Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
534
UXUS97 KGJT 171306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Saturday, May 17, 2025
This forecast is for Saturday, May 17, 2025:
If the trigger temperature of 57.7 F/14.3 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1584 ft/min (8.0 m/s)
Maximum height of thermals.................. 24799 ft MSL (19188 ft AGL)
Forecast maximum temperature................... 79.0 F/26.6 C
Time of trigger temperature.................... 0630 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast thin middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 20760 ft MSL (15150 ft AGL)
Thermal soaring outlook for Sunday 05/18....... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 05:58:47 / 20:22:20 MDT
Total possible sunshine........... 14 hr 23 min 33 sec (863 min 33 sec)
Altitude of sun at 13:10:34 MDT... 70.27 degrees
Upper air data from rawinsonde observation taken on 05/17/2025 at 0600 MDT
Freezing level.................. 10528 ft MSL (4917 ft AGL)
Convective condensation level... 14715 ft MSL (9104 ft AGL)
Lifted condensation level....... 18269 ft MSL (12659 ft AGL)
Lifted index.................... -5.0
K index......................... +20.3
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 -55.7 -68.3 240 32 17 1.3 0.7 M M M M M
45000 -53.7 -64.7 230 34 18 1.2 0.7 M M M M M
40000 -51.9 -61.4 225 45 23 1.2 0.7 M M M M M
38000 -51.2 -60.2 220 51 26 1.0 0.6 M M M M M
36000 -50.6 -59.1 215 58 30 1.0 0.6 M M M M M
34000 -49.9 -57.8 210 66 34 3.2 1.8 M M M M M
32000 -47.0 -52.6 210 62 32 4.3 2.4 M M M M M
30000 -44.1 -47.4 205 59 30 7.7 4.2 30.6 87.1 3.4 M M
29000 -41.9 -43.4 210 57 30 7.5 4.1 29.6 85.3 2.7 M M
28000 -39.7 -39.5 210 56 29 7.5 4.1 28.7 83.7 2.0 M M
27000 -37.5 -35.5 210 54 28 7.5 4.1 28.0 82.4 1.4 M M
26000 -35.2 -31.4 210 51 26 7.7 4.2 27.1 80.8 0.8 M M
25000 -32.8 -27.0 210 47 24 7.8 4.3 26.3 79.4 0.1 M M
24000 -30.5 -22.9 210 43 22 7.8 4.3 25.7 78.2 -0.4 1708 8.7
23000 -28.3 -18.9 205 42 21 7.2 4.0 24.8 76.6 -1.2 1613 8.2
22000 -26.2 -15.2 205 42 21 7.3 4.0 23.9 74.9 -2.0 1519 7.7
21000 -24.0 -11.2 205 42 21 7.3 4.0 23.1 73.5 -2.7 1425 7.2
20000 -21.9 -7.4 200 40 21 7.3 4.0 22.1 71.9 -3.6 1331 6.8
19500 -20.8 -5.4 200 39 20 7.3 4.0 21.7 71.1 -4.0 1284 6.5
19000 -19.2 -2.6 200 38 19 7.3 4.0 21.1 70.0 -4.5 1213 6.2
18500 -18.1 -0.6 200 37 19 7.2 4.0 20.8 69.4 -4.9 1165 5.9
18000 -17.0 1.4 195 36 18 7.1 3.9 20.3 68.5 -5.4 1119 5.7
17500 -16.0 3.2 195 35 18 7.1 3.9 19.8 67.7 -5.8 1072 5.4
17000 -14.9 5.2 195 34 18 7.8 4.3 19.5 67.0 -6.2 1025 5.2
