Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
445
UXUS97 KBOU 050020
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1820 MDT Saturday, October 4, 2025
This forecast is for Sunday, October 5, 2025:
If the trigger temperature of 63.0 F/17.2 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 573 ft/min (2.9 m/s)
Maximum height of thermals.................. 12419 ft MSL (7133 ft AGL)
Forecast maximum temperature................... 68.0 F/20.5 C
Time of trigger temperature.................... 1130 MDT
Time of overdevelopment........................ 1700 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 9040 ft MSL (3754 ft AGL)
Thermal soaring outlook for Monday 10/06....... Poor
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....................... 39946 ft MSL (34660 ft AGL)
Wave soaring outlook for Monday 10/06.......... Fair
Remarks...
Sunrise/Sunset.................... 07:00:15 / 18:35:13 MDT
Total possible sunshine........... 11 hr 34 min 58 sec (694 min 58 sec)
Altitude of sun at 12:47:44 MDT... 45.09 degrees
Upper air data from numerical model forecast valid on 10/05/2025 at 0600 MDT
Freezing level.................. 11780 ft MSL (6494 ft AGL)
Convective condensation level... 19313 ft MSL (14027 ft AGL)
Lifted condensation level....... 15944 ft MSL (10659 ft AGL)
Lifted index.................... +6.5
K index......................... -1.9
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 -58.9 -74.0 235 39 20 2.2 1.2 M M M M M
45000 -55.7 -68.3 240 65 33 1.6 0.9 M M M M M
40000 -53.3 -63.9 245 73 38 1.4 0.8 M M M M M
38000 -51.1 -60.0 245 71 37 4.1 2.2 M M M M M
36000 -48.6 -55.5 240 68 35 4.1 2.2 M M M M M
34000 -45.8 -50.4 240 66 34 5.9 3.2 M M M M M
32000 -42.2 -44.0 240 67 34 5.9 3.2 M M M M M
30000 -38.2 -36.8 240 66 34 8.2 4.5 38.4 101.1 13.8 M M
29000 -35.1 -31.2 240 64 33 8.2 4.5 37.6 99.6 13.4 M M
28000 -32.7 -26.9 240 62 32 8.2 4.5 37.1 98.7 13.2 M M
27000 -30.3 -22.5 240 60 31 7.7 4.2 36.4 97.6 12.9 M M
26000 -27.9 -18.2 240 58 30 7.7 4.3 35.6 96.1 12.4 M M
25000 -25.6 -14.1 240 55 28 7.8 4.3 34.9 94.8 11.9 M M
24000 -23.3 -9.9 240 53 27 7.2 4.0 34.2 93.5 11.5 M M
23000 -21.2 -6.2 240 50 26 7.2 4.0 33.2 91.7 10.8 M M
22000 -19.0 -2.2 240 48 25 7.2 4.0 32.3 90.1 10.1 M M
21000 -16.9 1.6 240 45 23 6.9 3.8 31.4 88.5 9.5 M M
20000 -14.8 5.4 240 43 22 6.9 3.8 30.3 86.6 8.7 M M
19500 -13.8 7.2 240 41 21 6.9 3.8 29.8 85.7 8.3 M M
19000 -12.8 9.0 240 40 21 6.9 3.8 29.4 84.9 8.0 M M
