Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
063
UXUS97 KBOU 040115
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1913 MDT Saturday, October 3, 2026
This forecast is for Sunday, October 4, 2026:
If the trigger temperature of 70.4 F/21.3 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 591 ft/min (3.0 m/s)
Maximum height of thermals.................. 13444 ft MSL (8148 ft AGL)
Forecast maximum temperature................... 82.0 F/28.2 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................. 11798 ft MSL (6501 ft AGL)
Thermal soaring outlook for Monday 10/05....... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... 12195 ft MSL (6899 ft AGL)
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 12687 ft MSL (7391 ft AGL)
Wave soaring outlook for Monday 10/05.......... Poor
Remarks...
Sunrise/Sunset.................... 06:59:02 / 18:37:11 MDT
Total possible sunshine........... 11 hr 38 min 10 sec (698 min 10 sec)
Altitude of sun at 12:48:07 MDT... 45.57 degrees
Upper air data from numerical model forecast valid on 10/04/2026 at 0600 MDT
Freezing level.................. 14966 ft MSL (9670 ft AGL)
Convective condensation level... 13112 ft MSL (7816 ft AGL)
Lifted condensation level....... 13477 ft MSL (8180 ft AGL)
Lifted index.................... -4.8
K index......................... +21.3
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 -62.5 -80.5 305 36 19 3.6 2.0 M M M M M
45000 -57.0 -70.6 305 41 21 3.8 2.1 M M M M M
40000 -51.3 -60.3 310 41 21 3.1 1.7 M M M M M
38000 -49.4 -56.9 305 35 18 3.1 1.7 M M M M M
36000 -47.5 -53.5 305 29 15 3.2 1.8 M M M M M
34000 -44.0 -47.2 305 27 14 6.9 3.8 M M M M M
32000 -39.3 -38.7 305 27 14 6.7 3.7 M M M M M
30000 -34.7 -30.5 305 23 12 7.8 4.3 40.9 105.6 9.9 M M
29000 -32.4 -26.3 305 20 10 7.8 4.3 40.2 104.3 9.5 M M
28000 -30.1 -22.2 305 18 9 7.7 4.2 39.5 103.2 9.1 M M
27000 -27.8 -18.0 300 16 8 7.6 4.2 38.6 101.5 8.5 M M
26000 -25.5 -13.9 290 15 8 7.6 4.2 37.8 100.0 7.9 M M
25000 -23.2 -9.8 280 14 7 7.7 4.2 37.1 98.8 7.5 M M
24000 -20.8 -5.4 280 14 7 8.1 4.4 36.4 97.5 7.0 M M
23000 -18.4 -1.1 275 14 7 8.1 4.4 35.8 96.4 6.6 M M
22000 -15.9 3.4 270 14 7 7.9 4.3 35.3 95.5 6.2 M M
21000 -13.7 7.3 270 14 7 7.5 4.1 34.4 93.9 5.6 M M
20000 -11.4 11.5 265 14 7 7.5 4.1 33.6 92.5 4.9 M M
19500 -10.3 13.5 265 14 7 7.5 4.1 33.3 91.9 4.7 M M
19000 -9.2 15.4 265 14 7 7.4 4.0 32.9 91.2 4.3 M M
18500 -8.1 17.4 275 14 7 7.4 4.1 32.5 90.4 4.0 M M
