Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
557
UXUS97 KGJT 091306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Wednesday, April 9, 2025
This forecast is for Wednesday, April 9, 2025:
If the trigger temperature of 63.4 F/17.4 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1058 ft/min (5.4 m/s)
Maximum height of thermals.................. 17825 ft MSL (12216 ft AGL)
Forecast maximum temperature................... 77.0 F/25.5 C
Time of trigger temperature.................... 1045 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................. 13473 ft MSL (7864 ft AGL)
Thermal soaring outlook for Thursday 04/10..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:45:19 / 19:45:47 MDT
Total possible sunshine........... 13 hr 0 min 28 sec (780 min 28 sec)
Altitude of sun at 13:15:33 MDT... 58.57 degrees
Upper air data from rawinsonde observation taken on 04/09/2025 at 0600 MDT
Freezing level.................. 12569 ft MSL (6960 ft AGL)
Convective condensation level... 18936 ft MSL (13327 ft AGL)
Lifted condensation level....... 18761 ft MSL (13152 ft AGL)
Lifted index.................... +0.6
K index......................... -3.8
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 -64.3 -83.7 290 59 30 2.7 1.5 M M M M M
45000 -60.5 -76.9 290 62 32 0.6 0.3 M M M M M
40000 -59.5 -75.1 290 55 28 0.1 0.1 M M M M M
38000 -56.7 -70.1 295 52 27 5.4 3.0 M M M M M
36000 -53.5 -64.3 295 50 26 5.4 3.0 M M M M M
34000 -49.6 -57.3 295 49 25 7.8 4.3 M M M M M
32000 -44.3 -47.7 300 50 26 7.8 4.3 M M M M M
30000 -39.8 -39.6 295 48 25 7.5 4.1 34.8 94.7 7.4 M M
29000 -37.5 -35.5 295 47 24 7.5 4.1 33.9 93.1 6.8 M M
28000 -35.3 -31.5 295 46 24 7.5 4.1 33.2 91.7 6.3 M M
27000 -33.0 -27.4 295 44 23 7.7 4.2 32.3 90.2 5.7 M M
26000 -30.7 -23.3 295 43 22 7.7 4.2 31.5 88.8 5.2 M M
25000 -28.4 -19.1 295 42 21 7.7 4.3 30.8 87.5 4.7 M M
24000 -26.0 -14.8 295 40 21 8.1 4.4 30.2 86.3 4.2 M M
23000 -23.6 -10.5 295 39 20 8.1 4.4 29.5 85.2 3.7 M M
22000 -21.1 -6.0 300 37 19 8.2 4.5 29.0 84.2 3.3 M M
21000 -18.9 -2.0 300 35 18 7.1 3.9 28.2 82.7 2.6 M M
20000 -16.8 1.8 300 34 17 7.1 3.9 27.2 81.0 1.9 M M
19500 -15.7 3.7 300 33 17 7.1 3.9 26.8 80.3 1.5 M M
19000 -14.6 5.7 300 32 16 7.0 3.8 26.4 79.5 1.2 M M
18500 -13.1 8.4 305 31 16 6.8 3.7 25.6 78.1 0.5 M M
18000 -12.1 10.2 305 30 15 7.1 3.9 25.2 77.3 0.1 M M
17500 -11.0 12.2 305 30 15 7.3 4.0 24.7 76.5 -0.4 1017 5.2
