Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
890
UXUS97 KBOU 201328
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0727 MDT Friday, June 20, 2025
This forecast is for Friday, June 20, 2025:
If the trigger temperature of 91.3 F/33.0 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1646 ft/min (8.4 m/s)
Maximum height of thermals.................. 21863 ft MSL (16527 ft AGL)
Forecast maximum temperature................... 100.0 F/38.2 C
Time of trigger temperature.................... 1045 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................. 18535 ft MSL (13200 ft AGL)
Thermal soaring outlook for Saturday 06/21..... 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....................... 18629 ft MSL (13293 ft AGL)
Wave soaring outlook for Saturday 06/21........ Fair
Remarks...
Sunrise/Sunset.................... 05:31:31 / 20:30:53 MDT
Total possible sunshine........... 14 hr 59 min 22 sec (899 min 22 sec)
Altitude of sun at 13:01:12 MDT... 73.67 degrees
Upper air data from numerical model forecast valid on 06/20/2025 at 0600 MDT
Freezing level.................. 16581 ft MSL (11245 ft AGL)
Convective condensation level... 23270 ft MSL (17934 ft AGL)
Lifted condensation level....... 22852 ft MSL (17516 ft AGL)
Lifted index.................... +1.1
K index......................... +4.2
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 -66.0 -86.8 250 31 16 2.5 1.4 M M M M M
45000 -60.7 -77.3 255 41 21 5.6 3.1 M M M M M
40000 -52.1 -61.8 255 44 22 6.9 3.8 M M M M M
38000 -47.9 -54.2 250 43 22 6.9 3.8 M M M M M
36000 -43.8 -46.8 245 43 22 6.8 3.7 M M M M M
34000 -38.4 -37.1 245 44 23 8.1 4.5 M M M M M
32000 -33.5 -28.3 250 45 23 8.2 4.5 M M M M M
30000 -28.6 -19.5 250 42 21 8.1 4.5 46.8 116.2 6.9 M M
29000 -26.2 -15.2 250 40 21 8.1 4.5 46.2 115.2 6.5 M M
28000 -23.8 -10.8 250 38 20 7.1 3.9 45.7 114.2 6.2 M M
27000 -21.8 -7.2 250 34 18 6.7 3.7 44.4 111.9 5.2 M M
26000 -19.8 -3.6 250 30 16 6.7 3.7 43.2 109.8 4.3 M M
25000 -17.8 -0.0 255 27 14 6.7 3.7 42.2 107.9 3.6 M M
24000 -16.0 3.2 255 25 13 6.0 3.3 40.8 105.4 2.4 M M
23000 -14.2 6.4 255 23 12 6.0 3.3 39.4 102.9 1.3 M M
22000 -12.4 9.7 255 22 11 6.1 3.4 38.1 100.6 0.2 M M
21000 -10.4 13.3 255 24 13 6.8 3.7 37.0 98.6 -0.8 1576 8.0
20000 -8.4 16.9 250 28 15 6.9 3.8 35.9 96.7 -1.7 1487 7.6
19500 -7.4 18.7 250 30 15 6.9 3.8 35.5 95.9 -2.2 1442 7.3
19000 -6.4 20.5 250 32 16 7.7 4.2 35.1 95.1 -2.6 1396 7.1
18500 -4.7 23.5 250 33 17 7.8 4.3 34.6 94.2 -3.1 1322 6.7
