Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
681
UXUS97 KBOU 301319
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0714 MDT Tuesday, September 30, 2025
This forecast is for Tuesday, September 30, 2025:
If the trigger temperature of 72.6 F/22.6 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 576 ft/min (2.9 m/s)
Maximum height of thermals.................. 14333 ft MSL (9012 ft AGL)
Forecast maximum temperature................... 79.0 F/26.6 C
Time of trigger temperature.................... 1145 MDT
Time of overdevelopment........................ None
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................. 10213 ft MSL (4892 ft AGL)
Thermal soaring outlook for Wednesday 10/01.... 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)................ Neither
Potential height of wave....................... 23511 ft MSL (18190 ft AGL)
Wave soaring outlook for Wednesday 10/01....... Poor
Remarks...
Sunrise/Sunset.................... 06:55:22 / 18:43:14 MDT
Total possible sunshine........... 11 hr 47 min 52 sec (707 min 52 sec)
Altitude of sun at 12:49:18 MDT... 47.04 degrees
Upper air data from numerical model forecast valid on 09/30/2025 at 0600 MDT
Freezing level.................. 13923 ft MSL (8602 ft AGL)
Convective condensation level... 14018 ft MSL (8697 ft AGL)
Lifted condensation level....... 14200 ft MSL (8879 ft AGL)
Lifted index.................... -1.1
K index......................... +21.5
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 -63.3 -81.9 250 25 13 3.6 2.0 M M M M M
45000 -56.7 -70.1 255 43 22 5.6 3.1 M M M M M
40000 -48.5 -55.3 260 58 30 3.2 1.8 M M M M M
38000 -46.4 -51.5 260 52 27 3.4 1.9 M M M M M
36000 -44.4 -47.9 260 46 23 3.4 1.9 M M M M M
34000 -41.0 -41.8 260 38 20 6.7 3.7 M M M M M
32000 -37.0 -34.6 265 30 16 6.7 3.7 M M M M M
30000 -32.3 -26.1 275 26 13 7.2 3.9 43.8 110.9 13.5 M M
29000 -30.1 -22.2 280 26 13 7.2 3.9 42.8 109.1 12.9 M M
28000 -28.0 -18.4 285 26 13 7.0 3.9 42.0 107.5 12.3 M M
27000 -26.1 -15.0 285 23 12 6.1 3.3 40.5 105.0 11.4 M M
26000 -24.3 -11.7 285 19 10 6.1 3.4 39.1 102.4 10.4 M M
25000 -22.5 -8.5 285 16 8 6.1 3.3 37.9 100.1 9.4 M M
24000 -20.4 -4.7 275 13 7 7.5 4.1 36.8 98.2 8.7 M M
23000 -18.2 -0.8 270 12 6 7.5 4.1 35.9 96.7 8.1 M M
22000 -15.9 3.4 260 10 5 7.6 4.2 35.2 95.4 7.5 M M
21000 -13.9 7.0 250 11 5 6.7 3.7 34.2 93.5 6.7 M M
20000 -11.9 10.6 245 11 6 6.7 3.7 33.1 91.5 5.8 M M
19500 -10.9 12.4 240 11 6 6.6 3.6 32.6 90.6 5.4 M M
