Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
754
UXUS97 KBOU 040115
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1913 MDT Sunday, August 3, 2025
This forecast is for Monday, August 4, 2025:
If the trigger temperature of 83.9 F/28.8 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1469 ft/min (7.5 m/s)
Maximum height of thermals.................. 20715 ft MSL (15427 ft AGL)
Forecast maximum temperature................... 95.0 F/35.5 C
Time of trigger temperature.................... 1030 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................. 13373 ft MSL (8085 ft AGL)
Thermal soaring outlook for Tuesday 08/05...... 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)................ Weak PVA
Potential height of wave....................... 40422 ft MSL (35134 ft AGL)
Wave soaring outlook for Tuesday 08/05......... Poor
Remarks... Hot and dry with no storms
Sunrise/Sunset.................... 06:01:51 / 20:09:15 MDT
Total possible sunshine........... 14 hr 7 min 25 sec (847 min 25 sec)
Altitude of sun at 13:05:33 MDT... 67.21 degrees
Upper air data from numerical model forecast valid on 08/04/2025 at 0600 MDT
Freezing level.................. 16166 ft MSL (10878 ft AGL)
Convective condensation level... 17586 ft MSL (12298 ft AGL)
Lifted condensation level....... 18612 ft MSL (13324 ft AGL)
Lifted index.................... -3.6
K index......................... +11.5
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 -62.6 -80.7 270 19 10 1.6 0.9 M M M M M
45000 -59.3 -74.7 280 46 24 4.0 2.2 M M M M M
40000 -52.6 -62.7 285 76 39 5.8 3.2 M M M M M
38000 -49.2 -56.6 285 75 39 5.8 3.2 M M M M M
36000 -45.7 -50.3 290 75 38 5.6 3.1 M M M M M
34000 -41.3 -42.3 290 70 36 7.6 4.2 M M M M M
32000 -36.7 -34.1 290 65 33 7.6 4.2 M M M M M
30000 -32.4 -26.3 290 57 29 7.1 3.9 43.5 110.3 6.5 M M
29000 -30.3 -22.5 285 52 27 7.1 3.9 42.5 108.6 5.8 M M
28000 -27.6 -17.7 285 47 24 6.7 3.7 41.4 106.5 5.0 M M
27000 -25.6 -14.1 285 43 22 6.7 3.7 40.1 104.2 4.0 M M
26000 -23.6 -10.5 290 39 20 6.7 3.7 38.9 102.1 3.1 M M
25000 -21.6 -6.9 290 35 18 7.5 4.1 37.9 100.3 2.3 M M
24000 -19.0 -2.2 290 32 16 8.8 4.8 37.4 99.4 2.0 M M
23000 -16.4 2.5 290 29 15 8.8 4.8 37.1 98.8 1.7 M M
22000 -13.8 7.2 290 26 13 7.5 4.1 36.8 98.3 1.5 M M
21000 -11.9 10.6 290 24 12 6.3 3.5 35.5 95.9 0.3 M M
20000 -10.1 13.8 290 22 11 6.4 3.5 34.3 93.8 -0.7 1410 7.2
19500 -9.2 15.4 290 21 11 6.5 3.6 33.8 92.8 -1.3 1368 6.9