18500 -11.8 10.8 245 39 20 6.3 3.5 28.9 84.0 7.6 M M
18000 -10.8 12.6 245 38 19 6.2 3.4 28.3 82.9 7.1 M M
17500 -9.9 14.2 245 36 19 6.0 3.3 27.7 81.8 6.6 M M
17000 -9.1 15.6 245 35 18 5.1 2.8 26.9 80.4 6.0 M M
16500 -8.3 17.1 250 33 17 5.2 2.9 26.1 79.1 5.3 M M
16000 -7.6 18.3 250 31 16 4.7 2.6 25.3 77.6 4.6 M M
15500 -6.9 19.6 250 28 15 4.7 2.6 24.5 76.0 3.9 M M
15000 -6.3 20.7 255 26 13 5.0 2.7 23.6 74.6 3.1 M M
14500 -5.1 22.8 255 22 11 5.2 2.9 22.5 72.5 2.1 M M
14000 -4.3 24.3 255 19 10 6.2 3.4 21.8 71.3 1.5 M M
13500 -3.4 25.9 255 16 8 6.3 3.4 21.3 70.3 0.9 M M
13000 -2.4 27.7 255 14 7 6.9 3.8 20.7 69.3 0.4 M M
12500 -1.4 29.5 255 13 6 7.2 3.9 20.3 68.6 -0.0 573 2.9
12000 -0.3 31.5 255 11 6 7.3 4.0 19.9 67.8 -0.4 526 2.7
11500 0.8 33.4 255 10 5 7.3 4.0 19.5 67.1 -0.8 479 2.4
11000 1.8 35.2 260 10 5 6.3 3.4 19.1 66.4 -1.2 432 2.2
10500 2.7 36.9 260 10 5 4.7 2.6 18.5 65.2 -1.8 393 2.0
10250 3.1 37.6 260 10 5 9.0 4.9 18.1 64.6 -2.2 373 1.9
10000 3.9 39.0 265 9 5 10.0 5.5 18.3 64.9 -2.1 341 1.7
9750 4.4 39.9 265 9 5 6.2 3.4 18.0 64.5 -2.3 318 1.6
9500 4.9 40.8 265 9 4 7.8 4.3 17.8 64.1 -2.5 295 1.5
9250 5.4 41.7 265 8 4 5.4 2.9 17.6 63.7 -2.7 272 1.4
9000 5.8 42.4 260 7 4 5.6 3.1 17.2 63.0 -3.1 255 1.3
8750 6.3 43.3 260 6 3 8.4 4.6 17.1 62.7 -3.3 231 1.2
8500 6.9 44.4 260 6 3 8.6 4.7 17.0 62.5 -3.4 205 1.0
8250 7.6 45.7 255 5 3 7.3 4.0 16.8 62.3 -3.5 179 0.9
8000 8.0 46.4 250 5 2 6.0 3.3 16.6 61.8 -3.8 158 0.8
7750 8.5 47.3 240 4 2 7.5 4.1 16.3 61.4 -4.1 136 0.7
7500 9.1 48.4 235 4 2 8.5 4.6 16.2 61.2 -4.2 111 0.6
7250 9.7 49.5 235 4 2 7.2 4.0 16.1 61.0 -4.3 85 0.4
7000 10.2 50.4 235 4 2 6.2 3.4 15.8 60.5 -4.6 64 0.3
6750 10.7 51.3 235 4 2 7.0 3.9 15.6 60.1 -4.9 42 0.2
6500 11.2 52.2 235 4 2 6.5 3.6 15.4 59.7 -5.1 19 0.1
6250 11.6 52.9 230 4 2 4.4 2.4 15.1 59.1 -5.4 M M
6000 11.9 53.4 230 5 2 4.0 2.2 14.6 58.3 -5.9 M M
5750 12.2 54.0 225 5 2 2.9 1.6 14.2 57.5 -6.4 M M
5500 12.0 53.6 215 5 3 -7.9 -4.3 13.4 56.0 -7.2 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/05/2025 at 0900 MDT | 10/05/2025 at 1200 MDT
|
CAPE... 0.0 LI... +6.1 | CAPE... 0.0 LI... +4.8
CINH... 0.0 K Index... +4.6 | CINH... -0.6 K Index... +11.1
|
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 -59.4 -74.9 230 42 22 2.8 1.5 | -59.6 -75.3 225 46 24 2.4 1.3
45000 -55.3 -67.5 235 66 34 2.0 1.1 | -56.0 -68.8 235 72 37 2.3 1.2
40000 -52.2 -62.0 235 74 38 1.9 1.1 | -52.4 -62.3 235 80 41 2.2 1.2
