Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
173
UXUS97 KBOU 270012
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1711 MST Wednesday, November 26, 2025
This forecast is for Thursday, November 27, 2025:
If the trigger temperature of 50.9 F/10.5 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 367 ft/min (1.9 m/s)
Maximum height of thermals.................. 10452 ft MSL (5159 ft AGL)
Forecast maximum temperature................... 54.0 F/12.7 C
Time of trigger temperature.................... 1200 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................. 8561 ft MSL (3269 ft AGL)
Thermal soaring outlook for Friday 11/28....... Good
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... Little change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Neither
Potential height of wave....................... 39248 ft MSL (33955 ft AGL)
Wave soaring outlook for Friday 11/28.......... Poor
Remarks...
Sunrise/Sunset.................... 06:57:59 / 16:36:33 MST
Total possible sunshine........... 9 hr 38 min 34 sec (578 min 34 sec)
Altitude of sun at 11:47:16 MST... 28.89 degrees
Upper air data from numerical model forecast valid on 11/27/2025 at 0500 MST
Freezing level.................. 5365 ft MSL (72 ft AGL)
Additional freezing level....... 7995 ft MSL (2702 ft AGL)
Convective condensation level... 17569 ft MSL (12276 ft AGL)
Lifted condensation level....... 13456 ft MSL (8163 ft AGL)
Lifted index.................... +11.2
K index......................... -1.2
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 -65.6 -86.1 310 55 28 -1.6 -0.9 M M M M M
45000 -68.1 -90.6 310 70 36 0.1 0.1 M M M M M
40000 -65.6 -86.1 310 75 39 1.6 0.9 M M M M M
38000 -62.0 -79.6 310 77 40 8.5 4.7 M M M M M
36000 -56.9 -70.4 310 79 41 8.5 4.7 M M M M M
34000 -51.7 -61.1 305 81 42 9.1 5.0 M M M M M
32000 -46.2 -51.2 305 81 42 9.1 5.0 M M M M M
30000 -40.3 -40.5 305 80 41 8.2 4.5 36.1 97.0 18.0 M M
29000 -37.8 -36.0 305 77 40 8.2 4.5 35.4 95.8 17.7 M M
28000 -35.4 -31.7 305 75 39 8.2 4.5 34.9 94.9 17.5 M M
27000 -33.0 -27.4 310 73 38 8.1 4.4 34.4 93.8 17.2 M M
26000 -30.6 -23.1 310 71 37 8.1 4.4 33.6 92.5 16.9 M M
25000 -28.1 -18.6 310 70 36 8.1 4.4 33.0 91.5 16.6 M M
24000 -25.8 -14.4 310 68 35 7.2 4.0 32.4 90.4 16.3 M M
23000 -23.6 -10.5 310 68 35 7.3 4.0 31.4 88.6 15.6 M M
22000 -21.5 -6.7 310 67 34 7.3 4.0 30.5 87.0 15.1 M M
21000 -19.5 -3.1 310 66 34 5.5 3.0 29.5 85.1 14.4 M M
20000 -17.8 -0.0 315 63 32 5.6 3.1 28.0 82.3 13.2 M M
