Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
139
UXUS97 KBOU 180007
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1707 MST Monday, November 17, 2025
This forecast is for Tuesday, November 18, 2025:
If the trigger temperature of 57.8 F/14.3 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 516 ft/min (2.6 m/s)
Maximum height of thermals.................. 12810 ft MSL (7522 ft AGL)
Forecast maximum temperature................... 63.0 F/17.7 C
Time of trigger temperature.................... 1100 MST
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Overcast thin high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 8952 ft MSL (3664 ft AGL)
Thermal soaring outlook for Wednesday 11/19.... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... No change
Height of stable layer (12-18K ft MSL)......... 14864 ft MSL (9576 ft AGL)
Weak PVA/NVA (through 1700 MST)................ Neither
Potential height of wave....................... 39416 ft MSL (34128 ft AGL)
Wave soaring outlook for Wednesday 11/19....... Poor
Remarks...
Sunrise/Sunset.................... 06:48:10 / 16:41:18 MST
Total possible sunshine........... 9 hr 53 min 7 sec (593 min 7 sec)
Altitude of sun at 11:44:44 MST... 30.71 degrees
Upper air data from numerical model forecast valid on 11/18/2025 at 0500 MST
Freezing level.................. 10211 ft MSL (4923 ft AGL)
Convective condensation level... 17282 ft MSL (11994 ft AGL)
Lifted condensation level....... 14291 ft MSL (9003 ft AGL)
Lifted index.................... +4.9
K index......................... +8.0
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 -59.7 -75.5 245 28 15 0.4 0.2 M M M M M
45000 -59.2 -74.6 255 45 23 0.3 0.2 M M M M M
40000 -58.7 -73.7 255 62 32 0.3 0.2 M M M M M
38000 -57.1 -70.8 255 61 32 4.1 2.2 M M M M M
36000 -54.6 -66.3 255 58 30 4.1 2.2 M M M M M
34000 -51.7 -61.1 260 53 27 7.3 4.0 M M M M M
32000 -47.2 -53.0 260 45 23 7.4 4.1 M M M M M
30000 -42.5 -44.5 260 38 19 9.2 5.0 33.6 92.5 12.3 M M
29000 -39.7 -39.5 260 36 19 9.2 5.1 33.3 92.0 12.2 M M
28000 -37.0 -34.6 255 35 18 9.2 5.1 33.1 91.7 12.3 M M
27000 -33.7 -28.7 255 33 17 7.6 4.2 32.8 91.1 12.2 M M
26000 -31.3 -24.3 255 30 15 7.8 4.3 32.0 89.6 11.7 M M
25000 -29.0 -20.2 250 27 14 7.8 4.3 31.3 88.3 11.2 M M
24000 -26.7 -16.1 250 24 13 7.9 4.3 30.6 87.1 10.8 M M
23000 -24.3 -11.7 250 21 11 7.9 4.3 29.9 85.8 10.4 M M
22000 -22.0 -7.6 250 18 9 7.9 4.4 29.2 84.6 9.9 M M
21000 -19.6 -3.3 255 16 8 7.7 4.2 28.6 83.5 9.5 M M
