Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
750
UXUS97 KBOU 021258
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0657 MDT Saturday, August 2, 2025
This forecast is for Saturday, August 2, 2025:
If the trigger temperature of 85.0 F/29.5 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1465 ft/min (7.4 m/s)
Maximum height of thermals.................. 18070 ft MSL (12816 ft AGL)
Forecast maximum temperature................... 89.0 F/32.1 C
Time of trigger temperature.................... 1130 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................. 8158 ft MSL (2905 ft AGL)
Thermal soaring outlook for Sunday 08/03....... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT).........
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 40409 ft MSL (35155 ft AGL)
Wave soaring outlook for Sunday 08/03.......... Poor
Remarks...
Sunrise/Sunset.................... 06:00:00 / 20:11:28 MDT
Total possible sunshine........... 14 hr 11 min 28 sec (851 min 28 sec)
Altitude of sun at 13:05:44 MDT... 67.74 degrees
Upper air data from numerical model forecast valid on 08/02/2025 at 0600 MDT
Freezing level.................. 15625 ft MSL (10371 ft AGL)
Convective condensation level... 16070 ft MSL (10816 ft AGL)
Lifted condensation level....... 16378 ft MSL (11124 ft AGL)
Lifted index.................... -4.1
K index......................... +26.7
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 -59.9 -75.8 265 23 12 3.7 2.1 M M M M M
45000 -54.7 -66.5 270 48 25 3.0 1.7 M M M M M
40000 -49.7 -57.5 280 67 35 4.2 2.3 M M M M M
38000 -47.2 -53.0 280 68 35 4.2 2.3 M M M M M
36000 -44.7 -48.5 285 68 35 4.1 2.2 M M M M M
34000 -40.9 -41.6 285 61 31 6.6 3.6 M M M M M
32000 -37.0 -34.6 280 53 27 6.5 3.6 M M M M M
30000 -33.1 -27.6 285 45 23 6.4 3.5 42.9 109.2 8.5 M M
29000 -31.2 -24.2 285 42 21 6.4 3.5 41.7 107.0 7.6 M M
28000 -29.2 -20.6 290 38 20 7.0 3.8 40.5 105.0 6.9 M M
27000 -26.5 -15.7 290 34 18 7.4 4.1 39.3 102.7 6.0 M M
26000 -24.2 -11.6 290 31 16 7.4 4.1 38.4 101.2 5.4 M M
25000 -22.0 -7.6 295 28 14 7.3 4.0 37.7 99.8 4.8 M M
24000 -19.9 -3.8 295 28 14 7.2 4.0 36.6 97.9 4.0 M M
23000 -17.7 0.1 300 27 14 7.2 4.0 35.7 96.3 3.3 M M
22000 -15.6 3.9 300 27 14 7.2 4.0 34.9 94.8 2.6 M M
21000 -13.4 7.9 300 25 13 7.3 4.0 33.9 93.1 1.8 M M
20000 -11.3 11.7 300 23 12 7.4 4.1 33.1 91.6 1.0 M M
19500 -10.3 13.5 300 22 11 7.9 4.3 32.8 91.0 0.7 M M
19000 -9.0 15.8 300 21 11 8.8 4.8 32.5 90.6 0.4 M M