19500 -17.0 1.4 315 62 32 5.6 3.1 27.3 81.1 12.7 M M
19000 -16.1 3.0 315 60 31 5.8 3.2 26.6 79.8 12.1 M M
18500 -15.4 4.3 315 59 30 4.4 2.4 25.8 78.4 11.5 M M
18000 -14.7 5.5 320 57 30 4.4 2.4 24.9 76.7 10.7 M M
17500 -14.1 6.6 320 56 29 4.7 2.6 24.0 75.1 10.0 M M
17000 -13.3 8.1 320 54 28 5.1 2.8 23.1 73.7 9.4 M M
16500 -12.5 9.5 320 51 26 5.1 2.8 22.4 72.3 8.7 M M
16000 -11.7 10.9 320 49 25 5.9 3.2 21.7 71.0 8.2 M M
15500 -10.4 13.3 320 45 23 5.8 3.2 20.7 69.2 7.4 M M
15000 -9.5 14.9 320 43 22 5.7 3.1 20.0 68.0 6.8 M M
14500 -8.7 16.3 320 42 21 5.7 3.1 19.3 66.8 6.2 M M
14000 -7.9 17.8 320 40 20 4.4 2.4 18.5 65.4 5.5 M M
13500 -7.2 19.0 320 38 19 4.6 2.5 17.7 63.8 4.8 M M
13000 -6.6 20.1 320 35 18 4.1 2.2 16.8 62.2 4.0 M M
12500 -6.0 21.2 315 32 17 4.1 2.3 15.9 60.6 3.2 M M
12000 -5.4 22.3 315 29 15 4.2 2.3 15.0 59.0 2.3 M M
11500 -4.8 23.4 310 26 13 4.0 2.2 14.1 57.4 1.5 M M
11000 -4.1 24.6 305 23 12 5.5 3.0 13.3 55.9 0.7 M M
10500 -3.3 26.1 305 20 10 5.5 3.0 12.6 54.7 0.0 M M
10250 -3.0 26.6 305 18 9 4.4 2.4 12.2 54.0 -0.3 349 1.8
10000 -2.7 27.1 305 18 9 4.4 2.4 11.8 53.2 -0.8 333 1.7
9750 -2.3 27.9 305 17 9 6.4 3.5 11.4 52.6 -1.1 314 1.6
9500 -1.8 28.8 300 16 8 6.1 3.3 11.2 52.1 -1.4 292 1.5
9250 -1.4 29.5 300 15 8 3.7 2.1 10.8 51.4 -1.8 274 1.4
9000 -1.2 29.8 300 14 7 2.7 1.5 10.3 50.5 -2.3 261 1.3
8750 -1.0 30.2 295 13 6 5.1 2.8 9.8 49.6 -2.8 246 1.2
8500 -0.6 30.9 295 10 5 5.2 2.8 9.5 49.1 -3.1 226 1.1
8250 -0.3 31.5 295 8 4 3.5 1.9 9.0 48.3 -3.5 209 1.1
8000 -0.0 32.0 295 7 3 3.3 1.8 8.6 47.4 -4.0 194 1.0
7750 0.3 32.5 290 5 3 4.6 2.5 8.1 46.6 -4.5 179 0.9
7500 0.7 33.3 295 3 1 5.4 3.0 7.8 46.0 -4.8 159 0.8
7250 1.0 33.8 295 2 1 4.6 2.5 7.4 45.3 -5.2 141 0.7
7000 1.4 34.5 290 1 0 4.9 2.7 7.0 44.6 -5.6 123 0.6
6750 1.8 35.2 000 0 0 4.6 2.5 6.6 43.9 -6.0 104 0.5
6500 2.1 35.8 000 0 0 4.6 2.5 6.2 43.2 -6.4 86 0.4
6250 2.5 36.5 075 1 0 5.6 3.1 5.9 42.6 -6.7 68 0.3
6000 2.9 37.2 075 1 1 3.2 1.7 5.5 41.9 -7.1 49 0.2
5750 2.7 36.9 080 1 1 -11.1 -6.1 4.6 40.3 -8.0 47 0.2
5500 1.1 34.0 120 1 1 -27.9 -15.3 2.3 36.2 -10.3 86 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/27/2025 at 0800 MST | 11/27/2025 at 1100 MST
|
CAPE... 0.0 LI... +7.6 | CAPE... 0.0 LI... +6.7
CINH... -0.1 K Index... +7.2 | CINH... 0.0 K Index... +7.8
|
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 -86.4 310 54 28 -2.9 -1.6 | -65.6 -86.1 310 50 26 -1.7 -0.9
45000 -70.3 -94.5 300 67 35 0.5 0.3 | -68.1 -90.6 305 59 31 0.3 0.1
