Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
220
UXUS97 KBOU 261235
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0633 MDT Saturday, April 26, 2025
This forecast is for Saturday, April 26, 2025:
If the trigger temperature of 62.2 F/16.8 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 607 ft/min (3.1 m/s)
Maximum height of thermals.................. 13756 ft MSL (8424 ft AGL)
Forecast maximum temperature................... 75.0 F/24.3 C
Time of trigger temperature.................... 1045 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................. 10985 ft MSL (5654 ft AGL)
Thermal soaring outlook for Sunday 04/27....... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 44862 ft MSL (39530 ft AGL)
Wave soaring outlook for Sunday 04/27.......... Poor
Remarks...
Sunrise/Sunset.................... 06:05:30 / 19:48:53 MDT
Total possible sunshine........... 13 hr 43 min 22 sec (823 min 22 sec)
Altitude of sun at 12:57:12 MDT... 64.01 degrees
Upper air data from numerical model forecast valid on 04/26/2025 at 0600 MDT
Freezing level.................. 13051 ft MSL (7719 ft AGL)
Convective condensation level... 13693 ft MSL (8361 ft AGL)
Lifted condensation level....... 13898 ft MSL (8566 ft AGL)
Lifted index.................... -4.6
K index......................... +15.3
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 -59.1 -74.4 240 43 22 -2.5 -1.4 M M M M M
45000 -62.8 -81.0 235 72 37 -0.9 -0.5 M M M M M
40000 -61.3 -78.3 220 74 38 1.0 0.6 M M M M M
38000 -58.7 -73.7 220 71 36 6.1 3.3 M M M M M
36000 -55.0 -67.0 220 65 33 6.1 3.3 M M M M M
34000 -51.1 -60.0 220 60 31 7.7 4.2 M M M M M
32000 -46.5 -51.7 220 56 29 7.7 4.2 M M M M M
30000 -41.3 -42.3 220 51 26 7.7 4.2 33.9 93.0 7.6 M M
29000 -39.0 -38.2 220 48 25 7.7 4.2 33.0 91.5 7.0 M M
28000 -36.7 -34.1 220 45 23 7.7 4.2 32.3 90.2 6.5 M M
27000 -34.3 -29.7 220 43 22 8.2 4.5 31.6 88.9 6.0 M M
26000 -31.9 -25.4 225 42 22 8.2 4.5 30.9 87.7 5.6 M M
25000 -29.5 -21.1 225 40 21 8.2 4.5 30.4 86.7 5.2 M M
24000 -27.0 -16.6 225 39 20 8.2 4.5 29.9 85.8 4.8 M M
23000 -24.6 -12.3 225 39 20 8.2 4.5 29.2 84.6 4.3 M M
22000 -22.1 -7.8 225 38 20 8.2 4.5 28.7 83.7 4.0 M M
21000 -19.7 -3.5 230 38 20 7.4 4.0 28.1 82.6 3.5 M M
20000 -17.5 0.5 230 39 20 7.4 4.1 27.2 81.0 2.8 M M
19500 -16.4 2.5 230 39 20 7.5 4.1 26.8 80.3 2.4 M M
19000 -15.3 4.5 235 39 20 7.4 4.1 26.5 79.6 2.1 M M
18500 -14.2 6.4 235 40 20 7.9 4.3 26.1 79.0 1.8 M M
18000 -13.1 8.4 235 39 20 7.9 4.3 25.8 78.4 1.5 M M
