414
UXUS97 KBOU 190117
SRGBOU
SOARING FORECAST
NATIONAL WEATHER SERVICE DENVER/BOULDER, COLORADO
1816 MST THURSDAY, DECEMBER 18, 2025
THIS FORECAST IS FOR FRIDAY, DECEMBER 19, 2025:
IF THE TRIGGER TEMPERATURE OF 61.8 F/16.6 C IS REACHED...THEN
THERMAL SOARING INDEX....................... FAIR
MAXIMUM RATE OF LIFT........................ 207 FT/MIN (1.1 M/S)
MAXIMUM HEIGHT OF THERMALS.................. 11447 FT MSL (6168 FT AGL)
FORECAST MAXIMUM TEMPERATURE................... 70.0 F/21.6 C
TIME OF TRIGGER TEMPERATURE.................... 1030 MST
TIME OF OVERDEVELOPMENT........................ NONE
MIDDLE/HIGH CLOUDS DURING SOARING WINDOW....... BROKEN/OVERCAST THIN MIDDLE
SURFACE WINDS DURING SOARING WINDOW............ 20 MPH OR LESS
HEIGHT OF THE -3 THERMAL INDEX................. 9954 FT MSL (4675 FT AGL)
THERMAL SOARING OUTLOOK FOR SATURDAY 12/20..... POOR
WAVE SOARING INDEX............................. POOR
WAVE SOARING INDEX TREND (TO 1700 MST)......... NO CHANGE
HEIGHT OF STABLE LAYER (12-18K FT MSL)......... NONE
WEAK PVA/NVA (THROUGH 1700 MST)................ WEAK PVA
POTENTIAL HEIGHT OF WAVE....................... 14613 FT MSL (9334 FT AGL)
WAVE SOARING OUTLOOK FOR SATURDAY 12/20........ GOOD
REMARKS...
SUNRISE/SUNSET.................... 07:16:20 / 16:37:20 MST
TOTAL POSSIBLE SUNSHINE........... 9 HR 21 MIN 0 SEC (561 MIN 0 SEC)
ALTITUDE OF SUN AT 11:56:50 MST... 26.80 DEGREES
UPPER AIR DATA FROM NUMERICAL MODEL FORECAST VALID ON 12/19/2025 AT 0500 MST
FREEZING LEVEL.................. 13312 FT MSL (8033 FT AGL)
CONVECTIVE CONDENSATION LEVEL... 22207 FT MSL (16928 FT AGL)
LIFTED CONDENSATION LEVEL....... 17780 FT MSL (12501 FT AGL)
LIFTED INDEX.................... +8.0
K INDEX......................... -15.7
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 -81.9 305 58 30 -2.8 -1.5 M M M M M
45000 -67.5 -89.5 305 80 41 0.5 0.3 M M M M M
40000 -62.9 -81.2 285 68 35 3.1 1.7 M M M M M
38000 -58.7 -73.7 285 63 33 8.5 4.7 M M M M M
36000 -53.6 -64.5 290 58 30 8.5 4.7 M M M M M
34000 -48.4 -55.1 295 55 28 8.8 4.8 M M M M M
32000 -43.1 -45.6 300 55 28 8.8 4.8 M M M M M
