Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
781
UXUS97 KBOU 150119
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1916 MDT Monday, September 14, 2026
This forecast is for Tuesday, September 15, 2026:
If the trigger temperature of 69.0 F/20.5 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 281 ft/min (1.4 m/s)
Maximum height of thermals.................. 12250 ft MSL (6890 ft AGL)
Forecast maximum temperature................... 78.0 F/26.0 C
Time of trigger temperature.................... 1245 MDT
Time of overdevelopment........................ 1500 MDT
Middle/high clouds during soaring window....... Broken/overcast thin middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 10276 ft MSL (4916 ft AGL)
Thermal soaring outlook for Wednesday 09/16.... Good
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....................... 46414 ft MSL (41054 ft AGL)
Wave soaring outlook for Wednesday 09/16....... Poor
Remarks...
Sunrise/Sunset.................... 06:40:56 / 19:08:16 MDT
Total possible sunshine........... 12 hr 27 min 20 sec (747 min 20 sec)
Altitude of sun at 12:54:36 MDT... 53.01 degrees
Upper air data from numerical model forecast valid on 09/15/2026 at 0600 MDT
Freezing level.................. 14821 ft MSL (9461 ft AGL)
Convective condensation level... 17337 ft MSL (11977 ft AGL)
Lifted condensation level....... 14777 ft MSL (9417 ft AGL)
Lifted index.................... +3.4
K index......................... +18.9
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 -66.2 -87.2 250 58 30 2.2 1.2 M M M M M
45000 -61.2 -78.2 250 75 39 5.7 3.1 M M M M M
40000 -52.4 -62.3 240 75 38 7.3 4.0 M M M M M
38000 -48.0 -54.4 240 71 37 7.3 4.0 M M M M M
36000 -43.6 -46.5 240 67 35 7.4 4.0 M M M M M
34000 -39.6 -39.3 245 62 32 6.6 3.6 M M M M M
32000 -35.1 -31.2 245 57 29 6.3 3.5 M M M M M
30000 -30.4 -22.7 245 50 26 8.0 4.4 45.8 114.4 15.3 M M
29000 -28.0 -18.4 245 47 24 8.0 4.4 45.1 113.3 15.0 M M
28000 -25.6 -14.1 245 44 22 7.3 4.0 44.6 112.3 14.8 M M
27000 -23.6 -10.5 250 41 21 6.8 3.7 43.3 110.0 14.0 M M
26000 -21.6 -6.9 250 38 20 6.8 3.7 42.2 108.0 13.2 M M
25000 -19.6 -3.3 250 36 18 6.7 3.7 41.2 106.2 12.6 M M
24000 -17.4 0.7 250 34 18 7.6 4.1 40.3 104.5 11.9 M M
23000 -15.1 4.8 250 33 17 7.6 4.2 39.4 103.0 11.4 M M
22000 -12.9 8.8 250 31 16 7.6 4.1 38.7 101.7 10.9 M M
21000 -10.8 12.6 250 30 15 7.1 3.9 37.8 100.0 10.1 M M
20000 -8.8 16.2 245 28 14 7.1 3.9 36.8 98.3 9.3 M M