38000 -50.6 -59.1 235 74 38 2.8 1.5 | -50.9 -59.6 235 81 42 2.6 1.5
36000 -48.9 -56.0 235 74 38 2.8 1.5 | -49.3 -56.7 235 81 42 2.6 1.5
34000 -46.4 -51.5 235 73 38 6.7 3.7 | -46.8 -52.2 235 80 41 6.8 3.8
32000 -42.4 -44.3 235 72 37 6.7 3.6 | -42.7 -44.9 235 76 39 6.8 3.7
30000 -37.8 -36.0 235 68 35 7.1 3.9 | -38.0 -36.4 235 70 36 7.2 3.9
29000 -35.7 -32.3 235 65 34 7.1 3.9 | -35.9 -32.6 235 68 35 7.2 4.0
28000 -33.5 -28.3 235 63 32 7.2 3.9 | -33.7 -28.7 235 65 33 7.2 4.0
27000 -31.3 -24.3 235 60 31 8.2 4.5 | -31.5 -24.7 235 62 32 7.9 4.3
26000 -28.9 -20.0 235 58 30 8.1 4.4 | -29.1 -20.4 235 60 31 7.8 4.3
25000 -26.4 -15.5 235 56 29 8.1 4.4 | -26.8 -16.2 235 58 30 7.8 4.3
24000 -24.1 -11.4 235 54 28 7.2 3.9 | -24.5 -12.1 235 55 29 7.3 4.0
23000 -22.0 -7.6 235 52 27 7.1 3.9 | -22.3 -8.1 235 53 27 7.3 4.0
22000 -19.8 -3.6 235 49 25 7.1 3.9 | -20.2 -4.4 235 50 26 7.3 4.0
21000 -17.8 -0.0 235 46 24 6.6 3.6 | -18.1 -0.6 235 48 24 6.3 3.5
20000 -15.8 3.6 235 43 22 6.7 3.7 | -16.2 2.8 235 44 23 6.4 3.5
19500 -14.8 5.4 235 42 22 6.7 3.7 | -15.2 4.6 235 43 22 6.5 3.5
19000 -13.8 7.2 235 40 21 6.7 3.7 | -14.3 6.3 235 41 21 6.5 3.6
18500 -12.8 9.0 235 39 20 6.1 3.4 | -13.4 7.9 235 39 20 5.5 3.0
18000 -11.9 10.6 240 37 19 6.0 3.3 | -12.6 9.3 235 37 19 5.3 2.9
17500 -11.0 12.2 240 35 18 5.9 3.2 | -11.8 10.8 235 34 18 5.2 2.8
17000 -10.2 13.6 240 34 17 5.0 2.8 | -10.8 12.6 240 30 15 4.5 2.5
16500 -9.1 15.6 245 31 16 5.1 2.8 | -10.1 13.8 240 27 14 4.4 2.4
16000 -8.4 16.9 245 28 14 5.0 2.7 | -9.5 14.9 245 24 12 4.3 2.4
15500 -7.7 18.1 245 25 13 5.0 2.7 | -8.9 16.0 245 21 11 4.3 2.3
15000 -6.9 19.6 250 22 12 5.6 3.1 | -8.1 17.4 245 18 9 6.0 3.3
14500 -6.1 21.0 250 20 10 5.5 3.0 | -7.3 18.9 240 15 8 5.8 3.2
14000 -5.2 22.6 250 18 9 6.3 3.4 | -6.3 20.7 240 12 6 7.1 3.9
13500 -4.3 24.3 250 16 8 6.3 3.5 | -5.3 22.5 240 11 6 7.1 3.9
13000 -3.4 25.9 255 14 7 6.8 3.7 | -4.2 24.4 235 10 5 7.5 4.1
12500 -2.4 27.7 255 13 7 7.0 3.8 | -3.1 26.4 235 8 4 7.5 4.1
12000 -1.3 29.7 255 12 6 7.0 3.8 | -2.0 28.4 235 7 4 7.3 4.0
11500 -0.3 31.5 260 10 5 6.9 3.8 | -1.0 30.2 230 5 3 7.2 4.0
11000 0.7 33.3 265 9 5 6.5 3.6 | 0.1 32.2 215 3 2 7.0 3.8
10500 1.6 34.9 270 7 3 5.6 3.1 | 1.1 34.0 195 2 1 6.0 3.3
10250 2.1 35.8 275 6 3 9.1 5.0 | 1.6 34.9 180 2 1 10.9 6.0
10000 2.9 37.2 270 6 3 10.0 5.5 | 2.6 36.7 170 2 1 11.9 6.5
9750 3.5 38.3 270 5 3 7.0 3.8 | 3.2 37.8 155 2 1 7.5 4.1
9500 4.1 39.4 270 4 2 8.0 4.4 | 3.8 38.8 140 2 1 9.2 5.1
9250 4.6 40.3 270 4 2 6.8 3.7 | 4.5 40.1 125 2 1 6.6 3.6
