Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
397
UXUS97 KBOU 031315
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0712 MDT Thursday, April 3, 2025
This forecast is for Thursday, April 3, 2025:
If the trigger temperature of 42.4 F/5.8 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 6940 ft MSL (1603 ft AGL)
Forecast maximum temperature................... 39.0 F/4.3 C
Time of trigger temperature.................... None
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Overcast opaque high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 5465 ft MSL (129 ft AGL)
Thermal soaring outlook for Friday 04/04....... Poor
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....................... 17398 ft MSL (12061 ft AGL)
Wave soaring outlook for Friday 04/04.......... Poor
Remarks...
Sunrise/Sunset.................... 06:39:23 / 19:25:46 MDT
Total possible sunshine........... 12 hr 46 min 23 sec (766 min 23 sec)
Altitude of sun at 13:02:34 MDT... 55.85 degrees
Upper air data from numerical model forecast valid on 04/03/2025 at 0600 MDT
Freezing level.................. 5380 ft MSL (43 ft AGL)
Additional freezing level....... 6520 ft MSL (1183 ft AGL)
Convective condensation level... 13540 ft MSL (8203 ft AGL)
Lifted condensation level....... 11858 ft MSL (6521 ft AGL)
Lifted index.................... +5.7
K index......................... +9.9
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 -53.1 -63.6 230 34 17 1.3 0.7 M M M M M
45000 -51.1 -60.0 230 46 24 1.4 0.7 M M M M M
40000 -51.0 -59.8 225 61 31 -0.2 -0.1 M M M M M
38000 -51.1 -60.0 225 67 34 -1.1 -0.6 M M M M M
36000 -52.2 -62.0 220 68 35 -1.7 -1.0 M M M M M
34000 -53.4 -64.1 220 69 35 -1.6 -0.9 M M M M M
32000 -52.3 -62.1 215 71 36 3.1 1.7 M M M M M
30000 -50.4 -58.7 215 73 37 3.1 1.7 M M M M M
29000 -49.1 -56.4 215 70 36 5.1 2.8 24.1 75.4 15.3 M M
28000 -47.6 -53.7 215 65 34 5.1 2.8 22.2 72.0 14.0 M M
27000 -46.1 -51.0 215 60 31 5.1 2.8 20.4 68.8 12.8 M M
26000 -44.5 -48.1 215 55 28 6.3 3.4 18.9 65.9 11.7 M M
25000 -42.6 -44.7 215 48 25 6.4 3.5 17.5 63.4 10.7 M M
24000 -40.7 -41.3 215 42 22 6.4 3.5 16.2 61.2 9.9 M M
23000 -38.7 -37.7 210 36 19 7.8 4.3 15.2 59.3 9.1 M M
22000 -36.3 -33.3 210 33 17 8.0 4.4 14.4 58.0 8.7 M M
21000 -33.9 -29.0 210 31 16 8.1 4.4 13.9 57.0 8.3 M M
20000 -31.5 -24.7 205 28 15 8.0 4.4 13.3 55.9 7.9 M M
19500 -30.3 -22.5 205 27 14 8.0 4.4 12.9 55.3 7.6 M M
19000 -29.1 -20.4 200 27 14 8.0 4.4 12.6 54.7 7.4 M M
