Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
806
UXUS97 KBOU 130125
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1924 MDT Saturday, July 12, 2025
This forecast is for Sunday, July 13, 2025:
If the trigger temperature of 83.4 F/28.6 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1441 ft/min (7.3 m/s)
Maximum height of thermals.................. 18601 ft MSL (13304 ft AGL)
Forecast maximum temperature................... 93.0 F/34.3 C
Time of trigger temperature.................... 1100 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................. 15163 ft MSL (9867 ft AGL)
Thermal soaring outlook for Monday 07/14....... 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)................ Neither
Potential height of wave....................... 16142 ft MSL (10845 ft AGL)
Wave soaring outlook for Monday 07/14.......... Poor
Remarks...
Sunrise/Sunset.................... 05:43:01 / 20:27:40 MDT
Total possible sunshine........... 14 hr 44 min 39 sec (884 min 39 sec)
Altitude of sun at 13:05:20 MDT... 71.90 degrees
Upper air data from numerical model forecast valid on 07/13/2025 at 0600 MDT
Freezing level.................. 15628 ft MSL (10331 ft AGL)
Convective condensation level... 15122 ft MSL (9825 ft AGL)
Lifted condensation level....... 16496 ft MSL (11199 ft AGL)
Lifted index.................... -4.4
K index......................... +26.6
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 -62.6 -80.7 350 15 8 0.0 0.0 M M M M M
45000 -61.4 -78.5 355 21 11 2.8 1.6 M M M M M
40000 -56.5 -69.7 355 25 13 7.5 4.1 M M M M M
38000 -51.9 -61.4 005 20 10 7.5 4.1 M M M M M
36000 -47.4 -53.3 020 16 8 7.4 4.1 M M M M M
34000 -41.6 -42.9 025 15 8 8.7 4.8 M M M M M
32000 -36.4 -33.5 025 16 8 8.9 4.9 M M M M M
30000 -31.3 -24.3 025 16 8 8.4 4.6 44.1 111.3 7.8 M M
29000 -28.8 -19.8 020 17 9 8.4 4.6 43.6 110.5 7.5 M M
28000 -26.3 -15.3 015 17 9 7.5 4.1 43.2 109.7 7.2 M M
27000 -24.1 -11.4 010 17 9 7.5 4.1 42.2 107.9 6.5 M M
26000 -21.9 -7.4 005 16 8 7.5 4.1 41.3 106.4 5.9 M M
25000 -19.6 -3.3 360 17 9 7.5 4.1 40.6 105.1 5.3 M M
24000 -17.5 0.5 355 16 8 7.2 4.0 39.6 103.3 4.5 M M
23000 -15.4 4.3 355 14 7 7.2 4.0 38.7 101.6 3.8 M M
22000 -13.2 8.2 350 13 7 7.1 3.9 37.9 100.2 3.1 M M
21000 -11.2 11.8 355 12 6 6.9 3.8 36.8 98.2 2.2 M M
20000 -9.1 15.6 355 11 6 6.9 3.8 35.8 96.4 1.3 M M
19500 -8.1 17.4 355 11 6 6.9 3.8 35.3 95.6 0.9 M M
19000 -7.1 19.2 355 11 6 6.8 3.7 34.8 94.7 0.5 M M
