Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
946
UXUS97 KBOU 011222
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0621 MDT Tuesday, September 1, 2026
This forecast is for Tuesday, September 1, 2026:
If the trigger temperature of 78.2 F/25.7 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 693 ft/min (3.5 m/s)
Maximum height of thermals.................. 14873 ft MSL (9449 ft AGL)
Forecast maximum temperature................... 87.0 F/31.0 C
Time of trigger temperature.................... 1215 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Overcast thin high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 11353 ft MSL (5929 ft AGL)
Thermal soaring outlook for Wednesday 09/02.... 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....................... 23908 ft MSL (18484 ft AGL)
Wave soaring outlook for Wednesday 09/02....... Fair
Remarks...
Sunrise/Sunset.................... 06:27:55 / 19:30:53 MDT
Total possible sunshine........... 13 hr 2 min 58 sec (782 min 58 sec)
Altitude of sun at 12:59:24 MDT... 58.29 degrees
Upper air data from numerical model forecast valid on 09/01/2026 at 0600 MDT
Freezing level.................. 16000 ft MSL (10576 ft AGL)
Convective condensation level... 14560 ft MSL (9136 ft AGL)
Lifted condensation level....... 14795 ft MSL (9371 ft AGL)
Lifted index.................... -3.4
K index......................... +22.0
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 -60.8 -77.4 245 37 19 2.9 1.6 88.9 192.0 34.2 M M
45000 -57.6 -71.7 235 49 25 0.3 0.2 71.1 160.0 25.4 M M
40000 -55.4 -67.7 215 58 30 8.9 4.9 51.2 124.1 13.8 M M
38000 -50.1 -58.2 210 55 28 9.0 4.9 50.3 122.5 13.6 M M
36000 -44.7 -48.5 205 52 27 9.0 5.0 50.0 122.0 13.7 M M
34000 -39.6 -39.3 205 51 26 8.5 4.7 48.7 119.7 13.2 M M
32000 -34.5 -30.1 200 49 25 8.6 4.7 47.9 118.2 12.8 M M
30000 -29.9 -21.8 205 45 23 7.6 4.2 46.2 115.1 11.8 M M
29000 -27.6 -17.7 210 43 22 7.6 4.2 45.4 113.6 11.3 M M
28000 -25.4 -13.7 210 40 21 7.3 4.0 44.7 112.4 10.8 M M
27000 -23.4 -10.1 210 40 21 6.9 3.8 43.5 110.2 10.0 M M
26000 -20.8 -5.4 210 39 20 6.9 3.8 42.1 107.8 9.0 M M
25000 -18.8 -1.8 210 39 20 6.8 3.7 41.1 106.1 8.3 M M
24000 -16.8 1.8 215 39 20 6.7 3.7 39.9 103.8 7.4 M M
23000 -14.8 5.4 215 39 20 6.7 3.7 38.8 101.8 6.5 M M
22000 -12.8 9.0 220 39 20 7.3 4.0 37.8 100.0 5.7 M M
21000 -10.4 13.3 225 35 18 7.9 4.4 37.0 98.7 5.2 M M
20000 -8.0 17.6 230 32 17 7.9 4.4 36.4 97.6 4.7 M M
19500 -6.8 19.8 230 31 16 8.0 4.4 36.2 97.1 4.5 M M
