Issued by NWS Denver/Boulder, CO
000 UXUS97 KBOU 070049 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 649 PM MDT Wednesday May 6, 2009 This forecast is for Thursday May 7, 2009: If the trigger temperature of 64.2 F/17.9 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 815 ft/min (4.1 m/s) Maximum height of thermals.................. 15858 ft MSL (10535 ft AGL) Forecast maximum temperature................... 80.0 F/27.1 C Time of trigger temperature.................... 1015 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................. 13502 ft MSL (8179 ft AGL) Thermal soaring outlook for Friday 05/08....... Good Wave Soaring Index............................. Good 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....................... 45458 ft MSL (40135 ft AGL) Wave soaring outlook for Friday 05/08.......... Poor Remarks... None Sunrise/Sunset.................... 05:52:48 / 19:59:01 MDT Total possible sunshine........... 14 hr 6 min 13 sec (846 min 13 sec) Altitude of sun at 12:56:05 MDT... 67.23 degrees Upper air data from numerical model forecast valid on 05/07/2009 at 0600 MDT Freezing level.................. 12668 ft MSL (7345 ft AGL) Convective condensation level... 18484 ft MSL (13161 ft AGL) Lifted condensation level....... 17398 ft MSL (12075 ft AGL) Lifted index.................... +1.0 K index......................... +2.3 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 -62.9 -81.2 282 64 33 0.1 0.0 89.1 192.3 36.2 M M 45000 -61.8 -79.2 282 93 48 4.4 2.4 67.8 154.1 25.5 M M 40000 -55.3 -67.5 289 95 49 4.3 2.4 55.4 131.8 19.1 M M 38000 -51.7 -61.1 290 94 48 6.2 3.4 51.7 125.1 17.1 M M 36000 -48.0 -54.4 291 92 47 6.2 3.4 48.7 119.7 15.4 M M 34000 -43.6 -46.5 292 88 46 6.8 3.7 45.7 114.2 13.7 M M 32000 -39.5 -39.1 293 84 43 6.8 3.7 43.3 109.9 12.2 M M 30000 -35.7 -32.3 294 77 40 6.1 3.3 40.6 105.1 10.5 M M 29000 -33.9 -29.0 295 73 38 6.1 3.3 39.1 102.5 9.5 M M 28000 -32.0 -25.6 295 69 36 6.2 3.4 37.8 100.1 8.6 M M 27000 -30.0 -22.0 295 65 33 7.5 4.1 36.7 98.1 7.8 M M 26000 -27.8 -18.0 292 61 31 7.5 4.1 35.8 96.4 7.2 M M 25000 -25.5 -13.9 288 57 29 7.5 4.1 35.0 95.0 6.7 M M 24000 -23.1 -9.6 285 53 27 8.8 4.8 34.3 93.8 6.2 M M 23000 -20.5 -4.9 281 48 25 8.6 4.7 33.9 92.9 5.9 M M 22000 -18.0 -0.4 277 44 23 8.6 4.7 33.5 92.3 5.6 M M 21000 -15.5 4.1 273 42 21 7.3 4.0 32.9 91.3 5.2 M M 20000 -13.3 8.1 272 41 21 7.3 4.0 32.0 89.7 4.5 M M 19500 -12.2 10.0 271 41 21 7.4 4.0 31.6 88.9 4.2 M M 19000 -11.1 12.0 271 41 