896 UXUS97 KBOU 170116 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 1912 MDT Saturday, August 16, 2025 This forecast is for Sunday, August 17, 2025: If the trigger temperature of 82.3 F/28.0 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 1425 ft/min (7.2 m/s) Maximum height of thermals.................. 18591 ft MSL (13308 ft AGL) Forecast maximum temperature................... 93.0 F/34.3 C Time of trigger temperature.................... 1000 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................. 15844 ft MSL (10561 ft AGL) Thermal soaring outlook for Monday 08/18....... 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)................ Neither Potential height of wave....................... 19563 ft MSL (14280 ft AGL) Wave soaring outlook for Monday 08/18.......... Fair Remarks... Sunrise/Sunset.................... 06:14:04 / 19:52:50 MDT Total possible sunshine........... 13 hr 38 min 46 sec (818 min 46 sec) Altitude of sun at 13:03:27 MDT... 63.37 degrees Upper air data from numerical model forecast valid on 08/17/2025 at 0600 MDT Freezing level.................. 15449 ft MSL (10166 ft AGL) Convective condensation level... 15915 ft MSL (10632 ft AGL) Lifted condensation level....... 17278 ft MSL (11994 ft AGL) Lifted index.................... -1.0 K index......................... +25.4 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 -64.4 -83.9 235 17 9 1.4 0.8 M M M M M 45000 -59.5 -75.1 240 23 12 6.3 3.4 M M M M M 40000 -49.8 -57.6 240 32 17 7.4 4.0 M M M M M 38000 -45.4 -49.7 245 38 19 7.3 4.0 M M M M M 36000 -41.0 -41.8 250 43 22 7.3 4.0 M M M M M 34000 -36.9 -34.4 245 41 21 6.8 3.7 M M M M M 32000 -32.8 -27.0 245 38 20 6.8 3.8 M M M M M 30000 -28.6 -19.5 240 32 16 6.1 3.3 47.3 117.2 10.3 M M 29000 -26.8 -16.2 240 28 15 6.1 3.3 46.0 114.8 9.3 M M 28000 -24.8 -12.6 240 26 13 8.0 4.4 44.8 112.7 8.5 M M 27000 -22.4 -8.3 240 25 13 7.9 4.3 44.0 111.2 8.0 M M 26000 -20.1 -4.2 240 24 12 7.9 4.3 43.3 110.0 7.6 M M 25000 -17.7 0.1 240 23 12 7.7 4.2 42.8 109.0 7.2 M M 24000 -15.5 4.1 240 23 12 7.3 4.0 41.8 107.2 6.5 M M 23000 -13.3 8.1 240 22 11 7.3 4.0 40.9 105.6 5.8 M M 22000 -11.1 12.0 240 21 11 6.5 3.5 40.1 104.2 5.2 M M 21000 -9.5 14.9 240 20 10 5.2 2.9 38.4 101.2 3.8 M M 20000 -8.0 17.6 245 18 10 5.3 2.9 36.9 98.3 2.5 M M 19500 -7.2 19.0 245 18 9 5.6 3.1 36.1 97.0 1.9 M M 19000 -6.6 20.1 250 17 9 3.1 1.7 35.2 95.4 1.0 M M 18500 -6.2 20.8 250 