Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
905
UXUS97 KBOU 200021
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1720 MST Wednesday, November 19, 2025
This forecast is for Thursday, November 20, 2025:
If the trigger temperature of 60.0 F/15.5 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 6916 ft MSL (1618 ft AGL)
Forecast maximum temperature................... 54.0 F/12.7 C
Time of trigger temperature.................... None
Time of overdevelopment........................ 1000 MST
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................. 5893 ft MSL (596 ft AGL)
Thermal soaring outlook for Friday 11/21....... Poor
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 PVA
Potential height of wave....................... 22759 ft MSL (17461 ft AGL)
Wave soaring outlook for Friday 11/21.......... Poor
Remarks...
Sunrise/Sunset.................... 06:50:24 / 16:40:00 MST
Total possible sunshine........... 9 hr 49 min 35 sec (589 min 35 sec)
Altitude of sun at 11:45:12 MST... 30.26 degrees
Upper air data from numerical model forecast valid on 11/20/2025 at 0500 MST
Freezing level.................. 10947 ft MSL (5649 ft AGL)
Convective condensation level... 13639 ft MSL (8341 ft AGL)
Lifted condensation level....... 11195 ft MSL (5898 ft AGL)
Lifted index.................... +3.0
K index......................... +23.6
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 -58.9 -74.0 250 25 13 2.5 1.4 M M M M M
45000 -55.1 -67.2 245 30 15 1.3 0.7 M M M M M
40000 -52.9 -63.2 235 42 22 1.5 0.8 M M M M M
38000 -52.5 -62.5 230 51 26 0.1 0.1 M M M M M
36000 -52.4 -62.3 225 65 33 0.1 0.1 M M M M M
34000 -51.8 -61.2 220 76 39 6.1 3.3 M M M M M
32000 -48.5 -55.3 215 77 40 5.5 3.0 M M M M M
30000 -44.2 -47.6 210 75 39 9.0 4.9 31.2 88.1 14.3 M M
29000 -41.5 -42.7 210 69 35 9.0 4.9 30.8 87.5 14.2 M M
28000 -38.8 -37.8 215 63 32 9.0 5.0 30.6 87.0 14.1 M M
27000 -36.2 -33.2 220 56 29 6.5 3.6 30.3 86.5 14.1 M M
26000 -34.5 -30.1 225 46 24 5.6 3.0 28.6 83.4 12.9 M M
25000 -32.9 -27.2 235 36 19 5.6 3.1 27.0 80.6 11.8 M M
24000 -31.2 -24.2 250 28 14 7.1 3.9 25.6 78.0 10.7 M M
23000 -28.5 -19.3 240 23 12 9.2 5.0 25.2 77.4 10.6 M M
22000 -25.8 -14.4 225 20 10 9.2 5.0 25.0 77.0 10.5 M M
21000 -23.2 -9.8 210 19 10 7.4 4.1 24.8 76.6 10.4 M M
20000 -21.0 -5.8 210 18 9 7.2 3.9 23.8 74.8 9.7 M M
19500 -20.0 -4.0 210 18 9 7.2 4.0 23.4 74.0 9.3 M M
19000 -18.9 -2.0 215 18 9 7.2 4.0 22.9 73.3 9.0 M M
