Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
366
UXUS97 KBOU 051321
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0620 MST Friday, December 5, 2025
This forecast is for Friday, December 5, 2025:
If the trigger temperature of 47.0 F/8.3 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 6229 ft MSL (904 ft AGL)
Forecast maximum temperature................... 39.0 F/4.3 C
Time of trigger temperature.................... None
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Overcast opaque high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 5529 ft MSL (203 ft AGL)
Thermal soaring outlook for Saturday 12/06..... Good
Wave Soaring Index............................. Fair
Wave Soaring Index trend (to 1700 MST)......... Little change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Weak PVA
Potential height of wave....................... 45031 ft MSL (39706 ft AGL)
Wave soaring outlook for Saturday 12/06........ Fair
Remarks...
Sunrise/Sunset.................... 07:05:52 / 16:34:46 MST
Total possible sunshine........... 9 hr 28 min 54 sec (568 min 54 sec)
Altitude of sun at 11:50:19 MST... 27.72 degrees
Upper air data from numerical model forecast valid on 12/05/2025 at 0500 MST
Freezing level.................. 5511 ft MSL (186 ft AGL)
Additional freezing level....... 7032 ft MSL (1707 ft AGL)
Convective condensation level... 15711 ft MSL (10386 ft AGL)
Lifted condensation level....... 11546 ft MSL (6220 ft AGL)
Lifted index.................... +11.4
K index......................... +10.2
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 -57.3 -71.1 315 42 21 3.9 2.2 M M M M M
45000 -51.4 -60.5 315 58 30 4.0 2.2 M M M M M
40000 -45.3 -49.5 305 56 29 4.1 2.2 M M M M M
38000 -44.3 -47.7 300 55 29 -2.4 -1.3 M M M M M
36000 -45.7 -50.3 290 56 29 -2.3 -1.3 M M M M M
34000 -47.1 -52.8 285 58 30 -2.0 -1.1 M M M M M
32000 -47.8 -54.0 280 58 30 -1.1 -0.6 M M M M M
30000 -48.4 -55.1 275 59 30 1.8 1.0 M M M M M
29000 -46.3 -51.3 275 56 29 7.7 4.2 26.6 79.8 17.2 M M
28000 -44.0 -47.2 280 54 28 7.7 4.2 25.7 78.3 16.7 M M
27000 -41.7 -43.1 280 51 26 7.7 4.2 25.0 77.0 16.4 M M
26000 -39.3 -38.7 285 49 25 8.2 4.5 24.3 75.7 16.0 M M
25000 -36.9 -34.4 290 48 24 8.2 4.5 23.6 74.5 15.7 M M
24000 -34.4 -29.9 290 46 24 8.2 4.5 23.1 73.6 15.4 M M
23000 -32.1 -25.8 295 45 23 7.4 4.1 22.4 72.4 15.0 M M
22000 -29.9 -21.8 295 43 22 7.4 4.1 21.5 70.7 14.5 M M
21000 -27.6 -17.7 295 42 21 7.5 4.1 20.7 69.3 14.0 M M
20000 -25.5 -13.9 295 40 21 7.0 3.8 19.8 67.6 13.3 M M
