Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
256
UXUS97 KBOU 081227
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0627 MDT Tuesday, April 8, 2025
This forecast is for Tuesday, April 8, 2025:
If the trigger temperature of 64.3 F/17.9 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 787 ft/min (4.0 m/s)
Maximum height of thermals.................. 18149 ft MSL (12849 ft AGL)
Forecast maximum temperature................... 74.0 F/23.8 C
Time of trigger temperature.................... 1030 MDT
Time of overdevelopment........................ 1300 MDT
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 14562 ft MSL (9262 ft AGL)
Thermal soaring outlook for Wednesday 04/09.... Good
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....................... 21828 ft MSL (16528 ft AGL)
Wave soaring outlook for Wednesday 04/09....... Good
Remarks...
Sunrise/Sunset.................... 06:31:33 / 19:30:46 MDT
Total possible sunshine........... 12 hr 59 min 14 sec (779 min 14 sec)
Altitude of sun at 13:01:10 MDT... 57.75 degrees
Upper air data from numerical model forecast valid on 04/08/2025 at 0600 MDT
Freezing level.................. 11391 ft MSL (6091 ft AGL)
Convective condensation level... 18418 ft MSL (13118 ft AGL)
Lifted condensation level....... 18515 ft MSL (13215 ft AGL)
Lifted index.................... +0.1
K index......................... +8.2
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 -61.1 -78.0 285 31 16 0.4 0.2 M M M M M
45000 -60.6 -77.1 285 38 20 -0.1 -0.1 M M M M M
40000 -64.2 -83.6 290 49 25 -2.5 -1.3 M M M M M
38000 -62.9 -81.2 290 50 26 7.1 3.9 M M M M M
36000 -58.1 -72.6 295 49 25 7.1 3.9 M M M M M
34000 -53.6 -64.5 295 47 24 8.5 4.7 M M M M M
32000 -48.4 -55.1 295 43 22 8.5 4.7 M M M M M
30000 -43.3 -45.9 295 39 20 8.6 4.7 32.2 89.9 6.6 M M
29000 -40.7 -41.3 290 38 20 8.6 4.7 31.6 88.9 6.3 M M
28000 -38.1 -36.6 290 37 19 8.6 4.7 31.2 88.2 6.1 M M
27000 -35.6 -32.1 290 36 19 7.2 3.9 30.8 87.5 5.8 M M
26000 -33.5 -28.3 285 33 17 7.0 3.9 29.7 85.4 5.0 M M
25000 -31.4 -24.5 285 31 16 7.0 3.9 28.6 83.6 4.2 M M
24000 -29.3 -20.7 285 28 14 7.5 4.1 27.8 82.0 3.5 M M
23000 -27.0 -16.6 285 27 14 7.8 4.3 26.9 80.5 2.9 M M
22000 -24.6 -12.3 285 26 13 7.8 4.3 26.3 79.3 2.3 M M
21000 -22.3 -8.1 285 25 13 8.0 4.4 25.6 78.1 1.8 M M
20000 -19.9 -3.8 290 23 12 8.0 4.4 24.9 76.9 1.2 M M
19500 -18.7 -1.7 290 22 11 8.0 4.4 24.6 76.3 0.9 M M
19000 -17.6 0.3 290 21 11 8.0 4.4 24.4 75.8 0.7 M M
