Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
316 UXUS97 KBOU 290124 SRGBOU Soaring Forecast National Weather Service Denver/Boulder, Colorado 1923 MDT Tuesday, May 28, 2024 This forecast is for Wednesday, May 29, 2024: If the trigger temperature of 75.9 F/24.4 C is reached...then Thermal Soaring Index....................... Excellent Maximum rate of lift........................ 1270 ft/min (6.5 m/s) Maximum height of thermals.................. 18538 ft MSL (13243 ft AGL) Forecast maximum temperature................... 83.0 F/28.8 C Time of trigger temperature.................... 1045 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................. 10318 ft MSL (5023 ft AGL) Thermal soaring outlook for Thursday 05/30..... Fair 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....................... 45841 ft MSL (40546 ft AGL) Wave soaring outlook for Thursday 05/30........ Poor Remarks... Sunrise/Sunset.................... 05:34:21 / 20:19:41 MDT Total possible sunshine........... 14 hr 45 min 20 sec (885 min 20 sec) Altitude of sun at 12:57:01 MDT... 72.00 degrees Upper air data from numerical model forecast valid on 05/29/2024 at 0600 MDT Freezing level.................. 14308 ft MSL (9013 ft AGL) Convective condensation level... 15793 ft MSL (10498 ft AGL) Lifted condensation level....... 16283 ft MSL (10988 ft AGL) Lifted index.................... -4.1 K index......................... +19.8 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 -56.5 -69.7 275 31 16 0.6 0.3 M M M M M 45000 -56.1 -69.0 265 37 19 -1.7 -0.9 M M M M M 40000 -58.8 -73.8 265 40 21 -0.6 -0.3 M M M M M 38000 -55.7 -68.3 260 40 20 5.6 3.1 M M M M M 36000 -52.3 -62.1 260 39 20 5.6 3.1 M M M M M 34000 -48.1 -54.6 260 37 19 8.1 4.4 M M M M M 32000 -43.3 -45.9 260 34 18 8.1 4.4 M M M M M 30000 -38.6 -37.5 260 30 15 7.7 4.2 37.1 98.8 6.6 M M 29000 -35.7 -32.3 260 26 13 7.7 4.2 36.1 97.0 6.0 M M 28000 -33.4 -28.1 265 23 12 7.7 4.2 35.4 95.8 5.5 M M 27000 -31.1 -24.0 265 21 11 7.7 4.2 34.6 94.2 4.9 M M 26000 -28.8 -19.8 265 20 10 7.7 4.2 33.8 92.8 4.3 M M 25000 -26.5 -15.7 265 18 9 7.8 4.3 33.1 91.6 3.8 M M 24000 -24.2 -11.6 265 18 9 7.7 4.2 32.3 90.2 3.2 M M 23000 -21.9 -7.4 270 18 9 7.7 4.2 31.6 88.8 2.5 M M 22000 -19.6 -3.3 275 19 10 7.7 4.2 30.9 87.6 2.0 M M 21000 -17.3 0.9 275 18 9 7.9 4.3 30.2 86.3 1.4 M M 20000 -15.0 5.0 280 16 8 8.0 4.4 29.5 85.2 0.8 M M 19500 -13.8 7.2 285 16 8 8.0 4.4 29.2 84.6 0.5 M M 19000 -12.7 9.1 285 15 8 8.2 