Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
770 UXUS97 KBOU 210016 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 1815 MDT Friday, September 20, 2024 This forecast is for Saturday, September 21, 2024: If the trigger temperature of 76.1 F/24.5 C is reached...then Thermal Soaring Index....................... Poor Maximum rate of lift........................ 0 ft/min (0.0 m/s) Maximum height of thermals.................. 6246 ft MSL (927 ft AGL) Forecast maximum temperature................... 68.0 F/20.5 C Time of trigger temperature.................... None Time of overdevelopment........................ 1300 MDT 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................. 5436 ft MSL (116 ft AGL) Thermal soaring outlook for Sunday 09/22....... 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)................ Weak PVA Potential height of wave....................... 39935 ft MSL (34616 ft AGL) Wave soaring outlook for Sunday 09/22.......... Poor Remarks... Sunrise/Sunset.................... 06:47:01 / 18:57:35 MDT Total possible sunshine........... 12 hr 10 min 34 sec (730 min 34 sec) Altitude of sun at 12:52:18 MDT... 50.48 degrees Upper air data from numerical model forecast valid on 09/21/2024 at 0600 MDT Freezing level.................. 14669 ft MSL (9350 ft AGL) Convective condensation level... 18043 ft MSL (12724 ft AGL) Lifted condensation level....... 14484 ft MSL (9164 ft AGL) Lifted index.................... +7.1 K index......................... +19.5 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 -63.5 -82.3 240 52 27 3.2 1.7 M M M M M 45000 -58.2 -72.8 230 69 35 4.5 2.5 M M M M M 40000 -51.0 -59.8 230 82 42 6.1 3.4 M M M M M 38000 -47.4 -53.3 230 84 43 6.0 3.3 M M M M M 36000 -43.8 -46.8 225 86 44 6.0 3.3 M M M M M 34000 -40.0 -40.0 225 83 43 6.4 3.5 M M M M M 32000 -36.2 -33.2 225 77 40 6.4 3.5 M M M M M 30000 -32.6 -26.7 225 67 35 5.7 3.1 44.0 111.3 18.2 M M 29000 -30.5 -22.9 230 59 30 5.7 3.1 42.1 107.8 17.0 M M 28000 -28.8 -19.8 230 53 27 6.0 3.3 40.7 105.2 16.1 M M 27000 -26.7 -16.1 230 49 25 7.1 3.9 39.5 103.1 15.4 M M 26000 -24.6 -12.3 230 45 23 7.1 3.9 38.5 101.3 14.7 M M 25000 -22.4 -8.3 230 42 21 7.1 3.9 37.6 99.7 14.2 M M 24000 -20.2 -4.4 225 38 19 7.7 4.2 36.8 98.2 13.7 M M 23000 -17.9 -0.2 225 34 17 7.7 4.2 36.0 96.8 13.2 M M 22000 -15.6 3.9 220 30 15 8.0 4.4 35.3 95.6 12.8 M M 21000 -13.9 7.0 220 28 15 4.8 2.6 33.8 92.9 11.6 M M 20000 -12.5 9.5 