16 8 3.7 2.0 34.1 93.4 -0.0 1225 6.2 18000 -5.7 21.7 255 15 8 5.4 2.9 33.1 91.6 -1.1 1197 6.1 17500 -4.8 23.4 255 14 7 7.2 3.9 32.6 90.7 -1.6 1153 5.9 17000 -3.8 25.2 255 13 7 7.3 4.0 32.2 90.0 -2.1 1109 5.6 16500 -2.7 27.1 260 12 6 8.0 4.4 31.8 89.3 -2.5 1062 5.4 16000 -1.6 29.1 260 11 6 8.0 4.4 31.5 88.8 -2.8 1013 5.1 15500 0.2 32.4 265 9 5 8.4 4.6 31.1 88.0 -3.3 938 4.8 15000 1.4 34.5 265 8 4 8.3 4.6 30.9 87.6 -3.5 887 4.5 14500 2.7 36.9 270 7 4 9.0 5.0 30.7 87.3 -3.7 834 4.2 14000 4.0 39.2 280 6 3 9.1 5.0 30.6 87.1 -3.9 779 4.0 13500 5.3 41.5 285 6 3 8.9 4.9 30.5 86.9 -4.0 725 3.7 13000 6.6 43.9 295 5 3 8.9 4.9 30.3 86.6 -4.2 671 3.4 12500 7.9 46.2 305 5 3 8.9 4.9 30.2 86.4 -4.4 617 3.1 12000 9.2 48.6 315 6 3 8.9 4.9 30.1 86.1 -4.6 563 2.9 11500 10.5 50.9 320 6 3 8.9 4.9 29.9 85.9 -4.7 509 2.6 11000 11.9 53.4 320 7 4 8.6 4.7 29.8 85.7 -4.9 454 2.3 10500 13.2 55.8 320 8 4 3.5 1.9 29.7 85.5 -5.0 400 2.0 10250 13.3 55.9 320 8 4 4.9 2.7 29.0 84.2 -5.7 390 2.0 10000 14.1 57.4 320 8 4 12.6 6.9 29.1 84.4 -5.6 358 1.8 9750 14.9 58.8 320 9 5 11.3 6.2 29.2 84.6 -5.6 326 1.7 9500 15.7 60.3 320 9 5 8.7 4.8 29.3 84.8 -5.5 294 1.5 9250 16.2 61.2 320 9 5 5.5 3.0 29.0 84.2 -5.8 273 1.4 9000 16.7 62.1 320 9 5 9.0 5.0 28.8 83.9 -6.0 250 1.3 8750 17.5 63.5 320 9 5 11.4 6.3 28.9 84.0 -5.9 219 1.1 8500 18.3 64.9 320 10 5 8.8 4.8 29.0 84.1 -5.9 188 1.0 8250 18.8 65.8 320 10 5 6.2 3.4 28.7 83.7 -6.1 166 0.8 8000 19.3 66.7 320 9 5 8.1 4.5 28.5 83.3 -6.4 143 0.7 7750 20.0 68.0 320 9 5 9.7 5.3 28.5 83.3 -6.4 115 0.6 7500 20.7 69.3 315 9 5 7.2 3.9 28.4 83.1 -6.5 87 0.4 7250 21.1 70.0 315 9 5 5.1 2.8 28.1 82.6 -6.8 67 0.3 7000 21.5 70.7 315 9 5 6.4 3.5 27.8 82.0 -7.1 47 0.2 6750 21.9 71.4 310 9 5 4.3 2.4 27.5 81.5 -7.5 27 0.1 6500 22.0 71.6 305 9 5 -0.1 -0.1 26.9 80.4 -8.1 16 0.1 6250 21.9 71.4 300 9 4 -3.1 -1.7 26.0 78.9 -9.0 13 0.1 6000 21.8 71.2 290 9 4 2.9 1.6 25.2 77.3 -9.9 10 0.1 5750 21.9 71.4 285 10 5 -5.2 -2.9 24.7 76.4 -10.5 M M 5500 20.3 68.5 270 6 3 -34.3 -18.8 22.4 72.3 -12.8 38 0.2 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 08/17/2025 at 0900 MDT | 08/17/2025 at 1200 MDT | CAPE... +10.7 LI... +0.6 | CAPE... +62.1 LI... -0.9 CINH... -65.6 K Index... +24.6 | CINH... -8.4 K Index... +25.4 | 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 -64.3 -83.7 235 16 8 1.6 0.9 | -63.7 -82.7 235 14 7 0.9 0.5 45000 -59.4 -74.9 230 23 12 6.0 3.3 | -59.5 -75.1 230 23 12 6.0 3.3 40000 -50.0 -58.0 