17000 -10.0 14.0 305 30 15 7.3 4.0 24.3 75.7 -0.7 970 4.9
16500 -8.8 16.2 305 30 15 8.0 4.4 24.0 75.1 -1.1 921 4.7
16000 -7.6 18.3 305 29 15 7.9 4.4 23.6 74.6 -1.3 871 4.4
15500 -6.5 20.3 310 29 15 7.7 4.2 23.3 74.0 -1.6 821 4.2
15000 -5.3 22.5 310 28 15 7.7 4.2 23.0 73.4 -2.0 772 3.9
14500 -4.2 24.4 310 28 14 7.5 4.1 22.6 72.8 -2.3 723 3.7
14000 -3.1 26.4 310 27 14 7.4 4.1 22.2 72.0 -2.6 675 3.4
13500 -2.0 28.4 310 26 13 7.3 4.0 21.9 71.4 -3.0 627 3.2
13000 -0.9 30.4 310 24 12 7.2 3.9 21.4 70.6 -3.4 580 2.9
12500 0.2 32.4 310 22 12 7.1 3.9 21.0 69.9 -3.8 533 2.7
12000 1.2 34.2 315 20 10 6.7 3.7 20.6 69.0 -4.3 489 2.5
11500 2.2 36.0 315 18 9 6.6 3.6 20.1 68.2 -4.8 445 2.3
11000 3.0 37.4 320 15 8 5.9 3.2 19.5 67.1 -5.4 403 2.0
10500 3.9 39.0 320 12 6 4.2 2.3 18.9 66.1 -6.0 362 1.8
10250 4.1 39.4 320 10 5 4.8 2.6 18.4 65.2 -6.6 348 1.8
10000 4.6 40.3 325 8 4 7.5 4.1 18.2 64.8 -6.8 326 1.7
9750 5.1 41.2 330 6 3 6.9 3.8 18.0 64.4 -7.1 304 1.5
9500 5.6 42.1 335 5 2 6.5 3.6 17.8 64.0 -7.3 282 1.4
9250 6.1 43.0 355 4 2 6.8 3.7 17.5 63.5 -7.6 261 1.3
9000 6.6 43.9 015 3 2 7.9 4.3 17.3 63.2 -7.8 237 1.2
8750 7.2 45.0 040 3 2 7.8 4.3 17.2 62.9 -8.0 213 1.1
8500 7.7 45.9 055 4 2 6.8 3.8 17.0 62.6 -8.2 189 1.0
8250 8.2 46.8 060 4 2 6.2 3.4 16.7 62.1 -8.5 167 0.8
8000 8.7 47.7 065 5 2 7.0 3.8 16.5 61.7 -8.7 145 0.7
7750 9.2 48.6 070 5 3 7.0 3.9 16.3 61.3 -9.0 122 0.6
7500 9.7 49.5 070 6 3 6.7 3.7 16.1 60.9 -9.2 99 0.5
7250 10.2 50.4 070 6 3 6.4 3.5 15.8 60.5 -9.5 77 0.4
7000 10.7 51.3 070 6 3 6.8 3.8 15.6 60.0 -9.7 55 0.3
6750 11.1 52.0 070 6 3 2.0 1.1 15.3 59.5 -10.1 36 0.2
6500 11.0 51.8 075 6 3 -2.5 -1.4 14.4 57.9 -11.0 32 0.2
6250 10.9 51.6 080 6 3 0.1 0.1 13.6 56.4 -11.8 28 0.1
6000 10.8 51.4 080 5 3 -5.3 -2.9 12.8 55.0 -12.7 23 0.1
5750 9.7 49.5 080 5 3 -27.2 -14.9 10.9 51.6 -14.6 50 0.3
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 * * * * * *
04/09/2025 at 0900 MDT | 04/09/2025 at 1200 MDT
|
CAPE... 0.0 LI... +3.9 | CAPE... 0.0 LI... +3.9
CINH... 0.0 K Index... +8.0 | CINH... 0.0 K Index... +11.8
|
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 -61.8 -79.2 290 57 29 3.8 2.1 | -62.2 -80.0 285 58 30 3.3 1.8
45000 -56.8 -70.2 295 75 39 -2.6 -1.4 | -57.8 -72.0 290 74 38 -2.1 -1.1
40000 -60.1 -76.2 290 73 38 -2.2 -1.2 | -60.5 -76.9 295 78 40 -1.7 -0.9
38000 -58.6 -73.5 295 72 37 5.1 2.8 | -58.5 -73.3 295 76 39 5.5 3.0
36000 -55.1 -67.2 295 72 37 5.1 2.8 | -54.8 -66.6 295 73 37 5.5 3.0
