Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
698
UXUS97 KBOU 040113
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1912 MDT Thursday, April 3, 2025
This forecast is for Friday, April 4, 2025:
If the trigger temperature of 45.2 F/7.3 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 7897 ft MSL (2578 ft AGL)
Forecast maximum temperature................... 40.0 F/4.9 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................. 7028 ft MSL (1709 ft AGL)
Thermal soaring outlook for Saturday 04/05..... Good
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 PVA
Potential height of wave....................... 14427 ft MSL (9108 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.................. 5501 ft MSL (182 ft AGL)
Convective condensation level... 11711 ft MSL (6392 ft AGL)
Lifted condensation level....... 9618 ft MSL (4300 ft AGL)
Lifted index.................... +6.3
K index......................... +5.4
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 -54.0 -65.2 215 26 13 1.2 0.7 M M M M M
45000 -52.1 -61.8 230 35 18 1.2 0.7 M M M M M
40000 -52.4 -62.3 215 56 29 -0.4 -0.2 M M M M M
38000 -52.6 -62.7 215 65 34 0.1 0.1 M M M M M
36000 -52.5 -62.5 210 75 39 0.1 0.1 M M M M M
34000 -52.5 -62.5 205 85 44 0.1 0.1 M M M M M
32000 -50.4 -58.7 205 85 44 3.8 2.1 M M M M M
30000 -48.1 -54.6 200 83 43 3.9 2.2 M M M M M
29000 -46.8 -52.2 205 73 38 4.4 2.4 26.5 79.8 16.7 M M
28000 -45.5 -49.9 205 62 32 4.4 2.4 24.4 75.8 15.2 M M
27000 -44.2 -47.6 205 51 27 4.5 2.5 22.4 72.2 13.9 M M
26000 -42.4 -44.3 210 45 23 8.4 4.6 21.0 69.8 13.0 M M
25000 -39.9 -39.8 210 44 23 8.4 4.6 20.4 68.7 12.7 M M
24000 -37.4 -35.3 210 44 22 8.3 4.6 19.9 67.9 12.4 M M
23000 -35.1 -31.2 210 42 21 6.6 3.6 19.2 66.5 12.0 M M
22000 -33.1 -27.6 210 37 19 6.7 3.7 18.0 64.4 11.1 M M
21000 -31.1 -24.0 210 33 17 6.7 3.7 16.9 62.5 10.4 M M
20000 -29.0 -20.2 215 27 14 6.8 3.7 15.8 60.5 9.6 M M
19500 -28.0 -18.4 215 23 12 6.8 3.7 15.3 59.5 9.2 M M
19000 -27.0 -16.6 215 20 10 6.8 3.7 14.8 58.6 8.8 M M
18500 -26.0 -14.8 220 16 8 6.7 3.7 14.3 57.7 8.4 M M
18000 -25.0 -13.0 220 13 7 7.4 4.1 13.8 56.9 8.1 M M
17500 -23.3 -9.9 225 10 5 7.5 4.1 13.3 55.9 7.6 M M
17000 -22.1 -7.8 225 8 4 8.4 4.6 13.0 55.3 7.4 M M
16500 -20.8 -5.4 230 6 3 8.4 4.6 12.7 54.9 7.2 M M
16000 -19.6 -3.3 235 5 2 8.2 4.5 12.5 54.5 7.1 M M
15500 -18.4 -1.1 250 4 2 8.0 4.4 12.2 54.0 6.8 M M
