Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
423
UXUS97 KBOU 021228
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0627 MDT Thursday, October 2, 2025
This forecast is for Thursday, October 2, 2025:
If the trigger temperature of 77.0 F/25.0 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 876 ft/min (4.4 m/s)
Maximum height of thermals.................. 15093 ft MSL (9794 ft AGL)
Forecast maximum temperature................... 83.0 F/28.8 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................. 10254 ft MSL (4955 ft AGL)
Thermal soaring outlook for Friday 10/03....... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... 16394 ft MSL (11095 ft AGL)
Weak PVA/NVA (through 1800 MDT)................ Weak NVA
Potential height of wave....................... 28476 ft MSL (23177 ft AGL)
Wave soaring outlook for Friday 10/03.......... Fair
Remarks...
Sunrise/Sunset.................... 06:57:18 / 18:40:00 MDT
Total possible sunshine........... 11 hr 42 min 42 sec (702 min 42 sec)
Altitude of sun at 12:48:39 MDT... 46.26 degrees
Upper air data from numerical model forecast valid on 10/02/2025 at 0600 MDT
Freezing level.................. 14429 ft MSL (9130 ft AGL)
Convective condensation level... 18660 ft MSL (13361 ft AGL)
Lifted condensation level....... 16236 ft MSL (10937 ft AGL)
Lifted index.................... +1.7
K index......................... +17.7
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 -67.2 -89.0 265 34 17 1.8 1.0 M M M M M
45000 -62.9 -81.2 265 36 19 5.8 3.2 M M M M M
40000 -53.9 -65.0 270 34 17 7.1 3.9 M M M M M
38000 -49.6 -57.3 275 32 16 7.1 3.9 M M M M M
36000 -45.3 -49.5 280 30 15 7.1 3.9 M M M M M
34000 -40.2 -40.4 280 29 15 7.6 4.2 M M M M M
32000 -35.6 -32.1 280 28 14 7.7 4.2 M M M M M
30000 -31.4 -24.5 280 31 16 6.9 3.8 44.5 112.1 12.3 M M
29000 -29.4 -20.9 280 33 17 6.9 3.8 43.4 110.2 11.6 M M
28000 -27.3 -17.1 280 34 17 7.5 4.1 42.5 108.5 11.0 M M
27000 -25.0 -13.0 280 30 15 7.8 4.3 41.6 106.9 10.5 M M
26000 -22.6 -8.7 275 26 14 7.8 4.3 40.9 105.5 10.0 M M
25000 -20.3 -4.5 270 23 12 7.8 4.3 40.2 104.4 9.6 M M
24000 -18.0 -0.4 270 20 11 7.5 4.1 39.4 102.8 9.0 M M
23000 -15.8 3.6 265 19 10 7.5 4.1 38.5 101.3 8.4 M M
22000 -13.6 7.5 265 17 9 7.6 4.2 37.8 100.1 7.8 M M
21000 -11.2 11.8 270 16 8 7.9 4.3 37.1 98.7 7.3 M M
20000 -8.8 16.2 275 14 7 7.9 4.3 36.4 97.6 6.8 M M
19500 -7.6 18.3 280 14 7 8.0 4.4 36.1 97.1 6.6 M M
19000 -6.5 20.3 285 14 7 7.6 4.1 35.8 96.5 6.4 M M