19000 -9.9 14.2 235 12 6 6.2 3.4 32.1 89.7 5.0 M M
18500 -9.1 15.6 240 12 6 5.7 3.1 31.3 88.4 4.4 M M
18000 -8.3 17.1 240 12 6 5.6 3.1 30.7 87.2 3.8 M M
17500 -7.4 18.7 240 12 6 6.3 3.4 30.0 86.0 3.2 M M
17000 -6.5 20.3 245 12 6 6.3 3.4 29.4 84.9 2.6 M M
16500 -5.1 22.8 245 12 6 7.0 3.8 28.6 83.4 1.9 M M
16000 -4.1 24.6 245 11 6 7.0 3.8 28.1 82.6 1.4 M M
15500 -3.1 26.4 245 11 6 7.2 4.0 27.7 81.8 0.9 M M
15000 -2.1 28.2 245 10 5 7.3 4.0 27.2 81.0 0.5 M M
14500 -1.1 30.0 245 10 5 7.5 4.1 26.9 80.3 0.1 M M
14000 -0.0 32.0 245 9 4 7.7 4.2 26.5 79.7 -0.3 736 3.7
13500 1.1 34.0 240 8 4 7.8 4.3 26.2 79.1 -0.7 688 3.5
13000 2.2 36.0 245 7 3 7.9 4.3 25.9 78.6 -1.0 640 3.3
12500 3.4 38.1 245 6 3 7.9 4.4 25.6 78.1 -1.3 591 3.0
12000 4.5 40.1 245 5 3 7.9 4.4 25.3 77.5 -1.7 542 2.8
11500 5.7 42.3 250 5 3 7.9 4.3 25.0 77.0 -2.0 493 2.5
11000 6.8 44.2 255 4 2 7.5 4.1 24.7 76.4 -2.3 444 2.3
10500 7.9 46.2 265 4 2 6.6 3.6 24.3 75.8 -2.7 396 2.0
10250 8.3 46.9 270 4 2 5.4 2.9 24.0 75.2 -3.0 376 1.9
10000 8.8 47.8 275 4 2 8.0 4.4 23.7 74.7 -3.2 355 1.8
9750 9.5 49.1 285 4 2 9.6 5.3 23.7 74.7 -3.3 327 1.7
9500 10.2 50.4 295 4 2 9.0 4.9 23.7 74.6 -3.3 299 1.5
9250 10.8 51.4 300 4 2 7.5 4.1 23.6 74.4 -3.4 272 1.4
9000 11.3 52.3 300 4 2 7.6 4.2 23.4 74.1 -3.6 249 1.3
8750 11.9 53.4 300 4 2 8.8 4.8 23.3 73.9 -3.8 224 1.1
8500 12.5 54.5 300 4 2 8.2 4.5 23.2 73.7 -3.9 198 1.0
8250 13.1 55.6 300 4 2 7.9 4.3 23.0 73.5 -4.1 173 0.9
8000 13.7 56.7 295 3 2 7.2 4.0 22.9 73.2 -4.2 149 0.8
7750 14.2 57.6 290 3 1 6.7 3.7 22.7 72.8 -4.5 127 0.6
7500 14.6 58.3 290 3 1 5.1 2.8 22.4 72.3 -4.8 106 0.5
7250 14.9 58.8 285 2 1 3.5 1.9 21.9 71.5 -5.2 90 0.5
7000 15.2 59.4 280 2 1 3.9 2.1 21.5 70.7 -5.7 75 0.4
6750 15.4 59.7 275 2 1 3.5 1.9 21.0 69.8 -6.2 59 0.3
6500 15.5 59.9 275 2 1 -3.2 -1.8 20.4 68.7 -6.9 51 0.3
6250 15.0 59.0 270 3 1 -8.3 -4.5 19.1 66.4 -8.2 59 0.3
6000 14.4 57.9 270 3 2 -5.3 -2.9 17.8 64.1 -9.4 67 0.3
5750 13.9 57.0 265 4 2 -10.3 -5.7 16.6 61.9 -10.7 74 0.4
5500 12.5 54.5 245 3 2 -25.0 -13.7 14.6 58.3 -12.8 109 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/30/2025 at 0900 MDT | 09/30/2025 at 1200 MDT
|
CAPE... 0.0 LI... +1.1 | CAPE... +6.6 LI... +1.7
CINH... 0.0 K Index... +21.5 | CINH... -47.0 K Index... +20.7
|
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 -62.7 -80.9 235 25 13 3.7 2.0 | -62.2 -80.0 220 29 15 3.7 2.0
45000 -56.1 -69.0 245 42 22 5.5 3.0 | -55.7 -68.3 230 45 23 5.2 2.9