18500 -6.1 21.0 360 12 6 6.9 3.8 34.3 93.8 0.0 M M
18000 -5.1 22.8 360 13 7 6.8 3.7 33.8 92.9 -0.4 1196 6.1
17500 -4.2 24.4 360 14 7 6.8 3.7 33.3 92.0 -1.0 1153 5.9
17000 -2.7 27.1 005 16 8 7.1 3.9 32.6 90.6 -1.7 1087 5.5
16500 -1.7 28.9 005 16 8 7.4 4.1 32.2 89.9 -2.1 1041 5.3
16000 -0.6 30.9 005 17 9 7.6 4.2 31.8 89.2 -2.6 994 5.1
15500 0.6 33.1 005 17 9 8.7 4.8 31.5 88.7 -2.9 944 4.8
15000 1.8 35.2 005 16 8 8.6 4.7 31.3 88.4 -3.1 892 4.5
14500 3.1 37.6 005 15 8 9.3 5.1 31.2 88.2 -3.3 839 4.3
14000 4.5 40.1 005 14 7 9.2 5.1 31.1 88.0 -3.4 782 4.0
13500 5.9 42.6 005 13 7 9.2 5.0 31.0 87.9 -3.5 726 3.7
13000 7.2 45.0 005 13 7 9.2 5.0 30.9 87.7 -3.6 670 3.4
12500 8.6 47.5 005 12 6 9.2 5.0 30.9 87.5 -3.7 614 3.1
12000 10.0 50.0 005 11 6 9.1 5.0 30.8 87.4 -3.8 558 2.8
11500 11.4 52.5 005 10 5 8.9 4.9 30.7 87.2 -3.9 502 2.5
11000 12.6 54.7 005 8 4 8.3 4.6 30.5 86.9 -4.1 449 2.3
10500 13.9 57.0 005 7 3 4.4 2.4 30.3 86.6 -4.3 397 2.0
10250 14.0 57.2 005 6 3 5.8 3.2 29.7 85.5 -4.9 384 2.0
10000 14.8 58.6 360 6 3 11.8 6.5 29.8 85.6 -4.9 354 1.8
9750 15.6 60.1 360 5 3 11.1 6.1 29.9 85.8 -4.9 324 1.6
9500 16.3 61.3 355 4 2 7.9 4.3 30.0 85.9 -4.8 293 1.5
9250 16.7 62.1 350 4 2 4.5 2.5 29.6 85.3 -5.2 275 1.4
9000 17.2 63.0 345 4 2 8.4 4.6 29.3 84.8 -5.5 253 1.3
8750 17.9 64.2 340 3 2 10.3 5.7 29.3 84.8 -5.5 226 1.1
8500 18.5 65.3 330 3 1 7.6 4.2 29.3 84.7 -5.6 199 1.0
8250 18.9 66.0 320 3 1 5.3 2.9 29.0 84.2 -6.0 179 0.9
8000 19.3 66.7 315 3 1 7.4 4.1 28.7 83.7 -6.3 160 0.8
7750 19.9 67.8 300 2 1 8.8 4.8 28.6 83.5 -6.5 135 0.7
7500 20.4 68.7 290 2 1 6.0 3.3 28.5 83.2 -6.7 112 0.6
7250 20.8 69.4 280 2 1 4.3 2.3 28.1 82.5 -7.1 94 0.5
7000 21.1 70.0 275 3 1 5.1 2.8 27.7 81.8 -7.5 76 0.4
6750 21.4 70.5 265 3 1 2.7 1.5 27.3 81.1 -7.9 59 0.3
6500 21.5 70.7 255 3 2 -0.4 -0.2 26.6 79.9 -8.6 50 0.3
6250 21.4 70.5 250 3 2 -0.2 -0.1 25.8 78.5 -9.5 45 0.2
6000 21.4 70.5 245 3 2 -1.5 -0.8 25.1 77.1 -10.3 39 0.2
5750 21.0 69.8 240 3 2 -10.2 -5.6 23.9 75.1 -11.4 44 0.2
5500 19.7 67.5 225 3 2 -20.1 -11.0 22.0 71.6 -13.4 74 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
07/13/2025 at 0900 MDT | 07/13/2025 at 1200 MDT
|
CAPE... +692.7 LI... -2.1 | CAPE... +683.6 LI... -1.2
CINH... -81.8 K Index... +25.1 | CINH... -12.1 K Index... +24.3
|
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 -62.2 -80.0 005 13 7 -0.4 -0.2 | -62.3 -80.1 020 10 5 -0.3 -0.2
45000 -61.5 -78.7 010 19 10 2.7 1.5 | -61.4 -78.5 030 18 9 2.8 1.6