19500 -23.9 -11.0 300 39 20 7.0 3.8 19.0 66.2 12.8 M M
19000 -22.9 -9.2 300 38 19 7.0 3.8 18.6 65.4 12.5 M M
18500 -21.9 -7.4 300 37 19 7.0 3.8 18.1 64.6 12.1 M M
18000 -20.9 -5.6 300 36 19 6.6 3.6 17.6 63.7 11.8 M M
17500 -19.9 -3.8 300 35 18 6.7 3.7 17.1 62.7 11.3 M M
17000 -18.9 -2.0 300 35 18 6.5 3.6 16.5 61.8 10.9 M M
16500 -17.9 -0.2 300 34 17 6.5 3.5 16.0 60.8 10.5 M M
16000 -17.0 1.4 300 33 17 6.3 3.5 15.4 59.8 10.0 M M
15500 -16.1 3.0 300 32 16 6.1 3.4 14.8 58.6 9.5 M M
15000 -15.1 4.8 295 31 16 6.1 3.4 14.2 57.6 9.0 M M
14500 -14.2 6.4 295 29 15 6.1 3.4 13.6 56.5 8.5 M M
14000 -13.3 8.1 295 28 14 6.1 3.3 13.0 55.4 8.0 M M
13500 -12.4 9.7 295 26 14 6.7 3.7 12.4 54.4 7.5 M M
13000 -11.4 11.5 295 25 13 6.6 3.6 11.9 53.5 7.1 M M
12500 -10.4 13.3 295 23 12 6.9 3.8 11.4 52.6 6.7 M M
12000 -9.4 15.1 300 21 11 6.8 3.7 11.0 51.7 6.3 M M
11500 -8.3 17.1 300 19 10 7.1 3.9 10.5 50.9 5.9 M M
11000 -7.3 18.9 305 16 8 7.2 4.0 10.1 50.1 5.5 M M
10500 -6.3 20.7 305 15 8 6.0 3.3 9.6 49.2 5.1 M M
10250 -5.9 21.4 305 15 8 5.2 2.9 9.3 48.7 4.8 M M
10000 -5.4 22.3 305 15 8 8.9 4.9 9.0 48.1 4.5 M M
9750 -4.6 23.7 310 13 7 9.5 5.2 9.0 48.3 4.6 M M
9500 -4.1 24.6 310 13 7 6.2 3.4 8.8 47.9 4.4 M M
9250 -3.6 25.5 310 14 7 7.3 4.0 8.6 47.5 4.2 M M
9000 -3.0 26.6 305 15 8 6.1 3.4 8.4 47.1 4.0 M M
8750 -2.7 27.1 300 18 9 4.2 2.3 8.0 46.4 3.7 M M
8500 -2.4 27.7 300 17 9 3.8 2.1 7.6 45.6 3.2 M M
8250 -2.1 28.2 300 17 9 3.5 1.9 7.1 44.8 2.8 M M
8000 -1.8 28.8 295 17 9 5.1 2.8 6.6 44.0 2.4 M M
7750 -1.3 29.7 295 17 9 6.4 3.5 6.4 43.5 2.1 M M
7500 -0.9 30.4 295 15 8 5.8 3.2 6.1 42.9 1.8 M M
7250 -0.5 31.1 295 14 7 5.9 3.2 5.8 42.4 1.5 M M
7000 -0.0 32.0 295 12 6 5.4 2.9 5.5 41.8 1.2 M M
6750 0.4 32.7 300 11 5 5.7 3.1 5.1 41.2 0.9 M M
6500 0.8 33.4 300 9 4 6.7 3.7 4.9 40.7 0.6 M M
6250 1.2 34.2 295 6 3 2.1 1.1 4.5 40.1 0.3 M M
6000 1.1 34.0 285 4 2 -2.7 -1.5 3.7 38.6 -0.6 38 0.2
5750 1.0 33.8 250 3 1 1.7 0.9 2.9 37.2 -1.4 33 0.2
5500 0.9 33.6 210 4 2 -10.5 -5.8 2.1 35.7 -2.2 28 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
12/05/2025 at 0800 MST | 12/05/2025 at 1100 MST
|
CAPE... 0.0 LI... +4.6 | CAPE... +4.2 LI... +3.7
CINH... 0.0 K Index... +11.6 | CINH... -7.7 K Index... +14.1
|
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 -57.5 -71.5 305 40 21 4.8 2.6 | -57.5 -71.5 295 44 23 5.3 2.9
45000 -50.3 -58.5 310 59 31 4.6 2.5 | -49.6 -57.3 300 56 29 4.8 2.6
40000 -43.7 -46.7 310 59 30 4.3 2.4 | -43.8 -46.8 310 64 33 3.8 2.1
38000 -42.5 -44.5 305 58 30 -2.8 -1.5 | -42.7 -44.9 310 66 34 -2.3 -1.2
