Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
591 UXUS97 KGJT 191306 SRGGJT Soaring Forecast National Weather Service Grand Junction, Colorado 706 AM MDT Thursday, September 19, 2024 This forecast is for Thursday, September 19, 2024: If the trigger temperature of 75.1 F/23.9 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 969 ft/min (4.9 m/s) Maximum height of thermals.................. 15647 ft MSL (10808 ft AGL) Forecast maximum temperature................... 82.0 F/28.2 C Time of trigger temperature.................... 1230 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................. 9810 ft MSL (4971 ft AGL) Thermal soaring outlook for Friday 09/20....... Excellent Wave Soaring Index............................. Not available Remarks... Sunrise/Sunset.................... 06:59:54 / 19:15:25 MDT Total possible sunshine........... 12 hr 15 min 31 sec (735 min 31 sec) Altitude of sun at 13:07:40 MDT... 51.91 degrees Upper air data from rawinsonde observation taken on 09/19/2024 at 0600 MDT Freezing level.................. 13430 ft MSL (8591 ft AGL) Convective condensation level... 19063 ft MSL (14224 ft AGL) Lifted condensation level....... 17344 ft MSL (12505 ft AGL) Lifted index.................... +5.8 K index......................... +17.1 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 -63.2 -81.8 250 63 33 4.9 2.7 88.7 191.6 35.4 M M 45000 -56.3 -69.3 240 81 42 5.2 2.8 75.8 168.4 29.8 M M 40000 -49.5 -57.1 245 97 50 5.8 3.2 63.5 146.2 23.7 M M 38000 -46.2 -51.2 245 98 51 5.5 3.0 59.7 139.5 21.8 M M 36000 -42.6 -44.7 245 95 49 7.6 4.2 56.5 133.7 20.1 M M 34000 -39.0 -38.2 240 88 45 5.3 2.9 52.4 126.2 17.7 M M 32000 -35.2 -31.4 250 77 40 6.0 3.3 49.4 121.0 16.0 M M 30000 -31.6 -24.9 250 62 32 6.9 3.8 46.5 115.7 14.1 M M 29000 -29.2 -20.6 250 60 31 8.0 4.4 45.8 114.4 13.8 M M 28000 -26.8 -16.2 245 57 29 8.5 4.7 45.2 113.4 13.5 M M 27000 -24.2 -11.6 245 59 30 8.5 4.7 44.7 112.5 13.2 M M 26000 -21.6 -6.9 245 62 32 7.3 4.0 44.3 111.7 13.0 M M 25000 -20.1 -4.2 245 54 28 5.2 2.8 42.5 108.6 11.8 M M 24000 -18.2 -0.8 245 50 26 7.7 4.2 41.3 106.3 10.9 M M 23000 -15.9 3.4 240 44 23 7.5 4.1 40.6 105.0 10.4 M M 22000 -13.6 7.5 240 45 23 6.8 3.7 39.7 103.5 9.8 M M 21000 -12.0 10.4 245 39 20 5.4 2.9 38.2 100.7 8.6 M M 20000 -10.6 12.9 245 28 15 1.5 0.8 36.4 97.6 7.2 M M 19500 -10.9 12.4 245 28 14 1.1 0.6 34.5 94.1 5.5 M M 19000 -10.4 13.3 245 28 15 5.0 2.7 33.4 92.2 4.5 M M 18500 -8.9 16.0 240 28 14 5.9 