Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
959
UXUS97 KBOU 060115
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1915 MDT Saturday, September 5, 2026
This forecast is for Sunday, September 6, 2026:
If the trigger temperature of 83.1 F/28.4 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1075 ft/min (5.5 m/s)
Maximum height of thermals.................. 17356 ft MSL (11932 ft AGL)
Forecast maximum temperature................... 93.0 F/34.3 C
Time of trigger temperature.................... 1045 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................. 13929 ft MSL (8505 ft AGL)
Thermal soaring outlook for Monday 09/07....... 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....................... 15981 ft MSL (10557 ft AGL)
Wave soaring outlook for Monday 09/07.......... Fair
Remarks...
Sunrise/Sunset.................... 06:32:34 / 19:22:57 MDT
Total possible sunshine........... 12 hr 50 min 22 sec (770 min 22 sec)
Altitude of sun at 12:57:45 MDT... 56.44 degrees
Upper air data from numerical model forecast valid on 09/06/2026 at 0600 MDT
Freezing level.................. 16350 ft MSL (10926 ft AGL)
Convective condensation level... 13684 ft MSL (8260 ft AGL)
Lifted condensation level....... 15125 ft MSL (9701 ft AGL)
Lifted index.................... -4.6
K index......................... +28.5
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 -65.7 -86.3 260 43 22 2.9 1.6 80.1 176.2 27.2 M M
45000 -59.1 -74.4 255 52 27 6.7 3.7 66.7 152.0 20.7 M M
40000 -49.3 -56.7 255 56 29 5.8 3.2 59.7 139.5 17.4 M M
38000 -45.8 -50.4 260 51 26 5.8 3.2 56.1 132.9 15.3 M M
36000 -42.4 -44.3 265 47 24 5.9 3.2 53.1 127.6 13.6 M M
34000 -37.7 -35.9 255 42 22 7.2 3.9 50.3 122.6 11.9 M M
32000 -33.4 -28.1 240 39 20 7.4 4.0 48.5 119.3 10.8 M M
30000 -28.7 -19.7 240 34 17 7.9 4.3 46.8 116.2 9.8 M M
29000 -26.4 -15.5 245 31 16 7.9 4.4 46.1 115.1 9.3 M M
28000 -24.1 -11.4 245 28 14 7.9 4.3 45.5 114.0 8.9 M M
27000 -21.7 -7.1 245 26 14 7.9 4.3 44.7 112.5 8.4 M M
26000 -19.3 -2.7 245 24 13 7.9 4.3 44.0 111.3 8.0 M M
25000 -16.9 1.6 245 23 12 7.7 4.2 43.5 110.3 7.6 M M
24000 -14.7 5.5 245 20 10 7.3 4.0 42.5 108.5 7.0 M M
23000 -12.5 9.5 245 18 9 7.3 4.0 41.6 106.9 6.3 M M
22000 -10.3 13.5 245 16 8 6.8 3.7 40.8 105.5 5.8 M M
21000 -8.2 17.2 240 14 7 5.7 3.1 39.0 102.1 4.2 M M
20000 -6.6 20.1 235 13 7 5.7 3.1 37.6 99.6 3.0 M M
19500 -5.7 21.7 235 12 6 5.8 3.2 36.9 98.5 2.4 M M
19000 -4.9 23.2 230 12 6 6.0 3.3 36.3 97.3 1.8 M M
