Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
307
UXUS97 KBOU 041232
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0632 MDT Friday, April 4, 2025
This forecast is for Friday, April 4, 2025:
If the trigger temperature of 45.7 F/7.6 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 7256 ft MSL (1976 ft AGL)
Forecast maximum temperature................... 38.0 F/3.8 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................. 5842 ft MSL (561 ft AGL)
Thermal soaring outlook for Saturday 04/05..... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT).........
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 14642 ft MSL (9362 ft AGL)
Wave soaring outlook for Saturday 04/05........ Poor
Remarks...
Sunrise/Sunset.................... 06:37:48 / 19:26:46 MDT
Total possible sunshine........... 12 hr 48 min 58 sec (768 min 58 sec)
Altitude of sun at 13:02:17 MDT... 56.24 degrees
Upper air data from numerical model forecast valid on 04/04/2025 at 0600 MDT
Freezing level.................. Entire airmass below 32 F / 0 C
Convective condensation level... 11680 ft MSL (6400 ft AGL)
Lifted condensation level....... 9310 ft MSL (4030 ft AGL)
Lifted index.................... +7.1
K index......................... +7.7
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 -54.2 -65.6 215 29 15 1.0 0.6 M M M M M
45000 -52.6 -62.7 235 40 20 1.0 0.6 M M M M M
40000 -52.1 -61.8 220 59 31 0.2 0.1 M M M M M
38000 -51.9 -61.4 215 68 35 1.0 0.5 M M M M M
36000 -51.3 -60.3 210 73 38 1.0 0.5 M M M M M
34000 -50.7 -59.3 205 79 41 1.0 0.5 M M M M M
32000 -49.4 -56.9 205 78 40 2.2 1.2 M M M M M
30000 -48.1 -54.6 205 76 39 2.4 1.3 M M M M M
29000 -46.9 -52.4 205 70 36 4.4 2.4 26.6 79.8 17.5 M M
28000 -45.6 -50.1 205 62 32 4.4 2.4 24.4 75.9 16.1 M M
27000 -44.3 -47.7 205 55 28 4.5 2.5 22.4 72.2 14.7 M M
26000 -42.5 -44.5 210 50 26 8.1 4.4 20.9 69.7 13.8 M M
25000 -40.1 -40.2 210 48 25 8.1 4.4 20.2 68.4 13.4 M M
24000 -37.7 -35.9 205 47 24 8.0 4.4 19.6 67.4 13.1 M M
23000 -35.5 -31.9 210 44 23 5.9 3.2 18.7 65.7 12.5 M M
22000 -33.7 -28.7 210 40 20 6.0 3.3 17.3 63.1 11.5 M M
21000 -31.9 -25.4 215 35 18 5.9 3.2 16.0 60.8 10.5 M M
20000 -30.0 -22.0 220 28 15 6.9 3.8 14.8 58.7 9.7 M M
19500 -28.9 -20.0 220 25 13 6.9 3.8 14.3 57.8 9.3 M M
19000 -27.9 -18.2 225 21 11 6.9 3.8 13.8 56.9 9.0 M M
18500 -26.8 -16.2 225 17 9 6.9 3.8 13.4 56.1 8.6 M M
18000 -25.7 -14.3 225 14 7 8.1 4.4 13.0 55.4 8.3 M M
