Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
715
UXUS97 KBOU 041242
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0641 MDT Saturday, October 4, 2025
This forecast is for Saturday, October 4, 2025:
If the trigger temperature of 75.5 F/24.1 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1030 ft/min (5.2 m/s)
Maximum height of thermals.................. 15641 ft MSL (10320 ft AGL)
Forecast maximum temperature................... 82.0 F/28.2 C
Time of trigger temperature.................... 1030 MDT
Time of overdevelopment........................ 1400 MDT
Middle/high clouds during soaring window....... Overcast thin high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 10511 ft MSL (5190 ft AGL)
Thermal soaring outlook for Sunday 10/05....... Good
Wave Soaring Index............................. Good
Wave Soaring Index trend (to 1800 MDT)......... Little change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 40526 ft MSL (35205 ft AGL)
Wave soaring outlook for Sunday 10/05.......... Good
Remarks... Strong southwest flow today, mixing to surface through afternoon.
Gusty outflow winds from any pm showers/storms.
Sunrise/Sunset.................... 06:59:16 / 18:36:48 MDT
Total possible sunshine........... 11 hr 37 min 32 sec (697 min 32 sec)
Altitude of sun at 12:48:02 MDT... 45.48 degrees
Upper air data from numerical model forecast valid on 10/04/2025 at 0600 MDT
Freezing level.................. 14091 ft MSL (8770 ft AGL)
Convective condensation level... 13776 ft MSL (8455 ft AGL)
Lifted condensation level....... 14512 ft MSL (9191 ft AGL)
Lifted index.................... -1.9
K index......................... +29.4
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 -64.1 -83.4 235 50 26 0.8 0.5 M M M M M
45000 -61.8 -79.2 230 73 38 4.4 2.4 M M M M M
40000 -55.2 -67.4 225 85 44 5.2 2.8 M M M M M
38000 -51.6 -60.9 225 77 40 5.9 3.3 M M M M M
36000 -48.1 -54.6 220 69 35 5.9 3.3 M M M M M
34000 -43.8 -46.8 220 54 28 6.6 3.6 M M M M M
32000 -39.8 -39.6 215 39 20 6.7 3.7 M M M M M
30000 -35.0 -31.0 210 35 18 8.6 4.7 40.1 104.2 9.4 M M
29000 -32.5 -26.5 210 36 18 8.6 4.7 39.7 103.5 9.1 M M
28000 -29.9 -21.8 210 36 19 8.6 4.7 39.4 102.9 9.0 M M
27000 -27.2 -17.0 210 36 19 9.3 5.1 39.1 102.3 8.8 M M
26000 -24.5 -12.1 215 36 18 9.3 5.1 38.9 101.9 8.7 M M
25000 -21.7 -7.1 215 35 18 9.3 5.1 38.8 101.8 8.7 M M
24000 -19.3 -2.7 215 35 18 7.2 3.9 38.2 100.8 8.3 M M
23000 -17.2 1.0 215 34 18 7.1 3.9 37.2 98.9 7.5 M M
22000 -15.1 4.8 215 34 17 7.2 3.9 36.3 97.4 6.8 M M
21000 -13.1 8.4 215 33 17 6.6 3.6 35.3 95.5 5.9 M M