16500 -13.7 7.3 195 33 17 7.7 4.2 19.1 66.4 -6.5 976 5.0
16000 -12.6 9.3 195 32 17 7.4 4.1 18.8 65.8 -6.9 927 4.7
15500 -11.5 11.3 195 31 16 7.4 4.0 18.3 65.0 -7.3 880 4.5
15000 -10.4 13.3 195 30 15 7.3 4.0 18.0 64.3 -7.7 832 4.2
14500 -9.4 15.1 195 28 14 7.2 3.9 17.5 63.5 -8.2 786 4.0
14000 -8.3 17.1 195 27 14 7.2 4.0 17.1 62.8 -8.6 740 3.8
13500 -7.2 19.0 195 25 13 7.6 4.2 16.7 62.1 -9.1 693 3.5
13000 -6.1 21.0 200 23 12 7.6 4.2 16.4 61.5 -9.5 645 3.3
12500 -5.0 23.0 200 22 11 8.3 4.5 16.1 61.0 -9.8 595 3.0
12000 -3.7 25.3 200 22 11 8.2 4.5 15.8 60.5 -10.1 543 2.8
11500 -2.5 27.5 205 22 11 8.7 4.8 15.6 60.1 -10.4 491 2.5
11000 -1.2 29.8 205 22 12 8.7 4.8 15.4 59.8 -10.6 438 2.2
10500 0.0 32.0 210 23 12 8.1 4.4 15.2 59.4 -10.9 387 2.0
10250 0.6 33.1 210 23 12 8.4 4.6 15.1 59.2 -11.0 361 1.8
10000 1.2 34.2 210 23 12 8.5 4.6 15.0 59.0 -11.2 335 1.7
9750 1.9 35.4 210 23 12 8.8 4.8 14.9 58.9 -11.3 308 1.6
9500 2.6 36.7 210 23 12 9.3 5.1 14.9 58.8 -11.4 281 1.4
9250 3.2 37.8 210 23 12 7.7 4.2 14.8 58.6 -11.5 253 1.3
9000 3.7 38.7 210 23 12 6.8 3.7 14.6 58.2 -11.7 231 1.2
8750 4.3 39.7 210 23 12 8.5 4.7 14.4 57.9 -11.9 206 1.0
8500 5.0 41.0 205 23 12 9.5 5.2 14.4 57.8 -12.0 178 0.9
8250 5.7 42.3 205 23 12 7.9 4.4 14.3 57.7 -12.1 151 0.8
8000 6.2 43.2 205 23 12 6.8 3.7 14.1 57.4 -12.3 128 0.6
7750 6.7 44.1 205 22 11 8.0 4.4 13.9 57.0 -12.5 104 0.5
7500 7.4 45.3 205 22 11 8.3 4.5 13.8 56.8 -12.6 78 0.4
7250 8.0 46.4 200 21 11 8.6 4.7 13.7 56.6 -12.8 52 0.3
7000 8.6 47.5 200 20 10 7.8 4.3 13.6 56.5 -12.9 25 0.1
6750 9.1 48.4 200 19 10 6.1 3.3 13.4 56.0 -13.2 2 0.0
6500 9.6 49.3 195 18 9 8.2 4.5 13.1 55.6 -13.4 M M
6250 10.1 50.2 190 17 9 1.3 0.7 12.9 55.2 -13.7 M M
6000 9.8 49.6 185 17 9 -8.7 -4.8 11.8 53.2 -14.8 M M
5750 9.2 48.6 180 13 7 -5.0 -2.7 10.5 50.8 -16.2 M M
5500 M M M M M M M M M M M M
5250 M M M M M M M M M M M M
5000 M M M M M M M M M M M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/17/2025 at 0900 MDT | 05/17/2025 at 1200 MDT
|
CAPE... +10.1 LI... -1.5 | CAPE... +81.2 LI... -1.1
CINH... -34.3 K Index... +22.1 | CINH... -8.3 K Index... +23.2
|
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 -56.1 -69.0 235 35 18 0.4 0.2 | -55.8 -68.4 235 37 19 0.8 0.5
45000 -55.6 -68.1 235 39 20 -1.9 -1.1 | -54.7 -66.5 235 43 22 -2.7 -1.5
40000 -59.0 -74.2 235 43 22 -2.3 -1.2 | -59.8 -75.6 235 47 24 -3.4 -1.9
38000 -57.5 -71.5 230 43 22 5.2 2.9 | -58.9 -74.0 235 48 25 5.7 3.1
36000 -54.4 -65.9 235 42 22 5.2 2.9 | -55.0 -67.0 235 47 24 5.7 3.2
34000 -50.7 -59.3 235 41 21 8.0 4.4 | -51.2 -60.2 235 46 24 7.8 4.3
