Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
505
UXUS97 KBOU 181255
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0651 MDT Monday, August 18, 2025
This forecast is for Monday, August 18, 2025:
If the trigger temperature of 85.6 F/29.8 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1373 ft/min (7.0 m/s)
Maximum height of thermals.................. 17654 ft MSL (12354 ft AGL)
Forecast maximum temperature................... 92.0 F/33.8 C
Time of trigger temperature.................... 1130 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................. 10319 ft MSL (5020 ft AGL)
Thermal soaring outlook for Tuesday 08/19...... 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)................ Weak PVA
Potential height of wave....................... 31182 ft MSL (25882 ft AGL)
Wave soaring outlook for Tuesday 08/19......... Poor
Remarks...
Sunrise/Sunset.................... 06:15:00 / 19:51:26 MDT
Total possible sunshine........... 13 hr 36 min 26 sec (816 min 26 sec)
Altitude of sun at 13:03:13 MDT... 63.05 degrees
Upper air data from numerical model forecast valid on 08/18/2025 at 0600 MDT
Freezing level.................. 16241 ft MSL (10941 ft AGL)
Convective condensation level... 15713 ft MSL (10413 ft AGL)
Lifted condensation level....... 16109 ft MSL (10810 ft AGL)
Lifted index.................... -5.0
K index......................... +29.6
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 -63.5 -82.3 250 17 9 1.5 0.8 M M M M M
45000 -58.7 -73.7 260 27 14 6.3 3.4 M M M M M
40000 -49.3 -56.7 255 30 16 6.2 3.4 M M M M M
38000 -45.6 -50.1 255 30 16 6.2 3.4 M M M M M
36000 -41.9 -43.4 250 31 16 6.2 3.4 M M M M M
34000 -37.6 -35.7 250 32 16 6.4 3.5 M M M M M
32000 -33.7 -28.7 250 32 17 6.5 3.6 M M M M M
30000 -29.5 -21.1 245 29 15 7.1 3.9 46.3 115.4 9.9 M M
29000 -27.3 -17.1 240 28 14 7.1 3.9 45.4 113.7 9.3 M M
28000 -25.3 -13.5 240 26 13 6.0 3.3 44.4 111.9 8.6 M M
27000 -23.5 -10.3 235 24 12 5.9 3.3 42.8 109.0 7.5 M M
26000 -21.7 -7.1 230 21 11 6.0 3.3 41.4 106.5 6.4 M M
25000 -19.9 -3.8 225 19 10 6.2 3.4 40.1 104.1 5.4 M M
24000 -18.0 -0.4 230 19 10 6.7 3.7 38.8 101.9 4.5 M M
23000 -16.0 3.2 230 19 10 6.8 3.7 37.7 99.9 3.6 M M
22000 -14.0 6.8 235 19 10 7.3 4.0 36.8 98.2 2.8 M M
21000 -11.7 10.9 235 19 10 7.9 4.3 36.0 96.8 2.1 M M
20000 -9.4 15.1 235 19 10 8.0 4.4 35.4 95.7 1.5 M M
19500 -8.2 17.2 235 20 10 8.1 4.4 35.1 95.2 1.2 M M
19000 -7.1 19.2 235 19 10 7.9 4.3 34.8 94.7 0.9 M M
