Issued by NWS Denver/Boulder, CO
000 UXUS97 KBOU 050051 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 650 PM MDT Monday May 4, 2009 This forecast is for Tuesday May 5, 2009: If the trigger temperature of 61.9 F/16.6 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 843 ft/min (4.3 m/s) Maximum height of thermals.................. 15613 ft MSL (10290 ft AGL) Forecast maximum temperature................... 74.0 F/23.8 C Time of trigger temperature.................... 1030 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................. 13561 ft MSL (8238 ft AGL) Thermal soaring outlook for Wednesday 05/06.... 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 NVA Potential height of wave....................... 39983 ft MSL (34660 ft AGL) Wave soaring outlook for Wednesday 05/06....... Fair Remarks... None Sunrise/Sunset.................... 05:55:02 / 19:57:02 MDT Total possible sunshine........... 14 hr 1 min 59 sec (841 min 59 sec) Altitude of sun at 12:56:13 MDT... 66.67 degrees Upper air data from numerical model forecast valid on 05/05/2009 at 0600 MDT Freezing level.................. 11205 ft MSL (5882 ft AGL) Convective condensation level... 13488 ft MSL (8165 ft AGL) Lifted condensation level....... 14942 ft MSL (9619 ft AGL) Lifted index.................... +0.3 K index......................... +17.8 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 -63.3 -81.9 286 55 28 -1.7 -0.9 90.8 195.4 38.9 M M 45000 -65.4 -85.7 284 74 38 3.4 1.9 63.6 146.4 24.8 M M 40000 -60.4 -76.7 283 89 46 3.3 1.8 48.4 119.1 16.6 M M 38000 -56.1 -69.0 284 83 43 8.3 4.6 45.9 114.6 15.4 M M 36000 -51.1 -60.0 284 74 38 8.3 4.6 44.7 112.4 14.9 M M 34000 -46.0 -50.8 284 65 33 8.8 4.8 43.7 110.7 14.6 M M 32000 -40.7 -41.3 282 56 29 8.8 4.8 42.9 109.3 14.4 M M 30000 -35.4 -31.7 282 50 25 6.5 3.6 41.3 106.3 13.5 M M 29000 -33.5 -28.3 285 48 25 6.5 3.6 40.0 104.0 12.7 M M 28000 -31.6 -24.9 288 48 24 6.5 3.6 38.8 101.9 11.9 M M 27000 -29.7 -21.5 290 46 24 6.0 3.3 37.6 99.6 11.1 M M 26000 -27.9 -18.2 290 43 22 6.1 3.3 36.1 97.0 10.0 M M 25000 -26.1 -15.0 289 40 21 6.1 3.3 34.7 94.5 9.0 M M 24000 -24.2 -11.6 288 38 19 6.4 3.5 33.5 92.3 8.1 M M 23000 -22.3 -8.1 287 37 19 6.5 3.5 32.2 89.9 7.1 M M 22000 -20.4 -4.7 287 37 19 6.5 3.5 31.0 87.8 6.2 M M 21000 -18.5 -1.3 286 37 19 6.9 3.8 29.9 85.9 5.3 M M 20000 -16.4 2.5 286 36 19 6.8 3.8 28.8 83.9 4.4 M M 19500 -15.4 4.3 286 36 19 6.8 3.8 28.3 83.0 4.0 M M 19000 -14.4 6.1 