20000 -11.2 11.8 215 33 17 6.6 3.6 34.1 93.4 4.9 M M
19500 -10.2 13.6 215 33 17 6.6 3.6 33.6 92.4 4.5 M M
19000 -9.3 15.3 215 33 17 6.5 3.5 33.1 91.5 4.0 M M
18500 -8.4 16.9 215 33 17 5.7 3.1 32.4 90.3 3.4 M M
18000 -7.6 18.3 215 33 17 5.7 3.1 31.7 89.1 2.8 M M
17500 -6.3 20.7 215 33 17 6.3 3.5 30.7 87.3 2.0 M M
17000 -5.4 22.3 220 32 17 6.3 3.5 30.2 86.3 1.4 M M
16500 -4.5 23.9 220 32 16 6.2 3.4 29.6 85.2 0.9 M M
16000 -3.6 25.5 220 32 16 6.2 3.4 29.0 84.1 0.3 M M
15500 -2.7 27.1 220 31 16 6.4 3.5 28.4 83.1 -0.3 911 4.6
15000 -1.7 28.9 225 31 16 6.7 3.7 27.9 82.2 -0.8 867 4.4
14500 -0.8 30.6 225 30 15 6.8 3.7 27.4 81.2 -1.3 823 4.2
14000 0.4 32.7 225 29 15 8.8 4.8 27.1 80.7 -1.6 774 3.9
13500 1.7 35.1 230 28 15 8.6 4.7 26.9 80.4 -1.7 720 3.7
13000 3.0 37.4 230 27 14 9.5 5.2 26.8 80.2 -1.9 666 3.4
12500 4.4 39.9 230 26 13 9.5 5.2 26.7 80.1 -2.0 609 3.1
12000 5.7 42.3 235 25 13 8.3 4.5 26.6 79.9 -2.1 554 2.8
11500 7.0 44.6 240 23 12 8.2 4.5 26.3 79.4 -2.3 503 2.6
11000 8.1 46.6 240 22 11 7.5 4.1 26.1 78.9 -2.6 453 2.3
10500 9.2 48.6 245 21 11 6.9 3.8 25.7 78.3 -3.0 405 2.1
10250 9.8 49.6 245 20 11 9.4 5.2 25.5 78.0 -3.2 382 1.9
10000 10.6 51.1 250 20 10 10.0 5.5 25.6 78.1 -3.2 351 1.8
9750 11.2 52.2 250 20 10 8.0 4.4 25.5 77.9 -3.3 325 1.7
9500 11.8 53.2 255 20 10 8.6 4.7 25.4 77.7 -3.4 299 1.5
9250 12.4 54.3 255 20 10 8.2 4.5 25.3 77.5 -3.5 273 1.4
9000 13.0 55.4 255 19 10 8.1 4.4 25.2 77.3 -3.6 248 1.3
8750 13.6 56.5 260 19 10 8.1 4.4 25.0 77.1 -3.8 223 1.1
8500 14.2 57.6 260 19 10 8.0 4.4 24.9 76.8 -3.9 197 1.0
8250 14.8 58.6 260 19 10 8.3 4.5 24.8 76.6 -4.1 172 0.9
8000 15.4 59.7 260 18 9 7.7 4.2 24.7 76.4 -4.2 147 0.7
7750 15.9 60.6 260 17 9 6.5 3.6 24.4 76.0 -4.5 124 0.6
7500 16.4 61.5 255 17 9 6.6 3.6 24.2 75.6 -4.7 102 0.5
7250 16.8 62.2 255 16 8 5.6 3.1 23.9 75.1 -5.0 81 0.4
7000 17.2 63.0 255 16 8 4.5 2.5 23.6 74.4 -5.4 63 0.3
6750 17.5 63.5 255 15 8 4.0 2.2 23.2 73.7 -5.8 47 0.2
6500 17.7 63.9 255 15 8 3.1 1.7 22.7 72.8 -6.3 32 0.2
6250 17.9 64.2 255 14 7 2.0 1.1 22.1 71.8 -6.9 20 0.1
6000 18.0 64.4 250 12 6 1.7 0.9 21.5 70.7 -7.6 10 0.1
5750 18.0 64.4 240 11 6 1.1 0.6 20.9 69.6 -8.2 0 0.0
5500 18.0 64.4 230 10 5 -1.9 -1.0 20.2 68.3 -9.0 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/04/2025 at 0900 MDT | 10/04/2025 at 1200 MDT
|
CAPE... +182.7 LI... -1.2 | CAPE... +374.1 LI... -2.5
CINH... -207.3 K Index... +23.9 | CINH... -63.4 K Index... +23.8
|
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 -62.6 -80.7 230 43 22 1.3 0.7 | -61.5 -78.7 230 43 22 1.8 1.0
