Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
923
UXUS97 KBOU 161316
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0715 MDT Thursday, October 16, 2025
This forecast is for Thursday, October 16, 2025:
If the trigger temperature of 69.9 F/21.0 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 226 ft/min (1.2 m/s)
Maximum height of thermals.................. 8742 ft MSL (3440 ft AGL)
Forecast maximum temperature................... 69.0 F/21.0 C
Time of trigger temperature.................... 1415 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................. 6314 ft MSL (1012 ft AGL)
Thermal soaring outlook for Friday 10/17....... 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 NVA
Potential height of wave....................... 31347 ft MSL (26045 ft AGL)
Wave soaring outlook for Friday 10/17.......... Poor
Remarks... Breezy westerly winds expected this afternoon
Sunrise/Sunset.................... 07:11:25 / 18:18:23 MDT
Total possible sunshine........... 11 hr 6 min 58 sec (666 min 58 sec)
Altitude of sun at 12:44:54 MDT... 40.92 degrees
Upper air data from numerical model forecast valid on 10/16/2025 at 0600 MDT
Freezing level.................. 13052 ft MSL (7750 ft AGL)
Convective condensation level... 13647 ft MSL (8345 ft AGL)
Lifted condensation level....... 12439 ft MSL (7137 ft AGL)
Lifted index.................... +1.7
K index......................... +17.3
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 -63.1 -81.6 220 47 24 1.3 0.7 M M M M M
45000 -60.6 -77.1 220 81 42 4.0 2.2 M M M M M
40000 -54.4 -65.9 210 86 44 5.1 2.8 M M M M M
38000 -49.9 -57.8 210 86 44 7.5 4.1 M M M M M
36000 -45.4 -49.7 210 87 45 7.5 4.1 M M M M M
34000 -41.3 -42.3 210 88 45 6.2 3.4 M M M M M
32000 -37.6 -35.7 205 91 47 6.2 3.4 M M M M M
30000 -33.8 -28.8 205 92 48 6.6 3.6 43.4 110.1 17.3 M M
29000 -31.3 -24.3 205 92 47 6.6 3.6 41.8 107.2 16.3 M M
28000 -29.3 -20.7 205 92 47 6.6 3.6 40.7 105.3 15.7 M M
27000 -27.4 -17.3 205 91 47 6.0 3.3 39.4 102.9 14.8 M M
26000 -25.6 -14.1 205 90 46 6.0 3.3 37.9 100.2 13.8 M M
25000 -23.8 -10.8 205 88 45 6.0 3.3 36.5 97.8 12.9 M M
24000 -22.0 -7.6 205 86 44 7.0 3.8 35.3 95.6 12.0 M M
23000 -19.9 -3.8 200 83 43 6.9 3.8 34.2 93.5 11.2 M M
22000 -17.9 -0.2 200 80 41 6.9 3.8 33.2 91.7 10.5 M M
21000 -15.9 3.4 200 77 40 6.3 3.5 32.1 89.8 9.7 M M
20000 -14.0 6.8 200 76 39 6.4 3.5 30.8 87.5 8.7 M M
19500 -13.1 8.4 200 75 39 6.4 3.5 30.3 86.5 8.2 M M