18000 -7.0 19.4 280 15 8 7.4 4.1 32.1 89.7 3.6 M M
17500 -6.0 21.2 290 15 8 7.5 4.1 31.6 89.0 3.2 M M
17000 -5.0 23.0 300 16 8 7.6 4.2 31.3 88.3 2.8 M M
16500 -3.3 26.1 300 17 9 7.7 4.2 30.7 87.3 2.2 M M
16000 -2.3 27.9 300 18 9 8.0 4.4 30.4 86.7 1.9 M M
15500 -1.1 30.0 300 17 9 8.8 4.8 30.2 86.3 1.6 M M
15000 0.2 32.4 295 16 8 9.0 4.9 30.0 86.0 1.4 M M
14500 1.3 34.3 295 14 7 6.3 3.5 29.7 85.4 1.0 M M
14000 2.2 36.0 285 13 7 6.7 3.7 29.1 84.5 0.5 M M
13500 3.1 37.6 275 12 6 4.9 2.7 28.5 83.3 -0.0 589 3.0
13000 3.9 39.0 255 12 6 4.8 2.6 27.7 81.9 -0.8 553 2.8
12500 4.5 40.1 240 13 7 3.4 1.9 26.8 80.3 -1.6 519 2.6
12000 4.9 40.8 225 14 7 3.1 1.7 25.8 78.4 -2.7 492 2.5
11500 5.4 41.7 210 16 8 5.6 3.1 24.8 76.6 -3.7 463 2.4
11000 6.3 43.3 200 16 8 6.6 3.6 24.3 75.7 -4.2 420 2.1
10500 7.2 45.0 190 16 8 5.7 3.1 23.8 74.8 -4.7 377 1.9
10250 7.7 45.9 190 16 8 5.4 3.0 23.4 74.2 -5.1 357 1.8
10000 8.1 46.6 190 16 8 7.2 4.0 23.1 73.6 -5.4 336 1.7
9750 8.7 47.7 190 16 8 7.5 4.1 23.0 73.4 -5.5 312 1.6
9500 9.1 48.4 185 16 8 5.5 3.0 22.7 72.9 -5.8 291 1.5
9250 9.4 48.9 185 15 8 4.7 2.6 22.3 72.2 -6.3 275 1.4
9000 9.7 49.5 185 15 8 6.0 3.3 22.0 71.5 -6.7 259 1.3
8750 10.1 50.2 185 14 7 5.6 3.1 21.7 71.1 -7.1 240 1.2
8500 10.4 50.7 185 14 7 3.8 2.1 21.3 70.3 -7.6 224 1.1
8250 10.6 51.1 185 14 7 3.8 2.1 20.8 69.5 -8.1 210 1.1
8000 10.8 51.4 185 14 7 3.6 2.0 20.4 68.7 -8.6 195 1.0
7750 11.0 51.8 190 14 7 0.9 0.5 19.8 67.7 -9.2 184 0.9
7500 10.9 51.6 185 15 8 -0.4 -0.2 19.0 66.3 -10.0 178 0.9
7250 10.9 51.6 185 17 9 -1.1 -0.6 18.3 64.9 -10.8 171 0.9
7000 10.9 51.6 180 18 9 3.0 1.6 17.5 63.5 -11.6 165 0.8
6750 11.3 52.3 180 18 9 7.2 4.0 17.3 63.1 -11.9 144 0.7
6500 11.8 53.2 180 17 9 6.1 3.3 17.0 62.6 -12.2 123 0.6
6250 12.2 54.0 175 17 9 6.3 3.5 16.7 62.1 -12.5 102 0.5
6000 12.7 54.9 175 17 9 6.7 3.7 16.5 61.7 -12.8 81 0.4
5750 13.2 55.8 175 15 8 5.6 3.0 16.2 61.2 -13.1 60 0.3
5500 13.4 56.1 170 12 6 2.5 1.4 15.8 60.4 -13.6 44 0.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/04/2026 at 0900 MDT | 10/04/2026 at 1200 MDT
|
CAPE... +51.9 LI... -0.3 | CAPE... +171.1 LI... -0.6
CINH... -52.7 K Index... +20.6 | CINH... -118.9 K Index... +15.8
|
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 -63.0 -81.4 305 32 17 3.4 1.8 | -63.5 -82.3 295 29 15 3.5 1.9
45000 -57.5 -71.5 305 35 18 4.3 2.3 | -57.8 -72.0 300 31 16 4.5 2.5
40000 -51.2 -60.2 315 32 16 3.4 1.9 | -51.0 -59.8 310 25 13 4.2 2.3
