Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
517
UXUS97 KBOU 151313
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0713 MDT Wednesday, October 15, 2025
This forecast is for Wednesday, October 15, 2025:
If the trigger temperature of 73.3 F/22.9 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 354 ft/min (1.8 m/s)
Maximum height of thermals.................. 12504 ft MSL (7191 ft AGL)
Forecast maximum temperature................... 80.0 F/27.1 C
Time of trigger temperature.................... 1230 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................. 10420 ft MSL (5107 ft AGL)
Thermal soaring outlook for Thursday 10/16..... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... Little change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 40450 ft MSL (35137 ft AGL)
Wave soaring outlook for Thursday 10/16........ Poor
Remarks...
Sunrise/Sunset.................... 07:10:23 / 18:19:51 MDT
Total possible sunshine........... 11 hr 9 min 28 sec (669 min 28 sec)
Altitude of sun at 12:45:07 MDT... 41.29 degrees
Upper air data from numerical model forecast valid on 10/15/2025 at 0600 MDT
Freezing level.................. 15574 ft MSL (10261 ft AGL)
Convective condensation level... 16240 ft MSL (10927 ft AGL)
Lifted condensation level....... 14402 ft MSL (9089 ft AGL)
Lifted index.................... -0.3
K index......................... +0.7
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 -66.9 -88.4 220 58 30 3.3 1.8 M M M M M
45000 -61.6 -78.9 225 80 41 4.5 2.5 M M M M M
40000 -54.3 -65.7 220 93 48 7.4 4.0 M M M M M
38000 -50.0 -58.0 220 92 47 7.1 3.9 M M M M M
36000 -45.7 -50.3 220 90 46 7.1 3.9 M M M M M
34000 -41.7 -43.1 220 82 42 6.4 3.5 M M M M M
32000 -37.9 -36.2 220 72 37 6.4 3.5 M M M M M
30000 -33.2 -27.8 220 60 31 7.3 4.0 42.2 108.0 11.8 M M
29000 -31.0 -23.8 220 55 28 7.3 4.0 41.3 106.4 11.3 M M
28000 -28.8 -19.8 220 50 26 7.6 4.2 40.5 104.9 10.8 M M
27000 -26.3 -15.3 220 48 25 8.1 4.5 39.8 103.6 10.3 M M
26000 -23.9 -11.0 220 46 24 8.1 4.5 39.2 102.5 10.0 M M
25000 -21.5 -6.7 220 44 23 8.2 4.5 38.6 101.6 9.7 M M
24000 -19.1 -2.4 220 42 22 7.9 4.4 38.0 100.3 9.2 M M
23000 -16.7 1.9 220 40 20 7.9 4.4 37.3 99.1 8.8 M M
22000 -14.3 6.3 215 37 19 7.9 4.4 36.7 98.1 8.4 M M
21000 -12.0 10.4 215 37 19 7.9 4.3 36.0 96.8 7.9 M M
20000 -9.6 14.7 215 37 19 7.9 4.4 35.4 95.6 7.4 M M
19500 -8.4 16.9 215 37 19 7.9 4.4 35.1 95.1 7.2 M M
19000 -7.2 19.0 215 37 19 7.5 4.1 34.8 94.6 7.0 M M
18500 -6.1 21.0 215 36 19 7.3 4.0 34.3 93.8 6.6 M M
