Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
487 UXUS97 KBOU 200022 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 1820 MDT Wednesday, June 19, 2024 This forecast is for Thursday, June 20, 2024: If the trigger temperature of 79.7 F/26.5 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 1170 ft/min (5.9 m/s) Maximum height of thermals.................. 16305 ft MSL (11041 ft AGL) Forecast maximum temperature................... 89.0 F/32.1 C Time of trigger temperature.................... 1130 MDT Time of overdevelopment........................ 1800 MDT Middle/high clouds during soaring window....... None Surface winds during soaring window............ 20 mph or less Height of the -3 thermal index................. 11105 ft MSL (5840 ft AGL) Thermal soaring outlook for Friday 06/21....... 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....................... 46387 ft MSL (41123 ft AGL) Wave soaring outlook for Friday 06/21.......... Poor Remarks... Sunrise/Sunset.................... 05:31:34 / 20:30:56 MDT Total possible sunshine........... 14 hr 59 min 22 sec (899 min 22 sec) Altitude of sun at 13:01:15 MDT... 73.67 degrees Upper air data from numerical model forecast valid on 06/20/2024 at 0600 MDT Freezing level.................. 15665 ft MSL (10401 ft AGL) Convective condensation level... 14404 ft MSL (9140 ft AGL) Lifted condensation level....... 15005 ft MSL (9740 ft AGL) Lifted index.................... -5.0 K index......................... +27.0 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 -61.6 -78.9 235 60 31 1.3 0.7 M M M M M 45000 -58.0 -72.4 240 83 43 4.5 2.4 M M M M M 40000 -51.2 -60.2 235 73 38 5.3 2.9 M M M M M 38000 -48.0 -54.4 235 65 33 5.3 2.9 M M M M M 36000 -44.9 -48.8 235 56 29 5.1 2.8 M M M M M 34000 -40.7 -41.3 230 52 27 7.4 4.0 M M M M M 32000 -36.2 -33.2 225 50 26 7.2 4.0 M M M M M 30000 -31.3 -24.3 225 46 24 7.4 4.0 44.5 112.1 9.7 M M 29000 -29.0 -20.2 225 44 23 7.4 4.0 43.6 110.5 9.2 M M 28000 -26.8 -16.2 230 42 22 7.0 3.8 42.8 109.0 8.6 M M 27000 -24.8 -12.6 230 41 21 6.9 3.8 41.6 106.9 7.8 M M 26000 -22.7 -8.9 235 40 20 6.9 3.8 40.5 105.0 7.0 M M 25000 -20.6 -5.1 240 39 20 7.1 3.9 39.6 103.3 6.3 M M 24000 -18.4 -1.1 240 37 19 7.6 4.2 38.7 101.7 5.6 M M 23000 -16.2 2.8 240 36 18 7.6 4.2 37.9 100.2 5.0 M M 22000 -13.9 7.0 240 35 18 7.4 4.1 37.3 99.1 4.5 M M 21000 -11.9 10.6 240 31 16 6.9 3.8 36.2 97.1 3.5 M M 20000 -9.9 14.2 240 28 15 7.0 3.8 35.2 95.3 2.7 M M 19500 -8.9 16.0 240 27 14 6.9 3.8 34.7 