19000 -5.7 21.7 235 29 15 6.6 3.6 35.7 96.3 4.2 M M
18500 -4.7 23.5 235 27 14 6.7 3.7 35.2 95.4 3.7 M M
18000 -3.7 25.3 235 25 13 6.6 3.6 34.7 94.5 3.3 M M
17500 -2.8 27.0 240 24 12 6.4 3.5 34.1 93.4 2.8 M M
17000 -1.9 28.6 240 23 12 6.4 3.5 33.6 92.4 2.3 M M
16500 -1.0 30.2 240 21 11 6.4 3.5 33.0 91.4 1.7 M M
16000 -0.0 32.0 240 20 10 6.5 3.5 32.4 90.4 1.2 M M
15500 0.9 33.6 240 19 10 6.7 3.7 31.9 89.5 0.7 M M
15000 1.9 35.4 240 18 9 6.8 3.7 31.4 88.5 0.2 M M
14500 2.8 37.0 245 17 9 7.0 3.8 30.9 87.7 -0.3 764 3.9
14000 3.9 39.0 245 16 8 7.4 4.0 30.5 86.9 -0.8 718 3.6
13500 4.9 40.8 245 15 8 7.4 4.1 30.1 86.2 -1.2 672 3.4
13000 6.0 42.8 240 15 8 7.6 4.2 29.8 85.6 -1.6 624 3.2
12500 7.1 44.8 240 14 7 7.6 4.2 29.4 84.9 -1.9 577 2.9
12000 8.1 46.6 240 14 7 7.2 3.9 29.0 84.2 -2.4 531 2.7
11500 9.2 48.6 235 14 7 7.3 4.0 28.6 83.5 -2.8 485 2.5
11000 10.2 50.4 230 14 7 7.0 3.8 28.2 82.8 -3.3 439 2.2
10500 11.2 52.2 230 15 7 6.9 3.8 27.8 82.0 -3.7 394 2.0
10250 11.7 53.1 225 15 8 7.4 4.1 27.6 81.6 -4.0 372 1.9
10000 12.2 54.0 225 15 7 7.8 4.3 27.4 81.3 -4.2 348 1.8
9750 12.8 55.0 225 14 7 7.5 4.1 27.2 81.0 -4.4 324 1.6
9500 13.3 55.9 225 14 7 7.8 4.3 27.1 80.7 -4.6 301 1.5
9250 13.9 57.0 225 14 7 6.8 3.8 26.9 80.4 -4.7 277 1.4
9000 14.3 57.7 225 13 7 6.6 3.6 26.6 79.9 -5.0 257 1.3
8750 15.3 59.5 230 12 6 7.3 4.0 26.2 79.2 -5.5 212 1.1
8500 15.8 60.4 230 12 6 5.5 3.0 26.0 78.8 -5.8 190 1.0
8250 16.1 61.0 235 11 6 4.8 2.6 25.6 78.1 -6.2 172 0.9
8000 16.5 61.7 235 10 5 6.1 3.4 25.3 77.5 -6.5 153 0.8
7750 17.0 62.6 240 10 5 5.9 3.2 25.0 77.0 -6.9 133 0.7
7500 17.3 63.1 240 9 5 5.2 2.8 24.7 76.5 -7.2 114 0.6
7250 17.7 63.9 245 9 5 4.7 2.6 24.3 75.8 -7.6 96 0.5
7000 18.0 64.4 245 8 4 3.7 2.0 23.9 75.0 -8.1 80 0.4
6750 18.2 64.8 245 7 4 3.2 1.8 23.4 74.1 -8.6 66 0.3
6500 18.4 65.1 245 7 4 3.6 2.0 22.9 73.3 -9.1 52 0.3
6250 18.6 65.5 240 6 3 3.7 2.0 22.5 72.4 -9.7 38 0.2
6000 18.9 66.0 240 6 3 3.3 1.8 22.0 71.6 -10.2 24 0.1
5750 19.0 66.2 235 5 3 1.4 0.8 21.5 70.6 -10.8 12 0.1
5500 18.9 66.0 230 4 2 -1.5 -0.8 20.7 69.3 -11.7 8 0.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/01/2026 at 0900 MDT | 09/01/2026 at 1200 MDT
|
CAPE... +197.4 LI... -1.2 | CAPE... +268.2 LI... -0.5
CINH... -112.3 K Index... +23.6 | CINH... -39.4 K Index... +20.0
|
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 -60.3 -76.5 250 39 20 3.2 1.8 | -61.9 -79.4 245 51 26 2.8 1.6
45000 -55.8 -68.4 250 55 28 2.0 1.1 | -56.7 -70.1 255 63 33 4.3 2.4
