Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
490
UXUS97 KBOU 200117
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1917 MDT Saturday, July 19, 2025
This forecast is for Sunday, July 20, 2025:
If the trigger temperature of 84.9 F/29.4 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1225 ft/min (6.2 m/s)
Maximum height of thermals.................. 18399 ft MSL (13115 ft AGL)
Forecast maximum temperature................... 94.0 F/34.9 C
Time of trigger temperature.................... 1030 MDT
Time of overdevelopment........................ 1800 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 13826 ft MSL (8542 ft AGL)
Thermal soaring outlook for Monday 07/21....... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 19551 ft MSL (14267 ft AGL)
Wave soaring outlook for Monday 07/21.......... Poor
Remarks...
Sunrise/Sunset.................... 05:48:31 / 20:23:18 MDT
Total possible sunshine........... 14 hr 34 min 48 sec (874 min 48 sec)
Altitude of sun at 13:05:55 MDT... 70.69 degrees
Upper air data from numerical model forecast valid on 07/20/2025 at 0600 MDT
Freezing level.................. 16153 ft MSL (10869 ft AGL)
Convective condensation level... 18151 ft MSL (12867 ft AGL)
Lifted condensation level....... 18417 ft MSL (13132 ft AGL)
Lifted index.................... -1.0
K index......................... +20.7
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 -65.5 -85.9 235 28 14 1.2 0.7 M M M M M
45000 -60.9 -77.6 230 43 22 6.1 3.4 M M M M M
40000 -51.2 -60.2 230 52 27 8.2 4.5 M M M M M
38000 -46.3 -51.3 235 53 27 8.2 4.5 M M M M M
36000 -41.4 -42.5 235 53 27 7.9 4.4 M M M M M
34000 -36.9 -34.4 235 51 26 7.4 4.0 M M M M M
32000 -32.5 -26.5 240 49 25 7.3 4.0 M M M M M
30000 -27.7 -17.9 240 44 22 7.2 4.0 48.3 119.0 10.5 M M
29000 -25.5 -13.9 240 41 21 7.3 4.0 47.4 117.3 9.9 M M
28000 -23.5 -10.3 240 39 20 5.3 2.9 46.3 115.4 9.2 M M
27000 -21.9 -7.4 240 36 18 5.5 3.0 44.6 112.3 7.9 M M
26000 -20.3 -4.5 245 33 17 5.6 3.1 43.0 109.5 6.7 M M
25000 -18.7 -1.7 250 30 15 6.5 3.5 41.6 106.9 5.5 M M
24000 -16.5 2.3 245 29 15 7.6 4.2 40.7 105.3 4.8 M M
23000 -14.2 6.4 245 28 14 7.6 4.2 39.9 103.9 4.2 M M
22000 -12.0 10.4 240 27 14 7.0 3.8 39.2 102.6 3.6 M M
21000 -10.0 14.0 245 24 13 6.4 3.5 38.0 100.3 2.6 M M
20000 -8.0 17.6 250 22 11 6.4 3.5 36.8 98.3 1.7 M M
19500 -7.0 19.4 250 21 11 6.4 3.5 36.3 97.3 1.3 M M
19000 -6.1 21.0 255 20 10 6.1 3.4 35.7 96.3 0.8 M M