18000 -3.5 25.7 250 33 17 8.5 4.7 34.3 93.7 -3.4 1272 6.5
17500 -2.2 28.0 250 32 16 8.7 4.8 34.1 93.3 -3.6 1218 6.2
17000 -0.9 30.4 250 30 16 8.9 4.9 33.9 93.1 -3.8 1165 5.9
16500 0.5 32.9 250 29 15 9.5 5.2 33.8 92.9 -3.9 1108 5.6
16000 1.9 35.4 250 27 14 9.4 5.2 33.8 92.8 -3.9 1051 5.3
15500 3.3 37.9 250 25 13 9.7 5.3 33.8 92.8 -4.0 993 5.0
15000 4.8 40.6 250 23 12 9.7 5.3 33.7 92.7 -4.0 935 4.7
14500 6.2 43.2 255 22 11 9.7 5.3 33.7 92.7 -4.0 877 4.5
14000 7.7 45.9 255 21 11 9.7 5.3 33.7 92.7 -4.1 819 4.2
13500 9.1 48.4 255 20 10 9.7 5.3 33.7 92.7 -4.1 760 3.9
13000 10.6 51.1 255 19 10 9.6 5.3 33.7 92.6 -4.1 702 3.6
12500 12.0 53.6 250 18 9 9.6 5.3 33.7 92.6 -4.2 644 3.3
12000 13.4 56.1 250 18 9 9.5 5.2 33.6 92.6 -4.2 587 3.0
11500 14.8 58.6 250 18 9 9.6 5.3 33.6 92.5 -4.3 530 2.7
11000 16.1 61.0 250 17 9 8.0 4.4 33.4 92.2 -4.5 476 2.4
10500 17.3 63.1 250 17 9 11.0 6.0 33.2 91.7 -4.8 425 2.2
10250 18.3 64.9 245 16 8 12.4 6.8 33.4 92.2 -4.5 389 2.0
10000 19.1 66.4 245 16 8 9.2 5.1 33.5 92.2 -4.5 359 1.8
9750 19.8 67.6 240 16 8 9.5 5.2 33.4 92.2 -4.6 330 1.7
9500 20.5 68.9 240 16 8 9.8 5.4 33.4 92.1 -4.6 302 1.5
9250 21.2 70.2 240 16 8 8.5 4.7 33.4 92.1 -4.6 273 1.4
9000 21.8 71.2 240 16 8 8.4 4.6 33.3 91.9 -4.8 248 1.3
8750 22.5 72.5 235 16 8 9.6 5.3 33.2 91.8 -4.9 220 1.1
8500 23.2 73.8 235 16 8 9.4 5.2 33.2 91.8 -4.9 192 1.0
8250 23.9 75.0 230 16 8 9.0 5.0 33.2 91.7 -4.9 163 0.8
8000 24.5 76.1 230 16 8 8.3 4.5 33.1 91.6 -5.1 137 0.7
7750 25.1 77.2 230 17 9 8.2 4.5 33.0 91.3 -5.2 112 0.6
7500 25.7 78.3 225 17 9 8.2 4.5 32.8 91.1 -5.3 86 0.4
7250 26.3 79.3 225 18 9 7.1 3.9 32.7 90.9 -5.5 61 0.3
7000 26.7 80.1 225 18 9 5.2 2.8 32.4 90.4 -5.8 41 0.2
6750 27.0 80.6 225 18 9 4.4 2.4 32.0 89.7 -6.2 24 0.1
6500 27.2 81.0 220 18 9 0.7 0.4 31.5 88.8 -6.8 10 0.1
6250 26.9 80.4 220 18 9 -8.4 -4.6 30.5 86.9 -7.8 12 0.1
6000 26.0 78.8 220 18 9 -12.4 -6.8 28.9 84.0 -9.5 32 0.2
5750 25.0 77.0 220 18 9 -15.8 -8.7 27.2 81.0 -11.3 55 0.3
5500 23.1 73.6 220 14 7 -37.5 -20.6 24.6 76.3 -13.9 106 0.5
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/20/2025 at 0900 MDT | 06/20/2025 at 1200 MDT
|
CAPE... 0.0 LI... +1.8 | CAPE... 0.0 LI... +1.5
CINH... -1.0 K Index... +6.9 | CINH... -0.0 K Index... +11.2
|
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 -65.3 -85.5 240 36 18 3.1 1.7 | -66.2 -87.2 225 41 21 2.6 1.4
45000 -59.6 -75.3 250 45 23 5.1 2.8 | -60.6 -77.1 235 50 25 5.8 3.2
40000 -51.8 -61.2 255 47 24 6.3 3.5 | -51.7 -61.1 250 51 27 6.8 3.7
