Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
577 UXUS97 KBOU 221318 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 0717 MDT Saturday, June 22, 2024 This forecast is for Saturday, June 22, 2024: If the trigger temperature of 79.3 F/26.3 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 1091 ft/min (5.5 m/s) Maximum height of thermals.................. 17627 ft MSL (12319 ft AGL) Forecast maximum temperature................... 91.0 F/33.2 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................. 13682 ft MSL (8374 ft AGL) Thermal soaring outlook for Sunday 06/23....... 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 NVA Potential height of wave....................... 16117 ft MSL (10809 ft AGL) Wave soaring outlook for Sunday 06/23.......... Fair Remarks... Sunrise/Sunset.................... 05:32:03 / 20:31:19 MDT Total possible sunshine........... 14 hr 59 min 16 sec (899 min 16 sec) Altitude of sun at 13:01:41 MDT... 73.65 degrees Upper air data from numerical model forecast valid on 06/22/2024 at 0600 MDT Freezing level.................. 15527 ft MSL (10219 ft AGL) Convective condensation level... 16721 ft MSL (11413 ft AGL) Lifted condensation level....... 17301 ft MSL (11992 ft AGL) Lifted index.................... +0.1 K index......................... +4.5 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 -62.8 -81.0 250 55 28 3.4 1.9 M M M M M 45000 -57.0 -70.6 255 79 40 4.9 2.7 M M M M M 40000 -48.8 -55.8 245 93 48 6.9 3.8 M M M M M 38000 -44.7 -48.5 245 89 46 6.9 3.8 M M M M M 36000 -40.6 -41.1 245 85 44 6.9 3.8 M M M M M 34000 -36.7 -34.1 245 77 40 6.4 3.5 M M M M M 32000 -32.9 -27.2 245 68 35 6.4 3.5 M M M M M 30000 -29.0 -20.2 245 60 31 6.5 3.5 47.8 118.1 11.4 M M 29000 -26.6 -15.9 250 56 29 6.5 3.5 46.3 115.3 10.4 M M 28000 -24.6 -12.3 250 52 27 7.6 4.2 45.2 113.4 9.7 M M 27000 -22.3 -8.1 255 49 25 7.6 4.2 44.3 111.7 9.1 M M 26000 -20.0 -4.0 255 45 23 7.6 4.2 43.5 110.3 8.6 M M 25000 -17.7 0.1 260 42 22 7.4 4.1 42.8 109.1 8.1 M M 24000 -15.7 3.7 265 39 20 6.8 3.7 41.7 107.1 7.3 M M 23000 -13.6 7.5 270 35 18 6.8 3.7 40.6 105.1 6.5 M M 22000 -11.6 11.1 275 32 16 6.3 3.4 39.7 103.4 5.8 M M 21000 -10.0 14.0 280 28 14 5.1 2.8 38.0 100.3 4.4 M M 20000 -8.5 16.7 285 25 13 5.1 2.8 36.3 97.4 3.0 M M 19500 -7.8 18.0 290 23 12 5.0 2.8 35.6 96.0 2.3 M M 19000 -7.0 19.4 290 22 11 5.9 3.2 34.8 94.7 1.7 M M 18500 -6.1 21.0 295 22 11 5.9 3.2 34.1 93.5 1.1 M M 18000 -5.3 