230 32 16 7.5 4.1 | -50.2 -58.4 225 33 17 7.5 4.1 38000 -45.5 -49.9 235 35 18 7.4 4.1 | -45.7 -50.3 225 34 18 7.5 4.1 36000 -41.0 -41.8 240 38 20 7.4 4.0 | -41.1 -42.0 230 36 18 7.5 4.1 34000 -37.0 -34.6 240 38 20 6.7 3.7 | -37.0 -34.6 230 37 19 6.9 3.8 32000 -32.4 -26.3 240 38 20 6.7 3.7 | -32.3 -26.1 235 38 20 6.8 3.8 30000 -28.6 -19.5 240 36 19 6.3 3.5 | -28.5 -19.3 235 40 20 6.2 3.4 29000 -26.7 -16.1 235 35 18 6.3 3.5 | -26.7 -16.1 235 40 21 6.2 3.4 28000 -24.7 -12.5 235 34 17 7.6 4.1 | -24.7 -12.5 235 40 21 7.2 4.0 27000 -22.5 -8.5 235 32 16 7.5 4.1 | -22.6 -8.7 235 38 20 7.2 4.0 26000 -20.2 -4.4 235 30 16 7.5 4.1 | -20.4 -4.7 235 37 19 7.2 4.0 25000 -18.0 -0.4 230 29 15 7.3 4.0 | -18.2 -0.8 240 35 18 7.1 3.9 24000 -15.9 3.4 235 28 14 6.9 3.8 | -16.1 3.0 240 33 17 7.0 3.8 23000 -13.8 7.2 235 27 14 6.9 3.8 | -14.1 6.6 240 32 16 7.0 3.8 22000 -11.7 10.9 235 26 13 6.2 3.4 | -12.0 10.4 240 30 15 5.9 3.2 21000 -10.2 13.6 240 24 12 5.0 2.8 | -10.6 12.9 240 27 14 4.5 2.4 20000 -8.8 16.2 240 22 11 5.1 2.8 | -9.4 15.1 240 24 12 4.6 2.5 19500 -8.0 17.6 240 21 11 5.3 2.9 | -8.7 16.3 245 22 11 4.7 2.6 19000 -7.4 18.7 245 19 10 4.5 2.4 | -8.0 17.6 245 20 11 5.4 3.0 18500 -6.7 19.9 250 18 9 4.7 2.6 | -7.3 18.9 245 18 9 5.5 3.0 18000 -6.1 21.0 250 16 8 5.2 2.9 | -6.6 20.1 250 16 8 6.2 3.4 17500 -5.3 22.5 255 14 7 5.9 3.3 | -5.6 21.9 250 15 8 6.9 3.8 17000 -4.5 23.9 255 12 6 5.9 3.2 | -4.1 24.6 250 13 7 8.2 4.5 16500 -2.9 26.8 255 9 5 8.6 4.7 | -2.8 27.0 250 11 6 9.0 5.0 16000 -1.6 29.1 260 8 4 8.7 4.8 | -1.5 29.3 250 10 5 9.1 5.0 15500 -0.3 31.5 260 7 4 8.7 4.8 | -0.1 31.8 255 9 5 8.9 4.9 15000 0.9 33.6 265 6 3 8.7 4.8 | 1.2 34.2 255 8 4 8.9 4.9 14500 2.2 36.0 270 5 3 9.1 5.0 | 2.5 36.5 255 7 4 9.2 5.1 14000 3.6 38.5 275 5 2 9.1 5.0 | 3.9 39.0 260 7 3 9.2 5.1 13500 4.9 40.8 285 4 2 9.2 5.1 | 5.2 41.4 260 6 3 9.3 5.1 13000 6.3 43.3 295 4 2 9.2 5.1 | 6.6 43.9 265 6 3 9.4 5.1 12500 7.7 45.9 310 4 2 9.1 5.0 | 8.0 46.4 265 5 3 9.4 5.1 12000 9.0 48.2 315 5 2 9.0 4.9 | 9.4 48.9 270 5 3 9.4 5.1 11500 10.3 50.5 315 6 3 8.9 4.9 | 10.8 51.4 275 5 3 9.4 5.1 11000 11.7 53.1 320 7 3 8.5 4.7 | 12.2 54.0 280 5 2 9.0 5.0 10500 13.0 55.4 320 8 4 3.4 1.9 | 13.6 56.5 285 4 2 4.1 2.3 10250 13.0 55.4 320 8 4 5.0 2.7 | 13.7 56.7 285 4 2 6.1 3.3 10000 13.9 57.0 320 8 4 12.8 7.0 | 14.6 58.3 285 4 2 13.8 7.6 9750 14.7 58.5 315 8 4 11.6 6.3 | 15.5 59.9 290 4 2 12.8 7.0 9500 15.5 59.9 315 9 4 8.7 4.8 | 16.4 61.5 290 4 2 