18500 -5.3 22.5 255 19 10 6.2 3.4 35.1 95.1 0.2 M M
18000 -4.4 24.1 260 18 9 6.8 3.8 34.5 94.1 -0.4 1197 6.1
17500 -3.3 26.1 260 18 9 7.3 4.0 34.1 93.3 -0.8 1151 5.8
17000 -2.3 27.9 260 17 9 7.4 4.1 33.7 92.6 -1.2 1105 5.6
16500 -1.1 30.0 265 17 9 8.4 4.6 33.4 92.0 -1.5 1056 5.4
16000 0.1 32.2 265 16 8 8.3 4.6 33.1 91.6 -1.8 1004 5.1
15500 1.3 34.3 270 16 8 8.3 4.6 32.9 91.2 -2.0 952 4.8
15000 3.2 37.8 275 15 8 8.4 4.6 32.5 90.6 -2.4 876 4.4
14500 4.4 39.9 280 14 7 8.0 4.4 32.3 90.1 -2.7 825 4.2
14000 5.5 41.9 285 13 7 8.0 4.4 32.0 89.6 -3.0 775 3.9
13500 6.7 44.1 290 12 6 8.2 4.5 31.7 89.1 -3.2 724 3.7
13000 8.0 46.4 295 12 6 8.3 4.6 31.5 88.7 -3.5 673 3.4
12500 9.2 48.6 300 11 6 8.7 4.8 31.3 88.3 -3.7 621 3.2
12000 10.5 50.9 305 11 6 8.9 4.9 31.1 88.0 -3.9 567 2.9
11500 11.8 53.2 305 11 6 9.0 4.9 31.0 87.8 -4.1 513 2.6
11000 13.1 55.6 310 11 6 8.7 4.8 30.9 87.6 -4.2 458 2.3
10500 14.5 58.1 315 12 6 4.5 2.5 30.8 87.4 -4.4 403 2.0
10250 14.7 58.5 315 12 6 5.8 3.2 30.2 86.4 -4.9 391 2.0
10000 15.5 59.9 315 12 6 12.3 6.7 30.3 86.6 -4.8 359 1.8
9750 16.3 61.3 315 12 6 11.3 6.2 30.4 86.7 -4.8 327 1.7
9500 17.1 62.8 320 12 6 8.8 4.8 30.5 86.9 -4.7 295 1.5
9250 17.6 63.7 320 13 6 6.1 3.4 30.3 86.5 -4.9 273 1.4
9000 18.2 64.8 320 13 7 9.1 5.0 30.1 86.2 -5.1 249 1.3
8750 18.9 66.0 320 13 7 10.9 6.0 30.1 86.2 -5.1 219 1.1
8500 19.6 67.3 320 13 7 8.4 4.6 30.2 86.3 -5.1 189 1.0
8250 20.1 68.2 320 13 7 5.5 3.0 29.9 85.9 -5.4 167 0.8
8000 20.6 69.1 320 13 7 8.0 4.4 29.7 85.4 -5.6 145 0.7
7750 21.3 70.3 320 12 6 10.5 5.8 29.7 85.4 -5.7 117 0.6
7500 22.0 71.6 320 12 6 7.2 3.9 29.6 85.3 -5.7 89 0.5
7250 22.4 72.3 320 11 6 4.6 2.5 29.3 84.7 -6.1 70 0.4
7000 22.8 73.0 320 11 6 5.7 3.1 28.9 84.1 -6.4 51 0.3
6750 23.2 73.8 320 11 6 3.9 2.1 28.6 83.4 -6.8 32 0.2
6500 23.3 73.9 320 10 5 -0.1 -0.0 28.0 82.4 -7.4 21 0.1
6250 23.2 73.8 315 9 5 -3.1 -1.7 27.1 80.8 -8.3 17 0.1
6000 23.0 73.4 310 8 4 2.5 1.4 26.2 79.2 -9.1 13 0.1
5750 23.2 73.8 305 8 4 -6.8 -3.7 25.7 78.2 -9.7 2 0.0
5500 21.3 70.3 290 5 3 -38.9 -21.3 23.2 73.7 -12.3 50 0.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
07/20/2025 at 0900 MDT | 07/20/2025 at 1200 MDT
|
CAPE... +6.5 LI... +1.0 | CAPE... +22.4 LI... -0.0
CINH... -24.1 K Index... +21.4 | CINH... -21.5 K Index... +22.0
|
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 -65.6 -86.1 235 26 13 1.2 0.6 | -65.5 -85.9 230 26 13 1.0 0.6
45000 -61.5 -78.7 230 40 21 6.1 3.4 | -61.0 -77.8 230 41 21 6.2 3.4
