Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
495
UXUS97 KBOU 031215
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0513 MST Wednesday, December 3, 2025
This forecast is for Wednesday, December 3, 2025:
If the trigger temperature of 38.3 F/3.5 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 5304 ft MSL (0 ft AGL)
Forecast maximum temperature................... 30.0 F/-1.6 C
Time of trigger temperature.................... None
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. None
Thermal soaring outlook for Thursday 12/04..... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Weak NVA
Potential height of wave....................... 15142 ft MSL (9838 ft AGL)
Wave soaring outlook for Thursday 12/04........ Fair
Remarks... Light snow off/on through early afternoon, then ending completely
around sunset. Westerly flow starts to pick up again late Thursday.
Sunrise/Sunset.................... 07:04:00 / 16:35:00 MST
Total possible sunshine........... 9 hr 31 min 0 sec (571 min 0 sec)
Altitude of sun at 11:49:30 MST... 27.97 degrees
Upper air data from numerical model forecast valid on 12/03/2025 at 0500 MST
Freezing level.................. Entire airmass below 32 F / 0 C
Convective condensation level... 8656 ft MSL (3352 ft AGL)
Lifted condensation level....... 7164 ft MSL (1860 ft AGL)
Lifted index.................... +8.1
K index......................... +17.4
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 -56.0 -68.8 265 31 16 1.6 0.9 M M M M M
45000 -53.5 -64.3 260 42 21 1.6 0.9 M M M M M
40000 -52.4 -62.3 250 53 27 0.6 0.4 M M M M M
38000 -52.0 -61.6 245 58 30 -0.3 -0.2 M M M M M
36000 -52.2 -62.0 245 64 33 -0.3 -0.2 M M M M M
34000 -52.4 -62.3 250 69 36 -0.3 -0.2 M M M M M
32000 -51.9 -61.4 250 74 38 1.4 0.8 M M M M M
30000 -50.9 -59.6 245 78 40 0.9 0.5 M M M M M
29000 -49.6 -57.3 250 74 38 5.9 3.2 23.4 74.2 18.5 M M
28000 -47.8 -54.0 250 67 35 5.9 3.2 21.8 71.3 17.5 M M
27000 -46.1 -51.0 255 60 31 5.9 3.2 20.4 68.7 16.6 M M
26000 -44.2 -47.6 255 53 27 7.3 4.0 19.1 66.4 15.8 M M
25000 -42.0 -43.6 255 46 24 7.2 4.0 18.1 64.5 15.2 M M
24000 -39.9 -39.8 250 39 20 7.2 4.0 17.1 62.9 14.7 M M
23000 -37.6 -35.7 250 33 17 8.6 4.7 16.4 61.5 14.2 M M
22000 -35.1 -31.2 250 31 16 8.5 4.6 15.9 60.5 13.9 M M
21000 -32.6 -26.7 255 29 15 8.5 4.6 15.4 59.8 13.8 M M
20000 -30.0 -22.0 250 28 14 8.9 4.9 15.1 59.1 13.6 M M
19500 -28.6 -19.5 250 27 14 8.9 4.9 14.9 58.8 13.5 M M
19000 -27.3 -17.1 250 27 14 8.9 4.9 14.8 58.6 13.5 M M
