Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
466
UXUS97 KBOU 300135
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1834 MST Saturday, November 29, 2025
This forecast is for Sunday, November 30, 2025:
If the trigger temperature of 42.1 F/5.6 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 7315 ft MSL (2037 ft AGL)
Forecast maximum temperature................... 29.0 F/-2.1 C
Time of trigger temperature.................... None
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................. 6196 ft MSL (917 ft AGL)
Thermal soaring outlook for Monday 12/01....... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... Trending the same
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Weak NVA
Potential height of wave....................... 38699 ft MSL (33421 ft AGL)
Wave soaring outlook for Monday 12/01.......... Fair
Remarks...
Sunrise/Sunset.................... 07:01:03 / 16:35:36 MST
Total possible sunshine........... 9 hr 34 min 33 sec (574 min 33 sec)
Altitude of sun at 11:48:20 MST... 28.40 degrees
Upper air data from numerical model forecast valid on 11/30/2025 at 0500 MST
Freezing level.................. Entire airmass below 32 F / 0 C
Convective condensation level... 17246 ft MSL (11968 ft AGL)
Lifted condensation level....... 10351 ft MSL (5072 ft AGL)
Lifted index.................... +15.4
K index......................... -2.4
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 -57.7 -71.9 280 50 26 0.4 0.2 M M M M M
45000 -57.1 -70.8 275 63 33 0.4 0.2 M M M M M
40000 -58.8 -73.8 270 73 37 -1.3 -0.7 M M M M M
38000 -59.3 -74.7 270 75 39 1.0 0.5 M M M M M
36000 -58.8 -73.8 270 72 37 0.9 0.5 M M M M M
34000 -58.2 -72.8 270 70 36 0.4 0.2 M M M M M
32000 -54.5 -66.1 270 64 33 6.9 3.8 M M M M M
30000 -50.4 -58.7 275 58 30 7.3 4.0 M M M M M
29000 -47.9 -54.2 270 56 29 8.5 4.7 25.5 78.0 20.5 M M
28000 -44.7 -48.5 270 55 28 8.5 4.7 24.9 76.8 20.3 M M
27000 -42.2 -44.0 270 54 28 8.6 4.7 24.5 76.1 20.3 M M
26000 -39.9 -39.8 265 53 27 7.2 3.9 23.6 74.5 19.8 M M
25000 -37.8 -36.0 265 51 26 7.2 3.9 22.6 72.7 19.3 M M
24000 -35.6 -32.1 265 50 26 7.1 3.9 21.7 71.1 18.8 M M
23000 -33.3 -27.9 265 48 25 8.2 4.5 21.0 69.8 18.4 M M
22000 -30.9 -23.6 265 46 24 8.2 4.5 20.4 68.8 18.2 M M
21000 -28.4 -19.1 260 44 23 8.1 4.5 20.0 67.9 18.0 M M
20000 -26.2 -15.2 260 41 21 7.2 3.9 19.0 66.3 17.4 M M
19500 -25.2 -13.4 260 39 20 7.2 3.9 18.6 65.4 17.1 M M
19000 -24.1 -11.4 260 37 19 7.2 3.9 18.1 64.6 16.8 M M