15000 -17.2 1.0 265 4 2 7.9 4.4 11.9 53.5 6.6 M M
14500 -16.0 3.2 285 4 2 7.8 4.3 11.6 52.8 6.3 M M
14000 -14.9 5.2 300 5 3 7.9 4.3 11.3 52.3 6.1 M M
13500 -13.6 7.5 310 6 3 8.4 4.6 11.0 51.8 5.9 M M
13000 -12.4 9.7 320 7 4 8.4 4.6 10.8 51.4 5.7 M M
12500 -11.2 11.8 320 9 5 8.0 4.4 10.5 51.0 5.5 M M
12000 -10.0 14.0 325 11 5 8.0 4.4 10.3 50.5 5.2 M M
11500 -8.8 16.2 325 12 6 7.6 4.2 9.9 49.9 4.9 M M
11000 -7.7 18.1 325 13 7 7.5 4.1 9.6 49.3 4.6 M M
10500 -6.7 19.9 330 13 7 6.4 3.5 9.1 48.5 4.2 M M
10250 -6.2 20.8 330 14 7 7.3 4.0 8.9 48.0 4.0 M M
10000 -5.7 21.7 330 14 7 4.2 2.3 8.7 47.6 3.7 M M
9750 -5.5 22.1 335 14 7 4.0 2.2 8.1 46.6 3.2 M M
9500 -5.1 22.8 335 13 7 6.9 3.8 7.8 46.1 2.9 M M
9250 -4.6 23.7 335 13 7 6.5 3.5 7.6 45.6 2.7 M M
9000 -4.2 24.4 340 13 7 5.3 2.9 7.3 45.1 2.4 M M
8750 -3.9 25.0 340 13 6 3.8 2.1 6.9 44.3 2.0 M M
8500 -3.6 25.5 340 12 6 4.4 2.4 6.4 43.5 1.5 M M
8250 -3.3 26.1 345 12 6 3.4 1.8 6.0 42.8 1.1 M M
8000 -3.2 26.2 345 11 6 -0.1 -0.1 5.4 41.7 0.5 M M
7750 -3.4 25.9 345 11 6 -2.5 -1.4 4.5 40.1 -0.4 193 1.0
7500 -3.6 25.5 345 10 5 -4.0 -2.2 3.5 38.3 -1.4 193 1.0
7250 -3.9 25.0 350 10 5 0.0 0.0 2.5 36.5 -2.5 194 1.0
7000 -3.7 25.3 350 9 4 4.1 2.3 2.0 35.6 -3.0 180 0.9
6750 -3.5 25.7 355 8 4 3.7 2.0 1.5 34.8 -3.5 166 0.8
6500 -3.1 26.4 360 7 4 6.8 3.7 1.2 34.1 -3.8 147 0.7
6250 -2.5 27.5 360 7 3 10.2 5.6 1.1 34.0 -4.0 121 0.6
6000 -1.7 28.9 360 6 3 11.5 6.3 1.2 34.1 -3.9 90 0.5
5750 -0.9 30.4 360 6 3 9.7 5.3 1.3 34.3 -3.9 59 0.3
5500 -0.3 31.5 355 5 3 8.3 4.5 1.2 34.1 -4.0 33 0.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/04/2025 at 0900 MDT | 04/04/2025 at 1200 MDT
|
CAPE... +3.8 LI... +3.0 | CAPE... +55.5 LI... +2.1
CINH... 0.0 K Index... +9.4 | CINH... 0.0 K Index... +11.1
|
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 -54.6 -66.3 220 29 15 1.4 0.8 | -53.7 -64.7 225 26 13 0.9 0.5
45000 -52.5 -62.5 220 32 16 1.4 0.8 | -52.3 -62.1 210 32 17 1.0 0.5
40000 -51.0 -59.8 215 46 24 1.0 0.5 | -51.3 -60.3 215 42 21 0.6 0.3
38000 -50.6 -59.1 210 53 27 -0.2 -0.1 | -51.0 -59.8 215 47 24 0.1 0.0
36000 -50.7 -59.3 205 63 32 -0.2 -0.1 | -50.9 -59.6 210 59 30 0.1 0.0
34000 -50.8 -59.4 205 73 37 -0.2 -0.1 | -50.9 -59.6 205 72 37 0.2 0.1
32000 -49.7 -57.5 200 72 37 2.1 1.1 | -49.8 -57.6 200 71 37 2.0 1.1
30000 -48.5 -55.3 200 70 36 2.5 1.4 | -48.6 -55.5 200 69 36 2.3 1.3
29000 -47.3 -53.1 200 63 33 4.3 2.4 | -47.3 -53.1 195 66 34 4.6 2.5