30000 -37.9 -36.2 300 55 28 8.7 4.8 38.4 101.2 13.0 M M
29000 -35.3 -31.5 300 55 28 8.7 4.8 37.9 100.3 12.8 M M
28000 -32.1 -25.8 305 55 28 8.7 4.8 37.5 99.5 12.7 M M
27000 -29.5 -21.1 305 55 28 8.1 4.4 37.1 98.7 12.5 M M
26000 -27.1 -16.8 305 55 28 8.1 4.5 36.3 97.4 12.0 M M
25000 -24.7 -12.5 305 55 28 8.1 4.5 35.8 96.4 11.7 M M
24000 -22.3 -8.1 305 54 28 7.9 4.3 35.2 95.4 11.4 M M
23000 -19.9 -3.8 305 55 28 7.8 4.3 34.5 94.0 10.9 M M
22000 -17.6 0.3 305 55 28 7.8 4.3 33.8 92.8 10.5 M M
21000 -15.3 4.5 310 56 29 7.4 4.1 33.1 91.6 10.0 M M
20000 -13.1 8.4 305 57 29 7.4 4.1 32.2 90.0 9.4 M M
19500 -11.9 10.6 305 58 30 7.4 4.1 31.8 89.3 9.1 M M
19000 -10.8 12.6 305 58 30 7.4 4.1 31.5 88.6 8.8 M M
18500 -9.7 14.5 305 59 30 7.1 3.9 31.1 88.0 8.5 M M
18000 -8.7 16.3 305 60 31 6.9 3.8 30.6 87.1 8.1 M M
17500 -7.7 18.1 305 61 32 6.9 3.8 30.1 86.2 7.8 M M
17000 -6.7 19.9 305 62 32 6.5 3.6 29.6 85.3 7.4 M M
16500 -5.7 21.7 300 64 33 6.6 3.6 29.1 84.3 6.9 M M
16000 -4.7 23.5 300 65 33 6.2 3.4 28.5 83.4 6.5 M M
15500 -3.8 25.2 300 66 34 6.0 3.3 27.9 82.2 5.9 M M
15000 -2.9 26.8 300 67 34 5.9 3.2 27.3 81.1 5.4 M M
14500 -2.1 28.2 300 68 35 5.5 3.0 26.6 79.8 4.8 M M
14000 -1.3 29.7 295 68 35 5.5 3.0 25.9 78.6 4.2 M M
13500 -0.1 31.8 295 69 35 5.0 2.7 24.7 76.5 3.2 M M
13000 0.6 33.1 295 69 35 4.7 2.6 24.0 75.1 2.5 M M
12500 1.3 34.3 290 67 35 4.2 2.3 23.1 73.5 1.7 M M
12000 1.9 35.4 290 66 34 4.1 2.3 22.2 71.9 0.9 M M
11500 2.5 36.5 290 63 32 3.5 1.9 21.2 70.2 -0.1 406 2.1
11000 3.0 37.4 285 60 31 3.5 1.9 20.2 68.4 -1.0 375 1.9
10500 3.4 38.1 285 56 29 2.4 1.3 19.2 66.5 -2.0 348 1.8
10250 3.6 38.5 285 54 28 3.4 1.8 18.6 65.5 -2.6 335 1.7
10000 3.9 39.0 285 52 27 4.8 2.7 18.2 64.7 -3.0 319 1.6
9750 4.2 39.6 285 49 25 3.7 2.0 17.8 64.0 -3.4 302 1.5
9500 4.4 39.9 285 46 24 2.9 1.6 17.2 63.0 -4.0 288 1.5
9250 4.6 40.3 280 44 23 2.4 1.3 16.7 62.1 -4.5 275 1.4
9000 4.8 40.6 280 41 21 5.3 2.9 16.2 61.1 -5.0 261 1.3
8750 5.3 41.5 280 39 20 5.8 3.2 15.9 60.7 -5.3 239 1.2
8500 5.6 42.1 280 35 18 3.0 1.7 15.5 59.8 -5.8 224 1.1
8250 5.8 42.4 280 31 16 4.1 2.2 15.0 59.0 -6.3 209 1.1
8000 6.1 43.0 275 27 14 2.8 1.5 14.5 58.2 -6.8 194 1.0
