Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
291
UXUS97 KGJT 271307
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
707 AM MDT Thursday, March 27, 2025
This forecast is for Thursday, March 27, 2025:
If the trigger temperature of 61.2 F/16.2 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1399 ft/min (7.1 m/s)
Maximum height of thermals.................. 21414 ft MSL (15804 ft AGL)
Forecast maximum temperature................... 81.0 F/27.7 C
Time of trigger temperature.................... 0945 MDT
Time of overdevelopment........................ 1800 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 18236 ft MSL (12626 ft AGL)
Thermal soaring outlook for Friday 03/28....... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:05:29 / 19:33:07 MDT
Total possible sunshine........... 12 hr 27 min 38 sec (747 min 38 sec)
Altitude of sun at 13:19:18 MDT... 53.54 degrees
Upper air data from rawinsonde observation taken on 03/27/2025 at 0600 MDT
Freezing level.................. 11415 ft MSL (5805 ft AGL)
Convective condensation level... 16108 ft MSL (10498 ft AGL)
Lifted condensation level....... 18540 ft MSL (12930 ft AGL)
Lifted index.................... -2.2
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 -59.9 -75.8 260 30 15 -0.0 -0.0 M M M M M
45000 -60.0 -76.0 260 33 17 -1.3 -0.7 M M M M M
40000 -62.9 -81.2 265 50 26 -2.0 -1.1 M M M M M
38000 -61.0 -77.8 265 53 27 7.2 3.9 M M M M M
36000 -56.7 -70.1 260 53 27 7.2 3.9 M M M M M
34000 -52.2 -62.0 255 53 27 8.8 4.8 M M M M M
32000 -46.2 -51.2 255 51 26 8.9 4.9 M M M M M
30000 -40.9 -41.6 255 49 25 8.7 4.8 33.7 92.6 4.9 M M
29000 -38.3 -36.9 250 49 25 8.7 4.8 33.2 91.8 4.6 M M
28000 -35.7 -32.3 250 48 25 8.7 4.8 32.9 91.2 4.3 M M
27000 -33.2 -27.8 245 48 25 7.8 4.3 32.5 90.6 4.1 M M
26000 -30.9 -23.6 245 47 24 7.7 4.2 31.7 89.0 3.4 M M
25000 -28.6 -19.5 245 45 23 7.7 4.2 30.9 87.6 2.9 M M
24000 -26.3 -15.3 245 44 23 7.3 4.0 30.3 86.5 2.4 M M
23000 -24.3 -11.7 245 44 23 6.8 3.7 29.1 84.4 1.4 M M
22000 -22.2 -8.0 240 43 22 6.8 3.7 28.1 82.5 0.5 M M
21000 -20.2 -4.4 240 43 22 6.9 3.8 27.1 80.8 -0.3 1368 7.0
20000 -18.2 -0.8 240 41 21 6.9 3.8 26.0 78.8 -1.2 1278 6.5
19500 -17.2 1.0 235 40 21 6.9 3.8 25.5 78.0 -1.7 1233 6.3
19000 -16.2 2.8 235 39 20 6.9 3.8 25.1 77.1 -2.1 1188 6.0
18500 -14.7 5.5 235 38 20 6.0 3.3 24.3 75.8 -2.8 1121 5.7
18000 -13.8 7.2 235 37 19 6.1 3.3 23.7 74.6 -3.4 1079 5.5
17500 -12.9 8.8 235 36 19 6.4 3.5 23.1 73.5 -4.0 1037 5.3
