Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
366
UXUS97 KGJT 221306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Tuesday, April 22, 2025
This forecast is for Tuesday, April 22, 2025:
If the trigger temperature of 66.1 F/18.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1658 ft/min (8.4 m/s)
Maximum height of thermals.................. 22468 ft MSL (16858 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................. 18588 ft MSL (12977 ft AGL)
Thermal soaring outlook for Wednesday 04/23.... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:26:36 / 19:58:29 MDT
Total possible sunshine........... 13 hr 31 min 53 sec (811 min 53 sec)
Altitude of sun at 13:12:32 MDT... 63.22 degrees
Upper air data from rawinsonde observation taken on 04/22/2025 at 0600 MDT
Freezing level.................. 12163 ft MSL (6553 ft AGL)
Convective condensation level... 18404 ft MSL (12794 ft AGL)
Lifted condensation level....... 19935 ft MSL (14325 ft AGL)
Lifted index.................... -1.7
K index......................... +14.0
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 -59.2 -74.6 255 44 22 1.4 0.8 M M M M M
45000 -57.1 -70.8 255 48 25 -0.7 -0.4 M M M M M
40000 -60.9 -77.6 255 55 28 -2.6 -1.4 M M M M M
38000 -60.3 -76.5 255 55 28 4.6 2.5 M M M M M
36000 -57.6 -71.7 250 51 26 4.6 2.5 M M M M M
34000 -54.5 -66.1 250 48 25 8.3 4.6 M M M M M
32000 -49.0 -56.2 250 43 22 8.1 4.4 M M M M M
30000 -44.1 -47.4 250 40 21 8.6 4.7 30.0 85.9 3.7 M M
29000 -41.5 -42.7 250 40 20 8.6 4.7 29.4 85.0 3.4 M M
28000 -39.0 -38.2 245 39 20 8.6 4.7 29.0 84.3 3.1 M M
27000 -36.5 -33.7 245 39 20 7.8 4.3 28.7 83.6 2.8 M M
26000 -34.2 -29.6 245 39 20 7.6 4.2 27.7 81.9 2.1 M M
25000 -31.9 -25.4 245 39 20 7.7 4.2 27.0 80.5 1.5 M M
24000 -29.6 -21.3 245 39 20 7.8 4.3 26.3 79.4 1.0 M M
23000 -27.3 -17.1 245 38 19 7.9 4.3 25.5 78.0 0.3 M M
22000 -24.9 -12.8 240 36 18 7.9 4.3 24.9 76.8 -0.2 1618 8.2
21000 -22.6 -8.7 240 34 17 7.0 3.9 24.2 75.6 -0.8 1519 7.7
20000 -20.5 -4.9 240 31 16 7.0 3.8 23.2 73.7 -1.7 1428 7.3
19500 -19.5 -3.1 240 30 15 7.0 3.8 22.7 72.8 -2.1 1382 7.0
19000 -18.5 -1.3 235 28 15 7.0 3.8 22.2 72.0 -2.6 1337 6.8
18500 -16.9 1.6 235 27 14 7.4 4.1 21.6 70.9 -3.2 1267 6.4
18000 -15.8 3.6 235 26 13 7.4 4.1 21.2 70.1 -3.6 1220 6.2
17500 -14.7 5.5 235 25 13 8.6 4.7 20.9 69.5 -3.9 1172 6.0
17000 -13.4 7.9 235 24 13 9.1 5.0 20.7 69.3 -4.1 1117 5.7
