Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
927
UXUS97 KBOU 050005
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1805 MDT Wednesday, June 4, 2025
This forecast is for Thursday, June 5, 2025:
If the trigger temperature of 65.0 F/18.3 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 367 ft/min (1.9 m/s)
Maximum height of thermals.................. 12661 ft MSL (7338 ft AGL)
Forecast maximum temperature................... 72.0 F/22.7 C
Time of trigger temperature.................... 1045 MDT
Time of overdevelopment........................ 1200 MDT
Middle/high clouds during soaring window....... Broken/overcast thin middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 10068 ft MSL (4745 ft AGL)
Thermal soaring outlook for Friday 06/06....... 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....................... 17384 ft MSL (12061 ft AGL)
Wave soaring outlook for Friday 06/06.......... Poor
Remarks...
Sunrise/Sunset.................... 05:31:51 / 20:24:21 MDT
Total possible sunshine........... 14 hr 52 min 30 sec (892 min 30 sec)
Altitude of sun at 12:58:06 MDT... 72.86 degrees
Upper air data from numerical model forecast valid on 06/05/2025 at 0600 MDT
Freezing level.................. 12748 ft MSL (7425 ft AGL)
Convective condensation level... 11358 ft MSL (6035 ft AGL)
Lifted condensation level....... 12008 ft MSL (6685 ft AGL)
Lifted index.................... -1.9
K index......................... +21.3
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 -59.6 -75.3 250 48 25 0.8 0.4 M M M M M
45000 -58.2 -72.8 255 62 32 1.4 0.8 M M M M M
40000 -56.0 -68.8 250 66 34 1.1 0.6 M M M M M
38000 -53.2 -63.8 250 60 31 5.3 2.9 M M M M M
36000 -50.0 -58.0 245 52 27 5.3 2.9 M M M M M
34000 -46.2 -51.2 245 48 25 7.7 4.2 M M M M M
32000 -41.0 -41.8 250 46 24 7.7 4.2 M M M M M
30000 -36.3 -33.3 255 44 23 7.9 4.3 39.6 103.3 13.2 M M
29000 -33.9 -29.0 255 44 22 7.9 4.3 38.9 102.0 12.8 M M
28000 -31.5 -24.7 260 43 22 7.9 4.3 38.3 100.9 12.4 M M
27000 -29.3 -20.7 260 41 21 7.3 4.0 37.4 99.3 11.9 M M
26000 -27.1 -16.8 260 38 19 7.3 4.0 36.4 97.5 11.2 M M
25000 -25.0 -13.0 260 34 18 7.3 4.0 35.5 96.0 10.6 M M
24000 -22.8 -9.0 260 32 16 7.8 4.3 34.7 94.5 10.1 M M
23000 -20.5 -4.9 260 31 16 7.8 4.3 33.9 93.1 9.5 M M
22000 -18.2 -0.8 255 31 16 7.8 4.3 33.3 91.9 9.0 M M
21000 -16.0 3.2 255 30 15 7.1 3.9 32.5 90.4 8.4 M M
20000 -13.8 7.2 260 27 14 7.1 3.9 31.5 88.7 7.7 M M
19500 -12.7 9.1 260 26 13 7.1 3.9 31.1 87.9 7.4 M M
