Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
212
UXUS97 KGJT 081306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
606 AM MST Saturday, November 8, 2025
This forecast is for Saturday, November 8, 2025:
If the trigger temperature of 54.2 F/12.3 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 354 ft/min (1.8 m/s)
Maximum height of thermals.................. 10671 ft MSL (5063 ft AGL)
Forecast maximum temperature................... 58.0 F/14.9 C
Time of trigger temperature.................... 1145 MST
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................. 9118 ft MSL (3510 ft AGL)
Thermal soaring outlook for Sunday 11/09....... Fair
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:50:07 / 17:05:37 MST
Total possible sunshine........... 10 hr 15 min 29 sec (615 min 29 sec)
Altitude of sun at 11:57:52 MST... 34.07 degrees
Upper air data from rawinsonde observation taken on 11/08/2025 at 0500 MST
Freezing level.................. 9833 ft MSL (4225 ft AGL)
Convective condensation level... 21478 ft MSL (15870 ft AGL)
Lifted condensation level....... 15732 ft MSL (10124 ft AGL)
Lifted index.................... +10.6
K index......................... -9.9
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 -64.6 -84.3 330 61 31 0.0 0.0 M M M M M
45000 -64.5 -84.1 340 66 34 -0.3 -0.2 M M M M M
40000 -65.0 -85.0 335 76 39 -1.4 -0.8 M M M M M
38000 -60.3 -76.5 345 74 38 8.8 4.8 M M M M M
36000 -55.1 -67.2 350 73 37 8.8 4.8 M M M M M
34000 -49.6 -57.3 355 72 37 9.4 5.1 M M M M M
32000 -44.0 -47.2 350 73 37 9.4 5.1 M M M M M
30000 -38.7 -37.7 350 69 36 8.2 4.5 36.7 98.0 16.8 M M
29000 -36.3 -33.3 345 66 34 8.2 4.5 36.1 96.9 16.6 M M
28000 -33.8 -28.8 345 63 32 8.2 4.5 35.6 96.0 16.4 M M
27000 -31.5 -24.7 340 59 30 7.2 4.0 34.8 94.6 15.9 M M
26000 -29.4 -20.9 335 55 28 7.2 3.9 33.7 92.7 15.3 M M
25000 -27.2 -17.0 330 51 26 7.2 4.0 32.8 91.1 14.7 M M
24000 -24.9 -12.8 330 49 25 8.3 4.6 32.1 89.7 14.3 M M
23000 -22.4 -8.3 325 47 24 8.3 4.5 31.5 88.6 14.0 M M
22000 -19.3 -2.7 325 46 24 8.4 4.6 30.9 87.6 13.7 M M
21000 -17.0 1.4 325 45 23 7.6 4.2 30.1 86.2 13.2 M M
20000 -14.8 5.4 330 43 22 7.6 4.2 29.3 84.8 12.6 M M
19500 -13.6 7.5 330 43 22 7.6 4.2 29.0 84.2 12.4 M M
19000 -12.5 9.5 330 42 22 7.2 4.0 28.6 83.5 12.1 M M
18500 -11.4 11.5 330 42 22 7.1 3.9 28.2 82.7 11.8 M M
18000 -10.4 13.3 330 42 22 7.0 3.9 27.7 81.9 11.5 M M
