Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
628
UXUS97 KBOU 120039
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1838 MDT Friday, September 11, 2026
This forecast is for Saturday, September 12, 2026:
If the trigger temperature of 77.0 F/25.0 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 530 ft/min (2.7 m/s)
Maximum height of thermals.................. 13363 ft MSL (8003 ft AGL)
Forecast maximum temperature................... 85.0 F/29.9 C
Time of trigger temperature.................... 1345 MDT
Time of overdevelopment........................ 1500 MDT
Middle/high clouds during soaring window....... Overcast thin high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 9978 ft MSL (4618 ft AGL)
Thermal soaring outlook for Sunday 09/13....... Good
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... Little change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 46275 ft MSL (40915 ft AGL)
Wave soaring outlook for Sunday 09/13.......... Poor
Remarks... A few showers possible Saturday afternoon, cooler
Sunrise/Sunset.................... 06:38:09 / 19:13:12 MDT
Total possible sunshine........... 12 hr 35 min 3 sec (755 min 3 sec)
Altitude of sun at 12:55:40 MDT... 54.17 degrees
Upper air data from numerical model forecast valid on 09/12/2026 at 0600 MDT
Freezing level.................. 15401 ft MSL (10041 ft AGL)
Convective condensation level... 15667 ft MSL (10307 ft AGL)
Lifted condensation level....... 15441 ft MSL (10081 ft AGL)
Lifted index.................... -2.1
K index......................... +24.2
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 -86.1 280 55 28 1.8 1.0 M M M M M
45000 -62.0 -79.6 280 70 36 4.0 2.2 M M M M M
40000 -55.5 -67.9 280 70 36 8.7 4.8 M M M M M
38000 -49.8 -57.6 280 69 35 8.4 4.6 M M M M M
36000 -44.7 -48.5 280 68 35 8.5 4.6 M M M M M
34000 -40.0 -40.0 285 64 33 7.8 4.3 M M M M M
32000 -35.3 -31.5 285 60 31 7.8 4.3 M M M M M
30000 -30.8 -23.4 285 54 28 7.4 4.1 45.4 113.8 12.2 M M
29000 -28.5 -19.3 285 51 26 7.4 4.1 44.6 112.2 11.6 M M
28000 -26.3 -15.3 285 47 24 6.9 3.8 43.8 110.9 11.2 M M
27000 -24.5 -12.1 280 45 23 6.0 3.3 42.3 108.1 10.1 M M
26000 -22.7 -8.9 280 43 22 6.0 3.3 40.8 105.5 9.1 M M
25000 -20.9 -5.6 275 41 21 5.9 3.2 39.5 103.1 8.1 M M
24000 -19.0 -2.2 275 37 19 6.8 3.7 38.3 101.0 7.2 M M
23000 -16.9 1.6 270 34 17 6.9 3.8 37.2 99.0 6.3 M M
22000 -14.9 5.2 270 30 15 6.9 3.8 36.3 97.3 5.6 M M
21000 -12.5 9.5 270 27 14 6.5 3.6 34.8 94.6 4.3 M M
20000 -10.6 12.9 265 25 13 6.6 3.6 33.7 92.6 3.4 M M