18500 -17.9 -0.2 215 18 9 7.3 4.0 22.5 72.6 8.7 M M
18000 -16.8 1.8 215 18 9 7.3 4.0 22.1 71.8 8.3 M M
17500 -15.7 3.7 215 18 9 7.3 4.0 21.7 71.1 8.0 M M
17000 -14.6 5.7 210 18 9 7.2 4.0 21.3 70.3 7.7 M M
16500 -13.6 7.5 210 18 9 7.2 3.9 20.8 69.5 7.3 M M
16000 -12.5 9.5 210 17 9 7.7 4.2 20.4 68.8 7.0 M M
15500 -10.8 12.6 210 17 9 7.7 4.2 19.9 67.9 6.5 M M
15000 -9.6 14.7 205 17 9 8.4 4.6 19.7 67.4 6.3 M M
14500 -8.4 16.9 205 17 9 8.3 4.6 19.4 67.0 6.1 M M
14000 -7.2 19.0 205 17 9 8.3 4.5 19.2 66.5 5.9 M M
13500 -6.0 21.2 205 18 9 8.3 4.5 18.9 66.1 5.7 M M
13000 -4.8 23.4 200 18 9 8.0 4.4 18.7 65.7 5.4 M M
12500 -3.6 25.5 200 18 9 8.0 4.4 18.4 65.1 5.2 M M
12000 -2.4 27.7 200 18 9 8.0 4.4 18.1 64.6 4.9 M M
11500 -1.2 29.8 195 17 9 8.1 4.4 17.8 64.1 4.7 M M
11000 -0.0 32.0 195 16 8 7.8 4.3 17.6 63.6 4.4 M M
10500 1.1 34.0 195 15 8 8.4 4.6 17.2 63.0 4.1 M M
10250 1.7 35.1 195 15 8 4.3 2.3 17.0 62.7 4.0 M M
10000 1.9 35.4 195 14 7 4.9 2.7 16.5 61.7 3.4 M M
9750 2.5 36.5 190 13 7 9.5 5.2 16.4 61.5 3.3 M M
9500 3.1 37.6 190 13 6 8.4 4.6 16.3 61.3 3.3 M M
9250 3.7 38.7 185 12 6 8.1 4.4 16.2 61.1 3.2 M M
9000 4.3 39.7 185 11 6 6.7 3.7 16.0 60.8 3.0 M M
8750 4.7 40.5 180 10 5 6.5 3.6 15.7 60.3 2.7 M M
8500 5.2 41.4 180 9 5 6.9 3.8 15.5 59.9 2.5 M M
8250 5.7 42.3 180 9 4 5.8 3.2 15.3 59.5 2.3 M M
8000 6.1 43.0 180 8 4 4.5 2.5 14.9 58.8 1.9 M M
7750 6.4 43.5 175 6 3 4.1 2.3 14.5 58.1 1.5 M M
7500 6.7 44.1 175 5 3 3.8 2.1 14.0 57.3 1.0 M M
7250 7.0 44.6 170 5 2 4.0 2.2 13.6 56.5 0.6 M M
7000 7.3 45.1 170 4 2 3.8 2.1 13.1 55.7 0.2 M M
6750 7.6 45.7 170 3 1 4.5 2.5 12.7 54.9 -0.2 83 0.4
6500 7.9 46.2 170 2 1 1.4 0.8 12.3 54.1 -0.7 67 0.3
6250 7.8 46.0 195 2 1 -2.8 -1.5 11.4 52.5 -1.5 63 0.3
6000 7.6 45.7 230 2 1 -2.3 -1.3 10.5 50.8 -2.5 62 0.3
5750 7.4 45.3 250 2 1 -4.0 -2.2 9.5 49.2 -3.4 60 0.3
5500 6.8 44.2 255 3 2 -12.2 -6.7 8.2 46.8 -4.7 70 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/20/2025 at 0800 MST | 11/20/2025 at 1100 MST
|
CAPE... 0.0 LI... +1.4 | CAPE... 0.0 LI... +1.5
CINH... 0.0 K Index... +20.7 | CINH... -0.1 K Index... +20.3
|
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 -58.7 -73.7 265 21 11 2.5 1.4 | -58.4 -73.1 275 19 10 3.2 1.8
45000 -54.9 -66.8 255 19 10 1.4 0.8 | -53.7 -64.7 250 16 8 0.9 0.5
40000 -52.6 -62.7 220 30 15 1.5 0.8 | -51.9 -61.4 215 31 16 1.2 0.7
38000 -52.1 -61.8 220 38 20 0.2 0.1 | -51.4 -60.5 210 37 19 0.5 0.3
