Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
931
UXUS97 KBOU 090123
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1822 MST Monday, December 8, 2025
This forecast is for Tuesday, December 9, 2025:
If the trigger temperature of 60.4 F/15.8 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 295 ft/min (1.5 m/s)
Maximum height of thermals.................. 9508 ft MSL (4222 ft AGL)
Forecast maximum temperature................... 61.0 F/16.6 C
Time of trigger temperature.................... 1330 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................. 7920 ft MSL (2635 ft AGL)
Thermal soaring outlook for Wednesday 12/10.... Poor
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Weak NVA
Potential height of wave....................... 16842 ft MSL (11556 ft AGL)
Wave soaring outlook for Wednesday 12/10....... Fair
Remarks...
Sunrise/Sunset.................... 07:09:21 / 16:34:46 MST
Total possible sunshine........... 9 hr 25 min 25 sec (565 min 25 sec)
Altitude of sun at 11:52:04 MST... 27.31 degrees
Upper air data from numerical model forecast valid on 12/09/2025 at 0500 MST
Freezing level.................. 11577 ft MSL (6291 ft AGL)
Convective condensation level... 19537 ft MSL (14251 ft AGL)
Lifted condensation level....... 15028 ft MSL (9742 ft AGL)
Lifted index.................... +9.1
K index......................... +5.0
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 -66.8 -88.2 310 46 24 -1.5 -0.8 M M M M M
45000 -69.1 -92.4 300 49 25 -1.1 -0.6 M M M M M
40000 -65.3 -85.5 330 83 43 2.5 1.4 M M M M M
38000 -61.4 -78.5 335 83 43 8.6 4.7 M M M M M
36000 -56.2 -69.2 330 75 39 8.6 4.7 M M M M M
34000 -51.0 -59.8 330 68 35 8.8 4.8 M M M M M
32000 -45.7 -50.3 330 63 33 8.8 4.8 M M M M M
30000 -40.4 -40.7 325 59 30 9.1 5.0 35.9 96.6 14.9 M M
29000 -37.0 -34.6 325 56 29 9.1 5.0 35.5 95.9 14.8 M M
28000 -34.3 -29.7 325 54 28 9.1 5.0 35.3 95.6 14.8 M M
27000 -31.7 -25.1 325 52 27 8.3 4.5 35.0 95.1 14.8 M M
26000 -29.2 -20.6 320 50 26 8.3 4.6 34.4 93.9 14.4 M M
25000 -26.7 -16.1 320 49 25 8.3 4.6 33.9 93.0 14.2 M M
24000 -24.3 -11.7 320 48 24 7.2 4.0 33.4 92.1 13.9 M M
23000 -22.2 -8.0 315 46 24 7.1 3.9 32.3 90.2 13.2 M M
22000 -20.1 -4.2 315 45 23 7.1 3.9 31.4 88.5 12.6 M M
21000 -18.0 -0.4 315 43 22 6.7 3.7 30.5 86.8 11.9 M M
20000 -16.0 3.2 320 43 22 6.7 3.7 29.3 84.8 11.0 M M
19500 -15.0 5.0 320 42 22 6.7 3.7 28.8 83.8 10.6 M M
19000 -14.0 6.8 320 42 22 6.7 3.7 28.3 82.9 10.3 M M
18500 -13.0 8.6 320 42 21 7.3 4.0 27.8 82.1 9.9 M M
18000 -11.9 10.6 320 42 22 7.5 4.1 27.4 81.4 9.6 M M
