UXUS97 KGJT 151306 SRGGJT Soaring Forecast National Weather Service Grand Junction, Colorado 706 AM MDT Wednesday, April 15, 2026 This forecast is for Wednesday, April 15, 2026: If the trigger temperature of 59.4 F/15.2 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 1025 ft/min (5.2 m/s) Maximum height of thermals.................. 16770 ft MSL (11160 ft AGL) Forecast maximum temperature................... 67.0 F/19.9 C Time of trigger temperature.................... 1245 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................. 12987 ft MSL (7377 ft AGL) Thermal soaring outlook for Thursday 04/16..... Excellent Wave Soaring Index............................. Not available Remarks... Sunrise/Sunset.................... 06:36:47 / 19:51:24 MDT Total possible sunshine........... 13 hr 14 min 37 sec (794 min 37 sec) Altitude of sun at 13:14:05 MDT... 60.69 degrees Upper air data from rawinsonde observation taken on 04/15/2026 at 0600 MDT Freezing level.................. 10787 ft MSL (5177 ft AGL) Convective condensation level... 16512 ft MSL (10902 ft AGL) Lifted condensation level....... 16772 ft MSL (11162 ft AGL) Lifted index.................... +1.4 K index......................... +11.6 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 -60.3 -76.5 245 45 23 0.6 0.3 M M M M M 45000 -59.4 -74.9 245 53 27 0.6 0.3 M M M M M 40000 -61.9 -79.4 255 54 28 -1.8 -1.0 M M M M M 38000 -60.9 -77.6 255 54 28 6.4 3.5 M M M M M 36000 -56.6 -69.9 255 54 28 6.4 3.5 M M M M M 34000 -52.6 -62.7 255 53 27 7.8 4.3 M M M M M 32000 -47.9 -54.2 250 51 26 7.8 4.3 M M M M M 30000 -43.3 -45.9 250 50 26 7.2 3.9 31.7 89.0 9.2 M M 29000 -41.2 -42.2 250 50 26 7.2 4.0 30.6 87.0 8.5 M M 28000 -39.0 -38.2 245 50 26 7.2 4.0 29.6 85.3 7.8 M M 27000 -36.8 -34.2 245 50 26 7.4 4.1 28.8 83.8 7.3 M M 26000 -34.5 -30.1 245 50 26 7.7 4.2 27.9 82.2 6.7 M M 25000 -32.2 -26.0 245 49 25 7.7 4.2 27.1 80.8 6.1 M M 24000 -29.9 -21.8 245 48 25 7.7 4.2 26.5 79.7 5.6 M M 23000 -27.6 -17.7 245 48 25 7.6 4.2 25.6 78.2 5.0 M M 22000 -25.4 -13.7 245 47 24 7.6 4.2 24.9 76.8 4.4 M M 21000 -23.1 -9.6 245 47 24 7.5 4.1 24.2 75.6 3.9 M M 20000 -20.4 -4.7 245 44 23 7.3 4.0 23.0 73.5 2.9 M M 19500 -19.3 -2.7 240 43 22 7.3 4.0 22.6 72.7 2.6 M M 19000 -18.2 -0.8 240 42 21 7.4 4.0 22.2 72.0 2.2 M M 18500 -17.2 1.0 240 40 21 6.2 3.4 21.8 71.2 1.8 M M 18000 -16.3 2.7 240 39 20 6.1 3.3 21.1 70.0 1.3 M M 17500 -15.4 4.3 240 38 19 6.1 3.3 20.5 68.9 0.7 M M 17000 -14.4 6.1 240 36 19 6.1 3.4 19.9 67.8 0.2 M M 16500 -13.5 7.7 240 35 18 