Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
060
UXUS97 KGJT 151306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Wednesday, October 15, 2025
This forecast is for Wednesday, October 15, 2025:
If the trigger temperature of 49.6 F/9.8 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1373 ft/min (7.0 m/s)
Maximum height of thermals.................. 21407 ft MSL (15798 ft AGL)
Forecast maximum temperature................... 71.0 F/22.1 C
Time of trigger temperature.................... None
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................. 17509 ft MSL (11900 ft AGL)
Thermal soaring outlook for Thursday 10/16..... Good
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:24:24 / 18:35:09 MDT
Total possible sunshine........... 11 hr 10 min 45 sec (670 min 45 sec)
Altitude of sun at 12:59:46 MDT... 42.06 degrees
Upper air data from rawinsonde observation taken on 10/15/2025 at 0600 MDT
Freezing level.................. 8643 ft MSL (3034 ft AGL)
Convective condensation level... 11481 ft MSL (5872 ft AGL)
Lifted condensation level....... 15618 ft MSL (10009 ft AGL)
Lifted index.................... -4.2
K index......................... +8.7
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 -59.3 -74.7 220 40 21 3.2 1.8 M M M M M
45000 -54.3 -65.7 230 56 29 4.3 2.4 M M M M M
40000 -47.7 -53.9 230 77 39 4.4 2.4 M M M M M
38000 -44.5 -48.1 230 85 44 4.8 2.6 M M M M M
36000 -41.7 -43.1 225 92 47 4.8 2.6 M M M M M
34000 -38.9 -38.0 225 98 50 4.1 2.2 M M M M M
32000 -36.4 -33.5 220 100 51 4.1 2.2 M M M M M
30000 -34.4 -29.9 220 99 51 0.1 0.1 44.1 111.4 16.9 M M
29000 -34.3 -29.7 220 93 48 0.3 0.2 40.2 104.4 14.2 M M
28000 -34.2 -29.6 220 87 45 0.3 0.2 36.6 97.8 11.5 M M
27000 -34.1 -29.4 220 81 42 0.2 0.1 33.1 91.6 8.9 M M
26000 -33.5 -28.3 225 75 38 2.7 1.5 30.1 86.2 6.7 M M
25000 -32.7 -26.9 225 69 35 2.7 1.5 27.4 81.3 4.6 M M
24000 -31.9 -25.4 225 63 32 2.4 1.3 24.9 76.7 2.6 M M
23000 -30.2 -22.4 230 58 30 7.1 3.9 23.3 74.0 1.3 M M
22000 -28.0 -18.4 230 55 28 7.2 3.9 22.3 72.2 0.5 M M
21000 -25.3 -13.5 235 51 26 7.5 4.1 21.3 70.3 -0.4 1322 6.7
20000 -23.1 -9.6 235 49 25 7.6 4.2 20.4 68.8 -1.1 1225 6.2
19500 -21.9 -7.4 235 47 24 7.6 4.2 20.1 68.1 -1.4 1176 6.0
19000 -20.8 -5.4 235 46 24 7.6 4.2 19.7 67.5 -1.7 1127 5.7
18500 -19.7 -3.5 240 44 23 6.9 3.8 19.4 66.9 -2.0 1078 5.5
18000 -18.7 -1.7 240 42 22 6.5 3.6 18.8 65.8 -2.6 1034 5.3
17500 -17.7 0.1 240 40 21 6.4 3.5 18.2 64.8 -3.1 991 5.0