17500 -10.8 12.6 320 42 22 7.5 4.1 27.1 80.7 9.3 M M
17000 -9.7 14.5 320 43 22 7.4 4.0 26.7 80.0 9.0 M M
16500 -8.6 16.5 320 43 22 7.4 4.1 26.3 79.3 8.7 M M
16000 -7.5 18.5 320 44 23 6.6 3.6 25.8 78.5 8.3 M M
15500 -6.6 20.1 320 44 23 6.5 3.6 25.3 77.5 7.9 M M
15000 -5.6 21.9 320 44 23 6.1 3.4 24.7 76.5 7.4 M M
14500 -4.3 24.3 320 44 23 5.8 3.2 23.7 74.7 6.6 M M
14000 -3.5 25.7 315 44 23 5.5 3.0 23.1 73.5 6.0 M M
13500 -2.7 27.1 315 43 22 5.4 3.0 22.3 72.2 5.4 M M
13000 -1.9 28.6 315 43 22 4.8 2.6 21.6 70.9 4.7 M M
12500 -1.2 29.8 310 40 21 4.5 2.5 20.8 69.4 3.9 M M
12000 -0.6 30.9 310 38 20 5.0 2.8 19.9 67.8 3.2 M M
11500 0.2 32.4 305 36 19 5.5 3.0 19.2 66.6 2.5 M M
11000 1.1 34.0 305 34 17 4.8 2.6 18.6 65.4 1.9 M M
10500 1.7 35.1 305 32 17 3.3 1.8 17.7 63.8 1.1 M M
10250 2.0 35.6 300 32 16 7.7 4.2 17.2 63.0 0.7 M M
10000 2.7 36.9 300 31 16 8.2 4.5 17.3 63.1 0.7 M M
9750 3.1 37.6 300 30 15 3.9 2.1 16.9 62.4 0.3 M M
9500 3.5 38.3 300 29 15 5.3 2.9 16.5 61.7 -0.1 292 1.5
9250 3.8 38.8 295 28 14 3.9 2.1 16.1 61.0 -0.4 274 1.4
9000 4.0 39.2 295 28 14 2.6 1.4 15.6 60.1 -0.9 260 1.3
8750 4.3 39.7 290 29 15 4.0 2.2 15.1 59.1 -1.4 245 1.2
8500 4.6 40.3 290 30 15 5.7 3.1 14.7 58.4 -1.8 227 1.2
8250 5.0 41.0 285 31 16 3.3 1.8 14.3 57.8 -2.2 209 1.1
8000 5.1 41.2 285 31 16 0.1 0.1 13.7 56.6 -2.8 198 1.0
7750 5.2 41.4 280 30 15 3.8 2.1 13.0 55.4 -3.5 189 1.0
7500 5.6 42.1 280 27 14 7.1 3.9 12.7 54.9 -3.7 167 0.8
7250 6.1 43.0 275 25 13 4.7 2.6 12.5 54.4 -4.0 146 0.7
7000 6.4 43.5 275 23 12 4.2 2.3 12.0 53.7 -4.5 130 0.7
6750 6.7 44.1 270 21 11 1.6 0.9 11.6 52.8 -4.9 114 0.6
6500 6.6 43.9 265 18 9 -2.9 -1.6 10.7 51.3 -5.7 109 0.6
6250 6.3 43.3 260 16 8 -5.2 -2.9 9.7 49.5 -6.8 110 0.6
6000 5.9 42.6 250 14 7 -5.3 -2.9 8.5 47.4 -8.0 116 0.6
5750 5.4 41.7 240 12 6 -8.1 -4.5 7.4 45.3 -9.2 122 0.6
5500 4.3 39.7 225 11 6 -24.5 -13.4 5.5 41.9 -11.1 149 0.8
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
12/09/2025 at 0800 MST | 12/09/2025 at 1100 MST
|
CAPE... 0.0 LI... +4.7 | CAPE... 0.0 LI... +4.8
CINH... 0.0 K Index... +6.9 | CINH... 0.0 K Index... +8.6
|
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 -66.4 -87.5 310 46 24 -1.7 -0.9 | -66.7 -88.1 310 44 23 -3.1 -1.7
45000 -68.9 -92.0 310 55 28 2.0 1.1 | -71.4 -96.5 310 67 35 2.7 1.5
40000 -64.9 -84.8 325 74 38 2.7 1.5 | -64.8 -84.6 310 75 39 4.4 2.4
38000 -60.9 -77.6 320 74 38 8.5 4.7 | -60.5 -76.9 310 72 37 8.6 4.7
36000 -55.8 -68.4 320 70 36 8.5 4.7 | -55.3 -67.5 310 67 35 8.6 4.7
34000 -50.6 -59.1 320 67 34 8.9 4.9 | -50.1 -58.2 310 63 32 8.6 4.7