40000 -65.9 -86.6 300 59 30 2.9 1.6 | -65.3 -85.5 285 51 26 1.9 1.0
38000 -62.0 -79.6 300 60 31 8.4 4.6 | -61.7 -79.1 280 52 27 8.2 4.5
36000 -56.9 -70.4 295 64 33 8.4 4.6 | -56.8 -70.2 275 54 28 8.2 4.5
34000 -51.8 -61.2 295 67 34 9.0 5.0 | -51.3 -60.3 275 55 28 8.2 4.5
32000 -45.7 -50.3 295 66 34 9.0 5.0 | -46.3 -51.3 280 56 29 8.2 4.5
30000 -40.4 -40.7 300 65 34 8.6 4.7 | -41.3 -42.3 285 56 29 8.5 4.6
29000 -37.8 -36.0 300 65 34 8.6 4.7 | -38.8 -37.8 285 55 28 8.5 4.6
28000 -35.2 -31.4 300 65 34 8.6 4.7 | -36.2 -33.2 285 55 28 8.5 4.6
27000 -32.8 -27.0 300 64 33 7.3 4.0 | -33.7 -28.7 290 54 28 8.5 4.6
26000 -30.6 -23.1 305 62 32 7.4 4.1 | -31.2 -24.2 290 54 28 8.5 4.6
25000 -28.4 -19.1 305 60 31 7.5 4.1 | -28.6 -19.5 290 54 28 8.5 4.6
24000 -26.2 -15.2 305 59 30 7.4 4.0 | -26.2 -15.2 295 53 27 7.2 4.0
23000 -24.0 -11.2 305 58 30 7.4 4.1 | -24.0 -11.2 295 52 27 7.3 4.0
22000 -21.8 -7.2 305 57 29 7.4 4.1 | -21.8 -7.2 295 51 26 7.3 4.0
21000 -19.7 -3.5 310 56 29 6.2 3.4 | -19.8 -3.6 300 49 25 6.5 3.6
20000 -17.9 -0.2 310 55 28 6.3 3.5 | -17.8 -0.0 300 47 24 6.6 3.6
19500 -16.9 1.6 310 54 28 6.3 3.5 | -16.9 1.6 300 46 24 6.6 3.6
19000 -16.0 3.2 310 53 27 6.5 3.6 | -15.9 3.4 305 45 23 6.7 3.7
18500 -15.2 4.6 310 52 27 4.9 2.7 | -14.6 5.7 305 44 22 5.6 3.1
18000 -14.4 6.1 315 52 27 5.0 2.7 | -13.8 7.2 305 42 22 5.7 3.1
17500 -13.3 8.1 315 50 26 5.0 2.7 | -13.0 8.6 305 41 21 4.9 2.7
17000 -12.6 9.3 315 48 25 5.0 2.7 | -12.3 9.9 305 40 20 5.0 2.7
16500 -11.9 10.6 320 46 23 5.3 2.9 | -11.6 11.1 305 38 20 4.9 2.7
16000 -11.0 12.2 320 44 23 5.5 3.0 | -10.8 12.6 305 37 19 4.9 2.7
15500 -10.2 13.6 320 42 22 5.5 3.0 | -10.1 13.8 310 35 18 5.2 2.8
15000 -9.4 15.1 320 40 20 5.2 2.9 | -9.3 15.3 310 34 17 6.0 3.3
14500 -8.6 16.5 320 37 19 5.2 2.9 | -8.4 16.9 305 32 17 5.9 3.3
14000 -7.9 17.8 320 35 18 4.8 2.6 | -7.5 18.5 305 31 16 5.6 3.1
13500 -7.2 19.0 320 32 17 4.9 2.7 | -6.7 19.9 305 29 15 5.7 3.1
13000 -6.5 20.3 315 30 15 4.0 2.2 | -5.8 21.6 300 27 14 5.4 3.0
12500 -5.9 21.4 315 28 14 4.2 2.3 | -5.0 23.0 295 25 13 5.6 3.1
12000 -5.3 22.5 310 25 13 3.7 2.0 | -4.3 24.3 295 23 12 4.5 2.4
11500 -4.8 23.4 305 23 12 3.6 2.0 | -3.6 25.5 290 20 10 4.5 2.5
11000 -4.2 24.4 300 20 10 4.7 2.6 | -2.9 26.8 285 18 9 4.6 2.5
10500 -3.5 25.7 295 17 9 4.7 2.6 | -2.2 28.0 280 15 8 4.6 2.5
10250 -3.1 26.4 295 15 8 4.1 2.2 | -1.9 28.6 280 14 7 4.0 2.2
10000 -2.8 27.0 295 14 7 4.9 2.7 | -1.6 29.1 280 13 7 4.5 2.4
9750 -2.5 27.5 290 13 7 3.3 1.8 | -1.2 29.8 280 12 6 5.8 3.2