36000 -51.9 -61.4 220 48 25 0.2 0.1 | -51.1 -60.0 210 41 21 0.5 0.3
34000 -51.5 -60.7 220 57 29 5.1 2.8 | -50.3 -58.5 210 45 23 3.7 2.0
32000 -48.4 -55.1 210 54 28 4.5 2.5 | -48.1 -54.6 200 46 24 3.7 2.1
30000 -44.9 -48.8 205 51 26 9.3 5.1 | -45.0 -49.0 195 45 23 9.2 5.0
29000 -42.1 -43.8 200 48 25 9.4 5.2 | -42.2 -44.0 195 43 22 9.4 5.2
28000 -39.3 -38.7 195 46 24 9.4 5.2 | -39.4 -38.9 195 41 21 9.4 5.2
27000 -36.5 -33.7 190 43 22 8.1 4.5 | -36.5 -33.7 190 39 20 9.0 4.9
26000 -34.3 -29.7 190 37 19 7.4 4.1 | -34.0 -29.2 190 36 19 8.6 4.7
25000 -32.1 -25.8 190 31 16 7.4 4.1 | -31.4 -24.5 190 34 18 8.7 4.7
24000 -29.9 -21.8 190 25 13 7.4 4.1 | -28.8 -19.8 190 32 16 8.4 4.6
23000 -27.7 -17.9 185 21 11 7.2 4.0 | -26.6 -15.9 185 28 14 7.3 4.0
22000 -25.6 -14.1 185 18 9 7.3 4.0 | -24.4 -11.9 175 23 12 7.3 4.0
21000 -23.4 -10.1 185 15 7 7.8 4.3 | -22.3 -8.1 165 20 10 7.1 3.9
20000 -21.1 -6.0 175 14 7 8.0 4.4 | -20.2 -4.4 160 19 10 6.9 3.8
19500 -19.9 -3.8 170 14 7 8.0 4.4 | -19.2 -2.6 160 18 9 6.9 3.8
19000 -18.7 -1.7 165 13 7 7.9 4.3 | -18.2 -0.8 155 18 9 6.9 3.8
18500 -17.5 0.5 160 13 7 7.2 4.0 | -17.2 1.0 155 17 9 6.6 3.6
18000 -16.6 2.1 160 13 7 6.5 3.6 | -15.8 3.6 145 17 9 6.0 3.3
17500 -15.6 3.9 165 13 7 6.4 3.5 | -14.9 5.2 145 17 9 6.2 3.4
17000 -14.2 6.4 165 12 6 6.3 3.4 | -14.0 6.8 135 17 9 6.4 3.5
16500 -13.3 8.1 170 12 6 6.3 3.5 | -13.1 8.4 130 17 9 6.4 3.5
16000 -12.3 9.9 165 12 6 6.8 3.7 | -12.1 10.2 130 17 9 6.6 3.6
15500 -11.3 11.7 165 12 6 6.7 3.7 | -11.1 12.0 125 17 9 6.6 3.6
15000 -10.3 13.5 165 12 6 7.3 4.0 | -10.2 13.6 125 17 9 6.5 3.6
14500 -9.3 15.3 160 12 6 7.3 4.0 | -9.2 15.4 125 17 9 6.5 3.6
14000 -8.2 17.2 160 12 6 7.6 4.2 | -8.3 17.1 125 16 8 7.0 3.8
13500 -7.1 19.2 160 13 7 7.7 4.2 | -7.2 19.0 125 16 8 7.3 4.0
13000 -5.9 21.4 160 14 7 7.8 4.3 | -6.1 21.0 130 16 8 7.4 4.1
12500 -4.8 23.4 160 15 7 7.9 4.3 | -5.1 22.8 135 15 8 7.6 4.1
12000 -3.6 25.5 160 15 8 8.2 4.5 | -4.0 24.8 135 15 8 7.7 4.2
11500 -2.3 27.9 160 15 8 8.4 4.6 | -2.8 27.0 140 14 7 7.7 4.2
11000 -1.1 30.0 160 15 8 8.2 4.5 | -1.6 29.1 145 13 7 7.2 4.0
10500 0.1 32.2 160 14 7 8.7 4.8 | -0.7 30.7 145 12 6 5.9 3.3
10250 0.6 33.1 160 13 7 4.6 2.5 | -0.2 31.6 145 12 6 8.5 4.7
10000 0.9 33.6 160 14 7 4.7 2.6 | 0.5 32.9 140 11 6 8.6 4.7
9750 1.4 34.5 160 12 6 8.8 4.8 | 1.0 33.8 140 10 5 5.6 3.1
9500 2.0 35.6 155 11 6 7.8 4.3 | 1.5 34.7 140 9 5 6.0 3.3
9250 2.6 36.7 155 9 5 7.6 4.2 | 1.9 35.4 135 8 4 5.8 3.2
9000 3.1 37.6 150 8 4 5.8 3.2 | 2.3 36.1 130 7 4 4.9 2.7