32000 -45.2 -49.4 315 64 33 8.9 4.9 | -44.3 -47.7 310 57 29 8.6 4.7
30000 -39.3 -38.7 315 60 31 8.5 4.7 | -39.2 -38.6 310 53 27 8.4 4.6
29000 -36.8 -34.2 315 59 30 8.5 4.7 | -36.7 -34.1 310 51 26 8.4 4.6
28000 -34.2 -29.6 320 57 29 8.5 4.7 | -34.2 -29.6 310 49 25 8.4 4.6
27000 -31.7 -25.1 320 55 28 8.2 4.5 | -31.7 -25.1 315 48 25 8.2 4.5
26000 -29.3 -20.7 320 52 27 8.2 4.5 | -29.2 -20.6 315 48 25 8.2 4.5
25000 -26.9 -16.4 320 49 25 8.2 4.5 | -26.8 -16.2 315 48 24 8.2 4.5
24000 -24.5 -12.1 320 47 24 7.8 4.3 | -24.3 -11.7 315 47 24 8.3 4.6
23000 -22.1 -7.8 320 45 23 7.8 4.3 | -21.8 -7.2 315 47 24 8.3 4.6
22000 -19.8 -3.6 325 44 23 7.8 4.3 | -19.4 -2.9 315 46 24 8.3 4.6
21000 -17.6 0.3 325 43 22 7.4 4.0 | -16.9 1.6 315 46 24 8.1 4.5
20000 -15.4 4.3 330 42 22 7.4 4.1 | -14.5 5.9 315 45 23 8.2 4.5
19500 -14.3 6.3 330 41 21 7.4 4.1 | -13.3 8.1 315 45 23 8.2 4.5
19000 -13.2 8.2 330 41 21 7.4 4.1 | -12.0 10.4 315 44 23 8.2 4.5
18500 -12.1 10.2 330 41 21 7.5 4.1 | -10.8 12.6 315 44 23 7.8 4.3
18000 -10.9 12.4 330 41 21 7.5 4.1 | -9.7 14.5 315 44 22 7.8 4.3
17500 -9.8 14.4 330 41 21 7.4 4.1 | -8.5 16.7 315 43 22 7.7 4.2
17000 -8.7 16.3 330 41 21 7.2 3.9 | -6.9 19.6 315 43 22 7.5 4.1
16500 -7.7 18.1 330 41 21 7.2 3.9 | -5.7 21.7 315 43 22 7.4 4.0
16000 -6.6 20.1 330 41 21 7.4 4.1 | -4.7 23.5 315 43 22 7.1 3.9
15500 -5.5 22.1 330 41 21 7.4 4.1 | -3.6 25.5 315 43 22 7.1 3.9
15000 -3.8 25.2 330 41 21 7.5 4.1 | -2.6 27.3 315 43 22 6.9 3.8
14500 -2.7 27.1 330 41 21 7.6 4.2 | -1.6 29.1 315 44 22 7.0 3.8
14000 -1.7 28.9 325 41 21 6.8 3.7 | -0.6 30.9 310 44 23 6.5 3.6
13500 -0.7 30.7 325 42 22 6.8 3.7 | 0.4 32.7 310 45 23 6.5 3.5
13000 0.3 32.5 320 42 22 5.9 3.2 | 1.3 34.3 310 45 23 5.5 3.0
12500 1.1 34.0 320 43 22 5.5 3.0 | 2.0 35.6 310 45 23 4.9 2.7
12000 1.9 35.4 315 44 22 4.8 2.6 | 2.7 36.9 305 44 23 4.8 2.7
11500 2.5 36.5 310 44 23 4.1 2.3 | 3.4 38.1 305 44 23 4.7 2.6
11000 3.1 37.6 310 45 23 3.3 1.8 | 4.1 39.4 305 44 23 3.9 2.2
10500 3.5 38.3 305 45 23 2.1 1.1 | 4.6 40.3 300 43 22 2.1 1.2
10250 3.7 38.7 305 45 23 4.3 2.4 | 4.8 40.6 300 43 22 6.4 3.5
10000 4.1 39.4 300 44 23 4.2 2.3 | 5.4 41.7 300 43 22 7.1 3.9
9750 4.2 39.6 300 44 22 1.6 0.9 | 5.7 42.3 300 42 21 2.8 1.5
9500 4.4 39.9 300 43 22 2.6 1.4 | 6.0 42.8 300 41 21 3.8 2.1
9250 4.5 40.1 295 42 22 1.2 0.7 | 6.2 43.2 295 40 21 2.4 1.3
9000 4.6 40.3 295 42 21 0.6 0.3 | 6.3 43.3 295 39 20 1.5 0.8
8750 4.7 40.5 295 40 21 2.9 1.6 | 6.5 43.7 295 37 19 3.7 2.0
8500 5.0 41.0 290 38 20 4.2 2.3 | 6.8 44.2 295 35 18 5.1 2.8