18500 -23.0 -9.4 260 35 18 7.2 3.9 17.7 63.9 16.5 M M
18000 -21.9 -7.4 260 33 17 7.9 4.3 17.4 63.3 16.3 M M
17500 -20.7 -5.3 265 32 17 7.8 4.3 17.0 62.6 16.1 M M
17000 -19.5 -3.1 265 31 16 8.3 4.6 16.7 62.1 16.0 M M
16500 -18.2 -0.8 265 30 15 8.5 4.7 16.5 61.7 15.9 M M
16000 -17.0 1.4 265 28 15 8.4 4.6 16.3 61.4 15.8 M M
15500 -15.7 3.7 265 27 14 8.1 4.4 16.0 60.8 15.6 M M
15000 -14.5 5.9 265 25 13 8.1 4.4 15.8 60.4 15.5 M M
14500 -13.4 7.9 265 23 12 7.3 4.0 15.4 59.7 15.2 M M
14000 -11.7 10.9 260 20 10 6.9 3.8 14.8 58.7 14.8 M M
13500 -10.8 12.6 260 18 9 6.4 3.5 14.3 57.7 14.4 M M
13000 -9.8 14.4 255 16 8 6.2 3.4 13.7 56.7 14.0 M M
12500 -9.0 15.8 250 13 7 5.7 3.1 13.1 55.5 13.5 M M
12000 -8.1 17.4 245 11 6 5.2 2.9 12.4 54.4 12.9 M M
11500 -7.5 18.5 240 9 5 4.0 2.2 11.6 52.8 12.2 M M
11000 -6.9 19.6 230 7 4 3.1 1.7 10.7 51.2 11.4 M M
10500 -6.6 20.1 220 6 3 1.3 0.7 9.4 48.9 10.2 M M
10250 -6.5 20.3 210 5 3 1.6 0.9 8.7 47.7 9.6 M M
10000 -6.4 20.5 200 5 2 0.5 0.3 8.1 46.5 9.0 M M
9750 -6.5 20.3 200 5 2 -0.7 -0.4 7.3 45.1 8.3 M M
9500 -6.5 20.3 190 4 2 -0.5 -0.3 6.4 43.6 7.5 M M
9250 -6.6 20.1 180 4 2 -0.7 -0.4 5.6 42.1 6.8 M M
9000 -6.6 20.1 170 4 2 -0.6 -0.3 4.8 40.7 6.0 M M
8750 -6.7 19.9 160 4 2 -1.8 -1.0 4.0 39.2 5.2 M M
8500 -6.9 19.6 155 4 2 -3.2 -1.8 3.0 37.4 4.3 M M
8250 -7.1 19.2 145 4 2 -2.4 -1.3 2.0 35.7 3.3 M M
8000 -7.3 18.9 140 3 2 -1.1 -0.6 1.2 34.1 2.5 M M
7750 -7.4 18.7 135 3 2 -2.3 -1.3 0.3 32.5 1.6 M M
7500 -7.6 18.3 125 3 1 -3.5 -1.9 -0.7 30.7 0.7 M M
7250 -7.8 18.0 115 2 1 -1.1 -0.6 -1.7 29.0 -0.3 256 1.3
7000 -7.8 18.0 110 1 1 -0.6 -0.3 -2.4 27.6 -1.0 249 1.3
6750 -7.9 17.8 000 0 0 1.7 0.9 -3.2 26.3 -1.8 242 1.2
6500 -7.6 18.3 330 1 0 3.2 1.7 -3.7 25.4 -2.2 227 1.2
6250 -7.5 18.5 330 1 1 1.6 0.9 -4.3 24.3 -2.8 215 1.1
6000 -7.3 18.9 330 2 1 1.8 1.0 -4.9 23.3 -3.4 204 1.0
5750 -7.2 19.0 330 3 1 2.8 1.6 -5.4 22.2 -4.0 192 1.0
5500 -6.8 19.8 340 3 1 6.6 3.6 -5.8 21.5 -4.4 174 0.9
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/30/2025 at 0800 MST | 11/30/2025 at 1100 MST
|
CAPE... 0.0 LI... +5.1 | CAPE... 0.0 LI... +5.5
CINH... 0.0 K Index... -4.0 | CINH... 0.0 K Index... +7.8
|
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 -57.5 -71.5 280 48 25 -0.0 -0.0 | -57.4 -71.3 280 45 23 -0.2 -0.1
45000 -57.5 -71.5 275 60 31 -0.0 -0.0 | -57.7 -71.9 270 58 30 -0.2 -0.1
40000 -58.9 -74.0 270 70 36 -1.0 -0.6 | -58.3 -72.9 265 68 35 -0.4 -0.2
38000 -59.3 -74.7 270 72 37 0.7 0.4 | -58.5 -73.3 265 72 37 0.1 0.1
36000 -58.9 -74.0 270 72 37 0.6 0.3 | -58.4 -73.1 260 75 39 0.1 0.0