4.5 29.0 84.2 0.3 M M 18500 -11.4 11.5 290 15 8 8.4 4.6 28.7 83.7 0.0 M M 18000 -10.2 13.6 290 14 7 8.4 4.6 28.5 83.3 -0.2 1221 6.2 17500 -8.9 16.0 290 14 7 8.6 4.7 28.3 82.9 -0.4 1169 5.9 17000 -7.7 18.1 290 13 7 8.6 4.7 28.1 82.6 -0.6 1115 5.7 16500 -6.4 20.5 290 13 7 9.1 5.0 27.9 82.3 -0.8 1062 5.4 16000 -5.0 23.0 290 13 7 9.3 5.1 27.8 82.1 -0.9 1006 5.1 15500 -3.6 25.5 285 13 7 9.3 5.1 27.8 82.0 -0.9 950 4.8 15000 -1.6 29.1 285 13 7 9.2 5.0 27.6 81.7 -1.1 867 4.4 14500 -0.2 31.6 280 13 7 9.2 5.1 27.5 81.6 -1.2 811 4.1 14000 1.2 34.2 275 12 6 9.3 5.1 27.5 81.4 -1.3 755 3.8 13500 2.5 36.5 275 12 6 9.1 5.0 27.4 81.3 -1.4 699 3.5 13000 3.9 39.0 265 11 6 8.9 4.9 27.3 81.1 -1.5 644 3.3 12500 5.2 41.4 260 10 5 8.7 4.8 27.1 80.8 -1.7 590 3.0 12000 6.4 43.5 250 9 5 8.2 4.5 26.9 80.4 -1.9 539 2.7 11500 7.6 45.7 240 8 4 8.2 4.5 26.7 80.0 -2.1 487 2.5 11000 8.8 47.8 225 8 4 7.7 4.2 26.4 79.5 -2.4 437 2.2 10500 10.0 50.0 215 8 4 5.6 3.1 26.1 79.0 -2.7 387 2.0 10250 10.2 50.4 210 8 4 4.2 2.3 25.6 78.1 -3.2 372 1.9 10000 10.7 51.3 205 8 4 8.4 4.6 25.4 77.7 -3.5 350 1.8 9750 11.4 52.5 195 8 4 9.9 5.4 25.3 77.6 -3.5 322 1.6 9500 12.1 53.8 190 9 5 8.3 4.6 25.3 77.5 -3.6 294 1.5 9250 12.6 54.7 185 9 5 4.5 2.5 25.1 77.1 -3.8 273 1.4 9000 12.8 55.0 180 10 5 5.0 2.8 24.6 76.3 -4.3 257 1.3 8750 13.3 55.9 180 10 5 7.4 4.1 24.4 75.9 -4.6 236 1.2 8500 13.8 56.8 175 11 5 5.9 3.2 24.1 75.5 -4.9 215 1.1 8250 14.1 57.4 170 11 6 4.2 2.3 23.8 74.8 -5.3 197 1.0 8000 14.4 57.9 170 11 6 4.1 2.3 23.3 74.0 -5.7 181 0.9 7750 14.7 58.5 170 11 6 5.2 2.9 22.9 73.3 -6.1 164 0.8 7500 15.0 59.0 175 11 6 3.8 2.1 22.6 72.6 -6.5 147 0.7 7250 15.2 59.4 180 11 6 2.1 1.2 22.0 71.6 -7.1 134 0.7 7000 15.4 59.7 185 11 6 2.8 1.5 21.5 70.7 -7.7 122 0.6 6750 15.5 59.9 195 11 6 0.6 0.3 20.9 69.6 -8.3 110 0.6 6500 15.3 59.5 200 11 6 -5.1 -2.8 20.0 68.0 -9.2 109 0.6 6250 14.8 58.6 205 11 6 -7.8 -4.3 18.7 65.7 -10.6 118 0.6 6000 14.2 57.6 210 11 6 -6.2 -3.4 17.4 63.4 -11.9 128 0.6 5750 13.6 56.5 215 13 6 -10.7 -5.9 16.2 61.1 -13.2 138 0.7 5500 12.4 54.3 215 10 5 -20.5 -11.2 14.3 57.7 -15.2 168 0.9 * * * * * * Numerical weather prediction model forecast data valid * * * * * * 05/29/2024 at 0900 MDT | 05/29/2024 at 1200 MDT | CAPE... +433.9 LI... -1.4 | CAPE... +505.5 LI... -2.5 CINH... -213.6 K Index... +16.4 | CINH... -23.6 K Index... +17.9 | 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 -56.0 -68.8 275 27 14 0.1 0.1 | -56.5 -69.7 265 25 13 0.1 0.1 45000 -56.2 -69.2 270 35 18 -1.6 -0.9 | -56.5 -69.7 265 32 16 -0.9 -0.5 40000 -58.7 -73.7 260 44 22 -1.0 -0.6 | -58.0 -72.4 260 46 24 -0.1 -0.1 38000 -55.8 -68.4 260 43 22 5.5 3.0 | -55.0 -67.0 260 47 24 5.4 3.0 36000 -52.5 -62.5 265 43 22 5.5 3.0 | -51.8 -61.2 255 47 24 5.4 3.0 34000 -48.3 -54.9 265 41 21 8.2 4.5 | -47.7 -53.9 255 45 23 8.0 4.4 32000 -43.4 -46.1 270 37 19 8.2 4.5 | -42.8 -45.0 260 40 20 8.0 4.4 30000 -38.0 -36.4 270 31 16 7.9 4.3 | -37.6 -35.7 260 32 17 7.5 4.1 29000 -35.7 -32.3 270 28 14 7.9 4.3 | -35.4 -31.7 265 29 15 7.5 4.1 28000 -33.3 -27.9 265 25 13 7.9 4.3 | -33.1 -27.6 265 25 13 7.6 4.2 27000 -31.0 -23.8 265 22 11 7.7 4.2 | -30.9 -23.6 265 23 12 7.2 4.0 26000 -28.7 -19.7 265 20 10 7.7 4.3 | -28.8 -19.8 265 21 11 7.2 4.0 25000 -26.3 -15.3 260 18 9 7.8 4.3 | -26.6 -15.9 270 19 10 7.2 4.0 24000 -24.1 -11.4 260 17 9 7.2 3.9 | -24.4 -11.9 270 18 9 7.5 4.1 23000 -22.0 -7.6 265 17 9 7.2 3.9 | -22.2 -8.0 270 17 9 7.5 4.1 22000 -19.9 -3.8 265 17 9 7.2 3.9 | -20.0 -4.0 270 17 9 7.5 4.1 21000 -17.6 0.3 265 16 8 7.9 4.4 | -17.6 0.3 270 16 8 8.4 4.6 20000 -15.2 4.6 265 14 7 8.0 4.4 | -15.1 4.8 265 16 8 8.5 4.6 19500 -14.1 6.6 265 13 7 8.0 4.4 | -13.9 7.0 265 16 8 8.5 4.7 19000 -12.9 8.8 265 13 6 8.6 4.7 | -12.7 9.1 260 16 8 8.5 4.7 18500 -11.6 11.1 265 12 6 9.0 4.9 | -11.4 11.5 260 16 8 8.5 4.7 18000 -10.2 13.6 265 12 6 9.1 5.0 | -10.1 13.8 255 16 8 8.5 4.7 17500 -8.9 16.0 265 11 6 8.9 4.9 | -8.8 16.2 255 16 8 9.1 5.0 17000 -7.6 18.3 265 12 6 8.9 4.9 | -7.5 18.5 260 16 8 9.1 5.0 16500 -5.6 21.9 265 12 6 9.0 4.9 | -5.5 22.1 260 14 7 9.2 5.0 16000 -4.3 24.3 265 12 6 8.9 4.9 | -4.1 24.6 260 13 7 9.1 5.0 15500 -2.9 26.8 265 13 7 9.5 5.2 | -2.7 27.1 265 12 6 9.6 5.2 15000 -1.5 29.3 265 13 7 9.6 5.3 | -1.3 29.7 265 12 6 9.6 5.3 14500 -0.1 31.8 265 13 7 9.5 5.2 | 0.1 32.2 265 11 6 9.4 5.2 14000 1.3 34.3 265 13 7 9.4 5.1 | 1.5 34.7 265 11 6 9.3 5.1 13500 2.7 36.9 265 13 7 9.4 5.2 | 2.9 37.2 265 11 5 9.3 5.1 13000 4.1 39.4 260 12 6 9.6 5.3 | 4.3 39.7 265 10 5 9.3 5.1 12500 5.5 41.9 260 11 6 9.4 5.2 | 5.7 42.3 270 10 5 9.2 5.1 12000 6.8 44.2 255 11 6 8.4 4.6 | 7.0 44.6 270 9 5 8.9 4.9 11500 8.0 46.4 250 10 5 8.4 4.6 | 8.3 46.9 265 8 4 8.8 4.9 11000 9.2 48.6 240 9 5 7.7 4.2 | 9.6 49.3 260 7 4 8.1 4.4 10500 10.4 50.7 235 9 5 5.4 3.0 | 10.8 51.4 255 6 3 4.2 2.3 10250 10.6 51.1 230 9 4 4.6 2.5 | 11.0 51.8 250 6 3 4.6 2.5 10000 11.2 52.2 225 8 4 8.9 4.9 | 11.6 52.9 240 5 3 10.1 5.6 9750 11.9 53.4 225 8 4 9.7 5.3 | 12.3 54.1 230 5 3 8.8 4.8 9500 12.5 54.5 220 8 4 