9000 5.1 41.2 275 2 1 6.4 3.5 | 4.9 40.8 105 3 2 7.1 3.9
8750 5.6 42.1 275 2 1 7.4 4.1 | 5.6 42.1 095 4 2 9.9 5.4
8500 6.2 43.2 275 2 1 7.5 4.1 | 6.3 43.3 085 4 2 9.6 5.3
8250 6.7 44.1 275 1 1 7.2 4.0 | 7.0 44.6 080 5 2 8.8 4.8
8000 7.2 45.0 000 0 0 6.9 3.8 | 7.6 45.7 075 5 3 8.4 4.6
7750 7.7 45.9 120 1 0 7.2 3.9 | 8.3 46.9 075 6 3 10.1 5.5
7500 8.3 46.9 080 1 0 7.4 4.0 | 9.0 48.2 070 6 3 10.5 5.8
7250 8.8 47.8 050 1 1 6.7 3.7 | 9.8 49.6 070 6 3 9.0 4.9
7000 9.3 48.7 070 2 1 6.0 3.3 | 10.4 50.7 070 6 3 8.1 4.5
6750 9.8 49.6 070 2 1 8.1 4.4 | 11.1 52.0 065 6 3 10.8 6.0
6500 10.4 50.7 045 2 1 8.1 4.4 | 12.0 53.6 065 6 3 11.9 6.5
6250 10.9 51.6 040 2 1 5.4 3.0 | 12.8 55.0 065 7 3 10.8 5.9
6000 11.3 52.3 055 2 1 4.8 2.7 | 13.6 56.5 065 7 3 10.5 5.7
5750 11.6 52.9 060 2 1 5.6 3.1 | 14.4 57.9 060 7 3 11.5 6.3
5500 12.1 53.8 040 2 1 8.1 4.5 | 15.5 59.9 060 6 3 19.6 10.8
10/05/2025 at 1500 MDT | 10/05/2025 at 1800 MDT
|
CAPE... +2.1 LI... +3.1 | CAPE... +2.7 LI... +1.0
CINH... -2.6 K Index... +18.6 | CINH... -2.9 K Index... +24.7
|
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 -60.4 -76.7 225 51 26 2.1 1.1 | -60.3 -76.5 235 45 23 3.0 1.7
45000 -57.2 -71.0 240 76 39 2.5 1.4 | -55.9 -68.6 240 65 34 2.4 1.3
40000 -53.2 -63.8 240 86 44 2.5 1.4 | -52.1 -61.8 240 87 45 2.4 1.3
38000 -51.4 -60.5 235 85 44 3.1 1.7 | -50.5 -58.9 240 88 45 2.7 1.5
36000 -49.6 -57.3 235 82 42 3.1 1.7 | -48.9 -56.0 240 87 45 2.7 1.5
34000 -46.7 -52.1 235 79 41 7.4 4.1 | -46.4 -51.5 235 85 44 6.6 3.6
32000 -42.3 -44.1 235 76 39 7.4 4.1 | -42.4 -44.3 235 82 42 6.6 3.6
30000 -37.9 -36.2 235 71 37 7.3 4.0 | -38.4 -37.1 235 77 40 6.7 3.7
29000 -35.2 -31.4 235 68 35 7.3 4.0 | -35.9 -32.6 240 72 37 6.7 3.7
28000 -33.0 -27.4 235 65 33 7.3 4.0 | -33.9 -29.0 240 68 35 6.7 3.7
27000 -30.8 -23.4 235 62 32 7.2 3.9 | -31.9 -25.4 240 64 33 7.1 3.9
26000 -28.7 -19.7 235 59 31 7.2 3.9 | -29.8 -21.6 240 61 32 7.1 3.9
25000 -26.6 -15.9 235 57 29 7.2 3.9 | -27.6 -17.7 240 58 30 7.1 3.9
24000 -24.4 -11.9 235 55 28 7.4 4.0 | -25.5 -13.9 240 55 28 7.1 3.9
23000 -22.2 -8.0 235 53 27 7.4 4.0 | -23.4 -10.1 240 51 26 7.1 3.9
22000 -20.0 -4.0 235 50 26 7.3 4.0 | -21.3 -6.3 240 47 24 7.1 3.9
21000 -17.9 -0.2 235 47 24 6.1 3.4 | -19.3 -2.7 240 43 22 6.3 3.4
20000 -16.1 3.0 235 42 22 6.2 3.4 | -17.4 0.7 235 39 20 6.4 3.5
19500 -15.2 4.6 240 40 20 6.3 3.4 | -16.5 2.3 235 37 19 6.4 3.5
19000 -14.3 6.3 240 37 19 6.4 3.5 | -15.5 4.1 230 35 18 6.5 3.6