17500 -24.5 -12.1 230 13 7 8.3 4.5 12.7 54.9 8.1 M M
17000 -23.2 -9.8 230 11 6 8.2 4.5 12.5 54.5 8.0 M M
16500 -22.0 -7.6 235 10 5 8.2 4.5 12.2 54.0 7.8 M M
16000 -20.8 -5.4 235 9 5 8.2 4.5 12.0 53.5 7.6 M M
15500 -19.1 -2.4 245 7 3 7.7 4.2 11.4 52.6 7.1 M M
15000 -18.0 -0.4 255 5 3 7.5 4.1 11.1 52.0 6.9 M M
14500 -16.9 1.6 270 4 2 7.3 4.0 10.7 51.2 6.5 M M
14000 -15.8 3.6 295 3 1 7.6 4.2 10.3 50.5 6.1 M M
13500 -14.6 5.7 315 3 1 8.7 4.8 10.0 50.1 5.9 M M
13000 -13.3 8.1 335 3 1 8.8 4.8 9.9 49.8 5.8 M M
12500 -11.9 10.6 335 3 2 9.5 5.2 9.8 49.6 5.7 M M
12000 -10.5 13.1 335 4 2 9.3 5.1 9.7 49.5 5.7 M M
11500 -9.2 15.4 330 5 3 8.6 4.7 9.6 49.3 5.6 M M
11000 -7.9 17.8 330 6 3 8.4 4.6 9.4 49.0 5.5 M M
10500 -6.7 19.9 330 7 4 7.6 4.2 9.1 48.4 5.2 M M
10250 -6.1 21.0 330 8 4 8.8 4.8 9.0 48.2 5.1 M M
10000 -5.5 22.1 330 8 4 4.5 2.5 8.8 47.9 5.0 M M
9750 -5.4 22.3 325 9 4 4.1 2.3 8.3 46.9 4.4 M M
9500 -4.8 23.4 325 9 5 8.0 4.4 8.1 46.5 4.2 M M
9250 -4.3 24.3 325 9 5 7.1 3.9 7.9 46.1 4.0 M M
9000 -3.8 25.2 325 9 5 5.1 2.8 7.6 45.7 3.8 M M
8750 -3.6 25.5 325 9 5 4.1 2.3 7.2 44.9 3.4 M M
8500 -3.2 26.2 325 9 5 5.9 3.2 6.8 44.3 3.0 M M
8250 -2.8 27.0 325 8 4 4.2 2.3 6.5 43.6 2.7 M M
8000 -2.6 27.3 325 8 4 1.8 1.0 5.9 42.7 2.1 M M
7750 -2.6 27.3 325 7 3 0.6 0.4 5.3 41.5 1.5 M M
7500 -2.6 27.3 325 6 3 0.2 0.1 4.5 40.2 0.7 M M
7250 -2.6 27.3 325 4 2 1.2 0.6 3.8 38.9 -0.0 161 0.8
7000 -2.5 27.5 325 4 2 1.9 1.0 3.2 37.8 -0.7 151 0.8
6750 -2.4 27.7 330 3 1 1.9 1.0 2.6 36.7 -1.3 141 0.7
6500 -2.2 28.0 340 3 1 3.4 1.9 2.1 35.7 -1.9 129 0.7
6250 -1.9 28.6 345 3 1 4.9 2.7 1.6 35.0 -2.3 113 0.6
6000 -1.6 29.1 350 3 1 4.4 2.4 1.3 34.3 -2.7 95 0.5
5750 -1.2 29.8 355 3 1 6.4 3.5 0.9 33.6 -3.1 77 0.4
5500 -0.6 30.9 360 2 1 10.9 6.0 0.8 33.5 -3.2 51 0.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/04/2025 at 0900 MDT | 04/04/2025 at 1200 MDT
|
CAPE... +4.4 LI... +1.4 | CAPE... +67.1 LI... +1.3
CINH... 0.0 K Index... +13.7 | CINH... -2.1 K Index... +10.9
|
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 -54.2 -65.6 225 28 15 1.5 0.8 | -53.7 -64.7 220 29 15 0.6 0.3
45000 -52.0 -61.6 220 29 15 1.5 0.8 | -52.8 -63.0 210 37 19 0.5 0.3
40000 -51.3 -60.3 215 51 26 0.4 0.2 | -50.8 -59.4 215 44 23 1.4 0.8
38000 -51.1 -60.0 210 60 31 0.1 0.0 | -50.2 -58.4 215 50 26 -0.5 -0.3
36000 -51.0 -59.8 205 71 37 0.1 0.0 | -50.5 -58.9 210 61 32 -0.6 -0.3
34000 -51.0 -59.8 205 84 43 0.1 0.1 | -50.9 -59.6 205 73 38 -0.8 -0.5