19000 -11.7 10.9 260 25 13 7.2 4.0 30.7 87.2 7.0 M M
18500 -10.7 12.7 265 23 12 5.8 3.2 30.1 86.2 6.6 M M
18000 -9.8 14.4 270 21 11 5.9 3.2 29.4 85.0 6.0 M M
17500 -8.6 16.5 275 18 10 5.6 3.1 28.4 83.2 5.1 M M
17000 -7.8 18.0 285 18 9 5.6 3.1 27.7 81.9 4.5 M M
16500 -7.0 19.4 290 18 9 5.7 3.1 27.0 80.7 3.9 M M
16000 -6.2 20.8 295 18 9 5.7 3.1 26.3 79.4 3.2 M M
15500 -5.3 22.5 305 17 9 6.0 3.3 25.7 78.2 2.6 M M
15000 -4.4 24.1 305 17 9 6.9 3.8 25.1 77.3 2.1 M M
14500 -3.4 25.9 310 17 9 6.9 3.8 24.7 76.4 1.7 M M
14000 -2.4 27.7 310 16 8 6.8 3.7 24.2 75.5 1.2 M M
13500 -1.4 29.5 310 16 8 6.8 3.7 23.7 74.7 0.7 M M
13000 -0.4 31.3 310 15 8 7.0 3.8 23.2 73.8 0.3 M M
12500 0.6 33.1 310 14 7 7.1 3.9 22.8 73.0 -0.2 549 2.8
12000 1.6 34.9 310 13 7 6.3 3.4 22.3 72.1 -0.7 505 2.6
11500 2.5 36.5 310 12 6 6.2 3.4 21.7 71.1 -1.2 463 2.4
11000 3.3 37.9 310 10 5 6.3 3.5 21.2 70.1 -1.8 422 2.1
10500 4.2 39.6 305 9 5 6.8 3.7 20.6 69.1 -2.4 380 1.9
10250 4.7 40.5 300 9 4 4.7 2.6 20.4 68.7 -2.7 359 1.8
10000 5.0 41.0 300 8 4 5.3 2.9 19.9 67.8 -3.1 343 1.7
9750 5.5 41.9 300 7 4 7.8 4.3 19.7 67.5 -3.3 320 1.6
9500 6.0 42.8 295 7 4 7.2 3.9 19.5 67.1 -3.6 297 1.5
9250 6.5 43.7 290 6 3 7.4 4.0 19.3 66.8 -3.8 274 1.4
9000 7.0 44.6 290 6 3 6.8 3.7 19.1 66.4 -4.0 252 1.3
8750 7.5 45.5 285 5 3 6.4 3.5 18.9 66.0 -4.3 231 1.2
8500 7.9 46.2 285 5 2 6.5 3.6 18.6 65.5 -4.6 210 1.1
8250 8.4 47.1 280 4 2 6.1 3.4 18.4 65.1 -4.9 189 1.0
8000 8.8 47.8 275 4 2 5.7 3.1 18.1 64.5 -5.2 170 0.9
7750 9.2 48.6 275 4 2 5.3 2.9 17.7 63.9 -5.6 151 0.8
7500 9.5 49.1 270 4 2 5.3 2.9 17.4 63.3 -6.0 133 0.7
7250 9.9 49.8 270 4 2 5.9 3.3 17.1 62.7 -6.3 114 0.6
7000 10.3 50.5 265 4 2 6.3 3.4 16.8 62.2 -6.7 94 0.5
6750 10.7 51.3 260 4 2 4.7 2.6 16.5 61.7 -7.0 75 0.4
6500 11.0 51.8 260 5 2 3.0 1.7 16.0 60.9 -7.5 60 0.3
6250 11.2 52.2 245 4 2 2.7 1.5 15.5 59.9 -8.1 47 0.2
6000 11.3 52.3 230 4 2 3.4 1.9 15.0 59.0 -8.7 34 0.2
5750 11.5 52.7 215 4 2 0.9 0.5 14.5 58.1 -9.2 22 0.1
5500 11.2 52.2 205 4 2 -9.0 -4.9 13.5 56.3 -10.3 23 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/05/2025 at 0900 MDT | 06/05/2025 at 1200 MDT
|
CAPE... +534.8 LI... -1.7 | CAPE... +608.2 LI... -3.0
CINH... -47.9 K Index... +19.4 | CINH... -18.0 K Index... +20.4
|
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 -59.9 -75.8 250 50 26 1.5 0.8 | -59.7 -75.5 250 51 26 1.0 0.5
45000 -57.6 -71.7 250 58 30 1.3 0.7 | -58.0 -72.4 250 62 32 2.1 1.1
40000 -55.7 -68.3 250 66 34 0.8 0.4 | -54.9 -66.8 250 74 38 1.8 1.0