7750 6.3 43.3 275 23 12 4.9 2.7 14.0 57.2 -7.3 180 0.9
7500 6.8 44.2 270 20 10 7.7 4.2 13.8 56.8 -7.5 157 0.8
7250 7.3 45.1 265 17 9 6.8 3.7 13.6 56.5 -7.8 134 0.7
7000 7.8 46.0 260 14 7 6.2 3.4 13.4 56.1 -8.0 113 0.6
6750 8.3 46.9 255 13 7 6.3 3.4 13.1 55.5 -8.3 92 0.5
6500 8.8 47.8 245 12 6 9.3 5.1 12.9 55.2 -8.5 68 0.3
6250 9.4 48.9 235 12 6 1.8 1.0 12.7 54.9 -8.7 44 0.2
6000 9.1 48.4 225 11 6 -3.8 -2.1 11.8 53.2 -9.7 44 0.2
5750 8.7 47.7 215 11 6 -12.2 -6.7 10.6 51.1 -10.9 49 0.2
5500 6.7 44.1 205 10 5 -41.1 -22.6 7.9 46.3 -13.6 101 0.5
* * * * * * NUMERICAL WEATHER PREDICTION MODEL FORECAST DATA VALID * * * * * *
12/19/2025 AT 0800 MST | 12/19/2025 AT 1100 MST
|
CAPE... 0.0 LI... +9.2 | CAPE... 0.0 LI... +9.2
CINH... -0.0 K INDEX... -12.8 | CINH... 0.0 K INDEX... -9.1
|
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 -65.3 -85.5 295 69 36 -2.7 -1.5 | -64.6 -84.3 290 60 31 -3.8 -2.1
45000 -69.3 -92.7 295 81 42 2.1 1.2 | -70.1 -94.2 285 78 40 2.6 1.4
40000 -63.3 -81.9 290 63 32 4.0 2.2 | -63.3 -81.9 275 55 28 4.6 2.5
38000 -59.2 -74.6 290 57 30 8.4 4.6 | -59.0 -74.2 270 49 25 8.4 4.6
36000 -53.5 -64.3 290 53 27 8.4 4.6 | -53.3 -63.9 275 43 22 8.4 4.6
34000 -48.4 -55.1 295 50 26 8.7 4.8 | -48.1 -54.6 275 40 20 8.9 4.9
32000 -43.2 -45.8 295 48 25 8.7 4.8 | -42.8 -45.0 280 40 20 8.9 4.9
30000 -37.9 -36.2 295 48 25 8.7 4.8 | -37.4 -35.3 285 41 21 8.9 4.9
29000 -35.3 -31.5 295 49 25 8.7 4.8 | -34.8 -30.6 285 42 22 8.9 4.9
28000 -32.7 -26.9 295 49 25 8.7 4.8 | -32.1 -25.8 290 44 22 8.9 4.9
27000 -30.1 -22.2 300 50 26 8.4 4.6 | -29.5 -21.1 290 45 23 8.4 4.6
26000 -27.6 -17.7 300 50 26 8.5 4.6 | -26.9 -16.4 290 47 24 8.5 4.7
25000 -25.0 -13.0 300 50 26 8.5 4.6 | -24.4 -11.9 290 48 25 8.5 4.7
24000 -22.5 -8.5 300 51 26 8.3 4.6 | -21.8 -7.2 290 50 26 8.1 4.4
23000 -20.0 -4.0 300 52 27 8.2 4.5 | -19.5 -3.1 290 52 27 8.0 4.4
22000 -17.5 0.5 300 52 27 8.2 4.5 | -17.1 1.2 290 53 28 8.0 4.4
21000 -15.1 4.8 300 53 27 7.7 4.2 | -14.7 5.5 290 55 28 6.9 3.8
20000 -12.8 9.0 300 55 28 7.7 4.2 | -12.7 9.1 290 57 29 6.9 3.8
19500 -11.6 11.1 300 56 29 7.7 4.2 | -11.2 11.8 290 58 30 6.9 3.8