17500 -9.4 15.1 335 42 21 6.6 3.6 27.2 80.9 11.1 M M
17000 -8.4 16.9 335 41 21 6.6 3.6 26.7 80.0 10.6 M M
16500 -7.4 18.7 335 41 21 6.4 3.5 26.1 79.0 10.2 M M
16000 -6.5 20.3 335 40 21 6.4 3.5 25.5 78.0 9.7 M M
15500 -5.5 22.1 340 39 20 5.2 2.9 25.0 77.0 9.3 M M
15000 -4.9 23.2 340 38 20 4.3 2.4 24.1 75.3 8.5 M M
14500 -4.3 24.3 340 37 19 4.1 2.3 23.2 73.7 7.7 M M
14000 -3.7 25.3 340 35 18 3.7 2.0 22.2 71.9 6.9 M M
13500 -3.1 26.4 340 33 17 3.7 2.0 21.2 70.1 6.0 M M
13000 -2.6 27.3 340 30 16 3.4 1.9 20.2 68.3 5.1 M M
12500 -2.1 28.2 340 28 14 3.4 1.9 19.1 66.5 4.2 M M
12000 -1.7 28.9 340 24 13 1.9 1.0 18.0 64.4 3.1 M M
11500 -1.4 29.5 340 21 11 2.0 1.1 16.7 62.1 2.0 M M
11000 -1.1 30.0 340 18 9 2.3 1.3 15.5 60.0 0.8 M M
10500 -0.7 30.7 340 14 7 1.9 1.0 14.4 57.8 -0.3 347 1.8
10250 -0.6 30.9 345 12 6 3.0 1.6 13.7 56.7 -0.9 336 1.7
10000 -0.3 31.5 350 11 6 4.7 2.6 13.3 55.9 -1.3 319 1.6
9750 0.0 32.0 355 10 5 4.8 2.6 12.9 55.2 -1.7 302 1.5
9500 0.4 32.7 360 9 5 4.0 2.2 12.5 54.5 -2.1 284 1.4
9250 0.6 33.1 005 9 4 3.0 1.6 12.0 53.6 -2.6 270 1.4
9000 0.9 33.6 015 8 4 4.3 2.4 11.5 52.7 -3.1 255 1.3
8750 1.2 34.2 020 8 4 5.2 2.8 11.1 52.0 -3.5 237 1.2
8500 1.6 34.9 030 8 4 4.9 2.7 10.8 51.4 -3.9 218 1.1
8250 1.9 35.4 040 7 4 4.9 2.7 10.4 50.7 -4.3 201 1.0
8000 2.3 36.1 050 7 4 5.5 3.0 10.0 50.1 -4.7 182 0.9
7750 2.7 36.9 055 7 4 6.3 3.5 9.7 49.5 -5.0 162 0.8
7500 3.2 37.8 060 7 4 6.6 3.6 9.5 49.1 -5.2 140 0.7
7250 3.7 38.7 070 7 4 7.2 4.0 9.3 48.7 -5.5 117 0.6
7000 4.2 39.6 075 7 4 5.8 3.2 9.1 48.3 -5.7 95 0.5
6750 4.6 40.3 080 7 4 2.9 1.6 8.6 47.5 -6.1 78 0.4
6500 4.7 40.5 080 7 3 1.4 0.8 8.0 46.5 -6.7 66 0.3
6250 4.8 40.6 080 6 3 3.6 2.0 7.5 45.4 -7.3 54 0.3
6000 5.0 41.0 080 6 3 -3.6 -2.0 6.9 44.4 -8.0 43 0.2
5750 3.8 38.8 085 5 2 -28.2 -15.5 5.0 41.0 -9.8 70 0.4
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 * * * * * *
11/08/2025 at 0800 MST | 11/08/2025 at 1100 MST
|
CAPE... 0.0 LI... +9.1 | CAPE... 0.0 LI... +9.3
CINH... -0.2 K Index... +0.8 | CINH... -0.0 K Index... -0.3
|
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 -81.4 305 55 28 1.7 0.9 | -63.0 -81.4 305 56 29 2.1 1.1
45000 -60.6 -77.1 305 65 33 -0.5 -0.3 | -60.1 -76.2 300 70 36 -1.3 -0.7
40000 -61.6 -78.9 300 78 40 -0.4 -0.2 | -62.1 -79.8 305 75 39 -1.4 -0.8
38000 -58.8 -73.8 300 76 39 6.5 3.6 | -59.2 -74.6 300 73 38 7.1 3.9
36000 -54.9 -66.8 295 73 38 6.5 3.6 | -55.0 -67.0 300 70 36 7.1 3.9