19500 -7.7 18.1 245 27 14 7.2 4.0 36.4 97.5 9.0 M M
19000 -6.3 20.7 245 26 13 6.1 3.4 35.6 96.1 8.3 M M
18500 -5.4 22.3 245 25 13 6.3 3.4 35.0 95.0 7.8 M M
18000 -4.6 23.7 245 24 12 5.4 3.0 34.4 93.9 7.2 M M
17500 -3.9 25.0 245 24 12 5.1 2.8 33.6 92.4 6.5 M M
17000 -3.2 26.2 245 23 12 5.0 2.8 32.8 91.0 5.8 M M
16500 -2.5 27.5 245 22 11 4.5 2.5 31.9 89.5 5.0 M M
16000 -1.9 28.6 245 21 11 4.4 2.4 31.1 87.9 4.1 M M
15500 -1.2 29.8 240 20 10 6.6 3.6 30.3 86.6 3.4 M M
15000 -0.2 31.6 240 18 9 6.8 3.7 29.8 85.7 2.9 M M
14500 0.7 33.3 235 16 8 6.6 3.6 29.3 84.8 2.4 M M
14000 1.6 34.9 230 14 7 6.5 3.6 28.8 83.8 1.9 M M
13500 2.6 36.7 225 13 6 6.3 3.4 28.3 82.9 1.4 M M
13000 3.5 38.3 215 10 5 5.8 3.2 27.6 81.8 0.8 M M
12500 4.3 39.7 210 8 4 5.9 3.3 27.0 80.6 0.3 M M
12000 5.3 41.5 190 7 3 6.4 3.5 26.5 79.6 -0.2 458 2.3
11500 6.3 43.3 165 6 3 6.0 3.3 25.9 78.7 -0.7 414 2.1
11000 6.9 44.4 155 4 2 2.1 1.1 25.0 76.9 -1.5 379 1.9
10500 7.4 45.3 130 2 1 2.1 1.2 23.8 74.9 -2.4 349 1.8
10250 7.6 45.7 085 1 1 1.3 0.7 23.2 73.7 -3.0 337 1.7
10000 7.8 46.0 040 2 1 2.8 1.6 22.6 72.6 -3.6 325 1.6
9750 8.0 46.4 035 3 2 4.0 2.2 22.1 71.7 -4.0 309 1.6
9500 8.3 46.9 035 5 2 3.9 2.1 21.6 70.9 -4.5 293 1.5
9250 8.6 47.5 035 6 3 4.6 2.5 21.2 70.1 -4.9 276 1.4
9000 8.9 48.0 035 6 3 4.7 2.6 20.8 69.4 -5.4 260 1.3
8750 9.2 48.6 035 6 3 5.7 3.1 20.4 68.8 -5.8 244 1.2
8500 9.5 49.1 035 7 4 2.8 1.5 20.1 68.1 -6.3 228 1.2
8250 9.4 48.9 030 8 4 -1.6 -0.9 19.3 66.8 -7.1 223 1.1
8000 9.3 48.7 030 9 5 -1.7 -0.9 18.4 65.2 -8.0 221 1.1
7750 9.1 48.4 025 11 5 -2.5 -1.4 17.5 63.6 -8.9 218 1.1
7500 9.1 48.4 020 12 6 3.1 1.7 16.7 62.1 -9.7 211 1.1
7250 9.6 49.3 020 12 6 7.9 4.3 16.5 61.7 -9.9 188 1.0
7000 10.1 50.2 020 12 6 6.6 3.6 16.3 61.3 -10.1 165 0.8
6750 10.7 51.3 020 13 7 8.2 4.5 16.1 61.0 -10.3 141 0.7
6500 11.4 52.5 020 13 6 8.9 4.9 16.0 60.8 -10.4 113 0.6
6250 12.0 53.6 020 12 6 8.3 4.5 15.9 60.7 -10.6 87 0.4
6000 12.6 54.7 020 12 6 8.9 4.9 15.8 60.5 -10.7 61 0.3
5750 13.3 55.9 020 11 6 9.5 5.2 15.8 60.4 -10.7 32 0.2
5500 14.0 57.2 015 10 5 9.0 4.9 15.8 60.4 -10.8 4 0.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/15/2026 at 0900 MDT | 09/15/2026 at 1200 MDT
|
CAPE... +0.2 LI... +2.9 | CAPE... 0.0 LI... +1.5
CINH... -0.3 K Index... +18.8 | CINH... -0.1 K Index... +21.3
|
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 -65.9 -86.6 250 59 30 1.8 1.0 | -65.6 -86.1 250 60 31 1.6 0.9
45000 -61.2 -78.2 250 77 39 5.7 3.1 | -61.2 -78.2 250 76 39 5.7 3.1
