Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
000
UXUS97 KGJT 261307
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
707 AM MDT Saturday, April 26, 2025
This forecast is for Saturday, April 26, 2025:
If the trigger temperature of 58.9 F/14.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1400 ft/min (7.1 m/s)
Maximum height of thermals.................. 21596 ft MSL (15985 ft AGL)
Forecast maximum temperature................... 80.0 F/27.1 C
Time of trigger temperature.................... 0730 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 18324 ft MSL (12714 ft AGL)
Thermal soaring outlook for Sunday 04/27....... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:21:18 / 20:02:24 MDT
Total possible sunshine........... 13 hr 41 min 5 sec (821 min 5 sec)
Altitude of sun at 13:11:51 MDT... 64.53 degrees
Upper air data from rawinsonde observation taken on 04/26/2025 at 0600 MDT
Freezing level.................. 10953 ft MSL (5342 ft AGL)
Convective condensation level... 19303 ft MSL (13692 ft AGL)
Lifted condensation level....... 20559 ft MSL (14948 ft AGL)
Lifted index.................... -0.4
K index......................... -3.3
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 -57.6 -71.7 220 33 17 0.7 0.4 M M M M M
45000 -56.6 -69.9 220 40 21 -0.3 -0.2 M M M M M
40000 -57.0 -70.6 220 64 33 -0.3 -0.1 M M M M M
38000 -55.8 -68.4 215 67 34 3.6 2.0 M M M M M
36000 -53.7 -64.7 215 65 34 3.6 2.0 M M M M M
34000 -51.1 -60.0 210 64 33 7.7 4.2 M M M M M
32000 -46.0 -50.8 210 64 33 7.6 4.1 M M M M M
30000 -41.3 -42.3 210 63 33 8.2 4.5 33.5 92.2 5.1 M M
29000 -38.9 -38.0 210 63 32 8.2 4.5 32.8 91.0 4.7 M M
28000 -36.4 -33.5 210 62 32 8.2 4.5 32.2 90.0 4.3 M M
27000 -34.0 -29.2 205 62 32 7.8 4.3 31.7 89.1 3.9 M M
26000 -31.7 -25.1 205 61 31 7.6 4.2 30.8 87.4 3.2 M M
25000 -29.5 -21.1 205 60 31 7.6 4.2 30.0 86.0 2.6 M M
24000 -27.2 -17.0 205 59 30 7.4 4.1 29.3 84.8 2.1 M M
23000 -25.1 -13.2 205 57 30 7.0 3.8 28.2 82.8 1.2 M M
22000 -23.1 -9.6 205 56 29 7.0 3.8 27.2 81.0 0.4 M M
21000 -21.0 -5.8 205 54 28 6.8 3.8 26.3 79.4 -0.4 1352 6.9
20000 -19.0 -2.2 205 52 27 6.8 3.7 25.2 77.3 -1.4 1262 6.4
19500 -18.0 -0.4 205 50 26 6.8 3.7 24.7 76.4 -1.8 1217 6.2
19000 -16.9 1.6 200 49 25 6.8 3.7 24.2 75.5 -2.3 1172 6.0
18500 -15.4 4.3 200 48 25 6.5 3.6 23.4 74.2 -2.9 1104 5.6
18000 -14.5 5.9 200 47 24 6.5 3.6 22.9 73.1 -3.4 1060 5.4
17500 -13.5 7.7 200 47 24 6.4 3.5 22.3 72.2 -3.9 1016 5.2