17000 -11.8 10.8 235 36 18 6.7 3.7 22.5 72.6 -4.4 992 5.0
16500 -10.8 12.6 235 35 18 6.7 3.7 22.0 71.7 -4.9 946 4.8
16000 -9.8 14.4 235 34 18 7.2 4.0 21.6 70.8 -5.3 900 4.6
15500 -8.7 16.3 235 33 17 7.2 3.9 21.1 70.1 -5.7 852 4.3
15000 -7.6 18.3 235 32 17 7.3 4.0 20.7 69.3 -6.1 805 4.1
14500 -6.5 20.3 235 31 16 7.3 4.0 20.3 68.6 -6.5 757 3.8
14000 -5.4 22.3 230 30 15 7.1 3.9 19.9 67.8 -6.9 710 3.6
13500 -4.4 24.1 230 29 15 7.0 3.8 19.4 67.0 -7.4 665 3.4
13000 -3.4 25.9 230 28 14 7.1 3.9 19.0 66.2 -7.9 619 3.1
12500 -2.3 27.9 230 27 14 7.2 4.0 18.6 65.4 -8.3 573 2.9
12000 -1.3 29.7 230 25 13 7.3 4.0 18.2 64.7 -8.8 527 2.7
11500 -0.2 31.6 230 24 13 7.3 4.0 17.8 64.0 -9.2 480 2.4
11000 0.9 33.6 235 24 12 7.4 4.1 17.4 63.3 -9.7 433 2.2
10500 1.9 35.4 235 22 11 8.0 4.4 17.1 62.7 -10.1 386 2.0
10250 2.6 36.7 235 21 11 8.9 4.9 17.0 62.5 -10.2 360 1.8
10000 3.2 37.8 235 21 11 8.8 4.8 16.9 62.4 -10.3 333 1.7
9750 3.9 39.0 235 21 11 8.6 4.7 16.8 62.2 -10.5 307 1.6
9500 4.5 40.1 235 21 11 8.4 4.6 16.7 62.1 -10.6 281 1.4
9250 5.1 41.2 235 21 11 9.4 5.2 16.6 61.9 -10.7 254 1.3
9000 5.8 42.4 235 20 10 9.5 5.2 16.6 61.9 -10.7 225 1.1
8750 6.5 43.7 235 19 10 8.6 4.7 16.6 61.8 -10.8 199 1.0
8500 7.1 44.8 235 19 10 8.9 4.9 16.5 61.7 -11.0 172 0.9
8250 7.8 46.0 240 18 9 8.5 4.7 16.4 61.5 -11.1 145 0.7
8000 8.4 47.1 235 16 8 7.4 4.1 16.3 61.3 -11.2 120 0.6
7750 8.9 48.0 235 15 8 6.9 3.8 16.1 60.9 -11.5 97 0.5
7500 9.4 48.9 235 13 7 7.0 3.8 15.9 60.5 -11.7 75 0.4
7250 9.9 49.8 235 12 6 7.2 4.0 15.6 60.2 -12.0 52 0.3
7000 10.4 50.7 230 10 5 6.0 3.3 15.4 59.8 -12.2 29 0.1
6750 10.8 51.4 220 9 5 4.6 2.5 15.1 59.1 -12.6 11 0.1
6500 11.2 52.2 210 8 4 5.6 3.1 14.7 58.5 -13.0 M M
6250 11.4 52.5 195 7 4 -0.2 -0.1 14.3 57.7 -13.5 M M
6000 11.0 51.8 175 7 4 -11.7 -6.4 13.1 55.5 -14.7 M M
5750 9.8 49.6 160 5 3 -16.7 -9.1 11.2 52.2 -16.6 10 0.1
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 * * * * * *
03/27/2025 at 0900 MDT | 03/27/2025 at 1200 MDT
|
CAPE... 0.0 LI... -0.3 | CAPE... +13.1 LI... +0.1
CINH... -0.4 K Index... +21.1 | CINH... -33.3 K Index... +21.8
|
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 -60.3 -76.5 260 17 9 2.0 1.1 | -60.2 -76.4 250 17 9 2.4 1.3
45000 -57.4 -71.3 255 23 12 -0.5 -0.3 | -56.7 -70.1 250 24 13 -0.9 -0.5
40000 -59.7 -75.5 280 22 11 -1.4 -0.8 | -61.3 -78.3 280 27 14 -2.8 -1.5
38000 -57.9 -72.2 280 21 11 5.2 2.8 | -59.2 -74.6 295 25 13 6.4 3.5