40000 -52.4 -62.3 240 80 41 7.5 4.1 | -52.3 -62.1 240 79 41 7.4 4.1
38000 -47.9 -54.2 240 74 38 7.6 4.1 | -47.9 -54.2 240 75 38 7.5 4.1
36000 -43.4 -46.1 240 68 35 7.6 4.2 | -43.4 -46.1 240 70 36 7.5 4.1
34000 -39.3 -38.7 245 59 30 6.6 3.6 | -38.9 -38.0 240 58 30 6.5 3.6
32000 -34.9 -30.8 245 48 25 6.4 3.5 | -35.0 -31.0 240 47 24 6.6 3.6
30000 -30.5 -22.9 245 43 22 7.5 4.1 | -30.6 -23.1 240 40 20 7.5 4.1
29000 -28.3 -18.9 250 40 21 7.5 4.1 | -28.3 -18.9 245 36 19 7.5 4.1
28000 -26.1 -15.0 250 38 20 7.3 4.0 | -26.1 -15.0 245 33 17 7.6 4.2
27000 -23.9 -11.0 250 36 18 7.3 4.0 | -23.8 -10.8 245 31 16 7.7 4.2
26000 -21.7 -7.1 250 34 17 7.3 4.0 | -21.5 -6.7 245 30 15 7.7 4.2
25000 -19.6 -3.3 250 32 16 7.3 4.0 | -19.2 -2.6 240 28 14 7.6 4.2
24000 -17.4 0.7 250 31 16 7.3 4.0 | -17.1 1.2 240 27 14 7.0 3.8
23000 -15.2 4.6 245 30 15 7.3 4.0 | -15.0 5.0 240 27 14 7.0 3.8
22000 -13.1 8.4 245 29 15 7.2 4.0 | -12.9 8.8 240 27 14 6.9 3.8
21000 -11.1 12.0 245 29 15 6.6 3.6 | -11.0 12.2 245 26 14 6.4 3.5
20000 -9.2 15.4 245 28 15 6.7 3.7 | -9.1 15.6 245 26 14 6.5 3.5
19500 -8.2 17.2 240 28 14 6.8 3.7 | -8.2 17.2 245 26 14 6.5 3.6
19000 -6.9 19.6 240 28 14 5.7 3.1 | -6.8 19.8 245 26 13 6.5 3.6
18500 -6.1 21.0 240 27 14 5.8 3.2 | -5.8 21.6 245 26 14 6.6 3.6
18000 -5.3 22.5 240 27 14 6.4 3.5 | -4.9 23.2 245 26 13 5.8 3.2
17500 -4.3 24.3 245 26 13 6.5 3.6 | -4.1 24.6 245 26 13 5.8 3.2
17000 -3.4 25.9 245 25 13 6.5 3.6 | -3.4 25.9 245 26 13 6.1 3.4
16500 -2.5 27.5 245 25 13 6.5 3.6 | -2.4 27.7 245 25 13 6.9 3.8
16000 -1.6 29.1 250 24 12 6.5 3.6 | -1.5 29.3 250 24 12 6.9 3.8
15500 -0.7 30.7 250 23 12 6.4 3.5 | -0.5 31.1 250 23 12 7.2 3.9
15000 0.3 32.5 250 22 11 6.4 3.5 | 0.6 33.1 250 22 11 7.2 3.9
14500 1.2 34.2 245 20 11 6.3 3.5 | 1.6 34.9 245 21 11 7.2 3.9
14000 2.1 35.8 240 19 10 6.3 3.5 | 2.6 36.7 245 21 11 7.2 3.9
13500 2.9 37.2 235 18 9 6.2 3.4 | 3.7 38.7 245 20 10 7.2 3.9
13000 3.8 38.8 230 17 9 6.0 3.3 | 4.7 40.5 240 20 10 7.2 3.9
12500 4.7 40.5 225 16 8 5.7 3.2 | 5.7 42.3 235 20 10 7.0 3.8
12000 5.5 41.9 220 14 7 4.9 2.7 | 6.7 44.1 235 19 10 6.6 3.6
11500 6.3 43.3 210 12 6 4.1 2.3 | 7.7 45.9 230 18 9 6.2 3.4
11000 6.6 43.9 200 10 5 0.4 0.2 | 8.5 47.3 220 17 9 4.5 2.5
10500 6.7 44.1 190 9 4 0.5 0.3 | 9.2 48.6 215 16 8 3.4 1.9
10250 6.8 44.2 190 8 4 0.3 0.2 | 9.3 48.7 210 16 8 -0.4 -0.2
10000 6.8 44.2 185 7 4 0.8 0.5 | 9.2 48.6 210 15 8 -1.9 -1.1
9750 6.8 44.2 175 6 3 1.3 0.7 | 9.1 48.4 205 13 7 -2.0 -1.1
9500 6.9 44.4 160 5 2 1.3 0.7 | 9.0 48.2 195 11 6 -1.5 -0.8
