Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
441
UXUS97 KBOU 280009
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1809 MDT Thursday, March 27, 2025
This forecast is for Friday, March 28, 2025:
If the trigger temperature of 69.1 F/20.6 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1205 ft/min (6.1 m/s)
Maximum height of thermals.................. 18209 ft MSL (12904 ft AGL)
Forecast maximum temperature................... 78.0 F/26.0 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................. 13550 ft MSL (8246 ft AGL)
Thermal soaring outlook for Saturday 03/29..... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 14407 ft MSL (9102 ft AGL)
Wave soaring outlook for Saturday 03/29........ Poor
Remarks...
Sunrise/Sunset.................... 06:48:58 / 19:19:44 MDT
Total possible sunshine........... 12 hr 30 min 47 sec (750 min 47 sec)
Altitude of sun at 13:04:21 MDT... 53.53 degrees
Upper air data from numerical model forecast valid on 03/28/2025 at 0600 MDT
Freezing level.................. 12585 ft MSL (7280 ft AGL)
Convective condensation level... 16901 ft MSL (11596 ft AGL)
Lifted condensation level....... 17712 ft MSL (12408 ft AGL)
Lifted index.................... +0.2
K index......................... +13.7
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 -60.3 -76.5 245 29 15 0.4 0.2 M M M M M
45000 -59.7 -75.5 250 34 18 -2.1 -1.2 M M M M M
40000 -64.7 -84.5 260 42 22 -3.4 -1.9 M M M M M
38000 -62.5 -80.5 260 43 22 8.5 4.7 M M M M M
36000 -57.4 -71.3 265 42 22 8.5 4.7 M M M M M
34000 -52.3 -62.1 265 42 21 8.7 4.8 M M M M M
32000 -47.1 -52.8 260 40 21 8.7 4.8 M M M M M
30000 -41.1 -42.0 255 39 20 9.1 5.0 33.8 92.9 6.2 M M
29000 -38.4 -37.1 250 38 19 9.1 5.0 33.5 92.3 6.1 M M
28000 -35.7 -32.3 245 37 19 9.1 5.0 33.3 92.0 6.0 M M
27000 -33.0 -27.4 245 37 19 8.6 4.7 33.1 91.6 5.9 M M
26000 -30.4 -22.7 250 37 19 8.6 4.7 32.6 90.6 5.5 M M
25000 -27.8 -18.0 255 38 19 8.6 4.7 32.2 89.9 5.3 M M
24000 -25.3 -13.5 260 38 20 7.2 3.9 31.8 89.2 5.0 M M
23000 -23.3 -9.9 260 34 17 6.7 3.7 30.6 87.0 4.1 M M
22000 -21.3 -6.3 255 29 15 6.7 3.7 29.5 85.1 3.2 M M
21000 -19.3 -2.7 255 25 13 7.5 4.1 28.5 83.3 2.4 M M
20000 -17.1 1.2 250 21 11 7.5 4.1 27.6 81.8 1.7 M M
19500 -15.9 3.4 245 19 10 7.5 4.1 27.3 81.1 1.3 M M
19000 -14.8 5.4 240 17 9 7.5 4.1 26.9 80.4 1.0 M M
18500 -13.8 7.2 235 15 8 5.4 3.0 26.5 79.6 0.7 M M
18000 -13.2 8.2 230 14 7 4.5 2.5 25.5 77.9 -0.2 1197 6.1
17500 -12.5 9.5 225 12 6 4.8 2.6 24.6 76.3 -1.0 1164 5.9