32000 -49.6 -57.3 205 85 44 2.4 1.3 | -50.0 -58.0 205 74 38 1.8 1.0
30000 -48.2 -54.8 200 85 44 2.7 1.5 | -48.9 -56.0 205 72 37 1.5 0.8
29000 -46.9 -52.4 205 77 40 4.5 2.5 | -47.6 -53.7 205 67 34 5.2 2.8
28000 -45.6 -50.1 205 68 35 4.5 2.5 | -46.1 -51.0 205 61 31 5.2 2.8
27000 -44.3 -47.7 205 59 30 4.5 2.5 | -44.5 -48.1 205 54 28 5.2 2.8
26000 -42.5 -44.5 205 52 27 7.6 4.2 | -42.0 -43.6 205 48 25 8.4 4.6
25000 -40.3 -40.5 205 49 25 7.6 4.1 | -39.5 -39.1 205 44 23 8.5 4.7
24000 -38.0 -36.4 210 45 23 7.6 4.1 | -36.9 -34.4 210 40 21 8.5 4.7
23000 -35.9 -32.6 210 41 21 6.4 3.5 | -34.6 -30.3 210 37 19 6.9 3.8
22000 -33.9 -29.0 210 36 19 6.4 3.5 | -32.6 -26.7 215 34 17 6.9 3.8
21000 -32.0 -25.6 215 31 16 6.5 3.6 | -30.5 -22.9 220 31 16 7.0 3.8
20000 -30.1 -22.2 220 26 13 6.1 3.3 | -28.9 -20.0 220 25 13 4.8 2.6
19500 -29.2 -20.6 220 23 12 6.1 3.3 | -28.2 -18.8 225 21 11 4.8 2.7
19000 -28.3 -18.9 220 20 10 6.1 3.3 | -27.5 -17.5 225 18 9 4.8 2.6
18500 -27.4 -17.3 225 17 9 5.9 3.2 | -26.8 -16.2 225 14 7 4.5 2.5
18000 -26.4 -15.5 225 15 8 8.1 4.4 | -25.8 -14.4 230 12 6 8.9 4.9
17500 -25.1 -13.2 225 13 7 8.3 4.5 | -24.5 -12.1 230 11 6 8.5 4.7
17000 -23.9 -11.0 220 12 6 7.9 4.3 | -23.3 -9.9 225 10 5 7.4 4.1
16500 -22.8 -9.0 220 9 5 7.4 4.1 | -22.3 -8.1 225 8 4 7.0 3.9
16000 -21.1 -6.0 215 6 3 7.1 3.9 | -21.2 -6.2 220 6 3 6.7 3.7
15500 -20.1 -4.2 205 5 2 7.1 3.9 | -20.3 -4.5 210 5 2 6.2 3.4
15000 -19.1 -2.4 195 3 2 7.6 4.2 | -19.4 -2.9 190 3 2 6.3 3.4
14500 -17.9 -0.2 185 2 1 8.1 4.4 | -18.4 -1.1 175 3 1 7.3 4.0
14000 -16.7 1.9 170 2 1 8.6 4.7 | -17.3 0.9 165 2 1 7.2 4.0
13500 -15.3 4.5 000 0 0 9.3 5.1 | -16.2 2.8 155 1 1 7.8 4.3
13000 -13.9 7.0 355 1 0 8.8 4.8 | -15.1 4.8 035 1 0 8.1 4.4
12500 -12.8 9.0 010 3 2 7.4 4.1 | -14.2 6.4 005 3 2 4.2 2.3
12000 -11.6 11.1 015 5 3 7.2 4.0 | -13.2 8.2 005 10 5 5.3 2.9
11500 -10.7 12.7 015 8 4 6.6 3.6 | -12.3 9.9 005 14 7 5.9 3.3
11000 -9.7 14.5 020 10 5 6.3 3.4 | -11.5 11.3 005 19 10 6.9 3.8
10500 -8.9 16.0 015 12 6 5.6 3.1 | -10.4 13.3 015 20 10 7.8 4.3
10250 -8.5 16.7 015 14 7 5.8 3.2 | -9.8 14.4 020 21 11 6.1 3.4
10000 -8.1 17.4 015 15 8 3.6 2.0 | -9.5 14.9 020 22 11 4.0 2.2
9750 -7.8 18.0 015 15 8 5.4 3.0 | -9.1 15.6 025 21 11 7.5 4.1
9500 -7.2 19.0 015 17 9 8.8 4.8 | -8.4 16.9 025 21 11 10.7 5.9
9250 -6.7 19.9 015 18 9 7.3 4.0 | -7.7 18.1 030 21 11 8.0 4.4
9000 -6.2 20.8 015 19 10 4.7 2.6 | -7.3 18.9 030 20 10 5.1 2.8
8750 -5.9 21.4 015 19 10 5.2 2.9 | -6.8 19.8 025 18 9 8.7 4.8
