Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
532
UXUS97 KBOU 181333
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0729 MDT Wednesday, June 18, 2025
This forecast is for Wednesday, June 18, 2025:
If the trigger temperature of 73.9 F/23.3 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1102 ft/min (5.6 m/s)
Maximum height of thermals.................. 17520 ft MSL (12202 ft AGL)
Forecast maximum temperature................... 84.0 F/29.3 C
Time of trigger temperature.................... 1045 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................. 13546 ft MSL (8228 ft AGL)
Thermal soaring outlook for Thursday 06/19..... Excellent
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 NVA
Potential height of wave....................... 40694 ft MSL (35376 ft AGL)
Wave soaring outlook for Thursday 06/19........ Poor
Remarks...
Sunrise/Sunset.................... 05:31:09 / 20:30:22 MDT
Total possible sunshine........... 14 hr 59 min 13 sec (899 min 13 sec)
Altitude of sun at 13:00:46 MDT... 73.65 degrees
Upper air data from numerical model forecast valid on 06/18/2025 at 0600 MDT
Freezing level.................. 13952 ft MSL (8634 ft AGL)
Convective condensation level... 15630 ft MSL (10312 ft AGL)
Lifted condensation level....... 16528 ft MSL (11211 ft AGL)
Lifted index.................... +0.2
K index......................... +16.9
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 -62.3 -80.1 305 40 21 2.0 1.1 M M M M M
45000 -58.4 -73.1 305 56 29 4.7 2.6 M M M M M
40000 -50.9 -59.6 310 63 32 5.2 2.8 M M M M M
38000 -47.8 -54.0 310 59 31 5.1 2.8 M M M M M
36000 -44.7 -48.5 315 56 29 5.2 2.8 M M M M M
34000 -41.0 -41.8 310 53 27 6.6 3.6 M M M M M
32000 -37.0 -34.6 310 51 26 6.6 3.6 M M M M M
30000 -32.4 -26.3 310 49 25 7.0 3.8 43.6 110.4 11.2 M M
29000 -30.3 -22.5 305 48 25 7.0 3.8 42.5 108.5 10.5 M M
28000 -28.2 -18.8 305 47 24 7.1 3.9 41.6 106.9 9.9 M M
27000 -26.0 -14.8 305 46 24 7.4 4.0 40.6 105.0 9.2 M M
26000 -23.8 -10.8 305 46 23 7.4 4.0 39.6 103.4 8.6 M M
25000 -21.6 -6.9 305 45 23 7.4 4.1 38.9 101.9 8.0 M M
24000 -19.4 -2.9 305 44 22 7.2 4.0 37.9 100.2 7.4 M M
23000 -17.2 1.0 310 42 22 7.2 4.0 37.0 98.5 6.7 M M
22000 -15.1 4.8 310 41 21 7.4 4.1 36.1 97.0 6.0 M M
21000 -13.4 7.9 310 39 20 5.1 2.8 34.7 94.4 4.8 M M
20000 -11.9 10.6 310 37 19 5.1 2.8 33.0 91.4 3.5 M M
19500 -11.1 12.0 310 36 18 5.1 2.8 32.2 90.0 2.8 M M
19000 -10.4 13.3 310 34 18 5.1 2.8 31.5 88.6 2.2 M M