16500 -12.0 10.4 235 24 12 9.1 5.0 20.6 69.1 -4.2 1061 5.4
16000 -10.7 12.7 235 23 12 9.0 4.9 20.5 68.9 -4.3 1006 5.1
15500 -9.3 15.3 235 22 12 9.0 4.9 20.4 68.7 -4.5 951 4.8
15000 -7.9 17.8 235 22 11 9.3 5.1 20.3 68.5 -4.6 895 4.5
14500 -6.6 20.1 235 21 11 9.2 5.1 20.2 68.4 -4.7 839 4.3
14000 -5.2 22.6 235 21 11 9.4 5.1 20.1 68.2 -4.8 783 4.0
13500 -3.8 25.2 235 20 10 9.4 5.2 20.1 68.1 -4.9 726 3.7
13000 -2.4 27.7 235 20 10 9.4 5.2 20.0 68.0 -4.9 669 3.4
12500 -0.9 30.4 235 19 10 9.5 5.2 20.0 67.9 -5.0 612 3.1
12000 0.5 32.9 235 19 10 9.3 5.1 19.9 67.9 -5.1 554 2.8
11500 1.8 35.2 230 18 9 9.1 5.0 19.8 67.7 -5.2 498 2.5
11000 3.2 37.8 230 17 9 8.8 4.8 19.7 67.5 -5.3 442 2.2
10500 4.5 40.1 225 16 8 9.0 4.9 19.5 67.1 -5.5 390 2.0
10250 5.2 41.4 225 16 8 10.3 5.6 19.5 67.1 -5.5 361 1.8
10000 5.9 42.6 225 16 8 8.9 4.9 19.5 67.2 -5.5 331 1.7
9750 6.5 43.7 220 16 8 7.6 4.2 19.4 66.9 -5.7 306 1.6
9500 7.1 44.8 215 15 8 7.9 4.3 19.2 66.6 -5.9 281 1.4
9250 7.7 45.9 210 15 8 8.4 4.6 19.1 66.4 -6.0 256 1.3
9000 8.3 46.9 205 15 8 6.9 3.8 19.0 66.2 -6.1 230 1.2
8750 8.8 47.8 200 14 7 5.5 3.0 18.7 65.6 -6.5 210 1.1
8500 9.2 48.6 195 14 7 5.6 3.0 18.4 65.0 -6.8 190 1.0
8250 9.6 49.3 185 14 7 6.7 3.7 18.1 64.5 -7.1 170 0.9
8000 10.1 50.2 180 13 7 5.7 3.1 17.8 64.1 -7.3 147 0.7
7750 10.4 50.7 175 13 6 3.7 2.0 17.4 63.3 -7.8 131 0.7
7500 10.7 51.3 165 12 6 4.3 2.3 17.0 62.5 -8.2 114 0.6
7250 11.0 51.8 160 12 6 3.9 2.2 16.5 61.8 -8.7 98 0.5
7000 11.3 52.3 155 11 6 3.0 1.6 16.1 60.9 -9.2 83 0.4
6750 11.5 52.7 150 11 5 2.9 1.6 15.5 60.0 -9.7 70 0.4
6500 11.7 53.1 145 10 5 1.6 0.9 15.0 59.0 -10.3 56 0.3
6250 11.6 52.9 135 9 4 -3.3 -1.8 14.2 57.6 -11.1 51 0.3
6000 11.0 51.8 125 7 4 -15.4 -8.4 12.9 55.1 -12.5 63 0.3
5750 9.2 48.6 115 6 3 -29.3 -16.1 10.4 50.7 -15.1 109 0.6
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 * * * * * *
04/22/2025 at 0900 MDT | 04/22/2025 at 1200 MDT
|
CAPE... 0.0 LI... +0.3 | CAPE... +2.0 LI... +1.5
CINH... -0.1 K Index... +13.9 | CINH... -0.2 K Index... +14.1
|
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 -58.0 -72.4 265 41 21 0.2 0.1 | -58.5 -73.3 260 43 22 0.0 0.0
45000 -57.6 -71.7 260 45 23 0.6 0.3 | -58.5 -73.3 255 50 26 0.2 0.1
40000 -61.4 -78.5 265 59 30 -2.5 -1.4 | -61.6 -78.9 265 57 29 -2.1 -1.1
38000 -60.4 -76.7 270 59 31 5.8 3.2 | -60.4 -76.7 265 57 29 5.7 3.1
36000 -56.9 -70.4 270 56 29 5.9 3.2 | -56.9 -70.4 265 55 28 5.7 3.1
34000 -53.3 -63.9 270 52 27 6.5 3.5 | -53.3 -63.9 265 52 27 7.1 3.9