9250 6.9 44.4 145 4 2 1.6 0.9 | 8.9 48.0 190 10 5 -1.0 -0.5
9000 7.0 44.6 135 4 2 1.6 0.9 | 8.8 47.8 185 9 5 -0.0 -0.0
8750 7.1 44.8 125 4 2 2.0 1.1 | 8.7 47.7 175 8 4 0.2 0.1
8500 7.2 45.0 115 4 2 0.8 0.5 | 8.7 47.7 165 8 4 2.3 1.3
8250 7.2 45.0 110 4 2 -0.5 -0.3 | 9.0 48.2 160 8 4 4.3 2.4
8000 7.2 45.0 100 4 2 0.0 0.0 | 9.3 48.7 150 8 4 4.9 2.7
7750 7.2 45.0 090 4 2 2.4 1.3 | 9.7 49.5 145 8 4 7.9 4.4
7500 7.6 45.7 075 3 2 6.4 3.5 | 10.4 50.7 140 8 4 8.7 4.8
7250 8.1 46.6 065 3 2 7.6 4.2 | 11.0 51.8 135 8 4 7.9 4.3
7000 8.7 47.7 060 3 2 7.8 4.3 | 11.6 52.9 130 8 4 8.8 4.8
6750 9.4 48.9 055 3 2 10.4 5.7 | 12.4 54.3 130 8 4 11.5 6.3
6500 10.2 50.4 045 3 2 10.6 5.8 | 13.3 55.9 125 8 4 11.3 6.2
6250 10.9 51.6 045 3 2 9.6 5.3 | 14.0 57.2 125 8 4 10.2 5.6
6000 11.7 53.1 040 3 2 9.5 5.2 | 14.8 58.6 125 7 4 9.7 5.3
5750 12.4 54.3 040 3 1 12.1 6.6 | 15.7 60.3 125 7 4 16.3 8.9
5500 13.6 56.5 040 3 1 17.8 9.8 | 17.4 63.3 120 7 4 29.9 16.4
09/15/2026 at 1500 MDT | 09/15/2026 at 1800 MDT
|
CAPE... 0.0 LI... +1.2 | CAPE... 0.0 LI... +0.5
CINH... 0.0 K Index... +22.5 | CINH... -0.0 K Index... +26.6
|
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 -65.3 -85.5 250 59 30 1.7 0.9 | -64.5 -84.1 250 55 28 1.3 0.7
45000 -61.0 -77.8 250 74 38 5.6 3.1 | -60.8 -77.4 250 72 37 5.0 2.7
40000 -52.4 -62.3 245 79 41 7.1 3.9 | -52.8 -63.0 240 83 43 7.9 4.3
38000 -48.1 -54.6 245 76 39 7.1 3.9 | -48.0 -54.4 240 80 41 7.9 4.4
36000 -43.3 -45.9 245 73 38 7.0 3.8 | -42.7 -44.9 240 77 40 7.5 4.1
34000 -39.3 -38.7 240 61 31 6.6 3.6 | -38.7 -37.7 240 65 34 6.6 3.6
32000 -35.3 -31.5 240 49 25 6.3 3.5 | -34.7 -30.5 240 53 28 6.8 3.7
30000 -30.5 -22.9 240 43 22 8.2 4.5 | -29.9 -21.8 240 47 24 8.2 4.5
29000 -28.1 -18.6 240 41 21 8.2 4.5 | -27.5 -17.5 240 44 22 8.2 4.5
28000 -25.6 -14.1 240 39 20 8.0 4.4 | -25.0 -13.0 240 41 21 8.3 4.6
27000 -23.2 -9.8 240 37 19 8.0 4.4 | -22.5 -8.5 240 40 21 8.4 4.6
26000 -20.9 -5.6 240 36 18 8.0 4.4 | -20.0 -4.0 240 40 20 8.4 4.6
25000 -18.5 -1.3 235 34 18 8.0 4.4 | -17.5 0.5 240 39 20 8.3 4.6
24000 -16.5 2.3 235 32 17 6.6 3.6 | -15.5 4.1 240 38 20 6.6 3.6
23000 -14.5 5.9 235 30 16 6.7 3.7 | -13.5 7.7 240 38 19 6.6 3.6
22000 -12.6 9.3 235 28 15 6.6 3.6 | -11.6 11.1 240 37 19 6.5 3.6
21000 -10.7 12.7 240 27 14 6.3 3.5 | -9.9 14.2 245 37 19 5.4 3.0
20000 -8.4 16.9 245 26 13 6.3 3.5 | -8.0 17.6 255 36 19 5.5 3.0
19500 -7.5 18.5 250 26 13 6.3 3.5 | -7.2 19.0 255 36 19 5.5 3.0
19000 -6.6 20.1 250 26 13 6.2 3.4 | -6.4 20.5 255 35 18 5.5 3.0