40000 -56.6 -69.9 025 21 11 7.6 4.2 | -56.0 -68.8 045 19 10 7.6 4.2
38000 -52.0 -61.6 030 15 8 7.8 4.3 | -51.4 -60.5 045 12 6 7.6 4.2
36000 -47.3 -53.1 045 10 5 7.7 4.2 | -46.9 -52.4 045 6 3 7.9 4.3
34000 -41.4 -42.5 050 10 5 8.9 4.9 | -41.6 -42.9 050 5 2 8.9 4.9
32000 -36.0 -32.8 050 11 6 9.0 4.9 | -36.2 -33.2 060 5 2 8.9 4.9
30000 -30.9 -23.6 045 13 6 8.5 4.7 | -31.1 -24.0 055 6 3 8.5 4.7
29000 -28.4 -19.1 040 13 7 8.5 4.7 | -27.9 -18.2 055 7 4 8.5 4.7
28000 -25.9 -14.6 035 14 7 7.7 4.2 | -25.4 -13.7 050 8 4 7.8 4.3
27000 -23.6 -10.5 030 14 7 7.7 4.2 | -23.1 -9.6 045 8 4 7.8 4.3
26000 -21.3 -6.3 025 14 7 7.7 4.2 | -20.8 -5.4 040 7 4 7.8 4.3
25000 -19.0 -2.2 020 14 7 7.5 4.1 | -18.5 -1.3 035 7 4 7.7 4.2
24000 -16.8 1.8 010 13 7 7.2 4.0 | -16.2 2.8 020 7 4 7.7 4.2
23000 -14.7 5.5 360 13 7 7.2 4.0 | -13.9 7.0 010 8 4 7.7 4.2
22000 -12.5 9.5 350 13 7 6.8 3.8 | -11.7 10.9 360 8 4 6.6 3.6
21000 -10.7 12.7 345 13 6 6.4 3.5 | -9.8 14.4 345 10 5 6.3 3.5
20000 -8.8 16.2 340 13 7 6.4 3.5 | -8.0 17.6 335 12 6 6.3 3.5
19500 -7.9 17.8 335 13 7 6.5 3.5 | -7.1 19.2 330 13 7 6.2 3.4
19000 -7.0 19.4 335 13 7 6.0 3.3 | -6.2 20.8 325 13 7 5.6 3.1
18500 -5.7 21.7 335 14 7 6.1 3.3 | -5.4 22.3 325 14 7 5.6 3.1
18000 -4.9 23.2 340 14 7 6.4 3.5 | -4.6 23.7 325 15 8 6.1 3.3
17500 -4.0 24.8 340 14 7 6.4 3.5 | -3.8 25.2 325 15 8 6.2 3.4
17000 -3.1 26.4 345 15 7 7.0 3.8 | -2.9 26.8 325 15 8 6.4 3.5
16500 -2.0 28.4 345 14 7 7.3 4.0 | -2.0 28.4 325 15 8 6.9 3.8
16000 -1.0 30.2 350 14 7 7.5 4.1 | -1.0 30.2 325 13 7 6.8 3.7
15500 0.2 32.4 355 14 7 8.3 4.6 | 0.6 33.1 325 11 6 7.8 4.3
15000 1.4 34.5 355 13 7 8.2 4.5 | 1.7 35.1 330 10 5 7.8 4.3
14500 2.7 36.9 360 12 6 9.0 5.0 | 2.9 37.2 330 9 4 8.5 4.7
14000 4.1 39.4 005 11 6 9.0 4.9 | 4.2 39.6 335 7 4 8.4 4.6
13500 5.5 41.9 010 10 5 8.9 4.9 | 5.5 41.9 340 6 3 8.8 4.8
13000 6.8 44.2 015 9 5 8.9 4.9 | 6.8 44.2 350 5 3 8.8 4.8
12500 8.2 46.8 020 9 4 9.1 5.0 | 8.1 46.6 355 4 2 8.9 4.9
12000 9.5 49.1 025 8 4 9.2 5.0 | 9.4 48.9 010 4 2 8.9 4.9
11500 10.9 51.6 030 8 4 9.1 5.0 | 10.7 51.3 025 4 2 8.9 4.9
11000 12.2 54.0 030 7 4 8.6 4.7 | 12.0 53.6 030 4 2 8.9 4.9
10500 13.5 56.3 030 7 3 3.4 1.9 | 13.2 55.8 040 4 2 3.6 2.0
10250 13.5 56.3 030 7 3 4.9 2.7 | 13.4 56.1 040 4 2 7.2 3.9
10000 14.4 57.9 030 6 3 13.1 7.2 | 14.3 57.7 040 4 2 13.6 7.5
9750 15.2 59.4 025 6 3 11.7 6.4 | 15.1 59.2 040 5 2 11.8 6.4
9500 15.9 60.6 020 6 3 8.4 4.6 | 15.9 60.6 040 5 2 8.2 4.5
