Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
401
UXUS97 KBOU 171332
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0631 MST Monday, November 17, 2025
This forecast is for Monday, November 17, 2025:
If the trigger temperature of 58.5 F/14.7 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 291 ft/min (1.5 m/s)
Maximum height of thermals.................. 9449 ft MSL (4168 ft AGL)
Forecast maximum temperature................... 59.0 F/15.5 C
Time of trigger temperature.................... 1245 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................. 6969 ft MSL (1688 ft AGL)
Thermal soaring outlook for Tuesday 11/18...... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST).........
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Weak NVA
Potential height of wave....................... 18302 ft MSL (13021 ft AGL)
Wave soaring outlook for Tuesday 11/18......... Poor
Remarks...
Sunrise/Sunset.................... 06:47:03 / 16:41:59 MST
Total possible sunshine........... 9 hr 54 min 57 sec (594 min 57 sec)
Altitude of sun at 11:44:31 MST... 30.94 degrees
Upper air data from numerical model forecast valid on 11/17/2025 at 0500 MST
Freezing level.................. 10766 ft MSL (5485 ft AGL)
Convective condensation level... 14033 ft MSL (8752 ft AGL)
Lifted condensation level....... 13144 ft MSL (7864 ft AGL)
Lifted index.................... +2.7
K index......................... +11.4
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 -56.2 -69.2 225 20 10 2.1 1.2 M M M M M
45000 -53.0 -63.4 215 25 13 1.6 0.9 M M M M M
40000 -53.3 -63.9 230 55 28 -0.2 -0.1 M M M M M
38000 -52.8 -63.0 230 63 33 1.9 1.1 M M M M M
36000 -51.6 -60.9 230 68 35 1.9 1.1 M M M M M
34000 -50.3 -58.5 235 73 38 5.8 3.2 M M M M M
32000 -46.4 -51.5 235 75 39 6.5 3.6 M M M M M
30000 -42.5 -44.5 235 77 40 7.4 4.0 34.6 94.2 14.7 M M
29000 -40.2 -40.4 235 74 38 7.5 4.1 33.5 92.4 14.1 M M
28000 -37.4 -35.3 235 70 36 7.5 4.1 32.5 90.4 13.5 M M
27000 -35.2 -31.4 240 66 34 7.3 4.0 31.7 89.1 13.1 M M
26000 -33.5 -28.3 235 60 31 5.2 2.9 30.1 86.1 11.9 M M
25000 -31.9 -25.4 235 52 27 5.2 2.9 28.3 83.0 10.7 M M
24000 -30.4 -22.7 230 45 23 5.2 2.8 26.8 80.2 9.5 M M
23000 -28.6 -19.5 225 38 20 6.3 3.4 25.3 77.6 8.4 M M
22000 -26.7 -16.1 220 31 16 6.3 3.4 24.0 75.2 7.4 M M
21000 -24.9 -12.8 210 25 13 6.4 3.5 22.9 73.2 6.5 M M
20000 -22.8 -9.0 210 22 12 7.2 4.0 21.9 71.3 5.7 M M
19500 -21.7 -7.1 215 21 11 7.2 4.0 21.4 70.5 5.3 M M
19000 -20.6 -5.1 215 20 11 7.2 4.0 21.0 69.8 5.0 M M