45000 -59.9 -75.8 230 68 35 3.8 2.1 | -58.3 -72.9 230 72 37 3.3 1.8
40000 -54.2 -65.6 220 79 40 4.0 2.2 | -53.3 -63.9 220 82 42 3.3 1.8
38000 -51.4 -60.5 220 74 38 4.7 2.6 | -51.0 -59.8 220 80 41 3.8 2.1
36000 -48.6 -55.5 220 69 35 4.7 2.6 | -48.7 -55.7 220 79 41 3.8 2.1
34000 -44.6 -48.3 220 61 31 6.9 3.8 | -45.4 -49.7 215 75 39 7.3 4.0
32000 -40.4 -40.7 220 53 27 6.9 3.8 | -40.5 -40.9 215 69 36 7.3 4.0
30000 -35.7 -32.3 220 48 25 8.6 4.7 | -35.9 -32.6 215 65 34 8.0 4.4
29000 -33.1 -27.6 220 47 24 8.6 4.7 | -33.5 -28.3 215 64 33 8.0 4.4
28000 -30.6 -23.1 220 46 24 8.6 4.7 | -31.1 -24.0 215 63 32 8.0 4.4
27000 -28.1 -18.6 215 44 23 8.1 4.4 | -28.7 -19.7 210 60 31 8.2 4.5
26000 -25.7 -14.3 215 42 21 8.1 4.4 | -26.2 -15.2 210 55 28 8.2 4.5
25000 -23.2 -9.8 210 39 20 8.0 4.4 | -23.8 -10.8 205 51 26 8.2 4.5
24000 -21.1 -6.0 210 37 19 6.0 3.3 | -21.4 -6.5 200 48 25 7.2 3.9
23000 -19.3 -2.7 205 36 18 6.1 3.3 | -19.3 -2.7 200 45 23 7.3 4.0
22000 -17.6 0.3 205 34 17 6.3 3.4 | -17.1 1.2 200 42 22 7.3 4.0
21000 -15.5 4.1 205 33 17 7.8 4.3 | -15.2 4.6 200 40 21 5.9 3.2
20000 -13.2 8.2 205 32 16 7.9 4.3 | -13.5 7.7 195 37 19 6.0 3.3
19500 -12.0 10.4 200 32 16 7.9 4.3 | -12.6 9.3 195 36 19 6.0 3.3
19000 -10.9 12.4 200 31 16 7.9 4.4 | -11.8 10.8 190 35 18 6.0 3.3
18500 -9.7 14.5 200 31 16 8.1 4.5 | -10.8 12.6 190 35 18 7.7 4.2
18000 -8.5 16.7 200 31 16 8.1 4.5 | -9.7 14.5 190 35 18 7.6 4.2
17500 -6.7 19.9 200 30 16 8.4 4.6 | -8.6 16.5 190 35 18 8.5 4.6
17000 -5.4 22.3 200 31 16 8.4 4.6 | -6.5 20.3 190 34 18 9.2 5.1
16500 -4.2 24.4 205 31 16 8.3 4.6 | -5.2 22.6 185 34 17 9.0 4.9
16000 -3.0 26.6 205 31 16 8.3 4.6 | -3.9 25.0 190 34 17 8.9 4.9
15500 -1.8 28.8 210 32 16 8.3 4.5 | -2.5 27.5 190 33 17 9.0 4.9
15000 -0.6 30.9 210 32 16 8.2 4.5 | -1.2 29.8 190 33 17 9.2 5.1
14500 0.6 33.1 215 32 17 8.2 4.5 | 0.2 32.4 190 32 17 9.3 5.1
14000 1.8 35.2 220 32 16 8.0 4.4 | 1.5 34.7 195 33 17 8.5 4.6
13500 2.9 37.2 220 31 16 8.2 4.5 | 2.7 36.9 195 34 17 8.7 4.8
13000 4.0 39.2 225 29 15 6.9 3.8 | 3.9 39.0 200 34 18 7.1 3.9
12500 5.0 41.0 225 26 14 6.9 3.8 | 4.9 40.8 205 33 17 7.0 3.8
12000 6.0 42.8 225 23 12 6.8 3.7 | 5.9 42.6 205 32 16 7.2 3.9
11500 7.0 44.6 220 18 9 6.7 3.7 | 6.9 44.4 205 29 15 7.2 4.0
11000 8.0 46.4 215 15 7 7.5 4.1 | 8.0 46.4 200 26 13 7.4 4.1
10500 9.2 48.6 215 13 7 7.3 4.0 | 9.1 48.4 205 25 13 7.2 3.9
10250 9.7 49.5 215 12 6 9.7 5.3 | 9.7 49.5 210 24 12 9.8 5.4
10000 10.5 50.9 215 11 6 9.1 5.0 | 10.5 50.9 215 25 13 8.9 4.9
9750 11.0 51.8 215 11 6 6.5 3.6 | 10.9 51.6 215 24 12 6.0 3.3