18500 -16.4 2.5 295 20 10 7.2 3.9 24.0 75.3 0.4 M M
18000 -14.8 5.4 300 17 9 6.9 3.8 23.3 73.9 -0.2 1162 5.9
17500 -13.8 7.2 305 16 8 7.2 3.9 22.8 73.1 -0.6 1116 5.7
17000 -12.7 9.1 305 14 7 7.3 4.0 22.4 72.3 -1.0 1068 5.4
16500 -11.6 11.1 305 13 7 7.2 4.0 22.0 71.6 -1.4 1021 5.2
16000 -10.5 13.1 310 12 6 7.2 4.0 21.5 70.8 -1.8 973 4.9
15500 -9.5 14.9 310 11 6 7.2 4.0 21.1 70.0 -2.2 926 4.7
15000 -8.4 16.9 310 10 5 6.6 3.6 20.6 69.2 -2.6 880 4.5
14500 -7.4 18.7 315 8 4 6.6 3.6 20.1 68.3 -3.1 836 4.2
14000 -6.3 20.7 315 7 3 8.0 4.4 19.7 67.5 -3.5 788 4.0
13500 -5.2 22.6 320 6 3 8.0 4.4 19.4 67.0 -3.8 738 3.7
13000 -4.0 24.8 320 5 2 8.1 4.5 19.2 66.5 -4.1 687 3.5
12500 -2.8 27.0 325 4 2 8.1 4.5 18.9 66.0 -4.4 636 3.2
12000 -1.5 29.3 330 3 2 8.7 4.8 18.7 65.6 -4.6 584 3.0
11500 -0.2 31.6 330 3 2 8.8 4.8 18.5 65.3 -4.8 530 2.7
11000 1.1 34.0 330 3 2 9.7 5.3 18.4 65.2 -5.0 475 2.4
10500 2.6 36.7 325 5 2 10.7 5.9 18.4 65.2 -5.0 416 2.1
10250 3.4 38.1 320 5 3 6.3 3.5 18.4 65.2 -5.0 386 2.0
10000 3.7 38.7 320 5 3 7.1 3.9 18.0 64.4 -5.4 368 1.9
9750 4.5 40.1 320 7 3 12.0 6.6 18.1 64.6 -5.3 336 1.7
9500 5.4 41.7 315 8 4 10.8 5.9 18.2 64.8 -5.2 304 1.5
9250 6.2 43.2 315 9 5 10.9 6.0 18.3 65.0 -5.2 272 1.4
9000 7.0 44.6 315 11 6 10.2 5.6 18.4 65.1 -5.1 241 1.2
8750 7.7 45.9 310 13 7 10.0 5.5 18.4 65.1 -5.1 211 1.1
8500 8.5 47.3 310 15 8 10.1 5.6 18.4 65.2 -5.1 181 0.9
8250 9.2 48.6 310 18 9 9.7 5.3 18.5 65.2 -5.1 152 0.8
8000 9.9 49.8 305 20 10 8.8 4.8 18.4 65.1 -5.2 124 0.6
7750 10.5 50.9 305 23 12 7.4 4.1 18.3 64.9 -5.3 98 0.5
7500 11.0 51.8 300 25 13 6.6 3.6 18.1 64.5 -5.5 75 0.4
7250 11.5 52.7 300 27 14 6.9 3.8 17.8 64.1 -5.8 53 0.3
7000 12.0 53.6 295 27 14 6.4 3.5 17.6 63.7 -6.0 30 0.2
6750 12.5 54.5 295 27 14 6.7 3.7 17.3 63.2 -6.3 8 0.0
6500 12.8 55.0 290 26 13 -4.0 -2.2 16.9 62.3 -6.8 M M
6250 11.9 53.4 285 22 11 -14.2 -7.8 15.3 59.5 -8.4 11 0.1
6000 10.9 51.6 275 18 9 -12.1 -6.7 13.5 56.3 -10.1 34 0.2
5750 9.9 49.8 255 15 8 -15.7 -8.6 11.8 53.3 -11.9 57 0.3
5500 8.0 46.4 240 13 7 -35.5 -19.5 9.3 48.7 -14.5 105 0.5
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/08/2025 at 0900 MDT | 04/08/2025 at 1200 MDT
|
CAPE... 0.0 LI... +2.1 | CAPE... 0.0 LI... +0.9
CINH... 0.0 K Index... +11.6 | CINH... -0.2 K Index... +12.5
|
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 -61.6 -78.9 290 33 17 2.3 1.2 | -61.9 -79.4 280 34 17 2.4 1.3
45000 -58.2 -72.8 280 38 20 1.5 0.8 | -58.3 -72.9 285 39 20 1.8 1.0
40000 -62.8 -81.0 295 54 28 -3.1 -1.7 | -63.1 -81.6 295 57 29 -3.3 -1.8
