Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
328 UXUS97 KBOU 300144 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 1943 MDT Sunday, September 29, 2024 This forecast is for Monday, September 30, 2024: If the trigger temperature of 82.7 F/28.2 C is reached...then Thermal Soaring Index....................... Good Maximum rate of lift........................ 459 ft/min (2.3 m/s) Maximum height of thermals.................. 10978 ft MSL (5683 ft AGL) Forecast maximum temperature................... 84.0 F/29.3 C Time of trigger temperature.................... 1415 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................. 6352 ft MSL (1057 ft AGL) Thermal soaring outlook for Tuesday 10/01...... 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....................... 30646 ft MSL (25351 ft AGL) Wave soaring outlook for Tuesday 10/01......... Poor Remarks... Sunrise/Sunset.................... 06:55:36 / 18:42:51 MDT Total possible sunshine........... 11 hr 47 min 15 sec (707 min 15 sec) Altitude of sun at 12:49:13 MDT... 46.95 degrees Upper air data from numerical model forecast valid on 09/30/2024 at 0600 MDT Freezing level.................. 15604 ft MSL (10309 ft AGL) Convective condensation level... 18222 ft MSL (12927 ft AGL) Lifted condensation level....... 17157 ft MSL (11862 ft AGL) Lifted index.................... +0.2 K index......................... +17.6 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 -63.7 -82.7 255 37 19 3.0 1.6 M M M M M 45000 -58.2 -72.8 255 50 26 4.8 2.6 M M M M M 40000 -50.9 -59.6 250 52 27 5.4 3.0 M M M M M 38000 -47.7 -53.9 250 47 24 5.4 3.0 M M M M M 36000 -44.4 -47.9 255 42 22 5.4 2.9 M M M M M 34000 -41.5 -42.7 255 37 19 4.8 2.6 M M M M M 32000 -38.6 -37.5 260 32 16 4.9 2.7 M M M M M 30000 -34.2 -29.6 270 26 13 7.2 3.9 40.7 105.3 9.0 M M 29000 -32.1 -25.8 275 23 12 7.2 3.9 39.7 103.5 8.3 M M 28000 -29.9 -21.8 280 20 10 7.8 4.3 38.9 102.0 7.7 M M 27000 -27.5 -17.5 280 19 10 8.3 4.5 38.2 100.8 7.2 M M 26000 -25.0 -13.0 285 17 9 8.3 4.5 37.6 99.8 6.8 M M 25000 -22.6 -8.7 290 16 8 8.3 4.6 37.2 99.0 6.5 M M 24000 -20.1 -4.2 295 16 8 8.4 4.6 36.6 97.9 6.1 M M 23000 -17.6 0.3 295 16 8 8.4 4.6 36.1 97.0 5.7 M M 22000 -15.1 4.8 295 17 9 8.1 4.4 35.7 96.3 5.5 M M 21000 -13.0 8.6 290 16 8 7.0 3.8 34.7 94.5 4.7 M M 20000 -10.9 12.4 280 15 8 7.0 3.8 33.7 92.7 3.9 M M 19500 -9.9 14.2 275 15 8 6.9 3.8 33.3 91.9 3.5 M M 19000 -8.8 16.2 270 14 7 7.5 