3.3 32.6 90.6 3.9 M M 18000 -7.8 18.0 240 29 15 6.4 3.5 32.0 89.5 3.5 M M 17500 -6.8 19.8 230 29 15 6.7 3.7 31.4 88.5 3.1 M M 17000 -5.8 21.6 240 22 11 4.2 2.3 30.8 87.4 2.6 M M 16500 -5.4 22.3 235 21 11 3.3 1.8 29.7 85.4 1.6 M M 16000 -5.0 23.0 235 27 14 3.3 1.8 28.6 83.4 0.6 M M 15500 -4.6 23.7 225 30 15 1.5 0.8 27.6 81.6 -0.5 957 4.9 15000 -4.1 24.6 225 31 16 10.1 5.6 26.7 80.1 -1.5 928 4.7 14500 -2.7 27.1 225 29 15 8.9 4.9 26.6 79.9 -1.6 872 4.4 14000 -1.4 29.5 230 25 13 8.9 4.9 26.5 79.7 -1.7 818 4.2 13500 -0.1 31.8 235 24 13 8.9 4.9 26.4 79.5 -1.8 763 3.9 13000 1.3 34.3 235 24 12 8.9 4.9 26.2 79.2 -2.0 708 3.6 12500 2.6 36.7 230 20 10 8.9 4.9 26.1 79.0 -2.1 653 3.3 12000 3.9 39.0 225 13 7 8.9 4.9 26.0 78.7 -2.2 599 3.0 11500 5.3 41.5 230 15 8 8.9 4.9 25.8 78.4 -2.4 544 2.8 11000 6.6 43.9 220 14 7 9.5 5.2 25.6 78.1 -2.6 489 2.5 10500 8.0 46.4 215 15 8 10.5 5.8 25.7 78.2 -2.6 431 2.2 10250 8.8 47.8 210 17 9 8.5 4.6 25.7 78.3 -2.6 402 2.0 10000 9.2 48.6 210 15 8 6.9 3.8 25.5 77.9 -2.9 380 1.9 9750 9.8 49.6 210 13 7 7.7 4.2 25.3 77.6 -3.0 356 1.8 9500 10.4 50.7 205 11 6 7.3 4.0 25.1 77.3 -3.2 332 1.7 9250 10.9 51.6 205 9 5 7.4 4.1 25.0 76.9 -3.4 308 1.6 9000 11.5 52.7 220 7 4 7.4 4.1 24.8 76.6 -3.5 283 1.4 8750 12.1 53.8 210 7 4 7.4 4.1 24.6 76.3 -3.7 259 1.3 8500 12.6 54.7 185 9 5 7.4 4.0 24.4 75.9 -3.9 235 1.2 8250 13.2 55.8 170 11 6 7.5 4.1 24.2 75.6 -4.1 211 1.1 8000 13.7 56.7 160 14 7 6.9 3.8 24.0 75.3 -4.3 186 0.9 7750 14.1 57.4 160 14 7 2.3 1.2 23.7 74.6 -4.6 167 0.9 7500 14.1 57.4 155 12 6 -2.7 -1.5 22.9 73.2 -5.4 161 0.8 7250 13.9 57.0 145 10 5 -1.6 -0.9 21.9 71.5 -6.3 159 0.8 7000 13.9 57.0 135 8 4 2.5 1.4 21.2 70.2 -7.0 151 0.8 6750 14.2 57.6 135 9 5 4.2 2.3 20.7 69.3 -7.5 135 0.7 6500 14.5 58.1 140 10 5 3.1 1.7 20.3 68.5 -8.0 119 0.6 6250 14.8 58.6 140 9 5 5.7 3.1 19.8 67.7 -8.4 103 0.5 6000 15.4 59.7 145 9 5 8.8 4.8 19.7 67.4 -8.6 78 0.4 5750 16.0 60.8 130 9 5 6.6 3.6 19.5 67.2 -8.8 53 0.3 5500 16.5 61.7 120 9 5 10.2 5.6 19.3 66.8 -9.0 31 0.2 5250 16.9 62.4 115 9 5 -6.5 -3.6 19.1 66.4 -9.4 11 0.1 5000 14.7 58.5 120 11 6 -51.3 -28.2 16.2 61.1 -12.3 69 0.4 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 09/19/2024 at 0900 MDT | 09/19/2024 at 1200 MDT | CAPE... 0.0 LI... +5.9 | CAPE... 0.0 LI... +5.8 CINH... -0.2 K Index... +2.4 | CINH... -0.0 K Index... +1.8 | 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 -62.5 -80.5 240 57 29 2.6 1.5 | -62.8 -81.0 240 59 30 2.6 1.4 45000 -57.3 -71.1 240 77 40 5.1 