Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
330
UXUS97 KBOU 071251
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0650 MDT Monday, April 7, 2025
This forecast is for Monday, April 7, 2025:
If the trigger temperature of 51.8 F/11.0 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 791 ft/min (4.0 m/s)
Maximum height of thermals.................. 15555 ft MSL (10269 ft AGL)
Forecast maximum temperature................... 67.0 F/19.9 C
Time of trigger temperature.................... 1000 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................. 13976 ft MSL (8690 ft AGL)
Thermal soaring outlook for Tuesday 04/08...... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... 15881 ft MSL (10595 ft AGL)
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 39042 ft MSL (33756 ft AGL)
Wave soaring outlook for Tuesday 04/08......... Fair
Remarks...
Sunrise/Sunset.................... 06:33:06 / 19:29:46 MDT
Total possible sunshine........... 12 hr 56 min 40 sec (776 min 40 sec)
Altitude of sun at 13:01:26 MDT... 57.37 degrees
Upper air data from numerical model forecast valid on 04/07/2025 at 0600 MDT
Freezing level.................. 5325 ft MSL (39 ft AGL)
Additional freezing level....... 8877 ft MSL (3591 ft AGL)
Convective condensation level... 17231 ft MSL (11945 ft AGL)
Lifted condensation level....... 16333 ft MSL (11048 ft AGL)
Lifted index.................... +2.0
K index......................... +3.4
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 -59.8 -75.6 305 20 10 -0.5 -0.3 M M M M M
45000 -60.6 -77.1 335 25 13 -0.5 -0.3 M M M M M
40000 -63.1 -81.6 010 40 21 -1.7 -1.0 M M M M M
38000 -61.8 -79.2 015 44 23 6.9 3.8 M M M M M
36000 -57.6 -71.7 020 43 22 6.9 3.8 M M M M M
34000 -53.5 -64.3 025 43 22 7.2 3.9 M M M M M
32000 -48.7 -55.7 020 44 23 7.1 3.9 M M M M M
30000 -44.2 -47.6 020 44 22 7.8 4.3 31.6 88.9 9.2 M M
29000 -41.9 -43.4 020 42 22 7.9 4.3 30.8 87.4 8.6 M M
28000 -39.5 -39.1 020 40 21 7.9 4.3 30.1 86.2 8.2 M M
27000 -37.2 -35.0 020 39 20 7.9 4.3 29.5 85.1 7.8 M M
26000 -34.8 -30.6 020 36 19 7.9 4.4 28.7 83.6 7.3 M M
25000 -32.4 -26.3 020 34 17 8.0 4.4 28.0 82.4 6.8 M M
24000 -30.0 -22.0 015 31 16 8.1 4.4 27.5 81.4 6.5 M M
23000 -27.5 -17.5 015 30 16 8.3 4.6 26.8 80.3 6.0 M M
22000 -25.0 -13.0 010 29 15 8.3 4.6 26.3 79.4 5.7 M M
21000 -22.6 -8.7 010 29 15 7.5 4.1 25.8 78.5 5.3 M M
20000 -20.4 -4.7 010 29 15 7.3 4.0 24.9 76.8 4.6 M M
19500 -19.3 -2.7 005 29 15 7.3 4.0 24.5 76.0 4.2 M M