18500 -7.8 18.0 295 20 10 8.9 4.9 32.4 90.3 0.2 M M
18000 -6.5 20.3 295 18 10 8.8 4.8 32.2 90.0 -0.0 1262 6.4
17500 -5.3 22.5 295 18 9 8.8 4.8 32.0 89.7 -0.2 1209 6.1
17000 -4.0 24.8 295 17 9 9.0 4.9 31.9 89.4 -0.4 1156 5.9
16500 -2.6 27.3 300 15 8 9.3 5.1 31.8 89.2 -0.5 1100 5.6
16000 -1.3 29.7 300 14 7 9.3 5.1 31.7 89.1 -0.6 1044 5.3
15500 0.1 32.2 300 13 7 9.4 5.2 31.6 89.0 -0.7 988 5.0
15000 1.5 34.7 305 13 7 9.4 5.2 31.6 88.9 -0.7 931 4.7
14500 2.9 37.2 305 12 6 9.5 5.2 31.5 88.8 -0.8 874 4.4
14000 4.3 39.7 305 11 6 9.5 5.2 31.5 88.7 -0.8 818 4.2
13500 5.7 42.3 305 11 6 9.6 5.2 31.5 88.6 -0.9 761 3.9
13000 7.1 44.8 305 10 5 9.6 5.3 31.4 88.6 -1.0 704 3.6
12500 9.3 48.7 305 10 5 9.6 5.3 31.4 88.5 -1.0 618 3.1
12000 10.7 51.3 305 10 5 9.6 5.3 31.4 88.5 -1.1 561 2.8
11500 12.1 53.8 305 10 5 9.5 5.2 31.3 88.4 -1.1 504 2.6
11000 13.4 56.1 305 10 5 9.8 5.4 31.3 88.3 -1.2 449 2.3
10500 14.5 58.1 300 10 5 2.7 1.5 31.0 87.8 -1.6 401 2.0
10250 14.7 58.5 300 10 5 6.9 3.8 30.4 86.8 -2.1 387 2.0
10000 15.6 60.1 295 10 5 13.9 7.6 30.6 87.1 -2.0 354 1.8
9750 16.5 61.7 290 10 5 10.7 5.9 30.8 87.5 -1.8 319 1.6
9500 17.2 63.0 285 10 5 6.8 3.7 30.7 87.3 -1.9 292 1.5
9250 17.6 63.7 280 10 5 5.6 3.1 30.4 86.8 -2.2 272 1.4
9000 18.1 64.6 270 10 5 8.6 4.7 30.2 86.4 -2.4 250 1.3
8750 18.8 65.8 260 10 5 8.7 4.8 30.2 86.3 -2.4 221 1.1
8500 19.3 66.7 255 10 5 6.2 3.4 30.0 86.0 -2.7 198 1.0
8250 19.8 67.6 250 10 5 5.2 2.9 29.7 85.4 -2.9 177 0.9
8000 20.2 68.4 250 10 5 8.6 4.7 29.4 84.9 -3.2 156 0.8
7750 20.9 69.6 245 10 5 6.8 3.8 29.4 84.9 -3.3 128 0.6
7500 21.1 70.0 240 10 5 1.6 0.9 28.9 83.9 -3.8 115 0.6
7250 21.3 70.3 240 9 5 3.5 1.9 28.3 82.9 -4.4 103 0.5
7000 21.4 70.5 240 9 5 0.1 0.1 27.8 82.0 -5.0 91 0.5
6750 21.1 70.0 240 9 4 -7.8 -4.3 26.7 80.1 -6.1 94 0.5
6500 20.3 68.5 235 8 4 -10.6 -5.8 25.2 77.4 -7.6 110 0.6
6250 19.5 67.1 235 7 3 -9.6 -5.3 23.7 74.7 -9.1 126 0.6
6000 18.7 65.7 230 6 3 -10.8 -5.9 22.3 72.1 -10.7 143 0.7
5750 17.7 63.9 220 5 3 -14.3 -7.8 20.6 69.1 -12.4 165 0.8
5500 16.4 61.5 210 4 2 -17.2 -9.5 18.6 65.6 -14.5 197 1.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/02/2025 at 0900 MDT | 08/02/2025 at 1200 MDT
|
CAPE... +192.1 LI... -2.2 | CAPE... +705.9 LI... -3.1
CINH... -230.6 K Index... +28.6 | CINH... -13.0 K Index... +23.6
|
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 -60.9 -77.6 265 25 13 3.6 2.0 | -60.2 -76.4 270 30 15 3.3 1.8
45000 -55.5 -67.9 275 48 25 3.5 1.9 | -55.0 -67.0 270 52 27 3.7 2.0
