592 UXUS97 KBOU 190120 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 1914 MDT Thursday, September 18, 2025 This forecast is for Friday, September 19, 2025: If the trigger temperature of 74.7 F/23.7 C is reached...then Thermal Soaring Index....................... Good Maximum rate of lift........................ 780 ft/min (4.0 m/s) Maximum height of thermals.................. 14592 ft MSL (9291 ft AGL) Forecast maximum temperature................... 83.0 F/28.8 C Time of trigger temperature.................... 1130 MDT Time of overdevelopment........................ 1900 MDT Middle/high clouds during soaring window....... None Surface winds during soaring window............ 20 mph or less Height of the -3 thermal index................. 10912 ft MSL (5611 ft AGL) Thermal soaring outlook for Saturday 09/20..... Good 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....................... 40320 ft MSL (35019 ft AGL) Wave soaring outlook for Saturday 09/20........ Poor Remarks... Sunrise/Sunset.................... 06:44:54 / 19:01:17 MDT Total possible sunshine........... 12 hr 16 min 22 sec (736 min 22 sec) Altitude of sun at 12:53:05 MDT... 51.36 degrees Upper air data from numerical model forecast valid on 09/19/2025 at 0600 MDT Freezing level.................. 14740 ft MSL (9439 ft AGL) Convective condensation level... 17953 ft MSL (12652 ft AGL) Lifted condensation level....... 16920 ft MSL (11619 ft AGL) Lifted index.................... +0.6 K index......................... -8.2 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 -62.6 -80.7 295 34 17 3.1 1.7 M M M M M 45000 -58.3 -72.9 295 48 25 2.2 1.2 M M M M M 40000 -54.8 -66.6 290 58 30 5.8 3.2 M M M M M 38000 -51.0 -59.8 300 57 29 6.3 3.5 M M M M M 36000 -46.7 -52.1 305 57 29 6.3 3.4 M M M M M 34000 -42.0 -43.6 305 53 27 8.2 4.5 M M M M M 32000 -37.1 -34.8 300 48 25 8.2 4.5 M M M M M 30000 -33.0 -27.4 300 43 22 6.3 3.4 43.1 109.6 11.2 M M 29000 -31.1 -24.0 300 41 21 6.3 3.4 41.8 107.2 10.3 M M 28000 -29.2 -20.6 295 39 20 6.4 3.5 40.6 105.1 9.5 M M 27000 -27.0 -16.6 295 37 19 7.3 4.0 39.5 103.1 8.8 M M 26000 -24.9 -12.8 295 36 18 7.3 4.0 38.5 101.3 8.1 M M 25000 -22.7 -8.9 295 35 18 7.2 4.0 37.7 99.8 7.5 M M 24000 -20.4 -4.7 300 33 17 7.7 4.2 36.8 98.3 6.9 M M 23000 -18.1 -0.6 300 33 17 7.7 4.2 36.1 96.9 6.4 M M 22000 -15.7 3.7 300 32 16 7.8 4.3 35.4 95.7 5.9 M M 21000 -13.5 7.7 300 30 15 7.1 3.9 34.5 94.1 5.2 M M 20000 -11.4 11.5 300 28 14 7.1 3.9 33.5 92.4 