286 36 19 6.9 3.8 27.9 82.2 3.6 M M 18500 -13.4 7.9 286 36 19 7.0 3.9 27.4 81.4 3.2 M M 18000 -12.4 9.7 286 36 18 7.1 3.9 26.9 80.5 2.8 M M 17500 -11.3 11.7 285 36 18 7.0 3.9 26.5 79.7 2.4 M M 17000 -10.4 13.3 284 36 18 6.1 3.3 25.9 78.7 1.9 M M 16500 -9.0 15.8 283 36 19 5.9 3.2 25.0 77.1 1.1 M M 16000 -8.2 17.2 282 36 19 4.9 2.7 24.3 75.7 0.4 M M 15500 -7.5 18.5 281 37 19 4.9 2.7 23.4 74.2 -0.3 827 4.2 15000 -6.8 19.8 280 37 19 5.3 2.9 22.7 72.8 -1.0 791 4.0 14500 -6.0 21.2 280 36 19 5.2 2.9 21.9 71.4 -1.8 753 3.8 14000 -5.3 22.5 279 36 18 5.3 2.9 21.2 70.1 -2.5 716 3.6 13500 -4.5 23.9 279 35 18 5.3 2.9 20.4 68.8 -3.2 678 3.4 13000 -3.7 25.3 279 34 17 6.2 3.4 19.7 67.5 -3.9 639 3.2 12500 -2.7 27.1 278 32 16 6.8 3.7 19.2 66.6 -4.4 595 3.0 12000 -1.7 28.9 278 30 15 7.3 4.0 18.8 65.8 -4.8 550 2.8 11500 -0.6 30.9 276 27 14 7.7 4.2 18.4 65.2 -5.2 502 2.5 11000 0.5 32.9 275 24 13 8.0 4.4 18.1 64.7 -5.5 453 2.3 10500 1.7 35.1 273 22 11 8.3 4.5 17.9 64.2 -5.8 402 2.0 10250 2.4 36.3 272 21 11 8.3 4.5 17.8 64.0 -5.9 376 1.9 10000 3.0 37.4 271 19 10 8.4 4.6 17.7 63.8 -6.1 350 1.8 9750 3.6 38.5 268 18 9 8.5 4.6 17.6 63.6 -6.2 324 1.6 9500 4.2 39.6 264 17 9 8.5 4.6 17.5 63.4 -6.3 299 1.5 9250 4.8 40.6 261 16 8 8.4 4.6 17.4 63.3 -6.5 273 1.4 9000 5.4 41.7 256 15 8 8.2 4.5 17.3 63.1 -6.6 247 1.3 8750 6.0 42.8 251 13 7 8.1 4.4 17.1 62.8 -6.8 222 1.1 8500 6.6 43.9 244 12 6 8.1 4.4 17.0 62.6 -6.9 197 1.0 8250 7.2 45.0 236 11 6 8.1 4.4 16.9 62.4 -7.1 171 0.9 8000 7.8 46.0 230 10 5 7.9 4.4 16.7 62.1 -7.2 146 0.7 7750 8.4 47.1 225 9 5 8.0 4.4 16.6 61.9 -7.4 121 0.6 7500 9.0 48.2 219 9 4 7.7 4.2 16.5 61.6 -7.5 96 0.5 7250 9.6 49.3 213 8 4 8.8 4.8 16.3 61.4 -7.7 71 0.4 7000 10.3 50.5 220 8 4 9.6 5.3 16.3 61.3 -7.7 42 0.2 6750 11.0 51.8 226 9 4 10.0 5.5 16.3 61.3 -7.8 14 0.1 6500 11.7 53.1 232 9 5 7.4 4.1 16.3 61.3 -7.8 M M 6250 12.0 53.6 233 9 5 -0.3 -0.2 15.8 60.5 -8.3 M M 6000 11.7 53.1 229 8 4 -3.9 -2.1 14.9 58.7 -9.3 M M 5750 11.5 52.7 225 8 4 -1.2 -0.6 13.9 57.0 -10.3 M M 5500 11.2 52.2 219 7 4 -12.6 -6.9 12.9 55.2 -11.3 M M * * * * * * Numerical weather prediction model forecast data valid * * * * * * 05/05/2009 at 0900 MDT | 05/05/2009 at 1200 MDT | K index... +15.1 | K index... +20.7 | 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 -61.9 -79.4 287 49 25 0.1 0.0 | -60.6 -77.1 288 41 21 0.5 0.3 45000 -61.7 -79.1 280 60 31 1.0 0.5 | -59.9 -75.8 288 58 30 0.4 0.2 40000 -60.3 -76.5 282 59 31 1.1 0.6 | -59.2 -74.6 286 61 31 0.5 