19000 -8.1 17.4 290 20 10 8.7 4.8 33.4 92.2 -1.6 1320 6.7
18500 -6.8 19.8 290 19 10 8.5 4.7 33.2 91.8 -1.8 1268 6.4
18000 -5.6 21.9 285 19 10 9.3 5.1 33.0 91.4 -2.0 1215 6.2
17500 -4.1 24.6 285 18 9 9.8 5.4 33.0 91.5 -2.0 1156 5.9
17000 -2.6 27.3 285 17 9 9.9 5.4 33.1 91.5 -2.0 1097 5.6
16500 -1.2 29.8 285 16 8 9.2 5.1 33.0 91.4 -2.1 1040 5.3
16000 0.2 32.4 285 16 8 9.3 5.1 32.9 91.3 -2.2 983 5.0
15500 1.6 34.9 285 15 8 9.0 4.9 32.9 91.1 -2.2 927 4.7
15000 2.9 37.2 285 14 7 9.0 4.9 32.7 90.9 -2.4 873 4.4
14500 4.9 40.8 285 13 7 8.9 4.9 32.5 90.5 -2.6 792 4.0
14000 6.2 43.2 285 11 6 8.9 4.9 32.4 90.3 -2.8 738 3.7
13500 7.4 45.3 280 10 5 8.7 4.7 32.2 90.0 -3.0 684 3.5
13000 8.7 47.7 275 9 5 8.6 4.7 32.0 89.6 -3.2 632 3.2
12500 9.9 49.8 270 8 4 8.2 4.5 31.8 89.3 -3.4 580 2.9
12000 11.1 52.0 255 8 4 7.9 4.3 31.5 88.8 -3.8 531 2.7
11500 12.2 54.0 245 8 4 7.5 4.1 31.2 88.2 -4.1 482 2.4
11000 13.3 55.9 235 9 4 6.9 3.8 30.8 87.5 -4.6 436 2.2
10500 14.3 57.7 220 9 5 3.0 1.6 30.4 86.8 -5.0 391 2.0
10250 14.4 57.9 220 10 5 4.8 2.6 29.8 85.6 -5.7 381 1.9
10000 15.1 59.2 220 10 5 11.2 6.2 29.8 85.6 -5.7 352 1.8
9750 15.8 60.4 215 11 6 10.2 5.6 29.8 85.6 -5.7 322 1.6
9500 16.6 61.9 215 12 6 8.0 4.4 29.8 85.7 -5.7 293 1.5
9250 17.0 62.6 215 13 7 5.5 3.0 29.5 85.1 -6.0 273 1.4
9000 17.5 63.5 215 14 7 7.8 4.3 29.3 84.7 -6.3 251 1.3
8750 18.1 64.6 210 15 8 8.9 4.9 29.2 84.5 -6.4 226 1.1
8500 18.7 65.7 210 16 8 8.2 4.5 29.1 84.4 -6.6 200 1.0
8250 19.2 66.6 205 17 9 8.0 4.4 29.0 84.1 -6.8 176 0.9
8000 19.8 67.6 205 18 9 7.5 4.1 28.8 83.9 -6.9 152 0.8
7750 20.3 68.5 205 19 10 6.6 3.6 28.6 83.5 -7.2 130 0.7
7500 20.7 69.3 200 19 10 6.1 3.3 28.3 83.0 -7.5 109 0.6
7250 21.1 70.0 200 19 10 5.5 3.0 28.0 82.5 -7.8 89 0.5
7000 21.6 70.9 195 18 9 6.6 3.6 27.7 81.9 -8.2 70 0.4
6750 21.9 71.4 195 18 9 2.3 1.3 27.4 81.4 -8.5 50 0.3
6500 21.8 71.2 195 17 9 -4.8 -2.7 26.5 79.8 -9.4 48 0.2
6250 21.3 70.3 195 14 7 -8.3 -4.5 25.3 77.5 -10.7 56 0.3
6000 20.8 69.4 195 11 6 -1.2 -0.7 24.1 75.3 -12.0 64 0.3
5750 20.7 69.3 205 8 4 -9.2 -5.1 23.3 73.9 -12.8 59 0.3
5500 18.7 65.7 205 6 3 -41.1 -22.6 20.6 69.1 -15.6 112 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/04/2025 at 0900 MDT | 08/04/2025 at 1200 MDT
|
CAPE... +83.2 LI... +0.1 | CAPE... +217.6 LI... -0.3
CINH... -158.0 K Index... +8.9 | CINH... -28.0 K Index... +10.4
|
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 -80.5 265 22 11 2.0 1.1 | -62.6 -80.7 265 27 14 1.4 0.8
45000 -58.7 -73.7 285 48 25 3.8 2.1 | -59.4 -74.9 285 47 24 3.9 2.1