19000 -12.1 10.2 200 74 38 6.4 3.5 29.7 85.5 7.8 M M
18500 -11.2 11.8 200 73 38 6.2 3.4 29.1 84.5 7.3 M M
18000 -10.3 13.5 200 71 37 6.1 3.4 28.5 83.3 6.8 M M
17500 -9.4 15.1 205 70 36 6.2 3.4 27.9 82.2 6.3 M M
17000 -8.5 16.7 205 69 35 6.4 3.5 27.3 81.2 5.8 M M
16500 -7.5 18.5 205 68 35 6.3 3.5 26.7 80.1 5.3 M M
16000 -6.6 20.1 210 66 34 7.3 4.0 26.2 79.2 4.8 M M
15500 -5.5 22.1 210 65 34 7.3 4.0 25.8 78.5 4.4 M M
15000 -3.9 25.0 215 64 33 7.5 4.1 25.2 77.4 3.8 M M
14500 -2.9 26.8 215 63 32 7.6 4.2 24.9 76.7 3.5 M M
14000 -1.8 28.8 215 62 32 7.2 4.0 24.5 76.1 3.1 M M
13500 -0.8 30.6 220 60 31 7.2 3.9 24.1 75.3 2.7 M M
13000 0.3 32.5 220 59 30 8.4 4.6 23.7 74.7 2.3 M M
12500 1.6 34.9 220 57 29 8.8 4.8 23.5 74.4 2.1 M M
12000 2.9 37.2 220 56 29 8.8 4.8 23.4 74.1 2.0 M M
11500 4.1 39.4 220 52 27 8.7 4.8 23.2 73.8 1.8 M M
11000 5.4 41.7 220 49 25 8.1 4.4 23.1 73.5 1.7 M M
10500 6.5 43.7 220 43 22 7.1 3.9 22.7 72.9 1.3 M M
10250 7.1 44.8 215 41 21 9.6 5.3 22.6 72.6 1.1 M M
10000 7.8 46.0 210 36 19 8.8 4.9 22.6 72.7 1.2 M M
9750 8.3 46.9 215 35 18 5.7 3.1 22.3 72.2 0.9 M M
9500 8.8 47.8 215 34 17 6.4 3.5 22.1 71.7 0.6 M M
9250 9.2 48.6 215 32 17 6.8 3.7 21.8 71.3 0.4 M M
9000 9.8 49.6 215 33 17 7.3 4.0 21.6 70.9 0.2 M M
8750 10.3 50.5 215 32 16 7.2 3.9 21.4 70.6 -0.0 226 1.2
8500 10.8 51.4 210 31 16 7.0 3.8 21.2 70.2 -0.2 203 1.0
8250 11.4 52.5 210 29 15 7.9 4.3 21.0 69.9 -0.4 180 0.9
8000 12.0 53.6 210 28 15 9.2 5.1 21.0 69.7 -0.5 154 0.8
7750 12.6 54.7 210 27 14 8.3 4.6 20.9 69.6 -0.6 128 0.6
7500 13.2 55.8 205 27 14 8.0 4.4 20.7 69.3 -0.8 104 0.5
7250 13.7 56.7 205 26 13 7.1 3.9 20.6 69.1 -1.0 80 0.4
7000 14.1 57.4 205 26 13 5.3 2.9 20.3 68.6 -1.3 62 0.3
6750 14.3 57.7 205 25 13 3.3 1.8 19.9 67.9 -1.8 47 0.2
6500 14.5 58.1 205 24 12 2.4 1.3 19.4 66.9 -2.4 35 0.2
6250 14.5 58.1 205 23 12 -1.0 -0.5 18.8 65.8 -3.1 26 0.1
6000 14.3 57.7 200 22 11 -3.1 -1.7 17.8 64.0 -4.1 27 0.1
5750 14.0 57.2 195 20 10 -6.6 -3.6 16.8 62.2 -5.1 29 0.1
5500 13.0 55.4 190 16 8 -17.4 -9.5 15.1 59.3 -6.8 50 0.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/16/2025 at 0900 MDT | 10/16/2025 at 1200 MDT
|
CAPE... 0.0 LI... +1.4 | CAPE... +4.2 LI... +0.2
CINH... 0.0 K Index... -6.3 | CINH... -55.5 K Index... -13.3
|
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 -61.3 -78.3 225 41 21 1.1 0.6 | -61.3 -78.3 225 43 22 1.5 0.8
45000 -59.0 -74.2 220 73 37 3.0 1.7 | -58.6 -73.5 225 72 37 3.0 1.6
40000 -54.5 -66.1 215 85 44 3.1 1.7 | -54.1 -65.4 220 86 44 2.8 1.5