20000 -17.3 0.9 260 16 8 7.7 4.2 27.8 82.1 9.0 M M
19500 -16.2 2.8 260 16 8 7.7 4.2 27.5 81.4 8.7 M M
19000 -15.0 5.0 260 15 8 7.7 4.2 27.2 80.9 8.5 M M
18500 -13.9 7.0 265 15 8 7.6 4.2 26.8 80.3 8.2 M M
18000 -12.8 9.0 265 15 8 7.6 4.2 26.4 79.6 7.9 M M
17500 -11.6 11.1 270 14 7 7.4 4.1 26.1 79.0 7.6 M M
17000 -10.6 12.9 270 14 7 6.4 3.5 25.6 78.0 7.2 M M
16500 -9.7 14.5 275 14 7 6.6 3.6 25.0 77.0 6.7 M M
16000 -8.8 16.2 275 14 7 4.9 2.7 24.4 75.9 6.2 M M
15500 -8.1 17.4 280 14 7 4.8 2.6 23.5 74.4 5.4 M M
15000 -7.5 18.5 280 15 7 3.7 2.1 22.7 72.9 4.7 M M
14500 -7.1 19.2 275 14 7 3.0 1.6 21.6 70.8 3.6 M M
14000 -6.5 20.3 270 12 6 3.1 1.7 19.9 67.8 2.1 M M
13500 -6.0 21.2 265 11 6 3.0 1.7 18.8 65.8 1.1 M M
13000 -5.5 22.1 255 9 5 4.8 2.6 17.8 64.0 0.1 M M
12500 -4.7 23.5 255 7 4 5.2 2.9 17.1 62.7 -0.6 585 3.0
12000 -3.9 25.0 260 5 2 6.8 3.7 16.4 61.5 -1.2 546 2.8
11500 -2.8 27.0 310 3 2 7.5 4.1 16.0 60.9 -1.6 499 2.5
11000 -1.7 28.9 350 5 3 8.0 4.4 15.7 60.3 -2.0 451 2.3
10500 -0.6 30.9 005 8 4 8.9 4.9 15.4 59.8 -2.2 401 2.0
10250 0.0 32.0 005 9 5 4.9 2.7 15.3 59.6 -2.4 376 1.9
10000 0.3 32.5 005 9 5 6.2 3.4 14.8 58.7 -2.8 360 1.8
9750 1.1 34.0 005 9 5 11.0 6.0 14.9 58.7 -2.8 330 1.7
9500 1.8 35.2 005 9 5 10.2 5.6 14.9 58.8 -2.8 300 1.5
9250 2.6 36.7 005 10 5 8.7 4.8 14.9 58.8 -2.8 270 1.4
9000 3.1 37.6 005 9 5 6.3 3.4 14.7 58.5 -3.0 247 1.3
8750 3.6 38.5 005 7 4 6.9 3.8 14.4 58.0 -3.2 224 1.1
8500 4.1 39.4 005 6 3 7.5 4.1 14.3 57.7 -3.4 201 1.0
8250 4.7 40.5 005 4 2 6.4 3.5 14.1 57.3 -3.6 177 0.9
8000 5.1 41.2 360 5 2 5.2 2.9 13.7 56.7 -3.9 157 0.8
7750 5.5 41.9 360 6 3 5.4 3.0 13.4 56.1 -4.2 137 0.7
7500 5.9 42.6 355 7 4 5.2 2.8 13.1 55.5 -4.6 118 0.6
7250 6.3 43.3 345 8 4 4.8 2.6 12.7 54.9 -5.0 100 0.5
7000 6.6 43.9 330 9 5 4.3 2.4 12.3 54.1 -5.4 83 0.4
6750 6.9 44.4 315 11 6 5.0 2.7 11.9 53.4 -5.8 66 0.3
6500 7.2 45.0 305 14 7 0.8 0.4 11.5 52.6 -6.3 51 0.3
6250 7.0 44.6 300 12 6 -3.7 -2.0 10.5 51.0 -7.2 49 0.2
6000 6.8 44.2 290 11 6 -2.4 -1.3 9.6 49.2 -8.2 49 0.2
5750 6.5 43.7 280 9 5 -5.4 -3.0 8.6 47.5 -9.2 48 0.2
5500 5.6 42.1 260 7 3 -21.6 -11.8 7.0 44.5 -10.9 68 0.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/18/2025 at 0800 MST | 11/18/2025 at 1100 MST
|
CAPE... 0.0 LI... +5.4 | CAPE... 0.0 LI... +5.9
CINH... 0.0 K Index... +6.4 | CINH... -0.1 K Index... +4.8
|
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 -60.7 -77.3 240 36 19 0.3 0.2 | -60.5 -76.9 240 41 21 0.1 0.0
45000 -60.2 -76.4 245 52 27 0.9 0.5 | -60.3 -76.5 245 59 30 0.9 0.5
