Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
443
UXUS97 KBOU 040135
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1930 MDT Friday, October 3, 2025
This forecast is for Saturday, October 4, 2025:
If the trigger temperature of 77.3 F/25.2 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 381 ft/min (1.9 m/s)
Maximum height of thermals.................. 12465 ft MSL (7160 ft AGL)
Forecast maximum temperature................... 82.0 F/28.2 C
Time of trigger temperature.................... 1200 MDT
Time of overdevelopment........................ None
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................. 8784 ft MSL (3478 ft AGL)
Thermal soaring outlook for Sunday 10/05....... Poor
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... Becoming fair
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 40516 ft MSL (35211 ft AGL)
Wave soaring outlook for Sunday 10/05.......... Poor
Remarks... Scattered afternoon thunderstorms
Sunrise/Sunset.................... 06:59:16 / 18:36:48 MDT
Total possible sunshine........... 11 hr 37 min 32 sec (697 min 32 sec)
Altitude of sun at 12:48:02 MDT... 45.48 degrees
Upper air data from numerical model forecast valid on 10/04/2025 at 0600 MDT
Freezing level.................. 15199 ft MSL (9894 ft AGL)
Convective condensation level... 16277 ft MSL (10972 ft AGL)
Lifted condensation level....... 15438 ft MSL (10132 ft AGL)
Lifted index.................... -2.2
K index......................... +22.4
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 -64.4 -83.9 230 49 25 1.6 0.9 M M M M M
45000 -61.0 -77.8 220 76 39 4.1 2.3 M M M M M
40000 -54.8 -66.6 220 85 44 5.0 2.8 M M M M M
38000 -51.2 -60.2 220 79 41 5.9 3.3 M M M M M
36000 -47.7 -53.9 220 73 38 5.9 3.3 M M M M M
34000 -44.0 -47.2 220 66 34 6.3 3.5 M M M M M
32000 -39.7 -39.5 225 56 29 6.3 3.5 M M M M M
30000 -35.2 -31.4 220 49 25 8.3 4.6 40.0 104.0 9.3 M M
29000 -32.7 -26.9 220 45 23 8.3 4.6 39.4 103.0 8.9 M M
28000 -30.2 -22.4 220 42 22 8.4 4.6 39.0 102.2 8.7 M M
27000 -27.9 -18.2 215 40 20 7.5 4.1 38.2 100.7 8.1 M M
26000 -25.7 -14.3 215 38 20 7.5 4.1 37.3 99.1 7.5 M M
25000 -23.4 -10.1 215 36 19 7.5 4.1 36.5 97.7 6.9 M M
24000 -21.2 -6.2 215 35 18 7.3 4.0 35.6 96.1 6.3 M M
23000 -19.1 -2.4 215 33 17 7.3 4.0 34.7 94.4 5.5 M M
22000 -16.9 1.6 210 32 16 7.4 4.0 33.9 93.0 4.8 M M
21000 -14.7 5.5 205 30 16 7.9 4.3 33.1 91.6 4.2 M M
20000 -12.4 9.7 205 30 15 8.0 4.4 32.5 90.4 3.7 M M
19500 -11.2 11.8 200 29 15 8.0 4.4 32.2 89.9 3.4 M M
