525 UXUS97 KBOU 030003 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 1802 MDT Thursday, October 2, 2025 This forecast is for Friday, October 3, 2025: If the trigger temperature of 81.6 F/27.5 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 954 ft/min (4.8 m/s) Maximum height of thermals.................. 15678 ft MSL (10379 ft AGL) Forecast maximum temperature................... 87.0 F/31.0 C Time of trigger temperature.................... 1200 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................. 9207 ft MSL (3908 ft AGL) Thermal soaring outlook for Saturday 10/04..... 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 NVA Potential height of wave....................... 17081 ft MSL (11782 ft AGL) Wave soaring outlook for Saturday 10/04........ Poor Remarks... Sunrise/Sunset.................... 06:58:17 / 18:38:24 MDT Total possible sunshine........... 11 hr 40 min 7 sec (700 min 7 sec) Altitude of sun at 12:48:21 MDT... 45.87 degrees Upper air data from numerical model forecast valid on 10/03/2025 at 0600 MDT Freezing level.................. 15412 ft MSL (10113 ft AGL) Convective condensation level... 17673 ft MSL (12374 ft AGL) Lifted condensation level....... 17055 ft MSL (11756 ft AGL) Lifted index.................... -0.6 K index......................... +17.0 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 -66.9 -88.4 255 45 23 2.8 1.5 M M M M M 45000 -61.6 -78.9 255 63 32 5.5 3.0 M M M M M 40000 -53.0 -63.4 260 63 33 5.6 3.1 M M M M M 38000 -49.6 -57.3 260 57 29 5.6 3.1 M M M M M 36000 -46.2 -51.2 255 51 26 5.5 3.0 M M M M M 34000 -42.0 -43.6 250 44 23 7.4 4.1 M M M M M 32000 -37.5 -35.5 245 38 20 7.4 4.1 M M M M M 30000 -33.0 -27.4 240 31 16 7.6 4.1 42.9 109.2 9.4 M M 29000 -30.8 -23.4 240 27 14 7.6 4.2 42.0 107.7 8.8 M M 28000 -27.9 -18.2 235 22 11 7.8 4.3 41.2 106.1 8.2 M M 27000 -25.6 -14.1 235 20 10 7.8 4.3 40.3 104.6 7.7 M M 26000 -23.2 -9.8 235 17 9 7.8 4.3 39.6 103.3 7.2 M M 25000 -20.9 -5.6 230 15 8 7.8 4.3 39.0 102.2 6.8 M M 24000 -18.6 -1.5 230 14 7 7.5 4.1 38.1 100.6 6.1 M M 23000 -16.4 2.5 225 14 7 7.5 4.1 37.3 99.1 5.5 M M 22000 -14.1 6.6 225 13 7 7.3 4.0 36.6 97.9 5.0 M M 21000 -12.1 10.2 220 14 7 6.9 3.8 35.5 95.9 4.1 M M 20000 -10.1 13.8 220 15 8 6.9 3.8 34.5 94.1 3.3 M M 19500 -9.0 15.8 220 15 8 6.8 3.7 34.1 93.3 2.9 M M 19000 -7.9 17.8 220 16 8 8.1 4.5 33.7 92.6 2.6 M M 18500 -6.7 19.9 220 16 8 8.0 4.4 33.4 92.1 2.3 M M 18000 -5.6 