Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
567
UXUS97 KBOU 011225
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0523 MST Monday, December 1, 2025
This forecast is for Monday, December 1, 2025:
If the trigger temperature of 39.4 F/4.1 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 224 ft/min (1.1 m/s)
Maximum height of thermals.................. 8521 ft MSL (3219 ft AGL)
Forecast maximum temperature................... 37.0 F/3.2 C
Time of trigger temperature.................... None
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................. 7422 ft MSL (2121 ft AGL)
Thermal soaring outlook for Tuesday 12/02...... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... Becoming fair to good by 1500 MD
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Weak NVA
Potential height of wave....................... 14415 ft MSL (9113 ft AGL)
Wave soaring outlook for Tuesday 12/02......... Good
Remarks... A little warmer with weak thermals today and Tuesday. Mountain wave
develops late this afternoon and evening-better Tuesday.
Sunrise/Sunset.................... 07:02:03 / 16:35:22 MST
Total possible sunshine........... 9 hr 33 min 19 sec (573 min 19 sec)
Altitude of sun at 11:48:43 MST... 28.25 degrees
Upper air data from numerical model forecast valid on 12/01/2025 at 0500 MST
Freezing level.................. Entire airmass below 32 F / 0 C
Convective condensation level... 14368 ft MSL (9066 ft AGL)
Lifted condensation level....... 11556 ft MSL (6255 ft AGL)
Lifted index.................... +8.3
K index......................... +2.7
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 -56.5 -69.7 305 32 16 0.8 0.4 M M M M M
45000 -55.4 -67.7 295 35 18 0.8 0.4 M M M M M
40000 -52.7 -62.9 305 29 15 1.9 1.1 M M M M M
38000 -51.5 -60.7 310 27 14 1.3 0.7 M M M M M
36000 -50.7 -59.3 320 27 14 1.4 0.8 M M M M M
34000 -49.9 -57.8 325 28 14 1.4 0.8 M M M M M
32000 -48.7 -55.7 345 28 14 1.8 1.0 M M M M M
30000 -47.7 -53.9 360 30 15 1.5 0.8 M M M M M
29000 -46.4 -51.5 005 30 16 5.1 2.8 27.7 81.8 18.8 M M
28000 -44.9 -48.8 005 31 16 5.1 2.8 25.8 78.4 17.5 M M
27000 -43.4 -46.1 005 31 16 5.1 2.8 24.0 75.2 16.4 M M
26000 -41.9 -43.4 005 30 15 4.7 2.6 22.2 72.0 15.2 M M
25000 -40.5 -40.9 360 25 13 4.7 2.6 20.2 68.4 13.8 M M
24000 -39.1 -38.4 350 21 11 4.7 2.6 18.4 65.1 12.5 M M
23000 -37.5 -35.5 340 18 9 7.4 4.0 16.8 62.2 11.4 M M
22000 -35.3 -31.5 325 19 10 7.1 3.9 15.7 60.3 10.7 M M
21000 -33.2 -27.8 315 21 11 7.1 3.9 14.8 58.7 10.0 M M
20000 -30.9 -23.6 315 22 11 8.2 4.5 14.1 57.3 9.5 M M