40000 -51.4 -60.5 230 50 26 8.0 4.4 | -51.4 -60.5 235 48 24 7.5 4.1
38000 -46.6 -51.9 235 50 26 7.9 4.4 | -46.9 -52.4 240 49 25 7.4 4.1
36000 -41.9 -43.4 240 51 26 7.9 4.3 | -42.4 -44.3 240 50 26 7.6 4.2
34000 -37.3 -35.1 240 50 26 7.7 4.2 | -37.7 -35.9 240 49 25 7.9 4.3
32000 -32.7 -26.9 240 48 25 7.6 4.2 | -32.9 -27.2 240 47 24 7.9 4.3
30000 -27.6 -17.7 240 44 23 7.5 4.1 | -27.8 -18.0 240 44 23 7.7 4.2
29000 -25.4 -13.7 240 42 22 7.5 4.1 | -25.5 -13.9 240 43 22 7.7 4.2
28000 -23.3 -9.9 240 40 20 5.4 3.0 | -23.3 -9.9 240 42 22 5.3 2.9
27000 -21.7 -7.1 240 36 19 5.7 3.1 | -21.7 -7.1 240 39 20 5.6 3.1
26000 -20.0 -4.0 240 33 17 5.8 3.2 | -20.1 -4.2 240 37 19 5.6 3.1
25000 -18.4 -1.1 240 29 15 5.9 3.3 | -18.5 -1.3 240 34 17 6.0 3.3
24000 -16.6 2.1 240 28 14 6.0 3.3 | -16.6 2.1 240 32 16 6.4 3.5
23000 -14.8 5.4 245 26 13 6.1 3.3 | -14.8 5.4 245 30 15 6.4 3.5
22000 -13.1 8.4 245 25 13 6.5 3.6 | -12.9 8.8 245 28 14 6.5 3.6
21000 -11.0 12.2 245 23 12 6.9 3.8 | -11.0 12.2 250 26 13 6.6 3.6
20000 -9.0 15.8 250 22 11 6.9 3.8 | -9.1 15.6 250 24 12 6.6 3.6
19500 -7.9 17.8 250 21 11 6.9 3.8 | -8.1 17.4 250 23 12 6.6 3.6
19000 -6.9 19.6 250 20 10 7.2 3.9 | -7.1 19.2 255 21 11 7.0 3.8
18500 -5.8 21.6 255 18 9 7.2 3.9 | -6.1 21.0 255 19 10 6.9 3.8
18000 -4.7 23.5 260 17 9 7.3 4.0 | -5.0 23.0 255 18 9 7.2 3.9
17500 -3.7 25.3 265 16 8 7.5 4.1 | -3.9 25.0 260 17 9 7.3 4.0
17000 -2.6 27.3 270 15 8 7.5 4.1 | -2.9 26.8 265 15 8 7.4 4.0
16500 -1.5 29.3 275 14 7 7.8 4.3 | -1.7 28.9 270 14 7 8.4 4.6
16000 0.2 32.4 285 13 7 7.9 4.3 | 0.1 32.2 275 13 7 8.4 4.6
15500 1.4 34.5 285 12 6 8.0 4.4 | 1.4 34.5 280 12 6 8.6 4.7
15000 2.5 36.5 290 12 6 8.0 4.4 | 2.7 36.9 285 11 6 8.5 4.7
14500 3.7 38.7 295 11 6 8.3 4.5 | 3.9 39.0 285 10 5 8.7 4.8
14000 4.9 40.8 300 10 5 8.2 4.5 | 5.2 41.4 290 9 5 8.7 4.8
13500 6.2 43.2 305 10 5 8.5 4.7 | 6.5 43.7 290 8 4 8.9 4.9
13000 7.4 45.3 305 9 5 8.6 4.7 | 7.8 46.0 290 8 4 9.0 4.9
12500 8.7 47.7 310 9 5 8.8 4.8 | 9.2 48.6 295 7 3 9.0 4.9
12000 10.0 50.0 310 8 4 8.9 4.9 | 10.5 50.9 300 6 3 9.0 4.9
11500 11.3 52.3 315 8 4 8.9 4.9 | 11.8 53.2 305 5 3 9.0 4.9
11000 12.7 54.9 320 8 4 8.5 4.6 | 13.1 55.6 315 5 3 8.7 4.8
10500 14.0 57.2 325 8 4 3.9 2.2 | 14.5 58.1 325 5 2 3.9 2.1
10250 14.1 57.4 325 8 4 5.4 2.9 | 14.6 58.3 325 4 2 5.8 3.2
10000 14.9 58.8 330 8 4 12.3 6.7 | 15.5 59.9 330 4 2 13.4 7.4
9750 15.7 60.3 330 9 5 11.2 6.2 | 16.3 61.3 335 4 2 12.4 6.8
9500 16.5 61.7 335 9 5 8.6 4.7 | 17.2 63.0 335 4 2 9.0 4.9