18500 -26.0 -14.8 250 26 14 8.9 4.9 14.6 58.4 13.4 M M
18000 -24.7 -12.5 250 26 13 7.5 4.1 14.5 58.1 13.4 M M
17500 -23.7 -10.7 245 24 12 6.7 3.7 14.0 57.1 13.0 M M
17000 -22.7 -8.9 240 23 12 6.4 3.5 13.4 56.2 12.6 M M
16500 -22.0 -7.6 235 20 10 4.3 2.4 12.6 54.7 11.9 M M
16000 -21.0 -5.8 225 16 8 4.8 2.6 11.3 52.3 10.8 M M
15500 -20.2 -4.4 210 13 7 5.4 3.0 10.5 50.9 10.2 M M
15000 -19.4 -2.9 195 12 6 5.8 3.2 9.8 49.6 9.6 M M
14500 -18.3 -0.9 180 10 5 8.4 4.6 9.4 48.9 9.3 M M
14000 -17.1 1.2 165 9 4 8.2 4.5 9.2 48.5 9.1 M M
13500 -16.0 3.2 155 8 4 6.7 3.7 8.8 47.8 8.8 M M
13000 -15.0 5.0 150 8 4 6.9 3.8 8.3 46.9 8.4 M M
12500 -14.0 6.8 150 7 4 6.5 3.5 7.8 46.0 7.9 M M
12000 -13.1 8.4 150 7 4 6.5 3.6 7.3 45.1 7.5 M M
11500 -12.1 10.2 140 6 3 6.9 3.8 6.8 44.2 7.0 M M
11000 -11.1 12.0 115 7 3 6.8 3.7 6.3 43.3 6.6 M M
10500 -10.2 13.6 105 8 4 4.9 2.7 5.7 42.2 6.0 M M
10250 -9.9 14.2 105 9 5 5.5 3.0 5.3 41.5 5.7 M M
10000 -9.5 14.9 105 10 5 3.8 2.1 4.9 40.9 5.3 M M
9750 -9.3 15.3 105 11 6 4.5 2.5 4.4 40.0 4.9 M M
9500 -8.8 16.2 095 11 6 6.6 3.6 4.1 39.4 4.6 M M
9250 -8.4 16.9 090 12 6 6.3 3.4 3.9 38.9 4.3 M M
9000 -7.9 17.8 085 13 7 5.4 3.0 3.6 38.5 4.1 M M
8750 -7.5 18.5 080 14 7 5.3 2.9 3.2 37.8 3.7 M M
8500 -7.1 19.2 080 15 8 6.3 3.4 2.9 37.2 3.4 M M
8250 -6.7 19.9 075 16 8 6.0 3.3 2.6 36.7 3.1 M M
8000 -6.2 20.8 075 16 8 6.4 3.5 2.4 36.2 2.9 M M
7750 -5.8 21.6 075 16 8 5.7 3.1 2.1 35.8 2.6 M M
7500 -5.4 22.3 075 16 8 4.8 2.6 1.7 35.1 2.3 M M
7250 -5.0 23.0 075 16 8 5.0 2.7 1.4 34.4 1.9 M M
7000 -4.7 23.5 075 15 8 5.2 2.8 1.0 33.8 1.5 M M
6750 -4.3 24.3 080 14 7 4.5 2.5 0.6 33.1 1.2 M M
6500 -4.0 24.8 080 12 6 5.6 3.0 0.2 32.4 0.8 M M
6250 -3.5 25.7 080 11 6 8.4 4.6 0.0 32.1 0.6 M M
6000 -2.8 27.0 070 9 5 9.0 5.0 -0.0 32.0 0.5 M M
5750 -2.2 28.0 060 8 4 9.0 5.0 -0.1 31.9 0.4 M M
5500 -1.5 29.3 045 6 3 10.6 5.8 -0.1 31.8 0.4 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
12/03/2025 at 0800 MST | 12/03/2025 at 1100 MST
|
CAPE... +17.7 LI... +4.5 | CAPE... +42.2 LI... +5.8
CINH... 0.0 K Index... +14.5 | CINH... 0.0 K Index... +13.5
|
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 -55.8 -68.4 270 26 14 1.6 0.9 | -55.9 -68.6 270 29 15 1.5 0.8
45000 -53.3 -63.9 265 40 21 1.5 0.8 | -53.5 -64.3 270 40 20 1.5 0.8
40000 -52.4 -62.3 250 50 26 0.5 0.3 | -52.5 -62.5 255 51 26 0.6 0.3
38000 -52.1 -61.8 250 55 28 0.1 0.1 | -52.1 -61.8 255 56 29 0.4 0.2
36000 -52.1 -61.8 250 59 30 0.1 0.1 | -51.9 -61.4 250 59 31 0.3 0.2