19000 -18.2 -0.8 005 30 15 7.4 4.0 24.1 75.3 3.9 M M
18500 -17.1 1.2 005 30 15 7.7 4.2 23.7 74.7 3.6 M M
18000 -15.9 3.4 005 29 15 7.9 4.4 23.4 74.1 3.4 M M
17500 -14.7 5.5 005 29 15 8.0 4.4 23.1 73.6 3.1 M M
17000 -13.7 7.3 005 28 14 5.2 2.8 22.5 72.5 2.6 M M
16500 -12.9 8.8 005 27 14 5.5 3.0 21.8 71.2 2.0 M M
16000 -12.0 10.4 360 27 14 2.7 1.5 20.3 68.6 0.7 M M
15500 -11.6 11.1 355 27 14 2.8 1.6 19.2 66.5 -0.4 782 4.0
15000 -11.2 11.8 355 27 14 3.9 2.2 18.1 64.6 -1.4 754 3.8
14500 -10.6 12.9 350 27 14 3.7 2.0 17.1 62.9 -2.3 723 3.7
14000 -9.9 14.2 350 27 14 6.7 3.7 16.3 61.4 -3.1 687 3.5
13500 -8.9 16.0 350 27 14 7.0 3.8 15.9 60.6 -3.5 641 3.3
13000 -7.8 18.0 350 28 14 7.4 4.1 15.5 59.8 -3.9 594 3.0
12500 -6.7 19.9 345 28 15 7.6 4.1 15.1 59.2 -4.3 545 2.8
12000 -5.6 21.9 345 29 15 7.1 3.9 14.7 58.5 -4.7 497 2.5
11500 -4.6 23.7 340 27 14 7.0 3.9 14.3 57.7 -5.2 452 2.3
11000 -3.6 25.5 335 25 13 5.3 2.9 13.8 56.8 -5.7 409 2.1
10500 -2.9 26.8 335 21 11 5.2 2.9 13.0 55.3 -6.5 373 1.9
10250 -2.6 27.3 330 19 10 3.0 1.7 12.6 54.6 -6.9 355 1.8
10000 -2.4 27.7 330 18 9 4.0 2.2 12.0 53.6 -7.5 343 1.7
9750 -1.9 28.6 330 16 8 7.6 4.2 11.7 53.1 -7.7 321 1.6
9500 -1.4 29.5 335 14 7 7.5 4.1 11.5 52.8 -7.9 297 1.5
9250 -0.8 30.6 335 13 6 7.4 4.1 11.4 52.5 -8.1 273 1.4
9000 -0.3 31.5 335 12 6 7.6 4.2 11.2 52.2 -8.3 249 1.3
8750 0.3 32.5 335 11 6 8.3 4.6 11.1 51.9 -8.5 224 1.1
8500 1.0 33.8 335 10 5 8.6 4.7 11.0 51.7 -8.6 197 1.0
8250 1.6 34.9 335 10 5 8.3 4.5 10.9 51.6 -8.7 171 0.9
8000 2.2 36.0 335 9 5 8.0 4.4 10.7 51.3 -8.9 145 0.7
7750 2.8 37.0 330 9 4 8.6 4.7 10.6 51.1 -9.0 119 0.6
7500 3.5 38.3 330 8 4 8.4 4.6 10.5 51.0 -9.1 93 0.5
7250 4.1 39.4 330 8 4 7.7 4.2 10.4 50.7 -9.3 67 0.3
7000 4.6 40.3 325 8 4 7.4 4.1 10.2 50.4 -9.5 43 0.2
6750 5.2 41.4 325 7 4 8.2 4.5 10.1 50.1 -9.7 19 0.1
6500 5.7 42.3 320 7 4 1.8 1.0 9.8 49.7 -10.0 M M
6250 5.5 41.9 310 7 4 -4.5 -2.5 8.9 47.9 -10.9 M M
6000 5.2 41.4 300 7 4 -0.4 -0.2 7.9 46.2 -11.9 M M
5750 5.0 41.0 295 8 4 -10.3 -5.7 7.0 44.5 -12.9 M M
5500 3.1 37.6 285 6 3 -41.1 -22.6 4.4 39.9 -15.6 44 0.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/07/2025 at 0900 MDT | 04/07/2025 at 1200 MDT
|
CAPE... 0.0 LI... +7.4 | CAPE... 0.0 LI... +6.6
CINH... 0.0 K Index... -3.7 | CINH... 0.0 K Index... -4.0
|
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 -60.2 -76.4 305 26 13 -0.3 -0.2 | -60.6 -77.1 310 27 14 0.1 0.0
45000 -60.7 -77.3 325 25 13 -0.4 -0.2 | -60.5 -76.9 320 28 14 0.1 0.1