17000 -16.8 1.8 235 38 20 5.9 3.2 17.6 63.7 -3.7 949 4.8
16500 -16.0 3.2 235 37 19 5.9 3.3 17.0 62.5 -4.3 908 4.6
16000 -15.1 4.8 235 35 18 5.8 3.2 16.3 61.3 -4.9 867 4.4
15500 -14.2 6.4 235 34 17 5.8 3.2 15.6 60.1 -5.5 827 4.2
15000 -13.4 7.9 235 33 17 6.2 3.4 15.0 59.0 -6.2 787 4.0
14500 -12.4 9.7 230 31 16 6.6 3.6 14.4 58.0 -6.7 743 3.8
14000 -11.5 11.3 230 30 15 6.9 3.8 13.9 57.1 -7.3 700 3.6
13500 -10.4 13.3 225 28 15 7.4 4.0 13.5 56.3 -7.7 653 3.3
13000 -9.4 15.1 225 27 14 7.3 4.0 13.1 55.6 -8.2 606 3.1
12500 -8.3 17.1 225 25 13 7.2 3.9 12.7 54.9 -8.6 560 2.8
12000 -7.3 18.9 220 24 12 7.2 4.0 12.3 54.1 -9.1 514 2.6
11500 -6.2 20.8 220 22 12 7.3 4.0 11.9 53.4 -9.6 468 2.4
11000 -5.2 22.6 220 21 11 7.1 3.9 11.5 52.7 -10.0 421 2.1
10500 -4.2 24.4 225 20 10 6.4 3.5 11.0 51.9 -10.6 377 1.9
10250 -3.7 25.3 225 19 10 7.7 4.2 10.8 51.5 -10.8 354 1.8
10000 -3.1 26.4 225 18 9 8.0 4.4 10.7 51.2 -11.0 329 1.7
9750 -2.5 27.5 225 18 9 7.1 3.9 10.5 50.9 -11.2 306 1.6
9500 -2.0 28.4 230 17 9 6.9 3.8 10.3 50.5 -11.5 283 1.4
9250 -1.5 29.3 230 17 9 7.8 4.3 10.1 50.1 -11.7 260 1.3
9000 -0.9 30.4 230 16 8 8.0 4.4 10.0 49.9 -11.9 234 1.2
8750 -0.4 31.3 235 15 8 7.2 3.9 9.8 49.6 -12.1 211 1.1
8500 0.2 32.4 235 14 7 7.6 4.1 9.6 49.3 -12.3 187 1.0
8250 0.7 33.3 240 14 7 6.9 3.8 9.4 48.9 -12.5 164 0.8
8000 1.2 34.2 240 13 7 7.1 3.9 9.2 48.5 -12.8 141 0.7
7750 1.8 35.2 245 12 6 7.7 4.2 9.0 48.2 -13.0 117 0.6
7500 2.3 36.1 245 11 6 7.6 4.2 8.8 47.9 -13.2 93 0.5
7250 2.9 37.2 250 11 6 7.3 4.0 8.7 47.6 -13.4 69 0.4
7000 3.4 38.1 255 10 5 6.6 3.6 8.5 47.2 -13.7 47 0.2
6750 3.9 39.0 255 9 5 6.6 3.6 8.2 46.8 -14.0 25 0.1
6500 4.3 39.7 260 8 4 6.3 3.5 8.0 46.4 -14.3 3 0.0
6250 4.8 40.6 270 7 4 5.4 3.0 7.7 45.8 -14.6 M M
6000 5.1 41.2 280 6 3 5.5 3.0 7.4 45.2 -15.0 M M
5750 5.5 41.9 285 5 3 5.1 2.8 7.0 44.7 -15.4 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 * * * * * *
10/15/2025 at 0900 MDT | 10/15/2025 at 1200 MDT
|
CAPE... +8.1 LI... -0.1 | CAPE... +263.8 LI... -1.0
CINH... -12.4 K Index... +21.5 | CINH... -2.1 K Index... +18.3
|
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 -62.7 -80.9 210 58 30 2.6 1.4 | -62.4 -80.3 205 59 31 3.1 1.7
45000 -58.5 -73.3 215 79 41 3.8 2.1 | -57.8 -72.0 215 80 41 3.3 1.8
40000 -52.9 -63.2 210 92 48 3.9 2.2 | -52.9 -63.2 210 100 52 3.2 1.8
38000 -49.8 -57.6 210 94 49 5.2 2.9 | -50.0 -58.0 210 101 52 5.0 2.8
36000 -46.3 -51.3 210 96 49 5.2 2.9 | -46.6 -51.9 205 100 51 5.0 2.8