4.1 32.9 91.2 3.1 M M 18500 -7.7 18.1 270 13 7 7.5 4.1 32.5 90.5 2.8 M M 18000 -6.6 20.1 270 12 6 7.9 4.4 32.1 89.8 2.5 M M 17500 -5.3 22.5 270 11 6 8.8 4.8 31.9 89.4 2.3 M M 17000 -4.0 24.8 270 10 5 8.8 4.8 31.7 89.1 2.1 M M 16500 -2.7 27.1 270 9 5 9.0 4.9 31.6 88.9 2.0 M M 16000 -0.7 30.7 275 9 4 9.0 4.9 31.4 88.5 1.8 M M 15500 0.6 33.1 280 9 4 8.9 4.9 31.3 88.3 1.6 M M 15000 1.9 35.4 290 9 5 9.0 4.9 31.1 88.0 1.5 M M 14500 3.2 37.8 295 9 5 8.6 4.7 31.0 87.8 1.4 M M 14000 4.5 40.1 295 10 5 8.6 4.7 30.8 87.4 1.2 M M 13500 5.8 42.4 300 10 5 8.5 4.7 30.6 87.1 1.0 M M 13000 7.0 44.6 300 11 6 8.5 4.7 30.4 86.7 0.8 M M 12500 8.3 46.9 300 12 6 8.5 4.7 30.2 86.4 0.6 M M 12000 9.5 49.1 305 13 7 8.5 4.6 30.0 86.0 0.4 M M 11500 10.8 51.4 305 14 7 8.4 4.6 29.8 85.6 0.2 M M 11000 12.0 53.6 300 14 7 8.1 4.5 29.6 85.2 -0.0 456 2.3 10500 13.3 55.9 300 13 7 4.3 2.4 29.4 84.9 -0.2 405 2.1 10250 13.5 56.3 300 13 7 6.0 3.3 28.8 83.8 -0.8 391 2.0 10000 14.3 57.7 295 13 7 12.2 6.7 28.9 84.0 -0.7 360 1.8 9750 15.1 59.2 295 13 6 11.1 6.1 29.0 84.2 -0.6 328 1.7 9500 15.9 60.6 295 12 6 9.2 5.1 29.1 84.4 -0.5 296 1.5 9250 16.4 61.5 300 12 6 6.3 3.5 28.9 84.0 -0.7 273 1.4 9000 17.0 62.6 300 12 6 9.1 5.0 28.7 83.7 -0.9 249 1.3 8750 17.8 64.0 300 12 6 11.3 6.2 28.8 83.8 -0.9 218 1.1 8500 18.5 65.3 300 12 6 9.4 5.2 28.8 83.9 -0.8 187 0.9 8250 19.1 66.4 305 12 6 7.2 4.0 28.7 83.7 -0.9 162 0.8 8000 19.7 67.5 305 12 6 8.9 4.9 28.6 83.4 -1.1 137 0.7 7750 20.5 68.9 305 12 6 11.6 6.4 28.6 83.5 -1.0 107 0.5 7500 21.3 70.3 305 12 6 9.1 5.0 28.7 83.7 -1.0 75 0.4 7250 21.8 71.2 305 13 7 6.8 3.7 28.5 83.3 -1.2 52 0.3 7000 22.4 72.3 305 14 7 7.9 4.3 28.3 83.0 -1.4 28 0.1 6750 22.9 73.2 300 14 7 5.8 3.2 28.2 82.7 -1.6 5 0.0 6500 23.0 73.4 295 14 7 -2.2 -1.2 27.6 81.7 -2.2 M M 6250 22.6 72.7 290 13 7 -6.8 -3.7 26.4 79.6 -3.4 M M 6000 22.1 71.8 280 12 6 -4.1 -2.2 25.3 77.5 -4.5 6 0.0 5750 21.6 70.9 265 12 6 -11.7 -6.4 24.1 75.3 -5.8 14 0.1 5500 20.0 68.0 250 9 4 -28.5 -15.6 21.8 71.3 -8.1 54 0.3 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 09/30/2024 at 0900 MDT | 09/30/2024 at 1200 MDT | CAPE... 0.0 LI... +0.4 | CAPE... +25.3 LI... -0.0 CINH... -12.8 K Index... +18.2 | CINH... -7.7 K Index... +15.1 | 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 -64.1 -83.4 255 40 20 2.9 1.6 | -63.7 -82.7 255 43 22 2.6 1.4 45000 -58.9 -74.0 260 47 24 4.2 2.3 | -59.5 -75.1 255 47 24 3.5 1.9 40000 -52.5 -62.5 260 37 19 5.7 3.1 | -53.7 -64.7 270 29 