9.1 5.0 9250 16.0 60.8 315 8 4 5.5 3.0 | 16.9 62.4 290 4 2 6.3 3.5 9000 16.5 61.7 315 8 4 9.0 5.0 | 17.6 63.7 295 4 2 11.2 6.1 8750 17.3 63.1 315 8 4 10.8 5.9 | 18.5 65.3 295 3 2 12.7 7.0 8500 18.0 64.4 310 9 4 8.7 4.8 | 19.4 66.9 300 3 2 9.9 5.5 8250 18.6 65.5 310 8 4 6.7 3.7 | 20.0 68.0 300 3 2 7.1 3.9 8000 19.1 66.4 310 8 4 8.6 4.7 | 20.6 69.1 300 3 1 10.2 5.6 7750 19.8 67.6 310 8 4 10.0 5.5 | 21.5 70.7 305 3 1 12.3 6.8 7500 20.5 68.9 305 9 4 7.3 4.0 | 22.3 72.1 305 3 1 9.4 5.2 7250 20.9 69.6 305 8 4 5.4 3.0 | 22.9 73.2 310 3 1 7.4 4.0 7000 21.4 70.5 300 8 4 6.7 3.7 | 23.5 74.3 310 2 1 10.2 5.6 6750 21.9 71.4 300 8 4 7.1 3.9 | 24.4 75.9 315 2 1 13.1 7.2 6500 22.3 72.1 295 8 4 5.5 3.0 | 25.3 77.5 315 2 1 11.0 6.0 6250 22.7 72.9 290 7 4 4.8 2.6 | 26.1 79.0 320 2 1 9.6 5.3 6000 23.0 73.4 285 7 3 4.8 2.7 | 26.8 80.2 325 2 1 10.0 5.5 5750 23.5 74.3 275 6 3 9.3 5.1 | 27.7 81.9 320 2 1 16.7 9.2 5500 24.4 75.9 265 5 3 17.2 9.4 | 29.4 84.9 330 2 1 28.0 15.4 08/17/2025 at 1500 MDT | 08/17/2025 at 1800 MDT | CAPE... +70.6 LI... -1.3 | CAPE... +131.5 LI... -1.7 CINH... -6.0 K Index... +25.8 | CINH... -34.8 K Index... +24.8 | 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 -63.6 -82.5 215 13 7 0.9 0.5 | -64.3 -83.7 220 17 9 1.3 0.7 45000 -59.5 -75.1 225 23 12 6.0 3.3 | -59.6 -75.3 230 25 13 6.5 3.5 40000 -50.1 -58.2 230 31 16 7.4 4.1 | -49.8 -57.6 235 28 14 7.1 3.9 38000 -45.7 -50.3 235 32 17 7.4 4.1 | -45.1 -49.2 240 31 16 7.1 3.9 36000 -41.2 -42.2 235 34 18 7.4 4.0 | -40.8 -41.4 245 34 18 7.0 3.8 34000 -36.9 -34.4 235 36 18 7.1 3.9 | -36.7 -34.1 245 36 19 6.9 3.8 32000 -32.1 -25.8 240 38 19 6.9 3.8 | -32.5 -26.5 245 38 19 7.0 3.9 30000 -28.4 -19.1 240 40 20 6.2 3.4 | -29.0 -20.2 245 38 20 5.9 3.2 29000 -26.6 -15.9 240 41 21 6.2 3.4 | -27.2 -17.0 245 39 20 5.9 3.2 28000 -24.7 -12.5 240 41 21 7.1 3.9 | -25.4 -13.7 245 39 20 6.8 3.8 27000 -22.5 -8.5 240 40 20 7.0 3.9 | -23.3 -9.9 245 36 19 7.2 4.0 26000 -20.4 -4.7 245 39 20 7.1 3.9 | -21.1 -6.0 250 33 17 7.3 4.0 25000 -18.3 -0.9 245 38 19 6.9 3.8 | -18.5 -1.3 250 30 15 7.1 3.9 24000 -16.4 2.5 245 35 18 6.6 3.6 | -16.4 2.5 255 29 15 7.0 3.8 23000 -14.5 5.9 245 32 16 6.7 3.7 | -14.4 6.1 260 28 15 7.0 3.8 22000 -12.6 9.3 250 29 15 6.3 3.4 | -12.4 9.7 265 27 14 6.2 3.4 21000 -10.9 12.4 250 25 13 5.8 3.2 | -10.7 12.7 270 25 13 5.9 3.3 20000 -9.3 15.3 250 21 11 5.9 3.2 | -9.0 15.8 270 22 12 6.0 3.3 19500 -8.5 16.7 250 18 9 5.9 3.3 | -8.1 17.4 275 