18000 -5.0 23.0 215 36 18 7.3 4.0 33.9 93.0 6.3 M M
17500 -4.0 24.8 215 35 18 6.5 3.6 33.4 92.2 5.9 M M
17000 -3.0 26.6 215 34 17 6.6 3.6 32.9 91.2 5.4 M M
16500 -2.1 28.2 220 33 17 6.6 3.6 32.4 90.2 5.0 M M
16000 -0.6 30.9 220 31 16 6.7 3.7 31.6 88.8 4.3 M M
15500 0.4 32.7 220 29 15 7.0 3.8 31.1 87.9 3.9 M M
15000 1.4 34.5 220 29 15 7.0 3.9 30.6 87.1 3.4 M M
14500 2.4 36.3 220 28 14 6.3 3.5 30.2 86.3 3.0 M M
14000 3.2 37.8 220 28 14 5.5 3.0 29.5 85.1 2.3 M M
13500 4.0 39.2 220 28 14 5.4 2.9 28.8 83.8 1.7 M M
13000 4.6 40.3 220 27 14 4.3 2.4 28.0 82.3 0.8 M M
12500 5.1 41.2 220 25 13 4.6 2.5 27.1 80.8 -0.1 550 2.8
12000 5.7 42.3 220 23 12 4.3 2.4 26.3 79.3 -1.0 518 2.6
11500 6.2 43.2 220 22 11 4.3 2.4 25.4 77.7 -1.9 487 2.5
11000 7.1 44.8 215 21 11 7.9 4.3 24.8 76.7 -2.6 446 2.3
10500 8.2 46.8 215 19 10 6.8 3.7 24.5 76.1 -2.9 399 2.0
10250 8.6 47.5 215 18 10 5.4 2.9 24.2 75.5 -3.2 379 1.9
10000 9.1 48.4 215 19 10 8.3 4.6 23.9 75.1 -3.5 357 1.8
9750 9.8 49.6 220 20 10 10.5 5.8 23.9 75.1 -3.5 328 1.7
9500 10.5 50.9 225 22 11 9.9 5.4 24.0 75.1 -3.5 299 1.5
9250 11.2 52.2 225 23 12 7.4 4.1 23.9 75.1 -3.6 272 1.4
9000 11.6 52.9 230 23 12 6.6 3.6 23.7 74.6 -3.9 251 1.3
8750 12.2 54.0 230 24 12 7.9 4.3 23.5 74.3 -4.1 228 1.2
8500 12.7 54.9 230 24 12 7.5 4.1 23.3 74.0 -4.3 204 1.0
8250 13.2 55.8 230 24 12 7.5 4.1 23.1 73.7 -4.5 181 0.9
8000 13.8 56.8 225 24 12 7.2 3.9 23.0 73.3 -4.7 158 0.8
7750 14.2 57.6 225 23 12 6.5 3.6 22.7 72.9 -5.0 136 0.7
7500 14.7 58.5 225 23 12 6.6 3.6 22.5 72.5 -5.2 115 0.6
7250 15.2 59.4 220 22 11 7.0 3.8 22.3 72.1 -5.5 93 0.5
7000 15.7 60.3 220 21 11 6.8 3.7 22.1 71.7 -5.8 70 0.4
6750 16.2 61.2 220 21 11 6.9 3.8 21.8 71.3 -6.0 48 0.2
6500 16.5 61.7 220 20 10 -2.3 -1.3 21.4 70.5 -6.5 32 0.2
6250 15.8 60.4 215 18 9 -9.9 -5.4 20.0 68.1 -7.8 43 0.2
6000 15.2 59.4 215 17 9 -6.3 -3.4 18.7 65.6 -9.2 55 0.3
5750 14.7 58.5 210 15 8 -9.4 -5.2 17.5 63.4 -10.5 63 0.3
5500 13.5 56.3 205 11 6 -25.4 -14.0 15.5 59.9 -12.4 92 0.5
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/15/2025 at 0900 MDT | 10/15/2025 at 1200 MDT
|
CAPE... 0.0 LI... +4.1 | CAPE... 0.0 LI... +1.4
CINH... 0.0 K Index... -12.0 | CINH... 0.0 K Index... +14.5
|
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 -66.4 -87.5 220 54 28 3.3 1.8 | -66.6 -87.9 220 52 27 3.7 2.0
45000 -61.1 -78.0 225 78 40 4.4 2.4 | -60.8 -77.4 220 80 41 4.5 2.5
40000 -53.9 -65.0 220 95 49 6.8 3.8 | -53.5 -64.3 220 92 47 6.7 3.7
38000 -50.0 -58.0 220 92 47 6.6 3.6 | -49.6 -57.3 215 90 46 6.5 3.5
