Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
646 UXUS97 KBOU 111324 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 0722 MDT Friday, July 11, 2025 This forecast is for Friday, July 11, 2025: If the trigger temperature of 83.0 F/28.4 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 1197 ft/min (6.1 m/s) Maximum height of thermals.................. 17794 ft MSL (12494 ft AGL) Forecast maximum temperature................... 89.0 F/32.1 C Time of trigger temperature.................... 1045 MDT Time of overdevelopment........................ 1500 MDT Middle/high clouds during soaring window....... None Surface winds during soaring window............ 20 mph or less Height of the -3 thermal index................. 10226 ft MSL (4926 ft AGL) Thermal soaring outlook for Saturday 07/12..... 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)................ Weak PVA Potential height of wave....................... 19054 ft MSL (13754 ft AGL) Wave soaring outlook for Saturday 07/12........ Poor Remarks... Sunrise/Sunset.................... 05:41:34 / 20:28:38 MDT Total possible sunshine........... 14 hr 47 min 3 sec (887 min 3 sec) Altitude of sun at 13:05:06 MDT... 72.19 degrees Upper air data from numerical model forecast valid on 07/11/2025 at 0600 MDT Freezing level.................. 15711 ft MSL (10411 ft AGL) Convective condensation level... 16057 ft MSL (10757 ft AGL) Lifted condensation level....... 16307 ft MSL (11007 ft AGL) Lifted index.................... -2.6 K index......................... +21.8 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 -61.3 -78.3 290 26 13 2.7 1.5 M M M M M 45000 -57.6 -71.7 295 36 19 1.9 1.0 M M M M M 40000 -53.9 -65.0 305 36 18 6.8 3.7 M M M M M 38000 -49.7 -57.5 305 34 18 6.9 3.8 M M M M M 36000 -45.6 -50.1 305 33 17 6.9 3.8 M M M M M 34000 -41.3 -42.3 300 31 16 7.2 4.0 M M M M M 32000 -36.9 -34.4 300 28 15 7.3 4.0 M M M M M 30000 -32.3 -26.1 305 26 14 8.0 4.4 43.7 110.6 9.1 M M 29000 -29.3 -20.7 310 25 13 8.0 4.4 42.8 109.1 8.6 M M 28000 -26.9 -16.4 315 25 13 8.1 4.4 42.3 108.1 8.3 M M 27000 -24.5 -12.1 320 23 12 8.1 4.5 41.5 106.8 7.8 M M 26000 -22.1 -7.8 325 23 12 8.1 4.5 40.9 105.7 7.4 M M 25000 -19.6 -3.3 325 22 11 7.8 4.3 40.4 104.8 7.1 M M 24000 -17.8 -0.0 325 19 10 5.8 3.2 39.0 102.2 6.0 M M 23000 -16.1 3.0 320 17 9 5.8 3.2 37.5 99.6 4.8 M M 22000 -14.4 6.1 310 15 8 5.8 3.2 36.2 97.2 3.7 M M 21000 -12.7 9.1 310 15 8 6.1 3.4 34.8 94.7 2.5 M M 20000 -10.9 