36000 -54.8 -66.6 275 19 10 5.2 2.8 | -55.3 -67.5 305 24 12 6.4 3.5
34000 -51.2 -60.2 275 18 9 7.4 4.0 | -51.2 -60.2 315 23 12 7.8 4.3
32000 -46.8 -52.2 275 18 9 7.4 4.1 | -46.5 -51.7 305 20 11 7.8 4.3
30000 -42.6 -44.7 275 19 10 6.0 3.3 | -42.0 -43.6 295 19 10 7.0 3.8
29000 -40.9 -41.6 265 20 10 5.9 3.3 | -39.9 -39.8 290 18 9 7.0 3.8
28000 -39.1 -38.4 255 22 11 5.9 3.3 | -37.8 -36.0 280 17 9 7.0 3.8
27000 -37.2 -35.0 250 23 12 8.4 4.6 | -35.7 -32.3 270 17 9 7.1 3.9
26000 -34.6 -30.3 250 24 12 8.5 4.7 | -33.5 -28.3 265 18 9 7.1 3.9
25000 -31.4 -24.5 250 25 13 8.6 4.7 | -30.9 -23.6 250 19 10 7.1 3.9
24000 -28.9 -20.0 245 25 13 8.2 4.5 | -28.6 -19.5 245 20 10 8.5 4.7
23000 -26.4 -15.5 240 23 12 8.3 4.5 | -26.1 -15.0 245 21 11 8.4 4.6
22000 -24.0 -11.2 235 22 11 8.2 4.5 | -23.6 -10.5 240 22 11 8.4 4.6
21000 -21.7 -7.1 235 22 11 7.4 4.0 | -21.3 -6.3 235 22 11 7.4 4.0
20000 -19.5 -3.1 230 22 11 7.4 4.0 | -19.1 -2.4 235 22 12 7.4 4.1
19500 -18.4 -1.1 230 22 11 7.4 4.1 | -18.0 -0.4 235 23 12 7.4 4.1
19000 -17.3 0.9 225 22 11 7.6 4.2 | -16.9 1.6 230 23 12 7.4 4.1
18500 -16.1 3.0 225 22 11 8.5 4.7 | -15.8 3.6 230 23 12 7.4 4.1
18000 -14.9 5.2 225 22 11 8.5 4.7 | -14.7 5.5 230 23 12 7.4 4.1
17500 -13.6 7.5 230 22 11 8.8 4.8 | -13.6 7.5 230 23 12 8.0 4.4
17000 -12.3 9.9 230 21 11 8.8 4.9 | -12.4 9.7 230 23 12 8.2 4.5
16500 -11.0 12.2 230 21 11 8.9 4.9 | -11.2 11.8 230 22 12 8.4 4.6
16000 -9.7 14.5 230 20 10 9.0 4.9 | -9.9 14.2 225 22 11 8.9 4.9
15500 -8.3 17.1 230 19 10 9.0 4.9 | -8.6 16.5 225 21 11 8.9 4.9
15000 -7.0 19.4 230 19 10 9.0 4.9 | -7.3 18.9 225 21 11 9.2 5.0
14500 -5.7 21.7 230 18 9 9.0 4.9 | -5.9 21.4 225 20 10 9.1 5.0
14000 -4.3 24.3 235 17 9 9.0 4.9 | -4.5 23.9 225 20 10 9.3 5.1
13500 -3.0 26.6 235 16 8 9.0 4.9 | -3.1 26.4 225 19 10 9.3 5.1
13000 -1.6 29.1 235 15 8 8.9 4.9 | -1.8 28.8 220 18 9 9.3 5.1
12500 -0.3 31.5 235 14 7 8.8 4.9 | -0.4 31.3 220 17 9 9.3 5.1
12000 1.0 33.8 235 13 7 8.8 4.9 | 1.0 33.8 220 16 8 9.1 5.0
11500 2.3 36.1 235 12 6 8.9 4.9 | 2.4 36.3 220 15 8 9.0 5.0
11000 3.6 38.5 230 11 6 7.6 4.2 | 3.7 38.7 220 14 7 7.7 4.2
10500 4.7 40.5 225 11 5 6.5 3.6 | 4.7 40.5 220 14 7 6.1 3.4
10250 5.2 41.4 225 10 5 9.7 5.3 | 5.3 41.5 220 13 7 11.0 6.0
10000 6.0 42.8 220 10 5 10.0 5.5 | 6.3 43.3 220 13 6 11.8 6.4
9750 6.6 43.9 220 10 5 7.0 3.8 | 6.9 44.4 220 12 6 7.2 3.9
9500 7.2 45.0 215 10 5 8.0 4.4 | 7.5 45.5 215 12 6 9.1 5.0
9250 7.8 46.0 210 10 5 7.0 3.8 | 8.1 46.6 215 11 6 6.0 3.3