19500 -29.7 -21.5 315 22 11 8.2 4.5 13.8 56.8 9.3 M M
19000 -28.5 -19.3 315 22 11 8.2 4.5 13.5 56.3 9.1 M M
18500 -27.2 -17.0 320 22 11 8.2 4.5 13.3 55.9 9.0 M M
18000 -26.0 -14.8 320 22 11 8.6 4.7 13.0 55.5 8.8 M M
17500 -24.7 -12.5 320 22 12 9.0 4.9 12.9 55.2 8.7 M M
17000 -22.7 -8.9 325 23 12 8.3 4.6 12.7 54.8 8.6 M M
16500 -21.5 -6.7 325 24 12 8.0 4.4 12.4 54.3 8.4 M M
16000 -20.3 -4.5 325 24 12 7.7 4.2 12.1 53.8 8.2 M M
15500 -19.2 -2.6 325 25 13 6.9 3.8 11.6 52.9 7.8 M M
15000 -18.2 -0.8 330 25 13 6.9 3.8 11.1 52.1 7.4 M M
14500 -17.3 0.9 330 26 13 6.3 3.5 10.6 51.1 6.9 M M
14000 -16.3 2.7 330 27 14 6.4 3.5 10.0 50.1 6.5 M M
13500 -15.4 4.3 330 28 14 6.2 3.4 9.5 49.0 6.0 M M
13000 -14.5 5.9 330 28 15 6.3 3.4 8.9 48.0 5.5 M M
12500 -13.5 7.7 330 29 15 6.1 3.3 8.3 47.0 4.9 M M
12000 -12.6 9.3 330 30 16 6.1 3.3 7.7 45.9 4.4 M M
11500 -11.7 10.9 330 31 16 6.6 3.6 7.2 44.9 3.9 M M
11000 -10.7 12.7 335 31 16 6.6 3.6 6.7 44.0 3.4 M M
10500 -9.8 14.4 335 31 16 5.5 3.0 6.1 42.9 2.9 M M
10250 -9.4 15.1 335 31 16 6.2 3.4 5.7 42.3 2.6 M M
10000 -9.0 15.8 335 31 16 4.1 2.2 5.4 41.8 2.3 M M
9750 -8.7 16.3 335 31 16 4.1 2.3 4.9 40.8 1.8 M M
9500 -8.3 17.1 335 30 15 6.2 3.4 4.6 40.3 1.5 M M
9250 -7.9 17.8 340 29 15 5.8 3.2 4.3 39.7 1.2 M M
9000 -7.5 18.5 340 28 14 5.2 2.9 4.0 39.2 0.9 M M
8750 -7.2 19.0 340 27 14 3.4 1.9 3.6 38.4 0.5 M M
8500 -6.9 19.6 335 25 13 2.9 1.6 3.0 37.4 -0.0 223 1.1
8250 -6.7 19.9 335 23 12 2.9 1.6 2.5 36.5 -0.6 210 1.1
8000 -6.6 20.1 335 21 11 0.4 0.2 1.9 35.4 -1.1 198 1.0
7750 -6.6 20.1 335 18 9 -1.0 -0.5 1.1 33.9 -1.9 192 1.0
7500 -6.7 19.9 330 16 8 0.2 0.1 0.3 32.6 -2.7 186 0.9
7250 -6.7 19.9 330 14 7 -1.0 -0.5 -0.4 31.2 -3.5 179 0.9
7000 -6.8 19.8 325 12 6 -2.3 -1.2 -1.3 29.6 -4.4 176 0.9
6750 -7.0 19.4 315 9 5 -2.4 -1.3 -2.3 27.9 -5.3 174 0.9
6500 -7.2 19.0 305 8 4 -2.5 -1.4 -3.2 26.3 -6.2 172 0.9
6250 -7.4 18.7 285 6 3 -2.1 -1.1 -4.1 24.6 -7.1 170 0.9
6000 -7.5 18.5 260 5 3 -2.1 -1.2 -5.0 23.0 -8.0 167 0.9
5750 -7.7 18.1 235 6 3 -1.4 -0.8 -5.9 21.4 -8.9 165 0.8
5500 -7.7 18.1 215 6 3 2.4 1.3 -6.6 20.1 -9.7 157 0.8
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
12/01/2025 at 0800 MST | 12/01/2025 at 1100 MST
|
CAPE... 0.0 LI... +5.5 | CAPE... 0.0 LI... +6.8
CINH... 0.0 K Index... -16.4 | CINH... 0.0 K Index... -8.4
|
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 -57.6 -71.7 305 29 15 0.8 0.4 | -58.8 -73.8 315 29 15 0.8 0.4
45000 -56.4 -69.5 305 31 16 0.8 0.5 | -57.6 -71.7 325 33 17 0.8 0.4
40000 -53.4 -64.1 325 31 16 2.1 1.2 | -55.8 -68.4 350 42 22 1.3 0.7