12.4 305 14 7 6.3 3.5 33.6 92.4 1.4 M M 19500 -10.0 14.0 305 14 7 6.2 3.4 33.0 91.4 0.8 M M 19000 -9.0 15.8 305 14 7 9.1 5.0 32.6 90.8 0.4 M M 18500 -7.7 18.1 310 14 7 9.0 4.9 32.5 90.5 0.2 M M 18000 -6.4 20.5 315 14 7 9.1 5.0 32.4 90.3 0.1 M M 17500 -5.1 22.8 315 13 7 9.1 5.0 32.3 90.1 -0.1 1173 6.0 17000 -3.7 25.3 320 13 7 9.1 5.0 32.2 89.9 -0.2 1118 5.7 16500 -2.4 27.7 325 12 6 9.0 4.9 32.0 89.7 -0.3 1064 5.4 16000 -1.1 30.0 330 11 6 9.0 4.9 31.9 89.4 -0.4 1009 5.1 15500 0.3 32.5 330 10 5 8.9 4.9 31.8 89.2 -0.5 954 4.8 15000 2.2 36.0 335 9 5 8.9 4.9 31.6 88.8 -0.8 872 4.4 14500 3.6 38.5 340 9 4 8.8 4.8 31.4 88.6 -0.9 818 4.2 14000 4.8 40.6 335 7 4 8.7 4.8 31.2 88.2 -1.1 765 3.9 13500 6.1 43.0 335 6 3 8.6 4.7 31.1 88.0 -1.2 711 3.6 13000 7.4 45.3 325 4 2 8.5 4.7 30.9 87.6 -1.4 659 3.3 12500 8.6 47.5 300 3 1 8.4 4.6 30.7 87.2 -1.7 607 3.1 12000 9.9 49.8 265 2 1 8.3 4.6 30.4 86.8 -1.9 555 2.8 11500 11.1 52.0 220 2 1 8.4 4.6 30.2 86.4 -2.1 503 2.6 11000 12.4 54.3 220 3 1 8.4 4.6 30.0 86.1 -2.3 450 2.3 10500 13.7 56.7 220 3 2 4.5 2.5 29.9 85.8 -2.5 397 2.0 10250 13.9 57.0 225 3 2 5.6 3.1 29.3 84.8 -3.0 384 2.0 10000 14.6 58.3 225 4 2 11.5 6.3 29.4 84.8 -3.0 355 1.8 9750 15.3 59.5 225 5 2 10.3 5.7 29.4 84.9 -3.0 325 1.7 9500 16.1 61.0 225 5 3 9.3 5.1 29.5 85.0 -3.0 296 1.5 9250 16.6 61.9 225 6 3 6.9 3.8 29.3 84.8 -3.2 272 1.4 9000 17.1 62.8 220 6 3 7.6 4.2 29.1 84.4 -3.5 250 1.3 8750 17.7 63.9 220 7 4 8.4 4.6 29.0 84.2 -3.7 226 1.1 8500 18.2 64.8 215 8 4 8.1 4.5 28.9 83.9 -3.8 201 1.0 8250 18.8 65.8 215 8 4 8.1 4.5 28.7 83.7 -4.0 177 0.9 8000 19.4 66.9 210 9 4 8.1 4.5 28.6 83.5 -4.1 152 0.8 7750 20.0 68.0 210 9 5 8.4 4.6 28.5 83.3 -4.3 127 0.6 7500 20.5 68.9 210 9 5 7.8 4.3 28.4 83.1 -4.5 103 0.5 7250 21.1 70.0 205 9 5 7.1 3.9 28.2 82.7 -4.7 79 0.4 7000 21.6 70.9 205 9 5 7.4 4.1 28.0 82.4 -4.9 56 0.3 6750 22.1 71.8 205 9 5 6.3 3.5 27.8 82.1 -5.1 33 0.2 6500 22.4 72.3 205 9 5 -1.6 -0.9 27.3 81.2 -5.6 18 0.1 6250 21.9 71.4 205 8 4 -7.3 -4.0 26.1 79.1 -6.8 24 0.1 6000 21.5 70.7 205 8 4 -3.3 -1.8 25.0 77.0 -7.9 29 0.1 5750 21.2 70.2 210 8 4 -9.1 -5.0 23.9 75.1 -8.9 30 0.2 5500 19.7 67.5 205 7 3 -29.2 -16.0 21.8 71.2 -11.2 67 0.3 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 07/11/2025 at 0900 MDT | 07/11/2025 at 1200 MDT | CAPE... +228.9 LI... -3.4 | CAPE... +996.6 LI... -4.5 CINH... -168.1 K Index... +22.6 | CINH... -11.9 K Index... +27.1 | 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 -61.5 -78.7 295 26 