19000 -10.0 14.0 200 29 15 8.1 4.4 31.9 89.4 3.2 M M
18500 -8.8 16.2 200 29 15 8.5 4.7 31.7 89.0 3.0 M M
18000 -7.5 18.5 200 28 15 8.5 4.7 31.5 88.6 2.8 M M
17500 -6.2 20.8 200 28 15 8.6 4.7 31.3 88.3 2.6 M M
17000 -4.3 24.3 200 28 14 8.6 4.7 31.0 87.7 2.3 M M
16500 -3.1 26.4 200 28 14 8.7 4.8 30.8 87.4 2.2 M M
16000 -1.8 28.8 200 27 14 8.7 4.8 30.6 87.1 2.0 M M
15500 -0.5 31.1 205 27 14 8.4 4.6 30.4 86.8 1.8 M M
15000 0.7 33.3 205 27 14 8.1 4.4 30.1 86.2 1.6 M M
14500 1.9 35.4 210 27 14 8.0 4.4 29.9 85.8 1.3 M M
14000 3.0 37.4 215 26 14 7.7 4.2 29.5 85.2 1.0 M M
13500 4.2 39.6 220 26 14 7.8 4.3 29.2 84.6 0.7 M M
13000 5.3 41.5 220 26 13 7.6 4.2 28.9 84.0 0.3 M M
12500 6.4 43.5 225 26 13 7.7 4.2 28.6 83.4 -0.0 579 2.9
12000 7.5 45.5 230 25 13 7.7 4.2 28.2 82.8 -0.4 531 2.7
11500 8.6 47.5 230 23 12 7.8 4.3 27.9 82.2 -0.7 482 2.4
11000 9.7 49.5 230 22 11 6.4 3.5 27.5 81.5 -1.1 435 2.2
10500 10.6 51.1 235 21 11 5.6 3.1 26.9 80.5 -1.6 393 2.0
10250 11.1 52.0 235 20 10 9.0 5.0 26.7 80.0 -1.9 372 1.9
10000 11.8 53.2 240 19 10 9.4 5.2 26.8 80.2 -1.9 342 1.7
9750 12.4 54.3 240 18 9 6.3 3.4 26.5 79.8 -2.1 319 1.6
9500 12.9 55.2 240 18 9 7.3 4.0 26.3 79.4 -2.3 296 1.5
9250 13.4 56.1 245 17 9 6.4 3.5 26.1 79.0 -2.5 274 1.4
9000 13.8 56.8 245 17 9 6.7 3.7 25.8 78.5 -2.8 252 1.3
8750 14.4 57.9 245 16 8 7.5 4.1 25.6 78.2 -3.0 229 1.2
8500 14.9 58.8 245 16 8 7.7 4.2 25.5 77.8 -3.2 205 1.0
8250 15.4 59.7 250 15 8 6.3 3.4 25.3 77.5 -3.4 182 0.9
8000 15.8 60.4 250 15 8 5.3 2.9 24.9 76.9 -3.8 163 0.8
7750 16.3 61.3 250 15 7 6.4 3.5 24.7 76.4 -4.1 142 0.7
7500 16.8 62.2 250 14 7 6.8 3.7 24.4 75.9 -4.3 120 0.6
7250 17.2 63.0 250 14 7 4.9 2.7 24.2 75.5 -4.6 99 0.5
7000 17.5 63.5 250 14 7 3.2 1.7 23.7 74.6 -5.1 84 0.4
6750 17.7 63.9 250 13 7 4.4 2.4 23.2 73.8 -5.6 69 0.4
6500 18.0 64.4 250 13 7 3.5 1.9 22.8 73.1 -6.0 53 0.3
6250 18.1 64.6 245 12 6 -0.2 -0.1 22.2 72.0 -6.6 42 0.2
6000 18.0 64.4 240 12 6 -1.9 -1.1 21.3 70.4 -7.5 39 0.2
5750 17.9 64.2 235 12 6 -0.9 -0.5 20.5 68.9 -8.4 35 0.2
5500 17.7 63.9 225 10 5 -4.5 -2.5 19.6 67.3 -9.3 33 0.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/04/2025 at 0900 MDT | 10/04/2025 at 1200 MDT
|
CAPE... +6.4 LI... -0.0 | CAPE... +181.4 LI... -0.5
CINH... -68.9 K Index... +22.2 | CINH... -38.9 K Index... +27.0
|
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 -62.9 -81.2 230 45 23 1.6 0.9 | -62.1 -79.8 225 45 23 1.7 0.9
45000 -59.8 -75.6 225 75 38 3.4 1.9 | -59.1 -74.4 230 77 39 2.9 1.6
40000 -54.8 -66.6 220 79 41 3.6 2.0 | -54.7 -66.5 220 78 40 2.9 1.6