38000 -52.3 -62.1 330 32 16 0.5 0.3 | -54.8 -66.6 355 47 24 2.8 1.5
36000 -51.9 -61.4 345 35 18 0.6 0.3 | -53.0 -63.4 360 52 27 2.7 1.5
34000 -51.6 -60.9 360 39 20 0.6 0.4 | -51.3 -60.3 005 57 29 3.3 1.8
32000 -49.7 -57.5 005 42 22 3.3 1.8 | -48.4 -55.1 010 57 29 5.0 2.7
30000 -47.7 -53.9 005 44 22 3.5 1.9 | -45.4 -49.7 015 57 29 5.1 2.8
29000 -46.1 -51.0 005 43 22 5.9 3.3 | -43.8 -46.8 010 53 27 5.3 2.9
28000 -44.3 -47.7 005 43 22 5.9 3.3 | -42.2 -44.0 005 49 25 5.3 2.9
27000 -42.5 -44.5 005 43 22 5.9 3.3 | -40.7 -41.3 005 45 23 5.3 2.9
26000 -40.6 -41.1 005 42 22 7.0 3.9 | -38.9 -38.0 360 41 21 6.7 3.7
25000 -38.5 -37.3 005 41 21 7.0 3.8 | -36.9 -34.4 355 37 19 6.7 3.7
24000 -36.4 -33.5 005 40 21 7.0 3.8 | -34.9 -30.8 350 33 17 6.7 3.7
23000 -34.5 -30.1 005 37 19 4.8 2.6 | -32.9 -27.2 345 30 16 6.4 3.5
22000 -33.1 -27.6 360 30 15 4.9 2.7 | -31.0 -23.8 340 28 15 6.4 3.5
21000 -31.6 -24.9 345 24 12 4.9 2.7 | -29.1 -20.4 340 27 14 6.5 3.6
20000 -29.8 -21.6 340 22 11 6.7 3.7 | -27.5 -17.5 330 27 14 4.4 2.4
19500 -28.8 -19.8 340 22 11 6.7 3.7 | -26.9 -16.4 330 29 15 4.4 2.4
19000 -27.8 -18.0 335 22 11 6.7 3.7 | -26.2 -15.2 325 30 15 4.4 2.4
18500 -26.7 -16.1 335 21 11 6.7 3.7 | -25.2 -13.4 320 32 16 4.4 2.4
18000 -25.7 -14.3 335 21 11 7.8 4.3 | -24.5 -12.1 320 33 17 5.5 3.0
17500 -24.5 -12.1 335 22 11 8.3 4.5 | -23.6 -10.5 315 34 17 5.4 2.9
17000 -23.2 -9.8 335 23 12 8.2 4.5 | -22.8 -9.0 315 34 18 6.8 3.7
16500 -22.0 -7.6 335 23 12 8.0 4.4 | -21.7 -7.1 315 34 17 7.1 3.9
16000 -20.8 -5.4 340 23 12 8.0 4.4 | -20.7 -5.3 315 33 17 7.0 3.9
15500 -19.1 -2.4 340 22 11 7.5 4.1 | -19.6 -3.3 320 33 17 7.0 3.8
15000 -18.0 -0.4 340 21 11 7.1 3.9 | -18.6 -1.5 320 32 17 6.8 3.7
14500 -17.0 1.4 340 22 11 6.2 3.4 | -17.6 0.3 320 31 16 5.9 3.2
14000 -16.1 3.0 340 23 12 6.1 3.3 | -16.8 1.8 320 31 16 5.9 3.2
13500 -15.2 4.6 340 24 12 5.2 2.8 | -15.9 3.4 320 30 15 5.4 3.0
13000 -14.5 5.9 345 24 12 5.3 2.9 | -15.1 4.8 320 28 15 5.5 3.0
12500 -13.7 7.3 345 25 13 5.4 3.0 | -14.3 6.3 320 28 14 5.6 3.1
12000 -12.9 8.8 345 25 13 5.5 3.0 | -13.4 7.9 325 27 14 5.6 3.1
11500 -12.0 10.4 345 25 13 5.9 3.2 | -12.6 9.3 330 26 13 5.9 3.2
11000 -11.2 11.8 345 25 13 6.0 3.3 | -11.7 10.9 330 26 13 6.0 3.3
10500 -10.2 13.6 350 27 14 6.7 3.7 | -10.8 12.6 335 25 13 6.5 3.5
10250 -9.7 14.5 350 27 14 7.8 4.3 | -10.3 13.5 335 24 13 7.2 4.7
10000 -9.2 15.4 350 28 14 3.4 1.9 | -9.8 14.4 335 24 12 4.2 2.3
9750 -9.0 15.8 350 28 14 4.6 2.5 | -9.5 14.9 340 24 12 5.1 2.8
9500 -8.4 16.9 350 28 15 9.7 5.3 | -8.9 16.0 340 23 12 8.6 4.7