21 7.5 4.1 31.2 88.2 3.9 M M 18500 -10.1 13.8 270 40 21 6.0 3.3 30.8 87.4 3.5 M M 18000 -8.8 16.2 271 40 21 6.3 3.4 29.8 85.7 2.7 M M 17500 -7.9 17.8 272 40 20 5.3 2.9 29.1 84.5 2.1 M M 17000 -7.1 19.2 274 40 21 5.4 3.0 28.4 83.1 1.4 M M 16500 -6.3 20.7 276 40 21 5.4 3.0 27.7 81.8 0.7 M M 16000 -5.5 22.1 278 40 20 5.5 3.0 26.9 80.5 0.1 M M 15500 -4.7 23.5 279 39 20 5.6 3.1 26.2 79.2 -0.6 780 4.0 15000 -3.9 25.0 280 39 20 6.0 3.3 25.6 78.0 -1.2 740 3.8 14500 -3.0 26.6 282 39 20 6.1 3.3 24.9 76.9 -1.8 699 3.5 14000 -2.1 28.2 283 39 20 5.7 3.1 24.3 75.7 -2.4 658 3.3 13500 -1.3 29.7 284 40 21 5.7 3.1 23.6 74.5 -3.1 619 3.1 13000 -0.5 31.1 285 41 21 5.6 3.1 23.0 73.4 -3.7 579 2.9 12500 0.3 32.5 286 39 20 5.6 3.1 22.3 72.1 -4.4 540 2.7 12000 1.1 34.0 287 38 20 5.5 3.0 21.6 70.9 -5.1 501 2.5 11500 1.9 35.4 289 37 19 5.4 3.0 20.9 69.7 -5.8 463 2.4 11000 2.7 36.9 290 35 18 6.0 3.3 20.3 68.5 -6.5 424 2.2 10500 3.6 38.5 292 33 17 6.2 3.4 19.7 67.5 -7.1 382 1.9 10250 4.1 39.4 293 32 17 6.3 3.5 19.4 67.0 -7.4 362 1.8 10000 4.5 40.1 294 31 16 6.6 3.6 19.2 66.5 -7.7 340 1.7 9750 5.0 41.0 295 30 15 6.7 3.7 18.9 66.0 -7.9 318 1.6 9500 5.5 41.9 296 29 15 6.6 3.6 18.7 65.6 -8.2 296 1.5 9250 6.0 42.8 297 28 14 6.9 3.8 18.4 65.2 -8.5 274 1.4 9000 6.5 43.7 298 26 14 7.3 4.0 18.2 64.8 -8.7 251 1.3 8750 7.1 44.8 299 25 13 7.4 4.1 18.0 64.5 -8.9 228 1.2 8500 7.6 45.7 300 23 12 7.3 4.0 17.9 64.2 -9.1 204 1.0 8250 8.1 46.6 301 22 11 7.6 4.2 17.7 63.8 -9.3 180 0.9 8000 8.7 47.7 302 20 10 7.9 4.3 17.5 63.6 -9.5 156 0.8 7750 9.3 48.7 302 18 9 7.9 4.3 17.4 63.3 -9.7 131 0.7 7500 9.9 49.8 303 17 9 7.9 4.3 17.2 63.0 -9.9 106 0.5 7250 10.5 50.9 304 15 8 8.0 4.4 17.1 62.8 -10.0 81 0.4 7000 11.1 52.0 304 12 6 7.9 4.3 17.0 62.5 -10.2 56 0.3 6750 11.7 53.1 304 10 5 8.3 4.6 16.8 62.3 -10.4 31 0.2 6500 12.2 54.0 304 8 4 6.8 3.7 16.7 62.1 -10.5 6 0.0 6250 12.6 54.7 290 7 3 4.0 2.2 16.4 61.4 -10.9 M M 6000 13.0 55.4 268 6 3 6.1 3.4 16.0 60.7 -11.3 M M 5750 13.3 55.9 244 6 3 -1.6 -0.9 15.6 60.0 -11.7 M M 5500 12.1 53.8 224 6 3 -33.1 -18.2 13.6 56.5 -13.7 M M * * * * * * Numerical weather prediction model forecast data valid * * * * * * 05/07/2009 at 0900 MDT | 05/07/2009 at 1200 MDT | K index... -0.6 | K index... +9.9 | 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 -63.2 -81.8 286 66 34 0.8 0.5 | -64.5 -84.1 286 63 32 1.5 0.8 45000 -61.3 -78.3 285 94 48 3.8 2.1 | -61.6 -78.9 286 88 45 4.4 2.4 40000 -55.7 -68.3 286 99 51 3.5 1.9 | -55.0 -67.0 282 90 47 4.4 2.4 38000 -52.2 -62.0 287 