38000 -49.1 -56.4 320 27 14 3.5 1.9 | -48.5 -55.3 315 23 12 4.2 2.3
36000 -47.0 -52.6 325 23 12 3.6 2.0 | -46.0 -50.8 325 21 11 4.2 2.3
34000 -43.0 -45.4 320 22 11 6.6 3.6 | -42.3 -44.1 320 17 9 5.8 3.2
32000 -39.1 -38.4 310 21 11 6.4 3.5 | -38.8 -37.8 310 15 8 5.6 3.1
30000 -34.4 -29.9 310 22 11 8.0 4.4 | -34.3 -29.7 305 16 8 7.9 4.3
29000 -32.0 -25.6 310 22 12 8.0 4.4 | -31.9 -25.4 305 17 9 7.9 4.3
28000 -29.7 -21.5 310 23 12 7.5 4.1 | -29.5 -21.1 305 18 9 7.7 4.2
27000 -27.5 -17.5 305 22 11 7.4 4.0 | -27.3 -17.1 305 19 10 7.6 4.2
26000 -25.3 -13.5 305 20 10 7.4 4.0 | -25.0 -13.0 305 19 10 7.7 4.2
25000 -23.1 -9.6 300 19 10 7.3 4.0 | -22.7 -8.9 305 19 10 7.6 4.1
24000 -20.9 -5.6 295 18 9 7.3 4.0 | -20.6 -5.1 305 19 10 6.9 3.8
23000 -18.7 -1.7 295 17 9 7.3 4.0 | -18.6 -1.5 305 18 9 6.9 3.8
22000 -16.5 2.3 290 16 8 7.2 4.0 | -16.5 2.3 305 17 9 7.1 3.9
21000 -14.4 6.1 290 14 7 7.2 3.9 | -14.3 6.3 310 16 8 7.5 4.1
20000 -12.3 9.9 295 12 6 7.2 3.9 | -12.0 10.4 310 15 7 7.5 4.1
19500 -11.2 11.8 295 11 6 7.2 3.9 | -10.9 12.4 315 14 7 7.5 4.1
19000 -10.1 13.8 300 11 6 7.5 4.1 | -9.8 14.4 315 13 7 7.5 4.1
18500 -8.5 16.7 310 10 5 7.4 4.1 | -8.1 17.4 315 13 6 7.5 4.1
18000 -7.4 18.7 315 11 6 7.9 4.3 | -7.0 19.4 315 12 6 7.5 4.1
17500 -6.2 20.8 320 11 6 7.9 4.4 | -5.9 21.4 310 12 6 7.5 4.1
17000 -5.1 22.8 320 12 6 8.1 4.4 | -4.8 23.4 310 12 6 7.7 4.2
16500 -3.9 25.0 320 13 6 8.2 4.5 | -3.7 25.3 310 12 6 7.8 4.3
16000 -2.7 27.1 320 13 7 8.4 4.6 | -2.5 27.5 310 11 6 7.9 4.4
15500 -1.4 29.5 320 13 7 9.0 4.9 | -1.3 29.7 310 11 6 8.3 4.5
15000 -0.1 31.8 320 13 7 9.0 4.9 | -0.1 31.8 310 11 6 8.3 4.5
14500 1.2 34.2 320 13 7 8.3 4.6 | 1.1 34.0 310 11 6 8.5 4.7
14000 2.4 36.3 315 13 7 8.5 4.6 | 2.3 36.1 310 11 6 8.5 4.7
13500 3.6 38.5 310 13 7 7.7 4.2 | 3.6 38.5 315 11 6 8.5 4.7
13000 4.7 40.5 305 12 6 7.7 4.2 | 4.8 40.6 315 12 6 8.6 4.7
12500 5.7 42.3 300 11 6 6.5 3.6 | 6.1 43.0 315 12 6 8.5 4.7
12000 6.6 43.9 285 11 6 6.2 3.4 | 7.3 45.1 315 12 6 8.5 4.7
11500 7.5 45.5 275 11 6 5.7 3.1 | 8.5 47.3 315 12 6 8.1 4.4
11000 8.2 46.8 255 11 6 5.6 3.1 | 9.7 49.5 310 11 6 7.9 4.3
10500 9.0 48.2 240 12 6 4.9 2.7 | 10.8 51.4 310 11 6 4.9 2.7
10250 9.3 48.7 235 13 7 4.7 2.6 | 11.1 52.0 310 11 6 5.4 3.0
10000 9.7 49.5 230 14 7 5.5 3.0 | 11.6 52.9 310 10 5 9.4 5.1
9750 10.0 50.0 225 16 8 5.7 3.1 | 12.3 54.1 305 9 5 9.0 5.0
9500 10.4 50.7 220 17 9 5.5 3.0 | 12.9 55.2 300 9 4 6.6 3.6
9250 10.8 51.4 215 19 10 5.6 3.1 | 13.3 55.9 300 8 4 4.9 2.7