18500 -5.3 22.5 285 14 7 7.5 4.1 35.4 95.8 6.1 M M
18000 -4.2 24.4 290 14 7 6.7 3.7 35.1 95.1 5.8 M M
17500 -3.2 26.2 285 14 7 4.3 2.4 33.8 92.8 4.7 M M
17000 -2.5 27.5 285 15 8 3.6 2.0 32.9 91.1 3.8 M M
16500 -2.2 28.0 280 14 7 2.3 1.3 31.6 88.9 2.7 M M
16000 -1.9 28.6 275 14 7 2.3 1.3 30.4 86.7 1.5 M M
15500 -1.5 29.3 270 13 7 5.4 3.0 29.4 84.9 0.5 M M
15000 -0.8 30.6 260 12 6 5.2 2.8 28.6 83.6 -0.3 863 4.4
14500 0.0 32.0 255 11 5 8.0 4.4 28.1 82.5 -0.9 824 4.2
14000 1.3 34.3 255 10 5 8.5 4.7 27.9 82.1 -1.2 771 3.9
13500 2.5 36.5 255 9 5 8.5 4.6 27.7 81.8 -1.4 719 3.7
13000 3.8 38.8 250 9 5 8.4 4.6 27.4 81.4 -1.6 667 3.4
12500 5.0 41.0 250 9 5 8.7 4.8 27.2 81.0 -1.8 615 3.1
12000 6.3 43.3 250 9 5 9.1 5.0 27.1 80.8 -2.0 560 2.8
11500 7.7 45.9 250 9 5 8.7 4.8 27.0 80.6 -2.1 505 2.6
11000 8.9 48.0 250 10 5 7.9 4.4 26.8 80.2 -2.3 453 2.3
10500 10.2 50.4 245 11 5 5.0 2.7 26.5 79.8 -2.5 401 2.0
10250 10.4 50.7 245 11 6 4.4 2.4 26.0 78.8 -3.0 387 2.0
10000 11.0 51.8 245 11 6 10.5 5.7 25.9 78.6 -3.2 361 1.8
9750 11.9 53.4 245 11 6 12.3 6.8 26.0 78.8 -3.1 328 1.7
9500 12.7 54.9 245 12 6 8.8 4.8 26.1 79.0 -3.0 295 1.5
9250 13.1 55.6 240 12 6 4.6 2.5 25.8 78.5 -3.2 274 1.4
9000 13.6 56.5 240 13 6 6.7 3.7 25.5 77.9 -3.6 255 1.3
8750 14.1 57.4 240 13 7 8.2 4.5 25.3 77.6 -3.7 230 1.2
8500 14.7 58.5 235 13 7 7.2 3.9 25.2 77.3 -3.9 206 1.0
8250 15.2 59.4 235 14 7 6.5 3.6 25.0 76.9 -4.1 183 0.9
8000 15.7 60.3 230 14 7 7.1 3.9 24.7 76.5 -4.4 161 0.8
7750 16.2 61.2 230 14 7 7.0 3.8 24.5 76.2 -4.6 137 0.7
7500 16.7 62.1 230 14 7 4.7 2.6 24.2 75.6 -4.9 116 0.6
7250 16.9 62.4 230 13 7 2.7 1.5 23.8 74.8 -5.4 101 0.5
7000 17.2 63.0 230 12 6 5.6 3.1 23.3 73.9 -5.9 86 0.4
6750 17.6 63.7 230 11 6 1.9 1.0 23.0 73.4 -6.2 66 0.3
6500 17.3 63.1 235 10 5 -7.2 -4.0 22.0 71.5 -7.2 68 0.3
6250 16.7 62.1 240 9 4 -7.2 -4.0 20.6 69.1 -8.6 79 0.4
6000 16.1 61.0 245 7 4 -11.2 -6.1 19.3 66.7 -10.0 90 0.5
5750 14.8 58.6 245 7 3 -19.8 -10.9 17.3 63.2 -12.0 121 0.6
5500 13.1 55.6 230 5 3 -20.8 -11.4 15.0 59.0 -14.5 164 0.8
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/02/2025 at 0900 MDT | 10/02/2025 at 1200 MDT
|
CAPE... 0.0 LI... +4.2 | CAPE... 0.0 LI... +3.9
CINH... 0.0 K Index... +18.4 | CINH... 0.0 K Index... +16.2
|
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 -66.3 -87.3 265 31 16 1.9 1.0 | -66.3 -87.3 255 31 16 2.0 1.1
45000 -62.3 -80.1 260 36 19 4.8 2.7 | -62.1 -79.8 255 39 20 4.7 2.6