38000 -50.5 -58.9 210 87 45 7.1 3.9 | -50.2 -58.4 215 88 45 6.9 3.8
36000 -46.2 -51.2 205 88 45 7.1 3.9 | -46.1 -51.0 210 90 46 6.9 3.8
34000 -41.9 -43.4 205 90 46 7.1 3.9 | -42.0 -43.6 210 91 47 6.9 3.8
32000 -37.7 -35.9 205 91 47 7.1 3.9 | -37.8 -36.0 205 89 46 6.9 3.8
30000 -33.0 -27.4 200 92 48 6.9 3.8 | -33.2 -27.8 205 88 45 6.9 3.8
29000 -30.9 -23.6 200 93 48 6.9 3.8 | -31.1 -24.0 205 88 45 6.9 3.8
28000 -28.9 -20.0 200 93 48 6.8 3.7 | -29.1 -20.4 205 87 45 6.9 3.8
27000 -27.0 -16.6 200 94 48 5.8 3.2 | -27.0 -16.6 205 88 45 7.2 3.9
26000 -25.2 -13.4 205 94 48 5.8 3.2 | -24.8 -12.6 205 89 46 7.2 3.9
25000 -23.5 -10.3 205 94 48 5.8 3.2 | -22.7 -8.9 205 90 46 7.2 3.9
24000 -21.7 -7.1 205 94 48 5.4 3.0 | -20.7 -5.3 205 90 46 3.7 2.0
23000 -20.1 -4.2 205 91 47 5.4 2.9 | -19.9 -3.8 205 87 45 2.7 1.5
22000 -18.5 -1.3 205 89 46 5.4 3.0 | -19.1 -2.4 210 84 43 2.7 1.5
21000 -16.9 1.6 205 86 44 5.3 2.9 | -18.1 -0.6 210 79 41 4.3 2.3
20000 -15.4 4.3 205 81 42 5.3 2.9 | -16.9 1.6 210 71 36 4.3 2.3
19500 -14.6 5.7 210 79 41 5.3 2.9 | -16.2 2.8 210 66 34 4.3 2.3
19000 -13.8 7.2 210 77 40 5.3 2.9 | -15.6 3.9 215 62 32 4.3 2.3
18500 -13.0 8.6 210 75 38 6.2 3.4 | -14.9 5.2 215 58 30 5.8 3.2
18000 -12.0 10.4 210 72 37 6.5 3.6 | -13.9 7.0 215 53 27 6.5 3.6
17500 -11.0 12.2 210 70 36 6.5 3.6 | -12.9 8.8 220 49 25 6.7 3.7
17000 -10.1 13.8 215 67 35 6.3 3.5 | -11.9 10.6 220 45 23 7.8 4.3
16500 -8.6 16.5 215 62 32 6.4 3.5 | -10.7 12.7 220 41 21 7.7 4.2
16000 -7.6 18.3 215 59 30 6.9 3.8 | -9.5 14.9 220 38 20 8.4 4.6
15500 -6.6 20.1 215 54 28 7.0 3.8 | -7.6 18.3 220 35 18 8.4 4.6
15000 -5.6 21.9 215 50 26 5.7 3.1 | -6.3 20.7 220 33 17 8.8 4.8
14500 -4.8 23.4 220 44 23 5.8 3.2 | -5.0 23.0 220 33 17 8.8 4.9
14000 -4.0 24.8 220 40 21 6.0 3.3 | -3.7 25.3 225 33 17 8.2 4.5
13500 -3.1 26.4 220 38 19 6.1 3.4 | -2.5 27.5 225 34 17 8.1 4.4
13000 -2.3 27.9 225 35 18 6.5 3.5 | -1.3 29.7 230 35 18 7.2 3.9
12500 -1.3 29.7 225 34 17 6.6 3.6 | -0.4 31.3 225 31 16 6.8 3.7
12000 -0.3 31.5 230 32 17 7.3 4.0 | 0.6 33.1 225 28 15 6.9 3.8
11500 0.8 33.4 230 29 15 8.1 4.5 | 1.7 35.1 225 23 12 7.0 3.9
11000 1.9 35.4 230 25 13 8.2 4.5 | 2.7 36.9 220 17 9 5.2 2.8
10500 3.1 37.6 230 23 12 7.4 4.0 | 3.1 37.6 225 14 7 3.5 1.9
10250 3.7 38.7 230 22 11 10.9 6.0 | 3.3 37.9 225 12 6 3.2 1.7
10000 4.6 40.3 230 21 11 11.1 6.1 | 3.5 38.3 230 10 5 5.9 3.3
9750 5.2 41.4 230 20 10 7.8 4.3 | 4.0 39.2 230 9 5 8.2 4.5
9500 5.8 42.4 230 18 9 8.5 4.7 | 4.5 40.1 225 8 4 7.7 4.2