21.9 220 16 8 7.7 4.2 33.1 91.6 2.0 M M 17500 -4.5 23.9 215 16 8 7.3 4.0 32.7 90.8 1.6 M M 17000 -3.4 25.9 215 16 8 7.4 4.0 32.2 90.0 1.3 M M 16500 -2.4 27.7 210 15 8 7.0 3.8 31.8 89.3 0.8 M M 16000 -1.4 29.5 205 14 7 7.0 3.9 31.3 88.4 0.4 M M 15500 -0.4 31.3 195 14 7 7.2 4.0 30.9 87.6 -0.1 948 4.8 15000 0.6 33.1 190 14 7 7.4 4.1 30.5 86.9 -0.5 903 4.6 14500 2.2 36.0 185 14 7 9.1 5.0 30.0 86.1 -1.1 832 4.2 14000 3.5 38.3 185 14 7 9.1 5.0 29.9 85.8 -1.3 778 4.0 13500 4.9 40.8 180 14 7 9.2 5.0 29.8 85.7 -1.4 724 3.7 13000 6.2 43.2 185 14 7 9.2 5.1 29.7 85.5 -1.5 667 3.4 12500 7.6 45.7 185 13 7 9.1 5.0 29.7 85.4 -1.5 610 3.1 12000 9.0 48.2 195 13 7 9.0 5.0 29.5 85.2 -1.6 555 2.8 11500 10.4 50.7 210 13 7 8.8 4.8 29.4 85.0 -1.7 500 2.5 11000 11.6 52.9 215 13 7 8.2 4.5 29.2 84.6 -1.9 446 2.3 10500 12.9 55.2 225 14 7 3.5 1.9 29.1 84.3 -2.1 393 2.0 10250 13.0 55.4 225 14 7 4.7 2.6 28.4 83.1 -2.8 383 1.9 10000 13.7 56.7 225 14 7 11.8 6.5 28.4 83.1 -2.8 354 1.8 9750 14.5 58.1 225 15 8 10.5 5.8 28.5 83.2 -2.7 324 1.6 9500 15.2 59.4 230 15 8 8.8 4.8 28.5 83.4 -2.7 294 1.5 9250 15.7 60.3 230 15 8 6.2 3.4 28.3 82.9 -3.0 273 1.4 9000 16.2 61.2 230 15 8 8.0 4.4 28.1 82.6 -3.2 250 1.3 8750 16.8 62.2 230 15 8 9.0 4.9 28.0 82.4 -3.3 224 1.1 8500 17.5 63.5 230 15 8 8.1 4.4 27.9 82.3 -3.4 198 1.0 8250 18.0 64.4 230 15 8 7.5 4.1 27.8 82.0 -3.6 174 0.9 8000 18.6 65.5 230 15 7 7.7 4.2 27.6 81.7 -3.8 150 0.8 7750 19.1 66.4 230 14 7 7.5 4.1 27.4 81.4 -4.0 126 0.6 7500 19.6 67.3 230 14 7 6.1 3.4 27.2 81.0 -4.2 103 0.5 7250 20.0 68.0 230 14 7 5.1 2.8 26.9 80.4 -4.6 84 0.4 7000 20.4 68.7 230 13 7 5.9 3.2 26.6 79.8 -4.9 64 0.3 6750 20.8 69.4 230 12 6 2.0 1.1 26.2 79.1 -5.3 46 0.2 6500 20.7 69.3 235 11 6 -4.8 -2.6 25.3 77.6 -6.2 43 0.2 6250 20.3 68.5 240 11 6 -3.4 -1.8 24.2 75.5 -7.3 47 0.2 6000 19.9 67.8 245 11 6 -11.7 -6.4 23.1 73.6 -8.4 51 0.3 5750 18.2 64.8 240 10 5 -30.4 -16.7 20.7 69.3 -10.8 95 0.5 5500 15.5 59.9 225 7 4 -35.1 -19.3 17.4 63.3 -14.3 167 0.8 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 10/03/2025 at 0900 MDT | 10/03/2025 at 1200 MDT | CAPE... 0.0 LI... +2.5 | CAPE... 0.0 LI... +2.0 CINH... -0.0 K Index... +12.1 | CINH... -0.1 K Index... +11.9 | 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 -67.4 -89.3 245 44 23 2.7 1.5 | -67.6 -89.7 245 47 24 3.0 1.7 45000 -61.9 -79.4 250 62 32 6.1 3.3 | -61.8 -79.2 245 63 32 6.1 3.3 40000 -52.9 -63.2 255 67 34 5.7 3.1 | -52.7 -62.9 250 71 36 6.0 3.3 38000 -49.4 -56.9 250 59 30 5.7 3.1 | -49.1 -56.4 250 64 33 6.0 3.3 36000 -46.0 -50.8 250 52 27 5.8 3.2 | -45.4 -49.7 245 58 30 6.0 3.3 34000 -41.4 -42.5 240 44 22 7.0 3.9 | -41.0 -41.8 240 50 26 6.7 3.7 32000 -37.2 -35.0 235 37 19 7.0 3.8 | -37.0 -34.6 235 42 22 6.6 3.6 30000 -32.6 -26.7 235 32 16 7.6 4.2 | -32.4 -26.3 230 37 19 7.8 4.3 29000 -30.3 -22.5 235 30 15 7.7 4.2 | -30.1 -22.2 230 35 18 7.8 4.3 28000 -28.0 -18.4 230 27 14 7.7 4.2 | -27.7 -17.9 225 33 17 7.5 4.1 27000 -25.8 -14.4 230 25 13 7.7 4.2 | -25.5 -13.9 225 31 16 7.3 4.0 26000 -23.5 -10.3 225 22 12 7.7 4.2 | -23.4 -10.1 225 28 14 7.3 4.0 25000 -21.2 -6.2 225 20 10 7.7 4.2 | -21.2 -6.2 220 26 13 7.4 4.0 24000 -19.1 -2.4 220 19 10 6.8 3.7 | -19.1 -2.4 220 25 13 6.7 3.7 23000 -17.0 1.4 220 19 10 6.8 3.7 | -17.1 1.2 220 24 13 6.7 3.7 22000 -15.0 5.0 220 18 9 6.9 3.8 | -15.1 4.8 220 24 12 6.7 3.7 21000 -12.9 8.8 220 19 10 7.2 4.0 | -13.1 8.4 220 24 13 6.9 3.8 20000 -10.7 12.7 215 19 10 7.3 4.0 | -11.0 12.2 215 25 13 7.0 3.8 19500 -9.7 14.5 215 19 10 7.3 4.0 | -10.0 14.0 215 25 13 7.0 3.8 19000 -8.6 16.5 210 19 10 6.7 3.7 | -8.5 16.7 215 25 13 6.8 3.7 18500 -7.1 19.2 210 19 10 6.7 3.7 | -7.5 18.5 210 24 12 6.8 3.7 18000 -6.1 21.0 205 19 10 7.2 3.9 | -6.5 20.3 210 23 12 7.6 4.2 17500 -5.1 22.8 205 19 10 7.2 4.0 | -5.3 22.5 205 23 12 7.7 4.2 17000 -4.0 24.8 200 18 10 7.6 4.1 | -4.2 24.4 205 22 11 7.7 4.2 16500 -2.8 27.0 200 18 9 8.1 4.4 | -3.1 26.4 205 21 11 7.7 4.3 16000 -1.7 28.9 195 17 9 8.1 4.4 | -1.9 28.6 205 21 11 7.7 4.2 15500 -0.4 31.3 195 16 8 8.5 4.6 | -0.7 30.7 205 20 10 8.3 4.6 15000 0.8 33.4 200 16 8 8.4 4.6 | 0.5 32.9 205 19 10 8.2 4.5 14500 2.1 35.8 200 15 8 8.7 4.8 | 1.7 35.1 210 18 9 8.8 4.8 14000 3.5 38.3 205 14 7 8.7 4.8 | 3.1 37.6 215 17 9 8.9 4.9 13500 4.8 40.6 210 13 7 8.4 4.6 | 4.4 39.9 215 16 8 8.7 4.8 13000 6.0 42.8 220 12 6 8.2 4.5 | 5.7 42.3 220 15 7 8.6 4.7 12500 7.2 45.0 225 12 6 8.2 4.5 | 6.9 44.4 225 13 7 8.7 4.8 12000 8.3 46.9 235 11 6 8.2 4.5 | 8.2 46.8 230 13 6 8.9 4.9 11500 9.5 49.1 245 11 5 8.3 4.5 | 9.5 49.1 235 12 6 8.7 4.8 11000 10.6 51.1 250 10 5 7.9 4.3 | 10.7 51.3 235 11 6 7.9 4.4 10500 11.8 53.2 260 10 5 3.2 1.7 | 11.9 53.4 230 10 5 3.8 2.1 10250 11.9 53.4 260 10 5 4.0 2.2 | 12.0 53.6 230 9 5 5.5 3.0 10000 12.6 54.7 265 10 5 12.1 6.6 | 12.8 55.0 230 8 4 12.3 6.8 9750 13.5 56.3 265 10 5 12.0 6.6 | 13.6 56.5 230 8 4 10.9 6.0 9500 14.3 57.7 270 10 5 9.1 5.0 | 14.4 57.9 225 7 3 9.7 5.3 9250 14.8 58.6 270 9 