18500 -6.0 21.2 235 18 9 8.0 4.4 34.5 94.1 0.5 M M
18000 -4.8 23.4 235 16 8 8.4 4.6 34.2 93.6 0.2 M M
17500 -2.9 26.8 230 15 8 8.6 4.7 33.9 93.1 -0.1 1143 5.8
17000 -1.7 28.9 225 14 7 8.8 4.8 33.8 92.8 -0.3 1090 5.5
16500 -0.4 31.3 225 13 7 8.9 4.9 33.6 92.5 -0.5 1037 5.3
16000 0.9 33.6 220 13 7 8.9 4.9 33.4 92.2 -0.7 984 5.0
15500 2.2 36.0 220 13 6 9.0 4.9 33.3 92.0 -0.8 930 4.7
15000 3.5 38.3 220 13 6 9.1 5.0 33.2 91.7 -1.0 877 4.5
14500 4.7 40.5 220 13 7 8.4 4.6 33.0 91.4 -1.2 824 4.2
14000 6.0 42.8 220 13 7 8.4 4.6 32.8 91.1 -1.5 772 3.9
13500 7.2 45.0 215 14 7 8.7 4.8 32.6 90.7 -1.7 720 3.7
13000 8.5 47.3 215 14 7 8.8 4.8 32.5 90.4 -1.9 666 3.4
12500 9.8 49.6 210 14 7 9.2 5.0 32.3 90.2 -2.0 612 3.1
12000 11.2 52.2 210 14 7 9.4 5.2 32.3 90.1 -2.1 556 2.8
11500 12.6 54.7 210 14 7 8.9 4.9 32.2 90.0 -2.2 499 2.5
11000 13.8 56.8 205 14 7 8.0 4.4 32.0 89.6 -2.4 447 2.3
10500 15.1 59.2 205 13 7 4.1 2.2 31.8 89.2 -2.6 396 2.0
10250 15.2 59.4 205 13 7 5.2 2.9 31.2 88.1 -3.2 384 1.9
10000 16.0 60.8 205 12 6 11.1 6.1 31.2 88.1 -3.2 354 1.8
9750 16.7 62.1 200 12 6 10.1 5.6 31.2 88.1 -3.2 325 1.6
9500 17.4 63.3 200 11 6 8.2 4.5 31.2 88.2 -3.2 295 1.5
9250 17.9 64.2 200 10 5 5.6 3.1 30.9 87.7 -3.5 274 1.4
9000 18.3 64.9 200 9 5 7.1 3.9 30.7 87.2 -3.8 253 1.3
8750 18.9 66.0 200 8 4 8.2 4.5 30.5 86.9 -4.0 229 1.2
8500 19.4 66.9 200 7 3 6.1 3.3 30.4 86.6 -4.2 206 1.0
8250 19.7 67.5 205 5 3 4.3 2.4 30.0 85.9 -4.6 189 1.0
8000 20.0 68.0 210 4 2 4.4 2.4 29.6 85.2 -5.0 172 0.9
7750 20.3 68.5 220 3 1 3.5 1.9 29.1 84.4 -5.5 157 0.8
7500 20.5 68.9 250 2 1 2.1 1.1 28.6 83.5 -6.0 143 0.7
7250 20.6 69.1 295 2 1 0.9 0.5 27.9 82.3 -6.7 133 0.7
7000 20.7 69.3 320 3 1 1.9 1.0 27.3 81.1 -7.4 123 0.6
6750 20.8 69.4 330 4 2 -1.4 -0.7 26.6 79.9 -8.0 114 0.6
6500 20.4 68.7 330 4 2 -6.9 -3.8 25.5 78.0 -9.1 117 0.6
6250 19.8 67.6 330 4 2 -8.8 -4.8 24.2 75.5 -10.5 129 0.7
6000 19.1 66.4 325 4 2 -5.8 -3.2 22.9 73.1 -11.9 140 0.7
5750 18.9 66.0 320 4 2 -1.0 -0.6 21.9 71.4 -13.0 141 0.7
5500 18.8 65.8 280 2 1 -0.8 -0.4 21.1 70.0 -13.8 136 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/18/2025 at 0900 MDT | 08/18/2025 at 1200 MDT
|
CAPE... +123.3 LI... -1.7 | CAPE... +442.3 LI... -2.9
CINH... -347.8 K Index... +28.7 | CINH... -87.1 K Index... +27.2
|
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 -64.1 -83.4 250 16 8 1.6 0.9 | -64.3 -83.7 245 15 8 1.1 0.6
45000 -58.8 -73.8 255 24 12 6.8 3.7 | -59.7 -75.5 260 27 14 6.5 3.6
