Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
015
UXUS97 KBOU 211327
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0727 MDT Saturday, June 21, 2025
This forecast is for Saturday, June 21, 2025:
If the trigger temperature of 85.9 F/30.0 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1002 ft/min (5.1 m/s)
Maximum height of thermals.................. 16932 ft MSL (11612 ft AGL)
Forecast maximum temperature................... 98.0 F/37.1 C
Time of trigger temperature.................... 1000 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................. 13847 ft MSL (8528 ft AGL)
Thermal soaring outlook for Sunday 06/22....... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No chnage
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 15641 ft MSL (10321 ft AGL)
Wave soaring outlook for Sunday 06/22.......... Poor
Remarks...
Sunrise/Sunset.................... 05:31:44 / 20:31:06 MDT
Total possible sunshine........... 14 hr 59 min 21 sec (899 min 21 sec)
Altitude of sun at 13:01:25 MDT... 73.67 degrees
Upper air data from numerical model forecast valid on 06/21/2025 at 0600 MDT
Freezing level.................. 17693 ft MSL (12373 ft AGL)
Convective condensation level... 25752 ft MSL (20432 ft AGL)
Lifted condensation level....... 24237 ft MSL (18917 ft AGL)
Lifted index.................... +3.7
K index......................... -20.3
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 -65.3 -85.5 235 50 25 2.9 1.6 M M M M M
45000 -60.3 -76.5 235 60 31 4.0 2.2 M M M M M
40000 -53.8 -64.8 220 51 26 7.4 4.0 M M M M M
38000 -49.3 -56.7 220 41 21 7.5 4.1 M M M M M
36000 -44.9 -48.8 225 31 16 7.5 4.1 M M M M M
34000 -40.3 -40.5 225 23 12 7.6 4.2 M M M M M
32000 -35.8 -32.4 230 17 9 7.6 4.2 M M M M M
30000 -30.5 -22.9 230 16 8 8.0 4.4 44.3 111.7 5.8 M M
29000 -28.1 -18.6 230 16 8 8.0 4.4 43.6 110.6 5.4 M M
28000 -25.7 -14.3 225 17 9 8.1 4.4 43.1 109.6 5.0 M M
27000 -23.3 -9.9 225 16 8 8.2 4.5 42.4 108.3 4.5 M M
26000 -20.8 -5.4 220 15 8 8.2 4.5 41.8 107.2 4.1 M M
25000 -18.4 -1.1 220 14 7 8.1 4.5 41.3 106.3 3.7 M M
24000 -15.8 3.6 215 13 7 8.7 4.8 40.8 105.5 3.4 M M
23000 -13.2 8.2 215 13 7 8.7 4.8 40.4 104.7 3.1 M M
22000 -10.6 12.9 215 12 6 8.7 4.8 40.1 104.2 2.9 M M
21000 -8.1 17.4 215 12 6 8.3 4.5 39.6 103.3 2.5 M M
20000 -5.6 21.9 225 13 7 8.3 4.5 39.1 102.3 2.0 M M
19500 -4.3 24.3 225 13 7 8.3 4.5 38.8 101.9 1.9 M M
19000 -3.1 26.4 230 14 7 7.8 4.3 38.6 101.5 1.7 M M
