Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
217
UXUS97 KBOU 190128
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1927 MDT Wednesday, June 18, 2025
This forecast is for Thursday, June 19, 2025:
If the trigger temperature of 85.1 F/29.5 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1435 ft/min (7.3 m/s)
Maximum height of thermals.................. 20414 ft MSL (15101 ft AGL)
Forecast maximum temperature................... 96.0 F/36.0 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................. 14971 ft MSL (9658 ft AGL)
Thermal soaring outlook for Friday 06/20....... 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....................... 16152 ft MSL (10839 ft AGL)
Wave soaring outlook for Friday 06/20.......... Poor
Remarks...
Sunrise/Sunset.................... 05:31:19 / 20:30:38 MDT
Total possible sunshine........... 14 hr 59 min 19 sec (899 min 19 sec)
Altitude of sun at 13:00:59 MDT... 73.66 degrees
Upper air data from numerical model forecast valid on 06/19/2025 at 0600 MDT
Freezing level.................. 16369 ft MSL (11056 ft AGL)
Convective condensation level... 17878 ft MSL (12565 ft AGL)
Lifted condensation level....... 18714 ft MSL (13400 ft AGL)
Lifted index.................... -2.8
K index......................... +10.9
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 -65.3 -85.5 305 35 18 0.2 0.1 M M M M M
45000 -62.4 -80.3 305 46 24 6.0 3.3 M M M M M
40000 -53.2 -63.8 310 49 25 7.3 4.0 M M M M M
38000 -48.8 -55.8 310 46 23 7.4 4.0 M M M M M
36000 -44.3 -47.7 305 42 22 7.4 4.1 M M M M M
34000 -39.6 -39.3 300 38 20 7.0 3.8 M M M M M
32000 -35.4 -31.7 295 35 18 7.0 3.9 M M M M M
30000 -30.8 -23.4 290 31 16 7.7 4.2 44.6 112.2 6.9 M M
29000 -28.5 -19.3 285 29 15 7.7 4.2 43.8 110.9 6.4 M M
28000 -26.2 -15.2 280 26 14 7.3 4.0 43.1 109.6 5.9 M M
27000 -24.0 -11.2 280 24 12 7.3 4.0 42.1 107.7 5.1 M M
26000 -21.9 -7.4 275 22 11 7.3 4.0 41.1 106.0 4.5 M M
25000 -19.7 -3.5 265 20 10 7.2 4.0 40.3 104.6 3.8 M M
24000 -17.5 0.5 265 20 10 7.1 3.9 39.3 102.7 3.0 M M
23000 -15.4 4.3 270 20 11 7.1 3.9 38.3 101.0 2.3 M M
22000 -13.3 8.1 270 21 11 7.0 3.8 37.5 99.5 1.6 M M
21000 -11.2 11.8 270 19 10 6.8 3.7 36.4 97.4 0.6 M M
20000 -9.2 15.4 275 17 9 6.9 3.8 35.3 95.6 -0.3 1406 7.1
19500 -8.2 17.2 275 17 9 6.7 3.7 34.9 94.8 -0.7 1361 6.9
19000 -7.1 19.2 280 16 8 8.7 4.8 34.5 94.2 -1.0 1312 6.7
18500 -5.8 21.6 280 16 8 8.5 4.7 34.3 93.8 -1.3 1260 6.4