5 5.4 3.0 | 15.0 59.0 220 6 3 7.4 4.0 9000 15.3 59.5 275 9 4 8.1 4.4 | 15.6 60.1 220 5 3 9.1 5.0 8750 16.0 60.8 275 9 5 10.2 5.6 | 16.4 61.5 215 5 3 10.5 5.7 8500 16.7 62.1 275 9 5 7.8 4.3 | 17.1 62.8 215 4 2 9.0 4.9 8250 17.2 63.0 280 8 4 5.9 3.2 | 17.7 63.9 205 4 2 7.4 4.0 8000 17.7 63.9 285 8 4 7.2 3.9 | 18.3 64.9 190 4 2 8.7 4.8 7750 18.2 64.8 290 8 4 8.1 4.4 | 19.0 66.2 185 4 2 10.2 5.6 7500 18.8 65.8 290 8 4 6.2 3.4 | 19.7 67.5 180 3 2 8.3 4.5 7250 19.2 66.6 290 7 4 4.6 2.5 | 20.2 68.4 175 3 2 6.5 3.6 7000 19.6 67.3 290 6 3 6.1 3.3 | 20.7 69.3 165 3 2 8.0 4.4 6750 20.0 68.0 290 6 3 4.4 2.4 | 21.4 70.5 165 3 2 11.0 6.1 6500 20.1 68.2 285 5 3 -0.4 -0.2 | 22.3 72.1 165 3 1 11.1 6.1 6250 20.0 68.0 275 5 2 -1.1 -0.6 | 23.1 73.6 165 3 1 10.5 5.7 6000 19.9 67.8 270 4 2 -2.5 -1.4 | 23.8 74.8 160 3 2 9.1 5.0 5750 19.5 67.1 240 4 2 -6.9 -3.8 | 24.6 76.3 165 3 1 13.5 7.4 5500 18.8 65.8 220 4 2 -8.6 -4.7 | 26.0 78.8 160 2 1 26.2 14.4 10/03/2025 at 1500 MDT | 10/03/2025 at 1800 MDT | CAPE... +5.9 LI... +1.3 | CAPE... +41.1 LI... +0.1 CINH... -77.7 K Index... +17.3 | CINH... -27.2 K Index... +28.1 | 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 -67.2 -89.0 245 43 22 2.8 1.6 | -67.2 -89.0 240 45 23 2.5 1.4 45000 -61.5 -78.7 250 63 33 5.8 3.2 | -61.9 -79.4 245 65 33 5.9 3.2 40000 -52.8 -63.0 250 73 38 6.2 3.4 | -53.0 -63.4 245 73 38 6.6 3.6 38000 -49.1 -56.4 245 68 35 6.2 3.4 | -49.0 -56.2 245 69 36 6.6 3.6 36000 -45.4 -49.7 245 63 32 6.2 3.4 | -45.0 -49.0 245 65 33 6.6 3.6 34000 -41.5 -42.7 240 55 29 6.6 3.6 | -41.0 -41.8 240 57 30 6.7 3.7 32000 -37.0 -34.6 235 47 24 6.5 3.5 | -36.4 -33.5 235 49 25 6.7 3.7 30000 -32.5 -26.5 230 43 22 7.8 4.3 | -32.1 -25.8 230 43 22 7.4 4.1 29000 -30.2 -22.4 230 41 21 7.8 4.3 | -29.9 -21.8 230 40 21 7.4 4.1 28000 -27.8 -18.0 225 39 20 7.4 4.0 | -27.7 -17.9 230 38 20 7.3 4.0 27000 -25.7 -14.3 225 37 19 7.0 3.9 | -25.5 -13.9 230 37 19 7.1 3.9 26000 -23.6 -10.5 230 34 17 7.0 3.9 | -23.4 -10.1 230 35 18 7.1 3.9 25000 -21.5 -6.7 230 31 16 7.0 3.8 | -21.3 -6.3 230 34 17 7.1 3.9 24000 -19.3 -2.7 230 30 15 7.5 4.1 | -19.2 -2.6 230 33 17 7.1 3.9 23000 -17.1 1.2 225 30 15 7.5 4.1 | -17.0 1.4 230 31 16 7.1 3.9 22000 -14.9 5.2 225 29 15 7.5 4.1 | -14.9 5.2 230 30 16 7.1 3.9 21000 -12.5 9.5 225 29 15 7.9 4.3 | -12.8 9.0 230 29 15 7.3 4.0 20000 -10.1 13.8 230 30 15 7.9 4.3 | -10.6 12.9 230 28 14 7.4 4.0 19500 -9.0 15.8 230 30 15 7.9 4.4 | -9.5 14.9 230 27 14 7.4 4.1 19000 -7.8 18.0 