36000 -44.2 -47.6 300 59 30 -2.7 -1.5 | -44.0 -47.2 305 64 33 -2.2 -1.2
34000 -45.8 -50.4 295 60 31 -2.7 -1.5 | -45.4 -49.7 300 63 32 -2.1 -1.1
32000 -47.2 -53.0 285 54 28 -2.2 -1.2 | -45.6 -50.1 295 58 30 -0.2 -0.1
30000 -48.5 -55.3 275 49 25 -1.5 -0.8 | -45.7 -50.3 290 54 28 -0.2 -0.1
29000 -47.1 -52.8 280 48 25 6.2 3.4 | -45.0 -49.0 285 53 28 3.1 1.7
28000 -45.2 -49.4 285 47 24 6.2 3.4 | -44.0 -47.2 285 54 28 3.1 1.7
27000 -43.4 -46.1 290 47 24 6.2 3.4 | -43.1 -45.6 285 55 28 3.1 1.7
26000 -41.2 -42.2 290 47 24 9.1 5.0 | -41.6 -42.9 280 56 29 8.5 4.7
25000 -38.5 -37.3 295 47 24 9.0 5.0 | -39.2 -38.6 280 57 29 8.2 4.5
24000 -35.8 -32.4 295 48 25 9.0 5.0 | -36.7 -34.1 280 58 30 8.2 4.5
23000 -33.2 -27.8 295 48 25 7.9 4.3 | -34.3 -29.7 280 58 30 7.7 4.2
22000 -30.8 -23.4 295 47 24 8.0 4.4 | -31.9 -25.4 285 55 29 7.7 4.3
21000 -27.8 -18.0 300 46 24 7.9 4.3 | -29.6 -21.3 290 54 28 7.8 4.3
20000 -25.8 -14.4 300 44 23 6.8 3.7 | -27.1 -16.8 295 50 26 6.2 3.4
19500 -24.7 -12.5 300 44 22 6.8 3.7 | -26.2 -15.2 295 48 25 6.2 3.4
19000 -23.7 -10.7 300 43 22 6.8 3.7 | -25.3 -13.5 295 47 24 6.3 3.4
18500 -22.7 -8.9 300 42 22 6.8 3.7 | -24.3 -11.7 295 45 23 6.3 3.5
18000 -21.8 -7.2 300 41 21 6.2 3.4 | -23.4 -10.1 295 43 22 6.2 3.4
17500 -20.8 -5.4 300 40 20 6.3 3.4 | -22.5 -8.5 295 42 22 6.2 3.4
17000 -19.9 -3.8 300 38 20 6.0 3.3 | -21.6 -6.9 300 41 21 6.0 3.3
16500 -19.0 -2.2 300 37 19 5.9 3.3 | -20.7 -5.3 300 39 20 5.9 3.3
16000 -18.2 -0.8 300 35 18 5.9 3.2 | -19.8 -3.6 300 37 19 5.9 3.2
15500 -17.3 0.9 300 33 17 5.9 3.2 | -19.0 -2.2 300 35 18 5.8 3.2
15000 -16.4 2.5 300 31 16 5.9 3.2 | -18.1 -0.6 300 33 17 5.9 3.2
14500 -15.5 4.1 300 29 15 5.9 3.3 | -17.2 1.0 300 31 16 6.5 3.6
14000 -14.7 5.5 300 27 14 5.9 3.3 | -16.2 2.8 300 29 15 6.4 3.5
13500 -13.7 7.3 300 25 13 6.2 3.4 | -15.2 4.6 300 26 14 7.1 3.9
13000 -12.8 9.0 300 22 11 6.1 3.4 | -14.2 6.4 300 24 12 7.0 3.8
12500 -11.9 10.6 300 20 10 6.9 3.8 | -13.1 8.4 300 22 11 7.5 4.1
12000 -10.8 12.6 300 18 9 6.8 3.7 | -12.0 10.4 300 20 10 7.3 4.0
11500 -9.8 14.4 305 17 9 7.2 4.0 | -10.7 12.7 300 19 10 9.0 4.9
11000 -8.7 16.3 305 17 9 7.3 4.0 | -9.4 15.1 300 19 10 8.9 4.9
10500 -7.8 18.0 310 17 9 5.8 3.2 | -8.3 17.1 300 20 10 6.7 3.7
10250 -7.3 18.9 310 18 9 4.8 2.6 | -7.8 18.0 300 20 10 5.5 3.0
10000 -6.9 19.6 310 19 10 9.2 5.1 | -7.3 18.9 300 21 11 11.1 6.1
9750 -6.0 21.2 310 18 9 10.4 5.7 | -6.3 20.7 300 21 11 11.3 6.2
9500 -5.5 22.1 310 18 9 6.5 3.6 | -5.7 21.7 300 20 10 5.8 3.2
