Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
626
UXUS97 KGJT 041306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Friday, July 4, 2025
This forecast is for Friday, July 4, 2025:
If the trigger temperature of 79.5 F/26.4 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1212 ft/min (6.2 m/s)
Maximum height of thermals.................. 18824 ft MSL (13215 ft AGL)
Forecast maximum temperature................... 91.0 F/33.2 C
Time of trigger temperature.................... 1130 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................. 16571 ft MSL (10962 ft AGL)
Thermal soaring outlook for Saturday 07/05..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 05:53:46 / 20:43:36 MDT
Total possible sunshine........... 14 hr 49 min 51 sec (889 min 51 sec)
Altitude of sun at 13:18:41 MDT... 73.20 degrees
Upper air data from rawinsonde observation taken on 07/04/2025 at 0600 MDT
Freezing level.................. 15056 ft MSL (9447 ft AGL)
Convective condensation level... 17928 ft MSL (12319 ft AGL)
Lifted condensation level....... 18607 ft MSL (12998 ft AGL)
Lifted index.................... -1.8
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 -62.2 -80.0 230 36 19 2.6 1.4 M M M M M
45000 -56.7 -70.1 235 51 27 5.2 2.9 M M M M M
40000 -49.0 -56.2 245 62 32 4.8 2.6 M M M M M
38000 -46.1 -51.0 250 59 30 4.8 2.6 M M M M M
36000 -43.3 -45.9 250 56 29 4.8 2.6 M M M M M
34000 -40.3 -40.5 250 45 23 5.0 2.8 M M M M M
32000 -36.9 -34.4 250 31 16 4.7 2.6 M M M M M
30000 -32.5 -26.5 250 28 14 7.6 4.2 42.0 107.5 7.0 M M
29000 -30.2 -22.4 250 27 14 7.6 4.2 41.2 106.1 6.5 M M
28000 -28.0 -18.4 250 26 14 7.7 4.3 40.5 104.9 6.0 M M
27000 -25.6 -14.1 250 28 14 7.8 4.3 39.6 103.3 5.4 M M
26000 -23.3 -9.9 250 29 15 7.8 4.3 38.9 102.0 4.9 M M
25000 -21.0 -5.8 250 31 16 7.8 4.3 38.3 100.9 4.4 M M
24000 -18.7 -1.7 250 31 16 7.6 4.2 37.4 99.4 3.8 M M
23000 -16.4 2.5 250 30 16 7.6 4.2 36.6 97.9 3.2 M M
22000 -14.2 6.4 255 30 15 7.5 4.1 36.0 96.7 2.6 M M
21000 -12.0 10.4 250 28 14 7.3 4.0 35.0 95.0 1.8 M M
20000 -9.8 14.4 250 25 13 7.3 4.0 34.2 93.5 1.1 M M
19500 -8.7 16.3 250 24 12 7.4 4.1 33.8 92.8 0.8 M M
19000 -7.3 18.9 245 22 11 6.1 3.3 33.0 91.3 0.1 M M
18500 -6.4 20.5 240 21 11 6.2 3.4 32.3 90.2 -0.5 1176 6.0
18000 -5.6 21.9 240 19 10 5.4 2.9 31.7 89.0 -1.2 1136 5.8
17500 -4.8 23.4 235 18 9 5.6 3.1 30.9 87.6 -1.9 1100 5.6