19000 -9.9 14.2 300 57 29 7.8 4.3 | -10.1 13.8 290 59 31 6.9 3.8
18500 -8.8 16.2 300 57 30 6.8 3.7 | -9.2 15.4 290 60 31 6.1 3.4
18000 -7.8 18.0 300 58 30 6.8 3.8 | -8.2 17.2 290 61 31 6.2 3.4
17500 -6.8 19.8 300 59 31 6.7 3.7 | -7.3 18.9 290 62 32 5.8 3.2
17000 -5.8 21.6 300 61 31 6.4 3.5 | -6.5 20.3 290 62 32 5.4 3.0
16500 -4.8 23.4 295 62 32 6.5 3.6 | -5.7 21.7 290 63 32 5.5 3.0
16000 -4.0 24.8 295 63 32 5.4 3.0 | -4.9 23.2 290 63 33 5.1 2.8
15500 -3.1 26.4 295 64 33 5.5 3.0 | -4.2 24.4 290 63 33 5.1 2.8
15000 -2.3 27.9 295 65 33 5.1 2.8 | -3.4 25.9 290 63 33 4.9 2.7
14500 -1.6 29.1 295 66 34 5.0 2.7 | -2.7 27.1 290 63 32 4.8 2.6
14000 -0.8 30.6 290 66 34 4.8 2.6 | -2.0 28.4 285 62 32 4.9 2.7
13500 -0.2 31.6 290 66 34 4.5 2.5 | -1.2 29.8 285 60 31 5.0 2.7
13000 0.5 32.9 290 66 34 4.4 2.4 | -0.5 31.1 285 59 30 5.1 2.8
12500 1.1 34.0 290 65 34 4.2 2.3 | 0.3 32.5 285 56 29 5.4 2.9
12000 1.8 35.2 290 64 33 4.2 2.3 | 1.1 34.0 285 53 27 5.4 3.0
11500 2.4 36.3 285 62 32 4.1 2.3 | 2.0 35.6 280 50 26 6.1 3.3
11000 3.0 37.4 285 59 30 4.1 2.2 | 2.9 37.2 280 46 24 5.9 3.2
10500 3.5 38.3 285 55 28 2.7 1.5 | 3.7 38.7 280 42 22 4.6 2.5
10250 3.7 38.7 285 53 27 4.1 2.2 | 4.0 39.2 280 40 21 6.6 3.6
10000 4.1 39.4 285 50 26 6.6 3.6 | 4.7 40.5 280 38 20 9.0 4.9
9750 4.6 40.3 280 48 25 5.8 3.2 | 5.3 41.5 280 36 19 7.1 3.9
9500 5.0 41.0 280 45 23 4.7 2.6 | 5.7 42.3 280 33 17 6.0 3.3
9250 5.3 41.5 280 42 22 4.5 2.5 | 6.2 43.2 275 30 15 5.9 3.3
9000 5.7 42.3 280 39 20 6.3 3.5 | 6.7 44.1 275 27 14 7.4 4.0
8750 6.2 43.2 280 36 19 7.2 4.0 | 7.3 45.1 275 25 13 7.9 4.4
8500 6.7 44.1 280 33 17 6.0 3.3 | 7.8 46.0 270 22 11 6.9 3.8
8250 7.2 45.0 275 29 15 6.2 3.4 | 8.3 46.9 270 19 10 7.0 3.9
8000 7.6 45.7 275 26 13 6.7 3.7 | 8.9 48.0 265 17 9 7.6 4.2
7750 8.2 46.8 275 22 11 8.1 4.5 | 9.5 49.1 265 14 7 8.6 4.7
7500 8.8 47.8 270 20 10 8.6 4.7 | 10.1 50.2 260 12 6 8.7 4.8
7250 9.5 49.1 265 17 9 8.4 4.6 | 10.8 51.4 250 11 5 8.5 4.7
7000 10.1 50.2 265 15 8 7.8 4.3 | 11.4 52.5 245 9 5 7.0 3.9
6750 10.6 51.1 260 13 7 7.1 3.9 | 11.9 53.4 245 8 4 6.3 3.5
6500 11.2 52.2 255 11 6 8.5 4.7 | 12.4 54.3 235 8 4 7.4 4.1