40000 -48.8 -55.8 260 28 14 6.2 3.4 | -49.6 -57.3 275 35 18 7.4 4.1
38000 -45.1 -49.2 265 27 14 6.2 3.4 | -45.2 -49.4 270 30 16 7.4 4.1
36000 -41.4 -42.5 265 26 13 6.2 3.4 | -40.7 -41.3 265 26 13 7.4 4.0
34000 -37.0 -34.6 260 28 14 6.5 3.6 | -36.0 -32.8 260 28 14 7.0 3.8
32000 -33.1 -27.6 260 30 16 6.4 3.5 | -31.8 -25.2 260 30 15 6.6 3.6
30000 -29.6 -21.3 255 28 14 5.8 3.2 | -28.6 -19.5 255 28 15 5.2 2.9
29000 -27.9 -18.2 250 27 14 5.8 3.2 | -27.0 -16.6 250 28 14 5.2 2.9
28000 -26.1 -15.0 245 25 13 5.8 3.2 | -25.4 -13.7 250 27 14 5.3 2.9
27000 -24.4 -11.9 240 23 12 5.9 3.2 | -23.8 -10.8 245 24 13 5.3 2.9
26000 -22.6 -8.7 235 21 11 5.9 3.3 | -22.2 -8.0 240 22 11 5.3 2.9
25000 -20.9 -5.6 225 20 10 6.4 3.5 | -20.7 -5.3 235 20 10 5.9 3.3
24000 -18.8 -1.8 220 20 10 7.1 3.9 | -18.7 -1.7 235 19 10 6.8 3.7
23000 -16.8 1.8 215 20 11 7.2 4.0 | -16.6 2.1 235 19 10 6.9 3.8
22000 -14.7 5.5 210 21 11 8.3 4.5 | -14.6 5.7 235 18 9 7.7 4.2
21000 -12.1 10.2 210 19 10 8.9 4.9 | -12.3 9.9 235 17 9 8.1 4.4
20000 -9.5 14.9 210 16 8 8.9 4.9 | -9.9 14.2 235 15 8 8.2 4.5
19500 -8.2 17.2 215 15 8 8.7 4.8 | -8.7 16.3 235 15 8 8.3 4.5
19000 -7.1 19.2 215 14 7 6.8 3.7 | -7.5 18.5 235 14 7 8.6 4.7
18500 -6.1 21.0 210 13 7 6.9 3.8 | -6.2 20.8 235 13 7 8.6 4.7
18000 -5.0 23.0 210 13 7 8.4 4.6 | -5.0 23.0 235 12 6 9.2 5.1
17500 -3.0 26.6 210 12 6 9.0 4.9 | -2.8 27.0 230 12 6 9.5 5.2
17000 -1.6 29.1 210 12 6 9.5 5.2 | -1.4 29.5 225 11 6 9.1 5.0
16500 -0.2 31.6 210 11 6 9.7 5.3 | -0.1 31.8 220 11 6 9.0 5.0
16000 1.2 34.2 205 11 5 9.5 5.2 | 1.2 34.2 215 11 6 9.1 5.0
15500 2.6 36.7 205 10 5 8.9 4.9 | 2.5 36.5 210 11 6 9.2 5.0
15000 3.9 39.0 205 10 5 9.0 4.9 | 3.9 39.0 205 11 6 9.2 5.0
14500 5.1 41.2 205 9 5 8.5 4.6 | 5.1 41.2 200 11 6 8.4 4.6
14000 6.4 43.5 205 9 5 8.5 4.7 | 6.3 43.3 200 11 6 8.5 4.7
13500 7.6 45.7 205 9 5 8.6 4.7 | 7.5 45.5 195 12 6 8.4 4.6
13000 8.9 48.0 200 9 5 8.6 4.7 | 8.8 47.8 195 12 6 8.4 4.6
12500 10.1 50.2 200 9 5 8.6 4.7 | 10.0 50.0 195 11 6 8.5 4.6
12000 11.4 52.5 195 9 5 8.6 4.7 | 11.2 52.2 195 11 6 8.5 4.7
11500 12.6 54.7 195 9 5 8.2 4.5 | 12.4 54.3 195 10 5 8.3 4.6
11000 13.8 56.8 195 8 4 7.7 4.2 | 13.7 56.7 195 9 5 8.1 4.5
10500 14.9 58.8 195 8 4 2.8 1.5 | 14.8 58.6 195 8 4 3.6 2.0
10250 15.0 59.0 195 7 4 4.2 2.3 | 15.0 59.0 195 7 4 5.4 3.0
10000 15.7 60.3 200 7 3 11.1 6.1 | 15.7 60.3 200 6 3 11.2 6.2
9750 16.4 61.5 205 6 3 9.7 5.3 | 16.5 61.7 205 5 3 9.9 5.4
9500 17.1 62.8 210 5 3 7.3 4.0 | 17.2 63.0 210 4 2 7.7 4.2
