Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
119
UXUS97 KBOU 240126
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1926 MDT Monday, June 23, 2025
This forecast is for Tuesday, June 24, 2025:
If the trigger temperature of 78.7 F/26.0 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 10361 ft MSL (5072 ft AGL)
Forecast maximum temperature................... 83.0 F/28.8 C
Time of trigger temperature.................... 1100 MDT
Time of overdevelopment........................ 1200 MDT
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 9043 ft MSL (3754 ft AGL)
Thermal soaring outlook for Wednesday 06/25.... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... Trending the same
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 19097 ft MSL (13808 ft AGL)
Wave soaring outlook for Wednesday 06/25....... Poor
Remarks...
Sunrise/Sunset.................... 05:32:35 / 20:31:33 MDT
Total possible sunshine........... 14 hr 58 min 58 sec (898 min 58 sec)
Altitude of sun at 13:02:04 MDT... 73.62 degrees
Upper air data from numerical model forecast valid on 06/24/2025 at 0600 MDT
Freezing level.................. 15566 ft MSL (10277 ft AGL)
Convective condensation level... 13778 ft MSL (8489 ft AGL)
Lifted condensation level....... 13088 ft MSL (7799 ft AGL)
Lifted index.................... -3.7
K index......................... +24.2
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 -64.6 -84.3 225 56 29 1.2 0.6 M M M M M
45000 -60.5 -76.9 225 80 41 6.1 3.3 M M M M M
40000 -51.3 -60.3 225 84 43 6.7 3.7 M M M M M
38000 -47.2 -53.0 225 79 41 6.7 3.7 M M M M M
36000 -43.2 -45.8 220 74 38 6.7 3.7 M M M M M
34000 -38.5 -37.3 220 67 34 7.0 3.9 M M M M M
32000 -34.2 -29.6 225 61 31 7.0 3.8 M M M M M
30000 -29.8 -21.6 225 56 29 7.5 4.1 46.4 115.6 13.8 M M
29000 -27.5 -17.5 225 53 27 7.5 4.1 45.6 114.1 13.3 M M
28000 -25.3 -13.5 225 51 26 7.4 4.1 44.8 112.7 12.9 M M
27000 -23.1 -9.6 225 47 24 7.4 4.1 43.8 110.9 12.2 M M
26000 -20.8 -5.4 230 43 22 7.4 4.1 42.9 109.3 11.7 M M
25000 -18.6 -1.5 230 40 20 7.3 4.0 42.2 107.9 11.2 M M
24000 -17.2 1.0 230 38 20 4.2 2.3 40.3 104.5 9.7 M M
23000 -15.9 3.4 230 37 19 4.3 2.4 38.2 100.8 8.1 M M
22000 -14.7 5.5 230 36 19 4.9 2.7 36.4 97.5 6.6 M M
21000 -12.8 9.0 230 34 18 7.0 3.9 35.2 95.4 5.6 M M
20000 -10.7 12.7 225 32 17 7.1 3.9 34.3 93.7 4.8 M M
19500 -9.7 14.5 225 31 16 7.0 3.8 33.8 92.9 4.4 M M
19000 -8.6 16.5 225 30 15 8.5 4.6 33.5 92.3 4.1 M M