17000 -12.5 9.5 200 46 24 6.2 3.4 21.7 71.1 -4.5 973 4.9
16500 -11.6 11.1 200 46 24 6.2 3.4 21.1 70.0 -5.0 931 4.7
16000 -10.7 12.7 195 46 24 6.7 3.7 20.6 69.0 -5.6 887 4.5
15500 -9.7 14.5 195 46 24 6.6 3.6 20.1 68.1 -6.1 843 4.3
15000 -8.7 16.3 195 46 24 7.1 3.9 19.6 67.2 -6.6 798 4.1
14500 -7.6 18.3 195 46 24 7.3 4.0 19.2 66.5 -7.0 751 3.8
14000 -6.5 20.3 195 46 24 7.4 4.1 18.8 65.8 -7.4 703 3.6
13500 -5.4 22.3 195 46 24 7.5 4.1 18.4 65.1 -7.8 655 3.3
13000 -4.2 24.4 195 46 23 7.4 4.0 18.0 64.5 -8.1 606 3.1
12500 -3.2 26.2 195 45 23 7.1 3.9 17.6 63.7 -8.6 560 2.8
12000 -2.1 28.2 200 44 23 7.0 3.8 17.2 62.9 -9.0 514 2.6
11500 -1.1 30.0 200 43 22 6.8 3.8 16.7 62.1 -9.5 469 2.4
11000 -0.1 31.8 200 41 21 6.8 3.8 16.3 61.3 -10.0 424 2.2
10500 0.8 33.4 200 38 19 7.0 3.9 15.8 60.4 -10.6 380 1.9
10250 1.4 34.5 200 36 19 8.2 4.5 15.6 60.1 -10.8 356 1.8
10000 2.0 35.6 200 35 18 8.2 4.5 15.5 59.9 -10.9 330 1.7
9750 2.6 36.7 200 34 17 7.8 4.3 15.4 59.6 -11.1 306 1.6
9500 3.2 37.8 200 32 16 7.9 4.3 15.2 59.4 -11.3 281 1.4
9250 3.7 38.7 200 30 16 7.6 4.2 15.1 59.1 -11.5 257 1.3
9000 4.3 39.7 200 29 15 8.2 4.5 14.9 58.8 -11.7 232 1.2
8750 4.9 40.8 200 28 14 9.0 4.9 14.8 58.7 -11.8 206 1.0
8500 5.6 42.1 200 26 13 9.2 5.1 14.8 58.6 -11.9 178 0.9
8250 6.3 43.3 200 24 13 8.2 4.5 14.7 58.5 -12.0 151 0.8
8000 6.8 44.2 200 23 12 7.6 4.2 14.5 58.2 -12.2 127 0.6
7750 7.4 45.3 200 22 11 8.3 4.5 14.4 57.9 -12.4 101 0.5
7500 8.0 46.4 200 21 11 8.1 4.5 14.3 57.7 -12.5 76 0.4
7250 8.6 47.5 200 20 10 8.0 4.4 14.2 57.5 -12.7 50 0.3
7000 9.2 48.6 200 20 10 7.4 4.0 14.0 57.2 -12.9 26 0.1
6750 9.7 49.5 195 18 9 6.5 3.6 13.8 56.8 -13.1 3 0.0
6500 10.3 50.5 195 17 9 8.3 4.6 13.6 56.4 -13.3 M M
6250 10.8 51.4 195 15 8 1.1 0.6 13.4 56.0 -13.6 M M
6000 10.2 50.4 185 14 7 -14.9 -8.2 12.1 53.7 -14.9 M M
5750 8.8 47.8 180 9 5 -20.4 -11.2 9.9 49.8 -17.1 2 0.0
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 * * * * * *
04/26/2025 at 0900 MDT | 04/26/2025 at 1200 MDT
|
CAPE... 0.0 LI... +3.8 | CAPE... 0.0 LI... +3.3
CINH... -1.0 K Index... +0.7 | CINH... -0.7 K Index... +5.7
|
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 -58.4 -73.1 230 40 21 0.2 0.1 | -58.2 -72.8 230 41 21 -0.4 -0.2
45000 -58.1 -72.6 235 43 22 -0.4 -0.2 | -58.8 -73.8 230 45 23 -0.7 -0.4
40000 -59.5 -75.1 240 56 29 -0.9 -0.5 | -60.2 -76.4 230 53 27 -0.9 -0.5
38000 -58.0 -72.4 235 57 30 4.5 2.4 | -58.3 -72.9 225 54 28 5.4 2.9
36000 -55.3 -67.5 235 56 29 4.5 2.4 | -55.1 -67.2 225 52 27 5.4 2.9
