Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
529
UXUS97 KBOU 010153
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1943 MDT Friday, October 31, 2025
This forecast is for Saturday, November 1, 2025:
If the trigger temperature of 54.9 F/12.7 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 595 ft/min (3.0 m/s)
Maximum height of thermals.................. 12992 ft MSL (7731 ft AGL)
Forecast maximum temperature................... 63.0 F/17.7 C
Time of trigger temperature.................... 1145 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................. 10457 ft MSL (5196 ft AGL)
Thermal soaring outlook for Sunday 11/02....... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Weak NVA
Potential height of wave....................... 39490 ft MSL (34229 ft AGL)
Wave soaring outlook for Sunday 11/02.......... Poor
Remarks...
Sunrise/Sunset.................... 07:28:50 / 17:57:10 MDT
Total possible sunshine........... 10 hr 28 min 21 sec (628 min 21 sec)
Altitude of sun at 12:43:00 MDT... 35.40 degrees
Upper air data from numerical model forecast valid on 11/01/2025 at 0600 MDT
Freezing level.................. 9535 ft MSL (4274 ft AGL)
Convective condensation level... 17323 ft MSL (12062 ft AGL)
Lifted condensation level....... 15737 ft MSL (10476 ft AGL)
Lifted index.................... +8.9
K index......................... -22.6
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 -62.3 -80.1 350 60 31 1.0 0.5 M M M M M
45000 -60.7 -77.3 360 77 39 1.4 0.8 M M M M M
40000 -58.5 -73.3 005 119 61 1.5 0.8 M M M M M
38000 -55.9 -68.6 360 119 61 5.7 3.1 M M M M M
36000 -52.5 -62.5 360 113 58 5.7 3.1 M M M M M
34000 -48.5 -55.3 360 106 55 8.3 4.5 M M M M M
32000 -43.5 -46.3 360 99 51 8.3 4.5 M M M M M
30000 -37.7 -35.9 360 93 48 9.2 5.1 39.3 102.8 16.6 M M
29000 -34.9 -30.8 360 92 47 9.2 5.1 39.1 102.3 16.7 M M
28000 -32.1 -25.8 360 91 47 9.2 5.1 38.9 102.1 16.8 M M
27000 -29.7 -21.5 360 89 46 5.8 3.2 38.4 101.2 16.6 M M
26000 -27.8 -18.0 360 86 44 6.1 3.4 36.9 98.5 15.6 M M
25000 -26.0 -14.8 355 83 43 6.1 3.4 35.6 96.1 14.7 M M
24000 -24.2 -11.6 355 80 41 4.7 2.6 34.3 93.7 13.8 M M
23000 -22.9 -9.2 355 76 39 4.3 2.3 32.2 89.9 12.2 M M
22000 -21.7 -7.1 355 71 37 4.3 2.3 30.2 86.3 10.7 M M
21000 -20.4 -4.7 355 66 34 4.3 2.4 28.3 82.9 9.3 M M
20000 -19.1 -2.4 355 59 31 4.3 2.4 26.3 79.3 7.7 M M
19500 -18.5 -1.3 355 56 29 4.3 2.3 25.3 77.5 6.9 M M
19000 -17.8 -0.0 350 52 27 4.2 2.3 24.4 75.9 6.1 M M