18500 -9.6 14.7 305 34 18 5.1 2.8 30.6 87.2 1.4 M M
18000 -8.9 16.0 305 34 17 5.1 2.8 29.9 85.8 0.7 M M
17500 -8.1 17.4 305 33 17 6.8 3.7 29.2 84.6 0.1 M M
17000 -7.1 19.2 305 33 17 6.7 3.7 28.7 83.6 -0.4 1065 5.4
16500 -6.2 20.8 305 32 17 7.1 3.9 28.2 82.7 -0.9 1022 5.2
16000 -4.6 23.7 300 29 15 7.4 4.1 27.6 81.6 -1.6 953 4.8
15500 -3.5 25.7 300 27 14 8.1 4.4 27.2 81.0 -2.0 905 4.6
15000 -2.3 27.9 305 23 12 8.2 4.5 27.0 80.5 -2.2 855 4.3
14500 -1.1 30.0 305 20 10 8.2 4.5 26.7 80.1 -2.5 804 4.1
14000 0.1 32.2 310 17 9 8.1 4.5 26.4 79.6 -2.8 754 3.8
13500 1.3 34.3 315 15 8 8.2 4.5 26.2 79.1 -3.1 703 3.6
13000 2.5 36.5 320 14 7 8.4 4.6 26.0 78.7 -3.3 652 3.3
12500 3.8 38.8 320 12 6 8.4 4.6 25.7 78.3 -3.5 600 3.0
12000 5.0 41.0 325 11 6 8.4 4.6 25.5 78.0 -3.8 548 2.8
11500 6.2 43.2 330 10 5 8.4 4.6 25.3 77.6 -4.0 496 2.5
11000 7.5 45.5 330 9 5 8.1 4.5 25.1 77.2 -4.3 444 2.3
10500 8.7 47.7 330 8 4 6.7 3.7 24.9 76.7 -4.5 393 2.0
10250 9.0 48.2 325 7 4 4.6 2.5 24.5 76.1 -4.9 375 1.9
10000 9.5 49.1 325 6 3 7.9 4.3 24.2 75.5 -5.2 354 1.8
9750 10.2 50.4 325 6 3 10.1 5.5 24.2 75.5 -5.2 326 1.7
9500 10.9 51.6 320 5 3 9.0 4.9 24.2 75.5 -5.3 297 1.5
9250 11.5 52.7 315 5 2 5.8 3.2 24.0 75.2 -5.4 273 1.4
9000 11.8 53.2 305 4 2 6.0 3.3 23.6 74.5 -5.8 254 1.3
8750 12.4 54.3 300 4 2 8.4 4.6 23.5 74.3 -6.0 230 1.2
8500 13.0 55.4 295 4 2 7.1 3.9 23.3 74.0 -6.2 205 1.0
8250 13.4 56.1 290 4 2 5.2 2.9 23.1 73.5 -6.4 184 0.9
8000 13.8 56.8 280 3 2 5.3 2.9 22.7 72.8 -6.8 166 0.8
7750 14.3 57.7 275 3 2 7.5 4.1 22.4 72.4 -7.1 145 0.7
7500 14.8 58.6 280 3 2 5.7 3.2 22.2 72.0 -7.3 121 0.6
7250 15.0 59.0 280 3 2 3.0 1.7 21.8 71.2 -7.8 106 0.5
7000 15.3 59.5 280 3 1 3.6 2.0 21.3 70.3 -8.3 92 0.5
6750 15.5 59.9 280 3 1 4.0 2.2 20.8 69.5 -8.8 77 0.4
6500 15.6 60.1 285 3 2 -1.0 -0.5 20.3 68.5 -9.5 67 0.3
6250 15.2 59.4 290 3 1 -5.4 -3.0 19.2 66.6 -10.6 71 0.4
6000 14.8 58.6 295 2 1 -2.4 -1.3 18.2 64.7 -11.8 76 0.4
5750 14.5 58.1 300 2 1 -8.8 -4.8 17.2 62.9 -12.9 79 0.4
5500 13.1 55.6 265 1 0 -26.0 -14.3 15.1 59.2 -15.0 113 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/18/2025 at 0900 MDT | 06/18/2025 at 1200 MDT
|
CAPE... +9.5 LI... +2.4 | CAPE... +14.6 LI... +1.5
CINH... -63.5 K Index... +13.4 | CINH... -14.0 K Index... +7.5
|
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 -62.5 -80.5 300 37 19 1.7 0.9 | -63.1 -81.6 290 36 18 1.8 1.0
45000 -58.5 -73.3 305 56 29 4.9 2.7 | -59.0 -74.2 300 49 25 4.8 2.6
40000 -51.1 -60.0 310 63 32 5.2 2.8 | -51.8 -61.2 310 56 29 5.4 3.0