34000 -52.0 -61.6 250 63 32 0.1 0.1 | -51.7 -61.1 245 63 32 0.3 0.2
32000 -51.9 -61.4 250 66 34 0.3 0.2 | -51.6 -60.9 245 64 33 0.0 0.0
30000 -51.7 -61.1 250 69 36 -0.3 -0.2 | -51.6 -60.9 245 64 33 -0.6 -0.3
29000 -50.3 -58.5 250 69 36 6.5 3.5 | -50.3 -58.5 245 62 32 6.3 3.4
28000 -48.4 -55.1 250 68 35 6.5 3.5 | -48.4 -55.1 245 59 30 6.3 3.4
27000 -46.4 -51.5 250 68 35 6.5 3.5 | -46.5 -51.7 245 56 29 6.3 3.4
26000 -44.4 -47.9 250 64 33 7.8 4.3 | -44.5 -48.1 245 53 27 7.8 4.3
25000 -42.0 -43.6 255 54 28 7.7 4.2 | -42.2 -44.0 245 47 24 7.7 4.2
24000 -39.7 -39.5 255 45 23 7.7 4.2 | -39.9 -39.8 245 41 21 7.7 4.2
23000 -37.4 -35.3 255 37 19 7.7 4.2 | -37.6 -35.7 245 36 19 7.9 4.4
22000 -35.1 -31.2 255 33 17 7.7 4.2 | -35.2 -31.4 245 32 17 7.9 4.3
21000 -32.8 -27.0 255 29 15 7.7 4.2 | -32.8 -27.0 245 29 15 7.9 4.3
20000 -30.4 -22.7 255 26 13 8.7 4.8 | -30.3 -22.5 250 26 13 8.9 4.9
19500 -29.0 -20.2 255 24 13 8.8 4.8 | -28.9 -20.0 250 25 13 8.9 4.9
19000 -27.7 -17.9 255 23 12 8.8 4.8 | -27.6 -17.7 250 25 13 8.9 4.9
18500 -26.4 -15.5 255 21 11 8.8 4.8 | -26.3 -15.3 250 24 12 8.9 4.9
18000 -25.2 -13.4 250 20 10 7.6 4.2 | -25.0 -13.0 250 23 12 8.2 4.5
17500 -24.1 -11.4 245 19 10 7.0 3.9 | -23.8 -10.8 250 22 11 7.8 4.3
17000 -23.1 -9.6 240 18 9 6.4 3.5 | -22.7 -8.9 245 21 11 7.3 4.0
16500 -22.4 -8.3 235 16 8 3.7 2.0 | -21.8 -7.2 240 19 10 5.2 2.8
16000 -21.8 -7.2 220 15 8 3.6 2.0 | -20.6 -5.1 225 17 9 4.4 2.4
15500 -21.1 -6.0 210 13 7 5.8 3.2 | -20.1 -4.2 210 15 8 3.6 2.0
15000 -19.9 -3.8 195 10 5 6.2 3.4 | -19.6 -3.3 200 14 7 4.1 2.2
14500 -18.8 -1.8 190 9 5 8.1 4.4 | -18.8 -1.8 190 13 7 5.9 3.2
14000 -17.6 0.3 185 8 4 7.9 4.3 | -17.9 -0.2 185 12 6 5.9 3.2
13500 -16.5 2.3 175 7 4 6.8 3.7 | -17.0 1.4 180 11 6 6.2 3.4
13000 -15.5 4.1 165 7 4 6.8 3.7 | -16.1 3.0 175 10 5 6.1 3.4
12500 -14.6 5.7 155 6 3 5.5 3.0 | -15.4 4.3 165 8 4 4.3 2.4
12000 -13.8 7.2 140 6 3 5.6 3.1 | -14.7 5.5 150 6 3 4.5 2.5
11500 -13.0 8.6 125 6 3 5.4 3.0 | -14.0 6.8 125 5 2 5.2 2.8
11000 -12.2 10.0 110 6 3 5.4 3.0 | -13.3 8.1 095 5 3 5.3 2.9
10500 -11.4 11.5 100 7 4 5.4 3.0 | -12.4 9.7 070 6 3 6.1 3.3
10250 -11.0 12.2 095 8 4 6.3 3.5 | -11.9 10.6 065 7 4 7.1 3.9
10000 -10.6 12.9 090 9 4 2.9 1.6 | -11.5 11.3 060 8 4 3.1 1.7
9750 -10.4 13.3 085 9 5 4.4 2.4 | -11.3 11.7 060 8 4 4.6 2.5
9500 -9.9 14.2 080 10 5 8.9 4.9 | -10.7 12.7 055 9 5 9.6 5.3
9250 -9.3 15.3 075 11 5 7.9 4.3 | -10.1 13.8 050 9 5 8.4 4.6
9000 -8.7 16.3 070 12 6 6.1 3.4 | -9.5 14.9 050 10 5 5.4 2.9