18500 -7.4 18.7 225 29 15 8.5 4.7 33.3 91.9 3.9 M M
18000 -6.1 21.0 220 27 14 8.5 4.7 33.1 91.5 3.7 M M
17500 -4.9 23.2 215 26 13 8.5 4.6 32.8 91.1 3.4 M M
17000 -3.1 26.4 210 24 13 8.3 4.5 32.5 90.5 3.1 M M
16500 -2.0 28.4 200 23 12 7.9 4.3 32.2 90.0 2.8 M M
16000 -0.8 30.6 195 23 12 7.9 4.3 31.9 89.4 2.5 M M
15500 0.4 32.7 195 22 11 8.7 4.8 31.7 89.0 2.3 M M
15000 1.7 35.1 195 21 11 8.6 4.7 31.5 88.6 2.1 M M
14500 3.0 37.4 195 20 10 8.9 4.9 31.3 88.3 2.0 M M
14000 4.4 39.9 195 19 10 9.0 4.9 31.2 88.1 1.9 M M
13500 5.7 42.3 195 17 9 8.8 4.8 31.0 87.9 1.8 M M
13000 7.0 44.6 195 16 8 8.7 4.8 30.9 87.5 1.6 M M
12500 8.3 46.9 200 16 8 8.5 4.7 30.7 87.2 1.4 M M
12000 9.5 49.1 200 15 8 8.3 4.6 30.5 86.8 1.2 M M
11500 10.8 51.4 200 14 7 8.1 4.4 30.2 86.4 1.0 M M
11000 11.9 53.4 200 13 7 7.3 4.0 29.9 85.8 0.6 M M
10500 12.9 55.2 200 13 6 5.0 2.7 29.5 85.2 0.2 M M
10250 13.1 55.6 200 12 6 2.0 1.1 29.0 84.1 -0.3 331 1.7
10000 13.3 55.9 200 12 6 4.3 2.3 28.4 83.2 -0.9 318 1.6
9750 13.6 56.5 200 11 6 5.6 3.1 28.1 82.5 -1.3 302 1.5
9500 13.9 57.0 205 10 5 3.6 2.0 27.7 81.9 -1.8 286 1.5
9250 13.9 57.0 205 10 5 0.5 0.3 27.1 80.8 -2.4 277 1.4
9000 13.9 57.0 205 10 5 0.3 0.2 26.3 79.4 -3.2 270 1.4
8750 13.9 57.0 210 9 5 0.8 0.4 25.6 78.1 -4.0 264 1.3
8500 13.8 56.8 210 9 5 0.5 0.3 24.9 76.9 -4.7 258 1.3
8250 13.8 56.8 215 9 5 0.1 0.1 24.2 75.5 -5.5 251 1.3
8000 13.8 56.8 220 9 5 0.2 0.1 23.4 74.2 -6.3 244 1.2
7750 13.7 56.7 220 10 5 0.3 0.2 22.7 72.9 -7.1 238 1.2
7500 13.7 56.7 225 10 5 1.8 1.0 22.0 71.7 -7.8 231 1.2
7250 13.9 57.0 230 9 5 2.7 1.5 21.5 70.7 -8.4 219 1.1
7000 14.1 57.4 235 9 5 3.0 1.7 20.9 69.7 -9.0 207 1.0
6750 14.3 57.7 240 8 4 4.4 2.4 20.5 68.9 -9.5 192 1.0
6500 14.5 58.1 240 7 4 2.5 1.4 20.0 68.1 -10.0 177 0.9
6250 14.6 58.3 240 6 3 1.3 0.7 19.4 66.9 -10.7 167 0.8
6000 14.7 58.5 240 5 3 0.3 0.1 18.8 65.8 -11.4 157 0.8
5750 14.6 58.3 245 4 2 -0.6 -0.3 18.0 64.4 -12.2 152 0.8
5500 14.7 58.5 255 2 1 2.6 1.4 17.3 63.1 -12.9 143 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/24/2025 at 0900 MDT | 06/24/2025 at 1200 MDT
|
CAPE... +449.1 LI... -3.1 | CAPE... +1133.1 LI... -5.1
CINH... -249.6 K Index... +23.7 | CINH... -72.9 K Index... +24.8
|
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 -64.6 -84.3 225 54 28 1.3 0.7 | -65.1 -85.2 220 55 28 1.6 0.9
45000 -60.5 -76.9 225 77 40 5.8 3.2 | -60.8 -77.4 225 76 39 5.8 3.2
40000 -51.6 -60.9 220 83 43 7.0 3.9 | -51.3 -60.3 220 83 43 7.6 4.2