40000 -63.3 -81.9 005 27 14 -1.8 -1.0 | -63.1 -81.6 340 20 10 -1.8 -1.0
38000 -61.9 -79.4 010 30 16 6.9 3.8 | -61.3 -78.3 340 20 10 6.5 3.6
36000 -57.3 -71.1 010 33 17 6.9 3.8 | -57.4 -71.3 340 23 12 6.6 3.6
34000 -53.0 -63.4 015 35 18 7.6 4.2 | -53.3 -63.9 340 25 13 7.7 4.2
32000 -48.4 -55.1 015 35 18 7.7 4.2 | -48.7 -55.7 340 27 14 7.7 4.2
30000 -43.7 -46.7 010 34 17 7.8 4.3 | -44.0 -47.2 340 27 14 8.0 4.4
29000 -41.4 -42.5 010 33 17 7.8 4.3 | -41.6 -42.9 340 27 14 8.0 4.4
28000 -39.0 -38.2 010 32 16 7.8 4.3 | -38.6 -37.5 340 27 14 8.0 4.4
27000 -36.7 -34.1 010 31 16 8.1 4.5 | -36.2 -33.2 340 27 14 8.4 4.6
26000 -34.2 -29.6 005 30 15 8.2 4.5 | -33.7 -28.7 340 26 13 8.3 4.6
25000 -31.7 -25.1 005 29 15 8.2 4.5 | -31.2 -24.2 340 25 13 8.3 4.6
24000 -29.3 -20.7 360 28 14 8.2 4.5 | -28.7 -19.7 335 24 12 8.2 4.5
23000 -26.8 -16.2 360 27 14 8.1 4.5 | -26.3 -15.3 335 24 12 8.2 4.5
22000 -24.4 -11.9 355 27 14 8.1 4.5 | -23.8 -10.8 335 23 12 8.2 4.5
21000 -22.0 -7.6 355 26 13 7.8 4.3 | -21.4 -6.5 335 23 12 7.6 4.2
20000 -19.6 -3.3 355 25 13 7.8 4.3 | -19.1 -2.4 335 21 11 7.7 4.2
19500 -18.5 -1.3 355 25 13 7.8 4.3 | -18.0 -0.4 335 21 11 7.7 4.2
19000 -17.3 0.9 355 25 13 7.8 4.3 | -16.8 1.8 335 20 10 7.8 4.3
18500 -16.1 3.0 355 25 13 7.5 4.1 | -15.7 3.7 335 20 10 7.1 3.9
18000 -14.5 5.9 355 24 12 7.3 4.0 | -14.7 5.5 335 19 10 7.0 3.8
17500 -13.4 7.9 355 23 12 6.7 3.6 | -13.6 7.5 335 19 10 6.7 3.7
17000 -12.4 9.7 355 22 11 6.3 3.5 | -12.7 9.1 335 18 9 6.2 3.4
16500 -11.4 11.5 355 21 11 5.4 3.0 | -11.7 10.9 335 17 9 6.5 3.6
16000 -11.0 12.2 350 21 11 2.4 1.3 | -11.0 12.2 335 17 9 3.6 2.0
15500 -10.6 12.9 350 21 11 2.5 1.4 | -10.4 13.3 335 18 10 3.8 2.1
15000 -10.2 13.6 350 22 11 3.1 1.7 | -9.8 14.4 335 20 10 4.1 2.3
14500 -9.8 14.4 345 23 12 3.0 1.6 | -8.9 16.0 335 21 11 4.1 2.2
14000 -9.3 15.3 345 23 12 5.3 2.9 | -8.2 17.2 335 21 11 6.1 3.4
13500 -8.5 16.7 345 23 12 5.3 2.9 | -7.4 18.7 330 22 11 6.0 3.3
13000 -7.7 18.1 345 23 12 6.4 3.5 | -6.5 20.3 330 21 11 6.4 3.5
12500 -6.7 19.9 345 23 12 6.5 3.6 | -5.6 21.9 330 21 11 6.4 3.5
12000 -5.7 21.7 345 22 11 7.9 4.3 | -4.6 23.7 330 20 10 7.3 4.0
11500 -4.4 24.1 345 23 12 8.3 4.6 | -3.5 25.7 335 19 10 7.4 4.1
11000 -3.2 26.2 345 23 12 7.4 4.0 | -2.3 27.9 335 18 9 7.8 4.3
10500 -2.1 28.2 345 21 11 7.8 4.3 | -1.2 29.8 335 17 9 8.8 4.9
10250 -1.6 29.1 345 21 11 4.6 2.5 | -0.6 30.9 335 16 8 3.6 2.0
10000 -1.4 29.5 345 20 10 4.3 2.4 | -0.5 31.1 335 15 8 4.9 2.7
9750 -0.9 30.4 340 18 9 7.7 4.2 | 0.3 32.5 335 14 7 10.9 6.0