40000 -52.8 -63.0 285 76 39 5.7 3.1 | -53.2 -63.8 290 73 38 6.5 3.6
38000 -49.4 -56.9 290 74 38 5.6 3.1 | -48.9 -56.0 290 71 37 6.4 3.5
36000 -45.6 -50.1 290 72 37 5.6 3.1 | -45.0 -49.0 290 69 36 6.5 3.5
34000 -41.3 -42.3 290 66 34 7.3 4.0 | -40.9 -41.6 290 63 32 6.9 3.8
32000 -36.9 -34.4 290 60 31 7.3 4.0 | -36.7 -34.1 290 57 29 6.9 3.8
30000 -32.5 -26.5 290 54 28 7.3 4.0 | -32.4 -26.3 290 51 26 7.2 3.9
29000 -30.4 -22.7 285 51 26 7.3 4.0 | -30.3 -22.5 290 48 25 7.2 3.9
28000 -28.2 -18.8 285 49 25 7.0 3.9 | -28.1 -18.6 285 45 23 6.8 3.7
27000 -26.1 -15.0 285 45 23 6.9 3.8 | -26.2 -15.2 285 42 22 6.6 3.6
26000 -24.0 -11.2 285 40 21 6.9 3.8 | -24.2 -11.6 285 39 20 6.6 3.6
25000 -22.0 -7.6 285 36 19 7.0 3.8 | -22.2 -8.0 285 36 18 6.8 3.7
24000 -19.7 -3.5 285 33 17 7.8 4.3 | -19.9 -3.8 285 33 17 7.9 4.4
23000 -17.3 0.9 285 29 15 7.8 4.3 | -17.5 0.5 280 30 15 8.0 4.4
22000 -15.0 5.0 290 26 13 7.7 4.2 | -15.1 4.8 280 27 14 8.0 4.4
21000 -12.8 9.0 285 23 12 7.4 4.0 | -12.7 9.1 275 24 12 8.1 4.5
20000 -10.1 13.8 285 20 10 7.5 4.1 | -9.7 14.5 275 21 11 8.2 4.5
19500 -9.0 15.8 285 19 10 8.1 4.4 | -8.5 16.7 270 19 10 8.2 4.5
19000 -7.7 18.1 285 18 9 8.7 4.8 | -7.3 18.9 270 18 9 8.3 4.5
18500 -6.4 20.5 285 17 9 8.7 4.8 | -6.1 21.0 270 16 8 8.2 4.5
18000 -5.1 22.8 285 16 8 9.2 5.0 | -4.8 23.4 270 15 8 9.3 5.1
17500 -3.7 25.3 285 15 8 9.2 5.0 | -3.4 25.9 265 13 7 9.2 5.1
17000 -2.3 27.9 290 14 7 9.2 5.1 | -2.0 28.4 265 12 6 9.2 5.1
16500 -0.9 30.4 285 13 7 9.3 5.1 | -0.6 30.9 265 11 6 9.2 5.1
16000 0.5 32.9 285 13 6 9.3 5.1 | 0.7 33.3 265 11 6 9.3 5.1
15500 1.8 35.2 285 12 6 9.1 5.0 | 2.1 35.8 260 10 5 9.5 5.2
15000 3.2 37.8 285 12 6 9.1 5.0 | 3.6 38.5 260 10 5 9.5 5.2
14500 4.6 40.3 285 11 6 9.2 5.0 | 5.0 41.0 255 9 5 9.3 5.1
14000 5.9 42.6 280 10 5 9.2 5.0 | 6.3 43.3 255 9 4 9.3 5.1
13500 7.3 45.1 275 10 5 9.0 4.9 | 7.7 45.9 250 8 4 9.3 5.1
13000 8.6 47.5 270 9 4 8.9 4.9 | 9.1 48.4 245 8 4 9.3 5.1
12500 9.9 49.8 265 8 4 8.7 4.8 | 10.5 50.9 240 7 4 9.2 5.1
12000 11.2 52.2 255 7 4 8.5 4.7 | 11.9 53.4 235 7 4 9.2 5.1
11500 12.4 54.3 245 7 4 8.4 4.6 | 13.2 55.8 230 7 4 9.2 5.0
11000 13.6 56.5 235 7 4 7.8 4.3 | 14.6 58.3 225 7 4 8.8 4.8
10500 14.8 58.6 225 8 4 3.2 1.7 | 15.9 60.6 215 7 4 4.3 2.3
10250 14.8 58.6 220 9 5 4.5 2.5 | 16.1 61.0 215 6 3 5.7 3.1
10000 15.6 60.1 215 10 5 11.7 6.4 | 16.9 62.4 215 7 3 12.6 6.9
9750 16.3 61.3 215 10 5 10.4 5.7 | 17.7 63.9 210 7 3 11.4 6.3
9500 17.1 62.8 210 11 6 8.6 4.7 | 18.5 65.3 205 7 4 9.3 5.1