9500 11.5 52.7 215 10 5 6.8 3.7 | 11.4 52.5 210 23 12 6.5 3.6
9250 12.0 53.6 215 10 5 8.3 4.6 | 11.9 53.4 210 22 11 7.6 4.2
9000 12.6 54.7 215 10 5 8.4 4.6 | 12.5 54.5 210 21 11 7.9 4.3
8750 13.2 55.8 210 9 5 6.8 3.7 | 13.0 55.4 205 20 10 6.9 3.8
8500 13.7 56.7 205 9 4 6.9 3.8 | 13.5 56.3 200 19 10 6.6 3.6
8250 14.2 57.6 205 8 4 8.2 4.5 | 14.0 57.2 195 18 9 8.7 4.8
8000 14.8 58.6 200 8 4 8.5 4.7 | 14.7 58.5 195 17 9 10.3 5.7
7750 15.4 59.7 195 8 4 6.4 3.5 | 15.4 59.7 190 17 9 8.7 4.8
7500 15.8 60.4 195 8 4 6.4 3.5 | 16.0 60.8 190 17 9 8.0 4.4
7250 16.3 61.3 195 8 4 5.8 3.2 | 16.6 61.9 190 17 8 10.1 5.5
7000 16.6 61.9 195 8 4 4.9 2.7 | 17.5 63.5 190 16 8 11.9 6.5
6750 17.0 62.6 200 8 4 3.9 2.1 | 18.3 64.9 190 16 8 9.7 5.3
6500 17.2 63.0 205 9 5 3.0 1.6 | 19.0 66.2 190 16 8 8.8 4.8
6250 17.4 63.3 205 10 5 2.7 1.5 | 19.7 67.5 190 16 8 10.7 5.9
6000 17.5 63.5 205 10 5 2.8 1.5 | 20.6 69.1 190 15 8 12.3 6.8
5750 17.7 63.9 200 10 5 1.5 0.8 | 21.4 70.5 190 14 7 10.4 5.7
5500 17.8 64.0 190 9 5 4.9 2.7 | 22.3 72.1 190 14 7 14.6 8.0
10/04/2025 at 1500 MDT | 10/04/2025 at 1800 MDT
|
CAPE... +493.7 LI... -1.9 | CAPE... +420.2 LI... -2.4
CINH... -2.6 K Index... +26.9 | CINH... -37.9 K Index... +15.4
|
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 -62.4 -80.3 230 42 21 2.4 1.3 | -61.2 -78.2 240 38 19 3.3 1.8
45000 -58.0 -72.4 230 65 33 4.2 2.3 | -56.1 -69.0 235 55 29 3.3 1.8
40000 -51.7 -61.1 225 78 40 4.2 2.3 | -51.0 -59.8 225 56 29 3.4 1.9
38000 -49.9 -57.8 220 81 42 2.9 1.6 | -49.3 -56.7 220 62 32 2.8 1.5
36000 -48.2 -54.8 220 83 43 2.9 1.6 | -47.6 -53.7 215 70 36 2.8 1.5
34000 -45.3 -49.5 215 83 43 6.9 3.8 | -44.7 -48.5 215 74 38 7.6 4.2
32000 -41.2 -42.2 215 79 41 6.9 3.8 | -40.1 -40.2 215 74 38 7.6 4.2
30000 -36.1 -33.0 210 74 38 8.2 4.5 | -35.4 -31.7 210 73 38 6.1 3.4
29000 -33.7 -28.7 210 71 37 8.2 4.5 | -33.6 -28.5 210 72 37 6.1 3.4
28000 -31.2 -24.2 210 69 36 8.2 4.5 | -31.8 -25.2 205 71 37 6.1 3.4
27000 -28.8 -19.8 210 67 34 7.7 4.2 | -29.9 -21.8 205 70 36 6.6 3.6
26000 -26.5 -15.7 210 65 34 7.7 4.2 | -27.9 -18.2 205 69 36 6.6 3.6
25000 -24.2 -11.6 205 64 33 7.7 4.2 | -25.9 -14.6 205 68 35 6.6 3.6
24000 -21.9 -7.4 205 62 32 7.9 4.3 | -23.8 -10.8 205 67 35 7.9 4.3
23000 -19.6 -3.3 205 60 31 7.9 4.3 | -21.5 -6.7 205 66 34 7.8 4.3
22000 -17.3 0.9 205 58 30 7.9 4.3 | -19.2 -2.6 205 65 33 7.8 4.3
21000 -15.0 5.0 205 54 28 7.0 3.9 | -16.9 1.6 205 63 33 7.6 4.2
20000 -13.0 8.6 205 48 25 7.1 3.9 | -14.6 5.7 205 61 31 7.6 4.2
19500 -12.0 10.4 205 45 23 7.1 3.9 | -13.5 7.7 205 60 31 7.6 4.2
19000 -10.9 12.4 205 42 22 7.0 3.8 | -12.3 9.9 205 59 30 7.6 4.2