17500 -11.9 10.6 235 39 20 8.2 4.5 25.5 77.9 1.2 M M
17000 -10.6 12.9 235 37 19 8.5 4.7 25.3 77.5 1.0 M M
16500 -8.7 16.3 235 34 18 8.8 4.8 25.0 77.0 0.7 M M
16000 -7.4 18.7 240 32 17 9.1 5.0 24.8 76.7 0.6 M M
15500 -6.0 21.2 240 30 15 9.1 5.0 24.7 76.5 0.5 M M
15000 -4.7 23.5 240 28 14 8.9 4.9 24.6 76.3 0.4 M M
14500 -3.4 25.9 240 26 14 9.0 4.9 24.5 76.0 0.3 M M
14000 -2.1 28.2 240 25 13 8.3 4.6 24.3 75.7 0.1 M M
13500 -0.9 30.4 240 24 12 8.5 4.6 24.1 75.3 -0.2 573 2.9
13000 0.2 32.4 235 24 12 6.8 3.8 23.7 74.7 -0.5 524 2.7
12500 1.2 34.2 235 24 12 6.7 3.7 23.2 73.8 -1.0 482 2.4
12000 2.1 35.8 230 24 12 6.0 3.3 22.7 72.9 -1.6 440 2.2
11500 2.8 37.0 225 25 13 5.8 3.2 22.1 71.7 -2.3 402 2.0
11000 3.6 38.5 225 26 13 4.5 2.5 21.4 70.5 -3.0 365 1.9
10500 4.1 39.4 225 26 14 4.2 2.3 20.5 68.8 -4.0 335 1.7
10250 4.3 39.7 220 26 14 2.4 1.3 20.0 68.0 -4.5 321 1.6
10000 4.4 39.9 220 27 14 1.4 0.8 19.3 66.8 -5.1 310 1.6
9750 4.5 40.1 220 27 14 2.4 1.3 18.7 65.7 -5.7 299 1.5
9500 4.7 40.5 220 27 14 2.3 1.2 18.1 64.7 -6.4 288 1.5
9250 4.8 40.6 220 27 14 1.9 1.1 17.6 63.6 -7.0 277 1.4
9000 4.9 40.8 215 27 14 1.6 0.9 16.9 62.5 -7.6 266 1.4
8750 5.0 41.0 215 26 13 2.1 1.2 16.3 61.4 -8.2 255 1.3
8500 5.2 41.4 210 25 13 2.1 1.1 15.7 60.3 -8.9 244 1.2
8250 5.3 41.5 210 24 12 2.9 1.6 15.1 59.3 -9.5 232 1.2
8000 5.5 41.9 205 24 12 3.8 2.1 14.7 58.4 -10.0 217 1.1
7750 5.8 42.4 200 23 12 2.7 1.5 14.2 57.5 -10.5 203 1.0
7500 5.9 42.6 200 23 12 2.0 1.1 13.6 56.5 -11.1 191 1.0
7250 6.0 42.8 195 23 12 1.1 0.6 13.0 55.4 -11.7 180 0.9
7000 6.1 43.0 190 23 12 0.1 0.0 12.3 54.1 -12.5 172 0.9
6750 6.1 43.0 185 22 11 0.9 0.5 11.6 52.8 -13.2 164 0.8
6500 6.2 43.2 180 21 11 -0.2 -0.1 10.9 51.6 -13.9 155 0.8
6250 6.1 43.0 175 18 9 -2.1 -1.1 10.0 50.1 -14.8 151 0.8
6000 5.9 42.6 175 14 7 -2.5 -1.4 9.1 48.5 -15.7 148 0.8
5750 5.7 42.3 170 11 6 -1.2 -0.6 8.2 46.8 -16.6 146 0.7
5500 5.6 42.1 160 8 4 -3.4 -1.9 7.4 45.4 -17.5 141 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/26/2025 at 0900 MDT | 04/26/2025 at 1200 MDT
|
CAPE... 0.0 LI... +1.7 | CAPE... +147.1 LI... -0.4
CINH... -1.5 K Index... +12.3 | CINH... -34.5 K Index... +9.5
|
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 -58.8 -73.8 245 37 19 -2.5 -1.4 | -59.1 -74.4 240 31 16 -2.2 -1.2
45000 -62.6 -80.7 240 62 32 1.0 0.5 | -62.4 -80.3 240 60 31 0.4 0.2
40000 -61.6 -78.9 230 61 32 0.6 0.3 | -62.1 -79.8 235 57 30 0.2 0.1
38000 -59.0 -74.2 225 60 31 6.4 3.5 | -59.4 -74.9 235 55 28 6.7 3.7