38000 -47.3 -53.1 220 82 42 7.1 3.9 | -46.7 -52.1 215 81 42 7.6 4.1
36000 -42.5 -44.5 215 80 41 7.0 3.8 | -42.2 -44.0 215 80 41 7.5 4.1
34000 -38.5 -37.3 220 71 37 6.8 3.7 | -38.2 -36.8 215 72 37 6.5 3.6
32000 -34.4 -29.9 220 63 32 6.7 3.7 | -34.3 -29.7 220 64 33 6.5 3.6
30000 -30.1 -22.2 225 55 28 7.1 3.9 | -30.1 -22.2 220 56 29 7.1 3.9
29000 -28.0 -18.4 225 51 26 7.1 3.9 | -28.0 -18.4 220 52 27 7.1 3.9
28000 -25.9 -14.6 225 48 24 7.0 3.9 | -25.9 -14.6 220 48 25 7.0 3.8
27000 -23.8 -10.8 225 45 23 7.0 3.9 | -23.3 -9.9 220 45 23 6.8 3.7
26000 -21.7 -7.1 220 42 22 7.0 3.9 | -21.3 -6.3 215 42 22 6.9 3.8
25000 -19.6 -3.3 220 40 21 7.0 3.8 | -19.3 -2.7 215 39 20 6.5 3.6
24000 -18.0 -0.4 220 38 19 5.3 2.9 | -17.6 0.3 215 37 19 5.8 3.2
23000 -16.4 2.5 220 36 19 5.4 3.0 | -15.9 3.4 215 35 18 5.9 3.2
22000 -14.9 5.2 225 34 18 5.9 3.2 | -14.2 6.4 215 33 17 6.5 3.6
21000 -12.9 8.8 225 32 16 7.1 3.9 | -12.2 10.0 215 31 16 7.1 3.9
20000 -10.8 12.6 225 29 15 7.1 3.9 | -10.1 13.8 215 28 15 7.2 3.9
19500 -9.7 14.5 225 28 14 7.0 3.8 | -9.1 15.6 215 27 14 7.2 3.9
19000 -8.6 16.5 225 27 14 8.1 4.5 | -8.0 17.6 215 26 13 7.9 4.4
18500 -6.8 19.8 225 24 13 8.1 4.4 | -6.8 19.8 210 25 13 7.9 4.3
18000 -5.6 21.9 225 23 12 8.6 4.7 | -5.7 21.7 210 24 12 8.1 4.4
17500 -4.3 24.3 220 22 11 8.6 4.7 | -4.5 23.9 210 23 12 8.2 4.5
17000 -3.1 26.4 220 21 11 8.7 4.8 | -3.2 26.2 205 22 11 8.2 4.5
16500 -1.8 28.8 215 21 11 8.9 4.9 | -2.0 28.4 205 21 11 8.5 4.6
16000 -0.5 31.1 210 20 10 8.9 4.9 | -0.8 30.6 210 21 11 8.4 4.6
15500 0.8 33.4 210 19 10 8.7 4.8 | 0.5 32.9 210 20 10 8.6 4.7
15000 2.1 35.8 205 19 10 8.8 4.8 | 1.8 35.2 210 19 10 8.6 4.7
14500 3.4 38.1 205 19 10 8.7 4.8 | 3.0 37.4 210 19 10 8.6 4.7
14000 4.7 40.5 200 18 10 8.7 4.8 | 4.9 40.8 210 18 9 8.5 4.6
13500 6.0 42.8 200 18 9 8.6 4.7 | 6.2 43.2 215 18 9 8.8 4.8
13000 7.2 45.0 200 18 9 8.5 4.7 | 7.5 45.5 215 17 9 8.9 4.9
12500 8.5 47.3 200 17 9 8.4 4.6 | 8.8 47.8 215 17 9 8.7 4.8
12000 9.7 49.5 200 17 9 8.3 4.6 | 10.0 50.0 215 16 8 8.6 4.7
11500 10.9 51.6 205 16 8 8.0 4.4 | 11.3 52.3 220 16 8 8.3 4.6
11000 12.0 53.6 205 15 8 7.3 4.0 | 12.4 54.3 215 15 8 7.7 4.2
10500 13.1 55.6 205 14 7 4.5 2.5 | 13.6 56.5 210 14 7 2.7 1.5
10250 13.2 55.8 205 14 7 2.9 1.6 | 13.6 56.5 215 14 7 1.3 0.7
10000 13.6 56.5 205 13 7 6.9 3.8 | 13.9 57.0 210 12 6 6.7 3.7
9750 14.1 57.4 205 12 6 8.0 4.4 | 14.2 57.6 200 11 6 6.1 3.3
9500 14.6 58.3 205 11 6 5.6 3.1 | 14.6 58.3 190 10 5 3.8 2.1
9250 14.9 58.8 205 11 6 2.4 1.3 | 14.6 58.3 185 9 5 1.0 0.6
