19 6.6 3.6
20000 -15.4 4.3 330 37 19 7.6 4.2 | -15.4 4.3 330 35 18 6.6 3.6
19500 -14.3 6.3 330 36 19 7.6 4.2 | -14.4 6.1 330 35 18 6.6 3.6
19000 -13.1 8.4 330 36 18 7.5 4.1 | -13.4 7.9 330 34 17 7.2 4.0
18500 -12.0 10.4 335 35 18 7.5 4.1 | -12.3 9.9 330 33 17 7.3 4.0
18000 -10.9 12.4 335 35 18 7.5 4.1 | -11.2 11.8 335 33 17 7.3 4.0
17500 -9.8 14.4 340 35 18 7.3 4.0 | -10.2 13.6 335 32 16 7.1 3.9
17000 -8.7 16.3 340 36 18 7.3 4.0 | -9.1 15.6 340 32 16 7.2 3.9
16500 -7.7 18.1 340 36 18 6.8 3.7 | -8.1 17.4 340 31 16 7.0 3.8
16000 -6.7 19.9 345 36 18 6.8 3.7 | -7.0 19.4 345 31 16 7.0 3.9
15500 -5.7 21.7 345 36 18 6.3 3.5 | -6.0 21.2 345 30 16 6.6 3.6
15000 -4.8 23.4 345 35 18 6.0 3.3 | -5.0 23.0 350 30 15 6.3 3.5
14500 -3.9 25.0 350 35 18 5.7 3.1 | -4.1 24.6 350 29 15 6.0 3.3
14000 -3.2 26.2 350 33 17 4.8 2.6 | -3.3 26.1 350 28 15 5.5 3.0
13500 -2.4 27.7 350 32 17 4.7 2.6 | -2.5 27.5 355 27 14 5.2 2.9
13000 -1.9 28.6 350 30 16 3.3 1.8 | -1.8 28.8 355 26 13 4.1 2.3
12500 -1.3 29.7 350 28 14 3.4 1.9 | -1.2 29.8 355 24 12 4.1 2.2
12000 -0.9 30.4 350 25 13 2.2 1.2 | -0.6 30.9 350 22 11 3.3 1.8
11500 -0.6 30.9 350 22 12 2.3 1.3 | -0.1 31.8 350 20 10 3.3 1.8
11000 -0.2 31.6 355 19 10 2.1 1.2 | 0.4 32.7 350 17 9 2.6 1.4
10500 0.1 32.2 355 16 8 2.1 1.2 | 0.8 33.4 355 15 8 2.6 1.4
10250 0.2 32.4 355 14 7 0.8 0.4 | 0.9 33.6 355 13 7 1.7 0.9
10000 0.2 32.4 355 13 6 1.8 1.0 | 1.1 34.0 355 12 6 2.6 1.4
9750 0.5 32.9 360 11 6 4.3 2.3 | 1.3 34.3 355 11 5 4.0 2.2
9500 0.8 33.4 005 10 5 4.5 2.5 | 1.6 34.9 360 9 5 4.2 2.3
9250 1.2 34.2 010 9 4 4.8 2.6 | 2.0 35.6 360 8 4 4.8 2.6
9000 1.9 35.4 020 6 3 3.4 1.9 | 2.3 36.1 005 7 4 4.7 2.6
8750 2.1 35.8 030 7 4 4.5 2.5 | 2.9 37.2 015 6 3 4.7 2.6
8500 2.5 36.5 040 7 3 6.1 3.4 | 3.4 38.1 020 5 3 5.9 3.3
8250 3.0 37.4 045 7 3 6.3 3.5 | 3.8 38.8 030 5 3 5.5 3.0
8000 3.4 38.1 050 7 3 3.1 1.7 | 4.2 39.6 035 5 2 5.1 2.8
7750 3.5 38.3 055 7 4 2.7 1.5 | 4.6 40.3 040 4 2 5.5 3.0
7500 3.9 39.0 060 7 3 5.3 2.9 | 5.0 41.0 040 4 2 7.1 3.9
7250 4.2 39.6 065 7 3 5.1 2.8 | 5.5 41.9 045 3 2 3.7 2.0
7000 4.6 40.3 070 7 3 4.9 2.7 | 5.7 42.3 050 3 2 5.0 2.7
6750 4.9 40.8 070 7 4 2.2 1.2 | 6.3 43.3 050 3 1 9.3 5.1