18500 -4.1 24.6 230 12 6 6.1 3.4 35.6 96.1 1.2 M M
18000 -3.2 26.2 225 11 6 7.1 3.9 35.1 95.1 0.6 M M
17500 -2.2 28.0 225 11 6 7.3 4.0 34.6 94.3 0.1 M M
17000 -1.2 29.8 225 10 5 7.3 4.0 34.2 93.6 -0.4 1039 5.3
16500 -0.2 31.6 225 9 5 7.1 3.9 33.8 92.8 -0.9 995 5.1
16000 0.7 33.3 230 9 4 7.2 3.9 33.4 92.0 -1.3 950 4.8
15500 1.8 35.2 235 8 4 7.3 4.0 32.9 91.3 -1.8 905 4.6
15000 2.8 37.0 240 7 4 7.3 4.0 32.5 90.5 -2.2 859 4.4
14500 3.9 39.0 250 6 3 7.6 4.2 32.1 89.8 -2.6 813 4.1
14000 5.0 41.0 260 5 2 7.7 4.2 31.8 89.2 -2.9 764 3.9
13500 6.1 43.0 280 3 2 8.1 4.4 31.5 88.6 -3.3 715 3.6
13000 7.4 45.3 310 2 1 8.7 4.8 31.3 88.3 -3.5 662 3.4
12500 8.7 47.7 360 2 1 8.7 4.8 31.1 88.0 -3.6 608 3.1
12000 10.0 50.0 025 3 1 9.1 5.0 31.0 87.8 -3.8 555 2.8
11500 11.3 52.3 035 3 2 9.0 4.9 30.9 87.6 -4.0 502 2.5
11000 12.5 54.5 040 4 2 8.3 4.6 30.7 87.3 -4.2 449 2.3
10500 13.8 56.8 040 4 2 7.4 4.0 30.5 86.9 -4.5 398 2.0
10250 14.2 57.6 035 4 2 7.2 4.0 30.3 86.5 -4.7 376 1.9
10000 14.8 58.6 030 4 2 8.5 4.7 30.1 86.2 -4.9 350 1.8
9750 15.4 59.7 020 4 2 8.2 4.5 30.0 86.0 -5.0 325 1.7
9500 16.0 60.8 015 4 2 8.2 4.5 29.9 85.8 -5.1 300 1.5
9250 16.6 61.9 005 4 2 7.1 3.9 29.8 85.6 -5.3 276 1.4
9000 17.0 62.6 355 5 2 6.2 3.4 29.5 85.1 -5.6 255 1.3
8750 17.5 63.5 345 5 3 6.4 3.5 29.2 84.6 -5.9 235 1.2
8500 17.9 64.2 340 6 3 5.7 3.1 29.0 84.1 -6.2 215 1.1
8250 18.2 64.8 335 6 3 2.9 1.6 28.6 83.4 -6.7 199 1.0
8000 18.3 64.9 325 6 3 1.2 0.7 27.3 81.1 -8.1 181 0.9
7750 18.3 64.9 320 5 3 0.3 0.2 26.6 79.9 -8.8 173 0.9
7500 18.2 64.8 315 5 3 -1.2 -0.7 25.8 78.5 -9.7 169 0.9
7250 18.0 64.4 315 4 2 -1.2 -0.7 25.0 76.9 -10.6 167 0.9
7000 17.8 64.0 310 4 2 -0.8 -0.4 24.2 75.5 -11.5 165 0.8
6750 17.7 63.9 300 3 1 1.3 0.7 23.4 74.1 -12.4 160 0.8
6500 17.9 64.2 305 2 1 2.9 1.6 22.9 73.1 -13.0 148 0.8
6250 18.0 64.4 310 1 1 2.5 1.4 22.3 72.2 -13.6 137 0.7
6000 18.2 64.8 000 0 0 3.3 1.8 21.8 71.2 -14.2 124 0.6
5750 18.4 65.1 105 1 0 3.0 1.7 21.3 70.4 -14.7 111 0.6
5500 18.5 65.3 110 1 1 -3.1 -1.7 20.7 69.2 -15.5 102 0.5
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/06/2026 at 0900 MDT | 09/06/2026 at 1200 MDT
|
CAPE... +250.1 LI... -0.7 | CAPE... +350.3 LI... -0.3
CINH... -102.5 K Index... +24.2 | CINH... -37.8 K Index... +25.0
|
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 -64.2 -83.6 265 43 22 2.1 1.2 | -63.9 -83.0 270 38 19 3.5 1.9
45000 -58.9 -74.0 260 55 28 6.0 3.3 | -58.1 -72.6 265 50 25 4.7 2.6
