Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
250
UXUS97 KBOU 171229
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0629 MDT Saturday, May 17, 2025
This forecast is for Saturday, May 17, 2025:
If the trigger temperature of 64.0 F/17.8 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 632 ft/min (3.2 m/s)
Maximum height of thermals.................. 16695 ft MSL (11355 ft AGL)
Forecast maximum temperature................... 72.0 F/22.7 C
Time of trigger temperature.................... 1030 MDT
Time of overdevelopment........................ 1900 MDT
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................. 11199 ft MSL (5859 ft AGL)
Thermal soaring outlook for Sunday 05/18....... 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....................... 39598 ft MSL (34258 ft AGL)
Wave soaring outlook for Sunday 05/18.......... Poor
Remarks...
Sunrise/Sunset.................... 05:42:28 / 20:09:21 MDT
Total possible sunshine........... 14 hr 26 min 54 sec (866 min 54 sec)
Altitude of sun at 12:55:55 MDT... 69.73 degrees
Upper air data from numerical model forecast valid on 05/17/2025 at 0600 MDT
Freezing level.................. 11830 ft MSL (6490 ft AGL)
Convective condensation level... 14151 ft MSL (8811 ft AGL)
Lifted condensation level....... 14628 ft MSL (9288 ft AGL)
Lifted index.................... -1.4
K index......................... +21.4
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 -58.3 -72.9 245 40 20 -0.4 -0.2 M M M M M
45000 -58.9 -74.0 245 48 25 0.1 0.1 M M M M M
40000 -58.8 -73.8 240 68 35 0.0 0.0 M M M M M
38000 -56.7 -70.1 240 65 33 5.6 3.1 M M M M M
36000 -52.9 -63.2 240 55 28 5.6 3.1 M M M M M
34000 -49.0 -56.2 240 49 25 7.8 4.3 M M M M M
32000 -44.4 -47.9 245 47 24 7.7 4.2 M M M M M
30000 -39.7 -39.5 245 45 23 7.9 4.3 36.4 97.6 10.7 M M
29000 -37.3 -35.1 250 43 22 7.9 4.4 35.7 96.2 10.2 M M
28000 -34.9 -30.8 250 42 22 7.9 4.4 35.0 95.0 9.9 M M
27000 -32.7 -26.9 250 41 21 6.2 3.4 34.3 93.7 9.4 M M
26000 -30.8 -23.4 255 40 21 6.3 3.4 32.8 91.1 8.4 M M
25000 -28.9 -20.0 255 39 20 6.3 3.5 31.6 88.8 7.4 M M
24000 -27.1 -16.8 255 38 20 6.1 3.4 30.4 86.7 6.5 M M
23000 -25.3 -13.5 255 36 19 6.0 3.3 28.9 84.0 5.3 M M
22000 -23.5 -10.3 255 34 18 6.0 3.3 27.6 81.6 4.3 M M
21000 -21.7 -7.1 255 32 17 6.6 3.6 26.3 79.4 3.3 M M
20000 -19.2 -2.6 260 32 16 6.6 3.6 24.9 76.8 2.0 M M
19500 -18.2 -0.8 260 32 16 6.7 3.7 24.3 75.8 1.6 M M
19000 -17.3 0.9 265 31 16 6.8 3.7 23.9 74.9 1.1 M M