18500 -17.1 1.2 350 50 26 5.9 3.3 23.6 74.4 5.5 M M
18000 -16.1 3.0 350 48 25 6.3 3.5 22.9 73.3 5.0 M M
17500 -15.2 4.6 345 47 24 6.2 3.4 22.4 72.3 4.5 M M
17000 -14.3 6.3 345 46 23 5.9 3.2 21.7 71.1 3.9 M M
16500 -13.4 7.9 345 45 23 5.8 3.2 21.1 69.9 3.4 M M
16000 -12.5 9.5 345 44 23 6.8 3.7 20.5 68.8 2.9 M M
15500 -11.5 11.3 345 43 22 6.7 3.7 20.0 67.9 2.4 M M
15000 -10.5 13.1 345 42 21 7.2 3.9 19.5 67.1 2.0 M M
14500 -9.4 15.1 340 40 21 7.3 4.0 19.1 66.3 1.6 M M
14000 -7.8 18.0 340 38 20 5.9 3.2 18.4 65.1 1.0 M M
13500 -6.9 19.6 340 37 19 6.0 3.3 17.8 64.0 0.4 M M
13000 -6.0 21.2 340 35 18 6.1 3.3 17.2 62.9 -0.1 587 3.0
12500 -5.1 22.8 335 33 17 6.1 3.4 16.6 61.8 -0.7 545 2.8
12000 -4.2 24.4 335 30 16 5.8 3.2 16.0 60.7 -1.3 504 2.6
11500 -3.4 25.9 335 28 14 5.8 3.2 15.3 59.6 -1.9 464 2.4
11000 -2.5 27.5 330 25 13 6.6 3.6 14.7 58.5 -2.5 423 2.1
10500 -1.6 29.1 330 23 12 7.4 4.1 14.2 57.6 -3.0 380 1.9
10250 -1.1 30.0 325 22 11 3.7 2.0 14.0 57.2 -3.3 358 1.8
10000 -0.9 30.4 325 21 11 3.9 2.1 13.4 56.1 -3.9 346 1.8
9750 -0.4 31.3 325 20 11 8.8 4.8 13.2 55.7 -4.1 323 1.6
9500 0.2 32.4 325 19 10 9.2 5.0 13.1 55.6 -4.2 297 1.5
9250 0.8 33.4 325 18 9 5.5 3.0 13.0 55.4 -4.4 272 1.4
9000 1.0 33.8 320 17 9 2.9 1.6 12.5 54.5 -4.9 258 1.3
8750 1.4 34.5 320 16 8 7.4 4.0 12.1 53.8 -5.3 239 1.2
8500 2.0 35.6 315 15 7 7.9 4.4 12.0 53.6 -5.4 214 1.1
8250 2.5 36.5 315 13 7 4.6 2.5 11.7 53.1 -5.7 193 1.0
8000 2.7 36.9 310 13 6 3.3 1.8 11.3 52.3 -6.2 177 0.9
7750 3.0 37.4 305 12 6 4.8 2.6 10.8 51.5 -6.7 162 0.8
7500 3.3 37.9 300 10 5 2.2 1.2 10.4 50.7 -7.1 145 0.7
7250 3.3 37.9 290 9 5 -1.0 -0.5 9.6 49.3 -7.9 138 0.7
7000 3.2 37.8 285 8 4 -0.2 -0.1 8.9 47.9 -8.7 132 0.7
6750 3.2 37.8 275 7 4 -0.9 -0.5 8.1 46.5 -9.4 126 0.6
6500 3.1 37.6 255 6 3 0.5 0.3 7.3 45.1 -10.3 121 0.6
6250 3.3 37.9 245 5 3 2.1 1.1 6.7 44.0 -10.9 110 0.6
6000 3.4 38.1 235 5 3 1.4 0.8 6.1 42.9 -11.5 98 0.5
5750 3.3 37.9 225 5 3 -6.5 -3.6 5.2 41.4 -12.4 94 0.5
5500 2.3 36.1 215 4 2 -19.1 -10.5 3.5 38.3 -14.2 118 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/01/2025 at 0900 MDT | 11/01/2025 at 1200 MDT
|
CAPE... 0.0 LI... +9.9 | CAPE... 0.0 LI... +10.9
CINH... -0.2 K Index... -39.7 | CINH... -0.3 K Index... -27.2
|
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 -64.3 -83.7 350 60 31 0.1 0.0 | -65.3 -85.5 350 59 30 0.4 0.2
45000 -63.7 -82.7 360 75 39 3.0 1.7 | -64.1 -83.4 360 74 38 3.6 2.0
40000 -59.0 -74.2 005 106 55 3.0 1.7 | -58.6 -73.5 360 93 48 3.3 1.8