18500 -9.8 14.4 205 40 21 8.7 4.8 | -11.2 11.8 205 58 30 7.6 4.2
18000 -8.5 16.7 210 40 21 8.6 4.7 | -10.1 13.8 210 58 30 7.6 4.2
17500 -7.2 19.0 210 40 21 8.2 4.5 | -8.9 16.0 210 57 30 7.7 4.3
17000 -6.1 21.0 215 43 22 7.6 4.2 | -7.8 18.0 210 57 29 8.0 4.4
16500 -5.0 23.0 215 46 24 7.7 4.2 | -6.6 20.1 210 57 29 8.0 4.4
16000 -4.0 24.8 220 48 25 7.0 3.8 | -5.4 22.3 215 56 29 8.1 4.5
15500 -2.9 26.8 220 49 25 7.1 3.9 | -4.2 24.4 215 55 28 8.1 4.5
15000 -1.9 28.6 220 50 26 6.3 3.5 | -3.0 26.6 215 54 28 8.3 4.6
14500 -0.6 30.9 220 47 24 6.0 3.3 | -1.7 28.9 215 53 27 8.5 4.7
14000 0.3 32.5 215 43 22 7.2 3.9 | 0.1 32.2 220 51 26 7.9 4.3
13500 1.3 34.3 210 39 20 7.2 3.9 | 1.2 34.2 220 48 25 8.0 4.4
13000 2.3 36.1 205 35 18 8.3 4.5 | 2.3 36.1 220 45 23 8.3 4.6
12500 3.5 38.3 200 32 17 8.6 4.7 | 3.5 38.3 220 41 21 8.5 4.7
12000 4.8 40.6 195 30 16 9.3 5.1 | 4.6 40.3 220 38 20 9.4 5.1
11500 6.2 43.2 195 30 15 9.7 5.3 | 6.1 43.0 220 36 18 9.9 5.4
11000 7.7 45.9 195 30 15 9.3 5.1 | 7.5 45.5 215 33 17 9.2 5.1
10500 9.0 48.2 195 29 15 9.0 4.9 | 8.8 47.8 215 32 16 8.2 4.5
10250 9.7 49.5 195 29 15 11.6 6.3 | 9.4 48.9 215 31 16 11.4 6.3
10000 10.7 51.3 195 29 15 11.4 6.3 | 10.4 50.7 215 31 16 11.5 6.3
9750 11.4 52.5 195 29 15 9.3 5.1 | 11.1 52.0 210 30 16 8.7 4.8
9500 12.1 53.8 190 29 15 10.0 5.5 | 11.8 53.2 210 30 15 9.3 5.1
9250 12.9 55.2 190 29 15 9.3 5.1 | 12.4 54.3 210 30 15 9.4 5.2
9000 13.5 56.3 190 29 15 9.6 5.3 | 13.1 55.6 210 29 15 9.2 5.0
8750 14.3 57.7 190 28 15 10.3 5.7 | 13.8 56.8 205 29 15 8.7 4.8
8500 15.1 59.2 190 28 15 9.9 5.4 | 14.4 57.9 205 29 15 8.6 4.7
8250 15.8 60.4 190 28 14 11.0 6.0 | 15.1 59.2 205 28 15 9.6 5.3
8000 16.7 62.1 190 28 14 10.7 5.9 | 15.8 60.4 200 28 14 9.4 5.2
7750 17.4 63.3 190 28 14 9.1 5.0 | 16.4 61.5 200 28 14 7.4 4.1
7500 18.1 64.6 190 27 14 9.1 5.0 | 16.9 62.4 195 28 14 7.2 4.0
7250 18.8 65.8 190 27 14 9.4 5.2 | 17.5 63.5 195 27 14 7.1 3.9
7000 19.5 67.1 190 27 14 10.1 5.5 | 17.9 64.2 190 27 14 6.4 3.5
6750 20.2 68.4 190 27 14 10.3 5.6 | 18.4 65.1 190 26 14 6.2 3.4
6500 21.0 69.8 190 26 13 10.2 5.6 | 18.8 65.8 185 25 13 6.0 3.3
6250 21.8 71.2 190 26 13 10.3 5.6 | 19.2 66.6 180 25 13 7.0 3.8
6000 22.5 72.5 190 25 13 10.3 5.7 | 19.8 67.6 180 23 12 8.0 4.4
5750 23.4 74.1 190 24 12 12.0 6.6 | 20.4 68.7 175 21 11 8.9 4.9
5500 24.4 75.9 190 20 11 18.2 10.0 | 21.1 70.0 175 17 9 11.5 6.3
________________________________________________________________________________
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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