18500 -16.1 3.0 260 32 16 8.4 4.6 23.5 74.3 0.8 M M
18000 -14.9 5.2 260 32 16 8.3 4.5 23.3 73.9 0.6 M M
17500 -13.7 7.3 260 32 17 8.2 4.5 23.0 73.4 0.4 M M
17000 -12.4 9.7 260 32 16 8.3 4.5 22.7 72.9 0.1 M M
16500 -11.2 11.8 255 31 16 8.5 4.6 22.5 72.5 -0.1 1005 5.1
16000 -9.9 14.2 255 29 15 8.9 4.9 22.3 72.2 -0.3 951 4.8
15500 -8.6 16.5 255 27 14 8.9 4.9 22.2 71.9 -0.4 897 4.6
15000 -7.3 18.9 255 25 13 8.8 4.9 22.0 71.7 -0.6 843 4.3
14500 -6.0 21.2 250 23 12 9.0 4.9 21.9 71.4 -0.8 789 4.0
14000 -4.8 23.4 245 21 11 7.6 4.2 21.7 71.0 -1.0 737 3.7
13500 -3.6 25.5 240 20 10 7.6 4.2 21.3 70.3 -1.3 688 3.5
13000 -2.5 27.5 235 18 9 7.3 4.0 20.9 69.7 -1.7 641 3.3
12500 -1.5 29.3 225 17 9 7.2 4.0 20.5 68.9 -2.1 594 3.0
12000 -0.4 31.3 215 16 8 7.7 4.2 20.1 68.3 -2.5 547 2.8
11500 0.8 33.4 205 16 8 7.9 4.3 19.8 67.7 -2.8 497 2.5
11000 1.9 35.4 200 17 9 7.3 4.0 19.5 67.2 -3.1 447 2.3
10500 3.0 37.4 195 16 8 6.5 3.6 19.1 66.4 -3.6 401 2.0
10250 3.5 38.3 190 16 8 9.2 5.0 18.9 66.0 -3.8 378 1.9
10000 4.3 39.7 185 16 8 9.5 5.2 19.0 66.1 -3.7 347 1.8
9750 4.9 40.8 185 15 8 7.1 3.9 18.8 65.8 -3.9 323 1.6
9500 5.4 41.7 185 15 7 7.8 4.3 18.6 65.5 -4.1 299 1.5
9250 6.0 42.8 180 14 7 7.4 4.1 18.5 65.2 -4.3 275 1.4
9000 6.5 43.7 180 13 7 7.5 4.1 18.3 64.9 -4.5 251 1.3
8750 7.1 44.8 180 12 6 7.9 4.3 18.1 64.6 -4.7 226 1.2
8500 7.7 45.9 180 12 6 7.8 4.3 18.0 64.3 -4.8 202 1.0
8250 8.2 46.8 175 11 6 8.2 4.5 17.8 64.1 -5.0 177 0.9
8000 8.9 48.0 175 10 5 8.0 4.4 17.7 63.9 -5.1 151 0.8
7750 9.4 48.9 175 9 4 5.9 3.2 17.5 63.5 -5.3 128 0.7
7500 9.7 49.5 175 8 4 4.9 2.7 17.2 62.9 -5.7 110 0.6
7250 10.1 50.2 180 7 3 3.9 2.1 16.8 62.2 -6.1 92 0.5
7000 10.3 50.5 180 4 2 2.9 1.6 16.3 61.3 -6.6 78 0.4
6750 10.5 50.9 190 2 1 2.0 1.1 15.7 60.3 -7.2 65 0.3
6500 10.5 50.9 230 1 1 -1.5 -0.8 15.0 59.0 -7.9 57 0.3
6250 10.2 50.4 320 2 1 -4.2 -2.3 14.0 57.3 -9.0 58 0.3
6000 9.9 49.8 335 3 2 -4.9 -2.7 12.9 55.3 -10.1 62 0.3
5750 9.5 49.1 345 5 3 -3.7 -2.0 11.9 53.4 -11.2 66 0.3
5500 9.3 48.7 345 6 3 -0.4 -0.2 11.0 51.8 -12.2 65 0.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/17/2025 at 0900 MDT | 05/17/2025 at 1200 MDT
|
CAPE... 0.0 LI... -0.0 | CAPE... +127.4 LI... -1.2
CINH... 0.0 K Index... +19.8 | CINH... -35.2 K Index... +22.9
|
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 -56.5 -69.7 240 40 21 0.0 0.0 | -56.2 -69.2 235 39 20 1.0 0.6
45000 -56.5 -69.7 235 51 26 -1.5 -0.8 | -54.8 -66.6 235 49 25 -2.4 -1.3
40000 -59.2 -74.6 230 56 29 -1.6 -0.9 | -58.8 -73.8 235 45 23 -2.7 -1.5