34000 -50.6 -59.1 295 70 36 7.8 4.3 | -50.6 -59.1 300 67 34 7.7 4.2
32000 -45.9 -50.6 300 67 34 7.8 4.3 | -45.9 -50.6 300 63 33 7.7 4.2
30000 -41.0 -41.8 300 64 33 8.7 4.8 | -41.2 -42.2 300 61 31 8.2 4.5
29000 -38.4 -37.1 305 64 33 8.7 4.8 | -38.7 -37.7 300 60 31 8.2 4.5
28000 -35.8 -32.4 305 64 33 8.7 4.8 | -36.3 -33.3 305 59 31 8.2 4.5
27000 -33.2 -27.8 305 63 33 8.3 4.6 | -33.8 -28.8 305 59 30 8.6 4.7
26000 -30.7 -23.3 305 62 32 8.4 4.6 | -31.2 -24.2 305 57 30 8.6 4.7
25000 -28.2 -18.8 305 60 31 8.4 4.6 | -28.6 -19.5 305 56 29 8.6 4.7
24000 -25.1 -13.2 305 59 30 8.3 4.6 | -25.5 -13.9 310 55 28 8.3 4.6
23000 -22.6 -8.7 305 57 30 8.3 4.6 | -23.0 -9.4 310 54 28 8.3 4.6
22000 -20.1 -4.2 305 56 29 8.3 4.6 | -20.5 -4.9 310 53 27 8.3 4.6
21000 -17.8 -0.0 305 55 28 6.8 3.7 | -18.1 -0.6 310 51 26 7.6 4.1
20000 -15.8 3.6 310 53 27 6.8 3.7 | -15.9 3.4 310 50 26 7.5 4.1
19500 -14.8 5.4 310 52 27 6.8 3.7 | -14.7 5.5 315 49 25 7.5 4.1
19000 -13.8 7.2 310 52 27 6.8 3.7 | -13.6 7.5 315 49 25 7.3 4.0
18500 -12.9 8.8 310 50 26 5.2 2.9 | -12.7 9.1 315 47 24 5.5 3.0
18000 -12.1 10.2 315 48 25 5.4 2.9 | -11.9 10.6 315 45 23 5.6 3.1
17500 -11.3 11.7 315 46 24 5.0 2.7 | -11.1 12.0 315 43 22 4.8 2.6
17000 -10.6 12.9 315 44 23 4.8 2.7 | -10.4 13.3 320 40 21 4.6 2.5
16500 -9.9 14.2 315 41 21 4.8 2.6 | -9.7 14.5 320 38 19 4.6 2.5
16000 -9.2 15.4 315 38 20 4.5 2.5 | -9.0 15.8 320 35 18 4.8 2.6
15500 -8.5 16.7 315 36 18 4.5 2.5 | -8.3 17.1 320 33 17 4.8 2.6
15000 -7.9 17.8 315 33 17 4.6 2.5 | -7.6 18.3 320 30 16 5.1 2.8
14500 -7.2 19.0 315 30 15 4.7 2.6 | -6.8 19.8 320 28 14 5.1 2.8
14000 -6.5 20.3 315 27 14 3.9 2.1 | -6.1 21.0 320 26 13 4.8 2.7
13500 -6.0 21.2 310 25 13 3.8 2.1 | -5.4 22.3 320 23 12 4.8 2.7
13000 -5.5 22.1 310 23 12 2.6 1.4 | -4.7 23.5 320 21 11 4.4 2.4
12500 -5.2 22.6 310 20 10 2.1 1.2 | -4.0 24.8 320 19 10 4.3 2.4
12000 -4.9 23.2 305 18 9 2.7 1.5 | -3.5 25.7 320 17 9 3.2 1.7
11500 -4.5 23.9 310 14 7 3.0 1.6 | -3.1 26.4 315 15 8 2.7 1.5
11000 -4.1 24.6 310 11 6 4.7 2.6 | -2.7 27.1 315 12 6 3.3 1.8
10500 -3.3 26.1 320 9 4 6.0 3.3 | -2.3 27.9 315 10 5 3.7 2.0
10250 -2.9 26.8 325 7 4 4.1 2.2 | -2.0 28.4 315 8 4 2.7 1.5
10000 -2.6 27.3 330 7 3 5.5 3.0 | -1.8 28.8 320 7 4 4.7 2.6
9750 -2.0 28.4 340 6 3 9.0 4.9 | -1.3 29.7 320 7 3 7.3 4.0
9500 -1.4 29.5 350 6 3 8.6 4.7 | -0.8 30.6 325 6 3 6.6 3.6
9250 -0.7 30.7 355 6 3 8.4 4.6 | -0.3 31.5 330 5 3 7.0 3.8