15 5.4 3.0 38000 -49.1 -56.4 270 31 16 5.7 3.1 | -50.5 -58.9 290 23 12 5.4 3.0 36000 -45.7 -50.3 280 27 14 5.7 3.1 | -47.2 -53.0 320 21 11 5.3 2.9 34000 -41.9 -43.4 295 23 12 6.4 3.5 | -42.9 -45.2 335 23 12 7.6 4.2 32000 -38.1 -36.6 320 21 11 6.5 3.6 | -38.4 -37.1 340 26 13 7.6 4.2 30000 -33.2 -27.8 325 21 11 7.5 4.1 | -32.6 -26.7 350 23 12 8.8 4.8 29000 -31.0 -23.8 325 21 11 7.5 4.1 | -30.0 -22.0 350 21 11 8.8 4.8 28000 -28.7 -19.7 320 21 11 7.0 3.8 | -27.4 -17.3 355 19 10 7.7 4.2 27000 -26.8 -16.2 310 18 9 6.7 3.7 | -25.2 -13.4 340 18 9 7.3 4.0 26000 -24.8 -12.6 300 16 8 6.7 3.7 | -23.1 -9.6 320 18 9 7.3 4.0 25000 -22.8 -9.0 285 15 8 6.8 3.7 | -20.9 -5.6 305 19 10 7.0 3.9 24000 -20.7 -5.3 280 15 8 7.3 4.0 | -19.3 -2.7 290 18 9 5.0 2.7 23000 -18.5 -1.3 275 14 7 7.4 4.0 | -17.8 -0.0 275 19 10 5.1 2.8 22000 -16.3 2.7 270 13 7 7.4 4.1 | -16.4 2.5 255 21 11 5.8 3.2 21000 -14.1 6.6 270 13 6 7.5 4.1 | -14.3 6.3 255 19 10 7.1 3.9 20000 -11.9 10.6 270 12 6 7.5 4.1 | -12.2 10.0 255 17 9 7.1 3.9 19500 -10.8 12.6 275 11 6 7.5 4.1 | -11.2 11.8 255 16 8 7.0 3.8 19000 -9.7 14.5 275 10 5 7.9 4.3 | -10.0 14.0 260 15 8 8.4 4.6 18500 -8.5 16.7 280 9 5 7.9 4.3 | -8.8 16.2 260 14 7 8.3 4.5 18000 -7.4 18.7 290 8 4 8.3 4.6 | -7.6 18.3 265 13 7 8.3 4.6 17500 -6.1 21.0 300 7 4 8.9 4.9 | -6.3 20.7 270 13 7 8.4 4.6 17000 -4.7 23.5 310 7 4 8.9 4.9 | -5.1 22.8 275 13 7 8.4 4.6 16500 -3.4 25.9 315 7 4 9.0 4.9 | -3.8 25.2 280 13 7 9.1 5.0 16000 -1.4 29.5 325 8 4 9.0 4.9 | -2.5 27.5 285 14 7 9.0 4.9 15500 -0.1 31.8 325 9 5 8.9 4.9 | -0.4 31.3 290 15 8 9.3 5.1 15000 1.2 34.2 325 10 5 8.9 4.9 | 0.9 33.6 290 16 8 9.3 5.1 14500 2.6 36.7 325 11 5 9.1 5.0 | 2.3 36.1 295 17 9 9.3 5.1 14000 3.9 39.0 325 12 6 9.1 5.0 | 3.7 38.7 295 17 9 9.4 5.1 13500 5.3 41.5 325 13 7 9.2 5.0 | 5.1 41.2 295 18 9 9.1 5.0 13000 6.7 44.1 320 14 7 9.2 5.1 | 6.4 43.5 295 18 10 9.1 5.0 12500 8.0 46.4 320 15 8 9.2 5.0 | 7.8 46.0 295 19 10 9.0 4.9 12000 9.4 48.9 320 16 8 9.1 5.0 | 9.1 48.4 300 18 9 8.9 4.9 11500 10.7 51.3 315 16 8 9.0 4.9 | 10.4 50.7 300 18 9 8.7 4.8 11000 12.0 53.6 315 16 8 8.5 4.7 | 11.6 52.9 300 16 8 8.1 4.4 10500 13.3 55.9 315 16 8 4.0 2.2 | 12.9 55.2 300 14 7 3.5 1.9 10250 13.5 56.3 315 16 8 5.5 3.0 | 12.9 55.2 300 15 8 5.0 2.8 10000 14.3 57.7 315 16 8 12.4 6.8 | 13.7 56.7 305 13 7 12.0 6.6 9750 15.1 59.2 315 15 8 11.3 6.2 | 14.5 58.1 305 11 6 11.1 6.1 9500 15.9 60.6 315 15 8 9.0 4.9 | 15.3 59.5 310 9 4 7.9 4.3 9250 16.4 61.5 315 15 8 6.4 3.5 | 15.6 60.1 315 8 4 4.5 2.4 9000 17.0 62.6 315 16 8 9.4 5.1 | 16.1 61.0 320 7 4 8.1 4.4 8750 17.8 64.0 315 15 8 11.1 6.1 | 16.8 62.2 335 6 3 9.7 5.3 8500 18.6 65.5 315 15 8 8.9 4.9 | 17.4 63.3 350 6 3 6.0 3.3 8250 19.1 66.4 310 15 8 6.7 3.7 | 17.7 63.9 005 7 3 2.5 1.3 8000 19.6 67.3 310 15 8 8.4 4.6 | 17.9 64.2 015 7 4 5.8 3.2 7750 20.3 68.5 310 14 7 9.7 5.3 | 18.5 65.3 020 8 4 8.5 4.7 7500 21.0 69.8 315 13 7 7.8 4.3 | 19.1 66.4 020 9 5 6.6 3.6 7250 21.5 70.7 310 13 7 6.1 3.4 | 19.5 67.1 020 9 5 4.7 2.6 7000 22.0 71.6 310 13 7 7.6 4.2 | 19.9 67.8 025 10 5 8.1 4.4 6750 22.5 72.5 305 12 6 6.7 3.7 | 20.7 69.3 025 10 5 12.8 7.0 6500 22.8 73.0 300 11 6 2.2 1.2 | 21.6 70.9 025 10 5 11.0 6.0 6250 22.9 73.2 295 9 5 0.6 0.3 | 22.3 72.1 025 10 5 10.3 5.6 6000 22.9 73.2 280 8 4 0.8 0.5 | 23.1 73.6 030 10 5 7.4 4.1 5750 22.9 73.2 270 8 4 -0.9 -0.5 | 23.6 74.5 030 10 5 11.7 6.4 5500 22.7 72.9 250 6 3 -2.7 -1.5 | 25.1 77.2 030 10 5 28.7 15.8 09/30/2024 at 1500 MDT | 09/30/2024 at 1800 MDT | CAPE... 0.0 LI... +1.0 | CAPE... 0.0 LI... +2.4 CINH... -1.0 K Index... +15.2 | CINH... 0.0 K Index... +12.3 | 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 -64.2 -83.6 260 41 21 1.5 0.8 | -64.0 -83.2 270 38 20 1.8 1.0 45000 -61.3 -78.3 260 44 23 3.3 1.8 | -61.1 -78.0 280 36 19 2.4 1.3 40000 -55.7 -68.3 290 34 17 6.5 3.6 | -56.6 -69.9 310 28 14 7.0 3.9 38000 -51.8 -61.2 305 29 15 6.5 3.6 | -52.4 -62.3 320 30 15 7.1 3.9 36000 -47.9 -54.2 325 28 14 6.4 3.5 | -48.1 -54.6 325 32 16 7.0 3.8 34000 -43.1 -45.6 335 27 14 8.4 4.6 | -43.0 -45.4 325 32 16 8.8 4.8 32000 -38.1 -36.6 340 25 13 8.3 4.6 | -37.7 -35.9 320 31 16 8.8 4.8 30000 -32.3 -26.1 335 21 11 8.7 4.8 | -32.6 -26.7 320 28 14 8.5 4.7 29000 -29.7 -21.5 335 19 10 8.7 4.8 | -30.1 -22.2 320 26 13 8.5 4.7 28000 -27.2 -17.0 330 18 9 8.2 4.5 | -26.9 -16.4 315 24 12 8.4 4.6 27000 -24.7 -12.5 320 19 10 8.1 4.4 | -24.4 -11.9 315 22 11 8.4 4.6 26000 -22.3 -8.1 315 20 10 8.1 4.4 | -21.8 -7.2 310 20 10 8.4 4.6 25000 -19.9 -3.8 305 22 11 7.7 4.2 | -19.3 -2.7 305 18 9 7.7 4.2 24000 -18.1 -0.6 295 22 12 5.7 3.1 | -17.6 0.3 300 20 10 5.7 3.1 23000 -16.5 2.3 285 24 13 5.7 3.1 | -15.9 3.4 290 23 12 5.7 3.1 22000 -14.8 5.4 275 27 14 5.9 3.2 | -14.2 6.4 285 26 13 5.9 3.2 21000 -12.9 8.8 275 27 14 6.3 3.5 | -12.4 9.7 285 27 14 6.2 3.4 20000 -11.1 12.0 275 26 13 6.4 3.5 | -10.6 12.9 280 28 14 6.2 3.4 19500 -10.2 13.6 275 26 13 6.2 3.4 | -9.7 14.5 275 29 15 6.0 3.3 19000 -9.1 15.6 275 25 13 