38000 -61.7 -79.1 295 57 30 5.8 3.2 | -61.8 -79.2 300 60 31 6.4 3.5
36000 -58.3 -72.9 300 58 30 5.8 3.2 | -57.9 -72.2 295 61 31 6.4 3.5
34000 -54.4 -65.9 300 58 30 8.6 4.7 | -53.8 -64.8 295 60 31 8.5 4.7
32000 -49.2 -56.6 295 53 27 8.6 4.7 | -48.6 -55.5 295 56 29 8.6 4.7
30000 -44.0 -47.2 295 49 25 8.6 4.7 | -43.5 -46.3 295 52 27 8.8 4.8
29000 -41.5 -42.7 290 46 24 8.6 4.7 | -40.2 -40.4 290 49 25 8.8 4.8
28000 -38.9 -38.0 290 44 23 8.6 4.7 | -37.6 -35.7 290 47 24 8.8 4.8
27000 -35.8 -32.4 290 42 22 7.2 4.0 | -35.0 -31.0 290 44 23 7.7 4.2
26000 -33.6 -28.5 285 39 20 7.4 4.1 | -32.7 -26.9 290 42 21 7.8 4.3
25000 -31.4 -24.5 285 37 19 7.4 4.1 | -30.3 -22.5 290 39 20 7.9 4.3
24000 -29.2 -20.6 280 35 18 7.3 4.0 | -28.0 -18.4 290 37 19 7.3 4.0
23000 -27.0 -16.6 275 31 16 7.3 4.0 | -25.9 -14.6 290 35 18 7.2 3.9
22000 -24.8 -12.6 270 28 14 7.3 4.0 | -23.7 -10.7 290 34 18 7.2 3.9
21000 -22.7 -8.9 270 25 13 7.5 4.1 | -21.7 -7.1 295 33 17 6.0 3.3
20000 -20.4 -4.7 275 24 12 7.5 4.1 | -19.9 -3.8 295 29 15 6.1 3.4
19500 -19.3 -2.7 275 23 12 7.5 4.1 | -19.0 -2.2 295 28 14 6.1 3.4
19000 -18.2 -0.8 280 22 12 7.5 4.1 | -18.1 -0.6 295 26 13 6.1 3.4
18500 -17.1 1.2 285 22 11 7.5 4.1 | -17.1 1.2 295 25 13 6.5 3.6
18000 -16.0 3.2 290 21 11 7.5 4.1 | -16.2 2.8 295 23 12 6.6 3.6
17500 -14.9 5.2 295 20 10 7.4 4.1 | -15.2 4.6 300 22 11 6.8 3.7
17000 -13.8 7.2 295 19 10 7.2 3.9 | -14.1 6.6 300 20 11 7.3 4.0
16500 -12.8 9.0 300 17 9 7.1 3.9 | -13.1 8.4 300 19 10 7.2 3.9
16000 -11.6 11.1 305 16 8 8.2 4.5 | -11.9 10.6 300 18 9 8.8 4.8
15500 -10.4 13.3 310 14 7 8.0 4.4 | -10.6 12.9 300 17 9 8.6 4.7
15000 -9.2 15.4 310 13 7 8.8 4.8 | -9.3 15.3 300 16 8 9.1 5.0
14500 -7.9 17.8 315 13 7 8.9 4.9 | -7.3 18.9 300 14 7 9.2 5.0
14000 -5.9 21.4 315 12 6 8.8 4.8 | -5.9 21.4 300 13 7 8.8 4.8
13500 -4.6 23.7 315 12 6 8.7 4.8 | -4.6 23.7 295 12 6 8.8 4.8
13000 -3.3 26.1 315 11 6 9.0 4.9 | -3.3 26.1 295 11 6 9.4 5.2
12500 -1.9 28.6 315 9 5 9.0 4.9 | -1.9 28.6 290 12 6 9.4 5.2
12000 -0.6 30.9 310 8 4 9.0 4.9 | -0.5 31.1 285 12 6 9.3 5.1
11500 0.8 33.4 305 8 4 9.1 5.0 | 0.9 33.6 290 14 7 9.3 5.1
11000 2.0 35.6 300 7 4 7.7 4.2 | 2.3 36.1 290 16 8 8.8 4.8
10500 3.2 37.8 285 6 3 8.3 4.5 | 3.6 38.5 295 17 9 9.5 5.2
10250 3.7 38.7 275 5 3 5.1 2.8 | 4.2 39.6 295 18 9 5.6 3.1
10000 4.1 39.4 270 5 3 6.6 3.6 | 4.5 40.1 295 18 9 6.6 3.6
9750 4.8 40.6 260 5 3 10.6 5.8 | 5.3 41.5 290 18 9 11.1 6.1
9500 5.5 41.9 250 5 3 10.3 5.6 | 6.0 42.8 290 18 9 10.4 5.7