0.3 38000 -57.0 -70.6 282 57 29 7.0 3.9 | -56.7 -70.1 284 60 31 6.0 3.3 36000 -52.8 -63.0 282 53 27 7.0 3.9 | -53.1 -63.6 281 57 29 6.0 3.3 34000 -48.3 -54.9 281 51 26 8.6 4.7 | -49.2 -56.6 278 54 28 7.9 4.3 32000 -43.1 -45.6 278 52 27 8.6 4.7 | -43.9 -47.0 277 51 26 7.9 4.3 30000 -37.6 -35.7 274 50 26 7.6 4.2 | -39.1 -38.4 277 51 26 8.3 4.5 29000 -35.4 -31.7 273 47 24 7.6 4.2 | -36.6 -33.9 278 53 27 8.3 4.5 28000 -33.1 -27.6 272 43 22 7.6 4.2 | -34.1 -29.4 279 55 28 8.3 4.5 27000 -30.8 -23.4 272 41 21 7.7 4.2 | -31.8 -25.2 279 55 29 7.2 4.0 26000 -28.5 -19.3 275 40 21 7.7 4.2 | -29.6 -21.3 278 51 26 7.4 4.0 25000 -26.2 -15.2 277 40 21 7.7 4.2 | -27.4 -17.3 277 47 24 7.4 4.1 24000 -24.0 -11.2 280 40 20 6.5 3.6 | -25.2 -13.4 276 42 22 6.3 3.5 23000 -22.1 -7.8 285 40 21 6.3 3.5 | -23.5 -10.3 279 40 20 5.9 3.2 22000 -20.2 -4.4 289 40 21 6.3 3.5 | -21.7 -7.1 283 37 19 5.9 3.2 21000 -18.3 -0.9 293 41 21 6.7 3.7 | -20.0 -4.0 286 35 18 6.4 3.5 20000 -16.4 2.5 295 39 20 6.6 3.6 | -18.1 -0.6 288 33 17 6.4 3.5 19500 -15.4 4.3 296 38 19 6.6 3.6 | -17.1 1.2 289 33 17 6.4 3.5 19000 -14.4 6.1 297 37 19 6.7 3.7 | -16.2 2.8 290 32 17 6.4 3.5 18500 -13.4 7.9 298 35 18 6.5 3.6 | -15.3 4.5 290 32 16 6.5 3.6 18000 -12.5 9.5 298 32 16 6.4 3.5 | -14.3 6.3 290 31 16 6.6 3.6 17500 -11.5 11.3 298 28 14 6.3 3.5 | -12.8 9.0 290 31 16 7.1 3.9 17000 -10.3 13.5 297 23 12 5.5 3.0 | -11.7 10.9 291 32 17 7.3 4.0 16500 -9.5 14.9 296 19 10 5.6 3.0 | -10.6 12.9 291 34 17 7.5 4.1 16000 -8.6 16.5 298 19 10 5.9 3.2 | -9.5 14.9 291 36 19 8.0 4.4 15500 -7.7 18.1 302 19 10 5.7 3.1 | -8.3 17.1 291 39 20 8.0 4.4 15000 -6.8 19.8 303 21 11 7.5 4.1 | -7.1 19.2 291 41 21 7.7 4.2 14500 -5.7 21.7 303 23 12 7.3 4.0 | -6.0 21.2 290 41 21 7.8 4.3 14000 -4.7 23.5 302 26 13 6.8 3.8 | -4.9 23.2 290 40 21 7.1 3.9 13500 -3.7 25.3 300 29 15 6.8 3.7 | -3.8 25.2 289 38 19 7.0 3.9 13000 -2.7 27.1 298 31 16 6.7 3.7 | -2.8 27.0 289 35 18 8.1 4.4 12500 -1.7 28.9 295 32 17 6.6 3.6 | -1.5 29.3 288 31 16 8.4 4.6 12000 -0.7 30.7 293 34 17 6.7 3.7 | -0.3 31.5 288 28 15 9.0 4.9 11500 0.3 32.5 290 33 17 6.9 3.8 | 1.1 34.0 289 26 14 9.2 5.1 11000 1.3 34.3 287 31 16 7.4 4.1 | 2.5 36.5 291 25 13 9.2 5.0 10500 2.4 36.3 284 28 15 7.8 4.3 | 3.8 38.8 292 23 12 9.1 5.0 10250 3.0 37.4 282 27 14 7.9 4.3 | 4.5 40.1 293 22 11 9.1 5.0 10000 3.6 38.5 280 25 13 8.6 4.7 | 5.2 41.4 294 21 11 9.2 5.1 9750 4.2 39.6 278 24 12 9.2 5.1 | 5.9 42.6 295 20 10 9.3 5.1 9500 4.9 40.8 277 23 12 9.1 5.0 | 6.6 43.9 