14 2.1 1.1 | -60.6 -77.1 290 29 15 1.9 1.0 45000 -58.4 -73.1 305 35 18 2.0 1.1 | -57.8 -72.0 290 37 19 1.8 1.0 40000 -54.4 -65.9 305 27 14 7.2 3.9 | -54.3 -65.7 280 29 15 6.6 3.6 38000 -50.0 -58.0 305 27 14 7.3 4.0 | -50.2 -58.4 280 25 13 6.8 3.7 36000 -45.7 -50.3 305 26 13 7.3 4.0 | -46.1 -51.0 280 20 10 6.8 3.7 34000 -41.3 -42.3 305 26 13 7.2 3.9 | -41.9 -43.4 280 19 10 7.1 3.9 32000 -37.1 -34.8 305 26 13 7.1 3.9 | -37.6 -35.7 285 18 9 7.1 3.9 30000 -32.4 -26.3 310 24 12 7.9 4.3 | -33.0 -27.4 290 18 9 7.8 4.3 29000 -29.5 -21.1 310 22 11 7.9 4.3 | -30.1 -22.2 295 18 9 7.8 4.3 28000 -27.1 -16.8 310 21 11 8.0 4.4 | -27.7 -17.9 295 18 9 8.2 4.5 27000 -24.7 -12.5 310 18 10 8.0 4.4 | -25.3 -13.5 290 17 9 8.3 4.5 26000 -22.3 -8.1 310 16 8 8.0 4.4 | -22.8 -9.0 285 17 9 8.3 4.5 25000 -19.9 -3.8 310 14 7 7.8 4.3 | -20.3 -4.5 285 16 8 7.8 4.3 24000 -17.9 -0.2 310 14 7 6.9 3.8 | -18.4 -1.1 285 15 8 6.0 3.3 23000 -15.8 3.6 310 14 7 6.9 3.8 | -16.7 1.9 290 14 7 6.1 3.3 22000 -13.7 7.3 305 13 7 6.4 3.5 | -14.9 5.2 295 14 7 6.3 3.5 21000 -12.2 10.0 305 13 7 5.3 2.9 | -13.0 8.6 290 12 6 6.8 3.7 20000 -10.7 12.7 300 13 7 5.5 3.0 | -11.0 12.2 285 11 6 6.9 3.8 19500 -9.9 14.2 300 13 7 5.2 2.9 | -10.1 13.8 280 11 5 6.8 3.7 19000 -8.9 16.0 300 12 6 9.3 5.1 | -8.9 16.0 275 10 5 9.6 5.3 18500 -7.7 18.1 300 11 6 9.0 4.9 | -7.6 18.3 275 8 4 9.4 5.2 18000 -6.4 20.5 305 10 5 9.0 4.9 | -6.2 20.8 270 6 3 9.1 5.0 17500 -5.1 22.8 305 9 5 8.9 4.9 | -5.0 23.0 265 6 3 8.8 4.8 17000 -3.8 25.2 310 8 4 8.9 4.9 | -3.7 25.3 255 5 3 8.9 4.9 16500 -2.5 27.5 315 6 3 9.0 4.9 | -2.4 27.7 250 5 2 8.2 4.5 16000 -1.1 30.0 320 5 3 9.0 4.9 | -1.1 30.0 235 4 2 8.2 4.5 15500 0.2 32.4 330 5 2 9.1 5.0 | 0.9 33.6 230 4 2 9.5 5.2 15000 2.3 36.1 335 4 2 9.1 5.0 | 2.3 36.1 230 4 2 9.4 5.2 14500 3.6 38.5 340 4 2 9.1 5.0 | 3.6 38.5 235 4 2 9.0 5.0 14000 5.0 41.0 325 3 2 9.1 5.0 | 5.0 41.0 235 4 2 9.0 5.0 13500 6.3 43.3 310 3 2 8.9 4.9 | 6.3 43.3 240 4 2 8.6 4.7 13000 7.6 45.7 290 3 2 8.7 4.8 | 7.5 45.5 225 4 2 8.5 4.7 12500 8.9 48.0 270 4 2 8.6 4.7 | 8.8 47.8 215 5 2 8.3 4.5 12000 10.1 50.2 240 3 2 8.4 4.6 | 10.0 50.0 195 4 2 8.1 4.5 11500 11.4 52.5 210 4 2 8.3 4.6 | 11.1 52.0 170 4 2 8.4 4.6 11000 12.6 54.7 195 4 2 8.1 4.4 | 12.3 54.1 140 4 2 8.6 4.7 10500 13.8 56.8 185 5 3 5.0 2.7 | 13.5 56.3 105 4 2 4.6 2.5 10250 14.1 57.4 185 5 3 6.3 3.5 | 13.7 56.7 100 4 2 6.4 3.5 10000 14.8 58.6 185 5 3 11.5 6.3 | 14.6 58.3 090 4 2 13.1 7.2 9750 15.5 59.9 185 5 3 10.6 5.8 | 15.4 59.7 