6.1 3.3 19.3 66.7 -0.4 997 5.1 16000 -12.6 9.3 240 34 18 6.5 3.6 18.7 65.7 -0.9 954 4.8 15500 -11.6 11.1 240 34 17 6.4 3.5 18.2 64.7 -1.4 911 4.6 15000 -10.6 12.9 240 33 17 7.3 4.0 17.7 63.8 -1.9 866 4.4 14500 -9.5 14.9 240 33 17 7.5 4.1 17.3 63.1 -2.2 818 4.2 14000 -8.4 16.9 240 33 17 8.1 4.5 16.9 62.5 -2.6 770 3.9 13500 -7.1 19.2 235 33 17 8.6 4.7 16.7 62.1 -2.8 717 3.6 13000 -5.9 21.4 235 33 17 8.7 4.7 16.6 61.8 -3.0 664 3.4 12500 -4.6 23.7 235 33 17 8.7 4.8 16.4 61.5 -3.2 610 3.1 12000 -3.3 26.1 235 33 17 8.8 4.8 16.2 61.2 -3.4 557 2.8 11500 -1.9 28.6 235 32 16 8.9 4.9 16.1 60.9 -3.5 502 2.5 11000 -0.6 30.9 235 31 16 8.7 4.8 16.0 60.7 -3.7 447 2.3 10500 0.6 33.1 230 30 15 8.5 4.7 15.7 60.3 -3.9 395 2.0 10250 1.3 34.3 230 29 15 10.3 5.6 15.7 60.2 -4.0 367 1.9 10000 2.1 35.8 230 29 15 9.9 5.4 15.7 60.3 -3.9 336 1.7 9750 2.8 37.0 230 28 14 8.7 4.8 15.7 60.2 -4.0 309 1.6 9500 3.4 38.1 230 27 14 8.9 4.9 15.6 60.1 -4.1 282 1.4 9250 4.1 39.4 230 26 13 8.7 4.8 15.5 60.0 -4.2 255 1.3 9000 4.7 40.5 225 25 13 8.2 4.5 15.4 59.8 -4.3 228 1.2 8750 5.3 41.5 225 24 12 8.0 4.4 15.3 59.5 -4.4 203 1.0 8500 5.9 42.6 220 23 12 8.2 4.5 15.2 59.3 -4.6 178 0.9 8250 6.5 43.7 220 23 12 7.8 4.3 15.0 59.1 -4.7 152 0.8 8000 7.1 44.8 215 21 11 6.7 3.6 14.9 58.7 -4.9 128 0.7 7750 7.5 45.5 215 20 10 6.1 3.3 14.6 58.2 -5.2 107 0.5 7500 8.0 46.4 210 19 10 6.3 3.5 14.3 57.8 -5.5 86 0.4 7250 8.4 47.1 210 19 10 6.0 3.3 14.0 57.3 -5.8 65 0.3 7000 8.8 47.8 200 20 10 3.6 2.0 13.7 56.7 -6.1 46 0.2 6750 9.0 48.2 195 18 9 2.4 1.3 13.1 55.7 -6.7 33 0.2 6500 9.2 48.6 185 17 9 1.9 1.0 12.6 54.7 -7.3 21 0.1 6250 9.1 48.4 180 16 8 -4.9 -2.7 11.8 53.2 -8.1 16 0.1 6000 8.4 47.1 165 14 7 -13.5 -7.4 10.3 50.6 -9.6 30 0.2 5750 7.2 45.0 160 10 5 -16.1 -8.8 8.4 47.2 -11.5 58 0.3 5500 M M M M M M M M M M M M 5250 M M M M M M M M M M M M 5000 M M M M M M M M M M M M * * * * * * Numerical weather prediction model forecast data valid * * * * * * 04/15/2026 at 0900 MDT | 04/15/2026 at 1200 MDT | CAPE... +17.4 LI... +3.2 | CAPE... +24.1 LI... +2.8 CINH... -9.7 K Index... +4.0 | CINH... -1.5 K Index... +10.0 | 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 -58.6 -73.5 245 31 16 0.6 0.3 | -59.0 -74.2 235 35 18 0.6 0.3 45000 -57.8 -72.0 245 30 15 0.8 0.4 | -58.1 -72.6 245 36 18 0.8 0.5 40000 -59.4 -74.9 305 24 12 -1.2 -0.6 | -60.8 -77.4 310 22 11 -1.9 -1.0 38000 -59.1 -74.4 325 28 14 3.6 2.0 | -60.2 -76.4 330 26 13 5.4 3.0 36000 -56.6 -69.9 345 34 17 3.6 2.0 | -56.6 -69.9 335 27 14 5.4 2.9 34000 -54.2 -65.6 350 39 20 7.5 4.1 | -53.2 -63.8 