34000 -43.0 -45.4 210 95 49 5.8 3.2 | -43.2 -45.8 205 99 51 6.1 3.3
32000 -39.5 -39.1 210 93 48 5.8 3.2 | -39.6 -39.3 205 97 50 6.1 3.3
30000 -35.5 -31.9 210 89 46 7.5 4.1 | -35.6 -32.1 205 94 49 7.3 4.0
29000 -33.2 -27.8 210 86 44 7.5 4.1 | -33.4 -28.1 205 93 48 7.3 4.0
28000 -31.0 -23.8 205 84 43 7.5 4.1 | -31.2 -24.2 205 91 47 7.3 4.0
27000 -28.8 -19.8 205 82 42 7.1 3.9 | -29.0 -20.2 205 90 46 7.0 3.8
26000 -26.7 -16.1 205 80 41 7.1 3.9 | -27.0 -16.6 205 87 45 7.0 3.8
25000 -24.5 -12.1 205 78 40 7.1 3.9 | -24.9 -12.8 205 85 44 7.0 3.8
24000 -22.4 -8.3 205 77 39 7.7 4.2 | -22.8 -9.0 205 82 42 7.5 4.1
23000 -20.1 -4.2 205 75 39 7.6 4.2 | -20.5 -4.9 205 79 41 7.4 4.1
22000 -17.3 0.9 205 73 38 7.7 4.2 | -17.8 -0.0 200 76 39 7.5 4.1
21000 -15.2 4.6 205 70 36 6.3 3.5 | -15.7 3.7 200 72 37 6.3 3.5
20000 -13.4 7.9 205 67 34 6.3 3.4 | -13.9 7.0 200 69 35 6.3 3.5
19500 -12.4 9.7 200 65 34 6.3 3.4 | -13.0 8.6 200 67 34 6.3 3.5
19000 -11.5 11.3 200 63 33 6.2 3.4 | -12.0 10.4 200 65 33 6.3 3.4
18500 -10.6 12.9 200 62 32 5.9 3.3 | -11.1 12.0 200 63 33 6.2 3.4
18000 -9.8 14.4 200 60 31 6.0 3.3 | -10.2 13.6 200 62 32 6.2 3.4
17500 -8.9 16.0 200 58 30 5.7 3.1 | -9.3 15.3 200 60 31 5.9 3.3
17000 -8.1 17.4 200 57 29 5.7 3.1 | -8.4 16.9 195 59 30 5.9 3.2
16500 -7.3 18.9 195 55 28 5.7 3.1 | -7.6 18.3 195 57 29 5.9 3.3
16000 -6.5 20.3 195 53 27 5.6 3.1 | -6.7 19.9 195 55 28 6.0 3.3
15500 -5.7 21.7 195 52 27 5.7 3.1 | -5.8 21.6 195 54 28 6.1 3.3
15000 -4.9 23.2 195 50 26 5.8 3.2 | -5.0 23.0 195 52 27 6.1 3.3
14500 -4.1 24.6 190 48 25 5.8 3.2 | -4.1 24.6 195 50 26 6.1 3.4
14000 -3.2 26.2 190 47 24 6.6 3.6 | -3.3 26.1 190 49 25 6.7 3.7
13500 -2.3 27.9 190 46 24 6.6 3.6 | -2.3 27.9 190 47 24 6.8 3.7
13000 -1.3 29.7 190 45 23 6.7 3.7 | -1.4 29.5 190 46 24 7.0 3.9
12500 -0.4 31.3 190 44 22 6.7 3.7 | -0.4 31.3 190 44 23 7.2 3.9
12000 0.5 32.9 190 43 22 7.0 3.8 | 0.7 33.3 190 43 22 7.1 3.9
11500 1.5 34.7 190 41 21 7.1 3.9 | 1.7 35.1 190 40 21 7.1 3.9
11000 2.5 36.5 190 39 20 7.1 3.9 | 2.7 36.9 190 38 19 6.9 3.8
10500 3.6 38.5 190 37 19 6.6 3.6 | 3.6 38.5 190 35 18 6.2 3.4
10250 4.1 39.4 190 36 19 9.1 5.0 | 4.1 39.4 190 33 17 8.5 4.7
10000 4.8 40.6 190 34 18 10.0 5.5 | 4.8 40.6 195 32 17 9.5 5.2
9750 5.4 41.7 190 33 17 8.2 4.5 | 5.4 41.7 195 31 16 8.0 4.4
9500 6.0 42.8 190 32 17 8.7 4.8 | 6.0 42.8 195 30 15 8.2 4.5
9250 6.7 44.1 190 31 16 8.3 4.6 | 6.6 43.9 195 29 15 9.0 5.0
9000 7.3 45.1 190 31 16 8.1 4.5 | 7.3 45.1 195 27 14 9.5 5.2