4.4 M M 19500 -10.3 13.5 295 27 14 7.1 3.9 33.1 91.6 4.1 M M 19000 -9.3 15.3 295 26 13 7.1 3.9 32.7 90.9 3.7 M M 18500 -8.2 17.2 295 25 13 7.1 3.9 32.2 90.0 3.4 M M 18000 -6.6 20.1 295 23 12 7.0 3.9 31.6 88.9 2.8 M M 17500 -5.6 21.9 295 22 11 7.0 3.8 31.1 88.0 2.4 M M 17000 -4.5 23.9 295 21 11 7.0 3.8 30.6 87.1 2.0 M M 16500 -3.5 25.7 300 21 11 7.0 3.8 30.1 86.3 1.6 M M 16000 -2.4 27.7 300 20 10 7.0 3.8 29.7 85.4 1.1 M M 15500 -1.4 29.5 300 20 10 7.0 3.8 29.2 84.6 0.7 M M 15000 -0.4 31.3 300 19 10 7.0 3.8 28.7 83.7 0.3 M M 14500 0.7 33.3 300 19 10 7.1 3.9 28.3 82.9 -0.1 765 3.9 14000 1.7 35.1 300 18 9 7.2 3.9 27.8 82.1 -0.6 718 3.6 13500 2.8 37.0 295 18 9 7.1 3.9 27.4 81.4 -1.0 672 3.4 13000 3.8 38.8 295 17 9 7.0 3.8 27.0 80.6 -1.4 626 3.2 12500 4.8 40.6 295 16 8 7.1 3.9 26.5 79.8 -1.9 581 3.0 12000 5.9 42.6 295 15 8 8.1 4.4 26.2 79.2 -2.3 533 2.7 11500 7.1 44.8 290 14 7 8.1 4.4 25.9 78.7 -2.6 483 2.5 11000 8.2 46.8 290 13 6 7.4 4.0 25.6 78.1 -2.9 435 2.2 10500 9.3 48.7 290 11 6 6.3 3.4 25.3 77.5 -3.4 388 2.0 10250 9.6 49.3 290 11 5 4.3 2.3 24.9 76.8 -3.7 370 1.9 10000 10.0 50.0 290 10 5 7.4 4.1 24.5 76.1 -4.1 351 1.8 9750 10.7 51.3 290 10 5 9.9 5.4 24.5 76.1 -4.2 324 1.6 9500 11.3 52.3 295 9 5 8.7 4.8 24.4 76.0 -4.3 297 1.5 9250 11.8 53.2 295 8 4 5.3 2.9 24.3 75.7 -4.5 274 1.4 9000 12.2 54.0 295 8 4 5.9 3.2 23.9 75.0 -4.9 257 1.3 8750 12.7 54.9 295 8 4 8.8 4.8 23.7 74.7 -5.1 233 1.2 8500 13.3 55.9 295 7 4 6.9 3.8 23.6 74.5 -5.3 208 1.1 8250 13.7 56.7 295 7 4 4.7 2.6 23.3 73.9 -5.6 189 1.0 8000 14.0 57.2 295 7 4 4.3 2.4 22.9 73.1 -6.1 173 0.9 7750 14.3 57.7 295 7 3 5.6 3.0 22.5 72.5 -6.5 155 0.8 7500 14.7 58.5 295 7 3 4.1 2.2 22.1 71.9 -6.9 137 0.7 7250 14.8 58.6 295 6 3 2.2 1.2 21.6 70.9 -7.5 125 0.6 7000 15.0 59.0 295 6 3 2.8 1.5 21.0 69.9 -8.0 113 0.6 6750 15.2 59.4 295 6 3 2.3 1.2 20.5 68.9 -8.6 100 0.5 6500 15.2 59.4 295 5 3 -0.6 -0.3 19.8 67.7 -9.3 92 0.5 6250 15.0 59.0 285 5 3 -2.9 -1.6 18.9 66.1 -10.3 89 0.5 6000 14.9 58.8 275 5 2 -0.5 -0.2 18.0 64.5 -11.2 87 0.4 5750 14.8 58.6 270 5 2 -5.5 -3.0 17.2 63.0 -12.1 83 0.4 5500 13.7 56.7 255 4 2 -20.4 -11.2 15.5 59.9 -13.9 106 0.5 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 09/19/2025 at 0900 MDT | 09/19/2025 at 1200 MDT | CAPE... 0.0 LI... +6.1 | CAPE... 0.0 LI... +5.3 CINH... -0.0 K Index... -4.0 | CINH... -0.3 K Index... +0.8 | 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 -62.8 -81.0 290 33 17 3.2 1.8 | -63.1 -81.6 285 32 17 2.8 1.6 45000 -58.5 -73.3 