32000 -45.9 -50.6 235 41 21 8.0 4.4 | -46.5 -51.7 235 42 21 7.8 4.3
30000 -41.3 -42.3 240 40 21 7.4 4.1 | -41.9 -43.4 235 38 19 7.7 4.2
29000 -39.1 -38.4 240 38 20 7.4 4.0 | -39.6 -39.3 235 36 18 7.7 4.2
28000 -36.8 -34.2 240 36 19 7.4 4.0 | -37.3 -35.1 235 34 17 7.7 4.2
27000 -34.6 -30.3 240 35 18 7.5 4.1 | -35.0 -31.0 235 32 16 7.6 4.2
26000 -32.4 -26.3 245 33 17 7.6 4.2 | -32.7 -26.9 240 31 16 7.6 4.2
25000 -30.1 -22.2 245 32 16 7.6 4.1 | -30.5 -22.9 240 30 16 7.6 4.2
24000 -27.8 -18.0 245 30 16 7.0 3.8 | -28.2 -18.8 240 29 15 7.2 4.0
23000 -25.7 -14.3 245 29 15 5.8 3.2 | -25.8 -14.4 240 28 14 6.5 3.6
22000 -24.0 -11.2 245 28 14 5.9 3.2 | -23.9 -11.0 240 27 14 6.5 3.6
21000 -22.2 -8.0 240 27 14 6.6 3.6 | -22.0 -7.6 235 26 14 6.6 3.6
20000 -20.2 -4.4 240 28 14 6.6 3.6 | -20.0 -4.0 235 26 13 6.7 3.6
19500 -19.3 -2.7 240 28 15 6.6 3.6 | -19.0 -2.2 230 26 13 6.6 3.6
19000 -18.3 -0.9 240 29 15 6.4 3.5 | -18.0 -0.4 230 26 13 6.5 3.6
18500 -17.2 1.0 235 29 15 8.2 4.5 | -17.0 1.4 230 26 13 8.2 4.5
18000 -16.0 3.2 235 29 15 8.1 4.5 | -15.8 3.6 225 25 13 8.1 4.5
17500 -14.8 5.4 235 29 15 8.3 4.6 | -14.6 5.7 225 25 13 8.2 4.5
17000 -13.6 7.5 235 29 15 8.5 4.7 | -13.4 7.9 225 24 12 8.3 4.6
16500 -12.3 9.9 235 28 14 8.6 4.7 | -12.1 10.2 225 23 12 8.3 4.6
16000 -11.0 12.2 235 27 14 8.8 4.8 | -10.9 12.4 225 22 12 8.6 4.7
15500 -9.7 14.5 240 25 13 8.8 4.8 | -9.6 14.7 225 22 11 8.6 4.7
15000 -8.4 16.9 240 24 12 9.0 5.0 | -8.3 17.1 220 21 11 9.0 4.9
14500 -7.1 19.2 240 23 12 9.1 5.0 | -7.0 19.4 220 20 10 9.0 4.9
14000 -5.8 21.6 240 22 11 9.1 5.0 | -5.6 21.9 220 20 10 9.3 5.1
13500 -4.4 24.1 235 20 10 9.1 5.0 | -4.2 24.4 220 19 10 9.4 5.2
13000 -3.1 26.4 235 19 10 8.9 4.9 | -2.8 27.0 220 18 9 9.4 5.2
12500 -1.8 28.8 235 17 9 8.7 4.8 | -1.4 29.5 220 18 9 9.4 5.2
12000 -0.6 30.9 230 14 7 8.6 4.7 | -0.0 32.0 220 17 9 9.5 5.2
11500 0.7 33.3 225 13 6 8.5 4.6 | 1.4 34.5 215 16 8 9.5 5.2
11000 2.0 35.6 220 11 6 7.7 4.2 | 2.8 37.0 215 16 8 9.0 4.9
10500 2.9 37.2 215 10 5 5.7 3.1 | 4.0 39.2 215 14 7 7.1 3.9
10250 3.4 38.1 210 9 5 9.0 4.9 | 4.6 40.3 215 14 7 10.7 5.9
10000 4.2 39.6 205 8 4 10.3 5.7 | 5.6 42.1 210 14 7 12.2 6.7
9750 4.8 40.6 200 8 4 7.2 3.9 | 6.3 43.3 210 13 7 8.8 4.8
9500 5.4 41.7 195 7 4 7.7 4.2 | 6.9 44.4 210 13 7 8.6 4.7
9250 5.9 42.6 185 7 3 6.2 3.4 | 7.6 45.7 205 12 6 9.4 5.2
9000 6.3 43.3 185 7 3 6.6 3.6 | 8.4 47.1 205 12 6 10.3 5.7
8750 6.9 44.4 180 6 3 8.3 4.5 | 9.1 48.4 205 12 6 9.8 5.4
8500 7.5 45.5 175 6 3 7.9 4.3 | 10.5 50.9 205 11 6 9.4 5.1
8250 8.7 47.7 160 6 3 6.9 3.8 | 11.2 52.2 200 11 5 9.1 5.0