96 50 6.0 3.3 | -51.6 -60.9 282 88 45 5.9 3.2 36000 -48.6 -55.5 287 92 48 6.0 3.3 | -47.6 -53.7 282 84 43 5.9 3.2 34000 -44.2 -47.6 288 87 45 6.9 3.8 | -43.8 -46.8 281 80 41 6.7 3.7 32000 -40.1 -40.2 288 80 41 6.9 3.8 | -39.8 -39.6 281 74 38 6.8 3.7 30000 -35.9 -32.6 289 74 38 7.2 3.9 | -35.5 -31.9 281 70 36 7.4 4.1 29000 -33.7 -28.7 288 70 36 7.2 3.9 | -33.3 -27.9 282 68 35 7.4 4.1 28000 -31.6 -24.9 288 66 34 7.2 3.9 | -31.0 -23.8 283 66 34 7.5 4.1 27000 -29.4 -20.9 287 62 32 6.9 3.8 | -28.8 -19.8 283 64 33 7.3 4.0 26000 -27.4 -17.3 286 57 29 6.9 3.8 | -26.6 -15.9 282 61 32 7.3 4.0 25000 -25.3 -13.5 284 52 27 6.9 3.8 | -24.4 -11.9 281 58 30 7.3 4.0 24000 -23.2 -9.8 282 48 25 7.8 4.3 | -22.2 -8.0 279 54 28 7.1 3.9 23000 -20.9 -5.6 280 44 22 7.8 4.3 | -20.1 -4.2 275 47 24 7.1 3.9 22000 -18.5 -1.3 277 39 20 7.7 4.3 | -17.9 -0.2 269 40 21 7.1 3.9 21000 -16.3 2.7 276 36 19 7.3 4.0 | -15.8 3.6 268 38 19 7.4 4.0 20000 -14.1 6.6 276 35 18 7.3 4.0 | -13.6 7.5 273 42 21 7.4 4.0 19500 -13.0 8.6 277 34 17 7.3 4.0 | -12.5 9.5 276 44 23 7.4 4.0 19000 -11.9 10.6 277 33 17 7.3 4.0 | -10.8 12.6 279 47 24 6.2 3.4 18500 -10.2 13.6 279 34 17 7.4 4.1 | -10.1 13.8 281 49 25 5.0 2.8 18000 -9.1 15.6 282 35 18 7.5 4.1 | -9.3 15.3 282 51 26 5.1 2.8 17500 -8.1 17.4 284 37 19 6.3 3.5 | -8.7 16.3 283 50 26 3.1 1.7 17000 -7.1 19.2 285 38 20 6.5 3.5 | -8.2 17.2 283 48 25 3.3 1.8 16500 -6.2 20.8 287 40 20 5.9 3.2 | -7.8 18.0 283 46 24 3.9 2.1 16000 -5.3 22.5 288 41 21 5.6 3.1 | -7.2 19.0 283 44 23 4.3 2.3 15500 -4.5 23.9 289 43 22 5.5 3.0 | -6.6 20.1 283 41 21 4.7 2.6 15000 -3.7 25.3 289 44 23 5.3 2.9 | -5.8 21.6 282 38 19 5.9 3.2 14500 -3.0 26.6 290 44 23 5.3 2.9 | -5.0 23.0 280 34 17 5.8 3.2 14000 -2.2 28.0 290 44 23 5.2 2.8 | -3.9 25.0 278 31 16 8.6 4.7 13500 -1.4 29.5 290 44 23 5.2 2.8 | -2.7 27.1 277 28 14 8.3 4.6 13000 -0.6 30.9 290 44 23 5.9 3.2 | -1.5 29.3 275 25 13 8.9 4.9 12500 0.2 32.4 290 42 22 5.9 3.3 | -0.1 31.8 274 23 12 8.9 4.9 12000 1.1 34.0 290 41 21 5.9 3.3 | 1.2 34.2 273 21 11 9.0 4.9 11500 1.9 35.4 290 38 20 5.9 3.3 | 2.5 36.5 273 20 10 9.1 5.0 11000 2.8 37.0 290 35 18 6.4 3.5 | 3.8 38.8 272 18 9 8.6 4.7 10500 3.7 38.7 290 32 16 6.4 3.5 | 5.1 41.2 271 16 8 8.6 4.7 10250 4.2 39.6 289 30 15 6.8 3.7 | 5.7 42.3 270 15 8 8.5 4.7 10000 4.7 40.5 289 28 14 7.4 4.1 | 6.3 43.3 269 14 7 8.4 4.6 9750 5.3 41.5 289 26 14 7.5 4.1 | 7.0 44.6 267 12 6 8.3 4.6 9500 5.8 42.4 289 24 13 7.6 4.2 | 7.6 45.7 265 11 6 8.4 4.6 9250 6.4 43.5 289 22 12 7.3 4.0 | 8.2 46.8 263 10 5 8.1 