18500 -2.0 28.4 230 15 8 7.5 4.1 38.2 100.8 1.3 M M
18000 -0.9 30.4 235 16 8 7.5 4.1 37.8 100.1 1.0 M M
17500 0.2 32.4 235 18 9 6.8 3.7 37.4 99.3 0.6 M M
17000 1.2 34.2 240 19 10 6.8 3.8 36.9 98.4 0.2 M M
16500 2.7 36.9 240 22 11 6.4 3.5 36.1 97.0 -0.5 951 4.8
16000 3.7 38.7 240 22 12 6.5 3.5 35.6 96.0 -1.0 908 4.6
15500 4.6 40.3 240 23 12 6.6 3.6 35.0 95.1 -1.5 865 4.4
15000 5.6 42.1 245 23 12 6.8 3.7 34.5 94.2 -2.0 820 4.2
14500 6.6 43.9 245 23 12 6.9 3.8 34.0 93.3 -2.5 775 3.9
14000 7.6 45.7 245 23 12 7.2 4.0 33.6 92.5 -2.9 729 3.7
13500 8.7 47.7 250 22 11 7.2 3.9 33.2 91.7 -3.4 683 3.5
13000 9.8 49.6 250 21 11 7.4 4.0 32.8 91.0 -3.8 636 3.2
12500 10.9 51.6 250 21 11 7.3 4.0 32.4 90.3 -4.2 588 3.0
12000 12.0 53.6 255 20 10 7.9 4.4 32.1 89.7 -4.5 540 2.7
11500 13.2 55.8 255 20 10 8.1 4.4 31.8 89.2 -4.8 490 2.5
11000 14.3 57.7 255 20 10 6.6 3.6 31.4 88.6 -5.2 442 2.2
10500 15.2 59.4 260 20 10 7.4 4.1 30.9 87.6 -5.8 399 2.0
10250 15.9 60.6 260 20 10 10.3 5.7 30.8 87.5 -5.8 372 1.9
10000 16.6 61.9 260 20 11 8.6 4.7 30.8 87.5 -5.8 342 1.7
9750 17.1 62.8 260 20 10 6.8 3.7 30.6 87.1 -6.1 319 1.6
9500 17.7 63.9 260 20 10 6.8 3.8 30.4 86.8 -6.3 296 1.5
9250 18.2 64.8 260 20 10 8.4 4.6 30.2 86.4 -6.5 273 1.4
9000 18.9 66.0 255 21 11 9.0 4.9 30.2 86.3 -6.5 245 1.2
8750 19.5 67.1 255 20 10 7.5 4.1 30.0 86.1 -6.7 220 1.1
8500 20.0 68.0 255 19 10 8.1 4.4 29.9 85.8 -6.9 195 1.0
8250 20.6 69.1 255 19 10 7.3 4.0 29.8 85.6 -7.0 171 0.9
8000 21.2 70.2 250 17 9 7.9 4.3 29.6 85.2 -7.2 147 0.7
7750 21.8 71.2 250 16 8 8.9 4.9 29.5 85.1 -7.4 120 0.6
7500 22.5 72.5 245 15 8 8.9 4.9 29.4 84.9 -7.5 93 0.5
7250 23.1 73.6 240 15 8 7.9 4.3 29.3 84.8 -7.6 67 0.3
7000 23.6 74.5 235 14 7 6.7 3.7 29.1 84.4 -7.8 44 0.2
6750 24.1 75.4 230 14 7 6.9 3.8 28.9 84.0 -8.0 21 0.1
6500 24.7 76.5 225 14 7 8.6 4.7 28.7 83.7 -8.2 M M
6250 25.2 77.4 220 14 7 1.6 0.9 28.5 83.3 -8.5 M M
6000 24.9 76.8 215 14 7 -5.4 -2.9 27.5 81.5 -9.5 M M
5750 24.4 75.9 210 13 7 -6.0 -3.3 26.4 79.5 -10.7 M M
5500 23.3 73.9 200 12 6 -27.6 -15.1 24.6 76.3 -12.6 9 0.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/21/2025 at 0900 MDT | 06/21/2025 at 1200 MDT
|
CAPE... 0.0 LI... +5.6 | CAPE... 0.0 LI... +4.6
CINH... 0.0 K Index... -25.5 | CINH... 0.0 K Index... -11.2
|
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 -64.6 -84.3 230 47 24 3.0 1.6 | -63.9 -83.0 225 47 24 2.6 1.4
45000 -59.6 -75.3 230 56 29 3.6 2.0 | -59.6 -75.3 225 53 27 3.8 2.1
40000 -53.7 -64.7 220 52 27 7.1 3.9 | -53.2 -63.8 220 48 25 6.7 3.7