8250 5.3 41.5 290 36 19 3.2 1.8 | 7.2 45.0 290 33 17 3.8 2.1
8000 5.5 41.9 285 33 17 2.7 1.5 | 7.4 45.3 290 31 16 2.5 1.4
7750 5.8 42.4 285 30 16 5.6 3.1 | 7.6 45.7 290 27 14 4.8 2.6
7500 6.3 43.3 285 27 14 8.0 4.4 | 8.1 46.6 285 25 13 6.9 3.8
7250 6.9 44.4 280 25 13 6.1 3.3 | 8.6 47.5 285 22 11 5.8 3.2
7000 7.2 45.0 280 22 11 4.5 2.5 | 9.0 48.2 285 19 10 5.1 2.8
6750 7.6 45.7 275 20 10 5.9 3.2 | 9.4 48.9 285 17 9 5.8 3.2
6500 8.0 46.4 270 17 9 4.1 2.2 | 9.8 49.6 280 14 7 6.1 3.3
6250 8.1 46.6 260 14 7 -2.3 -1.3 | 10.2 50.4 270 12 6 3.6 2.0
6000 7.8 46.0 250 13 7 -2.7 -1.5 | 10.4 50.7 265 10 5 2.9 1.6
5750 7.6 45.7 235 12 6 -8.1 -4.5 | 10.6 51.1 260 8 4 0.5 0.3
5500 6.1 43.0 215 11 5 -34.0 -18.6 | 10.4 50.7 240 6 3 -3.6 -2.0
12/09/2025 at 1400 MST | 12/09/2025 at 1700 MST
|
CAPE... 0.0 LI... +4.7 | CAPE... 0.0 LI... +4.6
CINH... -0.2 K Index... +11.4 | CINH... 0.0 K Index... +11.2
|
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 -65.8 -86.4 305 49 25 -3.2 -1.8 | -65.8 -86.4 300 53 27 -3.5 -1.9
45000 -70.5 -94.9 305 72 37 3.1 1.7 | -71.1 -96.0 300 67 34 3.4 1.9
40000 -64.3 -83.7 305 80 41 4.2 2.3 | -64.3 -83.7 300 81 42 4.6 2.5
38000 -59.9 -75.8 305 77 40 8.7 4.8 | -59.9 -75.8 300 80 41 8.4 4.6
36000 -54.6 -66.3 300 72 37 8.7 4.8 | -54.9 -66.8 300 76 39 8.4 4.6
34000 -49.5 -57.1 300 68 35 8.3 4.6 | -49.8 -57.6 300 72 37 8.7 4.8
32000 -44.5 -48.1 300 69 35 8.3 4.6 | -43.9 -47.0 300 69 35 8.7 4.8
30000 -38.8 -37.8 300 68 35 8.6 4.7 | -38.7 -37.7 300 66 34 8.6 4.7
29000 -36.2 -33.2 300 66 34 8.6 4.7 | -36.2 -33.2 305 64 33 8.6 4.7
28000 -33.7 -28.7 305 65 33 8.6 4.7 | -33.6 -28.5 305 63 32 8.6 4.7
27000 -31.1 -24.0 305 63 32 8.3 4.5 | -31.1 -24.0 310 62 32 8.3 4.6
26000 -28.6 -19.5 305 60 31 8.3 4.6 | -28.6 -19.5 310 61 31 8.3 4.6
25000 -26.2 -15.2 305 58 30 8.3 4.6 | -26.1 -15.0 310 60 31 8.3 4.6
24000 -23.7 -10.7 310 56 29 8.1 4.4 | -23.7 -10.7 310 59 30 8.0 4.4
23000 -21.3 -6.3 310 54 28 8.1 4.4 | -21.3 -6.3 310 58 30 8.0 4.4
22000 -18.9 -2.0 310 52 27 8.1 4.4 | -18.9 -2.0 310 57 30 8.0 4.4
21000 -16.5 2.3 315 51 26 7.8 4.3 | -16.6 2.1 315 57 29 7.6 4.2
20000 -14.2 6.4 315 50 26 7.9 4.3 | -14.3 6.3 315 56 29 7.7 4.2
19500 -13.0 8.6 315 49 25 7.9 4.3 | -13.2 8.2 315 55 28 7.7 4.2
19000 -11.9 10.6 315 49 25 7.9 4.3 | -12.0 10.4 315 55 28 7.7 4.2
18500 -10.7 12.7 315 48 25 7.5 4.1 | -10.9 12.4 315 55 28 7.2 4.0
18000 -9.6 14.7 315 48 25 7.5 4.1 | -9.9 14.2 315 54 28 7.2 3.9
17500 -8.5 16.7 315 47 24 7.4 4.1 | -8.8 16.2 315 54 28 7.2 3.9
17000 -7.4 18.7 315 47 24 7.2 3.9 | -7.7 18.1 315 54 28 7.2 3.9