19500 -9.7 14.5 265 23 12 6.8 3.7 33.2 91.7 2.9 M M
19000 -8.6 16.5 265 23 12 8.2 4.5 32.8 91.0 2.5 M M
18500 -7.4 18.7 265 23 12 8.1 4.4 32.5 90.5 2.3 M M
18000 -6.2 20.8 265 23 12 8.2 4.5 32.2 90.0 2.0 M M
17500 -5.0 23.0 265 23 12 8.2 4.5 32.0 89.5 1.7 M M
17000 -3.8 25.2 265 23 12 8.3 4.5 31.7 89.1 1.5 M M
16500 -2.6 27.3 270 23 12 8.5 4.7 31.5 88.6 1.2 M M
16000 -1.4 29.5 270 23 12 8.5 4.7 31.3 88.3 1.0 M M
15500 -0.2 31.6 270 22 11 8.8 4.8 31.1 87.9 0.8 M M
15000 1.1 34.0 270 22 11 8.8 4.8 30.9 87.6 0.6 M M
14500 2.4 36.3 270 21 11 8.7 4.8 30.8 87.4 0.4 M M
14000 3.7 38.7 270 20 10 8.7 4.8 30.6 87.0 0.2 M M
13500 5.0 41.0 270 19 10 8.6 4.7 30.4 86.8 0.1 M M
13000 6.2 43.2 270 17 9 8.4 4.6 30.2 86.4 -0.2 591 3.0
12500 7.5 45.5 270 16 8 8.3 4.6 30.0 86.0 -0.3 539 2.7
12000 8.7 47.7 270 14 7 7.8 4.3 29.7 85.5 -0.6 488 2.5
11500 9.8 49.6 275 12 6 7.8 4.3 29.4 84.9 -0.9 438 2.2
11000 10.9 51.6 280 10 5 6.0 3.3 28.9 84.1 -1.4 393 2.0
10500 11.8 53.2 290 9 5 5.7 3.1 28.4 83.1 -1.9 351 1.8
10250 12.1 53.8 295 9 4 3.1 1.7 28.0 82.3 -2.3 334 1.7
10000 12.3 54.1 300 8 4 2.8 1.6 27.4 81.3 -2.9 321 1.6
9750 12.5 54.5 310 8 4 4.1 2.2 26.9 80.4 -3.3 305 1.6
9500 12.8 55.0 320 8 4 3.3 1.8 26.4 79.6 -3.8 290 1.5
9250 13.0 55.4 330 8 4 0.5 0.3 25.9 78.5 -4.4 278 1.4
9000 12.9 55.2 335 8 4 -1.0 -0.6 25.0 77.1 -5.2 273 1.4
8750 12.8 55.0 340 9 5 -0.6 -0.3 24.2 75.6 -6.1 268 1.4
8500 12.7 54.9 345 9 5 -0.5 -0.3 23.4 74.2 -6.9 264 1.3
8250 12.6 54.7 355 10 5 -0.1 -0.0 22.6 72.8 -7.7 259 1.3
8000 12.6 54.7 010 10 5 -0.2 -0.1 21.9 71.4 -8.5 253 1.3
7750 12.4 54.3 020 12 6 -2.1 -1.1 21.1 69.9 -9.4 250 1.3
7500 12.2 54.0 025 14 7 -0.3 -0.2 20.2 68.3 -10.4 248 1.3
7250 12.4 54.3 025 14 7 2.4 1.3 19.5 67.2 -11.0 237 1.2
7000 12.5 54.5 020 14 7 2.0 1.1 18.9 66.1 -11.6 224 1.1
6750 12.7 54.9 015 15 7 3.0 1.6 18.4 65.1 -12.2 211 1.1
6500 13.0 55.4 010 14 7 4.8 2.6 17.9 64.3 -12.6 195 1.0
6250 13.4 56.1 005 14 7 5.3 2.9 17.6 63.7 -13.0 176 0.9
6000 13.8 56.8 360 14 7 5.4 3.0 17.3 63.1 -13.4 157 0.8
5750 14.2 57.6 355 14 7 4.4 2.4 16.9 62.4 -13.7 137 0.7
5500 14.4 57.9 355 11 6 1.7 0.9 16.4 61.5 -14.3 124 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/12/2026 at 0900 MDT | 09/12/2026 at 1200 MDT
|
CAPE... 0.0 LI... -0.1 | CAPE... +12.2 LI... -0.8
CINH... -0.0 K Index... +20.9 | CINH... -154.9 K Index... +24.5
|
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 -66.5 -87.7 280 56 29 0.5 0.3 | -66.7 -88.1 285 56 29 -0.1 -0.1