40000 -49.8 -57.6 260 55 28 6.4 3.5 | -50.4 -58.7 255 51 26 7.3 4.0
38000 -45.9 -50.6 260 48 25 6.4 3.5 | -46.1 -51.0 250 46 24 7.3 4.0
36000 -41.6 -42.9 260 41 21 6.5 3.6 | -41.2 -42.2 245 41 21 7.2 4.0
34000 -37.7 -35.9 255 36 18 6.5 3.6 | -36.8 -34.2 245 38 19 7.2 4.0
32000 -33.8 -28.8 245 31 16 7.0 3.8 | -32.5 -26.5 240 34 18 7.2 4.0
30000 -29.1 -20.4 245 27 14 8.0 4.4 | -28.2 -18.8 245 29 15 7.3 4.0
29000 -26.8 -16.2 245 26 13 8.0 4.4 | -26.1 -15.0 245 26 13 7.4 4.0
28000 -24.4 -11.9 240 24 12 7.8 4.3 | -23.9 -11.0 250 24 12 7.6 4.2
27000 -22.0 -7.6 240 22 11 7.8 4.3 | -21.6 -6.9 245 22 12 7.6 4.2
26000 -19.7 -3.5 235 19 10 7.9 4.3 | -19.3 -2.7 240 21 11 7.6 4.2
25000 -17.3 0.9 230 17 9 7.7 4.2 | -17.1 1.2 230 21 11 7.6 4.2
24000 -15.0 5.0 235 15 8 7.5 4.1 | -14.8 5.4 230 19 10 7.6 4.1
23000 -12.8 9.0 240 14 7 7.5 4.1 | -12.5 9.5 225 16 8 7.6 4.2
22000 -10.0 14.0 250 13 6 6.0 3.3 | -9.7 14.5 215 14 7 6.7 3.7
21000 -8.2 17.2 245 11 6 6.1 3.3 | -7.6 18.3 215 14 7 6.7 3.7
20000 -6.4 20.5 245 10 5 6.1 3.3 | -5.6 21.9 215 13 7 6.7 3.7
19500 -5.5 22.1 240 9 5 6.0 3.3 | -4.6 23.7 215 13 7 6.3 3.4
19000 -4.7 23.5 245 9 4 5.9 3.3 | -3.8 25.2 215 13 7 5.5 3.0
18500 -3.8 25.2 245 8 4 6.0 3.3 | -3.0 26.6 215 12 6 5.6 3.1
18000 -2.9 26.8 245 8 4 6.7 3.7 | -2.2 28.0 215 11 6 5.5 3.0
17500 -2.0 28.4 250 8 4 6.9 3.8 | -1.5 29.3 220 11 5 5.7 3.1
17000 -1.1 30.0 250 8 4 7.1 3.9 | -0.7 30.7 220 10 5 6.2 3.4
16500 -0.0 32.0 250 9 4 7.5 4.1 | 0.2 32.4 225 9 5 7.0 3.9
16000 1.0 33.8 250 9 4 7.5 4.1 | 1.1 34.0 230 9 5 7.1 3.9
15500 2.2 36.0 250 9 4 8.3 4.6 | 2.2 36.0 230 9 4 8.1 4.4
15000 3.3 37.9 250 8 4 8.3 4.6 | 3.3 37.9 230 8 4 8.1 4.4
14500 4.5 40.1 250 7 4 8.1 4.4 | 4.4 39.9 230 8 4 8.2 4.5
14000 5.6 42.1 250 6 3 8.0 4.4 | 5.6 42.1 230 7 4 8.3 4.5
13500 6.8 44.2 250 5 3 8.1 4.4 | 6.8 44.2 230 6 3 8.3 4.5
13000 7.9 46.2 250 3 2 8.1 4.4 | 8.0 46.4 225 6 3 8.2 4.5
12500 9.1 48.4 245 2 1 8.3 4.6 | 9.2 48.6 220 5 3 8.3 4.6
12000 10.4 50.7 220 1 0 8.9 4.9 | 10.5 50.9 210 5 2 8.7 4.8
11500 11.7 53.1 130 1 0 8.9 4.9 | 11.7 53.1 200 5 2 8.6 4.7
11000 13.0 55.4 125 1 0 8.6 4.7 | 12.9 55.2 195 4 2 7.9 4.3
10500 14.3 57.7 140 1 0 7.7 4.3 | 14.1 57.4 185 4 2 8.5 4.7
10250 14.8 58.6 155 1 0 7.6 4.2 | 14.7 58.5 185 4 2 8.3 4.6
10000 15.4 59.7 000 0 0 8.6 4.7 | 15.2 59.4 175 4 2 7.5 4.1
9750 16.0 60.8 235 1 0 8.5 4.6 | 15.8 60.4 165 4 2 7.8 4.3
9500 16.6 61.9 250 1 0 8.0 4.4 | 16.3 61.3 155 3 2 7.5 4.1
9250 17.1 62.8 260 1 1 6.5 3.6 | 16.8 62.2 145 3 2 7.9 4.3