9250 17.5 63.5 205 12 6 5.7 3.1 | 19.1 66.4 205 7 3 7.1 3.9
9000 18.0 64.4 205 13 7 8.1 4.4 | 19.7 67.5 200 7 3 9.7 5.3
8750 18.6 65.5 205 14 7 10.0 5.5 | 20.5 68.9 200 7 3 10.7 5.8
8500 19.3 66.7 205 14 7 7.8 4.3 | 21.2 70.2 195 7 3 9.5 5.2
8250 19.8 67.6 205 15 8 5.7 3.1 | 21.9 71.4 195 6 3 8.3 4.6
8000 20.2 68.4 200 17 8 6.2 3.4 | 22.5 72.5 195 6 3 8.8 4.8
7750 20.6 69.1 200 16 8 6.8 3.8 | 23.1 73.6 190 6 3 9.2 5.1
7500 21.1 70.0 200 16 8 4.8 2.6 | 23.8 74.8 190 6 3 8.9 4.9
7250 21.3 70.3 200 16 8 2.7 1.5 | 24.4 75.9 190 6 3 8.5 4.7
7000 21.5 70.7 200 16 8 4.0 2.2 | 25.0 77.0 190 5 3 9.5 5.2
6750 21.8 71.2 200 15 8 4.0 2.2 | 25.8 78.4 190 5 3 11.6 6.3
6500 21.9 71.4 200 12 6 -0.5 -0.3 | 26.7 80.1 185 5 3 11.5 6.3
6250 21.7 71.1 200 10 5 -2.7 -1.5 | 27.5 81.5 190 5 3 11.4 6.2
6000 21.4 70.5 205 8 4 -3.1 -1.7 | 28.3 82.9 190 5 2 9.5 5.2
5750 21.3 70.3 205 5 3 4.9 2.7 | 29.1 84.4 190 5 2 14.5 7.9
5500 22.2 72.0 210 4 2 21.7 11.9 | 30.7 87.3 190 4 2 30.3 16.6
08/04/2025 at 1500 MDT | 08/04/2025 at 1800 MDT
|
CAPE... +0.6 LI... +1.0 | CAPE... +11.9 LI... +0.9
CINH... -0.7 K Index... +8.6 | CINH... -21.9 K Index... +11.3
|
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 -62.8 -81.0 265 27 14 1.7 0.9 | -62.5 -80.5 260 18 9 1.0 0.5
45000 -59.4 -74.9 280 43 22 3.6 2.0 | -59.8 -75.6 275 35 18 4.0 2.2
40000 -53.1 -63.6 290 68 35 6.9 3.8 | -53.0 -63.4 285 70 36 6.8 3.7
38000 -49.0 -56.2 290 64 33 6.9 3.8 | -48.9 -56.0 285 64 33 6.8 3.7
36000 -44.8 -48.6 295 60 31 6.9 3.8 | -44.8 -48.6 290 58 30 6.8 3.7
34000 -40.5 -40.9 295 57 29 7.3 4.0 | -40.7 -41.3 290 53 27 6.9 3.8
32000 -36.1 -33.0 295 54 28 7.2 4.0 | -36.6 -33.9 290 47 24 6.8 3.7
30000 -31.2 -24.2 290 49 25 7.4 4.1 | -32.1 -25.8 290 45 23 7.6 4.2
29000 -28.9 -20.0 290 47 24 7.4 4.1 | -29.3 -20.7 285 43 22 7.6 4.2
28000 -26.8 -16.2 290 45 23 6.3 3.4 | -27.1 -16.8 285 42 22 6.4 3.5
27000 -24.9 -12.8 285 43 22 6.3 3.5 | -25.2 -13.4 280 40 20 6.6 3.6
26000 -23.0 -9.4 285 41 21 6.3 3.5 | -23.2 -9.8 275 38 19 6.6 3.6
25000 -21.1 -6.0 280 39 20 6.8 3.7 | -21.2 -6.2 270 36 18 7.5 4.1
24000 -18.9 -2.0 280 37 19 7.4 4.1 | -18.8 -1.8 270 33 17 8.3 4.5
23000 -16.7 1.9 275 35 18 7.5 4.1 | -16.4 2.5 265 30 15 8.4 4.6
22000 -14.5 5.9 275 33 17 8.4 4.6 | -13.9 7.0 265 27 14 8.9 4.9
21000 -11.9 10.6 270 29 15 9.0 4.9 | -11.2 11.8 265 24 12 9.1 5.0
20000 -9.3 15.3 270 26 13 9.1 5.0 | -8.5 16.7 265 22 11 9.1 5.0
19500 -8.0 17.6 265 24 13 9.1 5.0 | -7.1 19.2 265 20 11 9.2 5.0