45000 -63.7 -82.7 285 70 36 5.7 3.1 | -63.8 -82.8 295 71 37 6.7 3.7
40000 -54.3 -65.7 290 66 34 8.1 4.5 | -53.5 -64.3 295 68 35 7.7 4.2
38000 -49.4 -56.9 285 65 34 8.2 4.5 | -48.9 -56.0 290 65 33 7.7 4.2
36000 -44.5 -48.1 285 65 33 8.2 4.5 | -44.3 -47.7 280 62 32 7.8 4.3
34000 -40.0 -40.0 285 61 31 7.4 4.0 | -40.2 -40.4 280 58 30 6.7 3.7
32000 -35.6 -32.1 285 56 29 7.3 4.0 | -36.1 -33.0 275 54 28 6.7 3.7
30000 -31.0 -23.8 285 51 26 7.8 4.3 | -30.9 -23.6 275 48 25 8.1 4.5
29000 -28.6 -19.5 285 48 25 7.8 4.3 | -28.4 -19.1 275 45 23 8.1 4.5
28000 -26.3 -15.3 285 45 23 7.3 4.0 | -26.0 -14.8 280 42 22 7.2 4.0
27000 -24.3 -11.7 280 43 22 6.8 3.7 | -23.9 -11.0 275 41 21 7.1 3.9
26000 -22.2 -8.0 280 41 21 6.8 3.7 | -21.8 -7.2 275 40 20 7.1 3.9
25000 -20.2 -4.4 275 39 20 6.8 3.8 | -19.7 -3.5 275 38 20 6.9 3.8
24000 -18.3 -0.9 275 37 19 6.5 3.6 | -17.9 -0.2 270 36 19 6.2 3.4
23000 -16.3 2.7 275 35 18 6.5 3.6 | -16.1 3.0 270 34 18 6.2 3.4
22000 -13.9 7.0 270 32 16 6.3 3.5 | -14.2 6.4 265 33 17 6.4 3.5
21000 -12.1 10.2 270 29 15 6.2 3.4 | -12.3 9.9 260 31 16 6.8 3.8
20000 -10.3 13.5 265 27 14 6.3 3.4 | -10.3 13.5 255 30 15 7.0 3.8
19500 -9.4 15.1 265 25 13 6.5 3.6 | -9.4 15.1 255 29 15 7.0 3.9
19000 -8.3 17.1 265 24 13 7.8 4.3 | -8.3 17.1 255 28 14 7.6 4.2
18500 -7.2 19.0 265 23 12 7.8 4.3 | -7.2 19.0 255 27 14 7.6 4.2
18000 -6.0 21.2 265 22 11 7.9 4.4 | -6.1 21.0 255 25 13 7.6 4.1
17500 -4.8 23.4 265 22 11 8.0 4.4 | -4.5 23.9 255 23 12 7.5 4.1
17000 -3.7 25.3 260 21 11 8.1 4.4 | -3.4 25.9 255 22 12 7.8 4.3
16500 -2.5 27.5 265 20 10 8.3 4.6 | -2.2 28.0 255 21 11 8.2 4.5
16000 -1.2 29.8 265 20 10 8.3 4.5 | -1.0 30.2 255 20 10 8.2 4.5
15500 0.0 32.0 265 19 10 8.7 4.8 | 0.3 32.5 255 19 10 9.2 5.0
15000 1.3 34.3 265 19 10 8.7 4.8 | 1.7 35.1 260 19 10 9.1 5.0
14500 2.5 36.5 270 19 10 8.8 4.8 | 3.0 37.4 260 18 9 9.1 5.0
14000 3.8 38.8 270 19 10 8.8 4.8 | 4.4 39.9 265 18 9 9.1 5.0
13500 5.1 41.2 270 19 10 8.9 4.9 | 5.7 42.3 265 18 9 9.1 5.0
13000 6.4 43.5 270 19 10 9.0 4.9 | 7.0 44.6 265 17 9 9.1 5.0
12500 7.7 45.9 270 19 10 8.9 4.9 | 8.4 47.1 270 17 9 9.0 4.9
12000 9.0 48.2 275 18 9 8.5 4.6 | 9.6 49.3 270 16 8 8.9 4.9
11500 10.2 50.4 275 17 9 8.2 4.5 | 10.9 51.6 270 15 8 8.8 4.8
11000 11.3 52.3 275 16 8 6.8 3.7 | 12.2 54.0 270 14 7 8.3 4.5
10500 12.3 54.1 275 15 8 5.8 3.2 | 13.5 56.3 270 13 7 4.3 2.4
10250 12.7 54.9 270 14 7 3.0 1.6 | 13.6 56.5 270 13 7 4.4 2.4
10000 12.9 55.2 275 14 7 4.0 2.2 | 14.2 57.6 265 12 6 9.9 5.4
9750 13.2 55.8 275 13 7 5.7 3.1 | 14.9 58.8 265 11 6 9.2 5.0
