Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
716
UXUS97 KBOU 131255
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0654 MDT Monday, October 13, 2025
This forecast is for Monday, October 13, 2025:
If the trigger temperature of 57.7 F/14.3 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 45 ft/min (0.2 m/s)
Maximum height of thermals.................. 11542 ft MSL (6222 ft AGL)
Forecast maximum temperature................... 64.0 F/18.2 C
Time of trigger temperature.................... 1145 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 9755 ft MSL (4435 ft AGL)
Thermal soaring outlook for Tuesday 10/14...... Fair
Wave Soaring Index............................. Good
Wave Soaring Index trend (to 1800 MDT)......... Decreasing
Height of stable layer (12-18K ft MSL)......... 11953 ft MSL (6633 ft AGL)
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 40452 ft MSL (35132 ft AGL)
Wave soaring outlook for Tuesday 10/14......... Poor
Remarks... Cool and mostly cloudy, a few showers this afternoon
Sunrise/Sunset.................... 07:08:19 / 18:22:50 MDT
Total possible sunshine........... 11 hr 14 min 31 sec (674 min 31 sec)
Altitude of sun at 12:45:34 MDT... 42.03 degrees
Upper air data from numerical model forecast valid on 10/13/2025 at 0600 MDT
Freezing level.................. 10734 ft MSL (5414 ft AGL)
Convective condensation level... 22374 ft MSL (17054 ft AGL)
Lifted condensation level....... 16714 ft MSL (11395 ft AGL)
Lifted index.................... +11.0
K index......................... -0.5
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 -64.5 -84.1 235 83 43 2.3 1.3 M M M M M
45000 -60.3 -76.5 240 114 59 5.4 2.9 M M M M M
40000 -51.9 -61.4 235 126 65 4.9 2.7 M M M M M
38000 -49.9 -57.8 235 111 57 3.2 1.7 M M M M M
36000 -48.0 -54.4 235 95 49 3.2 1.8 M M M M M
34000 -44.8 -48.6 230 85 44 7.5 4.1 M M M M M
32000 -40.3 -40.5 230 79 41 7.5 4.1 M M M M M
30000 -35.2 -31.4 230 73 38 7.4 4.1 41.1 106.0 17.7 M M
29000 -33.0 -27.4 235 71 36 7.4 4.1 40.2 104.4 17.2 M M
28000 -30.8 -23.4 235 69 35 7.5 4.1 39.4 103.0 16.8 M M
27000 -28.5 -19.3 240 67 34 7.6 4.2 38.6 101.4 16.3 M M
26000 -26.3 -15.3 240 65 33 7.6 4.2 37.7 99.9 15.8 M M
25000 -24.0 -11.2 240 63 32 7.6 4.2 37.0 98.5 15.4 M M
24000 -21.8 -7.2 240 60 31 6.2 3.4 36.0 96.9 14.8 M M
23000 -20.0 -4.0 235 55 28 6.3 3.4 34.7 94.5 13.9 M M
22000 -18.1 -0.6 230 50 26 6.3 3.5 33.5 92.3 13.0 M M
21000 -16.1 3.0 230 47 24 7.2 3.9 32.4 90.3 12.3 M M
20000 -14.0 6.8 225 46 24 7.1 3.9 31.4 88.6 11.6 M M