34000 -52.0 -61.6 235 55 28 8.3 4.5 | -51.4 -60.5 220 51 26 8.1 4.5
32000 -47.0 -52.6 230 54 28 8.3 4.6 | -46.5 -51.7 220 51 26 8.2 4.5
30000 -42.0 -43.6 230 54 28 8.0 4.4 | -41.5 -42.7 225 51 26 8.3 4.6
29000 -39.6 -39.3 230 54 28 8.0 4.4 | -39.0 -38.2 225 51 26 8.3 4.6
28000 -37.2 -35.0 230 54 28 8.0 4.4 | -36.5 -33.7 225 52 27 8.3 4.6
27000 -34.9 -30.8 225 54 28 7.8 4.3 | -34.0 -29.2 225 52 27 8.0 4.4
26000 -32.6 -26.7 225 53 27 7.7 4.2 | -31.7 -25.1 220 51 26 7.8 4.3
25000 -29.7 -21.5 220 52 27 7.7 4.2 | -28.8 -19.8 220 50 26 7.8 4.3
24000 -27.4 -17.3 220 51 26 6.9 3.8 | -26.4 -15.5 220 50 26 7.3 4.0
23000 -25.4 -13.7 215 50 26 6.9 3.8 | -24.3 -11.7 215 49 25 7.3 4.0
22000 -23.4 -10.1 215 49 25 6.9 3.8 | -22.1 -7.8 215 49 25 7.3 4.0
21000 -21.3 -6.3 210 48 25 6.9 3.8 | -20.0 -4.0 215 48 25 6.0 3.3
20000 -19.2 -2.6 210 46 24 6.9 3.8 | -18.2 -0.8 215 47 24 6.1 3.3
19500 -18.2 -0.8 210 45 23 6.9 3.8 | -17.3 0.9 210 46 24 6.1 3.4
19000 -17.2 1.0 210 44 22 6.8 3.7 | -16.4 2.5 210 46 24 6.1 3.4
18500 -16.1 3.0 210 43 22 7.3 4.0 | -15.5 4.1 210 45 23 5.9 3.2
18000 -15.0 5.0 210 41 21 7.2 4.0 | -14.6 5.7 210 44 22 5.9 3.2
17500 -13.9 7.0 210 40 21 7.1 3.9 | -13.7 7.3 210 42 22 5.9 3.2
17000 -12.9 8.8 210 39 20 6.9 3.8 | -12.9 8.8 210 40 21 5.9 3.2
16500 -11.9 10.6 210 38 20 6.8 3.8 | -12.0 10.4 210 38 19 5.8 3.2
16000 -10.9 12.4 215 37 19 7.0 3.9 | -11.0 12.2 210 36 18 7.3 4.0
15500 -9.8 14.4 215 36 19 7.0 3.8 | -10.0 14.0 210 34 17 7.1 3.9
15000 -8.8 16.2 215 35 18 7.4 4.0 | -8.9 16.0 210 32 17 8.4 4.6
14500 -7.7 18.1 215 34 18 7.4 4.1 | -7.6 18.3 210 31 16 8.6 4.7
14000 -6.6 20.1 215 33 17 7.6 4.2 | -6.3 20.7 210 29 15 8.8 4.8
13500 -5.4 22.3 215 32 16 7.8 4.3 | -5.0 23.0 205 28 15 8.9 4.9
13000 -4.3 24.3 215 31 16 8.0 4.4 | -3.7 25.3 205 27 14 9.0 5.0
12500 -3.1 26.4 210 29 15 8.2 4.5 | -2.3 27.9 205 26 14 9.2 5.1
12000 -1.8 28.8 210 28 14 8.3 4.6 | -0.9 30.4 205 26 13 9.3 5.1
11500 -0.6 30.9 210 27 14 8.4 4.6 | 0.5 32.9 205 25 13 9.4 5.2
11000 0.7 33.3 210 25 13 8.1 4.5 | 1.9 35.4 205 24 12 9.0 4.9
10500 1.8 35.2 210 24 12 7.0 3.9 | 3.2 37.8 205 24 12 7.4 4.1
10250 2.4 36.3 210 24 12 10.0 5.5 | 3.8 38.8 205 23 12 11.0 6.0
10000 3.3 37.9 205 23 12 11.3 6.2 | 4.8 40.6 205 24 12 12.5 6.8
9750 4.0 39.2 205 22 11 8.8 4.8 | 5.5 41.9 205 23 12 9.3 5.1
9500 4.6 40.3 205 22 11 9.2 5.1 | 6.2 43.2 205 23 12 9.2 5.1
9250 5.3 41.5 205 21 11 8.2 4.5 | 6.9 44.4 205 23 12 10.3 5.6
9000 5.9 42.6 205 21 11 8.2 4.5 | 7.8 46.0 205 23 12 10.7 5.8