40000 -58.7 -73.7 245 64 33 1.0 0.5 | -58.8 -73.8 240 73 38 1.0 0.6
38000 -57.1 -70.8 250 66 34 3.8 2.1 | -56.9 -70.4 240 75 38 3.8 2.1
36000 -54.5 -66.1 250 66 34 3.8 2.1 | -54.6 -66.3 240 73 38 3.8 2.1
34000 -51.4 -60.5 250 63 33 7.7 4.2 | -51.4 -60.5 240 68 35 8.3 4.5
32000 -46.8 -52.2 250 57 29 7.7 4.2 | -46.4 -51.5 235 59 30 8.3 4.5
30000 -41.9 -43.4 250 50 26 9.0 4.9 | -41.3 -42.3 235 51 26 8.7 4.8
29000 -39.2 -38.6 250 46 24 9.0 4.9 | -38.7 -37.7 235 48 25 8.7 4.8
28000 -36.5 -33.7 250 42 22 9.0 4.9 | -36.1 -33.0 230 46 24 8.7 4.8
27000 -33.8 -28.8 245 38 20 8.5 4.7 | -33.6 -28.5 230 44 22 7.8 4.3
26000 -31.3 -24.3 245 37 19 8.5 4.7 | -31.3 -24.3 235 42 22 7.8 4.3
25000 -28.7 -19.7 245 36 18 8.5 4.7 | -28.9 -20.0 235 41 21 7.8 4.3
24000 -26.2 -15.2 245 34 18 7.9 4.3 | -26.6 -15.9 240 40 21 7.7 4.2
23000 -23.9 -11.0 245 30 15 7.5 4.1 | -24.3 -11.7 235 36 19 7.7 4.2
22000 -21.7 -7.1 240 25 13 7.5 4.1 | -22.0 -7.6 235 32 16 7.7 4.2
21000 -19.5 -3.1 235 21 11 6.8 3.7 | -19.7 -3.5 235 28 14 7.2 4.0
20000 -17.4 0.7 235 19 10 6.7 3.7 | -17.0 1.4 230 25 13 7.2 4.0
19500 -16.4 2.5 235 18 9 6.7 3.7 | -15.9 3.4 225 24 12 7.2 4.0
19000 -15.4 4.3 230 16 8 6.7 3.7 | -14.8 5.4 225 23 12 7.3 4.0
18500 -13.9 7.0 235 15 8 7.0 3.8 | -13.9 7.0 220 22 11 5.2 2.9
18000 -12.8 9.0 235 15 8 6.9 3.8 | -13.1 8.4 220 21 11 5.4 3.0
17500 -11.8 10.8 240 15 8 6.5 3.6 | -12.3 9.9 220 21 11 5.7 3.2
17000 -10.9 12.4 245 15 8 6.2 3.4 | -11.4 11.5 220 20 10 5.9 3.2
16500 -10.0 14.0 245 15 8 6.0 3.3 | -10.5 13.1 220 19 10 5.8 3.2
16000 -9.2 15.4 250 14 7 4.6 2.5 | -9.7 14.5 225 18 9 5.2 2.9
15500 -8.6 16.5 250 14 7 4.9 2.7 | -8.9 16.0 225 17 9 5.4 3.0
15000 -8.0 17.6 255 13 7 3.3 1.8 | -8.3 17.1 225 16 8 3.9 2.1
14500 -7.5 18.5 255 12 6 3.5 1.9 | -7.7 18.1 225 15 8 4.1 2.2
14000 -7.1 19.2 250 11 6 3.1 1.7 | -7.2 19.0 225 14 7 3.4 1.8
13500 -6.7 19.9 250 10 5 3.0 1.6 | -6.7 19.9 220 14 7 3.3 1.8
13000 -6.3 20.7 245 9 5 4.2 2.3 | -6.3 20.7 220 13 7 3.9 2.1
12500 -5.6 21.9 245 7 4 4.8 2.6 | -5.7 21.7 210 13 6 4.1 2.3
12000 -4.8 23.4 240 5 3 6.2 3.4 | -5.1 22.8 205 12 6 5.8 3.2
11500 -3.8 25.2 260 3 1 7.1 3.9 | -4.1 24.6 200 9 5 6.7 3.7
11000 -2.8 27.0 330 2 1 8.1 4.4 | -3.1 26.4 190 7 4 8.1 4.5
10500 -1.5 29.3 010 3 2 9.6 5.3 | -1.8 28.8 180 5 3 9.9 5.4
10250 -0.9 30.4 015 4 2 4.0 2.2 | -1.2 29.8 170 4 2 4.1 2.2
10000 -0.7 30.7 015 5 3 5.7 3.1 | -1.0 30.2 160 3 2 5.6 3.1
9750 0.1 32.2 020 5 3 12.3 6.7 | -0.2 31.6 150 4 2 12.4 6.8