36000 -46.0 -50.8 220 89 46 6.6 3.6 | -45.7 -50.3 215 88 46 6.5 3.5
34000 -42.1 -43.8 220 81 42 6.5 3.5 | -41.7 -43.1 215 82 42 6.8 3.7
32000 -38.2 -36.8 220 71 36 6.5 3.6 | -37.7 -35.9 215 75 38 6.8 3.7
30000 -34.0 -29.2 215 60 31 7.3 4.0 | -33.0 -27.4 210 63 32 6.9 3.8
29000 -31.3 -24.3 215 54 28 7.3 4.0 | -30.9 -23.6 210 57 30 6.9 3.8
28000 -29.1 -20.4 215 48 25 7.7 4.2 | -28.9 -20.0 210 52 27 7.3 4.0
27000 -26.6 -15.9 215 46 24 8.3 4.5 | -26.4 -15.5 210 50 26 8.4 4.6
26000 -24.2 -11.6 210 45 23 8.3 4.5 | -23.9 -11.0 210 49 25 8.4 4.6
25000 -21.7 -7.1 210 44 22 8.3 4.5 | -21.4 -6.5 210 48 25 8.4 4.6
24000 -19.3 -2.7 210 42 22 8.0 4.4 | -19.1 -2.4 210 48 25 7.6 4.2
23000 -16.9 1.6 210 41 21 8.0 4.4 | -16.8 1.8 210 47 24 7.6 4.2
22000 -14.5 5.9 210 40 20 7.9 4.4 | -14.5 5.9 210 47 24 7.7 4.2
21000 -12.1 10.2 210 39 20 8.0 4.4 | -12.3 9.9 210 46 24 7.0 3.8
20000 -9.7 14.5 210 38 20 8.0 4.4 | -10.3 13.5 210 46 24 7.0 3.8
19500 -8.5 16.7 210 38 20 8.0 4.4 | -9.2 15.4 210 46 24 7.0 3.8
19000 -7.4 18.7 210 38 20 7.8 4.3 | -8.2 17.2 210 46 23 6.6 3.6
18500 -6.2 20.8 210 37 19 7.7 4.2 | -7.2 19.0 210 45 23 6.3 3.4
18000 -5.0 23.0 210 37 19 7.8 4.3 | -6.3 20.7 210 45 23 6.2 3.4
17500 -3.9 25.0 215 36 19 7.0 3.8 | -5.4 22.3 210 45 23 6.8 3.7
17000 -2.9 26.8 215 36 18 7.1 3.9 | -4.4 24.1 210 46 23 6.8 3.7
16500 -1.8 28.8 215 35 18 7.4 4.1 | -3.4 25.9 210 46 24 6.7 3.7
16000 -0.7 30.7 220 35 18 7.6 4.2 | -2.0 28.4 215 46 24 6.8 3.7
15500 1.0 33.8 220 33 17 6.4 3.5 | -1.0 30.2 215 46 24 7.0 3.9
15000 1.9 35.4 220 33 17 6.1 3.4 | -0.0 32.0 215 47 24 7.2 3.9
14500 2.8 37.0 225 32 16 5.9 3.2 | 1.0 33.8 215 47 24 7.2 4.0
14000 3.6 38.5 225 31 16 5.6 3.1 | 2.0 35.6 215 46 24 7.2 4.0
13500 4.4 39.9 225 30 15 5.5 3.0 | 3.0 37.4 215 45 23 7.3 4.0
13000 5.0 41.0 220 29 15 4.4 2.4 | 3.9 39.0 215 43 22 6.9 3.8
12500 5.7 42.3 220 27 14 4.6 2.5 | 4.9 40.8 215 41 21 6.9 3.8
12000 6.3 43.3 220 26 13 5.4 2.9 | 6.0 42.8 215 37 19 7.9 4.3
11500 7.0 44.6 215 25 13 5.3 2.9 | 7.1 44.8 215 34 17 7.8 4.3
11000 7.9 46.2 215 23 12 6.7 3.7 | 8.3 46.9 210 31 16 8.2 4.5
10500 8.8 47.8 210 21 11 6.3 3.5 | 9.5 49.1 210 30 16 8.9 4.9
10250 9.2 48.6 205 20 10 4.8 2.6 | 10.0 50.0 210 30 15 5.2 2.9
10000 9.6 49.3 210 21 11 7.8 4.3 | 10.3 50.5 210 31 16 5.5 3.0
9750 10.3 50.5 215 22 11 10.6 5.8 | 10.9 51.6 210 32 17 9.2 5.1
9500 11.0 51.8 215 23 12 10.0 5.5 | 11.5 52.7 215 34 17 8.5 4.7
9250 11.7 53.1 220 24 12 7.6 4.2 | 12.1 53.8 215 35 18 7.1 3.9