38000 -49.4 -56.9 220 46 23 7.1 3.9 | -49.1 -56.4 220 45 23 6.7 3.7
36000 -45.1 -49.2 220 40 20 7.1 3.9 | -45.1 -49.2 220 42 22 6.7 3.7
34000 -40.7 -41.3 220 31 16 7.6 4.2 | -40.7 -41.3 220 35 18 7.6 4.2
32000 -36.1 -33.0 215 21 11 7.6 4.2 | -36.1 -33.0 215 27 14 7.6 4.2
30000 -30.7 -23.3 220 19 10 8.2 4.5 | -30.8 -23.4 220 21 11 8.0 4.4
29000 -28.3 -18.9 220 19 10 8.2 4.5 | -28.4 -19.1 225 20 10 8.0 4.4
28000 -25.8 -14.4 220 19 10 8.1 4.4 | -26.0 -14.8 230 18 9 8.0 4.4
27000 -23.4 -10.1 220 18 9 8.0 4.4 | -23.6 -10.5 225 18 9 8.0 4.4
26000 -21.0 -5.8 215 17 9 8.0 4.4 | -21.2 -6.2 225 19 10 8.0 4.4
25000 -18.6 -1.5 210 16 8 8.0 4.4 | -18.8 -1.8 225 19 10 8.0 4.4
24000 -16.1 3.0 205 16 8 8.7 4.8 | -16.4 2.5 215 20 10 8.1 4.5
23000 -13.5 7.7 200 15 8 8.7 4.8 | -13.9 7.0 210 21 11 8.1 4.5
22000 -10.9 12.4 195 15 8 8.7 4.8 | -11.5 11.3 200 22 11 8.1 4.5
21000 -8.3 17.1 195 15 8 8.4 4.6 | -9.1 15.6 200 23 12 8.1 4.4
20000 -5.8 21.6 195 16 8 8.4 4.6 | -6.7 19.9 195 23 12 8.1 4.4
19500 -4.6 23.7 200 16 8 8.4 4.6 | -5.4 22.3 195 24 12 8.1 4.4
19000 -3.3 26.1 200 17 9 7.9 4.3 | -4.2 24.4 195 24 12 8.1 4.5
18500 -2.2 28.0 205 17 9 7.5 4.1 | -3.0 26.6 195 24 12 8.1 4.5
18000 -1.1 30.0 210 17 9 7.6 4.2 | -1.8 28.8 195 23 12 8.2 4.5
17500 0.0 32.0 215 17 9 6.8 3.7 | -0.7 30.7 200 22 11 6.8 3.7
17000 1.0 33.8 225 17 9 6.9 3.8 | 0.3 32.5 205 21 11 7.0 3.8
16500 2.5 36.5 230 17 9 6.5 3.5 | 1.4 34.5 210 20 10 7.0 3.9
16000 3.5 38.3 235 17 9 6.5 3.6 | 2.9 37.2 215 18 9 7.1 3.9
15500 4.5 40.1 240 17 9 6.7 3.7 | 4.0 39.2 220 17 9 7.6 4.2
15000 5.5 41.9 245 16 8 6.9 3.8 | 5.2 41.4 225 16 8 7.8 4.3
14500 6.5 43.7 245 16 8 7.0 3.9 | 6.3 43.3 230 15 8 7.9 4.3
14000 7.6 45.7 250 16 8 7.5 4.1 | 7.5 45.5 235 14 7 8.1 4.4
13500 8.7 47.7 255 16 8 7.5 4.1 | 8.7 47.7 235 14 7 8.1 4.4
13000 9.8 49.6 255 16 8 7.2 4.0 | 9.8 49.6 240 13 7 7.3 4.0
12500 10.9 51.6 255 17 9 7.3 4.0 | 10.9 51.6 240 13 7 7.5 4.1
12000 11.9 53.4 260 17 9 6.9 3.8 | 12.0 53.6 240 12 6 7.0 3.8
11500 12.9 55.2 260 17 9 7.0 3.8 | 13.0 55.4 235 11 6 7.1 3.9
11000 13.9 57.0 260 17 9 5.5 3.0 | 14.0 57.2 230 10 5 6.1 3.4
10500 14.6 58.3 260 18 9 6.3 3.5 | 14.8 58.6 220 7 4 7.8 4.3
10250 15.2 59.4 260 18 9 9.3 5.1 | 15.6 60.1 215 7 4 11.2 6.1
10000 15.9 60.6 260 17 9 7.5 4.1 | 16.3 61.3 210 7 3 9.5 5.2
9750 16.3 61.3 260 17 9 5.6 3.1 | 17.0 62.6 210 6 3 8.5 4.7
9500 16.7 62.1 255 17 9 5.5 3.0 | 17.6 63.7 205 6 3 8.2 4.5
9250 17.2 63.0 255 17 9 7.8 4.3 | 18.3 64.9 200 5 3 10.6 5.8