18500 -27.3 -17.1 200 25 13 8.1 4.4 12.2 54.0 7.1 M M
18000 -26.1 -15.0 195 25 13 7.5 4.1 11.9 53.4 6.8 M M
17500 -25.0 -13.0 190 24 12 7.5 4.1 11.5 52.7 6.5 M M
17000 -23.9 -11.0 185 23 12 7.1 3.9 11.1 52.0 6.2 M M
16500 -22.9 -9.2 180 22 11 6.7 3.7 10.6 51.1 5.8 M M
16000 -21.9 -7.4 170 22 11 6.8 3.7 10.1 50.2 5.4 M M
15500 -20.8 -5.4 165 22 11 7.7 4.2 9.7 49.4 5.0 M M
15000 -19.6 -3.3 165 22 11 7.6 4.2 9.3 48.8 4.7 M M
14500 -18.5 -1.3 160 22 11 8.0 4.4 9.0 48.2 4.5 M M
14000 -17.3 0.9 155 22 11 8.0 4.4 8.7 47.7 4.2 M M
13500 -16.1 3.0 155 22 11 8.2 4.5 8.4 47.2 4.0 M M
13000 -14.9 5.2 155 22 11 8.2 4.5 8.2 46.7 3.8 M M
12500 -13.6 7.5 150 21 11 8.1 4.4 7.9 46.3 3.6 M M
12000 -12.4 9.7 150 20 10 8.1 4.4 7.6 45.8 3.3 M M
11500 -11.3 11.7 150 18 9 7.4 4.0 7.3 45.2 3.0 M M
11000 -10.2 13.6 145 17 9 7.3 4.0 6.9 44.5 2.7 M M
10500 -9.1 15.6 145 16 8 7.4 4.1 6.6 43.8 2.3 M M
10250 -8.6 16.5 145 15 8 6.7 3.7 6.4 43.4 2.1 M M
10000 -8.0 17.6 145 15 8 9.4 5.2 6.2 43.1 1.9 M M
9750 -7.2 19.0 145 15 8 10.0 5.5 6.2 43.2 2.0 M M
9500 -6.6 20.1 140 14 7 7.5 4.1 6.1 43.0 1.9 M M
9250 -6.0 21.2 140 14 7 8.3 4.6 6.0 42.8 1.8 M M
9000 -5.4 22.3 140 14 7 7.6 4.1 5.8 42.5 1.6 M M
8750 -4.9 23.2 140 13 7 7.3 4.0 5.7 42.2 1.4 M M
8500 -4.3 24.3 140 13 7 7.7 4.2 5.5 41.9 1.3 M M
8250 -3.8 25.2 135 12 6 7.9 4.3 5.3 41.6 1.1 M M
8000 -3.2 26.2 135 12 6 6.7 3.7 5.2 41.3 1.1 M M
7750 -2.7 27.1 130 11 6 6.8 3.7 4.9 40.8 0.7 M M
7500 -2.2 28.0 130 11 6 8.0 4.4 4.7 40.5 0.5 M M
7250 -1.6 29.1 130 10 5 7.5 4.1 4.6 40.2 0.4 M M
7000 -1.1 30.0 130 10 5 6.0 3.3 4.4 39.9 0.1 M M
6750 -0.7 30.7 130 10 5 6.3 3.5 4.1 39.3 -0.2 39 0.2
6500 -0.1 31.8 135 9 4 8.4 4.6 3.9 39.0 -0.3 15 0.1
6250 0.5 32.9 140 7 4 5.6 3.1 3.7 38.7 -0.5 M M
6000 0.7 33.3 145 6 3 2.7 1.5 3.3 37.9 -1.0 M M
5750 1.0 33.8 150 5 3 5.0 2.7 2.8 37.0 -1.5 M M
5500 1.2 34.2 165 3 2 -0.7 -0.4 2.3 36.2 -1.9 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/03/2025 at 0900 MDT | 04/03/2025 at 1200 MDT
|
CAPE... 0.0 LI... +2.7 | CAPE... +12.6 LI... +2.4
CINH... -0.2 K Index... +12.7 | CINH... -0.1 K Index... +16.4
|
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 -52.9 -63.2 225 35 18 1.2 0.7 | -53.2 -63.8 220 36 18 1.2 0.7
45000 -51.1 -60.0 225 46 24 1.3 0.7 | -51.3 -60.3 225 43 22 1.2 0.7
40000 -51.1 -60.0 225 58 30 -0.2 -0.1 | -50.8 -59.4 220 52 27 0.2 0.1
38000 -51.3 -60.3 225 63 32 -1.4 -0.7 | -50.7 -59.3 220 56 29 -0.9 -0.5
36000 -52.7 -62.9 215 65 33 -2.2 -1.2 | -51.9 -61.4 210 60 31 -1.7 -0.9