2.8 | -57.7 -71.9 240 78 40 5.0 2.7 40000 -49.7 -57.5 245 92 48 5.4 2.9 | -50.1 -58.2 245 94 49 5.3 2.9 38000 -46.5 -51.7 245 92 47 5.3 2.9 | -46.9 -52.4 240 93 48 5.3 2.9 36000 -43.3 -45.9 240 91 47 5.3 2.9 | -43.7 -46.7 240 91 47 5.3 2.9 34000 -39.5 -39.1 245 87 45 5.9 3.2 | -40.0 -40.0 240 86 44 6.4 3.5 32000 -36.0 -32.8 245 81 42 5.9 3.3 | -36.2 -33.2 240 79 41 6.4 3.5 30000 -31.8 -25.2 245 71 37 7.4 4.1 | -31.7 -25.1 240 72 37 8.0 4.4 29000 -29.6 -21.3 245 65 34 7.4 4.1 | -29.3 -20.7 240 68 35 8.0 4.4 28000 -27.3 -17.1 245 60 31 7.4 4.1 | -26.9 -16.4 240 63 33 8.0 4.4 27000 -25.1 -13.2 245 57 29 7.7 4.2 | -24.2 -11.6 240 59 30 7.2 4.0 26000 -22.8 -9.0 245 56 29 7.7 4.2 | -22.0 -7.6 240 55 29 7.2 4.0 25000 -20.5 -4.9 245 54 28 7.7 4.2 | -19.8 -3.6 240 52 27 7.3 4.0 24000 -18.3 -0.9 245 52 27 6.9 3.8 | -17.7 0.1 240 49 25 6.8 3.7 23000 -16.3 2.7 240 48 25 6.8 3.7 | -15.7 3.7 240 47 24 6.8 3.7 22000 -14.2 6.4 240 45 23 6.8 3.8 | -13.7 7.3 235 44 23 6.9 3.8 21000 -12.0 10.4 240 40 21 5.5 3.0 | -11.8 10.8 235 42 22 6.1 3.4 20000 -10.4 13.3 235 37 19 5.5 3.0 | -10.0 14.0 235 40 20 6.2 3.4 19500 -9.6 14.7 235 35 18 5.6 3.1 | -9.1 15.6 230 39 20 6.2 3.4 19000 -8.8 16.2 235 33 17 4.9 2.7 | -8.2 17.2 230 38 19 5.4 3.0 18500 -8.1 17.4 235 32 16 4.7 2.6 | -7.4 18.7 230 36 19 5.1 2.8 18000 -7.4 18.7 235 30 16 4.8 2.6 | -6.7 19.9 230 35 18 5.1 2.8 17500 -6.7 19.9 235 28 15 5.1 2.8 | -5.9 21.4 230 33 17 5.2 2.9 17000 -5.9 21.4 230 27 14 5.1 2.8 | -5.2 22.6 230 32 16 5.2 2.9 16500 -5.2 22.6 230 25 13 4.6 2.5 | -4.4 24.1 230 30 15 4.9 2.7 16000 -4.5 23.9 230 23 12 4.5 2.5 | -3.7 25.3 225 28 14 4.8 2.6 15500 -3.8 25.2 230 22 11 4.5 2.5 | -2.9 26.8 225 26 13 4.5 2.5 15000 -3.2 26.2 225 21 11 4.6 2.5 | -2.4 27.7 225 23 12 3.9 2.2 14500 -2.6 27.3 225 19 10 4.9 2.7 | -1.8 28.8 220 21 11 4.0 2.2 14000 -1.7 28.9 225 18 9 7.0 3.8 | -1.1 30.0 220 19 10 5.7 3.1 13500 -0.8 30.6 220 17 9 6.8 3.7 | -0.4 31.3 215 17 9 5.4 2.9 13000 0.3 32.5 220 16 8 8.5 4.7 | 0.6 33.1 210 16 8 8.2 4.5 12500 1.6 34.9 220 15 8 8.3 4.6 | 1.8 35.2 210 15 8 8.0 4.4 12000 2.8 37.0 215 14 7 8.6 4.7 | 3.0 37.4 210 14 7 8.7 4.8 11500 4.1 39.4 215 14 7 8.7 4.8 | 4.3 39.7 205 14 7 8.8 4.8 11000 5.3 41.5 215 13 7 8.2 4.5 | 5.5 41.9 205 13 7 8.1 4.5 10500 6.6 43.9 210 13 7 8.8 4.8 | 6.7 44.1 205 12 6 7.5 4.1 10250 7.2 45.0 210 13 6 5.7 3.1 | 7.3 45.1 205 12 6 10.6 5.8 10000 7.5 45.5 210 12 6 6.2 3.4 | 8.2 46.8 205 12 6 11.0 6.0 9750 8.1 46.6 205 12 6 9.6 5.2 | 8.9 48.0 205 12 6 8.2 