94.5 2.2 M M 19000 -7.8 18.0 240 25 13 7.7 4.2 34.3 93.8 1.9 M M 18500 -6.7 19.9 240 23 12 7.6 4.2 33.9 93.1 1.5 M M 18000 -5.6 21.9 240 21 11 7.6 4.2 33.6 92.5 1.2 M M 17500 -4.5 23.9 245 20 10 7.6 4.2 33.2 91.8 0.8 M M 17000 -3.4 25.9 245 19 10 7.6 4.2 32.9 91.1 0.5 M M 16500 -2.3 27.9 245 18 9 8.2 4.5 32.5 90.6 0.2 M M 16000 -1.1 30.0 250 17 9 8.2 4.5 32.3 90.1 -0.1 949 4.8 15500 0.1 32.2 250 17 9 8.0 4.4 32.0 89.6 -0.4 898 4.6 15000 1.3 34.3 245 16 8 8.0 4.4 31.7 89.1 -0.7 849 4.3 14500 2.4 36.3 240 14 7 8.1 4.5 31.4 88.5 -1.0 800 4.1 14000 4.3 39.7 230 15 8 8.5 4.7 31.1 87.9 -1.4 722 3.7 13500 5.5 41.9 230 16 8 8.4 4.6 30.9 87.6 -1.6 670 3.4 13000 6.7 44.1 225 18 9 8.4 4.6 30.6 87.2 -1.8 619 3.1 12500 8.0 46.4 225 19 10 8.2 4.5 30.4 86.8 -2.1 568 2.9 12000 9.1 48.4 220 21 11 8.0 4.4 30.2 86.3 -2.4 518 2.6 11500 10.2 50.4 220 23 12 7.8 4.3 29.9 85.8 -2.7 469 2.4 11000 11.3 52.3 220 23 12 7.2 4.0 29.5 85.1 -3.1 422 2.1 10500 12.4 54.3 215 24 12 3.9 2.2 29.2 84.5 -3.5 375 1.9 10250 12.5 54.5 215 24 12 3.2 1.7 28.5 83.3 -4.1 364 1.9 10000 13.0 55.4 215 24 12 8.5 4.7 28.3 82.9 -4.4 342 1.7 9750 13.6 56.5 210 25 13 9.7 5.3 28.2 82.8 -4.5 316 1.6 9500 14.3 57.7 210 25 13 6.4 3.5 28.2 82.7 -4.6 289 1.5 9250 14.5 58.1 210 25 13 2.2 1.2 27.7 81.8 -5.1 274 1.4 9000 14.8 58.6 210 25 13 4.4 2.4 27.2 80.9 -5.6 260 1.3 8750 15.2 59.4 210 24 13 6.7 3.7 26.8 80.3 -5.9 241 1.2 8500 15.5 59.9 210 24 12 2.6 1.4 26.5 79.7 -6.3 222 1.1 8250 15.5 59.9 210 24 12 -0.4 -0.2 25.8 78.4 -7.1 215 1.1 8000 15.5 59.9 210 24 12 -0.5 -0.3 25.0 77.0 -7.8 208 1.1 7750 15.3 59.5 210 23 12 -2.2 -1.2 24.2 75.5 -8.7 206 1.0 7500 15.2 59.4 210 22 11 -0.3 -0.1 23.3 73.9 -9.7 203 1.0 7250 15.2 59.4 210 21 11 1.2 0.7 22.6 72.7 -10.4 194 1.0 7000 15.3 59.5 210 21 11 0.8 0.5 21.9 71.5 -11.1 185 0.9 6750 15.3 59.5 215 20 10 0.4 0.2 21.2 70.2 -11.8 177 0.9 6500 15.3 59.5 210 18 9 0.2 0.1 20.5 68.9 -12.6 171 0.9 6250 15.2 59.4 205 16 8 -0.1 -0.0 19.8 67.6 -13.4 164 0.8 6000 15.2 59.4 200 14 7 1.5 0.8 19.1 66.3 -14.2 157 0.8 5750 15.4 59.7 200 12 6 1.9 1.1 18.5 65.4 -14.7 145 0.7 5500 15.4 59.7 195 9 4 -2.3 -1.3 17.8 64.0 -15.6 139 0.7 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 06/20/2024 at 0900 MDT | 06/20/2024 at 1200 MDT | CAPE... +350.1 LI... -1.8 | CAPE... +639.8 LI... -2.7 CINH... -143.8 K Index... +23.8 | CINH... -26.5 K Index... +23.7 | 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 -61.1 -78.0 235 62 32 1.8 1.0 | -62.1 -79.8 235 65 33 2.0 1.1 45000 -57.5 -71.5 235 79 41 