40000 -52.3 -62.1 225 55 28 5.8 3.2 | -50.1 -58.2 260 49 25 5.3 2.9
38000 -48.8 -55.8 215 59 30 5.9 3.2 | -46.9 -52.4 250 46 23 5.3 2.9
36000 -45.3 -49.5 205 64 33 5.8 3.2 | -43.7 -46.7 235 44 23 5.3 2.9
34000 -40.0 -40.0 210 63 32 8.2 4.5 | -39.7 -39.5 230 42 22 6.2 3.4
32000 -35.2 -31.4 210 61 31 8.3 4.6 | -36.0 -32.8 230 40 21 6.0 3.3
30000 -30.8 -23.4 215 53 27 7.1 3.9 | -31.3 -24.3 235 38 20 8.1 4.4
29000 -28.7 -19.7 220 49 25 7.1 3.9 | -28.9 -20.0 235 37 19 8.1 4.4
28000 -26.5 -15.7 225 45 23 7.2 3.9 | -26.5 -15.7 235 36 19 7.5 4.1
27000 -24.4 -11.9 225 41 21 7.2 4.0 | -24.4 -11.9 235 35 18 7.1 3.9
26000 -22.2 -8.0 225 38 19 7.2 4.0 | -22.3 -8.1 235 34 18 7.1 3.9
25000 -20.1 -4.2 230 34 18 7.2 4.0 | -20.2 -4.4 235 33 17 7.1 3.9
24000 -17.9 -0.2 230 32 16 7.2 4.0 | -18.0 -0.4 230 31 16 7.5 4.1
23000 -15.8 3.6 225 29 15 7.2 4.0 | -15.7 3.7 230 30 15 7.5 4.1
22000 -13.6 7.5 225 27 14 7.3 4.0 | -13.5 7.7 225 28 14 7.5 4.1
21000 -11.2 11.8 225 25 13 6.7 3.7 | -10.7 12.7 225 26 13 7.5 4.1
20000 -9.2 15.4 225 23 12 6.8 3.7 | -8.5 16.7 225 25 13 7.5 4.1
19500 -8.2 17.2 230 23 12 6.9 3.8 | -7.4 18.7 225 24 12 7.5 4.1
19000 -7.2 19.0 230 22 11 7.0 3.8 | -6.3 20.7 225 23 12 7.5 4.1
18500 -6.2 20.8 230 21 11 7.0 3.8 | -5.2 22.6 225 22 11 7.5 4.1
18000 -5.2 22.6 230 21 11 6.9 3.8 | -4.1 24.6 225 21 11 7.3 4.0
17500 -4.2 24.4 235 20 10 6.9 3.8 | -3.1 26.4 230 20 10 7.2 4.0
17000 -3.2 26.2 235 19 10 6.9 3.8 | -2.0 28.4 230 19 10 7.2 3.9
16500 -2.3 27.9 235 17 9 6.7 3.6 | -1.1 30.0 235 18 9 6.4 3.5
16000 -1.3 29.7 240 16 8 6.6 3.6 | -0.1 31.8 235 17 9 6.6 3.6
15500 -0.3 31.5 240 14 7 7.0 3.9 | 0.7 33.3 240 16 8 5.8 3.2
15000 0.7 33.3 240 12 6 7.1 3.9 | 1.5 34.7 245 15 8 5.8 3.2
14500 1.7 35.1 240 10 5 7.4 4.1 | 2.3 36.1 250 14 7 6.3 3.5
14000 2.8 37.0 240 9 4 7.7 4.2 | 3.2 37.8 250 13 7 6.6 3.6
13500 3.9 39.0 240 7 4 7.7 4.2 | 4.1 39.4 255 12 6 7.0 3.9
13000 5.1 41.2 240 6 3 7.9 4.3 | 5.3 41.5 255 11 6 7.9 4.4
12500 6.2 43.2 250 5 3 7.9 4.4 | 6.4 43.5 250 10 5 8.0 4.4
12000 7.4 45.3 260 5 3 7.9 4.3 | 7.6 45.7 250 9 5 8.5 4.6
11500 8.5 47.3 275 5 3 7.9 4.3 | 8.8 47.8 250 8 4 8.4 4.6
11000 9.6 49.3 290 6 3 7.9 4.3 | 10.0 50.0 250 7 4 8.4 4.6
10500 10.8 51.4 300 6 3 7.4 4.1 | 11.2 52.2 250 6 3 8.1 4.4
10250 11.3 52.3 310 6 3 7.5 4.1 | 11.8 53.2 250 6 3 7.7 4.2
10000 11.9 53.4 315 7 3 8.1 4.4 | 12.3 54.1 250 5 3 7.8 4.3
9750 12.4 54.3 315 7 3 7.9 4.4 | 12.9 55.2 255 5 3 7.9 4.3
9500 13.0 55.4 320 7 4 7.9 4.4 | 13.4 56.1 255 4 2 7.7 4.2