40000 -49.9 -57.8 280 67 34 3.7 2.0 | -49.3 -56.7 270 65 33 3.6 2.0
38000 -47.7 -53.9 280 67 35 3.7 2.0 | -47.2 -53.0 275 66 34 3.6 2.0
36000 -45.5 -49.9 280 68 35 3.6 1.9 | -45.0 -49.0 275 67 34 3.3 1.8
34000 -41.5 -42.7 280 65 33 7.0 3.8 | -41.6 -42.9 275 65 33 6.1 3.3
32000 -37.3 -35.1 280 61 31 6.9 3.8 | -38.0 -36.4 275 62 32 5.9 3.3
30000 -33.0 -27.4 280 52 27 7.3 4.0 | -33.5 -28.3 280 55 28 7.8 4.3
29000 -30.9 -23.6 280 48 24 7.3 4.0 | -30.5 -22.9 280 50 26 7.8 4.3
28000 -28.2 -18.8 280 41 21 6.4 3.5 | -28.3 -18.9 280 46 24 6.5 3.6
27000 -26.3 -15.3 280 33 17 6.5 3.6 | -26.3 -15.3 275 39 20 6.7 3.6
26000 -24.4 -11.9 275 26 13 6.6 3.6 | -24.3 -11.7 275 33 17 6.7 3.7
25000 -22.5 -8.5 265 19 10 7.1 3.9 | -22.4 -8.3 265 28 14 6.8 3.8
24000 -20.3 -4.5 275 19 10 7.3 4.0 | -20.3 -4.5 270 23 12 7.0 3.9
23000 -18.1 -0.6 280 19 10 7.3 4.0 | -18.3 -0.9 270 18 10 7.2 3.9
22000 -15.9 3.4 285 19 10 8.1 4.5 | -16.2 2.8 275 14 7 8.3 4.5
21000 -13.5 7.7 280 19 10 8.3 4.6 | -13.6 7.5 280 15 8 8.6 4.7
20000 -11.0 12.2 280 18 9 8.3 4.6 | -11.1 12.0 285 15 8 8.6 4.7
19500 -9.8 14.4 280 18 9 8.3 4.5 | -9.8 14.4 290 16 8 8.6 4.7
19000 -8.6 16.5 275 17 9 8.1 4.5 | -8.5 16.7 290 16 8 8.7 4.8
18500 -7.4 18.7 270 17 9 8.1 4.5 | -7.2 19.0 290 17 9 8.7 4.8
18000 -6.2 20.8 270 16 8 8.5 4.7 | -5.9 21.4 290 17 9 9.1 5.0
17500 -5.0 23.0 270 15 8 8.6 4.7 | -4.6 23.7 290 17 9 9.2 5.0
17000 -3.7 25.3 265 15 8 8.7 4.8 | -3.2 26.2 285 16 8 9.1 5.0
16500 -2.4 27.7 265 14 7 8.9 4.9 | -1.9 28.6 285 16 8 9.0 4.9
16000 -1.1 30.0 265 13 7 8.9 4.9 | -0.6 30.9 285 16 8 9.0 4.9
15500 0.2 32.4 265 12 6 9.1 5.0 | 0.8 33.4 285 16 8 9.0 4.9
15000 1.5 34.7 260 12 6 9.0 5.0 | 2.7 36.9 280 15 8 9.0 4.9
14500 2.8 37.0 260 11 6 9.4 5.2 | 4.1 39.4 280 15 8 9.1 5.0
14000 4.2 39.6 260 11 6 9.5 5.2 | 5.4 41.7 275 15 8 9.2 5.0
13500 6.3 43.3 255 10 5 9.3 5.1 | 6.7 44.1 275 15 8 9.0 5.0
13000 7.6 45.7 260 10 5 9.4 5.1 | 8.1 46.6 275 15 8 9.0 5.0
12500 9.0 48.2 260 10 5 9.2 5.0 | 9.4 48.9 275 15 8 9.2 5.0
12000 10.3 50.5 260 10 5 9.2 5.0 | 10.7 51.3 275 15 8 9.2 5.1
11500 11.7 53.1 260 10 5 9.3 5.1 | 12.1 53.8 275 15 8 8.8 4.8
11000 13.0 55.4 260 10 5 9.6 5.3 | 13.3 55.9 275 14 7 9.0 4.9
10500 14.1 57.4 265 11 5 2.8 1.5 | 14.4 57.9 275 13 7 4.0 2.2
10250 14.4 57.9 265 11 5 7.6 4.2 | 14.7 58.5 275 13 7 7.9 4.3
10000 15.3 59.5 265 11 6 14.2 7.8 | 15.6 60.1 275 11 6 12.8 7.0
9750 16.2 61.2 270 12 6 10.7 5.9 | 16.4 61.5 275 10 5 10.8 5.9
9500 16.9 62.4 270 12 6 7.0 3.8 | 17.1 62.8 275 9 5 7.7 4.3