9000 11.1 52.0 210 20 10 5.0 2.8 | 13.7 56.7 300 8 4 6.9 3.8
8750 11.4 52.5 205 20 11 5.0 2.7 | 14.2 57.6 285 7 4 7.2 3.9
8500 11.8 53.2 205 21 11 6.0 3.3 | 14.6 58.3 270 6 3 5.0 2.7
8250 12.3 54.1 205 22 11 6.1 3.3 | 14.9 58.8 255 5 3 4.5 2.5
8000 12.7 54.9 200 23 12 6.4 3.5 | 15.2 59.4 235 5 3 4.7 2.6
7750 13.2 55.8 200 22 11 5.7 3.1 | 15.6 60.1 205 7 3 6.2 3.4
7500 13.6 56.5 195 22 11 4.9 2.7 | 16.1 61.0 200 7 4 7.8 4.3
7250 14.0 57.2 195 22 11 5.2 2.8 | 16.6 61.9 200 7 4 6.9 3.8
7000 14.3 57.7 190 21 11 4.8 2.6 | 17.1 62.8 200 7 4 9.8 5.4
6750 14.6 58.3 190 22 11 3.3 1.8 | 17.9 64.2 195 8 4 11.3 6.2
6500 14.8 58.6 190 20 10 2.7 1.5 | 18.6 65.5 190 8 4 9.5 5.2
6250 15.0 59.0 185 19 10 2.2 1.2 | 19.4 66.9 190 7 4 9.6 5.3
6000 15.2 59.4 180 17 9 4.8 2.6 | 20.1 68.2 190 7 4 11.2 6.1
5750 15.7 60.3 180 16 8 10.1 5.5 | 21.2 70.2 200 6 3 17.8 9.8
5500 16.5 61.7 175 13 7 10.8 5.9 | 22.7 72.9 195 6 3 23.5 12.9
10/04/2026 at 1500 MDT | 10/04/2026 at 1800 MDT
|
CAPE... +391.6 LI... -1.5 | CAPE... +340.8 LI... -1.9
CINH... -66.5 K Index... +12.1 | CINH... -74.8 K Index... +22.0
|
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 -63.3 -81.9 295 30 15 3.5 1.9 | -63.7 -82.7 290 27 14 3.5 1.9
45000 -57.8 -72.0 295 33 17 3.9 2.2 | -58.2 -72.8 295 30 15 4.2 2.3
40000 -51.7 -61.1 295 25 13 5.2 2.9 | -51.6 -60.9 300 25 13 5.6 3.1
38000 -48.6 -55.5 300 22 12 5.2 2.9 | -48.2 -54.8 300 21 11 5.6 3.1
36000 -45.4 -49.7 310 20 10 5.2 2.9 | -44.9 -48.8 300 17 9 5.6 3.1
34000 -41.8 -43.2 310 19 10 5.3 2.9 | -41.0 -41.8 300 16 8 5.7 3.1
32000 -38.6 -37.5 305 18 10 5.1 2.8 | -37.6 -35.7 300 16 8 5.5 3.0
30000 -34.1 -29.4 300 19 10 7.9 4.3 | -33.4 -28.1 295 17 9 7.3 4.0
29000 -31.8 -25.2 295 20 10 7.9 4.3 | -31.2 -24.2 295 17 9 7.3 4.0
28000 -29.4 -20.9 295 21 11 7.8 4.3 | -29.0 -20.2 295 17 9 7.4 4.1
27000 -27.1 -16.8 295 20 10 7.8 4.3 | -26.8 -16.2 300 17 9 7.5 4.1
26000 -24.7 -12.5 300 19 10 7.8 4.3 | -24.6 -12.3 300 17 9 7.5 4.1
25000 -22.4 -8.3 300 18 9 7.7 4.2 | -22.3 -8.1 300 17 9 7.4 4.1
24000 -20.3 -4.5 305 18 9 7.2 3.9 | -20.2 -4.4 300 17 9 7.1 3.9
23000 -18.1 -0.6 305 17 9 7.2 3.9 | -18.1 -0.6 305 16 8 7.1 3.9
22000 -16.0 3.2 305 17 9 7.4 4.1 | -16.1 3.0 305 16 8 7.3 4.0
21000 -13.7 7.3 305 16 8 7.7 4.2 | -13.8 7.2 310 16 8 7.5 4.1
20000 -11.4 11.5 305 15 8 7.7 4.2 | -11.5 11.3 310 16 8 7.5 4.1
19500 -10.2 13.6 305 14 7 7.7 4.2 | -10.4 13.3 310 16 8 7.5 4.1
19000 -9.1 15.6 305 14 7 7.4 4.0 | -9.3 15.3 310 16 8 7.4 4.1