6250 11.7 53.1 240 9 5 4.0 2.2 | 12.9 55.2 225 7 4 5.2 2.9
6000 11.8 53.2 235 8 4 0.1 0.0 | 13.2 55.8 220 6 3 3.0 1.7
5750 11.6 52.9 225 7 4 -7.6 -4.2 | 13.3 55.9 210 5 3 0.8 0.5
5500 10.0 50.0 205 6 3 -40.3 -22.1 | 13.2 55.8 200 4 2 -3.0 -1.7
12/19/2025 AT 1400 MST | 12/19/2025 AT 1700 MST
|
CAPE... 0.0 LI... +8.7 | CAPE... 0.0 LI... +7.9
CINH... 0.0 K INDEX... -5.4 | CINH... 0.0 K INDEX... +0.4
|
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 -64.6 -84.3 290 72 37 -3.3 -1.8 | -64.1 -83.4 290 77 40 -1.6 -0.9
45000 -69.4 -92.9 280 81 42 1.4 0.8 | -66.4 -87.5 285 81 42 0.6 0.3
40000 -62.9 -81.2 270 62 32 4.3 2.3 | -63.0 -81.4 265 59 31 2.4 1.3
38000 -58.6 -73.5 270 55 29 8.1 4.4 | -58.8 -73.8 265 58 30 8.7 4.8
36000 -53.7 -64.7 265 49 25 8.1 4.4 | -53.6 -64.5 270 58 30 8.7 4.8
34000 -48.6 -55.5 265 44 23 9.3 5.1 | -48.4 -55.1 270 59 30 8.7 4.8
32000 -43.0 -45.4 270 41 21 9.3 5.1 | -43.2 -45.8 275 59 31 8.7 4.8
30000 -37.5 -35.5 270 40 21 9.0 4.9 | -38.0 -36.4 275 59 31 8.5 4.7
29000 -34.8 -30.6 275 41 21 9.0 4.9 | -35.5 -31.9 275 58 30 8.5 4.7
28000 -32.1 -25.8 275 42 22 9.0 4.9 | -32.3 -26.1 275 57 29 8.5 4.7
27000 -28.8 -19.8 275 44 23 8.5 4.7 | -29.8 -21.6 275 56 29 8.5 4.6
26000 -26.3 -15.3 275 46 23 8.5 4.7 | -27.2 -17.0 275 56 29 8.5 4.6
25000 -23.8 -10.8 280 47 24 8.5 4.7 | -24.7 -12.5 275 56 29 8.5 4.6
24000 -21.3 -6.3 280 49 25 7.6 4.2 | -22.2 -8.0 275 56 29 7.9 4.3
23000 -19.0 -2.2 280 51 26 7.5 4.1 | -19.9 -3.8 275 56 29 7.7 4.2
22000 -16.8 1.8 280 52 27 7.5 4.1 | -17.6 0.3 275 57 29 7.7 4.2
21000 -14.6 5.7 280 54 28 6.3 3.5 | -15.4 4.3 275 58 30 6.8 3.7
20000 -12.8 9.0 285 56 29 6.3 3.5 | -13.4 7.9 280 59 30 6.8 3.7
19500 -11.8 10.8 285 57 29 6.4 3.5 | -12.3 9.9 280 59 31 6.8 3.7
19000 -10.9 12.4 285 58 30 6.3 3.5 | -11.3 11.7 280 60 31 6.8 3.7
18500 -9.9 14.2 285 59 30 6.0 3.3 | -10.3 13.5 280 61 31 6.4 3.5
18000 -9.1 15.6 285 60 31 5.7 3.1 | -9.4 15.1 280 61 31 6.0 3.3
17500 -8.3 17.1 285 61 32 5.7 3.1 | -8.6 16.5 280 61 31 6.1 3.3
17000 -7.4 18.7 285 62 32 5.4 2.9 | -7.7 18.1 280 61 31 5.7 3.1
16500 -6.6 20.1 285 63 33 5.4 3.0 | -6.9 19.6 280 61 32 5.7 3.1