230 29 15 7.6 4.2 | -8.4 16.9 230 26 13 7.3 4.0 18500 -6.7 19.9 230 29 15 7.5 4.1 | -7.4 18.7 230 25 13 7.3 4.0 18000 -5.5 22.1 225 29 15 7.3 4.0 | -6.3 20.7 230 24 12 7.2 4.0 17500 -4.6 23.7 225 28 14 6.3 3.5 | -5.4 22.3 225 22 12 6.3 3.5 17000 -3.2 26.2 225 27 14 6.3 3.5 | -4.5 23.9 220 21 11 6.4 3.5 16500 -2.3 27.9 225 26 13 6.2 3.4 | -3.1 26.4 210 19 10 7.2 3.9 16000 -1.4 29.5 225 25 13 6.2 3.4 | -2.1 28.2 200 19 10 7.2 3.9 15500 -0.4 31.3 225 24 12 8.6 4.7 | -1.0 30.2 195 18 9 9.1 5.0 15000 0.8 33.4 225 23 12 8.4 4.6 | 0.3 32.5 190 17 9 9.0 5.0 14500 2.0 35.6 220 21 11 8.5 4.6 | 1.6 34.9 185 17 9 9.5 5.2 14000 3.2 37.8 220 20 10 8.5 4.7 | 3.1 37.6 180 16 8 9.7 5.3 13500 4.4 39.9 220 18 9 8.5 4.7 | 4.5 40.1 180 15 8 9.7 5.3 13000 5.7 42.3 215 17 9 8.6 4.7 | 6.0 42.8 180 15 8 9.7 5.3 12500 6.9 44.4 210 15 8 8.6 4.7 | 7.4 45.3 180 15 8 9.6 5.3 12000 8.2 46.8 200 14 7 8.6 4.7 | 8.9 48.0 180 14 7 9.5 5.2 11500 9.5 49.1 195 12 6 8.7 4.8 | 10.3 50.5 175 14 7 9.5 5.2 11000 10.7 51.3 185 10 5 8.6 4.7 | 11.7 53.1 175 13 7 9.4 5.2 10500 12.0 53.6 175 9 5 5.3 2.9 | 13.1 55.6 170 12 6 6.5 3.6 10250 12.3 54.1 170 9 4 6.7 3.7 | 13.5 56.3 170 12 6 7.5 4.1 10000 13.1 55.6 170 8 4 12.1 6.7 | 14.3 57.7 165 11 6 12.0 6.6 9750 13.9 57.0 170 8 4 11.1 6.1 | 15.2 59.4 160 10 5 11.0 6.0 9500 14.7 58.5 165 8 4 9.9 5.4 | 16.0 60.8 160 10 5 10.5 5.8 9250 15.3 59.5 165 8 4 7.7 4.2 | 16.7 62.1 155 9 5 8.5 4.7 9000 16.0 60.8 165 8 4 9.6 5.3 | 17.3 63.1 155 9 4 8.8 4.8 8750 16.8 62.2 160 8 4 10.9 6.0 | 18.0 64.4 150 8 4 9.6 5.2 8500 17.6 63.7 160 8 4 10.4 5.7 | 18.7 65.7 150 8 4 9.4 5.2 8250 18.3 64.9 160 7 4 10.5 5.8 | 19.4 66.9 145 7 4 9.9 5.4 8000 19.1 66.4 160 7 4 10.0 5.5 | 20.2 68.4 140 6 3 9.5 5.2 7750 19.8 67.6 160 7 4 9.2 5.0 | 20.9 69.6 140 6 3 8.9 4.9 7500 20.5 68.9 160 7 4 10.0 5.5 | 21.5 70.7 135 5 3 9.1 5.0 7250 21.3 70.3 160 7 4 10.8 5.9 | 22.2 72.0 130 5 2 9.2 5.1 7000 22.1 71.8 160 7 4 10.1 5.6 | 22.9 73.2 125 4 2 9.3 5.1 6750 22.8 73.0 160 7 3 9.1 5.0 | 23.6 74.5 120 4 2 9.4 5.2 6500 23.5 74.3 160 7 3 9.9 5.4 | 24.3 75.7 115 3 2 9.6 5.3 6250 24.3 75.7 160 6 3 11.3 6.2 | 25.0 77.0 105 3 1 9.6 5.3 6000 25.1 77.2 160 6 3 9.7 5.3 | 25.7 78.3 095 2 1 9.7 5.3 5750 25.9 78.6 160 6 3 12.7 7.0 | 26.4 79.5 075 2 1 8.1 4.5 5500 27.2 81.0 160 6 3 22.2 12.2 | 26.9 80.4 055 2 1 5.4 2.9 ________________________________________________________________________________ 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