9500 -2.1 28.2 285 12 6 13.1 7.2 | -0.8 30.6 275 11 6 5.5 3.0
9250 -0.8 30.6 255 7 4 9.7 5.3 | -0.4 31.3 275 10 5 4.3 2.3
9000 -0.8 30.6 255 7 4 -2.2 -1.2 | -0.1 31.8 275 10 5 3.6 2.0
8750 -0.8 30.6 255 7 4 0.5 0.3 | 0.2 32.4 270 9 5 4.0 2.2
8500 -0.8 30.6 255 7 4 1.5 0.8 | 0.5 32.9 265 8 4 3.5 1.9
8250 -0.6 30.9 250 6 3 4.0 2.2 | 0.7 33.3 265 7 3 2.7 1.5
8000 -0.3 31.5 240 6 3 3.6 2.0 | 0.9 33.6 255 6 3 2.9 1.6
7750 0.0 32.0 230 5 3 4.6 2.5 | 1.1 34.0 250 5 3 1.8 1.0
7500 0.4 32.7 220 5 2 5.4 2.9 | 1.2 34.2 240 4 2 3.0 1.7
7250 0.8 33.4 210 4 2 4.9 2.7 | 1.5 34.7 225 3 2 5.0 2.8
7000 1.2 34.2 200 4 2 5.3 2.9 | 1.8 35.2 195 3 1 4.0 2.2
6750 1.5 34.7 185 3 2 4.2 2.3 | 2.2 36.0 165 3 1 6.1 3.3
6500 1.8 35.2 170 3 2 3.3 1.8 | 2.8 37.0 155 3 1 8.9 4.9
6250 2.1 35.8 150 3 1 4.5 2.5 | 3.4 38.1 140 3 1 9.4 5.1
6000 2.4 36.3 130 3 1 1.9 1.0 | 4.1 39.4 130 3 1 8.6 4.7
5750 2.2 36.0 125 3 1 -7.0 -3.8 | 4.8 40.6 125 3 2 11.7 6.4
5500 1.4 34.5 135 2 1 -14.2 -7.8 | 6.0 42.8 120 3 1 19.2 10.5
11/27/2025 at 1400 MST | 11/27/2025 at 1700 MST
|
CAPE... 0.0 LI... +5.0 | CAPE... 0.0 LI... +3.3
CINH... 0.0 K Index... +10.7 | CINH... 0.0 K Index... +8.0
|
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 -64.8 -84.6 305 48 25 -0.1 -0.0 | -64.3 -83.7 295 51 26 0.4 0.2
45000 -65.0 -85.0 295 56 29 0.4 0.2 | -63.6 -82.5 290 60 31 0.1 0.1
40000 -63.6 -82.5 275 53 27 0.9 0.5 | -63.8 -82.8 285 65 34 -0.2 -0.1
38000 -61.1 -78.0 275 54 28 6.4 3.5 | -61.5 -78.7 285 67 34 6.7 3.7
36000 -57.2 -71.0 275 56 29 6.4 3.5 | -57.0 -70.6 285 67 35 6.7 3.7
34000 -52.5 -62.5 280 58 30 7.9 4.3 | -52.5 -62.5 285 66 34 8.8 4.8
32000 -47.8 -54.0 280 59 30 7.9 4.3 | -47.3 -53.1 285 62 32 8.8 4.8
30000 -42.9 -45.2 280 59 30 8.7 4.8 | -42.2 -44.0 280 60 31 8.0 4.4
29000 -40.3 -40.5 280 59 30 8.7 4.7 | -39.7 -39.5 280 59 30 8.0 4.4
28000 -37.7 -35.9 280 58 30 8.7 4.8 | -37.3 -35.1 285 59 30 8.0 4.4
27000 -35.0 -31.0 280 58 30 9.1 5.0 | -34.9 -30.8 285 58 30 8.3 4.5
26000 -32.3 -26.1 285 58 30 9.1 5.0 | -32.4 -26.3 285 58 30 8.2 4.5
25000 -29.6 -21.3 285 57 30 9.1 5.0 | -29.9 -21.8 280 57 29 8.2 4.5
24000 -26.9 -16.4 285 56 29 7.8 4.3 | -27.5 -17.5 280 57 29 7.8 4.3
23000 -24.6 -12.3 285 54 28 7.8 4.3 | -25.1 -13.2 285 54 28 7.8 4.3
22000 -22.3 -8.1 285 51 26 7.8 4.3 | -22.8 -9.0 285 52 27 7.8 4.3
21000 -20.1 -4.2 290 48 25 6.0 3.3 | -20.6 -5.1 285 49 25 6.0 3.3
20000 -18.3 -0.9 290 45 23 6.3 3.4 | -18.8 -1.8 290 45 23 6.2 3.4
19500 -17.3 0.9 290 44 23 6.3 3.5 | -17.9 -0.2 290 43 22 6.2 3.4