18000 -4.6 23.7 285 16 8 8.7 4.8 34.1 93.4 -1.5 1207 6.1
17500 -2.6 27.3 295 17 9 8.9 4.9 33.9 93.0 -1.7 1125 5.7
17000 -1.3 29.7 300 18 9 8.5 4.7 33.8 92.8 -1.8 1070 5.4
16500 -0.1 31.8 305 18 9 8.3 4.5 33.5 92.3 -2.1 1020 5.2
16000 1.1 34.0 305 19 10 8.3 4.6 33.2 91.8 -2.4 970 4.9
15500 2.3 36.1 305 19 10 8.1 4.5 33.0 91.3 -2.7 920 4.7
15000 3.5 38.3 305 19 10 8.2 4.5 32.7 90.9 -3.0 870 4.4
14500 4.6 40.3 305 19 10 8.5 4.7 32.5 90.4 -3.3 819 4.2
14000 5.9 42.6 305 18 9 8.5 4.7 32.3 90.1 -3.5 767 3.9
13500 7.2 45.0 305 17 9 8.4 4.6 32.1 89.7 -3.7 714 3.6
13000 8.4 47.1 305 17 9 8.4 4.6 31.8 89.3 -4.0 662 3.4
12500 9.7 49.5 305 16 8 8.5 4.7 31.6 88.9 -4.2 610 3.1
12000 11.0 51.8 305 15 8 8.6 4.7 31.4 88.6 -4.4 556 2.8
11500 12.3 54.1 305 14 7 8.5 4.7 31.3 88.3 -4.6 503 2.6
11000 13.5 56.3 305 13 7 8.1 4.5 31.0 87.8 -4.8 450 2.3
10500 14.7 58.5 305 12 6 5.2 2.8 30.8 87.5 -5.1 398 2.0
10250 15.0 59.0 305 12 6 6.1 3.3 30.3 86.6 -5.5 383 1.9
10000 15.7 60.3 300 11 6 10.6 5.8 30.3 86.6 -5.6 354 1.8
9750 16.4 61.5 300 10 5 9.8 5.4 30.3 86.6 -5.6 326 1.7
9500 17.1 62.8 300 10 5 8.6 4.7 30.3 86.6 -5.7 297 1.5
9250 17.7 63.9 300 10 5 6.6 3.6 30.1 86.2 -5.9 274 1.4
9000 18.2 64.8 300 9 5 7.8 4.3 29.9 85.9 -6.1 251 1.3
8750 18.8 65.8 300 9 5 8.8 4.8 29.8 85.7 -6.3 226 1.1
8500 19.4 66.9 300 9 4 8.2 4.5 29.7 85.5 -6.4 201 1.0
8250 19.9 67.8 300 9 4 7.7 4.2 29.6 85.2 -6.6 178 0.9
8000 20.4 68.7 300 8 4 7.8 4.3 29.4 85.0 -6.9 155 0.8
7750 21.0 69.8 300 8 4 8.3 4.5 29.3 84.7 -7.1 131 0.7
7500 21.5 70.7 295 8 4 7.0 3.8 29.2 84.5 -7.3 107 0.5
7250 21.9 71.4 290 8 4 5.7 3.1 28.9 83.9 -7.6 88 0.4
7000 22.3 72.1 280 8 4 6.3 3.4 28.6 83.4 -8.0 68 0.3
6750 22.6 72.7 270 8 4 2.4 1.3 28.2 82.8 -8.4 51 0.3
6500 22.5 72.5 260 9 4 -6.4 -3.5 27.3 81.2 -9.3 48 0.2
6250 21.7 71.1 255 9 5 -11.2 -6.1 25.9 78.6 -10.8 64 0.3
6000 20.9 69.6 245 9 5 -6.1 -3.3 24.4 75.9 -12.4 80 0.4
5750 20.4 68.7 240 10 5 -12.8 -7.0 23.2 73.7 -13.6 88 0.4
5500 18.4 65.1 230 8 4 -38.7 -21.2 20.5 69.0 -16.4 142 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/19/2025 at 0900 MDT | 06/19/2025 at 1200 MDT
|
CAPE... +6.3 LI... +1.5 | CAPE... +18.0 LI... +0.1
CINH... -46.1 K Index... +7.9 | CINH... -38.8 K Index... +7.9
|
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 -65.0 -85.0 305 33 17 1.4 0.8 | -65.3 -85.5 310 30 16 2.5 1.3
45000 -61.2 -78.2 300 46 23 5.1 2.8 | -60.6 -77.1 310 43 22 4.7 2.6
40000 -53.2 -63.8 305 47 24 7.4 4.1 | -52.6 -62.7 305 44 23 7.5 4.1