28000 -46.0 -50.8 200 55 29 4.3 2.4 | -45.9 -50.6 195 63 32 4.6 2.5
27000 -44.7 -48.5 200 48 24 4.4 2.4 | -44.5 -48.1 195 60 31 4.8 2.6
26000 -42.8 -45.0 205 42 22 8.7 4.8 | -42.6 -44.7 195 54 28 8.4 4.6
25000 -40.2 -40.4 205 41 21 8.7 4.8 | -40.1 -40.2 200 46 23 8.4 4.6
24000 -37.5 -35.5 205 39 20 8.7 4.8 | -37.6 -35.7 210 37 19 8.4 4.6
23000 -35.1 -31.2 205 36 19 7.2 3.9 | -35.3 -31.5 215 31 16 7.1 3.9
22000 -33.0 -27.4 210 33 17 7.2 4.0 | -33.1 -27.6 215 28 14 7.1 3.9
21000 -30.8 -23.4 210 29 15 7.3 4.0 | -31.0 -23.8 220 24 12 7.3 4.0
20000 -28.8 -19.8 215 24 12 6.5 3.6 | -29.2 -20.6 215 18 9 5.6 3.1
19500 -27.8 -18.0 220 21 11 6.5 3.6 | -28.3 -18.9 210 14 7 5.6 3.1
19000 -26.8 -16.2 220 18 9 6.5 3.6 | -27.5 -17.5 205 10 5 5.6 3.1
18500 -25.9 -14.6 230 16 8 6.5 3.6 | -26.6 -15.9 195 7 4 5.5 3.0
18000 -24.9 -12.8 230 13 7 7.0 3.8 | -25.0 -13.0 170 5 2 8.3 4.5
17500 -23.8 -10.8 230 10 5 7.0 3.9 | -23.8 -10.8 155 4 2 8.3 4.6
17000 -22.7 -8.9 230 8 4 7.2 3.9 | -22.7 -8.9 145 5 2 7.2 3.9
16500 -21.1 -6.0 230 5 3 7.4 4.1 | -21.6 -6.9 135 5 3 7.2 4.0
16000 -20.0 -4.0 225 4 2 7.4 4.0 | -20.5 -4.9 125 6 3 7.3 4.0
15500 -18.9 -2.0 235 3 2 7.3 4.0 | -19.4 -2.9 125 5 3 7.3 4.0
15000 -17.8 -0.0 250 2 1 7.4 4.1 | -18.3 -0.9 115 5 2 6.9 3.8
14500 -16.7 1.9 285 2 1 7.6 4.2 | -17.4 0.7 095 4 2 6.3 3.5
14000 -15.5 4.1 310 3 2 7.5 4.1 | -16.4 2.5 065 3 2 5.5 3.0
13500 -14.5 5.9 330 4 2 7.3 4.0 | -15.9 3.4 030 5 2 3.6 2.0
13000 -13.4 7.9 340 6 3 6.9 3.8 | -15.4 4.3 015 7 4 4.2 2.3
12500 -12.6 9.3 355 7 4 5.1 2.8 | -14.6 5.7 010 10 5 5.9 3.2
12000 -11.8 10.8 360 8 4 5.3 2.9 | -13.7 7.3 010 14 7 6.2 3.4
11500 -11.1 12.0 005 10 5 5.3 2.9 | -12.7 9.1 015 16 8 7.4 4.1
11000 -10.3 13.5 005 13 7 5.3 2.9 | -11.6 11.1 020 17 9 7.4 4.0
10500 -9.6 14.7 005 15 8 5.1 2.8 | -10.5 13.1 025 18 10 7.3 4.0
10250 -9.2 15.4 005 17 9 5.6 3.1 | -10.0 14.0 025 19 10 7.5 4.1
10000 -8.8 16.2 005 18 9 3.8 2.1 | -9.5 14.9 030 20 10 3.9 2.1
9750 -8.5 16.7 005 18 9 6.6 3.6 | -9.3 15.3 030 20 10 5.7 3.1
9500 -7.8 18.0 005 20 10 10.6 5.8 | -8.6 16.5 030 21 11 10.1 5.6
9250 -7.1 19.2 005 21 11 9.3 5.1 | -8.0 17.6 035 21 11 8.3 4.6
9000 -6.5 20.3 005 22 11 6.9 3.8 | -7.4 18.7 035 21 11 6.3 3.5
8750 -6.0 21.2 005 23 12 6.4 3.5 | -7.0 19.4 030 21 11 6.8 3.7
8500 -5.4 22.3 005 23 12 8.0 4.4 | -6.4 20.5 030 20 10 8.1 4.5
8250 -4.9 23.2 005 24 12 7.2 3.9 | -5.8 21.6 025 19 10 7.9 4.3