215 28 14 4.9 2.7 32.1 89.7 10.2 M M 19500 -11.9 10.6 215 27 14 5.1 2.8 31.3 88.3 9.5 M M 19000 -11.2 11.8 210 27 14 6.4 3.5 30.5 86.9 8.8 M M 18500 -10.1 13.8 215 27 14 7.6 4.2 30.1 86.3 8.5 M M 18000 -9.0 15.8 215 27 14 7.6 4.2 29.8 85.6 8.1 M M 17500 -7.8 18.0 220 27 14 10.0 5.5 29.6 85.3 8.0 M M 17000 -6.4 20.5 215 25 13 9.8 5.4 29.6 85.3 7.9 M M 16500 -5.0 23.0 215 23 12 9.3 5.1 29.6 85.4 7.9 M M 16000 -3.7 25.3 220 21 11 9.0 5.0 29.5 85.1 7.8 M M 15500 -1.7 28.9 220 18 9 7.9 4.3 29.3 84.7 7.6 M M 15000 -0.5 31.1 220 15 8 7.6 4.2 28.9 84.1 7.4 M M 14500 0.6 33.1 220 12 6 7.2 3.9 28.6 83.4 7.2 M M 14000 1.7 35.1 220 8 4 6.6 3.6 28.1 82.5 6.8 M M 13500 2.7 36.9 215 5 2 6.7 3.7 27.6 81.6 6.4 M M 13000 3.7 38.7 215 2 1 7.3 4.0 27.1 80.8 6.0 M M 12500 4.7 40.5 000 0 0 7.3 4.0 26.7 80.1 5.6 M M 12000 5.9 42.6 050 3 2 8.8 4.9 26.5 79.6 5.3 M M 11500 7.2 45.0 060 7 3 8.8 4.8 26.3 79.3 5.2 M M 11000 8.5 47.3 055 9 5 8.0 4.4 26.1 79.0 5.1 M M 10500 9.8 49.6 045 11 6 6.9 3.8 25.8 78.5 4.9 M M 10250 10.2 50.4 040 12 6 5.4 3.0 25.5 77.9 4.6 M M 10000 10.7 51.3 040 12 6 8.2 4.5 25.3 77.5 4.4 M M 9750 11.4 52.5 040 12 6 9.7 5.3 25.2 77.4 4.4 M M 9500 12.1 53.8 035 12 6 9.3 5.1 25.2 77.4 4.3 M M 9250 12.7 54.9 035 12 6 8.5 4.7 25.2 77.3 4.3 M M 9000 13.3 55.9 035 14 7 7.8 4.3 25.0 77.0 4.2 M M 8750 13.9 57.0 035 15 8 8.1 4.4 24.9 76.8 4.1 M M 8500 14.5 58.1 040 16 8 7.7 4.2 24.7 76.5 3.9 M M 8250 15.1 59.2 040 17 9 6.7 3.7 24.6 76.2 3.8 M M 8000 15.5 59.9 035 17 9 5.0 2.7 24.3 75.7 3.5 M M 7750 15.8 60.4 035 19 10 3.6 2.0 23.8 74.9 3.1 M M 7500 16.0 60.8 035 20 10 3.2 1.8 23.3 74.0 2.6 M M 7250 16.3 61.3 030 23 12 3.1 1.7 22.8 73.1 2.1 M M 7000 16.5 61.7 030 25 13 3.1 1.7 22.3 72.2 1.6 M M 6750 16.7 62.1 025 28 14 2.5 1.4 21.8 71.3 1.1 M M 6500 16.9 62.4 020 30 15 3.4 1.9 21.3 70.3 0.5 M M 6250 17.2 63.0 020 25 13 4.1 2.2 20.8 69.5 0.1 M M 6000 17.5 63.5 015 21 11 5.1 2.8 20.4 68.7 -0.3 33 0.2 5750 17.8 64.0 005 17 9 1.2 0.6 20.0 68.0 -0.7 16 0.1 5500 17.4 63.3 355 11 6 -13.4 -7.4 18.9 65.9 -1.9 23 0.1 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 09/21/2024 at 0900 MDT | 09/21/2024 at 1200 MDT | CAPE... 0.0 LI... +4.5 | CAPE... 0.0 LI... +3.4 CINH... 0.0 K Index... +16.2 | CINH... -0.1 K Index... +17.5 | 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 -62.2 -80.0 235 44 23 1.7 0.9 | -60.8 -77.4 225 42 22 1.7 0.9 45000 -58.5 -73.3 225 67 35 4.8 2.6 | -57.8 -72.0 220 72 37 3.2 1.7 40000 -51.3 -60.3 225 83 