18500 -19.6 -3.3 220 19 10 7.2 4.0 20.6 69.0 4.7 M M
18000 -18.5 -1.3 220 19 10 7.5 4.1 20.2 68.3 4.3 M M
17500 -17.4 0.7 225 19 10 7.5 4.1 19.8 67.6 4.0 M M
17000 -16.3 2.7 230 19 10 7.8 4.3 19.4 67.0 3.7 M M
16500 -15.1 4.8 235 18 10 8.0 4.4 19.1 66.4 3.4 M M
16000 -13.9 7.0 235 18 9 8.0 4.4 18.8 65.9 3.1 M M
15500 -12.8 9.0 240 18 9 7.7 4.2 18.5 65.3 2.9 M M
15000 -11.6 11.1 240 17 9 7.6 4.2 18.2 64.7 2.6 M M
14500 -10.4 13.3 245 17 9 9.0 4.9 17.9 64.2 2.3 M M
14000 -8.4 16.9 250 15 8 9.0 4.9 17.7 63.8 2.2 M M
13500 -7.0 19.4 260 16 8 9.4 5.2 17.6 63.7 2.1 M M
13000 -5.6 21.9 265 17 9 9.4 5.1 17.6 63.6 2.1 M M
12500 -4.2 24.4 265 19 10 8.8 4.8 17.4 63.4 2.0 M M
12000 -2.9 26.8 265 20 10 8.9 4.9 17.3 63.2 1.9 M M
11500 -1.6 29.1 265 22 11 8.2 4.5 17.1 62.8 1.7 M M
11000 -0.4 31.3 265 24 12 8.2 4.5 16.9 62.3 1.5 M M
10500 0.7 33.3 265 27 14 5.9 3.3 16.4 61.6 1.1 M M
10250 1.1 34.0 265 29 15 6.5 3.6 16.1 61.1 0.8 M M
10000 1.6 34.9 265 31 16 7.3 4.0 15.9 60.7 0.6 M M
9750 2.1 35.8 265 33 17 6.3 3.4 15.7 60.3 0.4 M M
9500 2.5 36.5 270 33 17 5.2 2.8 15.4 59.7 0.0 M M
9250 2.9 37.2 270 33 17 5.5 3.0 15.0 59.1 -0.3 273 1.4
9000 3.3 37.9 270 34 17 5.4 2.9 14.7 58.5 -0.7 255 1.3
8750 3.6 38.5 270 34 17 5.6 3.1 14.4 57.9 -1.1 236 1.2
8500 4.0 39.2 275 32 16 6.0 3.3 14.1 57.3 -1.4 217 1.1
8250 4.4 39.9 275 30 15 5.7 3.1 13.8 56.8 -1.7 197 1.0
8000 4.8 40.6 275 28 14 6.7 3.7 13.5 56.2 -2.1 178 0.9
7750 5.4 41.7 280 25 13 7.4 4.1 13.3 55.9 -2.3 154 0.8
7500 5.9 42.6 280 23 12 7.0 3.8 13.1 55.5 -2.5 132 0.7
7250 6.4 43.5 280 21 11 7.1 3.9 12.9 55.2 -2.7 109 0.6
7000 6.9 44.4 285 19 10 6.0 3.3 12.6 54.7 -3.0 87 0.4
6750 7.3 45.1 285 17 9 6.0 3.3 12.3 54.2 -3.3 67 0.3
6500 7.8 46.0 290 15 8 7.8 4.3 12.1 53.8 -3.5 45 0.2
6250 8.3 46.9 295 12 6 4.5 2.5 11.9 53.4 -3.8 23 0.1
6000 8.4 47.1 300 10 5 2.1 1.1 11.3 52.4 -4.4 11 0.1
5750 8.4 47.1 305 7 4 -3.4 -1.9 10.7 51.2 -5.1 3 0.0
5500 7.6 45.7 310 3 2 -16.4 -9.0 9.2 48.5 -6.7 21 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/17/2025 at 0800 MST | 11/17/2025 at 1100 MST
|
CAPE... 0.0 LI... +2.2 | CAPE... +5.8 LI... +0.9
CINH... 0.0 K Index... +4.8 | CINH... -85.7 K Index... +15.5
|
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 -56.3 -69.3 230 23 12 2.3 1.3 | -56.2 -69.2 240 26 13 1.8 1.0
45000 -52.9 -63.2 245 27 14 2.0 1.1 | -53.4 -64.1 260 34 17 2.0 1.1
40000 -51.0 -59.8 240 56 29 1.2 0.6 | -49.5 -57.1 250 56 29 2.5 1.4
38000 -50.3 -58.5 235 62 32 1.0 0.6 | -47.9 -54.2 245 60 31 2.9 1.6