8750 -8.4 16.9 070 11 6 5.2 2.9 | -9.2 15.4 045 12 6 5.6 3.1
8500 -7.9 17.8 065 11 6 6.7 3.7 | -8.6 16.5 045 13 7 8.7 4.8
8250 -7.4 18.7 060 11 6 5.4 3.0 | -8.0 17.6 040 15 7 7.3 4.0
8000 -7.1 19.2 055 11 6 3.5 1.9 | -7.6 18.3 040 16 8 6.3 3.4
7750 -6.9 19.6 050 11 6 3.5 1.9 | -7.1 19.2 040 16 8 6.4 3.5
7500 -6.6 20.1 045 11 6 4.1 2.2 | -6.6 20.1 045 17 9 6.8 3.7
7250 -6.3 20.7 040 11 6 5.8 3.2 | -6.1 21.0 040 16 8 6.9 3.8
7000 -5.8 21.6 035 11 6 7.0 3.8 | -5.6 21.9 040 15 8 7.3 4.0
6750 -5.3 22.5 030 11 6 7.0 3.8 | -5.1 22.8 035 13 7 6.4 3.5
6500 -4.7 23.5 025 11 6 8.4 4.6 | -4.6 23.7 025 12 6 8.2 4.5
6250 -4.1 24.6 020 10 5 9.2 5.0 | -3.9 25.0 025 11 6 10.4 5.7
6000 -3.4 25.9 015 10 5 8.8 4.8 | -3.2 26.2 020 10 5 9.5 5.2
5750 -2.8 27.0 010 10 5 10.0 5.5 | -2.5 27.5 015 10 5 10.9 6.0
5500 -1.9 28.6 005 8 4 12.9 7.1 | -1.5 29.3 015 9 4 14.5 8.0
12/03/2025 at 1400 MST | 12/03/2025 at 1700 MST
|
CAPE... +75.5 LI... +5.7 | CAPE... +38.1 LI... +6.0
CINH... 0.0 K Index... +12.4 | CINH... -0.1 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 -55.1 -67.2 275 29 15 1.6 0.9 | -55.4 -67.7 280 26 13 1.5 0.8
45000 -52.8 -63.0 275 33 17 1.5 0.8 | -53.2 -63.8 275 27 14 1.5 0.8
40000 -52.0 -61.6 265 40 21 0.3 0.2 | -51.3 -60.3 270 30 16 1.2 0.6
38000 -51.8 -61.2 265 44 22 0.1 0.0 | -50.7 -59.3 270 32 16 0.1 0.1
36000 -51.8 -61.2 255 50 26 0.0 0.0 | -50.6 -59.1 270 33 17 0.2 0.1
34000 -51.8 -61.2 250 57 29 0.1 0.0 | -50.5 -58.9 270 34 17 0.2 0.1
32000 -51.7 -61.1 245 58 30 0.3 0.1 | -50.7 -59.3 260 36 18 -0.4 -0.2
30000 -51.5 -60.7 240 57 30 -0.2 -0.1 | -50.9 -59.6 255 39 20 -0.4 -0.2
29000 -50.3 -58.5 240 55 28 5.7 3.1 | -50.2 -58.4 250 39 20 4.7 2.6
28000 -48.6 -55.5 240 52 27 5.7 3.1 | -48.7 -55.7 245 37 19 4.9 2.7
27000 -46.9 -52.4 240 49 25 5.7 3.1 | -46.9 -52.4 240 36 18 5.0 2.7
26000 -44.9 -48.8 240 45 23 8.5 4.7 | -44.9 -48.8 235 34 17 9.0 5.0
25000 -42.4 -44.3 240 42 22 8.3 4.6 | -42.2 -44.0 235 30 15 9.0 4.9
24000 -39.9 -39.8 240 38 20 8.3 4.6 | -39.5 -39.1 240 26 13 9.0 4.9
23000 -37.4 -35.3 240 35 18 8.7 4.8 | -37.0 -34.6 240 22 11 7.7 4.2
22000 -34.8 -30.6 245 30 16 8.7 4.8 | -34.7 -30.5 250 18 9 7.8 4.3
21000 -32.2 -26.0 250 26 13 8.7 4.8 | -32.4 -26.3 260 14 7 7.8 4.3
20000 -29.7 -21.5 250 23 12 8.3 4.5 | -30.1 -22.2 275 12 6 7.9 4.3
19500 -28.4 -19.1 250 22 11 8.3 4.5 | -28.9 -20.0 280 12 6 7.9 4.3
19000 -27.2 -17.0 255 21 11 8.3 4.5 | -27.7 -17.9 285 11 6 7.9 4.3