8750 7.9 46.2 190 29 15 8.2 4.5 | 7.9 46.2 195 26 13 8.8 4.8
8500 8.5 47.3 190 28 14 8.4 4.6 | 8.6 47.5 195 25 13 8.9 4.9
8250 9.6 49.3 190 25 13 7.1 3.9 | 9.2 48.6 195 25 13 9.0 5.0
8000 10.1 50.2 190 23 12 7.6 4.2 | 10.6 51.1 195 23 12 9.3 5.1
7750 10.7 51.3 185 21 11 8.1 4.4 | 11.3 52.3 195 22 12 9.3 5.1
7500 11.3 52.3 185 18 9 6.7 3.7 | 11.9 53.4 195 22 11 9.1 5.0
7250 11.7 53.1 185 17 9 5.5 3.0 | 12.6 54.7 195 21 11 9.0 4.9
7000 12.1 53.8 180 16 8 6.6 3.6 | 13.3 55.9 195 21 11 9.9 5.5
6750 12.6 54.7 175 13 7 6.5 3.6 | 14.1 57.4 200 20 10 10.6 5.8
6500 13.1 55.6 170 11 6 5.1 2.8 | 14.8 58.6 200 19 10 10.6 5.8
6250 13.4 56.1 165 10 5 4.8 2.6 | 15.6 60.1 200 18 9 11.3 6.2
6000 13.8 56.8 155 9 4 4.5 2.5 | 16.4 61.5 200 17 9 8.4 4.6
5750 14.0 57.2 145 6 3 -0.3 -0.2 | 16.9 62.4 200 16 8 8.9 4.9
5500 13.4 56.1 120 4 2 -17.9 -9.8 | 18.8 65.8 200 13 7 55.4 30.4
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
10/15/2025 at 1500 MDT | 10/15/2025 at 1800 MDT
|
CAPE... +219.6 LI... -0.6 | CAPE... +208.4 LI... -1.1
CINH... -2.5 K Index... +19.6 | CINH... -21.2 K Index... +23.1
|
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 -61.6 -78.9 210 56 29 2.5 1.4 | -60.9 -77.6 215 52 27 3.0 1.7
45000 -57.6 -71.7 215 83 43 2.7 1.5 | -56.3 -69.3 215 75 39 2.3 1.3
40000 -53.7 -64.7 210 101 52 2.4 1.3 | -52.8 -63.0 210 98 50 2.3 1.2
38000 -50.6 -59.1 210 102 53 5.4 3.0 | -49.7 -57.5 210 102 53 5.4 3.0
36000 -47.4 -53.3 205 103 53 5.4 3.0 | -46.5 -51.7 205 106 55 5.4 3.0
34000 -43.4 -46.1 205 102 53 6.4 3.5 | -43.0 -45.4 205 107 55 6.1 3.3
32000 -39.6 -39.3 205 100 51 6.4 3.5 | -39.3 -38.7 205 106 55 6.1 3.3
30000 -35.4 -31.7 205 97 50 7.3 4.0 | -35.5 -31.9 205 104 54 6.6 3.6
29000 -33.3 -27.9 205 96 49 7.3 4.0 | -33.6 -28.5 205 103 53 6.6 3.6
28000 -31.1 -24.0 205 94 48 7.3 4.0 | -31.6 -24.9 205 101 52 6.6 3.6
27000 -29.0 -20.2 205 92 47 6.9 3.8 | -29.2 -20.6 205 99 51 6.3 3.4
26000 -26.9 -16.4 205 90 46 6.9 3.8 | -27.3 -17.1 205 96 49 6.3 3.4
25000 -24.8 -12.6 200 88 45 7.0 3.8 | -25.4 -13.7 205 93 48 6.3 3.4
24000 -22.8 -9.0 200 85 44 6.6 3.6 | -23.6 -10.5 200 90 46 6.2 3.4
23000 -20.8 -5.4 200 82 42 6.6 3.6 | -21.7 -7.1 200 86 44 6.2 3.4
22000 -18.8 -1.8 200 79 41 6.6 3.6 | -19.9 -3.8 200 82 42 6.2 3.4
21000 -16.4 2.5 200 75 39 6.5 3.6 | -18.0 -0.4 200 78 40 6.4 3.5
20000 -14.4 6.1 200 72 37 6.5 3.6 | -16.1 3.0 200 73 38 6.4 3.5
19500 -13.5 7.7 200 70 36 6.5 3.6 | -15.1 4.8 200 70 36 6.4 3.5
19000 -12.5 9.5 200 69 35 6.5 3.5 | -14.2 6.4 200 68 35 6.5 3.5