42 5.1 2.8 | -53.0 -63.4 210 94 48 4.5 2.5 38000 -47.8 -54.0 220 85 44 5.1 2.8 | -49.5 -57.1 210 91 47 5.2 2.8 36000 -44.7 -48.5 220 88 45 5.2 2.8 | -46.4 -51.5 205 89 46 5.3 2.9 34000 -41.2 -42.2 220 81 42 6.1 3.3 | -42.2 -44.0 205 85 44 7.7 4.2 32000 -37.6 -35.7 220 72 37 6.1 3.3 | -37.5 -35.5 200 79 41 7.7 4.2 30000 -33.8 -28.8 220 60 31 6.5 3.6 | -33.0 -27.4 200 71 37 7.4 4.1 29000 -31.8 -25.2 220 54 28 6.5 3.6 | -30.8 -23.4 205 67 34 7.4 4.1 28000 -29.9 -21.8 220 48 25 6.4 3.5 | -28.6 -19.5 205 63 32 7.6 4.2 27000 -27.6 -17.7 220 44 23 8.0 4.4 | -26.7 -16.1 210 58 30 5.9 3.2 26000 -25.2 -13.4 220 41 21 8.0 4.4 | -24.9 -12.8 215 53 28 5.9 3.2 25000 -22.8 -9.0 220 38 19 8.0 4.4 | -23.2 -9.8 220 49 25 5.9 3.3 24000 -20.4 -4.7 220 35 18 8.0 4.4 | -21.2 -6.2 225 45 23 7.0 3.8 23000 -18.0 -0.4 220 33 17 8.0 4.4 | -19.2 -2.6 230 39 20 7.0 3.8 22000 -15.5 4.1 220 30 16 8.1 4.5 | -17.1 1.2 235 34 17 7.0 3.9 21000 -13.5 7.7 215 29 15 6.3 3.4 | -15.0 5.0 235 30 15 6.9 3.8 20000 -11.2 11.8 215 29 15 6.3 3.5 | -12.5 9.5 235 27 14 6.9 3.8 19500 -10.2 13.6 215 29 15 6.4 3.5 | -11.5 11.3 230 25 13 7.0 3.8 19000 -9.4 15.1 210 28 15 5.7 3.1 | -10.5 13.1 230 24 12 6.4 3.5 18500 -8.5 16.7 210 28 14 5.8 3.2 | -9.6 14.7 225 22 12 6.4 3.5 18000 -7.7 18.1 210 28 14 6.3 3.4 | -8.7 16.3 220 21 11 6.5 3.6 17500 -6.8 19.8 205 27 14 7.0 3.9 | -7.7 18.1 215 18 9 6.8 3.7 17000 -5.8 21.6 205 26 13 7.1 3.9 | -6.7 19.9 205 16 8 6.8 3.7 16500 -4.7 23.5 205 24 12 8.2 4.5 | -5.7 21.7 190 14 7 7.5 4.1 16000 -3.5 25.7 205 21 11 8.2 4.5 | -4.5 23.9 170 14 7 7.5 4.1 15500 -2.4 27.7 200 18 9 7.6 4.2 | -3.4 25.9 155 14 7 7.7 4.2 15000 -1.3 29.7 195 15 8 7.3 4.0 | -2.2 28.0 145 15 8 7.8 4.3 14500 -0.2 31.6 185 12 6 6.9 3.8 | -1.0 30.2 135 16 8 7.7 4.2 14000 0.8 33.4 175 10 5 6.1 3.3 | 0.1 32.2 130 17 9 7.5 4.1 13500 1.7 35.1 150 8 4 6.2 3.4 | 1.2 34.2 125 18 9 7.5 4.1 13000 2.7 36.9 135 8 4 7.2 3.9 | 2.4 36.3 120 18 9 8.5 4.7 12500 3.8 38.8 120 8 4 7.1 3.9 | 3.7 38.7 120 19 10 8.5 4.7 12000 4.9 40.8 110 8 4 7.8 4.3 | 4.9 40.8 115 19 10 6.9 3.8 11500 6.1 43.0 105 9 5 7.9 4.4 | 5.9 42.6 115 19 10 7.6 4.2 11000 7.1 44.8 095 9 5 5.6 3.1 | 6.6 43.9 110 18 9 1.9 1.0 10500 7.9 46.2 085 10 5 6.1 3.4 | 6.9 44.4 105 16 8 2.6 1.4 10250 8.3 46.9 085 10 5 2.8 1.6 | 7.1 44.8 100 15 8 2.0 1.1 10000 8.4 47.1 085 10 5 3.0 1.7 | 7.1 44.8 100 15 8 -2.7 -1.5 9750 8.8 47.8 075 11 6 6.1 3.4 | 6.6 43.9 095 12 6 -5.6 -3.0 9500 9.2 48.6 070 13 7 5.2 2.8 | 6.2 43.2 080 