9500 1.0 33.8 020 5 3 11.0 6.0 | 0.6 33.1 140 4 2 11.1 6.1
9250 1.8 35.2 025 5 3 9.5 5.2 | 1.5 34.7 135 4 2 9.4 5.1
9000 2.4 36.3 025 5 3 7.4 4.0 | 2.1 35.8 130 5 3 7.7 4.2
8750 3.0 37.4 030 4 2 9.1 5.0 | 2.7 36.9 130 5 3 10.0 5.5
8500 3.8 38.8 030 3 1 10.6 5.8 | 3.5 38.3 135 6 3 11.1 6.1
8250 4.5 40.1 035 2 1 8.1 4.5 | 4.4 39.9 140 6 3 9.2 5.0
8000 5.0 41.0 070 1 1 5.7 3.1 | 4.9 40.8 145 7 4 7.5 4.1
7750 5.5 41.9 110 1 1 6.1 3.3 | 5.6 42.1 145 7 4 8.9 4.9
7500 5.9 42.6 000 0 0 5.7 3.1 | 6.2 43.2 150 7 4 8.4 4.6
7250 6.3 43.3 000 0 0 5.0 2.8 | 6.8 44.2 155 7 4 5.6 3.1
7000 6.7 44.1 285 1 1 4.1 2.3 | 7.1 44.8 155 7 3 3.9 2.2
6750 7.0 44.6 285 2 1 6.3 3.4 | 7.5 45.5 160 6 3 7.4 4.1
6500 7.5 45.5 285 3 1 3.3 1.8 | 8.2 46.8 160 5 3 10.2 5.6
6250 7.4 45.3 270 3 2 -1.5 -0.8 | 8.9 48.0 160 5 3 9.7 5.3
6000 7.4 45.3 260 4 2 -0.2 -0.1 | 9.7 49.5 160 5 2 9.3 5.1
5750 7.3 45.1 250 4 2 -2.6 -1.4 | 10.4 50.7 155 5 2 11.5 6.3
5500 6.7 44.1 235 4 2 -16.5 -9.1 | 11.5 52.7 155 4 2 18.9 10.4
11/18/2025 at 1400 MST | 11/18/2025 at 1700 MST
|
CAPE... 0.0 LI... +6.0 | CAPE... 0.0 LI... +5.6
CINH... 0.0 K Index... +1.0 | CINH... 0.0 K Index... +3.6
|
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 -61.0 -77.8 245 42 21 0.8 0.5 | -61.0 -77.8 240 40 21 0.9 0.5
45000 -59.7 -75.5 240 64 33 1.0 0.6 | -59.4 -74.9 240 62 32 1.9 1.0
40000 -58.0 -72.4 240 76 39 1.1 0.6 | -56.6 -69.9 235 84 43 1.9 1.0
38000 -56.4 -69.5 240 77 40 3.5 1.9 | -54.9 -66.8 235 87 45 3.3 1.8
36000 -54.3 -65.7 235 76 39 3.5 1.9 | -52.9 -63.2 235 88 45 3.3 1.8
34000 -51.2 -60.2 235 73 38 8.9 4.9 | -50.4 -58.7 235 84 43 6.7 3.7
32000 -45.8 -50.4 230 65 34 9.0 4.9 | -46.3 -51.3 230 71 37 6.8 3.7
30000 -40.6 -41.1 230 57 29 8.0 4.4 | -41.1 -42.0 225 57 29 9.4 5.1
29000 -37.6 -35.7 225 51 26 8.0 4.4 | -38.3 -36.9 230 51 26 9.4 5.1
28000 -35.3 -31.5 225 47 24 8.0 4.4 | -35.5 -31.9 230 45 23 9.4 5.2
27000 -33.0 -27.4 225 43 22 6.6 3.6 | -33.0 -27.4 230 40 21 6.0 3.3
26000 -31.0 -23.8 225 40 21 6.7 3.7 | -31.1 -24.0 230 38 20 6.4 3.5
25000 -29.0 -20.2 230 38 20 6.7 3.7 | -29.1 -20.4 235 36 19 6.4 3.5
24000 -26.9 -16.4 235 36 19 8.1 4.5 | -27.2 -17.0 235 34 18 6.8 3.7
23000 -24.4 -11.9 230 33 17 8.4 4.6 | -25.2 -13.4 235 33 17 6.9 3.8
22000 -21.8 -7.2 230 30 15 8.4 4.6 | -23.1 -9.6 235 33 17 6.9 3.8
21000 -19.4 -2.9 225 27 14 7.1 3.9 | -20.9 -5.6 235 32 17 8.4 4.6
20000 -17.2 1.0 225 28 14 7.3 4.0 | -18.4 -1.1 240 33 17 8.3 4.5
19500 -16.1 3.0 225 28 14 7.3 4.0 | -17.2 1.0 240 34 17 8.3 4.5
19000 -15.1 4.8 225 28 15 7.3 4.0 | -15.9 3.4 240 34 18 8.3 4.6