34000 -54.1 -65.4 210 67 35 -2.0 -1.1 | -52.9 -63.2 205 65 33 -1.5 -0.8
32000 -52.7 -62.9 210 70 36 3.9 2.1 | -52.0 -61.6 205 66 34 2.5 1.4
30000 -50.3 -58.5 210 72 37 3.8 2.1 | -50.5 -58.9 205 65 34 2.5 1.4
29000 -48.6 -55.5 210 70 36 7.1 3.9 | -48.8 -55.8 205 64 33 7.6 4.2
28000 -46.5 -51.7 210 66 34 7.1 3.9 | -46.5 -51.7 205 62 32 7.7 4.2
27000 -44.3 -47.7 210 61 32 7.1 3.9 | -44.2 -47.6 205 59 31 7.7 4.2
26000 -42.2 -44.0 210 57 29 5.8 3.2 | -41.9 -43.4 205 56 29 5.7 3.1
25000 -40.5 -40.9 210 49 25 5.7 3.1 | -40.3 -40.5 205 48 25 5.5 3.0
24000 -38.8 -37.8 205 42 21 5.7 3.1 | -38.6 -37.5 200 41 21 5.5 3.0
23000 -37.1 -34.8 205 35 18 6.4 3.5 | -36.9 -34.4 200 34 17 6.6 3.6
22000 -35.1 -31.2 200 31 16 6.5 3.6 | -34.9 -30.8 190 31 16 6.8 3.7
21000 -33.1 -27.6 190 27 14 6.6 3.6 | -32.9 -27.2 180 30 15 6.8 3.7
20000 -31.0 -23.8 185 25 13 7.8 4.3 | -30.7 -23.3 175 29 15 7.8 4.3
19500 -29.9 -21.8 180 25 13 7.8 4.3 | -29.6 -21.3 175 29 15 7.7 4.2
19000 -28.2 -18.8 180 24 12 7.8 4.3 | -27.8 -18.0 175 29 15 7.7 4.2
18500 -27.0 -16.6 180 24 12 7.8 4.3 | -26.7 -16.1 175 29 15 7.7 4.2
18000 -25.8 -14.4 180 23 12 7.7 4.2 | -25.5 -13.9 175 29 15 7.9 4.4
17500 -24.7 -12.5 175 23 12 7.7 4.2 | -24.3 -11.7 175 29 15 8.0 4.4
17000 -23.6 -10.5 170 23 12 7.6 4.2 | -23.2 -9.8 180 29 15 8.1 4.4
16500 -22.5 -8.5 165 23 12 7.4 4.1 | -21.9 -7.4 180 28 14 8.2 4.5
16000 -21.4 -6.5 160 24 12 7.4 4.1 | -20.7 -5.3 180 27 14 8.2 4.5
15500 -20.3 -4.5 155 24 12 7.0 3.9 | -19.6 -3.3 180 26 13 7.7 4.2
15000 -19.2 -2.6 150 23 12 7.1 3.9 | -18.4 -1.1 180 24 12 7.9 4.3
14500 -18.2 -0.8 145 23 12 6.4 3.5 | -17.4 0.7 180 22 11 6.5 3.6
14000 -17.3 0.9 140 22 11 6.5 3.6 | -16.4 2.5 175 20 10 6.7 3.7
13500 -16.3 2.7 140 21 11 6.3 3.5 | -15.5 4.1 170 18 10 5.5 3.0
13000 -15.4 4.3 135 21 11 6.3 3.4 | -14.7 5.5 165 17 9 5.4 3.0
12500 -14.4 6.1 135 20 10 7.0 3.8 | -13.9 7.0 155 15 8 5.5 3.0
12000 -13.4 7.9 135 19 10 7.0 3.8 | -13.1 8.4 145 14 7 5.5 3.0
11500 -12.3 9.9 135 19 10 7.9 4.3 | -12.2 10.0 135 12 6 5.5 3.0
11000 -11.1 12.0 135 19 10 8.1 4.4 | -11.4 11.5 125 11 6 5.6 3.1
10500 -9.9 14.2 135 19 10 7.2 3.9 | -10.6 12.9 115 10 5 5.2 2.9
10250 -9.4 15.1 135 18 10 6.2 3.4 | -10.3 13.5 115 10 5 4.3 2.3
10000 -8.9 16.0 135 18 9 9.9 5.5 | -9.9 14.2 110 10 5 7.6 4.2
9750 -8.0 17.6 130 18 9 10.6 5.8 | -9.2 15.4 105 10 5 9.6 5.3
9500 -7.4 18.7 130 17 9 7.2 4.0 | -8.6 16.5 105 10 5 7.4 4.1
9250 -6.8 19.8 125 16 8 8.2 4.5 | -8.0 17.6 100 10 5 8.1 4.4
9000 -6.2 20.8 125 16 8 7.6 4.2 | -7.4 18.7 100 10 5 6.8 3.7