36000 -55.1 -67.2 225 57 30 6.4 3.5 | -55.4 -67.7 230 53 27 6.7 3.7
34000 -51.0 -59.8 225 55 28 7.9 4.3 | -51.0 -59.8 230 51 26 8.3 4.6
32000 -46.2 -51.2 225 53 27 7.9 4.4 | -45.4 -49.7 230 49 25 8.3 4.6
30000 -40.9 -41.6 225 51 26 7.7 4.2 | -40.4 -40.7 235 47 24 8.3 4.6
29000 -38.7 -37.7 230 49 25 7.7 4.2 | -37.9 -36.2 235 46 24 8.3 4.6
28000 -36.4 -33.5 230 48 24 7.7 4.2 | -35.4 -31.7 235 45 23 8.3 4.6
27000 -34.1 -29.4 230 46 24 7.7 4.2 | -33.0 -27.4 235 45 23 7.6 4.2
26000 -31.7 -25.1 230 45 23 7.7 4.2 | -30.7 -23.3 235 45 23 7.6 4.2
25000 -29.4 -20.9 230 43 22 7.8 4.3 | -28.4 -19.1 235 45 23 7.6 4.2
24000 -27.1 -16.8 230 42 22 8.1 4.4 | -26.2 -15.2 235 45 23 7.6 4.2
23000 -24.7 -12.5 230 42 21 8.1 4.4 | -23.9 -11.0 235 44 23 7.6 4.2
22000 -22.3 -8.1 230 41 21 8.1 4.4 | -21.6 -6.9 235 44 23 7.6 4.2
21000 -19.9 -3.8 230 40 21 7.6 4.1 | -19.4 -2.9 235 43 22 7.5 4.1
20000 -17.6 0.3 235 39 20 7.6 4.2 | -17.1 1.2 235 42 22 7.5 4.1
19500 -16.5 2.3 235 38 20 7.6 4.2 | -16.0 3.2 235 41 21 7.5 4.1
19000 -15.4 4.3 235 38 19 7.7 4.2 | -14.9 5.2 235 41 21 7.6 4.2
18500 -14.3 6.3 235 37 19 6.7 3.7 | -13.8 7.2 235 40 20 7.0 3.9
18000 -13.3 8.1 235 35 18 6.7 3.7 | -12.7 9.1 235 38 20 7.0 3.9
17500 -12.3 9.9 235 33 17 7.0 3.8 | -11.7 10.9 235 36 19 6.9 3.8
17000 -11.3 11.7 235 32 16 7.2 4.0 | -10.7 12.7 235 34 17 6.8 3.7
16500 -9.7 14.5 240 29 15 8.1 4.5 | -9.2 15.4 235 30 16 6.7 3.7
16000 -8.4 16.9 240 27 14 8.7 4.8 | -8.2 17.2 235 28 15 6.6 3.6
15500 -7.1 19.2 240 25 13 8.9 4.9 | -7.3 18.9 235 26 14 6.8 3.7
15000 -5.7 21.7 240 23 12 9.2 5.1 | -6.2 20.8 235 25 13 7.6 4.2
14500 -4.4 24.1 240 22 11 9.2 5.1 | -5.1 22.8 235 23 12 7.5 4.1
14000 -3.0 26.6 240 20 10 9.1 5.0 | -3.9 25.0 230 21 11 8.6 4.7
13500 -1.6 29.1 240 19 10 9.1 5.0 | -2.6 27.3 230 20 10 8.5 4.7
13000 -0.3 31.5 240 17 9 8.7 4.8 | -1.3 29.7 225 18 9 9.3 5.1
12500 1.0 33.8 240 16 8 8.7 4.8 | 0.0 32.0 220 17 9 9.3 5.1
12000 2.2 36.0 240 16 8 7.5 4.1 | 1.4 34.5 220 16 8 9.2 5.1
11500 3.3 37.9 240 15 8 7.3 4.0 | 2.8 37.0 215 16 8 9.3 5.1
11000 4.3 39.7 235 14 7 6.8 3.7 | 4.1 39.4 215 15 8 7.5 4.1
10500 5.2 41.4 235 15 8 7.4 4.1 | 5.1 41.2 210 14 7 5.8 3.2
10250 5.7 42.3 235 16 8 3.6 2.0 | 5.6 42.1 210 14 7 11.9 6.5
10000 5.8 42.4 235 16 8 3.0 1.7 | 6.7 44.1 210 13 7 12.4 6.8
9750 6.2 43.2 235 16 8 6.3 3.5 | 7.3 45.1 215 13 7 6.5 3.6
9500 6.6 43.9 230 17 9 5.9 3.2 | 7.9 46.2 215 12 6 8.7 4.8
9250 7.0 44.6 230 18 9 4.5 2.5 | 8.5 47.3 215 12 6 6.0 3.3
