Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
507 UXUS97 KBOU 211235 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 0634 MDT Friday, June 21, 2024 This forecast is for Friday, June 21, 2024: If the trigger temperature of 79.4 F/26.3 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 966 ft/min (4.9 m/s) Maximum height of thermals.................. 16058 ft MSL (10787 ft AGL) Forecast maximum temperature................... 87.0 F/31.0 C Time of trigger temperature.................... 1130 MDT Time of overdevelopment........................ 1600 MDT Middle/high clouds during soaring window....... Overcast opaque high Surface winds during soaring window............ 20 mph or less Height of the -3 thermal index................. 10373 ft MSL (5101 ft AGL) Thermal soaring outlook for Saturday 06/22..... 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....................... 15114 ft MSL (9843 ft AGL) Wave soaring outlook for Saturday 06/22........ Poor Remarks... Sunrise/Sunset.................... 05:31:48 / 20:31:08 MDT Total possible sunshine........... 14 hr 59 min 21 sec (899 min 21 sec) Altitude of sun at 13:01:28 MDT... 73.66 degrees Upper air data from numerical model forecast valid on 06/21/2024 at 0600 MDT Freezing level.................. 15323 ft MSL (10052 ft AGL) Convective condensation level... 13822 ft MSL (8551 ft AGL) Lifted condensation level....... 14307 ft MSL (9036 ft AGL) Lifted index.................... -2.0 K index......................... +26.4 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 -61.9 -79.4 235 48 25 4.9 2.7 M M M M M 45000 -54.7 -66.5 240 71 37 4.1 2.2 M M M M M 40000 -48.3 -54.9 240 86 44 4.9 2.7 M M M M M 38000 -45.4 -49.7 240 77 39 4.9 2.7 M M M M M 36000 -42.4 -44.3 235 67 35 5.9 3.3 M M M M M 34000 -37.0 -34.6 230 65 33 9.3 5.1 M M M M M 32000 -31.4 -24.5 225 63 33 9.2 5.0 M M M M M 30000 -26.4 -15.5 220 56 29 7.3 4.0 50.3 122.6 15.0 M M 29000 -24.2 -11.6 220 53 27 7.3 4.0 49.5 121.0 14.4 M M 28000 -22.1 -7.8 215 49 25 6.2 3.4 48.5 119.4 13.8 M M 27000 -20.3 -4.5 215 45 23 6.3 3.4 47.1 116.8 12.8 M M 26000 -18.4 -1.1 210 40 21 6.3 3.5 45.8 114.4 11.9 M M 25000 -16.6 2.1 210 36 19 6.1 3.3 44.6 112.3 11.1 M M 24000 -15.0 5.0 205 30 15 5.4 3.0 43.0 109.4 9.8 M M 23000 -13.4 7.9 200 24 12 5.5 3.0 41.4 106.5 8.6 M M 22000 -11.8 10.8 195 18 9 5.0 2.8 40.0 103.9 7.4 M M 21000 -10.6 12.9 200 14 7 4.1 2.2 37.9 100.2 5.7 M M 20000 -9.4 15.1 215 12 6 4.1 2.2 35.9 96.6 4.0 