17000 -11.5 11.3 220 11 6 8.5 4.7 24.2 75.5 -1.5 1118 5.7
16500 -10.3 13.5 215 11 6 8.2 4.5 23.9 75.0 -1.7 1067 5.4
16000 -8.4 16.9 215 11 5 9.1 5.0 23.6 74.5 -2.0 987 5.0
15500 -7.0 19.4 215 11 6 9.1 5.0 23.5 74.3 -2.1 932 4.7
15000 -5.7 21.7 225 11 6 8.4 4.6 23.3 74.0 -2.3 878 4.5
14500 -4.5 23.9 235 11 6 8.5 4.7 23.1 73.6 -2.6 826 4.2
14000 -3.2 26.2 240 12 6 8.3 4.5 22.9 73.2 -2.8 775 3.9
13500 -2.0 28.4 250 13 7 8.3 4.5 22.7 72.8 -3.1 724 3.7
13000 -0.8 30.6 255 15 7 8.2 4.5 22.4 72.4 -3.3 673 3.4
12500 0.4 32.7 260 16 8 8.2 4.5 22.1 71.9 -3.6 622 3.2
12000 1.5 34.7 265 17 9 8.2 4.5 21.9 71.4 -3.9 572 2.9
11500 2.8 37.0 265 17 9 8.3 4.6 21.7 71.0 -4.2 520 2.6
11000 4.0 39.2 265 16 8 8.5 4.7 21.5 70.6 -4.4 468 2.4
10500 5.3 41.5 270 17 9 8.3 4.5 21.3 70.3 -4.6 414 2.1
10250 6.0 42.8 270 18 9 10.5 5.8 21.2 70.2 -4.7 387 2.0
10000 6.9 44.4 270 18 9 10.6 5.8 21.4 70.4 -4.5 354 1.8
9750 7.5 45.5 270 17 9 8.4 4.6 21.3 70.3 -4.6 326 1.7
9500 8.2 46.8 270 16 8 8.9 4.9 21.2 70.2 -4.7 299 1.5
9250 8.8 47.8 270 15 8 8.7 4.8 21.1 70.0 -4.8 272 1.4
9000 9.5 49.1 275 16 8 8.5 4.7 21.0 69.9 -4.9 245 1.2
8750 10.1 50.2 275 15 8 8.5 4.7 20.9 69.7 -5.0 219 1.1
8500 10.7 51.3 275 14 7 8.2 4.5 20.8 69.5 -5.1 193 1.0
8250 11.4 52.5 275 14 7 9.2 5.0 20.7 69.3 -5.2 166 0.8
8000 12.1 53.8 275 13 7 10.1 5.5 20.8 69.4 -5.2 137 0.7
7750 12.8 55.0 275 14 7 8.2 4.5 20.7 69.3 -5.2 108 0.6
7500 13.4 56.1 275 14 7 7.1 3.9 20.5 69.0 -5.4 84 0.4
7250 13.9 57.0 275 14 7 7.4 4.1 20.4 68.6 -5.6 61 0.3
7000 14.5 58.1 270 14 7 7.6 4.1 20.2 68.3 -5.8 37 0.2
6750 15.0 59.0 270 13 7 5.5 3.0 20.0 67.9 -6.1 14 0.1
6500 15.3 59.5 265 12 6 6.5 3.6 19.6 67.3 -6.4 M M
6250 15.6 60.1 255 10 5 -7.1 -3.9 19.1 66.4 -7.0 M M
6000 14.3 57.7 245 11 6 -17.6 -9.7 17.1 62.8 -9.0 12 0.1
5750 13.0 55.4 235 11 6 -21.3 -11.7 15.1 59.2 -11.0 43 0.2
5500 10.5 50.9 220 12 6 -47.3 -26.0 11.9 53.4 -14.3 112 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
03/28/2025 at 0900 MDT | 03/28/2025 at 1200 MDT
|
CAPE... 0.0 LI... +2.4 | CAPE... 0.0 LI... +2.3
CINH... 0.0 K Index... +11.3 | CINH... -0.2 K Index... +14.9
|
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 -60.6 -77.1 250 32 16 1.2 0.7 | -60.7 -77.3 250 34 17 1.4 0.8
45000 -58.8 -73.8 255 42 22 -1.7 -0.9 | -58.6 -73.5 260 47 24 -1.4 -0.8
40000 -64.1 -83.4 265 52 27 -3.6 -2.0 | -64.2 -83.6 255 57 29 -3.8 -2.1
38000 -62.2 -80.0 265 52 27 8.1 4.4 | -62.2 -80.0 255 58 30 8.3 4.5
36000 -57.3 -71.1 265 49 25 8.1 4.4 | -57.2 -71.0 255 56 29 8.3 4.5
34000 -52.4 -62.3 260 47 24 8.7 4.8 | -52.2 -62.0 250 54 28 8.6 4.7