18500 -5.7 21.7 255 26 13 6.3 3.4 | -5.7 21.7 260 33 17 5.5 3.0
18000 -4.8 23.4 260 26 13 6.1 3.4 | -4.9 23.2 260 32 16 6.5 3.5
17500 -4.0 24.8 260 26 13 6.1 3.4 | -4.0 24.8 265 29 15 6.7 3.7
17000 -3.1 26.4 260 25 13 6.3 3.4 | -3.0 26.6 265 25 13 6.7 3.7
16500 -2.2 28.0 260 24 12 6.8 3.7 | -2.1 28.2 265 23 12 6.8 3.7
16000 -1.2 29.8 260 23 12 6.8 3.7 | -1.1 30.0 265 20 10 6.8 3.7
15500 -0.3 31.5 260 21 11 6.8 3.7 | -0.1 31.8 265 18 9 7.0 3.9
15000 0.7 33.3 260 20 10 6.8 3.7 | 0.9 33.6 260 17 9 7.0 3.9
14500 1.7 35.1 260 18 9 7.1 3.9 | 1.9 35.4 255 15 8 7.2 4.0
14000 2.7 36.9 255 17 9 7.2 3.9 | 3.0 37.4 250 14 7 7.3 4.0
13500 3.8 38.8 250 17 9 6.9 3.8 | 4.1 39.4 245 14 7 7.4 4.1
13000 4.7 40.5 240 16 8 6.6 3.6 | 5.2 41.4 235 13 7 7.5 4.1
12500 5.7 42.3 230 15 8 6.5 3.5 | 6.3 43.3 225 13 7 7.5 4.1
12000 6.6 43.9 220 15 8 6.0 3.3 | 7.4 45.3 220 13 7 7.3 4.0
11500 7.5 45.5 210 14 7 6.2 3.4 | 8.5 47.3 215 13 7 6.9 3.8
11000 8.6 47.5 200 14 7 6.6 3.6 | 9.2 48.6 205 14 7 4.0 2.2
10500 9.6 49.3 190 14 7 5.2 2.9 | 9.8 49.6 200 14 7 2.9 1.6
10250 10.0 50.0 185 14 7 4.4 2.4 | 10.0 50.0 195 14 7 3.7 2.0
10000 10.4 50.7 185 14 7 6.3 3.4 | 10.4 50.7 190 14 7 6.6 3.6
9750 10.9 51.6 180 14 7 6.8 3.7 | 10.9 51.6 185 14 7 6.4 3.5
9500 11.4 52.5 175 14 7 5.6 3.1 | 11.4 52.5 180 15 7 6.5 3.6
9250 11.7 53.1 170 14 7 3.2 1.8 | 11.9 53.4 175 15 7 6.6 3.6
9000 11.9 53.4 165 12 6 5.6 3.1 | 12.4 54.3 175 15 7 8.7 4.8
8750 12.4 54.3 155 12 6 7.6 4.2 | 13.1 55.6 170 15 8 10.2 5.6
8500 12.8 55.0 150 11 6 8.0 4.4 | 13.9 57.0 165 15 8 9.4 5.1
8250 13.5 56.3 145 11 6 9.3 5.1 | 14.5 58.1 160 16 8 8.6 4.7
8000 14.2 57.6 145 11 6 9.6 5.3 | 15.2 59.4 160 16 8 8.9 4.9
7750 14.9 58.8 145 11 6 10.2 5.6 | 15.9 60.6 160 16 8 9.7 5.3
7500 15.7 60.3 140 11 6 10.0 5.5 | 16.6 61.9 155 17 9 9.6 5.3
7250 16.4 61.5 140 11 6 9.6 5.3 | 17.3 63.1 155 17 9 9.4 5.2
7000 17.2 63.0 140 11 6 10.0 5.5 | 18.0 64.4 155 17 9 9.7 5.3
6750 17.9 64.2 140 11 5 11.1 6.1 | 18.8 65.8 155 17 9 10.4 5.7
6500 18.8 65.8 135 11 5 10.7 5.9 | 19.6 67.3 150 17 9 10.3 5.6
6250 19.5 67.1 135 10 5 10.6 5.8 | 20.3 68.5 150 17 9 10.0 5.5
6000 20.3 68.5 135 10 5 9.0 4.9 | 21.0 69.8 150 16 8 9.6 5.3
5750 21.1 70.0 135 10 5 15.2 8.3 | 21.8 71.2 150 16 8 11.3 6.2
5500 22.8 73.0 130 9 5 30.8 16.9 | 22.8 73.0 150 14 7 16.1 8.8
________________________________________________________________________________
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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