22.5 295 22 11 6.1 3.3 33.5 92.3 0.5 M M 17500 -4.4 24.1 300 22 11 6.5 3.6 32.9 91.2 -0.0 1088 5.5 17000 -3.4 25.9 300 23 12 6.4 3.5 32.4 90.2 -0.6 1044 5.3 16500 -2.4 27.7 305 24 12 7.4 4.1 31.9 89.4 -1.0 1000 5.1 16000 -1.3 29.7 305 24 12 7.4 4.1 31.5 88.6 -1.4 952 4.8 15500 0.3 32.5 310 25 13 8.0 4.4 30.9 87.7 -1.9 880 4.5 15000 1.5 34.7 310 25 13 8.0 4.4 30.6 87.1 -2.2 831 4.2 14500 2.7 36.9 310 25 13 8.0 4.4 30.3 86.6 -2.5 781 4.0 14000 3.8 38.8 310 25 13 8.0 4.4 30.0 86.1 -2.9 731 3.7 13500 5.0 41.0 315 25 13 8.1 4.4 29.8 85.6 -3.2 682 3.5 13000 6.2 43.2 315 25 13 8.1 4.5 29.5 85.1 -3.5 631 3.2 12500 7.4 45.3 315 24 12 8.1 4.4 29.2 84.6 -3.7 581 3.0 12000 8.6 47.5 315 24 12 8.0 4.4 28.9 84.1 -4.1 531 2.7 11500 9.7 49.5 315 23 12 7.9 4.3 28.7 83.6 -4.4 481 2.4 11000 10.8 51.4 310 23 12 7.3 4.0 28.3 83.0 -4.7 433 2.2 10500 11.9 53.4 310 23 12 3.4 1.9 28.0 82.4 -5.1 385 2.0 10250 12.0 53.6 310 23 12 3.7 2.1 27.3 81.2 -5.8 376 1.9 10000 12.6 54.7 310 22 12 10.2 5.6 27.2 81.0 -5.9 350 1.8 9750 13.3 55.9 305 22 11 9.9 5.5 27.2 81.0 -6.0 322 1.6 9500 14.0 57.2 305 22 11 8.2 4.5 27.2 81.0 -6.0 294 1.5 9250 14.4 57.9 305 21 11 4.9 2.7 27.0 80.5 -6.3 273 1.4 9000 14.8 58.6 300 21 11 6.8 3.7 26.6 79.9 -6.7 254 1.3 8750 15.4 59.7 300 20 10 9.3 5.1 26.5 79.7 -6.8 229 1.2 8500 16.0 60.8 300 19 10 6.7 3.7 26.4 79.5 -7.0 204 1.0 8250 16.3 61.3 300 18 10 4.2 2.3 26.0 78.9 -7.4 187 0.9 8000 16.6 61.9 300 18 9 4.7 2.6 25.6 78.1 -7.8 170 0.9 7750 17.0 62.6 295 16 8 5.3 2.9 25.3 77.5 -8.3 154 0.8 7500 17.3 63.1 295 14 7 4.4 2.4 24.9 76.8 -8.7 137 0.7 7250 17.5 63.5 295 13 7 3.3 1.8 24.4 76.0 -9.3 123 0.6 7000 17.7 63.9 295 11 6 4.1 2.2 24.0 75.2 -9.8 109 0.6 6750 17.9 64.2 290 9 5 4.1 2.3 23.6 74.4 -10.3 95 0.5 6500 18.1 64.6 280 6 3 2.4 1.3 23.1 73.5 -10.9 82 0.4 6250 18.2 64.8 270 5 2 0.2 0.1 22.4 72.4 -11.6 73 0.4 6000 18.2 64.8 250 3 2 4.4 2.4 21.8 71.2 -12.3 64 0.3 5750 18.4 65.1 220 3 2 -4.9 -2.7 21.3 70.3 -12.9 52 0.3 5500 16.9 62.4 195 3 2 -31.3 -17.1 19.2 66.5 -15.1 88 0.4 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 06/22/2024 at 0900 MDT | 06/22/2024 at 1200 MDT | CAPE... +1.0 LI... +1.1 | CAPE... +29.7 LI... -0.6 CINH... -4.1 K Index... +7.8 | CINH... -21.1 K Index... +16.1 | 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 -80.5 250 58 30 3.4 1.8 | -62.2 -80.0 245 60 31 3.3 1.8 45000 -56.8 -70.2 250 79 41 4.7 2.6 | -56.6 -69.9 250 83 43 4.7 2.6 40000 -48.8 -55.8 250 92 47 6.8 3.7 | -48.7 -55.7 250 