M M 19500 -8.8 16.2 220 11 6 3.8 2.1 34.9 94.9 3.2 M M 19000 -8.0 17.6 230 11 6 6.5 3.6 34.1 93.5 2.5 M M 18500 -7.1 19.2 230 12 6 6.5 3.5 33.6 92.4 2.0 M M 18000 -6.2 20.8 230 13 7 6.9 3.8 33.0 91.4 1.5 M M 17500 -5.1 22.8 230 15 8 7.6 4.2 32.6 90.7 1.1 M M 17000 -4.0 24.8 225 16 8 7.6 4.2 32.2 90.0 0.8 M M 16500 -2.9 26.8 225 17 9 7.5 4.1 31.9 89.4 0.4 M M 16000 -1.8 28.8 220 18 9 7.5 4.1 31.5 88.7 0.0 M M 15500 -0.7 30.7 215 20 10 8.2 4.5 31.1 88.0 -0.3 923 4.7 15000 0.5 32.9 215 20 10 8.5 4.7 30.9 87.7 -0.5 870 4.4 14500 1.8 35.2 215 21 11 8.6 4.7 30.7 87.3 -0.7 817 4.2 14000 3.8 38.8 220 21 11 8.9 4.9 30.5 86.9 -1.0 736 3.7 13500 5.1 41.2 225 21 11 8.5 4.7 30.4 86.7 -1.1 682 3.5 13000 6.3 43.3 225 20 10 8.3 4.6 30.1 86.2 -1.3 631 3.2 12500 7.5 45.5 230 20 10 8.4 4.6 29.9 85.8 -1.6 579 2.9 12000 8.8 47.8 230 20 10 8.4 4.6 29.7 85.4 -1.8 527 2.7 11500 10.0 50.0 230 20 10 8.0 4.4 29.5 85.1 -2.0 475 2.4 11000 11.1 52.0 230 19 10 7.1 3.9 29.1 84.4 -2.4 428 2.2 10500 12.1 53.8 230 19 10 3.5 1.9 28.7 83.7 -2.8 382 1.9 10250 12.3 54.1 230 19 10 4.0 2.2 28.1 82.5 -3.5 371 1.9 10000 12.8 55.0 225 19 10 9.7 5.3 28.0 82.3 -3.6 346 1.8 9750 13.5 56.3 225 19 10 9.3 5.1 27.9 82.2 -3.7 319 1.6 9500 14.1 57.4 225 19 10 7.6 4.2 27.9 82.2 -3.8 293 1.5 9250 14.5 58.1 220 19 10 4.9 2.7 27.6 81.6 -4.1 273 1.4 9000 14.9 58.8 220 19 10 6.5 3.6 27.2 81.0 -4.5 254 1.3 8750 15.4 59.7 220 19 10 8.1 4.4 27.1 80.7 -4.7 231 1.2 8500 16.0 60.8 215 20 10 6.4 3.5 26.9 80.4 -4.9 208 1.1 8250 16.3 61.3 215 20 10 5.0 2.7 26.6 79.8 -5.3 189 1.0 8000 16.7 62.1 215 20 10 5.6 3.1 26.2 79.2 -5.7 171 0.9 7750 17.1 62.8 210 19 10 6.1 3.3 25.9 78.6 -6.0 152 0.8 7500 17.5 63.5 210 19 10 5.7 3.2 25.6 78.1 -6.3 132 0.7 7250 17.9 64.2 210 19 10 5.5 3.0 25.3 77.5 -6.7 113 0.6 7000 18.3 64.9 205 19 10 5.5 3.0 25.0 77.0 -7.1 95 0.5 6750 18.6 65.5 205 19 10 3.9 2.1 24.6 76.3 -7.5 78 0.4 6500 18.8 65.8 205 19 10 2.8 1.5 24.1 75.4 -8.1 65 0.3 6250 18.9 66.0 200 17 9 2.0 1.1 23.6 74.4 -8.7 53 0.3 6000 19.1 66.4 200 16 8 5.3 2.9 23.0 73.4 -9.3 41 0.2 5750 19.5 67.1 195 16 8 3.1 1.7 22.8 73.0 -9.6 22 0.1 5500 19.1 66.4 195 11 6 -10.3 -5.7 21.7 71.1 -10.7 25 0.1 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 06/21/2024 at 0900 MDT | 06/21/2024 at 1200 MDT | CAPE... 0.0 LI... +1.7 | CAPE... +0.6 LI... +1.8 CINH... 0.0 K Index... +26.2 | CINH... -45.3 K Index... +16.6 | 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 -63.2 -81.8 230 53 27 4.1 2.2 | -62.9 -81.2 235 57 29 