9250 6.3 43.3 240 5 3 7.8 4.3 | 6.8 44.2 290 18 9 8.8 4.9
9000 6.8 44.2 240 5 3 8.1 4.4 | 7.4 45.3 290 17 9 8.5 4.7
8750 7.5 45.5 250 6 3 11.3 6.2 | 8.1 46.6 285 16 8 10.3 5.6
8500 8.3 46.9 260 6 3 10.7 5.9 | 8.8 47.8 285 15 8 9.8 5.4
8250 9.1 48.4 270 7 4 9.5 5.2 | 9.6 49.3 280 14 7 9.7 5.3
8000 9.8 49.6 280 8 4 8.7 4.8 | 10.3 50.5 275 13 7 9.6 5.2
7750 10.5 50.9 285 9 5 9.8 5.4 | 11.0 51.8 275 13 7 9.8 5.4
7500 11.2 52.2 285 10 5 9.8 5.4 | 11.7 53.1 270 13 6 9.9 5.4
7250 11.9 53.4 285 12 6 9.7 5.3 | 12.5 54.5 270 12 6 10.2 5.6
7000 12.6 54.7 285 14 7 8.9 4.9 | 13.2 55.8 270 12 6 10.3 5.7
6750 13.3 55.9 285 15 8 12.1 6.7 | 14.0 57.2 270 12 6 9.4 5.1
6500 14.1 57.4 285 17 9 1.2 0.7 | 14.7 58.5 270 12 6 10.0 5.5
6250 13.5 56.3 275 16 8 -9.9 -5.4 | 15.5 59.9 265 12 6 11.5 6.3
6000 12.9 55.2 270 15 8 -6.8 -3.7 | 16.3 61.3 265 11 6 10.6 5.8
5750 12.3 54.1 255 15 8 -8.7 -4.8 | 17.1 62.8 265 11 6 12.3 6.7
5500 11.6 52.9 240 12 6 -7.9 -4.4 | 18.3 64.9 265 11 5 19.2 10.5
04/08/2025 at 1500 MDT | 04/08/2025 at 1800 MDT
|
CAPE... 0.0 LI... +0.4 | CAPE... +11.5 LI... -0.4
CINH... -0.2 K Index... +16.0 | CINH... -18.4 K Index... +19.2
|
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 -62.8 -81.0 280 37 19 1.5 0.8 | -62.7 -80.9 290 37 19 1.9 1.0
45000 -60.6 -77.1 290 46 23 1.0 0.6 | -59.9 -75.8 300 51 26 -1.3 -0.7
40000 -64.3 -83.7 295 67 35 -2.5 -1.4 | -63.2 -81.8 300 67 34 -2.2 -1.2
38000 -62.1 -79.8 295 69 35 7.5 4.1 | -61.5 -78.7 300 69 35 6.4 3.5
36000 -57.6 -71.7 295 65 34 7.5 4.1 | -57.6 -71.7 300 68 35 6.4 3.5
34000 -52.9 -63.2 290 62 32 8.7 4.8 | -53.4 -64.1 305 65 33 9.1 5.0
32000 -47.7 -53.9 290 58 30 8.7 4.8 | -47.8 -54.0 300 56 29 9.2 5.0
30000 -42.5 -44.5 290 53 27 8.7 4.8 | -41.9 -43.4 300 49 25 8.3 4.6
29000 -39.2 -38.6 290 49 25 8.7 4.8 | -39.4 -38.9 300 49 25 8.3 4.6
28000 -36.6 -33.9 290 46 24 8.7 4.8 | -36.9 -34.4 300 49 25 8.3 4.6
27000 -34.1 -29.4 290 44 22 7.3 4.0 | -34.4 -29.9 300 48 25 7.8 4.3
26000 -31.9 -25.4 290 43 22 7.5 4.1 | -32.1 -25.8 300 45 23 7.8 4.3
25000 -29.7 -21.5 290 43 22 7.5 4.1 | -29.7 -21.5 300 43 22 7.8 4.3
24000 -27.5 -17.5 285 43 22 6.2 3.4 | -27.4 -17.3 300 41 21 6.8 3.8
23000 -25.7 -14.3 285 42 21 6.0 3.3 | -25.4 -13.7 300 40 21 6.7 3.7
22000 -23.9 -11.0 285 40 21 6.0 3.3 | -23.5 -10.3 295 40 20 6.7 3.7
21000 -22.1 -7.8 285 39 20 6.9 3.8 | -21.5 -6.7 295 39 20 6.0 3.3
20000 -20.0 -4.0 285 37 19 6.8 3.7 | -19.7 -3.5 290 38 20 6.1 3.3
19500 -19.0 -2.2 285 36 19 6.8 3.7 | -18.9 -2.0 290 38 19 6.1 3.3