38000 -48.0 -54.4 250 48 25 6.4 3.5 | -47.6 -53.7 245 52 27 6.8 3.7
36000 -44.1 -47.4 245 49 25 6.2 3.4 | -43.6 -46.5 245 52 27 6.7 3.7
34000 -39.0 -38.2 245 47 24 7.9 4.3 | -38.5 -37.3 240 51 26 7.7 4.2
32000 -34.2 -29.6 240 45 23 7.9 4.3 | -33.9 -29.0 235 50 26 7.7 4.2
30000 -29.3 -20.7 240 40 21 8.2 4.5 | -29.2 -20.6 230 46 24 7.8 4.3
29000 -26.9 -16.4 235 38 19 8.2 4.5 | -26.8 -16.2 230 44 23 7.8 4.3
28000 -24.4 -11.9 235 35 18 7.7 4.2 | -24.5 -12.1 230 42 22 7.3 4.0
27000 -22.2 -8.0 235 33 17 7.5 4.1 | -22.4 -8.3 225 40 21 7.1 3.9
26000 -19.9 -3.8 230 30 16 7.5 4.1 | -20.3 -4.5 225 38 19 7.1 3.9
25000 -17.6 0.3 225 28 14 7.5 4.1 | -18.2 -0.8 220 35 18 7.1 3.9
24000 -15.6 3.9 225 26 13 6.6 3.6 | -16.0 3.2 220 34 17 7.2 4.0
23000 -13.7 7.3 220 24 12 6.6 3.6 | -13.8 7.2 220 33 17 7.2 4.0
22000 -11.7 10.9 220 22 12 6.6 3.6 | -11.7 10.9 220 31 16 7.1 3.9
21000 -9.9 14.2 225 25 13 5.9 3.2 | -9.9 14.2 225 31 16 6.0 3.3
20000 -8.2 17.2 235 29 15 6.0 3.3 | -8.1 17.4 230 32 16 6.1 3.3
19500 -7.3 18.9 240 31 16 6.0 3.3 | -7.3 18.9 235 32 16 6.1 3.4
19000 -6.5 20.3 240 33 17 6.3 3.5 | -6.4 20.5 240 32 17 6.7 3.6
18500 -5.1 22.8 245 37 19 6.4 3.5 | -5.4 22.3 240 32 17 6.8 3.7
18000 -4.1 24.6 245 38 20 8.0 4.4 | -3.9 25.0 240 32 17 8.0 4.4
17500 -2.9 26.8 245 38 20 8.5 4.6 | -2.6 27.3 240 32 16 8.5 4.6
17000 -1.6 29.1 245 38 20 8.7 4.7 | -1.4 29.5 240 31 16 8.6 4.7
16500 -0.3 31.5 245 38 19 9.4 5.2 | -0.0 32.0 245 30 16 9.3 5.1
16000 1.1 34.0 250 37 19 9.3 5.1 | 1.3 34.3 245 30 15 9.3 5.1
15500 2.6 36.7 250 36 18 9.6 5.2 | 2.7 36.9 240 30 15 9.5 5.2
15000 4.0 39.2 250 34 17 9.6 5.2 | 4.2 39.6 240 29 15 9.6 5.2
14500 5.4 41.7 250 32 17 9.5 5.2 | 5.6 42.1 240 29 15 9.5 5.2
14000 6.9 44.4 250 30 16 9.5 5.2 | 7.0 44.6 240 28 14 9.4 5.2
13500 8.3 46.9 245 28 15 9.4 5.2 | 8.4 47.1 240 28 14 9.5 5.2
13000 9.7 49.5 245 26 14 9.4 5.2 | 9.8 49.6 240 27 14 9.6 5.3
12500 11.1 52.0 245 24 13 9.4 5.1 | 11.3 52.3 240 26 14 9.6 5.3
12000 12.5 54.5 245 22 12 9.2 5.1 | 12.7 54.9 235 26 13 9.6 5.3
11500 13.9 57.0 245 21 11 9.3 5.1 | 14.1 57.4 235 25 13 9.8 5.4
11000 15.2 59.4 240 19 10 8.1 4.5 | 15.5 59.9 235 25 13 8.1 4.5
10500 16.4 61.5 240 18 9 11.3 6.2 | 16.7 62.1 235 24 12 11.7 6.4
10250 17.4 63.3 240 17 9 12.0 6.6 | 17.7 63.9 230 24 12 13.0 7.1
10000 18.1 64.6 240 16 8 8.3 4.6 | 18.5 65.3 230 23 12 9.0 4.9
9750 18.8 65.8 240 16 8 9.3 5.1 | 19.2 66.6 230 23 12 9.6 5.3
9500 19.5 67.1 240 15 8 9.2 5.1 | 19.9 67.8 230 23 12 9.5 5.2
9250 20.1 68.2 240 15 8 8.3 4.6 | 20.6 69.1 230 22 12 9.2 5.1