34000 -51.1 -60.0 295 71 36 8.8 4.8 | -50.6 -59.1 295 69 36 8.5 4.7
32000 -45.9 -50.6 295 68 35 8.7 4.8 | -45.6 -50.1 290 66 34 8.5 4.7
30000 -40.9 -41.6 295 66 34 7.9 4.3 | -40.7 -41.3 290 64 33 7.7 4.2
29000 -38.5 -37.3 290 65 33 7.9 4.3 | -38.4 -37.1 290 63 32 7.8 4.3
28000 -36.1 -33.0 290 64 33 7.9 4.3 | -36.0 -32.8 290 62 32 7.7 4.3
27000 -33.8 -28.8 290 63 32 7.7 4.2 | -33.8 -28.8 290 61 32 7.2 4.0
26000 -31.5 -24.7 290 63 32 7.7 4.2 | -31.6 -24.9 290 61 31 7.2 4.0
25000 -29.2 -20.6 290 63 32 7.7 4.3 | -29.5 -21.1 290 60 31 7.2 4.0
24000 -26.9 -16.4 290 62 32 7.5 4.1 | -27.2 -17.0 290 59 31 8.1 4.5
23000 -24.6 -12.3 295 60 31 7.5 4.1 | -24.8 -12.6 290 57 29 8.1 4.4
22000 -21.8 -7.2 295 57 29 7.6 4.2 | -21.8 -7.2 290 55 28 8.1 4.5
21000 -19.8 -3.6 295 53 27 6.1 3.3 | -19.6 -3.3 290 52 27 6.7 3.7
20000 -18.0 -0.4 290 50 25 6.0 3.3 | -17.6 0.3 290 50 26 6.7 3.7
19500 -17.1 1.2 290 48 25 6.1 3.3 | -16.6 2.1 290 48 25 6.7 3.7
19000 -16.2 2.8 290 46 24 6.1 3.4 | -15.6 3.9 290 47 24 5.7 3.1
18500 -15.3 4.5 295 44 23 6.2 3.4 | -14.9 5.2 290 45 23 4.9 2.7
18000 -14.4 6.1 295 43 22 6.3 3.4 | -14.2 6.4 290 43 22 4.8 2.6
17500 -13.5 7.7 295 42 21 6.2 3.4 | -13.4 7.9 290 41 21 6.3 3.5
17000 -12.5 9.5 295 41 21 6.2 3.4 | -12.5 9.5 290 39 20 6.2 3.4
16500 -11.6 11.1 295 39 20 6.6 3.6 | -11.6 11.1 290 37 19 6.3 3.4
16000 -10.6 12.9 295 37 19 6.9 3.8 | -10.7 12.7 290 34 18 6.4 3.5
15500 -9.6 14.7 295 36 18 7.2 3.9 | -9.8 14.4 290 32 16 7.0 3.9
15000 -8.5 16.7 295 33 17 7.7 4.2 | -8.6 16.5 285 30 15 8.1 4.4
14500 -7.3 18.9 295 31 16 7.7 4.2 | -7.4 18.7 285 27 14 8.1 4.4
14000 -6.2 20.8 295 28 15 7.8 4.3 | -6.2 20.8 280 25 13 8.2 4.5
13500 -5.0 23.0 290 26 13 7.8 4.3 | -5.0 23.0 280 24 12 8.2 4.5
13000 -3.9 25.0 290 23 12 7.9 4.3 | -3.7 25.3 275 22 11 8.5 4.7
12500 -2.7 27.1 290 21 11 7.9 4.3 | -2.5 27.5 275 20 10 8.5 4.7
12000 -1.5 29.3 290 18 9 7.9 4.3 | -1.2 29.8 275 19 10 8.5 4.6
11500 -0.3 31.5 290 16 8 7.8 4.3 | 0.1 32.2 275 17 9 8.5 4.6
11000 0.8 33.4 290 15 8 8.0 4.4 | 1.3 34.3 270 15 8 8.6 4.7
10500 2.0 35.6 290 13 7 8.2 4.5 | 2.6 36.7 270 14 7 8.8 4.8
10250 2.6 36.7 290 12 6 7.5 4.1 | 3.2 37.8 270 13 7 7.3 4.0
10000 3.1 37.6 290 12 6 7.9 4.3 | 3.7 38.7 270 12 6 8.0 4.4
9750 3.8 38.8 290 11 6 8.8 4.8 | 4.4 39.9 270 11 6 9.9 5.4
9500 4.4 39.9 290 10 5 8.6 4.7 | 5.1 41.2 270 11 5 9.4 5.1
9250 5.0 41.0 290 9 4 8.2 4.5 | 5.8 42.4 270 10 5 8.4 4.6
9000 5.6 42.1 290 8 4 7.6 4.2 | 6.4 43.5 275 9 5 8.1 4.5