32000 -47.1 -52.8 265 45 23 8.7 4.8 | -47.1 -52.8 250 48 25 8.6 4.7
30000 -41.3 -42.3 265 43 22 8.4 4.6 | -41.3 -42.3 250 42 21 8.5 4.7
29000 -38.8 -37.8 265 41 21 8.4 4.6 | -38.8 -37.8 250 39 20 8.5 4.7
28000 -36.3 -33.3 260 39 20 8.4 4.6 | -36.3 -33.3 250 36 18 8.5 4.7
27000 -33.8 -28.8 260 37 19 7.9 4.4 | -33.8 -28.8 245 33 17 7.8 4.3
26000 -31.5 -24.7 255 35 18 8.0 4.4 | -31.4 -24.5 245 32 17 7.9 4.3
25000 -29.1 -20.4 255 33 17 8.0 4.4 | -29.1 -20.4 245 32 16 7.9 4.3
24000 -26.7 -16.1 250 31 16 7.8 4.3 | -26.7 -16.1 245 31 16 7.7 4.2
23000 -24.4 -11.9 250 29 15 7.7 4.2 | -24.4 -11.9 245 31 16 7.6 4.2
22000 -22.2 -8.0 250 27 14 7.7 4.2 | -22.2 -8.0 245 31 16 7.6 4.2
21000 -19.9 -3.8 245 26 13 7.6 4.2 | -19.9 -3.8 245 30 16 7.7 4.2
20000 -17.6 0.3 245 25 13 7.6 4.2 | -17.6 0.3 245 29 15 7.7 4.2
19500 -16.5 2.3 245 24 13 7.6 4.2 | -16.5 2.3 240 29 15 7.7 4.2
19000 -15.4 4.3 245 24 12 7.6 4.2 | -15.4 4.3 240 28 15 7.7 4.2
18500 -14.3 6.3 250 23 12 7.9 4.3 | -14.2 6.4 240 28 14 7.8 4.3
18000 -13.0 8.6 245 23 12 8.1 4.4 | -13.1 8.4 240 28 14 7.8 4.3
17500 -11.8 10.8 245 23 12 8.1 4.4 | -11.9 10.6 245 28 14 7.8 4.3
17000 -10.1 13.8 245 22 11 7.8 4.3 | -10.2 13.6 245 28 14 7.6 4.2
16500 -8.9 16.0 245 21 11 7.8 4.3 | -9.1 15.6 245 28 14 7.6 4.1
16000 -7.8 18.0 245 21 11 7.8 4.3 | -8.0 17.6 245 28 14 7.5 4.1
15500 -6.6 20.1 245 21 11 7.8 4.3 | -6.9 19.6 245 28 14 7.6 4.2
15000 -5.5 22.1 245 21 11 7.4 4.1 | -5.8 21.6 250 27 14 7.0 3.9
14500 -4.4 24.1 245 21 11 7.4 4.1 | -4.7 23.5 250 27 14 7.1 3.9
14000 -3.3 26.1 245 21 11 7.7 4.2 | -3.7 25.3 250 26 14 6.8 3.7
13500 -2.1 28.2 245 22 11 7.7 4.3 | -2.6 27.3 250 25 13 6.7 3.7
13000 -1.0 30.2 250 22 11 7.7 4.2 | -1.6 29.1 255 24 12 7.1 3.9
12500 0.2 32.4 250 22 11 7.7 4.2 | -0.5 31.1 255 21 11 7.5 4.1
12000 1.3 34.3 250 22 11 8.0 4.4 | 0.6 33.1 250 19 10 8.1 4.4
11500 2.5 36.5 250 22 11 8.2 4.5 | 1.9 35.4 250 17 9 8.9 4.9
11000 3.7 38.7 255 22 11 7.8 4.3 | 3.2 37.8 245 15 8 8.5 4.7
10500 4.8 40.6 255 20 10 6.7 3.7 | 4.4 39.9 245 14 7 7.3 4.0
10250 5.3 41.5 255 19 10 9.2 5.0 | 5.0 41.0 240 13 7 10.4 5.7
10000 6.1 43.0 260 20 10 9.8 5.4 | 5.9 42.6 245 13 7 11.5 6.3
9750 6.7 44.1 260 19 10 7.4 4.1 | 6.6 43.9 245 12 6 8.9 4.9
9500 7.3 45.1 260 18 9 7.7 4.2 | 7.2 45.0 240 12 6 9.2 5.1
9250 7.8 46.0 260 18 9 7.7 4.2 | 7.9 46.2 240 11 6 9.5 5.2
9000 8.4 47.1 260 17 9 7.8 4.3 | 8.6 47.5 240 12 6 9.2 5.1
8750 9.0 48.2 260 17 9 7.8 4.3 | 9.3 48.7 245 11 6 8.6 4.7
8500 9.6 49.3 260 16 8 7.7 4.2 | 9.9 49.8 245 10 5 8.7 4.8