38000 -52.9 -63.2 245 61 32 5.1 2.8 | -52.3 -62.1 245 69 35 4.7 2.6
36000 -49.9 -57.8 245 55 28 5.1 2.8 | -49.4 -56.9 245 62 32 4.7 2.6
34000 -45.7 -50.3 245 50 26 7.1 3.9 | -45.5 -49.9 245 55 29 6.9 3.8
32000 -41.5 -42.7 245 46 24 7.1 3.9 | -41.4 -42.5 245 50 26 6.9 3.8
30000 -37.0 -34.6 250 44 23 7.9 4.3 | -37.0 -34.6 245 46 24 7.6 4.2
29000 -34.6 -30.3 250 44 23 7.9 4.3 | -34.7 -30.5 245 44 23 7.6 4.2
28000 -32.3 -26.1 250 44 23 7.9 4.3 | -32.5 -26.5 250 43 22 7.6 4.2
27000 -30.0 -22.0 250 44 22 7.6 4.2 | -30.3 -22.5 250 41 21 7.2 4.0
26000 -27.7 -17.9 255 43 22 7.6 4.2 | -28.1 -18.6 250 41 21 7.2 4.0
25000 -25.5 -13.9 255 42 21 7.6 4.2 | -26.0 -14.8 250 40 21 7.3 4.0
24000 -23.2 -9.8 260 40 21 7.3 4.0 | -23.8 -10.8 250 38 20 7.4 4.1
23000 -21.0 -5.8 260 38 20 7.4 4.0 | -21.6 -6.9 255 36 18 7.5 4.1
22000 -18.9 -2.0 260 36 19 7.3 4.0 | -19.4 -2.9 255 33 17 7.5 4.1
21000 -16.8 1.8 260 33 17 6.5 3.6 | -17.4 0.7 255 31 16 6.5 3.5
20000 -14.8 5.4 260 29 15 6.5 3.6 | -15.4 4.3 255 30 15 6.5 3.5
19500 -13.9 7.0 260 27 14 6.5 3.6 | -14.5 5.9 255 29 15 6.5 3.5
19000 -12.9 8.8 260 25 13 6.5 3.6 | -13.0 8.6 255 28 14 6.5 3.6
18500 -11.6 11.1 265 23 12 5.5 3.0 | -12.1 10.2 260 26 14 6.6 3.6
18000 -10.8 12.6 270 21 11 5.5 3.0 | -11.1 12.0 260 25 13 6.6 3.6
17500 -9.9 14.2 275 20 10 7.1 3.9 | -10.1 13.8 260 24 12 7.0 3.9
17000 -8.9 16.0 280 19 10 6.9 3.8 | -9.0 15.8 265 24 12 7.0 3.8
16500 -7.9 17.8 285 19 10 7.1 3.9 | -8.0 17.6 270 24 12 7.4 4.1
16000 -6.8 19.8 290 19 10 7.2 3.9 | -6.8 19.8 275 23 12 7.5 4.1
15500 -5.8 21.6 295 20 10 7.4 4.1 | -5.7 21.7 275 23 12 7.6 4.2
15000 -4.6 23.7 295 20 10 8.0 4.4 | -4.6 23.7 280 23 12 7.7 4.2
14500 -3.5 25.7 300 20 11 8.0 4.4 | -3.4 25.9 285 24 12 7.7 4.2
14000 -2.4 27.7 300 21 11 7.6 4.1 | -2.3 27.9 290 24 12 7.6 4.2
13500 -1.3 29.7 305 21 11 7.6 4.2 | -1.2 29.8 290 23 12 7.7 4.2
13000 -0.2 31.6 305 21 11 7.8 4.3 | -0.1 31.8 295 23 12 7.8 4.3
12500 1.0 33.8 305 21 11 7.8 4.3 | 1.1 34.0 295 22 11 7.8 4.3
12000 2.1 35.8 305 20 11 7.4 4.0 | 2.2 36.0 300 21 11 8.0 4.4
11500 3.1 37.6 305 20 10 7.4 4.1 | 3.3 37.9 300 19 10 8.0 4.4
11000 4.2 39.6 305 19 10 7.3 4.0 | 4.4 39.9 305 17 9 7.9 4.3
10500 5.2 41.4 305 18 9 7.9 4.4 | 5.5 41.9 305 16 8 8.8 4.8
10250 5.7 42.3 305 17 9 4.7 2.6 | 6.1 43.0 305 15 8 4.5 2.5
10000 6.0 42.8 310 17 9 5.4 3.0 | 6.3 43.3 305 16 8 5.6 3.1
9750 6.6 43.9 310 16 8 9.1 5.0 | 7.0 44.6 310 14 7 10.5 5.8
9500 7.2 45.0 305 15 8 8.6 4.7 | 7.6 45.7 310 13 7 10.0 5.5