18500 -26.0 -14.8 255 19 10 8.3 4.6 | -26.6 -15.9 290 11 6 7.9 4.3
18000 -24.8 -12.6 255 18 9 6.3 3.5 | -25.4 -13.7 290 11 5 8.1 4.5
17500 -24.0 -11.2 255 17 9 5.4 3.0 | -24.2 -11.6 285 10 5 8.1 4.5
17000 -23.2 -9.8 255 15 8 5.5 3.0 | -23.0 -9.4 275 9 5 7.5 4.1
16500 -22.3 -8.1 245 15 8 6.3 3.4 | -22.0 -7.6 270 10 5 6.7 3.7
16000 -20.9 -5.6 230 17 9 5.5 3.0 | -21.0 -5.8 265 11 6 6.6 3.6
15500 -20.2 -4.4 220 16 8 4.8 2.6 | -20.1 -4.2 250 12 6 4.8 2.7
15000 -19.5 -3.1 210 17 9 4.5 2.5 | -19.4 -2.9 240 15 8 5.1 2.8
14500 -18.9 -2.0 205 16 8 3.7 2.0 | -18.7 -1.7 230 16 8 4.1 2.2
14000 -18.4 -1.1 200 14 7 3.7 2.0 | -18.1 -0.6 225 16 8 4.2 2.3
13500 -17.8 -0.0 195 11 6 4.0 2.2 | -17.3 0.9 215 15 8 2.9 1.6
13000 -17.2 1.0 190 8 4 4.1 2.3 | -16.9 1.6 215 13 7 3.1 1.7
12500 -16.4 2.5 185 6 3 6.2 3.4 | -16.4 2.5 215 10 5 4.2 2.3
12000 -15.6 3.9 175 3 2 6.2 3.4 | -15.8 3.6 220 7 4 4.7 2.6
11500 -14.6 5.7 110 2 1 7.2 3.9 | -14.9 5.2 210 5 3 6.5 3.6
11000 -13.5 7.7 060 4 2 7.1 3.9 | -13.9 7.0 185 4 2 6.5 3.6
10500 -12.5 9.5 055 6 3 6.7 3.7 | -13.0 8.6 130 3 1 6.6 3.6
10250 -12.0 10.4 050 8 4 8.0 4.4 | -12.5 9.5 110 4 2 7.2 3.9
10000 -11.4 11.5 050 9 5 3.2 1.7 | -12.0 10.4 095 5 2 3.0 1.6
9750 -11.3 11.7 050 10 5 4.0 2.2 | -11.9 10.6 090 5 3 4.4 2.4
9500 -10.7 12.7 050 12 6 9.5 5.2 | -11.3 11.7 075 7 3 9.3 5.1
9250 -10.1 13.8 055 14 7 8.0 4.4 | -10.7 12.7 065 8 4 7.6 4.2
9000 -9.6 14.7 055 15 8 6.5 3.6 | -10.2 13.6 065 10 5 6.2 3.4
8750 -9.1 15.6 055 16 8 6.2 3.4 | -9.8 14.4 060 10 5 6.7 3.7
8500 -8.6 16.5 055 17 9 7.5 4.1 | -9.2 15.4 060 11 6 8.4 4.6
8250 -8.1 17.4 055 17 9 6.9 3.8 | -8.6 16.5 060 12 6 7.2 3.9
8000 -7.6 18.3 055 17 9 6.6 3.6 | -8.1 17.4 060 13 7 6.1 3.4
7750 -7.1 19.2 050 16 8 6.8 3.7 | -7.7 18.1 060 13 7 7.1 3.9
7500 -6.6 20.1 050 16 8 7.2 4.0 | -7.1 19.2 060 14 7 7.8 4.3
7250 -6.1 21.0 045 15 8 7.7 4.2 | -6.5 20.3 060 14 7 7.5 4.1
7000 -5.5 22.1 045 14 7 7.9 4.3 | -6.0 21.2 060 14 7 7.5 4.1
6750 -4.9 23.2 040 13 7 8.1 4.5 | -5.5 22.1 060 14 7 7.4 4.1
6500 -4.3 24.3 035 12 6 9.2 5.0 | -4.9 23.2 055 13 7 8.3 4.6
6250 -3.6 25.5 035 11 6 9.9 5.4 | -4.3 24.3 050 13 6 9.2 5.0
6000 -2.9 26.8 030 11 5 9.3 5.1 | -3.6 25.5 050 12 6 8.8 4.8
5750 -2.2 28.0 030 10 5 10.9 6.0 | -2.9 26.8 045 11 6 9.9 5.4
5500 -1.3 29.7 030 9 4 14.4 7.9 | -2.2 28.0 045 9 4 11.9 6.5
________________________________________________________________________________
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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