38000 -57.3 -71.1 230 53 27 5.4 3.0 | -57.6 -71.7 235 43 22 4.6 2.5
36000 -54.1 -65.4 230 48 25 5.4 3.0 | -54.9 -66.8 235 40 21 4.6 2.5
34000 -50.3 -58.5 230 43 22 8.0 4.4 | -51.4 -60.5 240 38 20 7.9 4.4
32000 -45.5 -49.9 230 40 21 8.1 4.4 | -46.7 -52.1 240 37 19 7.9 4.4
30000 -40.7 -41.3 235 38 20 7.9 4.3 | -41.8 -43.2 240 37 19 8.5 4.7
29000 -38.4 -37.1 235 38 20 7.9 4.3 | -39.2 -38.6 240 37 19 8.5 4.7
28000 -35.4 -31.7 240 38 19 7.9 4.4 | -36.7 -34.1 240 37 19 8.5 4.7
27000 -33.1 -27.6 240 38 19 7.0 3.8 | -34.2 -29.6 245 37 19 7.4 4.0
26000 -31.0 -23.8 240 37 19 7.1 3.9 | -32.0 -25.6 245 37 19 7.3 4.0
25000 -28.9 -20.0 245 37 19 7.1 3.9 | -29.8 -21.6 245 37 19 7.3 4.0
24000 -26.9 -16.4 245 36 19 6.3 3.5 | -27.6 -17.7 245 37 19 7.1 3.9
23000 -25.0 -13.0 245 33 17 6.2 3.4 | -25.6 -14.1 245 35 18 6.9 3.8
22000 -23.2 -9.8 245 30 16 6.2 3.4 | -23.5 -10.3 245 33 17 6.9 3.8
21000 -21.3 -6.3 250 28 14 6.9 3.8 | -21.4 -6.5 245 31 16 7.7 4.2
20000 -19.3 -2.7 255 28 14 6.9 3.8 | -19.2 -2.6 245 28 15 7.8 4.3
19500 -18.2 -0.8 255 28 15 6.9 3.8 | -17.4 0.7 250 27 14 7.8 4.3
19000 -17.2 1.0 260 28 15 6.8 3.7 | -16.3 2.7 250 25 13 7.8 4.3
18500 -16.2 2.8 260 29 15 7.6 4.2 | -15.1 4.8 250 24 12 8.1 4.4
18000 -15.0 5.0 260 30 16 7.7 4.2 | -13.9 7.0 250 23 12 8.1 4.4
17500 -13.9 7.0 260 31 16 7.9 4.4 | -12.8 9.0 250 21 11 7.2 3.9
17000 -12.7 9.1 260 31 16 8.4 4.6 | -11.8 10.8 250 19 10 6.9 3.8
16500 -11.4 11.5 260 29 15 8.5 4.6 | -10.8 12.6 245 17 9 7.0 3.9
16000 -10.2 13.6 260 28 14 8.4 4.6 | -9.7 14.5 245 16 8 7.4 4.1
15500 -9.0 15.8 260 27 14 8.4 4.6 | -8.6 16.5 240 15 8 7.4 4.0
15000 -7.1 19.2 260 25 13 9.2 5.0 | -7.4 18.7 235 14 7 8.2 4.5
14500 -5.7 21.7 260 23 12 9.2 5.0 | -6.2 20.8 230 13 7 8.1 4.4
14000 -4.4 24.1 260 22 11 8.8 4.8 | -5.0 23.0 225 12 6 9.0 4.9
13500 -3.1 26.4 255 20 10 8.8 4.9 | -3.6 25.5 220 11 6 9.1 5.0
13000 -1.8 28.8 255 18 10 8.4 4.6 | -2.3 27.9 215 10 5 9.4 5.2
12500 -0.6 30.9 250 17 9 8.4 4.6 | -0.8 30.6 215 10 5 9.5 5.2
12000 0.6 33.1 245 16 8 7.6 4.2 | 0.6 33.1 210 9 5 9.3 5.1
11500 1.7 35.1 235 15 8 7.4 4.1 | 2.0 35.6 205 10 5 9.1 5.0
11000 2.8 37.0 230 14 7 6.3 3.5 | 3.4 38.1 200 10 5 8.0 4.4
10500 3.7 38.7 220 13 7 5.3 2.9 | 4.4 39.9 195 11 6 6.8 3.7
10250 4.1 39.4 215 13 7 8.6 4.7 | 5.0 41.0 190 11 6 9.0 5.0
10000 4.9 40.8 210 13 7 9.2 5.0 | 5.7 42.3 190 11 6 9.0 4.9
9750 5.4 41.7 210 13 7 6.2 3.4 | 6.2 43.2 185 11 5 6.5 3.6
9500 5.9 42.6 205 13 7 7.2 3.9 | 6.7 44.1 180 10 5 7.2 4.0