9250 17.0 62.6 335 9 5 6.2 3.4 | 17.7 63.9 340 4 2 6.8 3.7
9000 17.6 63.7 335 9 5 9.6 5.3 | 18.4 65.1 340 4 2 11.1 6.1
8750 18.3 64.9 335 10 5 11.2 6.2 | 19.3 66.7 345 4 2 12.3 6.7
8500 19.1 66.4 335 10 5 8.7 4.8 | 20.1 68.2 345 4 2 10.0 5.5
8250 19.6 67.3 335 10 5 5.9 3.2 | 20.7 69.3 350 4 2 7.2 4.0
8000 20.1 68.2 335 10 5 8.5 4.7 | 21.3 70.3 350 4 2 10.2 5.6
7750 20.9 69.6 335 10 5 10.4 5.7 | 22.2 72.0 355 4 2 12.3 6.7
7500 21.5 70.7 330 10 5 7.2 4.0 | 23.0 73.4 355 4 2 9.3 5.1
7250 21.9 71.4 330 9 5 5.0 2.7 | 23.6 74.5 360 4 2 7.2 3.9
7000 22.4 72.3 325 9 5 6.4 3.5 | 24.2 75.6 360 4 2 9.9 5.4
6750 22.9 73.2 320 8 4 7.5 4.1 | 25.1 77.2 005 4 2 13.2 7.2
6500 23.4 74.1 315 7 4 6.3 3.5 | 26.1 79.0 005 4 2 11.2 6.1
6250 23.8 74.8 310 6 3 5.5 3.0 | 26.8 80.2 010 4 2 9.9 5.4
6000 24.2 75.6 300 5 3 5.6 3.1 | 27.6 81.7 010 4 2 9.5 5.2
5750 24.7 76.5 290 5 3 9.8 5.4 | 28.4 83.1 010 4 2 16.2 8.9
5500 25.7 78.3 280 4 2 17.0 9.3 | 30.1 86.2 010 4 2 29.8 16.3
07/20/2025 at 1500 MDT | 07/20/2025 at 1800 MDT
|
CAPE... +20.6 LI... -0.3 | CAPE... +41.7 LI... -0.9
CINH... -46.6 K Index... +24.6 | CINH... -19.1 K Index... +27.5
|
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 -65.0 -85.0 235 29 15 1.4 0.8 | -65.0 -85.0 240 27 14 1.6 0.9
45000 -60.4 -76.7 235 41 21 5.7 3.1 | -60.4 -76.7 235 40 21 5.6 3.1
40000 -51.4 -60.5 235 46 24 7.4 4.1 | -51.5 -60.7 230 47 24 7.6 4.2
38000 -47.0 -52.6 235 49 25 7.4 4.1 | -46.9 -52.4 240 49 25 7.6 4.2
36000 -42.5 -44.5 240 52 27 7.5 4.1 | -42.4 -44.3 245 51 26 7.7 4.2
34000 -37.9 -36.2 240 50 26 7.7 4.2 | -37.6 -35.7 240 49 25 8.0 4.4
32000 -33.3 -27.9 245 48 25 7.6 4.2 | -32.8 -27.0 240 47 24 7.9 4.3
30000 -28.2 -18.8 245 46 24 7.6 4.2 | -28.0 -18.4 245 43 22 7.1 3.9
29000 -25.9 -14.6 245 45 23 7.6 4.2 | -25.9 -14.6 245 41 21 7.1 3.9
28000 -23.8 -10.8 240 43 22 5.5 3.0 | -23.8 -10.8 245 39 20 6.9 3.8
27000 -22.1 -7.8 240 40 20 5.8 3.2 | -21.7 -7.1 245 35 18 7.0 3.8
26000 -20.4 -4.7 240 36 19 5.8 3.2 | -19.7 -3.5 245 32 16 7.0 3.8
25000 -18.8 -1.8 240 33 17 6.6 3.6 | -17.6 0.3 240 28 14 6.5 3.6
24000 -16.6 2.1 245 30 16 7.3 4.0 | -15.8 3.6 250 24 12 6.1 3.4
23000 -14.5 5.9 245 28 14 7.3 4.0 | -14.0 6.8 255 21 11 6.2 3.4
22000 -12.4 9.7 250 25 13 7.0 3.8 | -12.2 10.0 265 18 9 6.4 3.5
21000 -10.4 13.3 255 23 12 6.8 3.7 | -10.3 13.5 275 17 9 6.6 3.6
20000 -8.4 16.9 265 21 11 6.8 3.7 | -8.4 16.9 280 16 8 6.6 3.6
19500 -7.4 18.7 265 20 10 6.8 3.7 | -7.4 18.7 285 15 8 6.7 3.7