080 4 2 11.8 6.5 9500 16.3 61.3 185 5 3 9.2 5.0 | 16.3 61.3 075 5 2 10.5 5.7 9250 16.8 62.2 185 6 3 7.2 3.9 | 16.9 62.4 070 5 3 8.3 4.5 9000 17.3 63.1 190 6 3 9.0 4.9 | 17.5 63.5 065 5 3 9.1 5.0 8750 18.0 64.4 195 7 3 10.4 5.7 | 18.2 64.8 060 6 3 9.3 5.1 8500 18.7 65.7 195 7 4 8.8 4.8 | 18.9 66.0 060 6 3 9.6 5.3 8250 19.2 66.6 200 7 4 7.2 3.9 | 19.6 67.3 055 6 3 10.0 5.5 8000 19.8 67.6 200 8 4 7.2 3.9 | 20.3 68.5 055 6 3 10.0 5.5 7750 20.3 68.5 200 8 4 7.6 4.2 | 21.1 70.0 050 6 3 10.0 5.5 7500 20.8 69.4 200 8 4 5.8 3.2 | 21.8 71.2 050 6 3 10.2 5.6 7250 21.1 70.0 200 7 4 4.0 2.2 | 22.6 72.7 050 6 3 10.3 5.7 7000 21.4 70.5 200 7 4 4.8 2.6 | 23.4 74.1 045 7 3 10.1 5.5 6750 21.7 71.1 200 7 3 4.9 2.7 | 24.1 75.4 045 7 3 10.1 5.5 6500 22.0 71.6 195 6 3 3.3 1.8 | 24.9 76.8 045 7 3 10.7 5.9 6250 22.2 72.0 200 4 2 2.7 1.5 | 25.7 78.3 045 7 3 11.7 6.4 6000 22.4 72.3 200 3 2 1.4 0.8 | 26.5 79.7 040 7 3 9.3 5.1 5750 22.6 72.7 210 1 1 7.6 4.2 | 27.3 81.1 040 7 3 14.4 7.9 5500 23.8 74.8 240 1 0 23.7 13.0 | 28.9 84.0 040 7 4 31.1 17.1 07/11/2025 at 1500 MDT | 07/11/2025 at 1800 MDT | CAPE... +759.5 LI... -3.7 | CAPE... +957.4 LI... -4.1 CINH... -1.2 K Index... +34.6 | CINH... -28.6 K Index... +35.7 | 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 -60.7 -77.3 280 33 17 1.9 1.0 | -60.4 -76.7 280 36 18 1.4 0.8 45000 -58.0 -72.4 280 44 23 1.6 0.9 | -58.6 -73.5 270 42 22 0.5 0.3 40000 -55.1 -67.2 275 39 20 7.7 4.2 | -56.6 -69.9 215 35 18 9.0 4.9 38000 -50.1 -58.2 265 37 19 7.3 4.0 | -51.0 -59.8 205 34 17 9.3 5.1 36000 -45.7 -50.3 255 36 18 7.3 4.0 | -45.4 -49.7 200 33 17 9.4 5.2 34000 -41.1 -42.0 260 33 17 7.8 4.3 | -40.7 -41.3 215 30 15 7.7 4.2 32000 -36.4 -33.5 270 30 15 7.7 4.2 | -36.0 -32.8 230 28 14 7.5 4.1 30000 -32.1 -25.8 275 27 14 6.9 3.8 | -31.4 -24.5 255 25 13 6.6 3.6 29000 -30.1 -22.2 280 25 13 6.9 3.8 | -29.4 -20.9 270 25 13 6.6 3.6 28000 -28.0 -18.4 285 24 12 7.4 4.0 | -27.4 -17.3 280 25 13 7.4 4.1 27000 -25.7 -14.3 285 22 11 7.8 4.3 | -25.2 -13.4 280 24 12 7.6 4.1 26000 -23.3 -9.9 285 20 10 7.8 4.3 | -22.9 -9.2 285 23 12 7.6 4.1 25000 -21.0 -5.8 285 19 10 7.8 4.3 | -20.7 -5.3 285 21 11 7.7 4.2 24000 -18.9 -2.0 285 18 9 6.9 3.8 | -18.3 -0.9 290 19 10 8.2 4.5 23000 -16.9 1.6 285 17 9 6.9 3.8 | -15.9 3.4 290 18 9 8.3 4.6 22000 -14.8 5.4 280 16 8 7.0 3.8 | -13.5 7.7 295 16 8 7.8 4.3 21000 -12.9 8.8 275 14 7 6.8 3.7 | -11.5 11.3 295 12 6 6.6 3.6 20000 -10.4 13.3 260 11 6 6.9 3.8 | -9.6 14.7 295 7 4 6.7 3.7 19500 -9.5 14.9 