9250 17.4 63.3 210 5 2 4.7 2.6 | 17.6 63.7 220 3 2 5.9 3.2
9000 17.9 64.2 215 4 2 6.9 3.8 | 18.1 64.6 230 2 1 7.8 4.3
8750 18.4 65.1 220 3 2 7.6 4.1 | 18.7 65.7 260 2 1 8.2 4.5
8500 18.9 66.0 230 2 1 6.1 3.4 | 19.3 66.7 295 2 1 6.9 3.8
8250 19.3 66.7 245 1 1 5.3 2.9 | 19.7 67.5 325 2 1 6.2 3.4
8000 19.6 67.3 285 1 0 5.5 3.0 | 20.2 68.4 345 2 1 6.5 3.6
7750 20.0 68.0 330 1 1 4.4 2.4 | 20.6 69.1 005 3 2 6.9 3.8
7500 20.3 68.5 340 2 1 2.1 1.2 | 21.2 70.2 010 3 2 7.5 4.1
7250 20.3 68.5 335 3 1 1.2 0.7 | 21.7 71.1 010 3 2 7.9 4.3
7000 20.4 68.7 330 4 2 1.3 0.7 | 22.3 72.1 010 3 2 7.3 4.0
6750 20.5 68.9 325 5 2 0.9 0.5 | 22.8 73.0 010 3 2 9.1 5.0
6500 20.6 69.1 320 5 2 1.2 0.7 | 23.6 74.5 010 3 2 11.1 6.1
6250 20.6 69.1 310 4 2 0.7 0.4 | 24.4 75.9 010 3 2 10.9 6.0
6000 20.7 69.3 295 4 2 2.8 1.5 | 25.2 77.4 010 3 1 11.0 6.0
5750 21.1 70.0 295 4 2 10.9 6.0 | 26.2 79.2 010 3 1 17.2 9.5
5500 22.2 72.0 290 3 2 17.7 9.7 | 27.9 82.2 010 3 1 27.5 15.1
08/18/2025 at 1500 MDT | 08/18/2025 at 1800 MDT
|
CAPE... +624.9 LI... -4.2 | CAPE... +125.8 LI... -2.1
CINH... -13.9 K Index... +33.8 | CINH... -220.5 K Index... +31.0
|
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 -64.4 -83.9 255 16 8 1.1 0.6 | -64.7 -84.5 265 13 6 0.4 0.2
45000 -59.9 -75.8 270 30 15 6.5 3.6 | -60.4 -76.7 275 27 14 7.1 3.9
40000 -49.3 -56.7 275 42 22 7.9 4.3 | -49.7 -57.5 275 41 21 7.5 4.1
38000 -44.6 -48.3 275 42 22 7.9 4.3 | -44.6 -48.3 275 43 22 7.5 4.1
36000 -39.9 -39.8 275 42 22 7.1 3.9 | -40.1 -40.2 275 44 23 6.4 3.5
34000 -36.0 -32.8 270 36 19 6.5 3.6 | -36.4 -33.5 265 24 12 6.2 3.4
32000 -32.1 -25.8 260 31 16 7.2 4.0 | -32.7 -26.9 215 8 4 8.0 4.4
30000 -28.5 -19.3 250 27 14 6.0 3.3 | -27.7 -17.9 180 9 5 8.4 4.6
29000 -26.7 -16.1 245 25 13 6.0 3.3 | -25.2 -13.4 170 11 5 8.4 4.6
28000 -24.5 -12.1 240 23 12 5.4 3.0 | -23.0 -9.4 165 12 6 5.0 2.7
27000 -22.9 -9.2 240 22 12 5.5 3.0 | -21.4 -6.5 175 12 6 5.4 2.9
26000 -21.2 -6.2 235 22 11 5.5 3.0 | -19.8 -3.6 180 13 7 5.4 2.9
25000 -19.5 -3.1 235 21 11 5.7 3.1 | -18.2 -0.8 185 14 7 5.9 3.3
24000 -17.9 -0.2 240 19 10 5.8 3.2 | -16.2 2.8 195 13 6 6.6 3.6
23000 -16.2 2.8 240 17 9 5.8 3.2 | -14.3 6.3 200 12 6 6.6 3.6
22000 -14.4 6.1 245 15 8 7.6 4.2 | -12.3 9.9 210 11 6 6.4 3.5
21000 -12.1 10.2 240 13 7 8.1 4.4 | -10.5 13.1 220 10 5 6.3 3.4
20000 -9.7 14.5 235 12 6 8.2 4.5 | -8.2 17.2 240 9 5 6.3 3.5
19500 -8.6 16.5 235 11 6 8.3 4.5 | -7.3 18.9 245 9 5 6.9 3.8