19500 -12.9 8.8 225 45 23 7.2 3.9 31.0 87.8 11.3 M M
19000 -11.8 10.8 225 44 23 7.2 4.0 30.6 87.0 11.0 M M
18500 -10.8 12.6 225 44 22 6.6 3.6 30.1 86.2 10.6 M M
18000 -9.8 14.4 230 43 22 6.7 3.7 29.6 85.2 10.2 M M
17500 -8.8 16.2 230 43 22 6.3 3.5 29.1 84.3 9.8 M M
17000 -8.0 17.6 230 42 22 5.9 3.2 28.4 83.1 9.2 M M
16500 -7.1 19.2 230 42 22 5.9 3.2 27.7 81.9 8.7 M M
16000 -5.9 21.4 230 42 21 5.2 2.8 26.6 79.9 7.7 M M
15500 -5.2 22.6 235 41 21 5.1 2.8 25.8 78.5 7.0 M M
15000 -4.6 23.7 230 40 21 4.4 2.4 25.0 77.0 6.2 M M
14500 -4.0 24.8 230 39 20 4.6 2.5 24.1 75.4 5.4 M M
14000 -3.4 25.9 230 37 19 4.1 2.3 23.2 73.8 4.5 M M
13500 -2.8 27.0 225 35 18 4.3 2.3 22.3 72.1 3.6 M M
13000 -2.3 27.9 225 33 17 3.6 2.0 21.4 70.5 2.8 M M
12500 -1.8 28.8 220 29 15 3.6 1.9 20.3 68.6 1.8 M M
12000 -1.3 29.7 215 26 14 2.9 1.6 19.3 66.8 0.8 M M
11500 -0.9 30.4 210 24 12 2.7 1.5 18.2 64.8 -0.2 440 2.2
11000 -0.4 31.3 200 22 11 4.4 2.4 17.2 62.9 -1.1 410 2.1
10500 0.4 32.7 195 21 11 5.3 2.9 16.4 61.5 -1.8 373 1.9
10250 0.7 33.3 190 21 11 2.3 1.2 16.0 60.8 -2.2 355 1.8
10000 0.9 33.6 190 21 11 3.7 2.0 15.3 59.6 -2.8 344 1.7
9750 1.4 34.5 185 21 11 7.7 4.2 15.1 59.2 -3.0 320 1.6
9500 1.9 35.4 185 21 11 6.9 3.8 14.9 58.8 -3.2 297 1.5
9250 2.5 36.5 180 21 11 6.1 3.3 14.7 58.4 -3.4 273 1.4
9000 2.9 37.2 180 21 11 5.3 2.9 14.3 57.8 -3.7 253 1.3
8750 3.4 38.1 175 21 11 6.5 3.6 14.0 57.2 -4.0 232 1.2
8500 3.9 39.0 175 21 11 6.7 3.7 13.8 56.8 -4.2 209 1.1
8250 4.4 39.9 170 20 11 6.3 3.5 13.5 56.4 -4.5 187 0.9
8000 4.8 40.6 170 21 11 6.1 3.3 13.3 55.9 -4.7 165 0.8
7750 5.3 41.5 170 21 11 6.9 3.8 13.0 55.4 -5.0 143 0.7
7500 5.9 42.6 165 20 11 7.0 3.8 12.8 55.0 -5.2 120 0.6
7250 6.4 43.5 165 20 10 6.2 3.4 12.5 54.6 -5.4 98 0.5
7000 6.8 44.2 165 21 11 5.8 3.2 12.3 54.1 -5.7 77 0.4
6750 7.3 45.1 165 21 11 6.9 3.8 12.0 53.6 -6.0 56 0.3
6500 7.7 45.9 160 18 9 5.2 2.9 11.8 53.2 -6.3 34 0.2
6250 8.0 46.4 160 16 8 2.5 1.3 11.3 52.3 -6.8 20 0.1
6000 8.2 46.8 155 15 8 4.5 2.5 10.8 51.4 -7.3 6 0.0
5750 8.4 47.1 155 13 7 -0.8 -0.4 10.3 50.5 -7.9 M M
5500 7.8 46.0 150 8 4 -15.4 -8.4 9.0 48.1 -9.3 4 0.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/13/2025 at 0900 MDT | 10/13/2025 at 1200 MDT
|
CAPE... 0.0 LI... +5.8 | CAPE... 0.0 LI... +5.4
CINH... -0.1 K Index... +10.0 | CINH... 0.0 K Index... +15.3
|
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 -65.2 -85.4 235 86 44 2.7 1.5 | -65.4 -85.7 235 85 44 2.7 1.5
45000 -59.9 -75.8 235 110 57 6.0 3.3 | -60.2 -76.4 235 108 56 5.8 3.2