9250 13.5 56.3 320 7 4 7.2 3.9 | 14.0 57.2 260 4 2 7.1 3.9
9000 14.0 57.2 325 7 3 6.9 3.8 | 14.5 58.1 255 3 1 7.9 4.3
8750 14.5 58.1 325 7 3 7.3 4.0 | 15.1 59.2 255 2 1 8.7 4.8
8500 15.1 59.2 320 6 3 7.0 3.8 | 15.7 60.3 255 2 1 8.5 4.7
8250 15.5 59.9 320 6 3 6.1 3.4 | 16.3 61.3 245 1 1 7.8 4.3
8000 16.4 61.5 320 5 3 6.4 3.5 | 17.6 63.7 000 0 0 10.3 5.6
7750 16.8 62.2 315 5 3 5.5 3.0 | 18.3 64.9 000 0 0 9.6 5.3
7500 17.1 62.8 315 4 2 4.2 2.3 | 19.0 66.2 000 0 0 8.7 4.8
7250 17.4 63.3 310 4 2 4.1 2.3 | 19.6 67.3 095 1 0 9.0 4.9
7000 17.7 63.9 305 3 2 3.7 2.0 | 20.4 68.7 090 1 0 11.0 6.0
6750 17.9 64.2 295 3 2 5.9 3.2 | 21.2 70.2 085 1 1 10.9 6.0
6500 18.4 65.1 295 3 1 8.1 4.4 | 22.0 71.6 080 1 1 10.1 5.6
6250 19.0 66.2 290 3 1 7.1 3.9 | 22.7 72.9 080 2 1 9.6 5.3
6000 19.5 67.1 285 2 1 9.1 5.0 | 23.5 74.3 080 2 1 12.7 6.9
5750 20.3 68.5 280 2 1 13.7 7.5 | 24.8 76.6 075 2 1 23.1 12.7
5500 21.3 70.3 285 2 1 10.9 6.0 | 26.6 79.9 075 2 1 24.6 13.5
09/01/2026 at 1500 MDT | 09/01/2026 at 1800 MDT
|
CAPE... +295.2 LI... -2.6 | CAPE... +144.6 LI... -1.0
CINH... -9.9 K Index... +29.5 | CINH... -20.8 K Index... +31.6
|
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 -62.9 -81.2 245 49 25 2.6 1.4 | -62.6 -80.7 245 53 27 2.0 1.1
45000 -57.5 -71.5 250 62 32 5.2 2.8 | -57.4 -71.3 250 68 35 5.9 3.2
40000 -49.9 -57.8 265 60 31 4.7 2.6 | -49.0 -56.2 265 70 36 4.3 2.3
38000 -47.1 -52.8 265 55 28 4.6 2.5 | -46.4 -51.5 260 64 33 4.2 2.3
36000 -44.3 -47.7 260 49 25 4.4 2.4 | -43.9 -47.0 260 58 30 4.0 2.2
34000 -39.2 -38.6 255 47 24 8.1 4.5 | -39.1 -38.4 255 50 26 7.7 4.2
32000 -34.4 -29.9 250 45 23 8.2 4.5 | -34.5 -30.1 250 43 22 7.7 4.2
30000 -30.0 -22.0 250 40 20 7.1 3.9 | -29.7 -21.5 245 40 21 8.0 4.4
29000 -27.9 -18.2 250 37 19 7.1 3.9 | -27.4 -17.3 245 39 20 8.0 4.4
28000 -25.8 -14.4 250 34 17 7.4 4.1 | -25.0 -13.0 245 38 19 7.7 4.2
27000 -23.5 -10.3 245 33 17 7.5 4.1 | -22.7 -8.9 245 35 18 7.6 4.2
26000 -21.3 -6.3 245 32 16 7.5 4.1 | -20.5 -4.9 245 33 17 7.6 4.2
25000 -19.0 -2.2 245 31 16 7.6 4.2 | -18.2 -0.8 245 31 16 7.7 4.2
24000 -17.1 1.2 245 30 15 6.2 3.4 | -16.3 2.7 245 29 15 6.0 3.3
23000 -15.2 4.6 240 28 15 6.2 3.4 | -14.6 5.7 245 28 14 6.1 3.4
22000 -13.4 7.9 240 27 14 6.2 3.4 | -12.4 9.7 250 26 13 6.6 3.6
21000 -11.3 11.7 245 27 14 5.9 3.2 | -10.4 13.3 245 25 13 6.9 3.8
20000 -9.7 14.5 245 27 14 6.2 3.4 | -8.4 16.9 240 24 12 7.0 3.8
19500 -8.8 16.2 245 27 14 6.6 3.6 | -7.5 18.5 235 23 12 6.9 3.8