290 44 23 1.8 1.0 | -59.1 -74.4 285 43 22 2.2 1.2 40000 -55.6 -68.1 290 48 25 6.6 3.6 | -55.5 -67.9 280 41 21 6.8 3.8 38000 -51.4 -60.5 295 46 23 6.9 3.8 | -51.4 -60.5 285 38 20 6.8 3.8 36000 -46.8 -52.2 300 43 22 6.8 3.7 | -46.8 -52.2 290 36 18 6.7 3.7 34000 -41.8 -43.2 300 42 22 8.6 4.7 | -41.7 -43.1 295 35 18 8.7 4.8 32000 -36.6 -33.9 300 41 21 8.6 4.7 | -36.5 -33.7 295 34 18 8.6 4.7 30000 -32.4 -26.3 300 38 20 6.4 3.5 | -32.3 -26.1 295 32 16 6.5 3.5 29000 -30.5 -22.9 300 36 19 6.4 3.5 | -30.3 -22.5 295 30 15 6.5 3.5 28000 -28.6 -19.5 300 34 18 6.5 3.5 | -28.4 -19.1 295 28 15 6.6 3.6 27000 -26.5 -15.7 300 34 17 7.0 3.8 | -26.3 -15.3 295 27 14 7.1 3.9 26000 -24.4 -11.9 300 33 17 7.0 3.8 | -24.2 -11.6 295 27 14 7.1 3.9 25000 -22.3 -8.1 300 33 17 7.0 3.8 | -22.0 -7.6 295 26 13 7.1 3.9 24000 -20.1 -4.2 300 32 17 7.5 4.1 | -19.7 -3.5 295 25 13 7.7 4.2 23000 -17.8 -0.0 305 32 16 7.5 4.1 | -17.4 0.7 300 25 13 7.7 4.2 22000 -15.6 3.9 305 31 16 7.5 4.1 | -15.1 4.8 300 25 13 7.8 4.3 21000 -13.4 7.9 305 29 15 7.1 3.9 | -12.9 8.8 300 24 13 7.0 3.8 20000 -11.3 11.7 300 27 14 7.1 3.9 | -10.8 12.6 295 24 12 7.0 3.8 19500 -10.2 13.6 300 26 13 7.1 3.9 | -9.8 14.4 290 23 12 7.0 3.8 19000 -9.2 15.4 300 25 13 6.7 3.7 | -8.7 16.3 290 23 12 6.8 3.7 18500 -7.7 18.1 295 24 12 6.5 3.5 | -7.2 19.0 285 23 12 6.6 3.6 18000 -6.8 19.8 295 23 12 6.6 3.6 | -6.3 20.7 285 23 12 6.4 3.5 17500 -5.8 21.6 295 22 12 6.6 3.6 | -5.3 22.5 285 22 12 6.2 3.4 17000 -4.8 23.4 290 22 11 6.7 3.6 | -4.4 24.1 285 22 11 6.3 3.4 16500 -3.8 25.2 295 21 11 6.6 3.6 | -3.5 25.7 290 22 11 6.5 3.6 16000 -2.9 26.8 295 21 11 6.6 3.6 | -2.5 27.5 290 21 11 6.6 3.6 15500 -1.9 28.6 295 20 10 6.8 3.8 | -1.6 29.1 290 21 11 6.4 3.5 15000 -0.9 30.4 295 19 10 6.9 3.8 | -0.7 30.7 295 20 10 6.4 3.5 14500 0.2 32.4 300 19 10 7.0 3.8 | 0.2 32.4 295 19 10 6.5 3.6 14000 1.2 34.2 300 18 9 7.1 3.9 | 1.2 34.2 300 18 9 6.6 3.6 13500 2.2 36.0 305 17 9 7.2 4.0 | 2.1 35.8 300 17 9 6.9 3.8 13000 3.3 37.9 305 17 9 7.5 4.1 | 3.2 37.8 305 16 8 7.3 4.0 12500 4.4 39.9 310 16 8 7.5 4.1 | 4.3 39.7 310 15 7 7.4 4.1 12000 5.5 41.9 310 15 8 7.8 4.3 | 5.4 41.7 310 13 7 7.8 4.3 11500 6.7 44.1 315 15 8 7.8 4.3 | 6.5 43.7 315 12 6 7.8 4.3 11000 7.8 46.0 315 15 8 7.7 4.2 | 7.7 45.9 320 10 5 8.0 4.4 10500 9.0 48.2 320 14 7 5.7 3.1 | 8.9 48.0 330 9 5 5.5 3.0 10250 9.3 48.7 320 14 7 3.7 2.0 | 9.2 48.6 330 9 5 4.8 2.6 10000 9.7 49.5 320 14 7 8.5 4.7 | 9.8 49.6 335 9 4 9.6 5.3 9750 10.5 50.9 320 13 7 11.1 6.1 | 10.5 50.9 340 8 4 