40000 -50.9 -59.6 235 123 63 4.8 2.6 | -51.5 -60.7 235 124 64 4.8 2.6
38000 -49.1 -56.4 235 110 56 2.8 1.5 | -49.3 -56.7 235 111 57 3.6 2.0
36000 -47.5 -53.5 235 96 49 2.8 1.5 | -47.2 -53.0 230 99 51 3.6 2.0
34000 -44.4 -47.9 230 86 44 7.0 3.8 | -44.0 -47.2 230 87 45 6.7 3.7
32000 -40.2 -40.4 230 80 41 7.0 3.9 | -39.4 -38.9 225 74 38 6.7 3.7
30000 -35.1 -31.2 230 74 38 8.1 4.4 | -34.9 -30.8 225 67 35 8.1 4.4
29000 -32.7 -26.9 230 72 37 8.1 4.4 | -32.5 -26.5 225 66 34 8.1 4.4
28000 -30.3 -22.5 230 70 36 8.1 4.4 | -30.1 -22.2 225 64 33 8.1 4.4
27000 -27.9 -18.2 230 68 35 7.8 4.3 | -27.8 -18.0 225 62 32 7.6 4.2
26000 -25.6 -14.1 230 65 34 7.8 4.3 | -25.5 -13.9 230 59 31 7.6 4.2
25000 -23.2 -9.8 230 63 33 7.8 4.3 | -23.2 -9.8 230 57 29 7.6 4.2
24000 -21.1 -6.0 230 61 32 6.4 3.5 | -21.0 -5.8 230 55 28 7.3 4.0
23000 -19.2 -2.6 230 60 31 6.5 3.6 | -18.9 -2.0 230 53 27 7.3 4.0
22000 -17.3 0.9 230 58 30 6.6 3.6 | -16.7 1.9 230 50 26 7.3 4.0
21000 -15.4 4.3 230 56 29 6.4 3.5 | -14.6 5.7 230 48 25 6.9 3.8
20000 -13.5 7.7 230 53 27 6.4 3.5 | -12.6 9.3 230 47 24 6.9 3.8
19500 -12.6 9.3 230 51 26 6.4 3.5 | -11.6 11.1 230 46 24 7.0 3.8
19000 -11.6 11.1 230 49 25 6.5 3.5 | -10.6 12.9 230 45 23 7.0 3.8
18500 -10.7 12.7 230 48 25 6.6 3.6 | -9.7 14.5 230 44 23 6.6 3.6
18000 -9.7 14.5 230 46 23 6.6 3.6 | -8.7 16.3 225 44 23 6.7 3.7
17500 -8.8 16.2 235 44 22 6.2 3.4 | -7.7 18.1 225 43 22 6.4 3.5
17000 -7.9 17.8 235 42 21 5.9 3.3 | -6.4 20.5 220 43 22 6.2 3.4
16500 -6.6 20.1 235 38 20 6.0 3.3 | -5.5 22.1 220 43 22 5.7 3.1
16000 -5.7 21.7 230 36 19 6.0 3.3 | -4.7 23.5 215 41 21 5.5 3.0
15500 -4.8 23.4 230 35 18 5.9 3.2 | -4.0 24.8 215 40 21 5.4 3.0
15000 -4.0 24.8 230 33 17 5.5 3.0 | -3.2 26.2 210 38 19 5.0 2.8
14500 -3.2 26.2 225 31 16 5.6 3.0 | -2.5 27.5 205 36 18 5.1 2.8
14000 -2.5 27.5 225 29 15 4.7 2.6 | -1.8 28.8 205 33 17 3.8 2.1
13500 -1.8 28.8 220 28 14 4.9 2.7 | -1.3 29.7 200 31 16 4.0 2.2
13000 -1.2 29.8 215 26 13 3.6 2.0 | -0.7 30.7 195 29 15 3.0 1.6
12500 -0.6 30.9 210 24 12 3.6 2.0 | -0.2 31.6 195 27 14 3.0 1.6
12000 -0.1 31.8 205 22 11 3.3 1.8 | 0.3 32.5 190 25 13 3.3 1.8
11500 0.4 32.7 200 20 11 3.3 1.8 | 0.8 33.4 190 23 12 3.4 1.9
11000 0.9 33.6 195 20 10 3.1 1.7 | 1.3 34.3 185 22 11 1.9 1.1
10500 1.4 34.5 190 20 10 3.7 2.0 | 1.6 34.9 185 22 11 2.0 1.1
10250 1.7 35.1 185 20 10 0.8 0.4 | 1.8 35.2 185 22 11 0.8 0.4
10000 1.7 35.1 185 20 10 1.8 1.0 | 1.8 35.2 180 21 11 2.5 1.4
9750 2.1 35.8 185 21 11 5.4 3.0 | 2.2 36.0 180 22 11 5.0 2.8
9500 2.4 36.3 180 21 11 4.7 2.6 | 2.5 36.5 180 22 11 4.5 2.4