9250 16.3 61.3 020 6 3 5.0 2.7 | 16.3 61.3 035 5 3 6.8 3.7
9000 16.8 62.2 015 6 3 8.1 4.4 | 17.0 62.6 035 5 3 11.1 6.1
8750 17.4 63.3 015 7 3 9.1 5.0 | 17.8 64.0 040 5 3 11.6 6.4
8500 17.9 64.2 010 7 4 6.5 3.6 | 18.5 65.3 040 5 3 9.0 4.9
8250 18.3 64.9 010 7 4 4.4 2.4 | 19.1 66.4 035 5 3 6.9 3.8
8000 18.6 65.5 010 7 4 6.3 3.4 | 19.7 67.5 035 5 3 10.8 5.9
7750 19.0 66.2 005 7 4 6.9 3.8 | 20.6 69.1 040 6 3 12.4 6.8
7500 19.4 66.9 005 7 3 4.2 2.3 | 21.3 70.3 040 6 3 9.0 4.9
7250 19.6 67.3 005 6 3 2.6 1.4 | 22.0 71.6 035 6 3 7.4 4.1
7000 19.8 67.6 005 6 3 4.5 2.5 | 22.6 72.7 035 6 3 11.6 6.3
6750 20.3 68.5 005 6 3 7.3 4.0 | 23.6 74.5 040 6 3 13.3 7.3
6500 20.8 69.4 005 5 3 7.1 3.9 | 24.4 75.9 040 6 3 10.1 5.5
6250 21.3 70.3 005 4 2 6.9 3.8 | 25.2 77.4 040 6 3 10.9 6.0
6000 21.8 71.2 005 4 2 5.3 2.9 | 26.0 78.8 040 6 3 9.3 5.1
5750 22.2 72.0 010 3 2 10.4 5.7 | 26.8 80.2 035 6 3 16.2 8.9
5500 23.5 74.3 010 3 1 24.4 13.4 | 28.6 83.5 035 6 3 31.7 17.4
07/13/2025 at 1500 MDT | 07/13/2025 at 1800 MDT
|
CAPE... +689.4 LI... -0.9 | CAPE... +687.1 LI... -1.1
CINH... -7.1 K Index... +29.8 | CINH... -10.2 K Index... +32.0
|
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 -63.2 -81.8 025 6 3 -0.3 -0.2 | -63.7 -82.7 010 5 3 -0.4 -0.2
45000 -61.9 -79.4 045 14 7 3.8 2.1 | -62.3 -80.1 040 6 3 4.2 2.3
40000 -55.2 -67.4 060 14 7 7.2 3.9 | -54.8 -66.6 110 1 1 7.7 4.2
38000 -50.9 -59.6 060 6 3 7.2 3.9 | -50.2 -58.4 280 3 2 7.7 4.2
36000 -46.6 -51.9 265 2 1 7.6 4.2 | -45.6 -50.1 280 8 4 7.8 4.3
34000 -41.5 -42.7 260 2 1 8.7 4.8 | -40.8 -41.4 265 8 4 8.0 4.4
32000 -36.2 -33.2 255 3 1 8.9 4.9 | -36.0 -32.8 250 9 5 8.2 4.5
30000 -31.1 -24.0 230 2 1 8.5 4.7 | -30.9 -23.6 240 8 4 8.6 4.7
29000 -28.6 -19.5 195 1 1 8.5 4.7 | -28.3 -18.9 235 7 4 8.6 4.7
28000 -25.4 -13.7 175 1 1 8.2 4.5 | -25.1 -13.2 235 6 3 8.1 4.5
27000 -23.0 -9.4 210 1 0 8.2 4.5 | -22.7 -8.9 235 6 3 8.2 4.5
26000 -20.5 -4.9 255 1 1 8.2 4.5 | -20.2 -4.4 240 6 3 8.2 4.5
25000 -18.1 -0.6 275 2 1 7.9 4.4 | -17.8 -0.0 245 6 3 8.1 4.4
24000 -15.7 3.7 300 3 2 7.9 4.3 | -15.4 4.3 260 5 3 8.1 4.5
23000 -13.4 7.9 305 5 2 7.9 4.3 | -13.0 8.6 280 5 2 8.1 4.5
22000 -11.1 12.0 310 6 3 6.7 3.7 | -10.6 12.9 305 6 3 6.7 3.7
21000 -9.2 15.4 310 10 5 6.7 3.7 | -8.8 16.2 315 10 5 6.7 3.7
20000 -7.2 19.0 310 14 7 6.7 3.7 | -6.9 19.6 315 15 8 7.0 3.9
19500 -6.3 20.7 310 16 8 6.5 3.6 | -6.0 21.2 320 17 9 7.1 3.9
19000 -5.5 22.1 305 16 8 6.0 3.3 | -5.0 23.0 315 18 9 6.9 3.8