40000 -48.1 -54.6 250 68 35 2.9 1.6 | -48.1 -54.6 240 69 36 2.5 1.3
38000 -46.2 -51.2 250 61 31 3.1 1.7 | -46.5 -51.7 240 61 31 2.7 1.5
36000 -44.3 -47.7 250 53 28 3.2 1.7 | -44.8 -48.6 240 52 27 2.8 1.5
34000 -41.5 -42.7 250 46 23 5.3 2.9 | -42.4 -44.3 240 45 23 4.8 2.6
32000 -38.3 -36.9 245 37 19 5.3 2.9 | -39.5 -39.1 235 39 20 4.8 2.6
30000 -33.5 -28.3 245 30 15 8.0 4.4 | -34.7 -30.5 235 32 17 8.3 4.5
29000 -31.1 -24.0 245 27 14 8.0 4.4 | -32.3 -26.1 235 29 15 8.3 4.5
28000 -28.8 -19.8 250 25 13 7.9 4.4 | -29.8 -21.6 235 25 13 8.2 4.5
27000 -26.5 -15.7 255 22 11 7.6 4.2 | -27.4 -17.3 240 24 12 7.9 4.3
26000 -24.2 -11.6 255 20 10 7.6 4.2 | -25.1 -13.2 240 23 12 7.9 4.4
25000 -21.9 -7.4 260 18 9 7.6 4.2 | -22.7 -8.9 245 23 12 7.9 4.4
24000 -19.8 -3.6 255 16 8 6.9 3.8 | -20.2 -4.4 245 22 11 8.4 4.6
23000 -17.7 0.1 250 15 8 6.9 3.8 | -17.7 0.1 245 22 11 8.4 4.6
22000 -15.7 3.7 240 14 7 7.0 3.8 | -15.2 4.6 245 21 11 8.6 4.7
21000 -13.8 7.2 235 13 7 6.1 3.4 | -13.0 8.6 240 20 10 6.8 3.8
20000 -12.0 10.4 235 12 6 6.1 3.4 | -11.0 12.2 235 19 10 6.9 3.8
19500 -11.1 12.0 230 12 6 6.1 3.3 | -9.9 14.2 235 19 10 6.8 3.8
19000 -10.2 13.6 230 11 6 5.4 3.0 | -8.9 16.0 230 18 10 6.0 3.3
18500 -9.5 14.9 225 11 6 4.8 2.6 | -8.1 17.4 230 17 9 5.4 3.0
18000 -8.8 16.2 220 11 5 4.8 2.6 | -7.3 18.9 225 17 9 5.6 3.1
17500 -8.1 17.4 220 11 5 5.7 3.1 | -6.7 19.9 220 16 8 3.5 1.9
17000 -7.3 18.9 215 11 6 5.7 3.1 | -6.2 20.8 220 15 8 3.8 2.1
16500 -6.4 20.5 215 11 6 6.8 3.7 | -5.7 21.7 215 14 7 5.3 2.9
16000 -4.9 23.2 210 10 5 7.5 4.1 | -4.8 23.4 210 14 7 6.2 3.4
15500 -3.8 25.2 210 10 5 7.6 4.2 | -3.5 25.7 210 14 7 7.5 4.1
15000 -2.7 27.1 210 9 5 7.6 4.2 | -2.3 27.9 205 13 7 7.7 4.2
14500 -1.6 29.1 205 8 4 7.7 4.2 | -1.2 29.8 200 13 6 7.8 4.3
14000 -0.5 31.1 200 6 3 7.8 4.3 | -0.1 31.8 200 12 6 7.8 4.3
13500 0.6 33.1 200 4 2 7.7 4.2 | 1.0 33.8 200 11 5 7.7 4.2
13000 1.7 35.1 200 3 2 7.3 4.0 | 2.1 35.8 200 9 5 7.2 4.0
12500 2.7 36.9 215 2 1 7.4 4.1 | 3.1 37.6 195 8 4 7.2 4.0
12000 3.8 38.8 255 1 1 7.8 4.3 | 4.1 39.4 195 7 3 7.0 3.9
11500 5.0 41.0 310 2 1 7.8 4.3 | 5.1 41.2 195 5 3 7.1 3.9
11000 6.1 43.0 325 3 1 7.5 4.1 | 6.3 43.3 195 4 2 8.1 4.4
10500 7.2 45.0 330 4 2 6.3 3.5 | 7.5 45.5 200 3 2 5.8 3.2
10250 7.6 45.7 330 4 2 5.3 2.9 | 7.7 45.9 205 3 2 4.5 2.4
10000 8.1 46.6 330 5 2 8.4 4.6 | 8.3 46.9 215 3 1 8.8 4.8
9750 8.8 47.8 330 6 3 10.0 5.5 | 9.0 48.2 230 2 1 10.3 5.6
9500 9.5 49.1 330 6 3 9.0 4.9 | 9.7 49.5 245 2 1 9.1 5.0