9000 7.2 45.0 230 19 10 2.0 1.1 | 8.8 47.8 210 11 6 5.4 3.0
8750 7.3 45.1 225 20 10 2.1 1.1 | 9.3 48.7 210 11 6 7.1 3.9
8500 7.4 45.3 220 21 11 2.4 1.3 | 9.7 49.5 210 12 6 7.0 3.8
8250 7.5 45.5 220 22 11 1.8 1.0 | 10.2 50.4 205 12 6 6.1 3.4
8000 7.6 45.7 215 23 12 1.3 0.7 | 10.5 50.9 200 11 6 6.0 3.3
7750 7.6 45.7 215 23 12 1.6 0.9 | 11.0 51.8 195 11 6 7.7 4.2
7500 7.7 45.9 210 23 12 1.7 0.9 | 11.5 52.7 190 11 6 8.1 4.4
7250 7.8 46.0 205 23 12 1.5 0.8 | 12.1 53.8 190 11 6 8.6 4.7
7000 7.9 46.2 200 22 11 1.5 0.8 | 12.8 55.0 190 11 5 9.2 5.1
6750 7.9 46.2 195 21 11 1.2 0.7 | 13.4 56.1 190 10 5 8.6 4.7
6500 8.0 46.4 190 19 10 3.3 1.8 | 14.1 57.4 190 10 5 10.0 5.5
6250 8.4 47.1 190 17 9 5.8 3.2 | 14.9 58.8 185 9 5 12.3 6.8
6000 8.8 47.8 190 14 7 4.6 2.5 | 15.9 60.6 190 9 5 13.0 7.1
5750 9.2 48.6 190 12 6 8.6 4.7 | 16.8 62.2 190 8 4 10.5 5.8
5500 10.2 50.4 190 11 5 19.3 10.6 | 17.6 63.7 185 8 4 15.7 8.6
04/26/2025 at 1500 MDT | 04/26/2025 at 1800 MDT
|
CAPE... +98.9 LI... -1.1 | CAPE... +976.6 LI... -4.0
CINH... -9.3 K Index... +22.9 | CINH... -38.0 K Index... +27.1
|
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 -59.7 -75.5 240 32 16 -1.5 -0.8 | -60.3 -76.5 245 30 15 -1.2 -0.6
45000 -61.9 -79.4 240 57 29 0.4 0.2 | -62.0 -79.6 245 56 29 1.0 0.5
40000 -61.6 -78.9 235 51 26 0.3 0.1 | -60.8 -77.4 240 51 26 0.8 0.5
38000 -58.9 -74.0 230 49 25 6.4 3.5 | -58.1 -72.6 240 49 25 6.4 3.5
36000 -55.1 -67.2 230 48 25 6.4 3.5 | -54.2 -65.6 240 48 25 6.4 3.5
34000 -50.9 -59.6 230 47 24 8.4 4.6 | -50.1 -58.2 240 46 24 7.8 4.3
32000 -45.2 -49.4 230 43 22 8.4 4.6 | -44.9 -48.8 235 44 22 7.8 4.3
30000 -40.2 -40.4 230 41 21 8.4 4.6 | -40.1 -40.2 235 42 22 8.0 4.4
29000 -37.6 -35.7 230 41 21 8.4 4.6 | -37.7 -35.9 235 42 22 8.0 4.4
28000 -35.1 -31.2 235 41 21 8.4 4.6 | -35.3 -31.5 235 41 21 8.0 4.4
27000 -32.6 -26.7 235 41 21 8.0 4.4 | -33.0 -27.4 235 41 21 7.5 4.1
26000 -30.2 -22.4 235 42 21 8.0 4.4 | -30.8 -23.4 235 41 21 7.5 4.1
25000 -27.8 -18.0 235 43 22 8.1 4.4 | -28.5 -19.3 235 41 21 7.5 4.1
24000 -25.5 -13.9 235 43 22 7.0 3.8 | -26.3 -15.3 235 41 21 7.7 4.2
23000 -23.4 -10.1 235 44 23 7.0 3.8 | -24.0 -11.2 240 39 20 7.7 4.2
22000 -21.3 -6.3 240 44 23 7.0 3.9 | -21.7 -7.1 240 38 20 7.7 4.2
21000 -19.3 -2.7 240 43 22 6.6 3.6 | -19.5 -3.1 240 36 18 7.6 4.2
20000 -17.3 0.9 240 41 21 6.7 3.7 | -17.2 1.0 240 32 17 7.7 4.2
19500 -16.4 2.5 240 39 20 6.7 3.7 | -16.1 3.0 240 30 16 7.7 4.2
19000 -15.4 4.3 240 38 19 6.7 3.7 | -15.0 5.0 240 29 15 7.7 4.2