9500 -0.3 31.5 340 15 8 7.9 4.3 | 1.0 33.8 335 12 6 9.8 5.4
9250 0.2 32.4 335 13 7 6.0 3.3 | 1.7 35.1 330 11 5 7.9 4.3
9000 0.6 33.1 335 11 6 4.3 2.3 | 2.2 36.0 330 9 5 6.4 3.5
8750 1.0 33.8 330 10 5 6.1 3.4 | 2.7 36.9 325 8 4 8.3 4.5
8500 1.4 34.5 330 8 4 6.7 3.7 | 3.3 37.9 315 6 3 8.1 4.5
8250 1.9 35.4 325 7 3 6.6 3.6 | 3.9 39.0 305 5 2 7.1 3.9
8000 2.4 36.3 325 6 3 6.6 3.6 | 4.4 39.9 285 3 2 6.7 3.7
7750 2.9 37.2 320 5 3 7.4 4.1 | 4.9 40.8 250 2 1 6.4 3.5
7500 3.5 38.3 315 4 2 8.4 4.6 | 5.4 41.7 215 3 1 8.1 4.4
7250 4.1 39.4 310 4 2 8.5 4.7 | 6.1 43.0 210 3 2 10.2 5.6
7000 4.8 40.6 305 4 2 8.8 4.8 | 6.8 44.2 205 3 2 10.2 5.6
6750 5.4 41.7 300 4 2 7.9 4.3 | 7.6 45.7 200 3 2 9.2 5.1
6500 5.9 42.6 295 4 2 4.8 2.6 | 8.2 46.8 200 3 2 10.0 5.5
6250 6.2 43.2 295 6 3 2.7 1.5 | 9.1 48.4 200 3 2 12.0 6.6
6000 6.4 43.5 290 7 4 5.1 2.8 | 9.9 49.8 200 3 2 10.2 5.6
5750 6.7 44.1 290 9 4 -2.4 -1.3 | 10.7 51.3 200 3 2 14.1 7.7
5500 5.7 42.3 270 5 3 -17.5 -9.6 | 12.2 54.0 195 3 2 24.9 13.6
04/07/2025 at 1500 MDT | 04/07/2025 at 1800 MDT
|
CAPE... 0.0 LI... +4.7 | CAPE... 0.0 LI... +3.1
CINH... 0.0 K Index... +2.3 | CINH... 0.0 K Index... +1.5
|
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 -60.9 -77.6 295 27 14 -0.9 -0.5 | -61.5 -78.7 290 26 13 0.0 0.0
45000 -62.2 -80.0 300 25 13 -0.9 -0.5 | -61.5 -78.7 300 26 14 -0.1 -0.0
40000 -63.8 -82.8 300 17 9 -1.1 -0.6 | -63.2 -81.8 295 23 12 -1.2 -0.7
38000 -61.7 -79.1 305 20 10 6.7 3.7 | -61.2 -78.2 295 27 14 6.5 3.6
36000 -57.7 -71.9 315 28 14 6.7 3.7 | -57.3 -71.1 295 33 17 6.5 3.6
34000 -53.5 -64.3 315 33 17 7.9 4.4 | -53.2 -63.8 295 38 20 7.6 4.2
32000 -48.7 -55.7 315 32 17 8.0 4.4 | -48.7 -55.7 300 39 20 7.6 4.2
30000 -43.9 -47.0 315 31 16 8.3 4.6 | -44.1 -47.4 300 38 20 7.9 4.3
29000 -41.4 -42.5 315 31 16 8.3 4.6 | -41.7 -43.1 305 37 19 7.9 4.3
28000 -38.9 -38.0 315 30 15 8.3 4.6 | -38.7 -37.7 305 35 18 7.9 4.3
27000 -35.8 -32.4 320 29 15 8.3 4.6 | -36.3 -33.3 310 33 17 9.1 5.0
26000 -33.3 -27.9 320 28 14 8.3 4.6 | -33.6 -28.5 310 32 16 9.0 4.9
25000 -30.8 -23.4 320 27 14 8.3 4.6 | -30.9 -23.6 310 31 16 9.0 4.9
24000 -28.3 -18.9 320 26 13 8.2 4.5 | -28.2 -18.8 310 30 15 8.4 4.6
23000 -25.9 -14.6 320 25 13 8.2 4.5 | -25.8 -14.4 310 29 15 8.3 4.6
22000 -23.4 -10.1 315 25 13 8.2 4.5 | -23.3 -9.9 305 28 14 8.3 4.6
21000 -21.0 -5.8 315 24 12 7.6 4.2 | -20.9 -5.6 305 27 14 7.4 4.0
20000 -18.8 -1.8 315 23 12 7.7 4.2 | -18.6 -1.5 305 26 13 7.4 4.1
19500 -17.6 0.3 315 22 11 7.7 4.2 | -17.5 0.5 300 25 13 7.4 4.1