9250 17.3 63.1 270 12 6 6.3 3.5 | 17.6 63.7 275 8 4 7.4 4.1
9000 17.9 64.2 270 12 6 10.7 5.9 | 18.3 64.9 270 7 3 11.3 6.2
8750 18.8 65.8 270 12 6 10.7 5.9 | 19.1 66.4 270 6 3 11.3 6.2
8500 19.4 66.9 275 12 6 7.5 4.1 | 19.9 67.8 270 5 3 9.1 5.0
8250 20.0 68.0 275 13 7 7.0 3.9 | 20.5 68.9 270 5 2 8.1 4.5
8000 20.5 68.9 280 14 7 8.1 4.5 | 21.1 70.0 270 4 2 10.1 5.5
7750 21.1 70.0 280 14 7 6.8 3.7 | 21.9 71.4 270 4 2 11.2 6.1
7500 21.5 70.7 285 14 7 4.7 2.6 | 22.7 72.9 275 4 2 10.0 5.5
7250 21.9 71.4 285 14 7 5.1 2.8 | 23.4 74.1 275 4 2 9.9 5.5
7000 22.2 72.0 285 13 7 4.9 2.7 | 24.2 75.6 275 4 2 10.6 5.8
6750 22.5 72.5 290 12 6 1.5 0.8 | 25.0 77.0 275 4 2 10.6 5.8
6500 22.5 72.5 290 12 6 -0.8 -0.4 | 25.7 78.3 275 3 2 10.0 5.5
6250 22.4 72.3 285 11 6 -0.3 -0.2 | 26.5 79.7 275 3 2 9.9 5.4
6000 22.4 72.3 285 10 5 0.1 0.1 | 27.2 81.0 275 3 2 10.7 5.9
5750 22.5 72.5 280 7 4 5.9 3.2 | 28.2 82.8 275 3 2 17.6 9.7
5500 23.2 73.8 270 5 3 13.4 7.3 | 29.9 85.8 280 3 1 26.3 14.5
08/02/2025 at 1500 MDT | 08/02/2025 at 1800 MDT
|
CAPE... +373.4 LI... -1.2 | CAPE... +1004.1 LI... -2.9
CINH... -13.0 K Index... +28.3 | CINH... -118.2 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 -59.5 -75.1 275 26 13 3.3 1.8 | -60.0 -76.0 280 29 15 2.7 1.5
45000 -55.0 -67.0 275 47 24 2.4 1.3 | -55.5 -67.9 275 50 26 3.6 2.0
40000 -50.9 -59.6 270 68 35 4.2 2.3 | -50.0 -58.0 270 56 29 3.5 1.9
38000 -48.4 -55.1 275 67 34 4.2 2.3 | -47.9 -54.2 270 53 27 3.5 1.9
36000 -45.9 -50.6 275 66 34 4.0 2.2 | -45.6 -50.1 270 51 26 3.8 2.1
34000 -41.9 -43.4 275 63 33 6.9 3.8 | -42.0 -43.6 265 46 24 6.1 3.3
32000 -37.8 -36.0 275 61 31 6.8 3.7 | -38.4 -37.1 260 42 22 6.0 3.3
30000 -33.2 -27.8 275 58 30 7.9 4.3 | -33.5 -28.3 260 38 20 8.4 4.6
29000 -30.3 -22.5 275 56 29 7.9 4.3 | -31.0 -23.8 260 36 18 8.4 4.6
28000 -28.0 -18.4 270 54 28 7.1 3.9 | -28.5 -19.3 260 34 17 8.4 4.6
27000 -25.9 -14.6 265 49 25 7.2 4.0 | -26.0 -14.8 265 32 16 8.4 4.6
26000 -23.7 -10.7 265 44 23 7.3 4.0 | -23.5 -10.3 265 29 15 8.4 4.6
25000 -21.6 -6.9 255 40 20 7.9 4.4 | -20.9 -5.6 265 27 14 7.9 4.3
24000 -19.1 -2.4 260 35 18 8.4 4.6 | -18.9 -2.0 265 29 15 6.8 3.7
23000 -16.7 1.9 260 30 15 8.5 4.6 | -16.9 1.6 260 32 16 6.9 3.8
22000 -14.3 6.3 260 25 13 7.9 4.3 | -14.9 5.2 260 35 18 7.8 4.3
21000 -12.0 10.4 265 21 11 7.8 4.3 | -12.3 9.9 265 33 17 8.8 4.8
20000 -9.8 14.4 265 17 9 7.8 4.3 | -9.8 14.4 265 32 17 8.8 4.9
19500 -8.6 16.5 265 15 8 7.5 4.1 | -8.5 16.7 265 32 16 8.9 4.9