6500 5.0 41.0 075 6 3 1.6 0.9 | 6.9 44.4 050 2 1 8.9 4.9
6250 5.1 41.2 085 5 3 0.7 0.4 | 7.6 45.7 050 2 1 7.5 4.1
6000 4.9 40.8 085 6 3 -7.1 -3.9 | 8.2 46.8 055 2 1 11.0 6.0
5750 4.0 39.2 085 4 2 -16.3 -8.9 | 9.4 48.9 060 2 1 21.9 12.0
5500 3.0 37.4 100 2 1 -2.6 -1.4 | 10.7 51.3 060 2 1 1.8 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
11/09/2025 at 1400 MST | 11/09/2025 at 1700 MST
|
CAPE... 0.0 LI... +7.1 | CAPE... 0.0 LI... +6.7
CINH... -0.3 K Index... -4.0 | CINH... -0.2 K Index... -1.0
|
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 -68.9 -92.0 340 65 34 -2.4 -1.3 | -68.6 -91.5 335 61 31 -1.6 -0.9
45000 -71.1 -96.0 345 73 38 6.3 3.4 | -69.6 -93.3 340 66 34 5.4 3.0
40000 -61.5 -78.7 350 67 35 6.5 3.6 | -61.4 -78.5 340 62 32 6.0 3.3
38000 -57.0 -70.6 345 62 32 7.6 4.2 | -56.6 -69.9 340 60 31 8.1 4.5
36000 -52.5 -62.5 345 55 28 7.6 4.2 | -51.2 -60.2 345 57 29 8.1 4.5
34000 -47.2 -53.0 345 50 26 8.1 4.4 | -46.5 -51.7 345 52 27 7.7 4.2
32000 -42.4 -44.3 345 46 24 8.1 4.4 | -41.9 -43.4 350 45 23 7.7 4.2
30000 -37.5 -35.5 340 43 22 8.2 4.5 | -37.1 -34.8 350 41 21 8.1 4.4
29000 -35.0 -31.0 340 42 22 8.2 4.5 | -34.7 -30.5 350 40 20 8.1 4.5
28000 -32.6 -26.7 340 41 21 8.3 4.5 | -32.3 -26.1 350 38 20 8.1 4.4
27000 -30.2 -22.4 340 39 20 7.9 4.4 | -29.8 -21.6 350 37 19 8.2 4.5
26000 -27.8 -18.0 340 38 19 7.9 4.4 | -27.4 -17.3 350 36 18 8.2 4.5
25000 -25.4 -13.7 335 36 19 7.9 4.3 | -24.9 -12.8 345 34 18 8.2 4.5
24000 -23.3 -9.9 335 35 18 6.6 3.6 | -22.6 -8.7 345 33 17 7.5 4.1
23000 -21.3 -6.3 335 34 18 6.5 3.6 | -20.4 -4.7 345 32 16 7.5 4.1
22000 -19.4 -2.9 335 33 17 6.6 3.6 | -17.6 0.3 345 30 15 7.0 3.9
21000 -17.1 1.2 335 32 17 6.1 3.3 | -16.0 3.2 345 29 15 5.3 2.9
20000 -15.3 4.5 335 32 16 6.1 3.3 | -14.4 6.1 340 28 15 5.3 2.9
19500 -14.4 6.1 335 31 16 6.0 3.3 | -13.6 7.5 340 28 14 5.3 2.9
19000 -13.4 7.9 335 31 16 7.0 3.8 | -12.8 9.0 340 28 14 5.8 3.2
18500 -12.4 9.7 335 31 16 7.0 3.8 | -12.0 10.4 340 27 14 5.8 3.2
18000 -11.4 11.5 335 30 15 7.1 3.9 | -11.1 12.0 340 27 14 6.1 3.3
17500 -10.3 13.5 335 29 15 7.2 4.0 | -10.2 13.6 340 27 14 6.5 3.6