3.6 2.0 | -58.1 -72.6 245 80 41 4.1 2.2 40000 -51.5 -60.7 235 70 36 6.4 3.5 | -51.4 -60.5 235 67 34 7.2 3.9 38000 -47.7 -53.9 235 62 32 6.4 3.5 | -47.0 -52.6 235 61 32 7.2 4.0 36000 -43.8 -46.8 235 54 28 6.4 3.5 | -42.7 -44.9 235 56 29 7.4 4.0 34000 -39.5 -39.1 230 47 24 6.5 3.6 | -38.6 -37.5 230 49 25 5.8 3.2 32000 -35.6 -32.1 225 43 22 6.8 3.7 | -35.1 -31.2 230 43 22 6.0 3.3 30000 -31.4 -24.5 225 39 20 7.0 3.8 | -30.9 -23.6 225 40 20 7.1 3.9 29000 -29.4 -20.9 225 38 19 7.0 3.8 | -28.8 -19.8 225 38 20 7.1 3.9 28000 -27.3 -17.1 225 36 19 6.9 3.8 | -26.7 -16.1 225 37 19 6.7 3.7 27000 -25.2 -13.4 225 35 18 6.9 3.8 | -24.7 -12.5 225 35 18 6.6 3.6 26000 -23.2 -9.8 230 33 17 6.9 3.8 | -22.7 -8.9 225 33 17 6.6 3.6 25000 -21.1 -6.0 230 32 17 7.0 3.9 | -20.8 -5.4 225 32 16 6.8 3.7 24000 -18.9 -2.0 230 31 16 7.5 4.1 | -18.6 -1.5 225 30 15 7.4 4.0 23000 -16.7 1.9 230 30 15 7.5 4.1 | -16.4 2.5 225 27 14 7.4 4.1 22000 -14.4 6.1 230 29 15 7.5 4.1 | -14.2 6.4 225 25 13 7.4 4.1 21000 -12.3 9.9 230 28 14 7.4 4.1 | -12.0 10.4 225 24 12 7.4 4.0 20000 -10.1 13.8 230 27 14 7.5 4.1 | -9.9 14.2 225 23 12 7.4 4.1 19500 -9.0 15.8 225 27 14 7.5 4.1 | -8.8 16.2 225 23 12 7.4 4.1 19000 -7.9 17.8 225 26 13 8.1 4.4 | -7.7 18.1 225 22 11 7.8 4.3 18500 -6.7 19.9 225 25 13 8.0 4.4 | -6.5 20.3 225 22 11 7.8 4.3 18000 -5.6 21.9 225 24 12 8.1 4.5 | -5.4 22.3 225 21 11 8.3 4.5 17500 -3.7 25.3 225 23 12 8.3 4.5 | -3.5 25.7 225 21 11 8.7 4.8 17000 -2.5 27.5 225 22 11 8.4 4.6 | -2.2 28.0 230 21 11 8.6 4.7 16500 -1.3 29.7 225 22 11 8.5 4.7 | -1.0 30.2 225 21 11 8.5 4.7 16000 0.0 32.0 225 21 11 8.5 4.7 | 0.3 32.5 225 20 10 8.5 4.7 15500 1.2 34.2 225 21 11 8.1 4.5 | 1.5 34.7 225 20 10 8.7 4.8 15000 2.4 36.3 220 19 10 8.1 4.5 | 2.8 37.0 225 20 10 8.7 4.7 14500 3.6 38.5 220 19 10 8.7 4.8 | 4.1 39.4 225 20 10 9.0 4.9 14000 4.9 40.8 220 19 10 8.7 4.8 | 5.4 41.7 225 20 10 9.0 4.9 13500 6.2 43.2 220 19 10 8.5 4.7 | 6.7 44.1 225 19 10 9.0 4.9 13000 7.5 45.5 220 19 10 8.5 4.6 | 8.0 46.4 225 19 10 9.0 4.9 12500 8.7 47.7 220 20 10 8.4 4.6 | 9.3 48.7 225 19 10 8.8 4.9 12000 9.9 49.8 220 20 10 8.3 4.6 | 10.6 51.1 225 18 9 8.7 4.8 11500 11.1 52.0 220 21 11 8.1 4.4 | 11.9 53.4 225 17 9 8.5 4.7 11000 12.3 54.1 220 22 11 7.5 4.1 | 13.1 55.6 225 16 8 7.9 4.3 10500 13.4 56.1 225 22 12 3.7 2.1 | 14.3 57.7 220 15 8 3.4 1.9 10250 13.5 56.3 225 23 12 4.1 2.3 | 14.4 57.9 220 15 8 5.1 2.8 10000 14.1 57.4 225 23 12 9.7 5.3 | 15.2 59.4 220 15 8 12.2 6.7 9750 14.7 58.5 225 23 12 9.2 5.0 | 16.0 60.8 220 14 7 11.2 6.1 9500 