9000 17.8 64.0 255 17 9 8.7 4.8 | 19.1 66.4 205 6 3 11.3 6.2
8750 18.4 65.1 255 16 8 6.8 3.7 | 19.9 67.8 200 6 3 9.3 5.1
8500 18.9 66.0 255 16 8 7.6 4.2 | 20.6 69.1 200 5 3 10.3 5.6
8250 19.4 66.9 255 15 8 6.2 3.4 | 21.3 70.3 200 5 3 8.3 4.5
8000 19.8 67.6 250 14 7 7.2 3.9 | 21.9 71.4 195 5 2 8.9 4.9
7750 20.5 68.9 250 13 7 9.0 4.9 | 22.7 72.9 195 5 2 10.9 6.0
7500 21.1 70.0 245 12 6 9.0 4.9 | 23.5 74.3 195 5 3 11.0 6.1
7250 21.8 71.2 240 12 6 7.3 4.0 | 24.3 75.7 195 5 3 8.5 4.7
7000 22.2 72.0 235 11 6 6.1 3.3 | 24.8 76.6 190 5 2 7.5 4.1
6750 22.8 73.0 230 11 5 8.6 4.7 | 25.5 77.9 190 5 2 11.4 6.2
6500 23.4 74.1 225 11 5 9.5 5.2 | 26.4 79.5 190 4 2 12.3 6.8
6250 24.1 75.4 220 10 5 8.9 4.9 | 27.3 81.1 190 4 2 10.6 5.8
6000 24.7 76.5 215 10 5 8.9 4.9 | 28.0 82.4 185 4 2 9.8 5.4
5750 25.4 77.7 210 9 5 9.0 4.9 | 28.8 83.8 185 4 2 9.9 5.5
5500 26.1 79.0 210 9 5 12.5 6.8 | 29.7 85.5 185 4 2 16.5 9.1
06/21/2025 at 1500 MDT | 06/21/2025 at 1800 MDT
|
CAPE... 0.0 LI... +1.1 | CAPE... +11.8 LI... +0.2
CINH... -0.0 K Index... +2.7 | CINH... -6.6 K Index... +6.9
|
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 -63.5 -82.3 230 48 25 2.4 1.3 | -63.9 -83.0 230 47 24 2.9 1.6
45000 -59.2 -74.6 230 52 27 3.5 1.9 | -59.0 -74.2 240 49 25 3.7 2.0
40000 -53.5 -64.3 225 49 25 6.9 3.8 | -53.0 -63.4 240 46 24 7.0 3.9
38000 -49.3 -56.7 230 42 22 7.0 3.8 | -48.7 -55.7 235 42 22 7.1 3.9
36000 -45.1 -49.2 230 34 18 7.0 3.8 | -44.5 -48.1 230 38 19 7.1 3.9
34000 -40.6 -41.1 225 30 15 7.6 4.2 | -40.0 -40.0 225 34 17 7.6 4.2
32000 -36.0 -32.8 225 26 13 7.7 4.2 | -35.5 -31.9 225 30 15 7.6 4.2
30000 -30.7 -23.3 225 22 11 7.9 4.4 | -30.4 -22.7 225 26 14 7.5 4.1
29000 -28.4 -19.1 230 20 10 7.9 4.4 | -28.2 -18.8 225 25 13 7.5 4.1
28000 -26.0 -14.8 230 18 9 8.0 4.4 | -26.0 -14.8 225 24 12 7.2 4.0
27000 -23.6 -10.5 230 19 10 8.0 4.4 | -23.9 -11.0 225 24 12 7.1 3.9
26000 -21.2 -6.2 230 19 10 8.0 4.4 | -21.8 -7.2 225 24 12 7.1 3.9
25000 -18.8 -1.8 230 20 10 8.1 4.5 | -19.6 -3.3 225 24 12 7.0 3.9
24000 -16.5 2.3 230 20 11 7.3 4.0 | -17.4 0.7 230 23 12 7.7 4.2
23000 -14.4 6.1 225 22 11 7.3 4.0 | -15.2 4.6 230 23 12 7.7 4.2
22000 -12.2 10.0 220 23 12 7.3 4.0 | -12.9 8.8 230 22 11 7.7 4.2
21000 -10.0 14.0 220 23 12 7.4 4.1 | -10.4 13.3 230 22 11 8.7 4.8
20000 -7.8 18.0 220 23 12 7.5 4.1 | -7.8 18.0 230 21 11 8.7 4.7
19500 -6.7 19.9 220 23 12 7.5 4.1 | -6.5 20.3 230 21 11 8.7 4.7
19000 -5.6 21.9 220 22 12 8.3 4.5 | -5.2 22.6 230 21 11 8.9 4.9