17000 -9.3 15.3 340 29 15 7.2 4.0 | -9.2 15.4 340 26 14 6.5 3.6
16500 -8.2 17.2 340 28 15 7.3 4.0 | -8.2 17.2 345 26 13 6.6 3.6
16000 -7.1 19.2 345 28 14 7.3 4.0 | -7.2 19.0 345 26 13 6.6 3.6
15500 -6.0 21.2 345 27 14 7.2 3.9 | -6.3 20.7 345 25 13 6.9 3.8
15000 -5.0 23.0 345 27 14 7.1 3.9 | -5.2 22.6 350 25 13 6.9 3.8
14500 -3.9 25.0 350 27 14 6.6 3.6 | -4.2 24.4 350 25 13 6.9 3.8
14000 -3.0 26.6 350 26 13 6.2 3.4 | -3.2 26.2 350 24 13 6.9 3.8
13500 -2.1 28.2 350 25 13 5.8 3.2 | -2.2 28.0 355 24 12 6.6 3.6
13000 -1.3 29.7 355 23 12 5.0 2.7 | -1.3 29.7 355 23 12 5.9 3.3
12500 -0.6 30.9 355 22 11 4.8 2.6 | -0.4 31.3 355 22 11 5.8 3.2
12000 0.0 32.0 355 20 10 3.9 2.1 | 0.4 32.7 355 21 11 5.1 2.8
11500 0.6 33.1 355 18 9 3.8 2.1 | 1.2 34.2 360 19 10 5.0 2.7
11000 1.2 34.2 355 16 8 3.5 1.9 | 1.9 35.4 360 18 9 4.3 2.4
10500 1.7 35.1 355 14 7 3.4 1.9 | 2.5 36.5 360 15 8 4.3 2.4
10250 2.0 35.6 360 13 7 2.9 1.6 | 2.9 37.2 360 15 8 3.9 2.2
10000 2.2 36.0 360 12 6 4.2 2.3 | 3.2 37.8 005 14 7 4.7 2.6
9750 2.6 36.7 360 11 6 5.4 3.0 | 3.6 38.5 005 12 6 5.2 2.9
9500 3.0 37.4 360 10 5 5.2 2.8 | 4.0 39.2 010 11 6 5.3 2.9
9250 3.4 38.1 005 9 4 5.4 3.0 | 4.4 39.9 010 10 5 5.8 3.2
9000 3.8 38.8 010 7 4 5.5 3.0 | 4.8 40.6 015 9 4 5.6 3.1
8750 4.2 39.6 010 7 3 5.6 3.0 | 5.2 41.4 020 8 4 5.1 2.8
8500 4.7 40.5 010 6 3 6.1 3.4 | 6.2 43.2 025 6 3 8.0 4.4
8250 5.1 41.2 015 5 3 6.5 3.6 | 6.8 44.2 025 5 3 7.1 3.9
8000 6.1 43.0 015 4 2 7.7 4.2 | 7.3 45.1 030 5 2 5.7 3.1
7750 6.7 44.1 015 4 2 8.1 4.5 | 7.7 45.9 025 4 2 6.5 3.6
7500 7.3 45.1 015 4 2 8.2 4.5 | 8.3 46.9 025 4 2 8.1 4.5
7250 7.9 46.2 015 3 2 6.8 3.7 | 8.8 47.8 025 3 2 6.4 3.5
7000 8.4 47.1 015 2 1 8.0 4.4 | 9.2 48.6 025 3 2 6.0 3.3
6750 9.1 48.4 010 2 1 10.2 5.6 | 9.8 49.6 020 2 1 7.4 4.1
6500 9.9 49.8 010 2 1 10.0 5.5 | 10.3 50.5 015 2 1 6.1 3.3
6250 10.6 51.1 010 3 1 8.4 4.6 | 10.8 51.4 005 2 1 10.0 5.5
6000 11.2 52.2 005 2 1 11.2 6.2 | 11.5 52.7 310 1 1 3.3 1.8
5750 12.4 54.3 005 2 1 21.3 11.7 | 10.9 51.6 285 1 1 -18.9 -10.4
5500 13.6 56.5 360 1 1 1.8 1.0 | 10.3 50.5 265 1 1 23.4 12.8
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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