Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
090
UXUS97 KBOU 091320
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0719 MDT Wednesday, July 9, 2025
This forecast is for Wednesday, July 9, 2025:
If the trigger temperature of 90.4 F/32.4 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1914 ft/min (9.7 m/s)
Maximum height of thermals.................. 24335 ft MSL (18997 ft AGL)
Forecast maximum temperature................... 101.0 F/38.8 C
Time of trigger temperature.................... 1030 MDT
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................. 22131 ft MSL (16793 ft AGL)
Thermal soaring outlook for Thursday 07/10..... 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)................ Weak PVA
Potential height of wave....................... 41057 ft MSL (35719 ft AGL)
Wave soaring outlook for Thursday 07/10........ Poor
Remarks...
Sunrise/Sunset.................... 05:40:12 / 20:29:28 MDT
Total possible sunshine........... 14 hr 49 min 16 sec (889 min 16 sec)
Altitude of sun at 13:04:50 MDT... 72.45 degrees
Upper air data from numerical model forecast valid on 07/09/2025 at 0600 MDT
Freezing level.................. 16516 ft MSL (11178 ft AGL)
Convective condensation level... 20491 ft MSL (15153 ft AGL)
Lifted condensation level....... 22304 ft MSL (16966 ft AGL)
Lifted index.................... -2.6
K index......................... +10.5
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 -63.9 -83.0 305 29 15 2.2 1.2 M M M M M
45000 -59.0 -74.2 305 48 25 5.2 2.8 M M M M M
40000 -50.9 -59.6 300 58 30 6.8 3.7 M M M M M
38000 -46.8 -52.2 305 56 29 6.8 3.7 M M M M M
36000 -42.2 -44.0 305 53 28 7.2 4.0 M M M M M
34000 -37.8 -36.0 305 52 27 7.4 4.0 M M M M M
32000 -33.4 -28.1 305 51 26 7.3 4.0 M M M M M
30000 -29.2 -20.6 310 47 24 6.9 3.8 46.5 115.7 6.3 M M
29000 -27.1 -16.8 315 46 24 6.9 3.8 45.5 113.9 5.5 M M
28000 -25.1 -13.2 315 43 22 5.4 3.0 44.4 111.8 4.7 M M
27000 -23.5 -10.3 315 38 19 5.6 3.1 42.6 108.8 3.4 M M
26000 -21.8 -7.2 315 32 17 5.6 3.1 41.1 106.0 2.2 M M
25000 -20.1 -4.2 320 27 14 5.5 3.0 39.7 103.4 1.1 M M
24000 -18.6 -1.5 315 24 12 5.4 2.9 37.9 100.3 -0.4 1893 9.6
23000 -17.0 1.4 310 21 11 5.5 3.0 36.3 97.4 -1.8 1816 9.2
22000 -15.4 4.3 305 18 9 7.5 4.1 35.0 95.0 -3.0 1738 8.8
21000 -12.9 8.8 305 17 9 8.5 4.7 34.5 94.0 -3.6 1633 8.3
20000 -10.4 13.3 305 15 8 8.6 4.7 34.0 93.3 -4.0 1528 7.8
19500 -8.4 16.9 310 14 7 9.5 5.2 33.8 92.9 -4.3 1448 7.4