18500 -14.3 6.3 240 36 18 7.6 4.2 | -13.9 7.0 240 27 14 7.9 4.3
18000 -13.2 8.2 240 33 17 7.7 4.2 | -12.7 9.1 240 25 13 7.9 4.3
17500 -12.1 10.2 240 30 16 7.7 4.2 | -11.6 11.1 240 24 12 7.9 4.4
17000 -10.4 13.3 245 27 14 7.9 4.3 | -10.4 13.3 235 23 12 8.0 4.4
16500 -9.2 15.4 245 24 12 8.1 4.4 | -8.6 16.5 235 21 11 8.3 4.5
16000 -8.0 17.6 245 22 11 8.3 4.6 | -7.4 18.7 235 20 11 8.6 4.7
15500 -6.8 19.8 245 19 10 8.3 4.6 | -6.1 21.0 230 19 10 8.6 4.7
15000 -5.6 21.9 240 18 9 8.5 4.6 | -4.8 23.4 230 18 10 8.7 4.8
14500 -4.3 24.3 240 16 8 8.4 4.6 | -3.5 25.7 225 18 9 8.7 4.8
14000 -3.1 26.4 235 15 8 8.5 4.7 | -2.2 28.0 225 17 9 9.0 5.0
13500 -1.8 28.8 230 15 7 8.5 4.7 | -0.9 30.4 220 16 8 9.0 4.9
13000 -0.6 30.9 225 14 7 8.6 4.7 | 0.5 32.9 220 15 8 9.2 5.0
12500 0.7 33.3 215 13 7 8.6 4.7 | 1.8 35.2 215 14 7 9.2 5.0
12000 2.0 35.6 205 13 7 9.0 5.0 | 3.2 37.8 210 14 7 9.4 5.1
11500 3.4 38.1 200 13 7 9.2 5.0 | 4.6 40.3 205 14 7 9.5 5.2
11000 4.7 40.5 195 12 6 8.1 4.4 | 6.0 42.8 205 13 7 8.1 4.4
10500 5.8 42.4 190 12 6 6.5 3.6 | 7.1 44.8 200 13 7 6.4 3.5
10250 6.4 43.5 190 12 6 12.4 6.8 | 7.6 45.7 200 13 7 11.8 6.5
10000 7.5 45.5 190 12 6 13.6 7.5 | 8.7 47.7 195 14 7 12.6 6.9
9750 8.3 46.9 190 12 6 8.5 4.7 | 9.3 48.7 190 15 8 7.6 4.1
9500 9.0 48.2 190 12 6 10.1 5.6 | 9.9 49.8 190 15 8 9.3 5.1
9250 9.7 49.5 185 12 6 8.7 4.8 | 10.6 51.1 185 16 8 7.5 4.1
9000 10.3 50.5 180 12 6 9.1 5.0 | 11.1 52.0 190 16 8 7.2 4.0
8750 11.1 52.0 180 12 6 10.3 5.6 | 11.6 52.9 185 18 9 8.4 4.6
8500 11.8 53.2 180 12 6 9.9 5.4 | 12.2 54.0 185 19 10 8.2 4.5
8250 12.5 54.5 180 12 6 10.1 5.5 | 12.8 55.0 180 20 10 7.8 4.3
8000 13.3 55.9 175 13 6 9.8 5.4 | 13.3 55.9 180 23 12 5.8 3.2
7750 14.0 57.2 175 12 6 9.4 5.2 | 13.6 56.5 180 24 12 4.7 2.6
7500 14.7 58.5 175 12 6 9.5 5.2 | 13.9 57.0 175 25 13 4.7 2.6
7250 15.4 59.7 175 12 6 9.0 5.0 | 14.2 57.6 175 25 13 5.0 2.7
7000 16.1 61.0 175 13 6 8.9 4.9 | 14.5 58.1 170 26 13 6.0 3.3
6750 16.8 62.2 175 13 6 10.7 5.9 | 15.1 59.2 170 26 13 9.7 5.3
6500 17.6 63.7 175 12 6 11.6 6.4 | 15.9 60.6 170 24 13 11.7 6.4
6250 18.5 65.3 175 12 6 11.0 6.0 | 16.7 62.1 165 23 12 10.0 5.5
6000 19.3 66.7 175 12 6 11.5 6.3 | 17.4 63.3 165 23 12 9.5 5.2
5750 20.1 68.2 170 12 6 9.0 4.9 | 18.1 64.6 165 23 12 10.3 5.7
5500 20.8 69.4 175 10 5 13.4 7.3 | 19.0 66.2 165 19 10 14.3 7.8
________________________________________________________________________________
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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