8000 -4.4 24.1 360 23 12 7.3 4.0 | -5.2 22.6 020 17 9 8.3 4.6
7750 -3.8 25.2 360 21 11 5.4 3.0 | -4.7 23.5 020 16 8 7.9 4.3
7500 -3.6 25.5 360 19 10 2.9 1.6 | -4.1 24.6 015 15 8 8.1 4.4
7250 -3.4 25.9 355 16 8 1.0 0.6 | -3.5 25.7 015 14 7 9.1 5.0
7000 -3.5 25.7 350 12 6 -0.7 -0.4 | -2.8 27.0 015 14 7 9.7 5.3
6750 -3.5 25.7 340 7 4 1.0 0.6 | -2.1 28.2 015 13 7 8.5 4.7
6500 -3.3 26.1 315 5 2 7.3 4.0 | -1.4 29.5 010 13 7 9.4 5.2
6250 -2.5 27.5 315 5 2 11.0 6.0 | -0.6 30.9 010 12 6 11.2 6.1
6000 -1.8 28.8 310 4 2 9.6 5.3 | 0.2 32.4 010 12 6 10.5 5.7
5750 -1.0 30.2 310 4 2 11.8 6.5 | 1.0 33.8 010 11 6 11.5 6.3
5500 0.1 32.2 305 4 2 17.2 9.4 | 1.9 35.4 010 11 5 14.5 8.0
04/04/2025 at 1500 MDT | 04/04/2025 at 1800 MDT
|
CAPE... +40.2 LI... +3.4 | CAPE... +15.6 LI... +5.7
CINH... -0.9 K Index... +10.8 | CINH... 0.0 K Index... +10.2
|
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 -53.5 -64.3 225 21 11 1.2 0.7 | -53.9 -65.0 220 18 9 1.6 0.9
45000 -51.7 -61.1 215 35 18 1.2 0.7 | -51.6 -60.9 225 30 15 1.6 0.9
40000 -51.5 -60.7 215 43 22 0.0 0.0 | -50.8 -59.4 215 36 18 0.4 0.2
38000 -51.4 -60.5 210 47 24 0.9 0.5 | -50.6 -59.1 215 38 20 0.0 0.0
36000 -50.8 -59.4 210 55 28 0.8 0.5 | -50.6 -59.1 215 42 22 0.0 0.0
34000 -50.3 -58.5 210 62 32 0.8 0.5 | -50.6 -59.1 220 46 24 0.0 0.0
32000 -49.6 -57.3 210 58 30 1.1 0.6 | -50.6 -59.1 220 41 21 -0.1 -0.0
30000 -49.0 -56.2 210 53 27 1.4 0.8 | -50.7 -59.3 225 36 18 -0.8 -0.4
29000 -47.9 -54.2 210 46 24 4.0 2.2 | -49.5 -57.1 230 32 17 5.5 3.0
28000 -46.7 -52.1 210 39 20 4.0 2.2 | -47.5 -53.5 230 28 14 5.4 3.0
27000 -45.5 -49.9 215 31 16 4.2 2.3 | -45.9 -50.6 235 24 12 5.3 2.9
26000 -43.6 -46.5 215 27 14 9.2 5.1 | -43.5 -46.3 235 22 12 9.2 5.0
25000 -40.8 -41.4 220 26 13 9.3 5.1 | -40.8 -41.4 235 23 12 9.2 5.1
24000 -38.0 -36.4 220 25 13 9.2 5.1 | -38.0 -36.4 230 23 12 9.3 5.1
23000 -35.4 -31.7 220 23 12 7.8 4.3 | -35.4 -31.7 230 22 11 8.4 4.6
22000 -33.1 -27.6 220 22 11 7.9 4.3 | -32.9 -27.2 230 20 10 8.3 4.6
21000 -30.7 -23.3 220 20 10 8.0 4.4 | -30.4 -22.7 230 19 10 8.3 4.6
20000 -28.7 -19.7 215 16 8 6.1 3.3 | -28.2 -18.8 230 16 8 7.3 4.0
19500 -27.8 -18.0 210 14 7 6.1 3.3 | -27.1 -16.8 225 15 8 7.3 4.0
19000 -26.9 -16.4 200 12 6 6.1 3.3 | -26.0 -14.8 220 14 7 7.3 4.0
18500 -25.6 -14.1 185 10 5 6.6 3.6 | -25.0 -13.0 220 12 6 7.3 4.0
18000 -24.4 -11.9 170 10 5 8.1 4.4 | -23.9 -11.0 215 12 6 7.3 4.0