10.6 5.8 9500 11.2 52.2 320 13 7 9.3 5.1 | 11.3 52.3 345 7 4 9.3 5.1 9250 11.8 53.2 320 12 6 5.2 2.9 | 11.8 53.2 350 7 4 6.1 3.3 9000 12.1 53.8 325 12 6 6.5 3.6 | 12.3 54.1 355 7 3 7.8 4.3 8750 12.8 55.0 320 12 6 9.9 5.4 | 13.0 55.4 360 6 3 10.6 5.8 8500 13.4 56.1 320 11 6 7.8 4.3 | 13.8 56.8 360 6 3 8.9 4.9 8250 13.9 57.0 320 11 5 6.0 3.3 | 14.4 57.9 005 5 3 7.1 3.9 8000 14.4 57.9 320 10 5 6.1 3.4 | 14.9 58.8 010 5 3 8.2 4.5 7750 14.9 58.8 320 10 5 7.7 4.2 | 15.6 60.1 010 5 2 10.9 6.0 7500 15.4 59.7 315 9 5 5.7 3.1 | 16.4 61.5 010 4 2 9.4 5.2 7250 15.7 60.3 315 9 4 3.4 1.9 | 17.0 62.6 015 4 2 7.3 4.0 7000 16.0 60.8 315 8 4 4.3 2.4 | 17.6 63.7 015 4 2 8.8 4.8 6750 16.3 61.3 310 8 4 4.0 2.2 | 18.4 65.1 015 4 2 12.6 6.9 6500 16.5 61.7 300 6 3 1.4 0.8 | 19.4 66.9 015 4 2 11.8 6.5 6250 16.4 61.5 290 5 3 -0.4 -0.2 | 20.1 68.2 015 4 2 9.6 5.3 6000 16.4 61.5 280 5 2 0.7 0.4 | 20.8 69.4 020 4 2 9.3 5.1 5750 16.5 61.7 265 4 2 3.4 1.9 | 21.6 70.9 020 4 2 14.8 8.1 5500 16.8 62.2 245 4 2 6.0 3.3 | 23.2 73.8 020 3 2 27.1 14.9 09/19/2025 at 1500 MDT | 09/19/2025 at 1800 MDT | CAPE... 0.0 LI... +4.1 | CAPE... 0.0 LI... +3.3 CINH... -0.2 K Index... +8.7 | CINH... -0.1 K Index... +15.0 | 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 -62.7 -80.9 285 31 16 2.5 1.4 | -62.2 -80.0 290 30 16 2.5 1.4 45000 -59.1 -74.4 280 40 21 2.2 1.2 | -58.7 -73.7 285 37 19 1.7 0.9 40000 -55.2 -67.4 275 37 19 6.9 3.8 | -55.5 -67.9 275 34 18 7.2 4.0 38000 -51.1 -60.0 275 35 18 6.7 3.7 | -51.4 -60.5 275 31 16 6.9 3.8 36000 -47.1 -52.8 280 33 17 6.7 3.7 | -47.2 -53.0 280 27 14 6.9 3.8 34000 -42.1 -43.8 280 30 15 8.9 4.9 | -42.1 -43.8 280 26 13 9.0 4.9 32000 -36.7 -34.1 285 27 14 8.9 4.9 | -36.7 -34.1 280 25 13 9.0 5.0 30000 -32.2 -26.0 290 26 13 6.9 3.8 | -31.9 -25.4 280 24 12 7.6 4.2 29000 -30.2 -22.4 295 25 13 7.0 3.8 | -29.7 -21.5 280 23 12 7.6 4.2 28000 -28.1 -18.6 295 24 13 7.0 3.9 | -27.4 -17.3 285 23 12 7.9 4.3 27000 -26.2 -15.2 295 24 12 6.2 3.4 | -25.3 -13.5 280 20 10 5.3 2.9 26000 -23.9 -11.0 285 23 12 6.2 3.4 | -23.7 -10.7 275 18 9 5.2 2.9 25000 -22.0 -7.6 280 22 12 6.1 3.3 | -22.1 -7.8 270 16 8 5.0 2.7 24000 -19.7 -3.5 280 21 11 7.9 4.4 | -20.0 -4.0 275 15 8 7.9 4.3 23000 -17.3 0.9 285 20 11 7.9 4.4 | -17.6 0.3 275 15 8 7.9 4.3 22000 -15.0 5.0 285 19 10 7.9 4.3 | -15.2 4.6 280 14 7 7.9 4.3 21000 -12.6 9.3 290 19 10 7.8 4.3 | -12.9 8.8 280 15 8 7.6 4.2 20000 -10.3 13.5 285 19 10 7.8 4.3 | -10.6 12.9 280 17 9 7.6 4.2 19500 -9.1 15.6 285 19 10 7.9 4.3 | -9.5 14.9 280 17 9 7.8 4.3 19000 -8.1 17.4 285 19 10 6.2 3.4 | -8.4 16.9 280 18 9 5.4 3.0 18500 -7.2 19.0 290 20 10 6.0 3.3 | -7.7 18.1 280 19 10 5.1 2.8 18000 -6.3 20.7 290 21 11 5.9 3.2 | -7.0 19.4 275 20 11 5.3 2.9 17500 -5.5 22.1 290 21 11 5.4 3.0 | -6.1 21.0 280 21 11 6.1 3.4 17000 -4.7 23.5 290 22 11 5.4 3.0 | -5.3 22.5 280 21 11 6.0 3.3 16500 -3.8 25.2 290 22 11 7.0 3.8 | -4.3 24.3 280 21 11 7.6 4.1 16000 -2.8 27.0 290 22 11 7.1 3.9 | -3.2 26.2 285 21 11 7.8 4.3 15500 -1.8 28.8 290 22 11 7.3 4.0 | -2.1 28.2 285 21 11 8.1 4.4 15000 -0.7 30.7 290 21 11 7.6 4.1 | -0.9 30.4 285 20 10 8.4 4.6 14500 0.4 32.7 290 21 11 7.6 4.2 | 0.3 32.5 285 19 10 8.4 4.6 14000 1.4 34.5 290 19 10 7.2 4.0 | 1.5 34.7 280 17 9 8.4 4.6 13500 2.4 36.3 290 17 9 7.2 4.0 | 3.4 38.1 280 14 7 8.1 4.4 13000 4.1 39.4 285 13 7 8.0 4.4 | 4.5 40.1 275 11 6 7.8 4.3 12500 5.2 41.4 280 10 5 7.9 4.4 | 5.6 42.1 270 9 4 7.6 4.2 12000 6.4 43.5 280 7 4 7.8 4.3 | 6.7 44.1 260 5 3 7.2 3.9 11500 7.5 45.5 280 4 2 7.9 4.3 | 7.7 45.9 220 3 1 7.5 4.1 11000 8.7 47.7 275 2 1 7.9 4.3 | 9.0 48.2 180 2 1 8.4 4.6 10500 10.0 50.0 185 1 0 3.6 2.0 | 10.3 50.5 155 3 1 4.3 2.3 10250 10.1 50.2 155 1 0 5.4 3.0 | 10.4 50.7 155 3 1 6.0 3.3 10000 10.9 51.6 135 1 1 12.3 6.8 | 11.3 52.3 140 3 2 12.7 7.0 9750 11.7 53.1 125 1 1 11.0 6.0 | 12.1 53.8 130 4 2 11.5 6.3 9500 12.5 54.5 120 2 1 9.3 5.1 | 13.0 55.4 125 4 2 9.6 5.3 9250 13.1 55.6 120 2 1 6.3 3.5 | 13.5 56.3 120 4 2 6.2 3.4 9000 13.7 56.7 115 2 1 9.9 5.4 | 14.1 57.4 120 5 2 9.4 5.2 8750 14.5 58.1 115 2 1 13.0 7.1 | 14.9 58.8 115 5 3 12.4 6.8 8500 15.4 59.7 110 3 1 10.1 5.5 | 15.8 60.4 110 6 3 9.8 5.4 8250 16.0 60.8 110 3 1 6.6 3.6 | 16.4 61.5 110 6 3 6.6 3.6 8000 16.6 61.9 110 3 1 9.3 5.1 | 16.9 62.4 110 6 3 8.9 4.9 7750 17.5 63.5 105 3 1 13.0 7.2 | 17.7 63.9 105 7 4 12.5 6.9 7500 18.4 65.1 105 3 2 10.2 5.6 | 18.6 65.5 105 8 4 9.9 5.4 7250 19.0 66.2 105 3 2 7.5 4.1 | 19.2 66.6 105 8 4 7.3 4.0 7000 19.6 67.3 105 3 2 9.5 5.2 | 19.8 67.6 100 8 4 9.0 4.9 6750 20.4 68.7 100 3 2 12.6 6.9 | 20.6 69.1 100 8 4 11.4 6.3 6500 21.4 70.5 100 3 2 11.0 6.0 | 21.4 70.5 100 9 4 10.1 5.6 6250 22.1 71.8 100 4 2 8.8 4.9 | 22.1 71.8 095 9 4 8.0 4.4 6000 22.8 73.0 100 4 2 9.6 5.2 | 22.7 72.9 095 9 4 9.5 5.2 5750 23.6 74.5 100 4 2 14.9 8.2 | 23.4 74.1 095 8 4 9.7 5.3 5500 25.1 77.2 095 4 2 23.4 12.8 | 24.0 75.2 090 7 4 6.8 3.7 ________________________________________________________________________________ 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