38000 -48.0 -54.4 310 58 30 5.2 2.8 | -48.6 -55.5 310 53 27 5.4 2.9
36000 -44.9 -48.8 315 53 27 5.2 2.9 | -45.4 -49.7 310 49 25 5.4 3.0
34000 -41.0 -41.8 315 49 25 7.1 3.9 | -41.4 -42.5 305 45 23 7.1 3.9
32000 -36.1 -33.0 315 44 23 7.1 3.9 | -36.6 -33.9 305 40 21 7.0 3.9
30000 -31.9 -25.4 310 44 23 7.0 3.8 | -32.1 -25.8 305 39 20 7.5 4.1
29000 -29.8 -21.6 310 44 23 7.0 3.8 | -29.9 -21.8 305 40 20 7.5 4.1
28000 -27.7 -17.9 310 45 23 7.1 3.9 | -27.7 -17.9 310 40 21 7.5 4.1
27000 -25.6 -14.1 310 45 23 7.3 4.0 | -25.4 -13.7 310 40 21 7.4 4.1
26000 -23.4 -10.1 310 45 23 7.3 4.0 | -23.2 -9.8 310 40 21 7.4 4.1
25000 -21.2 -6.2 310 45 23 7.2 4.0 | -21.0 -5.8 310 41 21 7.4 4.1
24000 -19.0 -2.2 310 45 23 7.5 4.1 | -18.7 -1.7 315 40 21 7.6 4.1
23000 -16.7 1.9 310 44 23 7.5 4.1 | -16.5 2.3 315 40 20 7.6 4.1
22000 -14.5 5.9 310 43 22 7.7 4.2 | -14.2 6.4 315 39 20 7.6 4.2
21000 -12.7 9.1 310 40 21 5.6 3.1 | -12.2 10.0 315 37 19 6.5 3.6
20000 -11.0 12.2 310 36 19 5.6 3.1 | -10.2 13.6 315 35 18 6.5 3.6
19500 -10.1 13.8 310 35 18 5.6 3.1 | -9.2 15.4 315 34 17 6.6 3.6
19000 -9.3 15.3 310 33 17 4.9 2.7 | -8.3 17.1 315 33 17 5.5 3.0
18500 -8.7 16.3 305 31 16 4.4 2.4 | -7.5 18.5 310 32 16 5.1 2.8
18000 -8.0 17.6 305 30 15 4.4 2.4 | -6.8 19.8 310 31 16 5.1 2.8
17500 -7.3 18.9 305 28 14 5.2 2.8 | -6.1 21.0 305 29 15 5.2 2.8
17000 -6.2 20.8 305 26 14 5.2 2.8 | -4.9 23.2 300 28 14 5.3 2.9
16500 -5.4 22.3 300 25 13 5.8 3.2 | -4.1 24.6 295 27 14 6.2 3.4
16000 -4.6 23.7 300 24 12 5.8 3.2 | -3.2 26.2 295 25 13 6.1 3.3
15500 -3.7 25.3 300 22 12 7.3 4.0 | -2.3 27.9 295 24 12 6.9 3.8
15000 -2.7 27.1 300 21 11 7.6 4.2 | -1.3 29.7 295 23 12 7.0 3.8
14500 -1.6 29.1 300 19 10 8.1 4.4 | -0.3 31.5 295 22 11 7.5 4.1
14000 -0.4 31.3 300 17 9 8.4 4.6 | 0.9 33.6 290 21 11 7.8 4.3
13500 0.8 33.4 300 15 8 8.6 4.7 | 2.0 35.6 290 19 10 8.0 4.4
13000 2.1 35.8 300 13 7 8.8 4.9 | 3.2 37.8 295 18 9 8.2 4.5
12500 3.4 38.1 300 12 6 8.8 4.8 | 4.3 39.7 295 16 8 8.2 4.5
12000 4.7 40.5 300 11 5 8.3 4.6 | 5.5 41.9 300 14 7 8.2 4.5
11500 5.9 42.6 300 9 5 8.3 4.5 | 6.7 44.1 300 12 6 8.1 4.4
11000 7.1 44.8 305 8 4 7.5 4.1 | 7.9 46.2 305 10 5 7.4 4.1
10500 8.2 46.8 310 7 4 6.0 3.3 | 9.0 48.2 310 8 4 4.7 2.6
10250 8.5 47.3 310 7 3 4.3 2.4 | 9.2 48.6 315 8 4 3.8 2.1
10000 8.9 48.0 310 6 3 7.7 4.2 | 9.7 49.5 315 7 4 8.8 4.9
9750 9.6 49.3 315 6 3 9.6 5.3 | 10.4 50.7 320 6 3 9.8 5.4
9500 10.3 50.5 320 5 3 8.3 4.5 | 11.0 51.8 330 5 2 8.4 4.6