8.9 4.9 | 13.0 55.4 220 5 3 8.7 4.8 9250 13.1 55.6 215 7 4 6.4 3.5 | 13.5 56.3 205 5 3 5.9 3.2 9000 13.5 56.3 210 7 4 6.5 3.5 | 13.9 57.0 190 5 2 6.8 3.7 8750 14.1 57.4 205 7 4 8.0 4.4 | 14.5 58.1 170 5 2 8.0 4.4 8500 14.6 58.3 200 7 3 7.1 3.9 | 15.1 59.2 155 5 3 9.9 5.5 8250 15.1 59.2 190 7 3 6.1 3.3 | 15.6 60.1 145 5 3 -2.7 -1.5 8000 15.5 59.9 180 6 3 5.5 3.0 | 16.0 60.8 135 5 2 38.4 21.1 7750 15.9 60.6 175 7 3 6.2 3.4 | 20.0 68.0 125 4 2 35.3 19.3 7500 16.2 61.2 170 7 3 3.8 2.1 | 20.0 68.0 125 4 2 -9.0 -4.9 7250 16.3 61.3 165 6 3 0.9 0.5 | 20.1 68.2 125 4 2 2.8 1.6 7000 16.4 61.5 165 5 3 1.3 0.7 | 20.1 68.2 125 4 2 -0.2 -0.1 6750 16.4 61.5 160 5 2 1.4 0.8 | 20.1 68.2 125 4 2 0.0 0.0 6500 16.4 61.5 160 4 2 -1.2 -0.7 | 20.2 68.4 125 4 2 5.8 3.2 6250 16.1 61.0 160 3 1 -2.4 -1.3 | 21.0 69.8 125 4 2 11.2 6.1 6000 15.9 60.6 155 1 1 -4.2 -2.3 | 21.7 71.1 125 4 2 8.9 4.9 5750 15.7 60.3 000 0 0 3.4 1.9 | 22.5 72.5 120 3 2 14.0 7.7 5500 16.7 62.1 000 0 0 25.5 14.0 | 23.9 75.0 120 3 2 25.4 14.0 05/29/2024 at 1500 MDT | 05/29/2024 at 1800 MDT | CAPE... +94.5 LI... -0.1 | CAPE... +51.7 LI... +0.3 CINH... -26.1 K Index... +19.9 | CINH... -101.2 K Index... +23.6 | 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 -56.2 -69.2 260 27 14 -0.5 -0.3 | -57.8 -72.0 265 29 15 -0.8 -0.4 45000 -57.0 -70.6 265 35 18 -0.8 -0.4 | -58.7 -73.7 265 29 15 0.6 0.3 40000 -58.3 -72.9 265 40 21 0.6 0.3 | -57.8 -72.0 275 28 15 1.9 1.0 38000 -55.2 -67.4 260 43 22 5.6 3.1 | -54.7 -66.5 265 29 15 5.4 3.0 36000 -51.8 -61.2 260 46 24 5.6 3.1 | -51.5 -60.7 260 31 16 5.4 3.0 34000 -47.7 -53.9 260 46 24 7.7 4.2 | -47.2 -53.0 255 28 15 8.4 4.6 32000 -43.1 -45.6 255 42 22 7.7 4.2 | -42.2 -44.0 245 24 12 8.4 4.6 30000 -38.3 -36.9 255 37 19 8.2 4.5 | -36.4 -33.5 235 20 10 8.6 4.7 29000 -35.9 -32.6 255 33 17 8.2 4.5 | -33.9 -29.0 235 18 9 8.6 4.7 28000 -32.9 -27.2 250 29 15 8.2 4.5 | -31.3 -24.3 230 17 9 8.7 4.8 27000 -30.4 -22.7 250 27 14 8.3 4.6 | -29.0 -20.2 230 16 8 7.6 4.2 26000 -27.9 -18.2 250 25 13 8.3 4.6 | -26.7 -16.1 230 15 8 7.7 4.2 25000 -25.5 -13.9 250 23 12 8.4 4.6 | -24.4 -11.9 235 15 8 7.7 4.2 24000 -23.1 -9.6 255 21 11 7.7 4.2 | -22.2 -8.0 235 14 7 7.6 4.2 23000 -20.8 -5.4 255 20 10 7.8 4.3 | -19.9 -3.8 240 14 7 7.6 4.2 22000 -18.5 -1.3 260 19 10 7.8 4.3 | -17.7 0.1 240 14 7 7.7 4.2 21000 -16.3 2.7 265 18 9 7.7 4.2 | -15.5 4.1 250 13 7 7.5 4.1 20000 -14.0 6.8 265 17 9 7.7 4.2 | -13.3 8.1 260 12 6 7.5 4.1 19500 -12.9 8.8 270 16 8 7.7 4.2 | -12.2 10.0 265 11 6 