19000 -7.3 18.9 230 11 6 8.5 4.7 | -6.2 20.8 250 9 5 7.2 3.9
18500 -6.1 21.0 225 11 6 8.5 4.6 | -5.2 22.6 250 9 5 7.2 3.9
18000 -4.8 23.4 220 11 6 8.9 4.9 | -4.1 24.6 250 9 5 7.7 4.2
17500 -3.5 25.7 215 11 6 8.9 4.9 | -3.0 26.6 250 9 5 7.7 4.2
17000 -2.2 28.0 210 11 6 8.9 4.9 | -1.9 28.6 250 9 5 7.9 4.3
16500 -0.9 30.4 205 12 6 8.8 4.8 | -0.8 30.6 245 9 5 8.0 4.4
16000 0.3 32.5 200 13 7 8.9 4.9 | 0.4 32.7 240 9 5 8.0 4.4
15500 1.6 34.9 195 13 7 8.7 4.8 | 1.5 34.7 240 9 5 7.8 4.3
15000 2.8 37.0 190 14 7 8.7 4.8 | 2.7 36.9 240 8 4 7.7 4.2
14500 4.6 40.3 185 14 7 9.0 4.9 | 3.9 39.0 240 8 4 8.5 4.7
14000 5.9 42.6 185 14 7 9.0 5.0 | 5.1 41.2 245 7 4 8.5 4.6
13500 7.2 45.0 180 14 7 8.8 4.8 | 6.3 43.3 250 6 3 8.2 4.5
13000 8.5 47.3 175 12 6 8.8 4.8 | 7.5 45.5 255 6 3 8.1 4.5
12500 9.8 49.6 175 11 5 9.1 5.0 | 8.7 47.7 260 5 3 8.2 4.5
12000 11.1 52.0 170 8 4 9.1 5.0 | 9.9 49.8 265 4 2 8.2 4.5
11500 12.5 54.5 160 5 3 9.0 4.9 | 11.1 52.0 270 4 2 7.7 4.2
11000 13.8 56.8 155 4 2 9.1 5.0 | 12.1 53.8 275 3 2 7.2 3.9
10500 15.0 59.0 145 3 2 4.8 2.7 | 13.2 55.8 275 3 2 4.7 2.6
10250 15.3 59.5 145 3 2 8.6 4.7 | 13.4 56.1 270 3 2 5.7 3.1
10000 16.2 61.2 145 3 2 13.3 7.3 | 14.1 57.4 265 3 1 9.9 5.4
9750 17.1 62.8 145 3 1 11.9 6.5 | 14.7 58.5 260 2 1 9.3 5.1
9500 18.0 64.4 145 3 1 9.5 5.2 | 15.4 59.7 255 2 1 7.7 4.2
9250 18.6 65.5 145 3 1 8.6 4.7 | 15.9 60.6 240 2 1 6.0 3.3
9000 19.3 66.7 145 3 1 10.6 5.8 | 16.4 61.5 225 2 1 7.8 4.3
8750 20.1 68.2 150 2 1 10.7 5.9 | 17.0 62.6 210 2 1 8.6 4.7
8500 20.9 69.6 150 2 1 9.9 5.4 | 17.7 63.9 195 3 1 7.7 4.2
8250 21.6 70.9 150 2 1 9.4 5.2 | 18.2 64.8 185 3 2 7.7 4.2
8000 22.4 72.3 150 2 1 10.0 5.5 | 18.7 65.7 175 4 2 6.3 3.5
7750 23.1 73.6 150 2 1 10.4 5.7 | 19.1 66.4 170 4 2 3.9 2.1
7500 23.9 75.0 150 2 1 10.2 5.6 | 19.4 66.9 175 5 2 3.6 2.0
7250 24.6 76.3 150 2 1 10.3 5.7 | 19.6 67.3 185 5 3 3.4 1.9
7000 25.4 77.7 150 2 1 10.0 5.5 | 19.8 67.6 190 6 3 4.2 2.3
6750 26.1 79.0 155 1 1 10.1 5.5 | 20.1 68.2 195 6 3 2.7 1.5
6500 26.9 80.4 155 1 1 10.6 5.8 | 20.1 68.2 200 7 4 0.5 0.3
6250 27.7 81.9 155 1 1 10.4 5.7 | 20.1 68.2 210 9 4 -0.2 -0.1
6000 28.5 83.3 155 1 1 11.2 6.2 | 20.1 68.2 215 10 5 3.0 1.6
5750 29.5 85.1 155 1 1 18.0 9.9 | 20.6 69.1 210 9 5 10.6 5.8
5500 31.2 88.2 160 1 0 26.5 14.5 | 21.4 70.5 200 7 4 13.5 7.4
________________________________________________________________________________
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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