8750 3.5 38.3 150 7 4 4.8 2.6 | 2.6 36.7 125 6 3 4.3 2.3
8500 3.8 38.8 145 6 3 5.0 2.7 | 2.9 37.2 120 5 3 4.6 2.5
8250 4.2 39.6 140 4 2 4.6 2.5 | 3.3 37.9 115 5 2 4.3 2.4
8000 4.5 40.1 125 3 2 4.2 2.3 | 3.6 38.5 105 4 2 3.8 2.1
7750 4.8 40.6 110 2 1 3.6 1.9 | 3.9 39.0 090 3 2 4.1 2.2
7500 5.0 41.0 090 2 1 3.1 1.7 | 4.2 39.6 075 3 2 4.9 2.7
7250 5.2 41.4 055 1 1 2.3 1.2 | 4.5 40.1 065 3 2 3.4 1.9
7000 5.4 41.7 360 2 1 1.2 0.7 | 4.7 40.5 040 4 2 1.4 0.7
6750 5.5 41.9 340 3 2 2.6 1.4 | 4.9 40.8 020 4 2 5.0 2.7
6500 5.7 42.3 335 3 1 1.6 0.9 | 5.4 41.7 015 5 2 7.8 4.3
6250 5.6 42.1 330 3 2 -0.8 -0.5 | 5.9 42.6 010 5 3 7.4 4.0
6000 5.6 42.1 330 4 2 -1.1 -0.6 | 6.5 43.7 005 5 3 6.8 3.8
5750 5.5 41.9 325 5 3 -0.4 -0.2 | 7.0 44.6 360 5 3 9.7 5.3
5500 5.5 41.9 310 4 2 -0.5 -0.3 | 8.1 46.6 005 5 2 19.4 10.6
11/20/2025 at 1400 MST | 11/20/2025 at 1700 MST
|
CAPE... 0.0 LI... +0.8 | CAPE... +23.3 LI... +1.8
CINH... 0.0 K Index... +24.9 | CINH... -2.7 K Index... +22.4
|
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 -58.7 -73.7 275 18 9 4.1 2.3 | -59.0 -74.2 270 24 12 4.4 2.4
45000 -52.7 -62.9 255 22 11 1.5 0.8 | -52.5 -62.5 270 33 17 3.3 1.8
40000 -50.1 -58.2 215 31 16 1.8 1.0 | -47.1 -52.8 245 31 16 3.5 1.9
38000 -49.6 -57.3 210 34 17 -0.2 -0.1 | -46.8 -52.2 230 27 14 -1.5 -0.8
36000 -49.8 -57.6 210 35 18 -0.2 -0.1 | -47.7 -53.9 210 22 11 -1.5 -0.8
34000 -49.3 -56.7 200 38 20 3.9 2.2 | -48.2 -54.8 185 21 11 2.9 1.6
32000 -47.0 -52.6 185 47 24 3.9 2.2 | -46.7 -52.1 165 26 14 2.5 1.4
30000 -43.8 -46.8 175 55 28 9.3 5.1 | -44.6 -48.3 150 33 17 10.3 5.6
29000 -41.0 -41.8 175 52 27 9.5 5.2 | -41.7 -43.1 145 33 17 9.7 5.3
28000 -38.2 -36.8 175 50 26 9.5 5.2 | -38.8 -37.8 140 34 18 9.7 5.3
27000 -35.3 -31.5 175 48 24 8.6 4.7 | -35.9 -32.6 135 35 18 9.7 5.3
26000 -33.1 -27.6 175 40 21 7.3 4.0 | -32.8 -27.0 135 31 16 8.0 4.4
25000 -31.0 -23.8 180 32 17 7.3 4.0 | -30.4 -22.7 135 26 13 8.0 4.4
24000 -28.8 -19.8 185 25 13 7.4 4.0 | -28.0 -18.4 135 21 11 8.2 4.5
23000 -26.3 -15.3 185 25 13 8.7 4.8 | -25.5 -13.9 130 20 10 8.6 4.7
22000 -23.7 -10.7 185 25 13 8.7 4.8 | -23.0 -9.4 125 20 10 8.6 4.7
21000 -21.1 -6.0 180 26 13 7.5 4.1 | -20.5 -4.9 115 19 10 7.1 3.9
20000 -19.3 -2.7 180 23 12 6.1 3.3 | -18.6 -1.5 110 20 11 6.2 3.4
19500 -18.4 -1.1 175 22 11 6.1 3.4 | -17.7 0.1 110 21 11 6.2 3.4
19000 -17.5 0.5 175 20 10 6.2 3.4 | -16.8 1.8 110 22 11 6.2 3.4