4.4 9000 6.9 44.4 289 20 10 6.8 3.7 | 8.8 47.8 258 9 5 7.6 4.2 8750 7.3 45.1 288 18 9 6.8 3.7 | 9.3 48.7 252 8 4 7.6 4.2 8500 7.8 46.0 287 16 8 6.8 3.7 | 9.9 49.8 244 7 3 7.6 4.2 8250 8.3 46.9 286 14 7 6.7 3.6 | 10.5 50.9 232 6 3 7.7 4.2 8000 8.8 47.8 284 12 6 6.5 3.6 | 11.1 52.0 223 5 3 7.8 4.3 7750 9.3 48.7 280 10 5 6.5 3.6 | 11.6 52.9 210 4 2 7.7 4.2 7500 9.8 49.6 275 8 4 6.7 3.7 | 12.2 54.0 195 4 2 8.1 4.4 7250 10.3 50.5 264 6 3 7.2 3.9 | 12.8 55.0 184 4 2 9.3 5.1 7000 10.8 51.4 244 5 2 7.5 4.1 | 13.6 56.5 181 4 2 9.8 5.4 6750 11.4 52.5 218 5 2 7.1 3.9 | 14.3 57.7 178 4 2 9.6 5.3 6500 11.9 53.4 194 5 3 8.3 4.5 | 15.0 59.0 174 3 2 9.9 5.4 6250 12.6 54.7 191 6 3 9.8 5.3 | 15.7 60.3 173 3 2 10.4 5.7 6000 13.3 55.9 189 6 3 8.9 4.9 | 16.5 61.7 173 3 2 9.7 5.3 5750 13.9 57.0 187 6 3 11.2 6.2 | 17.3 63.1 173 3 2 12.0 6.6 5500 15.0 59.0 187 6 3 18.3 10.1 | 18.4 65.1 172 3 1 20.2 11.1 05/07/2009 at 1500 MDT | 05/07/2009 at 1800 MDT | K index... +18.0 | K index... +15.6 | 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 -64.8 -84.6 276 59 30 1.5 0.8 | -65.3 -85.5 274 64 33 1.2 0.7 45000 -61.9 -79.4 283 85 44 4.7 2.6 | -62.6 -80.7 282 92 47 4.8 2.6 40000 -54.9 -66.8 278 87 45 4.7 2.6 | -55.4 -67.7 282 92 47 4.8 2.6 38000 -51.4 -60.5 279 84 43 5.8 3.2 | -52.4 -62.3 282 86 44 5.1 2.8 36000 -47.5 -53.5 280 81 42 5.8 3.2 | -49.3 -56.7 281 79 41 5.1 2.8 34000 -43.6 -46.5 279 78 40 6.8 3.7 | -45.5 -49.9 281 75 38 7.8 4.3 32000 -39.6 -39.3 278 75 39 6.8 3.8 | -40.2 -40.4 282 71 37 7.8 4.3 30000 -35.3 -31.5 277 72 37 7.4 4.1 | -35.5 -31.9 280 69 35 7.9 4.3 29000 -33.1 -27.6 276 71 36 7.4 4.1 | -33.1 -27.6 279 68 35 7.9 4.3 28000 -30.9 -23.6 276 70 36 7.4 4.1 | -30.8 -23.4 277 67 34 7.9 4.3 27000 -28.7 -19.7 276 68 35 7.5 4.1 | -28.5 -19.3 276 66 34 7.7 4.2 26000 -26.4 -15.5 276 65 33 7.5 4.1 | -26.2 -15.2 276 65 34 7.7 4.2 25000 -24.2 -11.6 277 62 32 7.5 4.1 | -23.9 -11.0 276 65 33 7.7 4.2 24000 -21.9 -7.4 277 59 30 7.5 4.1 | -21.7 -7.1 276 64 33 7.4 4.1 23000 -19.7 -3.5 276 55 28 7.5 4.1 | -19.4 -2.9 276 64 33 7.5 4.1 22000 -17.4 0.7 274 50 26 7.5 4.1 | -17.2 1.0 276 64 33 7.4 4.1 21000 -15.6 3.9 274 48 25 3.7 2.0 | -15.3 4.5 277 63 32 5.3 2.9 20000 -14.4 6.1 276 50 26 3.9 2.1 | -13.7 7.3 277 61 31 5.3 2.9 19500 -13.8 7.2 277 51 26 3.9 2.1 | -12.9 8.8 278 59 31 5.3 2.9 19000 -12.9 8.8 278 53 27 4.3 2.3 | -12.1 10.2 278 58 30 5.5 3.0 18500 -12.3 9.9 278 49 25 4.7 2.6 | -11.5 11.3 278 56 29 3.5 1.9 18000 -11.6 11.1 277 46 24 4.6 2.5 | -10.9 12.4 278 52 27 3.8 