32000 -49.4 -56.9 270 47 24 6.4 3.5 | -49.1 -56.4 265 48 24 7.0 3.9
30000 -45.4 -49.7 270 41 21 7.7 4.2 | -44.9 -48.8 270 42 22 6.8 3.7
29000 -43.1 -45.6 270 39 20 7.6 4.2 | -42.9 -45.2 265 38 20 6.8 3.7
28000 -40.8 -41.4 270 37 19 7.7 4.2 | -40.8 -41.4 265 34 18 6.8 3.7
27000 -38.5 -37.3 275 35 18 7.9 4.3 | -38.8 -37.8 265 30 16 7.6 4.2
26000 -35.4 -31.7 275 33 17 8.3 4.6 | -35.6 -32.1 270 28 14 8.6 4.7
25000 -32.9 -27.2 280 31 16 8.3 4.6 | -33.0 -27.4 270 26 13 8.6 4.7
24000 -30.4 -22.7 280 29 15 7.9 4.3 | -30.4 -22.7 275 25 13 8.4 4.6
23000 -28.1 -18.6 280 28 14 7.7 4.2 | -27.9 -18.2 275 24 12 8.4 4.6
22000 -25.8 -14.4 280 27 14 7.7 4.2 | -25.4 -13.7 275 23 12 8.4 4.6
21000 -23.6 -10.5 275 26 13 5.7 3.1 | -23.0 -9.4 275 23 12 6.8 3.7
20000 -21.8 -7.2 270 24 12 5.9 3.3 | -20.9 -5.6 270 23 12 7.0 3.8
19500 -21.0 -5.8 265 23 12 6.0 3.3 | -19.9 -3.8 270 22 12 7.0 3.8
19000 -20.1 -4.2 260 23 12 5.9 3.2 | -18.8 -1.8 265 22 11 7.1 3.9
18500 -19.1 -2.4 260 23 12 8.0 4.4 | -17.8 -0.0 265 22 11 6.2 3.4
18000 -17.9 -0.2 255 22 12 8.1 4.5 | -16.9 1.6 260 22 11 6.3 3.5
17500 -16.7 1.9 255 22 12 8.6 4.7 | -16.0 3.2 255 22 11 7.1 3.9
17000 -15.4 4.3 255 22 11 9.1 5.0 | -14.8 5.4 250 22 11 7.9 4.3
16500 -14.0 6.8 250 22 11 9.1 5.0 | -13.7 7.3 250 22 11 8.1 4.4
16000 -12.7 9.1 250 22 11 9.1 5.0 | -12.4 9.7 245 21 11 9.0 5.0
15500 -11.3 11.7 250 21 11 9.1 5.0 | -11.1 12.0 245 21 11 9.0 4.9
15000 -10.0 14.0 255 21 11 9.2 5.1 | -9.8 14.4 245 21 11 9.1 5.0
14500 -8.6 16.5 255 20 11 9.2 5.1 | -8.4 16.9 245 21 11 9.1 5.0
14000 -7.2 19.0 255 20 10 9.3 5.1 | -7.0 19.4 245 20 10 9.2 5.1
13500 -5.8 21.6 255 19 10 9.3 5.1 | -5.7 21.7 245 20 10 9.3 5.1
13000 -4.4 24.1 255 19 10 9.2 5.1 | -4.3 24.3 245 19 10 9.2 5.0
12500 -3.1 26.4 255 18 9 9.1 5.0 | -2.9 26.8 245 19 10 9.2 5.0
12000 -1.7 28.9 255 18 9 9.0 5.0 | -1.5 29.3 245 18 9 9.3 5.1
11500 -0.4 31.3 255 17 9 8.8 4.8 | -0.1 31.8 245 17 9 9.3 5.1
11000 1.0 33.8 255 16 8 7.9 4.4 | 1.3 34.3 245 17 9 8.3 4.6
10500 2.0 35.6 250 15 8 5.9 3.3 | 2.4 36.3 245 16 8 6.2 3.4
10250 2.5 36.5 250 15 8 10.6 5.8 | 2.9 37.2 245 16 8 11.6 6.4
10000 3.5 38.3 245 14 7 11.0 6.0 | 4.0 39.2 245 15 8 12.6 6.9
9750 4.1 39.4 245 13 7 6.5 3.5 | 4.6 40.3 245 15 8 7.6 4.2
9500 4.6 40.3 240 12 6 8.0 4.4 | 5.3 41.5 245 15 8 9.7 5.3
9250 5.2 41.4 240 12 6 6.4 3.5 | 5.9 42.6 245 14 7 6.4 3.5
9000 5.6 42.1 240 11 6 5.2 2.8 | 6.4 43.5 250 13 7 7.1 3.9