18500 -4.3 24.3 220 22 11 8.7 4.8 | -3.9 25.0 230 20 10 9.1 5.0
18000 -3.0 26.6 220 21 11 8.7 4.8 | -2.5 27.5 230 20 10 9.1 5.0
17500 -1.7 28.9 220 20 10 8.8 4.8 | -1.2 29.8 225 20 10 9.1 5.0
17000 -0.4 31.3 220 20 10 8.8 4.8 | 0.2 32.4 225 20 10 9.1 5.0
16500 0.9 33.6 220 19 10 8.9 4.9 | 1.5 34.7 220 20 10 9.3 5.1
16000 2.9 37.2 220 19 10 9.0 4.9 | 3.6 38.5 220 19 10 9.5 5.2
15500 4.2 39.6 215 18 9 8.9 4.9 | 5.0 41.0 220 19 10 9.5 5.2
15000 5.5 41.9 215 18 9 8.9 4.9 | 6.4 43.5 215 19 10 9.5 5.2
14500 6.8 44.2 210 18 9 8.9 4.9 | 7.8 46.0 215 19 10 9.5 5.2
14000 8.1 46.6 205 17 9 9.0 5.0 | 9.3 48.7 215 18 9 9.6 5.3
13500 9.5 49.1 205 16 8 9.0 5.0 | 10.7 51.3 210 18 9 9.6 5.3
13000 10.8 51.4 200 16 8 9.4 5.2 | 12.1 53.8 210 18 9 9.5 5.2
12500 12.2 54.0 195 15 8 9.4 5.1 | 13.5 56.3 210 17 9 9.5 5.2
12000 13.6 56.5 195 14 7 9.3 5.1 | 15.0 59.0 210 17 9 9.6 5.3
11500 15.0 59.0 190 13 7 9.4 5.2 | 16.4 61.5 205 17 9 9.7 5.3
11000 16.4 61.5 185 12 6 8.4 4.6 | 17.8 64.0 205 16 8 8.5 4.7
10500 17.6 63.7 180 11 6 9.8 5.4 | 19.0 66.2 210 15 8 9.7 5.3
10250 18.4 65.1 185 11 6 11.7 6.4 | 19.8 67.6 205 15 8 11.4 6.3
10000 19.2 66.6 180 11 5 9.7 5.3 | 20.6 69.1 205 15 8 9.9 5.4
9750 19.9 67.8 180 10 5 9.1 5.0 | 21.3 70.3 205 14 7 9.3 5.1
9500 20.6 69.1 180 10 5 8.9 4.9 | 22.0 71.6 210 14 7 9.5 5.2
9250 21.3 70.3 175 10 5 10.1 5.5 | 22.7 72.9 210 13 7 9.5 5.2
9000 22.1 71.8 180 10 5 10.5 5.8 | 23.4 74.1 200 13 7 9.5 5.2
8750 22.8 73.0 175 10 5 9.5 5.2 | 24.1 75.4 200 13 7 9.5 5.2
8500 23.5 74.3 175 9 5 10.0 5.5 | 24.8 76.6 200 12 6 9.5 5.2
8250 24.3 75.7 175 9 5 9.3 5.1 | 25.5 77.9 200 12 6 9.5 5.2
8000 24.9 76.8 170 9 5 9.5 5.2 | 26.3 79.3 210 12 6 9.6 5.3
7750 25.7 78.3 170 9 5 10.2 5.6 | 27.0 80.6 205 12 6 9.5 5.2
7500 26.4 79.5 170 9 4 10.4 5.7 | 27.7 81.9 205 11 6 9.9 5.4
7250 27.2 81.0 170 9 4 8.9 4.9 | 28.4 83.1 200 11 5 8.6 4.7
7000 27.8 82.0 165 8 4 8.5 4.6 | 29.0 84.2 205 11 6 8.2 4.5
6750 28.5 83.3 165 8 4 10.8 5.9 | 29.7 85.5 210 10 5 10.2 5.6
6500 29.4 84.9 165 8 4 11.5 6.3 | 30.5 86.9 205 10 5 11.0 6.0
6250 30.2 86.4 165 8 4 10.7 5.9 | 31.3 88.3 200 9 5 10.3 5.6
6000 31.0 87.8 160 7 4 10.5 5.7 | 32.0 89.6 205 9 5 9.8 5.4
5750 31.8 89.2 160 7 4 9.7 5.3 | 32.7 90.9 210 9 5 9.3 5.1
5500 32.6 90.7 160 6 3 15.6 8.5 | 33.4 92.1 205 7 4 11.7 6.4
________________________________________________________________________________
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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