9250 10.8 51.4 330 5 3 5.4 2.9 | 11.5 52.7 335 4 2 5.5 3.0
9000 11.1 52.0 335 5 3 6.4 3.5 | 11.9 53.4 340 4 2 7.3 4.0
8750 11.7 53.1 335 5 3 9.0 4.9 | 12.6 54.7 350 3 2 9.9 5.4
8500 12.4 54.3 340 5 3 7.0 3.8 | 13.3 55.9 005 3 1 7.8 4.3
8250 12.8 55.0 345 5 3 5.0 2.8 | 13.7 56.7 025 2 1 5.3 2.9
8000 13.1 55.6 345 5 3 5.0 2.7 | 14.1 57.4 045 3 1 7.0 3.9
7750 13.5 56.3 350 5 3 6.1 3.3 | 14.7 58.5 055 3 1 10.2 5.6
7500 13.9 57.0 350 5 2 3.7 2.0 | 15.3 59.5 065 3 2 8.6 4.7
7250 14.0 57.2 355 5 2 1.2 0.6 | 15.8 60.4 070 3 2 6.4 3.5
7000 14.1 57.4 360 5 2 2.2 1.2 | 16.3 61.3 070 3 2 8.2 4.5
6750 14.3 57.7 360 5 2 4.7 2.6 | 17.0 62.6 075 3 2 12.3 6.8
6500 14.6 58.3 360 4 2 4.7 2.6 | 18.0 64.4 070 3 2 11.5 6.3
6250 14.7 58.5 360 4 2 2.7 1.5 | 18.7 65.7 070 3 2 8.8 4.9
6000 14.9 58.8 360 3 2 4.4 2.4 | 19.4 66.9 075 3 2 10.3 5.7
5750 15.4 59.7 355 2 1 10.9 6.0 | 20.3 68.5 070 3 2 16.3 8.9
5500 16.4 61.5 350 2 1 18.4 10.1 | 21.8 71.2 070 3 2 24.3 13.3
06/18/2025 at 1500 MDT | 06/18/2025 at 1800 MDT
|
CAPE... +1.5 LI... +1.3 | CAPE... +38.8 LI... +0.3
CINH... -1.1 K Index... +13.8 | CINH... -50.9 K Index... +18.9
|
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 -63.5 -82.3 290 32 17 2.0 1.1 | -63.1 -81.6 280 27 14 1.8 1.0
45000 -59.1 -74.4 295 43 22 4.8 2.7 | -59.1 -74.4 290 36 19 4.4 2.4
40000 -51.8 -61.2 305 49 25 5.6 3.1 | -52.3 -62.1 305 44 23 6.3 3.4
38000 -48.5 -55.3 310 48 25 5.5 3.0 | -48.5 -55.3 310 44 22 6.3 3.4
36000 -45.1 -49.2 310 47 24 5.6 3.1 | -44.7 -48.5 315 44 22 6.3 3.4
34000 -41.2 -42.2 310 45 23 6.7 3.7 | -40.3 -40.5 315 43 22 6.6 3.6
32000 -36.7 -34.1 305 43 22 6.7 3.7 | -36.4 -33.5 310 41 21 6.5 3.6
30000 -32.3 -26.1 305 42 22 7.5 4.1 | -32.0 -25.6 310 39 20 7.4 4.1
29000 -30.0 -22.0 305 42 21 7.5 4.1 | -29.8 -21.6 310 38 20 7.4 4.1
28000 -27.7 -17.9 305 41 21 7.6 4.2 | -27.6 -17.7 310 37 19 7.5 4.1
27000 -25.4 -13.7 305 40 21 7.7 4.2 | -25.3 -13.5 310 37 19 7.6 4.2
26000 -23.1 -9.6 305 40 20 7.7 4.2 | -23.0 -9.4 310 37 19 7.6 4.2
25000 -20.8 -5.4 305 39 20 7.7 4.2 | -20.7 -5.3 310 37 19 7.6 4.2
24000 -18.5 -1.3 310 38 20 7.6 4.2 | -18.5 -1.3 310 36 19 7.3 4.0
23000 -16.2 2.8 310 37 19 7.6 4.2 | -16.4 2.5 310 35 18 7.3 4.0
22000 -14.0 6.8 310 36 18 7.6 4.2 | -14.2 6.4 305 35 18 7.2 4.0
21000 -12.0 10.4 310 34 17 6.3 3.5 | -12.2 10.0 305 33 17 6.8 3.8
20000 -10.1 13.8 305 31 16 6.3 3.5 | -10.1 13.8 295 31 16 6.9 3.8
19500 -9.2 15.4 305 30 15 6.3 3.5 | -9.1 15.6 295 30 15 6.8 3.7
19000 -8.3 17.1 300 29 15 6.2 3.4 | -8.1 17.4 290 29 15 7.9 4.3