38000 -55.5 -67.9 360 104 54 6.5 3.6 | -54.8 -66.6 355 90 47 6.8 3.7
36000 -51.6 -60.9 360 99 51 6.5 3.6 | -50.2 -58.4 355 85 44 6.8 3.7
34000 -47.3 -53.1 355 92 47 7.9 4.3 | -45.7 -50.3 355 79 41 7.9 4.3
32000 -42.0 -43.6 355 82 42 7.8 4.3 | -40.9 -41.6 355 71 37 7.9 4.3
30000 -37.2 -35.0 360 75 39 8.2 4.5 | -36.1 -33.0 355 65 34 8.1 4.5
29000 -34.7 -30.5 360 72 37 8.2 4.5 | -33.7 -28.7 355 63 32 8.1 4.5
28000 -32.3 -26.1 360 70 36 8.2 4.5 | -31.2 -24.2 350 61 31 8.1 4.5
27000 -29.8 -21.6 355 68 35 8.1 4.5 | -28.9 -20.0 350 59 30 7.6 4.1
26000 -27.4 -17.3 355 67 35 8.1 4.5 | -26.7 -16.1 350 58 30 7.6 4.1
25000 -24.9 -12.8 355 67 34 8.2 4.5 | -24.4 -11.9 350 56 29 7.6 4.2
24000 -22.6 -8.7 355 66 34 6.3 3.5 | -22.2 -8.0 350 55 28 6.9 3.8
23000 -20.6 -5.1 355 66 34 6.5 3.6 | -20.1 -4.2 350 54 28 6.9 3.8
22000 -18.6 -1.5 355 65 33 6.5 3.6 | -18.1 -0.6 350 53 27 6.9 3.8
21000 -16.9 1.6 360 63 33 4.2 2.3 | -16.1 3.0 350 51 26 6.0 3.3
20000 -15.6 3.9 355 59 30 4.3 2.4 | -14.2 6.4 350 49 25 6.1 3.3
19500 -15.0 5.0 355 57 29 4.3 2.4 | -13.3 8.1 350 48 25 6.1 3.4
19000 -14.3 6.3 355 55 28 4.4 2.4 | -12.3 9.9 355 47 24 6.3 3.5
18500 -13.7 7.3 355 53 27 3.8 2.1 | -11.5 11.3 355 45 23 4.1 2.2
18000 -13.1 8.4 355 51 26 3.9 2.1 | -10.5 13.1 350 43 22 4.5 2.5
17500 -12.5 9.5 355 48 25 4.2 2.3 | -10.0 14.0 350 42 22 3.1 1.7
17000 -11.8 10.8 350 46 24 4.8 2.6 | -9.5 14.9 350 40 21 3.2 1.8
16500 -10.8 12.6 350 43 22 4.8 2.6 | -9.0 15.8 350 39 20 3.4 1.9
16000 -10.0 14.0 350 42 22 4.9 2.7 | -8.5 16.7 345 38 19 3.5 1.9
15500 -9.3 15.3 350 41 21 5.1 2.8 | -8.0 17.6 345 36 19 3.7 2.1
15000 -8.5 16.7 345 39 20 5.8 3.2 | -7.4 18.7 345 35 18 4.3 2.3
14500 -7.6 18.3 345 38 19 5.7 3.1 | -6.7 19.9 345 34 18 4.4 2.4
14000 -6.7 19.9 345 36 19 6.5 3.6 | -5.9 21.4 340 33 17 6.1 3.4
13500 -5.8 21.6 345 35 18 6.4 3.5 | -5.1 22.8 340 32 17 5.9 3.3
13000 -4.8 23.4 345 34 17 6.5 3.6 | -4.1 24.6 340 31 16 6.9 3.8
12500 -3.8 25.2 345 32 16 6.6 3.6 | -3.1 26.4 340 30 15 6.7 3.7
12000 -2.9 26.8 345 30 15 6.1 3.3 | -2.0 28.4 340 28 14 7.2 4.0
11500 -2.0 28.4 345 28 14 6.1 3.4 | -0.9 30.4 340 26 14 7.2 3.9
11000 -1.1 30.0 340 26 13 5.9 3.2 | 0.1 32.2 340 25 13 7.2 3.9
10500 -0.2 31.6 340 24 12 6.9 3.8 | 1.2 34.2 340 23 12 7.9 4.3
10250 0.2 32.4 340 23 12 2.0 1.1 | 1.7 35.1 340 22 11 2.8 1.5
10000 0.2 32.4 340 23 12 3.5 1.9 | 1.8 35.2 340 22 11 4.8 2.6
9750 0.8 33.4 335 22 11 10.1 5.5 | 2.5 36.5 340 21 11 11.2 6.1
9500 1.5 34.7 335 20 11 9.0 5.0 | 3.2 37.8 340 19 10 9.2 5.1