9250 6.4 43.5 200 13 7 6.2 3.4 | 7.2 45.0 175 10 5 6.9 3.8
9000 6.8 44.2 200 13 7 6.1 3.3 | 7.7 45.9 170 9 5 6.8 3.7
8750 7.3 45.1 195 13 6 6.8 3.7 | 8.2 46.8 165 8 4 7.0 3.8
8500 7.8 46.0 190 12 6 6.9 3.8 | 8.7 47.7 155 7 4 6.7 3.7
8250 8.3 46.9 190 12 6 6.3 3.5 | 9.2 48.6 145 7 3 7.8 4.3
8000 8.7 47.7 185 11 5 5.0 2.7 | 9.8 49.6 135 6 3 9.1 5.0
7750 9.0 48.2 185 9 5 3.5 1.9 | 10.4 50.7 125 5 3 8.7 4.8
7500 9.2 48.6 180 8 4 2.7 1.5 | 11.0 51.8 120 5 3 7.9 4.3
7250 9.4 48.9 180 6 3 1.0 0.6 | 11.7 53.1 115 5 3 10.1 5.6
7000 9.3 48.7 180 4 2 0.1 0.1 | 12.5 54.5 115 5 2 12.1 6.7
6750 9.3 48.7 190 2 1 -1.4 -0.8 | 13.4 56.1 115 4 2 9.5 5.2
6500 9.1 48.4 295 1 0 0.6 0.3 | 14.0 57.2 110 4 2 9.0 5.0
6250 9.4 48.9 330 2 1 5.6 3.0 | 14.8 58.6 110 4 2 11.1 6.1
6000 9.8 49.6 340 2 1 4.9 2.7 | 15.7 60.3 105 4 2 12.4 6.8
5750 10.1 50.2 345 3 2 8.2 4.5 | 16.5 61.7 105 4 2 9.6 5.3
5500 11.1 52.0 345 3 2 19.8 10.9 | 17.3 63.1 100 3 2 14.2 7.8
05/17/2025 at 1500 MDT | 05/17/2025 at 1800 MDT
|
CAPE... +158.9 LI... -1.2 | CAPE... +251.2 LI... -1.3
CINH... -142.2 K Index... +26.1 | CINH... -77.9 K Index... +26.3
|
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 -55.4 -67.7 240 40 21 1.5 0.8 | -55.6 -68.1 245 42 22 0.6 0.3
45000 -53.3 -63.9 245 48 25 -2.3 -1.3 | -54.9 -66.8 250 45 23 -2.1 -1.1
40000 -58.6 -73.5 245 44 23 -3.4 -1.9 | -58.2 -72.8 250 47 24 -2.2 -1.2
38000 -57.8 -72.0 245 41 21 4.1 2.3 | -57.3 -71.1 250 46 24 3.6 2.0
36000 -55.3 -67.5 250 38 20 4.1 2.3 | -55.2 -67.4 255 45 23 3.6 2.0
34000 -52.2 -62.0 255 36 18 7.8 4.3 | -52.1 -61.8 255 42 22 8.0 4.4
32000 -47.5 -53.5 260 34 17 7.9 4.3 | -47.3 -53.1 255 37 19 8.0 4.4
30000 -42.6 -44.7 265 31 16 8.9 4.9 | -42.2 -44.0 255 32 17 9.0 5.0
29000 -39.3 -38.7 265 29 15 8.9 4.9 | -39.5 -39.1 255 29 15 9.0 5.0
28000 -36.7 -34.1 265 27 14 8.9 4.9 | -36.8 -34.2 255 27 14 9.0 5.0
27000 -34.1 -29.4 260 25 13 8.1 4.4 | -34.2 -29.6 255 25 13 8.0 4.4
26000 -31.6 -24.9 260 26 13 8.2 4.5 | -31.8 -25.2 250 27 14 8.0 4.4
25000 -29.2 -20.6 255 27 14 8.2 4.5 | -29.4 -20.9 250 29 15 8.0 4.4
24000 -26.8 -16.2 250 28 14 6.8 3.8 | -27.0 -16.6 245 32 16 7.5 4.1
23000 -24.9 -12.8 245 30 16 6.5 3.5 | -24.9 -12.8 240 33 17 7.1 3.9
22000 -23.0 -9.4 240 34 17 6.5 3.5 | -22.8 -9.0 235 35 18 7.1 3.9
21000 -21.0 -5.8 235 36 19 8.0 4.4 | -20.6 -5.1 230 36 19 8.0 4.4
20000 -18.7 -1.7 225 36 19 7.9 4.3 | -18.2 -0.8 225 34 18 8.1 4.4
19500 -17.5 0.5 220 37 19 7.9 4.4 | -16.4 2.5 220 33 17 8.1 4.5