8750 6.6 43.9 205 20 10 9.4 5.1 | 8.5 47.3 205 23 12 9.8 5.4
8500 8.0 46.4 200 18 10 9.1 5.0 | 10.0 50.0 205 22 12 9.7 5.3
8250 8.6 47.5 200 18 9 8.3 4.5 | 10.7 51.3 205 22 11 9.4 5.1
8000 9.2 48.6 200 17 9 8.5 4.7 | 11.4 52.5 205 22 11 10.1 5.5
7750 9.9 49.8 200 17 9 9.4 5.2 | 12.2 54.0 205 21 11 10.8 5.9
7500 10.6 51.1 195 16 8 7.8 4.3 | 13.0 55.4 205 21 11 9.7 5.3
7250 11.1 52.0 195 16 8 5.9 3.2 | 13.7 56.7 205 21 11 8.3 4.6
7000 11.6 52.9 190 16 8 7.8 4.3 | 14.3 57.7 200 21 11 10.1 5.6
6750 12.2 54.0 190 15 7 9.2 5.0 | 15.2 59.4 205 20 10 11.5 6.3
6500 12.9 55.2 185 14 7 8.5 4.7 | 16.0 60.8 205 19 10 11.1 6.1
6250 13.5 56.3 185 13 7 8.8 4.9 | 16.9 62.4 200 19 10 12.1 6.6
6000 14.2 57.6 180 12 6 7.5 4.1 | 17.7 63.9 200 19 10 8.8 4.8
5750 14.7 58.5 180 11 6 10.7 5.8 | 18.4 65.1 205 17 9 13.5 7.4
5500 16.6 61.9 175 10 5 49.1 26.9 | 21.4 70.5 205 16 8 87.2 47.9
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
04/26/2025 at 1500 MDT | 04/26/2025 at 1800 MDT
|
CAPE... +0.1 LI... +2.1 | CAPE... 0.0 LI... +1.4
CINH... -0.1 K Index... +7.6 | CINH... -0.1 K Index... +10.0
|
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 -57.7 -71.9 235 37 19 -0.4 -0.2 | -57.8 -72.0 230 32 17 -0.6 -0.3
45000 -58.3 -72.9 235 46 24 -0.9 -0.5 | -58.7 -73.7 235 48 25 -0.9 -0.5
40000 -60.2 -76.4 230 57 29 -1.2 -0.7 | -60.7 -77.3 235 59 30 -1.2 -0.7
38000 -58.3 -72.9 230 57 29 5.6 3.1 | -58.5 -73.3 235 59 30 6.1 3.4
36000 -54.9 -66.8 225 56 29 5.6 3.1 | -54.8 -66.6 230 57 29 6.1 3.4
34000 -51.1 -60.0 225 55 28 7.7 4.2 | -50.8 -59.4 230 55 28 8.1 4.4
32000 -46.5 -51.7 220 52 27 7.8 4.3 | -45.9 -50.6 225 54 28 8.1 4.4
30000 -41.7 -43.1 220 50 26 8.3 4.5 | -41.1 -42.0 225 53 27 7.7 4.3
29000 -39.2 -38.6 220 49 25 8.3 4.5 | -38.8 -37.8 225 51 26 7.7 4.2
28000 -36.8 -34.2 220 49 25 8.3 4.5 | -36.5 -33.7 220 50 26 7.7 4.2
27000 -34.3 -29.7 220 48 25 8.1 4.4 | -34.1 -29.4 220 49 25 7.9 4.3
26000 -31.3 -24.3 215 47 24 8.0 4.4 | -31.2 -24.2 215 48 25 7.9 4.3
25000 -28.9 -20.0 215 47 24 8.0 4.4 | -28.8 -19.8 215 47 24 7.9 4.3
24000 -26.5 -15.7 210 47 24 7.4 4.1 | -26.5 -15.7 215 46 24 7.3 4.0
23000 -24.3 -11.7 210 47 24 7.4 4.1 | -24.3 -11.7 215 46 24 7.3 4.0
22000 -22.0 -7.6 210 46 24 7.5 4.1 | -22.1 -7.8 210 45 23 7.3 4.0
21000 -19.9 -3.8 210 46 24 6.3 3.5 | -20.0 -4.0 210 44 23 6.4 3.5
20000 -18.0 -0.4 210 44 23 6.4 3.5 | -18.1 -0.6 210 42 22 6.5 3.6
19500 -17.1 1.2 210 44 22 6.5 3.5 | -17.1 1.2 205 42 21 6.6 3.6
19000 -16.1 3.0 210 43 22 6.5 3.6 | -16.2 2.8 205 41 21 6.5 3.6