9250 -4.9 23.2 310 19 10 8.3 4.5 | -5.2 22.6 300 20 10 7.6 4.2
9000 -4.3 24.3 310 19 10 5.3 2.9 | -4.7 23.5 300 20 10 5.7 3.1
8750 -4.0 24.8 305 21 11 5.1 2.8 | -4.3 24.3 295 19 10 6.5 3.6
8500 -3.5 25.7 305 21 11 7.6 4.1 | -3.7 25.3 295 18 9 8.6 4.7
8250 -3.0 26.6 300 20 10 7.1 3.9 | -3.1 26.4 295 16 8 8.0 4.4
8000 -2.5 27.5 300 19 10 6.1 3.3 | -2.5 27.5 295 15 8 7.8 4.3
7750 -2.1 28.2 300 18 10 6.1 3.4 | -1.9 28.6 290 13 7 7.1 3.9
7500 -1.5 29.3 300 16 8 7.3 4.0 | -1.4 29.5 290 11 6 7.0 3.8
7250 -1.0 30.2 295 13 7 6.9 3.8 | -0.9 30.4 290 9 5 6.9 3.8
7000 -0.5 31.1 295 12 6 6.6 3.6 | -0.4 31.3 290 8 4 6.1 3.3
6750 0.0 32.0 295 11 6 7.3 4.0 | 0.1 32.2 285 6 3 7.4 4.0
6500 0.6 33.1 290 8 4 8.0 4.4 | 0.7 33.3 275 5 3 8.7 4.8
6250 1.1 34.0 280 6 3 4.6 2.5 | 1.3 34.3 265 4 2 7.4 4.1
6000 1.3 34.3 260 5 3 1.3 0.7 | 1.8 35.2 260 4 2 7.3 4.0
5750 1.5 34.7 245 5 3 5.5 3.0 | 2.3 36.1 250 3 2 6.2 3.4
5500 1.7 35.1 220 6 3 -7.2 -4.0 | 2.6 36.7 235 3 1 2.1 1.2
12/05/2025 at 1400 MST | 12/05/2025 at 1700 MST
|
CAPE... +2.1 LI... +0.2 | CAPE... 0.0 LI... +3.3
CINH... -4.3 K Index... +15.2 | CINH... 0.0 K Index... +8.1
|
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 -57.4 -71.3 300 46 24 4.5 2.4 | -58.5 -73.3 300 50 26 4.4 2.4
45000 -50.7 -59.3 310 53 27 4.1 2.2 | -51.9 -61.4 305 53 27 4.1 2.2
40000 -45.4 -49.7 310 62 32 3.5 1.9 | -46.2 -51.2 305 62 32 3.8 2.1
38000 -44.0 -47.2 310 64 33 0.0 0.0 | -44.8 -48.6 310 66 34 -0.6 -0.4
36000 -44.0 -47.2 315 64 33 -0.0 -0.0 | -45.2 -49.4 325 71 37 -0.6 -0.4
34000 -44.0 -47.2 315 63 33 0.5 0.3 | -45.7 -50.3 335 80 41 0.8 0.4
32000 -42.9 -45.2 315 62 32 2.0 1.1 | -44.0 -47.2 335 92 47 2.8 1.5
30000 -41.7 -43.1 320 61 32 2.1 1.1 | -42.3 -44.1 340 104 53 3.0 1.6
29000 -40.8 -41.4 320 61 31 3.0 1.6 | -41.4 -42.5 340 100 51 3.2 1.7
28000 -39.9 -39.8 320 61 31 3.0 1.6 | -40.4 -40.7 340 95 49 3.2 1.7
27000 -39.0 -38.2 320 60 31 3.0 1.6 | -39.5 -39.1 340 90 46 3.2 1.8
26000 -38.1 -36.6 320 59 31 3.6 2.0 | -38.1 -36.6 340 86 44 6.4 3.5
25000 -37.0 -34.6 315 57 30 3.5 1.9 | -36.2 -33.2 340 83 43 6.4 3.5
24000 -36.0 -32.8 315 56 29 3.5 1.9 | -34.3 -29.7 340 81 42 6.4 3.5
23000 -34.8 -30.6 310 53 27 4.8 2.6 | -32.4 -26.3 340 78 40 6.4 3.5
22000 -33.4 -28.1 310 50 26 4.6 2.5 | -30.5 -22.9 340 73 37 6.4 3.5
21000 -32.0 -25.6 305 47 24 4.7 2.6 | -28.6 -19.5 335 68 35 6.4 3.5
20000 -30.4 -22.7 305 44 23 6.3 3.4 | -27.0 -16.6 335 61 32 4.6 2.5
19500 -29.5 -21.1 305 43 22 6.3 3.5 | -26.3 -15.3 330 58 30 4.5 2.5
19000 -28.1 -18.6 305 40 21 6.4 3.5 | -25.6 -14.1 330 54 28 4.5 2.5