18500 -11.6 11.1 200 67 34 6.1 3.3 | -13.3 8.1 200 65 34 5.8 3.2
18000 -10.7 12.7 200 65 33 6.1 3.4 | -12.4 9.7 195 63 33 5.9 3.2
17500 -9.8 14.4 200 62 32 5.5 3.0 | -11.5 11.3 195 61 31 6.1 3.3
17000 -9.1 15.6 195 60 31 5.4 2.9 | -10.6 12.9 195 59 31 6.3 3.5
16500 -8.3 17.1 195 57 29 5.4 3.0 | -9.7 14.5 195 58 30 6.4 3.5
16000 -7.5 18.5 195 55 28 5.4 3.0 | -8.8 16.2 190 56 29 7.0 3.8
15500 -6.7 19.9 195 52 27 5.3 2.9 | -7.8 18.0 190 54 28 7.0 3.8
15000 -5.9 21.4 195 50 26 6.5 3.6 | -6.8 19.8 190 52 27 7.7 4.2
14500 -5.0 23.0 195 48 25 6.4 3.5 | -5.6 21.9 190 50 26 7.9 4.3
14000 -4.1 24.6 190 46 24 7.3 4.0 | -4.5 23.9 185 48 24 7.8 4.3
13500 -3.0 26.6 190 44 23 7.5 4.1 | -3.4 25.9 190 46 24 7.8 4.3
13000 -1.9 28.6 190 42 22 8.2 4.5 | -2.2 28.0 190 44 23 7.8 4.3
12500 -0.7 30.7 190 40 21 8.5 4.7 | -1.1 30.0 190 42 21 7.7 4.2
12000 0.6 33.1 190 39 20 8.5 4.7 | 0.0 32.0 190 39 20 7.8 4.3
11500 1.8 35.2 195 36 19 8.5 4.6 | 1.1 34.0 195 36 19 7.8 4.3
11000 3.0 37.4 195 34 18 8.2 4.5 | 2.3 36.1 195 33 17 7.6 4.2
10500 4.1 39.4 195 32 17 7.5 4.1 | 3.3 37.9 200 31 16 6.6 3.6
10250 4.7 40.5 195 31 16 9.6 5.3 | 3.9 39.0 200 30 16 8.8 4.8
10000 5.5 41.9 195 30 16 10.6 5.8 | 4.6 40.3 205 28 15 10.1 5.6
9750 6.2 43.2 200 30 15 9.1 5.0 | 5.3 41.5 205 27 14 8.0 4.4
9500 6.9 44.4 200 29 15 9.8 5.4 | 5.8 42.4 210 26 14 7.6 4.2
9250 7.6 45.7 200 28 15 8.5 4.7 | 6.4 43.5 210 25 13 8.0 4.4
9000 8.2 46.8 200 28 14 8.6 4.7 | 7.7 45.9 215 23 12 9.3 5.1
8750 8.9 48.0 200 27 14 9.8 5.4 | 8.4 47.1 220 22 11 8.5 4.7
8500 9.6 49.3 205 26 14 9.5 5.2 | 9.0 48.2 220 21 11 8.6 4.7
8250 10.3 50.5 205 26 13 9.6 5.2 | 9.6 49.3 225 20 11 7.9 4.3
8000 11.0 51.8 205 26 13 9.6 5.2 | 10.2 50.4 225 20 10 8.1 4.5
7750 12.4 54.3 205 24 12 9.7 5.3 | 10.8 51.4 230 18 9 9.0 4.9
7500 13.1 55.6 210 23 12 9.1 5.0 | 11.5 52.7 230 17 9 8.0 4.4
7250 13.7 56.7 210 23 12 8.5 4.7 | 12.0 53.6 235 17 9 6.4 3.5
7000 14.4 57.9 210 23 12 9.8 5.4 | 12.5 54.5 240 16 8 8.0 4.4
6750 15.1 59.2 210 22 11 10.6 5.8 | 13.2 55.8 240 15 8 10.0 5.5
6500 15.9 60.6 210 20 11 10.4 5.7 | 13.8 56.8 245 13 7 8.4 4.6
6250 16.7 62.1 210 20 10 11.2 6.1 | 14.4 57.9 250 13 6 7.3 4.0
6000 17.5 63.5 215 19 10 8.4 4.6 | 14.9 58.8 255 12 6 8.2 4.5
5750 18.0 64.4 215 17 9 9.4 5.1 | 15.5 59.9 250 10 5 8.5 4.7
5500 19.9 67.8 215 15 8 55.2 30.3 | 16.0 60.8 260 8 4 3.2 1.7
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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