9250 2.1 35.8 335 19 10 5.7 3.1 | 3.9 39.0 335 18 9 6.0 3.3
9000 2.4 36.3 335 18 9 3.8 2.1 | 4.2 39.6 335 17 9 5.2 2.8
8750 2.8 37.0 330 17 9 7.6 4.2 | 4.7 40.5 335 16 8 8.8 4.8
8500 3.4 38.1 330 15 8 7.7 4.2 | 5.4 41.7 330 14 7 8.1 4.5
8250 3.9 39.0 325 14 7 5.6 3.1 | 5.9 42.6 330 12 6 5.9 3.2
8000 4.2 39.6 320 12 6 4.7 2.6 | 6.3 43.3 330 11 6 5.5 3.0
7750 4.6 40.3 315 11 6 7.9 4.3 | 6.8 44.2 325 10 5 8.2 4.5
7500 5.2 41.4 315 11 5 6.3 3.5 | 7.4 45.3 320 8 4 6.8 3.7
7250 5.5 41.9 310 10 5 2.5 1.4 | 7.7 45.9 315 7 4 4.1 2.3
7000 5.7 42.3 305 10 5 3.4 1.9 | 8.1 46.6 315 6 3 4.3 2.4
6750 5.9 42.6 300 9 5 3.5 1.9 | 8.4 47.1 315 5 3 8.4 4.6
6500 6.1 43.0 290 8 4 0.7 0.4 | 9.2 48.6 305 4 2 9.3 5.1
6250 6.0 42.8 275 7 4 -1.7 -0.9 | 9.7 49.5 300 3 2 7.1 3.9
6000 5.9 42.6 260 6 3 -1.1 -0.6 | 10.2 50.4 290 2 1 5.3 2.9
5750 5.6 42.1 235 6 3 -8.1 -4.4 | 10.6 51.1 235 1 0 9.1 5.0
5500 4.6 40.3 220 5 2 -18.7 -10.2 | 11.9 53.4 225 1 0 23.8 13.1
11/01/2025 at 1500 MDT | 11/01/2025 at 1700 MST
|
CAPE... 0.0 LI... +9.6 | CAPE... 0.0 LI... +7.9
CINH... 0.0 K Index... +0.3 | CINH... 0.0 K Index... +12.2
|
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 -66.2 -87.2 350 57 29 1.1 0.6 | -66.7 -88.1 350 55 28 1.0 0.5
45000 -64.0 -83.2 355 70 36 3.7 2.1 | -64.3 -83.7 355 65 33 4.1 2.2
40000 -58.0 -72.4 355 85 44 5.1 2.8 | -58.1 -72.6 350 78 40 5.8 3.2
38000 -53.7 -64.7 350 83 43 7.3 4.0 | -53.5 -64.3 350 78 40 7.7 4.2
36000 -49.3 -56.7 350 80 41 7.3 4.0 | -48.9 -56.0 350 79 40 7.7 4.2
34000 -44.9 -48.8 350 74 38 7.4 4.1 | -44.3 -47.7 355 74 38 7.6 4.2
32000 -40.4 -40.7 350 64 33 7.4 4.1 | -39.8 -39.6 355 67 34 7.6 4.2
30000 -35.8 -32.4 350 58 30 8.2 4.5 | -35.2 -31.4 355 61 31 7.7 4.2
29000 -33.3 -27.9 350 57 29 8.2 4.5 | -32.3 -26.1 355 58 30 7.7 4.2
28000 -30.9 -23.6 345 55 28 8.2 4.5 | -30.0 -22.0 355 55 28 7.7 4.2
27000 -28.0 -18.4 345 53 27 7.6 4.2 | -27.6 -17.7 350 53 27 7.9 4.3
26000 -25.7 -14.3 345 52 27 7.6 4.2 | -25.3 -13.5 350 51 26 7.9 4.3
25000 -23.5 -10.3 350 50 26 7.6 4.2 | -23.0 -9.4 355 50 26 7.9 4.3
24000 -21.3 -6.3 350 49 25 7.0 3.8 | -20.7 -5.3 350 48 25 7.3 4.0
23000 -19.2 -2.6 350 48 25 7.0 3.8 | -18.6 -1.5 350 46 23 7.3 4.0
22000 -17.2 1.0 350 48 24 7.0 3.8 | -16.4 2.5 350 43 22 7.3 4.0
21000 -15.2 4.6 350 47 24 6.4 3.5 | -14.4 6.1 350 42 22 6.9 3.8
20000 -13.4 7.9 350 46 24 6.4 3.5 | -12.3 9.9 350 42 22 6.9 3.8
19500 -12.5 9.5 345 46 24 6.4 3.5 | -11.3 11.7 350 42 22 6.9 3.8
19000 -11.5 11.3 345 46 23 6.5 3.6 | -10.3 13.5 350 42 21 6.7 3.7