19000 -6.4 20.5 270 19 10 7.0 3.9 | -6.4 20.5 285 14 7 7.4 4.1
18500 -5.4 22.3 270 17 9 7.0 3.8 | -5.4 22.3 285 13 7 7.4 4.0
18000 -4.3 24.3 275 16 8 7.2 4.0 | -4.3 24.3 280 12 6 7.3 4.0
17500 -3.3 26.1 275 15 8 7.3 4.0 | -3.2 26.2 275 11 6 7.3 4.0
17000 -2.2 28.0 275 14 7 7.4 4.1 | -2.2 28.0 270 10 5 7.4 4.1
16500 -1.0 30.2 275 13 7 8.5 4.7 | -1.0 30.2 265 9 5 8.6 4.7
16000 0.2 32.4 275 12 6 8.4 4.6 | 0.3 32.5 255 8 4 8.4 4.6
15500 1.5 34.7 275 11 6 8.6 4.7 | 1.6 34.9 245 7 4 9.1 5.0
15000 3.5 38.3 270 9 5 8.6 4.7 | 2.9 37.2 240 7 4 9.2 5.1
14500 4.8 40.6 265 8 4 9.1 5.0 | 4.3 39.7 230 7 3 9.4 5.1
14000 6.2 43.2 265 7 4 9.0 5.0 | 5.7 42.3 225 6 3 9.5 5.2
13500 7.5 45.5 255 6 3 9.1 5.0 | 7.9 46.2 210 6 3 9.3 5.1
13000 8.9 48.0 250 5 2 9.1 5.0 | 9.2 48.6 200 5 2 9.2 5.1
12500 10.3 50.5 240 4 2 9.0 4.9 | 10.6 51.1 190 4 2 9.2 5.1
12000 11.6 52.9 230 3 1 8.9 4.9 | 12.0 53.6 185 4 2 9.2 5.1
11500 12.9 55.2 215 2 1 9.1 5.0 | 13.4 56.1 180 3 2 9.2 5.0
11000 14.2 57.6 210 2 1 9.0 5.0 | 14.8 58.6 175 3 2 8.8 4.8
10500 15.6 60.1 205 2 1 4.8 2.6 | 16.1 61.0 175 3 1 4.2 2.3
10250 15.8 60.4 200 2 1 6.3 3.5 | 16.3 61.3 175 2 1 6.0 3.3
10000 16.7 62.1 200 2 1 13.0 7.1 | 17.2 63.0 175 2 1 13.2 7.2
9750 17.5 63.5 200 2 1 12.2 6.7 | 18.1 64.6 175 2 1 12.5 6.8
9500 18.4 65.1 200 2 1 8.6 4.7 | 18.9 66.0 175 2 1 8.3 4.5
9250 18.8 65.8 200 2 1 6.5 3.6 | 19.3 66.7 180 2 1 6.0 3.3
9000 19.5 67.1 200 2 1 10.9 6.0 | 20.0 68.0 180 2 1 11.1 6.1
8750 20.4 68.7 200 2 1 12.0 6.6 | 20.9 69.6 180 2 1 12.1 6.6
8500 21.2 70.2 200 2 1 9.8 5.4 | 21.7 71.1 180 2 1 9.4 5.2
8250 21.8 71.2 200 2 1 7.0 3.8 | 22.3 72.1 180 2 1 6.3 3.5
8000 22.4 72.3 200 2 1 10.2 5.6 | 22.8 73.0 185 2 1 9.9 5.4
7750 23.3 73.9 205 2 1 12.4 6.8 | 23.7 74.7 185 2 1 12.4 6.8
7500 24.1 75.4 205 2 1 9.7 5.3 | 24.5 76.1 185 2 1 9.1 5.0
7250 24.8 76.6 205 2 1 7.9 4.3 | 25.1 77.2 190 1 1 6.9 3.8
7000 25.4 77.7 210 2 1 10.1 5.5 | 25.7 78.3 195 1 1 9.8 5.4
6750 26.3 79.3 210 2 1 12.4 6.8 | 26.6 79.9 195 1 1 12.5 6.9
6500 27.1 80.8 215 2 1 10.4 5.7 | 27.4 81.3 200 1 1 10.0 5.5
6250 27.8 82.0 215 2 1 9.0 4.9 | 28.1 82.6 205 1 1 8.0 4.4
6000 28.5 83.3 220 2 1 9.6 5.3 | 28.7 83.7 215 1 1 9.7 5.3
5750 29.3 84.7 220 2 1 13.2 7.3 | 29.6 85.3 225 1 1 13.1 7.2
5500 30.5 86.9 225 2 1 18.6 10.2 | 30.6 87.1 230 1 1 14.9 8.2
________________________________________________________________________________
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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