8250 10.1 50.2 260 16 8 8.0 4.4 | 10.6 51.1 245 9 5 9.1 5.0
8000 10.7 51.3 265 15 8 8.1 4.5 | 11.3 52.3 250 8 4 9.8 5.4
7750 11.3 52.3 265 14 7 7.5 4.1 | 12.0 53.6 255 8 4 9.4 5.2
7500 11.9 53.4 260 14 7 7.2 3.9 | 12.7 54.9 255 8 4 9.1 5.0
7250 12.4 54.3 260 13 7 7.1 3.9 | 13.4 56.1 255 7 4 9.1 5.0
7000 12.9 55.2 255 12 6 7.0 3.8 | 14.0 57.2 255 7 4 9.1 5.0
6750 13.5 56.3 255 11 6 7.3 4.0 | 14.8 58.6 260 7 4 10.2 5.6
6500 14.0 57.2 245 10 5 8.6 4.7 | 15.6 60.1 260 7 3 10.9 6.0
6250 14.6 58.3 240 9 5 2.7 1.5 | 16.4 61.5 260 7 3 10.8 5.9
6000 14.5 58.1 230 9 5 -2.0 -1.1 | 17.2 63.0 260 6 3 11.5 6.3
5750 14.3 57.7 220 9 5 -3.2 -1.8 | 18.0 64.4 265 6 3 9.6 5.3
5500 13.8 56.8 215 9 4 -8.6 -4.7 | 18.7 65.7 265 6 3 12.5 6.9
03/28/2025 at 1500 MDT | 03/28/2025 at 1800 MDT
|
CAPE... 0.0 LI... +1.0 | CAPE... 0.0 LI... +1.9
CINH... 0.0 K Index... +20.3 | CINH... 0.0 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 -60.9 -77.6 245 36 19 0.5 0.3 | -60.2 -76.4 240 37 19 0.7 0.4
45000 -60.1 -76.2 255 49 25 -1.3 -0.7 | -59.2 -74.6 250 46 24 -1.4 -0.8
40000 -64.2 -83.6 250 62 32 -2.8 -1.5 | -64.1 -83.4 240 66 34 -3.3 -1.8
38000 -62.0 -79.6 245 63 32 8.3 4.6 | -62.2 -80.0 235 65 34 8.2 4.5
36000 -57.0 -70.6 245 61 31 8.3 4.6 | -57.2 -71.0 235 58 30 8.2 4.5
34000 -51.9 -61.4 245 57 29 9.1 5.0 | -52.2 -62.0 230 51 26 9.1 5.0
32000 -46.4 -51.5 235 50 25 9.1 5.0 | -46.7 -52.1 230 44 23 9.1 5.0
30000 -40.4 -40.7 235 43 22 8.7 4.8 | -40.6 -41.1 235 39 20 8.9 4.9
29000 -37.8 -36.0 235 41 21 8.7 4.8 | -38.0 -36.4 235 39 20 8.9 4.9
28000 -35.2 -31.4 235 40 21 8.7 4.8 | -35.3 -31.5 240 40 21 8.9 4.9
27000 -32.7 -26.9 235 39 20 7.9 4.4 | -32.7 -26.9 245 41 21 8.1 4.4
26000 -30.3 -22.5 235 39 20 8.0 4.4 | -30.3 -22.5 245 42 21 8.0 4.4
25000 -28.0 -18.4 240 39 20 8.0 4.4 | -28.0 -18.4 245 42 22 8.0 4.4
24000 -25.6 -14.1 240 39 20 7.1 3.9 | -25.6 -14.1 245 43 22 7.6 4.2
23000 -23.7 -10.7 240 39 20 6.5 3.5 | -23.5 -10.3 245 43 22 7.0 3.9
22000 -21.8 -7.2 245 39 20 6.5 3.6 | -21.4 -6.5 245 42 22 7.1 3.9
21000 -19.9 -3.8 245 38 20 7.1 3.9 | -19.4 -2.9 245 42 21 6.9 3.8
20000 -17.8 -0.0 245 32 17 7.2 3.9 | -17.4 0.7 240 39 20 6.8 3.7
19500 -16.7 1.9 240 29 15 7.2 3.9 | -16.4 2.5 240 38 19 6.8 3.7
19000 -15.7 3.7 240 26 14 7.2 4.0 | -15.4 4.3 240 36 19 6.8 3.7
18500 -14.6 5.7 240 24 12 7.6 4.2 | -14.4 6.1 240 35 18 6.5 3.6
18000 -13.4 7.9 240 22 11 7.8 4.3 | -13.5 7.7 235 33 17 6.0 3.3
17500 -12.3 9.9 235 20 10 7.9 4.4 | -12.6 9.3 235 31 16 6.0 3.3
17000 -11.2 11.8 240 20 10 6.2 3.4 | -11.8 10.8 230 28 15 5.7 3.1