295 19 10 9.3 5.1 9250 5.6 42.1 275 22 11 9.1 5.0 | 7.2 45.0 296 18 9 9.2 5.1 9000 6.3 43.3 272 20 11 9.1 5.0 | 7.9 46.2 297 17 9 9.0 5.0 8750 6.9 44.4 271 20 10 9.1 5.0 | 8.6 47.5 299 16 8 8.9 4.9 8500 7.6 45.7 268 19 10 9.1 5.0 | 9.2 48.6 300 15 8 9.0 4.9 8250 8.3 46.9 266 18 9 9.1 5.0 | 9.9 49.8 302 14 7 8.9 4.9 8000 9.0 48.2 264 17 9 9.2 5.0 | 10.5 50.9 304 12 6 8.7 4.8 7750 9.6 49.3 261 16 8 9.1 5.0 | 11.2 52.2 307 11 6 8.7 4.8 7500 10.3 50.5 258 15 8 9.2 5.0 | 11.8 53.2 310 10 5 8.6 4.7 7250 11.0 51.8 255 14 7 9.0 5.0 | 12.4 54.3 313 9 5 9.3 5.1 7000 11.6 52.9 252 13 7 8.8 4.8 | 13.1 55.6 314 9 5 10.0 5.5 6750 12.3 54.1 250 13 7 9.1 5.0 | 13.9 57.0 315 9 5 9.8 5.4 6500 12.9 55.2 247 12 6 8.1 4.4 | 14.6 58.3 317 8 4 9.9 5.4 6250 13.4 56.1 243 11 6 4.9 2.7 | 15.3 59.5 318 8 4 9.9 5.4 6000 13.6 56.5 238 9 5 3.9 2.1 | 16.1 61.0 320 8 4 10.1 5.6 5750 13.8 56.8 231 7 4 3.4 1.9 | 16.8 62.2 321 7 4 9.5 5.2 5500 14.1 57.4 218 5 3 6.6 3.6 | 17.6 63.7 323 7 3 11.9 6.5 05/05/2009 at 1500 MDT | 05/05/2009 at 1800 MDT | K index... +20.9 | K index... +18.5 | 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 -60.5 -76.9 289 40 20 0.0 0.0 | -60.1 -76.2 291 53 27 -0.6 -0.3 45000 -60.3 -76.5 292 67 35 1.4 0.8 | -60.8 -77.4 295 84 43 1.6 0.9 40000 -58.4 -73.1 289 70 36 1.3 0.7 | -58.6 -73.5 303 98 50 1.5 0.8 38000 -56.2 -69.2 290 70 36 5.0 2.8 | -56.0 -68.8 304 96 49 5.7 3.1 36000 -53.2 -63.8 291 71 36 5.0 2.7 | -52.6 -62.7 303 90 47 5.7 3.1 34000 -49.3 -56.7 291 68 35 7.1 3.9 | -48.5 -55.3 302 83 43 6.7 3.7 32000 -45.0 -49.0 291 61 32 7.1 3.9 | -44.5 -48.1 302 76 39 6.7 3.7 30000 -40.5 -40.9 290 56 29 8.0 4.4 | -40.3 -40.5 300 67 34 7.4 4.0 29000 -38.1 -36.6 289 55 29 8.0 4.4 | -38.1 -36.6 297 60 31 7.4 4.0 28000 -35.7 -32.3 288 55 28 8.1 4.4 | -35.9 -32.6 293 54 28 7.4 4.0 27000 -33.3 -27.9 287 53 27 8.4 4.6 | -33.6 -28.5 289 50 26 7.9 4.3 26000 -30.8 -23.4 285 50 26 8.3 4.6 | -31.3 -24.3 288 49 25 7.9 4.3 25000 -28.4 -19.1 283 47 24 8.4 4.6 | -28.9 -20.0 286 48 25 7.9 4.3 24000 -25.9 -14.6 281 44 22 7.4 4.1 | -26.6 -15.9 284 47 24 7.9 4.4 23000 -23.8 -10.8 282 43 22 7.1 3.9 | -24.2 -11.6 286 45 23 8.0 4.4 22000 -21.7 -7.1 284 43 22 7.1 3.9 | -21.9 -7.4 287 43 22 8.0 4.4 21000 -19.6 -3.3 286 43 22 6.7 3.7 | -19.5 -3.1 289 40 21 7.7 4.2 20000 -17.7 0.1 288 43 22 6.7 3.7 | -17.2 1.0 292 37 19 7.8 4.3 19500 -16.7 1.9 288 43 22 6.7 3.7 | -16.1 3.0 294 36 18 7.8 4.3 19000 -15.7 3.7 289 43 22 6.7 3.7 | -14.9 5.2 295 34 18 7.8 