19000 -7.0 19.4 310 14 7 9.8 5.3 33.8 92.9 -4.3 1389 7.1
18500 -5.5 22.1 310 13 7 9.8 5.4 33.8 92.9 -4.3 1331 6.8
18000 -4.1 24.6 310 13 7 9.7 5.3 33.8 92.9 -4.4 1273 6.5
17500 -2.6 27.3 310 12 6 9.7 5.3 33.8 92.9 -4.4 1215 6.2
17000 -1.2 29.8 310 12 6 9.6 5.3 33.8 92.9 -4.4 1157 5.9
16500 0.3 32.5 310 12 6 9.6 5.3 33.8 92.8 -4.5 1099 5.6
16000 1.7 35.1 310 11 6 9.6 5.3 33.8 92.8 -4.5 1041 5.3
15500 3.1 37.6 315 11 6 9.5 5.2 33.7 92.7 -4.6 983 5.0
15000 4.6 40.3 315 11 6 9.5 5.2 33.7 92.7 -4.6 925 4.7
14500 6.0 42.8 315 11 6 9.6 5.3 33.7 92.6 -4.7 867 4.4
14000 7.5 45.5 315 11 5 9.6 5.3 33.7 92.6 -4.7 809 4.1
13500 8.9 48.0 315 10 5 9.6 5.3 33.6 92.5 -4.8 751 3.8
13000 10.3 50.5 315 10 5 9.6 5.3 33.6 92.5 -4.8 693 3.5
12500 11.8 53.2 315 10 5 9.4 5.2 33.6 92.4 -4.9 635 3.2
12000 13.2 55.8 315 10 5 9.3 5.1 33.5 92.3 -4.9 578 2.9
11500 14.6 58.3 310 10 5 9.4 5.2 33.5 92.2 -5.0 521 2.6
11000 16.0 60.8 310 9 5 9.3 5.1 33.4 92.1 -5.1 464 2.4
10500 17.4 63.3 310 9 5 4.6 2.5 33.3 91.9 -5.2 408 2.1
10250 17.6 63.7 310 9 4 6.5 3.6 32.8 91.0 -5.7 394 2.0
10000 18.4 65.1 310 9 4 12.6 6.9 32.9 91.2 -5.6 361 1.8
9750 19.3 66.7 310 9 4 11.4 6.3 33.0 91.4 -5.5 329 1.7
9500 20.1 68.2 305 9 4 8.7 4.8 33.1 91.6 -5.5 297 1.5
9250 20.6 69.1 305 8 4 6.5 3.6 32.9 91.2 -5.7 275 1.4
9000 21.2 70.2 305 8 4 9.0 4.9 32.7 90.9 -5.9 250 1.3
8750 21.9 71.4 305 9 4 9.6 5.3 32.7 90.9 -5.9 222 1.1
8500 22.5 72.5 300 9 5 7.9 4.3 32.7 90.8 -6.0 195 1.0
8250 23.0 73.4 300 9 4 6.7 3.7 32.4 90.4 -6.3 172 0.9
8000 23.5 74.3 300 8 4 7.1 3.9 32.2 90.0 -6.5 150 0.8
7750 24.0 75.2 295 9 5 6.3 3.5 32.0 89.6 -6.8 128 0.6
7500 24.4 75.9 295 10 5 4.2 2.3 31.7 89.0 -7.1 109 0.6
7250 24.6 76.3 295 10 5 3.0 1.6 31.2 88.1 -7.7 95 0.5
7000 24.8 76.6 295 10 5 3.5 1.9 30.7 87.2 -8.2 81 0.4
6750 25.0 77.0 290 10 5 -0.9 -0.5 30.1 86.2 -8.8 69 0.4
6500 24.6 76.3 280 10 5 -5.7 -3.1 29.0 84.3 -9.9 72 0.4
6250 24.2 75.6 280 9 5 -6.1 -3.4 27.8 82.1 -11.1 79 0.4
6000 23.7 74.7 275 8 4 -4.9 -2.7 26.7 80.0 -12.4 86 0.4
5750 23.0 73.4 275 8 4 -17.7 -9.7 25.3 77.5 -13.8 100 0.5
5500 20.6 69.1 250 5 3 -41.9 -23.0 22.2 72.0 -17.0 164 0.8
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
07/09/2025 at 0900 MDT | 07/09/2025 at 1200 MDT
|
CAPE... +20.5 LI... -0.1 | CAPE... +8.1 LI... -0.1
CINH... -69.3 K Index... +12.2 | CINH... -5.8 K Index... +11.6
|
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 -63.2 -81.8 300 22 11 2.6 1.4 | -63.6 -82.5 295 21 11 2.4 1.3