335 27 14 6.7 3.7 32000 -49.9 -57.8 350 34 17 7.1 3.9 | -49.3 -56.7 330 26 13 6.6 3.6 30000 -45.6 -50.1 350 29 15 7.5 4.1 | -45.2 -49.4 330 25 13 7.9 4.3 29000 -43.4 -46.1 345 27 14 7.5 4.1 | -42.9 -45.2 325 24 12 7.8 4.3 28000 -41.2 -42.2 345 25 13 7.5 4.1 | -40.5 -40.9 325 23 12 7.8 4.3 27000 -38.9 -38.0 345 23 12 7.5 4.1 | -38.2 -36.8 325 21 11 7.8 4.3 26000 -36.6 -33.9 340 24 12 8.1 4.4 | -35.8 -32.4 325 21 11 7.9 4.3 25000 -34.1 -29.4 340 24 12 8.1 4.4 | -33.5 -28.3 325 21 11 7.9 4.3 24000 -31.7 -25.1 335 25 13 8.2 4.5 | -31.1 -24.0 325 21 11 7.9 4.3 23000 -29.4 -20.9 335 24 13 7.5 4.1 | -28.9 -20.0 325 21 11 7.5 4.1 22000 -26.6 -15.9 335 23 12 7.5 4.1 | -26.1 -15.0 330 20 10 7.5 4.1 21000 -24.4 -11.9 335 22 11 6.7 3.7 | -23.9 -11.0 330 20 10 7.1 3.9 20000 -22.5 -8.5 330 21 11 6.5 3.6 | -21.8 -7.2 330 19 10 7.1 3.9 19500 -21.5 -6.7 330 20 10 6.5 3.6 | -20.7 -5.3 330 19 10 7.1 3.9 19000 -20.5 -4.9 330 20 10 6.5 3.6 | -19.7 -3.5 330 19 10 7.1 3.9 18500 -19.5 -3.1 325 19 10 6.4 3.5 | -18.6 -1.5 330 19 10 6.7 3.7 18000 -18.6 -1.5 325 19 10 6.4 3.5 | -17.6 0.3 325 18 9 6.6 3.6 17500 -17.7 0.1 325 19 10 6.3 3.5 | -16.7 1.9 325 18 9 6.5 3.6 17000 -16.7 1.9 325 18 9 6.1 3.4 | -15.7 3.7 320 17 9 6.2 3.4 16500 -15.8 3.6 320 18 9 6.2 3.4 | -14.8 5.4 315 16 8 6.3 3.5 16000 -14.9 5.2 320 17 9 5.3 2.9 | -13.9 7.0 315 16 8 5.6 3.1 15500 -14.2 6.4 320 16 8 5.2 2.9 | -13.1 8.4 310 16 8 5.7 3.1 15000 -13.4 7.9 320 16 8 4.9 2.7 | -12.3 9.9 305 15 8 5.2 2.8 14500 -12.7 9.1 320 15 8 4.8 2.6 | -11.5 11.3 300 15 8 5.0 2.8 14000 -12.0 10.4 320 14 7 5.2 2.8 | -10.8 12.6 295 14 7 5.1 2.8 13500 -11.2 11.8 315 13 7 5.7 3.1 | -10.0 14.0 290 13 7 5.2 2.9 13000 -10.4 13.3 315 13 7 6.0 3.3 | -9.3 15.3 285 12 6 5.7 3.1 12500 -9.5 14.9 310 12 6 6.6 3.6 | -8.3 17.1 280 11 6 6.6 3.6 12000 -8.5 16.7 305 11 6 7.0 3.8 | -7.4 18.7 275 10 5 6.9 3.8 11500 -7.4 18.7 300 11 5 7.9 4.3 | -6.3 20.7 270 10 5 7.6 4.2 11000 -6.3 20.7 295 10 5 7.6 4.2 | -5.2 22.6 265 9 5 7.6 4.2 10500 -5.2 22.6 285 9 5 7.2 3.9 | -4.1 24.6 260 9 4 7.1 3.9 10250 -4.7 23.5 285 9 5 6.3 3.4 | -3.5 25.7 260 9 4 9.5 5.2 10000 -4.2 24.4 280 9 5 9.7 5.3 | -2.7 27.1 260 8 4 10.7 5.8 9750 -3.4 25.9 275 8 4 10.2 5.6 | -2.0 28.4 255 8 4 8.6 4.7 9500 -2.8 27.0 270 7 4 7.1 3.9 | -1.4 29.5 255 8 4 8.9 4.9 9250 -2.3 27.9 265 7 3 7.9 4.3 | -0.7 30.7 255 7 4 8.5 4.7 9000 -1.7 28.9 255 6 3 7.0 3.8 | -0.1 31.8 250 7 4 8.2 4.5 8750 -1.3 29.7 250 6 3 6.8 3.7 | 0.5 32.9 250 7 3 8.7 4.8 8500 -0.8 30.6 235 5 3 7.2 4.0 | 1.2 34.2 245 6 3 9.5 5.2 8250 -0.2 31.6 225 5 3 6.9 3.8 | 1.8 35.2 240 6 3 8.1 4.5 8000 0.7 33.3 205 5 3 7.7 4.2 | 2.9 37.2 240 5 3 9.8 5.4 7750 1.4 34.5 200 5 3 9.2 5.1 | 3.8 38.8 240 5 2 12.7 6.9 7500 2.0 35.6 190 5 3 7.2 4.0 | 4.6 40.3 235 4 2 9.1 5.0 7250 2.4 36.3 185 5 3 4.8 2.6 | 5.1 41.2 240 4 2 5.7 3.1 7000 2.8 37.0 180 5 3 8.9 4.9 | 5.7 42.3 240 4 2 11.3 6.2 6750 3.7 38.7 175 5 2 11.1 6.1 | 6.7 44.1 235 4 2 13.5 7.4 6500 4.4 39.9 175 5 2 8.5 4.7 | 7.5 45.5 235 4 2 9.9 5.4 6250 5.0 41.0 170 5 2 8.0 4.4 | 8.2 46.8 240 3 2 9.0 4.9 6000 5.6 42.1 165 5 2 9.6 5.3 | 8.9 48.0 245 3 1 10.9 6.0 5750 6.5 43.7 170 4 2 15.1 8.3 | 10.0 50.0 235 3 2 20.6 11.3 5500 7.7 45.9 160 3 2 17.5 9.6 | 12.2 54.0 245 2 1 40.2 22.1 5250 M M M M M M M | M M M M M M M 5000 M M M M M M M | M M M M M M M 04/15/2026 at 1500 MDT | 04/15/2026 at 1800 MDT | CAPE... +0.3 LI... +2.7 | CAPE... 0.0 LI... +2.5 CINH... -0.6 K Index... +13.7 | CINH... -0.1 K Index... +12.9 | 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 -60.1 -76.2 240 40 21 0.7 0.4 | -60.1 -76.2 245 41 21 0.6 0.3 45000 -59.1 -74.4 250 37 19 0.8 0.4 | -59.2 -74.6 255 40 20 0.5 0.3 40000 -61.7 -79.1 290 21 11 -1.8 -1.0 | -62.5 -80.5 270 23 12 -2.3 -1.2 38000 -60.2 -76.4 305 20 10 6.2 3.4 | -60.7 -77.3 280 21 11 7.1 3.9 36000 -56.5 -69.7 310 21 11 6.2 3.4 | -56.5 -69.7 280 22 11 7.1 3.9 34000 -52.7 -62.9 310 23 12 7.0 3.8 | -52.2 -62.0 285 23 12 7.2 3.9 32000 -48.5 -55.3 310 24 12 7.0 3.8 | -47.9 -54.2 290 24 13 7.2 3.9 30000 -44.3 -47.7 310 24 12 7.5 4.1 | -43.6 -46.5 290 25 13 7.5 4.1 29000 -42.0 -43.6 310 23 12 7.5 4.1 | -41.3 -42.3 290 25 13 7.5 4.1 28000 -39.8 -39.6 310 22 11 7.5 4.1 | -39.0 -38.2 290 24 13 7.6 4.1 27000 -37.5 -35.5 310 21 11 7.6 4.2 | -36.8 -34.2 290 24 12 7.6 4.1 26000 -35.2 -31.4 310 21 11 7.8 4.3 | -34.5 -30.1 290 23 12 7.6 4.2 25000 -32.9 -27.2 310 21 11 7.8 4.3 | -32.3 -26.1 285 23 12 7.6 4.2 24000 -30.5 -22.9 305 21 11 7.8 4.3 | -30.0 -22.0 285 22 11 7.6 4.2 23000 -27.6 -17.7 305 20 10 8.0 4.4 | -27.1 -16.8 285 22 11 7.9 4.3 22000 -25.2 -13.4 305 20 10 8.0 4.4 | -24.7 -12.5 285 22 11 7.9 4.3 21000 -22.9 -9.2 305 19 10 7.2 4.0 | -22.4 -8.3 285 21 11 7.2 3.9 20000 -20.7 -5.3 305 18 9 7.3 4.0 | -20.3 -4.5 280 21 11 7.2 4.0 19500 -19.6 -3.3 300 18 9 7.3 4.0 | -19.2 -2.6 280 21 11 7.3 4.0 19000 -18.5 -1.3 300 17 9 7.4 4.1 | -18.1 -0.6 275 21 11 7.4 4.0 18500 -17.5 0.5 300 16 8 6.6 3.6 | -17.1 1.2 275 21 11 6.2 3.4 18000 -16.5 2.3 295 16 8 6.6 3.6 | -16.2 2.8 275 21 11 6.2 3.4 17500 -15.5 4.1 295 15 8 6.5 3.6 | -15.3 4.5 270 21 11 6.2 3.4 17000 -14.6 5.7 290 15 8 6.3 3.4 | -14.3 