4.5 9500 8.8 47.8 205 11 6 9.0 4.9 | 9.5 49.1 200 11 6 8.9 4.9 9250 9.5 49.1 200 11 6 7.9 4.3 | 10.9 51.6 200 10 5 8.9 4.9 9000 10.0 50.0 200 11 5 6.8 3.7 | 11.5 52.7 200 9 5 8.6 4.7 8750 10.5 50.9 195 10 5 7.3 4.0 | 12.2 54.0 195 9 5 8.8 4.9 8500 11.0 51.8 190 10 5 7.4 4.0 | 12.8 55.0 195 9 5 7.9 4.3 8250 11.6 52.9 185 10 5 6.3 3.5 | 13.4 56.1 190 8 4 8.2 4.5 8000 12.4 54.3 180 10 5 6.2 3.4 | 14.1 57.4 190 8 4 10.2 5.6 7750 12.8 55.0 175 10 5 5.7 3.1 | 14.8 58.6 190 7 4 10.1 5.5 7500 13.2 55.8 170 9 5 3.6 2.0 | 15.5 59.9 185 7 4 8.6 4.7 7250 13.4 56.1 165 10 5 2.7 1.5 | 16.1 61.0 185 7 4 8.3 4.5 7000 13.7 56.7 160 10 5 4.6 2.5 | 16.8 62.2 180 7 3 11.2 6.1 6750 14.0 57.2 150 8 4 4.5 2.5 | 17.7 63.9 185 7 3 11.8 6.5 6500 14.3 57.7 145 8 4 3.2 1.7 | 18.6 65.5 180 6 3 10.4 5.7 6250 14.5 58.1 140 7 4 3.0 1.7 | 19.3 66.7 180 6 3 10.2 5.6 6000 14.8 58.6 135 7 4 4.4 2.4 | 20.1 68.2 175 6 3 11.0 6.0 5750 15.2 59.4 120 5 2 9.0 4.9 | 21.2 70.2 180 5 3 19.4 10.6 5500 16.0 60.8 105 4 2 9.5 5.2 | 23.4 74.1 170 5 2 43.3 23.8 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 09/19/2024 at 1500 MDT | 09/19/2024 at 1800 MDT | CAPE... 0.0 LI... +5.4 | CAPE... 0.0 LI... +5.2 CINH... -0.0 K Index... +7.7 | CINH... -0.1 K Index... +4.9 | 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 -62.7 -80.9 245 59 30 2.1 1.1 | -62.9 -81.2 245 57 29 1.9 1.0 45000 -58.1 -72.6 245 80 41 5.1 2.8 | -58.5 -73.3 245 81 41 5.3 2.9 40000 -50.4 -58.7 245 94 48 5.8 3.2 | -50.5 -58.9 245 97 50 6.3 3.4 38000 -47.0 -52.6 240 93 48 5.7 3.1 | -46.8 -52.2 240 94 49 6.2 3.4 36000 -43.1 -45.6 235 91 47 5.6 3.1 | -43.0 -45.4 240 92 47 6.2 3.4 34000 -39.2 -38.6 235 85 44 6.6 3.6 | -38.7 -37.7 235 88 45 6.6 3.6 32000 -35.3 -31.5 235 79 41 6.6 3.6 | -34.7 -30.5 235 84 43 6.5 3.6 30000 -30.9 -23.6 235 71 36 7.6 4.2 | -30.5 -22.9 235 77 39 7.1 3.9 29000 -28.6 -19.5 235 67 34 7.6 4.2 | -28.4 -19.1 235 72 37 7.1 3.9 28000 -26.4 -15.5 235 62 32 7.5 4.1 | -26.3 -15.3 235 67 35 7.1 3.9 27000 -24.3 -11.7 235 58 30 6.8 3.7 | -24.2 -11.6 235 62 32 6.9 3.8 26000 -22.3 -8.1 235 54 28 6.8 3.7 | -22.1 -7.8 235 57 30 6.9 3.8 25000 -20.2 -4.4 235 51 26 6.8 3.7 | -20.1 -4.2 235 52 27 6.9 3.8 24000 -18.2 -0.8 235 47 24 6.8 3.7 | -18.1 -0.6 235 48 25 6.4 3.5 23000 -16.1 3.0 235 45 23 6.8 3.8 | -16.2 2.8 235 43 22 6.4 3.5 22000 -13.6 7.5 235 41 21 6.8 3.8 | -14.3 6.3 230 39 20 6.4 3.5 21000 -11.5 11.3 235 40 21 6.9 3.8 | -11.8 10.8 230 35 18 6.8 3.8 20000 -9.5 14.9 235 39 20 6.9 3.8 | -9.7 