9250 7.8 46.0 305 14 7 7.0 3.9 | 8.3 46.9 315 11 6 7.3 4.0
9000 8.2 46.8 310 13 7 6.3 3.4 | 8.7 47.7 315 12 6 6.7 3.7
8750 8.8 47.8 305 12 6 7.6 4.2 | 9.4 48.9 320 11 5 9.6 5.2
8500 9.3 48.7 305 11 5 7.4 4.0 | 10.0 50.0 325 10 5 8.8 4.8
8250 9.8 49.6 305 9 5 6.6 3.6 | 10.6 51.1 330 9 4 7.5 4.1
8000 10.2 50.4 305 9 5 6.1 3.4 | 11.1 52.0 330 8 4 7.2 3.9
7750 10.7 51.3 305 8 4 7.0 3.9 | 11.7 53.1 335 7 4 8.8 4.8
7500 11.2 52.2 300 7 3 6.6 3.6 | 12.3 54.1 335 6 3 8.5 4.7
7250 11.6 52.9 300 6 3 5.1 2.8 | 12.9 55.2 340 6 3 7.5 4.1
7000 11.9 53.4 305 5 3 4.5 2.5 | 13.4 56.1 340 6 3 7.5 4.1
6750 12.3 54.1 305 5 2 6.3 3.4 | 14.0 57.2 340 6 3 11.0 6.1
6500 12.7 54.9 290 4 2 5.7 3.1 | 14.9 58.8 345 5 3 11.8 6.5
6250 13.0 55.4 290 3 2 4.4 2.4 | 15.7 60.3 340 5 3 10.3 5.6
6000 13.2 55.8 290 3 2 3.9 2.1 | 16.5 61.7 340 6 3 9.9 5.5
5750 13.4 56.1 295 3 1 7.6 4.2 | 17.2 63.0 340 6 3 12.5 6.9
5500 14.3 57.7 295 3 1 18.8 10.3 | 18.4 65.1 345 5 3 22.0 12.1
06/05/2025 at 1500 MDT | 06/05/2025 at 1800 MDT
|
CAPE... +405.0 LI... -2.2 | CAPE... +313.7 LI... -1.1
CINH... -8.1 K Index... +28.3 | CINH... -26.3 K Index... +27.8
|
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 -59.8 -75.6 250 52 27 0.7 0.4 | -59.4 -74.9 260 51 26 1.6 0.9
45000 -58.3 -72.9 245 65 33 2.4 1.3 | -57.3 -71.1 255 67 35 0.4 0.2
40000 -54.7 -66.5 245 75 39 2.2 1.2 | -56.6 -69.9 255 80 41 -0.0 -0.0
38000 -52.3 -62.1 245 70 36 4.4 2.4 | -53.9 -65.0 250 64 33 4.4 2.4
36000 -49.3 -56.7 245 63 33 4.3 2.4 | -51.3 -60.3 240 49 25 4.3 2.4
34000 -45.7 -50.3 245 57 29 7.0 3.8 | -46.8 -52.2 235 40 21 9.5 5.2
32000 -41.6 -42.9 245 51 26 6.9 3.8 | -41.1 -42.0 230 34 18 9.5 5.2
30000 -37.0 -34.6 245 48 25 8.0 4.4 | -35.9 -32.6 230 30 16 8.2 4.5
29000 -34.6 -30.3 245 48 25 8.0 4.4 | -33.4 -28.1 230 29 15 8.3 4.5
28000 -32.3 -26.1 250 48 25 8.0 4.4 | -31.0 -23.8 230 28 15 8.3 4.5
27000 -29.9 -21.8 250 47 24 7.9 4.3 | -28.6 -19.5 230 28 14 7.6 4.2
26000 -27.5 -17.5 255 46 24 7.9 4.3 | -26.3 -15.3 235 27 14 7.6 4.2
25000 -25.2 -13.4 255 45 23 7.9 4.4 | -24.1 -11.4 240 27 14 7.7 4.2
24000 -22.9 -9.2 260 44 23 6.8 3.7 | -21.9 -7.4 245 27 14 6.5 3.6
23000 -20.9 -5.6 260 42 22 6.9 3.8 | -20.0 -4.0 250 26 13 6.6 3.6
22000 -18.9 -2.0 265 41 21 6.9 3.8 | -17.5 0.5 255 26 13 6.5 3.6
21000 -16.8 1.8 265 39 20 7.1 3.9 | -15.5 4.1 260 25 13 7.1 3.9
20000 -14.7 5.5 265 35 18 7.1 3.9 | -13.5 7.7 265 24 12 7.1 3.9
19500 -13.7 7.3 260 34 17 7.1 3.9 | -12.4 9.7 265 24 12 7.1 3.9