9000 -0.1 31.8 005 7 3 8.0 4.4 | 0.2 32.4 330 5 2 7.3 4.0
8750 0.5 32.9 010 7 4 8.1 4.4 | 0.8 33.4 335 4 2 7.5 4.1
8500 1.7 35.1 020 7 4 7.3 4.0 | 1.9 35.4 360 4 2 6.5 3.6
8250 2.2 36.0 025 7 4 6.3 3.4 | 2.3 36.1 005 4 2 5.5 3.0
8000 2.7 36.9 030 7 4 7.8 4.3 | 2.8 37.0 010 4 2 9.1 5.0
7750 3.3 37.9 035 7 3 7.7 4.2 | 3.6 38.5 015 4 2 9.7 5.3
7500 3.8 38.8 040 7 3 5.6 3.1 | 4.2 39.6 020 4 2 6.6 3.6
7250 4.2 39.6 045 7 4 4.7 2.6 | 4.6 40.3 020 3 2 4.8 2.6
7000 4.6 40.3 055 7 4 6.2 3.4 | 5.1 41.2 020 3 2 10.7 5.9
6750 5.1 41.2 055 5 3 5.8 3.2 | 6.1 43.0 020 3 2 12.4 6.8
6500 5.5 41.9 065 5 3 3.7 2.0 | 6.8 44.2 020 3 2 8.6 4.7
6250 5.8 42.4 070 5 3 5.7 3.1 | 7.5 45.5 020 3 1 8.8 4.8
6000 6.1 43.0 080 5 3 -0.0 -0.0 | 8.2 46.8 020 2 1 11.8 6.5
5750 5.6 42.1 080 3 1 -15.2 -8.4 | 9.4 48.9 020 2 1 20.9 11.5
5500 4.6 40.3 105 1 1 -0.3 -0.1 | 10.8 51.4 020 2 1 7.2 4.0
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
11/08/2025 at 1400 MST | 11/08/2025 at 1700 MST
|
CAPE... 0.0 LI... +9.1 | CAPE... 0.0 LI... +8.7
CINH... -0.1 K Index... -1.0 | CINH... -0.1 K Index... -1.6
|
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 -63.0 -81.4 305 59 31 1.8 1.0 | -63.8 -82.8 305 59 30 0.6 0.3
45000 -60.4 -76.7 305 72 37 -0.6 -0.3 | -62.9 -81.2 305 69 35 0.7 0.4
40000 -61.4 -78.5 315 72 37 -0.7 -0.4 | -61.8 -79.2 320 80 41 0.7 0.4
38000 -59.0 -74.2 315 69 35 5.7 3.1 | -59.5 -75.1 330 77 39 4.8 2.6
36000 -55.5 -67.9 310 63 33 5.7 3.1 | -56.6 -69.9 330 70 36 4.8 2.6
34000 -51.5 -60.7 315 60 31 8.1 4.4 | -52.6 -62.7 335 65 34 9.3 5.1
32000 -46.7 -52.1 320 59 31 8.1 4.4 | -47.0 -52.6 335 62 32 9.3 5.1
30000 -41.6 -42.9 325 59 30 9.0 4.9 | -41.5 -42.7 335 59 31 9.2 5.1
29000 -38.9 -38.0 325 57 30 9.0 4.9 | -38.7 -37.7 335 58 30 9.2 5.1
28000 -36.2 -33.2 320 56 29 9.0 4.9 | -35.9 -32.6 335 57 29 9.2 5.1
27000 -33.6 -28.5 320 55 28 8.4 4.6 | -33.2 -27.8 335 56 29 8.6 4.7
26000 -31.1 -24.0 320 54 28 8.5 4.6 | -30.7 -23.3 330 54 28 8.6 4.7
25000 -28.5 -19.3 320 54 28 8.5 4.7 | -28.1 -18.6 330 53 27 8.6 4.7
24000 -25.4 -13.7 315 52 27 8.0 4.4 | -25.5 -13.9 330 51 26 7.8 4.3
23000 -23.0 -9.4 315 51 26 8.0 4.4 | -22.6 -8.7 330 50 26 7.8 4.3
22000 -20.6 -5.1 315 50 26 8.0 4.4 | -20.3 -4.5 330 49 25 7.8 4.3
21000 -18.3 -0.9 315 49 25 7.8 4.3 | -18.0 -0.4 330 48 25 7.6 4.2
20000 -16.0 3.2 320 47 24 7.8 4.3 | -15.7 3.7 330 47 24 7.6 4.2
19500 -14.8 5.4 320 47 24 7.8 4.3 | -14.6 5.7 330 46 24 7.6 4.2