18500 -16.6 2.1 170 19 10 6.3 3.5 | -15.9 3.4 105 23 12 6.3 3.4
18000 -15.6 3.9 165 18 9 7.0 3.8 | -15.0 5.0 105 23 12 6.4 3.5
17500 -14.6 5.7 160 18 9 7.0 3.8 | -14.0 6.8 105 23 12 6.4 3.5
17000 -13.6 7.5 155 17 9 6.4 3.5 | -13.1 8.4 100 23 12 5.9 3.2
16500 -12.7 9.1 145 17 9 6.3 3.5 | -12.3 9.9 100 23 12 5.9 3.2
16000 -11.7 10.9 135 18 9 5.6 3.1 | -11.4 11.5 100 23 12 6.1 3.3
15500 -10.7 12.7 120 20 10 4.6 2.5 | -10.5 13.1 100 23 12 6.2 3.4
15000 -10.0 14.0 110 22 11 4.8 2.6 | -9.6 14.7 100 23 12 6.2 3.4
14500 -9.3 15.3 105 23 12 4.9 2.7 | -8.8 16.2 095 23 12 5.6 3.1
14000 -8.6 16.5 100 24 12 5.9 3.3 | -7.9 17.8 090 23 12 5.7 3.1
13500 -7.6 18.3 100 23 12 7.2 3.9 | -7.1 19.2 090 24 12 5.5 3.0
13000 -6.5 20.3 100 22 11 7.5 4.1 | -6.3 20.7 085 25 13 5.5 3.0
12500 -5.4 22.3 100 21 11 8.2 4.5 | -5.5 22.1 085 25 13 5.6 3.1
12000 -4.2 24.4 100 20 10 7.9 4.3 | -4.7 23.5 085 25 13 5.6 3.1
11500 -3.2 26.2 105 19 10 6.8 3.7 | -3.5 25.7 085 25 13 5.5 3.0
11000 -2.2 28.0 105 17 9 6.6 3.6 | -2.7 27.1 085 24 13 5.0 2.8
10500 -1.3 29.7 105 16 8 5.6 3.1 | -2.1 28.2 085 24 12 3.9 2.1
10250 -0.9 30.4 105 15 8 6.5 3.5 | -1.8 28.8 085 23 12 4.2 2.3
10000 -0.3 31.5 105 14 7 8.0 4.4 | -1.5 29.3 090 23 12 6.0 3.3
9750 0.2 32.4 100 13 6 6.3 3.5 | -1.0 30.2 090 22 11 5.8 3.2
9500 0.6 33.1 095 12 6 4.6 2.5 | -0.7 30.7 090 21 11 4.8 2.7
9250 1.0 33.8 095 11 6 5.5 3.0 | -0.3 31.5 085 20 10 4.7 2.6
9000 1.3 34.3 090 10 5 3.5 1.9 | 0.0 32.0 085 19 10 6.4 3.5
8750 1.5 34.7 080 9 5 2.5 1.4 | 0.6 33.1 085 18 9 9.3 5.1
8500 1.8 35.2 065 9 4 3.4 1.9 | 1.3 34.3 085 18 9 9.9 5.4
8250 2.0 35.6 055 9 4 3.7 2.0 | 2.0 35.6 080 17 9 8.9 4.9
8000 2.4 36.3 045 9 5 6.4 3.5 | 2.5 36.5 080 17 9 5.9 3.2
7750 3.0 37.4 040 9 5 8.8 4.8 | 2.9 37.2 075 17 9 5.2 2.8
7500 3.7 38.7 040 9 5 8.9 4.9 | 3.3 37.9 075 17 9 6.3 3.5
7250 4.4 39.9 035 10 5 9.4 5.1 | 3.7 38.7 070 17 9 5.1 2.8
7000 5.1 41.2 035 10 5 10.1 5.5 | 4.0 39.2 065 17 9 3.9 2.1
6750 5.9 42.6 035 10 5 9.9 5.4 | 4.3 39.7 060 18 9 4.7 2.6
6500 6.6 43.9 035 10 5 9.8 5.4 | 4.7 40.5 055 18 9 5.4 3.0
6250 7.4 45.3 035 9 5 10.2 5.6 | 5.1 41.2 050 18 9 5.7 3.1
6000 8.1 46.6 035 9 5 10.5 5.8 | 5.5 41.9 045 16 8 5.4 3.0
5750 8.9 48.0 030 9 5 9.9 5.4 | 5.9 42.6 040 15 8 6.9 3.8
5500 9.7 49.5 030 9 4 12.0 6.6 | 6.5 43.7 030 12 6 11.3 6.2
________________________________________________________________________________
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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