9250 2.8 37.0 180 22 11 4.1 2.2 | 2.9 37.2 175 22 11 4.3 2.4
9000 3.1 37.6 180 22 11 3.7 2.1 | 3.2 37.8 175 21 11 5.1 2.8
8750 3.4 38.1 180 23 12 5.0 2.8 | 3.7 38.7 175 20 10 6.5 3.6
8500 3.8 38.8 175 23 12 5.3 2.9 | 4.1 39.4 170 19 10 6.6 3.6
8250 4.2 39.6 175 24 12 4.8 2.6 | 4.6 40.3 170 19 10 7.0 3.8
8000 4.6 40.3 175 24 13 4.5 2.5 | 5.2 41.4 170 19 10 7.5 4.1
7750 4.9 40.8 175 25 13 5.0 2.7 | 5.8 42.4 165 18 9 9.1 5.0
7500 5.3 41.5 175 24 12 5.0 2.7 | 6.5 43.7 165 18 9 9.2 5.1
7250 5.7 42.3 175 23 12 4.9 2.7 | 7.1 44.8 165 17 9 7.9 4.4
7000 6.0 42.8 175 24 12 4.3 2.4 | 7.7 45.9 165 17 9 7.4 4.0
6750 6.4 43.5 175 24 12 7.1 3.9 | 8.4 47.1 165 17 9 11.1 6.1
6500 7.0 44.6 170 21 11 7.5 4.1 | 9.3 48.7 165 16 8 11.6 6.3
6250 7.4 45.3 170 19 10 5.4 3.0 | 10.0 50.0 165 15 8 9.1 5.0
6000 7.9 46.2 170 17 9 5.4 3.0 | 10.7 51.3 165 15 8 9.0 5.0
5750 8.3 46.9 170 15 8 7.5 4.1 | 11.4 52.5 165 14 7 12.2 6.7
5500 9.1 48.4 165 11 6 13.7 7.5 | 12.7 54.9 160 12 6 20.4 11.2
10/13/2025 at 1500 MDT | 10/13/2025 at 1800 MDT
|
CAPE... 0.0 LI... +4.9 | CAPE... +0.4 LI... +2.9
CINH... -0.3 K Index... +18.4 | CINH... -0.1 K Index... +19.8
|
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 -65.2 -85.4 235 81 42 2.1 1.2 | -65.7 -86.3 235 79 41 2.5 1.4
45000 -60.7 -77.3 235 103 53 5.9 3.2 | -60.9 -77.6 235 96 49 5.9 3.2
40000 -51.8 -61.2 235 116 60 5.3 2.9 | -52.0 -61.6 235 109 56 6.2 3.4
38000 -48.8 -55.8 235 107 55 5.0 2.7 | -48.2 -54.8 235 107 55 6.3 3.5
36000 -45.8 -50.4 235 98 51 5.0 2.7 | -44.4 -47.9 235 105 54 6.3 3.5
34000 -42.5 -44.5 230 84 43 5.8 3.2 | -40.6 -41.1 235 93 48 5.2 2.9
32000 -38.6 -37.5 225 65 34 5.9 3.2 | -37.5 -35.5 230 79 41 5.2 2.9
30000 -34.2 -29.6 220 57 29 8.2 4.5 | -33.5 -28.3 230 67 34 7.5 4.1
29000 -31.8 -25.2 220 55 28 8.2 4.5 | -31.3 -24.3 225 61 31 7.5 4.1
28000 -29.4 -20.9 215 53 27 8.2 4.5 | -29.0 -20.2 225 55 28 7.5 4.1
27000 -27.0 -16.6 215 51 26 7.6 4.2 | -26.8 -16.2 225 52 27 7.3 4.0
26000 -24.8 -12.6 215 49 25 7.6 4.2 | -24.6 -12.3 225 50 26 7.3 4.0
25000 -22.5 -8.5 220 47 24 7.6 4.2 | -22.4 -8.3 225 48 25 7.3 4.0
24000 -20.3 -4.5 220 45 23 7.3 4.0 | -20.3 -4.5 225 47 24 7.0 3.9
23000 -18.2 -0.8 220 44 23 7.3 4.0 | -18.2 -0.8 225 46 24 7.0 3.9
22000 -16.0 3.2 225 44 22 7.3 4.0 | -16.1 3.0 225 46 23 7.0 3.9
21000 -13.9 7.0 225 43 22 7.0 3.9 | -14.1 6.6 225 44 23 6.7 3.7
20000 -11.8 10.8 225 44 23 7.1 3.9 | -12.2 10.0 225 42 22 6.7 3.7
19500 -10.8 12.6 225 44 23 7.1 3.9 | -11.2 11.8 225 41 21 6.7 3.7