3.9 2.2 45000 -56.1 -69.0 240 74 38 5.2 2.9 | -56.0 -68.8 240 77 40 5.1 2.8 40000 -48.0 -54.4 240 84 43 6.6 3.6 | -47.9 -54.2 240 91 47 6.8 3.7 38000 -44.0 -47.2 235 79 40 6.6 3.6 | -43.8 -46.8 235 85 44 6.8 3.7 36000 -40.1 -40.2 230 74 38 6.5 3.6 | -39.7 -39.5 230 80 41 6.6 3.6 34000 -36.3 -33.3 225 65 33 6.3 3.5 | -36.3 -33.3 230 73 38 5.7 3.1 32000 -32.5 -26.5 220 56 29 6.1 3.3 | -32.9 -27.2 225 67 35 5.6 3.1 30000 -27.2 -17.0 215 51 26 8.2 4.5 | -29.0 -20.2 225 60 31 6.7 3.7 29000 -24.8 -12.6 215 48 25 8.3 4.5 | -26.5 -15.7 225 56 29 6.7 3.7 28000 -22.4 -8.3 215 46 24 7.5 4.1 | -24.4 -11.9 225 52 27 7.8 4.3 27000 -20.2 -4.4 220 45 23 7.5 4.1 | -22.1 -7.8 225 50 25 7.7 4.2 26000 -18.0 -0.4 225 43 22 7.6 4.1 | -19.8 -3.6 225 47 24 7.8 4.3 25000 -15.8 3.6 235 42 22 7.3 4.0 | -17.5 0.5 225 44 23 7.6 4.2 24000 -13.8 7.2 235 39 20 6.5 3.6 | -15.4 4.3 230 38 20 7.4 4.1 23000 -11.9 10.6 240 34 18 6.5 3.6 | -13.2 8.2 240 33 17 7.5 4.1 22000 -10.0 14.0 245 31 16 6.4 3.5 | -11.0 12.2 255 29 15 7.4 4.1 21000 -8.2 17.2 245 29 15 6.3 3.4 | -8.9 16.0 260 23 12 7.1 3.9 20000 -6.4 20.5 245 27 14 6.3 3.5 | -6.8 19.8 265 17 9 7.1 3.9 19500 -5.5 22.1 245 26 13 6.4 3.5 | -5.7 21.7 275 15 8 7.0 3.8 19000 -4.6 23.7 245 25 13 5.3 2.9 | -4.6 23.7 280 13 7 7.9 4.3 18500 -3.9 25.0 245 24 12 5.3 2.9 | -3.4 25.9 290 12 6 7.8 4.3 18000 -3.1 26.4 245 23 12 5.3 2.9 | -2.2 28.0 300 11 6 7.5 4.1 17500 -2.4 27.7 245 22 11 5.5 3.0 | -1.2 29.8 305 11 5 7.0 3.8 17000 -1.6 29.1 250 21 11 5.5 3.0 | -0.2 31.6 305 11 5 7.2 4.0 16500 -0.8 30.6 250 20 10 5.6 3.1 | 0.7 33.3 310 11 6 4.7 2.6 16000 0.4 32.7 245 19 10 5.7 3.1 | 1.4 34.5 310 11 6 4.9 2.7 15500 1.2 34.2 245 18 9 5.3 2.9 | 2.0 35.6 310 12 6 4.9 2.7 15000 1.9 35.4 240 17 9 5.3 2.9 | 2.7 36.9 315 13 7 4.8 2.7 14500 2.7 36.9 240 16 8 5.8 3.2 | 3.4 38.1 315 14 7 5.0 2.8 14000 3.6 38.5 235 15 8 6.0 3.3 | 4.6 40.3 315 15 8 5.8 3.2 13500 4.4 39.9 230 15 7 6.2 3.4 | 5.4 41.7 315 16 8 6.4 3.5 13000 5.4 41.7 230 13 7 6.5 3.6 | 6.4 43.5 315 17 9 6.8 3.7 12500 6.3 43.3 225 12 6 6.4 3.5 | 7.4 45.3 315 17 9 6.8 3.7 12000 7.2 45.0 225 11 6 5.8 3.2 | 8.4 47.1 315 17 9 6.7 3.7 11500 8.0 46.4 225 9 5 5.8 3.2 | 9.4 48.9 315 17 9 6.8 3.7 11000 8.9 48.0 225 8 4 5.9 3.3 | 10.4 50.7 320 16 8 6.8 3.7 10500 9.8 49.6 220 7 4 4.5 2.5 | 11.4 52.5 320 16 8 3.0 1.6 10250 10.0 50.0 220 7 4 3.8 2.1 | 11.5 52.7 320 16 8 3.9 2.1 10000 10.4 50.7 220 6 3 6.5 3.5 | 12.1 53.8 320 15 8 9.7 5.3 9750 10.9 51.6 220 6 3 7.2 4.0 | 12.7 54.9 325 14 7 