38000 -48.7 -55.7 310 46 24 7.5 4.1 | -48.1 -54.6 305 42 22 7.4 4.1
36000 -43.6 -46.5 310 46 24 7.4 4.1 | -43.7 -46.7 305 41 21 7.4 4.1
34000 -39.3 -38.7 310 39 20 7.3 4.0 | -39.2 -38.6 300 37 19 7.4 4.1
32000 -34.9 -30.8 305 33 17 7.4 4.1 | -34.8 -30.6 295 34 17 7.3 4.0
30000 -30.2 -22.4 295 28 15 7.8 4.3 | -30.1 -22.2 285 28 14 7.9 4.3
29000 -27.8 -18.0 295 27 14 7.8 4.3 | -27.1 -16.8 280 24 13 7.9 4.4
28000 -25.5 -13.9 290 25 13 7.3 4.0 | -24.8 -12.6 275 22 12 7.3 4.0
27000 -23.4 -10.1 280 23 12 7.2 3.9 | -22.6 -8.7 270 23 12 7.4 4.0
26000 -21.2 -6.2 270 22 12 7.2 3.9 | -20.4 -4.7 265 24 12 7.4 4.0
25000 -19.0 -2.2 260 22 11 6.9 3.8 | -18.2 -0.8 260 25 13 5.9 3.2
24000 -17.3 0.9 260 22 11 5.8 3.2 | -16.9 1.6 260 26 13 4.2 2.3
23000 -15.5 4.1 260 22 12 5.8 3.2 | -15.7 3.7 255 28 14 4.3 2.3
22000 -13.8 7.2 255 22 12 6.3 3.5 | -14.4 6.1 255 29 15 6.1 3.4
21000 -11.7 10.9 260 21 11 7.2 3.9 | -12.3 9.9 255 26 13 7.6 4.2
20000 -9.6 14.7 270 19 10 7.2 3.9 | -10.1 13.8 260 23 12 7.7 4.2
19500 -8.5 16.7 275 19 10 7.1 3.9 | -9.0 15.8 265 22 11 7.9 4.3
19000 -7.3 18.9 275 18 9 8.6 4.7 | -7.7 18.1 265 21 11 9.2 5.1
18500 -6.1 21.0 275 17 9 8.5 4.6 | -6.4 20.5 270 20 10 9.1 5.0
18000 -4.2 24.4 280 16 8 8.4 4.6 | -5.0 23.0 270 19 10 8.8 4.8
17500 -2.9 26.8 280 15 8 8.4 4.6 | -3.6 25.5 270 18 9 8.7 4.8
17000 -1.7 28.9 285 14 7 8.4 4.6 | -2.3 27.9 270 17 9 8.7 4.8
16500 -0.5 31.1 290 14 7 8.4 4.6 | -1.0 30.2 275 16 8 8.9 4.9
16000 0.8 33.4 295 14 7 8.5 4.7 | 0.4 32.7 275 15 7 8.9 4.9
15500 2.0 35.6 295 14 7 9.0 4.9 | 1.7 35.1 280 14 7 9.0 4.9
15000 3.4 38.1 300 14 7 8.9 4.9 | 3.7 38.7 280 12 6 9.0 4.9
14500 4.7 40.5 300 14 7 8.9 4.9 | 5.0 41.0 285 12 6 9.2 5.1
14000 6.0 42.8 305 14 7 8.9 4.9 | 6.4 43.5 285 11 6 9.2 5.0
13500 7.3 45.1 305 14 7 9.0 4.9 | 7.7 45.9 285 11 5 9.2 5.0
13000 8.6 47.5 305 14 7 9.0 5.0 | 9.0 48.2 290 10 5 9.2 5.0
12500 10.0 50.0 310 14 7 8.9 4.9 | 10.4 50.7 290 10 5 9.3 5.1
12000 11.3 52.3 310 14 7 8.8 4.8 | 11.8 53.2 290 9 5 9.4 5.1
11500 12.6 54.7 310 13 7 8.7 4.8 | 13.1 55.6 290 9 5 9.0 4.9
11000 13.8 56.8 305 12 6 8.3 4.5 | 14.4 57.9 290 8 4 8.4 4.6
10500 15.1 59.2 305 12 6 3.6 2.0 | 15.7 60.3 290 7 4 5.9 3.2
10250 15.2 59.4 305 12 6 4.8 2.6 | 16.0 60.8 285 7 4 6.9 3.8
10000 16.0 60.8 305 11 6 12.0 6.6 | 16.8 62.2 280 6 3 11.0 6.0
9750 16.8 62.2 305 10 5 10.6 5.8 | 17.5 63.5 275 5 3 10.4 5.7
9500 17.6 63.7 305 10 5 9.1 5.0 | 18.3 64.9 270 5 2 8.6 4.7
9250 18.1 64.6 305 9 5 6.9 3.8 | 18.8 65.8 260 4 2 7.2 4.0