19000 -18.0 -0.4 285 36 18 6.7 3.7 | -18.0 -0.4 290 37 19 6.0 3.3
18500 -17.0 1.4 285 35 18 7.4 4.1 | -17.0 1.4 290 37 19 8.0 4.4
18000 -15.9 3.4 285 34 17 7.5 4.1 | -15.8 3.6 290 36 18 8.1 4.5
17500 -14.8 5.4 285 33 17 7.6 4.2 | -14.6 5.7 285 35 18 8.2 4.5
17000 -13.6 7.5 285 32 16 7.8 4.3 | -13.4 7.9 285 34 18 8.3 4.5
16500 -12.5 9.5 285 30 16 7.8 4.3 | -12.1 10.2 285 33 17 8.3 4.5
16000 -11.3 11.7 285 29 15 8.7 4.8 | -10.9 12.4 280 32 16 8.5 4.7
15500 -10.0 14.0 285 27 14 8.6 4.7 | -9.0 15.8 280 30 15 8.6 4.7
15000 -8.7 16.3 285 26 13 8.8 4.8 | -7.7 18.1 280 28 14 8.9 4.9
14500 -6.8 19.8 285 23 12 8.8 4.8 | -6.4 20.5 275 26 13 8.9 4.9
14000 -5.4 22.3 285 22 11 9.1 5.0 | -5.1 22.8 275 24 12 9.0 4.9
13500 -4.1 24.6 285 20 11 9.1 5.0 | -3.7 25.3 275 22 12 9.0 4.9
13000 -2.7 27.1 280 19 10 9.0 4.9 | -2.4 27.7 275 21 11 9.3 5.1
12500 -1.4 29.5 280 18 9 9.0 4.9 | -1.0 30.2 275 20 10 9.3 5.1
12000 -0.0 32.0 280 16 8 9.2 5.0 | 0.4 32.7 275 19 10 9.4 5.1
11500 1.3 34.3 280 14 7 9.3 5.1 | 1.8 35.2 275 18 9 9.5 5.2
11000 2.6 36.7 280 13 6 7.8 4.3 | 3.2 37.8 275 16 8 8.1 4.5
10500 3.8 38.8 280 12 6 6.5 3.6 | 4.4 39.9 280 15 8 7.2 3.9
10250 4.4 39.9 280 11 6 12.5 6.9 | 5.0 41.0 280 15 8 11.2 6.2
10000 5.5 41.9 280 11 6 13.8 7.6 | 5.9 42.6 285 14 7 12.0 6.6
9750 6.3 43.3 280 11 6 8.6 4.7 | 6.6 43.9 285 13 7 8.3 4.6
9500 7.0 44.6 275 11 5 10.6 5.8 | 7.3 45.1 285 13 7 9.5 5.2
9250 7.7 45.9 275 10 5 7.9 4.3 | 8.0 46.4 290 12 6 8.5 4.7
9000 8.3 46.9 275 10 5 8.5 4.6 | 8.6 47.5 290 12 6 9.1 5.0
8750 9.1 48.4 275 10 5 11.1 6.1 | 9.4 48.9 290 12 6 10.3 5.7
8500 9.8 49.6 275 10 5 10.5 5.7 | 10.1 50.2 290 12 6 9.9 5.4
8250 10.6 51.1 275 10 5 10.0 5.5 | 10.9 51.6 290 12 6 10.6 5.8
8000 11.3 52.3 275 10 5 9.6 5.3 | 11.7 53.1 290 11 6 10.4 5.7
7750 12.1 53.8 275 10 5 10.1 5.5 | 12.4 54.3 290 11 6 8.9 4.9
7500 12.8 55.0 275 10 5 10.1 5.6 | 13.0 55.4 290 11 6 9.0 4.9
7250 13.6 56.5 275 10 5 10.2 5.6 | 13.8 56.8 290 11 6 10.5 5.8
7000 14.4 57.9 275 10 5 10.2 5.6 | 14.6 58.3 290 11 6 11.2 6.1
6750 15.1 59.2 275 10 5 9.9 5.4 | 15.4 59.7 290 11 6 9.0 4.9
6500 15.8 60.4 275 10 5 10.2 5.6 | 16.0 60.8 295 11 5 9.1 5.0
6250 16.6 61.9 275 9 5 10.9 6.0 | 16.8 62.2 295 10 5 10.8 5.9
6000 17.4 63.3 275 9 5 10.4 5.7 | 17.6 63.7 295 10 5 10.8 5.9
5750 18.2 64.8 275 9 5 12.1 6.6 | 18.3 64.9 295 10 5 9.7 5.3
5500 19.4 66.9 275 9 5 19.5 10.7 | 19.0 66.2 295 9 5 8.9 4.9
________________________________________________________________________________
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