19000 -6.6 20.1 265 22 12 9.0 4.9 | -5.8 21.6 265 19 10 9.3 5.1
18500 -5.3 22.5 265 20 10 9.0 4.9 | -4.4 24.1 265 17 9 9.3 5.1
18000 -4.0 24.8 265 18 9 9.3 5.1 | -3.0 26.6 265 15 8 9.1 5.0
17500 -2.6 27.3 265 16 8 9.4 5.2 | -1.7 28.9 265 14 7 9.0 4.9
17000 -1.2 29.8 260 15 8 9.4 5.1 | -0.4 31.3 265 12 6 9.0 4.9
16500 0.2 32.4 255 13 7 8.8 4.8 | 1.0 33.8 265 10 5 9.3 5.1
16000 1.6 34.9 250 12 6 8.9 4.9 | 2.4 36.3 255 9 5 9.3 5.1
15500 3.6 38.5 240 10 5 8.8 4.9 | 4.5 40.1 245 7 4 9.3 5.1
15000 4.9 40.8 230 9 5 8.9 4.9 | 5.8 42.4 230 7 3 9.4 5.1
14500 6.2 43.2 225 8 4 8.7 4.8 | 7.2 45.0 220 6 3 8.9 4.9
14000 7.5 45.5 215 8 4 8.7 4.8 | 8.5 47.3 210 6 3 9.0 4.9
13500 8.8 47.8 210 8 4 8.9 4.9 | 9.9 49.8 200 7 3 8.9 4.9
13000 10.2 50.4 205 8 4 9.0 4.9 | 11.2 52.2 195 7 4 9.0 4.9
12500 11.5 52.7 200 8 4 9.0 5.0 | 12.5 54.5 190 7 4 9.1 5.0
12000 12.8 55.0 200 7 4 9.1 5.0 | 13.9 57.0 190 7 4 9.2 5.0
11500 14.2 57.6 195 7 3 9.2 5.0 | 15.3 59.5 185 8 4 9.3 5.1
11000 15.5 59.9 195 6 3 9.0 4.9 | 16.7 62.1 180 7 4 9.3 5.1
10500 16.9 62.4 195 6 3 6.2 3.4 | 18.1 64.6 180 7 4 6.3 3.5
10250 17.3 63.1 195 6 3 7.4 4.0 | 18.4 65.1 180 7 3 7.0 3.8
10000 18.1 64.6 195 6 3 11.9 6.6 | 19.2 66.6 175 7 3 11.4 6.2
9750 18.9 66.0 195 6 3 11.0 6.0 | 20.0 68.0 175 6 3 10.6 5.8
9500 19.7 67.5 195 6 3 10.3 5.7 | 20.8 69.4 175 6 3 9.2 5.0
9250 20.4 68.7 195 6 3 9.5 5.2 | 21.4 70.5 175 6 3 8.5 4.6
9000 21.1 70.0 195 6 3 10.2 5.6 | 22.1 71.8 180 6 3 10.3 5.6
8750 21.9 71.4 195 6 3 10.2 5.6 | 22.9 73.2 180 6 3 10.3 5.7
8500 22.7 72.9 195 5 3 10.3 5.6 | 23.6 74.5 180 6 3 10.3 5.6
8250 23.4 74.1 200 5 3 10.4 5.7 | 24.4 75.9 180 5 3 10.3 5.6
8000 24.2 75.6 200 5 3 10.0 5.5 | 25.1 77.2 180 5 3 9.7 5.3
7750 24.9 76.8 200 5 3 9.6 5.3 | 25.8 78.4 180 5 3 8.9 4.9
7500 25.7 78.3 200 5 3 9.9 5.4 | 26.5 79.7 185 5 3 9.8 5.4
7250 26.4 79.5 200 5 3 9.9 5.4 | 27.3 81.1 185 5 3 10.9 6.0
7000 27.2 81.0 200 5 3 10.1 5.5 | 28.1 82.6 185 5 3 10.1 5.5
6750 27.9 82.2 200 5 3 10.8 5.9 | 28.8 83.8 185 5 2 8.9 4.9
6500 28.7 83.7 205 5 3 10.9 6.0 | 29.5 85.1 190 5 2 10.1 5.5
6250 29.6 85.3 205 5 3 11.4 6.2 | 30.3 86.5 190 5 2 11.5 6.3
6000 30.4 86.7 205 5 3 9.6 5.2 | 31.1 88.0 190 4 2 10.5 5.8
5750 31.1 88.0 205 5 2 13.4 7.3 | 31.9 89.4 195 4 2 11.3 6.2
5500 32.6 90.7 205 5 2 27.5 15.1 | 32.9 91.2 195 4 2 15.7 8.6
________________________________________________________________________________
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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