6.3 270 20 11 6.2 3.4 16500 -13.7 7.3 285 15 8 6.3 3.5 | -13.4 7.9 265 20 10 6.2 3.4 16000 -12.8 9.0 280 15 8 5.4 3.0 | -12.5 9.5 260 20 10 6.8 3.7 15500 -12.0 10.4 275 15 8 5.5 3.0 | -11.5 11.3 260 19 10 6.7 3.7 15000 -11.2 11.8 270 15 8 5.7 3.1 | -10.5 13.1 255 19 10 7.2 3.9 14500 -10.3 13.5 265 15 8 5.7 3.1 | -9.4 15.1 250 18 9 7.2 4.0 14000 -9.5 14.9 260 15 8 6.4 3.5 | -8.3 17.1 245 18 9 7.8 4.3 13500 -8.5 16.7 255 15 8 6.9 3.8 | -7.2 19.0 245 18 9 8.1 4.4 13000 -7.5 18.5 250 15 8 7.4 4.1 | -6.0 21.2 240 18 9 8.4 4.6 12500 -6.3 20.7 250 15 8 8.0 4.4 | -4.7 23.5 240 17 9 8.8 4.8 12000 -5.2 22.6 245 14 7 8.3 4.6 | -3.4 25.9 240 17 9 9.0 4.9 11500 -3.9 25.0 245 14 7 8.7 4.8 | -2.0 28.4 235 16 8 9.3 5.1 11000 -2.6 27.3 245 13 7 8.3 4.6 | -0.6 30.9 235 16 8 8.6 4.7 10500 -1.4 29.5 245 12 6 7.2 4.0 | 0.5 32.9 235 15 8 6.8 3.7 10250 -0.8 30.6 245 12 6 10.3 5.6 | 1.1 34.0 235 14 7 10.1 5.6 10000 0.0 32.0 245 12 6 10.8 5.9 | 2.0 35.6 235 14 7 11.5 6.3 9750 0.7 33.3 245 11 6 8.1 4.5 | 2.7 36.9 235 13 7 8.4 4.6 9500 1.3 34.3 245 10 5 9.0 4.9 | 3.3 37.9 235 13 7 9.0 4.9 9250 2.0 35.6 245 10 5 8.4 4.6 | 4.0 39.2 235 12 6 7.8 4.3 9000 2.6 36.7 250 9 5 8.9 4.9 | 4.5 40.1 240 12 6 8.0 4.4 8750 3.3 37.9 250 9 5 9.9 5.4 | 5.2 41.4 240 11 6 9.7 5.3 8500 4.1 39.4 250 9 5 10.2 5.6 | 5.9 42.6 240 11 6 9.8 5.4 8250 4.8 40.6 250 9 4 9.1 5.0 | 6.7 44.1 240 10 5 9.5 5.2 8000 6.1 43.0 255 8 4 10.2 5.6 | 8.1 46.6 245 10 5 9.8 5.4 7750 7.0 44.6 255 8 4 12.2 6.7 | 8.8 47.8 245 10 5 10.5 5.8 7500 7.8 46.0 255 8 4 9.2 5.1 | 9.6 49.3 245 10 5 9.3 5.1 7250 8.3 46.9 260 7 4 6.4 3.5 | 10.2 50.4 245 10 5 7.8 4.3 7000 9.0 48.2 265 7 4 11.1 6.1 | 10.9 51.6 250 9 5 9.8 5.4 6750 9.9 49.8 260 7 4 13.2 7.2 | 11.7 53.1 245 9 5 11.1 6.1 6500 10.8 51.4 260 7 4 10.3 5.6 | 12.5 54.5 245 9 4 10.5 5.8 6250 11.5 52.7 265 6 3 9.8 5.4 | 13.3 55.9 250 9 4 11.2 6.1 6000 12.3 54.1 270 6 3 9.3 5.1 | 14.1 57.4 255 8 4 8.5 4.6 5750 13.1 55.6 260 6 3 16.6 9.1 | 14.6 58.3 250 8 4 8.6 4.7 5500 15.8 60.4 275 5 3 68.4 37.5 | 16.4 61.5 255 7 4 51.3 28.2 5250 M M M M M M M | M M M M M M M 5000 M M M M M M M | M M M M M M M ________________________________________________________________________________ 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 at Walker Field in Grand Junction, Colorado at North Latitude: 39 deg 07 min 00.001 sec West Longitude: 108 deg 31 min 59.998 sec Elevation: 4839 feet (1475 meters) and may not be representative of other areas along the Western Slope of Colorado. 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