9000 12.1 53.8 220 25 13 5.0 2.7 | 12.5 54.5 215 34 17 5.4 2.9
8750 12.4 54.3 220 26 13 5.2 2.9 | 12.9 55.2 210 32 16 5.8 3.2
8500 12.8 55.0 220 26 14 5.1 2.8 | 13.3 55.9 210 30 16 5.6 3.1
8250 13.1 55.6 220 26 13 4.8 2.7 | 13.7 56.7 210 28 15 5.6 3.1
8000 13.4 56.1 220 25 13 4.8 2.6 | 14.1 57.4 210 26 14 4.1 2.2
7750 13.7 56.7 220 24 12 5.2 2.9 | 14.3 57.7 210 24 13 1.7 0.9
7500 14.1 57.4 220 23 12 5.0 2.7 | 14.4 57.9 210 23 12 1.9 1.0
7250 14.4 57.9 220 22 11 4.6 2.5 | 14.6 58.3 210 19 10 3.0 1.6
7000 14.7 58.5 220 20 10 4.3 2.3 | 14.8 58.6 210 15 8 3.7 2.0
6750 15.1 59.2 215 19 10 5.5 3.0 | 15.1 59.2 205 12 6 4.8 2.7
6500 15.3 59.5 215 17 9 -3.4 -1.9 | 15.5 59.9 200 10 5 8.9 4.9
6250 14.6 58.3 215 16 8 -10.8 -5.9 | 16.3 61.3 200 9 5 11.7 6.4
6000 13.8 56.8 210 15 8 -9.9 -5.4 | 17.2 63.0 200 9 5 10.4 5.7
5750 13.1 55.6 210 13 7 -7.0 -3.9 | 18.0 64.4 200 8 4 11.8 6.5
5500 13.0 55.4 205 11 5 7.4 4.0 | 19.0 66.2 200 8 4 18.9 10.4
10/15/2025 at 1500 MDT | 10/15/2025 at 1800 MDT
|
CAPE... +409.0 LI... -0.8 | CAPE... +931.2 LI... -3.5
CINH... -4.7 K Index... +12.1 | CINH... -10.4 K Index... +20.2
|
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 -66.6 -87.9 215 59 31 3.4 1.9 | -66.7 -88.1 220 47 24 3.0 1.7
45000 -60.9 -77.6 215 84 43 5.0 2.7 | -61.5 -78.7 220 84 43 5.3 2.9
40000 -53.4 -64.1 215 93 48 6.0 3.3 | -53.4 -64.1 215 89 46 6.1 3.3
38000 -49.6 -57.3 215 92 48 6.3 3.5 | -49.5 -57.1 215 89 46 6.4 3.5
36000 -45.3 -49.5 215 91 47 6.3 3.5 | -45.2 -49.4 210 89 46 6.4 3.5
34000 -41.5 -42.7 215 85 44 6.4 3.5 | -41.2 -42.2 210 84 43 6.7 3.7
32000 -37.6 -35.7 215 76 39 6.4 3.5 | -37.2 -35.0 210 77 39 6.7 3.7
30000 -33.5 -28.3 215 66 34 7.0 3.9 | -33.1 -27.6 210 69 36 7.0 3.8
29000 -31.4 -24.5 215 61 31 7.0 3.9 | -31.0 -23.8 210 66 34 7.0 3.8
28000 -29.3 -20.7 210 56 29 6.9 3.8 | -28.9 -20.0 210 62 32 6.9 3.8
27000 -26.9 -16.4 210 53 27 8.5 4.7 | -26.6 -15.9 210 61 31 7.9 4.4
26000 -24.3 -11.7 210 52 27 8.5 4.7 | -24.2 -11.6 210 60 31 7.9 4.4
25000 -21.7 -7.1 210 50 26 8.5 4.7 | -21.9 -7.4 210 59 30 7.9 4.3
24000 -19.3 -2.7 210 50 26 8.1 4.4 | -19.5 -3.1 210 58 30 7.5 4.1
23000 -16.9 1.6 210 52 27 8.0 4.4 | -17.3 0.9 210 57 29 7.5 4.1
22000 -14.4 6.1 210 54 28 8.1 4.4 | -15.0 5.0 215 56 29 7.5 4.1
21000 -12.2 10.0 210 54 28 7.2 4.0 | -12.8 9.0 215 55 29 6.9 3.8
20000 -10.0 14.0 210 53 27 7.2 4.0 | -10.8 12.6 215 55 28 6.9 3.8
19500 -8.9 16.0 210 53 27 7.2 4.0 | -9.7 14.5 215 55 28 6.9 3.8
19000 -7.3 18.9 210 52 27 6.6 3.6 | -8.7 16.3 215 55 28 6.9 3.8