8750 -5.6 21.9 125 16 8 7.8 4.3 | -7.0 19.4 100 10 5 7.4 4.1
8500 -5.0 23.0 125 15 8 8.1 4.4 | -6.3 20.7 095 10 5 8.9 4.9
8250 -4.4 24.1 125 14 7 8.3 4.6 | -5.7 21.7 095 10 5 8.8 4.8
8000 -3.8 25.2 120 14 7 7.0 3.8 | -5.1 22.8 095 10 5 8.0 4.4
7750 -3.3 26.1 120 13 7 6.7 3.7 | -4.5 23.9 095 10 5 8.7 4.8
7500 -2.8 27.0 120 12 6 8.0 4.4 | -3.7 25.3 095 11 5 10.2 5.6
7250 -2.2 28.0 125 11 6 7.4 4.1 | -3.0 26.6 095 11 6 9.8 5.4
7000 -1.7 28.9 125 10 5 5.2 2.9 | -2.3 27.9 095 11 6 8.5 4.7
6750 -1.3 29.7 120 9 5 7.0 3.9 | -1.7 28.9 095 11 6 9.5 5.2
6500 -0.7 30.7 120 7 4 10.4 5.7 | -0.9 30.4 095 11 6 11.2 6.2
6250 0.1 32.2 120 6 3 8.6 4.7 | -0.0 32.0 095 11 6 10.7 5.9
6000 0.6 33.1 115 5 2 7.3 4.0 | 0.8 33.4 095 11 6 11.0 6.0
5750 1.2 34.2 105 4 2 8.7 4.7 | 1.6 34.9 095 11 6 10.2 5.6
5500 2.0 35.6 100 4 2 13.3 7.3 | 2.4 36.3 095 10 5 14.7 8.1
04/03/2025 at 1500 MDT | 04/03/2025 at 1800 MDT
|
CAPE... +50.6 LI... +1.0 | CAPE... +12.7 LI... +0.7
CINH... -0.3 K Index... +18.0 | CINH... -0.0 K Index... +19.8
|
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 -53.4 -64.1 230 36 19 0.7 0.4 | -53.4 -64.1 230 32 16 0.4 0.2
45000 -52.3 -62.1 225 47 24 0.7 0.4 | -52.7 -62.9 225 40 21 0.4 0.2
40000 -50.7 -59.3 220 52 27 1.1 0.6 | -49.4 -56.9 220 49 25 2.4 1.3
38000 -50.2 -58.4 215 53 28 -1.1 -0.6 | -48.4 -55.1 220 52 27 -3.5 -1.9
36000 -50.8 -59.4 215 56 29 -0.9 -0.5 | -50.0 -58.0 220 58 30 -2.8 -1.5
34000 -51.3 -60.3 215 59 30 -0.9 -0.5 | -51.7 -61.1 220 63 33 -2.8 -1.5
32000 -50.8 -59.4 215 61 32 1.4 0.8 | -51.7 -61.1 220 66 34 1.4 0.8
30000 -50.0 -58.0 215 64 33 1.4 0.8 | -50.7 -59.3 220 67 34 0.9 0.5
29000 -48.9 -56.0 215 62 32 5.5 3.0 | -49.2 -56.6 220 63 32 6.4 3.5
28000 -47.2 -53.0 215 57 30 5.6 3.1 | -47.3 -53.1 220 57 29 6.4 3.5
27000 -45.5 -49.9 215 53 27 5.6 3.1 | -45.4 -49.7 220 51 26 6.4 3.5
26000 -43.8 -46.8 215 49 25 7.2 4.0 | -43.4 -46.1 215 44 23 7.0 3.9
25000 -41.5 -42.7 215 45 23 7.4 4.1 | -41.4 -42.5 215 37 19 7.0 3.8
24000 -39.3 -38.7 215 42 22 7.4 4.1 | -39.3 -38.7 210 30 15 7.0 3.8
23000 -37.1 -34.8 215 39 20 7.5 4.1 | -37.1 -34.8 210 25 13 8.5 4.7
22000 -34.9 -30.8 210 35 18 7.5 4.1 | -34.6 -30.3 210 23 12 8.4 4.6
21000 -32.6 -26.7 210 32 16 7.5 4.1 | -32.1 -25.8 205 22 11 8.4 4.6
20000 -29.7 -21.5 205 29 15 8.0 4.4 | -29.6 -21.3 205 22 12 8.4 4.6
19500 -28.5 -19.3 205 29 15 8.0 4.4 | -28.4 -19.1 205 23 12 8.4 4.6
19000 -27.3 -17.1 205 29 15 8.0 4.4 | -27.1 -16.8 205 24 13 8.4 4.6