8.6 4.7 | -8.7 16.3 275 29 15 7.6 4.2 18500 -7.8 18.0 275 25 13 8.4 4.6 | -7.6 18.3 275 29 15 7.5 4.1 18000 -6.6 20.1 280 25 13 8.4 4.6 | -6.5 20.3 275 29 15 7.6 4.2 17500 -5.4 22.3 280 25 13 8.2 4.5 | -5.4 22.3 275 29 15 7.8 4.3 17000 -4.2 24.4 280 25 13 8.3 4.5 | -4.3 24.3 275 29 15 7.8 4.3 16500 -3.0 26.6 280 25 13 8.2 4.5 | -3.1 26.4 275 28 14 8.9 4.9 16000 -1.2 29.8 285 25 13 8.3 4.5 | -1.8 28.8 275 27 14 8.8 4.8 15500 0.1 32.2 285 25 13 9.0 4.9 | -0.5 31.1 275 26 13 8.9 4.9 15000 1.4 34.5 285 24 12 9.0 4.9 | 1.5 34.7 270 24 12 9.0 5.0 14500 2.7 36.9 285 23 12 9.0 4.9 | 2.8 37.0 270 23 12 8.4 4.6 14000 4.0 39.2 285 21 11 9.0 4.9 | 4.0 39.2 270 22 11 8.4 4.6 13500 5.3 41.5 285 20 10 8.8 4.8 | 5.2 41.4 265 20 11 6.4 3.5 13000 6.6 43.9 285 19 10 8.7 4.8 | 6.0 42.8 265 19 10 5.7 3.1 12500 7.9 46.2 290 18 9 8.1 4.4 | 6.8 44.2 260 17 9 4.1 2.2 12000 9.0 48.2 290 16 8 7.3 4.0 | 7.2 45.0 260 15 8 2.7 1.5 11500 10.1 50.2 290 14 7 6.3 3.5 | 7.5 45.5 255 12 6 2.0 1.1 11000 10.8 51.4 290 11 5 4.4 2.4 | 7.7 45.9 255 8 4 1.2 0.6 10500 11.4 52.5 295 7 4 1.8 1.0 | 7.8 46.0 250 4 2 1.2 0.7 10250 11.4 52.5 300 6 3 1.6 0.9 | 7.9 46.2 250 3 1 3.2 1.7 10000 11.7 53.1 315 4 2 5.5 3.0 | 8.3 46.9 000 0 0 5.6 3.1 9750 12.1 53.8 350 3 1 5.2 2.8 | 8.8 47.8 065 4 2 6.1 3.4 9500 12.4 54.3 035 3 2 4.6 2.5 | 9.2 48.6 065 7 4 5.9 3.2 9250 12.7 54.9 050 5 2 3.5 1.9 | 9.7 49.5 065 8 4 4.9 2.7 9000 13.0 55.4 055 7 4 5.3 2.9 | 10.1 50.2 060 9 5 8.8 4.8 8750 13.4 56.1 060 9 5 6.1 3.3 | 11.0 51.8 060 11 5 12.1 6.7 8500 13.9 57.0 060 12 6 7.0 3.9 | 11.8 53.2 060 12 6 9.2 5.0 8250 14.4 57.9 060 13 7 7.8 4.3 | 12.4 54.3 060 12 6 7.3 4.0 8000 15.0 59.0 060 13 7 9.0 5.0 | 13.0 55.4 060 12 6 9.9 5.5 7750 15.8 60.4 060 14 7 11.2 6.1 | 13.8 56.8 060 13 6 11.9 6.5 7500 16.6 61.9 060 14 7 9.9 5.5 | 14.7 58.5 060 13 7 9.7 5.3 7250 17.3 63.1 060 14 7 8.8 4.8 | 15.3 59.5 060 13 7 8.0 4.4 7000 18.0 64.4 060 14 7 9.7 5.3 | 16.0 60.8 060 14 7 10.5 5.8 6750 18.8 65.8 060 15 7 11.0 6.0 | 16.8 62.2 060 14 7 11.2 6.1 6500 19.6 67.3 060 15 8 10.7 5.9 | 17.6 63.7 060 14 7 9.3 5.1 6250 20.3 68.5 055 15 8 10.4 5.7 | 18.3 64.9 060 14 7 10.1 5.6 6000 21.1 70.0 055 15 8 9.7 5.3 | 19.0 66.2 060 14 7 8.5 4.7 5750 22.0 71.6 055 14 7 15.5 8.5 | 19.6 67.3 060 14 7 9.6 5.3 5500 23.6 74.5 055 13 7 27.5 15.1 | 20.6 69.1 060 12 6 15.6 8.5 ________________________________________________________________________________ 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