8750 6.1 43.0 290 7 4 7.6 4.2 | 7.0 44.6 275 8 4 9.0 5.0
8500 6.7 44.1 290 6 3 7.3 4.0 | 7.7 45.9 275 7 4 8.2 4.5
8250 7.6 45.7 285 4 2 5.5 3.0 | 8.2 46.8 275 7 3 6.1 3.3
8000 8.1 46.6 280 3 1 7.9 4.3 | 9.3 48.7 280 5 3 11.3 6.2
7750 8.7 47.7 265 2 1 6.9 3.8 | 10.2 50.4 280 5 2 10.1 5.6
7500 9.1 48.4 220 1 1 4.3 2.4 | 10.7 51.3 280 5 2 6.8 3.7
7250 9.4 48.9 180 2 1 4.2 2.3 | 11.3 52.3 280 4 2 7.6 4.2
7000 9.7 49.5 160 2 1 6.5 3.6 | 12.0 53.6 285 4 2 12.6 6.9
6750 10.3 50.5 145 3 1 5.6 3.1 | 13.0 55.4 280 4 2 12.4 6.8
6500 10.5 50.9 140 3 2 3.3 1.8 | 13.8 56.8 285 4 2 9.2 5.1
6250 10.8 51.4 135 4 2 3.3 1.8 | 14.5 58.1 285 3 2 8.9 4.9
6000 11.1 52.0 135 4 2 6.3 3.4 | 15.2 59.4 285 3 2 14.4 7.9
5750 11.8 53.2 130 4 2 12.8 7.0 | 16.8 62.2 285 3 2 28.0 15.4
5500 12.4 54.3 120 3 2 -4.7 -2.6 | 18.4 65.1 290 3 1 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
04/09/2025 at 1500 MDT | 04/09/2025 at 1800 MDT
|
CAPE... 0.0 LI... +3.5 | CAPE... +0.1 LI... +2.5
CINH... -0.4 K Index... +13.3 | CINH... -0.2 K Index... +15.8
|
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 -62.5 -80.5 290 61 31 2.6 1.4 | -62.8 -81.0 290 62 32 2.0 1.1
45000 -59.1 -74.4 295 74 38 -1.4 -0.8 | -60.1 -76.2 295 74 38 -0.2 -0.1
40000 -61.1 -78.0 300 74 38 -1.2 -0.6 | -60.4 -76.7 300 69 36 -0.0 -0.0
38000 -58.3 -72.9 295 72 37 6.1 3.3 | -57.4 -71.3 295 68 35 5.7 3.2
36000 -54.6 -66.3 295 70 36 6.1 3.3 | -54.0 -65.2 295 67 35 5.7 3.2
34000 -50.3 -58.5 290 68 35 8.3 4.6 | -49.8 -57.6 295 66 34 8.1 4.4
32000 -45.3 -49.5 295 65 33 8.3 4.6 | -45.0 -49.0 295 63 32 8.1 4.4
30000 -40.5 -40.9 295 63 32 7.7 4.2 | -40.2 -40.4 295 61 31 7.8 4.3
29000 -38.2 -36.8 295 62 32 7.7 4.2 | -37.9 -36.2 295 60 31 7.8 4.3
28000 -35.9 -32.6 290 61 31 7.7 4.2 | -35.6 -32.1 295 59 31 7.8 4.3
27000 -33.6 -28.5 290 60 31 7.4 4.1 | -33.3 -27.9 300 59 30 7.4 4.1
26000 -31.4 -24.5 295 60 31 7.4 4.1 | -31.0 -23.8 300 59 31 7.4 4.1
25000 -29.2 -20.6 295 59 30 7.4 4.1 | -28.8 -19.8 300 60 31 7.4 4.1
24000 -26.9 -16.4 295 58 30 8.1 4.5 | -26.0 -14.8 300 59 30 7.9 4.3
23000 -23.9 -11.0 295 56 29 8.1 4.4 | -23.6 -10.5 300 58 30 7.9 4.3
22000 -21.5 -6.7 295 55 28 8.1 4.4 | -21.3 -6.3 300 56 29 7.9 4.4
21000 -19.2 -2.6 295 53 27 7.5 4.1 | -19.1 -2.4 300 54 28 7.2 3.9
20000 -16.9 1.6 295 50 26 7.5 4.1 | -16.9 1.6 300 51 26 7.2 3.9
19500 -15.8 3.6 295 49 25 7.5 4.1 | -15.9 3.4 300 49 25 7.2 3.9
19000 -14.7 5.5 295 47 24 6.2 3.4 | -14.8 5.4 300 47 24 6.4 3.5