18500 -26.1 -15.0 200 28 15 8.0 4.4 | -25.9 -14.6 205 25 13 8.4 4.6
18000 -24.9 -12.8 200 28 14 8.1 4.5 | -24.6 -12.3 205 26 14 8.3 4.6
17500 -23.7 -10.7 200 27 14 8.2 4.5 | -23.4 -10.1 205 26 14 8.2 4.5
17000 -22.5 -8.5 200 27 14 8.1 4.4 | -22.2 -8.0 205 26 14 8.2 4.5
16500 -21.3 -6.3 200 25 13 8.0 4.4 | -20.5 -4.9 205 26 14 7.8 4.3
16000 -20.1 -4.2 200 24 12 8.0 4.4 | -19.3 -2.7 200 26 14 7.8 4.3
15500 -19.0 -2.2 200 22 11 6.9 3.8 | -18.1 -0.6 200 26 13 7.8 4.3
15000 -18.0 -0.4 200 20 10 7.0 3.9 | -17.0 1.4 200 25 13 7.8 4.3
14500 -16.9 1.6 195 18 9 7.2 3.9 | -15.9 3.4 200 24 12 6.9 3.8
14000 -15.9 3.4 195 17 9 7.2 3.9 | -14.9 5.2 195 23 12 7.1 3.9
13500 -14.8 5.4 190 16 8 6.8 3.7 | -13.9 7.0 195 21 11 6.6 3.6
13000 -13.8 7.2 185 15 8 6.8 3.7 | -12.9 8.8 195 19 10 6.7 3.7
12500 -12.9 8.8 180 13 7 5.9 3.2 | -12.0 10.4 190 18 9 6.7 3.7
12000 -12.1 10.2 175 11 6 5.6 3.1 | -11.0 12.2 185 16 8 6.7 3.7
11500 -11.2 11.8 170 9 5 6.1 3.4 | -10.0 14.0 180 14 7 6.7 3.7
11000 -10.3 13.5 160 7 4 6.3 3.5 | -9.1 15.6 175 13 7 6.8 3.7
10500 -9.4 15.1 145 6 3 5.6 3.1 | -8.2 17.2 170 11 6 5.5 3.0
10250 -9.0 15.8 130 6 3 4.9 2.7 | -7.8 18.0 165 10 5 4.8 2.6
10000 -8.6 16.5 120 6 3 7.1 3.9 | -7.4 18.7 160 9 5 7.1 3.9
9750 -8.0 17.6 115 6 3 8.1 4.4 | -6.8 19.8 155 8 4 6.9 3.8
9500 -7.5 18.5 105 6 3 6.3 3.4 | -6.5 20.3 145 7 4 4.5 2.4
9250 -7.1 19.2 095 7 3 6.2 3.4 | -6.1 21.0 135 7 4 4.4 2.4
9000 -6.6 20.1 090 7 4 6.8 3.7 | -5.8 21.6 125 7 4 6.2 3.4
8750 -6.1 21.0 090 7 4 7.6 4.2 | -5.3 22.5 120 7 3 6.3 3.4
8500 -5.5 22.1 085 8 4 7.5 4.1 | -4.9 23.2 110 7 3 4.3 2.4
8250 -5.0 23.0 080 9 5 7.7 4.2 | -4.6 23.7 100 7 4 5.2 2.9
8000 -4.4 24.1 080 10 5 7.2 3.9 | -4.2 24.4 090 8 4 3.5 1.9
7750 -3.9 25.0 075 11 6 7.8 4.3 | -4.0 24.8 080 9 5 5.0 2.7
7500 -3.3 26.1 075 11 6 8.7 4.8 | -3.5 25.7 075 10 5 7.6 4.2
7250 -2.7 27.1 075 11 6 8.6 4.7 | -3.0 26.6 070 10 5 7.0 3.9
7000 -2.0 28.4 075 11 6 7.0 3.8 | -2.5 27.5 065 11 6 5.8 3.2
6750 -1.5 29.3 075 12 6 8.3 4.6 | -2.1 28.2 065 12 6 7.3 4.0
6500 -0.8 30.6 070 12 6 10.9 6.0 | -1.4 29.5 060 12 6 9.7 5.3
6250 -0.0 32.0 070 11 6 9.9 5.5 | -0.7 30.7 060 11 6 8.9 4.9
6000 0.7 33.3 070 11 6 9.5 5.2 | -0.1 31.8 060 11 6 8.4 4.6
5750 1.4 34.5 070 11 6 9.8 5.4 | 0.5 32.9 055 11 6 9.3 5.1
5500 2.3 36.1 070 10 5 15.1 8.3 | 1.3 34.3 060 10 5 12.8 7.0
________________________________________________________________________________
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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