40000 -54.2 -65.6 260 39 20 7.5 4.1 | -54.2 -65.6 260 37 19 7.4 4.1
38000 -49.7 -57.5 265 33 17 7.5 4.1 | -49.7 -57.5 260 32 17 7.5 4.1
36000 -45.2 -49.4 270 28 14 7.5 4.1 | -45.2 -49.4 260 27 14 7.5 4.1
34000 -40.8 -41.4 270 27 14 7.5 4.1 | -40.6 -41.1 260 27 14 7.8 4.3
32000 -36.3 -33.3 265 27 14 7.5 4.1 | -35.9 -32.6 255 28 14 7.8 4.3
30000 -32.0 -25.6 265 29 15 7.0 3.8 | -31.9 -25.4 255 29 15 6.5 3.6
29000 -30.0 -22.0 265 30 15 7.0 3.8 | -29.4 -20.9 255 30 15 6.5 3.6
28000 -27.3 -17.1 265 30 16 7.7 4.2 | -27.4 -17.3 255 30 16 8.1 4.4
27000 -25.0 -13.0 265 28 14 7.7 4.2 | -25.0 -13.0 250 29 15 8.1 4.5
26000 -22.7 -8.9 260 25 13 7.7 4.2 | -22.5 -8.5 250 28 14 8.1 4.5
25000 -20.4 -4.7 255 23 12 7.7 4.2 | -20.1 -4.2 245 27 14 7.9 4.4
24000 -18.1 -0.6 255 21 11 7.8 4.3 | -17.8 -0.0 245 24 12 7.6 4.2
23000 -15.8 3.6 255 20 10 7.8 4.3 | -15.5 4.1 245 21 11 7.6 4.2
22000 -13.5 7.7 255 18 9 7.9 4.3 | -13.3 8.1 240 18 9 7.7 4.2
21000 -11.1 12.0 255 16 8 8.0 4.4 | -11.0 12.2 235 16 8 7.7 4.2
20000 -8.7 16.3 255 13 7 8.0 4.4 | -8.7 16.3 225 15 8 7.7 4.2
19500 -7.5 18.5 255 12 6 8.1 4.4 | -7.6 18.3 225 15 8 7.8 4.3
19000 -6.4 20.5 255 11 6 6.4 3.5 | -6.6 20.1 220 15 8 5.8 3.2
18500 -5.4 22.3 255 10 5 6.5 3.6 | -5.7 21.7 220 14 7 5.9 3.3
18000 -4.4 24.1 260 9 5 5.4 2.9 | -4.8 23.4 220 14 7 5.1 2.8
17500 -3.8 25.2 255 9 5 4.4 2.4 | -4.1 24.6 220 14 7 4.4 2.4
17000 -3.2 26.2 255 9 4 4.4 2.4 | -3.5 25.7 220 14 7 4.4 2.4
16500 -2.8 27.0 250 9 4 2.6 1.4 | -3.0 26.6 220 14 7 3.7 2.1
16000 -2.4 27.7 245 9 4 2.8 1.6 | -2.5 27.5 220 14 7 3.9 2.1
15500 -2.0 28.4 235 9 4 4.3 2.4 | -1.9 28.6 215 14 7 5.2 2.8
15000 -1.4 29.5 230 8 4 4.9 2.7 | -1.2 29.8 215 14 7 5.7 3.1
14500 -0.8 30.6 215 8 4 6.8 3.7 | 0.1 32.2 210 14 7 8.2 4.5
14000 1.1 34.0 210 6 3 9.1 5.0 | 1.3 34.3 205 13 7 8.1 4.5
13500 2.4 36.3 210 6 3 8.5 4.6 | 2.4 36.3 200 13 6 8.4 4.6
13000 3.6 38.5 215 5 3 8.3 4.6 | 3.7 38.7 200 11 6 8.4 4.6
12500 4.9 40.8 220 4 2 8.4 4.6 | 4.9 40.8 200 10 5 8.6 4.7
12000 6.1 43.0 235 3 2 8.5 4.6 | 6.2 43.2 195 8 4 8.7 4.8
11500 7.4 45.3 260 2 1 8.2 4.5 | 7.5 45.5 190 6 3 7.8 4.3
11000 8.6 47.5 295 3 1 8.0 4.4 | 8.5 47.3 185 4 2 7.1 3.9
10500 9.7 49.5 315 3 2 3.9 2.1 | 9.5 49.1 170 3 1 4.0 2.2
10250 9.9 49.8 320 4 2 4.1 2.3 | 9.8 49.6 170 2 1 5.1 2.8
10000 10.5 50.9 325 4 2 10.7 5.9 | 10.4 50.7 160 1 1 10.3 5.6
9750 11.3 52.3 330 5 2 11.1 6.1 | 11.2 52.2 000 0 0 10.1 5.6
9500 12.0 53.6 330 5 3 8.0 4.4 | 11.9 53.4 020 1 1 8.0 4.4