8750 6.6 43.9 230 10 5 7.5 4.1 | 7.8 46.0 245 12 6 10.0 5.5
8500 7.1 44.8 225 9 5 6.6 3.6 | 8.5 47.3 245 11 6 8.3 4.6
8250 7.6 45.7 220 9 4 5.2 2.9 | 9.1 48.4 250 9 5 6.7 3.7
8000 7.9 46.2 215 8 4 5.4 3.0 | 9.6 49.3 255 8 4 9.5 5.2
7750 8.4 47.1 205 8 4 6.3 3.5 | 10.4 50.7 250 8 4 11.5 6.3
7500 8.8 47.8 190 8 4 4.9 2.7 | 11.2 52.2 250 8 4 8.9 4.9
7250 9.1 48.4 190 8 4 3.1 1.7 | 11.8 53.2 255 7 4 6.7 3.7
7000 9.4 48.9 185 7 4 6.6 3.6 | 12.4 54.3 265 7 3 10.6 5.8
6750 10.0 50.0 175 7 4 8.5 4.6 | 13.3 55.9 255 7 4 12.5 6.8
6500 10.5 50.9 170 6 3 5.8 3.2 | 14.2 57.6 255 7 3 10.2 5.6
6250 10.9 51.6 165 6 3 4.6 2.5 | 14.9 58.8 265 6 3 10.0 5.5
6000 11.3 52.3 155 5 3 6.0 3.3 | 15.6 60.1 270 6 3 8.6 4.7
5750 11.9 53.4 155 4 2 11.9 6.5 | 16.4 61.5 255 6 3 14.5 8.0
5500 13.2 55.8 145 3 2 26.6 14.6 | 19.1 66.4 280 5 3 72.2 39.6
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
04/22/2025 at 1500 MDT | 04/22/2025 at 1800 MDT
|
CAPE... +6.9 LI... +1.1 | CAPE... 0.0 LI... +1.4
CINH... -1.8 K Index... +11.0 | CINH... -0.0 K Index... +5.2
|
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 -58.7 -73.7 260 46 24 -0.4 -0.2 | -58.7 -73.7 265 47 24 -0.2 -0.1
45000 -59.2 -74.6 260 55 28 -0.2 -0.1 | -59.0 -74.2 265 57 30 -0.1 -0.1
40000 -62.2 -80.0 265 59 30 -2.0 -1.1 | -62.7 -80.9 265 60 31 -2.5 -1.4
38000 -60.7 -77.3 265 58 30 5.9 3.3 | -61.1 -78.0 265 59 30 6.9 3.8
36000 -57.2 -71.0 265 54 28 6.0 3.3 | -56.9 -70.4 265 57 29 6.9 3.8
34000 -53.4 -64.1 260 51 26 7.4 4.0 | -52.8 -63.0 265 54 28 6.8 3.7
32000 -49.0 -56.2 260 47 24 7.4 4.0 | -48.7 -55.7 265 49 25 6.8 3.7
30000 -44.6 -48.3 265 43 22 7.1 3.9 | -44.5 -48.1 265 45 23 7.7 4.2
29000 -42.4 -44.3 260 40 20 7.1 3.9 | -42.1 -43.8 265 42 22 7.8 4.3
28000 -40.3 -40.5 260 37 19 7.1 3.9 | -39.8 -39.6 265 40 20 7.8 4.3
27000 -38.1 -36.6 260 34 17 7.4 4.0 | -37.5 -35.5 260 37 19 7.3 4.0
26000 -35.3 -31.5 260 29 15 7.6 4.2 | -34.9 -30.8 260 32 17 6.9 3.8
25000 -33.0 -27.4 255 26 13 7.6 4.2 | -32.8 -27.0 255 28 15 6.9 3.8
24000 -30.7 -23.3 255 23 12 8.1 4.5 | -30.7 -23.3 250 25 13 7.8 4.3
23000 -28.3 -18.9 255 21 11 8.2 4.5 | -28.3 -18.9 250 22 11 8.0 4.4
22000 -25.8 -14.4 260 20 10 8.2 4.5 | -25.9 -14.6 245 19 10 8.0 4.4
21000 -23.3 -9.9 260 18 9 8.2 4.5 | -23.4 -10.1 240 16 8 8.8 4.8
20000 -20.9 -5.6 260 17 9 8.3 4.5 | -20.8 -5.4 240 15 8 8.8 4.8
19500 -19.6 -3.3 260 16 8 8.3 4.5 | -19.5 -3.1 240 14 7 8.8 4.8
19000 -18.4 -1.1 255 16 8 8.3 4.6 | -18.2 -0.8 235 14 7 8.8 4.8