36000 -49.7 -57.5 230 63 32 1.0 0.6 | -46.1 -51.0 245 59 31 2.9 1.6
34000 -49.0 -56.2 225 64 33 4.1 2.3 | -44.4 -47.9 240 59 30 2.2 1.2
32000 -45.8 -50.4 225 66 34 5.4 3.0 | -43.6 -46.5 240 58 30 1.4 0.8
30000 -42.5 -44.5 230 68 35 6.0 3.3 | -42.7 -44.9 240 57 29 1.2 0.7
29000 -40.6 -41.1 230 67 35 6.3 3.5 | -42.8 -45.0 245 53 27 -0.3 -0.1
28000 -38.3 -36.9 230 67 34 6.3 3.5 | -42.8 -45.0 245 50 26 -0.2 -0.1
27000 -36.4 -33.5 235 66 34 6.5 3.6 | -42.9 -45.2 250 46 24 -0.9 -0.5
26000 -34.8 -30.6 235 61 32 4.8 2.6 | -41.3 -42.3 255 44 22 8.5 4.7
25000 -33.4 -28.1 235 56 29 4.8 2.6 | -38.7 -37.7 255 42 22 8.6 4.7
24000 -32.0 -25.6 235 50 26 4.7 2.6 | -36.2 -33.2 260 40 21 8.5 4.7
23000 -30.2 -22.4 235 44 23 6.8 3.7 | -33.5 -28.3 260 40 20 9.3 5.1
22000 -28.1 -18.6 235 40 20 6.8 3.7 | -30.7 -23.3 265 39 20 9.3 5.1
21000 -26.1 -15.0 235 35 18 6.8 3.7 | -27.9 -18.2 265 38 20 9.3 5.1
20000 -24.0 -11.2 230 31 16 7.0 3.9 | -25.3 -13.5 265 37 19 8.7 4.8
19500 -23.0 -9.4 230 29 15 7.0 3.9 | -24.0 -11.2 265 36 19 8.7 4.8
19000 -21.9 -7.4 230 27 14 7.0 3.9 | -22.7 -8.9 265 36 18 8.7 4.8
18500 -20.9 -5.6 225 25 13 6.9 3.8 | -21.4 -6.5 270 35 18 8.8 4.8
18000 -19.7 -3.5 225 23 12 8.1 4.4 | -20.1 -4.2 270 34 17 8.0 4.4
17500 -18.6 -1.5 225 23 12 8.0 4.4 | -18.9 -2.0 270 32 16 8.1 4.4
17000 -17.4 0.7 220 22 11 8.2 4.5 | -17.7 0.1 265 30 15 7.9 4.4
16500 -16.1 3.0 225 21 11 8.4 4.6 | -16.6 2.1 270 28 14 7.9 4.3
16000 -14.9 5.2 225 21 11 8.5 4.7 | -15.4 4.3 270 26 14 8.0 4.4
15500 -13.6 7.5 225 21 11 8.7 4.8 | -14.2 6.4 270 25 13 8.6 4.7
15000 -12.3 9.9 230 20 10 8.8 4.8 | -12.9 8.8 275 25 13 8.7 4.7
14500 -11.0 12.2 230 20 10 8.4 4.6 | -11.6 11.1 275 25 13 8.2 4.5
14000 -9.1 15.6 240 20 10 8.4 4.6 | -9.8 14.4 280 26 14 8.3 4.5
13500 -7.9 17.8 245 20 10 8.3 4.5 | -8.6 16.5 280 28 15 8.3 4.6
13000 -6.7 19.9 255 21 11 8.3 4.5 | -7.4 18.7 280 31 16 8.3 4.5
12500 -5.4 22.3 260 22 11 8.1 4.5 | -6.2 20.8 280 32 17 7.6 4.2
12000 -4.2 24.4 265 24 12 8.1 4.5 | -5.1 22.8 280 34 17 7.7 4.2
11500 -3.1 26.4 270 27 14 7.7 4.2 | -4.0 24.8 280 35 18 7.1 3.9
11000 -1.9 28.6 275 30 16 7.7 4.2 | -3.0 26.6 280 35 18 7.2 3.9
10500 -1.1 30.0 275 34 17 4.5 2.4 | -2.0 28.4 275 35 18 6.9 3.8
10250 -0.7 30.7 275 35 18 5.0 2.7 | -1.4 29.5 275 34 18 7.4 4.1
10000 -0.4 31.3 275 37 19 6.3 3.4 | -0.9 30.4 275 34 18 8.8 4.8
9750 0.1 32.2 275 38 19 6.0 3.3 | -0.2 31.6 275 34 17 8.0 4.4
9500 0.5 32.9 275 38 20 5.1 2.8 | 0.3 32.5 275 32 16 6.9 3.8
9250 0.9 33.6 275 39 20 5.2 2.9 | 0.8 33.4 275 29 15 7.4 4.1