8.7 4.8 9500 11.4 52.5 220 5 3 6.8 3.7 | 13.3 55.9 325 14 7 7.4 4.1 9250 11.9 53.4 215 5 2 6.2 3.4 | 13.7 56.7 325 12 6 4.9 2.7 9000 12.3 54.1 215 4 2 5.4 2.9 | 14.1 57.4 325 10 5 6.5 3.6 8750 12.7 54.9 210 4 2 5.1 2.8 | 14.5 58.1 330 8 4 7.5 4.1 8500 13.1 55.6 210 3 2 5.1 2.8 | 15.0 59.0 335 5 3 8.1 4.5 8250 13.5 56.3 205 3 1 5.1 2.8 | 15.6 60.1 340 4 2 8.8 4.8 8000 13.8 56.8 195 2 1 4.8 2.6 | 16.3 61.3 345 4 2 9.9 5.4 7750 14.1 57.4 185 2 1 4.5 2.5 | 17.1 62.8 345 4 2 11.7 6.4 7500 14.5 58.1 175 2 1 4.1 2.2 | 17.9 64.2 345 3 2 10.5 5.8 7250 14.7 58.5 175 3 1 3.8 2.1 | 18.7 65.7 350 3 2 9.6 5.2 7000 15.0 59.0 175 3 2 3.7 2.0 | 19.4 66.9 350 3 2 9.7 5.3 6750 15.3 59.5 175 4 2 4.2 2.3 | 20.1 68.2 350 3 2 9.9 5.5 6500 15.7 60.3 180 4 2 7.3 4.0 | 20.9 69.6 355 3 1 10.6 5.8 6250 16.3 61.3 190 6 3 9.6 5.3 | 21.7 71.1 355 3 1 11.5 6.3 6000 17.0 62.6 195 7 4 7.3 4.0 | 22.5 72.5 360 3 1 9.4 5.1 5750 17.6 63.7 200 9 5 11.3 6.2 | 23.3 73.9 360 3 1 15.8 8.7 5500 18.9 66.0 205 9 5 24.1 13.2 | 25.1 77.2 360 2 1 32.2 17.7 06/21/2024 at 1500 MDT | 06/21/2024 at 1800 MDT | CAPE... +211.0 LI... -1.1 | CAPE... +247.3 LI... -2.0 CINH... -81.6 K Index... +22.3 | CINH... -27.9 K Index... +32.8 | 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 -62.9 -81.2 235 55 29 4.6 2.5 | -62.1 -79.8 240 52 27 4.9 2.7 45000 -55.3 -67.5 245 76 39 5.1 2.8 | -54.4 -65.9 245 74 38 4.8 2.6 40000 -47.2 -53.0 240 97 50 6.5 3.6 | -46.8 -52.2 245 101 52 6.1 3.4 38000 -43.3 -45.9 240 89 46 6.5 3.6 | -43.1 -45.6 245 93 48 6.1 3.3 36000 -39.4 -38.9 235 82 42 6.4 3.5 | -39.5 -39.1 240 85 44 6.0 3.3 34000 -35.9 -32.6 230 79 41 5.7 3.1 | -36.2 -33.2 240 74 38 5.5 3.0 32000 -32.5 -26.5 230 77 40 5.6 3.1 | -32.5 -26.5 245 60 31 6.6 3.6 30000 -28.5 -19.3 230 69 35 6.1 3.3 | -28.2 -18.8 245 48 24 7.2 4.0 29000 -26.7 -16.1 230 65 33 6.0 3.3 | -26.1 -15.0 240 41 21 7.2 4.0 28000 -24.8 -12.6 230 61 31 7.3 4.0 | -24.0 -11.2 240 35 18 7.2 4.0 27000 -22.6 -8.7 230 57 29 7.3 4.0 | -21.8 -7.2 240 32 16 7.3 4.0 26000 -20.4 -4.7 230 53 27 7.3 4.0 | -19.7 -3.5 240 28 14 7.3 4.0 25000 -18.3 -0.9 230 49 25 7.2 3.9 | -17.5 0.5 240 24 12 7.1 3.9 24000 -16.2 2.8 230 44 23 7.0 3.8 | -15.6 3.9 235 22 12 6.7 3.7 23000 -14.2 6.4 230 39 20 7.1 3.9 | -13.6 7.5 235 21 11 6.7 3.7 22000 -12.1 10.2 235 35 18 7.2 4.0 | -11.7 10.9 230 19 10 6.5 3.6 21000 -10.1 13.8 235 26 14 7.0 3.8 | -9.9 14.2 225 18 10 6.3 3.4 20000 -8.0 17.6 235 18 9 7.0 3.8 | -8.0 17.6 225 18 9 6.3 3.5 19500 -6.9 19.6 240 14 7 6.8 