38000 -52.0 -61.6 220 76 39 4.7 2.6 | -52.3 -62.1 220 77 40 4.2 2.3
36000 -49.2 -56.6 220 72 37 4.7 2.6 | -49.7 -57.5 215 76 39 4.2 2.3
34000 -45.6 -50.1 220 67 35 7.3 4.0 | -46.2 -51.2 215 74 38 7.6 4.2
32000 -40.6 -41.1 220 61 31 7.3 4.0 | -41.0 -41.8 215 69 36 7.6 4.2
30000 -36.0 -32.8 220 55 28 7.9 4.4 | -36.2 -33.2 215 65 33 8.4 4.6
29000 -33.7 -28.7 220 53 27 7.9 4.4 | -33.6 -28.5 210 63 32 8.4 4.6
28000 -31.3 -24.3 220 50 26 7.9 4.4 | -31.1 -24.0 210 61 31 8.4 4.6
27000 -28.9 -20.0 215 48 24 8.1 4.5 | -28.7 -19.7 210 58 30 8.1 4.4
26000 -26.5 -15.7 215 45 23 8.1 4.5 | -26.2 -15.2 205 54 28 8.1 4.4
25000 -24.0 -11.2 210 43 22 8.1 4.5 | -23.8 -10.8 205 51 26 8.1 4.4
24000 -21.7 -7.1 210 41 21 7.4 4.1 | -21.5 -6.7 205 49 25 7.2 3.9
23000 -19.5 -3.1 205 39 20 7.4 4.1 | -19.4 -2.9 205 47 24 7.3 4.0
22000 -17.4 0.7 205 37 19 7.5 4.1 | -17.2 1.0 200 46 24 7.3 4.0
21000 -15.2 4.6 200 36 19 7.6 4.1 | -15.1 4.8 205 45 23 7.3 4.0
20000 -12.9 8.8 200 35 18 7.6 4.2 | -12.9 8.8 205 45 23 7.3 4.0
19500 -11.8 10.8 200 35 18 7.6 4.2 | -11.9 10.6 205 45 23 7.3 4.0
19000 -10.7 12.7 195 35 18 7.6 4.2 | -10.8 12.6 205 45 23 7.5 4.1
18500 -9.5 14.9 195 35 18 8.2 4.5 | -9.8 14.4 205 44 23 5.8 3.2
18000 -8.3 17.1 195 35 18 8.2 4.5 | -9.0 15.8 205 43 22 6.0 3.3
17500 -7.1 19.2 195 35 18 8.2 4.5 | -8.1 17.4 205 42 21 6.6 3.6
17000 -5.3 22.5 195 34 18 8.2 4.5 | -7.1 19.2 205 40 21 7.2 3.9
16500 -4.1 24.6 195 34 18 8.3 4.5 | -5.5 22.1 205 38 20 7.7 4.2
16000 -2.9 26.8 200 34 17 8.3 4.6 | -4.4 24.1 205 37 19 8.0 4.4
15500 -1.7 28.9 200 34 17 8.2 4.5 | -3.2 26.2 205 36 19 8.1 4.4
15000 -0.5 31.1 200 33 17 7.9 4.3 | -2.0 28.4 205 35 18 8.3 4.6
14500 0.7 33.3 205 33 17 7.9 4.3 | -0.8 30.6 205 34 18 8.3 4.5
14000 1.9 35.4 205 33 17 8.1 4.4 | 0.4 32.7 205 33 17 8.6 4.7
13500 3.1 37.6 210 33 17 8.2 4.5 | 1.7 35.1 205 33 17 8.6 4.7
13000 4.2 39.6 210 33 17 7.4 4.1 | 2.9 37.2 210 32 17 8.7 4.8
12500 5.3 41.5 215 32 17 7.4 4.1 | 4.2 39.6 210 32 16 8.7 4.8
12000 6.3 43.3 220 32 16 7.3 4.0 | 5.5 41.9 210 31 16 8.6 4.7
11500 7.4 45.3 220 31 16 7.4 4.1 | 6.8 44.2 210 30 16 8.6 4.7
11000 8.4 47.1 220 29 15 6.4 3.5 | 8.0 46.4 210 29 15 7.6 4.2
10500 9.3 48.7 220 28 14 5.4 3.0 | 9.1 48.4 210 29 15 7.0 3.8
10250 9.8 49.6 220 28 14 9.5 5.2 | 9.7 49.5 210 28 15 10.9 6.0
10000 10.6 51.1 220 25 13 10.3 5.6 | 10.6 51.1 210 28 14 10.4 5.7
9750 11.2 52.2 220 24 12 6.6 3.6 | 11.2 52.2 210 27 14 7.2 3.9
9500 11.7 53.1 225 23 12 7.9 4.3 | 11.7 53.1 205 26 14 7.7 4.2
9250 12.3 54.1 225 23 12 6.5 3.6 | 12.3 54.1 205 26 13 9.0 4.9