10 5 -4.6 -2.5 9250 9.5 49.1 065 14 7 3.8 2.1 | 5.9 42.6 070 8 4 -2.0 -1.1 9000 9.6 49.3 065 15 8 0.5 0.3 | 5.9 42.6 055 7 4 2.3 1.3 8750 9.5 49.1 060 16 8 -1.2 -0.7 | 6.1 43.0 045 6 3 4.1 2.3 8500 9.4 48.9 055 18 9 -2.5 -1.4 | 6.4 43.5 035 6 3 5.1 2.8 8250 9.0 48.2 050 19 10 -6.2 -3.4 | 6.9 44.4 025 6 3 7.1 3.9 8000 8.4 47.1 040 20 10 -6.8 -3.8 | 7.4 45.3 025 6 3 8.1 4.4 7750 8.0 46.4 030 21 11 -4.1 -2.3 | 8.1 46.6 025 6 3 9.8 5.4 7500 7.8 46.0 025 20 10 0.6 0.4 | 8.9 48.0 025 6 3 9.3 5.1 7250 8.0 46.4 020 19 10 4.1 2.2 | 9.5 49.1 025 6 3 7.7 4.2 7000 8.3 46.9 015 18 9 3.2 1.7 | 10.1 50.2 025 6 3 8.0 4.4 6750 8.7 47.7 010 17 9 9.9 5.4 | 10.8 51.4 020 6 3 12.2 6.7 6500 9.7 49.5 005 14 7 11.9 6.5 | 11.8 53.2 025 6 3 12.5 6.9 6250 10.4 50.7 005 14 7 8.3 4.6 | 12.5 54.5 025 6 3 9.8 5.4 6000 11.0 51.8 005 14 7 8.5 4.7 | 13.3 55.9 025 6 3 9.8 5.4 5750 11.7 53.1 005 13 7 12.7 7.0 | 14.1 57.4 025 6 3 14.3 7.8 5500 13.1 55.6 005 11 6 22.6 12.4 | 15.6 60.1 025 6 3 24.3 13.3 09/21/2024 at 1500 MDT | 09/21/2024 at 1800 MDT | CAPE... 0.0 LI... +1.4 | CAPE... +58.8 LI... +2.8 CINH... 0.0 K Index... +23.6 | CINH... 0.0 K Index... +23.9 | 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 -59.1 -74.4 215 42 22 3.1 1.7 | -59.0 -74.2 205 39 20 4.2 2.3 45000 -55.3 -67.5 215 70 36 0.2 0.1 | -54.1 -65.4 215 59 30 -0.4 -0.2 40000 -54.8 -66.6 200 95 49 4.4 2.4 | -54.8 -66.6 205 84 43 0.7 0.4 38000 -51.6 -60.9 200 88 45 5.3 2.9 | -52.1 -61.8 205 83 43 4.8 2.6 36000 -48.4 -55.1 195 82 42 5.3 2.9 | -48.8 -55.8 200 81 42 4.9 2.7 34000 -43.7 -46.7 195 77 40 9.2 5.0 | -44.3 -47.7 195 67 34 8.8 4.8 32000 -38.2 -36.8 195 73 38 9.2 5.0 | -39.1 -38.4 185 47 24 8.8 4.8 30000 -32.4 -26.3 195 68 35 8.2 4.5 | -34.3 -29.7 185 38 20 7.6 4.1 29000 -30.0 -22.0 195 65 34 8.2 4.5 | -32.0 -25.6 195 37 19 7.6 4.2 28000 -27.5 -17.5 195 63 32 8.4 4.6 | -29.7 -21.5 200 36 19 7.6 4.2 27000 -25.5 -13.9 200 57 29 6.6 3.6 | -27.6 -17.7 205 36 19 6.8 3.7 26000 -23.5 -10.3 200 50 26 6.7 3.7 | -25.6 -14.1 210 37 19 6.8 3.7 25000 -21.5 -6.7 200 44 22 6.7 3.7 | -23.6 -10.5 210 37 19 6.9 3.8 24000 -19.5 -3.1 205 37 19 7.2 3.9 | -21.2 -6.2 210 35 18 9.3 5.1 23000 -17.4 0.7 205 29 15 7.2 3.9 | -18.5 -1.3 205 31 16 9.3 5.1 22000 -15.3 4.5 210 22 11 7.2 4.0 | -15.8 3.6 195 28 14 9.3 5.1 21000 -13.5 7.7 220 16 8 5.6 3.1 | -13.5 7.7 185 22 11 6.2 3.4 20000 -11.8 10.8 230 11 6 5.6 3.1 | -11.7 10.9 165 17 8 6.1 3.4 19500 -11.0 12.2 240 9 5 5.6 3.1 | -10.8 12.6 145 15 