19000 -12.6 9.3 260 32 17 7.1 3.9 | -11.4 11.5 270 23 12 6.4 3.5
18500 -11.7 10.9 265 31 16 6.3 3.5 | -10.5 13.1 270 23 12 6.0 3.3
18000 -10.3 13.5 270 31 16 6.5 3.5 | -9.7 14.5 275 22 11 5.9 3.3
17500 -9.3 15.3 270 29 15 7.0 3.8 | -8.8 16.2 280 21 11 6.0 3.3
17000 -8.3 17.1 275 26 14 7.0 3.9 | -7.9 17.8 285 20 10 6.0 3.3
16500 -7.3 18.9 275 25 13 6.9 3.8 | -7.1 19.2 290 19 10 5.7 3.1
16000 -6.3 20.7 280 24 12 6.9 3.8 | -6.3 20.7 295 17 9 5.6 3.1
15500 -5.3 22.5 285 24 12 7.1 3.9 | -5.4 22.3 295 14 7 5.9 3.3
15000 -4.2 24.4 285 23 12 7.4 4.1 | -4.5 23.9 295 11 6 6.6 3.6
14500 -3.1 26.4 290 22 11 7.6 4.2 | -3.6 25.5 295 9 4 6.6 3.6
14000 -2.0 28.4 290 20 10 8.2 4.5 | -2.6 27.3 305 6 3 6.2 3.4
13500 -0.8 30.6 290 17 9 8.2 4.5 | -1.7 28.9 320 4 2 6.2 3.4
13000 0.4 32.7 295 15 8 8.0 4.4 | -0.8 30.6 345 4 2 6.4 3.5
12500 1.6 34.9 295 13 7 8.0 4.4 | 0.1 32.2 360 4 2 6.3 3.5
12000 2.8 37.0 300 10 5 8.1 4.4 | 1.1 34.0 010 4 2 8.0 4.4
11500 4.0 39.2 310 8 4 8.2 4.5 | 2.3 36.1 015 5 2 8.0 4.4
11000 5.1 41.2 325 6 3 7.4 4.0 | 3.4 38.1 010 5 3 8.2 4.5
10500 6.2 43.2 355 5 3 8.0 4.4 | 4.6 40.3 005 5 2 8.8 4.8
10250 6.7 44.1 010 5 2 5.1 2.8 | 5.2 41.4 005 5 2 6.0 3.3
10000 7.0 44.6 015 5 2 6.4 3.5 | 5.5 41.9 360 5 2 6.1 3.4
9750 7.7 45.9 020 5 2 10.2 5.6 | 6.1 43.0 360 4 2 9.0 4.9
9500 8.3 46.9 025 5 3 9.3 5.1 | 6.8 44.2 355 4 2 8.2 4.5
9250 9.0 48.2 025 5 3 9.3 5.1 | 7.4 45.3 350 4 2 8.7 4.8
9000 9.7 49.5 025 5 3 9.7 5.3 | 8.0 46.4 335 3 2 7.5 4.1
8750 10.5 50.9 025 5 3 10.4 5.7 | 8.4 47.1 320 3 2 6.3 3.5
8500 11.2 52.2 025 5 3 10.2 5.6 | 8.9 48.0 305 3 2 6.4 3.5
8250 12.0 53.6 025 5 3 11.0 6.0 | 9.4 48.9 285 3 2 7.0 3.9
8000 12.8 55.0 025 5 3 10.5 5.7 | 9.9 49.8 260 4 2 6.7 3.7
7750 13.5 56.3 025 5 3 8.6 4.7 | 10.3 50.5 250 5 3 4.2 2.3
7500 14.2 57.6 025 5 3 9.1 5.0 | 10.5 50.9 245 6 3 3.5 1.9
7250 14.9 58.8 025 5 3 10.3 5.7 | 10.8 51.4 235 8 4 4.3 2.4
7000 15.7 60.3 020 5 3 10.4 5.7 | 11.1 52.0 230 10 5 4.8 2.6
6750 16.4 61.5 020 5 3 9.5 5.2 | 11.3 52.3 225 12 6 1.2 0.7
6500 17.2 63.0 020 5 3 10.2 5.6 | 11.3 52.3 225 14 7 1.9 1.0
6250 18.0 64.4 020 5 3 11.8 6.5 | 11.6 52.9 220 15 8 5.6 3.1
6000 18.8 65.8 020 5 3 10.5 5.7 | 12.2 54.0 220 17 9 5.6 3.1
5750 19.7 67.5 020 5 2 14.0 7.7 | 12.7 54.9 215 16 8 12.0 6.6
5500 21.1 70.0 020 5 3 25.1 13.8 | 14.1 57.4 215 12 6 27.6 15.1
________________________________________________________________________________
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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