8000 9.2 48.6 160 6 3 6.9 3.8 | 11.9 53.4 200 10 5 9.9 5.4
7750 9.7 49.5 155 6 3 7.5 4.1 | 12.7 54.9 200 10 5 10.7 5.9
7500 10.3 50.5 150 6 3 6.6 3.6 | 13.5 56.3 200 10 5 9.6 5.3
7250 10.7 51.3 150 6 3 5.6 3.1 | 14.1 57.4 200 9 5 7.8 4.3
7000 11.2 52.2 150 7 3 7.5 4.1 | 14.7 58.5 195 9 5 9.7 5.3
6750 11.8 53.2 150 6 3 9.1 5.0 | 15.6 60.1 195 9 5 11.6 6.3
6500 12.5 54.5 145 6 3 8.1 4.4 | 16.4 61.5 200 9 5 10.7 5.9
6250 13.1 55.6 145 6 3 7.9 4.3 | 17.2 63.0 195 8 4 11.0 6.1
6000 13.7 56.7 145 5 3 7.6 4.2 | 18.0 64.4 190 8 4 8.9 4.9
5750 14.3 57.7 145 5 2 12.6 6.9 | 18.6 65.5 195 8 4 12.6 6.9
5500 16.2 61.2 140 5 2 46.0 25.2 | 21.0 69.8 190 7 3 64.9 35.6
5250 M M M M M M M | M M M M M M M
5000 M M M M M M M | M M M M M M M
05/17/2025 at 1500 MDT | 05/17/2025 at 1800 MDT
|
CAPE... +46.0 LI... +0.2 | CAPE... +12.1 LI... +0.3
CINH... -2.0 K Index... +23.5 | CINH... -3.8 K Index... +19.0
|
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 -55.7 -68.3 245 37 19 0.8 0.4 | -55.7 -68.3 245 36 18 0.8 0.4
45000 -54.7 -66.5 245 43 22 -2.0 -1.1 | -54.6 -66.3 245 39 20 -2.1 -1.2
40000 -58.5 -73.3 245 47 24 -2.5 -1.4 | -58.7 -73.7 250 52 27 -2.7 -1.5
38000 -57.7 -71.9 245 46 24 3.9 2.1 | -57.8 -72.0 250 51 26 4.4 2.4
36000 -55.3 -67.5 250 43 22 3.9 2.1 | -55.2 -67.4 255 46 24 4.4 2.4
34000 -52.2 -62.0 250 40 21 8.6 4.7 | -51.8 -61.2 255 41 21 8.7 4.8
32000 -47.0 -52.6 255 35 18 8.6 4.7 | -46.5 -51.7 250 34 17 8.8 4.8
30000 -41.9 -43.4 255 31 16 8.2 4.5 | -41.3 -42.3 240 29 15 8.3 4.5
29000 -39.5 -39.1 250 31 16 8.1 4.5 | -38.9 -38.0 240 29 15 8.2 4.5
28000 -37.0 -34.6 245 32 16 8.1 4.5 | -36.4 -33.5 235 30 15 8.3 4.5
27000 -34.6 -30.3 245 32 17 7.4 4.0 | -34.0 -29.2 235 30 16 7.0 3.9
26000 -32.5 -26.5 240 31 16 7.0 3.9 | -32.1 -25.8 230 31 16 6.5 3.6
25000 -30.4 -22.7 240 30 15 7.0 3.9 | -30.1 -22.2 230 31 16 6.5 3.6
24000 -28.3 -18.9 235 29 15 7.0 3.8 | -28.2 -18.8 230 31 16 6.7 3.7
23000 -25.7 -14.3 230 27 14 7.0 3.8 | -25.5 -13.9 225 30 15 7.2 3.9
22000 -23.7 -10.7 225 26 13 7.1 3.9 | -23.4 -10.1 225 28 15 7.2 3.9
21000 -21.5 -6.7 225 25 13 8.2 4.5 | -21.3 -6.3 220 27 14 7.9 4.3
20000 -19.1 -2.4 225 25 13 8.1 4.5 | -18.9 -2.0 220 26 14 7.9 4.3
19500 -17.9 -0.2 225 25 13 8.1 4.5 | -17.8 -0.0 220 26 13 7.9 4.3
19000 -16.7 1.9 220 25 13 8.2 4.5 | -16.6 2.1 215 25 13 7.9 4.3
18500 -15.6 3.9 220 25 13 7.6 4.2 | -15.5 4.1 215 25 13 8.0 4.4
18000 -14.4 6.1 220 24 12 7.6 4.2 | -14.3 6.3 215 25 13 8.0 4.4
17500 -13.3 8.1 220 24 12 7.5 4.1 | -13.1 8.4 215 24 13 8.2 4.5
17000 -12.2 10.0 220 24 12 7.3 4.0 | -11.8 10.8 215 24 12 8.5 4.6