96 49 6.9 3.8 38000 -44.7 -48.5 250 88 45 6.8 3.7 | -44.6 -48.3 250 94 49 6.8 3.8 36000 -40.7 -41.3 245 84 43 6.7 3.7 | -40.5 -40.9 245 92 48 6.8 3.7 34000 -37.0 -34.6 245 75 39 6.0 3.3 | -36.9 -34.4 245 82 42 5.8 3.2 32000 -33.5 -28.3 245 67 34 6.0 3.3 | -33.5 -28.3 245 70 36 5.8 3.2 30000 -29.7 -21.5 245 60 31 6.3 3.5 | -29.5 -21.1 250 61 31 5.9 3.2 29000 -27.4 -17.3 250 55 29 6.3 3.5 | -27.8 -18.0 250 57 29 5.8 3.2 28000 -25.4 -13.7 250 52 27 7.7 4.2 | -25.9 -14.6 250 53 27 7.6 4.2 27000 -23.1 -9.6 255 49 25 7.7 4.2 | -23.6 -10.5 255 50 26 7.7 4.2 26000 -20.8 -5.4 255 46 24 7.7 4.2 | -21.3 -6.3 255 48 25 7.7 4.2 25000 -18.5 -1.3 260 43 22 7.4 4.0 | -19.1 -2.4 260 45 23 7.3 4.0 24000 -16.5 2.3 260 39 20 6.4 3.5 | -17.1 1.2 260 41 21 6.6 3.6 23000 -14.6 5.7 265 35 18 6.4 3.5 | -15.1 4.8 265 36 19 6.6 3.6 22000 -12.7 9.1 270 30 16 6.0 3.3 | -13.1 8.4 265 32 16 5.8 3.2 21000 -11.1 12.0 270 27 14 5.3 2.9 | -11.8 10.8 270 29 15 4.6 2.5 20000 -9.6 14.7 275 24 12 5.3 2.9 | -10.5 13.1 280 26 13 4.7 2.6 19500 -8.8 16.2 280 23 12 5.1 2.8 | -9.8 14.4 280 24 12 4.5 2.5 19000 -7.9 17.8 280 22 11 7.2 4.0 | -8.9 16.0 285 24 12 8.2 4.5 18500 -6.8 19.8 285 22 11 7.1 3.9 | -7.8 18.0 285 23 12 7.8 4.3 18000 -5.8 21.6 290 22 11 7.2 3.9 | -6.6 20.1 290 23 12 7.9 4.3 17500 -4.7 23.5 295 22 12 7.3 4.0 | -5.4 22.3 290 24 12 8.0 4.4 17000 -3.7 25.3 295 23 12 7.3 4.0 | -4.3 24.3 295 25 13 8.0 4.4 16500 -2.6 27.3 300 24 12 8.1 4.4 | -3.0 26.6 295 25 13 8.6 4.7 16000 -1.4 29.5 300 25 13 8.0 4.4 | -1.8 28.8 295 25 13 8.5 4.7 15500 0.4 32.7 305 26 13 7.9 4.3 | -0.5 31.1 295 25 13 8.6 4.7 15000 1.5 34.7 305 26 13 8.0 4.4 | 1.4 34.5 300 25 13 8.6 4.7 14500 2.7 36.9 310 26 14 7.8 4.3 | 2.6 36.7 300 25 13 8.6 4.7 14000 3.8 38.8 310 26 14 7.8 4.3 | 3.9 39.0 300 24 12 8.6 4.7 13500 4.9 40.8 310 26 14 7.8 4.3 | 5.1 41.2 300 23 12 8.7 4.8 13000 6.1 43.0 310 26 13 7.7 4.3 | 6.4 43.5 300 22 11 8.8 4.8 12500 7.2 45.0 310 25 13 7.6 4.2 | 7.7 45.9 300 21 11 8.6 4.7 12000 8.3 46.9 310 24 12 7.5 4.1 | 8.9 48.0 300 20 10 8.5 4.7 11500 9.4 48.9 310 22 12 7.5 4.1 | 10.2 50.4 300 18 9 8.4 4.6 11000 10.5 50.9 310 21 11 7.3 4.0 | 11.4 52.5 305 16 8 8.0 4.4 10500 11.6 52.9 310 19 10 3.5 1.9 | 12.6 54.7 305 14 7 3.1 1.7 10250 11.7 53.1 310 19 10 4.7 2.6 | 12.7 54.9 305 14 7 5.1 2.8 10000 12.4 54.3 310 18 9 10.9 6.0 | 13.5 56.3 305 12 6 12.8 7.0 9750 13.1 55.6 310 17 9 10.1 5.6 | 14.3 57.7 305 11 6 11.6 6.4 9500 13.8 56.8 310 16 8 8.3 4.6 | 15.1 59.2 310 9 5 