9000 1.2 34.2 275 40 20 5.7 3.1 | 1.4 34.5 275 27 14 6.7 3.6
8750 1.7 35.1 280 39 20 6.0 3.3 | 1.8 35.2 275 25 13 7.3 4.0
8500 2.1 35.8 280 37 19 5.8 3.2 | 2.5 36.5 275 22 11 8.7 4.8
8250 2.5 36.5 280 35 18 5.5 3.0 | 3.1 37.6 275 20 10 7.8 4.3
8000 2.9 37.2 280 33 17 6.9 3.8 | 3.7 38.7 275 17 9 9.9 5.4
7750 3.5 38.3 280 30 15 7.8 4.3 | 4.5 40.1 275 15 8 10.3 5.7
7500 4.0 39.2 280 27 14 7.1 3.9 | 5.2 41.4 275 14 7 8.5 4.7
7250 4.5 40.1 280 25 13 7.3 4.0 | 5.8 42.4 270 13 7 9.3 5.1
7000 5.1 41.2 280 23 12 7.6 4.2 | 6.6 43.9 270 12 6 10.5 5.8
6750 5.6 42.1 280 20 10 7.4 4.1 | 7.4 45.3 270 12 6 10.2 5.6
6500 6.2 43.2 275 17 9 7.8 4.3 | 8.1 46.6 270 11 6 8.9 4.9
6250 6.7 44.1 275 14 7 5.7 3.2 | 8.8 47.8 270 11 6 10.4 5.7
6000 7.0 44.6 270 12 6 5.2 2.9 | 9.6 49.3 270 10 5 12.0 6.6
5750 7.3 45.1 265 9 4 0.1 0.0 | 10.5 50.9 270 10 5 10.9 6.0
5500 6.7 44.1 240 5 3 -14.0 -7.7 | 11.3 52.3 270 9 5 13.4 7.4
11/17/2025 at 1400 MST | 11/17/2025 at 1700 MST
|
CAPE... +0.6 LI... +1.2 | CAPE... 0.0 LI... +4.7
CINH... -7.0 K Index... +16.0 | CINH... 0.0 K Index... +10.6
|
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 -56.2 -69.2 240 32 16 0.9 0.5 | -57.0 -70.6 245 30 15 1.1 0.6
45000 -54.9 -66.8 255 43 22 1.9 1.0 | -55.3 -67.5 260 39 20 1.2 0.6
40000 -50.3 -58.5 265 53 27 3.1 1.7 | -53.3 -63.9 275 55 29 1.3 0.7
38000 -48.9 -56.0 270 56 29 1.3 0.7 | -52.4 -62.3 280 59 31 1.6 0.9
36000 -48.1 -54.6 270 58 30 1.3 0.7 | -51.4 -60.5 280 61 31 1.6 0.9
34000 -47.1 -52.8 270 60 31 3.0 1.7 | -50.2 -58.4 280 60 31 4.4 2.4
32000 -45.2 -49.4 270 63 33 3.3 1.8 | -47.6 -53.7 290 43 22 4.4 2.4
30000 -43.2 -45.8 275 65 34 3.7 2.0 | -44.8 -48.6 305 29 15 7.5 4.1
29000 -42.1 -43.8 275 60 31 3.7 2.0 | -42.6 -44.7 310 29 15 7.4 4.1
28000 -41.0 -41.8 280 54 28 3.7 2.0 | -40.4 -40.7 310 28 15 7.4 4.1
27000 -39.9 -39.8 280 48 25 3.5 1.9 | -37.6 -35.7 315 28 14 7.9 4.3
26000 -38.1 -36.6 285 45 23 7.1 3.9 | -35.0 -31.0 315 30 15 8.6 4.7
25000 -36.0 -32.8 285 44 22 7.1 3.9 | -32.5 -26.5 310 32 16 8.6 4.7
24000 -33.8 -28.8 285 42 22 7.1 3.9 | -29.9 -21.8 310 33 17 8.6 4.7
23000 -31.5 -24.7 285 41 21 8.3 4.6 | -27.4 -17.3 305 37 19 8.3 4.6
22000 -29.0 -20.2 285 39 20 8.4 4.6 | -24.9 -12.8 305 40 21 8.3 4.6
21000 -26.5 -15.7 285 38 19 8.5 4.6 | -22.4 -8.3 305 44 23 8.0 4.4
20000 -24.2 -11.6 285 36 18 7.6 4.2 | -20.1 -4.2 305 42 22 7.6 4.2
19500 -23.0 -9.4 285 35 18 7.6 4.2 | -19.0 -2.2 305 41 21 7.6 4.2
19000 -21.9 -7.4 285 34 17 7.7 4.2 | -17.8 -0.0 305 39 20 7.6 4.2