18500 -10.6 12.9 345 44 23 6.7 3.7 | -9.4 15.1 345 41 21 6.1 3.4
18000 -9.6 14.7 345 43 22 6.9 3.8 | -8.5 16.7 345 41 21 6.2 3.4
17500 -8.7 16.3 345 42 21 4.5 2.5 | -7.6 18.3 345 40 21 5.5 3.0
17000 -8.1 17.4 345 40 20 4.1 2.2 | -6.9 19.6 345 39 20 5.4 3.0
16500 -7.4 18.7 340 38 19 3.7 2.0 | -6.1 21.0 345 38 20 4.6 2.5
16000 -7.0 19.4 340 36 18 2.8 1.5 | -5.6 21.9 345 38 19 3.3 1.8
15500 -6.5 20.3 335 33 17 2.8 1.5 | -5.1 22.8 345 37 19 3.3 1.8
15000 -6.0 21.2 335 31 16 3.6 2.0 | -4.5 23.9 340 35 18 5.1 2.8
14500 -5.5 22.1 335 30 15 3.4 1.9 | -3.8 25.2 340 34 18 5.0 2.7
14000 -4.8 23.4 330 28 14 5.2 2.8 | -3.1 26.4 340 32 17 4.4 2.4
13500 -4.0 24.8 330 26 14 5.3 2.9 | -2.4 27.7 335 30 16 4.3 2.4
13000 -3.1 26.4 330 25 13 6.5 3.5 | -1.2 29.8 330 27 14 6.0 3.3
12500 -2.1 28.2 330 23 12 6.8 3.7 | -0.3 31.5 325 24 12 6.0 3.3
12000 -0.5 31.1 325 21 11 7.7 4.2 | 0.7 33.3 325 22 11 6.8 3.7
11500 0.7 33.3 325 20 10 7.6 4.2 | 1.8 35.2 320 20 10 6.8 3.7
11000 1.9 35.4 325 19 10 8.0 4.4 | 2.8 37.0 315 18 9 7.2 3.9
10500 3.1 37.6 325 18 9 7.4 4.1 | 3.9 39.0 305 17 9 6.6 3.6
10250 3.5 38.3 325 18 9 3.1 1.7 | 4.3 39.7 305 17 9 3.1 1.7
10000 3.7 38.7 325 17 9 6.4 3.5 | 4.5 40.1 305 17 8 6.8 3.8
9750 4.5 40.1 325 16 8 11.6 6.3 | 5.3 41.5 300 16 8 11.8 6.5
9500 5.3 41.5 325 14 7 9.1 5.0 | 6.1 43.0 295 16 8 9.5 5.2
9250 5.8 42.4 325 13 7 4.6 2.5 | 6.7 44.1 295 16 8 5.2 2.9
9000 6.1 43.0 320 12 6 5.4 3.0 | 7.1 44.8 290 17 9 6.0 3.3
8750 6.7 44.1 315 10 5 9.9 5.4 | 7.7 45.9 290 16 8 10.4 5.7
8500 7.4 45.3 310 8 4 7.9 4.4 | 8.5 47.3 285 16 8 8.3 4.6
8250 7.9 46.2 305 7 4 5.1 2.8 | 9.0 48.2 285 15 8 5.4 2.9
8000 8.2 46.8 300 6 3 5.9 3.2 | 9.4 48.9 280 14 7 6.0 3.3
7750 8.8 47.8 290 5 2 9.5 5.2 | 9.9 49.8 275 12 6 9.6 5.3
7500 9.5 49.1 275 3 2 8.9 4.9 | 10.7 51.3 270 10 5 8.1 4.4
7250 10.1 50.2 265 3 1 6.6 3.6 | 11.1 52.0 265 8 4 4.9 2.7
7000 10.6 51.1 250 2 1 7.6 4.2 | 11.6 52.9 255 7 4 6.0 3.3
6750 11.3 52.3 230 2 1 12.1 6.6 | 12.1 53.8 240 6 3 9.7 5.3
6500 12.3 54.1 225 2 1 12.0 6.6 | 12.9 55.2 225 5 3 9.5 5.2
6250 13.0 55.4 220 2 1 10.1 5.5 | 13.5 56.3 210 5 2 7.3 4.0
6000 13.8 56.8 220 2 1 7.3 4.0 | 14.1 57.4 195 5 2 6.3 3.4
5750 14.2 57.6 215 2 1 8.3 4.5 | 14.3 57.7 185 5 2 -0.9 -0.5
5500 15.3 59.5 215 1 1 21.0 11.5 | 14.0 57.2 175 4 2 -6.9 -3.8
________________________________________________________________________________
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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