9000 12.7 54.9 225 23 12 7.1 3.9 | 13.0 55.4 205 24 13 10.3 5.7
8750 13.3 55.9 220 22 11 8.4 4.6 | 13.8 56.8 205 24 12 9.5 5.2
8500 13.9 57.0 220 20 10 8.4 4.6 | 14.5 58.1 200 24 12 10.1 5.6
8250 14.5 58.1 220 19 10 6.9 3.8 | 15.2 59.4 200 23 12 8.6 4.7
8000 14.9 58.8 220 18 9 6.1 3.3 | 15.8 60.4 200 23 12 8.8 4.8
7750 15.4 59.7 220 18 9 7.5 4.1 | 16.6 61.9 200 23 12 10.7 5.9
7500 16.0 60.8 215 17 9 8.3 4.5 | 17.4 63.3 200 22 11 11.2 6.1
7250 16.6 61.9 210 16 8 6.0 3.3 | 18.2 64.8 200 22 11 8.9 4.9
7000 16.9 62.4 210 16 8 4.2 2.3 | 18.7 65.7 200 22 11 7.2 4.0
6750 17.3 63.1 210 15 8 6.7 3.7 | 19.4 66.9 200 22 11 10.8 5.9
6500 17.8 64.0 205 14 7 6.7 3.7 | 20.3 68.5 200 21 11 12.7 6.9
6250 18.2 64.8 205 13 7 3.1 1.7 | 21.2 70.2 200 20 10 10.5 5.8
6000 18.3 64.9 200 12 6 0.9 0.5 | 21.9 71.4 200 19 10 9.4 5.1
5750 18.4 65.1 195 12 6 4.1 2.2 | 22.6 72.7 200 19 10 10.5 5.8
5500 18.8 65.8 190 9 5 8.3 4.5 | 23.6 74.5 200 16 8 16.7 9.2
10/04/2025 at 1500 MDT | 10/04/2025 at 1800 MDT
|
CAPE... +294.7 LI... -1.4 | CAPE... +59.6 LI... -0.3
CINH... -7.8 K Index... +25.8 | CINH... -28.4 K Index... +20.5
|
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 -61.8 -79.2 230 46 24 2.1 1.1 | -60.8 -77.4 235 42 22 2.8 1.5
45000 -58.0 -72.4 230 67 34 4.0 2.2 | -56.3 -69.3 235 64 33 3.3 1.8
40000 -52.1 -61.8 220 79 41 4.1 2.2 | -51.4 -60.5 225 73 38 3.2 1.7
38000 -50.5 -58.9 215 81 41 2.5 1.3 | -48.9 -56.0 225 77 40 4.3 2.4
36000 -49.0 -56.2 215 81 42 2.5 1.3 | -46.3 -51.3 220 81 42 4.3 2.4
34000 -46.2 -51.2 210 80 41 7.6 4.2 | -43.2 -45.8 220 83 43 6.5 3.5
32000 -41.6 -42.9 210 76 39 7.6 4.2 | -39.3 -38.7 215 81 41 6.4 3.5
30000 -36.3 -33.3 205 72 37 8.2 4.5 | -35.4 -31.7 210 78 40 5.0 2.7
29000 -33.8 -28.8 205 70 36 8.2 4.5 | -33.9 -29.0 210 77 40 5.0 2.7
28000 -31.4 -24.5 205 68 35 8.2 4.5 | -32.4 -26.3 210 76 39 5.0 2.7
27000 -29.0 -20.2 205 65 33 7.7 4.2 | -30.8 -23.4 210 74 38 5.9 3.2
26000 -26.7 -16.1 205 61 31 7.7 4.2 | -29.1 -20.4 210 70 36 5.8 3.2
25000 -24.4 -11.9 205 57 30 7.7 4.2 | -27.3 -17.1 210 66 34 5.8 3.2
24000 -22.2 -8.0 200 54 28 7.4 4.1 | -25.5 -13.9 210 62 32 7.3 4.0
23000 -20.0 -4.0 200 50 26 7.4 4.1 | -23.2 -9.8 215 58 30 7.6 4.2
22000 -17.8 -0.0 200 47 24 7.5 4.1 | -21.0 -5.8 215 54 28 7.6 4.2
21000 -15.6 3.9 205 45 23 7.1 3.9 | -18.7 -1.7 220 50 26 7.5 4.1
20000 -13.5 7.7 205 43 22 7.2 3.9 | -16.5 2.3 220 47 24 7.5 4.1
19500 -12.5 9.5 210 43 22 7.2 4.0 | -15.3 4.5 225 45 23 7.5 4.1
19000 -11.5 11.3 210 43 22 7.3 4.0 | -14.2 6.4 225 43 22 7.6 4.2