9000 8.3 46.9 205 9 5 6.7 3.7 | 8.5 47.3 215 10 5 6.6 3.6
8750 8.8 47.8 200 9 5 7.2 3.9 | 9.8 49.6 210 9 5 9.1 5.0
8500 9.9 49.8 195 9 5 6.5 3.5 | 10.5 50.9 205 9 5 7.5 4.1
8250 10.3 50.5 190 9 5 5.4 2.9 | 10.9 51.6 200 8 4 6.6 3.6
8000 10.7 51.3 185 9 5 5.6 3.0 | 11.5 52.7 200 8 4 9.0 4.9
7750 11.1 52.0 180 9 5 5.6 3.1 | 12.2 54.0 195 7 4 9.9 5.4
7500 11.5 52.7 175 9 4 4.5 2.5 | 12.9 55.2 190 7 4 7.9 4.3
7250 11.8 53.2 170 9 5 3.5 1.9 | 13.4 56.1 190 7 3 6.6 3.6
7000 12.0 53.6 170 9 5 4.0 2.2 | 14.0 57.2 185 6 3 10.7 5.8
6750 12.3 54.1 165 8 4 2.7 1.5 | 14.9 58.8 185 6 3 12.2 6.7
6500 12.4 54.3 155 7 4 0.7 0.4 | 15.8 60.4 185 6 3 10.2 5.6
6250 12.4 54.3 150 6 3 -0.2 -0.1 | 16.5 61.7 185 5 3 10.1 5.6
6000 12.4 54.3 145 6 3 2.1 1.1 | 17.3 63.1 180 5 3 8.9 4.9
5750 12.7 54.9 125 4 2 5.3 2.9 | 18.0 64.4 185 5 3 13.9 7.6
5500 12.7 54.9 105 4 2 -10.6 -5.8 | 20.4 68.7 175 4 2 60.9 33.4
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
03/27/2025 at 1500 MDT | 03/27/2025 at 1800 MDT
|
CAPE... +52.5 LI... -0.7 | CAPE... +12.2 LI... +0.2
CINH... -11.2 K Index... +23.4 | CINH... -4.7 K Index... +20.2
|
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 -60.5 -76.9 240 21 11 1.8 1.0 | -60.8 -77.4 245 22 11 1.3 0.7
45000 -57.9 -72.2 250 29 15 -1.8 -1.0 | -58.8 -73.8 245 29 15 -1.6 -0.9
40000 -63.5 -82.3 275 29 15 -3.4 -1.9 | -63.4 -82.1 255 27 14 -3.1 -1.7
38000 -60.8 -77.4 280 28 15 8.1 4.4 | -60.9 -77.6 265 29 15 7.8 4.3
36000 -56.0 -68.8 280 27 14 8.1 4.4 | -56.2 -69.2 275 33 17 7.8 4.3
34000 -51.0 -59.8 285 27 14 8.6 4.7 | -51.3 -60.3 280 36 18 8.8 4.8
32000 -45.9 -50.6 285 29 15 8.6 4.7 | -46.0 -50.8 280 36 18 8.8 4.8
30000 -40.9 -41.6 285 30 16 7.9 4.4 | -40.9 -41.6 280 35 18 8.5 4.7
29000 -38.5 -37.3 285 30 15 7.9 4.3 | -38.3 -36.9 275 34 18 8.5 4.6
28000 -36.1 -33.0 285 29 15 7.9 4.4 | -35.8 -32.4 275 33 17 8.5 4.7
27000 -33.8 -28.8 280 28 14 7.0 3.9 | -33.3 -27.9 270 32 16 7.3 4.0
26000 -31.7 -25.1 275 23 12 7.0 3.9 | -31.1 -24.0 270 29 15 7.3 4.0
25000 -29.1 -20.4 270 18 9 7.0 3.9 | -28.9 -20.0 265 27 14 7.3 4.0
24000 -27.0 -16.6 260 15 8 7.0 3.8 | -26.2 -15.2 260 24 12 6.7 3.7
23000 -24.9 -12.8 250 16 8 7.0 3.9 | -24.2 -11.6 250 22 11 6.8 3.7
22000 -22.8 -9.0 240 18 9 7.1 3.9 | -22.2 -8.0 240 21 11 6.8 3.7
21000 -20.7 -5.3 235 20 10 7.0 3.9 | -20.2 -4.4 230 21 11 6.8 3.7
20000 -18.6 -1.5 230 21 11 7.1 3.9 | -18.2 -0.8 225 23 12 6.9 3.8
19500 -17.6 0.3 225 22 11 7.2 3.9 | -17.2 1.0 220 24 12 6.9 3.8