45000 -58.2 -72.8 300 42 22 4.7 2.6 | -58.4 -73.1 300 39 20 5.3 2.9
40000 -50.7 -59.3 300 57 29 6.2 3.4 | -50.3 -58.5 300 55 28 6.0 3.3
38000 -47.0 -52.6 300 54 28 6.2 3.4 | -46.7 -52.1 300 52 27 5.9 3.3
36000 -42.8 -45.0 305 51 26 7.2 4.0 | -43.1 -45.6 300 49 25 6.2 3.4
34000 -38.2 -36.8 305 49 25 7.6 4.2 | -38.2 -36.8 300 46 24 7.4 4.1
32000 -33.6 -28.5 305 47 24 7.5 4.1 | -33.7 -28.7 300 44 23 7.3 4.0
30000 -29.5 -21.1 310 44 23 6.9 3.8 | -29.7 -21.5 305 41 21 6.7 3.7
29000 -27.4 -17.3 310 42 22 6.9 3.8 | -27.7 -17.9 305 39 20 6.7 3.7
28000 -25.4 -13.7 315 40 21 6.0 3.3 | -25.7 -14.3 310 37 19 7.0 3.9
27000 -23.5 -10.3 315 36 19 6.1 3.4 | -23.6 -10.5 310 35 18 7.0 3.8
26000 -21.7 -7.1 315 32 17 6.1 3.4 | -21.5 -6.7 310 33 17 7.0 3.8
25000 -19.9 -3.8 315 28 15 5.7 3.1 | -19.4 -2.9 315 31 16 6.1 3.3
24000 -18.3 -0.9 315 24 12 5.4 2.9 | -17.7 0.1 310 28 14 5.6 3.1
23000 -16.7 1.9 310 20 10 5.5 3.0 | -16.1 3.0 305 25 13 5.6 3.1
22000 -15.1 4.8 305 17 9 7.4 4.0 | -14.4 6.1 300 22 11 7.4 4.1
21000 -12.7 9.1 305 15 8 8.1 4.5 | -12.0 10.4 300 20 10 8.0 4.4
20000 -10.3 13.5 305 13 7 8.3 4.5 | -9.7 14.5 295 18 9 8.1 4.5
19500 -9.1 15.6 305 12 6 8.6 4.7 | -8.5 16.7 295 17 9 8.4 4.6
19000 -7.0 19.4 310 11 6 9.5 5.2 | -7.2 19.0 295 16 8 9.2 5.0
18500 -5.6 21.9 310 11 6 9.5 5.2 | -5.8 21.6 295 15 8 9.1 5.0
18000 -4.2 24.4 315 10 5 9.6 5.3 | -4.5 23.9 295 14 7 9.5 5.2
17500 -2.8 27.0 315 10 5 9.6 5.3 | -2.4 27.7 295 13 7 9.5 5.2
17000 -1.3 29.7 320 10 5 9.7 5.3 | -0.9 30.4 295 12 6 9.5 5.2
16500 0.1 32.2 320 10 5 9.7 5.3 | 0.5 32.9 295 11 6 9.5 5.2
16000 1.6 34.9 325 9 5 9.7 5.3 | 1.9 35.4 295 11 5 9.6 5.2
15500 3.0 37.4 325 9 5 9.6 5.3 | 3.3 37.9 295 10 5 9.6 5.3
15000 4.5 40.1 325 9 5 9.6 5.3 | 4.8 40.6 295 9 5 9.6 5.3
14500 5.9 42.6 325 9 5 9.7 5.3 | 6.2 43.2 300 9 5 9.6 5.3
14000 7.4 45.3 325 9 5 9.7 5.3 | 7.7 45.9 300 8 4 9.7 5.3
13500 8.8 47.8 325 9 5 9.5 5.2 | 9.1 48.4 300 8 4 9.5 5.2
13000 10.3 50.5 325 9 5 9.5 5.2 | 10.5 50.9 305 7 4 9.5 5.2
12500 11.7 53.1 325 9 5 9.5 5.2 | 12.0 53.6 305 7 4 9.6 5.3
12000 13.1 55.6 325 9 5 9.5 5.2 | 13.4 56.1 310 7 3 9.6 5.3
11500 14.5 58.1 325 9 5 9.4 5.1 | 14.8 58.6 310 6 3 9.7 5.3
11000 15.9 60.6 320 9 5 9.4 5.2 | 16.3 61.3 315 6 3 9.9 5.4
10500 17.2 63.0 320 9 5 4.6 2.5 | 17.5 63.5 315 6 3 4.5 2.4
10250 17.5 63.5 320 9 5 7.8 4.3 | 17.9 64.2 315 5 3 8.6 4.7
10000 18.4 65.1 320 9 5 13.0 7.2 | 18.8 65.8 315 5 3 13.5 7.4
9750 19.3 66.7 315 9 5 11.4 6.3 | 19.7 67.5 315 5 3 12.0 6.6
9500 20.0 68.0 315 9 5 7.7 4.2 | 20.5 68.9 320 5 3 7.8 4.3