18500 -27.1 -16.8 300 39 20 6.2 3.4 | -24.9 -12.8 325 50 26 4.5 2.5
18000 -26.1 -15.0 300 38 19 7.9 4.3 | -24.3 -11.7 325 47 24 4.7 2.6
17500 -24.9 -12.8 305 37 19 7.7 4.2 | -23.2 -9.8 320 45 23 5.0 2.7
17000 -23.8 -10.8 305 37 19 8.5 4.6 | -22.4 -8.3 320 43 22 5.0 2.7
16500 -22.5 -8.5 305 37 19 8.8 4.8 | -21.7 -7.1 315 42 21 5.0 2.8
16000 -21.2 -6.2 305 37 19 8.6 4.7 | -21.0 -5.8 315 40 21 5.4 3.0
15500 -19.9 -3.8 305 37 19 8.1 4.4 | -20.1 -4.2 310 39 20 6.3 3.5
15000 -18.7 -1.7 305 37 19 8.1 4.4 | -19.2 -2.6 310 39 20 6.4 3.5
14500 -17.5 0.5 305 36 19 7.9 4.4 | -18.1 -0.6 310 38 20 7.6 4.2
14000 -16.4 2.5 305 36 18 8.0 4.4 | -17.0 1.4 305 37 19 7.5 4.1
13500 -15.2 4.6 300 35 18 8.0 4.4 | -15.8 3.6 305 36 19 8.7 4.8
13000 -14.0 6.8 300 33 17 8.1 4.4 | -14.6 5.7 305 35 18 8.6 4.7
12500 -12.8 9.0 300 32 16 7.8 4.3 | -13.3 8.1 305 35 18 8.4 4.6
12000 -11.7 10.9 300 31 16 7.8 4.3 | -12.0 10.4 305 34 17 8.4 4.6
11500 -10.5 13.1 300 29 15 7.8 4.3 | -10.8 12.6 305 33 17 8.4 4.6
11000 -9.4 15.1 295 28 14 8.0 4.4 | -9.6 14.7 300 32 16 8.5 4.7
10500 -8.4 16.9 295 26 14 5.8 3.2 | -8.5 16.7 300 31 16 6.8 3.7
10250 -7.9 17.8 295 26 13 5.1 2.8 | -8.0 17.6 300 31 16 6.0 3.3
10000 -7.5 18.5 290 25 13 9.0 4.9 | -7.5 18.5 300 31 16 9.9 5.4
9750 -6.7 19.9 290 21 11 9.9 5.4 | -6.6 20.1 300 28 14 10.6 5.8
9500 -6.1 21.0 290 19 10 6.4 3.5 | -6.0 21.2 295 26 14 7.0 3.9
9250 -5.6 21.9 290 17 9 8.0 4.4 | -5.4 22.3 295 24 13 8.2 4.5
9000 -5.1 22.8 290 15 8 5.1 2.8 | -4.9 23.2 295 23 12 7.1 3.9
8750 -4.8 23.4 285 12 6 5.1 2.8 | -4.4 24.1 295 22 11 6.6 3.6
8500 -4.2 24.4 285 10 5 7.5 4.1 | -3.9 25.0 290 19 10 6.9 3.8
8250 -3.7 25.3 290 8 4 7.2 3.9 | -3.4 25.9 290 16 8 7.0 3.9
8000 -3.2 26.2 290 6 3 4.8 2.6 | -2.9 26.8 285 14 7 5.4 2.9
7750 -2.9 26.8 285 3 1 5.3 2.9 | -2.6 27.3 280 12 6 4.9 2.7
7500 -2.4 27.7 290 2 1 8.3 4.6 | -2.1 28.2 275 10 5 6.1 3.4
7250 -1.8 28.8 295 1 0 6.6 3.6 | -1.7 28.9 270 8 4 5.5 3.0
7000 -1.4 29.5 085 1 1 3.3 1.8 | -1.4 29.5 260 7 3 4.0 2.2
6750 -1.1 30.0 090 4 2 7.8 4.3 | -1.0 30.2 245 6 3 6.1 3.3
6500 -0.3 31.5 085 3 2 12.8 7.0 | -0.5 31.1 235 5 3 8.5 4.7
6250 0.5 32.9 080 3 2 9.4 5.1 | 0.1 32.2 220 4 2 7.3 4.0
6000 1.2 34.2 080 4 2 7.7 4.2 | 0.6 33.1 205 4 2 6.4 3.5
5750 1.8 35.2 080 5 2 9.7 5.3 | 1.1 34.0 185 3 2 8.2 4.5
5500 2.6 36.7 075 3 1 12.6 6.9 | 1.7 35.1 190 3 2 4.1 2.3
________________________________________________________________________________
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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