14.5 225 33 17 6.9 3.8 19500 -8.4 16.9 235 38 20 7.0 3.8 | -8.7 16.3 225 32 16 6.9 3.8 19000 -7.5 18.5 235 37 19 6.0 3.3 | -7.7 18.1 225 31 16 6.4 3.5 18500 -6.6 20.1 230 36 19 5.9 3.2 | -6.8 19.8 225 30 15 6.4 3.5 18000 -5.7 21.7 230 35 18 5.6 3.1 | -5.8 21.6 225 28 15 6.3 3.4 17500 -5.0 23.0 230 34 17 4.5 2.5 | -5.0 23.0 225 27 14 5.8 3.2 17000 -4.4 24.1 230 32 16 4.6 2.5 | -4.1 24.6 220 26 13 5.9 3.2 16500 -3.7 25.3 230 30 15 4.8 2.6 | -3.3 26.1 220 24 12 5.3 2.9 16000 -3.0 26.6 230 27 14 4.8 2.7 | -2.5 27.5 220 22 11 5.3 2.9 15500 -2.4 27.7 225 25 13 5.1 2.8 | -1.8 28.8 220 20 10 5.6 3.1 15000 -1.6 29.1 225 23 12 5.4 3.0 | -1.0 30.2 215 19 10 5.9 3.2 14500 -0.8 30.6 220 21 11 5.6 3.1 | -0.2 31.6 210 17 9 6.2 3.4 14000 0.1 32.2 215 19 10 6.9 3.8 | 0.9 33.6 210 16 8 7.5 4.1 13500 1.1 34.0 210 18 9 6.8 3.7 | 1.9 35.4 205 15 8 7.4 4.1 13000 2.2 36.0 210 16 8 8.7 4.8 | 3.1 37.6 205 14 7 8.7 4.8 12500 3.4 38.1 205 16 8 8.5 4.7 | 4.4 39.9 205 14 7 8.6 4.7 12000 4.7 40.5 205 15 8 8.7 4.8 | 5.6 42.1 205 13 7 9.0 4.9 11500 6.0 42.8 205 14 7 8.8 4.8 | 7.0 44.6 210 12 6 9.1 5.0 11000 7.3 45.1 205 13 7 8.1 4.5 | 8.2 46.8 210 11 6 7.5 4.1 10500 8.5 47.3 205 11 6 8.0 4.4 | 9.3 48.7 210 10 5 7.4 4.1 10250 9.1 48.4 205 11 6 10.3 5.7 | 10.0 50.0 210 9 5 11.2 6.1 10000 10.0 50.0 205 11 6 10.4 5.7 | 10.9 51.6 215 10 5 11.0 6.1 9750 10.6 51.1 210 11 6 8.6 4.7 | 11.5 52.7 215 9 5 8.0 4.4 9500 11.3 52.3 210 10 5 9.0 4.9 | 12.2 54.0 215 9 5 9.3 5.1 9250 12.0 53.6 210 10 5 9.4 5.2 | 12.8 55.0 220 8 4 7.1 3.9 9000 12.7 54.9 215 8 4 9.9 5.5 | 13.3 55.9 225 7 4 7.6 4.1 8750 13.4 56.1 215 9 4 9.6 5.3 | 14.0 57.2 230 7 4 9.7 5.3 8500 14.9 58.8 215 9 5 8.9 4.9 | 14.7 58.5 235 7 4 9.5 5.2 8250 15.5 59.9 220 8 4 9.2 5.0 | 15.9 60.6 255 6 3 7.9 4.4 8000 16.3 61.3 220 8 4 10.7 5.9 | 16.6 61.9 255 6 3 9.9 5.5 7750 17.0 62.6 220 8 4 10.5 5.8 | 17.3 63.1 255 7 3 9.8 5.4 7500 17.8 64.0 220 8 4 8.9 4.9 | 18.1 64.6 255 7 4 8.6 4.7 7250 18.4 65.1 225 7 4 8.5 4.6 | 18.6 65.5 265 7 4 8.2 4.5 7000 19.1 66.4 230 7 4 11.1 6.1 | 19.3 66.7 270 7 4 10.3 5.6 6750 20.0 68.0 225 7 4 11.7 6.4 | 20.1 68.2 260 7 4 10.9 6.0 6500 20.8 69.4 225 7 4 10.6 5.8 | 20.9 69.6 265 7 4 10.1 5.5 6250 21.6 70.9 235 6 3 10.8 5.9 | 21.7 71.1 270 7 4 10.3 5.7 6000 22.4 72.3 235 6 3 8.8 4.8 | 22.4 72.3 275 7 4 8.2 4.5 5750 23.1 73.6 230 6 3 14.3 7.9 | 22.9 73.2 265 6 3 7.8 4.3 5500 25.7 78.3 245 5 3 69.2 38.0 | 24.3 75.7 280 6 3 37.0 20.3 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