34000 -58.6 -73.5 270 71 37 -0.3 -0.2 | -58.4 -73.1 260 79 41 -0.7 -0.4
32000 -54.6 -66.3 270 68 35 7.6 4.2 | -54.3 -65.7 260 76 39 7.9 4.4
30000 -50.0 -58.0 270 64 33 7.8 4.3 | -49.0 -56.2 260 72 37 8.3 4.5
29000 -46.9 -52.4 270 60 31 8.4 4.6 | -46.5 -51.7 260 67 34 8.2 4.5
28000 -44.4 -47.9 265 57 29 8.4 4.6 | -44.1 -47.4 260 62 32 8.2 4.5
27000 -41.9 -43.4 265 54 28 8.4 4.6 | -41.6 -42.9 255 57 29 8.2 4.5
26000 -39.4 -38.9 260 52 27 8.5 4.6 | -39.1 -38.4 255 54 28 8.4 4.6
25000 -36.8 -34.2 260 52 27 8.5 4.6 | -36.6 -33.9 255 53 27 8.4 4.6
24000 -34.3 -29.7 260 51 26 8.5 4.7 | -34.1 -29.4 255 52 27 8.4 4.6
23000 -32.3 -26.1 255 48 25 5.8 3.2 | -31.7 -25.1 260 50 26 7.5 4.1
22000 -30.5 -22.9 255 44 22 5.8 3.2 | -29.5 -21.1 260 48 25 7.5 4.1
21000 -28.8 -19.8 250 40 20 5.7 3.1 | -27.3 -17.1 260 47 24 7.6 4.2
20000 -26.7 -16.1 245 38 19 7.4 4.1 | -25.3 -13.5 260 45 23 6.6 3.6
19500 -25.6 -14.1 245 37 19 7.4 4.1 | -24.3 -11.7 260 44 23 6.6 3.6
19000 -24.5 -12.1 245 36 19 7.4 4.1 | -23.3 -9.9 260 43 22 6.6 3.6
18500 -23.4 -10.1 245 36 18 7.4 4.0 | -22.3 -8.1 260 42 22 6.7 3.7
18000 -22.2 -8.0 245 35 18 7.7 4.2 | -21.4 -6.5 260 41 21 5.6 3.1
17500 -21.1 -6.0 245 34 17 7.7 4.2 | -20.6 -5.1 255 39 20 5.5 3.0
17000 -19.9 -3.8 245 32 17 7.8 4.3 | -19.8 -3.6 255 37 19 5.6 3.1
16500 -18.8 -1.8 250 31 16 7.8 4.3 | -18.5 -1.3 255 34 18 5.7 3.1
16000 -17.6 0.3 250 30 15 7.8 4.3 | -17.7 0.1 255 32 17 6.3 3.4
15500 -15.9 3.4 250 28 14 7.9 4.3 | -16.7 1.9 255 30 15 6.6 3.6
15000 -14.7 5.5 250 26 14 7.7 4.2 | -15.7 3.7 255 27 14 6.8 3.8
14500 -13.6 7.5 245 25 13 7.6 4.1 | -14.6 5.7 255 26 13 7.4 4.0
14000 -12.5 9.5 245 23 12 7.4 4.1 | -13.5 7.7 250 24 13 7.3 4.0
13500 -11.4 11.5 240 21 11 7.0 3.9 | -12.5 9.5 250 23 12 7.2 3.9
13000 -10.4 13.3 235 19 10 6.7 3.7 | -11.4 11.5 250 21 11 7.2 3.9
12500 -9.5 14.9 230 17 9 5.5 3.0 | -10.4 13.3 250 20 10 6.4 3.5
12000 -8.6 16.5 220 15 8 5.2 2.9 | -9.4 15.1 245 18 9 6.5 3.6
11500 -8.0 17.6 215 14 7 3.5 1.9 | -8.5 16.7 245 16 8 5.2 2.8
11000 -7.5 18.5 205 13 7 3.3 1.8 | -7.7 18.1 235 14 7 5.2 2.8
10500 -7.1 19.2 195 12 6 2.1 1.2 | -7.3 18.9 230 12 6 1.3 0.7
10250 -7.0 19.4 190 11 6 2.6 1.4 | -7.1 19.2 225 11 6 1.7 0.9
10000 -6.8 19.8 190 11 6 1.2 0.6 | -7.0 19.4 220 10 5 1.7 1.0
9750 -6.8 19.8 185 11 6 -0.5 -0.3 | -7.0 19.4 220 10 5 -1.2 -0.7
9500 -6.8 19.8 185 10 5 -0.3 -0.2 | -7.2 19.0 210 9 5 -3.5 -1.9
9250 -6.9 19.6 180 10 5 -0.5 -0.3 | -7.4 18.7 205 9 4 -3.2 -1.8
9000 -6.9 19.6 175 9 5 0.1 0.0 | -7.7 18.1 195 8 4 -2.1 -1.2