18500 -6.3 20.7 210 52 27 6.6 3.6 | -7.2 19.0 215 54 28 6.6 3.6
18000 -5.3 22.5 210 51 26 6.5 3.6 | -6.2 20.8 215 53 27 6.6 3.6
17500 -4.4 24.1 210 51 26 6.4 3.5 | -5.2 22.6 215 52 27 6.9 3.8
17000 -3.4 25.9 210 51 26 6.5 3.5 | -4.2 24.4 215 52 27 6.9 3.8
16500 -2.5 27.5 210 51 26 6.1 3.3 | -3.2 26.2 220 51 26 6.5 3.6
16000 -1.6 29.1 215 50 26 6.1 3.4 | -2.3 27.9 220 50 26 6.5 3.6
15500 -0.7 30.7 215 50 26 6.3 3.5 | -1.4 29.5 220 49 25 6.5 3.5
15000 0.1 32.2 215 50 26 6.6 3.6 | -0.6 30.9 215 47 24 6.1 3.4
14500 1.0 33.8 215 49 25 6.9 3.8 | 0.2 32.4 215 45 23 6.5 3.6
14000 1.8 35.2 215 48 25 6.0 3.3 | 1.0 33.8 215 42 22 6.8 3.7
13500 2.5 36.5 215 46 24 6.5 3.6 | 1.9 35.4 210 39 20 7.0 3.8
13000 3.3 37.9 210 43 22 5.5 3.0 | 2.9 37.2 205 36 19 7.6 4.1
12500 4.1 39.4 210 38 19 5.4 3.0 | 3.9 39.0 205 32 17 7.5 4.1
12000 4.9 40.8 205 33 17 7.7 4.2 | 5.1 41.2 200 29 15 9.0 5.0
11500 6.0 42.8 200 28 14 7.6 4.2 | 6.4 43.5 195 28 14 9.3 5.1
11000 7.1 44.8 195 24 12 8.2 4.5 | 7.6 45.7 195 27 14 8.7 4.8
10500 8.4 47.1 190 22 11 7.8 4.3 | 8.9 48.0 190 26 14 8.4 4.6
10250 9.0 48.2 190 21 11 11.0 6.1 | 9.5 49.1 190 26 14 10.5 5.8
10000 9.9 49.8 185 20 10 11.7 6.4 | 10.3 50.5 185 27 14 10.0 5.5
9750 10.6 51.1 185 19 10 9.0 5.0 | 10.9 51.6 185 27 14 7.8 4.3
9500 11.3 52.3 185 18 9 9.8 5.4 | 11.5 52.7 180 28 14 8.2 4.5
9250 12.0 53.6 185 17 9 9.4 5.2 | 12.1 53.8 180 28 15 8.8 4.8
9000 12.7 54.9 185 17 9 9.7 5.3 | 12.8 55.0 175 28 15 9.1 5.0
8750 13.5 56.3 185 17 9 10.3 5.6 | 13.4 56.1 175 28 14 8.7 4.7
8500 14.2 57.6 185 16 8 9.7 5.3 | 14.0 57.2 175 28 14 8.4 4.6
8250 15.0 59.0 185 16 8 11.4 6.3 | 14.6 58.3 175 27 14 9.8 5.4
8000 15.9 60.6 185 15 8 11.0 6.1 | 15.4 59.7 170 27 14 10.2 5.6
7750 16.6 61.9 185 15 8 8.5 4.7 | 16.1 61.0 170 27 14 8.7 4.8
7500 17.2 63.0 185 15 8 8.8 4.8 | 16.8 62.2 170 26 14 8.5 4.7
7250 17.9 64.2 185 14 7 10.4 5.7 | 17.4 63.3 170 26 13 9.9 5.5
7000 18.8 65.8 185 14 7 11.1 6.1 | 18.2 64.8 170 26 13 10.8 5.9
6750 19.5 67.1 185 14 7 9.6 5.3 | 18.9 66.0 170 25 13 8.8 4.8
6500 20.2 68.4 185 13 7 9.8 5.4 | 19.6 67.3 170 24 13 8.4 4.6
6250 21.0 69.8 185 13 7 11.0 6.1 | 20.3 68.5 170 23 12 9.8 5.4
6000 21.8 71.2 185 12 6 11.3 6.2 | 21.0 69.8 170 22 11 10.4 5.7
5750 22.6 72.7 185 12 6 9.9 5.4 | 21.7 71.1 170 20 10 8.8 4.8
5500 23.4 74.1 185 11 6 12.6 6.9 | 22.3 72.1 165 17 9 5.0 2.7
________________________________________________________________________________
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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