18500 -10.4 13.3 215 42 22 6.9 3.8 | -13.1 8.4 225 41 21 7.3 4.0
18000 -9.4 15.1 215 42 22 7.0 3.8 | -12.1 10.2 225 40 20 7.2 4.0
17500 -8.4 16.9 215 42 22 7.3 4.0 | -11.0 12.2 225 38 20 7.4 4.0
17000 -7.2 19.0 220 42 22 7.7 4.2 | -9.9 14.2 225 37 19 7.9 4.3
16500 -6.1 21.0 220 41 21 7.8 4.3 | -8.7 16.3 225 37 19 7.9 4.3
16000 -5.0 23.0 220 41 21 7.2 4.0 | -7.6 18.3 225 36 19 8.1 4.5
15500 -3.9 25.0 220 40 21 7.3 4.0 | -6.4 20.5 225 36 18 8.2 4.5
15000 -2.8 27.0 225 39 20 7.6 4.2 | -4.6 23.7 220 35 18 9.1 5.0
14500 -1.1 30.0 220 38 19 7.6 4.2 | -3.2 26.2 220 35 18 9.1 5.0
14000 0.1 32.2 220 37 19 9.0 4.9 | -1.9 28.6 220 35 18 9.2 5.1
13500 1.4 34.5 220 35 18 9.0 5.0 | -0.5 31.1 220 35 18 9.2 5.1
13000 2.7 36.9 220 34 18 8.6 4.7 | 0.8 33.4 225 34 18 9.1 5.0
12500 3.9 39.0 215 33 17 8.6 4.7 | 2.2 36.0 225 34 17 9.1 5.0
12000 5.1 41.2 210 33 17 9.1 5.0 | 3.5 38.3 225 33 17 9.2 5.0
11500 6.5 43.7 210 33 17 9.4 5.2 | 4.9 40.8 225 33 17 9.2 5.1
11000 7.9 46.2 210 32 17 8.5 4.7 | 6.3 43.3 225 32 17 8.6 4.7
10500 9.1 48.4 210 32 17 7.7 4.2 | 7.5 45.5 230 32 16 7.3 4.0
10250 9.8 49.6 210 33 17 11.8 6.5 | 8.1 46.6 230 32 16 11.1 6.1
10000 10.7 51.3 210 33 17 11.4 6.2 | 9.0 48.2 230 31 16 11.7 6.4
9750 11.4 52.5 210 33 17 8.1 4.4 | 9.7 49.5 230 31 16 8.4 4.6
9500 12.0 53.6 210 33 17 8.3 4.6 | 10.4 50.7 230 30 16 8.8 4.8
9250 12.7 54.9 210 33 17 10.7 5.8 | 11.0 51.8 230 30 15 10.1 5.5
9000 13.6 56.5 210 33 17 11.3 6.2 | 11.8 53.2 230 29 15 10.5 5.7
8750 14.3 57.7 210 33 17 9.0 4.9 | 12.5 54.5 235 29 15 9.1 5.0
8500 15.0 59.0 210 33 17 10.0 5.5 | 13.2 55.8 235 28 15 9.8 5.4
8250 15.7 60.3 210 32 17 8.2 4.5 | 13.9 57.0 235 28 14 8.3 4.6
8000 16.3 61.3 210 32 17 8.5 4.6 | 14.5 58.1 235 27 14 7.8 4.3
7750 17.0 62.6 210 32 16 10.7 5.9 | 15.2 59.4 235 26 14 9.8 5.4
7500 17.8 64.0 210 31 16 11.0 6.0 | 15.9 60.6 235 26 13 10.7 5.9
7250 18.6 65.5 210 31 16 9.4 5.2 | 16.7 62.1 240 25 13 9.2 5.1
7000 19.2 66.6 210 31 16 7.8 4.3 | 17.3 63.1 240 24 12 7.5 4.1
6750 19.9 67.8 210 30 16 10.3 5.7 | 17.9 64.2 240 23 12 9.4 5.2
6500 20.7 69.3 210 29 15 12.4 6.8 | 18.7 65.7 240 22 11 11.5 6.3
6250 21.6 70.9 210 28 15 10.1 5.5 | 19.5 67.1 240 21 11 9.2 5.1
6000 22.2 72.0 210 27 14 7.8 4.3 | 20.1 68.2 245 19 10 7.0 3.8
5750 22.9 73.2 210 26 13 10.8 6.0 | 20.6 69.1 245 18 9 9.4 5.2
5500 23.9 75.0 210 22 11 15.4 8.4 | 21.4 70.5 245 15 7 11.1 6.1
________________________________________________________________________________
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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