9250 10.1 50.2 325 7 4 6.7 3.7 | 10.3 50.5 260 3 1 6.6 3.6
9000 10.6 51.1 325 7 4 7.8 4.3 | 10.8 51.4 270 3 2 7.9 4.3
8750 11.3 52.3 325 8 4 10.0 5.5 | 11.5 52.7 280 4 2 10.1 5.5
8500 12.0 53.6 325 9 4 8.5 4.7 | 12.2 54.0 285 4 2 9.0 4.9
8250 12.5 54.5 320 9 5 7.0 3.8 | 12.9 55.2 290 5 3 8.3 4.6
8000 13.0 55.4 320 9 5 7.1 3.9 | 13.5 56.3 290 5 3 8.3 4.6
7750 13.6 56.5 320 10 5 8.3 4.5 | 14.1 57.4 290 5 3 8.4 4.6
7500 14.2 57.6 320 10 5 7.3 4.0 | 14.7 58.5 290 5 3 9.0 4.9
7250 14.7 58.5 320 9 5 6.0 3.3 | 15.4 59.7 290 4 2 9.6 5.3
7000 15.1 59.2 320 9 5 6.6 3.6 | 16.0 60.8 285 4 2 9.2 5.0
6750 15.5 59.9 320 8 4 3.7 2.0 | 16.7 62.1 285 3 2 8.9 4.9
6500 15.6 60.1 315 7 4 -0.6 -0.3 | 17.4 63.3 285 3 2 10.2 5.6
6250 15.5 59.9 310 6 3 -1.8 -1.0 | 18.2 64.8 285 3 2 11.7 6.4
6000 15.4 59.7 300 5 3 -0.2 -0.1 | 19.0 66.2 285 3 1 9.8 5.4
5750 15.5 59.9 295 5 3 1.2 0.7 | 19.8 67.6 285 3 1 13.7 7.5
5500 15.4 59.7 270 4 2 -0.3 -0.1 | 21.2 70.2 280 3 1 25.0 13.7
09/30/2025 at 1500 MDT | 09/30/2025 at 1800 MDT
|
CAPE... +111.8 LI... +0.9 | CAPE... +203.3 LI... -0.9
CINH... -68.8 K Index... +20.5 | CINH... -35.9 K Index... +30.8
|
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 -60.6 -77.1 220 34 18 4.7 2.6 | -62.0 -79.6 230 38 19 3.9 2.1
45000 -54.0 -65.2 225 44 23 2.6 1.4 | -55.7 -68.3 235 43 22 5.0 2.7
40000 -50.0 -58.0 240 60 31 3.9 2.1 | -48.1 -54.6 245 47 24 0.6 0.3
38000 -47.7 -53.9 240 51 26 3.9 2.1 | -47.9 -54.2 245 43 22 0.3 0.2
36000 -45.3 -49.5 245 41 21 3.9 2.1 | -47.7 -53.9 245 38 20 0.3 0.2
34000 -42.8 -45.0 245 36 19 4.5 2.5 | -45.0 -49.0 245 35 18 7.0 3.9
32000 -40.1 -40.2 245 34 17 4.5 2.5 | -40.8 -41.4 250 32 16 7.0 3.8
30000 -35.6 -32.1 245 32 16 7.8 4.3 | -36.0 -32.8 250 29 15 8.6 4.7
29000 -33.3 -27.9 240 31 16 7.8 4.3 | -32.8 -27.0 250 27 14 8.6 4.7
28000 -30.9 -23.6 240 30 15 7.9 4.3 | -30.2 -22.4 255 26 13 8.5 4.7
27000 -28.6 -19.5 240 30 15 8.0 4.4 | -27.8 -18.0 250 25 13 8.0 4.4
26000 -26.2 -15.2 235 29 15 8.0 4.4 | -25.5 -13.9 250 24 13 8.0 4.4
25000 -23.8 -10.8 235 29 15 7.9 4.4 | -23.1 -9.6 250 24 12 8.1 4.4
24000 -21.2 -6.2 235 27 14 9.4 5.2 | -20.8 -5.4 245 23 12 7.6 4.2
23000 -18.3 -0.9 235 25 13 9.4 5.2 | -18.5 -1.3 235 23 12 7.6 4.2
22000 -15.5 4.1 235 22 11 9.7 5.3 | -16.3 2.7 230 23 12 7.7 4.2
21000 -13.2 8.2 235 21 11 7.1 3.9 | -14.3 6.3 230 21 11 6.7 3.7
20000 -11.1 12.0 235 21 11 7.1 3.9 | -12.4 9.7 235 19 10 6.8 3.7
19500 -10.0 14.0 235 20 11 7.1 3.9 | -11.4 11.5 240 18 9 6.8 3.7