9000 15.0 59.0 205 11 5 1.6 0.9 | 14.7 58.5 180 9 4 3.8 2.1
8750 15.0 59.0 200 9 5 1.8 1.0 | 15.0 59.0 165 7 4 5.0 2.8
8500 15.0 59.0 200 8 4 0.3 0.2 | 15.2 59.4 150 7 4 4.8 2.7
8250 14.9 58.8 200 8 4 -1.3 -0.7 | 15.5 59.9 140 7 3 4.1 2.2
8000 14.7 58.5 200 7 4 -1.6 -0.9 | 15.8 60.4 135 6 3 6.8 3.7
7750 14.4 57.9 200 6 3 -2.8 -1.5 | 16.4 61.5 130 6 3 9.8 5.4
7500 14.2 57.6 195 5 3 -0.6 -0.4 | 17.0 62.6 125 5 3 7.7 4.2
7250 14.2 57.6 195 4 2 1.1 0.6 | 17.4 63.3 120 5 3 5.3 2.9
7000 14.2 57.6 190 3 2 1.0 0.6 | 17.9 64.2 115 5 2 9.3 5.1
6750 14.4 57.9 180 2 1 6.6 3.6 | 18.8 65.8 110 5 2 14.7 8.1
6500 15.0 59.0 165 2 1 9.1 5.0 | 19.8 67.6 110 4 2 12.0 6.6
6250 15.6 60.1 155 2 1 8.7 4.8 | 20.6 69.1 110 4 2 11.2 6.1
6000 16.2 61.2 140 2 1 5.4 2.9 | 21.4 70.5 105 4 2 6.9 3.8
5750 16.5 61.7 130 1 1 8.8 4.8 | 21.9 71.4 090 3 2 11.3 6.2
5500 17.8 64.0 120 1 0 25.6 14.0 | 23.5 74.3 085 3 2 33.3 18.3
06/24/2025 at 1500 MDT | 06/24/2025 at 1800 MDT
|
CAPE... +721.4 LI... -3.3 | CAPE... +388.3 LI... -2.3
CINH... -22.5 K Index... +34.1 | CINH... -80.6 K Index... +29.0
|
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 -65.2 -85.4 220 57 29 1.8 1.0 | -65.7 -86.3 220 51 26 2.3 1.3
45000 -60.7 -77.3 220 75 39 5.7 3.1 | -60.7 -77.3 220 66 34 5.6 3.0
40000 -51.3 -60.3 220 81 42 7.7 4.2 | -51.3 -60.3 215 74 38 8.3 4.6
38000 -46.7 -52.1 215 80 41 7.7 4.2 | -46.3 -51.3 210 72 37 8.3 4.6
36000 -42.0 -43.6 215 79 41 7.6 4.2 | -41.3 -42.3 205 71 37 8.0 4.4
34000 -37.7 -35.9 215 70 36 7.1 3.9 | -36.7 -34.1 205 66 34 7.6 4.2
32000 -33.4 -28.1 220 61 31 7.0 3.9 | -32.2 -26.0 205 60 31 7.4 4.1
30000 -29.2 -20.6 215 52 27 7.2 3.9 | -28.0 -18.4 210 52 27 7.0 3.8
29000 -27.1 -16.8 215 48 25 7.2 3.9 | -25.9 -14.6 210 48 25 7.0 3.8
28000 -24.9 -12.8 215 44 23 7.4 4.0 | -23.8 -10.8 215 44 22 7.1 3.9
27000 -22.2 -8.0 215 41 21 7.5 4.1 | -21.2 -6.2 215 39 20 7.1 3.9
26000 -20.0 -4.0 215 39 20 7.6 4.1 | -19.1 -2.4 215 35 18 7.1 3.9
25000 -17.8 -0.0 215 36 19 7.3 4.0 | -17.0 1.4 220 31 16 6.9 3.8
24000 -15.7 3.7 215 34 17 6.9 3.8 | -15.1 4.8 220 29 15 6.6 3.6
23000 -13.7 7.3 215 31 16 6.9 3.8 | -13.2 8.2 225 27 14 6.6 3.6
22000 -11.7 10.9 210 28 14 6.7 3.7 | -11.3 11.7 225 24 13 6.5 3.6
21000 -9.9 14.2 210 25 13 6.5 3.5 | -9.4 15.1 230 24 13 6.3 3.5
20000 -8.0 17.6 210 22 12 6.5 3.6 | -7.6 18.3 235 25 13 6.4 3.5
19500 -7.1 19.2 210 21 11 6.5 3.6 | -6.7 19.9 235 25 13 6.4 3.5
19000 -6.2 20.8 210 20 10 6.1 3.4 | -5.8 21.6 240 25 13 5.7 3.1