3.8 | -7.1 19.2 220 17 9 6.3 3.5 19000 -5.8 21.6 240 11 6 8.5 4.6 | -6.2 20.8 220 17 9 6.2 3.4 18500 -4.5 23.9 245 11 6 8.3 4.5 | -5.3 22.5 215 17 9 6.2 3.4 18000 -3.2 26.2 250 11 6 7.7 4.2 | -4.4 24.1 215 17 9 6.3 3.5 17500 -2.2 28.0 255 12 6 6.9 3.8 | -3.5 25.7 215 16 8 6.5 3.5 17000 -1.3 29.7 260 13 7 6.9 3.8 | -2.6 27.3 215 15 8 6.4 3.5 16500 -0.2 31.6 265 14 7 7.7 4.2 | -1.6 29.1 215 14 7 7.0 3.9 16000 0.9 33.6 265 15 8 7.7 4.2 | -0.6 30.9 215 14 7 7.0 3.8 15500 2.0 35.6 270 16 8 8.1 4.4 | 0.4 32.7 215 13 7 7.7 4.2 15000 3.7 38.7 275 18 9 8.4 4.6 | 1.6 34.9 210 12 6 8.1 4.5 14500 4.9 40.8 280 19 10 7.8 4.3 | 2.8 37.0 210 12 6 8.3 4.5 14000 5.9 42.6 280 19 10 7.7 4.2 | 4.6 40.3 205 11 6 8.6 4.7 13500 7.0 44.6 285 19 10 7.9 4.3 | 5.9 42.6 205 11 5 8.0 4.4 13000 8.2 46.8 285 19 10 7.9 4.4 | 7.0 44.6 205 10 5 7.7 4.2 12500 9.3 48.7 285 18 9 7.8 4.3 | 8.2 46.8 205 8 4 7.7 4.2 12000 10.4 50.7 285 17 9 7.5 4.1 | 9.3 48.7 200 7 3 7.8 4.3 11500 11.4 52.5 285 15 8 6.9 3.8 | 10.4 50.7 200 5 2 8.0 4.4 11000 12.2 54.0 290 11 6 4.8 2.6 | 11.6 52.9 200 3 1 8.1 4.5 10500 12.9 55.2 290 6 3 2.5 1.4 | 12.9 55.2 195 1 0 3.1 1.7 10250 13.1 55.6 290 6 3 4.5 2.5 | 12.9 55.2 000 0 0 4.7 2.6 10000 13.6 56.5 295 4 2 9.1 5.0 | 13.7 56.7 000 0 0 12.7 6.9 9750 14.2 57.6 320 1 1 8.0 4.4 | 14.6 58.3 275 1 0 10.9 6.0 9500 14.8 58.6 065 1 1 7.8 4.3 | 15.4 59.7 290 1 0 9.9 5.5 9250 15.3 59.5 080 2 1 7.9 4.3 | 16.0 60.8 295 1 1 8.5 4.6 9000 16.0 60.8 080 2 1 10.2 5.6 | 16.7 62.1 295 1 1 10.4 5.7 8750 16.8 62.2 080 2 1 11.4 6.2 | 17.6 63.7 300 2 1 11.6 6.4 8500 17.6 63.7 080 2 1 10.5 5.8 | 18.4 65.1 300 2 1 10.3 5.7 8250 18.4 65.1 080 2 1 9.8 5.4 | 19.1 66.4 300 2 1 8.7 4.8 8000 19.1 66.4 080 2 1 9.9 5.4 | 19.8 67.6 300 3 1 9.9 5.4 7750 19.9 67.8 075 2 1 10.0 5.5 | 20.6 69.1 300 3 2 11.1 6.1 7500 20.6 69.1 075 2 1 10.0 5.5 | 21.4 70.5 300 3 2 10.1 5.6 7250 21.4 70.5 075 2 1 10.1 5.5 | 22.1 71.8 300 4 2 9.4 5.2 7000 22.1 71.8 075 2 1 10.1 5.6 | 22.8 73.0 300 4 2 9.9 5.4 6750 22.9 73.2 075 2 1 10.5 5.7 | 23.6 74.5 300 4 2 10.5 5.8 6500 23.7 74.7 075 2 1 10.7 5.9 | 24.3 75.7 300 5 2 10.1 5.5 6250 24.5 76.1 075 2 1 11.3 6.2 | 25.1 77.2 300 5 3 9.5 5.2 6000 25.3 77.5 075 2 1 9.7 5.3 | 25.8 78.4 300 5 3 10.0 5.5 5750 26.1 79.0 075 2 1 14.8 8.1 | 26.6 79.9 300 6 3 10.7 5.9 5500 27.7 81.9 070 3 1 29.7 16.3 | 27.4 81.3 305 5 3 10.7 5.9 ________________________________________________________________________________ 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