9250 6.4 43.5 235 17 9 9.1 5.0 | 5.0 41.0 220 6 3 7.7 4.2
9000 7.0 44.6 235 15 8 8.0 4.4 | 5.6 42.1 210 5 2 8.3 4.6
8750 7.5 45.5 240 13 7 6.3 3.5 | 6.2 43.2 205 4 2 9.1 5.0
8500 8.0 46.4 240 12 6 6.7 3.7 | 6.8 44.2 200 3 1 8.8 4.8
8250 8.5 47.3 245 11 6 6.8 3.7 | 7.4 45.3 195 2 1 9.5 5.2
8000 9.0 48.2 255 10 5 6.7 3.7 | 8.1 46.6 190 1 1 10.2 5.6
7750 9.4 48.9 265 10 5 5.9 3.2 | 8.9 48.0 195 1 0 9.5 5.2
7500 9.8 49.6 270 10 5 5.5 3.0 | 9.5 49.1 200 1 0 8.8 4.8
7250 10.2 50.4 275 10 5 5.9 3.2 | 10.2 50.4 205 1 0 10.2 5.6
7000 10.6 51.1 280 11 6 6.2 3.4 | 11.1 52.0 210 1 0 11.6 6.4
6750 11.1 52.0 280 12 6 5.4 3.0 | 11.9 53.4 000 0 0 9.6 5.3
6500 11.4 52.5 280 12 6 5.0 2.8 | 12.5 54.5 000 0 0 8.9 4.9
6250 11.8 53.2 275 12 6 5.8 3.2 | 13.3 55.9 000 0 0 10.7 5.9
6000 12.2 54.0 275 10 5 6.9 3.8 | 14.1 57.4 000 0 0 12.1 6.6
5750 12.6 54.7 270 8 4 3.9 2.2 | 15.0 59.0 000 0 0 9.4 5.1
5500 12.7 54.9 265 6 3 3.0 1.6 | 15.7 60.3 295 1 0 12.2 6.7
10/16/2025 at 1500 MDT | 10/16/2025 at 1800 MDT
|
CAPE... +7.8 LI... -0.0 | CAPE... +26.0 LI... -0.9
CINH... -23.4 K Index... -0.0 | CINH... -48.7 K Index... +10.9
|
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 -61.7 -79.1 225 47 24 2.1 1.1 | -61.4 -78.5 225 45 23 2.5 1.4
45000 -58.2 -72.8 225 70 36 3.3 1.8 | -57.5 -71.5 230 63 32 3.7 2.0
40000 -53.3 -63.9 220 79 41 3.0 1.6 | -51.7 -61.1 225 74 38 3.6 2.0
38000 -49.9 -57.8 215 81 42 6.0 3.3 | -49.0 -56.2 225 76 39 4.5 2.5
36000 -46.2 -51.2 215 83 43 6.0 3.3 | -46.3 -51.3 220 78 40 4.5 2.5
34000 -42.2 -44.0 210 84 43 7.7 4.2 | -42.8 -45.0 220 79 41 7.8 4.3
32000 -37.6 -35.7 210 84 43 7.7 4.2 | -38.1 -36.6 220 80 41 7.8 4.3
30000 -33.0 -27.4 210 83 42 5.6 3.1 | -33.9 -29.0 220 80 41 5.5 3.0
29000 -31.3 -24.3 210 81 42 5.6 3.1 | -31.9 -25.4 220 77 40 5.5 3.0
28000 -29.7 -21.5 210 80 41 5.6 3.1 | -30.3 -22.5 220 75 39 5.5 3.0
27000 -27.7 -17.9 210 78 40 8.2 4.5 | -28.4 -19.1 220 73 37 7.5 4.1
26000 -25.3 -13.5 210 75 39 8.1 4.4 | -26.2 -15.2 220 69 36 7.4 4.1
25000 -22.9 -9.2 210 72 37 8.1 4.4 | -24.0 -11.2 215 65 34 7.4 4.1
24000 -20.7 -5.3 210 69 36 4.1 2.2 | -21.9 -7.4 215 62 32 6.0 3.3
23000 -19.8 -3.6 210 68 35 2.9 1.6 | -20.2 -4.4 220 60 31 5.6 3.1
22000 -18.9 -2.0 215 67 34 2.9 1.6 | -18.5 -1.3 225 59 30 5.6 3.1
21000 -18.1 -0.6 215 65 33 2.7 1.5 | -17.2 1.0 225 57 29 -0.6 -0.3
20000 -17.3 0.9 220 57 29 2.7 1.5 | -17.4 0.7 225 49 25 -0.6 -0.3
19500 -16.9 1.6 220 53 27 2.7 1.5 | -17.5 0.5 225 45 23 -0.6 -0.3
19000 -16.5 2.3 220 49 25 2.7 1.5 | -17.6 0.3 225 41 21 -0.7 -0.4