19000 -16.4 2.5 290 42 22 6.4 3.5 | -17.0 1.4 295 41 21 6.1 3.4
18500 -15.5 4.1 290 41 21 6.4 3.5 | -16.0 3.2 295 40 21 7.0 3.9
18000 -14.5 5.9 295 40 21 6.4 3.5 | -14.4 6.1 295 39 20 7.1 3.9
17500 -13.2 8.2 295 39 20 6.0 3.3 | -13.4 7.9 295 38 19 6.4 3.5
17000 -12.3 9.9 295 39 20 6.1 3.3 | -12.5 9.5 300 37 19 6.5 3.5
16500 -11.4 11.5 295 39 20 6.0 3.3 | -11.5 11.3 300 36 18 6.7 3.7
16000 -10.5 13.1 295 37 19 6.0 3.3 | -10.5 13.1 295 34 18 6.8 3.8
15500 -9.7 14.5 295 35 18 6.0 3.3 | -9.5 14.9 295 33 17 6.8 3.7
15000 -8.8 16.2 295 34 17 6.0 3.3 | -8.6 16.5 295 32 16 6.4 3.5
14500 -7.9 17.8 290 32 16 6.0 3.3 | -7.6 18.3 295 31 16 6.5 3.6
14000 -7.0 19.4 290 30 15 6.3 3.4 | -6.7 19.9 290 29 15 6.8 3.8
13500 -6.1 21.0 290 28 14 6.2 3.4 | -5.7 21.7 285 28 14 6.8 3.7
13000 -5.1 22.8 290 26 13 6.9 3.8 | -4.7 23.5 285 26 13 7.4 4.0
12500 -4.1 24.6 290 24 13 6.9 3.8 | -3.6 25.5 285 25 13 7.4 4.0
12000 -3.1 26.4 290 23 12 6.1 3.4 | -2.6 27.3 280 24 12 6.8 3.7
11500 -2.2 28.0 290 21 11 6.3 3.5 | -1.5 29.3 280 22 12 7.3 3.8
11000 -1.3 29.7 290 19 10 5.2 2.8 | -0.6 30.9 280 21 11 5.4 3.0
10500 -0.5 31.1 290 17 9 5.5 3.0 | 0.2 32.4 275 18 9 6.1 3.3
10250 -0.2 31.6 290 16 8 3.3 1.8 | 0.6 33.1 275 17 9 2.6 1.4
10000 -0.0 32.0 290 16 8 2.7 1.5 | 0.6 33.1 275 17 9 1.6 0.9
9750 0.3 32.5 285 14 7 4.8 2.6 | 0.9 33.6 275 14 7 4.6 2.5
9500 0.7 33.3 285 12 6 4.2 2.3 | 1.3 34.3 270 12 6 4.2 2.3
9250 0.9 33.6 285 10 5 2.0 1.1 | 1.5 34.7 260 10 5 2.8 1.5
9000 1.0 33.8 280 9 5 1.0 0.6 | 1.7 35.1 260 9 5 1.9 1.1
8750 1.1 34.0 280 7 4 2.7 1.5 | 1.9 35.4 250 8 4 3.1 1.7
8500 1.4 34.5 270 4 2 3.5 1.9 | 2.2 36.0 235 7 3 3.4 1.8
8250 1.7 35.1 250 2 1 3.9 2.2 | 2.4 36.3 225 6 3 3.4 1.9
8000 1.9 35.4 190 2 1 3.8 2.1 | 2.7 36.9 215 5 2 3.2 1.8
7750 2.3 36.1 150 3 2 6.3 3.4 | 3.0 37.4 200 4 2 6.3 3.4
7500 2.9 37.2 135 4 2 8.1 4.5 | 3.6 38.5 185 3 2 8.4 4.6
7250 3.4 38.1 130 4 2 7.8 4.3 | 4.1 39.4 175 3 2 7.5 4.1
7000 4.0 39.2 130 4 2 6.9 3.8 | 4.7 40.5 160 3 2 7.3 4.0
6750 4.6 40.3 125 4 2 10.8 5.9 | 5.3 41.5 150 3 2 8.9 4.9
6500 5.5 41.9 125 3 2 12.1 6.7 | 6.0 42.8 145 3 2 9.0 5.0
6250 6.3 43.3 125 3 2 9.7 5.3 | 6.6 43.9 135 3 2 7.7 4.2
6000 7.0 44.6 120 3 2 8.7 4.8 | 7.2 45.0 125 3 2 7.8 4.3
5750 7.7 45.9 120 3 1 10.3 5.7 | 7.6 45.7 115 3 2 0.5 0.3
5500 8.8 47.8 120 3 1 19.1 10.5 | 7.2 45.0 100 3 1 -10.1 -5.5
________________________________________________________________________________
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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