9000 17.6 63.7 265 2 1 6.8 3.7 | 17.5 63.5 135 3 2 9.1 5.0
8750 18.1 64.6 270 2 1 7.8 4.3 | 18.1 64.6 130 4 2 9.5 5.2
8500 18.7 65.7 270 3 1 7.0 3.8 | 18.8 65.8 125 4 2 9.2 5.1
8250 19.1 66.4 270 3 2 5.1 2.8 | 19.4 66.9 120 4 2 7.6 4.1
8000 19.8 67.6 265 4 2 6.1 3.3 | 20.8 69.4 115 4 2 11.1 6.1
7750 20.2 68.4 265 5 2 3.6 2.0 | 21.6 70.9 110 5 2 10.1 5.5
7500 20.3 68.5 255 4 2 -0.1 -0.1 | 22.3 72.1 105 5 2 9.1 5.0
7250 20.3 68.5 245 4 2 -0.2 -0.1 | 22.9 73.2 105 5 3 9.3 5.1
7000 20.2 68.4 235 4 2 -0.7 -0.4 | 23.7 74.7 100 5 3 10.9 6.0
6750 20.1 68.2 220 4 2 3.8 2.1 | 24.5 76.1 100 5 3 10.7 5.9
6500 20.6 69.1 215 4 2 8.1 4.4 | 25.3 77.5 095 6 3 10.0 5.5
6250 21.1 70.0 210 4 2 6.4 3.5 | 26.0 78.8 095 6 3 9.7 5.3
6000 21.6 70.9 200 4 2 9.5 5.2 | 26.8 80.2 090 6 3 12.7 7.0
5750 22.5 72.5 195 3 2 16.4 9.0 | 28.0 82.4 090 6 3 22.6 12.4
5500 23.7 74.7 190 3 1 13.2 7.2 | 30.0 86.0 085 6 3 27.0 14.8
09/06/2026 at 1500 MDT | 09/06/2026 at 1800 MDT
|
CAPE... +388.4 LI... -1.2 | CAPE... +396.3 LI... -3.3
CINH... -6.6 K Index... +30.7 | CINH... -50.2 K Index... +32.5
|
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 -64.7 -84.5 255 38 20 4.7 2.6 | -65.1 -85.2 250 39 20 3.8 2.1
45000 -57.8 -72.0 250 47 24 4.4 2.4 | -58.6 -73.5 250 47 24 5.2 2.9
40000 -50.4 -58.7 250 47 24 7.8 4.3 | -50.0 -58.0 250 46 24 8.3 4.5
38000 -45.7 -50.3 250 46 24 7.8 4.3 | -44.5 -48.1 250 43 22 8.2 4.5
36000 -40.5 -40.9 250 46 24 6.7 3.7 | -39.6 -39.3 255 41 21 7.0 3.8
34000 -36.6 -33.9 245 43 22 6.5 3.6 | -35.5 -31.9 250 38 20 6.8 3.7
32000 -32.7 -26.9 240 41 21 6.9 3.8 | -31.5 -24.7 245 35 18 7.1 3.9
30000 -28.1 -18.6 240 32 16 7.8 4.3 | -27.0 -16.6 240 29 15 7.6 4.2
29000 -25.8 -14.4 235 27 14 7.9 4.3 | -24.7 -12.5 240 26 13 7.6 4.2
28000 -23.5 -10.3 235 23 12 7.6 4.2 | -22.4 -8.3 235 23 12 8.2 4.5
27000 -21.2 -6.2 230 22 12 7.6 4.2 | -20.0 -4.0 230 21 11 8.1 4.5
26000 -19.0 -2.2 225 22 11 7.6 4.2 | -17.5 0.5 230 20 10 8.1 4.5
25000 -16.7 1.9 220 21 11 7.6 4.2 | -15.1 4.8 225 19 10 7.8 4.3
24000 -14.4 6.1 220 20 11 7.5 4.1 | -13.0 8.6 230 20 10 6.9 3.8
23000 -11.6 11.1 220 20 10 7.5 4.1 | -10.5 13.1 240 22 11 7.0 3.8
22000 -9.4 15.1 225 19 10 6.1 3.4 | -8.6 16.5 245 23 12 4.2 2.3
21000 -7.6 18.3 230 19 10 6.1 3.3 | -7.6 18.3 240 24 12 3.8 2.1
20000 -5.8 21.6 230 18 9 6.1 3.3 | -6.6 20.1 240 25 13 4.0 2.2
19500 -4.9 23.2 235 17 9 5.8 3.2 | -6.1 21.0 235 25 13 4.9 2.7
19000 -4.2 24.4 235 18 9 5.3 2.9 | -5.1 22.8 235 23 12 7.8 4.3