19000 -9.0 15.8 240 20 10 5.9 3.2 | -10.4 13.3 240 17 8 6.1 3.4
18500 -8.3 17.1 240 21 11 4.9 2.7 | -9.7 14.5 245 15 8 5.6 3.1
18000 -7.6 18.3 240 21 11 4.8 2.7 | -8.9 16.0 245 13 7 5.4 3.0
17500 -6.8 19.8 240 21 11 5.1 2.8 | -7.9 17.8 245 12 6 7.6 4.2
17000 -6.1 21.0 240 21 11 5.2 2.8 | -6.9 19.6 240 11 6 7.4 4.1
16500 -5.4 22.3 240 20 11 5.5 3.0 | -5.8 21.6 230 11 5 8.0 4.4
16000 -4.6 23.7 240 19 10 5.7 3.1 | -4.6 23.7 230 11 6 8.4 4.6
15500 -3.3 26.1 235 17 9 7.4 4.1 | -3.4 25.9 230 11 6 8.0 4.4
15000 -2.2 28.0 235 16 8 7.8 4.3 | -2.0 28.4 225 11 5 6.3 3.5
14500 -1.1 30.0 235 15 8 8.2 4.5 | -1.1 30.0 220 11 5 6.6 3.6
14000 0.2 32.4 230 14 7 8.5 4.7 | -0.0 32.0 215 10 5 6.9 3.8
13500 1.4 34.5 230 13 7 8.4 4.6 | 1.0 33.8 205 10 5 7.5 4.1
13000 2.6 36.7 225 12 6 8.0 4.4 | 2.2 36.0 200 9 5 8.9 4.9
12500 3.8 38.8 225 11 6 8.1 4.4 | 3.6 38.5 195 8 4 8.9 4.9
12000 5.0 41.0 220 10 5 8.3 4.6 | 4.9 40.8 190 8 4 9.2 5.0
11500 6.2 43.2 215 10 5 8.3 4.5 | 6.3 43.3 180 7 4 9.1 5.0
11000 7.4 45.3 205 8 4 7.7 4.2 | 7.6 45.7 170 7 3 8.3 4.6
10500 8.5 47.3 195 7 4 5.7 3.1 | 8.8 47.8 160 6 3 5.5 3.0
10250 8.8 47.8 195 7 4 5.3 2.9 | 9.1 48.4 155 6 3 6.0 3.3
10000 9.4 48.9 190 6 3 9.1 5.0 | 9.8 49.6 155 5 3 11.0 6.0
9750 10.0 50.0 180 6 3 9.4 5.2 | 10.6 51.1 150 5 2 10.6 5.8
9500 10.7 51.3 170 5 3 9.0 5.0 | 11.4 52.5 145 4 2 10.3 5.6
9250 11.3 52.3 165 5 2 7.9 4.3 | 12.1 53.8 145 4 2 8.1 4.4
9000 11.8 53.2 165 4 2 9.1 5.0 | 12.7 54.9 140 3 2 8.2 4.5
8750 12.6 54.7 160 4 2 10.5 5.8 | 13.3 55.9 140 3 1 9.3 5.1
8500 13.3 55.9 160 4 2 10.2 5.6 | 14.0 57.2 135 2 1 9.1 5.0
8250 14.1 57.4 160 4 2 10.6 5.8 | 14.7 58.5 135 2 1 9.7 5.3
8000 14.9 58.8 160 4 2 10.1 5.6 | 15.4 59.7 130 1 1 9.3 5.1
7750 15.6 60.1 160 4 2 9.3 5.1 | 16.0 60.8 000 0 0 8.3 4.6
7500 16.3 61.3 160 4 2 9.6 5.3 | 16.7 62.1 000 0 0 8.5 4.7
7250 17.0 62.6 160 4 2 10.1 5.5 | 17.3 63.1 310 1 0 8.8 4.9
7000 17.8 64.0 160 4 2 10.0 5.5 | 18.0 64.4 305 2 1 8.9 4.9
6750 18.5 65.3 160 4 2 10.1 5.5 | 18.6 65.5 305 2 1 9.1 5.0
6500 19.3 66.7 165 4 2 10.5 5.8 | 19.3 66.7 305 3 2 9.3 5.1
6250 20.1 68.2 165 4 2 11.2 6.1 | 20.0 68.0 300 3 2 9.4 5.1
6000 20.9 69.6 165 4 2 10.0 5.5 | 20.7 69.3 300 4 2 9.3 5.1
5750 21.7 71.1 165 3 2 13.1 7.2 | 21.4 70.5 300 5 2 8.5 4.7
5500 23.0 73.4 165 3 2 22.7 12.4 | 21.9 71.4 300 4 2 7.9 4.4
________________________________________________________________________________
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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