9500 13.6 56.5 275 13 7 3.8 2.1 | 15.6 60.1 260 11 6 7.5 4.1
9250 13.7 56.7 275 12 6 -0.0 -0.0 | 15.9 60.6 260 10 5 3.5 1.9
9000 13.6 56.5 275 12 6 -2.4 -1.3 | 16.1 61.0 255 10 5 2.5 1.4
8750 13.3 55.9 275 11 6 -2.4 -1.3 | 16.3 61.3 250 9 4 3.4 1.9
8500 13.1 55.6 275 10 5 -3.7 -2.0 | 16.5 61.7 250 8 4 1.1 0.6
8250 12.7 54.9 275 8 4 -6.0 -3.3 | 16.4 61.5 240 6 3 -1.9 -1.0
8000 12.1 53.8 275 6 3 -5.9 -3.2 | 16.2 61.2 235 5 3 -2.1 -1.2
7750 11.6 52.9 275 4 2 -6.6 -3.6 | 16.0 60.8 225 4 2 -3.2 -1.8
7500 11.2 52.2 270 2 1 -2.2 -1.2 | 15.8 60.4 200 3 1 -0.3 -0.1
7250 11.3 52.3 270 2 1 2.1 1.2 | 15.9 60.6 170 2 1 2.3 1.3
7000 11.4 52.5 280 1 0 0.5 0.3 | 16.0 60.8 135 3 1 2.5 1.4
6750 11.4 52.5 000 0 0 3.1 1.7 | 16.3 61.3 120 3 2 8.6 4.7
6500 11.9 53.4 045 1 1 8.1 4.4 | 17.1 62.8 115 4 2 10.9 6.0
6250 12.6 54.7 045 1 1 10.1 5.5 | 17.8 64.0 110 4 2 9.8 5.4
6000 13.3 55.9 045 2 1 8.3 4.5 | 18.6 65.5 110 4 2 8.8 4.8
5750 13.9 57.0 045 2 1 11.8 6.5 | 19.3 66.7 105 4 2 15.2 8.3
5500 15.2 59.4 045 2 1 21.2 11.6 | 21.0 69.8 105 4 2 30.2 16.6
09/12/2026 at 1500 MDT | 09/12/2026 at 1800 MDT
|
CAPE... +155.5 LI... -1.2 | CAPE... +468.9 LI... -2.6
CINH... -78.3 K Index... +29.5 | CINH... -64.3 K Index... +28.7
|
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 -67.4 -89.3 290 53 27 -0.2 -0.1 | -67.3 -89.1 285 49 25 0.3 0.2
45000 -64.0 -83.2 295 69 36 7.5 4.1 | -63.3 -81.9 290 64 33 7.3 4.0
40000 -52.7 -62.9 290 64 33 7.8 4.3 | -52.3 -62.1 280 64 33 7.6 4.2
38000 -48.0 -54.4 285 59 30 7.8 4.3 | -47.8 -54.0 275 58 30 7.6 4.2
36000 -43.3 -45.9 285 54 28 7.9 4.4 | -43.2 -45.8 275 51 26 7.7 4.2
34000 -39.0 -38.2 280 52 27 7.1 3.9 | -38.8 -37.8 275 46 24 7.2 3.9
32000 -34.3 -29.7 275 50 26 7.2 3.9 | -34.0 -29.2 280 42 21 7.3 4.0
30000 -30.2 -22.4 275 47 24 6.8 3.7 | -30.0 -22.0 280 39 20 6.7 3.7
29000 -28.1 -18.6 275 45 23 6.8 3.7 | -27.9 -18.2 280 38 20 6.7 3.7
28000 -26.1 -15.0 270 43 22 7.5 4.1 | -25.9 -14.6 275 37 19 7.5 4.1
27000 -23.8 -10.8 270 41 21 7.6 4.2 | -23.6 -10.5 275 37 19 7.7 4.2
26000 -21.6 -6.9 270 39 20 7.6 4.2 | -21.3 -6.3 275 37 19 7.7 4.2
25000 -19.3 -2.7 265 37 19 7.5 4.1 | -19.0 -2.2 275 36 19 7.6 4.2
24000 -17.2 1.0 265 35 18 7.0 3.9 | -16.9 1.6 270 35 18 7.2 4.0
23000 -15.2 4.6 260 33 17 7.1 3.9 | -14.7 5.5 270 35 18 7.3 4.0
22000 -13.2 8.2 255 32 16 7.1 3.9 | -12.6 9.3 265 34 17 7.1 3.9
21000 -11.2 11.8 260 31 16 6.9 3.8 | -10.7 12.7 270 34 18 6.5 3.6
20000 -9.2 15.4 260 30 16 6.9 3.8 | -8.9 16.0 270 35 18 6.6 3.6
19500 -8.2 17.2 260 30 15 6.9 3.8 | -8.0 17.6 270 35 18 6.6 3.6