9000 18.7 65.7 305 8 4 8.5 4.7 | 19.4 66.9 245 4 2 9.1 5.0
8750 19.4 66.9 300 8 4 9.5 5.2 | 20.1 68.2 225 3 2 9.4 5.1
8500 20.0 68.0 300 7 4 8.2 4.5 | 20.8 69.4 205 4 2 9.1 5.0
8250 20.6 69.1 300 7 3 7.1 3.9 | 21.4 70.5 195 4 2 8.7 4.8
8000 21.1 70.0 300 6 3 7.6 4.2 | 22.0 71.6 185 4 2 9.3 5.1
7750 21.7 71.1 300 6 3 8.0 4.4 | 22.7 72.9 185 4 2 9.8 5.4
7500 22.2 72.0 295 5 3 6.6 3.6 | 23.4 74.1 185 4 2 10.0 5.5
7250 22.6 72.7 295 4 2 5.5 3.0 | 24.2 75.6 185 4 2 10.3 5.7
7000 23.1 73.6 290 4 2 6.0 3.3 | 24.9 76.8 180 4 2 9.7 5.3
6750 23.4 74.1 285 3 2 4.1 2.2 | 25.6 78.1 180 4 2 9.5 5.2
6500 23.5 74.3 280 3 2 -0.1 -0.0 | 26.4 79.5 180 4 2 10.8 5.9
6250 23.4 74.1 265 3 1 0.7 0.4 | 27.3 81.1 180 4 2 12.1 6.6
6000 23.3 73.9 250 3 1 -5.3 -2.9 | 28.1 82.6 180 4 2 9.6 5.3
5750 22.7 72.9 230 3 2 0.1 0.1 | 28.9 84.0 180 4 2 14.0 7.7
5500 23.7 74.7 220 3 2 28.6 15.7 | 30.4 86.7 180 3 2 28.6 15.7
06/19/2025 at 1500 MDT | 06/19/2025 at 1800 MDT
|
CAPE... +0.9 LI... +0.8 | CAPE... +11.5 LI... +0.2
CINH... -12.3 K Index... +15.6 | CINH... -30.2 K Index... +18.7
|
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 -65.7 -86.3 300 25 13 3.1 1.7 | -66.2 -87.2 285 27 14 3.0 1.7
45000 -60.2 -76.4 305 36 19 5.0 2.8 | -60.5 -76.9 290 33 17 5.5 3.0
40000 -51.8 -61.2 295 39 20 7.2 4.0 | -51.4 -60.5 285 39 20 7.2 4.0
38000 -47.5 -53.5 295 38 20 7.2 3.9 | -47.1 -52.8 285 38 19 7.2 4.0
36000 -43.2 -45.8 295 37 19 7.3 4.0 | -42.8 -45.0 285 37 19 7.6 4.1
34000 -38.6 -37.5 290 35 18 7.7 4.2 | -37.9 -36.2 285 35 18 8.2 4.5
32000 -33.9 -29.0 285 34 17 7.7 4.2 | -32.9 -27.2 285 33 17 8.4 4.6
30000 -29.4 -20.9 275 31 16 7.5 4.1 | -28.6 -19.5 280 32 17 7.1 3.9
29000 -26.6 -15.9 270 29 15 7.6 4.1 | -26.0 -14.8 275 32 16 7.1 3.9
28000 -24.4 -11.9 270 28 14 7.3 4.0 | -23.8 -10.8 275 31 16 7.5 4.1
27000 -22.2 -8.0 270 27 14 7.3 4.0 | -21.6 -6.9 275 29 15 7.5 4.1
26000 -20.0 -4.0 270 26 13 7.3 4.0 | -19.4 -2.9 275 27 14 7.5 4.1
25000 -17.8 -0.0 275 24 12 6.0 3.3 | -17.2 1.0 275 25 13 6.1 3.3
24000 -16.5 2.3 270 25 13 4.7 2.6 | -15.8 3.6 265 25 13 4.8 2.6
23000 -15.2 4.6 265 26 14 4.9 2.7 | -14.5 5.9 260 24 13 4.9 2.7
22000 -13.8 7.2 260 28 14 6.5 3.6 | -13.1 8.4 255 25 13 6.5 3.6
21000 -11.6 11.1 260 26 13 7.5 4.1 | -11.0 12.2 250 23 12 7.5 4.1
20000 -9.4 15.1 255 24 12 7.5 4.1 | -8.8 16.2 250 22 11 7.5 4.1
19500 -8.3 17.1 255 23 12 7.6 4.2 | -7.7 18.1 245 21 11 7.6 4.2
19000 -7.1 19.2 255 22 11 9.0 5.0 | -6.5 20.3 245 20 10 8.7 4.8