8.7 4.8 9250 14.3 57.7 315 16 8 5.7 3.1 | 15.6 60.1 310 9 5 6.4 3.5 9000 14.8 58.6 315 16 8 7.9 4.3 | 16.2 61.2 310 8 4 10.7 5.9 8750 15.4 59.7 315 15 8 9.6 5.3 | 17.1 62.8 310 8 4 12.2 6.7 8500 16.1 61.0 315 14 7 7.6 4.2 | 17.9 64.2 315 7 4 9.6 5.3 8250 16.5 61.7 315 14 7 6.0 3.3 | 18.5 65.3 315 7 3 6.9 3.8 8000 17.0 62.6 315 14 7 6.8 3.8 | 19.1 66.4 315 7 3 10.3 5.7 7750 17.5 63.5 315 13 7 7.0 3.9 | 20.0 68.0 320 6 3 12.5 6.9 7500 17.9 64.2 315 12 6 4.7 2.6 | 20.8 69.4 320 6 3 9.2 5.1 7250 18.1 64.6 315 10 5 2.8 1.5 | 21.4 70.5 325 5 3 6.9 3.8 7000 18.3 64.9 315 9 5 4.3 2.4 | 22.0 71.6 325 5 3 10.2 5.6 6750 18.7 65.7 315 7 4 8.1 4.4 | 22.9 73.2 325 5 2 13.3 7.3 6500 19.3 66.7 315 5 3 9.0 5.0 | 23.8 74.8 330 4 2 10.8 5.9 6250 19.9 67.8 315 4 2 8.5 4.7 | 24.6 76.3 335 4 2 9.2 5.0 6000 20.5 68.9 320 3 2 7.0 3.9 | 25.3 77.5 335 4 2 10.8 5.9 5750 21.0 69.8 330 3 1 11.5 6.3 | 26.3 79.3 340 4 2 18.0 9.9 5500 22.4 72.3 330 2 1 24.3 13.3 | 28.0 82.4 340 4 2 26.6 14.6 06/22/2024 at 1500 MDT | 06/22/2024 at 1800 MDT | CAPE... +103.4 LI... -1.3 | CAPE... +145.2 LI... -1.2 CINH... -14.8 K Index... +23.1 | CINH... -17.2 K Index... +26.8 | 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 -62.4 -80.3 245 61 32 3.0 1.6 | -62.4 -80.3 255 60 31 2.6 1.4 45000 -56.5 -69.7 250 84 43 5.1 2.8 | -56.8 -70.2 255 82 42 5.3 2.9 40000 -48.5 -55.3 255 95 49 6.7 3.7 | -48.6 -55.5 255 90 46 6.7 3.7 38000 -44.5 -48.1 250 93 48 6.7 3.7 | -44.6 -48.3 255 87 45 6.7 3.7 36000 -40.5 -40.9 250 92 47 6.7 3.7 | -40.6 -41.1 255 84 43 6.6 3.6 34000 -36.8 -34.2 250 83 43 6.1 3.3 | -37.1 -34.8 260 74 38 5.7 3.1 32000 -33.2 -27.8 255 74 38 6.1 3.3 | -33.7 -28.7 265 64 33 5.6 3.1 30000 -29.2 -20.6 255 65 33 5.9 3.2 | -29.6 -21.3 265 54 28 6.3 3.4 29000 -27.4 -17.3 255 61 31 5.9 3.2 | -27.7 -17.9 265 51 26 6.3 3.4 28000 -25.7 -14.3 255 57 29 6.2 3.4 | -25.9 -14.6 270 47 24 6.0 3.3 27000 -23.8 -10.8 260 53 27 6.3 3.4 | -24.1 -11.4 270 43 22 6.0 3.3 26000 -21.9 -7.4 260 49 25 6.3 3.5 | -22.3 -8.1 270 40 21 6.0 3.3 25000 -20.1 -4.2 260 45 23 6.4 3.5 | -20.6 -5.1 270 37 19 6.3 3.5 24000 -18.2 -0.8 265 41 21 6.4 3.5 | -18.6 -1.5 270 33 17 6.9 3.8 23000 -16.3 2.7 265 36 19 6.5 3.6 | -16.5 2.3 270 30 15 7.0 3.8 22000 -14.4 6.1 265 32 16 6.4 3.5 | -14.5 5.9 270 26 14 7.2 4.0 21000 -12.6 9.3 270 29 15 6.3 3.5 | -12.3 9.9 270 23 12 7.5 4.1 20000 -10.7 12.7 275 25 13 6.3 3.5 | -10.1 13.8 270 20 11 7.6 4.1 19500 -9.8 14.4 275 24 12 6.3 3.5 | -9.0 15.8 275 19 10 