18500 -14.0 6.8 225 28 15 6.5 3.6 | -14.7 5.5 245 35 18 7.6 4.2
18000 -13.0 8.6 225 28 14 6.4 3.5 | -13.6 7.5 245 34 18 7.4 4.1
17500 -12.1 10.2 225 27 14 6.3 3.4 | -12.5 9.5 245 34 17 7.3 4.0
17000 -11.2 11.8 230 26 14 5.9 3.3 | -11.5 11.3 245 33 17 6.7 3.7
16500 -10.3 13.5 230 26 13 6.0 3.3 | -10.5 13.1 245 32 16 6.8 3.7
16000 -9.4 15.1 230 25 13 5.4 3.0 | -9.5 14.9 245 30 16 6.0 3.3
15500 -8.7 16.3 230 25 13 5.4 3.0 | -8.6 16.5 245 28 15 6.1 3.3
15000 -7.9 17.8 230 24 12 5.4 3.0 | -7.5 18.5 250 25 13 4.3 2.4
14500 -6.7 19.9 230 23 12 5.6 3.1 | -6.8 19.8 250 23 12 4.6 2.5
14000 -5.9 21.4 225 22 12 4.3 2.4 | -6.2 20.8 250 20 10 4.1 2.3
13500 -5.3 22.5 225 21 11 4.4 2.4 | -5.7 21.7 250 18 9 4.2 2.3
13000 -4.8 23.4 225 20 10 3.1 1.7 | -5.1 22.8 250 16 8 5.2 2.8
12500 -4.4 24.1 215 18 9 2.8 1.5 | -4.3 24.3 245 13 7 5.4 3.0
12000 -3.9 25.0 210 17 9 4.7 2.6 | -3.5 25.7 235 11 6 4.5 2.5
11500 -3.2 26.2 190 15 8 5.2 2.9 | -2.9 26.8 220 9 5 4.1 2.3
11000 -2.4 27.7 175 15 8 7.4 4.0 | -2.1 28.2 195 8 4 7.8 4.3
10500 -1.2 29.8 165 13 7 8.8 4.8 | -0.8 30.6 180 8 4 9.6 5.3
10250 -0.7 30.7 155 13 6 4.5 2.5 | -0.2 31.6 175 8 4 5.2 2.9
10000 -0.4 31.3 155 12 6 6.8 3.7 | 0.1 32.2 170 8 4 6.5 3.6
9750 0.4 32.7 155 12 6 12.7 7.0 | 0.9 33.6 165 9 5 11.9 6.5
9500 1.3 34.3 150 12 6 11.6 6.4 | 1.7 35.1 160 9 5 10.7 5.9
9250 2.1 35.8 150 11 6 10.1 5.6 | 2.5 36.5 160 10 5 10.1 5.5
9000 2.8 37.0 150 11 6 9.0 4.9 | 3.2 37.8 160 10 5 9.0 4.9
8750 3.6 38.5 150 11 6 10.6 5.8 | 3.9 39.0 160 10 5 9.4 5.1
8500 4.4 39.9 150 11 5 10.8 5.9 | 4.6 40.3 160 11 5 9.4 5.1
8250 5.1 41.2 145 10 5 9.5 5.2 | 5.3 41.5 160 11 6 9.4 5.2
8000 5.8 42.4 145 10 5 8.7 4.8 | 6.0 42.8 155 11 6 9.4 5.2
7750 6.5 43.7 145 10 5 9.4 5.2 | 6.7 44.1 155 11 6 9.1 5.0
7500 7.2 45.0 145 9 5 9.8 5.4 | 7.4 45.3 155 11 6 9.2 5.0
7250 7.9 46.2 145 9 5 10.1 5.5 | 8.1 46.6 155 11 6 9.9 5.4
7000 8.7 47.7 145 9 4 10.3 5.7 | 8.8 47.8 150 11 5 10.0 5.5
6750 9.5 49.1 145 8 4 9.6 5.2 | 9.6 49.3 150 10 5 9.8 5.4
6500 10.2 50.4 140 8 4 9.8 5.4 | 10.3 50.5 150 10 5 9.0 5.0
6250 10.9 51.6 140 8 4 10.6 5.8 | 10.9 51.6 145 9 5 8.5 4.7
6000 11.7 53.1 140 8 4 10.2 5.6 | 11.6 52.9 140 9 4 9.0 5.0
5750 12.5 54.5 140 7 4 10.8 5.9 | 12.2 54.0 135 8 4 7.7 4.2
5500 13.3 55.9 140 7 3 12.8 7.0 | 12.6 54.7 125 6 3 2.2 1.2
________________________________________________________________________________
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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