9000 20.7 69.3 240 15 8 8.7 4.7 | 21.3 70.3 230 22 11 9.6 5.3
8750 21.4 70.5 240 15 7 9.8 5.4 | 22.0 71.6 230 22 11 10.3 5.6
8500 22.2 72.0 240 14 7 9.7 5.3 | 22.8 73.0 230 22 11 10.3 5.6
8250 22.9 73.2 240 14 7 8.2 4.5 | 23.6 74.5 230 21 11 9.7 5.3
8000 23.4 74.1 245 15 7 8.1 4.4 | 24.3 75.7 230 21 11 9.6 5.3
7750 24.1 75.4 245 15 8 9.4 5.2 | 25.0 77.0 230 21 11 10.1 5.5
7500 24.8 76.6 240 15 8 8.8 4.8 | 25.8 78.4 230 21 11 10.0 5.5
7250 25.4 77.7 240 15 8 6.8 3.7 | 26.5 79.7 230 20 11 8.7 4.8
7000 25.8 78.4 240 15 8 5.8 3.2 | 27.1 80.8 225 21 11 9.0 4.9
6750 26.3 79.3 240 15 8 7.2 4.0 | 27.9 82.2 225 20 10 11.6 6.3
6500 26.8 80.2 235 15 8 6.1 3.4 | 28.8 83.8 225 19 10 11.7 6.4
6250 27.1 80.8 235 14 7 3.5 1.9 | 29.6 85.3 225 19 10 10.5 5.8
6000 27.2 81.0 230 14 7 3.2 1.7 | 30.4 86.7 225 19 10 10.5 5.7
5750 27.4 81.3 225 13 7 2.5 1.4 | 31.1 88.0 225 18 9 9.8 5.4
5500 27.5 81.5 225 11 6 5.9 3.2 | 32.0 89.6 225 16 8 15.6 8.5
06/20/2025 at 1500 MDT | 06/20/2025 at 1800 MDT
|
CAPE... +17.9 LI... -0.6 | CAPE... +56.3 LI... -0.6
CINH... -1.7 K Index... +14.3 | CINH... -3.9 K Index... +15.4
|
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 -65.8 -86.4 235 40 20 3.0 1.7 | -65.2 -85.4 235 45 23 2.5 1.4
45000 -59.9 -75.8 240 50 26 5.3 2.9 | -60.1 -76.2 240 56 29 4.9 2.7
40000 -51.7 -61.1 240 55 28 6.6 3.6 | -52.3 -62.1 235 58 30 7.2 3.9
38000 -47.7 -53.9 240 55 29 6.6 3.6 | -47.9 -54.2 235 58 30 7.2 4.0
36000 -43.8 -46.8 240 56 29 6.5 3.6 | -43.6 -46.5 235 57 30 7.1 3.9
34000 -39.1 -38.4 235 55 28 8.0 4.4 | -38.8 -37.8 235 55 28 8.2 4.5
32000 -33.7 -28.7 230 54 28 8.1 4.4 | -33.3 -27.9 230 52 27 8.3 4.6
30000 -29.1 -20.4 230 50 26 7.7 4.2 | -28.7 -19.7 235 52 27 7.6 4.2
29000 -26.8 -16.2 235 48 25 7.7 4.2 | -26.4 -15.5 240 53 27 7.6 4.2
28000 -24.5 -12.1 235 46 24 6.9 3.8 | -24.2 -11.6 245 53 27 6.2 3.4
27000 -22.6 -8.7 235 44 23 6.6 3.6 | -22.5 -8.5 245 50 26 5.6 3.1
26000 -20.6 -5.1 235 42 21 6.6 3.6 | -20.9 -5.6 245 47 24 5.7 3.1
25000 -18.7 -1.7 235 40 20 6.7 3.6 | -19.2 -2.6 245 44 23 5.8 3.2
24000 -16.7 1.9 235 38 20 6.8 3.7 | -17.3 0.9 240 40 21 6.6 3.6
23000 -14.7 5.5 235 37 19 6.8 3.7 | -15.4 4.3 240 37 19 6.7 3.7
22000 -12.7 9.1 235 35 18 6.9 3.8 | -13.5 7.7 235 33 17 7.0 3.9
21000 -10.6 12.9 235 34 17 7.4 4.0 | -10.9 12.4 235 32 17 9.1 5.0
20000 -8.5 16.7 235 32 16 7.4 4.1 | -8.2 17.2 235 31 16 9.1 5.0
19500 -7.4 18.7 235 31 16 7.4 4.0 | -6.9 19.6 235 31 16 9.1 5.0
19000 -6.3 20.7 235 30 16 9.1 5.0 | -5.5 22.1 230 30 16 9.5 5.2
18500 -4.8 23.4 235 30 15 9.4 5.2 | -4.1 24.6 230 30 15 9.6 5.3