15.4 59.7 225 24 12 6.9 3.8 | 16.8 62.2 215 14 7 8.2 4.5 9250 15.7 60.3 225 24 13 3.8 2.1 | 17.2 63.0 215 14 7 5.9 3.2 9000 16.0 60.8 220 25 13 6.3 3.4 | 17.8 64.0 215 14 7 10.1 5.6 8750 16.5 61.7 220 25 13 8.5 4.6 | 18.6 65.5 215 14 7 11.7 6.4 8500 17.0 62.6 220 25 13 5.7 3.1 | 19.3 66.7 210 14 7 9.4 5.2 8250 17.3 63.1 220 25 13 3.0 1.7 | 19.9 67.8 210 14 7 6.8 3.7 8000 17.6 63.7 220 25 13 4.7 2.6 | 20.4 68.7 210 14 7 9.9 5.4 7750 17.9 64.2 220 25 13 5.7 3.1 | 21.3 70.3 210 14 7 12.2 6.7 7500 18.2 64.8 220 24 12 1.6 0.9 | 22.1 71.8 210 14 7 9.4 5.2 7250 18.1 64.6 215 22 11 -1.2 -0.7 | 22.7 72.9 210 14 7 7.3 4.0 7000 18.0 64.4 215 20 11 -0.7 -0.4 | 23.3 73.9 210 14 7 10.1 5.5 6750 18.0 64.4 210 18 9 3.7 2.0 | 24.2 75.6 205 13 7 13.2 7.3 6500 18.5 65.3 205 15 8 9.1 5.0 | 25.1 77.2 205 13 7 11.3 6.2 6250 19.2 66.6 205 14 7 9.7 5.3 | 25.9 78.6 205 13 7 9.9 5.4 6000 19.9 67.8 205 13 7 8.8 4.8 | 26.6 79.9 205 13 7 10.1 5.6 5750 20.7 69.3 205 14 7 13.0 7.1 | 27.5 81.5 205 12 6 17.0 9.3 5500 22.0 71.6 200 12 6 22.2 12.2 | 29.3 84.7 205 11 6 28.9 15.8 06/20/2024 at 1500 MDT | 06/20/2024 at 1800 MDT | CAPE... +665.2 LI... -2.5 | CAPE... +306.4 LI... -3.1 CINH... -4.7 K Index... +28.5 | CINH... -120.6 K Index... +34.2 | 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 -81.8 240 67 34 2.5 1.4 | -62.9 -81.2 245 56 29 2.0 1.1 45000 -58.2 -72.8 245 77 40 5.0 2.8 | -58.0 -72.4 245 68 35 5.8 3.2 40000 -49.9 -57.8 240 67 35 6.5 3.6 | -48.9 -56.0 240 69 36 5.5 3.0 38000 -46.0 -50.8 240 61 31 6.5 3.6 | -45.6 -50.1 240 61 32 5.5 3.0 36000 -42.2 -44.0 235 55 28 6.5 3.6 | -42.3 -44.1 235 53 27 6.4 3.5 34000 -38.2 -36.8 235 49 25 6.6 3.6 | -37.6 -35.7 240 44 23 7.9 4.3 32000 -34.3 -29.7 235 43 22 6.5 3.5 | -32.9 -27.2 245 35 18 8.6 4.7 30000 -30.1 -22.2 235 37 19 7.1 3.9 | -28.7 -19.7 245 33 17 7.0 3.8 29000 -28.0 -18.4 235 34 17 7.1 3.9 | -26.6 -15.9 245 32 17 7.0 3.8 28000 -25.9 -14.6 235 31 16 7.1 3.9 | -24.5 -12.1 245 32 16 7.5 4.1 27000 -23.3 -9.9 235 30 15 7.1 3.9 | -21.6 -6.9 245 30 15 7.8 4.3 26000 -21.2 -6.2 235 29 15 7.1 3.9 | -19.3 -2.7 245 28 14 7.8 4.3 25000 -19.1 -2.4 240 28 14 7.2 4.0 | -17.0 1.4 245 27 14 7.0 3.8 24000 -16.9 1.6 240 27 14 7.3 4.0 | -15.2 4.6 235 24 13 6.3 3.5 23000 -14.8 5.4 240 26 13 7.4 4.0 | -13.3 8.1 230 23 12 6.4 3.5 22000 -12.6 9.3 240 25 13 7.2 4.0 | -11.5 11.3 220 21 11 6.4 3.5 21000 -10.5 13.1 240 23 12 7.2 4.0 | -9.7 14.5 215 20 11 6.5 3.5 20000 -8.5 16.7 240 22 11 7.2 4.0 | -7.8 18.0 210 20 10 6.5 3.6 19500 -7.4 18.7 240 21 11 7.2 