4.3 18500 -14.1 6.6 289 43 22 7.4 4.1 | -13.7 7.3 297 33 17 7.9 4.3 18000 -13.0 8.6 289 43 22 7.4 4.1 | -12.0 10.4 299 31 16 8.0 4.4 17500 -11.9 10.6 289 43 22 7.1 3.9 | -10.8 12.6 300 29 15 7.4 4.1 17000 -10.9 12.4 287 43 22 7.1 3.9 | -9.7 14.5 301 27 14 7.4 4.0 16500 -9.9 14.2 286 43 22 7.2 4.0 | -8.6 16.5 303 24 12 7.4 4.0 16000 -8.8 16.2 285 42 22 7.6 4.2 | -7.5 18.5 304 21 11 7.4 4.0 15500 -7.6 18.3 283 41 21 7.6 4.1 | -6.4 20.5 304 19 10 7.4 4.0 15000 -6.5 20.3 281 39 20 7.6 4.2 | -5.3 22.5 303 18 9 8.0 4.4 14500 -5.4 22.3 279 37 19 7.6 4.2 | -4.1 24.6 300 18 9 8.0 4.4 14000 -4.2 24.4 278 34 18 8.6 4.7 | -2.9 26.8 298 18 9 8.6 4.7 13500 -3.0 26.6 277 33 17 8.6 4.7 | -1.6 29.1 297 20 10 8.6 4.7 13000 -1.7 28.9 275 31 16 9.1 5.0 | -0.4 31.3 295 21 11 8.4 4.6 12500 -0.3 31.5 275 29 15 9.2 5.1 | 0.9 33.6 294 22 11 8.4 4.6 12000 1.0 33.8 274 27 14 8.9 4.9 | 2.1 35.8 293 23 12 8.4 4.6 11500 2.3 36.1 274 25 13 8.7 4.8 | 3.3 37.9 292 24 12 8.5 4.7 11000 3.6 38.5 275 23 12 8.8 4.8 | 4.6 40.3 291 24 12 8.8 4.8 10500 5.0 41.0 277 21 11 8.9 4.9 | 5.8 42.4 290 24 12 8.9 4.9 10250 5.6 42.1 278 20 10 8.9 4.9 | 6.5 43.7 289 24 12 8.9 4.9 10000 6.3 43.3 279 19 10 9.1 5.0 | 7.2 45.0 289 24 12 9.3 5.1 9750 7.0 44.6 280 18 9 9.2 5.1 | 7.9 46.2 289 24 12 9.6 5.3 9500 7.7 45.9 281 17 9 9.2 5.0 | 8.6 47.5 289 23 12 9.5 5.2 9250 8.4 47.1 283 16 8 9.2 5.1 | 9.3 48.7 289 23 12 9.6 5.3 9000 9.1 48.4 284 16 8 9.4 5.2 | 10.0 50.0 289 23 12 9.9 5.4 8750 9.8 49.6 286 15 8 9.6 5.2 | 10.7 51.3 289 23 12 10.0 5.5 8500 10.5 50.9 288 14 7 9.5 5.2 | 11.5 52.7 290 22 12 10.0 5.5 8250 11.2 52.2 290 13 7 9.6 5.3 | 12.2 54.0 290 22 11 9.9 5.4 8000 11.9 53.4 292 13 7 9.7 5.3 | 13.0 55.4 290 22 11 9.7 5.3 7750 12.6 54.7 293 12 6 9.7 5.3 | 13.7 56.7 290 22 11 9.7 5.3 7500 13.4 56.1 295 12 6 9.6 5.3 | 14.4 57.9 290 22 11 9.6 5.3 7250 14.1 57.4 297 11 6 9.8 5.4 | 15.1 59.2 290 21 11 9.9 5.4 7000 14.8 58.6 298 11 6 10.1 5.5 | 15.9 60.6 291 21 11 10.1 5.5 6750 15.6 60.1 300 10 5 10.0 5.5 | 16.6 61.9 291 21 11 10.1 5.5 6500 16.3 61.3 301 10 5 10.1 5.5 | 17.4 63.3 291 20 10 10.1 5.5 6250 17.1 62.8 303 10 5 10.1 5.5 | 18.1 64.6 291 20 10 10.1 5.5 6000 17.8 64.0 304 9 5 10.3 5.7 | 18.9 66.0 292 18 9 10.2 5.6 5750 18.6 65.5 306 8 4 9.6 5.3 | 19.6 67.3 292 17 9 9.8 5.4 5500 19.3 66.7 307 8 4 12.3 6.8 | 20.4 68.7 292 15 8 11.0 6.0 ________________________________________________________________________________ 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