19000 -16.3 2.7 215 37 19 8.0 4.4 | -15.2 4.6 215 33 17 8.1 4.5
18500 -15.2 4.6 215 37 19 7.8 4.3 | -14.1 6.6 215 32 17 7.8 4.3
18000 -14.1 6.6 210 35 18 7.8 4.3 | -12.9 8.8 210 31 16 7.9 4.3
17500 -12.9 8.8 205 33 17 7.7 4.2 | -11.8 10.8 210 30 16 7.3 4.0
17000 -11.8 10.8 200 31 16 7.3 4.0 | -10.8 12.6 210 29 15 7.0 3.9
16500 -10.8 12.6 195 29 15 7.2 3.9 | -9.7 14.5 205 27 14 7.2 3.9
16000 -9.6 14.7 190 27 14 8.9 4.9 | -8.6 16.5 205 26 13 7.8 4.3
15500 -7.7 18.1 180 25 13 8.9 4.9 | -7.5 18.5 205 24 13 7.6 4.2
15000 -6.3 20.7 180 24 12 8.9 4.9 | -6.2 20.8 200 23 12 9.1 5.0
14500 -5.0 23.0 175 23 12 8.9 4.9 | -4.9 23.2 200 22 12 8.9 4.9
14000 -3.7 25.3 170 22 11 9.4 5.1 | -3.6 25.5 195 22 11 9.2 5.0
13500 -2.3 27.9 170 20 11 9.4 5.2 | -2.2 28.0 195 20 11 9.2 5.1
13000 -0.9 30.4 165 19 10 9.1 5.0 | -0.9 30.4 190 19 10 8.7 4.8
12500 0.4 32.7 160 17 9 8.9 4.9 | 0.4 32.7 190 17 9 8.4 4.6
12000 1.7 35.1 155 16 8 8.4 4.6 | 1.6 34.9 185 15 8 7.3 4.0
11500 2.9 37.2 150 13 7 8.0 4.4 | 2.6 36.7 185 12 6 6.3 3.5
11000 4.0 39.2 140 11 6 7.0 3.8 | 3.5 38.3 180 8 4 6.0 3.3
10500 4.9 40.8 130 8 4 5.8 3.2 | 4.3 39.7 185 5 2 5.5 3.0
10250 5.4 41.7 125 7 4 7.9 4.3 | 4.7 40.5 185 3 2 6.9 3.8
10000 6.1 43.0 115 6 3 7.8 4.3 | 5.3 41.5 200 1 1 7.9 4.3
9750 6.5 43.7 100 4 2 5.6 3.1 | 5.9 42.6 295 1 0 7.1 3.9
9500 6.9 44.4 075 4 2 6.1 3.3 | 6.4 43.5 330 2 1 7.1 3.9
9250 7.4 45.3 045 4 2 6.2 3.4 | 7.0 44.6 340 3 2 7.9 4.3
9000 7.8 46.0 015 5 2 5.7 3.1 | 7.6 45.7 340 4 2 8.7 4.7
8750 8.2 46.8 360 6 3 4.9 2.7 | 8.2 46.8 345 5 3 8.3 4.6
8500 8.6 47.5 350 7 4 5.0 2.8 | 8.8 47.8 345 6 3 8.4 4.6
8250 8.9 48.0 345 8 4 5.3 2.9 | 9.5 49.1 350 7 4 8.5 4.7
8000 9.3 48.7 335 10 5 5.4 3.0 | 10.1 50.2 350 8 4 8.4 4.6
7750 9.7 49.5 330 12 6 4.6 2.5 | 10.7 51.3 355 8 4 7.7 4.2
7500 10.0 50.0 325 13 7 4.0 2.2 | 11.2 52.2 355 8 4 7.3 4.0
7250 10.3 50.5 320 14 7 4.9 2.7 | 11.7 53.1 360 8 4 8.1 4.5
7000 10.7 51.3 315 16 8 5.9 3.3 | 12.4 54.3 005 8 4 9.1 5.0
6750 11.1 52.0 315 17 9 5.5 3.0 | 13.0 55.4 005 8 4 7.7 4.2
6500 11.5 52.7 310 18 9 6.1 3.3 | 13.5 56.3 010 8 4 7.2 4.0
6250 12.0 53.6 310 18 9 9.2 5.0 | 14.1 57.4 010 8 4 10.1 5.5
6000 12.7 54.9 305 18 9 11.5 6.3 | 14.9 58.8 010 8 4 12.3 6.7
5750 13.5 56.3 305 18 9 9.1 5.0 | 15.8 60.4 010 8 4 9.5 5.2
5500 14.2 57.6 305 17 9 13.9 7.7 | 16.4 61.5 010 8 4 9.7 5.3
________________________________________________________________________________
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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