18500 -16.0 3.2 220 45 23 6.0 3.3 | -17.5 0.5 225 37 19 4.9 2.7
18000 -14.8 5.4 220 44 23 7.6 4.2 | -16.4 2.5 225 34 17 7.6 4.2
17500 -13.7 7.3 225 43 22 7.7 4.2 | -15.3 4.5 225 30 16 7.8 4.3
17000 -12.5 9.5 225 41 21 7.5 4.1 | -14.2 6.4 225 28 14 7.7 4.2
16500 -11.4 11.5 225 39 20 7.5 4.1 | -13.0 8.6 220 25 13 7.6 4.2
16000 -10.3 13.5 225 37 19 8.1 4.4 | -11.8 10.8 210 23 12 9.8 5.4
15500 -9.1 15.6 225 35 18 8.2 4.5 | -10.3 13.5 205 23 12 10.0 5.5
15000 -7.2 19.0 225 31 16 8.2 4.5 | -8.8 16.2 205 23 12 9.7 5.3
14500 -6.0 21.2 220 29 15 8.2 4.5 | -6.7 19.9 195 23 12 9.5 5.2
14000 -4.8 23.4 220 26 14 8.0 4.4 | -5.4 22.3 195 22 12 8.5 4.7
13500 -3.7 25.3 220 23 12 8.0 4.4 | -4.1 24.6 190 21 11 8.4 4.6
13000 -2.5 27.5 220 20 11 8.2 4.5 | -2.9 26.8 185 20 10 9.1 5.0
12500 -1.3 29.7 215 18 9 8.3 4.6 | -1.5 29.3 185 19 10 9.3 5.1
12000 -0.1 31.8 205 16 8 7.7 4.2 | -0.1 31.8 185 18 9 9.3 5.1
11500 1.0 33.8 200 13 7 7.2 4.0 | 1.2 34.2 180 16 8 9.3 5.1
11000 2.0 35.6 185 10 5 7.0 3.8 | 2.6 36.7 175 14 7 7.8 4.3
10500 3.0 37.4 180 7 4 6.6 3.6 | 3.5 38.3 170 11 6 6.2 3.4
10250 3.5 38.3 175 6 3 8.5 4.6 | 4.0 39.2 160 9 5 9.8 5.4
10000 4.1 39.4 160 4 2 9.9 5.4 | 4.9 40.8 150 7 4 10.4 5.7
9750 4.8 40.6 160 3 2 9.1 5.0 | 5.4 41.7 145 5 3 7.0 3.9
9500 5.4 41.7 160 3 1 9.2 5.1 | 6.0 42.8 125 4 2 8.2 4.5
9250 6.1 43.0 155 2 1 9.7 5.3 | 6.6 43.9 095 3 2 6.8 3.7
9000 6.8 44.2 155 2 1 10.1 5.5 | 7.0 44.6 060 3 2 6.9 3.8
8750 7.6 45.7 155 2 1 9.9 5.4 | 7.6 45.7 035 4 2 8.2 4.5
8500 8.3 46.9 155 2 1 9.8 5.4 | 8.2 46.8 020 5 3 7.6 4.2
8250 9.1 48.4 160 2 1 10.4 5.7 | 8.8 47.8 010 7 3 8.6 4.7
8000 9.9 49.8 160 1 1 10.6 5.8 | 9.5 49.1 360 8 4 9.1 5.0
7750 10.6 51.1 165 1 1 9.7 5.3 | 10.1 50.2 360 9 5 8.1 4.5
7500 11.3 52.3 165 1 1 9.4 5.1 | 10.7 51.3 355 10 5 7.3 4.0
7250 12.0 53.6 170 1 0 9.7 5.3 | 11.3 52.3 355 11 6 9.3 5.1
7000 12.8 55.0 175 1 0 9.9 5.5 | 12.1 53.8 350 12 6 11.1 6.1
6750 13.5 56.3 185 1 0 9.6 5.3 | 12.8 55.0 350 13 7 9.3 5.1
6500 14.2 57.6 200 1 0 9.7 5.3 | 13.5 56.3 350 13 7 8.9 4.9
6250 15.0 59.0 000 0 0 10.7 5.9 | 14.2 57.6 350 14 7 9.9 5.4
6000 15.8 60.4 000 0 0 11.7 6.4 | 15.0 59.0 350 13 7 10.3 5.6
5750 16.7 62.1 260 1 0 10.0 5.5 | 15.7 60.3 350 13 7 9.4 5.2
5500 17.4 63.3 275 1 0 13.1 7.2 | 16.3 61.3 350 13 6 7.2 4.0
________________________________________________________________________________
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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