8750 -7.0 19.4 175 9 5 -1.9 -1.1 | -7.8 18.0 190 8 4 -4.0 -2.2
8500 -7.2 19.0 170 8 4 -4.4 -2.4 | -8.3 17.1 180 8 4 -7.1 -3.9
8250 -7.6 18.3 170 7 4 -4.3 -2.3 | -8.8 16.2 175 7 4 -6.2 -3.4
8000 -7.9 17.8 170 5 3 -4.3 -2.4 | -9.2 15.4 165 7 3 -5.0 -2.8
7750 -8.2 17.2 170 4 2 -4.6 -2.5 | -9.5 14.9 160 7 3 -1.4 -0.7
7500 -8.6 16.5 180 2 1 -5.3 -2.9 | -9.4 15.1 150 6 3 1.7 0.9
7250 -8.9 16.0 200 2 1 -3.0 -1.7 | -9.3 15.3 145 6 3 2.2 1.2
7000 -9.1 15.6 230 1 0 -2.0 -1.1 | -9.1 15.6 140 4 2 0.9 0.5
6750 -9.2 15.4 295 1 0 -0.3 -0.2 | -9.0 15.8 125 3 2 5.3 2.9
6500 -9.1 15.6 000 0 0 1.4 0.7 | -8.3 17.1 120 3 1 10.1 5.6
6250 -9.1 15.6 335 1 1 0.6 0.3 | -7.6 18.3 105 2 1 8.8 4.8
6000 -9.0 15.8 340 2 1 -0.5 -0.2 | -7.0 19.4 075 2 1 7.3 4.0
5750 -9.0 15.8 345 3 2 3.9 2.2 | -6.4 20.5 040 2 1 11.5 6.3
5500 -8.3 17.1 345 3 1 13.9 7.6 | -5.2 22.6 060 1 1 20.9 11.5
11/30/2025 at 1400 MST | 11/30/2025 at 1700 MST
|
CAPE... 0.0 LI... +4.8 | CAPE... 0.0 LI... +2.5
CINH... -0.2 K Index... +9.1 | CINH... 0.0 K Index... +13.5
|
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 -57.1 -70.8 275 44 23 -0.1 -0.0 | -56.9 -70.4 280 44 23 -0.0 -0.0
45000 -57.2 -71.0 270 56 29 -0.1 -0.0 | -57.0 -70.6 270 48 25 -0.0 -0.0
40000 -57.5 -71.5 265 70 36 -0.2 -0.1 | -55.6 -68.1 265 63 33 1.0 0.6
38000 -57.6 -71.7 260 76 39 0.4 0.2 | -55.1 -67.2 265 71 36 0.2 0.1
36000 -57.4 -71.3 260 80 41 0.4 0.2 | -55.0 -67.0 260 80 41 0.2 0.1
34000 -57.1 -70.8 255 84 43 -0.2 -0.1 | -54.9 -66.8 260 90 47 0.0 0.0
32000 -53.4 -64.1 255 84 43 7.4 4.1 | -52.2 -62.0 255 92 47 5.5 3.0
30000 -49.0 -56.2 255 82 42 7.5 4.1 | -48.9 -56.0 255 92 47 5.4 3.0
29000 -46.2 -51.2 255 77 40 7.5 4.1 | -46.7 -52.1 255 88 45 6.3 3.5
28000 -43.9 -47.0 255 72 37 7.5 4.1 | -44.8 -48.6 255 83 43 6.3 3.5
27000 -41.6 -42.9 255 67 35 7.5 4.1 | -42.9 -45.2 255 78 40 6.3 3.5
26000 -39.3 -38.7 255 63 32 8.0 4.4 | -40.8 -41.4 255 71 37 7.6 4.2
25000 -36.9 -34.4 255 59 30 8.1 4.4 | -38.5 -37.3 250 62 32 7.7 4.2
24000 -34.5 -30.1 255 54 28 8.0 4.4 | -36.2 -33.2 250 53 27 7.7 4.2
23000 -32.2 -26.0 255 51 26 7.4 4.0 | -33.9 -29.0 250 47 24 7.8 4.3
22000 -30.0 -22.0 255 48 25 7.4 4.0 | -31.6 -24.9 255 47 24 7.8 4.3
21000 -27.8 -18.0 255 46 24 7.4 4.1 | -29.3 -20.7 260 46 24 7.9 4.3
20000 -25.7 -14.3 260 45 23 7.0 3.8 | -27.0 -16.6 260 45 23 7.6 4.2
19500 -24.7 -12.5 260 45 23 7.0 3.8 | -25.9 -14.6 260 44 23 7.6 4.2
19000 -23.6 -10.5 260 46 23 7.0 3.8 | -24.7 -12.5 260 44 22 7.6 4.2