19000 -16.5 2.3 310 21 11 7.7 4.2 | -16.4 2.5 300 24 12 7.5 4.1
18500 -15.4 4.3 310 20 10 6.8 3.7 | -15.3 4.5 300 24 12 6.6 3.6
18000 -14.4 6.1 310 20 10 6.7 3.7 | -14.4 6.1 300 23 12 6.6 3.6
17500 -13.3 8.1 310 19 10 6.4 3.5 | -13.4 7.9 300 23 12 6.5 3.5
17000 -12.4 9.7 310 18 9 5.9 3.3 | -12.4 9.7 300 22 12 6.3 3.4
16500 -11.6 11.1 310 18 9 6.0 3.3 | -11.5 11.3 300 22 11 6.3 3.4
16000 -10.7 12.7 310 18 9 5.5 3.0 | -10.6 12.9 295 22 12 6.1 3.3
15500 -9.9 14.2 310 18 9 5.6 3.1 | -9.7 14.5 295 23 12 6.1 3.3
15000 -9.1 15.6 310 19 10 5.8 3.2 | -8.8 16.2 295 23 12 7.0 3.9
14500 -8.2 17.2 310 19 10 5.9 3.3 | -7.7 18.1 295 23 12 7.3 4.0
14000 -7.4 18.7 310 19 10 6.6 3.6 | -6.0 21.2 295 24 12 8.4 4.6
13500 -5.8 21.6 310 19 10 7.0 3.8 | -4.8 23.4 295 24 12 8.4 4.6
13000 -4.7 23.5 310 19 10 8.2 4.5 | -3.6 25.5 290 24 12 8.0 4.4
12500 -3.6 25.5 305 18 9 8.2 4.5 | -2.4 27.7 290 25 13 8.0 4.4
12000 -2.4 27.7 300 17 9 8.2 4.5 | -1.2 29.8 290 25 13 8.5 4.6
11500 -1.2 29.8 295 15 8 8.2 4.5 | -0.0 32.0 290 24 12 8.6 4.7
11000 0.0 32.0 295 14 7 7.8 4.3 | 1.2 34.2 285 22 11 8.2 4.5
10500 1.1 34.0 290 12 6 8.8 4.8 | 2.4 36.3 285 19 10 8.9 4.9
10250 1.7 35.1 290 11 6 3.7 2.0 | 3.0 37.4 285 18 9 5.6 3.1
10000 1.8 35.2 290 10 5 4.4 2.4 | 3.3 37.9 285 17 9 6.4 3.5
9750 2.5 36.5 285 9 4 9.9 5.4 | 4.0 39.2 280 15 8 10.1 5.6
9500 3.1 37.6 280 7 4 8.8 4.8 | 4.7 40.5 280 13 7 9.6 5.3
9250 3.8 38.8 270 5 3 7.5 4.1 | 5.3 41.5 275 11 6 8.0 4.4
9000 4.2 39.6 260 4 2 6.5 3.6 | 5.8 42.4 270 10 5 6.7 3.7
8750 4.8 40.6 240 4 2 7.7 4.2 | 6.4 43.5 265 9 5 7.8 4.3
8500 5.4 41.7 220 4 2 7.7 4.2 | 7.0 44.6 255 8 4 7.6 4.2
8250 6.0 42.8 205 4 2 8.7 4.8 | 7.5 45.5 240 7 4 7.5 4.1
8000 6.6 43.9 205 4 2 9.5 5.2 | 8.1 46.6 235 7 3 7.7 4.2
7750 7.4 45.3 200 4 2 10.0 5.5 | 8.6 47.5 235 6 3 8.5 4.7
7500 8.1 46.6 200 4 2 10.2 5.6 | 9.3 48.7 230 6 3 9.1 5.0
7250 8.9 48.0 200 4 2 9.9 5.5 | 10.0 50.0 230 6 3 9.5 5.2
7000 9.6 49.3 200 4 2 9.9 5.4 | 10.7 51.3 230 6 3 9.6 5.3
6750 10.4 50.7 200 4 2 10.4 5.7 | 11.4 52.5 230 6 3 10.1 5.5
6500 11.2 52.2 200 4 2 10.6 5.8 | 12.2 54.0 230 6 3 10.4 5.7
6250 12.0 53.6 200 4 2 10.7 5.9 | 13.0 55.4 230 6 3 10.3 5.6
6000 12.7 54.9 200 4 2 9.6 5.2 | 13.7 56.7 230 5 3 10.1 5.5
5750 13.5 56.3 200 4 2 14.1 7.7 | 14.5 58.1 230 5 3 10.6 5.8
5500 15.0 59.0 200 4 2 25.9 14.2 | 15.3 59.5 235 5 3 12.9 7.1
________________________________________________________________________________
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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