19000 -7.2 19.0 265 29 15 6.9 3.8 | -6.5 20.3 270 34 18 7.1 3.9
18500 -6.2 20.8 265 27 14 6.9 3.8 | -5.5 22.1 270 33 17 7.0 3.9
18000 -4.7 23.5 265 25 13 7.1 3.9 | -4.4 24.1 275 32 16 8.8 4.8
17500 -3.7 25.3 265 25 13 7.1 3.9 | -3.1 26.4 275 30 15 8.9 4.9
17000 -2.7 27.1 265 24 12 7.2 4.0 | -1.8 28.8 275 28 15 8.7 4.8
16500 -1.6 29.1 265 23 12 7.4 4.0 | -0.6 30.9 275 26 14 8.4 4.6
16000 -0.5 31.1 260 21 11 7.3 4.0 | 0.7 33.3 275 25 13 8.5 4.7
15500 0.6 33.1 260 20 10 8.6 4.7 | 1.8 35.2 275 22 12 7.7 4.2
15000 1.9 35.4 255 19 10 8.5 4.6 | 3.0 37.4 275 20 10 7.8 4.3
14500 3.1 37.6 250 18 9 9.1 5.0 | 4.1 39.4 275 18 9 8.3 4.6
14000 4.5 40.1 250 18 9 9.3 5.1 | 5.3 41.5 270 16 8 8.4 4.6
13500 5.9 42.6 245 17 9 9.2 5.0 | 6.6 43.9 270 15 8 8.5 4.7
13000 7.2 45.0 240 16 8 9.1 5.0 | 7.8 46.0 265 14 7 8.6 4.7
12500 8.5 47.3 240 16 8 9.1 5.0 | 9.1 48.4 265 13 7 8.6 4.7
12000 9.9 49.8 230 15 8 9.2 5.1 | 10.3 50.5 260 13 6 8.4 4.6
11500 11.3 52.3 225 14 7 9.0 4.9 | 11.6 52.9 250 12 6 8.2 4.5
11000 12.5 54.5 220 14 7 8.1 4.4 | 12.7 54.9 240 11 6 7.2 4.0
10500 13.8 56.8 215 13 6 6.0 3.3 | 13.7 56.7 230 12 6 5.5 3.0
10250 14.1 57.4 210 12 6 6.3 3.5 | 14.1 57.4 225 12 6 5.5 3.0
10000 14.8 58.6 205 12 6 9.5 5.2 | 14.6 58.3 220 12 6 7.9 4.3
9750 15.4 59.7 200 12 6 8.8 4.8 | 15.1 59.2 210 13 7 7.4 4.1
9500 16.1 61.0 195 11 6 8.3 4.6 | 15.6 60.1 205 13 7 7.2 4.0
9250 16.6 61.9 190 11 6 7.0 3.9 | 16.1 61.0 200 14 7 6.7 3.7
9000 17.2 63.0 190 11 6 7.4 4.1 | 16.6 61.9 195 15 8 7.6 4.2
8750 17.8 64.0 185 11 6 8.3 4.6 | 17.2 63.0 190 15 8 8.1 4.4
8500 18.3 64.9 180 11 6 6.7 3.7 | 17.8 64.0 185 16 8 8.1 4.5
8250 18.7 65.7 175 10 5 3.9 2.1 | 18.4 65.1 180 16 8 8.4 4.6
8000 19.0 66.2 170 9 5 4.1 2.3 | 19.0 66.2 180 15 8 8.9 4.9
7750 19.3 66.7 160 8 4 4.4 2.4 | 19.7 67.5 175 16 8 9.4 5.1
7500 19.6 67.3 150 8 4 6.5 3.6 | 20.4 68.7 170 16 8 9.1 5.0
7250 20.2 68.4 145 8 4 8.9 4.9 | 21.0 69.8 170 16 8 8.7 4.8
7000 20.8 69.4 140 8 4 9.0 4.9 | 21.7 71.1 170 16 8 9.0 4.9
6750 21.5 70.7 140 8 4 10.5 5.8 | 22.4 72.3 165 16 8 9.9 5.4
6500 22.3 72.1 135 8 4 10.8 5.9 | 23.1 73.6 165 16 8 10.3 5.7
6250 23.1 73.6 135 8 4 10.7 5.9 | 23.9 75.0 165 15 8 10.4 5.7
6000 23.9 75.0 135 8 4 9.8 5.4 | 24.6 76.3 165 15 8 10.2 5.6
5750 24.7 76.5 130 8 4 13.0 7.1 | 25.4 77.7 165 14 7 10.1 5.5
5500 26.0 78.8 130 7 4 23.2 12.7 | 26.2 79.2 160 13 6 11.5 6.3
________________________________________________________________________________
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.
042613