17000 -4.1 24.6 230 16 8 6.4 3.5 30.2 86.4 -2.6 1063 5.4
16500 -3.1 26.4 230 15 8 7.3 4.0 29.8 85.6 -3.1 1019 5.2
16000 -2.1 28.2 230 13 7 7.4 4.1 29.4 84.9 -3.6 974 4.9
15500 -1.0 30.2 230 12 6 8.6 4.7 29.1 84.4 -4.0 925 4.7
15000 0.3 32.5 235 11 6 8.5 4.6 28.9 84.0 -4.2 873 4.4
14500 1.6 34.9 235 10 5 9.4 5.2 28.7 83.7 -4.4 820 4.2
14000 3.0 37.4 240 9 5 9.5 5.2 28.7 83.7 -4.5 763 3.9
13500 4.4 39.9 240 9 4 9.2 5.0 28.7 83.6 -4.6 707 3.6
13000 5.7 42.3 245 8 4 9.0 4.9 28.5 83.4 -4.7 652 3.3
12500 7.0 44.6 250 8 4 8.9 4.9 28.4 83.2 -4.9 597 3.0
12000 8.3 46.9 255 7 4 8.8 4.8 28.3 82.9 -5.0 543 2.8
11500 9.7 49.5 265 7 3 8.3 4.6 28.1 82.6 -5.2 489 2.5
11000 10.8 51.4 270 6 3 7.4 4.0 27.8 82.0 -5.6 440 2.2
10500 12.0 53.6 270 6 3 10.3 5.7 27.5 81.5 -5.8 390 2.0
10250 12.8 55.0 270 6 3 9.8 5.4 27.6 81.7 -5.8 358 1.8
10000 13.4 56.1 265 5 3 7.5 4.1 27.5 81.5 -5.9 332 1.7
9750 14.0 57.2 265 5 3 8.7 4.8 27.3 81.2 -6.1 307 1.6
9500 14.6 58.3 260 5 3 6.1 3.3 27.2 81.0 -6.2 281 1.4
9250 15.0 59.0 255 4 2 5.7 3.1 26.8 80.3 -6.6 263 1.3
9000 15.5 59.9 245 4 2 7.9 4.3 26.7 80.0 -6.8 239 1.2
8750 16.1 61.0 235 4 2 7.5 4.1 26.5 79.7 -7.0 215 1.1
8500 16.6 61.9 225 4 2 6.7 3.7 26.3 79.4 -7.1 191 1.0
8250 17.0 62.6 220 4 2 5.6 3.1 26.0 78.8 -7.5 171 0.9
8000 17.5 63.5 205 4 2 6.0 3.3 25.7 78.3 -7.8 151 0.8
7750 17.9 64.2 195 4 2 5.8 3.2 25.4 77.7 -8.1 130 0.7
7500 18.3 64.9 190 5 2 5.3 2.9 25.1 77.2 -8.4 110 0.6
7250 18.7 65.7 180 6 3 4.6 2.5 24.7 76.5 -8.8 92 0.5
7000 19.0 66.2 175 6 3 4.8 2.6 24.3 75.8 -9.2 74 0.4
6750 19.3 66.7 170 7 3 2.5 1.4 23.9 75.0 -9.6 57 0.3
6500 19.4 66.9 160 6 3 -1.1 -0.6 23.2 73.8 -10.4 50 0.3
6250 19.2 66.6 155 6 3 -2.8 -1.5 22.3 72.2 -11.3 48 0.2
6000 19.1 66.4 145 6 3 3.1 1.7 21.5 70.7 -12.2 44 0.2
5750 19.2 66.6 130 6 3 -6.5 -3.6 20.9 69.7 -12.8 32 0.2
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 * * * * * *
07/04/2025 at 0900 MDT | 07/04/2025 at 1200 MDT
|
CAPE... +486.5 LI... -2.3 | CAPE... +612.0 LI... -1.2
CINH... -32.1 K Index... +27.5 | CINH... -7.3 K Index... +26.2
|
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 -62.6 -80.7 210 32 16 3.3 1.8 | -62.5 -80.5 215 32 17 2.9 1.6
45000 -55.7 -68.3 215 41 21 6.6 3.6 | -56.1 -69.0 215 46 24 6.4 3.5
40000 -46.3 -51.3 230 46 24 3.5 1.9 | -47.0 -52.6 225 54 28 3.3 1.8
38000 -44.3 -47.7 230 48 25 3.4 1.9 | -45.0 -49.0 230 55 28 3.2 1.8
36000 -42.2 -44.0 235 51 26 3.3 1.8 | -43.1 -45.6 235 56 29 3.3 1.8