19000 -16.6 2.1 225 23 12 7.3 4.0 | -16.2 2.8 220 25 13 7.0 3.8
18500 -15.4 4.3 225 23 12 8.6 4.7 | -15.1 4.8 220 25 13 8.3 4.5
18000 -14.2 6.4 220 23 12 8.5 4.7 | -13.9 7.0 220 25 13 8.2 4.5
17500 -12.9 8.8 220 22 11 8.3 4.6 | -12.7 9.1 220 24 12 7.8 4.3
17000 -11.7 10.9 220 22 11 8.3 4.5 | -11.6 11.1 220 24 12 7.6 4.2
16500 -10.5 13.1 220 21 11 8.2 4.5 | -10.5 13.1 220 24 12 7.8 4.3
16000 -9.3 15.3 220 20 10 8.0 4.4 | -9.2 15.4 220 23 12 8.6 4.7
15500 -8.1 17.4 220 19 10 8.0 4.4 | -8.0 17.6 220 23 12 8.4 4.6
15000 -6.9 19.6 220 19 10 9.0 5.0 | -6.6 20.1 220 23 12 9.5 5.2
14500 -5.5 22.1 220 18 9 8.9 4.9 | -5.2 22.6 225 23 12 9.4 5.2
14000 -4.2 24.4 220 17 9 9.5 5.2 | -3.8 25.2 225 23 12 9.6 5.3
13500 -2.7 27.1 220 17 9 9.6 5.3 | -2.4 27.7 225 22 11 9.6 5.3
13000 -1.3 29.7 220 16 8 9.5 5.2 | -0.9 30.4 225 22 11 9.6 5.3
12500 0.1 32.2 220 16 8 9.4 5.2 | 0.5 32.9 225 22 11 9.6 5.3
12000 1.5 34.7 225 15 8 9.3 5.1 | 2.0 35.6 230 21 11 9.6 5.3
11500 2.9 37.2 225 14 7 9.3 5.1 | 3.4 38.1 230 21 11 9.6 5.3
11000 4.3 39.7 225 14 7 8.5 4.6 | 4.8 40.6 230 20 11 9.1 5.0
10500 5.5 41.9 230 12 6 7.1 3.9 | 6.1 43.0 235 19 10 7.9 4.3
10250 6.1 43.0 230 11 6 11.2 6.2 | 6.8 44.2 235 19 10 10.8 5.9
10000 7.1 44.8 230 12 6 12.3 6.7 | 7.7 45.9 235 19 10 11.6 6.4
9750 7.8 46.0 235 12 6 8.7 4.8 | 8.4 47.1 235 19 10 9.0 4.9
9500 8.5 47.3 235 11 6 10.0 5.5 | 9.1 48.4 235 18 9 9.3 5.1
9250 9.2 48.6 235 11 6 8.3 4.6 | 9.8 49.6 235 18 9 9.6 5.3
9000 9.8 49.6 240 10 5 8.9 4.9 | 11.2 52.2 235 17 9 9.4 5.2
8750 10.6 51.1 240 10 5 10.7 5.8 | 12.0 53.6 235 17 9 9.5 5.2
8500 12.1 53.8 240 10 5 9.9 5.4 | 12.7 54.9 240 17 9 9.6 5.2
8250 12.8 55.0 245 10 5 9.5 5.2 | 13.4 56.1 240 16 8 9.6 5.3
8000 13.6 56.5 250 9 5 10.1 5.5 | 14.1 57.4 240 15 8 9.2 5.1
7750 14.3 57.7 245 9 5 10.6 5.8 | 14.8 58.6 240 15 8 9.2 5.1
7500 15.1 59.2 245 9 5 9.2 5.1 | 15.5 59.9 240 15 7 8.9 4.9
7250 15.7 60.3 250 9 5 8.1 4.4 | 16.1 61.0 245 14 7 8.3 4.5
7000 16.4 61.5 255 9 5 10.3 5.6 | 16.7 62.1 245 14 7 9.2 5.0
6750 17.2 63.0 250 9 4 11.5 6.3 | 17.4 63.3 245 13 7 9.6 5.3
6500 18.1 64.6 250 9 4 10.6 5.8 | 18.2 64.8 245 13 6 10.2 5.6
6250 18.9 66.0 255 8 4 10.9 6.0 | 19.0 66.2 245 12 6 11.6 6.4
6000 19.6 67.3 260 8 4 8.3 4.6 | 19.8 67.6 245 12 6 8.6 4.7
5750 20.2 68.4 255 8 4 10.9 6.0 | 20.3 68.5 245 11 6 6.8 3.7
5500 22.5 72.5 265 7 4 64.2 35.2 | 21.5 70.7 250 9 5 34.9 19.1
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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