18500 -13.5 7.7 240 35 18 4.9 2.7 | -14.6 5.7 230 34 17 5.5 3.0
18000 -12.8 9.0 240 34 18 4.9 2.7 | -13.9 7.0 225 32 17 5.5 3.0
17500 -12.0 10.4 245 34 17 4.9 2.7 | -13.1 8.4 225 31 16 5.6 3.1
17000 -11.4 11.5 240 32 16 4.7 2.6 | -12.2 10.0 220 30 16 5.9 3.2
16500 -10.7 12.7 240 30 15 4.7 2.6 | -11.4 11.5 210 30 15 5.9 3.2
16000 -9.9 14.2 235 28 14 5.6 3.1 | -10.5 13.1 205 29 15 6.9 3.8
15500 -9.1 15.6 230 25 13 5.6 3.1 | -9.5 14.9 195 28 14 6.8 3.8
15000 -8.0 17.6 220 21 11 4.8 2.6 | -7.9 17.8 185 26 14 7.6 4.2
14500 -7.3 18.9 210 18 9 4.6 2.5 | -6.8 19.8 180 25 13 7.6 4.2
14000 -6.5 20.3 200 15 8 7.0 3.9 | -5.8 21.6 175 23 12 6.7 3.7
13500 -5.5 22.1 190 14 7 6.7 3.7 | -4.8 23.4 170 21 11 7.0 3.8
13000 -4.4 24.1 180 13 7 8.1 4.5 | -4.0 24.8 160 18 9 5.0 2.7
12500 -3.2 26.2 175 12 6 8.2 4.5 | -3.2 26.2 150 16 8 4.7 2.6
12000 -1.9 28.6 165 11 6 8.4 4.6 | -2.4 27.7 140 15 7 8.0 4.4
11500 -0.7 30.7 155 9 5 8.4 4.6 | -1.1 30.0 130 14 7 8.3 4.5
11000 0.5 32.9 140 8 4 9.1 5.0 | 0.2 32.4 125 13 7 9.5 5.2
10500 1.9 35.4 130 8 4 10.0 5.5 | 1.6 34.9 120 13 7 10.5 5.8
10250 2.6 36.7 125 8 4 6.0 3.3 | 2.3 36.1 115 14 7 6.3 3.4
10000 2.9 37.2 125 8 4 7.3 4.0 | 2.7 36.9 115 14 7 7.3 4.0
9750 3.7 38.7 120 8 4 11.8 6.5 | 3.5 38.3 110 14 7 11.9 6.5
9500 4.6 40.3 120 8 4 11.7 6.4 | 4.3 39.7 110 14 7 11.5 6.3
9250 5.4 41.7 115 8 4 7.9 4.3 | 5.1 41.2 105 14 7 8.3 4.6
9000 5.8 42.4 115 8 4 7.8 4.3 | 5.6 42.1 100 14 7 7.7 4.2
8750 6.6 43.9 115 8 4 11.9 6.5 | 6.4 43.5 100 14 7 11.0 6.0
8500 7.5 45.5 110 8 4 11.2 6.1 | 7.2 45.0 095 14 7 10.5 5.8
8250 8.3 46.9 110 8 4 9.2 5.1 | 7.9 46.2 095 15 8 8.4 4.6
8000 8.9 48.0 110 8 4 8.2 4.5 | 8.5 47.3 090 15 8 7.5 4.1
7750 9.6 49.3 105 8 4 10.9 6.0 | 9.1 48.4 085 15 8 10.4 5.7
7500 10.4 50.7 105 8 4 10.8 5.9 | 9.9 49.8 085 15 8 10.3 5.7
7250 11.2 52.2 100 8 4 8.9 4.9 | 10.6 51.1 080 15 8 8.5 4.7
7000 11.8 53.2 100 8 4 8.2 4.5 | 11.2 52.2 080 15 8 7.9 4.3
6750 12.5 54.5 100 8 4 11.4 6.3 | 11.9 53.4 080 15 8 10.9 6.0
6500 13.4 56.1 095 9 4 11.5 6.3 | 12.8 55.0 075 15 8 10.8 5.9
6250 14.2 57.6 095 8 4 9.5 5.2 | 13.5 56.3 070 14 7 8.7 4.8
6000 14.9 58.8 090 8 4 9.1 5.0 | 14.1 57.4 070 14 7 9.0 4.9
5750 15.6 60.1 090 8 4 12.8 7.0 | 14.8 58.6 070 14 7 10.6 5.8
5500 16.9 62.4 085 8 4 23.3 12.8 | 15.7 60.3 065 12 6 13.9 7.6
________________________________________________________________________________
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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