18500 -4.7 23.5 305 17 9 6.1 3.3 | -4.0 24.8 315 19 10 6.9 3.8
18000 -3.8 25.2 305 17 9 6.4 3.5 | -3.0 26.6 315 18 10 6.6 3.6
17500 -2.9 26.8 300 15 8 6.5 3.5 | -2.1 28.2 310 17 9 6.6 3.6
17000 -2.1 28.2 300 13 7 6.9 3.8 | -1.2 29.8 310 15 8 6.6 3.6
16500 -1.0 30.2 300 11 6 8.0 4.4 | -0.3 31.5 305 13 6 6.3 3.5
16000 0.2 32.4 300 10 5 8.0 4.4 | 0.6 33.1 300 9 5 6.3 3.5
15500 1.3 34.3 300 8 4 7.7 4.2 | 1.5 34.7 295 6 3 6.9 3.8
15000 2.4 36.3 305 6 3 7.7 4.2 | 2.5 36.5 305 2 1 6.9 3.8
14500 3.6 38.5 315 4 2 8.0 4.4 | 3.5 38.3 090 1 1 8.2 4.5
14000 5.3 41.5 350 2 1 8.0 4.4 | 5.4 41.7 095 4 2 8.8 4.8
13500 6.6 43.9 025 2 1 9.2 5.1 | 6.8 44.2 095 5 2 9.5 5.2
13000 7.9 46.2 035 2 1 9.1 5.0 | 8.2 46.8 095 5 3 9.5 5.2
12500 9.3 48.7 040 2 1 9.4 5.2 | 9.6 49.3 095 5 3 9.6 5.2
12000 10.7 51.3 045 3 1 9.5 5.2 | 11.0 51.8 095 6 3 9.6 5.3
11500 12.1 53.8 050 3 1 9.6 5.3 | 12.4 54.3 095 6 3 9.6 5.3
11000 13.5 56.3 050 3 2 9.8 5.4 | 13.9 57.0 095 6 3 9.7 5.3
10500 14.8 58.6 055 3 2 4.8 2.6 | 15.2 59.4 095 7 3 4.5 2.5
10250 15.1 59.2 055 3 2 8.6 4.7 | 15.5 59.9 095 7 3 8.0 4.4
10000 16.1 61.0 055 4 2 13.8 7.6 | 16.4 61.5 095 7 4 13.6 7.5
9750 17.0 62.6 060 4 2 12.1 6.6 | 17.3 63.1 095 7 4 12.2 6.7
9500 17.8 64.0 060 4 2 7.9 4.3 | 18.2 64.8 095 7 4 7.9 4.4
9250 18.3 64.9 060 4 2 7.1 3.9 | 18.6 65.5 095 7 4 6.9 3.8
9000 19.0 66.2 060 4 2 12.0 6.6 | 19.3 66.7 095 8 4 12.0 6.6
8750 19.9 67.8 060 5 2 11.9 6.5 | 20.3 68.5 095 8 4 12.2 6.7
8500 20.7 69.3 060 5 3 9.0 5.0 | 21.1 70.0 095 8 4 9.2 5.0
8250 21.3 70.3 060 5 3 6.5 3.6 | 21.6 70.9 095 8 4 6.3 3.5
8000 21.9 71.4 060 5 3 11.3 6.2 | 22.2 72.0 095 8 4 10.7 5.9
7750 22.9 73.2 065 6 3 13.3 7.3 | 23.2 73.8 095 9 4 12.9 7.1
7500 23.7 74.7 065 6 3 9.1 5.0 | 24.0 75.2 095 9 5 9.1 5.0
7250 24.4 75.9 065 6 3 7.9 4.3 | 24.6 76.3 095 9 5 7.6 4.2
7000 25.0 77.0 065 6 3 10.8 5.9 | 25.2 77.4 095 9 5 10.6 5.8
6750 25.9 78.6 065 6 3 12.5 6.9 | 26.2 79.2 095 9 5 12.6 6.9
6500 26.8 80.2 065 6 3 10.4 5.7 | 27.0 80.6 095 9 5 10.3 5.6
6250 27.6 81.7 065 6 3 11.2 6.2 | 27.8 82.0 095 9 5 10.6 5.8
6000 28.4 83.1 065 7 3 8.7 4.8 | 28.5 83.3 095 9 5 8.2 4.5
5750 29.1 84.4 065 6 3 14.9 8.2 | 29.1 84.4 095 9 5 11.2 6.1
5500 30.8 87.4 065 6 3 32.3 17.7 | 30.4 86.7 090 8 4 23.4 12.8
________________________________________________________________________________
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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