8 6.2 3.4 19000 -10.2 13.6 255 7 4 5.5 3.0 | -9.9 14.2 130 15 8 6.1 3.3 18500 -9.4 15.1 245 3 1 5.3 2.9 | -9.2 15.4 125 15 8 4.5 2.5 18000 -8.7 16.3 095 4 2 5.4 3.0 | -8.2 17.2 130 15 7 4.7 2.6 17500 -7.9 17.8 095 10 5 5.0 2.7 | -7.5 18.5 125 16 8 4.8 2.6 17000 -7.2 19.0 105 15 7 4.9 2.7 | -6.8 19.8 115 20 10 4.8 2.6 16500 -6.1 21.0 115 21 11 6.5 3.6 | -6.0 21.2 110 23 12 5.4 3.0 16000 -5.1 22.8 115 21 11 6.7 3.7 | -5.2 22.6 110 23 12 5.5 3.0 15500 -4.1 24.6 120 22 11 6.0 3.3 | -4.4 24.1 110 24 12 5.1 2.8 15000 -3.4 25.9 120 23 12 5.2 2.9 | -3.8 25.2 115 24 13 4.4 2.4 14500 -2.6 27.3 120 23 12 5.3 2.9 | -3.2 26.2 115 25 13 4.6 2.5 14000 -1.9 28.6 120 24 12 5.6 3.1 | -2.4 27.7 115 25 13 5.9 3.2 13500 -1.1 30.0 120 24 12 5.7 3.1 | -1.6 29.1 120 25 13 5.9 3.3 13000 -0.3 31.5 125 23 12 4.6 2.5 | -0.9 30.4 120 24 12 4.2 2.3 12500 0.3 32.5 125 21 11 4.4 2.4 | -0.2 31.6 125 22 11 4.3 2.4 12000 1.2 34.2 125 20 10 7.3 4.0 | 0.5 32.9 130 19 10 5.2 2.8 11500 2.2 36.0 120 19 10 7.6 4.2 | 1.2 34.2 130 15 8 5.4 2.9 11000 3.0 37.4 115 18 9 2.5 1.4 | 1.8 35.2 125 12 6 2.8 1.6 10500 3.3 37.9 110 15 8 3.0 1.7 | 2.2 36.0 100 11 6 3.1 1.7 10250 3.5 38.3 105 14 7 1.2 0.6 | 2.4 36.3 090 12 6 2.0 1.1 10000 3.6 38.5 100 13 7 0.8 0.4 | 2.5 36.5 085 12 6 1.7 0.9 9750 3.7 38.7 090 11 6 2.4 1.3 | 2.7 36.9 080 13 7 2.6 1.4 9500 3.9 39.0 075 10 5 1.9 1.0 | 2.9 37.2 075 13 7 2.3 1.2 9250 4.0 39.2 060 10 5 2.6 1.4 | 3.1 37.6 070 14 7 3.3 1.8 9000 4.2 39.6 055 10 5 3.7 2.0 | 3.4 38.1 070 14 7 5.0 2.7 8750 4.5 40.1 050 9 5 4.1 2.2 | 3.8 38.8 070 15 8 6.1 3.3 8500 4.8 40.6 050 9 5 4.6 2.5 | 4.2 39.6 075 15 8 6.4 3.5 8250 5.2 41.4 050 8 4 6.8 3.7 | 4.7 40.5 075 15 8 6.0 3.3 8000 5.8 42.4 050 7 4 7.7 4.2 | 5.1 41.2 075 14 7 5.9 3.2 7750 6.3 43.3 050 7 3 5.5 3.0 | 5.5 41.9 080 14 7 5.6 3.0 7500 6.6 43.9 050 6 3 6.3 3.4 | 5.9 42.6 080 13 7 5.9 3.2 7250 7.2 45.0 050 5 3 8.5 4.7 | 6.3 43.3 080 12 6 6.5 3.6 7000 7.8 46.0 055 5 2 8.5 4.6 | 6.8 44.2 080 11 6 6.6 3.6 6750 8.4 47.1 060 4 2 7.7 4.2 | 7.2 45.0 080 10 5 5.4 2.9 6500 9.0 48.2 060 4 2 9.1 5.0 | 7.6 45.7 075 9 4 7.1 3.9 6250 9.8 49.6 060 4 2 11.0 6.0 | 8.2 46.8 075 7 4 9.5 5.2 6000 10.6 51.1 065 3 2 9.8 5.4 | 8.9 48.0 070 6 3 8.9 4.9 5750 11.3 52.3 070 3 2 11.2 6.2 | 9.5 49.1 065 5 3 11.3 6.2 5500 12.3 54.1 070 3 2 16.7 9.1 | 10.5 50.9 060 4 2 14.5 7.9 ________________________________________________________________________________ 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. 042613