17500 -23.2 -9.8 160 11 5 8.0 4.4 | -22.8 -9.0 210 13 6 7.3 4.0
17000 -22.0 -7.6 155 11 5 7.9 4.3 | -21.7 -7.1 205 13 7 7.8 4.3
16500 -20.8 -5.4 155 10 5 7.9 4.3 | -20.5 -4.9 200 13 7 8.0 4.4
16000 -19.7 -3.5 155 9 5 7.5 4.1 | -19.3 -2.7 195 13 7 8.0 4.4
15500 -18.6 -1.5 150 8 4 7.2 4.0 | -18.1 -0.6 200 12 6 7.9 4.3
15000 -17.5 0.5 140 8 4 6.0 3.3 | -17.0 1.4 200 10 5 7.7 4.2
14500 -16.8 1.8 135 6 3 4.6 2.5 | -16.1 3.0 200 7 4 5.1 2.8
14000 -16.2 2.8 130 5 3 3.9 2.2 | -14.9 5.2 190 2 1 2.4 1.3
13500 -15.8 3.6 100 3 2 2.6 1.4 | -15.0 5.0 010 2 1 0.0 0.0
13000 -15.4 4.3 045 3 2 3.2 1.8 | -15.0 5.0 010 6 3 1.1 0.6
12500 -14.8 5.4 015 6 3 5.1 2.8 | -14.7 5.5 010 10 5 2.8 1.5
12000 -14.0 6.8 360 10 5 5.8 3.2 | -14.3 6.3 010 14 7 4.4 2.4
11500 -12.9 8.8 005 11 6 7.9 4.4 | -13.4 7.9 010 14 7 6.2 3.4
11000 -11.8 10.8 005 12 6 7.7 4.2 | -12.5 9.5 010 14 7 7.6 4.2
10500 -10.7 12.7 020 13 7 7.3 4.0 | -11.2 11.8 015 14 7 8.8 4.8
10250 -10.2 13.6 025 13 7 7.4 4.1 | -10.6 12.9 015 13 7 7.8 4.3
10000 -9.7 14.5 030 14 7 4.9 2.7 | -10.2 13.6 015 13 7 2.8 1.6
9750 -9.3 15.3 030 14 7 7.0 3.8 | -10.1 13.8 015 14 7 1.8 1.0
9500 -8.6 16.5 035 15 8 10.9 6.0 | -9.8 14.4 025 16 8 3.5 1.9
9250 -7.9 17.8 035 16 8 8.5 4.7 | -9.6 14.7 025 18 9 3.3 1.8
9000 -7.4 18.7 035 17 9 4.3 2.3 | -9.3 15.3 030 20 10 2.7 1.5
8750 -7.2 19.0 035 20 10 4.3 2.3 | -9.1 15.6 025 21 11 5.6 3.1
8500 -6.8 19.8 030 22 11 5.9 3.3 | -8.5 16.7 025 22 11 8.6 4.7
8250 -6.3 20.7 030 25 13 6.1 3.3 | -7.9 17.8 020 22 11 7.8 4.3
8000 -5.9 21.4 025 25 13 6.7 3.7 | -7.3 18.9 020 21 11 8.3 4.6
7750 -5.4 22.3 020 25 13 7.1 3.9 | -6.8 19.8 015 20 10 7.3 4.0
7500 -4.8 23.4 015 25 13 8.0 4.4 | -6.3 20.7 010 19 10 7.1 3.9
7250 -4.2 24.4 015 24 12 8.5 4.7 | -5.7 21.7 010 19 10 8.3 4.5
7000 -3.6 25.5 010 24 12 8.7 4.8 | -5.1 22.8 010 19 10 7.9 4.3
6750 -3.0 26.6 010 23 12 8.6 4.7 | -4.5 23.9 010 18 9 9.2 5.0
6500 -2.3 27.9 010 22 12 9.3 5.1 | -3.7 25.3 010 18 9 10.0 5.5
6250 -1.6 29.1 010 22 11 10.0 5.5 | -3.0 26.6 010 17 9 9.2 5.1
6000 -0.8 30.6 005 21 11 9.0 4.9 | -2.3 27.9 005 17 9 9.6 5.2
5750 -0.1 31.8 005 21 11 12.3 6.8 | -1.6 29.1 005 16 8 11.6 6.4
5500 1.1 34.0 005 18 9 19.6 10.7 | -0.6 30.9 005 14 7 14.7 8.1
________________________________________________________________________________
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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