4.0 | -6.9 19.6 210 20 10 6.6 3.6 19000 -6.4 20.5 240 20 10 6.9 3.8 | -5.9 21.4 205 19 10 7.1 3.9 18500 -5.4 22.3 235 20 10 6.9 3.8 | -4.9 23.2 205 18 9 7.1 3.9 18000 -4.4 24.1 235 19 10 7.6 4.2 | -3.9 25.0 200 18 9 6.9 3.8 17500 -3.2 26.2 230 18 9 7.9 4.3 | -2.9 26.8 200 17 9 6.8 3.7 17000 -2.0 28.4 230 18 9 8.0 4.4 | -1.9 28.6 195 17 9 6.8 3.7 16500 -0.8 30.6 230 17 9 8.7 4.7 | -1.0 30.2 195 16 8 6.9 3.8 16000 0.4 32.7 225 17 9 8.6 4.7 | 0.0 32.0 190 16 8 6.8 3.8 15500 1.7 35.1 225 16 8 9.1 5.0 | 1.0 33.8 190 15 8 7.7 4.2 15000 3.1 37.6 225 16 8 9.1 5.0 | 2.2 36.0 185 15 8 7.9 4.3 14500 4.4 39.9 225 15 8 9.0 4.9 | 3.3 37.9 185 14 7 8.0 4.4 14000 5.7 42.3 225 15 8 8.9 4.9 | 4.5 40.1 185 14 7 8.1 4.4 13500 7.0 44.6 225 14 7 8.9 4.9 | 5.6 42.1 185 13 7 8.2 4.5 13000 8.9 48.0 220 13 7 8.9 4.9 | 6.8 44.2 185 12 6 8.4 4.6 12500 10.2 50.4 215 13 7 9.2 5.0 | 8.0 46.4 185 11 6 8.4 4.6 12000 11.5 52.7 210 13 6 9.3 5.1 | 9.8 49.6 190 10 5 8.1 4.5 11500 12.8 55.0 210 12 6 9.3 5.1 | 11.0 51.8 195 9 5 8.0 4.4 11000 14.2 57.6 205 12 6 9.0 4.9 | 12.2 54.0 200 8 4 7.6 4.2 10500 15.6 60.1 205 12 6 4.9 2.7 | 13.4 56.1 210 7 4 2.0 1.1 10250 15.8 60.4 205 11 6 6.4 3.5 | 13.3 55.9 210 7 4 3.2 1.8 10000 16.6 61.9 205 11 6 12.8 7.0 | 14.0 57.2 225 7 3 11.4 6.3 9750 17.5 63.5 200 11 6 12.0 6.6 | 14.7 58.5 235 7 3 10.3 5.6 9500 18.3 64.9 200 11 6 8.6 4.7 | 15.5 59.9 250 7 3 6.6 3.6 9250 18.8 65.8 200 11 6 7.0 3.8 | 15.7 60.3 255 7 4 2.9 1.6 9000 19.5 67.1 200 11 5 11.0 6.1 | 16.1 61.0 265 8 4 7.5 4.1 8750 20.3 68.5 195 10 5 11.9 6.5 | 16.8 62.2 275 9 5 9.5 5.2 8500 21.2 70.2 195 10 5 9.2 5.1 | 17.4 63.3 280 10 5 6.1 3.4 8250 21.7 71.1 195 10 5 6.0 3.3 | 17.7 63.9 285 11 6 3.0 1.7 8000 22.3 72.1 195 10 5 10.0 5.5 | 18.0 64.4 285 13 7 6.2 3.4 7750 23.2 73.8 195 10 5 12.7 7.0 | 18.6 65.5 290 14 7 8.5 4.7 7500 24.0 75.2 195 10 5 9.4 5.2 | 19.1 66.4 295 16 8 5.4 3.0 7250 24.6 76.3 195 10 5 7.3 4.0 | 19.4 66.9 295 17 9 3.4 1.9 7000 25.2 77.4 195 10 5 9.8 5.4 | 19.7 67.5 295 18 9 4.9 2.7 6750 26.0 78.8 190 10 5 12.4 6.8 | 20.1 68.2 295 20 10 7.6 4.2 6500 26.9 80.4 190 9 5 10.7 5.8 | 20.7 69.3 295 21 11 7.9 4.3 6250 27.6 81.7 190 9 5 9.2 5.1 | 21.2 70.2 295 21 11 8.3 4.5 6000 28.3 82.9 190 9 5 9.8 5.4 | 21.8 71.2 295 21 11 4.6 2.5 5750 29.2 84.6 190 9 4 16.3 8.9 | 22.1 71.8 295 20 10 6.6 3.6 5500 30.8 87.4 190 8 4 26.7 14.6 | 23.1 73.6 290 17 9 21.6 11.8 ________________________________________________________________________________ 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