18500 -13.9 7.0 290 45 23 5.6 3.0 | -14.0 6.8 300 44 23 6.1 3.3
18000 -13.1 8.4 290 43 22 5.5 3.0 | -13.1 8.4 300 41 21 6.0 3.3
17500 -12.3 9.9 290 40 20 5.1 2.8 | -12.2 10.0 300 38 19 5.7 3.1
17000 -11.6 11.1 290 36 19 5.1 2.8 | -11.4 11.5 295 34 17 5.7 3.1
16500 -10.8 12.6 290 33 17 6.5 3.6 | -10.5 13.1 295 30 16 7.5 4.1
16000 -9.8 14.4 285 30 15 6.8 3.7 | -9.3 15.3 295 27 14 7.8 4.3
15500 -8.9 16.0 285 27 14 7.3 4.0 | -8.2 17.2 295 25 13 8.2 4.5
15000 -7.7 18.1 285 25 13 7.9 4.3 | -6.9 19.6 295 23 12 8.6 4.7
14500 -6.6 20.1 280 22 12 8.1 4.5 | -5.7 21.7 290 21 11 8.7 4.8
14000 -5.3 22.5 280 21 11 8.9 4.9 | -4.3 24.3 290 20 10 9.1 5.0
13500 -4.0 24.8 275 20 10 8.9 4.9 | -3.0 26.6 290 19 10 9.1 5.0
13000 -2.6 27.3 275 19 10 9.4 5.2 | -1.6 29.1 290 18 9 9.2 5.0
12500 -1.2 29.8 275 18 9 9.4 5.2 | -0.2 31.6 285 18 9 9.2 5.0
12000 0.2 32.4 275 17 9 9.1 5.0 | 1.1 34.0 285 17 9 9.3 5.1
11500 1.6 34.9 270 17 9 9.2 5.0 | 2.5 36.5 285 17 9 9.3 5.1
11000 2.9 37.2 270 17 9 9.1 5.0 | 4.0 39.2 285 17 9 9.6 5.3
10500 4.3 39.7 270 16 8 9.0 5.0 | 5.4 41.7 280 16 8 9.5 5.2
10250 4.9 40.8 270 16 8 8.1 4.5 | 6.0 42.8 280 16 8 7.4 4.0
10000 5.5 41.9 275 15 8 8.9 4.9 | 6.6 43.9 280 16 8 8.5 4.6
9750 6.3 43.3 275 15 8 9.9 5.4 | 7.3 45.1 280 16 8 10.8 5.9
9500 7.0 44.6 275 14 7 9.6 5.3 | 8.1 46.6 280 16 8 10.1 5.5
9250 7.7 45.9 275 14 7 9.3 5.1 | 8.8 47.8 280 15 8 9.5 5.2
9000 8.4 47.1 275 13 7 9.1 5.0 | 9.5 49.1 280 15 8 9.0 4.9
8750 9.1 48.4 275 13 7 9.3 5.1 | 10.9 51.6 280 14 7 9.1 5.0
8500 9.8 49.6 275 12 6 8.9 4.9 | 11.6 52.9 280 14 7 8.0 4.4
8250 10.4 50.7 275 12 6 7.5 4.1 | 12.1 53.8 280 13 7 8.4 4.6
8000 11.7 53.1 275 12 6 12.1 6.6 | 12.9 55.2 280 13 7 10.3 5.7
7750 12.6 54.7 275 11 6 10.6 5.8 | 13.6 56.5 280 13 7 9.8 5.4
7500 13.2 55.8 275 11 6 7.7 4.2 | 14.3 57.7 280 12 6 8.4 4.6
7250 13.9 57.0 280 11 6 8.7 4.8 | 14.9 58.8 275 12 6 8.8 4.8
7000 14.6 58.3 280 11 6 12.5 6.8 | 15.7 60.3 275 12 6 11.2 6.2
6750 15.6 60.1 275 11 5 12.1 6.6 | 16.5 61.7 280 12 6 11.3 6.2
6500 16.4 61.5 280 11 5 10.0 5.5 | 17.3 63.1 275 11 6 10.0 5.5
6250 17.1 62.8 280 10 5 9.1 5.0 | 18.1 64.6 275 11 6 9.6 5.3
6000 17.9 64.2 280 10 5 14.9 8.2 | 18.8 65.8 275 11 6 10.7 5.9
5750 19.6 67.3 280 9 5 30.0 16.5 | 19.8 67.6 275 10 5 16.4 9.0
5500 21.4 70.5 285 9 5 5.0 2.7 | 21.0 69.8 275 9 5 14.7 8.1
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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