18000 -3.4 25.9 235 30 15 9.4 5.2 | -2.6 27.3 230 30 15 9.6 5.3
17500 -1.3 29.7 235 29 15 9.5 5.2 | -1.2 29.8 230 30 15 9.6 5.2
17000 0.1 32.2 230 29 15 9.5 5.2 | 0.2 32.4 230 29 15 9.6 5.2
16500 1.5 34.7 230 29 15 9.7 5.3 | 2.4 36.3 230 29 15 9.7 5.3
16000 3.0 37.4 230 28 15 9.7 5.3 | 3.8 38.8 230 29 15 9.7 5.3
15500 4.4 39.9 230 28 14 9.6 5.3 | 5.3 41.5 230 29 15 9.7 5.3
15000 5.9 42.6 230 28 14 9.6 5.3 | 6.7 44.1 230 29 15 9.7 5.3
14500 7.3 45.1 230 28 14 9.7 5.3 | 8.2 46.8 230 29 15 9.7 5.3
14000 8.8 47.8 230 27 14 9.7 5.3 | 9.6 49.3 230 29 15 9.7 5.3
13500 10.2 50.4 225 27 14 9.7 5.3 | 11.1 52.0 230 29 15 9.7 5.3
13000 11.6 52.9 225 27 14 9.6 5.3 | 12.5 54.5 230 29 15 9.6 5.3
12500 13.1 55.6 225 26 13 9.6 5.3 | 13.9 57.0 230 29 15 9.6 5.3
12000 14.5 58.1 225 26 13 9.6 5.3 | 15.4 59.7 230 28 15 9.6 5.3
11500 16.0 60.8 225 25 13 9.8 5.4 | 16.8 62.2 230 28 14 9.8 5.4
11000 17.3 63.1 225 25 13 8.6 4.7 | 18.2 64.8 230 28 14 8.2 4.5
10500 18.6 65.5 225 25 13 11.0 6.1 | 19.4 66.9 230 27 14 11.0 6.0
10250 19.6 67.3 220 25 13 12.4 6.8 | 20.4 68.7 230 27 14 13.0 7.1
10000 20.4 68.7 220 25 13 9.4 5.1 | 21.2 70.2 230 26 14 9.4 5.2
9750 21.1 70.0 220 24 13 9.5 5.2 | 21.9 71.4 230 26 13 9.2 5.1
9500 21.8 71.2 220 24 13 9.1 5.0 | 22.6 72.7 230 26 13 9.0 4.9
9250 22.5 72.5 220 24 12 10.7 5.9 | 23.3 73.9 230 26 13 10.7 5.9
9000 23.3 73.9 220 24 12 11.0 6.0 | 24.1 75.4 230 25 13 11.0 6.0
8750 24.1 75.4 220 23 12 9.6 5.2 | 24.8 76.6 230 25 13 9.4 5.2
8500 24.8 76.6 220 23 12 10.3 5.6 | 25.6 78.1 230 25 13 10.2 5.6
8250 25.6 78.1 220 23 12 8.9 4.9 | 26.3 79.3 230 24 12 8.7 4.7
8000 26.2 79.2 220 23 12 9.2 5.0 | 26.9 80.4 230 24 12 9.0 5.0
7750 27.0 80.6 220 23 12 10.4 5.7 | 27.7 81.9 230 24 12 10.5 5.8
7500 27.7 81.9 220 22 11 10.6 5.8 | 28.5 83.3 230 23 12 10.7 5.9
7250 28.5 83.3 220 22 11 8.5 4.7 | 29.2 84.6 230 23 12 8.3 4.6
7000 29.0 84.2 220 22 11 8.2 4.5 | 29.7 85.5 230 23 12 7.8 4.3
6750 29.8 85.6 215 22 11 11.4 6.2 | 30.5 86.9 230 22 11 11.2 6.1
6500 30.7 87.3 215 21 11 11.7 6.4 | 31.3 88.3 230 21 11 12.0 6.6
6250 31.5 88.7 215 20 10 10.7 5.9 | 32.2 90.0 230 20 10 10.3 5.7
6000 32.3 90.1 215 20 10 10.4 5.7 | 32.9 91.2 230 20 10 8.9 4.9
5750 33.1 91.6 215 19 10 10.5 5.7 | 33.6 92.5 230 18 10 10.3 5.6
5500 34.0 93.2 215 17 9 16.1 8.8 | 34.4 93.9 230 16 8 12.4 6.8
________________________________________________________________________________
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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