8500 -5.4 22.3 010 19 10 7.3 4.0 | -6.0 21.2 025 17 9 11.4 6.2
8250 -4.9 23.2 010 19 10 6.0 3.3 | -5.3 22.5 020 15 8 8.9 4.9
8000 -4.5 23.9 010 18 9 5.1 2.8 | -4.7 23.5 020 15 7 7.2 4.0
7750 -4.1 24.6 010 18 9 5.6 3.1 | -4.1 24.6 015 14 7 9.9 5.4
7500 -3.7 25.3 010 17 9 4.7 2.6 | -3.3 26.1 015 13 7 10.8 6.0
7250 -3.5 25.7 010 15 8 1.2 0.7 | -2.6 27.3 015 13 7 9.0 4.9
7000 -3.5 25.7 010 13 7 0.1 0.1 | -1.9 28.6 015 13 7 8.6 4.7
6750 -3.5 25.7 010 11 6 -0.5 -0.3 | -1.2 29.8 015 13 7 10.6 5.8
6500 -3.5 25.7 010 8 4 5.0 2.8 | -0.4 31.3 015 12 6 11.4 6.3
6250 -2.8 27.0 005 8 4 10.5 5.8 | 0.4 32.7 015 12 6 10.4 5.7
6000 -2.2 28.0 005 7 3 8.3 4.5 | 1.2 34.2 010 12 6 9.9 5.4
5750 -1.5 29.3 005 6 3 11.8 6.5 | 2.0 35.6 010 11 6 13.1 7.2
5500 -0.3 31.5 005 6 3 19.1 10.5 | 3.3 37.9 010 11 6 21.2 11.7
04/04/2025 at 1500 MDT | 04/04/2025 at 1800 MDT
|
CAPE... +1.7 LI... +3.2 | CAPE... +4.8 LI... +5.1
CINH... -0.1 K Index... +9.3 | CINH... -0.5 K Index... +10.6
|
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 -53.9 -65.0 230 28 14 0.9 0.5 | -54.2 -65.6 230 19 10 1.4 0.8
45000 -52.5 -62.5 220 38 20 0.9 0.5 | -52.1 -61.8 225 33 17 1.4 0.8
40000 -51.1 -60.0 210 43 22 0.9 0.5 | -51.3 -60.3 215 37 19 0.5 0.2
38000 -50.7 -59.3 210 47 24 0.3 0.2 | -51.0 -59.8 210 41 21 0.7 0.4
36000 -50.5 -58.9 210 57 30 0.3 0.2 | -50.6 -59.1 210 48 25 0.7 0.4
34000 -50.3 -58.5 210 68 35 0.1 0.1 | -50.2 -58.4 215 56 29 0.6 0.3
32000 -49.6 -57.3 210 69 36 1.4 0.8 | -49.5 -57.1 215 55 28 1.2 0.7
30000 -48.8 -55.8 210 70 36 1.1 0.6 | -48.8 -55.8 215 53 27 0.8 0.5
29000 -47.6 -53.7 210 63 33 4.9 2.7 | -47.8 -54.0 220 47 24 4.1 2.2
28000 -46.1 -51.0 210 55 28 4.8 2.7 | -46.3 -51.3 220 39 20 4.0 2.2
27000 -44.7 -48.5 210 47 24 4.9 2.7 | -45.1 -49.2 225 32 16 4.0 2.2
26000 -42.2 -44.0 215 39 20 8.1 4.5 | -43.1 -45.6 230 28 15 8.4 4.6
25000 -39.8 -39.6 215 36 19 8.2 4.5 | -40.6 -41.1 235 27 14 8.5 4.7
24000 -37.4 -35.3 220 33 17 8.2 4.5 | -38.0 -36.4 235 26 13 8.5 4.7
23000 -35.0 -31.0 220 31 16 7.5 4.1 | -35.6 -32.1 235 24 12 7.9 4.3
22000 -32.8 -27.0 225 28 14 7.5 4.1 | -33.2 -27.8 235 22 11 7.9 4.3
21000 -30.6 -23.1 225 26 13 7.5 4.1 | -30.9 -23.6 235 19 10 7.9 4.3
20000 -28.7 -19.7 225 22 11 5.8 3.2 | -28.9 -20.0 230 16 8 6.4 3.5
19500 -27.9 -18.2 225 20 10 5.8 3.2 | -27.9 -18.2 225 14 7 6.4 3.5
19000 -27.0 -16.6 220 18 9 5.8 3.2 | -27.0 -16.6 220 13 7 6.4 3.5
18500 -26.2 -15.2 215 16 8 5.6 3.1 | -26.0 -14.8 210 11 6 6.3 3.5