16000 -5.8 21.6 285 64 33 5.2 2.9 | -6.0 21.2 280 62 32 5.5 3.0
15500 -5.1 22.8 285 64 33 5.1 2.8 | -5.2 22.6 280 61 31 5.4 2.9
15000 -4.3 24.3 285 63 32 5.1 2.8 | -4.5 23.9 280 60 31 5.4 2.9
14500 -3.6 25.5 280 62 32 5.1 2.8 | -3.3 26.1 280 58 30 5.3 2.9
14000 -2.8 27.0 280 60 31 5.1 2.8 | -2.5 27.5 280 56 29 5.4 3.0
13500 -1.6 29.1 280 57 29 5.4 3.0 | -1.7 28.9 280 53 27 5.6 3.1
13000 -0.8 30.6 280 54 28 5.7 3.1 | -0.8 30.6 275 50 26 5.7 3.1
12500 0.1 32.2 280 51 26 6.3 3.4 | 0.1 32.2 275 46 24 6.1 3.3
12000 1.0 33.8 280 48 25 6.3 3.5 | 1.0 33.8 275 42 22 6.1 3.4
11500 2.0 35.6 275 45 23 6.5 3.6 | 1.9 35.4 275 38 20 6.6 3.6
11000 2.9 37.2 275 41 21 6.3 3.5 | 2.9 37.2 275 34 17 6.5 3.6
10500 3.8 38.8 275 38 20 5.3 2.9 | 3.9 39.0 270 31 16 5.8 3.2
10250 4.2 39.6 275 36 19 7.4 4.1 | 4.3 39.7 270 29 15 7.5 4.1
10000 4.9 40.8 270 34 18 9.3 5.1 | 5.0 41.0 270 28 14 9.1 5.0
9750 5.5 41.9 270 32 17 7.2 4.0 | 5.6 42.1 270 26 13 7.5 4.1
9500 6.0 42.8 270 29 15 6.4 3.5 | 6.1 43.0 270 24 12 6.7 3.7
9250 6.5 43.7 270 26 14 6.6 3.6 | 6.6 43.9 265 21 11 6.9 3.8
9000 7.0 44.6 265 24 12 8.1 4.5 | 7.2 45.0 265 19 10 8.1 4.5
8750 7.7 45.9 265 21 11 8.7 4.8 | 7.8 46.0 265 18 9 8.6 4.7
8500 8.3 46.9 260 19 10 7.9 4.3 | 8.4 47.1 260 15 8 7.8 4.3
8250 8.9 48.0 255 16 8 8.2 4.5 | 9.0 48.2 255 13 7 8.2 4.5
8000 9.5 49.1 250 14 7 7.8 4.3 | 9.6 49.3 245 10 5 7.6 4.2
7750 10.1 50.2 245 12 6 8.7 4.8 | 10.2 50.4 235 9 4 8.1 4.5
7500 10.8 51.4 235 11 6 9.7 5.3 | 10.8 51.4 230 8 4 9.0 4.9
7250 11.5 52.7 230 9 5 9.2 5.1 | 11.5 52.7 215 7 3 8.8 4.8
7000 12.1 53.8 220 8 4 7.0 3.9 | 12.1 53.8 205 6 3 7.3 4.0
6750 12.6 54.7 210 8 4 8.2 4.5 | 12.6 54.7 200 6 3 6.3 3.5
6500 13.4 56.1 200 7 4 11.0 6.0 | 13.1 55.6 195 5 3 7.1 3.9
6250 14.2 57.6 190 7 4 8.8 4.8 | 13.6 56.5 190 5 2 6.1 3.4
6000 14.7 58.5 180 7 4 6.4 3.5 | 14.0 57.2 185 4 2 4.1 2.2
5750 15.2 59.4 175 7 3 6.4 3.5 | 14.3 57.7 185 3 2 4.6 2.5
5500 15.7 60.3 165 6 3 6.3 3.4 | 14.4 57.9 175 3 2 -5.4 -2.9
________________________________________________________________________________
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page