21 11 6.6 3.6 19000 -7.5 18.5 250 16 8 7.4 4.1 | -7.0 19.4 275 19 10 8.6 4.7 18500 -6.5 20.3 250 14 7 7.3 4.0 | -5.8 21.6 275 17 9 8.6 4.7 18000 -5.4 22.3 250 12 6 7.2 4.0 | -4.5 23.9 270 15 8 8.8 4.8 17500 -4.3 24.3 250 11 5 7.1 3.9 | -3.2 26.2 270 14 7 8.8 4.8 17000 -3.2 26.2 245 9 5 7.2 3.9 | -2.0 28.4 270 12 6 8.8 4.8 16500 -2.0 28.4 240 8 4 8.9 4.9 | -0.7 30.7 265 11 6 8.8 4.8 16000 -0.7 30.7 235 7 4 8.7 4.8 | 0.7 33.3 260 10 5 8.8 4.8 15500 0.6 33.1 225 6 3 8.8 4.8 | 2.0 35.6 250 9 5 8.6 4.7 15000 1.9 35.4 225 5 3 8.8 4.8 | 3.2 37.8 245 8 4 8.6 4.7 14500 3.8 38.8 215 4 2 9.3 5.1 | 4.5 40.1 240 7 4 9.0 4.9 14000 5.2 41.4 220 4 2 9.2 5.1 | 5.9 42.6 240 7 4 9.2 5.0 13500 6.5 43.7 220 3 2 9.3 5.1 | 7.3 45.1 235 7 3 9.1 5.0 13000 7.9 46.2 220 3 1 9.3 5.1 | 8.6 47.5 230 6 3 8.9 4.9 12500 9.3 48.7 220 3 1 9.4 5.2 | 9.9 49.8 220 6 3 8.9 4.9 12000 10.7 51.3 220 3 1 9.5 5.2 | 11.9 53.4 215 6 3 9.0 4.9 11500 12.1 53.8 225 3 1 9.6 5.3 | 13.2 55.8 210 6 3 9.0 4.9 11000 13.6 56.5 225 2 1 9.4 5.2 | 14.5 58.1 205 6 3 8.8 4.8 10500 15.0 59.0 225 2 1 4.6 2.5 | 15.8 60.4 200 7 3 4.2 2.3 10250 15.2 59.4 225 2 1 6.2 3.4 | 16.0 60.8 200 7 3 5.8 3.2 10000 16.1 61.0 230 2 1 13.6 7.5 | 16.8 62.2 195 7 3 12.2 6.7 9750 17.0 62.6 230 2 1 12.7 7.0 | 17.6 63.7 195 7 3 11.5 6.3 9500 17.9 64.2 230 2 1 8.6 4.7 | 18.4 65.1 190 7 3 7.7 4.2 9250 18.3 64.9 230 2 1 6.3 3.5 | 18.8 65.8 190 7 3 6.4 3.5 9000 19.0 66.2 230 2 1 11.6 6.4 | 19.5 67.1 185 7 4 11.6 6.3 8750 20.0 68.0 235 2 1 12.7 7.0 | 20.4 68.7 185 7 4 12.3 6.8 8500 20.8 69.4 235 2 1 9.6 5.3 | 21.2 70.2 180 7 4 9.3 5.1 8250 21.4 70.5 235 2 1 6.1 3.4 | 21.8 71.2 180 7 4 5.8 3.2 8000 21.9 71.4 235 2 1 10.4 5.7 | 22.3 72.1 180 7 4 10.2 5.6 7750 22.9 73.2 240 2 1 13.2 7.2 | 23.2 73.8 175 7 4 13.1 7.2 7500 23.8 74.8 240 2 1 9.6 5.2 | 24.1 75.4 170 7 4 9.3 5.1 7250 24.4 75.9 240 2 1 7.5 4.1 | 24.6 76.3 170 8 4 7.2 4.0 7000 25.0 77.0 240 2 1 10.3 5.7 | 25.2 77.4 165 8 4 9.6 5.3 6750 25.9 78.6 245 2 1 12.7 7.0 | 26.1 79.0 165 8 4 11.5 6.3 6500 26.8 80.2 245 2 1 10.5 5.7 | 26.9 80.4 160 8 4 9.5 5.2 6250 27.5 81.5 245 2 1 8.7 4.8 | 27.5 81.5 160 8 4 7.9 4.4 6000 28.2 82.8 245 2 1 11.1 6.1 | 28.1 82.6 160 8 4 9.9 5.4 5750 29.3 84.7 250 2 1 17.8 9.8 | 29.0 84.2 155 8 4 13.3 7.3 5500 30.8 87.4 250 2 1 22.8 12.5 | 30.0 86.0 155 7 3 14.0 7.7 ________________________________________________________________________________ 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