16500 -10.3 13.5 240 21 11 6.4 3.5 | -10.5 13.1 220 26 13 5.7 3.1
16000 -9.3 15.3 245 22 11 6.6 3.6 | -9.6 14.7 220 23 12 6.3 3.5
15500 -7.8 18.0 240 21 11 6.5 3.6 | -8.7 16.3 215 21 11 6.2 3.4
15000 -6.7 19.9 240 20 10 8.5 4.6 | -7.8 18.0 210 19 10 6.7 3.7
14500 -5.5 22.1 235 18 9 8.5 4.7 | -6.8 19.8 210 15 8 6.8 3.7
14000 -4.2 24.4 225 16 8 8.8 4.8 | -5.8 21.6 205 11 6 7.3 4.0
13500 -2.8 27.0 220 15 8 9.0 4.9 | -4.6 23.7 205 8 4 7.8 4.3
13000 -1.5 29.3 215 14 7 8.9 4.9 | -3.5 25.7 210 6 3 8.3 4.6
12500 -0.2 31.6 210 13 7 8.9 4.9 | -2.1 28.2 210 5 3 9.3 5.1
12000 1.2 34.2 205 12 6 8.9 4.9 | -0.7 30.7 215 4 2 9.4 5.2
11500 2.5 36.5 200 10 5 8.9 4.9 | 0.7 33.3 220 4 2 9.9 5.4
11000 3.8 38.8 195 9 4 8.8 4.8 | 2.2 36.0 225 4 2 9.7 5.3
10500 5.1 41.2 180 6 3 8.2 4.5 | 3.6 38.5 230 4 2 9.0 4.9
10250 5.7 42.3 175 5 3 9.0 4.9 | 4.3 39.7 230 4 2 9.7 5.3
10000 6.4 43.5 165 4 2 10.1 5.5 | 5.1 41.2 235 4 2 10.5 5.8
9750 7.2 45.0 160 4 2 10.1 5.5 | 5.9 42.6 235 4 2 10.3 5.7
9500 7.9 46.2 155 3 2 10.6 5.8 | 6.6 43.9 240 4 2 10.5 5.7
9250 8.7 47.7 150 3 2 8.8 4.8 | 7.4 45.3 245 4 2 9.9 5.5
9000 9.3 48.7 150 3 2 8.0 4.4 | 8.1 46.6 250 4 2 8.5 4.7
8750 9.9 49.8 145 3 1 9.9 5.4 | 8.7 47.7 255 4 2 8.8 4.8
8500 10.7 51.3 145 3 1 9.7 5.3 | 9.4 48.9 260 4 2 9.7 5.3
8250 11.4 52.5 140 2 1 10.6 5.8 | 10.1 50.2 265 4 2 8.8 4.8
8000 12.3 54.1 135 2 1 12.1 6.7 | 10.8 51.4 270 4 2 11.8 6.5
7750 13.1 55.6 135 2 1 10.3 5.6 | 11.8 53.2 275 5 2 11.2 6.1
7500 13.8 56.8 130 2 1 8.6 4.7 | 12.4 54.3 280 5 3 7.7 4.2
7250 14.5 58.1 125 2 1 9.3 5.1 | 13.1 55.6 285 5 3 8.9 4.9
7000 15.2 59.4 125 2 1 10.0 5.5 | 13.8 56.8 290 6 3 9.9 5.4
6750 16.0 60.8 120 1 1 10.1 5.6 | 14.5 58.1 290 6 3 10.0 5.5
6500 16.7 62.1 110 1 1 9.9 5.4 | 15.2 59.4 295 6 3 9.2 5.0
6250 17.5 63.5 105 1 1 10.1 5.6 | 15.9 60.6 295 7 3 9.8 5.4
6000 18.2 64.8 100 1 1 10.5 5.8 | 16.7 62.1 300 7 3 10.4 5.7
5750 19.0 66.2 090 1 1 10.8 5.9 | 17.4 63.3 300 7 4 10.0 5.5
5500 20.0 68.0 075 1 1 16.9 9.3 | 18.2 64.8 305 7 4 9.7 5.3
________________________________________________________________________________
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 near the old Stapleton
Airport site in Denver, Colorado at
North Latitude: 39 deg 46 min 5.016 sec
West Longitude: 104 deg 52 min 9.984 sec
Elevation: 5285 feet (1611 meters)
and may not be representative of other areas along the Front Range of the
Colorado Rocky Mountains. 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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