34000 -39.3 -38.7 240 46 23 5.3 2.9 | -39.7 -39.5 235 50 26 5.5 3.0
32000 -36.1 -33.0 245 38 20 5.4 3.0 | -36.4 -33.5 235 43 22 5.4 3.0
30000 -31.7 -25.1 250 33 17 8.0 4.4 | -32.2 -26.0 235 38 20 7.4 4.1
29000 -29.3 -20.7 255 30 16 8.0 4.4 | -30.0 -22.0 240 36 19 7.4 4.1
28000 -26.9 -16.4 260 28 15 7.9 4.3 | -27.7 -17.9 240 34 18 7.4 4.1
27000 -24.2 -11.6 265 26 14 7.0 3.8 | -25.5 -13.9 245 31 16 7.4 4.1
26000 -22.1 -7.8 270 25 13 7.0 3.8 | -23.3 -9.9 255 29 15 7.4 4.1
25000 -20.0 -4.0 275 24 13 7.0 3.8 | -21.1 -6.0 260 27 14 7.3 4.0
24000 -18.0 -0.4 275 23 12 6.9 3.8 | -18.8 -1.8 265 25 13 8.1 4.5
23000 -15.9 3.4 275 22 11 6.9 3.8 | -16.3 2.7 270 24 12 8.1 4.5
22000 -13.8 7.2 275 20 10 6.7 3.7 | -13.9 7.0 275 23 12 8.2 4.5
21000 -12.1 10.2 275 19 10 5.9 3.2 | -11.1 12.0 275 23 12 7.5 4.1
20000 -10.4 13.3 270 18 10 6.0 3.3 | -8.9 16.0 275 22 12 7.5 4.1
19500 -9.6 14.7 270 18 9 6.1 3.3 | -7.8 18.0 275 22 11 7.3 4.0
19000 -8.7 16.3 270 18 9 5.7 3.1 | -6.9 19.6 275 22 11 5.1 2.8
18500 -7.9 17.8 270 18 9 5.8 3.2 | -6.1 21.0 270 21 11 5.3 2.9
18000 -7.1 19.2 270 18 9 5.9 3.2 | -5.4 22.3 270 20 10 4.5 2.5
17500 -6.2 20.8 270 19 10 6.1 3.3 | -4.9 23.2 265 19 10 4.1 2.3
17000 -5.4 22.3 270 19 10 6.1 3.3 | -4.3 24.3 265 19 10 4.3 2.4
16500 -4.5 23.9 270 19 10 6.6 3.6 | -3.7 25.3 265 18 9 5.3 2.9
16000 -3.5 25.7 275 19 10 6.6 3.6 | -3.0 26.6 265 18 9 5.3 2.9
15500 -2.6 27.3 275 18 9 6.7 3.7 | -2.2 28.0 260 17 9 7.0 3.8
15000 -1.6 29.1 280 18 9 6.8 3.7 | -1.2 29.8 260 16 8 7.1 3.9
14500 -0.7 30.7 280 17 9 6.9 3.8 | -0.2 31.6 260 16 8 7.5 4.1
14000 0.4 32.7 285 16 8 7.2 3.9 | 0.9 33.6 260 15 8 7.8 4.3
13500 1.4 34.5 285 16 8 7.3 4.0 | 2.1 35.8 260 14 7 8.0 4.4
13000 2.5 36.5 290 15 8 7.9 4.3 | 3.3 37.9 260 13 7 8.3 4.6
12500 3.6 38.5 290 15 8 7.9 4.3 | 4.5 40.1 260 13 7 8.4 4.6
12000 4.8 40.6 290 15 8 8.2 4.5 | 5.7 42.3 260 12 6 8.7 4.8
11500 6.0 42.8 285 15 8 8.2 4.5 | 7.0 44.6 260 12 6 8.7 4.8
11000 7.1 44.8 280 15 8 7.4 4.0 | 8.2 46.8 260 12 6 8.4 4.6
10500 8.2 46.8 275 14 7 7.3 4.0 | 9.5 49.1 260 11 6 6.4 3.5
10250 8.7 47.7 275 14 7 5.8 3.2 | 9.8 49.6 260 11 6 6.8 3.7
10000 9.1 48.4 270 14 7 6.5 3.6 | 10.5 50.9 260 11 6 9.7 5.3
9750 9.6 49.3 270 13 7 7.8 4.3 | 11.1 52.0 260 10 5 9.0 4.9
9500 10.2 50.4 265 13 7 7.4 4.1 | 11.8 53.2 260 10 5 9.0 4.9
9250 10.7 51.3 260 12 6 6.6 3.6 | 12.4 54.3 260 9 5 8.1 4.4
9000 11.1 52.0 260 12 6 6.1 3.3 | 12.9 55.2 260 8 4 8.2 4.5