9250 20.5 68.9 315 9 5 6.1 3.4 | 21.0 69.8 320 5 2 7.4 4.0
9000 21.1 70.0 315 9 5 9.9 5.4 | 21.8 71.2 320 5 2 12.2 6.7
8750 21.9 71.4 315 9 5 10.3 5.6 | 22.7 72.9 320 5 2 12.0 6.6
8500 22.5 72.5 310 9 5 7.8 4.3 | 23.5 74.3 325 4 2 9.2 5.0
8250 23.0 73.4 310 10 5 6.2 3.4 | 24.1 75.4 325 4 2 6.9 3.8
8000 23.5 74.3 310 10 5 8.1 4.4 | 24.7 76.5 325 4 2 11.0 6.1
7750 24.2 75.6 310 10 5 7.8 4.3 | 25.6 78.1 330 4 2 12.5 6.9
7500 24.6 76.3 305 10 5 4.6 2.6 | 26.4 79.5 330 4 2 8.7 4.8
7250 24.9 76.8 305 10 5 3.4 1.8 | 27.0 80.6 330 4 2 7.0 3.8
7000 25.2 77.4 305 10 5 5.6 3.1 | 27.6 81.7 335 4 2 11.4 6.2
6750 25.6 78.1 300 9 5 5.1 2.8 | 28.7 83.7 335 4 2 13.9 7.6
6500 25.8 78.4 295 8 4 2.0 1.1 | 29.5 85.1 335 3 2 10.4 5.7
6250 25.9 78.6 290 7 3 2.7 1.5 | 30.3 86.5 335 3 2 10.7 5.9
6000 26.1 79.0 285 6 3 0.9 0.5 | 31.1 88.0 340 3 2 9.1 5.0
5750 26.2 79.2 285 4 2 6.8 3.8 | 31.9 89.4 345 3 2 15.2 8.4
5500 27.2 81.0 280 3 2 21.6 11.8 | 33.6 92.5 345 3 2 30.0 16.4
07/09/2025 at 1500 MDT | 07/09/2025 at 1800 MDT
|
CAPE... +13.6 LI... -0.2 | CAPE... +18.8 LI... -0.1
CINH... -3.6 K Index... +11.2 | CINH... -28.0 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 -63.9 -83.0 285 24 12 1.7 0.9 | -63.7 -82.7 290 28 14 1.4 0.8
45000 -59.1 -74.4 295 39 20 5.8 3.2 | -59.4 -74.9 290 44 23 5.6 3.1
40000 -50.3 -58.5 300 54 28 6.2 3.4 | -50.8 -59.4 295 56 29 6.4 3.5
38000 -46.5 -51.7 300 51 26 6.2 3.4 | -46.9 -52.4 295 54 28 6.4 3.5
36000 -42.8 -45.0 295 48 25 6.4 3.5 | -43.1 -45.6 295 52 27 6.5 3.6
34000 -38.0 -36.4 295 46 24 7.1 3.9 | -38.3 -36.9 295 49 25 7.1 3.9
32000 -33.8 -28.8 295 44 23 7.0 3.8 | -34.1 -29.4 290 47 24 7.3 4.0
30000 -30.1 -22.2 295 40 21 6.1 3.3 | -30.3 -22.5 290 40 20 6.3 3.5
29000 -28.3 -18.9 295 38 20 6.1 3.3 | -28.4 -19.1 290 36 19 6.3 3.5
28000 -26.4 -15.5 295 36 19 6.8 3.7 | -26.4 -15.5 290 32 17 7.2 3.9
27000 -24.4 -11.9 300 34 17 6.8 3.7 | -24.3 -11.7 290 29 15 7.1 3.9
26000 -22.3 -8.1 300 31 16 6.8 3.7 | -22.2 -8.0 290 26 13 7.1 3.9
25000 -20.3 -4.5 300 29 15 7.2 4.0 | -20.1 -4.2 290 23 12 7.6 4.2
24000 -18.1 -0.6 300 27 14 7.4 4.1 | -17.8 -0.0 285 22 11 7.9 4.3
23000 -15.9 3.4 295 24 13 7.4 4.1 | -15.4 4.3 280 21 11 8.0 4.4
22000 -13.7 7.3 290 22 12 8.5 4.6 | -13.1 8.4 275 20 10 8.4 4.6
21000 -11.1 12.0 290 20 11 8.7 4.7 | -10.6 12.9 280 18 9 8.5 4.7
20000 -8.6 16.5 290 18 10 8.7 4.8 | -8.1 17.4 280 15 8 8.6 4.7
19500 -7.3 18.9 285 18 9 8.9 4.9 | -6.8 19.8 280 14 7 8.8 4.8