18500 -8.0 17.6 305 13 7 7.4 4.1 | -8.2 17.2 310 16 8 7.5 4.1
18000 -6.8 19.8 305 13 7 7.5 4.1 | -7.1 19.2 310 17 9 7.9 4.3
17500 -5.7 21.7 305 13 7 7.6 4.2 | -5.4 22.3 310 18 9 8.2 4.5
17000 -4.1 24.6 305 14 7 7.7 4.2 | -4.2 24.4 310 18 9 8.3 4.6
16500 -2.9 26.8 305 14 7 7.7 4.2 | -3.0 26.6 310 18 9 8.4 4.6
16000 -1.8 28.8 300 14 7 8.0 4.4 | -1.8 28.8 305 18 9 8.6 4.7
15500 -0.6 30.9 300 14 7 8.6 4.7 | -0.6 30.9 305 18 9 8.8 4.8
15000 0.7 33.3 300 14 7 8.6 4.7 | 0.7 33.3 305 17 9 8.9 4.9
14500 2.0 35.6 300 14 7 8.9 4.9 | 2.0 35.6 305 16 8 8.5 4.6
14000 3.4 38.1 300 14 7 8.9 4.9 | 3.2 37.8 305 15 8 8.5 4.7
13500 4.6 40.3 305 13 7 8.2 4.5 | 4.5 40.1 310 13 7 8.3 4.5
13000 5.8 42.4 305 13 6 8.1 4.5 | 5.7 42.3 310 11 6 8.3 4.6
12500 7.0 44.6 310 12 6 8.3 4.5 | 6.9 44.4 310 9 5 7.6 4.2
12000 8.2 46.8 315 11 6 8.3 4.6 | 8.1 46.6 315 7 4 7.4 4.1
11500 9.4 48.9 325 10 5 8.1 4.5 | 9.2 48.6 325 5 3 7.2 3.9
11000 10.6 51.1 330 10 5 8.1 4.4 | 10.3 50.5 340 4 2 7.1 3.9
10500 11.6 52.9 340 10 5 3.4 1.9 | 11.3 52.3 010 3 1 3.3 1.8
10250 11.8 53.2 340 10 5 6.1 3.3 | 11.5 52.7 015 2 1 5.8 3.2
10000 12.6 54.7 340 9 5 12.8 7.0 | 12.2 54.0 035 1 1 11.9 6.5
9750 13.5 56.3 345 9 5 11.3 6.2 | 13.0 55.4 120 1 0 10.9 6.0
9500 14.2 57.6 345 8 4 7.3 4.0 | 13.7 56.7 155 2 1 8.2 4.5
9250 14.6 58.3 345 7 4 5.2 2.8 | 14.2 57.6 165 2 1 6.5 3.6
9000 15.0 59.0 350 5 3 7.8 4.3 | 14.7 58.5 170 2 1 9.4 5.2
8750 15.6 60.1 360 3 2 8.4 4.6 | 15.4 59.7 175 2 1 10.6 5.8
8500 16.0 60.8 010 2 1 6.7 3.7 | 16.1 61.0 180 2 1 9.2 5.1
8250 16.4 61.5 030 1 1 6.3 3.4 | 16.7 62.1 180 2 1 8.9 4.9
8000 16.8 62.2 075 1 0 7.3 4.0 | 17.4 63.3 180 2 1 9.5 5.2
7750 17.4 63.3 095 1 0 9.2 5.0 | 18.1 64.6 180 2 1 10.1 5.5
7500 18.1 64.6 095 1 0 9.9 5.4 | 18.8 65.8 180 2 1 9.8 5.4
7250 18.8 65.8 100 1 0 9.4 5.2 | 19.5 67.1 180 2 1 10.0 5.5
7000 19.5 67.1 100 1 0 10.8 5.9 | 20.3 68.5 185 2 1 9.4 5.1
6750 20.4 68.7 105 1 0 10.8 5.9 | 21.0 69.8 185 2 1 9.5 5.2
6500 21.1 70.0 105 1 0 9.7 5.3 | 21.7 71.1 185 2 1 10.3 5.6
6250 21.9 71.4 105 1 0 9.6 5.3 | 22.5 72.5 190 2 1 10.1 5.5
6000 22.6 72.7 105 1 0 11.0 6.0 | 23.2 73.8 190 2 1 10.0 5.5
5750 23.6 74.5 110 1 0 16.1 8.9 | 23.9 75.0 195 2 1 9.3 5.1
5500 25.0 77.0 115 1 0 20.3 11.1 | 24.6 76.3 190 2 1 8.5 4.6
________________________________________________________________________________
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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