8750 12.0 53.6 250 10 5 6.1 3.4 | 13.5 56.3 255 7 4 8.9 4.9
8500 12.4 54.3 250 9 5 5.8 3.2 | 14.1 57.4 255 6 3 8.1 4.5
8250 12.8 55.0 250 8 4 5.6 3.1 | 14.6 58.3 255 6 3 5.7 3.1
8000 13.2 55.8 245 7 4 5.5 3.0 | 15.0 59.0 255 5 3 8.0 4.4
7750 13.5 56.3 235 6 3 5.5 3.0 | 16.7 62.1 250 4 2 10.2 5.6
7500 13.9 57.0 225 5 2 5.5 3.0 | 17.3 63.1 255 4 2 6.9 3.8
7250 14.3 57.7 220 4 2 5.8 3.2 | 17.8 64.0 255 4 2 8.4 4.6
7000 14.7 58.5 210 3 2 9.1 5.0 | 18.6 65.5 255 3 2 13.4 7.3
6750 15.5 59.9 195 3 2 9.6 5.3 | 19.6 67.3 250 4 2 12.3 6.7
6500 16.1 61.0 180 3 2 8.1 4.4 | 20.4 68.7 255 3 2 9.4 5.1
6250 16.7 62.1 170 3 2 7.9 4.3 | 21.1 70.0 260 3 1 8.9 4.9
6000 17.3 63.1 160 3 2 11.8 6.5 | 21.8 71.2 260 3 1 14.3 7.9
5750 18.5 65.3 165 3 1 20.6 11.3 | 23.4 74.1 255 3 1 29.9 16.4
5500 19.7 67.5 150 3 1 4.2 2.3 | 25.4 77.7 265 2 1 13.9 7.6
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
07/04/2025 at 1500 MDT | 07/04/2025 at 1800 MDT
|
CAPE... +342.6 LI... -0.5 | CAPE... +208.7 LI... -0.1
CINH... -10.2 K Index... +25.7 | CINH... -34.7 K Index... +24.9
|
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 -61.9 -79.4 215 32 17 3.0 1.6 | -61.8 -79.2 220 30 16 3.2 1.7
45000 -55.9 -68.6 220 46 24 6.0 3.3 | -55.7 -68.3 225 44 23 5.9 3.3
40000 -47.4 -53.3 230 56 29 3.7 2.0 | -47.1 -52.8 235 56 29 3.6 2.0
38000 -45.2 -49.4 235 57 29 3.6 2.0 | -45.0 -49.0 240 55 28 3.5 1.9
36000 -42.7 -44.9 240 58 30 3.6 2.0 | -42.7 -44.9 245 55 28 3.4 1.9
34000 -39.9 -39.8 240 49 25 4.8 2.7 | -40.3 -40.5 245 45 23 4.1 2.3
32000 -37.0 -34.6 240 39 20 4.7 2.6 | -37.8 -36.0 250 34 18 3.9 2.1
30000 -32.9 -27.2 245 33 17 7.3 4.0 | -33.5 -28.3 255 30 15 8.0 4.4
29000 -30.7 -23.3 250 31 16 7.3 4.0 | -31.1 -24.0 255 29 15 8.0 4.4
28000 -28.5 -19.3 250 28 15 7.7 4.2 | -28.7 -19.7 260 27 14 8.1 4.5
27000 -26.1 -15.0 255 27 14 8.1 4.4 | -26.2 -15.2 260 27 14 8.3 4.5
26000 -23.7 -10.7 255 26 13 8.1 4.4 | -23.7 -10.7 260 27 14 8.3 4.5
25000 -21.2 -6.2 260 25 13 8.1 4.5 | -21.3 -6.3 255 26 14 8.3 4.6
24000 -18.9 -2.0 260 24 13 7.6 4.2 | -19.0 -2.2 255 26 14 7.4 4.1
23000 -16.7 1.9 260 25 13 7.6 4.2 | -16.8 1.8 260 27 14 7.4 4.1
22000 -13.8 7.2 260 25 13 7.6 4.2 | -14.0 6.8 260 27 14 7.7 4.2
21000 -11.5 11.3 260 24 12 7.7 4.2 | -11.7 10.9 255 24 13 7.8 4.3
20000 -9.3 15.3 265 23 12 7.7 4.2 | -9.4 15.1 255 22 11 7.8 4.3
19500 -8.1 17.4 265 23 12 7.5 4.1 | -8.2 17.2 250 21 11 7.7 4.2