9250 -7.7 18.1 350 29 15 8.8 4.8 | -8.4 16.9 345 23 12 7.8 4.3
9000 -7.1 19.2 355 29 15 6.5 3.5 | -7.8 18.0 345 22 11 6.8 3.7
8750 -6.7 19.9 350 27 14 5.3 2.9 | -7.3 18.9 345 21 11 6.6 3.6
8500 -6.3 20.7 350 25 13 7.3 4.0 | -6.8 19.8 350 20 10 7.6 4.2
8250 -5.8 21.6 350 22 11 6.0 3.3 | -6.2 20.8 350 19 10 7.3 4.0
8000 -5.4 22.3 345 19 10 3.9 2.1 | -5.7 21.7 350 17 9 7.6 4.2
7750 -5.1 22.8 340 16 8 4.4 2.4 | -5.1 22.8 350 15 8 7.1 3.9
7500 -4.7 23.5 335 13 7 5.9 3.3 | -4.6 23.7 345 13 7 6.4 3.5
7250 -4.3 24.3 330 11 6 5.9 3.2 | -4.1 24.6 340 11 6 7.3 4.0
7000 -3.9 25.0 325 11 6 5.8 3.2 | -3.6 25.5 340 10 5 8.3 4.5
6750 -3.4 25.9 315 11 6 6.4 3.5 | -3.0 26.6 335 8 4 6.6 3.6
6500 -3.1 26.4 310 12 6 1.1 0.6 | -2.6 27.3 330 7 4 5.4 3.0
6250 -3.3 26.1 305 10 5 -4.9 -2.7 | -2.1 28.2 330 6 3 6.4 3.5
6000 -3.7 25.3 290 8 4 -4.6 -2.5 | -1.7 28.9 340 4 2 5.6 3.1
5750 -4.0 24.8 270 6 3 -5.3 -2.9 | -1.2 29.8 350 3 1 8.4 4.6
5500 -4.6 23.7 235 5 3 -11.3 -6.2 | -0.3 31.5 355 2 1 17.5 9.6
12/01/2025 at 1400 MST | 12/01/2025 at 1700 MST
|
CAPE... 0.0 LI... +8.4 | CAPE... 0.0 LI... +11.0
CINH... 0.0 K Index... -7.3 | CINH... 0.0 K Index... -6.3
|
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 -58.9 -74.0 320 30 15 0.1 0.1 | -59.6 -75.3 310 30 16 -0.1 -0.0
45000 -58.7 -73.7 340 43 22 0.2 0.1 | -59.7 -75.5 325 31 16 -0.1 -0.0
40000 -56.6 -69.9 360 58 30 1.4 0.8 | -57.0 -70.6 355 55 28 1.9 1.0
38000 -55.4 -67.7 360 63 32 3.3 1.8 | -55.5 -67.9 355 66 34 3.3 1.8
36000 -53.4 -64.1 360 64 33 3.3 1.8 | -53.6 -64.5 355 75 39 3.3 1.8
34000 -51.5 -60.7 360 66 34 3.9 2.1 | -51.6 -60.9 355 84 43 4.4 2.4
32000 -48.3 -54.9 355 58 30 5.3 2.9 | -48.4 -55.1 360 79 41 5.4 3.0
30000 -45.2 -49.4 355 51 26 5.8 3.2 | -45.1 -49.2 360 74 38 6.7 3.7
29000 -43.2 -45.8 355 50 26 6.8 3.8 | -42.3 -44.1 005 70 36 7.7 4.2
28000 -40.6 -41.1 355 48 25 6.8 3.8 | -40.0 -40.0 005 67 34 7.7 4.2
27000 -38.6 -37.5 360 48 24 6.8 3.7 | -37.7 -35.9 005 64 33 7.6 4.2
26000 -36.3 -33.3 355 47 24 7.9 4.3 | -35.3 -31.5 005 61 31 8.3 4.5
25000 -34.0 -29.2 355 46 24 7.9 4.3 | -32.8 -27.0 005 58 30 8.3 4.5
24000 -31.6 -24.9 355 45 23 7.9 4.3 | -30.3 -22.5 005 56 29 8.4 4.6
23000 -29.5 -21.1 350 44 23 6.4 3.5 | -28.2 -18.8 360 51 26 6.3 3.5
22000 -27.6 -17.7 345 43 22 6.3 3.5 | -26.4 -15.5 355 47 24 6.3 3.5
21000 -25.7 -14.3 340 43 22 6.6 3.6 | -24.5 -12.1 350 42 22 6.3 3.5
20000 -24.3 -11.7 335 40 20 4.5 2.5 | -22.5 -8.5 345 41 21 6.6 3.6
19500 -23.6 -10.5 330 38 20 4.5 2.5 | -21.5 -6.7 345 41 21 6.6 3.6
19000 -22.9 -9.2 325 36 19 4.5 2.5 | -20.6 -5.1 345 41 21 6.7 3.7