19000 -7.6 18.3 265 13 7 6.7 3.7 | -7.3 18.9 270 31 16 8.2 4.5
18500 -6.7 19.9 260 12 6 6.8 3.7 | -6.1 21.0 270 29 15 8.3 4.5
18000 -5.7 21.7 255 10 5 6.5 3.6 | -4.3 24.3 275 27 14 7.7 4.2
17500 -4.7 23.5 250 9 4 6.6 3.6 | -3.2 26.2 275 25 13 7.8 4.3
17000 -3.8 25.2 240 7 4 7.3 4.0 | -2.0 28.4 280 24 12 8.0 4.4
16500 -2.4 27.7 235 6 3 9.6 5.2 | -0.8 30.6 280 23 12 8.1 4.4
16000 -1.0 30.2 230 5 3 9.5 5.2 | 0.3 32.5 280 22 11 8.1 4.4
15500 0.4 32.7 225 5 2 9.6 5.3 | 1.5 34.7 280 20 10 7.8 4.3
15000 1.8 35.2 215 5 2 9.7 5.3 | 2.6 36.7 280 19 10 7.9 4.3
14500 3.9 39.0 205 4 2 8.9 4.9 | 3.8 38.8 275 18 9 7.4 4.1
14000 5.3 41.5 200 4 2 9.0 4.9 | 4.8 40.6 270 16 8 7.5 4.1
13500 6.6 43.9 195 5 2 9.2 5.0 | 5.9 42.6 265 15 8 7.5 4.1
13000 7.9 46.2 195 5 2 9.1 5.0 | 7.1 44.8 260 13 7 7.5 4.1
12500 9.3 48.7 200 5 3 9.6 5.3 | 8.2 46.8 255 12 6 7.4 4.1
12000 10.7 51.3 200 5 3 9.7 5.3 | 9.3 48.7 255 10 5 7.4 4.0
11500 12.2 54.0 205 5 3 9.5 5.2 | 10.4 50.7 250 9 5 7.7 4.2
11000 13.6 56.5 205 6 3 9.6 5.3 | 11.6 52.9 255 8 4 7.7 4.2
10500 14.8 58.6 205 6 3 4.0 2.2 | 12.7 54.9 260 6 3 3.8 2.1
10250 15.1 59.2 205 6 3 7.9 4.3 | 12.9 55.2 260 6 3 5.1 2.8
10000 16.0 60.8 205 6 3 13.5 7.4 | 13.6 56.5 270 5 3 11.1 6.1
9750 16.9 62.4 210 6 3 11.6 6.4 | 14.3 57.7 280 4 2 10.2 5.6
9500 17.7 63.9 210 7 3 8.6 4.7 | 15.0 59.0 290 4 2 8.2 4.5
9250 18.2 64.8 210 7 3 7.7 4.2 | 15.5 59.9 310 3 2 6.2 3.4
9000 18.9 66.0 210 7 4 11.1 6.1 | 16.0 60.8 335 3 1 8.4 4.6
8750 19.8 67.6 210 7 4 11.2 6.1 | 16.7 62.1 005 3 2 9.2 5.0
8500 20.5 68.9 210 7 4 9.3 5.1 | 17.3 63.1 025 4 2 7.0 3.8
8250 21.2 70.2 210 8 4 8.1 4.4 | 17.7 63.9 040 5 3 5.8 3.2
8000 21.8 71.2 215 8 4 10.2 5.6 | 18.1 64.6 045 7 3 6.3 3.4
7750 22.7 72.9 215 8 4 11.4 6.2 | 18.5 65.3 055 8 4 5.7 3.1
7500 23.4 74.1 215 8 4 9.9 5.4 | 18.8 65.8 055 9 5 4.4 2.4
7250 24.2 75.6 215 8 4 9.8 5.4 | 19.1 66.4 060 10 5 4.4 2.4
7000 24.9 76.8 215 8 4 9.8 5.4 | 19.3 66.7 065 12 6 3.4 1.9
6750 25.6 78.1 215 8 4 9.8 5.4 | 19.5 67.1 065 13 7 5.8 3.2
6500 26.4 79.5 215 8 4 10.0 5.5 | 20.1 68.2 070 13 7 9.0 4.9
6250 27.1 80.8 215 8 4 9.9 5.4 | 20.7 69.3 070 13 7 8.2 4.5
6000 27.9 82.2 215 8 4 10.2 5.6 | 21.3 70.3 070 13 6 9.4 5.2
5750 28.7 83.7 215 8 4 13.4 7.3 | 22.1 71.8 070 12 6 14.2 7.8
5500 29.9 85.8 215 7 4 17.7 9.7 | 23.4 74.1 070 11 6 18.8 10.3
________________________________________________________________________________
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.
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