19000 -5.9 21.4 290 17 9 9.4 5.2 | -5.4 22.3 280 13 7 9.3 5.1
18500 -4.5 23.9 290 16 8 9.4 5.1 | -4.1 24.6 280 12 6 9.2 5.1
18000 -3.1 26.4 290 15 8 9.6 5.2 | -2.7 27.1 285 11 6 9.5 5.2
17500 -1.0 30.2 290 14 7 9.6 5.2 | -0.5 31.1 285 10 5 9.5 5.2
17000 0.5 32.9 295 13 7 9.7 5.3 | 0.9 33.6 290 9 5 9.5 5.2
16500 1.9 35.4 295 12 6 9.7 5.3 | 2.3 36.1 290 8 4 9.5 5.2
16000 3.4 38.1 295 11 6 9.6 5.3 | 3.7 38.7 290 7 4 9.5 5.2
15500 4.8 40.6 295 11 5 9.5 5.2 | 5.2 41.4 290 6 3 9.5 5.2
15000 6.2 43.2 295 10 5 9.5 5.2 | 6.6 43.9 295 5 3 9.5 5.2
14500 7.6 45.7 300 9 5 9.5 5.2 | 8.0 46.4 295 5 2 9.6 5.2
14000 9.1 48.4 300 8 4 9.5 5.2 | 9.5 49.1 295 4 2 9.6 5.2
13500 10.5 50.9 300 8 4 9.4 5.2 | 10.9 51.6 300 4 2 9.5 5.2
13000 11.9 53.4 300 7 4 9.4 5.2 | 12.3 54.1 300 3 2 9.5 5.2
12500 13.3 55.9 300 7 3 9.5 5.2 | 13.7 56.7 305 3 1 9.6 5.3
12000 14.8 58.6 300 6 3 9.5 5.2 | 15.2 59.4 305 2 1 9.7 5.3
11500 16.2 61.2 305 6 3 9.7 5.3 | 16.6 61.9 310 2 1 9.5 5.2
11000 17.6 63.7 305 5 3 10.0 5.5 | 18.1 64.6 310 2 1 9.2 5.1
10500 18.8 65.8 305 5 3 4.1 2.2 | 19.4 66.9 315 2 1 4.8 2.6
10250 19.2 66.6 305 5 3 8.4 4.6 | 19.7 67.5 310 2 1 6.9 3.8
10000 20.1 68.2 310 5 3 13.7 7.5 | 20.6 69.1 315 2 1 13.1 7.2
9750 21.1 70.0 310 4 2 12.6 6.9 | 21.5 70.7 320 2 1 12.6 6.9
9500 21.9 71.4 310 4 2 7.8 4.3 | 22.3 72.1 325 1 1 8.4 4.6
9250 22.4 72.3 310 5 2 7.1 3.9 | 22.8 73.0 320 2 1 7.0 3.8
9000 23.2 73.8 310 4 2 12.3 6.7 | 23.5 74.3 320 2 1 11.5 6.3
8750 24.1 75.4 310 4 2 12.0 6.6 | 24.4 75.9 325 2 1 11.6 6.4
8500 24.9 76.8 315 4 2 9.3 5.1 | 25.2 77.4 330 1 1 9.6 5.3
8250 25.5 77.9 315 4 2 6.8 3.7 | 25.8 78.4 325 2 1 7.3 4.0
8000 26.1 79.0 315 4 2 11.1 6.1 | 26.4 79.5 325 2 1 10.3 5.7
7750 27.1 80.8 315 3 2 12.9 7.1 | 27.3 81.1 330 1 1 12.1 6.6
7500 27.9 82.2 320 3 2 9.0 4.9 | 28.2 82.8 335 1 1 9.2 5.1
7250 28.4 83.1 320 3 2 6.7 3.7 | 28.7 83.7 330 1 1 6.9 3.8
7000 29.0 84.2 320 4 2 10.8 5.9 | 29.3 84.7 325 2 1 9.9 5.4
6750 30.0 86.0 320 3 2 13.9 7.6 | 30.2 86.4 330 1 1 13.2 7.2
6500 30.9 87.6 320 3 1 10.6 5.8 | 31.1 88.0 340 1 1 10.6 5.8
6250 31.7 89.1 320 3 2 9.4 5.1 | 31.8 89.2 335 1 1 8.9 4.9
6000 32.4 90.3 320 3 2 10.5 5.8 | 32.5 90.5 330 1 1 9.2 5.0
5750 33.4 92.1 325 2 1 17.5 9.6 | 33.3 91.9 335 1 1 12.6 6.9
5500 35.0 95.0 325 2 1 26.4 14.5 | 34.5 94.1 335 1 1 19.2 10.6
________________________________________________________________________________
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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