18500 -5.7 21.7 255 21 11 8.9 4.9 | -5.2 22.6 245 19 10 8.6 4.7
18000 -4.3 24.3 250 21 11 9.3 5.1 | -3.9 25.0 245 18 9 9.3 5.1
17500 -2.9 26.8 250 20 10 9.5 5.2 | -2.4 27.7 245 17 9 9.6 5.3
17000 -1.5 29.3 250 19 10 9.5 5.2 | -1.0 30.2 245 17 9 9.6 5.3
16500 -0.1 31.8 245 18 9 9.2 5.0 | 0.4 32.7 240 16 8 9.2 5.0
16000 1.3 34.3 240 17 8 9.2 5.1 | 1.8 35.2 240 15 8 9.2 5.1
15500 2.6 36.7 235 15 8 8.9 4.9 | 3.2 37.8 235 14 7 8.9 4.9
15000 4.6 40.3 225 14 7 8.9 4.9 | 5.2 41.4 220 13 7 8.8 4.9
14500 5.9 42.6 220 13 7 8.9 4.9 | 6.5 43.7 215 13 7 9.0 4.9
14000 7.3 45.1 215 12 6 8.9 4.9 | 7.9 46.2 205 13 7 9.0 4.9
13500 8.6 47.5 205 12 6 9.0 4.9 | 9.2 48.6 200 12 6 9.1 5.0
13000 10.0 50.0 200 11 6 9.0 4.9 | 10.5 50.9 195 12 6 9.2 5.0
12500 11.4 52.5 195 10 5 8.8 4.8 | 11.9 53.4 185 12 6 9.3 5.1
12000 12.7 54.9 190 10 5 8.7 4.8 | 13.3 55.9 185 12 6 9.5 5.2
11500 14.0 57.2 185 9 5 8.7 4.8 | 14.7 58.5 180 12 6 9.5 5.2
11000 15.3 59.5 180 9 4 8.6 4.7 | 16.1 61.0 175 12 6 9.3 5.1
10500 16.6 61.9 175 8 4 5.6 3.1 | 17.5 63.5 170 12 6 5.5 3.0
10250 16.9 62.4 175 8 4 6.7 3.7 | 17.8 64.0 170 12 6 6.3 3.5
10000 17.6 63.7 175 8 4 11.4 6.2 | 18.6 65.5 165 12 6 12.0 6.6
9750 18.4 65.1 170 7 4 10.5 5.8 | 19.4 66.9 165 11 6 10.7 5.9
9500 19.2 66.6 170 7 4 9.3 5.1 | 20.2 68.4 165 11 6 10.3 5.7
9250 19.8 67.6 170 7 4 8.6 4.7 | 20.9 69.6 160 11 6 9.3 5.1
9000 20.5 68.9 170 7 4 10.6 5.8 | 21.6 70.9 160 10 5 9.6 5.2
8750 21.3 70.3 170 7 4 11.1 6.1 | 22.4 72.3 155 10 5 9.6 5.2
8500 22.1 71.8 170 7 3 10.1 5.5 | 23.1 73.6 150 10 5 9.9 5.4
8250 22.8 73.0 170 6 3 9.0 4.9 | 23.8 74.8 150 9 5 10.7 5.9
8000 23.5 74.3 170 6 3 9.3 5.1 | 24.6 76.3 145 9 4 9.2 5.1
7750 24.2 75.6 175 6 3 9.3 5.1 | 25.2 77.4 140 8 4 7.7 4.2
7500 24.9 76.8 175 6 3 9.9 5.4 | 25.8 78.4 140 8 4 8.7 4.8
7250 25.6 78.1 175 6 3 10.7 5.9 | 26.5 79.7 135 7 4 9.4 5.2
7000 26.4 79.5 175 6 3 9.7 5.3 | 27.2 81.0 130 6 3 8.8 4.8
6750 27.0 80.6 180 5 3 8.2 4.5 | 27.8 82.0 130 6 3 7.4 4.1
6500 27.7 81.9 180 5 3 9.8 5.4 | 28.4 83.1 125 5 3 8.4 4.6
6250 28.5 83.3 185 5 3 11.4 6.3 | 29.1 84.4 125 4 2 9.6 5.3
6000 29.3 84.7 185 5 2 10.4 5.7 | 29.7 85.5 120 3 2 9.1 5.0
5750 30.1 86.2 185 5 2 10.1 5.5 | 30.4 86.7 110 3 1 9.2 5.1
5500 30.9 87.6 185 4 2 12.2 6.7 | 31.0 87.8 105 2 1 10.0 5.5
________________________________________________________________________________
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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