18500 -5.3 22.5 210 18 9 6.2 3.4 | -5.0 23.0 240 25 13 5.8 3.2
18000 -4.4 24.1 205 17 9 6.1 3.3 | -4.1 24.6 240 26 13 6.2 3.4
17500 -3.5 25.7 205 16 8 6.0 3.3 | -3.2 26.2 245 26 13 6.5 3.6
17000 -2.7 27.1 200 15 8 6.0 3.3 | -2.2 28.0 245 26 13 6.5 3.6
16500 -1.8 28.8 195 14 7 6.7 3.7 | -1.2 29.8 245 26 13 7.4 4.1
16000 -0.8 30.6 195 14 7 6.7 3.7 | -0.2 31.6 245 25 13 7.3 4.0
15500 0.2 32.4 195 13 7 7.2 3.9 | 0.9 33.6 245 24 13 7.5 4.1
15000 1.2 34.2 190 12 6 7.3 4.0 | 2.0 35.6 250 23 12 7.5 4.1
14500 2.2 36.0 190 12 6 7.4 4.1 | 3.1 37.6 250 22 11 7.4 4.1
14000 3.3 37.9 185 11 6 7.6 4.2 | 4.1 39.4 245 20 11 7.2 4.0
13500 4.4 39.9 185 10 5 7.7 4.2 | 5.1 41.2 245 19 10 7.3 4.0
13000 5.5 41.9 185 9 5 7.8 4.3 | 6.2 43.2 240 17 9 7.7 4.2
12500 6.6 43.9 180 8 4 7.8 4.3 | 7.9 46.2 235 15 8 7.1 3.9
12000 8.2 46.8 170 7 3 7.9 4.3 | 8.8 47.8 230 14 7 6.5 3.6
11500 9.4 48.9 155 6 3 7.7 4.2 | 9.7 49.5 220 13 7 6.2 3.4
11000 10.4 50.7 140 5 2 7.2 3.9 | 10.5 50.9 215 12 6 5.6 3.1
10500 11.5 52.7 120 4 2 2.6 1.4 | 11.3 52.3 205 12 6 2.4 1.3
10250 11.5 52.7 115 4 2 4.1 2.2 | 11.3 52.3 205 11 6 2.8 1.6
10000 12.3 54.1 100 3 2 11.0 6.1 | 11.8 53.2 200 10 5 8.3 4.6
9750 13.0 55.4 080 3 2 10.1 5.5 | 12.4 54.3 195 10 5 8.5 4.7
9500 13.7 56.7 065 3 2 7.0 3.8 | 12.9 55.2 190 9 4 6.2 3.4
9250 14.0 57.2 050 3 2 4.3 2.3 | 13.3 55.9 185 8 4 3.1 1.7
9000 14.6 58.3 040 4 2 9.6 5.2 | 13.6 56.5 185 7 4 6.1 3.4
8750 15.4 59.7 030 4 2 12.1 6.6 | 14.2 57.6 175 6 3 9.3 5.1
8500 16.2 61.2 025 5 2 8.9 4.9 | 14.7 58.5 165 5 3 5.6 3.1
8250 16.7 62.1 020 5 2 5.7 3.1 | 15.0 59.0 155 5 3 2.3 1.3
8000 17.2 63.0 015 5 3 9.5 5.2 | 15.2 59.4 145 5 3 4.4 2.4
7750 18.1 64.6 015 5 3 12.4 6.8 | 15.5 59.9 125 5 2 6.0 3.3
7500 18.9 66.0 015 5 3 9.3 5.1 | 15.9 60.6 110 5 3 4.6 2.5
7250 19.5 67.1 015 5 3 6.9 3.8 | 16.2 61.2 100 6 3 3.4 1.9
7000 20.1 68.2 015 5 3 9.9 5.4 | 16.4 61.5 095 6 3 3.7 2.0
6750 21.0 69.8 015 5 3 13.3 7.3 | 16.7 62.1 090 8 4 5.4 3.0
6500 21.9 71.4 010 5 3 11.2 6.1 | 17.1 62.8 085 8 4 6.9 3.8
6250 22.7 72.9 010 6 3 10.5 5.8 | 17.6 63.7 085 8 4 7.5 4.1
6000 23.4 74.1 010 6 3 8.2 4.5 | 18.1 64.6 090 9 4 5.0 2.8
5750 24.0 75.2 010 5 3 12.5 6.9 | 18.5 65.3 090 9 4 9.2 5.0
5500 25.5 77.9 010 5 3 27.8 15.2 | 19.6 67.3 090 8 4 23.2 12.7
________________________________________________________________________________
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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