19000 -7.8 18.0 245 26 14 8.1 4.5 | -6.6 20.1 235 22 11 6.1 3.4
18500 -6.6 20.1 245 25 13 8.1 4.4 | -5.7 21.7 230 20 10 6.2 3.4
18000 -5.5 22.1 245 24 13 7.6 4.2 | -4.8 23.4 225 18 9 6.4 3.5
17500 -4.4 24.1 245 23 12 7.4 4.1 | -3.8 25.2 220 16 8 6.5 3.6
17000 -3.4 25.9 240 21 11 7.6 4.2 | -2.9 26.8 215 14 7 6.5 3.6
16500 -2.1 28.2 240 20 10 8.7 4.8 | -2.0 28.4 215 12 6 6.6 3.6
16000 -0.9 30.4 240 18 9 8.6 4.7 | -1.0 30.2 205 11 6 6.6 3.6
15500 0.4 32.7 240 17 9 8.3 4.6 | -0.1 31.8 200 9 5 6.7 3.7
15000 1.6 34.9 240 15 8 8.3 4.6 | 0.9 33.6 195 8 4 6.8 3.7
14500 2.8 37.0 240 13 7 8.1 4.4 | 1.8 35.2 185 7 3 7.3 4.0
14000 3.9 39.0 235 11 5 7.9 4.4 | 3.0 37.4 180 6 3 7.8 4.3
13500 5.1 41.2 230 8 4 8.2 4.5 | 4.1 39.4 170 4 2 8.3 4.6
13000 6.3 43.3 225 6 3 8.9 4.9 | 5.5 41.9 160 4 2 9.6 5.3
12500 7.6 45.7 210 5 3 8.9 4.9 | 6.9 44.4 145 3 1 9.5 5.2
12000 8.9 48.0 195 4 2 8.8 4.8 | 8.3 46.9 125 2 1 8.8 4.8
11500 10.2 50.4 175 4 2 8.8 4.8 | 9.6 49.3 100 2 1 8.8 4.9
11000 11.6 52.9 160 4 2 9.5 5.2 | 10.9 51.6 075 2 1 9.4 5.1
10500 13.0 55.4 150 4 2 9.7 5.3 | 12.3 54.1 060 3 1 10.0 5.5
10250 13.7 56.7 145 4 2 9.7 5.3 | 13.1 55.6 050 3 1 10.1 5.5
10000 14.4 57.9 140 4 2 9.4 5.2 | 13.8 56.8 045 3 2 9.2 5.0
9750 15.1 59.2 135 5 2 9.5 5.2 | 14.5 58.1 040 3 2 9.4 5.2
9500 15.8 60.4 135 5 2 9.4 5.2 | 15.2 59.4 040 4 2 9.3 5.1
9250 16.5 61.7 130 5 3 8.8 4.8 | 15.9 60.6 035 4 2 9.0 4.9
9000 17.1 62.8 130 5 3 9.3 5.1 | 16.6 61.9 035 4 2 9.4 5.1
8750 17.9 64.2 125 5 3 9.9 5.4 | 17.3 63.1 030 4 2 9.8 5.4
8500 18.6 65.5 120 6 3 9.7 5.3 | 18.0 64.4 025 5 2 9.6 5.3
8250 19.3 66.7 115 6 3 8.1 4.4 | 18.7 65.7 025 5 3 7.8 4.3
8000 20.7 69.3 110 7 3 11.4 6.3 | 20.0 68.0 015 5 3 10.6 5.8
7750 21.5 70.7 110 7 4 10.4 5.7 | 20.7 69.3 015 5 3 9.8 5.4
7500 22.2 72.0 105 7 4 9.1 5.0 | 21.4 70.5 010 6 3 8.8 4.9
7250 22.8 73.0 105 8 4 9.1 5.0 | 22.1 71.8 005 5 3 8.8 4.8
7000 23.6 74.5 105 8 4 10.7 5.9 | 22.8 73.0 360 6 3 10.2 5.6
6750 24.4 75.9 100 8 4 10.9 6.0 | 23.5 74.3 360 6 3 9.7 5.3
6500 25.2 77.4 100 9 4 10.6 5.8 | 24.2 75.6 355 6 3 8.4 4.6
6250 26.0 78.8 100 9 5 10.4 5.7 | 24.8 76.6 350 6 3 8.5 4.7
6000 26.8 80.2 100 9 5 11.1 6.1 | 25.4 77.7 340 6 3 9.0 4.9
5750 27.8 82.0 095 9 5 18.1 9.9 | 26.1 79.0 335 5 3 9.2 5.0
5500 29.8 85.6 095 8 4 41.6 22.8 | 26.6 79.9 335 5 2 4.9 2.7
________________________________________________________________________________
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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