7.5 4.1 19000 -11.7 10.9 270 15 8 8.2 4.5 | -11.1 12.0 270 11 6 7.4 4.0 18500 -10.5 13.1 270 14 7 8.4 4.6 | -10.1 13.8 275 11 6 7.1 3.9 18000 -9.2 15.4 275 14 7 8.4 4.6 | -9.0 15.8 280 10 5 7.1 3.9 17500 -7.9 17.8 270 13 7 8.8 4.8 | -8.0 17.6 285 10 5 7.5 4.1 17000 -6.6 20.1 270 12 6 8.8 4.8 | -6.9 19.6 290 10 5 7.5 4.1 16500 -5.3 22.5 265 11 6 8.6 4.7 | -5.2 22.6 295 9 5 7.9 4.3 16000 -4.1 24.6 260 10 5 8.5 4.7 | -4.0 24.8 295 8 4 7.9 4.3 15500 -2.8 27.0 255 10 5 8.5 4.7 | -2.9 26.8 295 8 4 8.0 4.4 15000 -1.5 29.3 245 9 5 8.5 4.7 | -1.7 28.9 290 7 4 8.1 4.4 14500 -0.3 31.5 235 9 5 8.5 4.6 | -0.5 31.1 280 7 3 8.1 4.5 14000 1.0 33.8 230 9 5 9.2 5.0 | 0.7 33.3 270 7 3 8.2 4.5 13500 2.4 36.3 220 9 5 9.1 5.0 | 1.9 35.4 260 7 4 8.3 4.6 13000 4.4 39.9 210 10 5 9.0 4.9 | 3.2 37.8 250 8 4 9.1 5.0 12500 5.7 42.3 205 10 5 9.0 4.9 | 4.5 40.1 240 8 4 9.1 5.0 12000 7.1 44.8 200 10 5 9.2 5.0 | 5.9 42.6 235 10 5 9.4 5.1 11500 8.5 47.3 195 10 5 9.1 5.0 | 7.3 45.1 235 11 6 9.4 5.1 11000 9.8 49.6 195 10 5 8.4 4.6 | 8.7 47.7 235 12 6 8.9 4.9 10500 11.1 52.0 190 10 5 4.1 2.2 | 10.0 50.0 235 14 7 7.0 3.8 10250 11.2 52.2 190 10 5 5.3 2.9 | 10.4 50.7 235 14 7 4.7 2.6 10000 12.0 53.6 190 10 5 12.0 6.6 | 10.9 51.6 235 15 8 9.1 5.0 9750 12.8 55.0 190 10 5 10.4 5.7 | 11.7 53.1 235 16 8 11.3 6.2 9500 13.6 56.5 190 10 5 10.1 5.5 | 12.5 54.5 235 17 9 10.8 5.9 9250 14.2 57.6 190 10 5 6.4 3.5 | 13.1 55.6 235 18 9 5.9 3.2 9000 14.7 58.5 190 9 5 8.2 4.5 | 13.5 56.3 235 19 10 6.4 3.5 8750 15.5 59.9 195 9 5 11.5 6.3 | 14.2 57.6 235 20 10 10.9 6.0 8500 16.3 61.3 195 9 5 9.8 5.4 | 14.9 58.8 235 20 11 9.2 5.1 8250 16.9 62.4 195 9 4 6.6 3.6 | 15.5 59.9 235 21 11 6.3 3.4 8000 17.3 63.1 200 8 4 7.7 4.2 | 15.9 60.6 235 23 12 6.3 3.4 7750 18.1 64.6 200 8 4 11.6 6.3 | 16.5 61.7 235 23 12 9.8 5.4 7500 18.9 66.0 205 8 4 9.6 5.3 | 17.2 63.0 240 24 13 8.0 4.4 7250 19.5 67.1 205 8 4 6.9 3.8 | 17.7 63.9 240 25 13 6.2 3.4 7000 20.0 68.0 210 8 4 7.7 4.2 | 18.1 64.6 240 26 13 2.3 1.3 6750 20.7 69.3 215 8 4 12.1 6.6 | 18.5 65.3 240 27 14 18.1 9.9 6500 21.7 71.1 220 8 4 10.8 5.9 | 20.3 68.5 235 22 11 14.4 7.9 6250 22.3 72.1 220 8 4 7.7 4.2 | 20.3 68.5 235 22 11 -3.0 -1.6 6000 22.9 73.2 220 8 4 8.3 4.5 | 20.3 68.5 235 22 11 1.3 0.7 5750 23.6 74.5 225 8 4 11.8 6.5 | 20.3 68.5 235 22 11 1.8 1.0 5500 24.7 76.5 225 8 4 19.1 10.5 | 20.7 69.3 230 19 10 10.2 5.6 ________________________________________________________________________________ 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