9250 12.5 54.5 330 6 3 5.1 2.8 | 12.3 54.1 010 2 1 6.1 3.3
9000 13.0 55.4 330 6 3 8.9 4.9 | 12.9 55.2 005 2 1 9.4 5.1
8750 13.8 56.8 330 6 3 11.0 6.0 | 13.7 56.7 005 3 1 10.8 5.9
8500 14.5 58.1 325 6 3 7.8 4.3 | 14.4 57.9 360 3 2 8.1 4.4
8250 15.0 59.0 325 6 3 6.7 3.7 | 14.9 58.8 360 4 2 6.9 3.8
8000 15.5 59.9 320 6 3 7.2 4.0 | 15.4 59.7 360 4 2 8.1 4.4
7750 16.0 60.8 320 6 3 5.8 3.2 | 16.1 61.0 360 4 2 8.1 4.4
7500 16.4 61.5 320 6 3 3.9 2.2 | 16.6 61.9 355 4 2 6.4 3.5
7250 16.6 61.9 315 6 3 3.2 1.7 | 17.1 62.8 355 4 2 6.2 3.4
7000 16.9 62.4 315 6 3 5.2 2.9 | 17.5 63.5 350 3 2 6.1 3.3
6750 17.2 63.0 315 6 3 -0.6 -0.4 | 18.0 64.4 345 3 2 7.8 4.3
6500 16.7 62.1 310 5 3 -6.9 -3.8 | 18.7 65.7 340 2 1 9.4 5.2
6250 16.3 61.3 300 5 2 -5.2 -2.9 | 19.3 66.7 335 2 1 8.7 4.8
6000 15.8 60.4 295 4 2 -5.5 -3.0 | 20.0 68.0 325 1 1 10.0 5.5
5750 15.6 60.1 280 4 2 -0.0 -0.0 | 20.9 69.6 315 1 1 15.9 8.7
5500 15.8 60.4 260 3 2 7.8 4.3 | 22.3 72.1 315 1 1 22.3 12.2
10/02/2025 at 1500 MDT | 10/02/2025 at 1800 MDT
|
CAPE... 0.0 LI... +2.8 | CAPE... 0.0 LI... +0.8
CINH... 0.0 K Index... +11.7 | CINH... 0.0 K Index... +26.1
|
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 -66.8 -88.2 255 37 19 2.3 1.2 | -66.9 -88.4 260 45 23 2.7 1.5
45000 -62.2 -80.0 260 43 22 5.1 2.8 | -61.7 -79.1 265 51 26 5.4 2.9
40000 -53.8 -64.8 255 34 17 7.3 4.0 | -53.5 -64.3 250 35 18 6.3 3.5
38000 -49.4 -56.9 250 31 16 7.4 4.0 | -49.7 -57.5 245 32 17 6.3 3.4
36000 -45.0 -49.0 245 28 15 7.4 4.0 | -45.4 -49.7 245 30 15 6.5 3.6
34000 -40.5 -40.9 250 27 14 7.5 4.1 | -40.8 -41.4 245 27 14 7.8 4.3
32000 -36.0 -32.8 250 26 14 7.5 4.1 | -36.1 -33.0 250 25 13 7.8 4.3
30000 -31.8 -25.2 250 29 15 6.9 3.8 | -31.5 -24.7 250 26 13 7.6 4.2
29000 -29.2 -20.6 250 31 16 6.9 3.8 | -29.2 -20.6 250 27 14 7.6 4.2
28000 -27.1 -16.8 250 32 17 8.3 4.6 | -27.0 -16.6 250 29 15 7.8 4.3
27000 -24.6 -12.3 245 32 16 8.3 4.6 | -24.6 -12.3 250 30 15 7.9 4.3
26000 -22.1 -7.8 245 31 16 8.3 4.6 | -22.2 -8.0 245 31 16 7.9 4.3
25000 -19.6 -3.3 240 31 16 7.9 4.4 | -19.8 -3.6 245 32 17 7.9 4.3
24000 -17.4 0.7 240 27 14 7.3 4.0 | -17.6 0.3 245 31 16 7.2 3.9
23000 -15.3 4.5 240 23 12 7.3 4.0 | -15.5 4.1 240 28 15 7.2 3.9
22000 -13.1 8.4 240 20 10 7.3 4.0 | -13.3 8.1 240 26 13 7.0 3.8
21000 -10.9 12.4 235 19 10 7.3 4.0 | -11.4 11.5 240 24 13 6.5 3.5
20000 -8.7 16.3 230 19 10 7.3 4.0 | -9.5 14.9 240 23 12 6.5 3.6
19500 -7.7 18.1 225 18 9 7.4 4.1 | -8.5 16.7 240 22 11 6.6 3.6
19000 -6.7 19.9 225 18 9 5.8 3.2 | -7.6 18.3 240 22 11 6.6 3.6