250 10 5 7.3 4.0 | -8.7 16.3 300 5 3 6.7 3.7 19000 -8.3 17.1 240 9 5 8.0 4.4 | -7.7 18.1 295 3 2 6.3 3.5 18500 -7.2 19.0 230 9 4 8.0 4.4 | -6.8 19.8 260 1 1 6.4 3.5 18000 -6.1 21.0 215 8 4 7.5 4.1 | -5.9 21.4 165 2 1 6.4 3.5 17500 -5.0 23.0 205 8 4 7.5 4.1 | -5.0 23.0 130 3 2 6.4 3.5 17000 -3.9 25.0 195 8 4 7.8 4.3 | -4.1 24.6 115 4 2 6.5 3.5 16500 -2.7 27.1 180 7 3 8.4 4.6 | -2.8 27.0 105 6 3 6.0 3.3 16000 -1.5 29.3 155 5 3 8.4 4.6 | -1.9 28.6 095 7 3 6.0 3.3 15500 -0.3 31.5 125 5 2 8.8 4.8 | -1.0 30.2 095 7 4 7.3 4.0 15000 0.9 33.6 095 5 3 8.8 4.8 | 0.1 32.2 090 7 4 7.1 3.9 14500 2.2 36.0 075 6 3 9.3 5.1 | 1.1 34.0 090 7 4 8.2 4.5 14000 3.6 38.5 070 6 3 9.4 5.1 | 2.3 36.1 090 7 4 8.3 4.6 13500 5.0 41.0 065 7 3 9.6 5.3 | 3.5 38.3 085 7 3 8.3 4.6 13000 6.5 43.7 060 7 4 9.8 5.4 | 4.6 40.3 085 7 3 8.3 4.5 12500 7.9 46.2 055 7 4 9.7 5.3 | 5.8 42.4 080 7 3 7.8 4.3 12000 9.4 48.9 050 8 4 9.6 5.3 | 6.8 44.2 075 7 3 7.3 4.0 11500 10.8 51.4 050 8 4 9.7 5.3 | 7.8 46.0 065 7 3 7.5 4.1 11000 12.3 54.1 045 9 4 9.6 5.3 | 8.9 48.0 055 7 3 7.5 4.1 10500 13.8 56.8 040 9 5 5.8 3.2 | 10.0 50.0 045 7 4 3.7 2.1 10250 14.1 57.4 040 9 5 6.6 3.6 | 10.1 50.2 045 7 4 4.1 2.2 10000 14.9 58.8 040 9 5 12.3 6.8 | 10.7 51.3 040 7 4 9.9 5.4 9750 15.7 60.3 040 9 5 11.0 6.0 | 11.4 52.5 030 8 4 9.4 5.1 9500 16.6 61.9 035 9 5 10.7 5.9 | 12.0 53.6 025 8 4 7.9 4.3 9250 17.3 63.1 035 10 5 9.8 5.4 | 12.5 54.5 020 9 4 5.9 3.2 9000 18.1 64.6 035 10 5 10.2 5.6 | 13.0 55.4 015 9 5 8.0 4.4 8750 18.8 65.8 035 10 5 10.3 5.6 | 13.7 56.7 010 9 5 9.3 5.1 8500 19.6 67.3 030 10 5 10.5 5.7 | 14.3 57.7 005 9 5 8.6 4.7 8250 20.4 68.7 030 10 5 11.2 6.1 | 15.0 59.0 005 9 4 8.5 4.7 8000 21.2 70.2 030 10 5 10.0 5.5 | 15.6 60.1 360 8 4 8.3 4.5 7750 21.9 71.4 030 10 5 8.5 4.7 | 16.2 61.2 360 8 4 7.9 4.4 7500 22.6 72.7 030 10 5 10.0 5.5 | 16.9 62.4 355 7 4 8.1 4.5 7250 23.4 74.1 025 10 5 11.3 6.2 | 17.5 63.5 355 6 3 8.7 4.8 7000 24.2 75.6 025 11 5 10.3 5.7 | 18.1 64.6 350 5 3 7.3 4.0 6750 24.9 76.8 025 11 5 9.1 5.0 | 18.6 65.5 345 4 2 6.5 3.6 6500 25.6 78.1 025 11 6 10.3 5.7 | 19.1 66.4 340 3 2 8.8 4.8 6250 26.5 79.7 025 11 5 12.1 6.6 | 19.8 67.6 335 2 1 9.3 5.1 6000 27.3 81.1 025 11 5 10.0 5.5 | 20.5 68.9 330 2 1 10.8 5.9 5750 28.1 82.6 020 11 5 12.8 7.0 | 21.4 70.5 320 1 1 14.3 7.9 5500 29.4 84.9 020 10 5 24.0 13.1 | 22.5 72.5 305 1 0 14.8 8.1 ________________________________________________________________________________ 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