16500 -11.2 11.8 220 23 12 7.3 4.0 | -10.6 12.9 215 24 12 8.5 4.6
16000 -10.0 14.0 220 23 12 8.0 4.4 | -9.3 15.3 215 24 12 8.6 4.7
15500 -8.9 16.0 220 23 12 7.9 4.4 | -8.0 17.6 210 24 12 8.6 4.7
15000 -7.6 18.3 220 22 11 8.5 4.7 | -6.7 19.9 210 23 12 8.8 4.9
14500 -6.4 20.5 220 22 11 8.6 4.7 | -5.4 22.3 210 23 12 8.9 4.9
14000 -5.1 22.8 220 21 11 8.9 4.9 | -4.1 24.6 210 23 12 9.0 4.9
13500 -3.7 25.3 220 21 11 9.0 5.0 | -2.7 27.1 210 23 12 9.1 5.0
13000 -2.4 27.7 220 21 11 9.2 5.0 | -1.4 29.5 215 22 12 9.2 5.0
12500 -1.0 30.2 220 20 10 9.4 5.2 | -0.0 32.0 215 22 11 9.3 5.1
12000 0.4 32.7 220 19 10 9.5 5.2 | 1.4 34.5 215 22 11 9.3 5.1
11500 1.9 35.4 220 19 10 9.6 5.3 | 2.8 37.0 215 21 11 9.7 5.3
11000 3.3 37.9 220 18 9 9.0 4.9 | 4.2 39.6 215 21 11 9.4 5.2
10500 4.5 40.1 220 17 9 6.0 3.3 | 5.6 42.1 215 20 10 7.9 4.3
10250 5.0 41.0 220 16 8 11.3 6.2 | 6.2 43.2 215 19 10 10.2 5.6
10000 6.1 43.0 220 16 8 14.0 7.7 | 7.1 44.8 215 20 10 11.8 6.5
9750 6.9 44.4 220 16 8 9.2 5.1 | 7.9 46.2 215 20 10 9.9 5.5
9500 7.6 45.7 220 15 8 8.5 4.7 | 8.6 47.5 215 19 10 9.6 5.3
9250 8.2 46.8 220 15 8 9.9 5.4 | 9.3 48.7 215 19 10 9.8 5.4
9000 9.1 48.4 220 15 8 11.4 6.3 | 10.1 50.2 215 19 10 9.9 5.4
8750 9.9 49.8 220 15 8 10.2 5.6 | 10.8 51.4 215 19 10 9.8 5.4
8500 11.3 52.3 225 14 7 9.8 5.4 | 12.3 54.1 215 18 9 9.7 5.3
8250 12.0 53.6 220 14 7 8.2 4.5 | 13.0 55.4 215 18 9 9.8 5.4
8000 12.6 54.7 220 13 6 8.9 4.9 | 13.7 56.7 215 17 9 9.7 5.3
7750 13.4 56.1 220 13 6 10.9 6.0 | 14.5 58.1 215 16 8 9.5 5.2
7500 14.2 57.6 225 12 6 9.6 5.3 | 15.2 59.4 215 16 8 9.5 5.2
7250 14.8 58.6 220 12 6 7.3 4.0 | 15.9 60.6 215 16 8 8.8 4.8
7000 15.4 59.7 220 11 6 9.2 5.1 | 16.5 61.7 215 15 8 9.0 4.9
6750 16.2 61.2 220 11 6 11.9 6.5 | 17.2 63.0 215 14 7 9.6 5.2
6500 17.0 62.6 225 11 6 10.5 5.8 | 17.9 64.2 215 13 7 9.6 5.3
6250 17.8 64.0 220 10 5 10.2 5.6 | 18.7 65.7 215 13 7 10.9 6.0
6000 18.5 65.3 220 10 5 8.5 4.6 | 19.4 66.9 215 12 6 8.1 4.4
5750 19.2 66.6 220 10 5 12.6 6.9 | 19.9 67.8 215 11 6 7.7 4.2
5500 21.4 70.5 220 8 4 59.7 32.8 | 21.6 70.9 215 9 5 49.5 27.1
5250 M M M M M M M | M M M M M M M
5000 M M M M M M M | M M M M M M M
________________________________________________________________________________
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 at Walker Field in Grand
Junction, Colorado at
North Latitude: 39 deg 07 min 00.001 sec
West Longitude: 108 deg 31 min 59.998 sec
Elevation: 4839 feet (1475 meters)
and may not be representative of other areas along the Western Slope of
Colorado. 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.
042613