18500 -3.5 25.7 240 19 10 5.3 2.9 | -4.0 24.8 235 21 11 7.7 4.2
18000 -2.7 27.1 235 20 10 7.4 4.1 | -2.9 26.8 230 19 10 8.1 4.4
17500 -1.6 29.1 235 19 10 7.7 4.2 | -1.7 28.9 230 16 8 8.2 4.5
17000 -0.6 30.9 230 18 10 7.8 4.3 | -0.5 31.1 230 13 7 8.1 4.4
16500 0.5 32.9 225 17 9 7.7 4.2 | 0.6 33.1 225 11 6 7.9 4.3
16000 1.6 34.9 220 16 8 7.7 4.2 | 1.7 35.1 225 9 5 7.9 4.3
15500 2.7 36.9 210 14 7 7.7 4.2 | 2.9 37.2 215 7 4 7.7 4.3
15000 3.8 38.8 205 12 6 7.7 4.2 | 4.0 39.2 200 7 3 7.8 4.3
14500 4.9 40.8 190 11 6 8.3 4.5 | 5.1 41.2 185 6 3 8.5 4.7
14000 6.2 43.2 180 10 5 8.6 4.7 | 6.4 43.5 175 7 4 9.0 4.9
13500 7.4 45.3 170 10 5 8.8 4.8 | 7.8 46.0 170 8 4 9.0 4.9
13000 8.8 47.8 165 9 5 9.2 5.0 | 9.1 48.4 165 9 4 8.9 4.9
12500 10.1 50.2 160 10 5 9.3 5.1 | 10.4 50.7 160 10 5 8.9 4.9
12000 11.5 52.7 150 10 5 9.5 5.2 | 11.7 53.1 160 11 5 9.1 5.0
11500 12.9 55.2 150 10 5 9.5 5.2 | 13.0 55.4 155 12 6 9.1 5.0
11000 14.3 57.7 145 10 5 9.2 5.1 | 14.4 57.9 155 12 6 9.0 5.0
10500 15.7 60.3 140 10 5 10.0 5.5 | 15.7 60.3 155 13 7 9.2 5.0
10250 16.5 61.7 140 10 5 10.3 5.7 | 16.4 61.5 150 13 7 9.2 5.0
10000 17.2 63.0 135 10 5 9.4 5.2 | 17.1 62.8 150 14 7 9.1 5.0
9750 17.9 64.2 135 10 5 9.7 5.3 | 17.7 63.9 150 14 7 9.0 5.0
9500 18.6 65.5 130 10 5 9.6 5.2 | 18.4 65.1 150 14 7 9.3 5.1
9250 19.3 66.7 130 10 5 9.4 5.2 | 19.1 66.4 150 14 7 8.4 4.6
9000 20.0 68.0 125 10 5 9.5 5.2 | 19.7 67.5 150 13 7 8.4 4.6
8750 20.7 69.3 125 10 5 9.6 5.3 | 20.3 68.5 150 14 7 9.1 5.0
8500 21.4 70.5 120 11 5 9.6 5.3 | 21.0 69.8 150 14 7 9.4 5.1
8250 22.8 73.0 115 11 6 9.5 5.2 | 22.1 71.8 145 13 7 7.5 4.1
8000 23.5 74.3 115 11 6 10.9 6.0 | 22.8 73.0 145 13 7 10.6 5.8
7750 24.3 75.7 110 11 6 10.3 5.7 | 23.5 74.3 145 13 7 9.7 5.3
7500 25.1 77.2 110 11 6 9.2 5.0 | 24.2 75.6 145 13 7 8.2 4.5
7250 25.7 78.3 105 11 6 9.1 5.0 | 24.8 76.6 145 13 7 7.9 4.3
7000 26.5 79.7 105 12 6 10.4 5.7 | 25.4 77.7 145 13 7 10.3 5.6
6750 27.2 81.0 105 12 6 10.7 5.8 | 26.2 79.2 145 13 6 10.2 5.6
6500 28.0 82.4 100 12 6 10.5 5.7 | 26.9 80.4 145 12 6 8.7 4.8
6250 28.8 83.8 100 12 6 10.8 5.9 | 27.5 81.5 145 12 6 8.4 4.6
6000 29.6 85.3 095 12 6 10.0 5.5 | 28.2 82.8 145 11 6 9.3 5.1
5750 30.4 86.7 095 11 6 15.9 8.7 | 28.9 84.0 145 9 5 10.9 6.0
5500 32.9 91.2 090 10 5 60.0 32.9 | 29.7 85.5 145 7 4 10.8 5.9
________________________________________________________________________________
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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