16500 -6.3 20.7 315 47 24 7.2 4.0 | -6.7 19.9 315 53 27 7.2 4.0
16000 -5.3 22.5 315 47 24 6.7 3.7 | -5.1 22.8 315 53 27 7.0 3.8
15500 -4.3 24.3 315 47 24 6.7 3.7 | -4.1 24.6 310 52 27 7.1 3.9
15000 -3.3 26.1 315 47 24 6.5 3.5 | -3.1 26.4 310 52 27 6.4 3.5
14500 -2.4 27.7 315 46 24 6.2 3.4 | -2.1 28.2 310 50 26 6.5 3.6
14000 -1.1 30.0 315 44 23 6.0 3.3 | -1.2 29.8 310 49 25 6.0 3.3
13500 -0.2 31.6 310 43 22 5.9 3.2 | -0.3 31.5 305 48 25 5.8 3.2
13000 0.6 33.1 310 42 21 5.3 2.9 | 0.5 32.9 305 46 24 5.2 2.9
12500 1.4 34.5 310 39 20 4.9 2.7 | 1.2 34.2 305 44 23 4.9 2.7
12000 2.1 35.8 305 36 19 5.2 2.9 | 1.9 35.4 305 41 21 5.1 2.8
11500 2.9 37.2 305 36 19 5.5 3.0 | 2.7 36.9 300 39 20 5.3 2.9
11000 3.7 38.7 305 37 19 4.6 2.5 | 3.5 38.3 300 37 19 4.9 2.7
10500 4.2 39.6 305 37 19 2.8 1.5 | 4.1 39.4 300 35 18 3.5 1.9
10250 4.5 40.1 300 37 19 6.3 3.5 | 4.4 39.9 300 35 18 7.2 3.9
10000 5.1 41.2 300 36 19 7.0 3.8 | 5.1 41.2 300 33 17 8.4 4.6
9750 5.4 41.7 300 36 18 3.6 2.0 | 5.5 41.9 295 34 17 4.9 2.7
9500 5.7 42.3 300 36 18 4.6 2.5 | 5.9 42.6 295 34 17 5.3 2.9
9250 6.0 42.8 295 35 18 2.9 1.6 | 6.3 43.3 295 34 18 4.6 2.5
9000 6.2 43.2 295 35 18 1.9 1.0 | 6.6 43.9 295 35 18 3.1 1.7
8750 6.4 43.5 295 34 17 3.9 2.2 | 6.8 44.2 290 35 18 3.7 2.0
8500 6.7 44.1 290 32 17 5.2 2.8 | 7.1 44.8 290 33 17 5.0 2.7
8250 7.0 44.6 290 30 16 3.8 2.1 | 7.5 45.5 290 32 16 3.8 2.1
8000 7.2 45.0 290 28 15 2.5 1.4 | 7.7 45.9 285 30 16 2.1 1.2
7750 7.5 45.5 290 26 13 5.7 3.1 | 7.9 46.2 285 28 14 4.6 2.5
7500 8.1 46.6 290 23 12 8.1 4.4 | 8.3 46.9 285 25 13 7.1 3.9
7250 8.6 47.5 290 21 11 7.0 3.8 | 8.8 47.8 285 22 11 5.5 3.0
7000 9.1 48.4 290 19 10 6.5 3.5 | 9.2 48.6 285 19 10 4.3 2.4
6750 9.7 49.5 290 18 9 8.2 4.5 | 9.5 49.1 285 17 9 4.9 2.7
6500 10.3 50.5 290 15 8 9.1 5.0 | 9.9 49.8 285 14 7 5.4 2.9
6250 10.9 51.6 290 13 7 6.0 3.3 | 10.2 50.4 290 12 6 4.3 2.3
6000 11.3 52.3 290 12 6 4.2 2.3 | 10.5 50.9 290 11 6 3.8 2.1
5750 11.6 52.9 295 11 6 5.8 3.2 | 10.8 51.4 290 9 5 3.3 1.8
5500 12.1 53.8 295 10 5 6.8 3.7 | 10.8 51.4 290 7 4 -6.8 -3.7
________________________________________________________________________________
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 near the old Stapleton
Airport site in Denver, Colorado at
North Latitude: 39 deg 46 min 5.016 sec
West Longitude: 104 deg 52 min 9.984 sec
Elevation: 5285 feet (1611 meters)
and may not be representative of other areas along the Front Range of the
Colorado Rocky Mountains. 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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