18500 -7.4 18.7 300 29 15 6.3 3.4 | -6.9 19.6 285 29 15 7.9 4.4
18000 -6.5 20.3 295 28 15 6.4 3.5 | -5.7 21.7 285 29 15 7.9 4.3
17500 -5.5 22.1 290 28 14 6.9 3.8 | -4.0 24.8 280 29 15 7.8 4.3
17000 -4.0 24.8 285 28 14 7.2 3.9 | -2.9 26.8 280 29 15 8.1 4.4
16500 -2.8 27.0 285 27 14 8.1 4.4 | -1.6 29.1 280 29 15 8.7 4.7
16000 -1.7 28.9 280 27 14 8.0 4.4 | -0.4 31.3 280 28 14 8.7 4.8
15500 -0.5 31.1 280 27 14 8.4 4.6 | 0.8 33.4 280 26 14 8.1 4.4
15000 0.7 33.3 280 25 13 8.4 4.6 | 2.0 35.6 280 24 12 8.2 4.5
14500 1.9 35.4 280 24 12 7.5 4.1 | 3.2 37.8 275 22 11 7.4 4.1
14000 2.9 37.2 280 21 11 7.2 4.0 | 4.2 39.6 270 19 10 7.3 4.0
13500 3.9 39.0 275 18 9 7.1 3.9 | 5.2 41.4 265 15 8 7.3 4.0
13000 4.9 40.8 275 14 7 7.0 3.9 | 6.2 43.2 260 13 7 7.3 4.0
12500 5.9 42.6 275 11 6 7.1 3.9 | 7.3 45.1 245 11 6 7.2 4.0
12000 7.0 44.6 275 8 4 7.3 4.0 | 8.3 46.9 230 9 5 7.1 3.9
11500 8.0 46.4 275 6 3 7.4 4.0 | 9.3 48.7 210 8 4 7.2 3.9
11000 9.1 48.4 270 3 2 7.3 4.0 | 10.4 50.7 190 7 4 7.3 4.0
10500 10.3 50.5 240 1 0 3.2 1.8 | 11.5 52.7 170 7 3 3.2 1.7
10250 10.4 50.7 000 0 0 4.9 2.7 | 11.6 52.9 170 7 3 5.2 2.9
10000 11.1 52.0 125 1 0 11.7 6.4 | 12.4 54.3 165 7 3 12.1 6.6
9750 11.9 53.4 110 2 1 10.5 5.8 | 13.2 55.8 160 7 4 10.7 5.9
9500 12.6 54.7 105 3 2 9.2 5.0 | 14.0 57.2 155 7 4 9.4 5.2
9250 13.2 55.8 105 4 2 6.3 3.5 | 14.6 58.3 155 7 4 7.0 3.8
9000 13.7 56.7 105 4 2 9.3 5.1 | 15.2 59.4 150 7 4 9.6 5.3
8750 14.5 58.1 105 4 2 12.1 6.7 | 16.0 60.8 145 7 4 11.8 6.5
8500 15.4 59.7 100 5 2 10.0 5.5 | 16.8 62.2 140 7 4 9.7 5.3
8250 16.0 60.8 100 5 3 7.5 4.1 | 17.4 63.3 140 8 4 6.8 3.7
8000 16.6 61.9 100 5 3 9.3 5.1 | 18.0 64.4 140 8 4 9.1 5.0
7750 17.4 63.3 100 5 3 12.4 6.8 | 18.8 65.8 135 8 4 12.6 6.9
7500 18.3 64.9 095 6 3 9.8 5.4 | 19.7 67.5 135 8 4 9.8 5.4
7250 18.9 66.0 095 6 3 7.1 3.9 | 20.3 68.5 130 8 4 6.9 3.8
7000 19.4 66.9 095 6 3 9.1 5.0 | 20.8 69.4 130 8 4 9.0 4.9
6750 20.3 68.5 095 6 3 12.7 7.0 | 21.6 70.9 130 8 4 12.4 6.8
6500 21.2 70.2 095 6 3 11.6 6.3 | 22.6 72.7 125 8 4 11.1 6.1
6250 22.0 71.6 090 6 3 9.6 5.2 | 23.3 73.9 125 8 4 9.0 4.9
6000 22.7 72.9 090 6 3 9.2 5.1 | 24.0 75.2 125 8 4 9.3 5.1
5750 23.5 74.3 090 6 3 15.4 8.5 | 24.7 76.5 125 8 4 12.4 6.8
5500 25.1 77.2 090 6 3 29.1 16.0 | 25.8 78.4 120 7 4 18.5 10.1
________________________________________________________________________________
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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