18000 -25.0 -13.0 215 14 7 9.2 5.1 | -25.0 -13.0 205 10 5 8.1 4.5
17500 -23.7 -10.7 210 13 6 8.9 4.9 | -23.8 -10.8 195 10 5 8.0 4.4
17000 -22.4 -8.3 210 11 6 8.7 4.8 | -22.6 -8.7 190 9 4 8.3 4.5
16500 -21.1 -6.0 215 10 5 8.6 4.7 | -21.3 -6.3 185 7 4 8.4 4.6
16000 -19.8 -3.6 220 8 4 7.9 4.4 | -20.1 -4.2 180 5 3 8.0 4.4
15500 -18.8 -1.8 220 6 3 6.6 3.6 | -19.0 -2.2 175 5 3 7.3 4.0
15000 -17.8 -0.0 220 4 2 6.5 3.5 | -17.9 -0.2 170 4 2 7.2 3.9
14500 -17.0 1.4 220 3 1 5.1 2.8 | -16.5 2.3 155 2 1 5.8 3.2
14000 -16.2 2.8 200 1 1 5.3 2.9 | -15.7 3.7 120 1 1 5.4 3.0
13500 -15.5 4.1 190 1 0 4.8 2.6 | -14.9 5.2 015 1 1 5.0 2.8
13000 -14.8 5.4 000 0 0 4.9 2.7 | -14.2 6.4 355 3 2 4.0 2.2
12500 -13.9 7.0 345 3 2 4.2 2.3 | -13.8 7.2 005 7 4 2.8 1.5
12000 -13.3 8.1 350 6 3 5.2 2.9 | -13.4 7.9 005 11 5 2.5 1.4
11500 -12.4 9.7 355 9 4 6.3 3.5 | -13.1 8.4 010 12 6 2.3 1.3
11000 -11.4 11.5 360 11 6 7.0 3.9 | -12.7 9.1 010 14 7 5.5 3.0
10500 -10.3 13.5 005 12 6 7.8 4.3 | -11.6 11.1 010 14 7 8.0 4.4
10250 -9.8 14.4 010 12 6 6.1 3.3 | -11.0 12.2 010 14 7 7.5 4.1
10000 -9.5 14.9 010 13 6 2.2 1.2 | -10.6 12.9 015 14 7 4.1 2.3
9750 -9.3 15.3 015 13 7 6.5 3.6 | -10.3 13.5 015 14 7 2.9 1.6
9500 -8.5 16.7 020 13 7 11.5 6.3 | -10.1 13.8 020 14 7 3.2 1.7
9250 -7.8 18.0 020 14 7 7.7 4.2 | -9.8 14.4 030 14 7 4.5 2.4
9000 -7.4 18.7 025 15 8 3.8 2.1 | -9.4 15.1 030 14 7 6.2 3.4
8750 -7.1 19.2 025 16 8 5.9 3.2 | -9.0 15.8 030 15 8 7.1 3.9
8500 -6.6 20.1 025 19 10 7.8 4.3 | -8.4 16.9 025 17 9 7.9 4.3
8250 -6.1 21.0 025 20 11 5.2 2.9 | -7.9 17.8 020 18 9 6.0 3.3
8000 -5.8 21.6 020 21 11 3.2 1.7 | -7.5 18.5 015 18 9 4.8 2.6
7750 -5.5 22.1 020 22 12 5.9 3.2 | -7.1 19.2 015 19 10 5.8 3.2
7500 -4.9 23.2 015 22 12 9.0 4.9 | -6.6 20.1 010 18 9 8.3 4.6
7250 -4.2 24.4 015 22 12 9.3 5.1 | -5.9 21.4 010 18 9 9.8 5.4
7000 -3.5 25.7 015 22 11 9.1 5.0 | -5.2 22.6 010 18 9 9.7 5.3
6750 -2.8 27.0 015 22 11 10.3 5.6 | -4.5 23.9 005 18 9 9.6 5.2
6500 -2.0 28.4 015 22 11 10.8 6.0 | -3.7 25.3 005 18 9 9.6 5.3
6250 -1.2 29.8 015 21 11 10.1 5.5 | -3.0 26.6 005 17 9 9.6 5.3
6000 -0.5 31.1 015 21 11 10.2 5.6 | -2.3 27.9 005 17 9 10.5 5.8
5750 0.3 32.5 015 20 10 12.3 6.7 | -1.4 29.5 005 16 8 12.5 6.8
5500 1.4 34.5 015 18 9 16.3 9.0 | -0.5 31.1 360 14 7 12.6 6.9
________________________________________________________________________________
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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