2.1 17500 -10.8 12.6 276 42 22 6.7 3.7 | -9.9 14.2 278 45 23 7.0 3.8 17000 -9.8 14.4 274 38 20 6.6 3.6 | -8.9 16.0 276 41 21 6.6 3.6 16500 -8.9 16.0 271 34 18 7.7 4.2 | -7.9 17.8 274 37 19 7.7 4.2 16000 -7.6 18.3 269 32 16 8.4 4.6 | -6.7 19.9 272 34 17 8.2 4.5 15500 -6.4 20.5 266 29 15 8.6 4.7 | -5.5 22.1 269 30 16 8.4 4.6 15000 -5.1 22.8 264 27 14 9.1 5.0 | -4.2 24.4 268 28 14 8.8 4.9 14500 -3.7 25.3 262 25 13 9.1 5.0 | -2.9 26.8 266 25 13 8.8 4.8 14000 -2.4 27.7 262 24 12 9.2 5.0 | -1.5 29.3 265 23 12 9.5 5.2 13500 -1.0 30.2 262 24 12 9.1 5.0 | -0.1 31.8 264 21 11 9.5 5.2 13000 0.4 32.7 262 23 12 9.6 5.2 | 1.3 34.3 264 20 10 9.6 5.3 12500 1.8 35.2 262 22 11 9.6 5.3 | 2.7 36.9 264 19 10 9.6 5.3 12000 3.2 37.8 263 21 11 9.1 5.0 | 4.1 39.4 264 18 9 9.6 5.2 11500 4.6 40.3 264 19 10 9.1 5.0 | 5.5 41.9 265 17 9 9.5 5.2 11000 5.9 42.6 264 17 9 8.9 4.9 | 7.0 44.6 265 17 9 9.9 5.4 10500 7.2 45.0 264 15 8 8.8 4.8 | 8.5 47.3 265 16 8 9.9 5.5 10250 7.9 46.2 264 14 7 8.8 4.8 | 9.2 48.6 265 16 8 10.0 5.5 10000 8.5 47.3 265 13 7 8.7 4.8 | 10.0 50.0 265 16 8 10.0 5.5 9750 9.2 48.6 266 12 6 8.8 4.8 | 10.7 51.3 265 16 8 10.0 5.5 9500 9.8 49.6 267 11 6 8.7 4.7 | 11.4 52.5 266 16 8 10.0 5.5 9250 10.4 50.7 268 10 5 9.1 5.0 | 12.2 54.0 266 16 8 9.9 5.4 9000 11.1 52.0 269 9 5 9.8 5.4 | 12.9 55.2 266 15 8 9.6 5.2 8750 11.8 53.2 269 9 5 9.9 5.4 | 13.6 56.5 266 15 8 9.5 5.2 8500 12.6 54.7 270 9 5 9.9 5.4 | 14.3 57.7 266 15 8 9.5 5.2 8250 13.3 55.9 271 9 4 10.0 5.5 | 15.1 59.2 266 15 8 9.6 5.3 8000 14.0 57.2 271 8 4 10.1 5.5 | 15.8 60.4 266 15 8 9.7 5.3 7750 14.8 58.6 272 8 4 10.0 5.5 | 16.5 61.7 266 15 8 9.7 5.3 7500 15.6 60.1 272 8 4 10.0 5.5 | 17.2 63.0 267 14 7 9.7 5.3 7250 16.3 61.3 273 8 4 9.9 5.4 | 17.9 64.2 267 14 7 10.0 5.5 7000 17.0 62.6 274 8 4 9.9 5.4 | 18.7 65.7 267 14 7 10.3 5.6 6750 17.8 64.0 275 7 4 9.8 5.4 | 19.5 67.1 267 14 7 10.2 5.6 6500 18.5 65.3 276 7 4 10.0 5.5 | 20.2 68.4 267 14 7 10.2 5.6 6250 19.3 66.7 277 7 4 10.3 5.6 | 21.0 69.8 267 13 7 10.1 5.5 6000 20.0 68.0 277 6 3 10.4 5.7 | 21.7 71.1 267 12 6 10.1 5.6 5750 20.8 69.4 278 6 3 10.2 5.6 | 22.5 72.5 267 12 6 9.7 5.3 5500 21.7 71.1 279 6 3 16.5 9.1 | 23.2 73.8 267 11 6 11.3 6.2 ________________________________________________________________________________ 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: 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 - 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, cirrostatus, 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. 071806