19000 -13.7 7.3 320 46 24 7.6 4.1 | -13.5 7.7 330 46 24 7.4 4.0
18500 -12.6 9.3 320 45 23 6.7 3.7 | -12.4 9.7 330 45 23 6.8 3.7
18000 -11.6 11.1 320 44 23 6.8 3.7 | -11.4 11.5 330 45 23 7.0 3.8
17500 -10.7 12.7 320 42 22 5.5 3.0 | -10.5 13.1 330 44 22 5.4 2.9
17000 -9.9 14.2 320 41 21 5.3 2.9 | -9.7 14.5 330 42 22 5.2 2.9
16500 -9.1 15.6 320 39 20 5.1 2.8 | -8.9 16.0 330 41 21 4.9 2.7
16000 -8.4 16.9 320 37 19 4.7 2.6 | -8.3 17.1 330 39 20 4.4 2.4
15500 -7.7 18.1 325 34 18 4.7 2.6 | -7.7 18.1 330 38 19 4.4 2.4
15000 -7.0 19.4 325 32 16 4.4 2.4 | -7.0 19.4 335 36 18 4.2 2.3
14500 -6.4 20.5 325 29 15 4.4 2.4 | -6.4 20.5 335 33 17 4.2 2.3
14000 -5.7 21.7 325 27 14 4.4 2.4 | -5.8 21.6 335 31 16 4.1 2.3
13500 -5.0 23.0 325 24 13 4.4 2.4 | -5.1 22.8 335 28 15 4.1 2.3
13000 -4.4 24.1 325 22 11 4.3 2.4 | -4.5 23.9 335 26 13 4.2 2.3
12500 -3.8 25.2 325 20 10 4.3 2.3 | -3.9 25.0 340 23 12 4.2 2.3
12000 -3.1 26.4 325 17 9 4.4 2.4 | -3.3 26.1 340 20 10 4.8 2.6
11500 -2.5 27.5 325 15 8 4.5 2.5 | -2.6 27.3 340 18 9 4.8 2.7
11000 -1.9 28.6 325 13 7 4.7 2.6 | -1.8 28.8 345 15 8 6.1 3.3
10500 -1.2 29.8 330 11 5 5.1 2.8 | -0.9 30.4 345 12 6 6.6 3.6
10250 -0.9 30.4 330 9 5 3.7 2.0 | -0.5 31.1 350 11 6 5.5 3.0
10000 -0.6 30.9 335 8 4 5.0 2.7 | -0.1 31.8 355 10 5 6.6 3.6
9750 -0.1 31.8 335 8 4 7.3 4.0 | 0.5 32.9 355 9 5 8.7 4.8
9500 0.4 32.7 335 7 4 6.7 3.7 | 1.1 34.0 355 9 5 7.9 4.3
9250 0.9 33.6 335 6 3 6.9 3.8 | 1.7 35.1 355 8 4 9.1 5.0
9000 1.4 34.5 340 6 3 7.5 4.1 | 2.4 36.3 355 8 4 9.1 5.0
8750 2.0 35.6 340 6 3 8.5 4.6 | 3.0 37.4 360 7 4 7.3 4.0
8500 3.3 37.9 335 5 3 7.3 4.0 | 4.1 39.4 360 6 3 7.8 4.3
8250 3.7 38.7 335 5 3 6.4 3.5 | 4.7 40.5 355 6 3 8.3 4.5
8000 4.3 39.7 335 5 2 10.4 5.7 | 5.3 41.5 355 5 3 8.3 4.5
7750 5.2 41.4 335 5 2 11.0 6.0 | 5.9 42.6 355 5 2 8.1 4.5
7500 5.9 42.6 335 5 2 7.9 4.3 | 6.5 43.7 350 4 2 7.7 4.2
7250 6.4 43.5 330 4 2 6.4 3.5 | 7.1 44.8 345 4 2 7.6 4.2
7000 7.0 44.6 325 4 2 12.4 6.8 | 7.6 45.7 335 3 2 8.1 4.5
6750 8.1 46.6 330 4 2 13.0 7.1 | 8.3 46.9 335 3 1 9.1 5.0
6500 8.8 47.8 330 4 2 8.6 4.7 | 9.0 48.2 320 2 1 8.8 4.8
6250 9.5 49.1 325 4 2 9.1 5.0 | 9.6 49.3 305 2 1 10.6 5.8
6000 10.2 50.4 320 4 2 11.6 6.3 | 10.3 50.5 285 2 1 3.5 1.9
5750 11.4 52.5 325 4 2 20.0 10.9 | 9.9 49.8 280 2 1 -13.6 -7.4
5500 12.8 55.0 320 3 2 10.7 5.9 | 9.6 49.3 260 2 1 19.9 10.9
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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