18500 -17.2 1.0 255 16 8 8.2 4.5 | -16.9 1.6 235 13 7 8.7 4.8
18000 -16.0 3.2 250 16 8 8.2 4.5 | -15.6 3.9 235 14 7 8.7 4.8
17500 -14.8 5.4 245 16 8 8.2 4.5 | -14.3 6.3 235 14 7 8.9 4.9
17000 -13.6 7.5 245 16 8 8.1 4.5 | -13.0 8.6 240 14 7 9.0 5.0
16500 -12.4 9.7 245 17 9 8.2 4.5 | -11.6 11.1 240 14 7 9.1 5.0
16000 -11.1 12.0 240 17 9 8.7 4.8 | -10.3 13.5 245 14 7 8.9 4.9
15500 -9.8 14.4 240 17 9 8.7 4.8 | -9.0 15.8 245 13 7 8.9 4.9
15000 -8.5 16.7 240 17 9 9.2 5.0 | -7.6 18.3 245 13 7 9.0 5.0
14500 -7.1 19.2 240 17 9 9.2 5.0 | -6.3 20.7 250 13 7 9.0 5.0
14000 -5.8 21.6 240 17 9 9.3 5.1 | -4.9 23.2 250 13 7 9.1 5.0
13500 -4.4 24.1 245 17 9 9.3 5.1 | -3.6 25.5 250 13 7 9.2 5.0
13000 -3.0 26.6 245 17 9 9.3 5.1 | -2.2 28.0 255 13 7 9.2 5.0
12500 -1.6 29.1 245 17 9 9.2 5.1 | -0.8 30.6 255 13 7 9.2 5.0
12000 -0.2 31.6 250 17 9 9.2 5.1 | 0.6 33.1 260 13 7 9.2 5.1
11500 1.2 34.2 250 16 8 9.2 5.0 | 1.9 35.4 260 14 7 9.2 5.0
11000 2.5 36.5 250 16 8 8.6 4.7 | 3.3 37.9 260 14 7 8.6 4.7
10500 3.7 38.7 255 16 8 7.1 3.9 | 4.5 40.1 260 14 7 7.0 3.8
10250 4.3 39.7 255 16 8 11.4 6.3 | 5.1 41.2 265 14 7 10.8 5.9
10000 5.4 41.7 255 16 8 12.3 6.7 | 6.1 43.0 265 13 7 11.8 6.5
9750 6.1 43.0 255 15 8 8.5 4.7 | 6.8 44.2 265 13 7 8.4 4.6
9500 6.7 44.1 255 15 8 9.8 5.4 | 7.4 45.3 265 13 7 8.4 4.6
9250 7.4 45.3 260 15 8 8.3 4.6 | 8.9 48.0 265 13 7 10.4 5.7
9000 8.0 46.4 260 15 8 9.0 4.9 | 9.6 49.3 265 12 6 8.6 4.7
8750 9.6 49.3 260 15 8 10.3 5.7 | 10.2 50.4 265 12 6 9.1 5.0
8500 10.4 50.7 260 15 8 10.0 5.5 | 10.9 51.6 270 12 6 8.8 4.8
8250 11.1 52.0 265 15 8 9.6 5.3 | 11.5 52.7 270 12 6 9.2 5.0
8000 11.8 53.2 265 15 8 10.2 5.6 | 12.3 54.1 270 12 6 9.9 5.5
7750 12.6 54.7 265 15 8 11.0 6.0 | 13.0 55.4 270 12 6 10.4 5.7
7500 13.4 56.1 265 14 7 9.2 5.1 | 13.8 56.8 270 11 6 9.2 5.1
7250 14.0 57.2 265 15 8 7.6 4.1 | 14.4 57.9 270 12 6 7.7 4.2
7000 14.7 58.5 265 15 8 10.4 5.7 | 15.0 59.0 275 12 6 9.8 5.4
6750 15.5 59.9 265 14 7 12.2 6.7 | 15.9 60.6 270 11 6 11.3 6.2
6500 16.4 61.5 265 14 7 10.8 5.9 | 16.7 62.1 270 11 6 10.6 5.8
6250 17.2 63.0 270 14 7 11.1 6.1 | 17.5 63.5 275 11 6 11.0 6.0
6000 18.0 64.4 270 14 7 8.4 4.6 | 18.2 64.8 275 11 6 8.4 4.6
5750 18.6 65.5 270 13 6 13.6 7.4 | 18.8 65.8 270 10 5 8.9 4.9
5500 21.6 70.9 275 12 6 84.8 46.5 | 20.6 69.1 275 10 5 51.1 28.1
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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