18500 -20.7 -5.3 285 32 17 7.8 4.3 | -16.7 1.9 305 38 20 7.1 3.9
18000 -19.7 -3.5 285 31 16 6.3 3.4 | -16.0 3.2 300 34 17 3.8 2.1
17500 -18.7 -1.7 285 28 14 6.3 3.5 | -15.4 4.3 295 29 15 3.9 2.1
17000 -17.3 0.9 285 23 12 6.3 3.5 | -14.7 5.5 285 25 13 5.3 2.9
16500 -16.4 2.5 290 20 10 6.3 3.4 | -13.9 7.0 285 21 11 5.5 3.0
16000 -15.4 4.3 290 17 9 7.9 4.3 | -13.1 8.4 285 18 9 5.4 3.0
15500 -14.1 6.6 300 15 8 8.5 4.7 | -12.4 9.7 290 15 8 5.2 2.9
15000 -12.9 8.8 305 14 7 9.0 4.9 | -11.6 11.1 290 11 6 5.4 2.9
14500 -11.5 11.3 305 15 8 9.6 5.2 | -10.6 12.9 300 10 5 8.3 4.5
14000 -10.0 14.0 305 16 8 9.6 5.3 | -9.4 15.1 315 9 5 7.9 4.3
13500 -8.6 16.5 305 19 10 9.7 5.3 | -7.4 18.7 325 10 5 9.7 5.3
13000 -7.2 19.0 300 21 11 9.5 5.2 | -5.9 21.4 330 11 6 9.7 5.3
12500 -5.9 21.4 300 25 13 7.4 4.1 | -4.5 23.9 325 14 7 9.6 5.3
12000 -4.8 23.4 295 28 14 7.6 4.2 | -3.0 26.6 320 16 8 9.1 5.0
11500 -3.7 25.3 290 31 16 7.5 4.1 | -1.9 28.6 315 20 10 6.6 3.6
11000 -2.6 27.3 285 33 17 7.5 4.1 | -0.9 30.4 310 24 12 6.5 3.5
10500 -1.6 29.1 285 33 17 6.1 3.3 | -0.1 31.8 300 28 14 4.9 2.7
10250 -1.1 30.0 285 33 17 6.5 3.6 | 0.3 32.5 300 30 16 5.8 3.2
10000 -0.6 30.9 280 32 17 8.2 4.5 | 0.7 33.3 295 32 17 6.7 3.7
9750 0.1 32.2 280 30 16 9.4 5.2 | 1.2 34.2 295 34 17 5.2 2.9
9500 0.7 33.3 280 29 15 9.3 5.1 | 1.5 34.7 290 34 18 4.4 2.4
9250 1.4 34.5 280 27 14 9.5 5.2 | 1.8 35.2 290 34 18 4.3 2.4
9000 2.1 35.8 280 26 13 8.5 4.7 | 2.2 36.0 285 35 18 5.4 3.0
8750 2.7 36.9 280 25 13 8.8 4.8 | 2.6 36.7 285 34 17 6.8 3.7
8500 3.5 38.3 280 25 13 10.2 5.6 | 3.1 37.6 285 32 17 6.6 3.6
8250 4.2 39.6 280 24 12 9.4 5.1 | 3.6 38.5 280 31 16 6.6 3.6
8000 5.0 41.0 280 24 12 11.4 6.3 | 4.1 39.4 280 29 15 8.4 4.6
7750 5.9 42.6 280 23 12 11.0 6.0 | 4.8 40.6 280 28 14 9.3 5.1
7500 6.5 43.7 280 23 12 8.6 4.7 | 5.5 41.9 280 27 14 8.5 4.7
7250 7.2 45.0 280 23 12 9.5 5.2 | 6.1 43.0 280 26 13 9.0 4.9
7000 8.0 46.4 280 22 11 10.5 5.8 | 6.8 44.2 280 24 13 9.5 5.2
6750 8.8 47.8 280 22 11 10.2 5.6 | 7.5 45.5 280 23 12 9.3 5.1
6500 9.5 49.1 280 21 11 9.0 4.9 | 8.2 46.8 280 22 11 9.0 5.0
6250 10.2 50.4 280 21 11 10.4 5.7 | 8.9 48.0 285 20 10 9.0 5.0
6000 11.0 51.8 280 20 10 11.9 6.5 | 9.5 49.1 285 18 9 8.7 4.8
5750 11.9 53.4 280 19 10 11.0 6.0 | 10.2 50.4 285 16 8 9.4 5.2
5500 12.8 55.0 280 17 9 13.1 7.2 | 10.8 51.4 285 13 7 6.5 3.6
________________________________________________________________________________
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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