18500 -5.8 21.6 230 18 9 5.9 3.3 | -6.2 20.8 255 23 12 6.9 3.8
18000 -4.9 23.2 235 19 10 5.8 3.2 | -5.4 22.3 260 24 12 4.9 2.7
17500 -4.1 24.6 235 18 9 5.6 3.1 | -4.7 23.5 260 22 12 5.1 2.8
17000 -3.3 26.1 235 18 9 5.6 3.1 | -4.1 24.6 260 21 11 6.2 3.4
16500 -2.5 27.5 235 18 9 5.3 2.9 | -3.0 26.6 255 19 10 7.5 4.1
16000 -1.8 28.8 235 17 9 5.3 2.9 | -2.0 28.4 250 16 8 7.6 4.1
15500 -1.0 30.2 235 17 9 6.1 3.4 | -0.9 30.4 245 15 8 7.3 4.0
15000 0.4 32.7 225 16 8 6.4 3.5 | 0.1 32.2 235 14 7 7.3 4.0
14500 1.4 34.5 220 16 8 7.3 4.0 | 1.2 34.2 225 14 7 7.3 4.0
14000 2.4 36.3 215 16 8 7.4 4.0 | 2.3 36.1 210 13 7 7.4 4.0
13500 3.4 38.1 210 16 8 8.0 4.4 | 3.4 38.1 195 13 6 7.9 4.4
13000 4.6 40.3 205 16 8 8.2 4.5 | 4.6 40.3 185 12 6 8.2 4.5
12500 5.7 42.3 200 15 8 8.3 4.5 | 5.8 42.4 170 13 6 8.7 4.8
12000 6.9 44.4 195 15 8 8.3 4.6 | 7.1 44.8 170 12 6 9.1 5.0
11500 8.1 46.6 190 14 7 8.6 4.7 | 8.5 47.3 165 12 6 9.1 5.0
11000 9.4 48.9 185 13 7 8.5 4.7 | 9.9 49.8 160 12 6 9.0 4.9
10500 10.6 51.1 180 11 6 3.9 2.1 | 11.2 52.2 155 12 6 5.5 3.0
10250 10.7 51.3 175 11 6 4.0 2.2 | 11.5 52.7 155 12 6 6.9 3.8
10000 11.4 52.5 170 9 4 10.4 5.7 | 12.4 54.3 155 11 6 12.8 7.0
9750 12.1 53.8 160 7 4 9.3 5.1 | 13.3 55.9 150 11 6 12.3 6.7
9500 12.8 55.0 140 5 3 8.2 4.5 | 14.2 57.6 150 11 5 9.9 5.4
9250 13.3 55.9 135 5 3 7.1 3.9 | 14.7 58.5 150 10 5 7.1 3.9
9000 13.9 57.0 130 5 2 8.8 4.8 | 15.3 59.5 145 9 5 9.2 5.0
8750 14.5 58.1 125 4 2 9.6 5.3 | 16.1 61.0 145 8 4 10.0 5.5
8500 15.2 59.4 125 4 2 9.5 5.2 | 16.8 62.2 140 8 4 9.2 5.0
8250 15.9 60.6 125 4 2 9.5 5.2 | 17.4 63.3 140 7 3 8.9 4.9
8000 16.7 62.1 125 4 2 9.9 5.4 | 18.1 64.6 140 6 3 8.6 4.7
7750 17.4 63.3 120 4 2 10.3 5.6 | 18.7 65.7 140 5 3 8.3 4.5
7500 18.2 64.8 120 3 2 9.8 5.4 | 19.4 66.9 140 4 2 8.9 4.9
7250 18.9 66.0 120 3 2 9.6 5.3 | 20.1 68.2 140 4 2 9.1 5.0
7000 19.6 67.3 120 3 2 10.0 5.5 | 20.7 69.3 145 3 1 9.5 5.2
6750 20.4 68.7 120 3 2 10.5 5.7 | 21.5 70.7 145 2 1 9.8 5.4
6500 21.2 70.2 120 3 1 10.6 5.8 | 22.2 72.0 150 2 1 9.2 5.1
6250 22.0 71.6 120 3 1 10.4 5.7 | 22.9 73.2 155 1 1 8.9 4.9
6000 22.7 72.9 120 2 1 11.1 6.1 | 23.5 74.3 000 0 0 9.5 5.2
5750 23.7 74.7 120 2 1 15.4 8.4 | 24.3 75.7 000 0 0 9.4 5.1
5500 25.0 77.0 120 2 1 20.4 11.2 | 24.8 76.6 280 1 0 7.4 4.0
________________________________________________________________________________
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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