18500 -22.6 -8.7 260 46 24 7.0 3.9 | -23.6 -10.5 260 43 22 7.6 4.2
18000 -21.6 -6.9 265 45 23 6.5 3.6 | -22.5 -8.5 260 42 22 7.4 4.0
17500 -20.6 -5.1 260 44 23 6.4 3.5 | -21.4 -6.5 260 40 21 7.3 4.0
17000 -19.7 -3.5 260 43 22 6.6 3.6 | -20.3 -4.5 260 39 20 7.5 4.1
16500 -18.7 -1.7 260 41 21 6.9 3.8 | -19.1 -2.4 260 38 20 8.3 4.5
16000 -17.7 0.1 255 37 19 6.8 3.7 | -17.9 -0.2 260 37 19 8.3 4.6
15500 -16.6 2.1 255 35 18 7.4 4.0 | -16.2 2.8 260 34 18 7.6 4.2
15000 -15.6 3.9 255 33 17 7.4 4.0 | -15.1 4.8 255 32 16 7.6 4.2
14500 -14.0 6.8 255 29 15 6.7 3.7 | -14.0 6.8 255 29 15 7.6 4.2
14000 -13.0 8.6 255 27 14 6.7 3.7 | -12.9 8.8 250 27 14 7.7 4.2
13500 -12.1 10.2 250 25 13 5.8 3.2 | -11.9 10.6 245 25 13 6.2 3.4
13000 -11.2 11.8 250 23 12 6.0 3.3 | -10.9 12.4 240 23 12 6.6 3.6
12500 -10.5 13.1 245 20 10 4.5 2.4 | -10.1 13.8 235 22 11 4.6 2.5
12000 -9.8 14.4 240 17 9 4.7 2.6 | -9.4 15.1 235 20 10 5.1 2.8
11500 -9.1 15.6 235 16 8 3.9 2.2 | -8.9 16.0 230 18 9 1.7 1.0
11000 -8.5 16.7 235 14 7 4.2 2.3 | -8.6 16.5 225 16 8 2.6 1.4
10500 -8.4 16.9 230 12 6 -1.8 -1.0 | -8.7 16.3 220 14 7 -4.1 -2.3
10250 -8.4 16.9 230 11 6 -0.9 -0.5 | -8.9 16.0 215 13 7 -2.2 -1.2
10000 -8.5 16.7 225 9 5 -1.8 -1.0 | -9.1 15.6 210 12 6 -6.2 -3.4
9750 -8.7 16.3 215 9 5 -4.3 -2.4 | -9.7 14.5 200 11 5 -5.3 -2.9
9500 -9.1 15.6 205 8 4 -5.2 -2.9 | -9.8 14.4 195 10 5 -0.9 -0.5
9250 -9.5 14.9 195 7 4 -5.6 -3.1 | -9.9 14.2 190 11 5 -2.6 -1.4
9000 -9.9 14.2 180 6 3 -3.2 -1.8 | -10.1 13.8 180 11 6 -0.1 -0.0
8750 -9.9 14.2 170 6 3 1.6 0.9 | -9.9 14.2 175 11 6 4.4 2.4
8500 -9.7 14.5 165 6 3 2.7 1.5 | -9.5 14.9 170 12 6 5.5 3.0
8250 -9.5 14.9 155 7 3 2.6 1.4 | -9.1 15.6 165 12 6 5.4 3.0
8000 -9.3 15.3 145 7 3 2.9 1.6 | -8.7 16.3 160 13 7 4.4 2.4
7750 -9.0 15.8 140 6 3 5.8 3.2 | -8.3 17.1 160 11 6 5.8 3.2
7500 -8.4 16.9 140 5 3 8.8 4.8 | -7.8 18.0 160 10 5 8.5 4.7
7250 -7.8 18.0 135 4 2 8.0 4.4 | -7.1 19.2 155 8 4 7.6 4.2
7000 -7.3 18.9 130 4 2 6.3 3.4 | -6.6 20.1 155 7 4 6.1 3.3
6750 -6.7 19.9 130 3 2 9.1 5.0 | -6.1 21.0 150 6 3 7.9 4.3
6500 -5.9 21.4 130 3 1 11.6 6.4 | -5.4 22.3 150 4 2 9.9 5.4
6250 -5.1 22.8 130 2 1 10.1 5.5 | -4.8 23.4 140 3 2 8.4 4.6
6000 -4.4 24.1 130 2 1 9.3 5.1 | -4.2 24.4 135 2 1 7.5 4.1
5750 -3.7 25.3 125 2 1 10.9 6.0 | -3.6 25.5 105 1 0 8.4 4.6
5500 -2.7 27.1 120 1 1 15.3 8.4 | -2.9 26.8 020 1 1 8.2 4.5
________________________________________________________________________________
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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