18500 -15.2 4.6 210 42 21 6.2 3.4 | -15.2 4.6 205 39 20 7.3 4.0
18000 -14.3 6.3 205 40 20 6.2 3.4 | -14.1 6.6 205 38 19 7.3 4.0
17500 -13.3 8.1 205 38 19 6.7 3.7 | -13.0 8.6 205 36 19 7.7 4.2
17000 -12.3 9.9 205 36 19 7.3 4.0 | -11.8 10.8 200 35 18 8.3 4.5
16500 -11.2 11.8 205 34 18 7.3 4.0 | -10.5 13.1 200 34 17 8.2 4.5
16000 -10.0 14.0 205 33 17 8.8 4.8 | -9.2 15.4 200 33 17 9.0 4.9
15500 -8.7 16.3 205 31 16 8.6 4.7 | -7.9 17.8 200 32 17 8.9 4.9
15000 -7.4 18.7 205 30 16 9.1 5.0 | -6.6 20.1 200 31 16 9.2 5.1
14500 -6.0 21.2 205 29 15 9.2 5.0 | -5.2 22.6 200 30 16 9.3 5.1
14000 -4.6 23.7 205 28 15 9.1 5.0 | -3.8 25.2 200 30 15 9.4 5.2
13500 -3.3 26.1 200 27 14 9.1 5.0 | -2.4 27.7 200 29 15 9.5 5.2
13000 -1.9 28.6 200 27 14 9.3 5.1 | -1.0 30.2 195 29 15 9.6 5.2
12500 -0.5 31.1 200 26 13 9.5 5.2 | 0.5 32.9 200 28 14 9.6 5.3
12000 0.9 33.6 200 26 13 9.6 5.3 | 1.9 35.4 200 28 14 9.7 5.3
11500 2.4 36.3 200 26 13 9.7 5.3 | 3.4 38.1 200 27 14 9.7 5.3
11000 3.8 38.8 200 25 13 9.2 5.1 | 4.8 40.6 200 27 14 9.4 5.1
10500 5.1 41.2 200 25 13 7.4 4.0 | 6.1 43.0 200 26 13 7.3 4.0
10250 5.7 42.3 200 25 13 10.7 5.9 | 6.7 44.1 200 26 13 10.7 5.8
10000 6.6 43.9 205 25 13 12.5 6.9 | 7.7 45.9 200 26 13 12.7 6.9
9750 7.4 45.3 205 25 13 9.7 5.3 | 8.5 47.3 200 26 13 9.7 5.3
9500 8.2 46.8 205 25 13 9.5 5.2 | 9.2 48.6 200 25 13 9.1 5.0
9250 8.9 48.0 205 24 13 10.0 5.5 | 9.9 49.8 200 25 13 9.5 5.2
9000 9.7 49.5 205 24 13 10.5 5.8 | 11.4 52.5 200 25 13 10.2 5.6
8750 11.2 52.2 205 24 12 9.9 5.4 | 12.1 53.8 200 24 13 9.9 5.4
8500 11.9 53.4 205 24 12 9.9 5.4 | 12.9 55.2 200 24 12 10.0 5.5
8250 12.7 54.9 205 24 12 9.5 5.2 | 13.6 56.5 200 24 12 9.7 5.3
8000 13.4 56.1 205 23 12 9.8 5.4 | 14.3 57.7 200 23 12 9.7 5.3
7750 14.1 57.4 205 23 12 10.4 5.7 | 15.1 59.2 200 23 12 10.0 5.5
7500 14.9 58.8 205 22 12 9.7 5.3 | 15.8 60.4 200 22 12 9.8 5.4
7250 15.6 60.1 205 22 12 8.6 4.7 | 16.5 61.7 200 22 11 8.4 4.6
7000 16.3 61.3 205 22 12 10.1 5.6 | 17.1 62.8 200 22 11 9.4 5.2
6750 17.1 62.8 205 21 11 11.7 6.4 | 17.9 64.2 200 21 11 11.1 6.1
6500 18.0 64.4 205 21 11 11.0 6.1 | 18.7 65.7 200 20 10 10.5 5.8
6250 18.8 65.8 205 20 10 11.6 6.4 | 19.6 67.3 200 20 10 11.0 6.0
6000 19.6 67.3 205 20 10 8.9 4.9 | 20.3 68.5 200 20 10 8.8 4.8
5750 20.3 68.5 205 19 10 14.5 7.9 | 21.0 69.8 200 18 9 10.1 5.6
5500 23.3 73.9 205 17 8 84.4 46.3 | 22.7 72.9 200 15 8 48.2 26.4
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.
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