19000 -9.8 14.4 225 44 23 7.1 3.9 | -10.2 13.6 225 40 21 6.7 3.7
18500 -8.8 16.2 225 44 23 6.3 3.5 | -9.3 15.3 225 39 20 6.8 3.7
18000 -7.9 17.8 225 44 23 6.4 3.5 | -8.3 17.1 225 38 19 6.8 3.7
17500 -7.0 19.4 225 44 23 6.0 3.3 | -6.9 19.6 230 36 19 6.5 3.6
17000 -6.2 20.8 220 44 23 5.9 3.2 | -5.9 21.4 230 36 19 6.5 3.6
16500 -4.9 23.2 220 44 23 5.5 3.0 | -5.0 23.0 230 36 18 6.6 3.6
16000 -4.2 24.4 220 43 22 5.3 2.9 | -4.0 24.8 230 35 18 6.6 3.6
15500 -3.4 25.9 220 43 22 5.3 2.9 | -3.1 26.4 230 34 18 6.5 3.5
15000 -2.6 27.3 220 42 22 5.2 2.9 | -2.2 28.0 230 34 18 6.2 3.4
14500 -1.9 28.6 220 42 22 5.3 2.9 | -1.3 29.7 230 34 17 6.2 3.4
14000 -1.2 29.8 215 40 21 4.1 2.3 | -0.5 31.1 225 33 17 4.4 2.4
13500 -0.6 30.9 215 38 19 4.4 2.4 | 0.1 32.2 225 31 16 4.7 2.6
13000 -0.1 31.8 215 35 18 2.8 1.5 | 0.7 33.3 225 29 15 3.0 1.6
12500 0.3 32.5 210 31 16 2.8 1.5 | 1.1 34.0 220 27 14 3.0 1.6
12000 0.8 33.4 205 27 14 2.4 1.3 | 1.6 34.9 220 26 13 3.8 2.1
11500 1.2 34.2 195 24 12 2.3 1.3 | 2.2 36.0 215 24 12 3.9 2.1
11000 1.7 35.1 190 22 11 4.5 2.5 | 2.8 37.0 210 22 11 3.9 2.1
10500 2.4 36.3 180 21 11 5.7 3.1 | 3.4 38.1 205 19 10 4.3 2.3
10250 2.8 37.0 180 21 11 1.7 0.9 | 3.7 38.7 205 18 9 2.2 1.2
10000 2.8 37.0 180 20 10 3.1 1.7 | 3.9 39.0 205 18 9 3.0 1.7
9750 3.4 38.1 175 20 10 8.1 4.4 | 4.2 39.6 200 17 9 5.6 3.1
9500 3.9 39.0 175 20 10 7.3 4.0 | 4.6 40.3 195 16 8 5.1 2.8
9250 4.4 39.9 170 20 10 5.5 3.0 | 5.0 41.0 190 16 8 4.5 2.5
9000 4.7 40.5 170 19 10 4.3 2.4 | 5.4 41.7 190 16 8 4.9 2.7
8750 5.2 41.4 170 18 9 6.1 3.4 | 5.8 42.4 185 15 8 6.6 3.6
8500 5.6 42.1 170 18 9 6.3 3.4 | 6.3 43.3 180 15 8 6.6 3.6
8250 6.1 43.0 165 17 9 5.1 2.8 | 6.8 44.2 175 14 7 5.3 2.9
8000 6.4 43.5 165 17 9 4.8 2.6 | 7.1 44.8 170 15 8 4.5 2.5
7750 6.9 44.4 160 16 8 7.7 4.2 | 7.5 45.5 170 14 7 6.1 3.3
7500 7.5 45.5 160 15 8 8.1 4.4 | 8.0 46.4 160 13 7 6.0 3.3
7250 8.0 46.4 155 14 7 6.0 3.3 | 8.4 47.1 160 13 7 5.0 2.7
7000 8.4 47.1 155 14 7 5.1 2.8 | 8.7 47.7 155 14 7 4.3 2.3
6750 8.9 48.0 155 13 7 9.8 5.4 | 9.1 48.4 150 13 7 8.9 4.9
6500 9.8 49.6 150 11 6 11.3 6.2 | 9.9 49.8 140 11 6 10.7 5.9
6250 10.5 50.9 150 11 6 8.9 4.9 | 10.6 51.1 140 11 6 8.2 4.5
6000 11.1 52.0 150 11 5 8.9 4.9 | 11.2 52.2 140 10 5 8.8 4.8
5750 11.9 53.4 150 10 5 11.8 6.5 | 11.9 53.4 140 10 5 9.2 5.1
5500 13.0 55.4 145 8 4 20.1 11.0 | 12.6 54.7 130 7 4 9.9 5.4
________________________________________________________________________________
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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