19000 -7.2 19.0 265 22 11 6.5 3.6 | -7.2 19.0 250 20 11 7.4 4.1
18500 -6.2 20.8 260 20 10 6.7 3.7 | -6.1 21.0 250 20 10 7.5 4.1
18000 -5.3 22.5 260 19 10 6.1 3.4 | -5.0 23.0 250 19 10 7.5 4.1
17500 -4.5 23.9 260 17 9 6.0 3.3 | -3.9 25.0 250 18 9 7.5 4.1
17000 -3.6 25.5 255 16 8 6.1 3.4 | -2.9 26.8 245 17 9 7.5 4.1
16500 -2.7 27.1 255 15 8 6.7 3.7 | -1.8 28.8 245 17 9 7.4 4.1
16000 -1.8 28.8 255 14 7 6.6 3.6 | -0.8 30.6 245 16 8 7.4 4.1
15500 -0.8 30.6 250 14 7 7.7 4.2 | 0.3 32.5 240 16 8 8.5 4.7
15000 0.3 32.5 250 13 7 7.7 4.2 | 1.5 34.7 240 16 8 8.5 4.7
14500 1.4 34.5 250 13 7 8.3 4.5 | 2.7 36.9 240 16 8 9.1 5.0
14000 2.6 36.7 245 13 6 8.6 4.7 | 4.1 39.4 235 15 8 9.3 5.1
13500 3.9 39.0 245 12 6 8.7 4.8 | 5.5 41.9 235 15 8 9.3 5.1
13000 5.1 41.2 245 12 6 8.9 4.9 | 6.8 44.2 235 15 8 9.2 5.1
12500 6.4 43.5 245 11 6 9.0 4.9 | 8.2 46.8 235 14 7 9.2 5.1
12000 7.7 45.9 250 11 6 9.0 5.0 | 9.5 49.1 235 13 7 9.1 5.0
11500 9.1 48.4 250 10 5 9.0 4.9 | 10.9 51.6 240 13 7 9.0 5.0
11000 10.4 50.7 250 10 5 8.8 4.8 | 12.2 54.0 240 12 6 8.5 4.7
10500 11.7 53.1 250 9 5 6.3 3.4 | 13.4 56.1 245 11 6 9.8 5.4
10250 12.1 53.8 255 8 4 7.1 3.9 | 14.2 57.6 240 11 6 10.1 5.5
10000 12.8 55.0 255 8 4 11.2 6.2 | 14.9 58.8 245 11 6 8.6 4.7
9750 13.6 56.5 255 8 4 10.2 5.6 | 15.5 59.9 245 11 5 9.0 4.9
9500 14.4 57.9 255 8 4 10.1 5.5 | 16.2 61.2 245 10 5 8.9 4.9
9250 15.1 59.2 260 7 4 9.1 5.0 | 16.9 62.4 250 10 5 8.9 4.9
9000 15.7 60.3 260 7 4 9.6 5.3 | 17.5 63.5 250 10 5 8.9 4.9
8750 16.5 61.7 260 7 4 10.3 5.6 | 18.2 64.8 250 9 5 8.8 4.8
8500 17.2 63.0 260 7 4 9.7 5.3 | 19.5 67.1 255 9 5 9.3 5.1
8250 17.9 64.2 260 7 4 8.2 4.5 | 20.2 68.4 260 9 5 10.0 5.5
8000 19.3 66.7 265 7 3 11.8 6.5 | 21.0 69.8 260 9 5 10.9 6.0
7750 20.2 68.4 265 7 4 10.1 5.5 | 21.8 71.2 255 9 5 9.9 5.4
7500 20.8 69.4 265 7 3 7.9 4.3 | 22.4 72.3 260 9 5 8.0 4.4
7250 21.4 70.5 270 6 3 8.9 4.9 | 23.1 73.6 260 9 5 8.6 4.7
7000 22.2 72.0 270 6 3 12.5 6.9 | 23.8 74.8 265 9 5 11.1 6.1
6750 23.2 73.8 270 6 3 11.9 6.5 | 24.6 76.3 260 8 4 11.2 6.2
6500 24.0 75.2 270 6 3 10.3 5.7 | 25.4 77.7 265 8 4 10.4 5.7
6250 24.7 76.5 275 6 3 9.6 5.2 | 26.2 79.2 265 8 4 10.1 5.5
6000 25.5 77.9 275 6 3 13.7 7.5 | 27.0 80.6 265 8 4 10.6 5.8
5750 27.0 80.6 275 6 3 28.6 15.7 | 27.9 82.2 265 7 4 17.8 9.8
5500 29.3 84.7 280 5 3 27.6 15.2 | 29.8 85.6 270 7 4 33.0 18.1
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.
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