18500 -22.3 -8.1 320 35 18 4.6 2.5 | -19.6 -3.3 345 41 21 7.0 3.9
18000 -21.6 -6.9 320 34 18 3.6 2.0 | -18.8 -1.8 345 40 20 2.7 1.5
17500 -21.1 -6.0 320 34 18 3.5 1.9 | -18.4 -1.1 340 38 20 2.8 1.5
17000 -20.6 -5.1 320 34 17 3.4 1.9 | -18.0 -0.4 335 37 19 2.7 1.5
16500 -20.1 -4.2 320 33 17 3.2 1.8 | -17.6 0.3 335 35 18 2.7 1.5
16000 -19.6 -3.3 320 33 17 3.2 1.8 | -17.2 1.0 330 34 18 2.7 1.5
15500 -19.1 -2.4 320 33 17 4.0 2.2 | -16.8 1.8 325 34 17 2.8 1.5
15000 -18.5 -1.3 315 32 17 3.8 2.1 | -16.2 2.8 325 32 17 3.2 1.7
14500 -17.8 -0.0 315 31 16 5.4 2.9 | -15.6 3.9 325 31 16 3.8 2.1
14000 -16.6 2.1 315 30 15 5.6 3.1 | -15.0 5.0 325 30 16 4.0 2.2
13500 -15.7 3.7 315 29 15 6.5 3.5 | -14.4 6.1 320 28 15 4.9 2.7
13000 -14.8 5.4 310 28 14 6.5 3.6 | -13.6 7.5 320 26 14 5.1 2.8
12500 -13.7 7.3 310 26 13 7.2 3.9 | -12.7 9.1 315 25 13 6.5 3.6
12000 -12.7 9.1 305 25 13 7.2 4.0 | -11.8 10.8 315 24 12 6.6 3.6
11500 -11.6 11.1 300 24 12 7.6 4.2 | -10.7 12.7 310 25 13 7.4 4.0
11000 -10.5 13.1 300 23 12 7.4 4.1 | -9.6 14.7 305 26 13 7.0 3.8
10500 -9.4 15.1 295 23 12 6.8 3.7 | -8.7 16.3 295 28 14 5.8 3.2
10250 -8.9 16.0 295 22 11 7.7 4.2 | -8.3 17.1 295 29 15 6.2 3.4
10000 -8.4 16.9 295 22 11 4.2 2.3 | -7.9 17.8 290 30 15 5.0 2.8
9750 -8.2 17.2 295 21 11 5.2 2.8 | -7.5 18.5 290 29 15 6.1 3.4
9500 -7.5 18.5 295 20 10 9.3 5.1 | -6.9 19.6 290 28 14 8.1 4.4
9250 -6.9 19.6 295 18 9 8.2 4.5 | -6.4 20.5 290 26 13 7.6 4.2
9000 -6.3 20.7 295 17 9 6.8 3.7 | -5.8 21.6 290 24 13 6.4 3.5
8750 -5.9 21.4 295 15 8 5.9 3.2 | -5.4 22.3 290 22 11 6.3 3.5
8500 -5.4 22.3 295 13 7 6.9 3.8 | -4.9 23.2 290 20 10 7.4 4.0
8250 -4.9 23.2 300 12 6 6.0 3.3 | -4.3 24.3 285 17 9 6.8 3.7
8000 -4.5 23.9 300 9 5 4.4 2.4 | -3.9 25.0 285 15 8 6.5 3.6
7750 -4.2 24.4 300 6 3 5.2 2.9 | -3.4 25.9 280 12 6 5.9 3.2
7500 -3.7 25.3 300 3 2 6.3 3.5 | -3.0 26.6 275 10 5 5.4 3.0
7250 -3.2 26.2 300 1 1 8.5 4.6 | -2.5 27.5 265 8 4 6.8 3.7
7000 -2.4 27.7 000 0 0 10.8 5.9 | -2.0 28.4 250 7 3 7.9 4.3
6750 -1.7 28.9 000 0 0 9.0 4.9 | -1.4 29.5 240 6 3 7.2 4.0
6500 -1.1 30.0 000 0 0 9.2 5.1 | -0.8 30.6 225 5 3 8.0 4.4
6250 -0.3 31.5 000 0 0 10.8 6.0 | -0.2 31.6 210 5 2 9.1 5.0
6000 0.5 32.9 000 0 0 10.5 5.7 | 0.5 32.9 195 4 2 9.7 5.3
5750 1.3 34.3 000 0 0 11.6 6.3 | 1.2 34.2 175 4 2 7.5 4.1
5500 2.3 36.1 080 1 0 15.3 8.4 | 1.5 34.7 160 4 2 0.4 0.2
________________________________________________________________________________
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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