7.6 4.2 19000 -8.7 16.3 280 23 12 8.2 4.5 | -8.0 17.6 275 18 9 7.4 4.1 18500 -7.6 18.3 280 22 11 8.1 4.4 | -6.9 19.6 275 17 9 7.4 4.1 18000 -6.4 20.5 285 21 11 8.3 4.6 | -5.8 21.6 275 17 9 7.6 4.2 17500 -5.1 22.8 285 21 11 8.5 4.6 | -4.6 23.7 275 16 8 7.8 4.3 17000 -3.9 25.0 290 20 10 8.5 4.7 | -3.5 25.7 275 15 8 7.8 4.3 16500 -2.6 27.3 290 20 10 9.0 5.0 | -1.7 28.9 275 14 7 8.3 4.6 16000 -0.6 30.9 290 19 10 9.1 5.0 | -0.5 31.1 275 14 7 8.4 4.6 15500 0.8 33.4 290 18 9 9.5 5.2 | 0.8 33.4 275 13 7 9.2 5.0 15000 2.2 36.0 290 18 9 9.5 5.2 | 2.2 36.0 275 12 6 9.2 5.0 14500 3.6 38.5 290 17 9 9.5 5.2 | 3.5 38.3 275 12 6 9.2 5.0 14000 5.0 41.0 290 16 8 9.5 5.2 | 4.9 40.8 275 11 6 9.2 5.0 13500 6.3 43.3 295 15 8 9.4 5.1 | 6.3 43.3 275 10 5 9.2 5.1 13000 7.7 45.9 295 14 7 9.4 5.1 | 7.6 45.7 275 9 5 9.2 5.1 12500 9.1 48.4 300 13 7 9.3 5.1 | 9.0 48.2 275 9 4 9.2 5.0 12000 10.5 50.9 300 11 6 9.3 5.1 | 10.3 50.5 275 8 4 9.1 5.0 11500 11.9 53.4 305 10 5 9.3 5.1 | 11.7 53.1 280 7 4 9.2 5.0 11000 13.2 55.8 305 9 4 9.0 4.9 | 13.1 55.6 280 7 4 9.0 4.9 10500 14.6 58.3 310 8 4 4.5 2.5 | 14.4 57.9 280 6 3 4.4 2.4 10250 14.8 58.6 310 8 4 6.4 3.5 | 14.6 58.3 280 7 3 6.2 3.4 10000 15.7 60.3 310 8 4 13.5 7.4 | 15.5 59.9 280 6 3 13.3 7.3 9750 16.6 61.9 310 7 4 12.5 6.8 | 16.4 61.5 280 6 3 12.3 6.7 9500 17.5 63.5 315 7 4 9.3 5.1 | 17.3 63.1 285 6 3 9.3 5.1 9250 18.0 64.4 315 7 4 7.3 4.0 | 17.8 64.0 285 6 3 7.1 3.9 9000 18.7 65.7 315 7 4 11.2 6.1 | 18.5 65.3 285 6 3 10.7 5.9 8750 19.6 67.3 315 7 3 12.3 6.8 | 19.3 66.7 285 6 3 12.0 6.6 8500 20.4 68.7 320 6 3 9.8 5.4 | 20.2 68.4 285 6 3 9.8 5.4 8250 21.0 69.8 320 6 3 6.7 3.7 | 20.8 69.4 290 6 3 7.0 3.8 8000 21.6 70.9 320 7 3 10.3 5.6 | 21.3 70.3 290 6 3 9.7 5.3 7750 22.6 72.7 320 6 3 12.8 7.0 | 22.2 72.0 290 6 3 11.9 6.5 7500 23.4 74.1 325 5 3 9.5 5.2 | 23.0 73.4 290 6 3 9.3 5.1 7250 24.0 75.2 325 6 3 7.2 4.0 | 23.6 74.5 290 6 3 7.2 4.0 7000 24.6 76.3 325 6 3 10.0 5.5 | 24.2 75.6 290 6 3 9.4 5.2 6750 25.5 77.9 325 5 3 13.2 7.2 | 25.0 77.0 290 6 3 12.3 6.7 6500 26.4 79.5 330 5 3 11.1 6.1 | 25.9 78.6 290 6 3 10.7 5.9 6250 27.2 81.0 330 5 3 9.6 5.3 | 26.6 79.9 290 6 3 9.3 5.1 6000 27.9 82.2 330 5 3 9.3 5.1 | 27.3 81.1 295 6 3 9.4 5.1 5750 28.7 83.7 335 5 2 16.0 8.8 | 28.1 82.6 290 6 3 11.9 6.5 5500 30.4 86.7 335 4 2 29.5 16.2 | 29.1 84.4 290 5 3 17.6 9.6 ________________________________________________________________________________ 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. 042613